Exam Question
Sate with reasons, how cracking in EACH of the following locations is caused, rectified and avoided:
(a) 'A'Frames (6)
(b) Bed plate transverse girders. (5)
(c) Bed plate longitudinal girders. (5)
Class 2 (2nd Engineer)
MEKG
📅 Jun 2023
Reference Answer
### (a) 'A' Frames (Entablature)
**Causes of Cracking (Why it happens):**
Cracking in 'A' frames, which form the main columnar structure of a large two-stroke engine supporting the cylinder block, is primarily due to a combination of high cyclic stresses and potential structural weaknesses.
* **Stress Concentration:** Sharp changes in the cross-section of the casting or fabricated structure act as stress raisers. High tensile and bending stresses from combustion and inertia forces are magnified at these points, leading to fatigue crack initiation.
**Causes of Cracking (Why it happens):**
Cracking in 'A' frames, which form the main columnar structure of a large two-stroke engine supporting the cylinder block, is primarily due to a combination of high cyclic stresses and potential structural weaknesses.
* **Stress Concentration:** Sharp changes in the cross-section of the casting or fabricated structure act as stress raisers. High tensile and bending stresses from combustion and inertia forces are magnified at these points, leading to fatigue crack initiation.
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