4. Nn
PP
Nn
Compression
P PA
σ =
Nn
A
+ =
P
A
Nn
− =P 0∵( )
Normal Stress
Normal Component of Stress to Cross-section
Nn
PP
Nn
σ =
Nn
A
=
−P
A
Nn
+ =P 0∵( )
−
P P
Tension
A
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7. Stress on Slant Cross-section
Normal stress
Shear stress
A’ =
cos θ
A
σ’
Pn
A’
=
=
P
A
cos2
θ
τ’ Ps
A’
=
=
P
A
cos θsin θ
P
P
P P
Aθ
PPn = cos θ
Ps P= sin θ
A’
θ
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9. Summary
1. Normal Stress
2. Shear Stress
3. Dependency on Cross-section
Internal force per Area [ N/m2, Pa ]
Tension is positive Compression is negative
Positive Negative
Cross-section A Cross-section A’
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