Torsional stress is the stress or deformation caused when one end of an object is twisted in one direction and the other end is held motionless or twisted in the opposite direction. Torsion strength is the measure of the ability of a material to withstand that twisting load. (Think axle twist) Ultimate tensile strength of a material is the maximum amount of pulling stress on the material that can be applied before the material fails. In racing, we are constantly searching for methods that can increase the torsional and tensile stress loads that our driveline components can absorb.The manufacturing process can also create high stress in some of the most important points in our cars, regardless of the material strength.
Even with the right manufacturing processes in place, fatigue crack failure can occur and generally starts on the surface of the material. Cracks can form easily in areas of high tensile stress because the forces are already working to pull the atoms of the metal apart. Shot peening helps eliminate this failure by creating a compressively stressed skin around the part that helps to prevent stress crack formation and growth. Shot peening is a cold work process where small round particles (shot) are blasted at the part and act like a peen hammer, dimpling the surface in a uniform way to create a hardened top layer of compressed material over the part. This process also eliminates microscopic defects in the thin surface shell of the shot peened part. The increased tensile strength of shot peened parts allows for lighter weight parts to be utilized, improves the fatigue resistance, and eliminate stress crack propagation. Mark Williams Enterprises uses the shot peening process on our Reduced Mass Transmission Yokes. Shot peening is a standard option on parts produced from 300M material and our top-of-the-line Ultimate axles. Peening is offered as an upgrade option for our Hi-Torque and Superlite Hi-Torque axles.
