Vibration durability testing is required for many components, but engine mounted automotive components have very consistent and severe levels of vibration. Engine mounted components like heat shields, fuel lines, brackets with attached parts, sensors and actuators that are attached to the engine all require durability testing. Typically this involves the component to be subjected to cyclic vibration for an extended period of time.
The greatest fatigue damage occurs when excitation is at or near the component’s resonance frequency. Since different components will have resonances at different frequencies, swept sine is typically used to ensure that all resonances in the frequency range are excited. However, sweeping a sine across the entire frequency range can be very time consuming.
To shorten the test time, Sine-on-Random (SoR) testing has been widely used for such tests since it provides short testing time, but with the trade-off that the amplitude is not identical to the engine excitation. To use the SoR approach, the random component is typically suppressed. This method has essential shortcomings in the frequency and time domain causing unpredictable test aborts and needed many compromises to finish tests.
The Multi Frequency Sine method involves use of multiple true sine tones swept simultaneously across the frequency range to excite all resonances. The primary advantage of this technique is that it significantly reduces the required test duration in such a way that the control is not compromised. Each sine tone utilizes a high quality tracking filter to ensure that testing is done at the correct level.
The Multi Frequency Sine control software for the Data Physics SignalStar vibration controllers enables multi frequency sine testing without sacrificing control accuracy and performance. The time reduction comes from dividing the sweep frequency range into multiple intervals. For example, four sine tones swept simultaneously across the same frequency range at the same sweep rate will reduce the time required to produce the same fatigue by 75 percent compared to a single frequency swept sine test. This can reduce a typical test that takes 84 hours per axis to just 21 hours per axis.
Learn more about SignalStar Vibration Controllers.