Parameters such as surface finish, dimensions, and various forms of non-destructive testing such as ultrasonic inspection are usually adequate for quality control of components. However, controlling the quality of dynamic systems, complex electrical components, and highly resonant components and systems often requires more evolved methods of testing. This is particularly true when the satisfactory response of a system to an external stimulus may be critical in order for it to be accepted. Noise and vibration measurements are often effective tools to evaluate these criteria.
Pass/fail production testing of structural responses is an ideal test for components that are particularly sensitive to external input or have very strict product specifications. For instance, both automotive mirror assemblies and turbine blades undergo production level structural testing. Automotive mirror assemblies, due to the fit of the system, or how loose the mirror is on the assembly, is one of the most important criteria in the quality of the mirror once installed in a vehicle. Turbine blades undergo testing because any internal flaw in the blade can cause loss of structural integrity, and it will easily be identified on test.
Impact testing has proven to be an ideal tool for this. The user measures an input to the system from a force-calibrated impact hammer and output from a structure mounted accelerometer or microphone. The frequency response function can be used to automatically determine if the associated resonance is within the region prescribed for mirrors with tight enough tolerance.
Important characteristics of a dynamic quality control test system include the ability to set complex conditional limits and failure detection criteria, accurate measurements and proper frequency domain processing, easy to use interfaces for operators that clearly indicate pass/fail conditions, the ability to automate by communicating with external platforms, generation of logs or reports, and storage of the raw data for later analysis and processing.
More advanced features enable users to determine limits using variation dispersion statistics, recalculate or relearn limits during testing, and perform horizontal axis smoothing to reduce the effects of frequency and/or time domain smearing. It is also often helpful to have data compatibility between production test systems and systems used by engineers for dynamic analysis and troubleshooting.
Learn more about SignalCalc Dynamic Signal Analyzers.