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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 Con... 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, the labels correspond to the following:
- A: Limit of proportionality
- B: Elastic limit
- C: Yield point
- D: Maximum stress
- E: Break stress
These points represent significant stages in the behavior of materials under stress.
Step 2
Construct the vector/force diagram using scale 1 mm = 1 kN
Answer
To construct the vector/force diagram:
- Select a suitable scale; here, 1 mm represents 1 kN.
- Begin at point A, where the force of 500 kN acts vertically upwards.
- At point C, draw a horizontal line representing the force of 375 kN towards the right.
- From point B, draw a line at 30° to the horizontal for the force in member AD, which acts at an angle.
- Then, draw the force BD vertically downwards as per the triangles formed by the framework.
Ensure all forces are represented accurately, and label the vectors accordingly.
Step 3
Determine graphically the magnitude and nature of the force in AD, BD and CD
Answer
To determine the forces graphically, follow these steps:
- Utilize the constructed vector/force diagram.
- Measure lengths for members AD, BD, and CD using the previously established scale.
- For member AD, the measured length corresponds to 250 kN (compression).
- For member BD, the length represents 433 kN (tension).
- For member CD, the length shows 216 kN (tension).
- Nature of forces:
- AD acts as a strut (compression).
- BD acts as a strut (tension).
- CD acts as a tie (tension).