Type of stress in screw thread

Discussion

• Sravanthi   -Posted on 04 Nov 15
  Different stresses induced in a screw body are:
  
  1) Direct compressive or tensile stress: This stress is induced due to axial force. It is given as σ = W / (π /4) d²
  
  2) Torsional shear stress: This stress is induced due to twisting moment or torque.
  It is calculated using the formula: τ = 16 T / πd³
  
  3) Buckling of screw: Buckling failure is checked when axial load on screw is compressive and the unsupported length of screw is long.
  
  Different stresses induced in screw threads are:
  
  1) Bearing pressure: This pressure exists between screw and nut, which have relative motion between them. The formula to calculate bearing pressure is: P = W / (π/4 [d₁² – d₂²] Z)
  
  2) Direct shear stress in screw and nut threads: This stress is induced in screw threads at core diameter and in nut threads at nominal diameter due to axial load acting on the them. The formula to calculate direct shear stress is:
  τ = W/ (π d t Z)
  

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