M Tehrani - Master of Science Student, Sharif University of Technology, Aerospace Engineering
A Abedian - Associate Professor, Sharif University of Technology, Aerospace Engineering

In aerospace applications structures weight is considered as a major performance parameter. One of the most effective ways for weight reduction is superplastic forming. By this technique, not only the weight, but also the stress concentration, the cost, and the manufacturing time are noticeably reduced. Additionally, the components with complicated shapes could be formed in a single manufacturing step. Due to the wide demand for whiskers reinforced metal matrix composites (MMCs) in aerospace industries, many research works have been designed to extend the borders of superplastic forming to MMCs materials. In the present study, an axisymmetric micromechanical finite element model is developed to predict the superplastic behavior of Al-SiC composite. Here, the effects of variations of materials properties on the superplastic forming process are highlighted. In most of the available numerical studies this phenomenon has been ignored. Here, the Internal Stress Superplasticity (ISS) mechanism is considered. This mechanism involves a thermal cycling load (e.g. 100°- 450°-100°c, 50s heating, 150s cooling) accompanied by a constant biasing mechanical load (e.g. 2, 4, 7, 10 Mpa). The effects of variation of yield strength, Coefficient of Thermal Expansion (CTE) withtemperature on plastic strain of the MMC are investigated. According to the results, in the mentioned temperature range, the properties of the MMC matrix material are highly changed. This potentially could affect both the plastic strain amount and rate. As it is seen, the effects of change in yield strength on plastic strain response of the composite are more pronounced than the CTE. In fact, it seems in ISS process, the variation of yield strength plays a key role.

Metal Matrix Composites (MMCs),Superplastic forming, Axisymmetric model, Material properties, Temperature