MBD Simulation on a Piston Assembly

AIM:-To create 3-D models of the piston assembly and analze their motion study using SOLIDWORKS with and without wrist pin offset.

THEORY AND PRINCIPLE:-Piston assembly consists of piston,gudgeonpin,connecting rod,crankshaft.All these assembled together tranforms rotary motion of crank into linear motion of pistion.The pistion moves from Bottom dead centre to top dead centre to complete one stroke and vice versa,this goes one continuing till it is stopped.Pistons are mainly used to compress air+ fuel mixture in combustion cylinder/chamber which results in dissipation of heat energy which is converted into mechanical energy by reciprocating the piston.The materials used for manufacturing the piston assembly should bear hign temperatures.The piston length of stroke is not the same as that of the length of the cylinder ,a small clearnance is provided at the top so that combustion takes palce ,high temperatures and presures are attainted to initiate the chemical reaction this is caleed clearance volume.Piston must not have clearance tolerance and piston must be updated with the oil rings so that to ensure right amount of energy is generated and transformed to mechanical energy.The parts of the piston assembly must be well lubricated if necessary.The movement of pistion determines the opening and closing of the valves so that air /air+fuel mixture enters and exhaust gases exit .The piston movement and valve movements can be plotted which results in valve timing diagram.

OBJECTIVE OF THE PROJECT:-

1. Creating 3-D model of piston assemblies.
2. Plotting the linear displacement of pistion and various other graphs.
3. Obtaining plots and results for with and without offset of the crank pin and superimposing them .

BODY OF THE CONTENT:-

CREATING 3-D MODEL OF THE PISTON:-

1. Choose the front plane and sketch an L shape and close the endind lines with an 3 point arc .
2. Assign the dimensions and exit the sketch.
3. Now select the longest line and make it as a reference line and revolve it using revolve command,this results in premature 3-D model of piston.
4. Now choose the front plane surface of the piston and using sketch command draw a rectangle and make it fully defined,exit the sketch.
5. Now use the extrude cut command and remove the material .
6. Now use linear pattern and regenerate the same extrude cut of required number .
7. Now choose front plane and draw a circle and exit the sketch ,now use extrude cut to remove material qual to circle dimension.
8. Now choose right plane and draw a 3 point arc and exit the sketch ,now using extruse cut remove the material,use fillets at sharp edges which results in 3-D model of piston.

CREATING 3-D MODEL OF CONNECTING ROD:-

1. Choose front plane and sketch the connecting rod using line, cirlce , line commands.
2. Use trim option to get desired sketch and exit the sketch.
3. Use extrude command and extrude it from mid plane 15mm on either sides.
4. Now choose the right plane and draw two circles and extrude,extrude cut it ,this forms the holes for connecting the connecting rod to crank shaft.
5. Use fillet to make smooth finishing.

CREATING 3-D MODEL OF ENDCAPS:-

1. Choose the front plane and draw two concentric circles .
2. Draw a line passing through origin such that the end points lies on exterior circle.
3. Now using trim command trim off one half of the circle and exit the sketch.
4. Nw using extrude command extrude the sketch from mid palne 15mm on either sides.
5. Now choose right plane and draw two circles extrude them and remove material by using extrude cut.This forms holes for connecting rod to assemble with crank rod.
6. Use fillet to obtain smooth finishing.

CREATING 3-D MODEL OF THE CRANK:-

1. Choose front plane and darw 2 circles of given dia,males lines tanent to both the circles .
2. Trim off the excess sketch and exit the sketch.
3. Now extrude it to from mid plane 10 mm on either sides.
4. Now choose right plane and darw a circle with centre as origin and extrude it to 20 mm.
5. Now choose right plane which is opposite to the right plane and draw a circle at a certain distance from the origin and extrude it to 16mm.
6. Use the fillet command to make smooth finishings.
7. Now draw a 3 point arc on right plane of crank and on the top side of the crank and use extrude command to remove material.
8. Now repeat the same above but now in below position of the crank and use extrude cut to remove the material.
9. Use the mirror command to mirror the crank .
10. This results in the 3-D model of crank.

CREATING 3-D MODEL OF GUDGEON PIN:-

1. Choose front plane and draw 2 concentric circles and extrude it from midplane 63.5 on either sides.
2. Now apply chamfer on both ends.
3. This ends in 3-D model of Gudegeon pin.

ASSEMBLY OF THE PISTON ASSEMBLY:-

1. Insert the components one by one into assembly model .
2. Constrain them one by one such that after assembly desired output is obtained.
3. Following mates were used to obtained desired output.

MOTION STUDY ANALYSIS:-

1. Now choose SOLIDWORKS Motion from the top ribbon.
2. Now select motion study from bottom ribbon and choose motion study by clicking the drop down arrow .
3. Now select motor and the assign it to the axis of the crank and give value of rpm.
4. Now using solid contact between various components of the piston assembly members so to ensure proper forces are transmitted.
5. Assign gravity along Y -direction.
6. Now go to results and plots to obtain various graphs of various components motion.
7. Now click on motion study properties and choose the number of frames and use precise contact option so that smooth plots and results are obtained.
8. Now click on calculate and run the motion study.
9. After calculations export the results to excel sheets.

PLOTS:-

Displacement of pistion without offset:-

Dispalcement of pistion with +ve offset:-

Dispalcement of piston with -ve offset:-

Superimposition of graphs:-

Inferences from the graph:-

2. By giving the offset to the stresses can be relieved.
3. Providing offset leades to decrease in friction resistance and speed ,power is increased.
4. By providing offset vibrations are reduced .
5. load on crank is reduced by giving the offset.

CONCLUSION:-

1. Created 3-D model of all the components.
2. Assembled the components.
3. Performed motion analysis.
4. Plotted the graphs,imported to excel sheets,created animation video,surerimpose the graphs.