OS-V: 0900 Constant Amplitude Stress-Life Analysis

A notched test specimen is subjected to tensile loading and a Constant Amplitude Stress-Life Analysis is performed using OptiStruct.

The Stress-Life result from OptiStruct is compared with the results from eFatigue calculator, for the element 215576.


Figure 1. Model with Loading Conditions

Benchmark Model

The model is a test specimen of thickness 9.5mm, subjected to tensile loading of 1150 N at circular holes, normal to the notch. The model was meshed with first-order shell elements and the loading is applied to RBE3 elements that are connected to the holes. The Signed von Mises (SGVON) combined stress was used.

The material used is Steel RQC-100:
Material Properties
Value
Young's modulus
203000 MPa
Poisson's ratio
0.3
Ultimate tensile strength (UTS)
863.0 MPa
Fatigue strength coefficient (SRI1)
1101.0 MPa
First fatigue strength exponent (B1)
-0.075
Cycle limit of endurance for one segment SN curve (NC1)
1000000 cycles
A constant amplitude load is applied in the FATLOAD entry with a scale factor of 14.1332, whose variation is:
Time Points
Load Curve Point
0
0.0
1
1.0
2
0.0
3
-1.0
4
0.0


Figure 2. Load Curve used in FATLOAD

All the modifying factors (Surface Roughness and Fatigue Strength Reduction factor) are set to 1.0.

Results

Comparison of the Stress-Life results between OptiStruct and eFatigue calculator for element 215576.
Result eFatigue

(Target Value)

 OptiStruct Normalized with the Target Value
Life (Nf) 152000 cycles 151881 cycles 1.0008

Model Files

Refer to Access the Model Files to download the required model file(s).

The model file used in this problem includes:

stress_life_fatigue.fem