05-05-2022, 07:39 AM
(This post was last modified: 05-05-2022, 07:40 AM by Andy Bennett.)
i must say I have always wondered about crack test kits, particularly on steering arms.
Whilst in my engineering role I wasn't involved in safety related issues, I was involved in designing joints for rare materials used in vacuum tube manufacture with stress joins from dissimilar expansions at high temperatures (2000 degrees for thoriated tungsten) etc, and micro stress cracks were always a 'thing' that could bite after xx cycles. The only way to find them was sectioned under a scanning electron microscope and a degree of calculation combined with trial, error and experience. It was frightening sometimes to see what cracks were lurking under an SEMs gaze waiting to emerge and cause micro fissures and vacuum leaks.
Appreciating that there is a difference between a micro crack causing a vacuum leak, but equally that wasn't under mechanical duress and it frightens me whenever I see a steering arm for sale on ebay with the reassuring statement 'crack tested'
Andy
Whilst in my engineering role I wasn't involved in safety related issues, I was involved in designing joints for rare materials used in vacuum tube manufacture with stress joins from dissimilar expansions at high temperatures (2000 degrees for thoriated tungsten) etc, and micro stress cracks were always a 'thing' that could bite after xx cycles. The only way to find them was sectioned under a scanning electron microscope and a degree of calculation combined with trial, error and experience. It was frightening sometimes to see what cracks were lurking under an SEMs gaze waiting to emerge and cause micro fissures and vacuum leaks.
Appreciating that there is a difference between a micro crack causing a vacuum leak, but equally that wasn't under mechanical duress and it frightens me whenever I see a steering arm for sale on ebay with the reassuring statement 'crack tested'
Andy
Enjoy yourself, it's later than you think!