A study of casting distortion and residual stresses in die casting
The use of numerical methods to analyze the design and performance of mechanical components has been widely used in industry for many years. The results obtained have been used to improve the design of the products by providing useful insights into the critical areas of the component during operation. However, the numerical analysis of the manufacturing process that integrates machine, tooling and products has not been widely done due to the greater complexity of the physical phenomena involved. This dissertation work presents a computer modeling methodology developed to predict the final dimensions and residual stresses in a die casting. The determination of the mechanical properties of the casting material needed for the computer model is also presented here. Furthermore, to validate the adequacy of the modeling methodology computer model predictions are compared against experimental measurements taken on productions castings. The methodology uses the finite element method to analyze the solidification and cooling conditions of a casting during the die casting process. An innovative method that uses a shell mesh is presented that allows tracking the elastic deflections in the die cavity resulting from the die casting process loads. A fully coupled thermal-mechanical analysis was done to model the die casting process. The finite element model was solved using the finite element package Abaqus. The determination of the casting constitutive model was done as part of this dissertation work. Tensile bars made of die casting aluminum alloy A380.0 in compliance with industrial testing standards were produced. A series of tensile tests at different combinations of temperatures and strain rates were conducted to determine the casting constitutive behavior using a Gleeble 1500 thermo-mechanical simulator. A Design of Experiments was done to validate the adequacy of the computer model predictions and to study the effect of process variables on casting dimensions. Castings were produced and precisely measured using a Coordinate Measurement Machine. An Analysis of Variance was performed using the experimental data and the statistical significance of the main variables was determined. The experimental results were compared against computer models predictions. The comparisons between the experimental and computer model distortion results are discussed.
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:die casting finite element method coordinate measurement machine aluminum a380 0 gleeble
Date of Publication:01/01/2007