This paper investigates eight suspension design factors used to support non-driven axles and their impact on suspension strain field. The particular suspensions are of a trailing arm and air spring design. These auxiliary suspensions are commonly added to give extra weight carrying capacity to medium and heavy commercial vehicles.
Eight design factors were studied. From the investigation, the main factors and seven two-way interactions were ranked by their effect on the strain in the axle according to strain gage location and road test type.
Two approaches were taken to study the impact of the design factors. The first approach was to develop computer code to model a two-degree of freedom (2DOF) bi-linear system. The design factors of the suspension that can be modeled in the simplified 2DOF system were input into the computer code using a full factorial design of experiment. The mathematical model uses road displacement input to predict the motions of the axle mass and the trailer mass, which is then converted into strain in the axle.
The second approach was to lay strain gages on the axle and collect strain data while the vehicle is in motion. A fractional factorial design of experiment was used to decide which factors of the suspension design or combinations of factors had an effect on the strain field in the axle.