Low Cycle Shock Fatigue

Some colleagues and I recently debated whether fatigue relationships could be applied to repetitive shock environments.  Each of us had a persuasive hypothesis as to whether fatigue was applicable, but none had any data to support his claim.

I thus perform my own test at home using Sony transistor radios, as presented in:

http://www.vibrationdata.com/low_cycle_fatigue.pdf

Each radio was subjected to a series of free-fall drop shocks from a given height and tested to failure by monitoring the audio output.

The radio test results may be considered as anecdotal given that the orientation of the radio at impact was uncontrolled.  Nevertheless, a fatigue-type relationship was observed roughly similar to that given by Steinberg in Vibration Analysis for Electronic Equipment.

* * *

Low-cycle fatigue from aftershocks is a concern in earthquake engineering.

Jun Iyama and James Ricles wrote:

A building may suffer damage during an earthquake as a result of inelastic deformations developed in the members or connections. It is important that the structural integrity of the building be assessed to ensure the safety of the occupants. This assessment includes evaluating the ability of the structure to resist the demand from subsequent aftershocks and a major earthquake.

Reference: Prediction of Fatigue Life of Welded Beam-to-Column Connections under Earthquake Loading, J. Struct. Eng. 135, 1472 (2009).

* * *
Tom Irvine

One thought on “Low Cycle Shock Fatigue

  1. Interesting. I am doing some work at Panasonic Avionics Corporation. For the most part LCD monitoors and other entretainment system flight-quality avionic boxes. I wonder how, say acoustic fatigue or others, can affect the life of the circuit board, say welds.

    Regards,

    Pedro M.

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