TB 26-09 Measured Hammer-Tap Inputs

Executive Briefing

According to reporting by NASA Space & Missions, For more information, contact Joel W. Sills, Langley Research Center, joel.w.sills@nasa.gov. Download the PDF version An instrumented hammer test does not require an idealized single half-sine waveform. When the complete force and response are measured.

Detailed Factual Report

For more information, contact Joel W. Sills, Langley Research Center, joel.w.sills@nasa.gov .

An instrumented hammer test does not require an idealized single half-sine waveform. When the complete force and response are measured accurately, crest ripples and separated contacts remain known inputs. Force shape changes excitation, but does not inherently invalidate the record. Adequacy depends on measurement accuracy, bandwidth, signal-to-noise ratio, and coverage of the test objective.

Background: What the Hammer Actually Measures Hammer tests support modal analysis [2–4] and can precede pyroshock testing [6]. Figure 1 compares a half-sine, maintained-contact rippling, and separated contacts. During a zero-force interval, the structure continues to vibrate; re-contact acts on that vibration.

If an exact model and test article receive the same force and initial conditions, uniqueness gives identical responses for each bounded measured history. An approximate model can show different errors as inputs excite different frequencies, amplitudes, or nonlinear states. See [1] for the exact-model derivation.

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Source & Verification Provenance

Information in this article was compiled directly from records provided by NASA Space & Missions. Access the primary source document at: https://www.nasa.gov/centers-and-facilities/nesc/tb-26-09-measured-hammer-tap-inputs/. Reporting and editorial review conducted by the USA NOW News Desk.