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We consider a cylinder immersed in viscous fluid moving near a flat substrate covered by an incompressible viscoelastic fluid layer, and study the effect of the fluid viscoelasticity on the lift force exerted on the cylinder. The lift force is zero when the viscoelastic layer is not deformed, but becomes non-zero when it is deformed. We calculate the lift force by considering both the tangential stress and the normal stress applied at the surface of the viscoelastic layer. Our analysis indicates that as the layer changes from the elastic limit to the viscous limit, the lift force decreases with the decrease of the Deborah number (De). For small De, the effect of the layer elasticity is taken over by the surface tension and the lift force can become negative. We also show that the tangential stress and the interface slip velocity (the surface velocity relative to the substrate), which have been ignored in the previous analysis, give important contributions to the lift force. Especially for thin elastic layers, they give dominant contributions to the lift force. [ABSTRACT FROM AUTHOR]

In this study, a novel micromechanics-based damage model is proposed for the damage evolution of a two-component microencapsulated-based self-healing polymer composite. In this way, a representative volume element (RVE) including an epoxy matrix with randomly distributed poly(methyl methacrylate) (PMMA) microcapsules is modeled in DigimatTM software and analyzed in Abaqus®. A new technique is developed to investigate the progressive damage by pre-inserted cohesive elements along all element boundaries of the epoxy matrix, PMMA shell, and capsule-matrix interfaces with the bilinear traction–separation law. Moreover, the impact of interface bonding strength, interface fracture energy, and PMMA microcapsules volume fraction on the load-carrying capacity of the RVEs under uniaxial tension loading was studied. The results indicated that the tensile strength of the self-healing polymer composite increased as the interfacial strength and fracture energy increased from 10 to 60 MPa and 100 to 1000 J/m2, respectively. Furthermore, the higher volume fraction of 5% PMMA microcapsules results in a lower load-carrying capacity of self-healing polymer composite with a strength of 4.9 N. A similar trend of Young's modulus was observed for microcapsule-loaded epoxy composite compared to the pristine epoxy matrix. The micromechanical model has proper accuracy in predicting the tension behavior of self-healing composite in comparison to experimental results. Finally, two healing strategies are considered for the damaged RVE. [ABSTRACT FROM AUTHOR]

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This study evaluates the crack performance of stone mastic asphalt (SMA) mixtures according to the performance of a modified asphalt binder, evaluated based on the asphalt performance grade (PG) and the elastic recovery of multiple stress creep and recovery (MSCR) according to AASHTO M 320 and T 350. The cracking performance of the mixture was evaluated using the asphalt mixture performance tester (AMPT) according to AASHTO T 378 and T 400 through dynamic modulus and direct tension cyclic fatigue tests. Furthermore, the recently developed viscoelastic continuum damage (VECD) theory was utilized to evaluate the cyclic fatigue index parameter (apparent damage capacity, Sapp) and the permissible heavy vehicle class. For performance evaluation, six modified asphalt mixtures were prepared and tested using SMA aggregate gradation with a nominal maximum aggregate size (NMAS) of 10 mm. The MSCR test results revealed that, of the six asphalt mixtures, the rubber-based PG76-28 exhibited the least initial strain and the highest elastic recovery. The dynamic modulus test results demonstrated that using a rubber-based modifier increased the elastic modulus at high temperatures and decreased it at low temperatures, thereby enhancing resistance to plastic deformation in the summer and reducing low-temperature cracking in the winter. Finally, the correlation between the Sapp performance index and the elastic recovery of modified asphalt and the number of direct tension cyclic loads until failure of the mixture was evaluated as 0.87 and 0.76, respectively. [ABSTRACT FROM AUTHOR]

Small-sized anchors (typically 6 mm [0.24 in.]) are commonly used for nonstructural applications. There has been increasing demand for seismic performance of fastenings for nonstructural applications; however, there have been no 6 mm (0.24 in.) size screw anchors with seismic prequalification for large crack width. This study investigated the feasibility of small-sized screw anchors to perform under tension loading in crack widths of up to 0.8 mm (0.03 in.). Tension tests were conducted in cracked concrete with varying crack widths (0.3, 0.5, and 0.8 mm [0.01, 0.02, and 0.03 in.]) under monotonic, pulsating, and varying crack width load protocol. Based on the findings of this study, 6 mm (0.24 in.) screw anchors exhibited load drop and slip behavior in large crack width during the residual capacity test, even for anchors with a deeper embedment. Finite element analysis was conducted to investigate the feasibility of a larger-sized thread width to perform in 0.8 mm (0.03 in.) crack width. [ABSTRACT FROM AUTHOR]

The commonly used aluminum–copper alloys in industry are mainly rolled plates and extruded or drawn bars. The aluminum–copper alloys' anisotropy generated in the manufacturing process is unfavorable for subsequent applications. Its underlying mechanism shall be interpreted from a microscopic perspective. This paper conducted the loading simulation on Al–4%Cu alloy crystals at the microscopic scale with molecular dynamics technology. Uniaxial tension and compression loading were carried out along three orientations: X-< 1 ¯ 12 >, Y-< 1 1 ¯ 1 >, and Z-<110>. It analyzes the micro-mechanisms that affect the performance changes of aluminum–copper alloys through the combination of stress–strain curves and different organizational analysis approaches. As shown by the results, the elastic modulus and yield strength are the highest under tension along the < 1 1 ¯ 1 > direction. Such is the case for the reasons below: The close-packed plane of atoms ensures large atomic binding forces. In addition, the Stair-rod dislocation forms a Lomer–Cottrell dislocation lock, which has a strengthening effect on the material. The elastic modulus and yield strength are the smallest under tension along the <110> direction, and the periodic arrangement of HCP atom stacking faults serves as the main deformation mechanism. This is because the atomic arrangement on the <110> plane is relatively loose, which tends to cause atomic misalignment. When compressed in different directions, the plastic deformation mechanism is mainly dominated by dislocations and stacking faults. When compressed along the <110> direction, it has a relatively high dislocation density and the maximum yield strength. That should be attributed to the facts below. As the atomic arrangement of the <110> plane itself was not dense originally, compression loading would cause an increasingly tighter arrangement. In such a case, the stress could only be released through dislocations. This research aims to provide a reference for optimizing the processing technology and preparation methods of aluminum–copper alloy materials. [ABSTRACT FROM AUTHOR]

Objective: The ideal tension on a cable is affected by several factors, and the tensioning process is a relatively complex procedure. Individual variations can occur during tensioning, and the strain applied by residents at different training levels has not been previously questioned. For this purpose, we investigated the variations in the peak tensions applied by orthopedic residents, using a cable fixation model created on sheep femur. Methods: The experiment was conducted on the distal diaphysis of a 1-year-old sheep femur. A cobalt chrome cable, tensioned with a strain-meter integrated tensioner, was utilized to stabilize a prosthetic stem. The minimum tension required for a stable fixation under 8 N/m torque was recorded. Strain measurements of 120 trials of 12 residents were recorded and compared to their experience level and to the measured optimal tension. Results: The mean tension required for a stable fixation was 550 ± 45 N. The overall measured tension load was 540.3 ± 262.9 N. The mean tension provided by the 12 residents were between 175.7 ± 33.7 N and 875.5 ± 222.9 N. A significant difference was found between their highest and the lowest values (P < .0001). The level of experience was not correlated with the mean tension applied (P = .89) or with the difference of the minimum and the maximum tension (P = .81). The intraclass correlation coefficient was calculated as 0.1361 (95% CI, 0.02338-0.4242). Conclusion: Our results suggest that the residents' decisions for the cable strain are not consistent or predictable, with high variations from the optimal value, regardless of their experience level. [ABSTRACT FROM AUTHOR]

The umbilical cable is a vital component of subsea production systems that provide power, chemical agents, control signals et al., and its requirement for reliability is exceedingly high. However, as the umbilical cable is a composite structure comprising multiple functional units, the reliability analysis of such cables involves numerous parameters that can impact calculation efficiency. In this paper, the reliability analysis of a new kind of umbilical cable with carbon fiber rod under tension is analyzed. The global dynamic analytical model is first established to determine the maximum tension load, then the local analytical model of umbilical cable including each unit are constructed by finite element method (FEM). Based on the mechanical analytical model, the reliability of umbilical cable under tension load is studied using response surface method (RSM) and Monte Carlo method. During the calculation process, a new tangent plane sampling method to calculate the response surface function (RSF) is proposed in this paper, which could make sampling points faster come close to the RSF curve, and it is proved that the calculation efficiency increases about 33% comparing with traditional method. [ABSTRACT FROM AUTHOR]

With increasing interest in the use of glassy carbon (GC) for a broad range of application areas, the need for developing a fundamental understanding of its mechanical properties has come to the forefront. Furthermore, recent theoretical and modeling works that highlight the synthesis of GC via the pyrolysis of polymer precursors has explored the possibilities of a revisit to the investigation of their mechanical properties at a fundamental level. Although there are isolated reports on the experimental determination of its elastic modulus, insights into the stress-strain behavior of a GC material under tension and compression obtained through simulations, either at the molecular level or for the bulk materials, are missing. This study fills the gap at the molecular level and investigates the mechanical properties of GC using molecular dynamics (MD) simulations, which model the atomistic-level formation and breaking of bonds using bond-order-based reactive force field formulations. The molecular model considered in this simulation has a characteristic 3D cage-like structure of five-, six-, and seven-membered carbon rings and graphitic domains of a flat graphene-like structure. The GC molecular model was subjected to loading under varying strain rates (0.4, 0.6, 1.25, and 2.5 ns−1) and temperatures (300 K – 800 K) in each of the three axes: x, y, and z. The simulations show that the GC nanostructure has distinct stress-strain curves under tension and compression. In tension, MD modeling predicted a mean elastic modulus of 5.71GPa for a single GC nanostructure with some dependency on the strain rate and temperature, whereas, in compression, the elastic modulus was also found to depend on the strain rate and temperature and was predicted to have a mean value of 35 GPa. To validate the simulation results and develop experimental insights into the bulk behavior, mechanical tests were conducted on dog-bone -shaped testing coupons that were subjected to uniaxial tension and loaded until failure. The GC test coupons demonstrated a bulk modulus of 17 ± 2.69 GPa in tension, which compares well with those reported in the literature. However, comparing MD simulation outcomes to those of uniaxial mechanical testing reveals that the bulk modulus of GC in tension found experimentally is higher than the modulus of single GC nanostructures predicted by MD modeling, which inherently underestimates the bulk modulus. With regard to failure modes, the MD simulations predicted failure in tension accompanied by the breaking of carbon rings within the molecular structure. In contrast, the mechanical testing demonstrated that failure modes are dominated by brittle failure planes largely due to the amorphous structure of GC. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete (UHPC) is widely used in precast concrete-steel composite beams because of its beneficial properties, including reduced structural weight, higher flexural rigidity, and reduced tensile crack formation. In comparison to conventional steel-concrete composite beams, steel-UHPC composite beams exhibit superior characteristics, including reduced structural deadweight, enhanced flexural stiffness, and the capacity to withstand tensile cracking. One successful attempt at meeting the current demands for expedited girder engineering is the development of steel-UHPC composite beams with full-depth precast slabs as key components affecting the overall structural performance using dismountable single embedded nut bolts (SENBs) and widely used studs as competitive alternatives. In contrast, shear connectors are exposed to a combined tensile and shear stress in service life rather than shear only. The corresponding scientific problem is the problem of combined effects under stress in practical applications, but there is currently no relevant research. The shear performance of SENBs in precast steel-UHPC composite beams under tension and shear loads remains unclear. For this purpose, ten push-out specimens and theoretical analyses were performed in this paper, considering the influence of the connector's type and tensile-to-shear ratio. However, ten specimens were conducted to investigate the tensile-to-shear ratio, and the connector's type on shear performance is limited. In the future, an increasing number of specimens and test parameters should be considered to investigate the shear performance of precast steel-UHPC composite beams. An increase in the tension-to-shear ratio resulted in a substantial reduction in the ultimate shear capacity, initial shear stiffness, and ductility of the studs. The increase in the tensile-shear ratio from 0 to 0.47 resulted in a 16.9% decline in the ultimate shear capacity, a 30.4% reduction in the initial shear stiffness, and a 21.7% decrease in the ductility of the Series I samples. However, an increase in the tensile-to-shear ratio of the Series II samples from 0 to 0.47 resulted in a 31.3% decline in ultimate shear strength, a 33.2% decline in initial shear stiffness, and a 41.9% decline in ductility. The SENBs demonstrated minimal deviations in ultimate shear capacity compared to their stud counterparts, despite exhibiting notable differences in shear stiffness, and ductility. A lower tensile-to-shear ratio was recommended in practical engineering, which might achieve a larger ultimate shear capacity, stiffness, and ductility. The design-oriented models with enhanced applicability were developed to predict the tension-shear relationship and the load-slip curve of SENBs in prefabricated steel-UHPC composite beams subjected to combined tensile and shear loads. For a tensile-shear relationship model, the point error range was 0 to 0.08, with an average error of 0.03. The square coefficient (R2) was 0.99 for a load-slip curve model. The study findings could offer a credible reference for the shear mechanism of such economical and environmentally friendly precast steel-UHPC composite beams in accelerated bridge construction. [ABSTRACT FROM AUTHOR]

Recently developed multi-scale fiber (i.e., CaCO3 whisker, polyvinyl alcohol (PVA) fiber, and steel fiber) reinforced rubberized concrete exhibits excellent mechanical properties and spalling resistance at high temperatures. Measurement of macro properties such as strength and Young's modulus cannot reveal and characterize damage mechanisms, particularly those relating to the multi-scale fiber strengthening effect. In this study, acoustic emission (AE) technology is applied to investigate the impact of multi-scale fiber on the damage evolution of rubberized concrete exposed to high temperatures, under the uniaxial compression and tension loading processes. The mechanical properties, AE event location, peak frequency, b-value, the ratio of rise time to amplitude (RA), average frequency (AF) values, and AE energy of specimens are investigated. The results show that the number of events observed using AE gradually increases as the loading progresses. The crumb rubber and fibers inhibit the generation and development of the cracks. It is concluded that both the peak frequency and b-value reflect the extension process of cracks. As the cracks develop from the micro scale to the macro scale, the peak frequency tends to be distributed in a lower frequency range, and the b-value decreases gradually. At the peak stress point, the AE energy increases rapidly and the b-value decreases. The specimens without multi-scale fibers exhibit brittle failure, while the specimens with fibers exhibit ductile failure. In addition, adding multi-scale fibers and crumb rubber increases the peak frequency in the medium and high frequency ranges, indicating a positive effect on inhibiting crack development. After being subjected to high temperatures, the maximum and minimum b-values decrease, reflecting an increase in the number of initial cracks due to thermal damage. Meanwhile, the RA and AF values are used to classify tensile and shear cracks. The specimens fracture with more shear cracks under compression, and there are more tensile cracks in specimens with multi-scale fibers under tension. [ABSTRACT FROM AUTHOR]

The base connection is flexible, not fully pinned/fixed, implying a nonlinear moment–rotation relationship. This deviates from a linear response, where rotation is not directly proportional to the applied moment. Numerical investigations using the commercial software ABAQUS were conducted to analyze the steel base plate connections. The finite element (FE) models were verified against previous experimental results. Moreover, numerical findings of a comprehensive parametric investigation were conducted. The studied connections were examined with different configurations, including variations in the diameter, spacing, and number of the anchor bolts; the thickness of the base plate; and the applied axial force. The current study aims to use numerical results combined with the whale optimization algorithm (WOA) and classical genetic algorithm (GA) to derive a formulation for the moment–rotation (M-θr) relationship. The distinctive aspect of this formulation is that it aims to simulate the nonlinear rotational behavior exhibited by flexible base connections under combined moment and tension loads, while also considering various parameters such as bolt number/diameter and plate thickness. The findings indicate that the WOA is capable of obtaining an optimal equation for accurately simulating the M-Ɵr relationship. This underscores the ability of the WOA to effectively address the complexity of the problem and provide a reliable equation for predicting the rotational behavior of such connections. Consequently, the WOA method can be utilized to calculate the rotational stiffness at H/150, offering valuable support for engineering design processes. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study conducted on the behavior of drop-in anchors in uncracked concrete slabs. Both seismic (cyclic) load tests and static load tests to collapse are performed on drop-in anchors subjected to tension or shear forces. Three different anchor sizes are subjected to seismic qualification testing, followed by a static load test to collapse. The test results confirm the capability of the tested anchors to sustain simulated pulsating seismic tension and shear loading with frequency ranges between 0.1 and 2.0 Hz. It was observed that no tension failure occurred at the end of the cyclic load tests for all the tested anchors, and their residual inelastic maximum displacement at the end of the cyclic tension test was relatively small. Moreover, the experimental results show that the anchors' ultimate capacities are higher than those specified by the anchor manufacturer. Finally, the anchors' experimental pullout shear capacities are compared with the failure prediction equations in the literature and design codes. It is found that the theoretical models provide a conservative prediction of the concrete breakout of anchors in tension compared to the experimental ultimate loads. The coefficient for pry-out strength (kcp) equal to 2 or slightly smaller than 2 is likely to predict a better pry-out capacity with the experimental results compared to the application of the high conservative value of kcp equal to 1, as given in the code. [ABSTRACT FROM AUTHOR]

Metal-plate-connected joints (MPC) are widely used in light timber buildings, while there are fewer studies on the joints under dynamic loads. For purpose of exploring a new possibility of application in bamboo structures, laminated bamboo lumber (LBL) and MPC have been incorporated in the current test. Four groups of metal-plate-connected tension joints using laminated bamboo lumber (LBL-MPC) are considered to be loaded by static and cyclic loading. Test specimens AA and AE refer to pairs of LBL member connected end-to-end in parallel, loaded in tension, connected with a rectangular shaped MPC oriented longitudinally (AA) or with the MPC oriented transversely (AE). Test specimens EA and EE refer to pairs of LBL members connected perpendicular, with a tension load on one of the members that imparts a perpendicular-to-grain loading on the other member. Both static and cyclic tests were performed using a displacement-controlled loading method with a loading rate of 1 mm/min. Under cyclic loading, the ultimate load of AA, AE, and EA joints was 7.6%, 10.4%, and 5.8% higher than that under static load, while EE joints were reduced by 6.4%. Two categories of skeleton curve models adapted to tensile joints of LBL-MPCs under cyclic loading were proposed. [ABSTRACT FROM AUTHOR]

The static and fatigue analysis of plates made of 2D woven roving composites with holes is conducted. The parametrization of convex holes is proposed. The experimental results of the specimens without holes and with different shapes of notches are discussed. The experiments and the appropriate procedures are carried out with the aid of ASTM codes. The fatigue behavior is considered with the use of the low cycle fatigue method. The analysis is supplemented by numerical finite element modeling. The present work is an extension of the results discussed in the literature. The damage of plates with holes subjected to tension always occurs at the tip of the holes, i.e., (x = a, b = 0), both for static and fatigue failure. The originality and the novelty of this approach are described by the failure's dependence on two parameters: n and the ratio of the a/b ratio characterizing the hole geometry. The fuzzy approach is employed to reduce the amount of experimental data. [ABSTRACT FROM AUTHOR]

The paper demonstrates the analysis of the stress and strain states of an inhomogeneous structure with an axial symmetrical spheroidal inclusion in an infinite solid under a remote uniform tension load derived from the conditions of the theory of elasticity. With respect to the inhomogeneous structure, the deformations produce constraints that require a complete 3-dimensional analysis in the z, r-coordinate system. The solution generates the stress state of the inclusion and at the interface of the matrix. Spheroidal inclusions in an uniform outer tension stress field deform self-similarly to a rather elongated spheroid. With respect to the compatibility condition and depending on the different elastic moduli and Poisson's ratios in the inclusion and matrix, the solution procedure leads to a system of two linear equations with the magnitudes of the two tractions as unknowns. In this way, the solution is shortened to a twofold statically indeterminate system. The analysis performed leads to an exact solution of the general spheroidal problem in a formulation of stress concentration factors considering the different stiffness parameters of inclusion and matrix. [ABSTRACT FROM AUTHOR]

In steel tied arch bridges where the hangers are made of rigid bars, the replacement of damaged hangers is rather complex. In fact, while generally the cable hangers are already prepared with anchors at the ends and their replacement traces the initial stages of construction with their prestressing, on the contrary, the rigid bars are welded to the arch and the deck, so their replacement must include the design of a new suspension system that allows the insertion of a pretension where this had never been considered. To check the reliability of this new system, a prototype of tensioner was studied for the case of a steel arch bridge in which the high level of corrosion made it necessary to replace all the original hangers with new ones. This entailed the need to test the tensioner performance with the aim of ensuring the axial force transmission between the two hanger segments without slippage in the threads, as well as to test the correct tension setting before construction and putting into service the hangers to be replaced. For this reason, a predictive experimental campaign was carried out on a prototype by means of tests for the mechanical characterization of the materials used, tensile tests of the system, and tensioning tests under load, measuring the displacements and strains of the system elements. The results of the tests, with slippage in the threads limited to the 2% of total elongation, and the turnaround-stressing curves were useful for the definition of the pieces to be assembled during on-site work and for addressing the operating procedures of the tensioning phases on-site during hanger replacement. Validation with the on-site monitoring of stressing operation was conducted at the end; the monitoring of tension through dynamic tests confirmed the agreement of on-site results with the predictive loading tests of the experimental campaign on the tensioner prototype. [ABSTRACT FROM AUTHOR]

Wire rope is a complex structure made by twisting wires of various sizes in the longitudinal direction. It is used to support or move engineering structures and is subject to various tensions. Dynamic properties are important parameters to evaluate the resistance to bending deformation and vibration reduction of various structures. They are affected by the magnitude of tension. In this study, an experimental method for measuring the frequency-dependent characteristics of wire rope under tension is proposed. The study analyzed flexural wave propagation employing a vibration transfer function. Experimental results showed that the transfer function of wire rope under tension is affected by tension and bending stiffness. The Newton–Raphson method was employed to numerically measure wavenumbers of the wire rope. The bending stiffness and loss factor were determined from the wavenumbers. Changes in the bending stiffness and loss factor as the tension increased were explained by the dynamic behavior of the structure under tension. As the tension increased, the bending stiffness increased, and the loss factor decreased. Hysteresis analysis indicated that the energy dissipation of wire rope is greater than that of a steel beam due to the friction between the wires. Statistical analysis confirmed a significant correlation between dynamic characteristics and tension in wire rope. [ABSTRACT FROM AUTHOR]

Expansive soil is one of the problematic soil types due to its potential to swell highly when moisture content increases and shrink when moisture decreases. The soil exhibits mechanical behavior that is highly sensitive to changes in natural moisture content influenced by environmental factors such as infiltration and evaporation. It has the potential to damage civil structures such as road pavement and lightweight buildings. An alternative method to overcome this phenomenon is the use of ground anchors, a structural element installed into a soil or rock layer to withstand the tension load. An expandable ground anchor is proposed as an alternative to overcome the drawback of a helical anchor. Wings are installed in such a way that additional passive pressure is developed. The study was firstly conducted by performing anchor pullout capacity tests on a dense sand layer, followed by a swelling test of expansive soil, and finally, the performance test of ground anchor to withstand swelling pressure using three different sizes of steel box anchor prototypes, 4 cm × 4 cm × 30.5 cm, 5.5 cm × 5.5 cm × 30.5 cm and 7 cm × 7 cm × 30.5 cm. A series of anchor pullout capacity tests were conducted on a 90 cm dense sand layer, continued by a swelling test of 25 cm expansive. The result indicates that an expandable anchor can significantly withstand the swelling of expansive soil. [ABSTRACT FROM AUTHOR]

Tensile instability is one of the major obstacles to particle methods in fluid simulation, which would cause particles to clump in pairs under tension and prevent fluid simulation to generate small-scale thin features. To address this issue, previous particle methods either use a background pressure or a finite difference scheme to alleviate the particle clustering artifacts, yet still fail to produce small-scale thin features in free-surface flows. In this article, we propose a dual-particle approach for simulating incompressible fluids. Our approach involves incorporating supplementary virtual particles designed to capture and store particle pressures. These pressure samples undergo systematic redistribution at each time step, grounded in the initial positions of the fluid particles. By doing so, we effectively reduce tensile instability in standard SPH by narrowing down the unstable regions for particles experiencing tensile stress. As a result, we can accurately simulate free-surface flows with rich small-scale thin features, such as droplets, streamlines, and sheets, as demonstrated by experimental results. [ABSTRACT FROM AUTHOR]

In this study, the effects of variations in the weld rip diameter on fatigue properties were investigated based on the fatigue fracture mechanism using tensile peeling‐type friction stir spot welding (FSSW) joints. The results of the fatigue test showed that the high and low applied force ranges exhibited base metal fracture and weld area fracture, respectively, and the difference in the weld rip diameter hardly affected the fatigue life. In contrast, in the middle‐applied force range, the fracture morphology changes as the weld rip diameter decreases, and it is apparent that joints exhibiting weld area fracture decrease the fatigue life. The fatigue fracture morphology of the tensile peeling‐type FSSW joints can be described by a competing risk model between the weld rip diameter. Increasing the heat input during joining, thereby increasing the crack propagation resistance at the pressure fusion interface, can suppress weld area fracture. Highlights: The rip diameters of the FSSW joints decreased as the number of joints increased.The difference in the rip diameter of the FSSW joints hardly affected the fatigue life.Fracture morphology of FSSW joints can be described by a competing risk model. [ABSTRACT FROM AUTHOR]

In this study, tension‐tension fatigue tests were conducted to investigate the residual stiffness degradation of carbon fiber‐reinforced polymer (CFRP) tendons. Different stress levels were used in the tests, and measurements of residual stiffness and the number of loading cycles were taken. Based on experimental data for CFRP tendons, a quantitative residual stiffness model was developed by modifying Yao's model. This model is applicable to various stress levels. To assess its accuracy and applicability, the predicted results of this model were compared with those of cited models from other researchers. The findings revealed a three‐stage degradation of residual stiffness in CFRP tendons under different stress levels. Furthermore, it was observed that the proportion of fatigue life accounted for by Stage III decreased with smaller stress ranges, while the proportion accounted for by Stage II increased. The proposed quantitative residual stiffness model was verified using both experimental and cited data. Highlights: Tension‐tension fatigue tests of CFRP tendons were conducted at various stress levels.A quantitative model was proposed based on the residual stiffness of the CFRP tendon.Stress level influence on stiffness degradation of composite material was discussed.Model accuracy was verified against experimental and cited data. [ABSTRACT FROM AUTHOR]

Objectives: (1) To determine stiffness, load at failure, and mode of failure of a novel fixation method with a tension modified-hemicerclage (MH) for tibial tuberosity transposition, and (2) to compare the biomechanical properties of this novel fixation technique to 2 pins (2Pins) and 2 pins and tension band wire fixation (2Pins + TBW). Study design: Thirty cadaveric stifles from dogs between 5.2 and 13.1 kg were assigned to 3 treatment groups: Group 1: fixation technique with MH; Group 2: 2Pins; Group 3: 2Pins + TBW. Biomechanical testing was performed with the tibia positioned at an angle of 135° relative to vertical position. Tensile force was applied to the patellar ligament until catastrophic failure was observed. The mode of failure, the load at failure, and the stiffness were compared among treatment groups. Results: The mean stiffness of the novel fixation (38.1 N/mm ± 7.1) and the 2Pins + TBW (40.2 N/mm ± 9.3) were greater than the 2Pins (26.7 N/mm ± 6.7). There was no significant difference between the novel fixation technique and 2Pins + TBW in stiffness and maximum load to failure. The 2Pins (284.3 N ± 70.5) failed at a significantly lower load than the tension modified-hemicerclage (555.7 N ± 225.9 N) and 2Pins + TBW (715.3 N ± 339.8 N). Conclusion: A fixation technique using a modified hemicerclage had the same strength and stiffness as the 2Pins + TBW and was stronger and stiffer than the 2 Pins technique in a cadaveric model. [ABSTRACT FROM AUTHOR]

An SHS-CFSHS X-joint is fabricated by welding two square hollow section (SHS) braces to a concrete-filled square hollow section (CFSHS) chord. In this paper, the stress concentration factors (SCFs) of SHS-CFSHS X-joints are investigated through experimental tests and finite element analysis (FEA), with the hot spot stress method serving as the analytical approach. Eight specimens are designed and manufactured, with FE models built in software ANSYS. These FE models are validated against the test results. The specimens are tested under brace axial tension to determine the SCFs of the X-joints. It shows that the concrete filled in the chord effectively reduces the SCFs of the X-joints. To further explore various load conditions and the influence of the parameters, FEA is carried out and a total of 64 FE models are built. Based on the FEA results, multiple regression analysis is used to obtain the SCF formulae of SHS-CFSHS X-joints under axial tension load and in-plane bending load in the brace, respectively. Comparison and analysis of the SCF results obtained from experimental tests, the proposed formulae, and FE simulations reveal that the formulae presented in this study are both conservative and suitable for predicting SCFs. [ABSTRACT FROM AUTHOR]

In high-voltage transmission lines, the tension tower needs to withstand the tension load of the overhead power line for a long time, which is prone to damage, and it is an important part of the inspection in the circuit inspection. In the modern circuit inspection process, operation and maintenance personnel mostly use unmanned aerial vehicles (UAVs) to photograph various parts of the tension tower, obtain inspection images, and manually classify and name the massive inspection images, which is low in accuracy and efficiency. Based on the above problems, this paper collects a large number of real-life UAV inspection images of various parts of a tension tower, and proposes the Stower-13 inspection image dataset, which is used to train the classification model to achieve automatic classification and naming of inspection images. Based on this dataset, this paper also proposes an improved MobileViT model, in which the Scale-Correlated Pyramid Convolution Block Attention Block (SCPCbam) module is introduced, which adds the Convolution Block Attention Module (CBAM) to the four branches of the original Scale-Correlated Pyramid Convolution (SCPC) module, so as to strengthen the ability of image multi-scale information extraction and improve the classification accuracy. This paper discusses a number of experiments on the model, and the experimental results show that the dataset proposed in this paper helps the model to understand the feature information. At the same time, the improved MobileViT model has a strong ability to extract image spatial feature information, the classification accuracy is higher than that of other models of the same type, so it is able to cope with a wide range of problems that arise in the course of practice, and it meets the practical needs of automatically naming transmission line inspection images. [ABSTRACT FROM AUTHOR]

Conventional mooring systems contribute significantly to the cost of floating wind projects, and innovative solutions with cost‐saving potentials are desired. In the present paper, we investigate the fundamental dynamic behavior of an innovative tethered‐buoy mooring system for a prototype wind farm in which two spar floating offshore wind turbines (FOWTs) are moored to five submerged tethered buoys. Numerical decay tests are used to characterize the fundamental frequencies and oscillatory modes of the system. The influence of net buoyancy is established through a parametric study. Finally, the dynamic response of the tethered‐buoy mooring system is compared against two alternative shared mooring configurations with catenary mooring lines. Time‐domain simulations are carried out for one accidental scenario with a parked and an operational FOWT, and one extreme scenario with two parked FOWTs. The results show that net buoyancy has a significant influence on platform motions and mooring loads. Compared to alternative configurations with catenary mooring lines, the tethered‐buoy mooring system exhibits substantially lower mooring tension loads and practically eliminates the threat of snap events. The reduction in the maximum characteristic fairlead tension is up to 85%. The mean positional offset of the wind turbines in the loading direction is larger, up to 36% of the water depth, however, the relative motions are comparable. The mean distance between the FOWTs is even smaller for the tethered‐buoy system. With the application of dynamic inter‐array cables, the proposed tethered‐buoy system can be a promising mooring solution for floating offshore wind farms. [ABSTRACT FROM AUTHOR]

The stress response behaviors of steel wires at the anchorage part of bridge cables under tension and bending coupling loads play a predominant role in determining their fatigue life and failure modes. The inherent complexity of the spiral geometry and the large diameter of actual bridge cables made the stress response behaviors of steel wires at the anchorage part unclear up to now. An analytical method was proposed for spiral steel wires at the anchorage part of semiparallel steel wire cables under tension and bending coupling loads. The corresponding refined numerical modeling method was also developed for studying the local anchorage part. Both the analytical formulation and numerical model agree well with the related experimental results in the literature. The presented analytical and numerical methods are thereby efficient and accurate to simulate bridge cables under tension and bending coupling loads. The critical slip curvature of steel wires increases linearly with the tensile strain of the bridge cable. The axial stresses of the steel wires of the bridge cable at a given longitudinal location display a linear relation with the angular change at the anchorage end. For steel wires located at the guide deviator part of the bridge cable, the axial stress behavior differs between the stick and slip states. It changes to a chord curve in the longitudinal direction in the stick state, while it follows an exponential function with respect to the polar angle in the slip state. The axial stress range of the outermost steel wire of the bridge cable increases linearly with the harmonic tension load range and the bending load range, separately. Regarding the phase difference between harmonic tension and bending coupling loads, a phase difference of 0 represents the most unfavorable combination for the bridge cable. By contrast, when the phase difference falls between 0 and π/2, the two harmonic loads tend to mutually inhibit each other's effects on the cable's behavior. [ABSTRACT FROM AUTHOR]

Next‐generation flexible electronics for healthcare applications require biocompatible flexible non‐volatile memory for data storage. Ultra‐thin ferroelectric hafnium oxide films offer great potential for flexible memories due to their potential flexibility and perfect compatibility with modern technologies. This study presents ultra‐flexible and stretchable memory devices based on 10‐nm‐thick Hf0.5Zr0.5O2 film fabricated by an innovative technology involving encapsulation of the devices in a biocompatible organic package. They exhibit high memory functionality (remanent polarization of 27 µC cm−2) and withstand extreme mechanical conditions, including folding in half, multiple bending up to 150 000 bending cycles as well as tension with loads up to 1.5 kg. Further, flexible devices are employed as a platform to elucidate the fundamental role of mechanical stress in ferroelectricity of hafnia both experimentally and theoretically. Direct in situ experiment demonstrates that in‐plane tension causes changes in spontaneous polarization, coercive voltage, permittivity, and conductivity. First‐principle calculations explain the role of mechanical stress in ferroelectric and dielectric properties of hafnia. In applications, this work establishes a foundation for the implementation of biocompatible, high‐performance flexible ferroelectric memory, and in the field of ferroelectric materials fundamentals, it provides insight into the critical role of the residual mechanical stress that is inevitably present in thin films. [ABSTRACT FROM AUTHOR]

Adjacent cyclic explosions significantly impact the stability of underground anchored caverns. Based on the similar model test of the vault explosion of the anchored cavern, the dynamic analysis finite element software ANSYS/LSDYNA(18.0) was used to establish a model of the straight wall side explosion of the underground anchored cavern and conduct a numerical simulation. When the total amount of explosion load is the same, we compared the stress time history curve, displacement time history curve, tunnel wall displacement, and circumferential strain curve of the surrounding rock in the underground anchored cavern (under both a high-level single-side blast and a low-level cyclic side blast). We obtained the dynamic response rules of the surrounding rock. By comparing the damage evolution process of the surrounding rock in the two situations, the damage accumulation law of the surrounding rock was analyzed. At the same time, the axial stress distribution characteristics of underground anchor cavern anchors under the action of cyclic explosion were studied. The findings demonstrate that when the total level of blast load adjacent to the cavern is the same, the displacement and circumferential peak strain of surrounding rock and the axial stress of rock bolt in the high-level single explosion are greater than those in the low-level cyclic explosion. However, compared to a single explosion, the rock mass suffers more damage in the cyclic explosion. This study will provide engineers with information that will assist them with a better understanding of the cumulative damage mechanisms of surrounding rock, as well as the stress characteristics of rock bolts under dynamic loads near the explosion site, which will be used to design underground caves with anti-blast features. [ABSTRACT FROM AUTHOR]

A deep foundation is used to transfer the load of tall and large structures to the underlying soil layers with a sufficient strength. Over the last few decades, a new type of piles has been executed in developed countries using torque with the development of hydraulic devices that can create high torques. Due to the emergence of these deep foundations, the scope of studies in this regard are limited. Thus, studying the behavior of these foundations can increase the breadth of their application in other countries while creating a better understanding of their behavior. In the present research, some models of this type of pile have been created and studied using laboratory equipment and static loading. Execution of drilled displacement and helical piles in the FCV-AUT device as well as running static compression and tension load tests were done according to ASTM D1143 and ASTM D3689 standards. Experiments on the executions have been studied in two modes of density: relative density of 20% to 25% and of 45% to 50%. Accordingly, drilled displacement piles show good performance in terms of compression and tension bearing capacity compared to other piles, while the required installation torque for this pile shows higher values. [ABSTRACT FROM AUTHOR]

In this paper, the effect of non‐relaxing torsion loadings on the fatigue lifetime reinforcement of carbon black filled natural rubber is fully addressed. Torsion fatigue tests with different loading ratios have been performed with highly notched axisymmetric‐shaped specimens. Finite element analysis is used to predict the mechanical state at any point in the specimens. The prediction is significantly improved by taking into account the heterogeneous accommodation. The first Haigh diagram under fatigue torsion is built and analyzed by calculating the minimum loading in terms of the Cauchy stress as the normal stress to the crack for the minimum angle prescribed during the cycle. A strong lifetime reinforcement has been observed, which is found to be of the same amplitude to the one obtained under uniaxial tension with the same material. This has been confirmed by specific tests that combined non‐relaxing torsion and non‐relaxing tension loadings. Post‐mortem analysis carried out at the macroscopic and the microscopic scales enabled us to identify damage mechanisms, especially in the cases where the lifetime reinforcement was observed. [ABSTRACT FROM AUTHOR]

This paper studies the influence of z‐pins on the impact resistance and residual tensile properties of composite large curvature components through low‐velocity impact and tension‐after‐impact tests to explore the damage mechanism. Unpinned and z‐pinned specimens with different diameters (0.3 and 0.5 mm) and spacing (3, 4, and 5 mm) were impacted at energies of 28 J and 14 J + 14 J and were stretched until failure. The theoretical models were used to predict impact dent depth and tensile strength, and the effectiveness of z‐pins and damage patterns were characterized by force‐time/displacement curves and through visual observation. The agreement between the experiments and predictions can thus validate the presented approach. Through the low‐velocity impact test, it is found that z‐pins with higher density and smaller diameter make the impact dent shallower and the surface damage less, thus showing better performance. Later, the impacted specimens mainly show delamination, explosion, breakage, and splitting after tension. During the first stage of the force‐displacement curves, since z‐pins mitigate the delamination, tensile strength shows a 29.58%–59.17% increase while in the third stage, a decrease of 3.95%–15.12% occurs due to initial damage caused by z‐pins. Highlights: Different impact energies are implemented on large curved CFRP laminates of z‐pins with different diameters and spacing to explore the damage mechanism.Low‐velocity impact and tension‐after‐impact (TAI) tests are used to simulate the centrifugal force of the blade subjected to impact and rotation after impact.Z‐pinned group with a small diameter and high density causes less damage and tensile strength in the first stage increases while decreasing in the third stage compared with the unpinned group. [ABSTRACT FROM AUTHOR]

The mechanical properties of frozen fissured rock masses are crucial considerations for engineering in frozen earth. However, there has been little research on the mechanical properties of frozen fissured sandstone, including its strength, deformation, and geometric parameters. In this study, sandstone samples with three open en echelon fissures were observed using high-speed photography and acoustic emissions during uniaxial compression tests. The aim was to investigate sandstone's strength, deformability, and failure process in order to elucidate the effects of freezing on its mechanical properties. In the frozen-saturated and dried states, the uniaxial compression strength (UCS) initially decreases and then increases with an increase in fissure inclination angle. Conversely, the UCS of samples in the saturated state continuously increases. The UCS follows a decreasing trend, as follows: frozen-saturated state > dried state > saturated state. The initial crack angle decreases as the fissure inclination increases in all states, irrespective of temperature and moisture conditions. However, the initial crack stress and time show an increasing trend. The uniaxial compression strength (UCS) of frozen fissured sandstone is influenced by four mechanisms: (1) ice provides support to the rock under compression, (2) ice fills microcracks, (3) unfrozen water films act as a cementing agent under tension or shearing loads, and (4) frost damage leads to softening of the rock. [ABSTRACT FROM AUTHOR]

Welded steel plates are widely used in various structural applications, and the presence of inclined welds is often encountered in practical scenarios. Carbon fiber reinforced polymer (CFRP) has been proven to be effective for strengthening steel structures. However, the behavior of CFRP-strengthened welded steel plates with inclined welds, particularly considering the influence of welding residual stress, is limited. This paper aims to investigate the tensile behavior of CFRP-strengthened welded Q355 steel plates with inclined welds considering welding residual stress (WRS). First, WRS data were obtained by the X-ray diffraction (XRD) method at different locations. The maximum tensile and compressive residual stresses are 0.39 and 0.14 times the yield strength of the steel, respectively. Then, finite element models were established to investigate the effects of weld angles, weld width, and height on the WRS distribution of welded steel plates. Finally, the tensile performance of CFRP-strengthened welded plates with WRS was studied by numerical simulation. The results showed that the weld angles have little effect on the distribution pattern of residual stress but significantly affect the peak tensile WRS. When the weld angle changes from 0° to 60°, the peak tensile WRS decreases significantly from 0.32 to 0.06 times the yield strength of steel; furthermore, the influence of weld width and height on WRS is relatively limited. Under tension loading, the maximum stress occurs near the weld. The ends of the weld enter the yielding state later than the middle part of the weld due to the distribution of the WRS. As the weld angle increases and the length of the weld increases, the stress in the weld zone decreases, while the stress in the base material zone correspondingly increases. In addition, CFRP strengthening can reduce the magnitude of stress. This study provides preliminary references for understanding the tensile behavior of CFRP-strengthened welded steel plates with inclined welds. [ABSTRACT FROM AUTHOR]

The accelerated testing methodology (ATM) developed by the authors is the methodology for predicting statistically long-term life of CFRP structures based on the viscoelasticity including the time-temperature superposition principle for matrix resin. The formulae of ATM are expressed as the product of static strength at room temperature, its dispersion, and the viscoelastic parameter of matrix resin that changes with time and temperature history. This methodology ATM was applied to the prediction of long-term creep failure life for unidirectional CFRP with heat-resistant epoxy resin as matrix under heat degradation in this study. Resin impregnated CFRP strands with heat-resistant epoxy resin were molded using a filament winding system as virgin specimens of unidirectional CFRP. Then, heat-degraded specimens were prepared by exposing the virgin specimens under acceleration conditions determined based on the time-temperature superposition principle for chemical deterioration assuming the condition of practical temperature 110°C and period 10 years. Second, the creep strengths of virgin and heat-degraded CFRP strands were statistically predicted based on ATM and the effect of heat degradation on the long-term life of CFRP strands was evaluated. As results, it was cleared that when the creep strength of CFRP strands undergoes thermal aging at the practical condition, in addition to the strength decrease to time due to the viscoelasticity of the resin, a comparable decrease in static strength and increase in this scatter occur. [ABSTRACT FROM AUTHOR]

Strain energy release rate calculations for various cases of delaminations emanating from matrix cracks are developed and used to predict the onset of delaminations and their growth size as a function of applied tension and shear loads in composite laminates. The method determines the matrix crack spacing, the delamination onset load, the delamination size at onset and, through the use of a newly proposed delamination resistance curve, the size of delaminations as they grow under load. The method can be applied to any symmetric laminate. Comparisons to test results in the literature for a variety of layups and materials shows very good agreement with the exception of cases where significant edge delaminations appear before delaminations caused by matrix cracks. [ABSTRACT FROM AUTHOR]

Gas turbine engines subject materials to extreme conditions. Their high temperature materials and co-developed coatings must survive combustion gas temperatures currently approaching 1800 °C, large thermal gradients, severe thermal shock, and static and fatigue inducing applied stresses, all the while operating in highly reactive, high-pressure, high-speed combustion gas flows containing significant partial pressures of water vapor, oxygen, and other reactive species for many tens of thousands of hours. We describe the design and development of a test facility for the study of materials under individual and combinations of test parameters similar to those experienced within legacy and future engines. A hydraulic load frame capable of applying static or cyclic tension-compression stresses up to 400 MPa to flat-dog bone-shaped test specimens is integrated within an environmental test chamber capable of sustaining gas pressures from 0.1 to 1.2 MPa (1–12 atm). An adjustable 0.1–2 kW power CO2 laser whose 10.6 µm wavelength radiation is strongly absorbed by ceramic coating materials is used to heat sample surfaces to temperatures of 1800 °C and above, while rear surface air jet cooling establishes through-thickness thermal gradients. Rapid laser heating in conjunction with transiently applied front and/or rear-side air cooling is used to create hot or cold thermal shock effects. This is accompanied by the impingement of a high pressure (up to 1.3 MPa) reactive gas jet upon the sample with speeds up to 300 m/s by preheating dry air, mixing it with steam to the desired humidity, heating to 850 °C, and then expanding it through a converging nozzle. Thermal imaging pyrometers measure specimen front and back surface temperature fields, while environmental test chamber view ports permit digital image correlation and strain mapping. [ABSTRACT FROM AUTHOR]

Atomic simulations within the classical mechanics' formalism are used to investigate the interfacial binding between carbon nanotubes (CNTs) and germanium nanowires (GeNWs) as well as the mechanical properties of the chain‐like coreshell germanium nanowires coated with CNTs. The simulations at the atomic scale provide the effect of temperature, systems' cross–sectional diameter, interfacial distance, applied tension loading on their binding degree, and deformation behaviors. The simulation results reveal that the spacing between CNT and nanowires as well as the interfaces formed between them directly affect the thermal stability and the degree of interfacial bonding of the systems. The coreshell GeNWs coated with CNTs present significantly excellent mechanical properties. The Lode‐Nadai parameters and the atomic hydrostatic pressures on the atoms can be used to identify atoms' bearing states in different regions and the stress‐transfer paths during different stages including elasticity, plasticity, and fracture of the confined systems. [ABSTRACT FROM AUTHOR]

To calculate the tension in cables with different boundary conditions, the relationship between cables with fixed–fixed and hinged–hinged boundary conditions in terms of the frequency was determined according to frequency characteristic equations of cables with the two boundary conditions. In this way, a simple calculation formula for tension with fixed–fixed boundary conditions was deduced. Similarly, a calculation formula for the tension in cables with a fixed–hinged boundary condition was proposed using the method. Results show that the proposed formulae, with high computational accuracy and wide ranges of application, can be used to calculate the cable tension under a dimensionless parameter (ξ) not lower than 6.9, so it is convenient to apply the formulae to calculate tension in practice. Meanwhile, changes in the frequency ratios of cables with different boundary conditions than those with a hinged–hinged boundary condition were analyzed. Results show that when ξ is not lower than 25, the frequency ratios of cables of various orders tend to be the same. The boundary coefficient(λ) was introduced. Given the cable stiffness, the tension and boundary coefficient(λ) can be calculated through linear regression. The method considers influences of unknown rotational end-restraints of cables and accurately calculates the cable tension. By using simulation examples and engineering examples, the method was verified to be accurate in calculating the cable tension, thus providing a novel, practical method for estimating tension in cables, booms, and anchor-span strands of suspension bridges. [ABSTRACT FROM AUTHOR]

Glued-in rods are proficient and high-performance connectors, finding application in the construction of new timber edifices as well as retrofitting of pre-existing timber structures. Given the prevalence of high-rise timber constructions facilitated by the advent of cross-laminated timber (CLT), there exists an opportunity for the incorporation of glued-in rods in the connectivity solutions for these load-bearing structural elements. This study examines the empirical behavior of CLT connections employing multiple glued-in rods. To achieve this objective, comprehensive experiments were conducted, involving full-scale tests on specimens subjected to both monotonic and cyclic loading conditions. The investigation included variations in the embedment lengths of the rods (250 and 350 mm) as well as their orientations with respect to the wood grain (parallel, perpendicular, and interposed amid layers). The monotonic test results showed that glued-in rods embedded on the edge of the CLT could provide high-capacity connections. The angle at which the rod was oriented relative to the wood grain had an impact on both the failure mode and the shape of the force-displacement curve in the connections. To calculate the pull-out strength of the glued-in rods anchored in CLT, a design equation is proposed based on the shear strength of the bondline. Additionally, a comparative investigation was performed to study the effect of the reinforcement by screws on the connections strength under monotonic loading in tension and in compression. Moreover, it was observed that glued-in rod connections keep their elastic properties until failure under cyclic loading. The results obtained from this research exemplified that this specific connection type could present a reliable and sturdy option for use in CLT construction projects. [ABSTRACT FROM AUTHOR]

Among other forces considered during the design of drillstring, the effects of collapse pressure due to the presence of drilling fluids and tensile stress due to the length of the drillstring, both in a vertical wellbore, are the primary considerations in this work. Field data, drilling fluid specifications, wellbore geometry and American Petroleum Institute tubular specifications were applied. Recommended design procedures for bottom-top approach, with pressure-area force considerations were used to account for the effects of buoyancy. It was observed that all the initial designs were revised due to slip crushing safety element and margin-of-overpull. Nonetheless, the slip crushing problem was the most prevalent in the design conditions considered. The revised designs included replacement of some sections of the original 5-in. grade E drillpipes with similar E grade pipe, but with greater weight per foot types which had higher tensile strength. The maximum allowable load was used as an indicator of a properly designed drillstring, with tensile capacity of the pipes as basis for design. It is deduced that slip crushing might be expected in every first-pass assessment of drillstring design for tensile failure. [ABSTRACT FROM AUTHOR]

This paper is devoted to an experimental and 3D atomistic study of the influence of loading rate on fracture toughness in dilute Fe–Si alloys and in bcc iron. We analyze new and previous experimental results from fracture tests performed at room temperature on bcc iron–silicon single crystals with edge cracks (1 ¯ 10) [110] (crack plane/crack front). The specimens of single edge notch-type were loaded in tension mode I under different loading rates. The ductile–brittle behavior at the crack front was monitored online via optical microscopy together with external force and prolongation of the specimens. About 30% decrease in fracture toughness was monitored in the new experiment under the highest loading rate. The nanoscopic processes produced by the crack itself were studied at room temperature via 3D molecular dynamics (MD) simulations in bcc iron under equivalent boundary conditions as in experiments to reveal (explain) the sensitivity of the crack to loading rate. For this purpose, this MD study utilizes the self-similar character of linear fracture mechanics. The results show that the emission of blunting dislocations from the crack is the most difficult under the highest loading rate, which leads to the reduced fracture toughness of the atomistic sample. This is in a qualitative agreement with the experimental (macro) results. Moreover, MD indicates that there may be some synergetic (resonant) effect between the loading rate and thermal activation that promotes dislocation emission. [ABSTRACT FROM AUTHOR]

Martensitic steels are widely used as a structural material in critical components of fossil fuel and nuclear power plants, such as boilers, pipes, and fittings. Martensitic steels are known to have a hierarchical microstructure that follows the Kurdjumov–Sachs (K–S) orientation relationship, where a prior austenite grain is composed of packets separated by high angle grain boundaries or packet boundaries, which are, in turn, divided into blocks or variants segregated by high angle grain boundaries called block boundaries. Blocks themselves are an agglomeration of laths divided by low angle grain boundaries named lath boundaries which have precipitates scattered on them. This work seeks to examine, using a couple dislocation dynamics—continuum mechanics approach called multiscale dislocation dynamics plasticity (MDDP), the interactions between dislocations and packet, block, lath boundaries, and precipitates under uniaxial tension loading and their effect on the mechanical response of the material. The simulations are conducted at a strain rate of 105 s−1 at room temperature. The main crystallographic features that arise during the deformation process were extracted and analyzed in terms of their contribution to the mechanical response of the material. The orientation relationship governing the microstructure of martensitic steels, namely, the K–S orientation relationship, was incorporated in MDDP in an effort to accurately capture the deformation behavior of the material in question. The strength of lath martensitic steel was analyzed as a function of the lath width, block size, and packet size to determine the appropriate effective grain size. [ABSTRACT FROM AUTHOR]

The mechanical properties of native cellulose are critical for understanding the properties of natural biomaterials. To investigate the elastic moduli of the cellulose crystalline fraction an isotropic mechanical load using hydrostatic pressure ranging from 0.01 to 0.5 GPa was applied to flax fibers, pine wood and tension wood samples. The response of the crystalline part was monitored by using microfocused synchrotron radiation. The compressibility of the crystalline fraction of native cellulose was anisotropic and dependent on the crystal size and possibly on the composition of the sample. The compressibilities along the [001] direction, where covalent bonds hold the cellulose chains together, varied between 2.1 and 2.9 TPa−1 for the different samples and confirm similar values found for cotton fibres. However, the compressibilities along the [100]-direction range from 56.2 TPa−1 to 63.5 TPa−1, slightly exceeding the previously determined value of 50 TPa−1, which can possibly be attributed to differences between individual samples. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) significantly provides opportunities to design and produce components with complex shapes and geometries without a demand for many conventional manufacturing steps. The AM technique has been also used for accomplishing such customized, multi-cell lattice structures for lightweight applications. However, an eligible design approach for integrating lattice structures is challenging so that desired mechanical properties in various advanced engineering structures can be achieved. Therefore, multi-cell lattice structures and graded design approaches for improving load-bearing capacities of additively manufactured parts were studied in this work. C-clip structures infilled with different lattice configurations were investigated under tension load. It was found that uniform BCC-Shell and SC-BCC-Shell lattice samples exhibited considerably higher overall stiffness values than the others due to their large normalized shear moduli. By both stress- and topology optimization-based tailored density methods, lattice structures with suitable effective properties, anisotropic characteristics, and relative densities could be employed, especially for highly loaded regions. The proposed strategies provided the structural performance which was just less than 3% from the benchmark. [ABSTRACT FROM AUTHOR]

Research purpose: The low patency rate (less than 50% at a 5-years follow-up) of commercial vascular grafts is strongly associated with compliance mismatch between graft und native artery. To address this deficit, we investigated the influence of the material and structural elasticity on the compliance behavior of small caliber vascular graft gaining for a stress-strain behavior adapted to the native vessel. Material & Methods: By combining different thermoplastic polycarbonate urethanes (TPU) fibers with different elasticity and non-elastic polyvinylidene fluoride (PVDF) fibers in different warp knitted tubular textile structures, we incorporate material and structural elasticity in a vascular graft (I.D. < 6 mm). The evaluation of the tubular fabrics is performed by determining the compliance properties in a mean pressure range between 20 and 120 mmHg by tensile testing. Results: We identified the draw ration of the TPU fiber production, the stitch course density of the fabric and the thread tension of the TPU yarn during the warp knitting process as statistically highly significant effects (p <.005) on the compliance. With an adapted setting of those parameters, we were able to improve the compliance of the textile vascular grafts over the entire physiological pressure range (20–120 mmHg) by 400–630 % compared to current clinical ePTFE (expanded polytetrafluoroethylene) grafts towards native vessels. Conclusion: By combining material and structural elasticity in a warp knitted textile structure, we were able to biomimic the compliance towards physiological properties. Our approach can be seen as blueprint to adapt elasticity properties in other implant applications. [ABSTRACT FROM AUTHOR]