Structural Analysis of Spoke Wheel Rim Assembly of Motorcycle.

Shantaram Jadhav Gyanendra Roy Manager CAE Department Head - CAE Mahindra 2 Wheelers Ltd Mahindra 2 Wheelers Ltd D1 Block, Plot No. 18/2 (part), D1 Block, Plot No. 18/2 (Part), Chinchwad MIDC, Chinchwad MIDC, Pune – 411019. India Pune – 411019. India jadhav.shantaram2@mahindra.com roy.gyanendra@mahindra.com

Abstract The motorcycle business segment is competitive and diverse in India. The new product development is an important phase of motorcycle companies to remain in competition. The motorcycle business rolls around fuel efficiency of product as one aspect of customer requirement. Light in weight and stronger is a new demand to achieve the good fuel economy. In ordered to achieve this, the vehicle weight should be minimum in comparison with competitor’s vehicle. The spoke wheel rim assembly contribute the major weight addition in motorcycle after engine. Hence the light spoke wheel rim plays an important role in overall optimise design of vehicle.

The motorcycle spoke wheel rim usage pattern and loading condition varying from place to place.

The strength requirement is evaluated through the standard load cases as per AIS 073 (Part1 & Part3) along with several RWUP (Real world usage pattern) load cases also. The strength analysis is carried out with Altair products like RADIOSS as a solver, Hypermesh for pre- processing and Hyperview for post-processing.

The strength analysis results validated thoroughly with AIS 073 standard testing, pave testing and different highway profiles testing. No structural failure like fine cracks, bends and significant deformation observed after completion of designated life cycles on optimise spoke wheel rim assembly.

Keywords: Spoke Wheel Rim, Motorcycle

Introduction:

The spoke wheel rims are generally less in weight and cost compared to cast alloy wheel rim. The cost effective product is also one of the requirement of customers from developing nations. Spoke wheel rim is excellent in weight to strength ratio. Additionally, the repair cost or maintenance cost of spoke wheel is generally less than alloy cast wheel. That’s why, spoke wheel rim is still popular in motorcycle and bicycle business.

The spoke wheel rim is one of the most important structural part of motorcycle as the different kind of loads acting on it continuously. The wheel rim assembly undergoes with radial load, torsion load, bending load and impact load. Hence the design of spoke wheel rim is really complex in nature.

The spoke wheel rim nomenclature shown in figure no. 1.

Figure no. 1

In this paper, the standard load cases with boundary conditions are described in detail. The methodology of analysis has been described as below.

1. FE modelling 2. Load cases and boundary conditions details 3. Measure stress results

FE Modelling:

The finite element method is used to analyse the part. The wheel hub, spoke nipples and wheel rim are discretized with second order tetrahedral element. The spokes are modelled as a CBEAM 1D element. The surface to surface contacts are assigned between spoke nipples and wheel rim. The spokes are fixed with RBE2 at the other end of wheel hub.

In Zoom View:

Figure no. 2 (Meshing)

Figure 2(a) Wheel rim and Spoke Nipple Figure 2(b) Surface to Surface Contact

Load Cases on Spoke Wheel Rim Assembly:

1. Radial Load Case: Radial load case is carried out as per AIS 073. The wheel rim bearing surfaces are fixed in all degree of freedom and radial load (Q) is applied on the wheel rim over the contact angle of 60 degree. The load (Q) is applied as cosine distribution over contact angle of 60 degree after every 10 degree up to 140 degree. The spoke wheel rim assembly should sustain the load before 5+10^5 life cycles.

The static radial load is calculated by below equation. Q =

Sr * W

Where

Sr is a coefficient equal to 2.25 and W is maximum design load

Figure No. 3

2. Impact Load Case :

Impact load case is carried out as per AIS 073. The wheel rim bearing surfaces are fixed in all degree of freedom. The impact load is applied on wheel rim top surfaces as shown in figure no. 4. The induced stresses should be less than the yield strength of the material. The impact load (total mass of striker) is calculated by below equation.

m1 + m2 = K*(W/ g)

Where,

m1 + m2: Total mass of striker weight (kg) m1: The mass of main striker weight ± 2% (kg) m2: The mass of auxiliary striker weight (including the mass of the springs) 40 ± 2 kg W: Maximum design load K: Coefficient- 1.5 g: Gravitation acceleration 9.8 (m/s2)

Figure No. 4

3. Bending Load Case :

The bending load case is carried out as per AIS 073. The wheel rim outer surface is fixed in all DOF as per AIS 073 standard testing and the bending load (M) is applied on bearing surface of wheel hub. The spoke wheel rim assembly should sustain the load before 1+10^5 life cycles. The bending moment load (M) is calculated by below equation.

M = Sm x µ x W x r

Where

Sm - is a coefficient equal to 0.7 µ - is the friction coefficient between tyre and road, equal to 0.7 W - is the maximum design load of the wheel rim, in Newtons (N) and r - is maximum static loaded radius for which wheel rim is designed in metres (m).

Figure No. 5

4. Torsion Load Case :

The torsion load case is carried out as per AIS 073. The wheel rim outer surface is fixed in all DOF as per AIS 073 standard testing and the torsion load (T) is applied on drive contact surfaces of wheel hub. The spoke wheel rim assembly should sustain the load before 1+10^5 life cycles. The torsion load (T) is calculated by below equation. T = ±

W. r

Where

W - is the maximum design load of the wheel rim, in Newtons (N) r - is maximum static loaded radius for which wheel rim is designed in metres (m).

Figure No. 6

5. Max Deflection Load Case :

As per AIS 073 part 3, the maximum wheel rim deflection should not exceed more than 10mm for 1.60 nominal width code. The amount of deflection is allowed with respect to nominal diameter code as below.

Nominal rim width code Nominal rim diameter code

15 max. 16,17,18 19 min 1,10 to 2.75 and MT 1.85 to MT 5.50 10 mm 15 mm 20mm

The loads and boundary conditions are explained in figure no. 7.

Figure no .7

Stress Results:

The induced stresses are within acceptance limit in all load cases. The induced stresses are within endurance limit in radial fatigue, bending fatigue and torsion fatigue. The maximum deflection is also within limit as per the AIS 073 part 3.

Von Misses and Max Principle Stresses: The stress plots are shown with acceptance limits.

Figure no. 8

Maximum deflection: The observed max displacement is 2.5mm, which is less than 10mm.

Figure no.9

Future Scope of Study: The spoke wheel pattern change has a significant effect on whole wheel rim structure. Hence radioss software can be effectively used for this complex study.

Benefits Summary:

Since, the FE results are validated with experimental tests, for new product development, FEM approach can be used to reduce design cycle time, number of prototypes and more importantly, testing time and its associated costs.

Conclusion:

The virtual simulation results validated with physical test results as there is no evidence of fine cracks and significant deformation on spoke wheel rim assembly after completing designated cycles. It is proven through endurance test also as there is no any field failure.

Acknowledgement

The authors would like to acknowledge our Design, Prototype and testing teams for extending their kind support. The authors would also like to thank the R&D Chief, Mahindra 2 Wheelers management and CAE Head for providing this opportunity for publishing the work. REFERENCES

1. AIS 073 Part (1) and Part (3) for Two Wheelers 2. Altair Hyperwork Radioss v 12.0