FKM Classification Parameters (Non-Welded)

The parameters for non-welded calculations are listed in both the Assign Material tab and the My Material tab of the Assign Material dialog.

The defaults are with respect to material = steel.

The following are the parameters listed in Assign Material tab.

Parameter Description
Effective Diameter (Deff) Effective diameter of the semi-finished product (default = 7.5mm)
Anisotropy factor (KA) Default = 0.9
Plastic Notch Factor – Nominal (Kp_sigma) Default = 1
Plastic Notch Factor – Shear (Kp_tau) Default = 1
Relative Stress Gradient X (G_sigmax) Relative stress gradient in normal direction (Default = 0.1 mm-1)
Relative Stress Gradient Y (G_sigmay) Relative stress gradient in normal direction (Default = 0.1 mm-1)
Relative Stress Gradient XY (G_sigmaxy) Relative stress gradient in shear direction (Default = 0.1 mm-1)
Overload Factor (Overloading) Parameter to decide overload situation. Options: F1, F2, F3, F4. Based on the selection, the fatigue limit calculation formula may vary. (Default – F2)
Surface Roughness (Rz) Average roughness of the component surface, (default = 100 μm)
Surface Treatment Factor (Kv) Default = 1
Coating Factor (Ks) Default = 1
Temperature Factor (Ktd) Default = 1
Material Safety factor (jF) Material safety factor for non-welded steel based on regular inspection (default = 1.5)
Load Safety factor (jS) Safety factor defined by design loads (default = 1.0)
Partial safety factor for allowable defects in castings (jG) Material safety factor for Casted materials (default =1, as just steel is supported)
Total Safety Factor (jD)

Total safety factor, based on jF, jS, jD and KT,D ,

jD = jS . (jF/ KT,D)

The following are the parameters listed in My Material tab.

Parameter Description
Tensile Strength (Rm) Listed in SN tab (default = 300 N/mm2)
Yield Strength (Rp) Listed in SN tab (default = 180 N/mm2)
Elastic Modulus (E) Listed in SN tab (default = 2e5 N/mm2)
Strain At Break Point (A%) Listed in SN tab (default = 10% or 0.1)
Normal Fatigue Limit (σ_wzd) Listed in SN tab (default = 140 N/mm2)
Shear Fatigue Limit (τ_wzd) Listed in SN tab (default = 80 N/mm2)
Number of Cycles at Knee Point, Normal Stress (Nd_σ) Listed in SN tab (default = 1e6 cycles)
Number of Cycles at Knee Point, Shear Stress (Nd_τ) Listed in SN tab (default = 1e6 cycles)
SN curve slope, Normal Stress (K_σ) Listed in SN tab (default = 5)
SN curve slope, Shear Stress (K_τ) Listed in SN tab (default = 8)
Fatigue Stress Factor, Fully Reversed, Normal (fw_σ) Listed in Other tab (default = 0.4)
Fatigue Stress Factor, Fully Reversed, Shear (fw_τ) Listed in Other tab (default = 0.577)
Constant, Technological Size Factor for Tensile Strength (adm) Listed in Other tab (default = 0.15)
Constant, Technological Size Factor for Yield Strength (adp) Listed in Other tab (default = 0.4)
Constant, Technological Size Factor @ adm (Deff,N,m) Listed in Other tab (default = 40mm)
Non-linear Strain Stress Factor under bending – GJL (KNL) Listed in Other tab (default = 1.0)
aG Constant for (Kt-Kf) ratio for Fatigue Strength Factor (aG) Listed in Other tab (default = 0.4)
bG Constant for (Kt-Kf) ratio for Fatigue Strength Factor (bG) Listed in Other tab (default = 2400)
Constant For Roughness Factor, Normal Stress (aR_σ) Listed in Other tab (default = 0.22)
Minimum permissible tensile strength constant (Rm,N,min) Listed in Other tab (default = 400 N/mm2)
Constant for Mean Stress Sensitivity (aM) Listed in Other tab (default = 0.35)
Constant for Mean Stress Sensitivity (bM) Listed in Other tab (default = -0.1)
Compression Strength Factor, for tension, compression (f_σ) Listed in Other tab (default = 1.0)
Compression Strength Factor, Shear (f_τ) Listed in Other tab (default = 1.0)
Material Parameter Epsilon_0 (Epsilon_0) Listed in Other tab (default = 0.05)
Ductility factor (q) Listed in Other tab (default = 0)

Formulation

Current support in the evaluation build is for steel only.

Cyclic degree of utilization for normal and shear stresses:

Assessment
[ Stress amplitude / (critical amplitude/total safety factor)]

aBKx=σax/(σBKx/jD)1,aBKx=σax/(σBKx/jD)1,
                        
aBKy=σay/(σBKy/jD)1,aBKy=σay/(σBKy/jD)1,
                            
aBKxy=Taxy/(TBKxy/jD)1,aBKxy=Taxy/(TBKxy/jD)1,
                            

Master Assessment Calculation
aNH=12·(|aBK,x+aBK,y|+(aBK,xaBK,y)2+4·aBK,τ2)aNH=12(aBK,x+aBK,y+(aBK,xaBK,y)2+4aBK,τ2)

aGH=a2BK,x+a2BK,yaBK,x·aBK,y+a2BK,τaGH=a2BK,x+a2BK,yaBK,xaBK,y+a2BK,τ

aBK,σv=q·aNH+(1q)·aGH1aBK,σv=qaNH+(1q)aGH1

Formulation for Static Assessment

The following process is followed for Static Assessment (non-welded):
  1. Equivalent Stress ( σVσV ) = Maximum combined stress across all loadcases in the event.
  2. Calculate Static Strength ( σSKσSK ).

    σSK = Rp * nplσSK = Rp * npl

    RpRp = Modified yield strength calculated from Size factor, Anisotropy factor and Yield strength.

    nplnpl = Plastic support factor.

  3. Calculate Static Utilization ( aSKaSK )(1)
    aSK=(σV(σSKjD))1aSK=σV(σSKjD)1

    jDjD = Total safety factor.