J. Ma¹, H. Lu¹, B. Wang¹, S. Roy¹, R. Hornung², A. Wissink², R. Komanduri^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 135-152, 2005, DOI:10.3970/cmes.2005.008.135

Abstract In the simulation of a wide range of mechanics problems including impact/contact/penetration and fracture, the material point method (MPM), Sulsky, Zhou and Shreyer (1995), demonstrated its computational capabilities. To resolve alternating stress sign and instability problems associated with conventional MPM, Bardenhagen and Kober (2004) introduced recently the generalized interpolation material point (GIMP) method and implemented for one-dimensional simulations. In this paper we have extended GIMP to 2D and applied to simulate simple tension and indentation problems. For simulations spanning multiple length scales, based on the continuum mechanics approach, we present a parallel GIMP computational method… More >

G. Himpel, E. Kuhl, A. Menzel, P. Steinmann¹

CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 119-134, 2005, DOI:10.3970/cmes.2005.008.119

Abstract The changing mass of biomaterials can either be modelled at the constitutive level or at the kinematic level. This contribution attends on the description of growth at the kinematic level. The deformation gradient will be multiplicatively split into a growth part and an elastic part. Hence, in addition to the material and the spatial configuration, we consider an intermediate configuration or grown configuration without any elastic deformations. With such an ansatz at hand, contrary to the modelling of mass changes at the constitutive level, both a change in density and a change in volume can More >

B. Chrasekhar¹, S. M. Rao²

CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 105-118, 2005, DOI:10.3970/cmes.2005.008.105

Abstract In this work, a simple, robust, and an efficient numerical algorithm to calculate the scattered acoustic fields from complex shaped objects such as aircrafts and missiles, subjected to a plane wave incidence is presented. The work is based on the recently proposed method of moments (MoM) and the potential theory, unlike the standard Helmholtz integral equation (HIE) solution method. For the numerical solution, the scattering structure is approximated by planar triangular patches. For the MoM solution of complex bodies involving open/closed/intersecting surfaces, a unified set of basis functions to approximate the source distribution is defined. More >

Charles E. Anderson, Jr.¹, Matthew S. Burkins², James D. Walker¹, William A. Gooch²

CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 91-104, 2005, DOI:10.3970/cmes.2005.008.091

Abstract A modification of Wilkins computational ceramics model is used to simulate experiments of the impact of the APM2 bullet against boron carbide/aluminum targets. Flash radiography provides time-resolved penetration histories. The simulation results are compared to the experimental data; generally, agreement is very good, including capturing dwell and then the onset of penetration. Crater width and debris diameter are also reproduced by the simulations reasonably well. A critical discussion of deficiencies of this computational engineering model is provided. More >

Y. Tomita ¹, M. Uchida ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 239-248, 2005, DOI:10.3970/cmes.2005.010.239

Abstract In this study, we clarified the micro- to mesoscopic deformation behavior of a semicrystalline polymer by employing a large-deformation finite element homogenization method. The crystalline plasticity theory with a penalty method for the inextensibility of the chain direction and the nonaffine molecular chain network theory were applied for the representation of the deformation behavior of the crystalline and amorphous phases, respectively, in the composite microstructure of the semicrystalline polymer. The 3D structure of lamellae in the spherulite of high-density polyethylene was modeled, and the tensile and compressive deformation behaviors were investigated. A series of computational More >

H. Okada ¹, T. Kamibeppu ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 229-238, 2005, DOI:10.3970/cmes.2005.010.229

Abstract In this paper, a three-dimensional VCCM (Virtual Crack Closure-Integral Method) for evaluating the energy release rate and the stress intensity factor is presented. Many engineers and researchers believe that hexahedral finite elements should be used to perform three-dimensional fracture analyses. Previous VCCM formulations assume the use of hexahedral finite elements. In present study, the authors have been developing a VCCM that works with tetrahedral finite elements. In the field of large-scale computation, the use of tetrahedral finite elements has becoming very popular as high performance mesh generation programs became available. Therefore, building a large and More >

M. Akamatsu¹, K. Nakane², N. Ohno^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 217-228, 2005, DOI:10.3970/cmes.2005.010.217

Abstract In this study, a fully implicit integration scheme is developed for a nonisothermal viscoplastic, nonlinear kinematic hardening model. Nonlinear dynamic recovery in addition to strain hardening is assumed for the evolution of multiple back stresses so that ratcheting and mean-stress relaxation can be properly simulated. Temperature dependence of back stress evolution is also taken into account in the constitutive model. By discretizing a set of such advanced constitutive relations using the backward Euler method, a tensor equation is derived and linearized to iteratively achieve the implicit integration of constitutive variables. The fully implicit integration scheme More >

Toshihisa Nishioka ¹,

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 209-216, 2005, DOI:10.3970/cmes.2005.010.209

Abstract Recent Advances in Numerical Simulation Technologies for Various Dynamic Fracture Phenomena are summarized. First, the basic concepts of fracture simulations are explained together with pertinent simulation results. Next, Examples of dynamic fracture simulations are presented. More >

Michihiko Nakagaki¹, Shuji Takashima², Ryosuke Matsumoto¹, Noriyuki Miyazaki²

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 199-208, 2005, DOI:10.3970/cmes.2005.010.199

Abstract The present paper focuses on the micromechanical phenomena occurring in the polycrystalline metal materials. Correlations between the material hardening and the plastic lattice dislocation were discussed with the presence of the grain boundary. The characteristic distribution of the plastic strain gradient is numerically recognized, and hence the validity of incorporating the strain gradient term in the constitutive law is demonstrated. Also, the modeling of the inclusion interface sliding and debonding was performed on the equivalent inclusion theory to develop the constitutive law for the composite. The sliding model is considered to be effective to model More >

R. Matsumoto, M. Nakagaki

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 187-198, 2005, DOI:10.3970/cmes.2005.010.187

Abstract Large-scale molecular dynamics simulations of tensile deformation of amorphous metals containing a nano-crystalline particle were performed in order to clarify the effects of particle size and crystal volume fraction on the deformation mechanism and strength. It became clear that particle size has very little effect, while crystal volume fraction has a substantial influence. Elastic modulus and flow stress intensify as crystal volume fraction increases. Furthermore, the stress in the crystal phase continues to increase, even after yielding in the amorphous phase. Consequently, work-hardening effects appear, preventing localization of plastic deformation. Thus, the dispersed nano-crystalline particles… More >