Shear Stress: Examining the Discrepancy

[fonseh]

Homework Statement

In the notes, the author stated that the shear stress is constant over the bottom face of the segment ... why in figure 7-4 , we can see that the shear stress varies ?

Homework Equations

The Attempt at a Solution

Which is correct ? The red circled part or the figure ? [/B]

 

[PhanthomJay]

Homework Statement

In the notes, the author stated that the shear stress is constant over the bottom face of the segment ... why in figure 7-4 , we can see that the shear stress varies ?

Homework Equations

The Attempt at a Solution

Which is correct ? The red circled part or the figure ? [/B]

They are both correct, the Profile view shows the shear stress at the bottom, constant across the width t, the other views show the varying bending stresses , not shear stresses, but if you look carefully in the 3D view you will find the constant longitudinal shear stress at the bottom of the plane ( $\tau$)

 

[fonseh]

the other views show the varying bending stresses , not shear stresses,

what do you mean by the other view here ? the figure 7-4 (b) in the first photo ?

 

[fonseh]

They are both correct, the Profile view shows the shear stress at the bottom, constant across the width t, the other views show the varying bending stresses , not shear stresses, but if you look carefully in the 3D view you will find the constant longitudinal shear stress at the bottom of the plane ( $\tau$)

shear stress at the bottom plane ?
In the profile view , we could see that the stress ( i am not sure bending stress or shear stress) varies linearly ... But , you said it's constant across the width ? I'm confused

 

[PhanthomJay]

You should have long learned about bending stresses before tackling distributed shear stress. Figure 7.4b shoes the bending stress varying from max compression to 0 from top to NA, then up to max tension at bottom. Shear stress is shown in fig 7,4c as constant at the bottom across the thickness, t.

 

[fonseh]

You should have long learned about bending stresses before tackling distributed shear stress. Figure 7.4b shoes the bending stress varying from max compression to 0 from top to NA, then up to max tension at bottom. Shear stress is shown in fig 7,4c as constant at the bottom across the thickness, t.

so , in figure 7.4 b , the figure shown is the bending stress across the vertical length of beam ?

 

[PhanthomJay]

so , in figure 7.4 b , the figure shown is the bending stress across the vertical length of beam ?

Yes, My/I bending stresses.