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Real Life Example 01.pptx

  1. Real Life Example in Mechanics of Material's By Sina Abedini n
  2. ELEMENTARY STRESS SYSTEMS 1.Stress and strain in uni -axial solid hollow bars Explain: Work through the example below: An iPod ; with a mass 30 grams in dangled its earplug cable. a)Assuming that copper wire of diameter 0.40mm inside the cable carries the entire load ; evaluate the stress in the wire due to the weight of the iPod b)If the wire in (a) is1.50m long ; by how much will it stretch? c)Assuming that the plastic insulation ; which fits snugly over the wire and has an external diameter of 1mm ; carries the entire load ; evaluate the stress in insulation due to the weight of iPod d)If the insulation is made from uPVC calculate the extension of the insulation in circumstances described in (c)
  3. 𝑎)𝜎 = 𝐹 𝐴 = 𝑚𝑔 𝜋 4 𝑑2 = 30 × 10−3 × 9.81 𝜋 4 × (0.4 × 10−3)2 0.4mm 𝐹 = 𝑚𝑔 = 30 × 10 −3 × 9.81 2.3 × 106 𝑁 𝑚2 1.5m 𝑏)δ = 𝑃𝑙 𝐴𝐸 = 𝑚𝑔 × 𝑙 𝜋 4 𝑑2 × 𝐸 = 30 × 10−3 × 9.81 × 1.5 𝜋 4 × (0.4 × 10−3)2× 110 × 109 31.9 × 10−6 𝑚
  4. 0.4mm 1mm 1.5m 𝐹 = 𝑚𝑔 = 30 × 10 −3 × 9.81 0.2mm c)𝜎 = 𝐹 𝐴 = 𝑚𝑔 𝜋 4 𝑑0 2 −𝑑1 2 𝐸 = 30×10−3×9.81 𝜋 4 (0.0012−0.0042) 0.29 𝑁 𝑚2 𝑑)𝛿 = 𝑃𝑙 𝐴𝐸 = 𝑚𝑔𝑙 𝜋 4 𝑑0 2 − 𝑑1 2 𝐸 = 30 × 10−3 × 9.81 × 1.5 𝜋 4 (0.0012 − 0.0042) × (2 × 109) 3.35 × 10−4𝑚
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