Papers by Keyword: Constitutive Model

Abstract: In the constant-temperature indoor environment, the static principles of rubber materials for vibration damping in vehicles and the load and application scope of the experiments are studied in this paper. Basic experiments are carried out for common rubber materials in vehicle system by using advanced experimental equipment.

Abstract: The dynamic mechanical properties of oxygen free copper has been tested under the different strain rate (4700s-1~21000s-1) at the room temperature by split Hopkinson pressure bar (SHPB), the true stress-true strain curves has been obtained. Power-Law constitutive model and Johnson-Cook constitutive model have been built to fit the experimental result from SHPB test of oxygen free copper, meanwhile, the constitutive model can be applied to the simulation analysis of cutting process. The results show that the oxygen free copper is sensitive to the strain rate. In addition, the Johnson-Cook constitutive model predicts the plastic flow stress of the oxygen free copper more accurately than the Power-Law constitutive model at the high strain rate.

Abstract: The AA5083 alloy is already being used in applications that require lightweight construction and moderate strengths. In order to carry out accurate simulations of the superplastic forming of this alloy, the used constitutive models should be able to predict the deformation and thinning behavior during the forming process. In this paper, we compare the dome height and pole thickness evolution during gas bulge forming using different AA5083 constitutive material models. The models considered have different levels of complexity and are fitted using either tensile or biaxial experimental data. The simulation results are also compared with experimental data from literature. In addition, recommendations are made for developing accurate material models for the considered AA5083 alloy.

Abstract: Finite element simulation of high speed machining of Ti6Al4V alloy was carried out based on the software of Abaqus. The Johnson-Cook constitutive model was chosen for the material of Ti6Al4V, the parameters of the model were obtained through the SHPB (Split Hopkinson Pressure Bar) experiment. The similarity of the chips obtained from the simulation and that obtained from the experiment indicated that the parameters of the Johnson-Cook constitutive model for Ti6Al4V alloy were reliable. Different cutting parameters and different tool geometric parameters were used in the simulations to find out their effects to the simulation results. Also a comparison was made between the results got form the simulations results and the experimental results, a good agreement between them indicated that the finite element simulation of high speed machining of Ti6Al4V is reliable, so it can be concluded that the finite element simulations of high speed machining can be widely used in practice to study the more about the machining process and reduce the experimental expenses.

Abstract: 300M ultrahigh strength steel has good mechanical properties. It has been widely used in the force bearing components of aircraft. In this paper, By using Gleeble1-500D thermal simulator, we studied the change regularity of stress-strain curve of 300M steel using hot compression deformation when temperature is from 800°C to1100°C, strain rate is from 0.001 S^-1to 1 S^-1 and the strain is 0.7.The experimental results showed that when the strain rate is constant, the flow stress and the peak stress decrease with the increase of deformation temperature. When the deformation temperature is constant, the flow stress and peak stress increase with the increase of strain rate. From the test, we got the true stress-strain curve, calculated the thermal deformation constants such as the deformation activation energy of 300M ultrahigh strength steel. Eventually, we built the thermal deformation constitutive model in hyperbolic sine form of 300M steel.

Abstract: A coupled model of damage and plasticity is presented to describe the dynamic behaviors of TiC-particulate reinforced titanium matrix composites (TiCp/TMCs) subjected to shock loadings. The TiCp/TMCs are assumed as homogeneous continuum with pre-existing micro-cracks and micro-voids. Damage to TiCp/TMCs is caused due to micro-crack nucleation, growth and coalescence, and defined as the probability of fracture at a given crack density. In terms of crack growth model, micro-cracks are activated, and begin to propagate gradually. When crack density reaches a critical value, the smashing destroy takes place. The model parameters for TiCp/TMCs are determined using plate impact experiments. Comparison with the test results shows that the proposed model can give consistent predictions of the dynamic behaviors of TiCp/TMCs subjected to impact loadings.

Abstract: This research aims at analyzing and optimizing the hydroforming process parameters to achieve a sound bulged tube without failure. Theoretical constitutive model is formulated to build up a working diagram including process window, which is used to optimise the process parameters and predict the formability and the failure of the tube accurately. The model is validated using the published experimental and analytical results of previous research works for 37% bulging ration of low carbon steel (C1010). The model gave a very good agreement with the published data.

Abstract: In this paper, according to the principle of building the constitutive model of polymer material, the one-dimensional structure of the ZWT material constitutive model is added to dashpot element in parallel, and in which strain rate and coefficient of viscosity is introduced and the nonlinear viscoelastic constitutive model of Polycarbonate material is achieved. Additionally, tensile test at low strain rate and Hopkinson test at high strain rate of polycarbonate material are carried out, and the change rule of yield strength of polycarbonate material is obtained both at high strain rate and low strain rate. According to the experimental data, the parameters of the constitutive model have been optimized and fitted using ant colony algorithm, and then the fitted results are compared with experimental results. The comparative results show that the improved ZWT constitutive model can reasonably represent the nonlinear characteristics of polycarbonate material at different strain rate.

Abstract: To explore the thermo-mechanical response of H96 brass alloy, the quasi-static (universal-testing machine) and dynamic (the split Hopkinson pressure bar apparatus) uniaxial compression experiments have been performed under the temperatures from 293 K to 873 K and the strain rates from 0.001 s^-1 to 6000 s^-1, and the strains over 60% are obtained. Results show that, H96 brass alloy has strong strain hardening behavior, and it becomes weaker with the increasing temperature. In addition, this alloy is sensitive to strain rates; and, it has temperature sensitivity, the dynamic strain aging occurs at the temperature of 473 K and a quasi-static strain rate of 0.001 s^-1. Based on the thermal activation dislocation mechanism, paralleled with the experimental results, a plastic flow constitutive model with the physical conception is developed. The model is suitable to predict the plastic flow stress at different temperatures and strain rates. According to comparing results, the model predictions are in good agreement with the experimental results.

Abstract: In constitutive models of polymers, there has been a long history of the use of strain-rate dependent viscous processes, such as the Eyring and Argon models. These are combined with elastic elements to generate viscoplastic models that exhibit typical phenomena such as rate dependent yield, creep and stress relaxation. The Eyring process is one of the most frequently used such mechanisms. It has two significant drawbacks: it implies a temperature dependence of mechanical behaviour that is in an opposite sense to that observed; and it predicts a strain rate dependence of yield stress that is less complex than that observed, leading to the requirement for two or more Eyring processes. In recent years, new ideas for amorphous polymers have been developed that lead to an alternative plastic mechanism that addresses these concerns. In this paper a constitutive model that incorporates this mechanism is developed, and its effectiveness in modelling macroscopic mechanical behaviour of polymers is explored with respect to published data.