Papers by Keyword: Phenomenological Model

Abstract: We study ultrafast magnetization dynamics induced by laser heating using various phenomenological temperature models. The temperature dynamics of the electrons, spins and lattice for thin foils is investigated. Numerical results for the temperature and magnetization dynamics for them are compared with those available in the literature.

Abstract: The crystal plasticity (CP) model is widely used in many applications to link microstructure and mechanical properties. There are varying CP constitutive laws with phenomenological or physical-based formulation to cover a large range of loading conditions. In order to predict the deformation behavior of an Al alloy during the sheet metal forming process with either linear or non-linear strain path, both phenomenological and physical-based CP constitutive laws have been chosen, and the prediction performance of both models is compared. For the linear loading condition, the uniaxial tensile tests are performed on the smooth-dog-bone (SDB) specimens along rolling and transverse directions (RD/TD). The non-linear strain path is achieved by the Marciniak testing followed by uniaxial tension. In the first stage, the Marciniak testing is performed under the stress states of RD-uniaxial, plane strain, and biaxial tension. After being loaded to a certain strain level, mini-SDB specimens are cut along RD and TD from the uniform deformation region and reloaded under RD-uniaxial tension. The digital image correlation (DIC) technique is employed to measure the strain during testing. The electron backscatter diffraction (EBSD) technique is used to characterize the initial microstructure as well as the microstructure evolution of the specimens after the first stage loading in the non-linear strain path. A phenomenological power law and a dislocation-density-based hardening law have been employed in this study. The parameters are calibrated based on the flow curve of the RD uniaxial tension. The model performance is validated by stress–strain response under all the rest loading conditions including the non-linear loading path.

Abstract: A phenomenological model presented by the authors in the previous study, which is a kind of two-region exponential function model, is used to describe flow stress behaviors of bearing steel, STB2. In this model, flow stress is calculated using two separated equations for hardening and softening regions. Peak stress, peak strain, hardening coefficient, steady state stress and softening coefficient are the required parameters for the model. These parameters are then either interpolated using linear regression or used to find some fitted functions of strain rate and temperature to identify the flow stress. The former is called the piecewise bi-linear function model (PLF model) while the latter the closed-form function model (CFF model). It has been shown that the flow stress curves of STB2 steel obtained by these two models are in good agreement with experimental results.

Abstract: The obtained phenomenological model of hardening G3Si1 and Sb08-G2S low-carbon welding wire during multistage drawing establishes the dependence of the hardening curve coefficients (hardening index and hardening modulus) on the integral tensile strain. The obtained model makes it possible to calculate the hardening curve, strength, and plasticity indicators of metal products based on the results of wire rod testing in the delivery state.

Abstract: Increase in engine speed increases the in-cylinder turbulence and hence the rate of mixing. However, it is difficult to directly measure the mixing rate and relating its effect on emissions. Hence, in this paper, the comparison of mixing rate at different engine speeds are demonstrated with a multi-zone phenomenological model which has been developed and validated on a wide range of engine operating conditions. The mixing rate is evaluated using a standard quasi-dimensional k-ε formulation. The quantitative predictions of mixing rates at different engine speed substantiate the cause of soot emission reduction at higher engine speed.

Abstract: This paper presents measurement of tensile proprieties of thermoplastics by digital image correlation method. The objectives are to characterize based on experimental data the pre-and post-yield regime of polyvinylchloride (PVC) under uniaxial tension and to investigate the rate-dependent large deformation behaviour over crosshead speeds of 1, 5 and 25 mm/min respectively. The true strain-stress curves of PVC tested with different loading speeds are experimentally obtained and based on these a phenomenological constitutive model is implemented. The theoretical material model considers the variation of strain rates due to the inhomogeneous deformation behaviour of thermoplastic polymer and includes six parameters (material constants) to be identified according to the experimental results. It can be found that the effect of the strain rate on the true stress strain curves is small for lower strain rates but cannot be ignored for higher strain rate.

Abstract: Based on phenomenological method, the paper carried out experimental study for a kind of typical bolted joint structure, three kinds of testing specimens was designed, from the test result, the phenomenological model was obtained and the nonlinear mechanics behavior was comprehended, at last, the phenomenological model was verified experimental and numerical

Abstract: The use of shape memory alloys (SMA) in an increasing number of applications in many ¯elds of engineering, such as biomedical engineering, is leading to a growing interest toward an exhaustive modeling of their macroscopic behavior in order to construct reliable simulation tools for SMA devices. In this paper we review a robust three-dimensional model able to reproduce both pseudo-elastic and shape-memory behaviors and we report numerical studies where it is used for the simulation of SMA-based biomedical devices.