OS-V: 0270 Torsional Creep of Circular Shaft
This benchmark illustrates the structural response of a power law creeping material in a geometrical configuration subjected to pure torsion. OptiStruct examines strain at the edge of the shaft.
The model examines the torsional creep in circular shaft with 2 variations:
- Relaxation at constant twist
- Forward creep at steady twist rate
Relaxation at Constant Twist
Twist is applied to the shaft and remains constant from 0 to 100 s. Total strain and
creep strains then analyzed.
Model Files
Before you begin, copy the file(s) used in this problem
to your working directory.
Benchmark Model
Four 20-noded brick elements, plus one 16-noded wedge are used. All nodes on lower
face are fixed in X, Y, Z.
- X, Y displacements given at all nodes of front face using cylindrical system: 0.002 mm
- Rotation is given at mid-side nodes: 0.001 radians
Uniform twist of 0.01 radians/unit length is held constant in time from 0 to 100 s.
Twist is instantaneously applied to the shaft and then maintained constant. The
initial response is elastic and subsequently the structure response with a
progressive accumulation of creep strain. Stress reduces (relaxes) slowly till 100 s
due to creep.
- Material Properties
- Value
- Young's modulus
- 10 GPa
- Poisson's ratio
- 0.3
- Creep law equation
Where,
- Equivalent creep strain rate
- Equivalent stress (Mises)
Nonlinear Static Analysis Results
An implicit visco-elastic solution method was used. Displacement, total strain and
creep strain results are analyzed at the edge of the shaft at 100 s.
OptiStruct | NAFEMS | Normalized Target Value | |
---|---|---|---|
Total Strain (*10-3) | 5.46 | 5.77 | 0.95 |
Creep Strain (*10-3) | 4.85 | 4.77 | 1.01 |
Comparison of strain plots.
Forward Creep at Steady Twist Rate
A steadily increasing twist is applied at constant rate to the shaft.
The stresses increase from zero to steady value. The loads, which cause this steady-state behavior are referred as “primary” loads.
This model is the same as used in Relaxation at Constant Twist; except the boundary
conditions.
Model Files
Before you begin, copy the file(s) used in this problem
to your working directory.
Benchmark Model
Four 20-noded brick elements, plus one 16-noded wedge are used. All nodes on lower
face are fixed in X, Y, Z.
- X, Y displacements given at all nodes of front face using cylindrical system: 0.004 mm/unit time
- Rotation is given at mid-side nodes: 0.002 radians/unit time
Uniform twist of 0.02 radians/unit time is steadily increating with time from 0 to
1.5 applied using table curve.
- Material Properties
- Value
- Young's modulus
- 10 GPa
- Poisson's ratio
- 0.3
- Creep law equation
Where,
- Equivalent creep strain rate
- Equivalent stress (Mises)
Nonlinear Static Analysis Results
An implicit visco-elastic solution method was used. Displacement, total strain and
creep strain results are analyzed at the edge of the shaft at 1.5s.
OptiStruct | NAFEMS | Normalized Target Value | |
---|---|---|---|
Total Strain (*10-2) | 1.62 | 1.7321 | 0.94 |
Creep Strain (*10-2) | 1.27 | 1.1693 | 1.094 |
Comparison of strain plots.
Reference
NAFEMS R0026 - Selected Benchmarks for Material Non-Linearity- Volume 1