Question

The plastic modulus of a section is 5 x 10-4m3. Its shape factor is 1.2 and the plastic moment capacity is 120 kNm. What is the value of the yield stress of the material ?A. 100 N/mm2 B. 200 N/mm2 C. 240 N/mm2 D. 288 N/mm2

Answer 1

Plastic Section Modulus = Zp = 5 * 10⁻⁴ m³
     Shape factor k = Zp / S  = 1.2
     So    S  = elastic section modulus = Zp / k = 4.17 * 10⁻⁴ m³

Plastic Moment Capacity = Mp = 120 kN-m
Fy = Yield strength of the material or Yield stress of the material

                 Mp = Fy * Zp

Fy = yield stress = 120 * 10³ /5 * 10⁻⁴ = 240 * 10⁶ N/m²
     = 240 N / mm²           as  mm = 10⁻³ m