Week 4 -Wire Bending Challenge

OBJECTIVE:

1. To simulate bending of wire for different cases of wire material,

1. Case-1: Copper Alloy NL
2. Case-2: Aluminium Alloy NL
3. Case-3: Magnesium Alloy NL

2. To find out Equivalent stress and Equivalent strain developed in wire for each case and compare the results.

1. THEORY

1.1 Wire Bending:

The process of wire bending involves using mechanical force to push the wire against a die, forcing the wire to conform to the shape of the die. Often, it is held firmly in place while the end is rotated and rolled around the die. Other forms of processing including pushing stock through rollers that bend it into a simple curve.

Rotary draw bending (RDB) is a precise technology, since it bends using tooling or "die sets" which have a constant centre line radius, alternatively indicated as mean bending radius. Rotary draw benders can be programmable to store multiple bend jobs with varying degrees of bending. The rotary-draw-bending method is a complex physical process with multi-factor interactive effects and is one of the advanced tube or wire forming processes with high efficiency, high forming precision, low consumption and good flexibility for bending angle changes. However, it may cause a wrinkling phenomenon, over thinning and cross-section distortion if the process parameters are inappropriate. Wrinkles propagate, but in some cases, localize in a finite zone and lead to failure.

Rotary draw benders create aesthetically pleasing bends when the right tooling is matched to the application. CNC rotary draw bending machines can be very complex and use sophisticated tooling to produce severe bends with high-quality requirements. Rotary draw benders are the most popular machines for use in bending tube, pipe and wires for applications like handrails, frames, motor vehicle roll cages, handles, light fittings, hanger hooks, key chains, refrigerator rack, stainless steel fruit baskets, and other metal wire and strip forming and bending.

2. STEPS FOR PERFORMING ANALYSIS:

1. Open ANSYS workbench.

2. Select the static structural module.

3. Select the proper Engineering data card.

4. Import geometry.

5. Open Mechanical model.

6. Give proper connections (contacts and joints).

7. Generate mesh.

8. Set Analysis Setting as given.

9. Insert output request

10. Analyze Result

3. ANALYSIS SETUP:

3.1 Geometry:

                                                                     

                                                                                                                 Fig. 3D CAD MODEL

• The given 3D model of wire bending setup assembly is imported into SpaceClaim. It consists of a wheel, lever and wire. The wire is held in the slot of the wheel and it is made to bend, forcing the wire to conform to the shape of the wheel using the rotating lever.

4. Meshed Model:

                                                                               

The element generated in meshing the model is ensured as tetrahedron elements by using the patch conforming method. The mesh size of the wire is refined to 2 mm by using the face sizing option. The mesh size of the contact region of wire and the curved region of the wheel is refined to 0.75 mm using face sizing option with sphere centre being created using user-defined coordinate system and sphere of influence radius being 7 mm.

• Details:

1. Global sizing = 5mm
2. Body sizing = 1.5mm
3. Face sizing = 0.75 mm 
4. No of Nodes = 14366.
5. No of Elements = 7699.

5. Material Properties:

5.1. CASE 1 = Copper Alloy non-linear

                           

5.2. CASE 2 = Aluminium Alloy NL

                          

5.3. CASE 3 = Magnesium Alloy NL

                         

6. PROCEDURE FOR ALL CASES:

6.1. Import model in ANSYS Workbench.

6.2. Assign material properties.

6.3. Open the mechanical module, where we going to perform analysis.

6.4. Meshed the model with desired element size.

6.5. Now after meshing, From Project Tree, select "Connections" and create "Contact".

• Contacts:

1. Contact Type = Frictional 
2. Frictional Coeff. = 0.2
3. Behaviour = Program Controlled
4. formulation = Augmented Lagrange
5. Normal Stiffness Factor = 0.1
6. Update stiffness = Each Iteration
7. Interface treatment = Add Offset, Ramped Effects.

• The first contact between Wire and Lever.

1. Contact Body = Wire 
2. Target Body = Lever

                                                                             

• The Second contact between Wheel and Wire.

1. Contact Body = Wheel 
2. Target Body = Wire

                                                                             

6.6. After defining proper contacts, Now define the revolute joint for the lever.

1. Connection Type = Body-ground.
2. Type = Revolute.

                                                                             

6.7. BOUNDARY CONDITIONS:

Now let's define the Boundary condition.

• Here we are going to look at stress, Strain and Deformation developed in the Wire during the Bending operation.
• In the analysis setting.

    1. For Step 1.

1. Initial Time Step = 0.1s
2. Minimum Time Step = 1e-2s
3. Maximum Time Step = 0.2s 
4. Solver Type = Direct
5. Turn ON Large Deflection.

                            

    2. For Steps 2 to 8.

1. Carry Over Time Step = ON
2. Minimum Time Step = 1e-2s
3. Maximum Time Step = 0.2s
4. Solver Type = Direct
5. Turn ON Large Deflection.

                              

• Other boundary conditions are given below:

     1. Fixed support is assigned to the wheel to remain stationary.

                                                                             

     2. Fixed Support is assigned to wire to avoid slippage.

                                                                             

    3. Rotation Joint to Lever.

• In order to bend the wire, the lever is made to rotate in a clockwise direction from 0⁰ to 140⁰, with an increment of 20⁰ in each step.

                                                                             

                                   

6.8. SOLUTION:

    After giving proper Boundary conditions, create a solution for the output result

1. Equivalent Stress of Wire. 
2. Equivalent Elastic Strain of Wire.

7. RESULT AND DISCUSSION:

A. CASE 1: Copper Alloy NL.

   1. Equivalent Stress of Wire:

                                                                               

                                                                                                            Maximum Stress = 337.23 MPa

• Stress Contours:

                                                   

2. Equivalent Elastic Strain of Wire:

                                                                               

                                                                                                   Maximum Strain = 0.0030918 mm/mm

• Strain Contours:

                                                   

                                                                                                                                                                                                                                                                                 

B. CASE 2: Aluminium Alloy NL.

1. Equivalent von-misses Stress of Wire:

                                                                               

                                                                                                           Maximum Stress = 306.88 Mpa

• Stress Contours:

                                                   

2. Equivalent Elastic Strain of Wire: 

                                                                               

                                                                                                    Maximum Strain = 0.0043495 mm/mm

• Strain Contours:

                                                   

                                                                                                                                                                                                                                                                                 

C. CASE 3: Magnesium Alloy NL.

1. Equivalent von-misses Stress of Wire:

                                                                               

                                                                                                          Maximum Stress = 255.66 MPa

• Stress Contours:

                                                   

2. Equivalent Elastic Strain of Wire:

                                                                               

                                                                                                    Maximum Strain = 0.0056885 mm/mm

• Strain Contours:

                                                   

8. COMPARISON of RESULT:

                                           

• From the table, it is observed that the maximum v-m stress developed in the wire material of magnesium alloy NL is the least compared to other wire materials. For all three cases of wire material the maximum v-m stress developed is more than its yield strength value, hence it undergoes plastic deformation and conforms to the shape of the wheel while bending. The maximum equivalent plastic strain developed in wire material of copper alloy NL is least compared to other wire materials which indicate that it is least deformed, hence it is the preferred wire material among the given wire materials

9. CONCLUSION:

• Simulation of bending of wire was carried out successfully for the following cases of wire material.

1. Case-1: Copper Alloy NL
2. Case-2: Aluminium Alloy NL
3. Case-3: Magnesium Alloy NL

• The maximum Equivalent (v-m) stress developed in Magnesium Alloy NL wire material is the least compared to other wire materials.
• For all three cases of wire material the maximum v-m stress developed is more than its yield strength value, hence it undergoes plastic deformation and conforms to the shape of the wheel while bending.
• The maximum Equivalent strain developed in Copper Alloy NL wire material is the least compared to other wire materials. Hence, it is the least deformed and preferred choice of material among the given wire materials.