Structures subjected to random vibration environments are routinely evaluated for stress using the von Mises criterion, which condenses the full multiaxial stress state into a single scalar suited for comparison against a yield or fatigue allowable. But von Mises stress is a nonlinear function of… Read more
The carbon fiber automotive part in the photo above shows two composite engineering choices worth examining before it ever sees the road: the woven fabric architecture visible through the surface, and the glossy clear coat protecting it. Composite structures rarely fail in the fiber direction… Read more
Updated August 10, 2026. The original post was written two days after the incident. This revision adds the investigation developments through early August, including the project engineer’s assertion that specified column reinforcement was never installed, and a new section on what that reinforcement would have… Read more
Pointed Gothic arches framing the choir, Notre-Dame de Paris. Smooth and Pointed Arches: Loads, Stress, Fracture, and Fatigue Introduction The accompanying photograph shows the interior of Notre-Dame de Paris, where every opening is spanned by a pointed arch. Stand in a Roman basilica instead and… Read more
Image credit: Nikhil Patil Introduction Most vibration-induced fatigue problems in aerospace and industrial structures live comfortably in the high cycle fatigue (HCF) regime, where nominal stresses remain below yield and the stress-life (S-N) method with rainflow cycle counting serves well. But some of the most… Read more
Image https://empowering-technologies.com/metal-improvement/ultrasonic-impact-treatment/process/: Introduction Welded joints are the fatigue-critical details in most steel structures. The weld toe combines a sharp geometric stress concentration, tensile residual stresses approaching yield, and microscopic slag intrusions that act as pre-existing cracks. As a result, the fatigue strength of an as-welded… Read more
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
\; K_{ISCC} \] where \( \sigma \) is the applied stress, \( a \) is the crack depth, and \( Y \) is a geometry factor. Eyebar 330’s tiny 0.1-inch flaw sat below this threshold for decades, then crossed it after four decades of slow… Read more
Image credit: https://www.sintechnology.com/portfolio-articoli/hole-drilling/ Drilling a hole into a structure is normally something an engineer tries to avoid — holes are stress concentrators, fatigue initiation sites, and sources of structural weakness. But in one important application, drilling a small hole is precisely how engineers measure the… Read more
By Tom Irvine While enjoying a glass of orange juice at an outdoor café in Madeira, Portugal on a sunny Independence Day morning, I noticed the reusable stainless steel straw resting across the glass — its elegant curved bend a perfect reminder that one of… Read more