NASA Langley Research Center Releases Technical Guidance on Instrumented Hammer Testing

Technical Guidance on Hammer Testing

NASA's Langley Research Center has published technical bulletin TB 26-09, which provides updated guidance on the use of instrumented hammer tests for structural analysis. According to the release, these tests do not necessitate the use of an idealized single half-sine waveform. Instead, the agency notes that when force and response are measured with precision, factors such as crest ripples and separated contacts remain valid inputs for analysis.

Evaluating Test Adequacy

The guidance states that the shape of the force does not inherently invalidate a test record. Rather, the adequacy of a test depends on several technical factors, including signal-to-noise ratio, bandwidth, and measurement accuracy. NASA advises that the appearance of a half-sine wave alone is insufficient to establish the validity or adequacy of a test. Instead, practitioners should evaluate each test based on its intended objective and ensure that the excitation covers the necessary frequency, amplitude, and nonlinear response ranges.

Recommended Best Practices

To ensure reliable results, NASA recommends that researchers measure the complete applied force using proper calibration, time synchronization, and dynamic range. Furthermore, response measurements must be verified to ensure they are not saturated or clipped. The agency suggests that tests should only be rejected or repeated if a specific deficiency in measurement, excitation, or coverage is identified.