Static-Structural Analysis Of Wire Bending Operation

ABSTRACT

Following study presents the static-structural analysis of wire bending operation using Ansys workbench & shows comparative analysis for three different wire materials. Wire bending is one of the common processes in manufacturing and has wide scale applications in automotive and home appliances.

In the analysis, a straight wire piece is made to undergo bending operation and during this various mechanical responses are examined. It is observed from the results that aluminum & magnesium alloys NL are more suitable as wire material for bending operation as they offered least resistance to bending & developed relatively lesser residual stress. However, depending upon the application requirement copper may also be used as wire material in case if high strength of final product is prime requirement.

INTRODUCTION

Wire bending operation is a process included in metal-working, in which a wire piece is plastically deformed into desired shape. Wire bending operation is widely used in various domains for example – construction industry for providing reinforcement to structures, in automotive industry for additional strength to wheels & other chassis components, used in various household products etc. In order to be efficient in its application quality of wire generated from the wire-bending machine must be well good enough. Moreover, its production must not causes significant damage to machine otherwise machine will require frequent maintenance.

In the following report, three different material for wire piece is chosen and individually made to undergo bending operation. And a comparative analysis is done to suggest which material will be more suitable in terms of its quality and easy of manufacturing. The materials chosen for the simulation are:

1. Copper Alloy NL
2. Aluminum Alloy NL
3. Magnesium Alloy NL

An assembly of Wheel & lever is used to perform bending operation. In wheel, wire is placed & held in a grooved inclusion. While lever revolves around the wheel & bend the wire such that wire takes the shape of the wheel geometry (as shown in fig.).

OBJECTIVE

To perform a static-structural analysis of wire bending operation using ANSYS and present a comparative analysis of results by assigning three different materials to the wire piece. Material to be used are: - 1. Copper Alloy NL 2. Aluminum Alloy NL 3. Magnesium Alloy NL

ANALYSIS PROCEDURE

1. Material Selection

In order to perform comparative analysis, wire is assigned with three different materials. While other parts which perform bending operation are assigned with structural steel.

Following are the properties of materials, which are assigned to the wire.

Properties of Copper Alloy NL

Properties of Aluminum Alloy NL

Properties of Magnesium Alloy NL

2. Geometry

An assembly of Wire bending apparatus consisting of Wheel & lever with wire piece is directly imported in the workbench from the available resources.

Fig. Detailed Geometry

3. Meshing

Below is the summary of mesh controls, which are applied on the geometry:

• All the parts of the geometry are meshed with tetrahedrons elements using patch conforming method.
• Face sizing is established at critical contact regions (i.e. areas that are subjected to excessive loading and deformation).
• Another Face sizing is applied on wire piece at the region of maximum distortion using sphere of influence.

Fig. Meshed Geometry

STATISTICS

Total No. of Elements : 4090

Total No. of Nodes : 8165

Avg. Element Quality : 0.7049

Fig. Mesh Element Quality

5. Setup

• Establishing Contacts & Joints

Frictional contact is established between interfaces of Wire piece and lever with frictional coefficient of 0.2. Similar contact is also made between contact regions of wire piece & wheel. Below are the details of the contacts, which are applied:

Fig. Frictional contact b/w Wire & lever Fig. Frictional contact b/w Wheel and Wire

In joints, in order to perform bending action a revolute joint is applied to the lever hence able to rotate in its position & perform bending operation.

Fig. Revolute Joint - Lever

• Boundary Condition

In boundary condition, to hold the rest of assembly in place a fixed support is assigned individually to wheel and one end of the wire which is inside the groove portion of wheel.

Fig. Rotation as Boundary Condition on Lever

• Analysis Settings

In order to save computational time and aid in easy convergence, various changes have been made & is summarized below:

• Eight time steps are used to simulate the bending action.
• Solver type is changed to Direct rather than iterative.
• Weak spring and Large deformation setting is enabled to counter unconstrained motion and deformations.
• Automatic time setting is also enabled to help in easy convergence by progressing the simulation in a small sub-time steps increments inside each steps.

Fig. Analysis Settings

RESULTS AND DISCUSSION

Results are presented at the end of 8th time step.

1. Equivalent Stress

• When copper alloy NL is used as wire material

Fig. Equivalent Stress Distribution ( When wire material is Copper Alloy NL)

Fig. Max. Equivalent Stress vs Time steps graph Fig. Max. & Min Value of Stress over time steps

• When Aluminum alloy NL is used as wire material

Fig. Equivalent Stress Distribution ( When wire material is Aluminum Alloy NL)

Fig. Max. Equivalent Stress vs Time steps graph Fig. Max. & Min Value of Stress over time steps

• When magnesium alloy NL is used as wire material

Fig. Equivalent Stress Distribution ( When wire material is Magnesium Alloy NL)

Fig. Max. Equivalent Stress vs Time steps graph Fig. Max. & Min Value of Stress over time steps

From the above results, it is clear that for all cases peak region of stress development take place in between 1st-2nd time step, after that an almost constant level of stress is maintained. Because in the beginning, high force is needed to bend the wire around the region which close to grooved portion of wheel, as at this point very sharp bending is taking place. But as bending continues comparatively lesser force is needed because now wire is only required to bend around the wheel’s outer circumferential surface. This will become clearer from the following figure, which shows the force reaction on lever in X-axis during wire bending operation.

Fig. Max. Force reaction in x-axis vs time steps(sec)

• Comparison Graph

For the bending operation, it is required that material must be less stiff and is flexible to undergo bending. Therefore, such material must have lower young modulus of elasticity & have lower yield strength so that they can be easily deformed plastically and have stable geometry with minimum residual stresses. From the comparison, it is clear that, when Aluminum alloy NL is applied as a wire material it offered least resistance to bending in the beginning while copper alloy NL offered highest resistance. And at the end of process, magnesium alloy NL has minimum stress value to resist deformation, which indicate it is more stable with its new deformed sturcture, while both copper & aluminum alloy ended up with higher stresses. So from the above comparison, Aluminum and magnesium alloy NL must be prefered as wire material for bending operation.

2. Equivalent Elastic Strain

• When copper alloy NL is used as wire material

Fig. Equivalent Strain Distribution ( When wire material is Copper Alloy NL)

Fig. Max. Equivalent Elastic Strain vs Time steps graph Fig. Max. & Min Value of Strain over time steps

• When Aluminum alloy NL is used as wire material

Fig. Equivalent Strain Distribution ( When wire material is Aluminum Alloy NL)

Fig. Max. Equivalent Elastic Strain vs Time steps graph Fig. Max. & Min Value of Strain over time steps

• When magnesium alloy NL is used as wire material

Fig. Equivalent Strain Distribution ( When wire material is Magnesium Alloy NL)

Fig. Max. Equivalent Elastic Strain vs Time steps graph Fig. Max. & Min Value of Strain over time steps

Comparison Graph

A similar trend is also observed in the results of Elastic Strain having high strain development during start and then constancy until end. However, by comparison it is noted that because of high young modulus of Copper alloy NL comparatively lesser strain is developed in the wire. Moreover, because of lower young modulus magnesium seemed to have max. strain development while copper places itself in between. So ,from results of strain also it is recommend to select either aluminum or magnesium alloy NL as wire material.

3. Equivalent Pastic Strain

• When copper alloy NL is used as wire material

• When Aluminum alloy NL is used as wire material

• When magnesium alloy NL is used as wire material

Results of Equivalent Plastic Strain indicates the development of highest plastic strain in Aluminum alloy NL which means it wil accept this strain permanently. However, the results are too close to make any conclusive decision based on plastic strain but it is also giving little bit intiation to use Aluminum alloy NL as wire material.

ANIMATION