Evaluating the berkovitz method to predict fatigue loads in mechanical failure investigations
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This article evaluates a proposed analytical-experimental methodology by which the fatigue load levels leading to failure of structural components is inferred. The so-called Berkovitz method is recognized to depend fundamentally on a 1:1 relationship of micro- and macroscopic crack propagation rates. Compact tensile specimens of a high-strength aluminum alloy were fatigue tested at room temperature according to ASTM-E647, in plane-stress and plane-strain conditions, respectively. Unloading elastic compliance and low-magnification visual techniques monitored crack propagation rates. Topographical survey of fractured surfaces was carried out in a scanning electron microscope to measure striation spacing at constant-ΔK locations. By inputting these values in the Berkovitz model, the load spectrum applied during the fatigue testing could be derived. Research results have shown that, if correctly and carefully used, the assessed procedure provides accurate estimation of fatigue loads, so constituting a powerful tool during failure analysis of mechanical components operating in constant amplitude loading conditions.
Keywordsaccident failure investigation Berkovitz’s method fatigue crack growth fatigue striation spacing quantitative fractography
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