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In this paper, fatigue response under cyclic loading of a high-modulus asphalt mixture (EME14) is numerically investigated based on a coupling approach between damage mechanics and visco-elastoplasticity. The DBN (Di Benedetto-Neifar) model along, an isotropic damage, and a fatigue damage law are adopted to implement both visco-elastoplastic and damage constitutive equations. A set of laboratory experiments are conducted to calibrate the numerical model parameters. In the small deformation domain, complex modulus test results (complex modulus and viscosity) were experimentally fitted based on the 2S2P1D model. Direct tension parameters (stress levels in tension and in compression) were identified through the Di Benedetto viscoplastic criterion. Then, the experimental results of the fatigue test were interpreted to evaluate the damage amount associated with each cycle N and accordingly processed by the DGCB method, developed at the ENTPE (École Nationale des Travaux Publics de l'Etat), to eliminate parasitic effects commonly present in fatigue tests. Hence, a MATLAB program was implemented for uniaxial tension and compression load to estimate damage and fatigue modulus. The consistency between the numerical model outcomes and the experimental measurements showcased the capability of our coupling approach to accurately predict fatigue response under cyclic loading of a high-modulus asphalt mixture (EME14). [ABSTRACT FROM AUTHOR]

Cast‐in anchor channels subjected to repeated cyclic actions need to be verified against fatigue failure. However, the fatigue behavior of these fasteners has rarely been investigated up to now. Consequently, the fatigue verification is not covered by the provisions of EN 1992‐4 and specific design rules apply for this product. This article gives a brief overview of the current design methods for anchor channels under fatigue loading and addresses its limitations. Results of experimental investigations within a recent research project are presented that focused on the fatigue resistance of fastenings under combined static and fatigue loading. Accompanying strain measurements provide insights about the distribution of cyclic tension loads through the channel profile to the anchors. In addition, tests under pulsating and alternating shear perpendicular to the channel axis were performed to outline the suitability under fatigue relevant shear loads. The test results obtained are discussed with respect to the existing state of knowledge. Finally, recommendations for the fatigue design of anchor channels are given. [ABSTRACT FROM AUTHOR]

Finite element model of a typical ultra-high voltage direct current transmission line section, in which buckling collapse of the tension plate took place during operation, is established. In the finite element model, the tension plate and the connected hardware fittings are discretized with 3D solid elements and the sub-conductors, spacers, clamps and insulator strings with spatial beam elements. Dynamic responses of the line after ice shedding are numerically simulated and the maximum loads on the tension plate in the cases with different ice thicknesses and ice-shedding are obtained. Buckling behaviors of the tension plate are analyzed and the conditions leading to buckling collapse are discussed. Finally, the topology optimization of the tension plate is performed and two optimized schemes of the tension plate are proposed based on the optimization result and manufacture cost. Efficiency analysis demonstrates that the buckling loads of the optimized tension plates increase more than 20% nearly without increasing weight. [ABSTRACT FROM AUTHOR]

With the rapid development of transmission-line engineering in western China and the frequent occurrence of extreme natural disasters, a great deal of attention has been paid to the bearing capacity of foundation systems. The uplift capacity is still the controlling factor in the design, but neglecting the horizontal load component will induce great potential risks to the stability of the foundation. This paper describes the model test of rock-socketed piles (with soil overlying rock) that were subjected to axial and oblique tension impacts. Furthermore, the load displacement response, failure mode, and load transfer mechanism of the model piles were compared and discussed. The research indicates that the uplift capacity of the model pile under the oblique load can be remarkably reduced by up to 27.3% in comparison with the vertical uplift. Moreover, the load–displacement curve of the model pile under axial and oblique loads present abrupt failure. Notably, the failure mode under the axial tension is an inverted cone-shaped axisymmetric failure, and the failure mode under the oblique tension shows the wedge failure on the compression side and the interface separation on the tension side. The compression side and tension side show the opposite load transfer mechanism, thus inducing the presence of a bending moment in oblique tension pile. The position of the maximum bending moment occurs at the depth of 2.3–2.8d below ground surface. In summary, the research results of this paper have important guiding significance for design of transmission tower foundation in similar geological settings. [ABSTRACT FROM AUTHOR]

Cracking is an inherent characteristic of a reinforced-concrete (RC) element subjected to tension or bending. The crack width growth with loading depends on the rebar-concrete bond behavior. RC bridges are designed under strict requirements to ensure their proper long lifetime performance. Limiting the crack widths improves the performance and safety of bridges that are exposed to harsh climatic and environmental effects and enhances bridge service life-cycle expectancy. This paper presents an extended one-dimensional formulation for analyzing RC elements subjected to tensile loads and solves the one-dimensional tension stiffening problem. The extended bond-slip model analyses the entire range of loading, following cracks growth up to their maximum allowed width, employing a bi-linear bond-slip relationship. The analytical solution refers to the early loading stage where the first bond-slip segment governs the entire element and a closed form solution is obtained, followed by the higher loading stage where two different bond-slip relationships govern two complementary segments of the element. Analytical expressions for the stresses, strains, and displacements in concrete, steel, and interface are developed. Cracking is followed until rebar yielding. Validation of the model with available test results shows good agreement that is superior to the commonly used linear bond-slip model. [ABSTRACT FROM AUTHOR]

Brexit has opened doors for renewed attention to contested, multi-scalar geopolitical forces grounded in everyday life in borderlands. In this paper, we aim to unravel 'everyday Brexits' in the Gibraltar–La Línea (Spain) borderlands. By studying the 2019 commemoration of the historic 1969 border closure, we concentrate on how local borderwork by residents is mobilised for bottom-up geopolitics in the context of Brexit negotiations. We use a conceptual approach that focuses on multiple layerings of the border and the selectivity of stakeholders to select among these layers to pursue their interests. Based on on-site observations, in-depth interviews, and informal conversations with residents and key actors of La Línea and Gibraltar, we argue that Brexit has increased the tension of already loaded core-periphery relations in Spain. Brexit does not represent a sudden disruption. Rather, we show how Brexit allowed the bottom-up geopolitical mobilisation of latent, strongly historically embedded and continuous cross-borders sentiments of residents. This mobilisation could potentially challenge local cross-border power relations. In the final analysis, we conclude that the bottom-up geopolitics of 'ordinary' residents through everyday bordering processes is central to geopolitics research, including with regard to Brexit and in particular for non-British geographies affected by Brexit. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the electronic and superconducting properties in nickelate compounds of NiO 2 through perturbative density functional theory (P-DFT) and extended multi-band Bardeen–Cooper–Schrieffer (BCS) theory. We consider four different cases of study: (i) the crystalline structure composed by one layer of NiO 2 , with a central single atom of Nd, Yb or Pr, which is subjected to mechanical compression and tension forces (pressure), (ii) the crystalline structure composed by two layers of NiO 2 with central atom pairs of Nd–Sr, Yb–Sr or Pr–Sr, with level doping x = 0.5 , (iii) the crystalline structure composed by three layers of NiO 2 with a setup of Nd–Nd(Sr)–Nd, Yb–Yb(Sr)–Yb or Pr–Pr(Sr)–Pr (Homogeneous and doping sample), with the level doping x = 0.3 and x = 0.75 and finally (iv) through multi-band theory we study the behavior in a single-layer Nd 1 - x Sr x NiO 2 when x = 0.5 through gaps Δ χ , p , with χ (number of band or orbitals), only with the presence of inter-band coupling V χ χ ′ . As results, for (i), (ii) and (iii) we present the electronic measures of the electronic band structures e-DOS, and density of phonons (mechanical and/or optic) p-DOS. In (i), we show that under pressure there are a redistribution of the band structures for e-DOS and p-DOS, allowing the destruction of Van Hove near Fermi level E F ; thus, in (ii) and (iii) we show the presence of a single flat band when the doping level is x = 0.5 , and for (iv), the inter-band coupling between orbitals plays a key role in the construction of a superconducting phase in nickelate compounds. [ABSTRACT FROM AUTHOR]

Micro finite-element (μFE) simulations serve as a crucial research tool to assist laboratory experiments in the biomechanical assessment of screw anchorage in bone. However, accurately modelling the interface between bone and screw threads at the microscale poses a significant challenge. Currently, the gold-standard approach involves employing computationally intensive physical contact models to simulate this interface. This study compared nonlinear μFE predictions of deformations, whole-construct stiffness, maximum force and damage patterns of three different computationally efficient simplified interface approaches to the general contact interface in Abaqus Explicit, which was defined as gold-standard and reference model. The μCT images (resolution: 32.8 μm) of two human radii with varying bone volume fractions were utilized and a screw was virtually inserted up to 50% and 100% of the volar-dorsal cortex distance. Materially nonlinear μFE models were generated and loaded in tension, compression and shear. In a first step, the common simplification of using a fully-bonded interface was compared to the general contact interface, revealing overestimations of whole-construct stiffness (19% on average) and maximum force (26% on average), along with inaccurate damage pattern replications. To enhance predictions, two additional simplified interface models were compared: tensionally strained element deletion (TED) and a novel modification of TED (TED-M). TED deletes interface elements strained in tension based on a linear-elastic simulation before the actual simulation. TED-M extends the remaining contact interface of TED by incorporating neighboring elements to the contact area. Both TED and TED-M reduced the errors in whole-construct stiffness and maximum force and improved the replication of the damage distributions in comparison to the fully-bonded approach. TED was better in predicting whole-construct stiffness (average error of 1%), while TED-M showed lowest errors in maximum force (1% on average). In conclusion, both TED and TED-M offer computationally efficient alternatives to physical contact modelling, although the fully-bonded interface may deliver sufficiently accurate predictions for many applications. [Display omitted] • Materially-nonlinear micro finite element modelling of single bone-screw systems. • Comparison of general contact to simplified contact models in Abaqus Explicit. • Fully-bonded interface overestimated whole-construct stiffness and maximum force. • Different damage patterns between general contact and fully-bonded interface. • Simplified interface models improved predictions and are computational-efficient. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Fighter pilots and military helicopter aircrew experience chronic neck and back pain at rates significantly higher than civilians. Their unique loading conditions, including high-G exposures and whole-body vibration, likely contribute to accelerated degenerative changes that can alter the response of the spine to external loads and contribute to spine-mediated pain. This study aimed to characterize mechanical changes to the annulus fibrosus (AF) associated with repeated loading modeling in the military aviation environment. METHODS: Fresh porcine AF specimens were used in this study which have been previously identified as representative of human tissue. Test specimens were harvested from the anterior superficial region of the AF and exercised in tension using a protocol that quantified pre- and post-damage stiffness and viscoelastic (i.e., time/rate dependent) properties. Tissue damage was induced using repeated subfailure tension loading with one of nine pre-defined groups with a combination of different strain magnitudes (11%,28%,44%) and cycle counts (400,1600,6400). Damage loading time ranged from 1 to 81 minutes. Following damage and post-damage material characterization, specimens were quasi-statically pulled to failure. RESULTS: Stiffness and viscoelasticity of AF tissues decreased significantly after damage loading for all damage groups and changes were correlated with both the magnitude of applied loading and the total number of cycles. Despite significant dose-dependent changes to the viscoelastic and elastic properties, the ultimate properties during quasistatic distraction to failure did not change. This indicates the mechanical response during low-strain magnitudes is significantly affected, but not the high-strain mechanical response. DISCUSSION: This study quantified changes in AF mechanics caused by tensile damage loading and found decreases in viscoelastic and elastic properties post-damage. These changes reduce the ability of the intervertebral disc to absorb energy associated with external loads and can contribute to disc laxity, which can lead to spine segmental instability. These changes can increase the loading of the surrounding apophyseal joints and may contribute to discogenic and radicular pain symptoms. These findings may partially explain a mechanism of acute flight-related pain symptoms in military aircrew, highlighting a need to reduce the magnitude of cyclic loads an AF is exposed to during flight. Learning Objectives 1. The audience will learn how the mechanical response of the annulus fibrosus changes in response to damage caused by cyclic loading. 2. The audience will be able to understand why changes in the mechanical response of the annulus fibrosus may contribute to discogenic and radicular pain symptoms. [ABSTRACT FROM AUTHOR]

The potential of using specimens with a double-semicircular-notched configuration for performing tensile tests of orthodontic thermoplastic aligner materials was explored. Unnotched and double-semicircular-notched specimens were loaded in tension using a universal testing machine to determine their tensile strength, while finite element analysis (FEA) and digital image correlation (DIC) were used to estimate stress and strain, respectively. The shape did affect the tensile strength, demonstrating the importance of unifying the form of the specimen. During the elastic phase under tension, double-semicircular-notched specimens showed similar behavior to unnotched specimens. However, great variance was observed in the strain patterns of the unnotched specimens, which exhibited greater chance of end-failure, while the strain patterns of the double-semicircular-notched specimens showed uniformity. Considerable agreement between the theoretical (FEA) and practical models (DIC) further confirmed the validity of the double-semicircular-notched models. [ABSTRACT FROM AUTHOR]

An improved numerical formulation for a self-centering frictional damper is presented. This was experimentally validated through quasi-static tests carried out on a steel-made prototype of the damper. Its design is ad hoc for implementation in the seismic protection of industrial storage racks. The conceptual model of the device was adjusted to the prototype built. The formulation of the analytical model, a parametric analysis of it, and the validation with experimental results are presented. The improvement of the model presented here explicitly considers elements included in the prototype, such as a system of load transmission rings and the friction between all of the components that slide or rotate relatively. In the experimental validation, the parameters of the improved model were determined. The numerical predictions for the improved model were contrasted with those obtained with the original one and with the experimental results. This demonstrates that the improvement leads to a better adjustment of the numerical predictions concerning the experimental measurements, which is useful for nonlinear analysis. The device withstood forces of considerable magnitude in addition to dissipating enough energy per load–unload cycle to be effective in the seismic protection of industrial storage racks.

Dynamics of foamed metal melt relates to the following problems: cavitations in melt at negative pressure; ablation and nanostructuring of the surface layer of materials under the action of powerful sub picosecond laser pulses; additive manufacturing; and production of solid foamed metals. We propose a mechanical model of the foamed melt evolution at the stage of bubble enlargement—after the completion of their nucleation and before the breaking of the inter-bubble walls. The foamed melt is considered as a system of strongly connected bubbles; their size variations are driven by surface forces. The interconnected system of equations for the second time derivatives of the bubble radii is derived by using the Lagrange formalism. The model is verified by comparison with the molecular dynamic (MD) simulation data for aluminum melt at high-rate uniform tension. An algorithm for searching of individual pores is developed and used to analyze the MD data. The size distribution of pores in the melt at the considered stage of enlargement is found to be close to the normal distribution on a finite interval. Evolution of the foamed melt structure is completely determined by the surface tension. The surface tension makes the largest bubbles growing and all the smaller bubbles collapsing, which leads to rapid reduction of the total number of bubbles. The foamed melt maintains negative pressure determined only by the size distribution of bubbles and the surface tension coefficient. [ABSTRACT FROM AUTHOR]

As a growing structural material in the engineering field, bamboo materials are mainly subjected to tension, bending, and a combination of the two during the service process when used as a beam structure. However, the asymmetric bending behavior of bamboo materials under combined loads has not been thoroughly investigated. Therefore, this paper aims to systematically study the asymmetric deformation and fracture of bamboo materials under tension, bending, and combined tension-bending loads. The tests were conducted on a novel self-made in situ apparatus. The periodic stresses fluctuations under three-point bending when loading on the lower fiber density side were analyzed, and the correlation between the shape, size and buckling performance of parenchymal cells was revealed from a mechanical point of view. Microscopy-based in situ three-point bending tests revealed a rich energy dissipation mechanism in the fracture process. It was found that the bending resistance and bending bearing capacity of the bamboo materials under combined tension-bending were significantly improved attributed to the coupling effect of tension and bending. The specimens under combined tension-bending exhibited a composite fracture mode with the combination of tensile fracture and three-point bending fracture mode. Additionally, an expression for the finite stress intensity factor was derived, which allows to characterize the fracture toughness of bamboo materials under tension, bending and combined tension-bending. This work is expected to provide new insights into the deformation and damage of bamboo materials, as well as guide the engineering applications of raw bamboo materials and the development of bionic bamboo structural materials. [ABSTRACT FROM AUTHOR]

The woven fabric composites were used in different industries for their special specification. This study aimed to address failure mechanisms in single-layer woven fabrics. The acoustic emission (AE) technique and wavelet transform were used for composite structural health monitoring and failure rate evaluation. From a mechanical study viewpoint, the load-displacement behavior of plain-woven glass composite was examined under tension in the principal directions (0 and 90°) and off-axis (30, 45, and 60°). The results indicated that off-axis samples are deformed and curled due to the slippage and rotation of warp and weft yarns. The mechanical measurements were synchronized with the AE data in an acousto-mechanical study. The load-displacement behavior of samples was zoned out with two criteria: frequency and energy. Eventually, three failure modes were identified: matrix damage, interface damage, and fiber breakage. The results showed that events with a frequency above 400 kHz at different angles could be attributed to fiber breakage. Also, the applied force angle effectively affects the type of fiber failure (tensile and shear failure). It was found that in addition to tensile failure, shear failure also increases sharply by increasing the angle between the main directions. So that the maximum number of shear fiber failures occurred at the angle of 45° between the main directions. On the off-axis, the number of fibers exposed to the load also increased, increasing the number of breakages. [ABSTRACT FROM AUTHOR]

Fatigue is an important factor leading to the structural failure of 3D braided composites during the service. In this paper, a meso-scale finite element analysis (FEA) model based on continuum damage mechanics (CDM) is developed to study the fatigue damage behavior and predict the fatigue life of 3D braided composites subjected to off-axial tension loadings. Stress analysis, failure criteria and material properties degradation scheme in the meso-scale model are implemented by a user-material subroutine UMAT based on ABAQUS/Standard solver. The damage initiation and propagation of 3D braided composites under diverse off-axial fatigue loadings are simulated and analyzed in detail and the corresponding off-axial fatigue lives are obtained from the predicted S - N curves. The proposed FE modeling provides a suitable reference for the numerical research on the off-axial fatigue problems in other textile composites. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical study on the influence of the geometry (layer thickness and length) and the magnitude of axially applied tension load on the delamination in a three-layer graphene/PMMA nanocomposite. Two different analytical solutions (Case 1 and Case 2) for the interface shear stress in the middle layer of the nanocomposite structure are obtained, based on the application of a two-dimensional stress-function method and minimization of the strain energy. The theoretical criterion for delamination in the interface layer, which is based on the model interface shear stress, is formulated. The obtained non-linear equation with respect to debond length is solved numerically, for both solutions, at different values of the mechanical load and geometry of the structure layers. For both solutions, it was found that the magnitude of the applied tension load influences strongly the appearance of delamination in the structure. For Case 1 (thinner PMMA layer) the delamination could be observed over 350 MPa external load; for Case 2 (thicker PMMA) it could be seen over 750 MPa. If the structure length decreases, under the above-mentioned conditions, the delamination begins at slightly lower values of the tension load. The magnitude of the applied load influences also the value of debond length. The obtained results could be used for fast prediction of safety intervals of applied loads and geometry design (without delamination) in similar nanocomposite devices to assure their safety working as sensors, nano- and optical electronic devices, energy devices, etc. [ABSTRACT FROM AUTHOR]

Direct Energy Deposition (DED), as one common type of additive manufacturing, is capable of fabricating metallic components close to net-shape with complex geometry. Surface mechanical attrition treatment (SMAT) is an advanced surface treatment technology which is able to yield a nanostructured surface layer characterized by compressive residual stresses and work hardening, thereby improving the fatigue performances of metallic specimens. In the present study, stainless steel 316L specimens were fabricated by DED and subsequently surface treated by SMAT. Both uniaxial tensile tests and uniaxial tension-compression low-cycle fatigue tests were conducted for as-built and SMAT processed specimens. The microstructure of both conditions was characterized by roughness and hardness measurements, scanning electron microscopy and transmission electron microscopy. After SMAT, nanocrystallites and microtwins were found in the top surface layer. These microstructural features contribute to superior properties of the treated surfaces. Finally, it can be concluded that the mechanical performance of additively manufactured steel under static and fatigue loading can be improved by the SMAT process. [ABSTRACT FROM AUTHOR]

In this investigation, a discrete element model of single-layer arranged particles, which is suitable for solving problems of plate structures, is proposed through the discrete element method (DEM) according to stress characteristics of thin plate structures. Additionally, mass of the particles and rotary inertia of the contact element corresponding to the discrete model are modified accordingly. Then, expressions of stiffness coefficient of the contact springs among the discrete particles of the plate are derived based on the energy equivalence principle. Afterward, the proposed discrete model is applied to solve elastic problems of plate structure, such as integrated plate and plate with an aperture under in-plane tension, cantilever plate under bending and large deformation plate subjected to transverse loads, the results of which are well consistent with results obtained through finite element method. The key of the discrete element model is interaction among the particles, which is obtained according to motion equations and contact relationships. Furthermore, the stiffness matrix and iteration are not required during the calculation process by adopting DEM. The model can automatically meet the requirements of large deformation. Therefore, it is suitable for solving highly nonlinear problems of plates with large deformation or large rotation. [ABSTRACT FROM AUTHOR]

In some instances, cast-in-place anchors need a little extra tension capacity in concrete breakout. One method of increasing capacity is to add a bearing plate at the embedded end of the anchor to increase the base area where the breakout cracking initiates. ACI 318-19 has a procedure for increasing the breakout area in Section 17.6.2.1.3. The American Association of State Highway and Transportation Officials (AASHTO) bridge code also has a procedure to design the bearing plates for post-tensioning anchors. These procedures have the same objective but yield different results. To effectively increase the breakout area, the bearing plate must be stiff enough to uniformly distribute the bearing stress to the concrete. This paper describes the analysis of previously published concrete breakout test data and the implications the tests have on determining if the bearing plate is rigid enough to uniformly distribute the bearing stress to the concrete. [ABSTRACT FROM AUTHOR]

Engineered cementitious composites (ECC) exhibit ultra-high ductility and post-cracking resistance, which makes it an attractive material in civil engineering. First, a monotonic uniaxial tensile test was performed, considering the effects of polyvinyl alcohol (PVA) fiber volume content and water-binder ratio. Then, the effects of the above variables on the tensile characteristics including the tensile stress–strain relationship, deformation capacity, and fracture energy were investigated based on test results; and when the water-binder ratio is 0.28 and the fiber volume content is 2%, the deformation performance of ECC is improved most significantly. Next, combined with damage mechanics theory, the damage evolution mechanism of ECC in monotonic uniaxial tension was revealed, based on which the damage factor and damage evolution equation of ECC were developed and the expressions of model parameters were proposed. Moreover, the comparison between the proposed model and test results demonstrated the accuracy of the proposed model. Finally, to further verify the feasibility of the proposed model, a finite element (FE) simulation analysis of the tensile performance of high-strength stainless steel wire rope (HSSWR) reinforced ECC by adopting the proposed model was compared with test results and the simulation analysis results by using anther existing model, the "trilinear model of ECC". The comparison shows that the proposed model in this paper can predict more accurately. [ABSTRACT FROM AUTHOR]

The rate-dependent tensile failure of rock with a cement inclusion was experimentally and numerically investigated to reveal the coupled dynamic response of inclusion-containing heterogeneous rock structures. Brazilian discs (BDs) with differently sized inclusion cores made of Portland cement were compressed using a split Hopkinson pressure bar loading system. The inclusions in the BD specimens changed the observed failure patterns compared to the splitting results observed in traditional monolithic rock BDs. The failure patterns observed in the composite rock–cement depend on the loading rate, inclusion size, and material strengths. The tensile BD failure patterns fall into three classes: single and double deflection along the interface with the inclusion and direct penetration through the heterogeneous structure. As the inclusion diameter or loading rate is increased, the failure pattern of the BD generally evolves from single to double deflection to penetration. The mechanism underlying the formation of the different failure patterns was further investigated using discrete element modelling. This paper may improve our understanding of the effect of loading rate on the failure and fracture behaviour of heterogeneous rock structures under tension. Highlights: Static and dynamic tensile failure characteristics of inclusion-containing rock heterogeneous structure were experimentally and numerically investigated. Failure patterns were classified into three categories in terms of loading rate and normalised inclusion diameter. The mechanism and threshold of different failure patterns were given with the assistance of DEM simulation. [ABSTRACT FROM AUTHOR]

The article presents the discussion on Domenico Starnone is one of the most prominent Italian writers today and one of the most acute observers of postwar Italian society. Topics include investigating the multiple ties that define, imprison, and save us in our everyday life: from the family to the couple, from friendship to intergenerational conflicts; and enormous tensions within an extremely calibrated structure.

Over the conventional limit equilibrium method and limit analysis method, the finite element method is advantageous, especially for slopes involving complex failure mechanisms where the critical slip surfaces cannot be represented by log spirals and other similarities. In the presence of tension cracks at slope crests, however, the finite element method encounters difficulties in convergence while handling Mohr–Coulomb's yielding surfaces with tensile strength cut-off. Meanwhile, the commonly used load-controlled method for the system of nonlinear equilibrium equations is hard to bring the slope into the limit equilibrium state. The two drawbacks drag down the finite element method in more extensive applications. By reducing the constitutive integration of plasticity with non-smooth yielding surfaces to the mixed complementarity problem, the convergence in numerical constitutive integration is established for arbitrarily large incremental strains. In order to bring the slope to the limit equilibrium state, a new displacement-controlled algorithm is designed for the system of nonlinear equilibrium equations, which is far more efficient than the load-controlled method. A procedure is proposed to locate tension cracks. Corresponding to the Mohr–Coulomb failure criterion with and without tensile strength cut-off, the failure mechanisms differ significantly, while the difference in the factor of safety might be ignorable. [ABSTRACT FROM AUTHOR]

In the present study, the fiber-bending around the needle during the piercing process of the carbon fabric is investigated. In this regard, a mathematical model is established to investigate the bending elongation of the carbon fiber around the needle and the interaction between the carbon fiber and the needle tip. Then the mechanical behavior of the carbon fabric when moving down the tip of the steel needle is analyzed. Based on the performed analysis, a shape curve equation that satisfies the puncture needle tip is established. Furthermore, the influence of different needle tip shapes on the mechanical behavior of the carbon fiber is analyzed. The performance of the needle tip is subjected to different loads, including the puncture template, horizontal tension of the fiber to the needle tip, frictional resistance between the fiber and the needle tip, sliding force, and the bending moment. The performed analysis shows that when the shape of the needle tip assumes the form of curve 10, the downward force, horizontal tension, friction resistance, sliding force, and bending moment are minimized. Accordingly, curve 10 is proposed as the optimal shape for the needle tip. The present study is expected to provide theoretical guidance for selecting overall puncture process parameters. [ABSTRACT FROM AUTHOR]

Fatigue-induced cracks of tubular joints are common in aged offshore structures which can be strengthened using grouted clamp connections. However, only limited guidance is available for design of these clamps. Hence, a comprehensive experimental and numerical investigation on the behavior and capacity of the grouted clamped joints has been carried out. In order to obtain the deformation and ultimate capacity of joints experiments were conducted using scaled model (1:8) in laboratory and nonlinear FE analysis was performed using modified RIKS method. The numerical model has been validated using the results obtained from experiments and found to be in good agreement. Parametric studies have been performed for the parameters such as crack length ratio, grout properties, sleeve friction length ratio and slenderness. The capacity of grouted clamp joint increases minimum by a factor of 2 and 1.6 for compression and tension loads compared to unclamped cracked joint for the tested range. [ABSTRACT FROM AUTHOR]

Background: Tissue adhesives are an alternative to conventional surgical sutures to reduce the time and cost of wound closure and to improve patient comfort. The use of tissue adhesives does not require any subsequent intervention and significantly lowers the volume and rate of blood loss, and reduces the need for transfusions during and after surgery. However, based on their formulation, tissue adhesives' safety profile and functional properties may differ. Therefore, this study aimed to evaluate the basic safety and performance of NE'X Glue® Surgical Sealant, BioGlue® Surgical Sealant, and PREVELEAKTM Surgical Sealant in vitro. Methods: The basic safety of commercially available tissue adhesives was evaluated using MEM elution assay according to ISO 10993–5 and endotoxin level according to 85. USP. The in vitro performance was evaluated using lap-shear by tension loading test, burst strength test, degradation, and swelling assays. Results: NE'X Glue®, BioGlue®, and PREVELEAKTM did not cause cytotoxicity in MEM elution assay. All surgical adhesives are below the general limit of endotoxin contamination of 20 EU/device. NE'X Glue® and BioGlue® showed the highest and comparable strength properties in lap shear and burst strength tests compared to PREVELEAKTM. NE'X Glue® and PREVELEAKTM are characterized by lower degradation potential than BioGlue®. PREVELEAKTM is characterized by the highest swelling when compared to NE'X Glue® and BioGlue®. Conclusions: NE'X Glue® is most versatile in terms of functional properties while maintaining the same safety profile as BioGlue® and PREVELEAKTM. [ABSTRACT FROM AUTHOR]

A prefabricated concrete structure is a building structure designed for sustainability and low comprehensive carbon emission. The grouted sleeve splice is a major connection method for prefabricated concrete structures. However, construction defects occur easily in the grouted sleeve splice connection at construction sites because of complex construction environments and the high connection accuracy. To determine the influence of rebar in steel half-grouted sleeve connections with construction defects, investigations were conducted using four different test groups (rebar offset, rebar bended, insufficient fluidity of grout, and control group). The load-displacement curve and load-stress curve were analyzed on 24 different specimens through uniaxial tension experiments. The experimental results showed that rebar fracture was the failure of specimens. The load-displacement curves consisted of elastic, yield, strength, and tight stages. The curves were similar to rebar under uniaxial tension, except for the rebar bended group. The axial stress and circumferential stress on the sleeve surface consistently followed a linear response before the specimen yield, whereas the axial stress and circumferential stress showed a rebound response after the specimen yielded. Different finite element models were established based on the different defects. Compared with the experimental results, the finite element analysis results coincided with those of the experimental results, and the errors were within 8% to evaluate the performance of steel half-grouted sleeve connections in construction. [ABSTRACT FROM AUTHOR]

Injury domain method does not let the cracks close to the critical level to start growing and lead to the critical length before the time of periodic visits. Until now, calculation method of the tension in a perforated plate has been assessed in two- or three-dimensional mode by considering the special opening (holes with different geometry). But, the tension calculation in a plate included opening with edge crack presence in three-dimensional mode has not been studied. So, in this study, in addition to the assessment of this mode, calculation method of the tension in the plates including different opening will be assessed. Generally, when the object endures the tensions for a long time, the geometric deformation will be occurred. Used plates in this study are made of isotropic materials. In these materials, when the force is applied, they show the same function in any direction and the direction of applying force has any on effect their treatment. For analyzing the data, the Abaqus software is used. The results of the research show that the kind of the boundary conditions has effect on the value of critical load in the tension and kind of created tension. In the joint-joint boundary conditions, tension critical load increases with length-to-width ratio increase, and local tension occurred in the higher penetration ratio. However, in the joint-open boundary conditions, by increasing the length-to-width ratio, the tension critical load is decreased and in often cases, the tensions are kind of general. According to this, the plates including cavity with bigger dimensions are subjected to local tension in smaller ratios of yielding dimension. [ABSTRACT FROM AUTHOR]

In the current research, we propose a novel non-ordinary state-based peridynamics (PD) fatigue model for multiple cracks' initiation and growth under tension–tension fatigue load. In each loading cycle, the fatigue loading is redistributed throughout the peridynamic solid body, leading to progressive fatigue damage formation and expansion in an autonomous fashion. The proposed fatigue model parameters are first verified by a 3D numerical solution, and then, the novel model is used to depict the widespread fatigue damage evolution of the aircraft wing corner box. The modified constitutive damage model has been implemented into the peridynamic framework. Furthermore, the criteria and processes from multiple initiations to propagation are discussed in detail. It was found that the computational results obtained from the PD fatigue model were consistent with those from the test data. The angular errors of multiple cracks are within 2.66% and the number of cycles errors are within 15%. A comparison of test data and computational results indicates that the fatigue model can successfully capture multiple crack formations and propagation, and other behaviors of aluminum alloy material. [ABSTRACT FROM AUTHOR]

Concrete exhibits a different deformation behavior in tension and compression when subjected to uniaxial and biaxial loads. It also reveals crack‐opening and crack‐closing effects under cyclic loads. This paper discusses a gradient‐enhanced continuum damage model to investigate the deformation and damage behavior of concrete subjected to cyclic and multiaxial loading conditions. An activating variable introduced in the model distinguishes the multiaxial stress states. A single damage criterion that relates the history variable to the equivalent strain limits the elastic domain. The evolution of internal variables confirms their thermodynamic consistency. The gradient enrichment of equivalent strains leads to proper localization of deformation. Comparison of numerical predictions with relevant experimental data and some previous models validates the capability of the model to describe softening/crack‐closure behavior under various loading. Application of the model to fracture problems demonstrates the ability of the model to describe damage initiation and propagation, and its localization. [ABSTRACT FROM AUTHOR]

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This paper analyses the deformation and force behavior of a wood-piled island cofferdam based on the principle of equivalent bending stiffness. The horizontal deformation and bending moments in wood piles and the axial stress in tension bars on top of piles were both analyzed by the finite difference (FD) method. Except for the analysis of the cofferdam construction process, the influence of the pile length, the dam width, the tension bar interval, and the pile interval, among the commonly adopted parameters, were detailly examined in numerical simulations. In addition, a reinforced wood-piled cofferdam model by steel pipe piles has been established to quantify the effect of reinforcement. It was found that the dewatering inside the cofferdam was detrimental to cofferdam stability. The pile deformation reached maxima (roughly 0.6% of the pile length) at solidifying stage after dewatering. The changing trend of the cofferdam structure force within a safe district was consistent with the displacement. The dam width had a vital effect on the stability of the cofferdam, especially on the horizontal deformation. The steel pipe pile reinforcement scheme performed better in further deformation control, providing a new idea for island-type cofferdams with rigorous structural deformation control. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to conduct a systematic scoping review of previous in vitro spine studies that used pig functional spinal units (FSU) as a model to gain an understanding of how different experimental methods are presented in the literature. Research guidelines are often used to achieve high quality in methods, results, and reports, but no research guidelines are available regarding in vitro biomechanical spinal studies. Methods: A systematic scoping review approach and protocol was used for the study with a systematic search in several data bases combined with an extra author search. The articles were examined in multiple stages by two different authors in a blinded manner. Data was extracted from the included articles and inserted into a previously crafted matrix with multiple variables. The data was analyzed to evaluate study methods and quality and included 70 studies. Results: The results display that there is a lack of consensus regarding how the material, methods and results are presented. Load type, duration and magnitude were heterogeneous among the studies, but sixty-seven studies (96%) did include compressive load or tension in the testing protocol. Conclusions: This study concludes that an improvement of reported data in the present field of research is needed. A protocol, modified from the ARRIVE guidelines, regarding enhanced report-structure, that would enable comparison between studies and improve the method quality is presented in the current study. There is also a clear need for a validated quality-assessment template for experimental animal studies. [ABSTRACT FROM AUTHOR]

To achieve long‐term and real‐time monitoring of the deformation of isolation bearings, a conductive composite with a natural rubber (NR) matrix modified by multiwalled carbon nanotubes (MWCNTs) is processed by prestrain. The resistance‐strain response of this composite indicates excellent uniformity, linearity, hysteresis, reproducibility and stability due to the prestrain process for the composite before application. To explain the mechanism of the resistance‐strain response for the composite, a theoretical model is developed to analyze the relation between the conductivity and the MWCNT network structure. Mechanical and electrical testing under cyclic loads indicates that the prestrain of the composite could reduce or even eliminate the 'shoulder peak' effect of the resistance‐strain curve. Meanwhile, the resistance‐strain response behavior is independent of the prestrain temperature and discontinuous before and after the interval time. Furthermore, the coarse‐grained molecular dynamics simulation and microstructure testing indicate that the resistance‐strain response is induced by the changing orientation of MWCNT molecules in the rubber matrix under tension loading. All of the results and findings provide potential applications of this MWCNT/NR composite for deformation monitoring. [ABSTRACT FROM AUTHOR]

Approximately half-scale tests were conducted to investigate the behavior of indeterminate prestressed concrete T beams with two different unbonded tendon profiles. Three T beams were employed for the tests: T beam specimen 1 (TB1) was the control specimen and had no eccentricity at the interior support and T beam specimens 2a and 2b (TB2a and TB2b) had eccentricity at the interior support. The results indicate that the specimens with eccentricity at the interior support had a greater number of cracks than the control specimen at the tension zone of the support. This finding was explained by hyperstatic moment reducing the negative moment in the control. The trend in the slope of the strain-applied load tension relationship was different in TB1 than in TB2a due to a difference between the specimens in terms of the distance from the extreme compression fiber to the centroid of reinforcement at the support. Although the interior support was a roller with no vertical restraint, hyperstatic moment at the support occurred due to a cold welding effect, creating a partial roller condition. The hyperstatic action then decreased as the loading was increased. In light of this, the authors conclude that the effect of hyperstatic moment should be accounted for in the calculation of concrete stress at the service level for continuous prestressed concrete beams with unbonded tendons and a vertically unconfined support condition. [ABSTRACT FROM AUTHOR]

This paper presents a novel anchorage structure for stay cables to reduce the load on the concrete pylon. Called the staggered-supported steel anchor box (SS-SAB), this anchorage structure provides self-balancing of the horizontal component of the cable tension force during cable tensioning; the vertical load is transferred to the concrete pylon through a staggered support. The SS-SAB can tolerate the forces within the spatial cable plane and reduce the cracking risks of the concrete pylon. To investigate the behavior of the SS-SAB, a half-scale specimen was designed and tested. Data on the deformation, crack patterns, local strains, and slippages were obtained that demonstrate that the SS-SAB can delay crack occurrences in the concrete pylon. In a supplementary analysis, a finite-element analysis performed using the ABAQUS software suite delivered good accuracy. From the test and numerical analysis, the influence of the cable angle on load sharing within the concrete pylon was investigated. The effective scope of applications of the SS-SAB is provided. [ABSTRACT FROM AUTHOR]

The accuracy and precision of lifetime predictions for cyclically loaded technical components are still lacking. One of the main reasons for the discrepancy between the calculated life time and experimental results is that it is not yet possible to create a model capable of describing the microstructural damage process that occurs in the tested material and to subsequently incorporate this model into the calculation. All of the presently available research results recognize that the growth of microcracks is significantly influenced by the microstructure of the material. In order to take into account the influence of the microstructure on the damage process, research on the very early fatigue damage is carried out. The results are obtained from tension and torsion fatigue testing. For this purpose, the surfaces of the tested specimens are carefully observed to discover and analyze microcracks, which are classified according to their orientation. Moreover, the mechanisms of crack initiation and propagation are major points of interest. Through a mix of mechanical and metallurgical points of view, calculations and multi-level FEA modeling are carried out to gain a better understanding of the properties of the phases. The simulation is based on continuum mechanics, which considers the positions and mechanical metallurgy, which account for each constituent character's failure laws. It is concluded that both the experimental and computational approaches conform, showing that such an approach is indeed a necessity and should become a trend in the near future. Statistically, microcracks under tension modes are highest at 45° (approximately 30%), while under torsion they are highest at 0° (approximately 20%) with respect to the sample orientation. The influence of the microstructure is explained via the finite element analysis. [ABSTRACT FROM AUTHOR]

Present work focused on the flexural and thermo-mechanical characteristics of epoxy based composites filled with 3 different calcium carbonate (CaCO3) concentrations: 1.5, 3 and 5 wt.%. Composite specimens were fabricated through conventional casting method and subjected to flexural test via 3 point bending fixture. Additionally, dynamic-mechanical analyzer (DMA) with single cantilever mode was used to reval the thermo-mechanical responses of samples. The findings showed that the filler concentration increase led to the increase of storage modulus (E') for all specimens while the glass transition temperature (Tg) slightly decreased for 1.5 wt. % CaCO3 filled epoxy composite. The 5 wt.% CaCO3 loaded composite showed maximum E' and Tg values with 10% and 1.5% improvement, respectively. Based on flexural test results it was surprisingly found that, 1.5% wt. CaCO3 addition attained the highest strength with ~30% improvement among all samples. However, 5 wt.% CaCO3 introduced composites displayed the lowest mechanical performance due to the presence of agglomerates/tactoids, which was verified from SEM images as well. [ABSTRACT FROM AUTHOR]

Fiber reinforced polymer (FRP) composites are alternative to the conventional materials for many civil applications because of their prominent properties. The advanced production technology allows standardized structural FRP sections, which plays an important role in progress of the structural engineering. Different fiber types can be rowed in these sections to improve the structural performance of these members. One of the most widely used FRP type is glass FRP (GFRP) in the market for structural use. The plate performance of GFRP materials as a lateral load resisting member within the moment frames was investigated in this study similar to the steel plate shear walls or timber shear walls. Post buckling performance of the GFRP plates including the experimental fracture values and different fiber orientations were studied. The tension field action was considered for the GFRP plates after the post buckling of the moment frame, and it was found that the gain for initial stiffness and story drifts gradually reduced from flexible to rigid moment frames. The least lateral load capacity gain was about 16% when the fiber main direction is oriented 0° angle within the most rigid moment frame. When the fiber orientation aligned within the tension field angle, the load capacity and the initial stiffness was reached to the ultimate values. Finally, analytical load capacity calculations were carried to verify the numerical results of the FRP plate shear walls employing the equivalent truss member approach, then plate thickness and panel aspect ratio effects on were investigated for the GFRP shear walls. [ABSTRACT FROM AUTHOR]

One of the most serious incidents that can occur in offshore drilling and exploration is damage to the well structure and subsea components which can result in uncontrolled hydrocarbon release to the environment and present a safety hazard to rig personnel. Over decades, there have been substantial developments to the mathematical models and algorithms used to analyze the stresses on the related structure and to define the operational and integrity windows in which operations can proceed safely and where the mechanical integrity of the well is preserved. The purpose of this work is to present a time-domain solution to the system of equations that model the dynamic behavior of the riser and casing strings, when connected for well drilling/completion during the event of drift-off of the rig. The model combines a solution using finite differences for the riser dynamics and a recursive method to analyze the behavior of the casing in the soil. It allows for the coupling between the equations related to the riser and casing and for the coupling with the equations that describe the dynamics of the rig when station keeping capabilities are lost. The use of the forward–backward finite-differences coupled with the recursive method does not require linearization of the forces acting on the structure making it an ideal methodology for riser analysis while improving convergence. The findings of this study can help improve understanding of the impact of the watch circle limits to riser/well integrity, whether these limits are set based on a quasi-static drive-off/drift-off or fully dynamic. The gain in accuracy in using the fully coupled equations of drift-off dynamics, where there is interaction between the rig and the top of the riser during drive-off/drift-off, is evaluated, and the effects of varying the riser top tension and the compressive loads on the casing string are also analyzed. In particular, it is shown that the results of the fully coupled system of equations representing the dynamics of the riser and casing during drift-off/drive-off are less conservative than the quasi-static approach. Another important finding is that the gain in accuracy in coupling the top of the riser and the rig during drift-off/drive-off is not substantial, which indicates that solving separately the rig dynamics equations and the riser-casing equations is an approach that provides reasonable results with less computational effort. The model can also be used to evaluate wellhead and casing fatigue during the life of the intervention. Finally, the model limitations are discussed. [ABSTRACT FROM AUTHOR]

This paper presents a data-driven approach for the prognosis of the gradual behavioural deterioration of conveyor belts used for the transportation of pallets between processing workstations of discrete manufacturing systems. The approach relies on the knowledge of the power consumption of a conveyor belt motor driver. Data are collected for two separate cases: the static case and dynamic case. In the static case, power consumption data are collected under different loads and belt tension. These data are used by a prognostic model (artificial neural network (ANN)) to learn the conveyor belt motor driver's power consumption pattern under different belt tensions and load conditions. The data collected during the dynamic case are used to investigate how the belt tension affects the movement of pallets between conveyor zones. During the run time, the trained prognostic model takes real-time power consumption measurements and load information from a testbench (a discrete multirobot mobile assembling line) and predicts a belt tension class. A consecutive mismatch between the predicted belt tension class and optimal belt tension class is an indication of failure, i.e., a gradual loss of belt tension. Hence, maintenance steps must be taken to avoid further catastrophic situations such as belt slippages on head pulleys, material slippages and belt wear and tear. [ABSTRACT FROM AUTHOR]

Featured Application: The grouted sleeve lapping connector proposed in this work has many advantages, including low cost, ease of construction, simple grout compaction, and a large diameter of the sleeve, and it can be used in precast concrete structures for resisting earthquakes and wind loads. In this study, uniaxial tension tests and high-stress repeated tension and compression tests were conducted on 32 APC (all vertical members precast in concrete structures) connectors. After high-stress repeated tension and compression, the bearing capacities of the connector specimens improved due to the strengthening of the steel bars, and the ductility of the specimens was reduced due to the further development of cracks between the steel bars and the grout. The residual deformation values of the specimens, namely u0 (uniaxial tension) and u20 (repeated tension and compression), were reduced with the increase in the lapping length of the specimens. The longitudinal compressive strain and hoop tensile strain of the middle section of the sleeve near the steel bar side were reduced under the ultimate load state when the specimens were stretched under uniaxial tension and in the last tension process after repeated loading with the increase in the lapping length. The distribution and development of the longitudinal compression stress of the sleeve were analysed based on the bonding stress of the steel bar and concrete. Finally, the ultimate bonding strength and critical lapping length formulas were proposed, which involved the introduction of a grouting defect coefficient ω. [ABSTRACT FROM AUTHOR]

With the development of urbanization, numerous excavations are carried out to facilitate the development of underground space. As a support for tunnel structures, uplift piles are often installed prior to tunnel excavation. The excavation inevitably causes disturbance to the soil below the excavation surface, changing the soil's mechanical behavior and stress state significantly. However, there is still a lack of a method to evaluate the change in pile capacity due to excavation. This paper proposes a semi-analytical approach for estimating the change in load-settlement behavior of an uplift pile considering the effects of excavation. A hyperbolic model was adopted to simulate the nonlinear interaction of the pile–soil interface. The nonlinear shear-induced soil displacement outside the pile–soil interface is introduced to obtain a more realistic load-displacement behavior of the uplift pile. An effective iterative program was implemented based on the proposed semi-analytical approach. The comparisons between the results from the proposed methods, well-documented field tests, centrifuge tests, and other analytical methods showed that the proposed approach is suitable for analyzing an uplift pile considering excavation effects. A parametric study was conducted to investigate the effects of main soil properties on the pile capacity loss caused by excavation. The results showed that the soil friction angle and the ratio of the excavation depth to the pile effective length have a great influence on the loss in pile uplift capacity caused by excavation. However, the loss of pile uplift capacity caused by excavation is not affected by the soil's shear modulus or Poisson's ratio. [ABSTRACT FROM AUTHOR]

Pipeline repair plays an important role in safe pipeline operation. Composite material repair technology has been widely used in pipeline repair due to its advantage of light weight and low cost. In this paper, the failure loads of repaired pipe with composite under tension and internal pressure are analysed by experiments, Finite Element Method (FEM) and theoretical method, and simple formula of failure loads is obtained based on theoretical analysis and verified by FEM and experiments. First, the tension experiment shows that debonding happens in the repaired pipe before its fracture, and then the debonding details are showed in FEM results considering the adhesive debonding criteria, finally a simple formula expression is obtained for the failure tension loads based on the analysis of interface stresses, and the results are almost consistent with the experimental method and FEM. Similarly, for the case under internal pressure, the blasting failure loads are obtained for the repaired pipe based on the theoretical analysis, which are consistent with FEM results. [ABSTRACT FROM AUTHOR]

The localized compressive deformation (LCD) effect generated by an indentation process at the crack tip on the fatigue crack growth of the 7075-T651 aluminum alloy is reported. Eccentrically loaded single-edge crack tension specimens (ESE(T)) were pre-cracked at a crack length of about 20 mm by applying a constant amplitude fatigue loading. Subsequently, the LCD process was performed by using a semi-spherical indenter with a radius of 16 mm to compress the crack tip zone at different forces (5.0, 7.0, 12.5, 13.5, 15.5 kN), applied on the opposite surfaces of the specimens. The fatigue cracking process was continued on the compressed samples until an overall crack length of about 30 mm was obtained. The compressive load and the number of delayed cycles is discussed in terms of crack length and crack tip opening displacement (CTOD). A direct relationship between the compressive force induced by the LCD process and the delay of the crack propagation due to the crack arrest was observed. This effect became evident at a compressive force of 5.0 kN, where the crack propagation was arrested for about 9000 cycles in comparison with the non-LCD sample. However, when the force increased, the crack arrest also increased. The crack was considered to be completely arrested at a compressive load of 15.5 kN, since the crack did not grow after the application of more than 3 × 106 cycles. [ABSTRACT FROM AUTHOR]

The non-linear material behaviour of low density polypropylene foams is investigated under several quasi-static loading conditions with a combined modelling technique based on computed tomography data and Voronoi diagrams. A simulation methodology for determining the linear elastic properties is introduced in Hössinger-Kalteis et al. (2021). In this paper, the methodology is extended regarding the material model, where additionally the non-linear region is considered. The model takes into account property determining microstructural features like orientation-dependent cell wall thicknesses and anisotropic cell shapes. Thus, the anisotropic material behaviour under tension and compression load is estimated for extrusion foams with different densities utilizing the microstructural simulation model. Based on the characterized behaviour under tension and compression, constitutive models are generated. These are implemented in bending test simulations due to lower computational effort. The simulation results are validated with experimental results, which shows that the model gives satisfactory results. [ABSTRACT FROM AUTHOR]

In this paper, failure mechanism of 20 carbon steel and QT400-15 specimens is in situ investigated by a microscope under combined torsion–tension loading (CTTL) at room temperature. Moreover, to obtain the effect of pre-torsional loading on the failure mechanism of materials under CTTL, a finite element analysis model is conducted to predict the specimen stress distribution. Results of theoretical calculation, finite element analysis, and experimental investigation indicate that the pre-torsional strain of materials is increased with an increase in the pre-torsional loading angle. The pre-torsional strain refined the material grains under CTTL, which in turn slowed down the crack growth. Consequently, material tensile strength is improved under CTTL. The in situ images effectively characterized grain refinement of materials under pre-torsional loading. Furthermore, the failure mechanism of materials under CTTL is different from the mechanism under pure tension loading, which was characterized by intergranular material fracture. However, the material fracture under CTTL was characterized by both transgranular and intergranular fractures. [ABSTRACT FROM AUTHOR]