Week 9 Tension and Torsion test challenge

SIMULATION OF TENSION AND TORSION TEST ON A SPECIMEN USING ANSYS WORKBENCH

OBJECTIVE

To perform the tension and torsion test simulation on the specimen by following the necessary boundary conditions,

1. For the tension test, one end of the specimen has to be displaced to 18mm while keeping the other end fixed.
2. For the torsion test, one end of the specimen has to be displaced through an angle of 1200 degree while keeping the other end fixed.

To find out Total Deformation, Equivalent (v-m) Stress, Equivalent Elastic Strain and Temperature on the specimen for both tension and torsion tests.

1. THEORY

1.1 Tension Test:

Tensile testing is a fundamental materials science and engineering test in which a specimen is subjected to a controlled tension until failure. Properties that are directly measured via a tensile test are ultimate tensile strength, breaking strength, maximum elongation and reduction in area. From these measurements the following properties can also be determined: Young's modulus, Poisson's ratio, yield strength, and strain-hardening characteristics. 

Fig.1.1 Tensile test specimen.

The preparation of test specimens depends on the purposes of testing and on the governing test method or specification. A tensile specimen is usually a standardized sample cross-section. It has two shoulders and a gauge (section) in between. The shoulders are large so they can be readily gripped, whereas the gauge section has a smaller cross-section so that the deformation and failure can occur in this area. Tensile tests are performed on universal testing machines.

1.2 Torsion Test:

Torsion testing is a type of mechanical testing that evaluates the properties of materials or devices while under stress from angular displacement. The most common mechanical properties measured by torsion testing are modulus of elasticity in shear, yield shear strength, ultimate shear strength, modulus of rupture in shear, and ductility.

Many products and components are subjected to torsional forces during their operation. Torsion testing is necessary when engineers wish to change or update the materials used in these products. Torsional testing can help the engineer identify an appropriate material that will possess the required torsional strength.

2. ANALYSIS SETUP

2.1 Geometry:

Fig.2.1 3D model of tensile and torsion test specimen.

The given 3D model of tensile and torsion test specimen is imported into SpaceClaim.

2.2 Material Properties:

Fig.2.2 Material property details of tensile and torsion test specimen.

The material assigned for tensile and torsion test specimen is steel 1006.

2.3 Co-ordinate Systems:

a. Tensile test specimen.                                                                                           b. Torsion test specimen.

Fig.2.3 Coordinate system specified on the specimen.

The coordinate system specified for tensile test specimen include a global coordinate system located at the center of specimen and two local cartesian coordinate system on either side of the gripping section, in alignment with the global coordinate axis to capture area necessary for mesh refinement. For torsion test specimen, an additional local cylindrical coordinate system is specified at the center of the specimen having rotational y-axis to assign the boundary condition having angular displacement.

2.4 Meshing:

a. Patch conforming method (tetrahedron).                                                               b. Face sizing at gripping section (sphere of influence).

Fig.2.4.1 Meshing details of tensile test specimen.

The element type chosen for meshing the specimen is tetrahedron, using patch conforming method option. The element size of the gripping section is refined to 3 mm using face sizing option having a sphere of influence with a radius of 22 mm. The total number of nodes and elements generated are 678 and 2432 respectively.

a. Face sizing at shoulder section.                                                                       b. Face sizing at gauge section (sphere of influence).

Fig.2.4.2 Meshing details of torsional test specimen.

The element size at the shoulder section is refined to 1.5 mm using face sizing option. To capture the small displacements and strain, the element size at the gauge length area is refined to 1 mm using face sizing option having sphere of influence with a radius of 8 mm. The total number of nodes and elements generated are 4542 and 20811 respectively.

Note: The academic version of software has the problem size limit of 128k nodes or elements.

2.5 Boundary Conditions:

2.5.1 Analysis settings:

Fig.2.5.1 Analysis settings.

In the analysis settings the number of steps considered is 1. The end time specified is 1e-003. The maximum no. of cycles is 1e+07. The maximum energy error is 0.1. The initial, minimum and maximum time step is set to ‘Program Controlled’.

2.5.2 Boundary condition:

a. Fixed support specified at one end of the specimen for both tensile and torsion test.

b. Displacement specified to the other end of the specimen for tensile test.

c. Displacement specified to the other end of the specimen for torsional test.

Fig.2.5.2 Boundary conditions applied to the given specimen for both tensile and torsion test.

For tensile test, one end is fixed and the other end is specified with a displacement of 18 mm along x-axis.

For torsion test, one end of the specimen is fixed and the other end is specified with a displacement at an angle of 1200 degrees along y-axis.

RESULTS AND DISCUSSIONS

3.1 Tension Test:

a. Total Deformation.                                                                                            b. Equivalent (v-m) Stress.

c. Equivalent Elastic Strain.                                                                                     d. Temperature.  

From the total deformation result, it is observed that the gauge length portion of the specimen starts necking as the load is increased and it is displaced 18 mm, linearly along x-axis.    

The maximum value of v-m stress is 627.22 MPa, which is observed at the necking region.

The temperature of the specimen starts to increase gradually as the load is increased, it is observed that, as the specimen is displaced to 18 mm, the temperature increased is equal to 268.99^o C.     

3.2 Torsion Test:

a. Total Deformation.                                                                                             b. Equivalent (v-m) Stress.

c. Equivalent Elastic Strain.                                                                                     d. Temperature.  

From the total deformation result, it is observed that the gauge length portion of the specimen starts shearing and leads to fracture as the specimen is twisted through an angle of 1200 degree.    

The maximum value of v-m stress is 684.12 MPa, which is observed at the region leading to fracture.

The temperature of the specimen starts to increase gradually as the load is increased, it is observed that, as the specimen is twisted through an angle of 1200 degree, the temperature increased is equal to 455.64^o C.     

4. ANIMATION OF RESULTS:

4.1 Tension Test:

a. Total Deformation.

b. Equivalent (v-m) Stress.

c. Temperature.

4.2 Torsion Test:

a. Total Deformation.

b. Equivalent (v-m) Stress.

c. Temperature.

CONCLUSION

1. The simulation of tensile and torsion test was carried out successfully by following to the given boundary conditions.
2. From the tensile test results, it was observed that, as the specimen was displaced to 18 mm, the cross section of the gauge length region starts to decrease, leading to necking. The v-m stress in necking region was maximum i.e., 627.22 MPa. The temperature of the specimen around necking region also was increased to 268.99^o C.
3. From the torsion test results, it was observed that, as the specimen was twisted through an angle of 1200 degree, the gauge length region starts to shear, leading to fracture. The v-m stress in the gauge length region was maximum i.e., 684.12 MPa. The temperature of the specimen around necking region also was increased to 455.64^o C.