Comparing Measured Field Data to Standards Example

Back to: Recording & Implementing Vibration Test Data

Identifying real failure modes is essential for the effective use of product development resources. For vibration testing, engineers should properly measure and analyze data to correlate an accelerated test or virtual twin to known customer use severity.

The following videos present a case study with an electric delivery truck battery to demonstrate the process of recording field data and comparing it to an industry standard.

In the long run, it is beneficial to define the purpose of the test before collecting field data. This step will help the engineer determine which events to record and how they relate to the severity of the design life. It will also include defining appropriate measurement points and recording parameters.

After recording data, engineers should perform integrity checks and process the data as required for the defined purpose.

Engineers often reference industry standards in testing plans. These standards typically use historical data to produce a widely applicable test profile. While standards offer a helpful starting point, they are a generic option that may over-test or under-test a product.

This case study references the SAE J2380 standard for vibration testing of electric vehicle batteries. Interestingly, the standard recommends using vehicle measurements to develop a test profile when possible. The case study will record field data to compare the standard test profile to a custom-defined one.

This case study highlights the fatigue damage spectrum (FDS) tool following data acquisition. The FDS processes recorded data to calculate the lifetime accumulated fatigue damage for the target customer usage. Applications include:

• Calculate fatigue damage for various usage scenarios measured by field data recordings
• Apply appropriate multipliers to aggregate the lifetime damage target
• Calculate an initial accelerated test profile

The ObserVIEW software’s Random Test Generation option also includes a shock response spectrum (SRS) trace to identify upper test acceleration limits and evaluate the test acceleration levels.

This case study involves a light delivery truck. Package delivery statistics are available online, which the engineers used to weigh the influence of the different environments in the accelerated test profile. The goal is to characterize the field damage levels based on the product’s overall exposure.

Referencing the delivery statistics, the engineers determined that data needed to be recorded from highway, rural, and city driving. They recorded data on a pre-determined route and isolated the portions of the route representative of these use cases. Using the overall lifetime distances provided by the statistics, the data were normalized with repetition values to produce a representative aggregate usage profile. The engineers then applied FDS to generate an accelerated random test profile from the field data.

The engineers compared the field-data generated profile to the SAE J2380 test standard. They determined that the standard would over-test the delivery truck in a large portion of the frequency spectrum. This final video discusses several caveats to consider when correlating test profiles to standards.