HL-V: 0020 Variable Amplitude Strain-Life Analysis

A notched plate subjected to variable stress time history.

HyperLife examines the strain life for a plate of 6mm thickness. The Strain-Life result from HyperLife is compared with the results from Reference for the element 1041.

Model Files

Before you begin, copy the file(s) used in this problem to your working directory:

Benchmark Model

The model is a test specimen of thickness 6.0 mm, width 16.0 mm and center hole of diameter 3.0 mm. The notched plate is subjected to variable stress time history (Load of 1N and scaled with a load history profile shown below) and is assumed to follow elastic behaviour. The model was meshed with first-order shell elements and the loading is applied to RBE3 element. The Absolute Max principal combined stress was used.

The material used is SAE 1005 Steel:

Table 1. Material Properties
Properties	Value
Youngs Modulus, E	207000 Mpa
Poisson’s Ratio, nu	0.29
Ultimate Strength, Su	320 MPa
Cyclic Strength Coefficient, K’,	1240 MPa
Cyclic strain hardening exponent , n’	0.27
Fatigue Strength Coefficient,	886 MPa
Fatigue Strength Exponent, b	-0.14
Fatigue Ductility Coefficient,	0.28
Fatigue Ductility Exponent, c	-0.5

Load History Profile

Figure 2. Load Curve used in Load History Channel

Table 2.
Time	Scale
0	12.68
1	-4.755
2	9.51
3	-9.51
4	12.68

Load points are further scaled by 1000 within the fatigue event.

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

Results

Comparison of the Strain-Life results between HyperLife and Reference for element 1041.


Result	Reference	HyperLife
Total Damage	3.83e-5	3.828e-5

Comparison results per cycle between HyperLife and Reference for the same element.

Table 3.
Result	Path	Strain Amplitude	Max Stress	Damage
HyperLife	2-3 (Cycle 1)	0.106348e-2	166.824	0.526742e-5
Reference	2-3	0.10635e-2	166.9	0.528e-5

HyperLife	1-4 (Cycle 2)	0.194512e-2	208.150	0.330117e-4
Reference	1-4	0.1945e-2	208.2	0.330e-4

Reference

Example 5.7: Fatigue testing and Analysis - Theory and Practice written by Yung-Li Lee et. al.