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发表于 2010-9-5 22:13:00
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来自 四川成都
对多轴疲劳,当了应力选用不同的应力计算得到的裂纹萌生寿命是相差很大的。
; H/ Z" H- N6 ]" x R一半要分单轴疲劳或多轴疲劳;多轴比例加载或非比例加载。
( E+ I, y, S/ P$ A, }3 ?摘录几段文字供大家参考:
& h. h% j% X) |! D- i6 X9 o: c/ y$ \1 Maximum Principal Stress and Strain! F2 ]3 u) K6 s$ q
The main benefit of this approach is its simplicity, however, its main difficulty is that no account is
1 e. ?% a$ l# I6 V- P+ W6 xtaken of the other two principals, σ2,σ3 and ε2, ε3. The direction of the maximum principal is also
( q. u9 b R0 g8 eassumed to be fixed. In addition, the method is really limited to the prediction of Stage II type cracks, ?7 I( t. D$ Y* c& O
which are by definition perpendicular to the principal directions. This method effectively describes the9 m& @! K9 s- L+ a& T
uniaxial stress state. It can be successfully applied in situations where the direction of the maximum6 n: V) r7 f* j' Q* o
principal stress has been demonstrated to be relatively fixed. The model is unsuited to non x) a( `; U2 H7 y
proportional loading conditions.! m! G4 d5 A$ E' p- a3 p! }
- r0 L# S% ^- k2 Maximum Shear Stress and Strain, Tresca
9 t& f9 R' J5 JThis model is a little more complicated to apply than the maximum principal stress approach.
2 q) J7 o* \# s* u' ^8 WHowever, it does take into account the magnitude of the minimum principal stress or strains and also
, ^6 [0 V3 Z% Q& r: K7 J( Eaccumulates damage of the plane of maximum shear and so the method should be more applicable* ]% P, I I) S/ l' C. ~: S& R
to the prediction of Stage I type cracks. As with the maximum principal approach, the maximum shear
: G X1 n$ H6 Q( l( w: napproach is limited to situations where the orientation of the plane of maximum shear is relatively
4 G) x2 o& T9 x( c" b% X# M, }fixed.2 F; g% B2 X) b* K
; |% r: `" d& X3 n/ [( w3 v1 P1 L
3 Von Mises' Effective Stress and Strains- u. A2 x# g4 J/ I7 `" v& M
As opposed to the maximum principal and shear models, the Von Mises' model does take into' E7 d. ?' m& n9 F! m" v
account the influence of the median principal. The effective Von Mises' stresses and strains are( n' _" q* R% X0 p* H" x: c; O, x
scalar quantities and offer no information on the physical damage observed during the fatigue
; T1 L4 K* m! s5 y" B/ Qprocess. The model, therefore, does not account for non proportional loading.; s5 [! f) m Z' W# A8 Q
* z7 m' i# d- t# R6 F
有很多人做过这方面的研究和总结,也总结了一些公式。但工程上常用的为以上三种外加带绝对值的。/ p/ Q3 I, c ]8 j* v
有条件的可通过万方或其它论文库查询。 |
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