metal report

8/6/2019 Metal Report

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MIDDLE EAST TECHNICAL UNIVERSITY

NORTHERN CYPRUS CAMPUS

METAL FORMING PROJECT

INSTRUCTOR: Volkan Esat

STUDENT NAME: Faizan Mir

STUDENT NUMBER: 1586692


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Overview:

The process of deep drawing is analyzed. A tool with a rigid dipole is pushed into a circular plate to

produce a perfect spherical indentation in the circular plate. The static analysis is done to analyze by

changing three critical dimensions and friction conditions of the deforming plate.

Background information:

It is the preparation of a contact analysis involving multiple rigid bodies(the tool ) and a deformable

body (the work piece) . The plate of the tool supports the entire work piece and it is released at the end

from the backing plate as well.

Idealization:

The edge of the work piece is clamp which prevents the rigid body motion of the work piece. The

backing plate that backs the work piece is modeled as a rigid body and is released at the end of the

process. The punch is also modeled as a rigid body and moves during the analysis towards the backing

plate while indenting the work piece. The total displacement of the punch is 0.1488 inches which is

reached in 0.4 seconds. For the first time the friction between the tool and the work piece is assumed to

be negligible.

Basic Dimensions:

Work piece:

Youngs Modulus= 30e6 psi

Poissons Ratio = 0.3

Yield Stress= 39000psi

Radius= 0.8 inches

Thickness: 0.1 inches

Punch:

Radius=0.24 inches

Fillet radius = 0.109inches

Vertical displacement = 0.1488 in 0.4s


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Backing plate:

Radius=0.24 inches

Fillet radius = 0.109inches

Die Holder:

Height = 0.3 inches

Width = 0.3 inches

Overview of the steps:

1) Create a model of a rectangular patch and convert it to finite elements

2) Create the curves required for the punch and the backing plate.

3) Apply the required fixed displacement to the rim of the work piece. Apply the material data.

4) Identify the contact bodies and created the table that defines the motion of the rigid die

representing the punch.

5) Define the increment steps and convergence testing paramenters.

6) Activate the large strain parameters and submit the job.

7) Post process the results by displaying the deformed structure and the residual stresses and

strains.


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The punch, work piece and the die is shown above in the diagram. The work piece is devided into 5 * 20

divisions as seen by the squares.

The tables are created for the work hardening procedure and its graph is drawn as shown in the figure

below.


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The punch moves during the analysis. A table of time versus velocity is defined. The axial distance of the

straight section of the punch and the workpiece is 0.1488 inches. The gap closes in 0.4s and the motion

is reversed and the release option is switched on. The punch is withdrawn with high velocity and after

that the back plate is also released.The graph for the punch movement is shown below:


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The graph for the backing plate movement is as shown below.,

Detailed description:

Step 1:

The first step is to create the workpiece. For that a point is created and then expanded to a line curve

which is followed by expanding to a quad surface.

The next step is to convert the geometric entities to finite elements. This is done by the Convert

processor. Five divisions are used through the thickness and 20 along the radius.

A sharp corner would be developed at the lip of the cylinder so the mesh is made more refined in that

area. The nodes near the radius are moved to that location. The y coordinates of these nodes are

determined by the SHOW commando n the NODES panel.

In the next step the sixth row of the element is sub devided. After that they are renumbered.

Step2.:

The next step is to create curves for the punch ,backing plate and the blank holder. The blank holder,

punch and the die are rigid bodies and the blank is taken as a deformable body. For the punch and the


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backing plate a point is made to create an arc. Another curve is made tanngent to it . The radius of the

arc is taken to be 0.109inches.

For the backing plate exactly same arcs would be required but a tangent line would also be required to

the second arc.

Step 3:

The stress vs plastic strain table is created under the name ofwork-hard.

Following table is added

0 39000

0.7e-3 58500

1.6e-3 63765

2.55e-3 67265

3.3e-3 68250

10e-3 72150

The following graph would be created.


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Step 4:

In this step the elements and curves are assigned to the correct contact bodies. The back plate,the

punch and the die holder are assigned as the rigid bodies and the work piece is assigned as a deformable

body. The ID contact button identifies the rigid bodies and their directions . The curves can be flipped by

using the FLIP CURVE button if the curve is defined such that rigid body is on the same side as thedeformable body.

The punch will move during the analysis and to define the motion a table of time vs velocity is formed.

The axial distance of the punch is 0.1488inches .This gap is closed in 0.4s and as soon as the horizontal

part touches the workpiece the motion is reversed and release option will be switched on. The punch is

withdrawn at a higher velocity and the back plate is withdrawn imidiately after that.

The table for the punch motion is as follows:

0 0.1488/0.4

0.4 0.1488/0.40.4 -10*0.1488/0.4

0.5 -10*0.1488/0.4

The table for the backing plate motion :

0 0

0.5 0

0.5 0.1488/0.1

0.6 0.1488/0.1


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Step 5:

In this step, the incremental steps and convergence test parameters would be defined. The load cases

describe the first and second part of the loading history and the loads used during those parts.

Indent:

Total load case time=0.4s

Number of Steps= 100

Max Number of Cycles= 20

Release:

Total load case time=0.1

Number of Steps= 1

Maximum number of Cycles= 20


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Punch would be selected in the end.

Backplate:

Total load case time=0.1

Number of Steps= 1

Maximum number of Cycles= 20

Backplate would be selected in the end.

Step 6:

The final step is preprocessing to create the job and then submit it to run in the background. The job

menu defines the special analysis options, the results saved and other global parameters. This is the

place where the loadcases are selected.

In the jobs section we will select the load cases, then constant dilation and small strains. As the figure is

axisymetric , it would be selected. Then it would be saved,submitted and then monitored.

There are a wide range of options which can be monitored but for our case Equivalent Von Mises stress

and equivalent plastic stress would be observed.

Step 7:

The deformed structure and the resual stresses can be observed. The last increment shows the residual

stresses after the punch has been withdrawn.


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Changing the Critical dimentions:

1) Decreasing the clearance by 0.01 inches:

This is done by moving the punch 0.01 inches upwards as shown in the diagram.


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The Maximum Total Equivalent plastic strain is 9.404e-1 psi and the MaximumVon Mises stress is

4.00e5 psi as shown in the diagrams above.


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2) Decreasing the fillet radius of the back plate while keeping the punch the same:

It can be seen in the simulation that the punch can not be released. The cause of that would be some

damage in the backing plate.

Max Equivalent Plastic strain = 1.099

Max Von Mises stress = 3.184e5 psi


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3) Reduction in thickness of the workpiece by half:


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As shown above by reducing the thickness of the work piece by half the max Von Mises stress becomes

3.018e5 psi and the maximum equivalent strain becomes 8.414e-1

Effects of friction:

Three different friction coefficients were analyzed for the punch, die-holder, die plate and the work

piece.

Coefficent of friction = 0

As seen in the graph below max Equivalent Plastic Strain is 9.137e-1 and the max Von Mises stress is

2.013e5 psi


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Friction Coefficent = 0.05

As seen in the graph the maximum Von mises stress is 2.295e5 psi and the maximum total equivalent

plastic strainis 9.035e-1.


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Friction Coefficent=0.1

As seen in the graph below the Maximum total equivalent Plastic Strain is 8.873e-1 and the maximum

Von Mises stress is 3.005e-5 psi.


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Discussion and Conclusion:

When the clearance was decreased by 0.01 inch the Plastic strain and Von Mises stress increased

considerably. When the fillet radius of the backing plate was decreased, the stresses and strains were

increased at the lip of the work piece by a large amount. These simulations showed that if the clearance

was made smaller or the backing plate radius is made smaller, the stresses and strains would increase.

By decreasing the thickness of the work piece the stresses and strains were increased. Another factor

which was considered was the friction factor after which a conclusion can be made that as the friction

increases the stresses and strains also increase. In all these cases it can be generalized that the

maximum stresses and strains occur in the same region all the time. Furthur analysis can be done for

those region to reduce the stresses there for the life of the product. Changes in radius may help in those

analysis.

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