Stress Softening Research Articles

Analysis of non-ionic surfactants on the rheological and interparticle response of polymer enhanced colloids for investment casting slurries

Dispersion of ceramic slurries for investment casting is governed by the colloidal solution and influenced by surfactants, where micelles form until a critical micelle concentration (CMC) is attained. Light scattering techniques and rheological methods were used to determine the CMC of three different non-ionic surfactants. The former provides an insight into the: zeta potential; electrical conductivity; and hydrodynamic diameter of the silica/polymer network, where the hydrodynamic diameter portrays a peak shift as the CMC is acquired. Rheological measurements display a reduction in the apparent viscosity with surfactant concentration before increasing by 3.7–15% upon approaching the CMC. The viscoelastic properties display an optimum surfactant concentration, where a stress softening behavior occurs at higher frequencies, known as the Payne effect. As the volume fraction increases, the elastic region extends to lower strains and the onset of recoverable energy occurs below the CMC, while the viscous response exhibits a resistance to flow.

Influence of pre‐strain and bake hardening on the static and fatigue strength of a DP600 steel sheet

AbstractThe influence of pre‐strain on the tensile and fatigue properties of a dual phase DP600 steel was studied. The material was pre‐strained by uni‐axial tension in rolling and transverse direction. Thereafter, specimens were cut from the deformed plates in parallel or orthogonal to pre‐strain direction. It was found that pre‐strain increases yield and tensile strength. Results suggested that strain path change primarily affects the elastic‐plastic transition during early stage of reloading. Pre‐strained specimens showed an increase in high cycle regimes as a consequence of yield strength increment, irrespective of imposed pre‐straining direction. A modified stress life equation that accounts for pre‐strain was proposed and showed good agreement with experimental data. Bake hardening enhanced both tensile and high cycle fatigue resistance. Walker equation was successfully fitted to account for tensile mean stress. In low cycle fatigue, negligible influence of pre‐strain was observed due to cyclic softening and residual stress relaxation.

Stress sensitivity of elastic moduli in high-porosity cemented sandstone — Heuristic models and experimental data

Quantitative description of the reservoir rock stress sensitivity is critical for seismic modeling and interpretation. Laboratory studies have indicated that the wave velocity of high porosity cemented sandstone is asymmetrically much more sensitive to stress unloading than stress loading. However, there is a lack of a simple rock physics model that is capable of describing the asymmetric stress sensitivity of reservoir rock. A new rock physics model is developed by extending an existing rock physics model based on contact theory combined with elastic bounds. The new model relates the stress softening of rock to cement cracking and crumbling induced by stress release. The diluting factor is introduced to describe the weakening of effective cement and analyze the increase of stress sensitivity when the stress is gradually removed. The combination of the new model and its base model forms a rock physics modeling workflow that can accurately describe the evolution of velocities measured in samples undergoing stress loading and unloading. The model performance is compared with samples representing synthetic weakly cemented glass bead pack and sandstone manufactured with different cements at different forming stress levels. The modeling results are in accordance with the measured stress sensitivities of wave velocities. The sequential model calibration using a simple constraint optimization approach yields important calibration parameters that are indicative of the elastic stress sensitivity and damage behavior in the studied rocks. The model can be particularly interesting for time-lapse monitoring of fluid injection and seismic interpretation of overpressured reservoir rock.

Study on mechanical behaviors and failure mechanism of polyurethane matrix composites inspired by mussel chemistry and arthropod exoskeleton structures under dynamic impact

Polyurethane elastomer (PUE), an elastic polymer material of lightweight and unexceptionable mechanical properties, is widely used into the military protective structural materials to resist dynamic impact and absorb energy. However, the mechanical and thermal properties of PUE need to be enhanced due to failure damage caused by the thermal stress softening under high-speed impact. Inspired by the mussel chemistry and the exoskeleton structures of arthropods, catechol and polyethyleneimine were used to functionalize micro carbon fibers (MCFs) to enhance the mechanical and thermal properties of PUE composites. Compared with Pure PUE, the static compression modulus of PUE composite with a filler content of 2.0 wt.% was increased by 99.25%. The dynamic maximum strength and energy absorption were improved by 74.08% and 102.92%, respectively. Besides, the modified MCFs could significantly enhance the viscoelasticity and thermal conductivity characteristics of composites. The enhancement of impact resistance and energy absorption capability of the composites are mainly due to the synergistic effect of tough mussel adhesion proteins and enhancing MCFs. Thereinto, MCFs could provide incredible strength, and plenty of crosslinking networks based on phenol-amine chemistry were served as supporting structures to resist dynamic impact by effective energy dissipation. Therefore, this work can provide a way to prepare PUE composites with excellent thermal and mechanical performance, and it is beneficial to understand the deformation and failure mechanisms of PUE and other soft polymer materials under dynamic impact.

A novel hybrid lattice structure for improving compression mechanical properties

Lattice structures are widely used in load-bearing and energy-absorption applications for their lightweight, high specific stiffness, high specific strength and excellent energy-absorption. A novel hybrid lattice cell that combining octet cell and body-centered cube cell was proposed, and quasi-static compression experiments and finite element simulations were performed to investigate their energy-absorption characteristic and deformation mechanisms. The effects of the relative density, configuration of cell and component ratio sub-cell on the compression responses were also explored. The results showed that hybrid lattice improves compression modulus and yield strength by 10% and 16% maximally, respectively, and the energy-absorption of enhancement is 20% higher than the conventional lattices. In addition, the hybrid lattice can significantly alleviate the stress softening. By increasing the volume ratio of body centered cubic in the hybrid lattice structures, the energy-absorption can be improved. Under dynamic loading, the proposed hybrid lattice structures displayed outstanding normalized yield strength, which is superior to majority of porous structures. Inspired by the precipitation hardening mechanisms used in metallurgy to design high-performance alloys, two dual-phase lattices are developed. The quasi-static compression of dual-phase lattices shows three stages plateau stress and has a higher third stage than that of traditional dual-phase lattices. These findings provided design strategy for lightweight structure.

A new ductile fracture model for Q460C high-strength structural steel under monotonic loading: Experimental and numerical investigation

Tensile fracture static tests on nine specimens covering different stress states were performed to investigate the ductile fracture behavior of Chinese Q460C high-strength structural steel (HSS). Based on combining the Rice-Tracey model and Xue model, the new model considering the effect of stress triaxiality and Lode angle was proposed to predict ductile fracture of Q460C HSS. Furthermore, the stress softening criterion was incorporated into the new fracture model to simulate the fracture propagation of Q460C HSS better. The material parameters of the proposed fracture model for Q460C HSS were identified using MATLAB optimization code. The VUMAT subroutine was developed to perform ductile fracture simulations for each specimen, and the fracture simulation results show satisfactory agreement with the experimental results. In addition, the five existing ductile fracture models were also selected to compare the prediction accuracy of the new model. The comparative results show that the new model has better accuracy and is more suitable for predicting fracture initiation and propagation of Q460C HSS. Finally, the applicability of the new model in predicting the fracture of Q460 HSS was furtherly verified by successfully simulating the existing fracture tests of the notched round bar specimens and the bolted connections.

Low-cycle fatigue behaviour of hot-rolled titanium-clad bimetallic steel

Titanium-clad (TC) bimetallic steel is able to integrate the superior corrosion resistance of titanium alloy into traditional corrosion-susceptible structural steels, producing prominent life-cycle safety, serviceability and durability. Nevertheless, the relevant seismic performance and fatigue behaviour reported in existing literature are still limited and insufficient to support the codification for structural design of such advanced steel. In order to develop proper plastic/seismic design methodology for TC bimetallic steel structure, the cyclic behaviours and low-cycle fatigue life prediction of such metal must be thoroughly investigated. This paper aims to study the low-cycle fatigue behaviour of hot-rolled bonded TC bimetallic steel manufactured from TA2 titanium alloy and Q355B structural steel. The strain amplitude of low-cycle fatigue (LCF) test ranges from 0.5% to 2.5%, and the strain ratio applied herein includes 0 and -1. The experimental phenomenon, LCF failure mechanism, cyclic stress-strain relationship of different tests are thoroughly compared and discussed. Besides, the influence of strain rate and bond strength are simultaneously demonstrated. The LCF life are fitted and validated through Basquin-Coffin-Manson model, Kuroda model and energy method, respectively. The research outcomes demonstrate that the LCF cracks of TC bimetallic steel tend to be initiated at the cladding layer and propagated into the substrate layer due to a coupled buckling-fatigue failure mechanism. Several representative fatigue behaviour of conventional mild (CM) steels including the three-stage cyclic softening and mean stress relaxation have not been observed in this experimental study. The strain rate exhibits distinct influence on the LCF life and failure mechanism. Both Basquin-Coffin-Manson model and energy method can provide more favourable prediction accuracy for LCF life of TC bimetallic steel than the Kuroda model. Generally the LCF life of TC bimetallic steel is shorter than that of structural steels, stainless steels, titanium alloys and stainless-clad (SC) bimetallic steels. The test records and fatigue-life model parameters obtained can lay a solid foundation for seismic analysis and damage evaluation of TC bimetallic steel structure.

Improved Thermo-Mechanical Fatigue Resistance of Al-Si-Cu 319 Alloys by Microalloying with Mo.

Thermo-mechanical fatigue (TMF) is one of the most detrimental failures of critical engine components and greatly limits their service life. In this study, the out-of-phase TMF (OP-TMF) behavior in Al-Si-Cu 319 cast alloys microalloyed with Mo was systematically investigated under various strain amplitudes ranging from 0.1-0.6% and temperature cycling at 60-300 °C and compared with the base 319 alloy free of Mo. Cyclic stress softening occurred in both experimental alloys when applying the TMF loading, resulting from the coarsening of θ'-Al2Cu precipitates. However, the softening rate of the Mo-containing alloy was lower than that of the base 319 alloy because of its lower θ'-Al2Cu precipitate coarsening rate per cycle. The Mo-containing alloy exhibited a longer TMF lifetime than the base alloy at the same strain amplitude. Microalloying 319 alloy with Mo enhanced the TMF resistance mainly by slowing the coarsening of θ'-Al2Cu precipitates and providing supplementary strengthening from thermally stable Mo-containing α-dispersoids distributed in the Al matrix. The energy-based model was successfully applied for predicting the TMF lifetime with a low life predictor factor, which agreed well with the experimentally measured fatigue cycles.

Influence of Uneven Subgrade Frost Heave on Deformation and Damage of CRTSIII Slab Track

The problem of uneven frost heave deformation of high-speed railway subgrade in seasonal freezing areas seriously affects the service state and service life of slab track structures and threatens the safe operation of high-speed vehicles. Based on the damage plasticity theory of concrete, in this study, an analytical model is established for CRTSIII slab track with damage plasticity and reinforcement. The influences of various frost heaving parameters on track structure deformation, interlayer seam, as well as the stress and damage behaviors were analyzed in detail. The results show that, as compared with a linear elastic model, the damage plastic model better reflects the softening behavior and stress attenuation of track structure concrete after reaching its tensile strength. The deformation and the interlayer seam reach their maximum values when the frost heaving wave peak acts at the position that is one-sixth of the base length from the edge of the concrete base. When the frost heaving wave peak acts on grooves at the base center, initially, the track structure is seriously damaged. The interlayer seam and damage decrease with an increase in frost heaving wavelength and increase with an increase in frost heaving wave amplitude. The interlayer seam of the track structure is more sensitive to frost heave deformation having a wavelength of less than 10 m. The extent of damage to the concrete base gradually increases with a decrease in the wave/amplitude ratio. It undergoes three stages of damage evolution: (i) no damage, (ii) upper surface bending damage, (iii) reverse bending damage. In order to improve efficiency, it is recommended, during track maintenance, to focus on the position of the central groove of the base and the position that is one-sixth of the base length from the edge of the concrete base.

Cyclic deformation mechanism and fracture behaviour of 316L stainless steel under thermomechanical fatigue loading

Thermomechanical fatigue (TMF) behaviour of 316L is investigated based on the internal stress and microstructural characterization at various cyclic stages. Results reveal that the cyclic stress response shows initial hardening followed by cyclic softening at a high strain amplitude, while presenting continuous cyclic hardening as the strain amplitude decreases. Among these, Out-of-phase TMF always shows cyclic softening irrespective of strain amplitude. It is important to note that the hardening of back stress and friction stress contribute to the initial and subsequent cyclic hardening. In contrast, the subsequent cyclic softening is mainly dominated by the reduced friction stress. It is observed that the proliferation of dislocations at grain boundaries and the enhanced dislocation interactions within the grains are primarily responsible for the hardening of back stress and friction stress, respectively. Specifically, the cyclic softening of friction stress is attributed to the annihilated dislocations as a result of cross-slip. It is also found from the hysteresis curves that the intensity of dynamic strain ageing is related to strain amplitude, loading history and phase angle, which correlates to the occurrence of cross-slip, the diffusion rate of the solute atom, the density of point defect and the mobility of vacancies. Finally, the effect of loading conditions on fracture behaviour is demonstrated from the point view of crack sources, secondary cracks, creep cavities and oxidation damage.

Designing Viscoelastic Gelatin-PEG Macroporous Hybrid Hydrogel with Anisotropic Morphology and Mechanical Properties for Tissue Engineering Application

The mechanical properties of scaffolds play a vital role in regulating key cellular processes in tissue development and regeneration in the field of tissue engineering. Recently, scaffolding material design strategies leverage viscoelasticity to guide stem cells toward specific tissue regeneration. Herein, we designed and developed a viscoelastic Gel-PEG hybrid hydrogel with anisotropic morphology and mechanical properties using a gelatin and functionalized PEG (as a crosslinker) under a benign condition for tissue engineering application. The chemical crosslinking/grafting reaction was mainly involved between epoxide groups of PEG and available functional groups of gelatin. FTIR spectra revealed the hybrid nature of Gel-PEG hydrogel. The hybrid hydrogel showed good swelling behavior (water content > 600%), high porosity and pore interconnectivity suitable for tissue engineering application. Simple unidirectional freezing followed by a freeze-drying technique allowed the creation of structurally stable 3D anisotropic macroporous architecture that showed tissue-like elasticity and was capable of withstanding high deformation (50% strain) without being damaged. The tensile and compressive modulus of Gel-PEG hybrid hydrogel were found to be 0.863 MPa and 0.330 MPa, respectively, which are within the range of normal human articular cartilage. In-depth mechanical characterizations showed that the Gel-PEG hybrid hydrogel possessed natural-tissue-like mechanics such as non-linear and J-shaped stress-strain curves, stress softening effect, high fatigue resistance and stress relaxation response. A month-long hydrolytic degradation test revealed that the hydrogel gradually degraded in a homogeneous manner over time but maintained its structural stability and anisotropic mechanics. Overall, all these interesting features provide a potential opportunity for Gel-PEG hybrid hydrogel as a scaffold in a wide range of tissue engineering applications.

Mechanical behavior of adhesively bonded butt‐joints under cyclic loading: Experiments and constitutive model

AbstractThe cyclic loading experiments on HP‐172B sealant bonded tubular butt‐joints were carried out with the strain‐controlled mode, and the effects of strain amplitude and mean strain on the cyclic relaxation stress and cyclic softening variable of the bonded butt‐joint were investigated. The experimental results show that the stress–strain response curve of the butt‐joint presents a corrugated shape under cyclic loading. The cyclic stress relaxation and cyclic softening of the bonded butt‐joint occur. The increase of mean strain and strain amplitude intensifies the cyclic stress relaxation and cyclic softening behaviors. According to the experimental observation, a nonlinear viscoelastic model is proposed to predict the mechanical behavior of butt‐joints under cyclic loading, which considers the cyclic stress relaxation and cyclic softening of the bonded butt‐joint. The comparisons between the model calculation and the experimental data show that the calculated stress–strain curve is in good agreement with the experimental data.

Deformation and failure of additively manufactured Voronoi foams under dynamic compressive loadings

Additive manufacturing (AM) enables the design and fabrication of foams with intricate cell architectures for enhanced mechanical performances in blast and impact mitigation applications. Although the crushing response of AM foams has been studied recently, there is limited research on their failure behaviours under dynamic loading. This work investigates the response of AM Voronoi foams under compressive loadings through a combined experimental and numerical effort, with the emphasis on the failure behaviour and its modelling. Voronoi foams with uniform and graded density distributions were fabricated via the Fused Deposition Modeling technique. Quasi-static (0.001 s−1) and low-speed impact (50 s−1) tests were carried out to quantify the mechanical response and to characterise the deformation and failure behaviours. Computational models of the Voronoi foams were built in ABAQUS and validated with the experiment to provide insights into the dynamic fracture behaviours. Results showed that although failure plays a minor role in the quasi-static loading case, dynamic compressive loading can yield complex fracture behaviours involving cell-wall buckling, cell-wall rupturing, large-scale shattering and shear band localisation, resulting in significant stress softening and strong stress fluctuations during the post-yield response. Consequently, the load-bearing and energy absorbing capacities materially deteriorated when transiting from quasi-static to dynamic loading conditions. The results reported in this work provide valuable guidance on the design of AM foams under dynamic loadings.

Photoinduced Dithiolane Crosslinking for Multiresponsive Dynamic Hydrogels.

While many hydrogels are elastic networks crosslinked by covalent bonds, viscoelastic hydrogels with adaptable crosslinks are increasingly being developed to better recapitulate time and position-dependent processes found in many tissues. In this work, 1,2-dithiolanes are presented as dynamic covalent photocrosslinkers of hydrogels, resulting in disulfide bonds throughout the hydrogel that respond to multiple stimuli. Using lipoic acid as a model dithiolane, disulfide crosslinks are formed under physiological conditions, enabling cell encapsulation via an initiator-free light-induced dithiolane ring-opening photopolymerization. The resulting hydrogels allow for multiple photoinduced dynamic responses including stress relaxation, stiffening, softening, and network functionalization using a single chemistry, which can be supplemented by permanent reaction with alkenes to further control network properties and connectivity using irreversible thioether crosslinks. Moreover, complementary photochemical approaches are used to achieve rapid and complete sample degradation via radical scission and post-gelation network stiffening when irradiated in the presence of reactive gel precursor. The results herein demonstrate the versatility of this material chemistry to study and direct 2D and 3D cell-material interactions. This work highlights dithiolane-based hydrogel photocrosslinking as a robust method for generating adaptable hydrogels with a range of biologically relevant mechanical and chemical properties that are varied on demand.

Hysteretic energy damage coupled elastoplastic constitutive model and its application to low-cycle fatigue life prediction of martensitic steel

The microstructure of martensitic steel is analyzed by transmission electron microscopy and X-ray diffraction. The low-cycle fatigue (LCF) test of martensitic steel with different strain amplitudes is carried out by MTS universal hydraulic servo testing machine. The damage accumulation and cyclic elastic-plastic constitutive model of martensitic steel are studied. The influence of tempering on hysteretic loop and fatigue damage is discussed. With the tempering temperature increasing, the area of hysteresis loop increase, the hysteresis energy increases, and the fatigue life decreases. According to the fatigue damage accumulation model of the hysteresis energy method, an improved kinematic and isotropic composite hardening model is proposed in tempering temperature. This model is used to simulate the LCF behavior before fracture under LCF load and to predict the fatigue life with the variation of applied strain amplitude and tempering temperature. The verification results show that the modified model can well describe the phenomenon of acceleration of cyclic softening and great reduction of cyclic stress.

Geometric and Material Modelling Aspects for Strength Prediction of Riveted Joints

The aim of this study is to develop a methodology for static strength and failure mode simulation of hot-driven riveted joints. The purpose is to be able to accurately estimate a rivet joint’s static strength behaviour and its failure mode without relying on experiments, to save both time and resources during the design of joints. The non-linear finite element analysis modelling framework considered the rivet joint configurations and geometry, the material properties of the plate and rivet as well as the clamping force of the hot-driven rivet. A ductile damage model was also implemented to capture the stress softening of the materials and the failure modes of the joints. Using experimental data from literature, the modelling framework is validated, and it is shown that it is able to capture the strength behaviour and failure modes of different configurations of rivet joints markedly well. The effect of the rivet pre-load on the mechanical response of the joint is also studied and it is shown that the strength of the joint increased with the increase in rivet pre-load. The modelling framework is then applied to an industrial component. The modelling framework is used to compare welding and riveting as joining methods in a component built in two grades of high-strength steel. It is found that the welded joint possessed greater strength compared to the proposed riveted joint. However, using the proposed simulation methodology developed, a riveted joint with matching strength to the welded joint could be designed.

Plastic deformation behavior of a Cu–10Ta alloy under strong impact loading

In this work, a Cu–10Ta alloy with a copper to tantalum mass ratio of 9:1 is prepared using powder metallurgy technology. Physical properties of the alloy, including density, microstructure, melting point, and constant-volume specific heat, are tested. Via the split Hopkinson pressure bar (SHPB) and flyer-plate impact experiments, the relationship between equivalent stress and equivalent plastic strain of the material is studied at temperatures of 298–823 K and under strain rates of 1 × 10−3–5.2 × 103 s−1, and the Hugoniot relationship at impact pressures of 1.46–17.25 GPa and impact velocities of 108–942 m/s is obtained. Evolution of the Cu–10Ta microstructure that occurs during high-strain-rate impact is analyzed. Results indicate that the Cu–10Ta alloy possesses good thermal stability, and at ambient temperatures of up to 50% its melting point, stress softening of less than 15% of the initial strength is observed. A modified J-C constitutive model is employed to accurately predict the variation of yield strength with strain rate. Under strong impact, the copper phase is identified as the primary source of plastic deformation in the Cu–10Ta alloy, while significant deformation of the high-strength tantalum particles is less pronounced. Furthermore, the longitudinal wave speed D is found to correlate linearly with the particle velocity u upon strong impact. Analysis reveals that the sound speed and spallation strength of the alloy increase with increasing impact pressure.

Effect of the secondary microcontact state induced by the all-factor thermal effect on bidirectional thermal contact performance

Contact interfaces are widespread in electronic systems, and the heat dissipation problem caused by the thermal contact resistance (TCR) has seriously affected the overall performance. Previous studies often disregarded the effect of the secondary microcontact state induced by thermal effects such as thermal stress and thermal softening on thermal contact performance, such as TCR, contact interface temperature distribution nonuniformity (CITDN), and the thermal rectification effect. Therefore, this paper proposes a thermomechanical coupled numerical model that considers the secondary microcontact state induced by all-factor thermal effects, and the effect of the thermal effect on bidirectional thermal contact performance under different temperatures, thermal expansion coefficients and constraints is revealed. Furthermore, a method to control the thermal rectification coefficient by controlling the contact gap was proposed. The results show that the influence of thermal effects on TCR and CITDN at high temperatures, with high thermal expansion coefficients and under strong constraint conditions cannot be disregarded and that the influence of temperature and thermal expansion coefficient on the strong constraint side is greater than that on the weak constraint side. The thermal rectification effect is effectively enhanced by adjusting the initial contact gap determined by the thermal expansion coefficient, elastic modulus and temperature.

Investigation of the relationship between the microstructural evolution mechanism and mechanical properties in hot rolled Fe-0.2C–6Mn–3Al steel

The objective of the present research is to investigate the influence of the microstructural evolution mechanism on mechanical properties during deformation. For this purpose, hot rolled Fe-0.22C-6.12Mn-3.08Al steel is subjected to intercritical annealing at 740 °C for 10 min. The annealed specimen contains a mixture of lath-like α-ferrite and reverted γ, whose volume fraction is approximately 38.7%. During deformation, once the critical stress caused by the severe dislocation pile-ups is reached, the strain/stress-induced phase transformation occurs. First, grain boundaries of γ/α serve as the preferential nucleation sites for fresh α′-martensite. Subsequently, fresh α′-martensite nucleates inside reverted γ. In the meantime, the interfacial α′-martensite grows continuously into the reverted γ interior. During deformation (prestrain at 0.0%, 5.1% and 7.8%), the misorientation (MO) in α-ferrite+α′-martensite continuously rises from 0.63° to 0.67°; nevertheless, the MO in reverted γ increases from 0.65° to 0.73° and then rapidly decreases to 0.69°. Hence, the phase transformation of reverted γ is accompanied by obvious stress softening; thus, effective work hardening occurs in the subsequent deformation region due to α-ferrite and fresh α′-martensite. This phenomenon greatly enhances the strength and delays necking, e.g., the annealed specimen possesses outstanding mechanical properties (992 MPa, 47.6% and 47.2 GPa × %). Once necking occurs, the residual reverted γ is rapidly consumed in the necking region. Hence, the hardness in the necking region (5.31 ± 0.20 GPa) is much higher than that in the uniform deformation region (4.53 ± 0.17 GPa) due to the abundant hard fresh α′-martensite.

Microstructural modeling by anisotropy Cosserat theory for nanotwinned copper

An anisotropy Cosserat continuum model is established for nanotwinned copper by introducing the special orientation relationship between the twin and the matrix. The anisotropy effect induced by the difference in crystal orientation and the strain gradient effect induced by the inhomogeneous deformation between the twin and the matrix in grains are considered. The results obtained by the model with the same parameters of the anisotropy Cosserat elastoplastic constitutive have a good agreement with stress-strain curve of nanotwinned copper collected over different experimental studies with varying twin thickness from 15 nm to 100 nm and coarse grain copper (CG-Cu) with micron level grain size. The effect of twin spacing, twin thickness and preferred orientation on the mechanical performance of nanotwinned copper, such as yield strength, elastic modulus and hardening exponent is systematically studied based on the proposed model. Our results show that the anisotropy effect mainly affects elastic modulus and yield strength, the strain gradient effect affects yield strength and strain hardening rate. The results also demonstrated that appropriate preferred orientation and twin spacing of the nanotwinned copper could make the stress softening or uniform stress distribution by the coordinated deformation between different nanotwinned structures.