Papers by Keyword: Unit Cell Model

Abstract: Aim of this study is to describe the ductile damage of metastable austenitic steels which show TRansformation Induced Plasticity (TRIP). Therefore, a criterion for the austenite to martensite transformation, the caused additional hardening and evolution equations for the TRIP-strain are incorporated into the damage model of Rousselier. As a first approach, the model is calibrated against unit cell simulations of the porous material for different stress triaxialities.

Abstract: The main aim of the paper is an estimation of the macroscopic mechanical properties of particulate composites using numerical methods. Matrix of the considered composite was cross-linked polymethyl methacrylate - PMMA in a rubbery state, which exhibits hyperelastic behaviour. The three parameter Mooney Rivlin material model, which is based on the strain energy density function, was chosen for description of the matrix behaviour. Alumina based particles (Al₂O₃) were used as a filler. Numerical modelling based on the finite element method (FEM) was performed to determine stress-strain curve of the considered particulate composite. Representative volume element (RVE) model was chosen for FE analyses as a modelling approach of a composite microstructure. Various geometry arrangements of particles and various directions of loading have been considered and composite anisotropy has been investigated. A good agreement between numerical calculations with damage model and experimental data has been found and the described method may have a great potential for numerical modelling of composite behaviour and design of new particulate composite materials.

Abstract: Based on micro structure of Ni-based single crystal superalloy, a γ/γ’ two-phase unit cell finite element model was established, and its cyclic stress-strain was simulated under tension/torsion cyclic loading. A low cycle fatigue (LCF) life prediction model of single crystal superalloy was proposed by using cyclic plasticity strain energy as a parameter based on energy dissipation theory. Calculation results of macro finite element model and γ/γ’ two-phase unit cell micro finite element model, and multiaxial LCF test data of CMSX-2 Ni-based single crystal superalloy along [001] orientation were applied to fit the LCF life model by multiple linear regression. The results show that the unit cell model not only reflects the microstructure characteristics of single crystal Ni-based superalloy, but also is better than the macro model in accuracy of analysis, and greatly improve the accuracy of fatigue life prediction. Almost test data fall into the factor of 2.0 scatter band.

Abstract: Based on three dimensional cubic unit cell models containing several particulates with certain particulate arrangements, the monotonic tensile and uniaxial ratcheting behaviors of particulate reinforced metal matrix composites (i.e., T6-treated SiCP/6061Al composites) were numerically simulated by using elastic-plastic finite element code ABAQUS with help of newly developed user material subroutine (UMAT). In the simulations, the effects of different particulate arrangements inside the unit cell models on the monotonic tensile and ratcheting behaviors of the composites were discussed. It is shown that the effect of particulate arrangement on the ratcheting of the composite depends on the arranged modes and the number of particulates contained in the model, and the interaction between particulates can be represented reasonably by the cubic unit cell model with a suitable distribution of multi-particulates.

Abstract: A numerical study on the effects of the distribution of rubber particles size on the fracture toughness of rubber-modified polymer alloys was computed. FEM analyses were conducted on the deformation field near the crack tip under mode I for small scale yielding condition. Near the crack tip is modelled as composite of matrix materials and rubber particles. On the other hand, outer region is modelled as homogeneous material whose constitutive equation has been obtained by analysing unit cell model of matrix and rubber particle. Perfect bonding or partial debonding of the interface is assumed in the computation. Matrix and rubber particles are treated as Mises and Mooney-Rivlin materials, respectively. It is shown that energy flux into fracture process zone; Ĵ -integral is smaller for bimodal type than monomodal one. This behavior largely occurred on the partial debonding case. These results imply that the screening effects occurred in the bimodal type larger than monomodal one.