Calculating Stresses at an Angle: Why Does it Matter?

  • Thread starter Thread starter fonseh
  • Start date Start date
  • Tags Tags
    Angle Matter
Click For Summary
SUMMARY

The discussion centers on the calculation of normal and shear stresses on a plane inclined at 30 degrees anticlockwise from plane AD using Mohr's Circle. The original poster (OP) applies the formula for maximum and minimum stresses, yielding results of 32.3 MPa and -22.3 MPa, which differ from the expected answers of 12.5 MPa and -2.3 MPa. The OP questions the validity of their calculations and whether their understanding of the concepts is flawed, particularly regarding the angle of principal stresses derived from the equations.

PREREQUISITES
  • Understanding of Mohr's Circle for stress analysis
  • Knowledge of normal and shear stress equations
  • Familiarity with trigonometric functions in engineering contexts
  • Basic principles of mechanics of materials
NEXT STEPS
  • Study the derivation and application of Mohr's Circle for two-dimensional stress analysis
  • Learn how to correctly calculate principal stresses and angles using the equations provided
  • Explore the impact of angle orientation on stress calculations
  • Review case studies involving normal and shear stress in engineering applications
USEFUL FOR

Students and professionals in mechanical engineering, civil engineering, and materials science who are involved in stress analysis and want to deepen their understanding of stress transformations and Mohr's Circle applications.

fonseh
Messages
521
Reaction score
2

Homework Statement


DSC_0038.JPG
Why can't i use the equation to determine the normal stress and shear stress ? Is my concept wrong ? I use the method in the link to do this question. The question said the
stress on a plane making angle 30 degree anticlockwise from plane AD .

Homework Equations

The Attempt at a Solution



When it's anticlockwise , the angle is positive
http://www.dummies.com/education/science/using-mohrs-circle-to-find-principal-stresses-and-angles/
Mod note: Image of work has been deleted. OP will be including work in a subsequent post.[/B]
 
Last edited by a moderator:
Physics news on Phys.org
$$\sigma _(max) $$ = ((25-15 )/2 ) + 20cos60 + 20sin60 = 32.3MPa$$\sigma x_(min) $$ = ((25-15 )/2 ) - 20cos60 - 20sin60 = -22.3MPa

But the ans is 12.5 and -2.3MPa
 
##r = sqrt ( ((\sigma _x -s \sigma_y) /2 )^2)+ (\tau_xy)^2) = 28##

##tan2\theta_p = 2\tau_xy / (\sigma _x -s \sigma_y)
= 2(20) / 40## , ##\theta_p = 22.5## degree ,
This is different from the ##\theta_p ## = -68 degree given
 
Last edited by a moderator:
Image for mohr's circle
https://www.physicsforums.com/attachments/dsc_0038-jpg.110448/
 
Is the ans provided wrong ? Or is my concept wrong ?
 
bump
 

Similar threads

Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
6
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
12
Views
3K