Vibration Fatigue for Chassis-Mounted, Cantilevered Components

Vehicle chassis mounted cantilevered components should meet two critical design targets: 1) NVH criterion to avoid resonance with road noise and engine vibration and 2) satisfied durability performance to avoid any incident in structure failure and dysfunction. Generally, two types of testing are performed to validate chassis mounted cantilevered component in the design process: shaker table testing and vehicle proving ground testing. Shaker table testing is a powered vibration endurance test performed with load input summarized from real proving ground data and accurate enough to replicate the physical test. The proving ground test is typically performed at critical milestones with full vehicles. Most tests are simplified lab testing to save cost and effort. CAE procedures that virtually replicate these lab tests is even more helpful in the design verification stages. A method for defining load input, Power Spectral Density or Sine Sweep, to predict the fatigue life of chassis component will be discussed. The CAE process for this topic, with an air suspension compressor support bracket as an example, is presented for vibration stress and fatigue as well as a process to predict and correlate a vibration shaker table key life test.