对于末端受力矩弯曲的梁来说,欧拉伯努利方程为:

d θ d s = M 0 E I \frac{\mathrm{d} \theta}{\mathrm{d} s}=\frac{M_{0}}{E I} dsdθ=EIM0

这其实是建立在小变形的基础上,否则曲率不是这么简单的。在这种情况下我们可以计算末端的变形大小。

末端的变形角

∫ θ 0   d θ = ∫ 0 L M 0 E I   d s θ 0 = M 0 L E I \begin{aligned} \int^{\theta_{0}} \mathrm{~d} \theta & =\int_{0}^{L} \frac{M_{0}}{E I} \mathrm{~d} s \\ \theta_{0} & =\frac{M_{0} L}{E I} \end{aligned} θ0 dθθ0=0LEIM0 ds=EIM0L

垂直方向的变形

M 0 E I = d θ d s = d θ d y d y   d s \frac{M_{0}}{E I}=\frac{\mathrm{d} \theta}{\mathrm{d} s}=\frac{\mathrm{d} \theta}{\mathrm{d} y} \frac{\mathrm{d} y}{\mathrm{~d} s} EIM0=dsdθ=dydθ dsdy

d y / d s = sin ⁡ θ \mathrm{d} y / \mathrm{d} s=\sin \theta dy/ds=sinθ

于是有:

M 0 E I = d θ d y sin ⁡ θ \frac{M_{0}}{E I}=\frac{\mathrm{d} \theta}{\mathrm{d} y} \sin \theta EIM0=dydθsinθ

积分计算:

∫ 0 b   d y = E I M 0 ∫ 0 θ 0 sin ⁡ θ d θ \int_{0}^{b} \mathrm{~d} y=\frac{E I}{M_{0}} \int_{0}^{\theta_{0}} \sin \theta \mathrm{d} \theta 0b dy=M0EI0θ0sinθdθ

计算y轴方向的变形b为:

b = E I M 0 ( − cos ⁡ θ 0 + 1 ) b=\frac{E I}{M_{0}}\left(-\cos \theta_{0}+1\right) b=M0EI(cosθ0+1)

水平方向的变形

M 0 E I = d θ d s = d θ d x d x   d s \frac{M_{0}}{E I}=\frac{\mathrm{d} \theta}{\mathrm{d} s}=\frac{\mathrm{d} \theta}{\mathrm{d} x} \frac{\mathrm{d} x}{\mathrm{~d} s} EIM0=dsdθ=dxdθ dsdx

d x / d s = cos ⁡ θ \mathrm{d} x / \mathrm{d} s=\cos \theta dx/ds=cosθ

于是有:

M 0 E I = d θ d x cos ⁡ θ \frac{M_{0}}{E I}=\frac{\mathrm{d} \theta}{\mathrm{d} x} \cos \theta EIM0=dxdθcosθ

积分计算:

∫ 0 a   d x = E I M 0 ∫ 0 θ 0 cos ⁡ θ d θ \int_{0}^{a} \mathrm{~d} x=\frac{E I}{M_{0}} \int_{0}^{\theta_{0}} \cos \theta \mathrm{d} \theta 0a dx=M0EI0θ0cosθdθ

计算x轴方向的变形a为:

a = E I M 0 ( sin ⁡ θ ) a=\frac{E I}{M_{0}}\left(\sin\theta\right) a=M0EI(sinθ)

05-25 20:35