《材料力学》课程PPT教学课件（双语版）第八章 强度理论

STRENGTH THEORIES 2 Theory of the maximum tensile strain( the second strength): This theory considers the main cause of rupture to be the maximum tensile strain The member will rupture as the maximum tensile strain reaches the limit strain in axial a tension a1=6.;(21>061=1[1-(2+3)=n 1)、 Criterion of failure:σ;-(o2+a3)=a 2) Strength condition G1-A(o2+o3)≤ ] 3) Application range: May be applied to the members with the failure form of brittle rupture

2、Theory of the maximum tensile strain（the second strength）： This theory considers the main cause of rupture to be the maximum tensile strain. The member will rupture as the maximum tensile strain reaches the limit strain in axial tension ;( 0)  1 =  b  1   ( ) E E  b  1 =  1 −   2 + 3 = 1 1)、Criterion of failure： 2)、Strength condition： 3)、Application range：May be applied to the members with the failure form of brittle rupture . ( )  1 −   2 + 3 =  b  − ( + )   1 2 3 11

强成论 最大伸长线应变(第二强度)理论: 认为构件的断裂是由最大伸长线应变引起的。当最大伸长线 应变达到单向拉伸试验下的极限应变时,构件就断了。 Ei1=Eb;(E1>0) E-(o2+0s=E 1、破坏判据:a1-(a2+a3)=a6 2、强度准则:a1-(o2+a)≤[] 3、实用范围:实用于破坏形式为脆断的构件

二、最大伸长线应变（第二强度）理论： 认为构件的断裂是由最大伸长线应变引起的。当最大伸长线 应变达到单向拉伸试验下的极限应变时，构件就断了。 1、破坏判据： ;( 0)  1 =  b  1  2、强度准则： 3、实用范围：实用于破坏形式为脆断的构件。  ( ) E E  b  1 =  1 −   2 + 3 = 1 ( )  1 −   2 + 3 =  b  − ( + )   1 2 3 12

STRENGTH THEORIES 3 Theory of the maximum shearing stress (the third strength): This theory considers the main cause ofrupture to be the maximum shearing stress The member will rupture as the maximum shearing stress reaches the limit shearing stress in axial tension max zmn=01-30s 2 2 1) Criterion of failure =6 2) 2) Strength condition: 01-O3 ≤[] 3)Application range: May be applied to the members with the failure form of plastic yield

3、Theory of the maximum shearing stress（the third strength）： This theory considers the main cause of rupture to be the maximum shearing stress. The member will rupture as the maximum shearing stress reaches the limit shearing stress in axial tension. s  max =  s s      = = − = 2 2 1 3 max 1)、Criterion of failure： 3)、Application range：May be applied to the members with the failure form of plastic yield .  1 − 3 =  s 2)、Strength condition：  −    1 3 13

强成论 三、最大剪应力(第三强度)理论: 认为构件的屈服是由最大剪应力引起的。当最大剪应力达 到单向拉伸试验的极限剪应力时,构件就破坏了。 max E T 03 = T 2 2 1、破坏判据:σ1-σ3=σ 2、强度准则:G1-3s[o] 3、实用范围:实用于破坏形式为屈服的构件

三、最大剪应力（第三强度）理论： 认为构件的屈服是由最大剪应力引起的。当最大剪应力达 到单向拉伸试验的极限剪应力时，构件就破坏了。 1、破坏判据： s  =  max 3、实用范围：实用于破坏形式为屈服的构件。 s s      = = − = 2 2 1 3 max  1 − 3 =  s 2、强度准则：  −    1 3 14