Fasthet
Fasthet
Fasthet
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RA nov 2007<br />
− − ( − fu , − fu<br />
)<br />
max stor τ<br />
σ2<br />
+ + ( fu , fu<br />
)<br />
Bruddkriterier<br />
+ −<br />
f : strekkbruddspenningen, f : trykkbruddspenningen<br />
u u<br />
Normalspenningskriteriet : σ < f og -σ<br />
< f<br />
+ −<br />
max u min u<br />
σ1<br />
max liten τ<br />
Indrefriksjonskriteriet<br />
Normalspenningskriteriet<br />
(Coulomb, Rankine)<br />
Indrefriksjonskriteriet :<br />
max min<br />
Brudd når: − ≥ 1<br />
+ −<br />
fu fu<br />
Bruddskjærspenning<br />
τ<br />
u<br />
+ −<br />
u u<br />
+ −<br />
u + u<br />
Ved isotrop strekkspenning σ = σ = σ = σ<br />
σ<br />
k<br />
=<br />
=<br />
f ⋅ f<br />
f f<br />
f ⋅ f<br />
f f<br />
+ −<br />
u u<br />
+ −<br />
u − u<br />
σ σ<br />
1 2 3<br />
fasthet 20<br />
k
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