Constitutive modeling of anisotropic sheet metals and application.
An appropriate expression of mechanical properties of anisotropic sheet metals is important to predict the formability of the automotive parts and optimize the manufacturing process. The sheet metal shows different flow stress along its direction. In addition, material’s mechanical properties is dependent on the strain history that material experienced. By expressing the anisotropic of the sheet metals accurately, successful evaluation of formability & springback prediction is possible.
Multi-scale/physics Computational Approach for Developing Improved Mechanical Properties of Metals
Integrated Computational Materials Engineering(ICME) is the integration of materials information, captured in computational tools, with engineering product performance analysis and manufacturing-process simulation . It is important to understand the effect of microstructure characteristics on mechanical properties of the final product or part in materials design for lightweight metals or high strength steels. Unlike previous trial and error dependent on the experiment, it will be more efficient for reducing cost and time to develop new materials and to optimize the process using computer simulation at materials design step based on the understanding in process-structure-properties. Considering the fact that metal production capacity by the nation has been high-quality equalized due to the advent of the 4th industrial revolution, the necessity for reducing cost and time of materials design and development must have been increased significantly. In this research using the concept of ICME, the new model has been suggested - coupled Crystal Plasticity FEM for grain-scale deformation mechanism with Phase-Field Model for microstructure evolution during annealing for predicting mechanical properties after the thermo-mechanical process.
Mechanical behavior of materials based on CP-FEM
Crystal plasticity finite element method(CP-FEM), one of constitutive model describes mechanical behavior of materials, is based on the microstructure. According to boundary condition, slip systems are activated which has largest Schmid factor. Activated slip systems determine deformed figure and stress state of materials.
CP-FEM is best and powerful tool to describe Lankford coefficient, stress-strain curve and forming limit diagram which represented anisotropy, hardening behavior and formability of materials respectively.
Characterizing the mechanical properties and modeling of heat treatable aluminum alloys
High strength aluminum alloys have drawn commercial interest due to its potential applications to lightweight vehicles. Inferior formability of high strength aluminum is still challenging area. Numerous investigations are studied such as Elevated temperature forming and W-tempered forming. In those formings, Identifying mechanical properties with considering the material features plays one of the key role to obtain accurately simulation results. The mechanical properties are characterized for finite element forming simulation implementations.
Simulation of friction stir welding and its application to prediction of mechanical properties of welded Al alloy
Friction stir welding (FSW) has been widely used to join hard-to-weld materials and dissimilar combination of materials. The FSW process is a highly complex process involving thermal, mechanical and metallurgical phenomena due to frictional heat generation and severe material flow around a rotating tool. It has been well known that temperature profile during the FSW process dramatically affects the mechanical properties of welded material. Accordingly, accurate calculation of temperature history is critical in the prediction for the mechanical properties of the welded materials. In this study, the FSW process was modeled by finite element method and temperature history in the welding zone was predicted. Then, the calculated temperature profile was used to calculate the yield stress of welded joint by using the classical precipitation nucleation and dislocation theories.
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