I do not think creep testing will provide the data that you need. The load application cycles are short and intense, which does not promote creep. I think high temperature strength and fatigue are the two important characteristics. The first reference that I mentioned in my previous message would have some good data for you.
A quick review of some data that I have (ASM HANDBOOK Volume 2) shows that typical room temperature properties of A356 are 165 MPa yield, 230 MPa tensile, and 3.5% elongation. At 150 C, the properties are 140/160/6 and at 205 C, they are 60/85/18. As you can see, the strength dramatically decreases as you increase above 150 C. This is because the typical aging temperature (T6 temper) for this grade is ~ 155 C.
If I were you, I would do the following:
1. Perform finite element analysis on this brake housing. The analysis should take into account both low temperature and high temperature properties. The stresses will likely be lower for the high temperature load case (because the elastic modulus is lower), but since the strength is lower, this will likely have the highest deformation potential.
2. Investigate fatigue loading history. What percentage of the stresses occur at relatively low temperature? What percentage occurs at high temperature? How many cycles do you need to withstand?
3. You obviously have forces, but stress and strain is what you need in order to solve this problem. Strain gauging the components may provide the necessary physical correlation to the FEA. If fatigue is the most important consideration, you will need more detailed information on defects in the housing-- inclusions, porosity, solidification defects, etc.
