The cab is an essential part of a light truck, and its fatigue durability performance plays an important role in the design and development stage. Accelerated fatigue bench test has been widely applied to product development of carmakers for its low cost and short development cycle. However, in reality, interference exists generally in torsional conditions for the light truck cab when tested on the 4-post vehicle road simulation system. To solve this problem and minimize the lateral force applied on the hydraulic cylinders, the direction and size combinations of displacement release about front and rear suspensions were discussed based on multi-body dynamics simulation and fixture design theory in this paper. Through comparative study, the optimum design and layout scheme of fixtures was determined to conduct the next test procedure. The weak positions of the light truck cab were firstly predicted by utilizing finite element method (FEM) and fatigue analysis theory. Then, the strain gage, which was used for monitoring the stress, was pasted on one weak position analyzed by simulation. According to the observation of stress using the LMS Test.Lab, a modified standardized programmed load spectrum was proposed for fatigue bench test. The test of the cab was conducted, and the design weaknesses of the light truck cab were checked out. Finally, required design modifications were applied to the cab. Bench test results demonstrated that compared with the initial cab, fatigue durability performance of the modified cab has improved.
