Calculator - Dynamically loaded screw joints, Basic joint diagram

Preloaded bolt under dynamic loading

Metric thread :

Initial tensile stress : σ_i=F_i/A_t

xR_p0.2

Minimum value of clamping force: F_m

Joint stiffness factor C=k_b/(k_b+k_m)

tensile stress area A_t =π/4 d₀²; d₀=(d₂+d₃)/2

mm²

ultimate tensile strength R_m

MPa

yield strength R_p0.2

MPa

initial tensile stress σ_t = σ'_t x R_p0.2

MPa

maximum tensile load F_0.2= R_p0.2 x A_t

initial preload F_i = σ_t x A_t

load fluctuation bolt dF_i=F_0.2- F_i

bolt stress fluctuation dσ_i= dF_i/ A_t

MPa

load fluctuation clamped material dF_m=dF_i *(1-C)/C

remaining clamping force F_m=F_i-dF_m

Total load fluctuation F_b= dF_i + dF_m

Static strength: The warning about the fatigue strength can be ignored.

Fatigue strength: In infinite life or safe stress designs stresses higher then the endurance limit are avoided and a factor of safety is taken into account. Most rotating and oscillating components must sustain over 10^6 load cycles during service life and thus are to be designed for infinite fatigue life.