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a) (i) Distinguish clearly between fatigue and creep with reference to deformation of metals - Leaving Cert Engineering - Question 2 - 2013
Question 2
a) (i) Distinguish clearly between fatigue and creep with reference to deformation of metals. Metal fatigue is defined as failure due to on/off loading or cyclic st... show full transcript
Worked Solution & Example Answer:a) (i) Distinguish clearly between fatigue and creep with reference to deformation of metals - Leaving Cert Engineering - Question 2 - 2013
Step 1
Distinguish clearly between fatigue and creep with reference to deformation of metals.
Answer
Metal fatigue refers to the failure of a material due to cyclic loading or fluctuating stresses, often leading to the formation of minute cracks under repeated stress. In contrast, creep is a gradual, time-dependent deformation that occurs when a material is subjected to a constant load over an extended period, especially at elevated temperatures.
Step 2
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Step 5
Determine the ultimate tensile strength (UTS);
Answer
To find the ultimate tensile strength, take the maximum load from the graph data and divide it by the cross-sectional area (C.S.A.). For this test, the UTS can be calculated using the formula:
ext{UTS} = rac{ ext{Max. Load}}{ ext{C.S.A.}}
Calculate the C.S.A. for a 10 mm diameter:
ext{C.S.A.} = rac{ ext{π} imes (5 mm)^{2}}{1000^2} = 78.54 mm^2
Then, using the maximum load of 108 kN:
ext{UTS} = rac{108 ext{ kN}}{C.S.A.} = 1.38 ext{ kN/mm}^2
Step 6
Determine the 0.1% proof stress;
Answer
To calculate the 0.1% proof stress, first understand that it is derived from the load corresponding to a permanent extension of 0.05 mm on a 50 mm gauge length specimen.
Given:
- Proof Load = 88 kN
- C.S.A calculated earlier = 78.54 mm^2
Applying the formula:
ext{0.1% proof stress} = rac{ ext{Proof Load}}{ ext{C.S.A.}} = rac{88 ext{ kN}}{C.S.A.} = 1.12 ext{ kN/mm}^2
Step 7
Outline three advantages of using non-destructive tests (NDT) in industrial engineering.
Answer
Non-destructive tests offer several advantages, including:
- Ensuring quality control as they allow for the examination of materials and components without causing any damage.
- Reducing costs as expensive components do not need to be destroyed during testing, leading to cost savings.
- Facilitating the detection of flaws at a surface level or internally, enhancing safety and reliability in engineering applications.
Step 8
Name the NDT shown below. Describe the principle of operation and the applications of this NDT.
Answer
The NDT shown is Eddy Current Testing. It involves the use of a coil energised with high-frequency alternating current, which generates a changing magnetic field. This field induces eddy currents in the material being tested. Any defects or variations in the material affect the flow of these currents, which can be detected using sensitive electrical equipment. Eddy current testing is primarily applied to non-ferrous metals for detecting surface and near-surface defects.