Scissor Car Jack PDF

Preview

Summary

Warning: TT: undefined function: 32 Force and Stress AnalysisThe force analysis is based on the assumption that the scissor car jack is loaded vertically symmetrical.The maximum capacity of the scissor car jack is the 1500kg.Maximum Load = F = 1500푘푔 × 9, 81푚푠 2 = 14715 푁The length of the arms from ...

Description

F

Force and Stress Analysis

x

𝐹2

𝐹1

α h

𝐹2′

𝐹1′

𝐹3

𝐹4 𝐹3′

𝐹4′

Figure 1.1. Force in Scissor Car Jack

The force analysis is based on the assumption that the scissor car jack is loaded vertically symmetrical. The maximum capacity of the scissor car jack is the 1500kg. 𝑚

Maximum Load = F = 1500𝑘𝑔 × 9,81 𝑠2 = 14715 𝑁 The length of the arms from hole center to hole center is x = 150 mm, and the length from base to top center of holes at minimum raising height which is the current minimum height at which the wheels of the vehicle do not touch the ground. That is h = 224.10 mm. We need to find angle (𝛼 ) to find forces on the arms. [𝐻0 = 285.10 𝑚𝑚, 𝐻𝑚𝑖𝑛 = 237.80 𝑚𝑚, 𝐻𝑚𝑎𝑥 = 372.78 𝑚𝑚.]

𝑐𝑜𝑠 𝛼 =

ℎ∕2 𝑥

𝛼 = 41,6°

=

148,81∕2 150

= 0,496

(1.1)

We can simplify the mechanism at the joint of the top section that shown in Figure 1.2.

Figure 1.2. Free Body Diagram of the Top Section

We write force equilibrium ; For x axis

∑𝐹𝑥 = 0

(1.2)

𝐹2 × 𝑠𝑖𝑛 𝛼 − 𝐹1 × 𝑠𝑖𝑛 𝛼 = 0 , so

(1.3)

𝐹2 × 𝑠𝑖𝑛 𝛼 = 𝐹1 × 𝑠𝑖𝑛 𝛼

(1.4)

𝐹1 = 𝐹2

(1.5)

For y axis

∑𝐹𝑦 = 0

(1.6)

𝐹2 × 𝑐𝑜𝑠 𝛼 + 𝐹1 × 𝑐𝑜𝑠 𝛼 − 𝐹 = 0

(1.7)

2 × 𝐹1 × 𝑐𝑜𝑠 𝛼 = 𝐹

(1.8)

𝐹

𝐹1 = 2 𝑐𝑜𝑠 𝛼

𝐹1 = 𝐹2 =

(1.9)

14715 2 𝑐𝑜𝑠 41.6

= 9843.4 N

The angle is decreasing with increasing “h” value. Consequently, the maximum force is decreasing. So maximum loading force will occur at minimum” h” (raising height) value, the design stresses will be analyzed at that point.

Figure 1.3. Free Body Diagram of the Joint of the Power Screw and Arms

We write force equilibrium; For y axis

∑𝐹𝑦 = 0

(1.10)

𝐹2 × 𝑐𝑜𝑠 𝛼 − 𝐹3 × 𝑐𝑜𝑠 𝛼 = 0

(1.11)

𝐹2 × 𝑐𝑜𝑠 𝛼 = 𝐹3 × 𝑐𝑜𝑠 𝛼

(1.12)

𝐹2 = 𝐹3

(1.13)

For x axis

∑𝐹𝑥 = 0

(1.14)

𝐹2 × 𝑠𝑖𝑛 𝛼 + 𝐹3 × 𝑠𝑖𝑛 𝛼 − 𝐹𝑃 = 0

(1.15)

2 × 𝐹2 × 𝑠𝑖𝑛 𝛼 = 𝐹𝑃

(1.16)

2 × 9843.4 × 𝑠𝑖𝑛 41.6 = 𝐹𝑃

(1.17)

𝐹𝑃 = 13078.5 𝑁

(1.18)

Because of symmetry we can write;

|𝐹1 | = |𝐹2 | = |𝐹3 | = |𝐹4 | = |𝐹1′ | = |𝐹2′| = |𝐹3′ | = |𝐹4′ | = 9843.4 𝑁

ANSYS Analysis The first target is to predict the maximum displacement and maximum stress of the scissor jack. Since the force is applied to the carrier member, we can predict that the maximum displacement will happen at the top side of this member which is shown in Figure 1.1.Since the maximum force occurs on the screw shaft which is calculated in the force and stress analysis. The maximum stress should be occurred joint of the screw and connecting pins.

1. We have started to design with the holder which is shown in Figure 2.1. and its technical drawing is shown in Appendix 1.

Figure 2.1. Holder Part in ANSYS

The top of the holder was loaded with a compressive force of 14715 N and the cylindrical part and the bottom of the holder was fixed. The material is AISI 1045 Steel. Its mechanical property as shown in Figure 2.2.

Figure 2.2. Mechanical Properties of AISI 1045 Steel

Several studies were performed for creating the mesh. Then, we ran the model for stress and displacement analysis.

HOLDER Mesh Density & Quality (Standard Mesh) Study 1 Study 2 Study 3 Study 4

Maximum Stress (MPa)

Maximum Displacement (μm)

Total # of Element

Total # of Nodes

105,27 116,97 135,23 137,35

2,32 2,32 2,32 2,32

27517 791854 2362603 5036327

47918 1107351 1671153 3645726

Table 2.1. The Result of The Mesh Studies for Holder

We decided to choose Study 3. Because study 3 and later began to have a fine mesh, but we found that there was no change in the maximum stress. That’s why we choose it because study 3 is closer to real life condition. The top of the Holder was less stress, which is approximately 50 MPa, than bottom corner of the holder which is approximately 135MPa. Holder has less deflection which is 2,32 micrometers.

High Stress Points

Figure 2.3. Equivalent (von-Misses) Stress Distribution of Holder (Study 3)

Maximum Displacement

Figure 2.4. Total Deformation Distribution of Holder (Study 3)

Figure 2.5. Mesh Preview of Holder (Study 3)

2. We have completed the second analysis with the Base Part which is shown in Figure 2.6. and its technical drawing is shown in Appendix 2.

Figure 2.6. Base Part in ANSYS

We will focus the compressive load by causing of the lower links that is 9843.4 N and we divided this load two because of the one link applies an equal load from the base part to the two holes so our load 4921.7 N. The load has 2 components because of position of links which is 41.6°, x-component = 3267.65 N, y-component = 3680.4 N. After the studies, we have found the maximum displacement approximately 3 μm around at the four holes and the maximum stress were found approximately 87 MPa in the four holes. Both patterns are shown in Figure 2.7. and Figure 2.8. respectively. We decided to choose Study 6. Because study 6 and later began to have a fine mesh, but we found that there was no change in the maximum stress. That’s why we choose it because study 6 is closer to real life condition

BASE PART Mesh Density & Quality (Standard Mesh) Study 1 Study 2 Study 3 Study 4 Study 5 Study 6

Maximum Stress (MPa)

Maximum Displacement (μm)

Total # of Element

Total # of Nodes

64,04 64,98 71,98 75,1 85,1 86,8

3,13 3,12 3,12 3,12 3,12 3,12

93374 148689 340825 608763 1358119 2330538

160465 253991 579630 1032136 2298176 3937320

Table 2.2. The Result of The Mesh Studies for Base Part

Maximum Displacement Figure 2.7. Total Deformation Distribution of Base Part (Study 6)

High Stress Area Figure 2.8. Equivalent (von-Misses) Stress Distribution of Base Part (Study 6)

Figure 2.9. Mesh Preview of Base Part (Study 6)

3. We have completed the third analysis with the Link which is shown in Figure 2.10. and its technical drawing is shown in Appendix 3. (We have three types of Link which are Link, Link with Holes and Lock Link)

Figure 2.10. Link in ANSYS

The force change with respect to its angular position. Firstly, we have applied the compressive force that is calculated in force and stress analysis section. The link must be able to withstand an axial force of 9843.4 N for compression that is shown in Figure 2.10. Several studies were performed to creating the mesh. Then we run the model for stress and displacement analysis.

LINK Mesh Density & Quality (Standard Mesh) Study 1 Study 2 Study 3 Study 4 Study 5

Maximum Stress (MPa)

Maximum Displacement (μm)

Total # of Element

Total # of Nodes

149,34 198,17 212,68 233,38 237,68

247 246,6 246,5 246,5 246,5

55611 785482 1170765 1853239 2528563

88814 1123954 1663100 2610052 3540224

Table 2.3. The Result of The Mesh Studies for Link

We decided to choose Study 5. Because study 5 and later began to have a fine mesh, but we found that there was no change in the maximum stress. That’s why we choose it because study 5 is closer to real life condition The study shows us the maximum displacement occurs at the top section of the link with approximately 247 μm. The maximum stress occurs in the pin holes that is shown in Figure 2.12. When we change the fixed place to top holes and loaded place to bottom holes, we have the similar results for the stress and displacement causing by the action and reaction forces.

Maximum Displacement

Figure 2.11. Total Deformation Distribution of Link (Study 5)

High Stress Area Figure 2.12. Equivalent (von-Misses) Stress Distribution of Link (Study 5)

Figure 2.13. Mesh Preview of Link (Study 5)

4. We have completed the fourth analysis with the Link with Holes which is shown in Figure 2.14. and its technical drawing is shown in Appendix 4.

Figure 2.14. Link with Holes in ANSYS

Several studies were performed to creating the mesh. Then we run the model for stress and displacement analysis.

LINK with HOLES Mesh Density & Quality (Standard Mesh) Study 1 Study 2 Study 3 Study 4 Study 5

Maximum Stress (MPa)

Maximum Displacement (μm)

Total # of Element

Total # of Nodes

238,69

259,1

123640

188399

238,69 238,69 238,69

259,1 259 259

235909 787968 1845625

349406 1129295 2598813

245,95

258,9

3194803

4463332

Table 2.4. The Result of The Mesh Studies for Link with Holes

We decided to choose Study 4. Because study 4 and later began to have a fine mesh, but we found that there was no change in the maximum stress. That’s why we choose it because study 4 is closer to real life condition The study shows us the maximum displacement occurs at the top section of the link with approximately 260 μm. The maximum stress occurs in the pin holes that is shown in Figure 2.16. When we change the fixed place to top holes and loaded place to bottom holes, we have the similar results for the stress and displacement causing by the action and reaction forces.

Maximum Displacement Figure 2.15. Total Deformation Distribution of Link with Holes (Study 4)

High Stress Area Figure 2.16. Equivalent (von-Misses) Stress Distribution of Link with Holes (Study 4)

Figure 2.17. Mesh Preview of Link with Holes (Study 4)

5. We have completed the fifth analysis with the Lock Link which is shown in Figure 2.18. and its technical drawing is shown in Appendix 5.

Figure 2.18. Lock Link in ANSYS

Several studies were performed to creating the mesh. Then we run the model for stress and displacement analysis.

LOCK LINK Mesh Density & Quality (Standard Mesh) Study 1 Study 2 Study 3 Study 4 Study 5

Maximum Stress (MPa)

Maximum Displacement (μm)

Total # of Element

Total # of Nodes

187,99 174,4 207,09 244,73 270

36,43 36,43 36,43 36,4 36,39

139818 264057 888470 2071445 3583394

215265 394794 1281899 2931608 5025894

Table 2.5. The Result of The Mesh Studies for Lock Link

We decided to choose Study 5. Because study 5 and later began to have a fine mesh, but we found that there was no change in the maximum stress. That’s why we choose it because study 5 is closer to real life condition The study shows us the maximum displacement occurs at the top section of the link with approximately 37 μm. The maximum stress occurs in the pin holes that is shown in Figure 2.20. When we change the fixed place to top holes and loaded place to bottom holes, we have the similar results for the stress and displacement causing by the action and reaction forces.

Maximum Displacement Figure 2.19. Total Deformation Distribution of Lock Link (Study 5)

High Stress Area Figure 2.20. Equivalent (von-Misses) Stress Distribution of Lock Link (Study 5)

Figure 2.21. Mesh Preview of Lock Link (Study 5)

6. We have completed the sixth analysis with the Top Plate which is shown in Figure 2.22. and its technical drawing is shown in Appendix 6.

Figure 2.22. Top Plate in ANSYS

The top surface of the model was loaded with a compressive force of 14715 N, and the holes were fixed as shown in Figure 2.22.

Several studies were performed to creating the mesh. Then we run the model for stress and displacement analysis.

TOP PLATE Mesh Density & Quality (Standard Mesh) Study 1 Study 2 Study 3 Study 4 Study 5 Study 6

Maximum Stress (MPa)

Maximum Displacement (μm)

Total # of Element

Total # of Nodes

57,27 60,8 62,81 62,39 63 66,37

2,06 2,06 2,06 2,06 2,06 2,06

167865 395765 998943 1328473 1821361 2591065

210940 559010 1390263 1842356 2516795 3567214

Table 2.6. The Result of The Mesh Studies for Top Plate

Maximum Displacement

Figure 2.23. Total Deformation Distribution of Top Plate (Study 5) The study shows us the maximum displacement occurs at the top section edge of the Top Plate with approximately 2 μm. The maximum stress occurs in the pin holes that is shown in Figure 2.24. Its approximately 63 MPa.

High Stress Area Figure 2.24. Equivalent (von-Misses) Stress Distribution of Top Plate (Study 5)

Figure 2.25. Mesh Preview of Top Plate (Study 5)

7. We have completed the seventh analysis with the Power Screw which is shown in Figure 2.26. and its technical drawing is shown in Appendix 7.

Figure 2.25. Power Screw in ANSYS We have applied a tensile force that is calculated in force and stress analysis in (eq. 1.15.) The power screw must be withstand an axial force of 13078.5 N for tension that is shown in Figure 2.26.

POWER SCREW Mesh Density & Quality (Standard Mesh) Study 1 Study 2 Study 3 Study 4 Study 5 Study 6

Maximum Stress (MPa)

Maximum Displacement (μm)

Total # of Element

Total # of Nodes

180,91 201,15 205,33 215,93 225,99 243,91

144,9 145 145 145 145 145

881877 1439507 1721278 2090732 2572800 3202935

1238492 2006815 2392643 2899371 3560764 4419756

Table 2.7. The Result of The Mesh Studies for Power Screw

The study shows us the maximum displacement occurs at the place where the force applied of the power screw with approximately 145 μm. Displacement occurs longitudinal direction. The maximum stress occurs at the same face with the displacement and its magnitude approximately 216 MPa. The both patterns shown in Figure 2.26. and Figure 2.28.

Maximum Displacement

Figure 2.27. Total Deformation Distribution of Top Plate (Study 4)

High Stress Area

Figure 2.28. Equivalent (von-Misses) Stress Distribution of Power Screw (Study 4)

Figure 2.29. Mesh Preview of Power Screw (Study 4)

8. We have completed the eighth analysis with the Power Screw again. In this study we will focus the torsional stress in the power screw.

Firstly, we need to find out that what is the maximum torque that a human can apply to the handle? The maximum force we could produce with a down push is (m*g) where m is our mass. We find that the maximum force that can be apply is 30-50 kg and we take 40 kg.

𝑚

𝐹 = 40 𝑘𝑔 𝑥 9.81 𝑠2 = 392.40 N

75 mm

When we consider the head of the crank that has a length of 150 mm and we took half of it because our handle is in the middle of the power screw.

Crank Figure 2.230. Handle

Torque is equal to: 392.40 N x 75 mm = 29430 N.mm

We could apply the torque to the head of the outer face of the power screw directly that is shown in Figure 2.31.

Torque: 29430 N.mm Fixed Support

Figure 2.31. Power Screw with Torque in ANSYS

POWER SCREW TORQUE Mesh Density & Quality (Standard Mesh) Study 1 Study 2 Study 3 Study 4 Study 5

Maximum Stress (MPa)

Maximum Displacement (μm)

Total # of Element

Total # of Nodes

65,43 66,25 70,36 71,192 73,66

20,69 20,7 20,7 20,7 20,8

878255 1426511 1715145 2079561 2558731

1228378 1981387 2378133 2876189 3531028

Table 2.8. The Result of The Mesh Studies for Power Screw Torque The study shows us the maximum displacement occurs at the place where the torque applied of the power screw with approximately 20.7 μm.. The maximum stress occurs at the bottom face of the head of the power screw and its magnitude approximately 72 MPa. The both patterns shown in Figure 2.32. and Figure 2.33.

Figure 2.32. Total Deformation Distribution of Power Screw with Torque (Study 4)

Figure 2.33. Equivalent (von-Misses) Stress Distribution of Power Screw with Torque (Study 4)

Figure 2.34. Mesh Preview of Power Screw (Study 4)

We did not need to analyze other parts because the load on the parts is low and the parts have a thick wall thickness. These parts are shown in Appendix 8,Appendix 9 and Appendix 14. Names of these parts are Cubical Bore 1, Cubical Bore 2 and Handle respectively.

When we put the assembled part into analysis, we saw that some points on the link and the holder have very critical stress values and we made some changes in our design. These changes we make are on the links and the holder. Its technical drawing is shown in Appendix 10.

Fixed Support

Force: 4921.7 N Figure 2.35. New Link in ANSYS We made some changes to the link in your new design. These are in line, we drilled a 5 mm hole on the upper surface of the link, which is to ensure that it absorbs incoming stress and distributes the load evenly. We aimed to distribute the load evenly by designing a hatshaped structure up to the gears on the link. And finally, we aimed to distribute the load as well as other processes by opening a slot on the right and left surfaces of the link and we saw this in the analysis.

NEW LINK Mesh Density & Quality (Standard Mesh)

Maximum Stress (MPa)

Maximum Displacement (μm)

Total # of Element

Total # of Nodes

Study 1 Study 2 Study 3 Study 4 Study 5

140,97 166,3 218,26 237,9 242,96

278,86 278,86 278,39 278,34 278,33

30267 125702 1199238 2437598 3250332

49911 1191778 1707827 3419731 4539560

Table 2.9. The Result of The Mesh Studies for New Link

The study shows us the maximum displacement occurs at the top section of the link with approximately 280 μm. The maximum stress occurs in around the pin holes that is shown in Figure 2.37. When we change the fixed place to top holes and loaded place to bottom holes, we have the similar results for the stress and displacement causing by the action and reaction forces.

Maximum Displacement Figure 2.36. Total Deformation Distribution of New Link (Study 4)

High Stress Area Figure 2.37. Equivalent (von-Misses) Stress Distribution of New Link (Study 4)

Figure 2.38. Mesh Preview of New Link (Study 4)

We applied all the changes made above to all links and the results came out pretty well from the previous design. Its technical drawing is shown in Appendix 11.

Fixed Support

Force: 4921.7 N Figure 2.39. New Lock Link in ANSYS

NEW LOCK LINK Mesh Density & Quality (Standard Mesh)

Maximum Stress (MPa)

Maximum Displacement (μm)

Total # of Element

Total # of Nodes

Study 1 Study 2 Study 3 Study 4 Study 5

161,33 190,97 224,77 250,33 276.3

32,12 32,13 32,29 32,27 32,95

86017 144665 917290 1364459 2153901

136074 222084 1320552 1947793 3...