Tension Deformation Research Articles

Numerical simulation of hydrodynamic characteristics of offshore wind power jacket base with net cage structure

ABSTRACT This study innovatively presents a structural solution that integrates aquaculture net cage onto the foundation of jacket-type offshore wind turbine. In the case study of a wind farm in Guangdong, the numerical model of the proposed integrated structure has been established. Various parameters, including incident wave and current angles, net solidity, mooring point arrangement, and net cage installation depth, are analysed to assess their influence on netting rope tension and net cage deformation. The findings reveal that reducing the mooring point density at the bottom of jacket legs, avoiding excessive netting rope arranged on steel wires, and considering greater net cage installation depth can optimise platform construction costs. The net cage installation scheme has minimal influence on the stress and overall displacement of the jacketed foundation members. The research outcomes provide valuable insights for the design of integrated structures combining jacket-type foundation and net cage in offshore wind farms.

Computational study of pre-deformation influence on grain-scale deformation of AZ31 magnesium alloy sheet with bimodal non-basal texture undergoing uniaxial tension deformation at room temperature

Computational study of pre-deformation influence on grain-scale deformation of AZ31 magnesium alloy sheet with bimodal non-basal texture undergoing uniaxial tension deformation at room temperature

Elastic conductivity of germanene nanoribbons with acceptor defects

This work is devoted to the theoretical researchers of the germanene nanoribbons piezoresistivity of various structural modifications (arm-chair and zig-zag) with the acceptor structural defects. Gallium atoms were chosen as impurities. A phenomenological expression for the band structure of nanoribbons deformed by tension and compression is proposed. The dependences of the longitudinal component of the elastic conductivity tensor on the relative deformation of tension and compression, the concentration of impurities and the width of the nanoribbon are analyzed.

Surface Roughening Behavior and Mechanism in Aluminum Alloy Under Tensile Deformation.

Surface roughening (SR) has been found to occur in solid solution 2219 aluminum alloy under tensile deformation, which will deteriorate its surface quality. To make a precise study of the surface roughening (SR) behavior and mechanism, the surface morphology of annealed and solid solution 2219 aluminum alloy was compared and crystal plasticity finite element (CPFE) simulation was carried out in this study. Thereinto, representative volume element (RVE) models of polycrystals were established according to the initial grain morphology measured by electron backscatter diffraction (EBSD). The results show that the surface roughening degree of the solid solution specimen is worse than that of annealed specimen after uniaxial tension deformation. In comparison with the annealed specimen, the grains show a larger size after solid solution treatment, thus resulting in the coarse surface to a certain extent. Moreover, texture type and density also have a significant influence on surface roughness. The rotation of grains with an S and Copper orientation intensifies the surface roughening during tensile deformation. The deformation difficulty of Goss texture in the normal direction (ND) and tangential direction (TD) varies, thus contributing to the different surface morphology. The research results will provide guidance for the improvement of the surface quality of high-strength aluminum alloy aerospace components.

Mechanical behavior of water ingress process for the locally damaged submerged floating tunnel and its interpretation: A full-length experimental study

The submerged floating tunnel (SFT) is an innovative transportation solution for traversing deep-water regions. However, local damage and subsequent water ingress pose significant threats to the structural integrity and safety of SFTs. This critical issue has been unexplored in the field. This study addresses this gap by presenting a comprehensive experimental investigation using a full-length physical model of the SFT. The dynamic response and failure mechanisms caused by water ingress within the SFT tube, influenced by various factors such as immersion depth, damaged opening angle, damaged opening area, and external connectivity, are systematically investigated. The results indicate that the failure of the anchor cable and tube structure of the SFT progresses through three stages after water ingress occurs in the damaged SFT. It is observed that damage closer to the bottom of the tube reduces the risk of failure in the mooring system. Notably, air pressure is a critical factor influencing the water ingress into the tube body. The attenuation of cable tension and tube deformation is significantly slower when the internal air is isolated from the external environment. The proposed novel structural sealing segmental disaster prevention design scheme substantially mitigates the risk of structural damage under compromised conditions and water ingress. This study provides valuable insights into enhancing disaster prevention strategies for SFTs and advances the understanding of their mechanical behavior in response to damage and water ingress.

Study on axial and bending stiffness characteristics of reinforced S-shaped bellows

PurposeReinforced S-shape bellows are novel metal bellows with high pressure resistance. Displacement compensation ability is a key index in the design of metal bellows. Axial-tension-compression deformation and bending deformation are two typical displacement compensation forms. Thus, analysis of axial and bending stiffness is important in structure design.Design/methodology/approachIn this study, theory analytics of axial tension and compression stiffness of reinforced S-shaped bellows structure is derived, and the load-displacement relationship during axial deformation is obtained by correcting the geometric parameters of waveform during axial tension and compression deformations. On the basis of them, the relationships of bending stiffness with axial tensile and compression stiffness under the action of bending loading are constructed, and thus, the theory analytics of bending stiffness is realized for S-shaped bellows.FindingsThis theory analytics is verified by comparing the results of theory analytics with those of numerical simulation for a few typical examples. An investigation on the axial and bending non-linear mechanical behaviors of multi-layer-reinforced S-shaped bellows was also carried out by numerical simulation and experiment, and the experimental results verified the reliability of the analysis method.Originality/valueIt is found that non-linearity behavior occurs greatly during the first loading course of reinforced S-shaped bellows, and the structure is strain-strengthened due to plastic deformation; however, stable stiffness characteristic is exhibited during the succeeding cyclic-loading course.

Effects of thermal treatments on the fracture behaviour of a silica-filled NBR: A study on the recovery of the Mullins effect and on the stretch-induced cavity formation

This research work is focused on the study of the fracture behaviour of a silica-filled NBR. The Mullins effect and its thermally-induced recovery are initially studied performing tensile tests: comparing the material's response in uniaxial tension and pure shear deformation conditions, a lower recovery is observed in the pure shear configuration. A similar study is then performed considering the fracture behaviour of the material. Tests are performed in quasi-static loading conditions and by applying a fracture mechanics approach. The fracture toughness is evaluated as J-integral at the crack onset and at the unstable fracture initiation; further, the crack propagation is analysed and the resistance curve is obtained. The dependence of the overall fracture behaviour of the material on the applied thermal history is evaluated. Even though the crosslinking degree seems not to be affected by the thermal treatment, the fracture behaviour is modified. A correlation of these results with a change in the material's propensity to form cavities under stretching is proposed.

A model for capturing the rate-dependent mechanical behaviour of liquid crystal elastomers

A modelling framework is adopted and adapted here to model the rate-dependent deformation behaviour of liquid crystal elastomers (LCEs). On using an isotropic hyperelastic strain energy function WI1,I2 of binomial form, previously employed for capturing the (quasi-static) deformation of polydomain LCEs, an extension is presented for application to the rate-dependent behaviour of LCEs by incorporating the deformation rate into the model parameters. That is, the model parameters of the core hyperelastic strain energy function W are considered to evolve with, i.e., be a function of, the deformation rate. A specific measure of deformation rate ɛ̇ is utilised, and a particular functional dependency of the hyperelastic model parameters on ɛ̇, of a skewed exponential form, is devised and presented. The ensuing rate-dependent model Wr is then applied to a range of extant experimental datasets, encompassing various LCE specimens and across different deformation rates, under uniaxial loading and including both tension and compression deformations. The model is shown to capture and predict the data favourably. Given the simplic of devising and implementing the presented modelling framework, the flexibility it provides for incorporating different choices of strain energy W function as well as the functional form(s) of the dependency of the model parameters on the deformation rate, and the accuracy of the modelling results, the application of this modelling approach to capturing the rate-dependent deformation behaviour of LCEs is hereby presented.

Criterion for unhomogeneous yielding of porous materials

A criterion is developed for the unhomogeneous yielding of materials containing arbitrarily oriented ellipsoidal voids. The criterion is built upon classical estimates for pure pressure and pure shear. A data-driven approach is then followed to incorporate the effects of void shape and orientation. A large number of micromechanical unit cell results are used to calibrate the yield criterion. A key feature of the criterion is that it predicts a significant reduction of the effective shear yield strength due to mere void inclination, with the reduction increasing with the void dimension perpendicular to the shear. The coupling between tension and shear deformation results in an apparent rotation of the yield surface, which provides a sound micromechanical basis for predicting void closure in shear among other new features. Once supplemented with evolution equations of relevant internal parameters, the resulting constitutive formulation will enable ductile failure simulations heretofore impossible to carry out on a sound physical basis for general loading conditions.

Effect of unusual texture on tension-compression asymmetry for Mg-RE alloy by viscoplastic self-consistent modeling

The tension-compression asymmetry presents notable challenges for the application of magnesium alloys in many fields. In this study, the solid-solution treated Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy's tension-compression asymmetry was examined using optical microscope (OM), x-ray diffraction (XRD), viscoplastic self-consistent (VPSC) modeling, and electron backscatter diffraction (EBSD). The VPSC hardening parameters were significantly adjusted based on the Schmid factor of deformation modes in rare earth magnesium (Mg-RE) alloy, which came from the EBSD data. Excellent agreement was found between the modified VPSC model's calculation results, especially the stress-strain curves and pole figures. The alloy exhibited good strength with a negligible tension-compression asymmetry and an impressive 0.98 ratio of compressive yield strength to tensile yield strength (CYS/TYS). The main cause could be attributed to the unusual texture of (11-20) <0001> in alloy, which eliminated the imbalance in tension and compression deformation by having a negative effect on the activation of {10-12} twinning in tensile and a positive effect in compressive deformation. The activation level of {10-12} twinning was 0.37 and 0.40 calculated by VPSC model, in the plastic deformation of tension and compression, respectively; in the tensile and compression samples, the EBSD data indicated that approximately 31.9% and 31.1% (area proportion) of the grains were deformed with twins, respectively. Both tension and compression deformation showed the {10-12} twinning in the early stage of deformation, which transformed to {11-22} twinning in the later stage. The considerable activation of pyramidal <c+a> during the later stages of deformation endowed the alloy with good ductility.

Dynamic recrystallization in a near β titanium alloy under different deformation modes – Transition and correlation

During the thermoforming of TC18 titanium alloy multi-cavity components, different deformation modes always exist and change, such as uniaxial compression (UC), shear-compression deformation (SCD), uniaxial tension (UT) and shear-tension deformation (STD). Dynamic recrystallization (DRX) of β grains occurs during the single-phase field deformation and has a great influence on the performance of components. In this study, the types and mechanisms of DRX in TC18 titanium alloy as well as transition and correlation under different deformation modes are investigated. It is found that discontinuous dynamic recrystallization (DDRX) initiates through grain boundary bulging at a low strain and dominates in different modes of deformation. Continuous dynamic recrystallization (CDRX) initiates at different strains depending on deformation modes, and the mechanisms vary, subgrain rotation within grains and lattice rotation near GBs under UC and STD, while only subgrain rotation under UT, in addition to these two mechanisms, grain fragmentation is also involved under SCD. Secondary dynamic recrystallization (SDRX) only occurs at a high strain under SCD and STD. Deformation modes lead to differences in orientation, slip and rotation of grains, further result in different dislocation density, distribution and accumulation, which contribute to the occurrence and transition of different types of DRX. Meanwhile deformation modes result in differences in the difficulty of GB migration and lattice rotation, ultimately in the initiation and degree of DDRX and CDRX. The shear stress in SCD and STD promotes the occurrence of CDRX. The present results can provide a guidance for obtaining good performance of the titanium alloy components.

A multiaxial multiscale compressive thermo-mechanical damage model for Fiber Reinforced Cementitious Composites (FRCC)

In the current study, a multiaxial multiscale compressive stress-strain model for Fiber Reinforced Cementitious Composites (FRCC) was innovatively developed. The proposed model was on the basis of the theory of thermodynamics, multiscale theory and internal variable theory. The free energy function and dissipation function were established to characterize the elastic and plastic deformation of FRCC, respectively. The multiscale behaviors of FRCC in meso-scale and macro-scale was taken into account. In meso-scale, the energy dissipation functions of fiber in tension and bond-slip deformation in the interface transition zone (ITZ) were established. The resistance to cracking of cementitious matrix through the fiber bond stress were taken into account. In macro-scale, the thermo-mechanical coupling contributions of plastic damage, thermal damage, yield surface and hardening evolution were creatively considered in the potential function within thermodynamics framework. The influence of types and volume fractions of fibers on the reinforcement mechanism was discussed. When the temperature is higher than the melting point of fiber, the fiber influence coefficients was employed. The sensitivity of yield surface was discussed. The numerical predictions of this developed model were carried out for validation. The nonlinear stress-strain responses of concrete were accurately captured at temperatures ranges from 20 °C to 800 °C compared with the experimental data, which indicates the accuracy and applicability of the proposed model.

A peridynamic differential operator modeling approach for ceramic matrix composites microstructure with uniform or non-uniform discretization

Based on the theory of peridynamic differential operator (PDDO), a novel three-dimensional (3D) peridynamic (PD) model for isotropic and orthotropic material is proposed to investigate the elastic mechanical behaviors and stress distribution of Ceramic Matrix Composites (CMC) microstructure. The non-local expressions of strain and stress tensors are derived by employing PDDO and the classical constitutive equations. The bond forces in interface region crossing two different constituent materials are obtained by converting the partial differential terms into the non-local forms. The weak form of PD equations of motion is derived by using the principle of virtual work and PDDO. The validity of this approach is verified by predicting the elastic response and stress distributions of isotropic and orthotropic materials under uniaxial tension and pure shear deformation. Finally, simulations are conducted on a CMC microstructure with fiber and matrix under periodic boundary conditions. It is demonstrated that the current approach can effectively build 3D CMC microstructure with uniform or non-uniform discretization, and accurately predict the stress fields and effective elastic properties.

Highly Flexible and Superelastic Graphene Nanofibrous Aerogels for Intelligent Sign Language.

Highly flexible and superelastic aerogels at large deformation have become urgent mechanical demands in practical uses, but both properties are usually exclusive. Here a trans-scale porosity design is proposed in graphene nanofibrous aerogels (GNFAs) to break the trade-off between high flexibility and superelasticity. The resulting GNFAs can completely recover after 1000 fatigue cycles at 60% folding strain, and notably maintain excellent structural integrity after 10000 cycles at 90% compressive strain, outperforming most of the reported aerogels. The mechanical robustness is demonstrated to be derived from the trans-scale porous structure, which is composed of hyperbolic micropores and porous nanofibers to enable the large elastic deformation capability. It is further revealed that flexible and superelastic GNFAs exhibit high sensitivity and ultrastability as an electrical sensors to detect tension and flexion deformation. As proof, The GNFA sensor is implemented onto a human finger and achieves the intelligent recognition of sign language with high accuracy by multi-layer artificial neural network. This study proposes a highly flexible and elastic graphene aerogel for wearable human-machine interfaces in sensor technology.

Dynamic strength differential and Bauschinger effects in an extruded AZ80 magnesium alloy

Quasi-static and high-rate tension and compression properties of an extruded AZ80 Mg alloy rod were investigated at loading rates of 0.001 and 500 s−1. Acquired stress – strain results show that tension and compression plastic deformations of AZ80 rod are asymmetric, and such strength differential effect is dependent of strain rate and loading orientation. Strength differential effect is weakened at 500 s−1 when the sample was loaded along the extrusion direction. Crystal plasticity simulations on the basis of the visco-plastic self-consistent method were performed. Numerical results indicate that the rate and orientation dependency of strength differential effect in AZ80 alloy is related to {101‾2} extension twinning. High-rate tests for pretension, unloading and reverse compression were realized to investigate the dynamic Bauschinger effect. Experimental results show that Bauschinger effect of AZ80 alloy is anisotropic and sensitive to the strain rate. A Bauschinger effect parameter considering strength differential effect was proposed, and it was found that the Bauchinger effect in the extrusion direction is reduced significantly at 500 s−1.

Modelling the rate-dependent mechanical behaviour of the brain tissue

A new modelling approach is employed in this work for application to the rate-dependent mechanical behaviour of the brain tissue, as an incompressible isotropic material. Extant datasets encompassing single- and multi-mode compression, tension and simple shear deformation(s) are considered, across a wide range of deformation rates from quasi-static to rates akin to blast loading conditions, in the order of 1000 s−1 . With a simple functional form and a reduced number of parameters, the model is shown to capture the considered rate-dependent behaviours favourably, including in both single- and multi-mode deformation fits, and over all range of deformation rates. The provided modelling results here are obtained from either first fitting the model to the quasi-static data, or/and predicting the behaviour at a different rate than those used for calibrating the model parameters. Given its simplicity, versatility, predictive capability and accuracy, the application of the utilised modelling framework in this work to the rate-dependent mechanical behaviour of the brain tissue is proposed.

Continuous Softening as a State of Hyperelasticity: Examples of Application to the Softening Behavior of the Brain Tissue.

The continuous softening behavior of the brain tissue, i.e., the softening in the primary loading path with an increase in deformation, is modeled in this work as a state of hyperelasticity up to the onset of failure. That is, the softening behavior is captured via a core hyperelastic model without the addition of damage variables and/or functions. Examples of the application of the model will be provided to extant datasets of uniaxial tension and simple shear deformations, demonstrating the capability of the model to capture the whole-range deformation of the brain tissue specimens, including their softening behavior. Quantitative and qualitative comparisons with other models within the brain biomechanics literature will also be presented, showing the clear advantages of the current approach. The application of the model is then extended to capturing the rate-dependent softening behavior of the tissue by allowing the parameters of the core hyperelastic model to evolve, i.e., vary, with the deformation rate. It is shown that the model captures the rate-dependent and softening behaviors of the specimens favorably and also predicts the behavior at other rates. These results offer a clear set of advantages in favor of the considered modeling approach here for capturing the quasi-static and rate-dependent mechanical properties of the brain tissue, including its softening behavior, over the existing models in the literature, which at best may purport to capture only a reduced set of the foregoing behaviors, and with ill-posed effects.

Manufacturing, characterization, and macromechanical modeling of short flax/hemp fiber-hybrid reinforced polypropylene

The present work focuses on the manufacturing, mechanical characterization, and modeling of hybrid Flax/Hemp/Polypropylene (PP) composites under dry conditions. Geometric parameters of the fibers were measured both before and after the melt processing. The results indicated that the processed fibers, especially the hybrid ones, had a narrowed length distribution with an average fiber length of 0.48 mm for hybrids compared to 0.62 mm for non-hybrids. The hybrid composites were mechanically characterized using basic and loading-unloading tensile tests with various fiber combinations and weight percentages. The study also examined the effect of strain rate and cutting angle on the behaviors of the composites. The results demonstrated the significance of fiber orientation as the primary factor in explaining mechanical variations. The tensile strength and Young's Modulus of FH30 composites (PP + 15 wt% flax + 15 wt% hemp) increased by about 24.1 % and 10.9 %, respectively, when the plates were cut into dumbbell shapes at a 90° angle to the injection molding flow direction, compared to a cut at 0° The study also showed that the tensile strength is directly proportional to the mass fraction of reinforcements, with an increase in tensile strength by 7.9 % for 0° cut angle specimens between FH10 (PP + 5 wt% flax + 5 wt% hemp) and FH30 bio-composites, while the uniform strain is inversely proportional to the mass fraction of reinforcements, evidenced by a reduction in uniform strain of 30 % between FH10 and FH30 samples. Morphological observations revealed the presence of bands indicating the propagation of micro-cracks, as well as debonding or cohesive failure. Finally, a Perzyna-type elasto-viscoplastic constitutive model was applied to accurately predict the overall mechanical response of a hybrid composite material. Specifically, the model successfully captured the tension deformation behavior of hybrid natural short-fiber thermoplastic composites, including the elastic stage, yield stress, and nonlinear hardening.

Multi-Mode Damage and Fracture Mechanisms of Thin-Walled Tubular Parts with Cross Inner Ribs Manufactured via Flow Forming.

In order to study the multi-mode damage and fracture mechanisms of thin-walled tubular parts with cross inner ribs (longitudinal and transverse inner ribs, LTIRs), the Gurson-Tvergaard-Needleman (GTN) model was modified with a newly proposed stress state function. Thus, tension damage and shear damage were unified by the new stress state function, which was asymmetric with respect to stress triaxiality. Tension damage dominated the modification, which coupled with the shear damage variable, ensured the optimal prediction of fractures of thin-walled tubular parts with LTIRs by the modified GTN model. This included fractures occurring at the non-rib zone (NRZ), the longitudinal rib (LIR) and the interface between the transverse rib (TIR) and the NRZ. Among them, the stripping of material from the outer surface of the tubular part was mainly caused by the shearing of built-up material in front of the rollers under a large wall thickness reduction (ΔT). Shear and tension deformation were the causes of fractures occurring at the NRZ, while axial tension under a large TIR interval (l) mainly resulted in fractures on LIRs. Fractures at the interface between the TIR and NRZ were due to the shearing applied by rib grooves and radial tension during the formation of ribs. This study can provide guidance for the manufacturing of high-performance aluminum alloy thin-walled tubular components with complex inner ribs.

Molecular Dynamics Simulation of Bauschinger Effect in Cu Nanowire with Different Crystallographic Orientation

In this study, the Bauschringer Effect (BE) resulting from tension-compression deformation applied to nanowires obtained by placing Cu atoms in , and highly symmetric crystallographic directions was investigated using the Molecular Dynamics (MD) simulation method. The forces between atoms were determined from the gradient of the Embedded Atom Method (EAM) potential function, which includes many-body interactions. It was determined that there is an asymmetry between the stress-strain curves obtained as a result of the tension and compression deformation process applied to the model system. From this asymmetry, it was determined that the yield stress obtained in the drawing process for nanowire with crystallographic orientation was greater than the yield strain obtained as a result of the compression process. In contrast, the opposite was found for nanowires with crystallographic orientation and . In addition, after the yield strain value is exceeded as a result of the drawing process applied to the model nanowire system, compression deformation process was applied at different pre-strain values. The existence of the Bauschinger Effect (BE), which is expressed as the yield strength value as a result of forward loading corresponding to the tension operation, is smaller than the yield value obtained as a result of the compression process in which the loading is removed, was determined. To clarify the effect of BE on Cu nanowires with different crystallographic orientations, Bauschinger Stress parameter (BSP) and Bauschinger Parameter (BP) values were calculated.