Independent Research Project

A) TITLE : - "Simulation of Pressing operation on a cube with cylinder" through static structural analysis module of Ansys workbench 2019 V3 version.

B) OBJECTIVES :- The main objectives of this simulation are :-

i) To find out and compare the equivalnet stress generated into the cube of different nonliner materials like stainless steel NL , aluminium alloy NL and copper NL.

ii) To find out and compare the total deformation generated into the cube of different nonliner materials like stainless steel NL , aluminium alloy NL and copper NL.

iii) To find out and compare the equivalnet plastic strain generated into the cube of different nonliner materials like stainless steel NL , aluminium alloy NL and copper NL.

iv)To find out and compare the contact pressure generated at contact regions.

v)To find out and compare the force required for pressing the cube of different nonliner materials like stainless steel NL , aluminium alloy NL and copper NL.

C) MODELING :-

The modeling of the part is done in solid edge. The cube with 40 mm side is generated in solid edge and the cylinder with 40 mm bore and 40 mm stroke is downloaded.

D) PARAMETER SETUP :-

1) The model has been imported into the structural module of Ansys. The model consists of a cylinder body , a rod with pressing head and a cube.

2) The cylinder body and rod with pressing head has been assigned with structrural steel properties and the cube has been assigned with different materilas as per the case.

3) Now in this process , the rod with pressin head is extented towards the fixed cube. then its head presses the cube and after that the rod retracts to its original position.

4) When the cylinder rod extends , its internal NBR seal rubs aganist the inner surface of the cylinder. hence considering this a frictional contact with coefficient of friction as 0.1 has been set. when the rod extends and head presses against the cube there is contact between the head surface and cube surface. hence acoording to the material pair the frictional contact with respective frictional coefficient has been set.

5)Meshing is very important. meshing has been done with different sizing. the cube surface which actually comes in contact with pressing head is assigned with 2 mm mesh size. while the inner surface of cylinder is assigned with 3 mm mesh. all other parts are assined with 10 mm mesh size.

6) the cube surfaces are made fixed as shown in the fig. the cube faces are fixed to avoid its deformation in Z-direction. hence top , bottom and back surfaces are fixed. the faces in Y-direction are kept free. The cylinder rod with pressing head has given a displacement of 30.5 mm forward and then again it is retracted to its original postion in 12 steps.

7) the analysis is carried out into 12 steps with minimum time step of 0.01 sec and maximum time step of 0.1 sec. the large defelction is made on.

8) the Simulation is then carried out and the post processin results obtained are as follows.

E) POST PROCESSING RESULTS :-

1) CASE 1:- CUBE MATERIAL - STAINLESS STEEL NL

2) CASE 2:- CUBE MATERIAL - ALUMINIUM ALLOY NL

3) CASE 3:- CUBE MATERIAL - COPPER NL

F) RESULTS AND DISCUSSIONS :-

I) Equivalent stress (MPa)

The results obtained from the simulation for different materilas are shown in a graph.

If we observe the above graph then the maximum stress( 941.51 MPa) is generated in stainless steel cube and the minimum stress (658.67 MPa) has been generated in copper cube. the maximum stress is generated at top and bottom edges as the top and bottom faces of cube are fixed and minimum stress is generated at side edges as the body can freely deform in these directions.

in each case the initial value of stress is zero when the cylinder rod extends towards the cube. as soon as the rod head touches the cube it strats pressing the material hence stress is generated into the material. this stress increases as there is strain hardeneing of material and hence more force is required and thus the stress also increases and reaches to maximum value. then again it becomes zero when the rod starts retracting. the properies of these different materilas are:-

the stainless steel offeres more resistance to deformation and its stiff material hence maximum stress is genrated into the same.

I) Total deformation (mm)

If we observe the results , the stainless steel cube has maximum total deformation of 0.8 mm while the copper has minimum total deformation of 0.64 mm. the total deformation seems to be uniform all over the face and at corners it is minimum as the pressing head has chamfer hence no force is applied in this region. in each case the initial value of deformation is zero when the cylinder rod extends towards the cube. as soon as the rod head touches the cube it strats deforming the material. the material thus goes under deformation.

III) Equivalnet plastic strain

If we observe the results , the stainless steel cube has maximum equivalent plastic strain of 0.39 while the copper has minimum equivalnet plastic strain of 0.32. the maximum plastic strain is obesrved at the top and bottom edges of the cube as the material is restricted to flow in these directions. upto elastic limit the material follows the Hook's law but as the material stress excceds the yield stress it enters into plastic deformation zone. in plastic zone the material starts strain hardened and the stress is depenedent on stength coefficient (K) and strain hardening exponent (n) of material which is different for different materials.

IV) Contact pressure

The contact pressure is found at two contacts :- 1) contact between cylinder inner face and rod outer face 2) pressing head face and cube face.

The maximum contact pressure has been found at contact between cylinder inner face and rod outer face for aluminium alloy NL cube (5071 MPa) and minimum for copper alloy NL ( 4427.4 MPa).

V) Maximum reaction force in X-direction (N)

This value of reaction force in X-direction is nothing but the force required to cause the deformation of the cube. so from graph it can be observed that maximum force ( 1.02E+06 N=102 tonne) is required for pressing the copper alloy NL material cube while the minimum force (9.64E + 05 N = 96.4 tonne) is required for pressing the stainless steel NL material cube.

the intial reaction force is very less as the rod extends towards the cube. when the head touches the cube the material offeres resistance to head and reaction force is exterted by material on head. as pressing continues because of strain hardening effect the material offers more and more resistance and hence the reaction force also incerases. The steel has minimum Poission's ratio (0.31) while the copper has maximum Poission's ratio (0.34). the Poission's ratio indicates the lateral deformation of material. hence more the Poission's ratio more will be the lateral deformation.

The following result shows the force converence. so it can be observed clearly that after 150 iterations the force as suddenly increased when the rod head touches the cube face.

G) ENGINEERING SIGNIFICANCE:-

• The pressing operation is performed with large pressing machines. The most important factor for these machines is capacity in Tonnes.
• From this simulation it is clear that the pressing force required is totally dependent on the material properties and different materials require different pressing force.
• hence the simulation can be useful to find out the tonnage capacity of a press.