While visiting your buddy who owns a machining joint in East Cleveland, you talk
ID: 1767327 • Letter: W
Question
While visiting your buddy who owns a machining joint in East Cleveland, you talked shop with him over a lunch of kielbasa and chili (it has beans in it). He lamented that one of his machined parts hasn't worked so well lately and his customer is at his throat. What he is trying to make is a clasp designed to grab a round bar, and he makes a drawing for you: While you try to suppress yourself from asking him why he carries around, he explains that the clasps are made out of a NiAleo alloy sideview Top view (installed) The clasp is a single piece of metal, and when the clasp is being installed unto the rod, it must first "open up"SO the jaws can make their ways around the rod. What made his client fume is after installation, the clasp does not grasp clasp rod Top view during the rod tightly, and he accuses your buddy of not machining the clasps precisely enough. Your b certain that his techniques are impeccable: he has m that there is a spring force that will hold the clasp in place. The resulting material is also quite d finds, so there wasn't a problem with brittle fracture achined the clasp just a bit smaller than the rod such You ask him about the material properties of the NigAleo alloy he is using and what condition he the alloy in. He mentions that elastic modulus of the alloy is 250 GPa, and the yield strength was 340 MPa The alloy was heat treated at 1200 'C for 2 hours and quickly water quenched (fast cooling) to temperature so that phase changes would not occur during this process. Being the versatile you are, you quickly do a mental calculation based on what you learned in the solid mechanics c determined that the maximum strain during installation on the clasps was 0.2%, while you were d this, your buddy mentioned that he has made like 10,000 units of this clasp, and would really I a way of fxing the loosening problem without changing their shape (otherwise he would have to re- machine each one of them again). room engi neer that oing Upon completing your calculation, your suddenly jump up to the dining table. In one swift motion, you stomp onto one of the kielbasas and send a bowl of chili flying across the room with a roundhouse kick, put one hand on your hip and strike a pose. You point right at your buddy and declare: your clasps aren't working because , and l can fix it without re-machining by !Explanation / Answer
Ans 1 (a)Quench Hardening
Ans 1 (b) Annealing
3.c - This happens due to the rapid quenching, hence making the material harder. The clasp becomes loose because when the clasp is pushed against the shaft, a slight deformation occurs due to excessive strain. This strain is caused due to the rapid cooling of the material which in turns changes the physical property of material hence making it harder. As a result of which the material is deformed upon installation.
3.d - This can be done with the help of Annealing. The process is done by reheating the clasp up to its critical temperature and then allowing it to cool to normal temperature in the air. During this process, the residual stress is removed as well as the material becomes less hardened. This property helps in bringing back the original elasticity.
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