Joe,Dan & Jason
To those that are bored by "Engineering", please do not read
this.
Joe and Jason , you are absolutely correct. Any engineer that has taken courses Metallurgy,Material Science, and Strenght of Materials knows that a designer CANNOT replace Steel with Aluminum , Carbon Fiber and / or any material WITHOUT CHANGING THE DESIGN based on static and dynamic material (fatique) properties.
First, the standard steel frame was digitized to establish fixed points such as body, drivetrain, suspension, bumpers ,etc.
Then ,the clearances (were defined) of the frame which must be maintained to mate with factory component which will still be utilized,
The Stock Steel frame mouted and measured to establisl a minimum Torsional Rigidity Target.
Next a Finite Element Model was created for the Stock Steel Frame utilizing the stock steel thickness and properties after a Metallugical analysis of a a variety of sections/pieces from all over the frame
A Finite Element Analysis was conducted and compared to the ACTUAL Torsional Rigidity measured . Of couse we assumed a Lineal Analysis with no permanent deformation
We also put strain gauges on my near stock vehicle to establish the strain rates in a variety of conditions would see on a road course, etc.
This data was compared to the fea prediction and adjustment made the FEA model and conctraints until in correlated to the actual data gathered from the stock steel frame.
Now we began trying different Aluminum Properties in the model and of course they did not correlete with the same steel shape/ thickness.
Now the time consuming trial and error modofications of the Finite Element Model in the areas of increasing thickness, enlarging sections (where clearances permitted) , adding gussets, etc .
Now we built our first Aluminum Frame to the redesigned FEA model. Actual overall Torsional Rigidity of the first aluminun frame was measured and did not meet the Steel Frame target. We revised the FEA Model until the Aluminum FEA model correlated with the Actual #1 ALuminum frame.
Obviously, the aluminum frame design was improved and a # 2 Aluminum frame was made and tested. This proccess was repeated until the Torsional Rigidity Target was met .
We DID NOT CONDUCT A NONLINEAR ANALYSIS which could conform 55 MPH , Barrier or corner impact.
I hope this brief summary of the frame development proccess
helps your understanding in the effort.
Engineering is what makes cars run /airplanes fly without selfdistructing
(with the right safety factor)