没事学学啵得颂
本帖最后由 373527271 于 2019-3-8 17:53 编辑The compression members in the machine orstructural like the stick, bar, column or strut whose sections may be thedifferent geometry e.g. round, rectangle, channel or other form should be consideredthe issue crookedness under applied load.There are several factors contribute to buckling and the following equation show the relation of them. P/A=C*(π^2)*E/(l/k)^2; Usually called Euler equation.P, applied axial load; A, sectional area ofmember; C, boundary condition constant on table 1.
Column end condition Theoretical valueConserve valueRecommended value
Fixed-free1/41/41/4
Rounded-rounded(pivoted)111
Fixed-rounded211.2
Fixed-Fixed411.2
Table 1E, Young’s modulus of material; l, the lengthof member; k, the equivalent radial of section.I is the second moment of section area. I=A*k^2; l/k is defined as slenderness ratio.Actually the column is divided into three modelsthat are long column, intermediate-length column and short members according tothe l/k value.How to determine the threshold ofslenderness ratio? Here is the equation. L1=(2C*E*π^2/Sy ), Sy is the yield strength of material.If the actualvalue of l/k of member is greater than the L1 , we called the member as a longcolumn. The Euler equation can fairly handle this problem. L2=0.282(AE/P)^1/2, P is the applied load.If the actual value of l/k of member is less than , we called the member as shortcolumn or strut. The member will be as a pure compression issue.If the actual value of l/k of member between the two thresholds,we should use correction equation to figure out. Here is the equation.P/A=Sy-1/C*E(Sy /2π*l/k)^2. Usually called parabolic curve.Because of the manufacturing,assembly or commissioning, the work point of applied load is hardly toconcentric with the centroid of member. Therefore, eccentric load moment shouldbe taken into account when deal with the intermediate-length column and shortcolumn issue.没事写写看书总结，写的比较简洁讲究看一下。以前8爷讲H型钢在做支撑件时，其受压的一翼也要考虑稳定性，这个当时没法理解。看了红毛的书以后想明白了，其实所有受压件达到一定长度时，都要考虑失稳问题，这是因为支撑件受压力时最外一层可以假想为纤维层会产生类似弹性片偏移平衡位置的现象达到一定应变极限时，最大偏移位置处被压溃。
叨扰几句，
结构力学下册，专门一章讲解结构稳定性，整体稳定性，最后就是非线性方程求解，俺很鄙视它的另外一个叫法：超越方程。。。
结构件受压翼缘是局部稳定性，无论是钢结构原理提到过基本的计算，其基础是弹性力学，板壳原理，配合上加劲肋，三边简支一边自由模型。
忒疯狂，还是按规范走稳妥一点。
八爷专业是船舶，力学基础起于此，也立于此。
我感觉不是纤维啊。你可以解一解那三个平衡方程，绕y，z轴稳定和h钢开口截面扭转，化简之后得出上面那个P/A。
反正我算一遍没有看到纤维的概念，我看到侧向承载力与整个截面，边界条件，受力位置有关的，这些值多大多小如何影响承载力都是严格的数学。
大佬莫怪 欧拉压杆失稳判据，要想看弯成啥样，还要算特征值。
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