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This study evaluates the potential use of discarded plasterboard paper as fibers from buildings to reinforce concrete. Various concentrations of wastepaper fibers (0.5%, 1%, 1.5%, 2%, and 2.5% by weight of the binder) were investigated in this research. To mitigate the water absorption effect of the paper fibers, metakaolin was employed as a partial cement replacement. The results demonstrate that the inclusion of the wastepaper fiber enhances the mechanical and durability performance of the concrete. The optimal fiber proportion was identified as 1%, leading to a 29% increase in the compressive strength, a 38% increase in the splitting tensile strength, a 12% decrease in the water absorption, and a 23% decrease in the drying shrinkage with respect to the concrete containing 20% metakaolin. However, exceeding this optimal fiber content results in decreased mechanical and durability properties due to the fiber agglomeration and non-uniform fiber distribution within the concrete matrix. Based on the microstructural analysis, the improved performance of the concrete is ascribed to decreased porosity, more refined pore structure, and reduced propagation of microcracks within the concrete matrix in the presence of wastepaper fiber. According to the results, concrete containing 20% metakaolin and 1% wastepaper fiber exhibits durability and mechanical properties comparable to those of the traditional concrete. This finding highlights the significant promise of reducing dependency on conventional cement and incorporating suitable recycled materials, such as discarded plasterboard, and secondary by-products like metakaolin. Such a strategy encourages the preservation of resources, reduction in carbon dioxide emissions, and a decrease in the ecological footprint resulting from concrete production. [ABSTRACT FROM AUTHOR]

In supporting the stable operation of high-penetration renewable energy grids, flywheel energy storage systems undergo frequent charge–discharge cycles, resulting in significant stress fluctuations in the rotor core. This paper investigates the fatigue life of flywheel energy storage rotors fabricated from 30Cr2Ni4MoV alloy steel, attempting to elucidate the material's mechanical properties, crack propagation behavior, and impact of internal defects on fatigue life. Tensile tests reveal that the material exhibited high yield (992 MPa) and tensile strengths (1130 MPa). The Paris formula is used to model crack growth rates, ending in good agreement with the experimental data. Fatigue tests at various stress conditions highlight the material's significant variability in fatigue life and emphasize the need for reliable design approaches. This paper also demonstrates that internal defect size and location critically affect fatigue life, calling for improvements in forging inspection standards. Overall, the present study provides a comprehensive analysis of 30Cr2Ni4MoV steel's suitability for flywheel rotors, balancing safety, and operational efficiency. [ABSTRACT FROM AUTHOR]

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It is necessary to study the propagation path of cracks in concrete materials and its influence on the loading capacity of specimens. The phase-field method for fracture offers a distinct benefit in simulating the crack propagation behavior of brittle materials, which is achieved by implementing a phase field that continuously fluctuates to approximate the crack configuration, abolishing the need for mesh reconstruction and tracking the cracks. In this paper, we have implemented a phase field model using ABAQUS, whose reliability is verified through a tensile test. Then, the splitting test of Brazilian disc is simulated and the results are similar to those of the laboratory experiment. Furthermore, the crack configuration of the prefabricated cracked discs with different tilt angles and different initial lengths is explored. The two important parameters of the phase field method, Gc and l0, are discussed in the Discussion section. A larger Gc value means a larger material toughness and a larger failure load, and a larger l0 value means a larger crack smear range as well as a smaller failure load. [ABSTRACT FROM AUTHOR]

The primary focus of this paper is to investigate the application of ANSYS Workbench 19.2 software's advanced feature, known as Separating Morphing and Adaptive Remeshing Technology (SMART), in simulating the growth of cracks within structures that incorporate holes. Holes are strategically utilized as crack arrestors in engineering structures to prevent catastrophic failures. This technique redistributes stress concentrations and alters crack propagation paths, enhancing structural integrity and preventing crack propagation. This paper explores the concept of using holes as crack arrestors, highlighting their significance in increasing structural resilience and mitigating the risks associated with crack propagation. The crack growth path is estimated by applying the maximum circumferential stress criterion, while the calculation of the associated stress intensity factors is performed by applying the interaction integral technique. To analyze the impact of holes on the crack growth path and evaluate their effectiveness as crack arrestors, additional specimens with identical external dimensions but without any internal holes were tested. This comparison was conducted to provide a basis for assessing the role of holes in altering crack propagation behavior and their potential as effective crack arrestors. The results of this study demonstrated that the presence of a hole had a significant influence on the crack growth behavior. The crack was observed to be attracted towards the hole, leading to a deviation in its trajectory either towards the hole or deflecting around it. Conversely, in the absence of a hole, the crack propagated without any alteration in its path. To validate these findings, the computed crack growth paths and associated stress intensity factors were compared with experimental and numerical data available in the open literature. The remarkable consistency between the computational study results for crack growth path, stress intensity factors, and von Mises stress distribution, and the corresponding experimental and numerical data, is a testament to the accuracy and reliability of the computational simulations. [ABSTRACT FROM AUTHOR]

The structural health monitoring (SHM) of buildings provides relevant data for the evaluation of the structural behavior over time, the efficiency of maintenance, strengthening, and post-earthquake conditions. This paper presents the design and implementation of a continuous SHM system based on dynamic properties, base accelerations, crack widths, out-of-plane rotations, and environmental data for the retrofitted church of Kuñotambo, a 17th century adobe structure, located in the Peruvian Andes. The system produces continuous hourly records. The organization, data collection, and processing of the SHM system follows different approaches and stages, concluding with the assessment of the structural and environmental conditions over time compared to predefined thresholds. The SHM system was implemented in May 2022 and is part of the Seismic Retrofitting Project of the Getty Conservation Institute. The initial results from the first twelve months of monitoring revealed seasonal fluctuations in crack widths, out-of-plane rotations, and natural frequencies, influenced by hygrothermal cycles, and an apparent positive trend, but more data are needed to justify the nature of these actions. This study emphasizes the necessity for extended data collection to establish robust correlations and refine monitoring strategies, aiming to enhance the longevity and safety of historic adobe structures under seismic risk. [ABSTRACT FROM AUTHOR]

Textured coating technology is an effective method to improve the friction and wear performance of mold surfaces. The adhesion strength at the interface between the texture and the coating is crucial for its long-term serviceability. This paper studies the adhesion strength of micro-dimple's topography textured coatings, aiming to reveal the influence mechanism of micro-dimples on the adhesion strength of textured coating interfaces. Different diameters or texture area ratios of micro-dimples were prepared on the sample surface using a picosecond laser, followed by PVD coating deposition. Scratching tests and indentation tests were then conducted on the textured coating surface. The adhesion strength and crack propagation behavior of the coating on the surface of different samples were studied under dynamic and static contact conditions. The results showed that under dynamic contact conditions, the critical load for coating failure of most textured samples was higher than that of non-textured samples. As the depth and diameter of the micro-dimple's topography increased, the critical load first increased and then decreased, with the maximum critical load being 14.9% higher than that of the non-textured samples. Under static contact conditions, almost no coating spalling was observed around the indentation on the surface of the micro-dimple's topography textured coating, while the spalling areas of non-textured samples were mainly at the edges and surrounding areas of the indentation. In contrast, the spalling regions of the textured samples were primarily concentrated at the edges of the texture. It can be seen that the dimpled texture hinders crack propagation and reduces the interlocking network of cracks, thereby reducing coating spalling. The research results provide important theoretical guidance for the design and optimization of textured coatings on mold surfaces. [ABSTRACT FROM AUTHOR]

Overloaded traffic is one of the major effects that cause more early damage to asphalt pavement than regular traffic. Moving overloaded traffic not only needs to consider dynamic coefficient and axle load coefficient when carrying out pavement mechanics calculations, but also accelerates pavement failure and boosts the cost of construction and maintenance. Although asphalt pavement of a stabilized base with inorganic binder has a strong bearing capacity, the shortcoming of reflective cracking also seriously restricts its performance. This paper describes the mechanical response and crack propagation of asphalt pavement of stabilized base with inorganic binder which has a crack, under the coupling effect of moving overloaded traffic and temperature. Extended finite-element method (XFEM) was conducted to simulate reflective cracks propagating freely from a stabilized base with inorganic binder to asphalt overlay. Dynamic analysis was also carried out by varying the axle weight and tire pressure, which could help highway builders understand the stress distribution of pavement under design traffic and the crack propagation law of pavement structures. Results indicated that the mechanical response of asphalt pavement was comprehensively related to tire pressure, axial weight, and its active position and that overloaded traffic accelerates crack propagation more than regular traffic. This research achievement contributes to providing roadway engineers with a more profound perception to potentially advance pavement design practitioners for specific traffic characteristics. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the application of 3D printing technology, particularly using sand-type materials, in the creation of artificial rock models for rock mechanics experimentation. Design/methodology/approach: Using a comprehensive analysis, this research explores the utilization of 3D printing technology in rock mechanics. Sand-type materials are specifically investigated for their ability to replicate natural rock characteristics. The methodology involves a review of recent achievements and experimentation in this field. Findings: The study reveals that sand-type 3D printing materials demonstrate comparable properties to natural rocks, including brittle characteristics, surface roughness, microstructural features and crack propagation patterns. Research limitations/implications: While the research establishes the viability of sand-type 3D printing materials, it acknowledges limitations such as the need for further exploration and validation. Generalizability may be constrained, warranting additional research to address these limitations. Originality/value: This research contributes insights into the potential application of sand-type 3D printing materials in indoor rock physics experiments. The findings may guide future endeavors in fabricating rock specimens with consistent structures for practical rock mechanics applications. [ABSTRACT FROM AUTHOR]

The peridynamics (PD), as a promising nonlocal continuum mechanics theory, shines in solving discontinuous problems. Up to now, various numericalmethods, such as the peridynamicmesh-free particle method (PD-MPM), peridynamic finite element method (PD-FEM), and peridynamic boundary element method (PD-BEM), have been proposed. PD-BEM, in particular, outperforms other methods by eliminating spurious boundary softening, efficiently handling infinite problems, and ensuring high computational accuracy. However, the existing PD-BEM is constructed exclusively for bond-based peridynamics (BBPD) with fixed Poisson's ratio, limiting its applicability to crack propagation problems and scenarios involving infinite or semi-infinite problems. In this paper, we address these limitations by introducing the boundary element method (BEM) for ordinary state-based peridynamics (OSPD-BEM). Additionally, we present a crack propagationmodel embeddedwithin the framework of OSPD-BEM to simulate crack propagations. To validate the effectiveness of OSPD-BEM, we conduct four numerical examples: deformation under uniaxial loading, crack initiation in a double-notched specimen, wedge-splitting test, and threepoint bending test. The results demonstrate the accuracy and efficiency of OSPD-BEM, highlighting its capability to successfully eliminate spurious boundary softening phenomena under varying Poisson's ratios. Moreover, OSPDBEMsignificantly reduces computational time and exhibits greater consistencywith experimental results compared to PD-MPM. [ABSTRACT FROM AUTHOR]

Cylindrical shell structures have excellent structural properties and load-bearing capacities in fields such as aerospace, marine engineering, and nuclear power. However, under high-pressure conditions, cylindrical shells are prone to cracking due to impact, corrosion, and fatigue, leading to a reduction in structural strength or failure. This paper proposes a static modeling method for damaged liquid-filled cylindrical shells based on the extended finite element method (XFEM). It investigated the impact of different initial crack angles on the crack propagation path and failure process of liquid-filled cylindrical shells, overcoming the difficulties of accurately simulating stress concentration at crack tips and discontinuities in the propagation path encountered in traditional finite element methods. Additionally, based on fluid-structure interaction theory, a dynamic model for damaged liquid-filled cylindrical shells was established, analyzing the changes in pressure and flow state of the fluid during crack propagation. Experimental results showed that although the initial crack angle had a slight effect on the crack propagation path, the crack ultimately extended along both sides of the main axis of the cylindrical shell. When the initial crack angle was 0°, the crack propagation path was more likely to form a through-crack, with the highest penetration rate, whereas when the initial crack angle was 75°, the crack propagation speed was slower. After fluid entered the cylindrical shell, it spurted along the crack propagation path, forming a wave crest at the initial ejection position. [ABSTRACT FROM AUTHOR]

The stress intensity factor (SIF) distribution of a semi‐elliptical surface crack is often used for evaluating the fatigue strength of structures. Virtually exact distributions of SIFs FISE,FIISE,FIIISE can be provided along the crack front by solving the hypersingular integral equation of the body force method. In this paper, to create a very accurate SIF variation formula, the elliptical crack SIF solutions FIE, FIIE, FIIIE are used and the SIF ratios FISE/FIE, FIISE/FIIE, FIIISE/FIIIE are mainly focused. Paying attention to the corner point singularity, by applying the least squares method to the ratio FISE/FIE, FIISE/FIIE in the whole range of parametric angle β, FISE and FIISE formulas can be proposed. Instead, FIIISE formula can be proposed by applying the method of least squares to the ratio of FIIISE/FIIIE in the range β≥15° but applying directly to FIIISE in the range β≤15°. In this way, all of formulas proposed in this paper provide the SIFs with better than 1.0% accuracy. Highlights: Accurate SIF formulas for semi‐elliptical surface cracks were created within 1% error.Similar to solving the HIEM, closed form solutions of an elliptical crack were utilized.This formula assume the crack front intersects the free surface at an angle θS≅100.5°.Using singularity r‐0.5 along the crack front, the shape FISE(β)≈const. was investigated. [ABSTRACT FROM AUTHOR]

This paper presents a numerical approach for investigating fatigue delamination propagation in composite stiffened panels loaded in compression in the post-buckling field. These components are widely utilized in aerospace structures due to their lightweight and high-strength properties. However, fatigue-induced damage, particularly delamination at the skin–stringer interface, poses a significant challenge. The proposed numerical approach, called the "Min–Max Load Approach", allows for the calculation of the local stress ratio in a single finite element analysis. It represents the ratio between the minimum and maximum values of the stress along the delamination front, enabling accurate evaluation of the crack growth rate. The methodology is applied here in conjunction with the cohesive zone model technique to evaluate the post-buckling fatigue behavior of a composite single-stringer specimen with an initial delamination. Comparisons with experimental data validate the predictive capabilities of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation of the R-curve effect in delamination propagation in composite materials. The R-curve effect refers to the phenomenon whereby resistance to crack propagation increases with the advancement of the delamination, due to toughening mechanisms, such as fiber bridging. Numerical models often neglect this effect assuming a constant value of the fracture toughness. A numerical approach based on cohesive elements and on the superposition of two bilinear traction-separation laws is adopted here to accurately predict the R-curve effect in skin-doubler composite specimens subjected to three-point bending tests. The carbon-epoxy material presents two different sensitivities to the fiber bridging phenomenon resulting in two different R-curves. Comparisons with literature experimental data, in terms of load and delaminated area vs. applied displacement, and ultrasonic C-scan images show the effectiveness of the adopted approach in simulating the R-curve effect. The predicted numerical stiffness aligns with the experimental scatter, although the maximum load is slightly underestimated by approximately 15% compared with the average experimental results. The numerical model accurately predict the R-curve effect observed in the experimental data, demonstrating a 31% increase in the maximum load for the material configuration exhibiting greater sensitivity to fiber bridging. [ABSTRACT FROM AUTHOR]

Sixteen-head automatic tape laying of non-crimped carbon-fibre-reinforced plastic is performed, and the fibre alignment is compared with that produced via hand laying. The effect of fibre alignment is tested via quasi-static and cyclic three-point bending tests. Using the Fill Multilayer (a 16-head tape-laying machine), precision fibre laying of unidirectional fabrics is performed with deliberate misalignment to examine the effect of fibre orientation and investigate the random effect on longitudinal misalignment. The automatic tape-layered coupons are compared with hand-layered carbon fibre tapes to investigate the relationship between the fibre alignment and the flexural strength. A 52% reduction in the fibre alignment scatter is achieved via the Fill Multilayer. Fibre orientation increases lead to a higher flexural strength of 16.08% for Fill Multilayer-made coupons compared with hand-layered samples. An investigation of the correlation between fibre alignment and flexural strength shows that shear-based failure increases exponentially as the alignment decreases. Fill Multilayer-made coupons have a higher void concentration due to ultrasonic welding, but also the highest modulus and flexural strength, as fibre misalignment is reduced to 1.68°, with a modulus degradation of 1.4%. [ABSTRACT FROM AUTHOR]

Patching is a common technology used in repairing asphalt-pavement potholes. Due to the differences in material properties between patched- and unpatched-asphalt mixtures, significant strain and stress concentrations could be induced; thus, further cracks and interfacial debonding distress could be caused. As a remedy, the strain and stress concentrations can be alleviated by utilizing optimum patching shapes. Therefore, this paper employed finite element methods (FEM) to deeply analyze the mechanical performance of patched-asphalt pavements embedded with different patching shapes. Three patching shapes, these being rectangular, stair, and trapezoid, were considered for use in pavement pothole repairs based on two- and three-dimensional finite element models. In the two-dimensional models, Top-Down and Bottom-Up crack propagations were simulated to assess the anti-damage performance of the patched pavements with different patching shapes. In addition, the thermal stress behaviors within patched-asphalt pavements were simulated using the two-dimensional model to analyze the performance of the patched pavements during the cooling process in construction. In addition, interface-debonding performance was simulated for the patched-asphalt pavements using three-dimensional models. In light of the simulation results, engineers are expected to better understand the mechanism within patched pavements and to improve the quality of the pavement patching. [ABSTRACT FROM AUTHOR]

The failure of premature thermal cycling spalling off is the bottleneck problem currently faced by yttrium oxide partially stabilized zirconia (YSZ) ceramic-based sealing coatings. Studies on the thermal cycling performance of coatings with "brick-mud" structures were carried out by experimental and simulation methods in this paper. The results showed that, as the thickness of "mud" layer increased, the bonding strength of the "brick-mud" structure coatings gradually decreased. When the thickness of the "mud" layer was about 3 μm and 10 μm, the thermal cycling lives of the T1 and T2 coatings were improved by 90.0% and 135.7%, respectively, compared with conventional coating (T0 coating), while that of the T3 coating (containing thick "mud" layers of about 20 μm) was decreased by 81.4%. The stress field of M2 "mud" layers with different thicknesses was subjected to a comprehensive effect by thermal mismatch stress and pores in "brick" layer. Compared with the medium and thick "mud" layers, the thin "mud" layer sustained obvious larger σ 22   m a x and σ 12   m a x , indicating its potential for the preferential initiation of transverse microcracks. In addition, the thin "mud" layer withstood the largest σ 11   m a x and had the strongest potential for longitudinal crack growth. Both transverse and longitudinal cracking could consume energy during thermal cycling and reduce the stress concentration at the top coating/bond coating interface. These were the main reasons for the improvements in the thermal cycling performances of the T1 and T2 coatings. The degree of crack deflection and the capacity of energy dissipation in the "mud" layer increased significantly with its thickness. However, the propagation length of transverse cracks also gradually increased in the meantime. Especially when the "mud" layer was 20 μm, the length of the transverse cracks increased rapidly. Thus, early interlayer delamination failure occurred in the T3 coating during thermal cycling. [ABSTRACT FROM AUTHOR]

According to the traditional blasting theory and practice, the slotted cartridge blasting can form straight cracks extending along the slot direction and achieve directional fracture. In this paper, an experimental study has been carried out to determine the influence of incident stress waves and reflected stress waves. Under the influence of stress waves, the propagation path of the main crack in slotted cartridge blasting is not straight, and the directional fracture effect is inadequate. Under the experimental conditions in this paper, the propagation of main cracks mainly experienced three stages: directional propagation stage, counterclockwise deflecting propagation stage, and clockwise deflecting propagation stage. The difference between incident stress waves and reflected stress waves results in the difference in the deflecting direction, transforming the main crack into a wing shape. In rock roadway drilling and blasting engineering, the propagation path of main cracks produced by peripheral boreholes using the slotted cartridge blasting is also affected by the incident and reflected stress waves. These stress waves are inevitably generated from free faces and adjacent boreholes; however, these are rarely considered in the design of blasting parameters. Therefore, the design and optimization of blasting parameters considering the interaction of stress waves and main cracks in the slotted cartridge blasting need to be further developed. [ABSTRACT FROM AUTHOR]

The growth of cracks between plies, i.e., delamination, in continuous fibre polymer matrix composites under cyclic-fatigue loading in operational aircraft structures has always been a very important factor, which has the potential to significantly decrease the service life of such structures. Whilst current designs are based on a 'no growth' design philosophy, delamination growth can nevertheless arise in operational aircraft and compromise structural integrity. To this end, the present paper outlines experimental and data reduction procedures for continuous fibre polymer matrix composites, based on a linear elastic fracture mechanics approach, which are capable of (a) determining and computing the fatigue crack growth (FCG) rate, da/dN, curve; (b) providing two different methods for determining the mandated worst-case FCG rate curve; and (c) calculating the fatigue threshold limit, below which no significant FCG occurs. Two data reduction procedures are proposed, which are based upon the Hartman-Schijve approach and a novel simple-scaling approach. These two different methodologies provide similar worst-case curves, and both provide an upper bound for all the experimental data. The calculated FCG threshold values as determined from both methodologies are also in very good agreement. [ABSTRACT FROM AUTHOR]

In this paper, a method of crack propagation analysis based on adaptive extension finite element is proposed. This method combines adaptive mesh reconstruction technology with the extended finite element method (XFEM). Firstly, the model of the engineering structure is discretized with the help of mesh generation software, and the initial mesh is divided. Secondly, the Construction of the XFEM model and the tip of the crack strengthening function are introduced to describe the physical field properties of the crack tip. The integral equation is solved to obtain the crack tip parameters. Then, the adaptive mesh reconstruction technology is built to refine the mesh of the crack tip area through the error estimation of the crack tip. Finally, the SIFs at the crack tip were calculated using the interaction integral, and the path direction of crack growth was determined using the maximum circumferential tensile stress criterion. Thus, the propagation path can be well traced. [ABSTRACT FROM AUTHOR]

Rivets are usually used to connect the skin of an aircraft with joints such as frames and stringers, so the skin of the connection part is a porous structure. During the service of the aircraft, cracks appear in some difficult-to-detect parts of the skin porous structure, which causes great difficulties in the service life prediction and health monitoring of the aircraft. In this paper, a secondary development subroutine in PYTHON based on ABAQUS-XFEM is compiled to analyze the cracks that are difficult to monitor in the porous structure of aircraft skin joints. The program can automatically analyze the stress intensity factor of the crack tip with different lengths in the porous structure, and then the residual fatigue life can be deduced. For the sake of safety, the program adopts a more conservative algorithm. In comparison with the physical fatigue test results, the fatigue life of the simulation results is 16% smaller. This project provides a feasible simulation method for fatigue life prediction of porous structures. It lays a foundation for the subsequent establishment of digital twins for damage monitoring of aircraft porous structures. [ABSTRACT FROM AUTHOR]

The vertical ice breaking of marine structures in ice-covered areas involves the deformation and failure of an ice sheet. Different from the existing conventional scenarios where the ice sheet is used as a transportation and support medium, the damage to the ice sheet will be more severe when a structure penetrates the ice sheet from below, due to the lack of elastic support from the fluid above the ice sheet. In order to investigate the failure mode of the ice sheet and the ice load characteristics during vertical penetration, a mesh-free bond-based peridynamic method is used in this paper to simulate the mechanical behaviors of the ice sheet. The cracks simulated in this study exhibit a higher level of similarity to experimental results, which improves the accuracy of the ice load. The numerical model established shows satisfactory applicability for the analysis of penetration failure of an ice sheet. In addition, the influence of ice thickness, impact velocity, and cylinder diameter on the failure characteristics of the ice sheet and breakthrough load are analyzed. The results of a parametric study indicate that the relationship between ice thickness and breakthrough load, as well as the relationship between load area and breakthrough pressure, can both be fitted using quadratic functions. [ABSTRACT FROM AUTHOR]

A computational framework of anisotropic phase field model is used to investigate the effects of effective critical energy release rate, interface property, and hole shape on the failure of composite material in this paper. This model is implemented in ABAQUS using a user‐defined element (UEL). First of all, the model is validated through a benchmark model. Second, the effective critical energy release rate is introduced, which can improve the accuracy of the simulation result. Then, the influence of strong and weak interfaces on the failure of composite material is studied. It can be found that the interface properties can change the evolution mode of crack and the final load–displacement response. Finally, the effect of hole shapes on the failure of the composite material is also explored, which shows that the bearing capacity of model can be improved by changing the shape of the hole. [ABSTRACT FROM AUTHOR]

This paper aims to determine the relationship between thermodynamic entropy generation and fatigue crack propagation life of superalloy GH4169 at 300–650°C. The entire specimen was considered as the thermodynamic system. The plastic energy dissipation in the crack tip was obtained by finite element simulation utilizing the Chaboche nonlinear hardening model. Then the cyclic entropy generation rate (CEGR) and the accumulated entropy generation are calculated by combining simulation and experimental methods. Results show that the CEGR is a power function of the stress intensity factor range, and it is almost a constant at fatigue failure. The fatigue fracture entropy (FFE) increases as fatigue cycles at failure increase at constant temperature, but it first decreases and then increases when temperature increases from 300 to 650°C. A fatigue life prediction model based on the thermodynamic damage parameter is established and verified by comparison with experimental results and available data in the literature. [ABSTRACT FROM AUTHOR]

This paper proposes a novel method based on a numerical simulation approach and fatigue fracture theory to analyze the fracture behavior and assess the fatigue life of spring clips. To this end, the finite element (FE) model of the vehicle‐track‐foundation system was developed including the key parts of the type II fastening system. Meanwhile, the spring clip FE model was validated through the natural vibration characteristics. Subsequently, the numerical simulations were performed under various working conditions to obtain the fatigue characteristics of the spring clips. The fatigue crack initiation life and damage were analyzed using FE results for the spring clips with ε‐N curve and Brown‐Miller criterion. Moreover, based on the initial crack geometry of the spring clips, the maximum circumferential stress criterion with the Paris equation was employed to analyze the crack extension behavior and assess the fatigue crack extension life. [ABSTRACT FROM AUTHOR]

To reduce the crushing rate and improve the yield of rice during the milling process, it is significant from a fundamental standpoint to understand the mechanical behaviors of rice under external loads. In this paper, the mechanical properties and fracture morphologies of rice with various moisture contents have been analyzed in detail by experiments and the finite‐element (FE) method. In FE simulations, two‐dimensional (2D) and three‐dimensional (3D) composite models have been established with the cohesive zone model characterizing the interface strength. The results show that the moisture content determines the endosperm cell wall interface strength, and a linear relationship between the interface strength and moisture content has been obtained. In particular, three fracture patterns of brown rice are observed by the competition between the interface strength of starch granule and endosperm cell wall interface strength. Good agreements between FE predictions and experimental results indicate that the combination of the 2D and 3D composite models with the cohesive zone model can provide accurate predictions of the fracture behaviors of brown rice. This investigation should be of great help for understanding the moisture content‐dependent compression and impact behaviors of rice. Practical applications: Brown rice can be obtained by removing the husk through a hulling machine. During these processes, external loads, such as compression and impact, will damage the microstructure of brown rice, which results in a loss rate as high as 25%. Understanding the mechanical properties of brown rice with different moisture contents will be of great help in designing the equipment used in rice processing operations and extending the yield of polished rice. [ABSTRACT FROM AUTHOR]

In this paper, the effects of static stresses on the blast‐induced crack in polymethyl methacrylate specimens with an empty hole were investigated by caustic system. The propagation behavior and re‐initiation process of blast‐induced crack under initial static stress and high stress unloading were investigated. The results show that when the direction of the empty hole is perpendicular to the static stress, the static stress reduces the length of the main crack. However, when the static stress is very high, the length of main cracks does not decrease. In addition, the static stress reduces the crack velocity and dynamic stress intensity factor (DSIF) and suppresses the increase of DSIFs and crack velocity due to reflected wave. The crack arrested under high stress unloading propagates again in the later stage. Moreover, the duration of high stress unloading lasts approximately 1 ms. Highlights: The dynamic unloading phenomenon is visualized by caustics for the first time.The blast‐induced crack (including secondary failure) under low/high stress is studied.Static stresses restrain the increase of DSIFs and crack velocity under reflected wave.The duration of high stress dynamic unloading is measured (approximately 1 ms). [ABSTRACT FROM AUTHOR]

It is known that crack defects exist in the machines initially. All that requires the creation of analysis methods that allow to research the propagation of cracks under real loading conditions based on the mechanics of destruction. Widely used criteria for these cases are stress intensity factor, J-integral and crack opening criterion. This paper discusses numerical research of the J-integral determination by finite element method for typical samples that simulating behavior of welded joints. Samples with edge and center cracks are considered as such samples. The expressions for the J-integral in typical welded joints are obtained from the positions of regression and correlation analyses, based on the planning of machine experiments. These expressions are depending on the geometry of cracks, external load and material parameters. A number of methodological examples for determining destructive stresses have been solved. Limits of application of linear fracture mechanics for typical samples with edge and center cracks are determined. Influence of residual stresses on value of J-integral in typical samples is estimated. Thus, regression dependencies for determining the J-integral have sufficient reliability and can be used in the practice of predicting the residual life of welded steel structures. [ABSTRACT FROM AUTHOR]

In this paper, a numerical simulation method based on the camshaft casting process and crack expansion was proposed to study the propagation characteristics of casting hot cracks. The dynamic visualisation process of hot crack growth indicates that the formation of hot tear is dominated by opening mode cracks. And during the propagation process, the equivalent stress intensity factor at the crack front first decreases and then increases. Furthermore, the propagation characteristics of the crack under different hot tear initiation conditions were studied by this method. The results reveal that the expansion ability of a hot crack is affected by the equilibrium solidification scale, solidification sequence, and solidification path of the casting. Finally, using the microscopic morphology of the cracks, the semi-quantitative analysis of the elements illustrates that the carbon content decreases sharply at the crack formation site, while manganese and sulphur are relatively rich. [ABSTRACT FROM AUTHOR]

Computer-aided engineering (CAE) is an essential tool in a digital twin not only to verify and validate a virtual twin before it is transformed into a physical twin, but also to monitor the use of the physical twin for enhanced sustainability. This paper aims to develop a CAE model for a digital twin to predict the fatigue life of materials. Fatigue damage is represented by the size of a macro-crack that grows with a cluster of micro-cracks subjected to three different loads. The growth angle is related to the maximum circumferential tensile stress, and the growth rate is determined by the stress intensity factor (SIF) at the crack tip. The prediction model takes into consideration the main factors, including micro-cracks, crack closures, and initial configurations. Simulations are developed for the growth of macro-cracks with radially distributed micro-cracks and randomly distributed micro-cracks, and we find that (1) the macro-crack in the second case grows faster than that in the first case; (2) a pure shear load affects the macro-crack propagation more than a combined shear and tensile load or a tensional load; (3) the external stresses required to propagate are reduced when the inclination angle of the micro-crack is small and within (−25° < β < 25°); (4) micro-cracks affect the propagating path of the macro-crack and generally guide the direction of propagation. The developed model has been verified and validated experimentally for its effectiveness in predicting the fracture or fatigue damage of a structure. [ABSTRACT FROM AUTHOR]

AbstractThis paper presents an extension of the recently developed smoothed floating node method (SFNM) with cohesive zone approach to model crack growth in elastic materials under thermo-elastic loading conditions. The SFNM utilizes floating nodes to accurately model the crack by activating dormant nodes at intersection points of crack path and the corresponding element edges. Through the activation of floating nodes, the cracked element transforms into sub-elements, facilitating separate integration of each sub-element. A smoothing cell-based integration technique is employed to convert the area integral to line integral which mitigates the element distortion issues. The temperature distribution is initially determined across the entire domain, and then imposed as thermal loads in the 2D domain. The thermal stress intensity factor is calculated for both homogeneous and bi-material specimens using the interaction energy integral approach, and the crack propagation is predicted using circumferential stress criterion. The accuracy of the proposed framework is demonstrated with several benchmark problems of fracture mechanics. The develop framework yields comparable results with the available literature with less modeling complexity. [ABSTRACT FROM AUTHOR]

In this paper, the anchorage mechanism and bearing capacity of the special type of pawl bolt anchored in concrete under uplift load were studied. Static tests were carried out on two typical pawl bolts, namely 135° and 180° pawl bolts, and the effects of anchorage depth and pawl type on their failure modes were studied. The experimental results show that the uplift bearing capacity of pawl bolt is improved more effectively than that of smooth bolt. The two typical failure modes of pawl bolts under uplift load are concrete breakout failure and bolt yield failure. The concrete breakout failure exclusively occurs with anchorage depth of 5 d , while the failure mode could change from concrete breakout failure to bolt yield failure with the increase of anchorage depth. The finite element model was established to elucidate the failure mechanism of anchorage bolt and concrete. The crack propagation and diffusion angle distribution of anchorage concrete can be directly judged by concrete tensile damage and stress vector in simulation analysis. Additionally, a calculation method to accurately predict the uplift bearing capacity of pawl bolt was proposed, which considered the effect of diffusion angle θ i on the uplift bearing capacity and further discusses the change law of cone diffusion angle θ i and concrete crack propagation. The calculated results exhibited a concordance with the experimental and numerical results, which shows that the formula presented in this paper can be considered reliable and can guide the practical engineering design. ● Studied design params' impact on pawl bolts force transfer mechanism and concrete cone diffusion angle. ● Examined concrete crack behavior under uplift load for pawl bolts. ● Proposed spatial angle-variation elliptic concrete cone calculation model for pawl bolts based on cone diffusion angle. [ABSTRACT FROM AUTHOR]