Vibration And Shock Testing From Recorded Data

Defining the problem

• Evolution of vibration and shock specification development
• How test tailoring relates to specification development
• Two scenarios employing specification development
• Overview of test cases presented later

Historical approaches to developing vibration test criteria

• Early work with propeller-driven aircraft
• Scaling; mass loading; modeling
• Evolution of jet aircraft specifications
• Generating missile and spacecraft criteria
• Land and sea vehicle specification development

Characteristics of measured data (content tailored to audience, e.g. automotive)

• Time series data; time domain descriptions
• Basic statistics that apply to random data
• Stationarity; handling non-stationary data
• Frequency domain descriptions, including Shock Response Spectrum (SRS)

Approaches to summarizing spectral data

• Benefits of proper experiment design
• Measurement locations
• Test conditions (sampling the life cycle)
• Organizing data collection (focus on maximizing payoff)
• Conducting the test
• Reducing the data
• Validating the data (eliminating redundant data)
• Creating data bases
• Summarizing spectral data (enveloping techniques)
• Developing the criteria

Data reduction techniques (time series)

• Line spectrum data reduction (analog; mainly digital)
• Continuous spectrum data reduction (analog; mainly digital)
• Shock spectrum data reduction (analog; mainly digital)

Practical examples (content tailored to audience, e.g. automotive)

• Test Case I: A land vehicle case which illustrates how to use data generated from a designed test which simulates all aspects of the end item's life cycle. Test severity scheduling is used to adjust test time. Measured data can lead to development of (1) broadband, (2) narrowband, (3) sine sweeping or (4) mixtures of these.
• Test Case II: A large scale laboratory test designed to acquire subsystem and component data for use in generating procurement specifications. Both sine and random environments are presented. The response data are summarized and used to generate subsystem criteria.
• Test Case III: The data generated in Test Case II are applied to testing a representative subsystem. Response levels are induced into computer PWBs, causing them to fail even though they did not fail in Test Case II. Here the PWB response data are used to tailor the input criteria in order to limit response levels to those seen in Test Case II.

Bibliography