Papers by Keyword: Constitutive Model

Abstract: This paper has established a viscoelasticplastic constitutive model for A7N01T6 alloy welding, which is temperature and deformation history dependent. The model uses elasticmixed hardening plastic and creep equation to describe the strain hardening at low temperatures and strain softening at high temperatures, respectively. Then it is applied for finite element numerical simulation of the welding process. By comparison with the conventional temperature dependent elasticperfectly plastic model, the overall longitudinal residual compressive plastic strain and the maximum deformation of welding sheet are larger. This is because that the plastic strain is mostly produced in high temperature range. Strain softening has great influence on the evolution of plastic strain. The compressive plastic strain during heating is larger than the tensile plastic strain during cooling. Strain hardening effect on welding residual strain and stress is almost negligible. Using the established constitutive model, welding residual stress and strain are in good agreement with the theoretical results.

Abstract: Hot forming process with synchronous cooling is implied to improve the formability of lightweight materials with poor forming performance at room temperature. Its applicability for 6181 H18 aluminum alloy was investigated in this paper, inspired by ultrahigh strength steel hot stamping method. Uniaxial tensile test at elevated temperature with various strain rates were carried out to obtain the constitutive model for simulation and determine the parameters for further orthogonal test. The influence of temperature, holding time and cooling rate on formability and mechanical properties in the hot forming process with synchronous cooling was discussed. An optimized combination of process parameters was obtained which increased its tensile strength and elongation remarkably.

Abstract: Uniaxial tensile deformation behavior of 2024 H18 aluminum sheet alloys was studied in the hot forming process with synchronous cooling temperature range of 300°C~475°C and in the strain rate range of 0.0005/s~0.1/s. The effects of temperature and strain rate on stress, elongation to facture were analyzed. And a constitutive model was proposed to describe the relationship of true stress-true stain by multiple linear regression analysis. It was found that the forming temperature and strain rate have great effect on the hot forming behavior of the alloys. The max stress reduced greatly with the increasing of temperature or reducing of strain rate, while the tensile elongation tended to rise first and then fall with the increasing of temperature and strain rate. The forming of 2024 H18 aluminum alloy at elevated temperature occurred with the strain hardening and dynamic softening. The constitutive model of 2024 H18 aluminum alloy agrees well with the experimental data.

Abstract: Through a series of drainage analysis of plane strain compression tests on the Toyoura sand under different stress path, we found that the plastic shear strain and stress path of great relevance. But due to that a yield locus represents a specific yield level and usually do not related with stress paths, the hardening parameter of the parametric should also has nothing to do with the stress path. This article based on the analysis of the laboratory test results, put forward a stress path-independent plastic shear strain energy modified function as shear yield hardening parameters. Then based on the above type of energy state function proposed to build a sandy soil elasto-plastic constitutive model, and compared with corresponding numerical calculation results to make an effective verification.

Abstract: Application of super elasticity theory and nonlinear theory, based on finite element method and the Abaqus software, the performance of Y ring rubber seal, such as the Von Mises stress, the sealing ring deformation and the contact pressure were simulated and analyzed under the influence of changeable hydraulic pressure. According to seal failure criterion, the effect of hydraulic pressure changes on the sealing performance were studied. Results show that, the maximum stress appears in the intersection of lips, the largest deformation area near the inner lip. The root has greater contact pressure, which would result in bitten phenomenon or aggravate wear.

Abstract: Different confined concrete models and their influences on column lateral load-deformation relations are compared and studied in this paper. The analytical results show that models have remarkable discrepancies on the descending branch of constitutive curves, and these discrepancies are weakened in predicting of column lateral load-defromation curves due to eccentric compression of confined concrete.

Abstract: Based on the statistical damage theory and the experimental phenomena, the statistical damage constitutive model for concrete under biaxial tension is proposed. The two meso-scale damage modes, rupture and yield are considered, and the whole damage evolution process is driven by the principal tensile damage strain. The results show that the proposed statistical damage model can accurately predict the constitutive behavior in the uniform damage phase for concrete under biaxial tension. The damage mechanism is discussed in the view point of biaxial strength and deformation properties.

Abstract: Starting from the thermodynamics, model of frozen soil is studied by energy dissipation theory and the inside and outside the state variables is given under isothermal conditions. Damage of frozen soil is re-flecked by effective stress and damage tensor in Damage Mechanics. Dissipation function is in form of plastic dissipation function (DP yield criterion) and the damage dissipation function. And plastic dissipation function is coupled of the damage variable. Through the elastic-plastic and damage evolution, frozen soil incremental elastic-plastic damage constitutive model is made. And finite element scheme is given.

Abstract: The tensile properties of alloy steel 35CrMoA were measured by dynamic tension experimental apparatus, and the stress-strain curves of the material at strain rate range from 10^-2/s to 10³/s were obtained. The fracture appearance and metallurgical structure were observed for the recovered specimens. The influence of strain rates on mechanical properties and microstructure of the 35CrMoA steel was analyzed. Based on the experimental data of mechanical properties, the JC constitutive parameters were fitted for 35CrMoA.

Abstract: An improved dynamic constitutive model is presented, aiming to describe the key mechanical properties and predict the bearing strength of concrete structure under static and dynamic load. This model is based on the concept of equivalent uniaxial strains and strain rate. In this paper, an equivalent uniaxial stressstrain curves are obtained by the WillamWarnke curve and take the same form as in Saenz models. Then, the bending strength of a concrete beam under different static and dynamic load was discussed.