Week 4- Rolling operation

AIM:

To simulate the rolling operation on a workpiece made of copper.

OBJECTIVE:

For this analysis, an ingot composed of copper alloy will be utilized. Two rollers will be rolled so that the ingot passes through them and, under pressure, deforms into the shape of a sheet. In opposition to one another, two rollers will rotate. On completion of the analysis, particular parameters including Total Deformation, Equivalent Elastic Strain, and Equivalent Stress will be analysed.

For this analysis, we have a 3D model that consists of various parts such as Roller 1, Roller 2 and workpiece. This is how the whole assembly looks like;

Theoretical FrameWork :

Rolling Process :

a. Rolling is the most important and widely used metal forming process because of its lower cost and higher productivity. The rolling process is best defined as the shaping of metals into semi-finished or finished forms by passing between rollers rotating in opposite direction.

b. The deformation takes place when a compressive force is applied by a set of rolls on ingot or any other product like billets, blooms, sheets, slabs, plates, strips, etc. This deformation decreases the cross-section area of the metal and converts it into the required shape.

c. The main purpose of rolling is to decrease the thickness of the metal. Steel, magnesium, aluminium, copper, and their alloys are the materials commonly rolled.

d. As a result of the friction between the rolls and the metal surface, the metal is subjected to high compressive stresses.

e. High production rate, grain structure, and surface-finish are obtained, which makes it a most suitable metal forming process for large length cross-section workpieces like plates and sheets of steel and aluminium for other works and structure.

f. However, the high set up cost of the rolling machine makes it an alternative process.

Working Principle of Rolling Process :

I. The rolling process is done both hot and cold, which is accomplished in rolling mills.

II. A rolling mill is a complex machine having two or more supporting rollers, working rollers, drive motor, roll stands, working rollers, coupling gear, flywheel, etc.

III. Each rolling mill consists of a minimum of two rolls. As per the process requirement, these numbers can extend even. Depending upon the shape of the rolled product, the rollers may be grooved or plain. The shape of the metal changes gradually during the period in which it's in contact with the two rollers. Compared to forging, rolling is a more economical method of deformation when metal is required in long lengths of uniform cross-section.

Hot Rolling Process-

· The hot rolling process occurs with the initial breakdown of ingots into billets and blooms. This is followed by further hot rolling into the sheet, plate, bar, rod, rail, and pipe. It's done at the above recrystallization temperature and used for large deformations. Hot rolling gives residual stresses free product, but due to scale formation, it gives poor dimension accuracy and surface finish. A major role in the industry is played by the cold-rolling of metals by providing sheet, strip, foil with high mechanical strength, good surface finish, along with dimension accuracy.

Cold Rolling Process-

· The cold rolling which is done to get the final product is done at below recrystallization temperature. We shall discuss here the types of rolling process and its applications in the manufacturing industry.

PROCEDURE-

• Open Ansys Workbench and choose static structural.
• In the Engineering data, let the material be structural steel and also choose Copper Alloy non-linear from General non-linear material with default values.

Material Specifications: (Copper Alloy NL)

Density: 8300 Kg/m3

Young’s Modulus: 1.1 E+05 MPa

Poisson’s Ratio: 0.34

Yield Strength: 280 MPa

Tangent Modulus: 1150 Mpa

DESIGN:

• For the geometry, right-click and import the given Copper_Rolling.stp and open with space claim.

• Using the 'Pull' option sketch edit elongate the workpiece length to 60mm and from either side reduce 8mm thickness.

• Now in the workbench go to Model -> Edit, in the model window check the Geometry for the material and assign Structural Steel to the wheel and Copper Alloy NL to the workpiece.
• For contacts, first, flip contact/target for both the contacts and select 'rename based on definition', for each contact select the required target and contact bodies.
• For both contact assign the contacts Type= Frictional and

1. Friction coefficient= 0.2,
2. Formulation= Augmented Lagrange,
3. Normal Stiffness= Factor,
4. Normal stiffness factor= 0.1,
5. update stiffness= each iteration and
6. Interface Treatment= Add Offset,
7. Ramped Effects.

For joints, the 2 wheels will have rotation along the z-axis so joints are created for the 2 wheels by Connection -> Joint -> Body to ground -> Cylindrical, click on Scope= select inner face of the wheel and also reverse the z-axis by clicking on Coordinate system= Reference coordinate system.

For mesh, as the scope of the result is for workpiece it should have meshed with a smaller element size 4 mm for that right-click on mesh select body sizing and choose the geometry as workpiece and element size 2 mm, click on generate mesh.

Details:

• Global Element Size: Default
• Body Sizing : Workpiece

Element Size = 1.5 mm

• Wheel_1 & Wheel_2

Element Size = 3 mm

• No. of Nodes: 25742
• No. of Elements: 4842

ANALYSIS SETTINGS:

• For the analysis setting, the number of steps will be 14 select all the steps and provide Large Deflection= on, under Non-Linear Control, stabilization= constant, method= energy and energy dissipation= 0.1.

• Now apply displacement to the workpiece by selecting the 2 sides of it in the Y-axis in tabular format such that the workpiece travels 90mm.

Rotational boundary condition was defined for both the cylindrical joints in which the rotation angle varies almost nearly from 0 to 195 degrees. Also, it is ensured that both the rollers will be rotating in the opposite direction.

In the Scope section, select the WHEEL 1 joint first. In the Definition section, click on DOF and select Rotation Z, in Type select Rotation and Magnitude select Tabular Data and enter the values in the table as follows

• With this, the model is ready for analysis. Before starting the analysis the required output result parameters are added to the analysis.
• To add the output parameters, right-click on Solutions and go to the Insert and select Stress and then select Equivalent (Von-Mises).
• Similarly, add the Equivalent Plastic Strain and in the Scope section, click on Geometry, select only the WORKPIECE body, and hit Apply.
• Now add the Directional Deformation and go to Geometry and select the two opposite faces of the WORKPIECE and hit Apply. Set the Orientation to be Z-Axis.

POST PROCESSING:

Simulation results for the rolling operation on a workpiece made of copper.

The above figures show the variation of the stress developed in the setup during the rolling operation. it shows that the maximum value of the stress reaches up to 3700 MPa during the operation.

Equivalent Plastic Strain:

The above figures show how the Plastic Strain is developed in the WORKPIECE and its variation during the operation. Plastic Strain attains a maximum value of 2.2 as shown above.

Deformation of WORKPIECE in Z-direction:

The above figure shows the deformation of the WORKPIECE along the Z-Axis during the rolling operation. Both the faces have different values for the maximum deformation. Copper plate is flattened, thus one face Is having maximum deformation of 7.6 mm and at the other face, it is -5 mm (negative sign implying deformed in negative Z-direction).

Deformation of the WORKPIECE in Y-Direction:

The above figures show the distance traveled by the WORKPIECE during the rolling process. As can be seen in the graph, the maximum deformation is equal to 95 mm along the negative Y-Direction. thus, it can be safely said that the WORKPIECE traveled a distance of 95 mm during the operation.

CONTACT STATUS:

Pressure:

The maximum pressure observed during this operation is 4830 Mpa

SUMMARIZATION OF ANALYSIS:

INFERENCES:

The above tabular data shows the equivalent stress, Equivalent Plastic Strain, directional deformation (Z-Axis).

Copper experiences a maximum equivalent stress of 3700 MPa, for the whole body

Equivalent Plastic strain for the workpiece is 2.2 mm

Maximum Directional Deformation in the Z axis for the workpiece is 7.6 mm

Hence it’s proved that the workpiece has displaced by approximately 95mm by assigning the displacement value randomly

COMMENTS:

The initial increase in the Equivalent Stress intensity is due to the initial increase in the amount of material that is crushed in the space between the rollers. High values of stress emerge as a result of more material being able to withstand deformation. In addition, the material experiences plastic deformation from the pressure of rollers, which results in compressive stresses in the rolling direction and tensile stresses in the transverse direction. The material is unevenly distributed under these forces, with the largest strains concentrated near the roller edges.

Here, we find As we are aware that plastic deformation happens when force is applied to a copper material beyond its yield strength. Plastic deformation occurs in copper during the operation. The copper material's cross-sectional area is reduced as a result of its thickness decreasing and lengthening when it is squeezed. Good plastic deformation capabilities are exhibited by the ductile substance copper. It won't break or crack when rolled into thin sheets or wires, for this reason.

We have also given the values accordingly in tabular data so that the workpiece has been displaced by 95 mm and it is proved so by selecting the bottom tip of the workpiece to show that the material displaced to a value of 95 mm.

Note:

* due to some issues for file uploading I have attached the file to the Skill Lync team via mail and i have attached the report below as I was trying to submit the report it was incomplete and I have contacted the team but I had no response.

Hence I have attached the report in .pdf format for your reference