It’s urgent! Please help quickly – stress calculation needed
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It’s a 20g tube with a diameter of Φ219*10; its ends are fixed, the length is 9 meters, and a force of 10 tons acts on it at the middle. I wonder if it can withstand this force. I’ve forgotten all my knowledge of mechanics – could someone help me calculate this? Thank you; it would be great if formulas could also be provided. Thanks a lot
There is a section on “Mechanics of Materials” in the resource block of the forum’s mechanical technology exchange area, where it can be downloaded. I just came from there
One regrets not having read enough books when the need arises. Too few conditions are provided; if it is to be used in a process, factors such as temperature and pressure also need to be taken into account. If it is only for temporary use, with no temperature difference or internal pressure, it is the simplest problem in material mechanics; only bending moment and the flexural modulus of the cross-section need to be considered, and it is related to the allowable stress of the material.
Calculated according to the American standard AISC: FAIL – the value exceeds 45%. Fy = 248.211 MPa. For the gross area, Ft = 0.6 * Fy = 0.6 * 248.211 = 148.927 MPa; for the net area, Ft = 0.5 * Fu = 0.5 * 399.896 = 199.948 MPa. Fv = 0.4 * Fy = 0.4 * 248.211 = 99.285 MPa. Fb = 0.66 * Fy = 0.66 * 248.211 = 163.82 MPa. For Design Member 1, under Load Case 3, in terms of bending tensile stress: fb > Fb, i.e., 237.703 > 163.82 – FAIL (exceeds by 45%). In terms of bending compressive stress: fb > Fb, i.e., 237.703 > 163.82 – FAIL (exceeds by 45%). For Design Member 1, under Load Case 3, considering both bending and tension stresses: fa/Ft + fbx/Fbx + fby/Fby = 0.0/199.948 + 237.703/163.82 + 0.0/163.82 = 1.451 > 1 – FAIL (exceeds by 45%). Last edited by ssmith2007 on 2008-3-1 11:24
Thank you all. I’ve done the calculations – I went through the mechanics of materials material again. Before, I used to dismiss such problems as too simple; I even scored 100 on the final exam in Mechanics of Materials (Part 2) in college. It’s been 5 years now, and I’ve almost forgotten everything. Sigh, I’ll review mechanics of materials again when I get home tonight :L :L :L :L :L
In the exams at your school, material mechanics tests don’t involve questions like 1+1, right? Or the exams will consist of questions like those you listed; for P, having a mechanical design manual is sufficient – there’s no need to learn mechanics of materials again
:(Sigh, what should I do? Even with the mechanical design manual in hand, I can’t understand the mechanical calculations – I can’t find the value for M.)
- -No way, right? First, create a basic stress diagram, then use that to produce a bending moment diagram; by identifying the most critical section, the value of M can be determined