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
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
By Tom Irvine The spruce soundboard of a concert grand piano and the sheet-steel housing of an industrial gearbox have more in common than their outward appearances suggest. Both are thin panels driven into vibration by an internal source. Both radiate sound into the surrounding… 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
A6061-RAM2 is a new aluminum alloy developed specifically for additive manufacturing (AM) that achieves mechanical properties comparable to wrought 6061-T6 — a capability that has eluded conventional AM processes for decades. Developed by Elementum 3D using Reactive Additive Manufacturing (RAM) technology and matured by NASA… 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
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
Image reference: https://onlinelibrary.wiley.com/doi/full/10.1002/adem.202300394 What Is Anodizing? Anodizing is widely used to improve corrosion resistance and surface durability in aluminum and other light metals. However, under cyclic loading, anodized coatings can play a surprising, and sometimes detrimental, role in fatigue performance. This post walks through why… Read more