Research of lightweight design method to CST

To reduce the quality of Cutting the Screw Thread and maintain the ability of absorption, optimize the size of thread pipe which is one of large quality parts of Cutting the Screw Thread by stress analysis and the ideal of topology optimize. Then lightweight design is done to impact bar which is another large quality parts of Cutting the Screw Thread by using lightweight material and optimizing size. The last although the quality is greatly reduced, the construction can still satisfy both European and USA frontal impact regulations.