Modelling and numerical analysis of heat treatments on aluminium parts

Abstract

SUMMARYA theoretical model suitable for the modelling and analysis of heat treatment problems is described. The presented formulations are implemented incrementally with a non-linear rate-dependent constitutive model, adequate to the simulation of a wide range temperature processes. The large deformation model is based on the additive decomposition of the strain rate tensor in elastic, thermal and viscoplastic parts. The flow rule is a function of the equivalent stress and the deviatoric stress tensor of the temperature field and of a set of internal state variables. The thermal problem is solved by a prediction/correction algorithm. The prediction, which uses a semi-implicit integration, provides a first estimation of the temperature field. The correction stage, performed with a Newton-Raphson implicit scheme, improves the solution until a satisfactory result is found. The thermomechanical coupled problem is solved with a staggered approach. The finite element formulations for coupled analysis of deformation and heat transfer given in this article are validated and applied to the process of quenching of aluminium parts into boiling water.

Time transient validation of residual stress prediction models for aluminium alloy quenching

“…In previous residual stress prediction models of rectilinear product forms published by many different research groups, [1][2][3][4][5] it has been assumed that a single time transient heat transfer coefficient curve could be used to predict cooling at all of a part's external surfaces. From residual stress measurements recorded and compared with predicted values, this approach has been clearly validated in the literature.…”

“…With the development of commercial finite elements packages, a number of researchers have developed models to predict this inherent stress distribution. [1][2][3][4] This information can then be used to develop methods of reducing residual stress during the quenching step by varying the quenchant type/temperature; improving methods of reducing residual stress during post-quench cold work (stretching/compression); and predicting the most reliable machining strategies to reduce distortion.…”

Numerical analysis of different heating systems for warm sheet metal forming

“…Therefore a prediction/ correction algorithm type is proposed in this work to solve the non-linear heat problem. In the prediction phase, an explicit/semi-implicit algorithm (α<1) is used to solve the thermal problem combined with an r minstrategy to control the size of the time increment [42,43]. The obtained solution is used to define the initial guess for the correction phase (α = 1).…”

Sensitivity of material properties on distortion and residual stresses during metal quenching processes

“…Instead of using the coefficient of thermal expansion (Smoljan, 2002;Andrade-Campos et al, 2007), E tp is expressed in terms of reference density R and current density (Â, f j ) of the mixture…”