Following the recent post on the Dang Van criterion, this companion post covers its two closest relatives: the Crossland criterion (1956) and the Sines criterion (1959). A quick note on nomenclature: the Crossland criterion is sometimes misremembered as “Crossfield” — the correct attribution is to… Read more
Most of the fatigue methods featured on this blog — rainflow counting, Dirlik and my Meta-Dirlik spectral correction, dwell-corrected rainflow — answer the question: how much damage does a stress history accumulate? The Dang Van criterion answers a different and complementary question: will a complex… Read more
Two incidents at the same wind farm, seven weeks apart, tell a single engineering story that’s worth unpacking carefully. On February 2, 2026, an 80-meter Vestas turbine at the Yeongdeok wind farm in North Gyeongsang Province, South Korea, snapped roughly a third of the way… Read more
One of the most counterintuitive repair techniques in structural engineering is also one of the oldest: to stop a fatigue crack from growing, you drill a hole at its tip. Adding material loss to an already cracked structure seems like exactly the wrong prescription —… Read more
Image Courtesy of http://www.mbrosia.co.kr/en/product/product0101.php Ultrasonic fatigue testing at 20 kHz has become the standard method for characterizing material fatigue in the Very High Cycle Fatigue (VHCF) regime — beyond 107 cycles, extending to 109 (gigacycle) and beyond. At 20 kHz, a test that would require… Read more
ZW12 (Mg–1Zn–2Y wt.%) is a research-stage magnesium alloy developed at Helmholtz-Zentrum Hereon (Geesthacht, Germany) targeting lightweight structural applications under cyclic loading. Recent work presented at IFC14 (14th International Fatigue Congress, 2026) by Trujillo-Tadeo et al. reveals that ZW12’s fatigue and corrosion-fatigue performance is strongly microstructure-dependent… Read more
Image courtesy of: https://martin-baker.com/ejection-seats/
Image courtesy of: https://incastt.com/inclusion-defects-in-investment-casting/ Non-metallic inclusions are unavoidable by-products of steelmaking, casting, and welding. They range in size from sub-micron oxide clusters to hundred-micron sulfide stringers, but their fatigue consequence is disproportionate to their size. This post catalogs the common inclusion species by alloy family,… Read more
Tom Irvine | VibrationData.com | Structural Dynamics, Shock, Vibration & Acoustics Abstract. The Dirlik method estimates spectral fatigue damage from a stress power spectral density (PSD) assuming Gaussian amplitude statistics. When a measured stress time history is stationary yet exhibits kurtosis κ > 3 (leptokurtic),… Read more
Hardness is cheap and fast to measure — but how far can it really predict fatigue behavior? Introduction Hardness is one of the cheapest and fastest mechanical properties to measure — a Rockwell or Brinell indenter, a few seconds, and a single number. Because hardness… Read more