The Constraint Factor You Inherited — Vibrationdata Vibrationdata Fracture & Fatigue Crack closure modeling The Constraint Factor You Inherited Newman’s crack opening equation contains a single user input, α, that most analysts take from a material file default without ever deciding on it. At the… Read more
Nearly every random vibration fatigue course teaches that the response of a single-degree-of-freedom system to broadband base excitation has Rayleigh-distributed peaks. The claim is repeated so often that it has hardened into doctrine. It is a good approximation for the largest peaks, which is why… Read more
Does Compression Grow Cracks? — Vibrationdata Vibrationdata Fracture & Fatigue Stress intensity conventions At a stress ratio of R = −1, the choice between full-range and clipped ΔK is worth a factor of 2n in life. It is usually the largest single lever in a… Read more
Fuse Pins: The Structural Fuse That Holds the Engine On Jet engine pylons contain deliberately weakened pins designed to shed the engine under extreme overload — and two Boeing 747 freighter accidents showed what happens when the fuse itself fails from fatigue. An electrical fuse… 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
The Ramesses II bust (Younger Memnon), British Museum, Room 4. The large diagonal fracture across the chest is clearly visible. A circular hole, likely an ancient lifting attachment point, is visible on the left side of the chest. Photograph by Tom Irvine, July 2026. Standing… Read more
intergranular SCC of an Inconel heat exchanger tube with the crack following the grain boundaries. photo courtesy Stress corrosion cracking (SCC) is a time-dependent fracture mechanism driven by the simultaneous presence of sustained tensile stress and a corrosive environment. Neither factor alone is sufficient. Their combination… Read more
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
Introduction Flow stress is one of those quantities that shows up everywhere in structural metals engineering, yet it rarely gets the dedicated treatment that stress intensity factor, S-N curves, or fatigue strength coefficients receive. It appears quietly in cyclic plasticity models, in fracture toughness test… Read more
Image reference: https://www.sciencedirect.com/science/article/abs/pii/S0020740323003296 Introduction Classical fatigue analysis is built on stress. The stress-life (S-N) approach correlates nominal stress amplitude to cycles to failure; the strain-life ($\varepsilon$-N) approach handles the plasticity at notch roots through the Coffin-Manson equation; linear elastic fracture mechanics (LEFM) characterizes crack growth… Read more