Find the dimensions of a circular cross section steel bar subjected to tension by a force N 20000 N in two hypotheses: a) the maximum allowable stress is 150 N/mm2, b) the maximum acceptable strain is 0.0005. Take E 207GPa

Respuesta :

Answer:

d = 13 mm

d =  15.68 mm

Explanation:

Given data

force = 20000 N

stress = 150 N/mm²

strain = 0.0005

E = 207 GPa

Solution

we know stress = force / area

so 0.0005 = 20000 / area

area = [tex]\pi[/tex]/4 × d²

put the area in stress equation and find out d

d² = 4×force / [tex]\pi[/tex] ×stress

d² = 4× 20000 / [tex]\pi[/tex] ×150

d = [tex]\sqrt{ 4× 20000 / [tex]\pi[/tex] ×150}[/tex]

d = 13 mm

and now we know starin = stress / E

same like stress we find d here

d = [tex]\sqrt{ 4× 20000 / [tex]\pi[/tex] ×0.0005×207×10³ }[/tex]

so d =  15.68 mm

Answer:

a). d = 13 mm

b). d = 16 mm

Explanation:

a). Given :

  Force = 20000 N

  Maximum stress, σ = 150 N/[tex]mm^{2}[/tex]

Therefore, we know that that

σ = [tex]\frac{Force}{area}[/tex]

150 = \frac{Force}{\frac{pi}{4}\times d^{2}}

150 = \frac{20000}{\frac{pi}{4}\times d^{2}}

[tex]d^{2}[/tex] = 169.76

d = 13.02 mm

d [tex]\simeq[/tex] 13 mm

b). Given :

   Strain, ε =  0.0005

   Young Modulus, E =  207 GPa

                                   = 207[tex]\times[/tex][tex]10^{3}[/tex] MPa

Therefore we know that, Stress σ = E[tex]\times[/tex]ε

                                                         = 207[tex]\times[/tex][tex]10^{3}[/tex][tex]\times[/tex]0.0005

                                                         = 103.5 N/[tex]mm^{2}[/tex]

We know that  

σ = [tex]\frac{Force}{Area}[/tex]

103.5 = [tex]\frac{Force}{\frac{pi}{4}\times d^{2}}[/tex]

[tex]d^{2}[/tex] = 246.27

d = 15.69 mm

d [tex]\simeq[/tex]16 mm