Tension-shear Coupling Research Articles

Modeling Analysis of Complex Deformation of Woven Coating Film during the Cyclic Tensile Process.

It is difficult for the existing Burgers model to accurately depict the off-axis cyclic drawing process of woven coatings. In this paper, the mechanical deformation of woven PVC (polyvinyl chloride)-coated film at different temperatures is investigated. One-dimensional (1D) and two-dimensional (2D) constitutive models were established to characterize cyclic deformation processes. The 1D model is an improved Burgers model. The effects of the time dependence of the viscosity coefficient and the ratio of elastic to viscous deformation are considered simultaneously. The accuracy of the 1D model for predicting the cyclic nonlinear deformation at different temperatures and loading rates is improved. The 2D model is a nonlinear orthotropic model using polynomials. On the basis of the single-objective genetic algorithm, the inverse algorithm is used to obtain the shear polynomial coefficients in the tension phase and the shear modulus in the unloading phase, which circumvents performing the difficult shear test. UMAT subroutines of off-axis stretching and off-axis cyclic stretching are written separately. The intelligent inverse algorithm program consists of a single-objective genetic algorithm program, a finite element parametric modelling program, and a UMAT subroutine. The simulation results are compared with the off-axis cyclic tensile test data to validate the effectiveness and accuracy of the proposed 2D model for the analysis of the woven PVC-coated films in the tension-shear coupling state.

Analytical solution of the stress field and plastic zone at the tip of a closed crack

The investigation of stress field and plastic zone distribution at the closed crack tip provides a fundamental basis for failure analysis and life prediction of geotechnical materials. Closed crack is a common crack in geotechnical materials. Studying the distribution of stress field and plastic zone at the tip of closed crack can provide theoretical basis for stability evaluation of geotechnical structures. In this study, we employ the superposition principle to obtain complex function solutions for the stress field and displacement field at the crack tip. Furthermore, we analyze the plastic zone distribution at the crack tip based on the Mohr Coulombs criterion. We investigate how factors such as crack angle, confining pressure, and material properties influence the stress field, displacement field, plastic zone size, and crack propagation direction. Our results demonstrate that this method effectively characterizes the distribution of stress field and displacement field at closed crack tips. Moreover, we elucidate that wing cracks are primarily formed due to tension-shear coupling effects. The solutions for the stress field and displacement field at the crack tip are obtained using the superposition principle. The distribution of the plastic zone at the crack tip is analyzed based on the M-C (Mohr-Coulomb) criterion. Subsequently, an analysis is conducted to investigate the influence of crack angle, confining pressure, and material properties on stress field, displacement field, plastic zone, and crack propagation direction. Lower crack angles and higher confining pressures effectively suppress slip between crack surfaces by reducing tension-shear coupling effects and inhibiting wing foil crack development. The results further indicate that the rock cohesion and internal friction angle exert negligible influence on the stress field, displacement field, plastic zone shape at the crack tip, as well as the growth direction of new cracks. The results demonstrate the effective representation of stress field and displacement field at the closed crack tip using this method. The stress distribution at the crack tip reveals that the tension-shear coupling effect primarily contributes to wing crack formation. Lower crack angles and higher confining pressures effectively suppress surface slip, reduce tension-shear coupling effects, and inhibit wing crack propagation. Furthermore, material properties do not influence the crack propagation angle, stress field, or displacement field.

A novel core-shell C/SiC bolt prepared by chemical vapor infiltration and its fiber strengthening mechanisms

Integrated manufacturing techniques have been extensively utilized to assemble thermal structural components made of continuous fiber reinforced silicon carbide composites (C/SiC) to fabricate large and complex components. The mechanical joint, always in terms of C/SiC bolts, become the weakest link in the components. Laminated C/SiC bolts have been invented to meet the requirements of the high temperature applications. Due to the low shear strengths of C/SiC, the threads are prone to be damaged. In order to fully employ the high tensile strength of carbon fibers, core-shell C/SiC bolt is proposed with the shell prepared by woven fiber architecture. Uniform circumferential microstructure of the threaded teeth has been obtained and the corresponding strength has been improved through fiber bridging mechanism. The results shows that the thread pull-off strength is 17.96% greater than that of the laminated thread tooth, and the stud tensile strength is slightly improved up to 2.96%. The stud shear strength is enhanced by 45.29% and 46.88% with unidirectional C/SiC rod and ZrO2 ceramic rod, respectively. The improvements are mainly caused by the fiber tension-shear coupling effects. Especially the introduction of unidirectional C/SiC rod improves the shear strength of the bolts by fully utilizing the fiber strengthening mechanisms under in-plane shear loading.

An experimental and numerical study on the coupling effect of CLT wall-to-floor angle bracket connections

Cross-laminated timber (CLT) wall panels are commonly connected to the floor or foundation using metal connections, which play a critical role in determining the seismic performance and energy dissipation of the CLT shear walls. In this study, to comprehend the tension–shear coupling effect of the CLT wall-to-floor angle bracket connections under seismic loads, both monotonic and cyclic shear tests were conducted on the angle brackets that were also simultaneously applied with different levels of prescribed vertical axial tension. The influence of the co-existent axial tension on the horizontal shear performance of the angle brackets was analyzed. Furthermore, a numerical model of the angle brackets was developed and validated with the experimental results, which could predict the tension–shear coupling effect based on the monotonic loading scenario. Based on the numerical model, parametric analysis was conducted, and an analytical tension–shear interaction diagram representing the coupling effect of the angle brackets under seismic loads was established. It is found that with an increase of the axial tension from 0 to 30 kN, the shear resisting capacity of the angle brackets is diminished by 33.29%, and the pinching effect of their hysteretic load–displacement curves is mitigated. When the number of the connection-to-floor screws of the angle brackets was increased from 10 to 14, the shear resisting capacity of the angle brackets can be enhanced by 6.43%, and their shear strength degradation can be relieved by 12.85–56.25%. For the CLT wall-to-floor angle brackets, the analytical interaction diagram can be described using one bilinear function, which consists of the ratio between the shear to the shear resistance and the ratio between the tension to the pull-out resistance.

Experimental investigation on seismic behavior of the precast shear wall systems with different connection methods under the coupling action of axial tension and cyclic horizontal load

The grouting sleeve connection and lapped steel bars connection are widely used for the connection, while they often require skilled workers, concealed work, and high installation accuracy, and can be expensive and cause significant damage to horizontal construction joints under earthquakes or extreme winds. To address these issues, based on the lap-spliced connection, the angle steel connectors were installed on the precast shear walls and foundation beams to improve the shear resistance and connection performance of horizontal construction joints and reduce construction issues. In practice, shear walls in high-rise structures may experience the coupling action of axial tension and cyclic horizontal load under strong earthquakes or extreme winds, resulting in an unfavorable state of tension bending or tension shear coupling stress for the shear wall systems. As the height-width ratio of these structures increases, there is a significantly increased possibility of shear wall structures experiencing tension bending or tension shear. In this study, five shear walls with different connection methods were manufactured and tested under the coupling action of axial tension and cyclic horizontal load. And the results suggested that the shear resistance of precast concrete shear walls at the horizontal construction joint significantly influenced their seismic performance and concrete damage when subjected to axial tension and cyclic horizontal loads. The precast shear wall system that utilized lapped steel bars and angle steel connectors for connections exhibited the best seismic performance. Additionally, the continuous horizontal construction joint formed by integral prefabrication (containing the edge components) slightly reduced the seismic behavior of the novel precast shear wall system utilizing lapped steel bars and angle steel connectors. The new precast shear wall system utilizing angle steel connectors has the potential to be an effective means of providing seismic resistance in high-rise structures that are subjected to the coupling action of axial tension and cyclic horizontal load.

Hybridization effects on ballistic impact behavior of carbon/ aramid fiber reinforced hybrid composite

Fiber reinforced polymer and its hybrid composites are widely used in bulletproof production. The ballistic limit, failure mode and energy absorption of a hybrid fiber reinforced polymer target (HFRPT) composed of carbon fiber reinforced polymer (CFRP) and aramid fiber composite (AF) were studied in this paper. A finite element model was formulated to investigate the hybridization effect of layer thickness and stacking sequence on the ballistic behavior. A theoretical method was proposed to predict the ballistic limits of HFRPT, demonstrating an error percentage of less than 10% in most of the hybridization. Four typical failure modes including compression failure, tensile failure, shear plugging failure and tension shear coupling failure were observed in HFRPT, and the influence of hybridization on the alternations of failure modes was observed. Additionally, the effect of stacking sequences and layer thickness on energy absorption of HFRPT was examined. For the HFRPTs with a total thickness of 10 mm, the AF/CFRP hybridization proves to offer better ballistic impact resistance performance than the CFRP/AF hybridization. The HFRPT with a stacking sequence of 9 mm AF and 1 mm CFRP achieves a maximum ballistic limit of 420 m/s and the highest impact energy areal density ratio of 323 J/(g/cm2).

Strength analysis of composite envelope structures considering the tension–shear coupling and cutting pattern effect

Various strength criteria have been extensively used in the structural design of stratospheric airships. However, it is still a critical challenge to accurately predict the failure strength for ensuring structural safety due to the complex mechanical behaviors of multi-layer composite envelope materials under various loading environments. This article thus aims to establish refined numerical models for the strength prediction of envelope structures. Firstly, the mechanical properties of envelope materials were tested and investigated comprehensively. The creative concept of tension–shear​ coupling is demonstrated by the shear constitutive relation and failure criterion. Secondly, with consideration of the cutting pattern effect originating from the manufacturing procedure, a new equal-diameter flattening method for cutting gores is proposed. Finally, inflation-bursting tests of spherical and ellipsoidal envelopes were conducted to validate the proposed refined numerical models. The maximum deviation of strengths predicted by the novel criterion is less than 8% for both envelope structures, indicating that the tension–shear effect plays a significant role in the failure mechanism of flexible thin-walled envelope structures.

The Tension-Shear and Compression-Shear Joint Strength Model for Unsaturated Clay and Its Application to Slopes

The capillary component and adsorptive component of matric suction differently impact the soil strength. Due to the cavitation effects of pore water, the adsorption effect dominates the behavior of soil when matric suction exceeds the cavitation tension. Based on the binary medium theory, a compression-shear strength model for unsaturated soils considering both capillary effect and adsorption effect is established. Compared with test data, the proposed compression-shear strength model has better prediction performance on the compression-shear strength of soil over a range of wide suction. The soil failure depends both on tension-shear stress and compression-shear stress. The tension-shear coupling mechanism in the soil is first investigated. A concept of closed stress point is introduced to divide the two zones of tension-shear coupling stress and compression-shear stress. According to the compression-shear strength model and tension-shear failure mechanism, the tension-shear and compression-shear joint strength model applicable to plane stress conditions is then established. Compared with test data, the proposed model in this article can better predict the nonlinear strength characteristics of clays and has better applicability. Finally, using the user material subroutine (UMAT), the secondary development of the joint strength model is conducted in ABAQUS and then applied to the slope stability analysis. The calculation results show that the established strength model presents a reasonable description of the development of the tension-shear coupling plastic zone in slope and gives an accurate safety factor.

Mechanical response and damage mechanism of 2D woven SiCf/SiC ceramic matrix composites under tension-shear coupling load

The macroscopic mechanical behavior and coupling damage mechanism of 2D woven SiCf/SiC ceramic matrix composites (CMC) prepared by chemical vapor infiltration (CVI) process under tension-shear coupling load were experimentally analyzed. At macroscale, the uniaxial tension, uniaxial shear and off-axis tension tests were completed and the results were compared. The tensile modulus and proportional limit have no significant difference with the increase of off-axis angle, while failure strength decreases by 22.3% compared the 45° tensile (165.4 MPa) with the 0° tensile (212.8 MPa). Based on the strain-difference analysis, the coupling damage effect of SiCf/SiC-CMC was characterized. At microscale, the main damage types of SiCf/SiC-CMC during loading were analyzed by scanning electron microscope (SEM), and the corresponding laws between micro damage development and macro mechanical behavior under different loading conditions were revealed by cluster analysis of acoustic emission (AE) signals. The test results show that the micro damage caused by tensile and shear stress components promote each other. The macro mechanical behavior of SiCf/SiC-CMC under complex loading is controlled by basic micro damage forms such as matrix cracking, interface debonding and fiber fracture. The tension-shear coupling load affects the evolution process of the basic damage forms, and then change the macro properties of SiCf/SiC-CMC.

On dynamic behavior and failure of high lock bolted joints: Testing, analysis and predicting

A bidirectional synchronous dynamic loading technique based on electromagnetic split Hopkinson tensile bar (ESHTB) system was employed to investigate the dynamic behavior and failure of high lock bolted joints. Force-displacement curves over wide ranges of loading speed (5 × 10−6 m/s to 15 m/s) and loading state (tension, shear and three kinds of tension-shear coupling) were obtained by combining with results obtained from quasi-static tests. An obvious elevation of failure load levels when changing the loading state from shear to tension or improving the loading speed was observed. Meanwhile, such strengthening effect of loading state on failure loads presented positive correlation with the loading speed. Detailed analysis for effect of loading state on mechanical behavior of bolted joints was conducted by applying von Mises yield criterion together with failure load analysis. Moreover, on this base, the influence of loading speed on failure loads was reasonably defined by applying a relation equal to the different strain rate effect between shear and tension for bolt material. Finally, a failure criterion considering coupling effect of loading speed and loading state on failure load of bolted joint was proposed. Prediction results showed a good agreement with the experimental results, indicating the determination of failure loads for bolted joints under different loading states over a wide range of loading speeds can be achieved.

Numerical implementation of rock bolts with yield and fracture behaviour under tensile-shear load

To realize the numerical analysis of rock bolt bearing-yield-fracture under tension-shear coupling and to provide an effective means for supporting the design of roadways or tunnels, a new numerical model was developed to analyse the tension-shear coupling fracture behaviour of rock bolts in engineering rock masses. Based on the study of the mechanical behaviour of rock bolts under tensile-shear coupling load, the mechanical criterion and constitutive model of the yield and fracture of rock bolts were proposed, and the secondary development of the FLAC3D platform was realized. At the same time, self-developed equipment was used to conduct the rock bolt tensile shear test. By comparing the numerical simulation results with the experimental results, we determine that the maximum difference in the shear displacement of the rock bolt does not exceed 2 mm during the yielding and breaking of the rock bolt, and the percent difference was approximately 3% and 10%, respectively. In the field of engineering, this result is generally considered acceptable. Using the numerical model we proposed, a numerical simulation experiment was conducted on the rock bolt support design of a coal mining roadway in engineering practice. The results show that under the original support scheme, a large amount of rock bolt tensile-shear failure occurs at the coal-rock interface, which makes the original support scheme unable to meet the engineering requirements with tensile-shear coupling failure tendency. In this regard, we adopted the support method of grouting anchorage at the interface of coal and rock. The results show that the deformation of the roadway surrounding rock has been effectively controlled.

A finite-strain micromechanical model for the hyperelasticity of tendons and ligaments with crimped fibers

The hyperelasticity of soft biological tissues such as tendons and ligaments is closely related to their microstructures consisting of wavy fibers embedded in a soft matrix. Large deformation of such composites involves both microstructural evolution and material nonlinearity, posing a challenge of theoretical analysis. In this paper, we propose a finite-strain micromechanical method to predict the hyperelastic constitutive relation of tendons and ligaments reinforced with crimped fibers. The Mori–Tanaka method is extended to account for the interaction of wavy fibers embedded in a soft matrix under large deformation. It is found that the tension–shear coupling mechanism induced by fiber–matrix interaction is crucial for the nonlinear behavior of tendons and ligaments. The hyperelasticity of such composites relies strongly on the initial crimp shape, Young's modulus, and volume fraction of fibers. This model is validated by finite element simulations of a unit cell model with crimped fibers. Furthermore, an explicit expression based on dimensional analysis is derived for the hyperelastic constitutive relation in terms of microstructural and material parameters, and it fits well with experimental data of tendons at different ages. This study can not only deepen the understanding of the mechanical behaviors of such soft tissues of tendons and ligaments, but also help the optimal design of biomimetic composites with superior elasticity.

Buckling of Rectangular Composite Pipes under Torsion

The numerical buckling load of rectangular composite pipes under torsional load was derived by using the energy method. The authors found no available simple design method or chart for the buckling loads of rectangular composite pipes, which are often used airplanes, spacecraft, and other lightweight structures, through their involvement in a Mars exploration airplane project. Thus, numerical results were obtained for length-to-width ratios (l/b) from 1 to 20, width-to-height ratios (h/b) from 1 to 6, and [0/90] layer ratios (r) from 0 to 1, which means [(0/90)r,(±45)1-r]s. The layups were assumed to be symmetric, and tension-bending, torsion-bending, and tension-shear coupling stiffnesses were ignored. To establish a simple design method, a closed-form polynomial equation for the buckling load factor was derived by minimizing the weighted residuals of the safe and non-safe side errors, which were obtained by comparing the derived numerical results with the polynomial equations. As a result, the errors of the polynomial equation for the buckling load factor were 4.95% for the non-safe side and 12.4% for the safe side. The errors are sufficiently good for preliminary design use and for parametric design studies and optimization.

Analysis of the influence of yarn angle on the mechanical behaviors of cured woven composites

Manufacturing process would modify the yarn angle of woven composites. To have a high-fidelity mechanical analysis, it is necessary to study its potential impact. In this article, experimental tests were specifically designed and conducted to investigate the influence of yarn angle on the mechanical behaviors of cured woven composites. The results show that yarn angle variation has a significant impact on the elastic modulus, Poisson’s ratio, and yield stress. The tensile deformation along yarn directions and shear deformation between two yarns were also investigated and their coupling with yarn angle variation was analyzed. It shows that when the yarn angle variation (from 90°) is less than 10°, the influence of the tension–shear coupling on the tensile behavior along yarn directions and shear behavior between two yarn directions is small and can be neglected. When the yarn angle variation is more than 20°, the influence of tension–shear coupling is significant and must be accounted for in constructing the constitutive law for the cured non-orthogonal woven composites.

An Analytical Model for the Tension-Shear Coupling of Woven Fabrics with Different Weave Patterns under Large Shear Deformation

It is essential to accurately describe the large shear behavior of woven fabrics in the composite preforming process. An analytical model is proposed to describe the shear behavior of fabrics with different weave patterns, in which tension-shear coupling is considered. The coupling is involved in two parts, the friction between overlapped yarns and the in-plane transverse compression between two parallel yarns. By introducing the concept of inflection points of a yarn, the model is applicable for fabrics with different weave patterns. The analytical model is validated by biaxial tension-shear experiments. A parametric study is conducted to investigate the effects of external load, yarn geometry, and weave structure on the large shear behavior of fabrics. The developed model can reveal the physical mechanism of tension-shear coupling of woven fabrics. Moreover, the model has a high computational efficiency due to its explicit expressions, thus benefiting the material design process.

Characteristics and Mechanism of Loess Landslides Induced by Strong Earthquake in The Loess Plateau of China

The Loess Plateau is the main loess distribution area in China with strong tectonic activity and frequent earthquakes. This paper systematically summarizes the characteristics and mechanism of loess landslides induced by strong earthquakes. The geometric characteristics of loess seismic landslide are gentle slope with 10°∼25°. The motion characteristics of earthquake-induced loess landslides are high-speed and long-distance. The distribution characteristics of loess seismic landslides are also basically consistent with the distribution of earthquake active region, and mainly distribute in loess hilly and gully area or the edges of the loess tableland. Based on the mechanism of seismic instability of loess slope, we consider that there are three types of loess landslides: seismic subsidence type, liquefaction type and tension-shear coupling type.

Impact of tensile strength and incident angles on a soil slope under earthquake SV-waves

The tensile strength and incident angles play important roles in seismically induced slope failures. In this paper, a new criterion for tension–shear coupling is proposed based on several sets of relevant lab data and is verified using the experimental data provided by previous researchers. This criterion can perfectly depict the tension region as well as the compression region in the entire stress space. Moreover, the tension–shear criterion was converted into an expression that could be directly used in a numerical method, and it was verified by a numerical example. In addition, the SV-waves were input using the equivalent nodal force method based on a viscous-spring artificial boundary. This process was implemented by the ABAQUS software, and two numerical examples were used to verify this method. Subsequently, based on the proposed new criterion and input method, the impacts of the strength criterion and incident angles on an analysis of seismically induced slope failures were studied. The results indicated that the evaluation of the tension–shear region is extremely important in the analysis of the seismically induced slope failures. The tensile strength of the seismically induced landslides was overestimated by the calculation of Mohr-Coulomb criterion owing to the ambiguous description of the tensile failure or the tension-shear failure, the assessment of the slope stability was thus not conservative. The incident angles of seismic waves affected the travel path and the directivity of slope seismic responses; the sliding displacement of the slope side near the epicenter rose with increasing angles of wave incidence, the critical slip surface deepened, and the hazard aggravated. Therefore, it is important to introduce both the tensile strength and incident angles when evaluating the stability of slopes subjected to seismic loads.

Determination of constitutive parameters for predicting dynamic behavior and failure of riveted joint: Testing, modeling and validation

For aircraft structures, dynamic failure of riveted joints occurs occasionally during in-service especially when a structure is impacted by such discrete sources as birds, hailstone, etc. Due to huge number of rivets and the smaller geometry scale compared with aircraft structure, the riveted joints are usually simplified to connector elements during numerical simulations. Therefore, the proper description of mechanical behavior especially the critical failure criterion for riveted joint is of great importance. In the present work, an experimental method based on the split Hopkinson bar technique was proposed to measure the dynamic mechanical response of riveted joint at different loading speeds. By careful design of specimen and texture, the riveted joint was loaded dynamically under simple tension, simple shear and different tension–shear coupling states. Combined with quasi-static experimental results, the parameters of a constitutive equation and failure criterion for riveted joint which has been embedded in the commercial finite element software were determined. Five simplified numerical models were established to validate the failure criterion employed as well as the parameters experimentally determined. Meanwhile, two simulated bird-impact tests were conducted by using two stiffened Ti-6Al-4V plates in which the plate and the rib was connected by several rivets, and the dynamic responses were performed both experimentally and numerically for further validation. The comparisons between experiments and simulations indicate not only the proposed experimental method but also the experimentally determined constitutive and failure parameters work very well in measuring the dynamic response of riveted joint.

Influence of tension–shear coupling on draping of plain weave fabrics

Although tension–shear coupling of weave fabrics in large deformation has been observed in experiments, most constitutive models for weave fabrics often ignore this coupling effect for simplicity. In this paper, a nonlinear anisotropic hyperelastic constitutive model is proposed to consider this tension–shear coupling effect. Draping experiments of a plain weave fabric over a tetrahedron mold are carried out to validate the proposed coupling constitutive model. Subsequently, the influences of tension–shear coupling on draping processes are investigated. Numerical simulation results indicate that the tension–shear coupling effect significantly changes fiber reorientation during draping process, which makes shear deformation tend to be uniform and reduces the local shear deformation concentration and should not be neglected in woven fabric stamping with salient double curvatures.

A numerical Bayesian-calibrated characterization method for multiscale prepreg preforming simulations with tension-shear coupling

Carbon fiber reinforced plastics (CFRPs) are attracting growing attention in industry because of their enhanced properties. Preforming of thermoset carbon fiber prepregs is one of the most common production techniques of CFRPs. To simulate preforming, several computational methods have been developed. Most of these methods, however, obtain the material properties directly from experiments such as uniaxial tension and bias-extension where the coupling effect between tension and shear is not considered. Neglecting this coupling effect deteriorates the prediction accuracy of simulations. To address this issue, we develop a Bayesian model calibration and material characterization approach in a multiscale finite element preforming simulation framework that utilizes mesoscopic representative volume element (RVE) to account for the tension-shear coupling. A new geometric modeling technique is first proposed to generate the RVE corresponding to the close-packed uncured prepreg. This RVE model is then calibrated with a modular Bayesian approach to estimate the yarn properties, test its potential biases against the experiments, and fit a stress emulator. The predictive capability of this multiscale approach is further demonstrated by employing the stress emulator in the macroscale preforming simulation which shows that this approach can provide accurate predictions.