# Machine Design Questions and Answers – Welded Joints Subjected to Bending Moments

This set of Machine Design MCQs focuses on “Welded Joints Subjected to Bending Moments”.

1. The following bracket is welded to the vertical column. The joint undergoes torsional stresses.
a) True
b) False

Explanation: This joint undergoes bending stresses but not torsional stresses.

2. A bracket is shown welded to a vertical column by means of two fillet welds. The bending stress induced in the welds can be given by
a) My/I
b) 2My/I
c) My/2I
d) None of the listed

Explanation: Formula.

3. Calculate the moment of inertia about the axis parallel to welds and shift it to CG by considering thickness of welds t.
a) tᵌ+2000t
b) None of the listed
c) 250000 t
d) 125000 t

Explanation: I=[50tᵌ/12 + (50t)x50² ] x 2, ignoring tᵌ term.

4. Find the bending stress in the top weld is if thickness of weld is t. Given P=15kN and e=120mm.
a) 230/t
b) 360/t
c) 200/t
d) None of the listed

Explanation: σ=My/I or M=15000×120, y=50 and I=250000t.

5. Find the thickness of the weld is if allowable shear stress in the welds is 70N/mm². Given P=15kN and e=120mm.
a) None of the listed
b) 3.35mm
c) 4mm
d) 4.73mm

Explanation: σ=My/I or M=15000×120, y=50 and I=250000t,τ₁=15000/100t or 150/t. Τ=√(σ/2)²+τ₁² or 234.3/t =70 or t=3.35mm and leg=3.35/0.707.

6. The bracket welded to the vertical plate by means of two fillet welds. Calculate the bending stress in the welds if P=40kN, leg=4mm and e=400mm.
a) None of the listed
b) 34N/mm²
c) 24 N/mm²
d)44 N/mm²

Explanation: σ=My/I where y=250mm,I=2xtx500ᵌ/12 where t=4/.707.

7. The bracket welded to the vertical plate by means of two fillet welds. Calculate size of the welds if P=40kN, leg=4mm and e=400mm. Maximum permissible value of shear stress in the weld is 70N/mm².
a) 1.4mm
b) 1.7mm
c) 2.1mm
d) 3mm

Explanation: σ=My/I where y=250mm,I=2xtx500ᵌ/12 and τ₁=P/2xtx500.τ=√σ²+τ₁² or 104/t=70 and h=t/0.707.

8. While calculating bending stress in the following welded joints which of the welds moment of inertia can be neglected?
a) 1
b) None of the listed
c) Both 1 & 3
d) Both 2 & 4

Explanation: Moment of inertia of 1 & 3 can be neglected about their axes but while shifting it to CG, the term Al² cannot be neglected.

9. If a circular shaft is welded to the plate by means of circumferential fillet, then the shaft is subjected to torsional moment M. If throat of weld is t, then torsional shear stress is given by
a) M/2πtr²
b) M/πtr²
c) M/4πtr²
d) None of the listed

Explanation: Stress=Mr/J, here J=2πtrᵌ[I(xx)+I(yy)].

10. Magnetic crack detection method in the welds is destructible examination.
a) True
b) False

Explanation: Magnetic crack detector passes magnetic waves through the sample and thus flux leakage is observed.

11. Testing the ultimate strength of the weld falls in nondestructive examination.
a) True
b) False

Explanation: Testing the ultimate strength leads to fracture of material and hence destructive.

Sanfoundry Global Education & Learning Series – Machine Design.
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