Numerical simulation of multi-hit impact on Ceramic/Composite armor

The numerical simulation of ballistic multi-hit impact on ceramic/composite armors is very challenging. The damage introduced by the previous hit affects the performance of the armor. In composite backings the damage is often more diffused than for metallic backings. Moreover, different sources of damage can intervene within the composite material. The present work proposes a mesoscopic scale approach to assess these issues. The 2D woven material is modelled with beams elements embedded in volume elements. Each component has its own material constitutive law and its damaging law. This approach allows to better model the damaging of the material, but also to better identify the material parameters from a set of basic experiments.

Likely equilibria of the stochastic Rivlin cube

The problem of the Rivlin cube is to determine the stability of all homogeneous equilibria of an isotropic incompressible hyperelastic body under equitriaxial dead loads. Here, we consider the stochastic version of this problem where the elastic parameters are random variables following standard probability laws. Uncertainties in these parameters may arise, for example, from inherent data variation between different batches of homogeneous samples, or from different experimental tests. As for the deterministic elastic problem, we consider the following questions: what are the likely equilibria and how does their stability depend on the material constitutive law? In addition, for the stochastic model, the problem is to derive the probability distribution of deformations, given the variability of the parameters. This article is part of the theme issue ‘Rivlin's legacy in continuum mechanics and applied mathematics’.

Evaluation of Rotation Capacity of RHS Aluminium Alloy Beams by FEM Simulation: Temper T6

The aim of this work is the numerical assessment of the ultimate behaviour of aluminium alloy beams subjected to non-uniform bending. An extensive numerical analysis has been performed by means of FE code ABAQUS with reference to RHS sections considering different values of the main geometrical and mechanical parameters. In particular, regarding the geometrical parameters the flange slenderness, the flange-to-web slenderness ratio and the moment gradient parameter have been considered. In particular, their influence on the ultimate behaviour of such beams has been investigated by adopting the material constitutive law proposed by Eurocode 9 based on the Ramberg-Osgood model. The investigations concern these parameters considered separately as well as their interaction. The results are herein reported with reference to temper T6 and show the importance of the investigated parameters on the buckling strength and the rotational capacity of aluminium alloy beams. Temper T6 gives rise to a quite low hardening compared to temper T4, which is analysed in a companion paper.

Modelization and Validation of Ti-6Al-4V Alloy Material Constitutive Law for Isothermal Forging Process

Isothermal forging is a near-net shape forming technology for manufacturing complex titanium alloy components. In order to characterize the workability of Ti-6Al-4V alloy during isothermal forging process, the material properties of Ti-6Al-4V alloy were investigated by isothermal compression tests under different strain rate-temperature, where the temperature range is 850~1000 °C and strain rate range is 0.001~0.05s−1. The obtained flow stress-strain data was used to develop the Arrhenius constitutive model of which material constants considered the compensation of strain. The developed constitutive model was used to simulate the isothermal forging process of Ti-6Al-4V alloy component by finite element (FE) based numerical method. The metal flow and potential defect locations were predicted by numerical simulation. Furthermore, the relevant simulation results were compared with the product in industrial workshop to demonstrate the validity of material constitutive model. Keywords: Isothermal forging; Ti-6Al-4V alloy; Hot compression test; Arrhenius constitutive model; FE analysis; Model validation;

Identification of Material Constitutive Laws Representative of Machining Conditions for Two Titanium Alloys: Ti6Al4V and Ti555-3

Determining a material constitutive law that is representative of the extreme conditions found in the cutting zone during machining operations is a very challenging problem. In this study, dynamic shear tests, which reproduce, as faithfully as possible, these conditions in terms of strain, strain rate, and temperature, have been developed using hat-shaped specimens. The objective was to identify the parameters of a Johnson–Cook material behavior model by an inverse method for two titanium alloys: Ti6Al4V and Ti555-3. In order to be as representative as possible of the experimental results, the parameters of the Johnson–Cook model were not considered to be constant over the total range of the strain rate and temperature investigated. This reflects a change in the mechanisms governing the deformation. The shear zones observed in hat-shaped specimens were analyzed and compared to those produced in chips during conventional machining for both materials. It is concluded that the observed shear bands can be classified as white-etching bands only for the Ti555-3 alloy. These white bands are assumed to form more easily in the Ti555-3 alloy due to its predominately β phase microstructure compared to the Ti6Al4V alloy with a α + β microstructure.

Identification parameters of material model and large deformation analysis of inflated air-spring shell made of rubber-textile cord composite

In the paper an orthotropic hyperelastic constitutive model is presented which can be applied to numerical simulation for the response of biological soft tissue and of the nonlinear anisotropic hyperelastic material of the cylindrical air-spring shell used in vibroisolation of driver's seat. The parameters of strain energy function of the proposed constitutive model are fitted to the experimental results by the nonlinear least squares method. The deformation of the inflated cylindrical air-spring shell is calculated by solving the system of five first-order ordinary differential equations with the material constitutive law and proper boundary conditions. Numerical results of principal stretches and deformed profiles of the inflated cylindrical air-spring shell obtained by numerical deformation analysis are compared with experimental ones.