# Homework Help: Stress concentration factor

1. Aug 16, 2006

### teng125

2. Aug 16, 2006

### Astronuc

Staff Emeritus
Without knowing the load distribution, one cannot tell if the local stress is tension, compression, bending or shear. Are there other considerations.

If a shaft is rotating between two bearing which are not properly aligned, on could have alternating states of tension and compression, with bending, during the cycle of rotation.

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3. Aug 16, 2006

### teng125

Rp0,2 = 450 MPa, Rm = 1000 MPa. It is loaded by a bending moment Mb = 6,0 kNm and a torque T = 3,0 kNm.

than is all data give.is it possible to solve??

4. Aug 16, 2006

### teng125

pls help.........

5. Aug 16, 2006

### teng125

pls help...........

6. Aug 16, 2006

### Astronuc

Staff Emeritus
Well, the bending moment would produce bending in the shaft, but the torque would produce torsion. It does not appear that there is a tensile or compressive load.

For the bending moment, one would use the appropriate b-stress concentration factor.

From the figure viewer1.bmp, there should be some other data besides the three columns: z, b, t There is usually a relationship between the diameter ratios, the fillet radius and the stress concentration factor.

Are there no examples in the course text book?

7. Aug 17, 2006

### teng125

nono,but from the shaft can we know whether it is torsion or bending stress that occur at the location 1 and 3??

8. Aug 17, 2006

### Astronuc

Staff Emeritus
If a torque is applied to a shaft, then the shaft experiences torsion.

If a moment (bending force) is applied to the shaft, the shaft will experience bending stress (moments) along its length. The magnitude of bending will depend on the magnitude of bending force and the distance between point of application and point of interest. Also, more bending would tend to occur in the smaller section.

The change in cross-section results in a reduction of area which increase the magnitude of stress in the smaller cross-section. The objective of the rounded shoulder fillet is to reduce the stress concentration which would occur if there was a sharp corner or transition from the greater diameter section to the smaller diameter section.

Then the matter becomes one of determining the magnitude and location of stress, and comparing it to technical limits like yield/proportional stress (practical upper limit of elastic range) or ultimate tensile stress, and performing a fatigue analysis.

Last edited: Aug 17, 2006
9. Aug 17, 2006

### teng125

while if the question ask where is the critical section if a torque is acting??

10. Aug 17, 2006

### teng125

' where is the critical section in the stepped shaft if a torque is acting '