OS-E: 0330 Sine Sweep Fatigue Analysis

Sine sweep fatigue analysis of a simple bracket is done to study the fatigue life of the structure under sinusoidal loading using OptiStruct.

Figure 1. FE Model with Loadcases and Loadstep

Model Files

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

The model file used in this example includes:


Model Description

Frequency Response Stress results from the Frequency Response Analysis are used to calculate the frequency-dependent stress range, which are subsequently used to calculate Fatigue damage based on sweep rate. Here the stress-life (SN) approach is used for calculating the fatigue life of the component.

The solid element properties are:
First order Tetra elements
The shell element properties are:
Skin Surface Near the Fillet Region
First order Tria elements
The material properties are:
Young's Modulus
2.1 x 105 N/mm2
Poisson's Ratio
7.9 x 10-9 ton/mm3
Shear Modulus
0.02 N/mm2
Yield Strength
180 MPa
Ultimate Tensile Strength
340 MPa
Fatigue Strength Coefficient
First Fatigue Strength Exponent
Limit of Endurance
1 x 1030
Fatigue Limit
Consists of a simple bracket constrained at the bolting locations and applied a force in the y direction at the free end on a connected RBE2. There are three loadcases for this example, Linear Static, Modal Frequency Response Analysis and Fatigue Loadcase. The stress results from the frequency response analysis are used to calculate the frequency-dependent stress range and subsequently used for calculating the Fatigue damage based on sweep rate.

Figure 2. All the Fatigue Cards used for this Analysis


Figure 3. Fatigue Damage Results

Figure 4. Fatigue Life Results