ENGINEERING ANALYSIS CDM 1372 ASSIGNMENT 3

Transcription

1 ENGINEERING ANALYSIS CDM 1372 ASSIGNMENT 3 GROUP MEMBERS : MUHAMMAD NAZHIF BIN SHAMSUDDIN. KHAIRUL AFANDI BIN SULAIMAN. BADARUSSHAM. HALIMATUS SAADIAH BINTI MOHD ARIEF MUSLIM BIN MAT GHANI. 1 GROUP NO : P16

2 Content Page Introduction 3-3 Objective 4 4 Solver & Software Detail 5 5 Unit 6 6 Result Summary 7 7 Assumptions & Note 8-9 CAD Modelling Product Structure FE Model Load Load Case Boundary Conditions Material Comparison Mass for Aluminium Different Load Maximum Yield Strength Simulation Result Appendix Conclusion

3 Introduction We have design a wheelchair that the seat can move sideways, up and down and the wheelchair can be fold to be stored away. We have done research that a person using the wheelchair is range from kg. So we need to do an analysis towards the lower frame because it is the most critical part of the wheelchair. The lower frame need to support the upper frame, seat and also the weight of user that used the wheelchair. We wanted to check whether the lower frame of our product is strong enough when receiving incoming force towards it. We also have to check what type of material to used for the lower frame of our product. 3

4 objective To do an analysis for different types of material. To know which material is the best for our product. To do meshing using Hypermesh software. To get result using OptiStruct software. To know the von misses stress, displacement and the total weight of every material. To study the structural integrity of the lower frame under incoming force towards the frame with different type of force acting in downward direction and check for the stresses. 4

5 SOLVER & SOFTWARE DETAILS Pre-processing : Hyper Mesh 12.0 Analysis & Optimization : Optistruct 12.0 Post processing : Hyper View

6 Units Displacement = mm Mass = Kilogram Density = Kg/mᶾ Modulus = MPa Force = Newton 6

7 Result summary Aluminium 800N (80kg) 5000N (500kg) Young Modulus 6.9e⁴Pa 6.9e⁴Pa Poisson s Ratio Density 2.7e ⁹kg/mᶾ 2.7e ⁹kg/mᶾ Displacement 0.264mm 1.65mm Von Mises Stress 13.6MPa 85.2MPa Weight 5kg 5kg The result that we get from the analysis is that, our frame is strong enough because the stress of the material is below the yield stress and also the weight is the most lightweight material compare to other material that we analized. *ALUMINIUM YIELD STRENGTH = 95 MPa 7

8 Assumptions & Note Analysis Type Structural linear static analysis has been performed on the lower frame assembly under incoming force toward the wheelchair assuming that the force is the human weight and the support is the wheels using OptiStruct. Element Type Lower frame wheelchair are modelled using combination of shell elements (CTRIA3, CQUAD4) of midsurface element. All components are assembled with the help of rigid elements and rbe element to wherever possible node to node connectivity has been maintained between the components. For details refer to slide titled FE model. 8

9 Assumptions & Note Material data Aluminium material has been modelled as an isotropic linear elastic material and has been assigned to the lower frame components. For details refer to slide titled Material Data. Loads FE analysis is performed for of following load cases LC1 using 800N to indicate the average weight of human LC2 using the maximum weight that the frame could go which is below 500 kg. Thus for both cases of the lower frame is being applied on middle spot of the frame to indicate the position of the user when they are seating. For details refer to slide titled Loads. Boundary Conditions The 3 support which are constrained in respective DOF are to indicate the wheels of the wheelchair. For details refer to slide titled Boundary Conditions. 9

10 Cad modelling 10

11 Product structure 11

12 Fe model Element size is 5mm. Midsurface is 3mm. Mixed element tria & quad. 12

13 Load We have located 4 location where the loads will be which is the joint to the upper frame and seat. Through this location, we have make the force to be at the centre of this location. Joint frame front Hydraulic joint 13 Joint frame rear Joint frame rear

14 Load case 1 The middle spot of the load will be the incoming force towards the lower frame. We give the force at the centre of lower frame with 800N/80kg at the ve Y-axis. The incoming force is determined by the average weight of human. 14

15 Boundary Conditions The support nodes is at the centre of every hole of the two main wheel and caster wheel. The nodes are selected at every point of the mesh around the holes by using rigid and select the middle point to be the support. The nodes are fixed at the degree of freedom at the rotational and transition of XYZ axis. This is to indicate the support are the wheels of the wheelchair. 15

16 Material Comparison Using 800N for the Force and different types of material at the LOWER FRAME. Using a same thickness which is 3mm at the LOWER FRAME. Material Young Modulus (Pa) Poisson s Ratio Density (kg/m 3 ) Displacement (mm) Von Mises Stress (MPa) Weight (kg) Aluminium 6.9e⁴ e ⁹ Stainless Steel 7.7e⁵ e ⁹ Mild Steel 2.1e⁵ e ⁹ *All material used on the frame did not fail because they are lower than their yield strength

17 Mass for aluminium We choose aluminium material because it is the most lightweight material compare to stainless steel and mild steel material. The total weight of the LOWER FRAME using aluminium material is 5kg compare to stainless steel and mild steel which are 17kg & 14kg. 17

18 Different load We do this analysis to get the maximum weight, the frame could handle before failure. By using an Aluminium material we assume a 5000N of incoming force towards the frame. Using the same thickness which is 3mm. *ALUMINIUM YIELD STRENGTH = 95 MPa Aluminium 800N (80kg) 5000N (500kg) Young Modulus 6.9e⁴Pa 6.9e⁴Pa Poisson s Ratio Density 2.7e ⁹kg/mᶾ 2.7e ⁹kg/mᶾ Displacement 0.264mm 1.65mm Von Mises Stress 13.6MPa 85.2MPa N of force towards the aluminium frame would be 85.2 MPa and by the material yield strength indicate that it is below the yield strength, thus the frame would not brake under 5000N of incoming force.

19 Stress (Mpa) Max. yield strength The red line shows the maximum yield strength of aluminium which is 95MPa. 100 Yield Strength Graph Force (N)

20 Simulation for load case 1 800n 20

21 displacement Using an aluminium material. Displacement result is 0.264mm for 800N at the LOWER FRAME. The red colour shows the maximum vibration at the frame. 21

22 Von mises stress Using an aluminium material. Von Mises Stress result is 13.6 mm for 800N at the LOWER FRAME. The red and yellow colour shows the maximum stress at the join frame. 22

23 Simulation for load case n 23

24 displacement Using an aluminium material. Displacement result is 1.65mm for 5000N at the LOWER FRAME. The red colour shows the maximum vibration at the frame. 24

25 Von mises stress Using an aluminium material. Von Mises Stress result is 85.2 mm for 5000N at the LOWER FRAME. The red and yellow colour shows the maximum stress at the join frame. 25

26 Appendix Force = weight 1(kg) x 10 (newton) 1 kg = 10 N Thus, 80 kg = 800 N 500 kg = 5000 N 26

27 CONCLUSION To determine the feasibility of the lower frame design Based on the spec given : The maximum allowable stress of the lower frame:- 95 Mpa ( Yield strength) The maximum allowable deflection of each gate is :- 3 mm Result from LC1 :- Deflection / displacement : mm< 3.00 mm Maximum stress : MPa < 95 MPa Result from LC2 :- Deflection / displacement : mm < 3.00 mm Maximum stress : MPa < 95 MPa Therefore, the lower frame design is feasibly safe to support the weight of the user. 27