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To address the challenges faced by designers of multi-field coupled cooling systems for high heat flux chips, this paper proposes a "near-source" microchannel cooling strategy and establishes a thermal–flow-force electrically coupled model for chips. The effects of chip Joule heat and cooling water flow rate on the cooling performance with respect to multi-field coupling effects were studied. The impact of multi-field coupling effects was revealed, and a method for enhancing microchannel cooling performance in light of multi-field coupling effects is proposed. The results indicated that considering multi-field coupling effects in the microchannel cooling process leads to a deterioration in the thermal performance of chips, accompanied by a significant increase in electrical fluctuations and thermal deformation amplitude. Compared to chips upstream of the cooling water, chips downstream subjected to thermal cascade effects were more sensitive to multi-field coupling effects. Moreover, the temperature variance index, output current, and strain energy density of high heat flux chips were positively correlated with Joule heat but inversely proportional to the Reynolds number of the cooling water for cases in respect of multi-field coupling effects. Additionally, serpentine microchannels maximized the operational performance of high heat flux chips by reducing temperature of chip by up to 55.1%, decreasing strain energy density by 96.7%, and increasing input potential by 120%. [ABSTRACT FROM AUTHOR]

Relaxed Si1−xGex layers on Si(001) serve as virtual substrates for strained Si or Ge layers. However, plastically relaxed layers inevitably contain misfit and threading dislocations, negatively affecting devices. Deposition of a SiGe layer on the backside of the substrate introduces a dislocation reservoir at the wafer edge that can reduce the threading dislocation density (TDD) of Si0.98Ge0.02/Si layers, as these preexisting dislocations start gliding toward the wafer center upon reaching the critical thickness. Here, we show that this low-strain system can be used effectively to study dislocation glide kinetics. In agreement with the literature, dislocation glide is a thermally activated process with an activation energy of 2.12–2.16 eV. Near the critical thickness, relaxation is sluggish and inefficient due to the linear dependence of the glide velocity on excess stress. At lower growth rates, dislocations from the edge reservoir are activated in a lower density due to the increase in the critical thickness through partial strain relaxation by already activated dislocations. Contrary to common models, here, the lowest possible growth rate is not essential for minimizing the TDD. Instead, a careful balance between low and high growth rates is beneficial. Overcoming the initial sluggish and inefficient relaxation phase is critical while also avoiding accumulation of strain energy, and, therefore, the activation of dislocation sources. Only in a later stage of buffer growth, the growth rate should be reduced to a minimum. With this method, the TDD of strain relaxed Si0.84Ge0.16 layers is reduced to 7 × 104 cm−2. [ABSTRACT FROM AUTHOR]

Amorphous intergranular films (AIFs) have been proven in experiments to improve the damage tolerance of nanocrystalline materials. However, a quantitative study is still lacking. Molecular dynamics simulations were performed here to investigate the effect of CuNb AIFs on the fracture toughness of nanocrystalline Nb. In order to clarify the role of AIFs, a bicrystal Nb model with one straight symmetrical tilt grain boundary and a mode-I crack in one of the grains was constructed, in which the AIF effect was introduced by replacing the normal grain boundary with a CuNb AIF. Then, AIF thickness-dependent tensile deformation of the bicrystal Nb samples was simulated. The work-of-fracture, which is defined as the released strain energy due to the newly generated unit area in the crack during stretching, was employed to quantify the fracture toughness of the bicrystal systems. The results show that the fracture toughness of the AIF sample can be tripled due to the blunted crack tip and the relieved stress concentration at the crack tip as compared to the AIF-free one that exhibits a brittle crack propagation behavior. Also, the thicker the AIFs, the more pronounced this reinforcing effect. More importantly, it is found that there exists a critical AIF width of 1.7 nm, below which the crack will eventually break through the AIF, and above which the crack failed to do this. It is revealed that the enhanced fracture toughness originated from the transformation of brittle crack propagation to abundant dislocation emission from AIFs. [ABSTRACT FROM AUTHOR]

In this study, the effectiveness of fatigue life prediction using Interfacial Plastic Strain Energy (IPSE) was investigated for off-axis unidirectional Carbon Fiber Reinforced Thermoplastic (CFRTP) specimens composed of PA6, a thermoplastic resin. Given the high hydrostatic pressure experienced by PA6 within the CFRTP, we employed the Drucker-Prager yield criterion. The internal friction angle of PA6, a key Drucker-Prager parameter, was determined to be 23.8° through uniaxial tensile and compressive tests, and was found to be suitable for analysis under high hydrostatic pressure conditions. Utilizing this friction angle, the IPSE of PA6 within the CFRTP was calculated via two-scale analysis. Our findings indicate that the use of IPSE enables accurate prediction of the fatigue life of CFRTP, based on the fatigue test results of pure PA6. This research provides valuable insights for the future design and utilization of CFRTP materials. [ABSTRACT FROM AUTHOR]

AbstractVarious intriguing morphological patterns emerge on the surfaces of growing, developing, or aging tissues, organs, and colonies of microorganisms. Our research draws inspiration from biological growth processes and applies differential growth to film-substrate systems. The strain mismatch induced by this approach leads to distinctive buckling patterns. Through a combination of finite element analysis (FEA) and theoretical analysis, we derive a comprehensive expression for the strain energy in a buckled film-substrate system subjected to differential growth. By solving the energy equations, our study investigates the intricate interplay of material properties, growth functions, and geometric characteristics. This exploration provides valuable insights into the deformations induced by growth in membrane structures and soft materials. Additionally, we establish a phase diagram that characterizes the buckling patterns. It opens avenues for innovative geometric design and 3D self-assembly techniques. Furthermore, our findings have the potential to inspire applications in fields such as soft robotics and flexible electronics. [ABSTRACT FROM AUTHOR]

The energy dissipation and stress-strain characteristics, and characteristic stresses, namely the crack initiation σci , dilatancy σcd , and peak σf stresses, of polypropylene fiber-reinforced recycled concrete under uniaxial compression were studied. According to the research results, the crack initiation and peak stresses of the specimen with single-blend polypropylene coarse fiber (No. 3) and the specimens with mixed-blend coarse and fine polypropylene fibers (No. 4 and No. 5) are higher than those of the specimen with single-blend fine fiber and plain concrete. The analysis of the energy characteristics and failure mechanism of polypropylene fiber-reinforced recycled concrete during loading based on the principle of energy conservation showed that the total strain energy, elastic strain energy, and dissipation energy absorbed per unit volume increase with the blending of polypropylene fiber. The strain energy and elastic strain energy of coarse aggregates with a 5-10 to 10-20 mm coarse aggregate size ratios of 5:5 are higher than those of 4:6 and 6:4. It was found that the continuous blending of polypropylene fiber increases the elastic strain energy, causing the point at which the dissipation energy exceeds the elastic strain energy move further and further back. The position where the dissipation energy exceeds the elastic strain energy can be used to evaluate the blending effect of polypropylene fiber. The further back the position, the better the blending effect. [ABSTRACT FROM AUTHOR]

The low-temperature performance of asphalt mixtures was a critical factor that investigated the thermal cracking of asphalt pavement in cold regions of the world. Many scholars have affirmed that the failure temperature of the thermal stress restrained specimen test (TSRST) could be an index to evaluate the low-temperature performance of asphalt mixtures. However, the influence of transient heat transfer on asphalt mixtures was ignored in the TSRST, potentially leading to inaccurate evaluation indexes for low-temperature performance. In this paper, the thermal contraction strain and the effective temperature of asphalt mixtures were analyzed considering transient heat transfer in the TSRST. First, the effective temperature and the thermal contraction strain were captured during the cooling process. Then, the calculation model of thermal stress was improved. The pseudo strain energy density was calculated based on the energy theory. Finally, the calculation model of thermal stress was evaluated with the failure temperature as the standard. The difference between the failure temperature calculated by the calculation model of thermal stress without considering the transient heat transfer and the failure temperature calculated considering the transient heat transfer was at least 2°C. [ABSTRACT FROM AUTHOR]

This research aims to propose a framework for selecting the optimum filler–binder (F-B) ratio in an asphalt mixture, with the objective to achieve desired fatigue performance at the lowest possible binder content. The asphalt mixtures were prepared with two types (VG-30 and PMB-40) of binders and three waste fillers (red mud, marble dust, and limestone dust), at varying filler contents (3%, 5%, and 7% by weight of aggregates). The fatigue resistance of the mixtures was quantified by the critical strain energy release rate (Jc), obtained from semicircular bending test. The results indicate that the fineness modulus, specific surface area, and Rigden voids were the primary filler characteristics influencing the behavior of unmodified mixtures, whereas the role of binder was determinant in the modified mixtures. Based on the findings of the study, it is proposed that the parameter FSR/|G*|·sinδ (where FSR is the ratio of fineness modulus and the product of specific surface area and Rigden voids, and |G*|·sinδ is a rheological parameter of the asphalt binder) can be used to estimate the optimum F-B ratio during the mix design of asphalt mixtures. [ABSTRACT FROM AUTHOR]

Study of stiffness characteristics plays a key role in application of parallel robots in precision manufacturing. In this study, stiffness index improvement is utilised as the objective function to obtain optimal configurations and dimensions for parallel robots. The optimisation goal is to maximise the stiffness index throughout workspace of the robots. First, stiffness of the robots is obtained by the strain energy of main components of the robots and Castigliano's theorem. For a more realistic simulation, compliance of moving platform of the robots is considered. Then a non-dominated sorting genetic algorithm (NSGA-II) is utilised to solve the optimisation problem. A comprehensive case study of stiffness analysis of three conventional SPS (spherical– prismatic–spherical) Stewart platforms to examine such a platform's optimised design is performed. The relationship between the objective and decision spaces is investigated. A similar approach can be utilised to study optimised design for other parallel robots. Findings of this study provide a general stepwise and conceptual approach to the stiffness analysis of parallel robots that depends on design parameters and configuration of the robots. In case of Stewart platforms, 3SPS configuration was found to be optimised in terms of stiffness performance in their workspace. [ABSTRACT FROM AUTHOR]

Modelling of Ni-P coating and substrate assembly is done using the finite element analysis framework. Coating having a thickness of 50 µm is applied over a stepped shaft made of stainless steel and analysed in Ansys Workbench at an elevated temperature of 200°C. The thermal effect on the system is studied and results are discussed in detail with respective figures. Elastic modulus of Ni-P coating required for the analysis is evaluated from the nanoindentation test under 10 mN load. The analysis focuses on the evaluation of the critical design parameters such as equivalent stress, total deformation, strain energy and thermal strain over the entire body. Besides, four separate paths are created on the model to study the difference of induced stress and strain energy between the contacting surfaces of the shaft and the coating. It is found that there is a sharp discontinuity in these values and this discontinuity is further interpreted as a measure of the stability of coating over the substrate. It is found that the higher the difference of stress and strain energy, lower is the stability of the assembly which is considered to be realistic and in accordance with the elasticity principles.. [ABSTRACT FROM AUTHOR]

• A new modeling approach for compressor blades is proposed by the Timoshenko beam theory. • The dynamic model of cracked blades is proposed considering the stiffness nonlinearity induced by breathing cracks. • The modeling method is verified by experiments and the proposed dynamic model is validated using ANSYS software. Aero-engine blades may crack under harsh operating environments. This reduces the reliability of the aero-engine and causes catastrophic accidents. Although dynamic modeling and vibration characteristics of simplified blades with cracks have been analyzed extensively, there are few studies on the actual compressor blade with varying sections and twisted shapes. Based on Timoshenko beam theory, a new modeling approach for the compressor blade is proposed. Next, according to the strain energy release rate and Castingliano theory, the dynamic model of cracked compressor blades is established considering the stiffness nonlinearity induced by the breathing crack. The modeling approach is validated by the measured natural frequencies of an intact blade. Then, the dynamic model of the cracked blade is verified by comparing the modal characteristics and vibration characteristics using ANSYS software. Finally, some results show that the natural frequencies f n1 , f n2 , and f n4 increase as the pre-twisted angle and stagger angle increase. Due to the breathing effect, some integer frequencies appear in the spectrum including 0 f e and 2 f e , and the variations in the amplitude of frequencies 0 f r and 2 f r are monotonic under different aerodynamic amplitudes. The research can provide some help for the modeling of the actual blade and fault diagnosis of cracked blades. [ABSTRACT FROM AUTHOR]

Phase-field models of brittle fracture are typically endowed with a decomposition of the elastic strain energy density in order to realistically describe fracture under multi-axial stress states. In this contribution, we identify the essential requirements for this decomposition to correctly describe both nucleation and propagation of cracks. Discussing the evolution of the elastic domains in the strain and stress spaces as damage evolves, we highlight the links between the nucleation and propagation conditions and the modulation of the elastic energy with the phase-field variable. In light of the identified requirements, we review some of the existing energy decompositions, showcasing their merits and limitations, and conclude that none of them is able to fulfil all requirements. As a partial remedy to this outcome, we propose a new energy decomposition, denoted as star-convex model, which involves a minimal modification of the volumetric-deviatoric decomposition. Predictions of the star-convex model are compared with those of the existing models with different numerical tests encompassing both nucleation and propagation. [ABSTRACT FROM AUTHOR]

In order to study the effects of pre‐crack inclination angle and filling material on granite, uniaxial compression tests were performed on pre‐cracked granite specimens without filling material and specimens filled with epoxy resin, gypsum, and organosilicon. Results indicate that the peak strength and apparent stiffness of pre‐cracked granite without filling materials increase with increasing pre‐crack inclination angle. The strain energy absorbed by the filling material improves the energy storage limit, inhibits the energy release effect when microcracks are connected to each other, and ultimately improves the compressive resistance and energy storage capacity. The strengthening effect of gypsum and epoxy resin is relatively better, which is more significant when the pre‐crack inclination angle equals 0°–60°. Finally, a damage constitutive model is established, which is in good agreement with the test and numerical simulation data. The results can provide reference for the research of grouting reinforcement of rock masses. Highlights: The effects of pre‐crack inclination angle and filling material are analyzed.The evolution law of energy mechanism is analyzed.The damage constitutive (DC) model of cracked rocks is proposed.The strengthening mechanism of energy storage effect of filled cracks was discussed. [ABSTRACT FROM AUTHOR]

A rapid and appropriate evaluation of the crack asymptote coefficients is essential for estimating the fracture growth in rock materials with inherent cracks and discontinuities. In the present study, the extended finite element method (XFEM), implemented with free coarse mesh, is used in conjunction with the finite element over‐deterministic (FEOD) method to determine the stress intensity factors (SIFs) and T‐stress for mixed‐mode I/II in‐plane loading of cracked rock specimens. Then, the generalized strain energy density (GSED) criterion is employed to estimate both fracture load and crack initiation angle for two types of rock pre‐cracked specimens. The predictions of the GSED criterion are then benchmarked against the experimental results, here obtained from three‐point bend tests on Neyriz marble. It is shown that such an approach to evaluate the fracture load dramatically reduces the computational cost and effort, meanwhile guaranteeing high accuracy and robustness. Highlights: XFEM is combined with FEOD to obtain stress fields around the crack tip.A new method for extracting test samples from rock cores is introduced.Various mixed‐mode fracture tests are conducted on rock samples.The results are satisfying even with unstructured coarse mesh. [ABSTRACT FROM AUTHOR]

Widening the martensitic hysteresis ( T Dhys ) in NiTiNb shape memory alloys (SMAs) holds potential for broadening their working temperature range while enabling the room-temperature storage. In this study, the T Dhys is divided into two parts: the thermal-induced hysteresis ( T hys ) and the deformation-induced hysteresis ( T hys ′ ). In addition to decreasing the martensitic transformation start temperature ( M S ), it is found that grain refinement is an effective method for widening both T hys and T hys ′ of the Ni47Ti44Nb9 alloy, a commercial SMA widely used for shape memory couplings. According to thermodynamic analysis, grain refinement increases the dissipation energy ( Δ E dis ) (caused by thermal friction at martensite/austenite interface), thereby widening T hys . Moreover, the Ni47Ti44Nb9 alloy with finer grains has the potential to release more elastic strain energy ( Δ E el ) after deformation, thereby exhibiting a wider T hys ′ . When deforming a large strain, the alloy with finer grains generates more dislocations which stabilize the martensitic phase, thus further widening T hys ′ . [ABSTRACT FROM AUTHOR]

A hyperelasticity modelling approach is employed for capturing various and complex mechanical behaviours exhibited by macroscopically isotropic polydomain liquid crystal elastomers (LCEs). These include the highly non-linear behaviour of nematic-genesis polydomain LCEs, and the soft elasticity plateau in isotropic-genesis polydomain LCEs, under finite multimodal deformations (uniaxial and pure shear) using in-house synthesised acrylate-based LCE samples. Examples of application to capturing continuous softening (i.e., in the primary loading path), discontinuous softening (i.e., in the unloading path) and auxetic behaviours are also demonstrated on using extant datasets. It is shown that our comparatively simple model, which breaks away from the neo-classical theory of liquid crystal elastomers, captures the foregoing behaviours favourably, simply as states of hyperelasticity. Improved modelling results obtained by our approach compared with the existing models are also discussed. Given the success of the considered model in application to these datasets and deformations, the simplicity of its functional form (and thereby its implementation), and comparatively low(er) number of parameters, the presented isotropic hyperelastic strain energy function here is suggested for: (i) modelling the general mechanical behaviour of LCEs, (ii) the backbone in the neo-classical theory, and/or (iii) the basic hyperelastic model in other frameworks where the incorporation of the director, anisotropy, viscoelasticity, temperature, softening etc parameters may be required. [ABSTRACT FROM AUTHOR]

In the constrained Cosserat theory of a rod with a rigid cross-section, the balance of angular momentum is satisfied by a restriction on the constitutive equations that requires a second order tensor to be symmetric. The kinematics of the rod are determined by satisfying the balances of linear and director momentum and kinematic constraints. In contrast, the Antman model for a special Cosserat theory of rods proposes constitutive equations directly for the force and mechanical moment applied to the rod and the kinematics are determined by the balances of linear and angular momentum. These two models differ by their treatment of angular momentum. This note poses and answers the question: Are the solutions of these two models identical for the same strain energy? [ABSTRACT FROM AUTHOR]

An analytical expression for the strain energy of a constrained extensible Cosserat elastica is developed for general planar shapes and deformations of the rod. This strain energy function naturally couples tangential stretch and reference and current curvatures of the centroidal curve. The model considers a rigid rectangular cross-section of the rod which remains normal to the centroidal curve. The constitutive equations for the tangential force, shear force and bending moment are consistent with a restriction based on the balance of angular momentum that requires a stress-like tensor to be symmetric in a similar manner to the symmetry of the Cauchy stress in a three-dimensional continuum. Examples show that coupling of tangential stretch and reference and current curvatures of the centroidal curve in the new strain energy function can significantly influence predictions of tangential force, shear force and bending moments. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing is a mature and effective method for deep oil and gas production, which provides a foundation for deep oil and gas production. One of the key aspects of implementing hydraulic fracturing technology lies in understanding mechanics response characteristics of rocks in deep reservoirs under complex stress conditions. In this work, based on outcrop core samples, high-stress triaxial compression tests were designed to simulate the rock mechanics behavior of deep reservoirs in Bozhong Sag. Additionally, this study analyzes the deformation and damage law for rock under different stress conditions. Wherein, with a particular focus on combining energy dissipation theory to further understand damage law for deep reservoirs. The experimental results show that regardless of stress conditions, the process of deformation/failure of deep-seated reservoirs goes through five stages: Fracture compaction, new fracture formation, stable fracture expansion, unstable fracture expansion, and post-peak residual deformation. Under different stress conditions, the energy change laws of specimens are similar. The energy dissipation process of rocks corresponds closely to the trend of deformation-failure curve, then displays distinctive stage characteristics. Wherein, in stage of rock fracture compaction, the input energy curve is approximately coincident with the elastic strain energy curve, while the dissipation energy curve remains near zero. With the increase of strain, the growth rate of elastic strain energy increases gradually, but with the deformation entering the crack propagation stage, the growth rate of elastic strain energy slows down and the dissipation energy increases gradually. Finally, in the post-peak stage, rock fracture releases a lot of energy, which leads to the sharp decline of elastic strain energy curve. In addition, the introduction of damage variable D quantifies the analysis of the extent of failure for rocks. During the process of increasing strain, rock damage exhibits nonlinear growth with increasing stress. [ABSTRACT FROM AUTHOR]

AbstractComposite materials are widely used in various aircraft due to their high specific strength, stiffness, corrosion resistance, and robust design flexibility. However, when subjected to complex loading conditions, composite structures are susceptible to damage, necessitating prompt repair upon aircraft return. Analyzing the re-damage process of repaired structures is crucial for assessing aircraft structural reliability, lifespan, and determining whether a repeat flight is warranted. In this study, a prediction method was proposed for re-damage behavior through meso-modeling and energy analysis of the repaired composite bolted joint. First, this article established a meso-mechanical model for composite laminates, analyzed force transfer characteristics at the fiber − matrix interface, and derived equations for stress field. Additionally, a strain energy distribution model was developed for composite bolted repaired joint near fibers and repaired area, proposing a damage prediction method based on the strain energy criterion. This method could anticipate the location, type, sequence, and magnitude of damage. Finally, simulation calculations yielded mechanical characteristics of the repaired area under typical load conditions, while loading tests verified the feasibility of the prediction method. This study offered an effective means of predicting performance degradation in composite structures and provided a vital direction for optimal spacecraft structure repairing methods and parameters. [ABSTRACT FROM AUTHOR]

In this paper, a physical index for quantitatively evaluating the non-proportional damping characteristics is proposed. Additionally, a direct design approach applicable to composite isolated structures (consisting of an upper damping structure and a base isolation system) is proposed for performance analysis of practical three-dimensional non-proportional damped structures. Furthermore, the elastic–plastic behavior of the structure under acceleration excitation is considered to determine the structural damage and response, improving computational accuracy and providing better solutions for the analysis and design of composite isolated structures. Analysis studies have shown that under rare and extremely rare earthquake events, structures designed using the complex modal response spectrum method (CM-RSM) exhibit less damage compared to those designed using the forced decoupling response spectrum method (FD-RSM) compared to the results obtained using the complex modal response spectrum method. For the seismic performance study of non-proportional damped structures, it is recommended to use the complex modal response spectrum method. With an increasing earthquake intensity, the proportion of energy dissipation due to the nonlinear strain energy dissipation of a structure increases, and the proportion of energy dissipation due to the isolators and dampers in the damping energy portion decreases. [ABSTRACT FROM AUTHOR]

In this research, five fracture criteria (maximum tangential stress (MTS), generalized maximum tangential stress (GMTS), minimum strain energy density (SED), generalized minimum strain energy density (GSED), and modified maximum tangential stress (MMTS)) were evaluated for asphalt concrete using fracture data from tests conducted under various loading modes and conditions. Tests were performed on semi‐circular bend (SCB) specimens of various sizes. Based on the results, the MTS criterion tends to overestimate fractures, while the GMTS criterion exhibits more precise predictions. The SED and GSED criteria inaccurately predict fractures, especially under certain loading conditions. The MMTS criterion shows superior predictive capability for asphalt concrete fractures. Specimen size influences fracture resistance, with larger specimens exhibiting higher fracture values. Overall, the MMTS criterion closely mirrors the crack growth behavior of asphalt concrete, highlighting its precision in predicting fracture results. The errors between the predictions of the fracture criteria MTS, GMTS, SED, GSED, and MMTS, and the experimental results ranged from 0% to 42.8%, 0% to 22.5%, 0% to 52.7%, 0% to 42.4%, and 0% to 14.5%, respectively. [ABSTRACT FROM AUTHOR]

The vibration characterization of ultra‐thick laminates widely used in aerospace and marine industries was different from that of thin laminates. However, modal testing and simulation methods were generally limited to relatively thin laminates. To explore the vibration behavior of ultra‐thick laminates, a novel multiscale simulation technology based on the representative volume modal strain energy (RVMSE) method is presented for predicting modal damping in this paper. The adaptive Greedy‐Based Generation (GBG) algorithm is used to create a 3D random distribution of fibers for composites. Modal shape information of the structure is obtained according to the Lanczos algorithm, which is used as an input parameter for the microscopic model. This is followed by homogenization based on the volumetric analysis performed on representative volume elements (RVEs) to determine the strain energy in six directions. The calculation of modal damping is performed by using the modal strain energy (MSE) method and the damping properties of the six directions. The fast rate of convergence and high accuracy of the method are demonstrated through different examples. The vibration response predictions produced by novel RVMSE methodology are shown to closely match experimental measurements, providing scope to expand the application of this approach to more complex, ultra‐thick laminate components. Highlights: The RVMSE method uses a higher level of homogenization to overcome the limitations of the traditional MSE method for calculating the damping of ultra‐thick CFRP laminates.The modal parameter error is controlled to less than 10%, and the experimental results fill the gap of the damping data of ultra‐thick CFRP structure.The proposed RVMSE model improves the accuracy of dynamic response prediction for ultra‐thick laminates. [ABSTRACT FROM AUTHOR]

Industrial solid waste (mine tailings) management has emerged as the key universal ecological challenge as a result of the unceasing creation of rising waste by-products. Employing tailings makes mine fill production economical and assists resolve disposal problems. Foamed cement-based tailings backfill (FCTB) is a mine fill consisting of tailing, cement, water, and foaming agents. It provides certain advantages such as lightweight, good fluidity, and thermal insulation yet is relatively weak in strength. Additionally, FCTB's strength properties can be intensely improved by adding fibers. A total of three diverse fibers: polypropylene (PP), glass (G), and basalt (B) as well as dodecyltrimethylammonium bromide (DTAB) as a foaming agent were used to prepare fiber-reinforced foamed cementitious tailings backfill (FR-FCTB). The mechanical properties, energy evolution, ductility, and microstructure of FR-FCTB were elaborately investigated by uniaxial compression tests (UCS) and SEM. Laboratory findings demonstrate the reinforcing effect of three fibers on FCTB specimens: glass > polypropylene > basalt. FR-FCTB showed the best strength features as a fiber content of 0.3% was adopted in FCTB. At this time, the UCS performance of glass fiber-reinforced FCTBs was 0.85 MPa increased by 18.1%. The addition of fibers can increase the fill's energy storage limit, slow down the discharge of elastic strain energy within the backfill, and enhance the fill's ductility and toughness. The ductility factor evaluates the degree of deterioration of filling in terms of post-peak drop, with all FR-FCTB values being greater than CTB. FR-FCTB's chief hydration product is the C-S–H gel. Fiber's bridging effect significantly rallies crack extension and thus fill's strength features. Lastly, the study's main results are instructive for the industrial application of FR-FCTB used in metallic mines. [ABSTRACT FROM AUTHOR]

The mechanical behavior of cable pylon anchorage zone in a cable‐stayed bridge is complex due to high localized stresses. A strut‐and‐tie model (STM) has been introduced in this paper, which is recommended as an efficient way to analyze the disturbed region. However, predicting the internal forces in the tie members in the STM by integrating stresses was time‐consuming and inefficient. To address this issue, the principle of minimum strain energy was used to analyze the STM of the cable pylon anchorage zone. A simplified method was presented to assess the internal forces in the cable pylon anchorage zone. Moreover, an actual bridge (Cao'e River Bridge) was employed to be analyzed, and the prestressed steel strands in the bridge were obtained by the simplified method. A full‐scale test model of the bridge was fabricated to validate the accuracy of the simplified method. Furthermore, based on the simplified method, the effect of the thickness of front wall, the length of inner opening straight section, the thickness of side wall, the thickness of inner wall and the width of inner opening straight section on the internal force in the tie members in the STM was studied. The results show that the length of inner opening straight section has negligible effect on the internal forces in all tie members. Compared with the thickness of the side wall, the thickness of inner wall and the width of inner opening straight section have limited effect on the internal force of tie members. This study was expected to promote the design of cable pylon anchorage zone. [ABSTRACT FROM AUTHOR]

This paper presents a size‐dependent energy‐based strain burst criterion linking strength, elasticity, fracture energies and specimen size effect with stress state due to changes in boundary conditions. It proposes the concept of a 'Burst Envelope', a surface in three‐dimensional principal stress space derived based on energy storing and dissipation characteristics of a rock sample, taking into account the size of the specimen and potential localised failure pattern. A scalar burst index is also proposed to quantify the bursting scale. To illustrate and verify its functioning, a numerical modelling framework based on the distinct element method and employing a new cohesive‐frictional contact model is used to perform virtual strain burst experiments under different polyaxial loading‐unloading scenarios, mimicking various underground excavation scenarios. The obtained results are in good agreement with the theoretical prediction of burst occurrence. On that basis, the variation of burst possibility and magnitude are investigated with key factors, including confinement level and the material's elastic, strength and fracture properties. The effect of the specimen's aspect ratio and size on the rock burst potential is elaborated and verified using virtual strain burst experiments, facilitating the linking of the proposed theoretical framework with the evaluation of in‐situ strain bursts in rock masses around underground openings. [ABSTRACT FROM AUTHOR]

In the process of mining, a large area of hard roof will be exposed above a goaf and may suddenly break. This can easily induce rock burst and has a significant impact on production safety. In this study, based on the engineering background of the hard roof of the 2102 working face in the Balasu coal mine, the spatial and temporal characteristics of the strain energy of the roof during the initial mining process were explored in depth. Based on a theoretical calculation, it is proposed that hydraulic fracturing should be carried out in the medium-grained sandstone layer that is 4.8–22.43 m above the roof, and that the effective fracturing section in the horizontal direction should be within 30.8 m of the cutting hole of the working face. The elastic strain energy fish model was established in FLAC3D to analyze the strain energy accumulation of the roof during the initial mining process. The simulation and elastic strain energy results show that, as the working face advances to 70–80 m, the hard roof undergoes significant bending deformation. The energy gradient increases with the rapid accumulation of strain energy to a peak value of 140.54 kJ/m3. If the first weighting occurs at this moment in time, the sudden fracture of the roof will be accompanied by the release of elastic energy, which will induce rock burst. Therefore, it is necessary to implement roof cutting and pressure relief before reaching the critical step of 77 m. To this end, the comprehensive hydraulic fracturing technology of 'conventional short drilling + directional long drilling' is proposed. A field test shows that the hydraulic fracturing technology effectively weakens the integrity of the rock layer. The first weighting interval is 55 m, and it continues until the end of the pressure at the 70 m position. The roof collapses well, and the mining safety is improved. This study provides an important reference for hard roof control. [ABSTRACT FROM AUTHOR]

Featured Application: Featured Application: Seismic design of steel moment-resisting frames equipped with viscoelastic dampers in the framework of the Eurocode 8 provisions. The effectiveness of viscoelastic dampers as passive control devices has been demonstrated in the past through both experimental and numerical investigations. Based on the Modal Strain Energy Method, some authors have also proposed design procedures to size the viscoelastic dampers assuming a fist-mode behavior of the structure. However, even if the damped structure is governed by the first mode of vibration, viscoelastic dampers are sensitive to the frequencies of the upper modes and transmit unexpected internal forces to braces. This paper aims to develop a simple design procedure for steel moment-resisting frames equipped with viscoelastic dampers considering the effects of the higher modes of vibrations on the internal forces transmitted from the dampers to the braces. In the perspective of a designer-oriented study, the seismic demand is evaluated through simple analytical tools, such as the lateral force method or the response spectrum analysis. The design procedure is applied to a set of steel moment-resisting frames considering two levels of seismic hazard and two types of soil. Finally, the effectiveness of the proposed procedure is verified through nonlinear dynamic analysis. Based on the results, it is found that the proposed design procedure ensures the control of the story drift below prefixed limits and to predict accurately the internal forces that arise in the braces. [ABSTRACT FROM AUTHOR]

Chalcopyrite selenide single crystals and epitaxial layers (CuIn1−xGaxSe2, x = 0.00, 0.08, 0.19, 1.00) were characterized by temperature‐dependent photoreflectance (PR), photoluminescence (PL), photoluminescence–excitation (PLE), and variable excitation‐energy photoluminescence (VEPL) spectroscopy. The transition energies Ea, Eb, and Ec of both CuInSe2 (CIS) and CuGaSe2 (CGS) layers sensed by PR were higher than the energies of single crystals. CuInSe2 and CuGaSe2 grown on GaAs(001) underlie compressive and tensile stresses, respectively, which lead to band‐gap broadening in CIS and band‐gap narrowing in CGS. The increase of the Ea, Eb, Ec energies of tensely stressed CuGaSe2 layers to energies higher than those of the bulk originates from the stress dependence of the non‐cubic crystal field. Band‐gap scanning of the CuGaSe2 layer with continuous‐wave Ti:sapphire‐laser confirmed the absence of correlation between band‐gap readjustment and intrinsic defects. The energy of the band‐edge exciton EFE, in the PL‐spectra, was lower than the Ea transition energy, in the PR‐spectra, which is assigned to partial quenching of ΔCF with the increase of external tensile stress by gallium‐segregation at the chalcopyrite/GaAs‐interface. The stress dependence of ΔCF is negligible in CuInSe2 and linear, with a rate of 9 meV/100 MPa, in CuGaSe2. It is revealed that the energy band‐gap of photovoltaic chalcopyrite absorbers can be tuned by simultaneous built‐in and external lattice‐tuning. [ABSTRACT FROM AUTHOR]

To explore the precursory information and instability fracture of rocks, we conducted a series of uniaxial compression tests on flawed sandstone. An integrated warning modeling is developed to predict the fracture in flawed sandstone. The results show that both the peak strength and elastic modulus of flawed sandstone demonstrate an “inverted” Gaussian distribution relative to the ligament angle, reaching the minimum values at 60°. The elastic strain energy proportion shows a sharp drop‐off, whereas the proportion of dissipative energy increases in steps. The coalescence modes of flawed sandstone change from a mixed tensile‐shear failure approximately aligned with the axis to an oblique shear failure. An integrated warning model is developed by integrating a Multi‐Output Classifier (MOC) and Grid optimization (GO). The integrated warning model has an accuracy of 97.95%. Additionally, the sensitivity of the model is recorded at 99.26%, confirming its effectiveness in predicting the likelihood of fracturing. [ABSTRACT FROM AUTHOR]

Assessing multiaxial fatigue theories requires experimental verification of a failure criterion, posing a significant challenge. This study aims to investigate the validity of a multiaxial fatigue method based on the Lagoda‐Macha‐Sakane (LMS) theory. The LMS theory links the critical strain energy density to the fatigue crack initiation cycles through a non‐linear equation defined by a set of empirical parameters calibrated by a strain‐controlled uniaxial fatigue test. This work adopts the LMS formulation, numerically calibrating the fatigue curve based on strain energy density from uniaxial fatigue experimental data and considering only the LMS theory for the critical strain energy density computation. This method avoids compatibility condition uncertainties and previous identification of material parameters. The study uses bi‐axial bending tests on AISI 316 L steel plate specimens with 3D finite element analyses to support computational assessment. The predictive capability of the model and the effectiveness of the testing method are presented and discussed. [ABSTRACT FROM AUTHOR]

The Qinling water conveyance tunnel has a large buried depth and high in-situ stress level, and rockburst disasters frequently occurred during excavation. In order to find out the mechanical mechanism of rockburst, the research work in this paper is as follows: (1) In-situ three-dimensional hydraulic fracturing method was used to measure the in-situ stress of the deep buried tunnel crossing the ridge. (2) Based on the measured in-situ stress results, the stress distribution characteristics of the tunnel crossing the ridge were obtained by the multiple linear regression method, and the rockburst tendency during construction was predicted. (3) A three-dimensional numerical model of tunnel excavation was established to analyze the dynamic adjustment characteristics of the surrounding rock stress and elastic strain energy during TBM excavation, and to clarify the mechanical mechanism of rockburst. The research results show that the maximum principal stress of the deep-buried tunnel crossing the ridge of Qinling is 40–66 MPa, which belongs to extremely high in-situ stress level, and medium-strong rockburst may occur during excavation. In the process of TBM excavation, the stress of the surrounding rock in the range of 2.6 times the diameter of the tunnel before and after the working face is adjusted violently, and the concentrated zones after the stress redistribution are mainly distributed in the arch roof and arch bottom, and the stress concentration coefficient can reach 2.06. The arch roof, arch waist, and arch bottom are susceptible to immediate rockburst due to stress transient unloading at the moment of excavation. After the elastic strain energy of the surrounding rock at the arch roof and the arch bottom is released and accumulated, it is easy to cause time delayed rockburst, and the depth of the rockburst pit can reach 3.5 m, which is consistent with the rockburst phenomenon in the field. [ABSTRACT FROM AUTHOR]

Deployable thin-film structure is an ideal requirement for space structures used for deep space exploration. One of the obstacles encountered by this structure is the problem of film surface accuracy caused by in-orbit temperature changes and plastic creases created by folding storage. This paper investigates how temperature and crease affect the wrinkling behaviors of thin films. A constitutive model accounting for temperature and crease effects is first derived, and by combining the maximum strain energy principle of tension field theory with the provided model, a numerical analysis method is established to analyze wrinkling films. The stress distribution and wrinkling direction of a rectangular film with or without crease under different temperatures are calculated using this method. Some important and interesting features are observed from the analysis results. The crease and temperature can affect the stress distribution and wrinkling angle of the wrinkling film. Furthermore, the wrinkling angle is more heavily affected by the crease, and the temperature's impact on the wrinkling angle of the creased film is magnified. This work explains the physical mechanism of the effects of both crease and temperature on wrinkles in deployable film structures and provides a simulation method for studying the wrinkling characteristics of thin films, considering the effects of both the temperature and the crease. [ABSTRACT FROM AUTHOR]

Energy drives the large deformation of soft rock tunnels, which is a nonlinear mechanical behavior of surrounding rock. This study aims to develop an analytical model for analyzing the energy conversion and absorption processes involved in tunneling. First, an analytical approach is presented for analyzing the energy conversion of the surrounding rock and energy absorption properties of the yielding support system during tunnel excavation. Subsequently, a comprehensive parametric investigation is conducted using the analytical model to investigate the impact of support pressure, tunnel radius, and initial stress on the energy conversion and dissipation of the surrounding rock. Similarly, the effect of support installation time, tunnel radius, and initial stress on the energy absorption properties of the yielding support system is explored. The results reveal that energy is input into the surrounding rock at the outer boundary through radial stress work. A portion of the energy is converted into elastic strain energy of the surrounding rock. Simultaneously, the plastic deformation of the surrounding rock consumes some of the input energy. Subsequently, the remaining energy flows from the excavation boundary as rock pressure work. Installing yielding components in the support system significantly enhances its maximum energy absorption capacity, which may be raised by up to 30 times. Moreover, the earlier the support installation time, the larger the tunnel radius, and the higher the initial stress, the more energy the yielding elements of the support system absorb. Highlights: Proposed an analytical model to characterize energy conversion in large deformation tunnels with yielding support. Quantitatively analyzed the energy conversion and dissipation properties in the surrounding rock. Explored the energy absorption characteristics of yielding support in large deformation tunnels. [ABSTRACT FROM AUTHOR]

To explore the energy evolution characteristics of rockbursts and the mechanism of excess energy in rockbursts, a self-developed rockburst experimental system was used. We performed true triaxial rapid unloading rockburst simulations and triaxial experiments based on the complete stress-displacement surface (CSDS) model prediction of the post-peak curve of rock uniaxial compression. By analyzing the characteristics of stress–strain curve and energy evolution of the rockburst experiment and comparing the energy storage characteristics of the two experiments, we arrived at the following conclusions Unlike the static failure of rock due to uniaxial compression, the occurrence of rockburst is mainly due to the generation of excess energy, which depends on the elastic strain energy stored before rock failure, outside energy input after rock failure and residual elastic strain energy. The intermediate principal stress of the rockburst experiment stored considerable residual elastic strain energy after the rockburst, resulting in an insufficient release of the elastic strain energy stored before the rockburst. The intensity of the rockburst is closely related to its excess energy release rate (EERR). With an increase in the EERR value, the cumulative energy of acoustic emission (AE) during rockbursts, the fractal dimension of rockburst fragments, and the rockburst intensity gradually increase. Highlights: The energy evolution and energy storage characteristics of true triaxial single-sided rapid-unloading rockburst experiment were studied using the graphic area method. The excess energy mechanism of the rockburst was discussed by comparing the energy storage characteristics of the true triaxial rockburst experiment and the static failure of the uniaxial compression rock. The correlation between rockburst intensity and EERR value was explored. [ABSTRACT FROM AUTHOR]

With growing consumer demand for plant‐based products that mimic the eating experience of animal‐based products, there is a need for improvement in instrumental measurements of sensory texture. This study aimed to characterize textural differences between dairy and non‐dairy cheeses, and to investigate whether Large Amplitude Oscillatory Shear (LAOS) rheometry could discriminate sensory texture better than Texture profile analysis. Commercial dairy and non‐dairy cheddar, mozzarella, and cream cheese were selected to provide a wide range of textures. Sensory evaluation used the check‐all‐that‐apply methodology with 73 consumers. Texture profile analysis force‐distance data were analyzed empirically, and also converted to stress and strain (see https://shiny.csiro.au/texture%5fdash). The major textural differences between dairy and non‐dairy cheddar were related to structural cohesion, according to both instrumental measures (dairy cheddar had 1.5‐fold higher failure stress and 2.2‐fold higher failure strain) and sensory measurements (dairy cheddar was more chewy and less crumbly). In contrast, cream cheeses showed similar textural properties using sensory testing but significant instrumental differences (non‐dairy cream cheese had 5.7‐fold higher modulus of deformability, 4.7‐fold higher failure stress). For mozzarella, there were large differences in both sensory attributes (chewy, crumbly, jelly‐like, stretchy) and instrumental parameters (13.6‐fold difference in modulus, 2.7‐fold difference in failure stress). LAOS rheometry gave insights into the mechanisms by which samples absorbed or dissipated mechanical energy at nonlinear strains. The LAOS parameter G3′/G1′$$ {G}_3^{\prime }/{G}_1^{\prime } $$ correlated well with sensory attributes creamy, fatty/oily, and moist, indicating the potential of this technique to measure structural phenomena linked to sensory attributes that resonate with consumers. [ABSTRACT FROM AUTHOR]

A novel method for determining the optimized parameter of the four-node incompatible generalized mixed element is presented based on the equilibrium between strain energy and complementary energy. The presented energy formulations are derived from the generalized mixed variational principle, which contains an arbitrary additional parameter. The initial solutions expressed by the displacement field are firstly assumed for the description of the energy of each generalized mixed element. Then, the identical relationship between strain energy and complementary energy is subsequently expressed at element level, which includes the arbitrary parameter. At the same time, a formulation for determining the optimized parameter at element level is proposed. Several representative examples with varying geometrical parameters, boundary and loading conditions are used to validate this method. By contrasting with the results of generalized mixed elements with different parameter values and other traditional finite elements. The effectiveness of the presented method has been demonstrated. On one hand, by ensuring the strain energy and complementary energy remain consistent under both coarse and fine meshes, the optimized parameter can adjust the stiffness of the generalized mixed element, thereby enhancing its resemblance to the real elastic body. On the other hand, the generalized mixed element has the additional advantage of conveniently introducing stress boundary conditions, thereby satisfying the requirement for zero-conditions of shear stresses on the exterior surfaces of beams. The numerical results obtained by the proposed method are accurate and stable. [ABSTRACT FROM AUTHOR]

The use of global displacement basis functions to solve boundary-value problems in linear elasticity is well established. No prior work uses a global stress tensor basis for such solutions. We present two such methods for solving stress problems in linear elasticity. In both methods, we split the sought stress σ into two parts, where neither part is required to satisfy strain compatibility. The first part, σ p , is any stress in equilibrium with the loading. The second part, σ h is a self-equilibrated stress field on the unloaded body. In both methods, σ h is expanded using tensor-valued global stress basis functions developed elsewhere. In the first method, the coefficients in the expansion are found by minimizing the strain energy based on the well-known complementary energy principle. For the second method, which is restricted to planar homogeneous isotropic bodies, we show that we merely need to minimize the squared L 2 norm of the trace of stress. For demonstration, we solve nine stress problems involving sharp corners, multiple-connectedness, non-zero net force and/or moment on an internal hole, body force, discontinuous surface traction, material inhomogeneity, and anisotropy. The first method presents a new application of a known principle. The second method presents a hitherto unreported principle, to the best of our knowledge. [ABSTRACT FROM AUTHOR]

The research aims to forecast the mechanical performance of a hybrid woven fabric natural composite subjected to compression, utilizing the three‐dimensional finite element method. A detailed finite element model of a plain woven fabric unit cell is created and analyzed for different materials like flax, basalt, and jute, and combinations of these materials (inter‐yarn hybrid basalt‐flax, jute‐flax and basalt‐jute fabrics). It is observed that fabric's response to compression is mainly influenced by the transverse longitudinal shear behaviour and the stiffness of the yarn cross‐section. Compression of single‐layer woven fabric involves yarn bending and compaction, resulting in varying fiber volume fractions in different areas due to compaction. The basalt‐jute hybrid plain woven fabric outperformed other plant‐based fiber fabrics with a polypropylene matrix in terms of mechanical performance under compression. Increase in yarn spacing and fabric thickness resulted in higher strain energy and displacement, attributed to changes in fiber volume fraction and crimp angle. Whereas, increasing yarn width led to a stiffer fabric due to increased contact area at the crossover region and higher bending rigidity, resulting in decreased strain energy and displacement. Importantly, this developed model can effectively simulate textile fabrics with diverse weaving patterns, material properties, and loading conditions. [ABSTRACT FROM AUTHOR]

Rock structures engineered during undersea mining are typically subjected to varying water distributions due to the motion of seawater, which considerably influences their stability. Hence, it is essential to understand the influence of seawater distribution on the mechanical behavior and energy characteristics of rocks. In this study, biaxial compression tests were conducted on red sandstone at various seawater immersion heights, and acoustic emission signals during compression were monitored. The results illustrate that the mechanical properties of the red sandstone deteriorate significantly upon seawater immersion. With an increase in seawater immersion height, the peak strength and elastic modulus of the rock specimens decreased exponentially. When the seawater immersion height was varied from 0 to 1/4 H under lateral stresses of 5, 10, 15, and 20 MPa, the peak strength decreased by 18.94%, 20.29%, 17.47%, and 14.87%, respectively, and the elastic modulus decreased by 4.6%, 8.1%, 11.7%, and 10.9%, respectively. Brittleness also decreased gradually. During compression, the acoustic emission (AE) and accumulated AE counts exhibited a stationary phenomenon, first increasing slowly and then suddenly. However, the AE counts decrease with increasing seawater immersion height. Meanwhile, with increasing seawater immersion height, the proportion of tensile cracks gradually increased and that of shear cracks gradually decreased. As the seawater immersion height increased, both the peak total input strain energy and peak total elastic strain energy decreased, whereas the peak total dissipated strain energy exhibited the opposite trend. [ABSTRACT FROM AUTHOR]

The stability of the immersed boundary (IB) method is a challenge in simulating fluid–structure interaction problems, where time step constraints are significantly stricter than in pure fluid simulations. We propose a novel unconditionally stable scheme for the immersed boundary finite element (IBFE) method. The structure is handled implicitly and characterized by strain energy functions, rather than being modeled as fibers or membranes. Through energy estimate, we prove the unconditional stability of the fully discrete approximation in the absence of the convective term. In real simulations of cardiac mechanics problems, the time step is much larger, only limited by the Courant–Friedrichs–Lewy condition of the fluid. The novelty of this work lies in the combination of dual interpolation and distribution operators, the Jacobian-free Newton–Krylov method for solving nonlinear algebraic systems, and the semi-Lagrangian method for handling the convective term. To validate the effectiveness and accuracy of our approach, we present various benchmarks and conduct a quasi-static simulation of a three-dimensional real left ventricular model. We have shown that the numerical stability of our scheme is very robust even with much larger time step compared to conventional explicit IB methods. Our work paves the way for further works on efficient solvers of the IBFE method. [ABSTRACT FROM AUTHOR]

Traditional medical imaging and biomechanical studies have challenges in analyzing the long-term evolution process of abdominal aortic aneurysm (AAA). The homogenized constrained mixture theory (HCMT) allows for quantitative analysis of the changes in the multidimensional morphology and composition of AAA. However, the accuracy of HCMT still requires further clinical verification. This study aims to establish a patient-specific AAA growth model based on HCMT, simulate the long-term growth and remodeling (G&R) process of AAA, and validate the feasibility and accuracy of the method using two additional AAA cases with five follow-up datasets. The media and adventitia layers of AAA were modeled as mixtures composed of elastin, collagen fibers, and smooth muscle cells (SMCs). The strain energy function was used to describe the continuous deposition and degradation effect of the mixture during the AAA evolution. Multiple sets of growth parameters were applied to finite element simulations, and the simulation results were compared with the follow-up data for gradually selecting the optimal growth parameters. Two additional AAA patients with different growth rates were used for validating this method, the optimal growth parameters were obtained using the first two follow-up imaging data, and the growth model was applied to simulate the subsequent four time points. The differences between the simulated diameters and the follow-up diameters of AAA were compared to validate the accuracy of the mechanistic model. The growth parameters, especially the stress-mediated substance deposition gain factor, are highly related to the AAA G&R process. When setting the optimal growth parameters to simulate AAA growth, the proportion of simulation results within the distance of less than 0.5 mm from the baseline models is above 80%. For the validating cases, the mean difference rates between the simulated diameter and the real-world diameter are within 2.5%, which basically meets the clinical demand for quantitatively predicting the AAA growth in maximum diameters. This study simulated the growth process of AAA, and validated the accuracy of this mechanistic model. This method was proved to be used to predict the G&R process of AAA caused by dynamic changes in the mixtures of the AAA vessel wall during long-term, assisting accurately and quantitatively predicting the multidimensional morphological development and mixtures evolution process of AAA in the clinic. [ABSTRACT FROM AUTHOR]

This work aims to reveal the effect of cyclic disturbance frequency, i.e., 0.01, 0.1, 0.5, and 1.0 Hz, on damage cracking and energy dissipation characteristics of rock‐backfill composite structure specimens. Testing results show that fatigue volumetric strain and secant modulus increase with increasing disturbance frequency; low‐frequency disturbance leads to an earlier volume expansion. In addition, the strain energy density increases with increasing disturbance frequency. Most of the energy are dissipated for the specimen under high‐frequency disturbance. Finally, computed tomography scanning reveals the influence of disturbance frequency on failure modes; tensile‐splitting failure and shear failure are likely to occur at the surrounding rock subjected to high‐ and low‐ frequency disturbances. Low‐frequency‐disturbed stress seems easily to stimulate cracks at the rock‐backfill interfaces and the backfill; the backfill can absorb much more energy than high‐frequency circumstances. It is suggested that the role of backfill in energy absorption, contact support, and stress isolation is disturbance frequency dependent. Highlights: The effects of cyclic disturbance frequency on damage‐cracking are revealed.The energy dissipation magnitude is negatively correlated to the disturbance frequency.Cracking at interfaces and backfill is relatively severe under low frequency disturbance.The backfill can absorb much more energy under low‐frequency disturbance conditions. [ABSTRACT FROM AUTHOR]

In this paper, mixed mode I/II and I/III fracture toughness of preplaced aggregate concrete was studied using an edge‐notched disc bend specimen. The results showed the dependency of the fracture toughness value on the mode mixity. The values of modes I, II, and III fracture toughness were obtained to be equal to 0.67MPam, 0.72MPam, and 0.42MPam, respectively. Several theoretical fracture criteria were examined for predicting the trends of experimental data in the tested preplaced aggregate concrete material. The 3D averaged strain energy density criteria provided the best predictions for the KIIIc/KIc ratio. Mixed mode I/III fracture toughness data were between the predicted envelopes of the maximum tensile stress and 3D maximum tangential strain theories. The generalized maximum tangential stress criterion provided accurate predictions for pure mode II and mixed mode I/II fracture data among the investigated mixed mode fracture criteria. By comparing the preplaced aggregate concrete fracture results with those of other types of concrete, it is observed that preplaced aggregate concrete has acceptable and in‐the‐range fracture resistance. Highlights: The compressive and tensile strengths of preplaced aggregate concrete were obtained.Pure mode I, II, and III and mixed mode I/II and I/III fracture toughness of preplaced aggregate concrete mixtures were obtained using ENDB specimen.The accuracy of the data relevant to the experimental results was examined by standard prediction criteria.The fracture parameters (equivalent fracture toughness and work of fracture trend) for mode mixities I/II and I/III were investigated. [ABSTRACT FROM AUTHOR]

Earthquakes cause nonstructural, if not structural, damage to buildings. This damage is proportional to interstory drift (ISD). Concentric braced frames (CBFs) are one of the most effective measures to limit the ISD in steel buildings. When compressed, conventional concentric hot-rolled (HR) steel braces tend to buckle when slender and are aesthetically unpleasant if stocky. This limitation of conventional concentric hot-rolled steel braces motivates the present work to use pretensioned carbon-fiber-reinforced polymer (CFRP) cables as braces in CBFs. The theoretically proposed self-balancing pretensioned CFRP cable braces (SPCCBs) in CBFs eliminate buckling in braces and provide a comparable elastic strain energy reserve for earthquake resistance design. Being slender, SPCCBs will add to the aesthetic beauty of buildings. The performance of the SPCCB system was evaluated by comparing it with conventional CBFs using stocky HR. CFRP cables with two different tensile strengths were used as braces in the SPCCB system, i.e., CFRP cable with tensile strength of 4,700 MPa (CB4700) and 3,600 MPa (CB3600). Fifty-seven models (19 each for HR, CB4700, and CB3600) were prepared using a commercially available code and were designed using Indian standards, keeping the compressive capacity of the braces similar for all three systems. The performance of all of the aforementioned systems was evaluated on the basis of energy dissipation (through total strain energy capacity of braces), fundamental time period, base shear attracted, ISD, and size of braces. This study showed that the SPCCB system has not only improved the strain energy capacity but also reduced the base shear compared to conventional hot-rolled steel brace CBFs. The overall performance of the building with CB4700 braces was found to be the best, followed by CB3600 and HR braces. Finally, a design guideline for the SPCCB system was proposed by following the Indian standards. [ABSTRACT FROM AUTHOR]

The objective of this classroom note is to propose a generalized model for a compressible elastically isotropic material with elastic-inelastic response. The model is generalized for an exponential Fung-type strain energy with a sum of new higher order elastic distortional deformation invariants that can model elastic-inelastic distortional deformation. In contrast with an Ogden-type model, the coefficients of the proposed higher order invariants do not affect the small deformation response. Moreover, there is no need to determine eigenvalues and eigenvectors of the elastic distortional deformation tensor. Examples show that the equations can model preconditioning of biological tissues as well as elastic instability. [ABSTRACT FROM AUTHOR]

A new scheme for hyperelastic material is developed based on applying the argument of calculus variation to two-factor multiplicative decomposition of the deformation gradient. Then, Piola–Kirchhoff stress is coupled with internal balance equation. Strain energy function is expressed in terms of principal invariants of the deformation gradient decomposed counterparts. Recent work introduces a strain energy function in terms of principal stretches of the deformation gradient multiplicatively decomposed counterparts directly. Hence, a new reformulation of Piola–Kirchhoff stress and internal balance equation are provided. This work focuses on developing the mathematical framework to calculate the elasticity tensor for material model formulated in terms of decomposed principal stretches. This paves the way for future implementation of these classes of material model in FE formulation. [ABSTRACT FROM AUTHOR]

This work aims to analyze the propagation of fully nonlinear waves, encompassing shear, extension, and bending deformation modes, within homogenized periodic nonlinear hexagonal and triangular networks, successively considering 1D and 2D situations. The wave analysis is conducted from the expression of the effective strain energy density of periodic hexagonal and triangular lattices in the nonlinear regime by a continualization of the discrete lattice equations, considering all forms of energy. We incorporate strain gradient effects into the continuous model to account for the wave‐dispersive nature. The resulting second‐gradient nonlinear continuum exhibits subsonic and supersonic propagation modes. We first examine in a 1D situation the dynamical response of the hexagonal and triangular lattices, considering varying levels of nonlinearity quantified by a single scalar valued parameter. We further evaluate the impact of a fully nonlinear analysis compared to an analysis solely based on the shear energy, regarding both supersonic and subsonic modes. The nonlinear wave propagation analysis is then extended to a 2D situation for the same two lattices. It is shown that the longitudinal mode exhibits a higher frequency at a low degree of nonlinearity; however, as the degree of nonlinearity increases, the shear mode surpasses the longitudinal mode in terms of frequency. As the wavenumber increases, the nonlinearity has a lesser impact on the frequency behavior, and the phase velocity is more influenced by other factors, such as the second gradient contributions of the effective constitutive law. Such a behavior indicates a transition from a highly nonlinear behavior at lower wave numbers to a more linear behavior at higher wave numbers. [ABSTRACT FROM AUTHOR]

This study aims to analyze the distribution characteristics of energy in deeply buried circular tunnels with a revealed cave. Analytical solutions for the stress and elastic strain energies in these tunnels are derived using the complex variable method and compared with numerical solutions obtained from finite element simulations. Subsequently, a parametric study investigates the effects of the cave's orientation, shape, and protrusion on the distribution of elastic strain energy. Finally, the influence of the revealed cave on the stability of the surrounding rock is analyzed using the evaluation index based on energy theory. The conclusions are as follows: the presence of the cave causes elastic strain energy to accumulate in the surrounding rock near the middle of the cave. The smaller the angle between the cave direction and the minimum principal stress, the more severe the energy accumulation near the cave. As the cave's protrusion increases and the b/a ratio of its shape decreases, energy accumulation near the cave becomes more severe. The presence of the cave increases the tendency for tunnel failure. The middle of the cave is susceptible to damage due to the accumulation of strain energy, while the intersection of the cave and the tunnel is more prone to damage because tensile stresses lower the energy threshold for surrounding rock failure. The study indicates that the middle of the cave and the junction between the cave and the tunnel are key areas requiring safety protection during construction. [ABSTRACT FROM AUTHOR]

Riveted railway bridges with already long structural lives can still be commonly found in service in Europe. In light of their peculiarities, they are often prone to fatigue damage; nevertheless, very few prescriptions regarding fatigue assessment of these structures can be found in current European provisions. Within this framework, the present paper illustrates the advanced fatigue assessment of an Italian riveted railway bridge selected as a case study. For this purpose, multi-scale finite element modelling of the bridge was developed, and the most critical details were assessed through application of the advanced strain energy density (SED) method. The obtained outcomes were compared both with other studies in the literature and prescriptions from the current and upcoming versions of EN1993-1-9. [ABSTRACT FROM AUTHOR]