Purpose Finite Element Analysis Research Articles

An induction heating process with coil design and solutions avoiding coarsening phenomena of Al-6 Pct Si-3 Pct Cu-0.3 Pct Mg alloy for thixoforming

During the thixoforming process, it is very important to obtain a uniform temperature, which affects the uniformity of the solid fraction, throughout the billet. Consequently, a heating method that can provide a suitable temperature profile throughout the billet must be chosen. Other parameters that must be considered include heating time (in order to minimize the total processing time), the level of control, and temperature consistency. An optimal design of the induction coil has been identified that best meets these criteria. In a previous study, the theoretical optimal coil design was verified through the FEM simulation of the induction heating process by using a general purpose finite element analysis code, ANSYS. So, in this study, the suitability of the coil design was also demonstrated by conducting induction-heating experiments. The optimal reheating conditions to apply the thixoforming (thixoforging and semisolid die casting) process were investigated by varying the reheating time, the holding time, the reheating temperatures, the capacity of the induction heating system, and the size of the adiabatic material. The final holding time was observed to be the most important factor in obtaining a fine globular microstructure and to prevent coarsening in the three-step reheating process.

Finite Element for Anchored Bars under Cyclic Load Reversals

The hysteretic behavior of reinforced concrete elements depends in large measure on the interaction between reinforcing steel and concrete through bond. This paper presents a new finite element for reinforcing bars anchored in concrete. The novel aspect of the element is the use of force instead of displacement interpolation functions. The force interpolation functions satisfy equilibrium in a strict sense and ensure the numerical stability of the results, even in the presence of significant strength loss and softening, as might be the case for reinforcing bars with insufficient anchorage length. Another novel aspect of the element formulation is its implementation in a general purpose finite element analysis program that is based on the stiffness method of analysis. Correlation studies with available experimental data demonstrate the ability of the proposed model to simulate the bond deterioration and eventual pull-out of anchored reinforcing bars under severe inelastic excursions.

Homogenization Method for Dynamic Viscoelastic Analysis of Composite Materials.

In this paper we propose a new homogenization method for composite materials in order to predict effective dynamic viscoelastic material properties in the frequency domain. The loss tangent, which is the ratio of storage modulus to loss modulus, is an important design variable for products made of viscoelastic materials. The proposed procedure, by which it is possible to compute the effective loss tangent of composite materials with periodic structure, is implemented in a homogenization analysis system based on the general purpose finite element analysis code, ABAQUS. The results of the numerical analysis are very close to experimental results which are obtained by using a rubber composite containing a stiff rubber and a soft rubber.

Failure Prediction for Cross-Rolled Beryllium Sheet Material

A failure model for cross-rolled beryllium SR-200 sheets is developed for material loaded in a complex state of stress. Coefficients of the Tsai-Wu criterion are determined from a series of special laboratory experiments. Tests include circular plates loaded by a concentric ring, as well as in-plane compression and off-axis plate specimens. Complex states of stress lead to brittle failure of the anisotropic material. Failure surfaces obtained from the criterion form a family of ellipses when plotted in standard Cartesian coordinates. The criterion is incorporated into a general purpose finite element analysis code. Numerical simulation incrementally applies loads to a structural component that is being designed and checks each nodal point in the model for exceedance of the failure criterion. To demonstrate applicability of the predictive capability of the criterion, a 2.54-mm thick beryllium plate is placed under clamped edge conditions and loaded to failure by a central transverse point load. A numerical model of the structure predicts the failure load to within three percent.

Homogenization Method for Analysis of Dynamic Viscoelastic Properties of Composite Materials.

In this paper, we propose a new homogenization method for composite materials in order to predict effective dynamic viscoelastic material properties in the frequency domain. The loss tangent, which is the ratio of storage modulus to loss modulus, is an important design variable for products made of viscoelastic materials. The proposed procedure, which makes it possible to compute the effective loss tangent of composite materials with periodic structure, is implemented in a homogenization analysis system based on the general purpose finite element analysis code, ABAQUS. The results of the numerical analysis are very close to experimental results obtained using rubber composite containing a stiff rubber and a soft rubber.

A {1,2}-order theory for elastodynamic analysis of thick orthotropic shells

A higher-order shell theory is developed for elastodynamic analysis of orthotropic shells. The theory accounts for all basic deformations including transverse shear and transverse normal strains and stresses. The theory is developed in orthogonal curvilinear coordinates in which the reference surface components of the displacement vector vary linearly through the thickness while the transverse displacement is parabolic. Transverse shear and transverse normal strains are formulated to satisfy physical traction conditions at the top and bottom shell surfaces, and are also made least-squares compatible with the corresponding strains that are derived directly from the strain-displacement relations of three-dimensional elasticity. In these variational statements of strain compatibility, transverse shear and transverse normal correction factors are introduced, and are determined from dynamic considerations in the manner originally proposed by Mindlin. Equations of motion and associated engineering (Poisson) boundary conditions are derived from a three-dimensional variational principle. An important feature of the present theory is the requirement of only simple C0 and C−1 continuity for the shell kinematic variables. This aspect makes the theory particularly attractive for the development of efficient shell finite elements suitable for general purpose finite element analysis of thick shell structures. Analytical solutions for the free vibration of isotropic and orthotropic cylindrical shells are obtained for a wide range of thickness/radius and thickness/wavelength ratios and found to be in close agreement with the exact elasticity solutions.

Generalized viscoelastic model for creep analysis coupled with plastic deformation

AbstractA creep analysis capability, using a generalized viscoelastic model, is introduced to process the creep behaviour coupled with elastoplastic deformation. The formulation is based on the step‐by‐step time integration of the Kelvin‐Maxwell rheological model with non‐constant parameters.The concept of a rheological model is extended to the multiaxial stresses by the Prandtl‐Reuss stress‐strain relationship, from which the tangential stiffness matrix is formed for Newton's iteration. If the plastic deformation is coupled with creep, the algorithm will seek a solution in two distinct steps. Various choices of empirical creep laws are available and small variations in temperature are allowed as implemented in the general purpose finite element analysis program.

Automated metalforming modeling utilizing adaptive remeshing and evolving geometry

An automated modeling system for the numerical analysis of two-dimensional metalforming problems is presented. The procedure combines an automatic mesh generator, geometry tracking procedures, and adaptive mesh refinements with the analysis capabilities of a general purpose finite element analysis program to provide a system that accepts a geometry-based problem definition as input and produces the complete simulation results as output.

The application of nonlinear analysis techniques to practical structural design problems

This paper treats two distinct types of commonly occuring structural nonlinear phenomena within the framework of finite element methods. The first is associated with the diagonal tension behavior of stiffened thin-skin structural components, and the second is concerned with the variable contact between two deformable surfaces. The methodology associated with each problem area is presented in a concise manner. Application to practical design problems illustrate the usefulness of the methods. Their implementation in the flow of a general purpose finite element analysis program is also discussed.