Question about thick walled cylinder

[spree]

Hi. I'm a third year ME student and I am confused about something. I've just started to take ME design course this semester and this is from my first hw. I solved everything but i don't know about the shear stress. since there is no torsion I want to say there is no shear stress but i doubt that if it was the case why would the teacher ask about it detailed like this. Any help would be appreciated. thanks.

''A thick walled open ended cylinder is made of steel ( E = 200 GPa) has an inside diameter of 80 mm and an outside diameter of 100 mm. The cylinder is subjected to an internal pressure of 20 MPa. Determine the stress components sigma(r), sigma(t) sigma(l) and the maximum shearing stress at the inner and outer surfaces of the cylinder and at r = 45 mm.''

 

[nvn]

spree: Because the cylinder is open ended, what does that tell you about sigma_L?

Can you compute the cylinder principal stresses? Let, e.g., sigma_x = sigma_t, and sigma_y = sigma_r. After you compute the principal stresses, put them in this order; sigma1 > sigma2 > sigma3. After that, look up the formula for maximum shear stress. You must post relevant equations yourself. See the homework template.

 

[spree]

Hi,
Thank you so much for your answer.
Cylinder is open ended so sigma_L must be zero. no force in that direction. I have found sigma_r and sigma_t also. but in the lecture the teacher had not said anything about shear stress in thick walled cylinders that's why i got confused in the first place. So I've looked up the formula and found it. but still, I'm having hard time figuring out why there is shear stress even tho there's no torsion.

 

[spree]

oh because there are two principle stresses? I think I got it now I was missing something basic.