RémiM
Active Member
That doesn't surprise me.
Stress concentration are well known. A hole in a structure creates stress concentration just by its geometry. A square hole is the worse, a round hole is better.
The surface of the hole is microscopically not perfectly smooth. It has a lot of small cracks.
If one of these cracks is longer than a critical value, the crack will propagate if the stress reaches a critical value. If there is an initial stress concentration, the propagation will occure even easier.
Holding the SP3 around the hole, i.e. applying a pressure that will be combined to the initial residual stress field, will propagate a critical crack as soon as the critical stress is reached.
Microsoft is to blame here because they must be able to control the critical cracks in there products.
That is what is done with planes, brake disks, and many other very sensitive structures. And it works perfectly.
Picture of the Comet III aiplane that had square windows.
Another one from a disc coupling part:
A quick FEA modelling result:
Stress concentration are well known. A hole in a structure creates stress concentration just by its geometry. A square hole is the worse, a round hole is better.
The surface of the hole is microscopically not perfectly smooth. It has a lot of small cracks.
If one of these cracks is longer than a critical value, the crack will propagate if the stress reaches a critical value. If there is an initial stress concentration, the propagation will occure even easier.
Holding the SP3 around the hole, i.e. applying a pressure that will be combined to the initial residual stress field, will propagate a critical crack as soon as the critical stress is reached.
Microsoft is to blame here because they must be able to control the critical cracks in there products.
That is what is done with planes, brake disks, and many other very sensitive structures. And it works perfectly.
Picture of the Comet III aiplane that had square windows.
![CM9ALYU.jpg](/proxy.php?image=http%3A%2F%2Fwww.tech.plym.ac.uk%2Fsme%2Finteractive_resources%2Ftutorials%2FFailureCases%2Fimages%2FCM9ALYU.jpg&hash=7eb47337ea9e5a5d35da98a796841c9c)
Another one from a disc coupling part:
A quick FEA modelling result:
![abaqus.jpg](/proxy.php?image=http%3A%2F%2Fwww.lingane.com%2Ffamily%2Fpatrick%2Fabaqus.jpg&hash=138c105b4c3f0b0d843a2b7f1e23b744)