ME 314 Quiz#6Weld Analysis

Analysis of welds under torsional and direct shear stresses

A bracket is welded to a wall. The weld pattern is all-around on a 4 inch by 3 inch rectangle. The bracket is parallel to the wall and under a load of 2000 lbs acting at a distance of 12 inches. The loading of the weld bead is primarily due to torsion and direct shear. The Electrode is E120 and the fillet weld size (leg) is 0.25 inch. Is the factor of safety guarding against weld metal yielding more than 3.5?

  1. (Statics) Transfer the load to the center of the weld group.
  2. Determine the shear stress in the weld as a result of the direct shear only.
  3. Throat:______
  4. Throat Area:______
  5. Shear stress due to direct shear force only and its direction:______
  6. The torque acting on the weld group:______
  7. The formula to estimate shear stress due to torque (this formula is similar to the torsion of a bar formula (from strength of materials):______
  8. Are the shear stresses due to torsion the same on all corners? (Yes No)
  9. Which corner(s) experience the maximum combined shear stress ______
  10. Distance from weld group centroid to the critical corner:______
  11. Unit area polar moment of inertia formula and value for the weld pattern from table:
  1. Actual polar moment of inertia based on the throat:______
  2. Shear stress due to torsional moment only and its direction:______
  3. The magnitude of the combined (resultant) shear stress:______
  4. Yield strength in shear Sys for the weld metal:______
  5. Factor of safety ______. Acceptable (Yes No).

Combining various shear stresses (based on AWS code)

  1. Direction of shear stress in direct tension or compression (In plane of weld Out of plane)
  2. Direction of shear stress in direct shear: (IP OP)
  3. Direction of shear stress due to bending moment: (IP OP)
  4. Direction of shear stress in torsional shear: (IP OP)

Combine all in-place shear stresses vectorially. Combine all out-of-place shear stresses vectorially. Combine IP and OP shear stresses vectorially.

Fatigue Analysis of Welds - Determining the endurance limit.

Scope: fully alternating stresses

  1. Write the endurance limit formula (S’e) with all the correction factors:______
  2. Estimate the endurance limit of the rotating bending test experiment for the weld material (E70 electrode – steel):______
  3. Determine the surface correction factor (assume hot-rolled or as forged surface): ______
  4. Reduce the S’e (endurance limit which is a bending stress - normal stress) to endurance limit in shear S’es(to compare to shear stress in weld):______

Assume the nominal shear stress  fluctuates with a fully reversible magnitude of 4717 psi. Also assume that stress concentration factor is 2.7 (associated with the end of the weld – Table 9-5). The book is not clear how to select the stress concentration factor – I will specify what values to be used. Would the factor of safety against eventual weld fracture is more than 3.0?

  1. Determine the actual magnitude of the fluctuating stress:______.
  2. Determine the factor of safety:______Acceptable (Yes No)
  3. When estimating the strength of the weld metal, we must use the properties of the base metal in hot rolled conditions if these are lower than the weld metal properties. (True False).
  4. Pieces of low carbon steel (AISI 1010) are to be welded with E60 electrodes. What value of Sy:______and Sut ______should be used in analysis of the weld metal?