A study of crack propagation in microforming tools

• Main Author: Muhammad Shahid Shith.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Mechanical engineering; DRNTU::Engineering::Mathematics and analysis::Simulations
• Online Access: http://hdl.handle.net/10356/40409
• Institution: Nanyang Technological University

The aim of this project is to simulate the effects of carbide concentration on crack propagation in tool steel. This is carried out by using properties of AISI M2 as a reference tool steel material and ABAQUS/Standard 6.9 to run simulations. The project is segmented into four different phases. The first phase consisted of modeling a global model of the predetermined microforming die. This included the loading and boundary conditions applied on the global model. In the second phase, displacement data of high stressed portion of the die is used to drive a submodel. The submodel is iterated twice to achieve a unit cell dimension of 0.01mm2 with highest stress concentration. Carbide concentrations of 10, 60 and 600 particles per mm2 with variations in orientation and distribution are configured to form 12 different cases in the third phase of the project. Simulations are run on the 12 cases and 3 critical cases which recorded the highest principle strain readings are chosen. The fourth phase used the critical cases to drive 3 crack models. XFEM is used to simulate the crack propagation. Initial crack of 0.5μm is modeled in each case with a direction perpendicular to maximum in-plane principle strain tensors at the carbide corner with the highest maximum principle strain value and into the matrix. From the results, it is observed that carbide particle size in the range of larger than 8μm give a single crack propagation direction from an initial crack. This is more critical than possible branching cracks in smaller particle size. Range of sizes smaller than 3μm provide best delay in crack initiation. Also, concentration has insignificant effects on crack initiation for this range of carbide particle sizes.