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7.3 FIGURE 7.3 below shows a stress-and-strain diagram - NSC Mechanical Technology Welding and Metalwork - Question 7 - 2021 - Paper 1
Question 7
7.3 FIGURE 7.3 below shows a stress-and-strain diagram. Label parts A–E. 7.4 FIGURE 7.4 below shows a steel framework. Answer the questions that follow. 7.4.1 Cons... show full transcript
Worked Solution & Example Answer:7.3 FIGURE 7.3 below shows a stress-and-strain diagram - NSC Mechanical Technology Welding and Metalwork - Question 7 - 2021 - Paper 1
Step 1
Label parts A–E in the stress-and-strain diagram
Answer
In the stress-and-strain diagram (FIGURE 7.3), the following labels are assigned:
- A: Limit of proportionality
- B: Elastic limit
- C: Yield point
- D: Maximum stress
- E: Break stress
These points represent the various stages in the relationship between stress and strain for a material, illustrating its elastic and plastic behavior.
Step 2
Construct the vector/force diagram using scale 1 mm = 1 kN
Answer
To construct the vector/force diagram for the steel framework (FIGURE 7.4):
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Identify all the forces acting on the framework:
- 500 kN acting vertically upwards at point B.
- 125 kN acting horizontally from point C to D.
- 375 kN acting horizontally from point D to A.
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Use the scale 1 mm = 1 kN to represent these forces accurately.
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From point B, draw a line vertically upwards representing the 500 kN force.
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Draw a horizontal line from point C to D for the 125 kN force, and then draw a line from point D to A for the 375 kN force.
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Ensure angles are represented as per the figure (30° and 60°).
Step 3
Determine graphically the magnitude and nature of the force in AD, BD and CD
Answer
To determine the forces graphically:
- Begin with the vector diagram from the previous step.
- Measure the lengths of each vector corresponding to the forces in members AD, BD, and CD.
- For member AD, the magnitude is 250 kN (compression).
- For member BD, the magnitude is 433 kN (tension).
- For member CD, the magnitude is 216 kN (tension).
- Indicate the nature of each force:
- AD is a strut (compression).
- BD and CD are ties (tension).
- Use these measurements to annotate the diagram appropriately.