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1.剪切的概念

F

F

F

F

2.挤压的概念

F

F

3.剪切的实用计算

• 切力FQ :剪切面上分布内力的合力。

F

F

m

FQ

F

FQ

m

F

M Pa

• 切应力

[ ]为材料的许用切应力，是根据试验得出的抗剪强度 除以安全系数确定的。

≤ [ ]

4.切应力在截面上的实际分布规律比较复杂，工程上通常采用挤压的实用计算

“实用计算法”，即认为挤压应力在挤压面上的分布是均匀的。故挤压应力为:

M Pa

Fjy为挤压力（N）；Ajy为挤压面积（ ）

≤ [ ]

M Pa

F

M

F

ΣMo(F)＝0

F 一 M ＝ 0

F = 2M / d = 2 x 181481 / 48 = 7561.7 N

FQ＝F j y＝F＝7561.7N

2.校核键的强度。

τ＝

=

M P a =17．4MPa＜[τ]

σjy＝ ＝ MPa＝54.2MPa＜[σjy]

8

10

2

A = 8 x 5 x 2 + 3.14 x 5 x 2 x 5

= 237mm

2

= 100KN / 237 mm

= 422 M Pa

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