Evaluation of fatigue life of aluminium alloy wheels under bending loads

Abstract

A B S T R A C TThis paper presents the details of S-N curve for aluminium alloy (Al) A356.2-T6 and fatigue life of alloy wheels under bending load of cornering fatigue test (CFT). Development of S-N curve has been carried out by conducting rotary bending fatigue test at different stress levels as per Standards IS 5075. The rotary bending fatigue test has been performed under constant amplitude fatigue loading. The CFT of the wheel in normal driving mode has been carried out as per the procedure given in Japanese Industrial Standard Disc Wheels (JIS D 4103). It has been observed from the test that the cracks are initiated at the spoke and hub joining area closer to spanner hole on the front face of the wheel. Fatigue life of the alloy wheel has been predicted by finite element analysis (FEA), simulating the realistic test conditions. From finite element analysis, it has been observed that the maximum stress occurs at the mounting face of the wheel. Further, it has been observed that there is significant difference between the computed fatigue life and experimental value. Parametric study has been carried out for reliable fatigue life estimation and proposed an appropriate safety factor for fatigue life estimation under rotary bending test.Keywords alloy wheels; cornering fatigue test; finite element analysis; safety factor; S-N curve. N O M E N C L A T U R Ed = offset F = the maximum value of wheel load HB = hardness M = bending moment S = coefficient depending upon the offset S u = ultimate tensile strength S y = yield strength R = static rolling radius e = elongation μ = coefficient of friction between the tyre and the road I N T R O D U C T I O NIn automotive engineering, the wheels are one of the most critical components and their function is of vital importance in human safety. With the changing requirements in the automotive industry in the last decade, the wheel manufacturers have been focusing attention to lightweight designs by introducing new materials and manufacturing technologies in contradiction to durability concerns due Correspondence: P. Ramamurty Raju. to the complex loading conditions on wheels. In the fatigue evaluation of a wheel design, the general procedure followed is to predict the accumulated number of cycles at which a small crack appears at a stress raising geometrical feature. The fatigue failure is related to the initiation and subsequent growth of these small cracks under repeated loading and unloading and the elasto-plastic stress state at the stress raising geometrical feature, or equivalently the notch. Analysis must be carried out in order to determine the deformation parameters describing the cyclic hysteresis loops. Due to the lack of closed-form analytical

A356‐T6 wheels: Influence of casting defects on fatigue design

“…36 The S-N curve obtained shows that N = 500 000 is in high cycle fatigue regime. In order to compare this value with the ones found in literature, we do not have to consider the infinite life fatigue regime but the finite regime.…”

“…Ramamurty et al obtained the Wöhler diagram carried out on specimens taken from the spokes of a wheel made of A356.2-T6 and referred to the breaking condition. 36 The S-N curve obtained shows that N = 500 000 is in high cycle fatigue regime. From this graph, the fatigue strength associated with 500 000 cycles results in approximately 130 MPa, which is higher than the one achieved with the staircase conducted in this research.…”

“…21,23,36,37 In particular, it can be pointed out that Ueno's equation (Equation 2) appositely introduced for aluminium cast alloys is less conservative than Murakami's one. 21,23,36,37 In particular, it can be pointed out that Ueno's equation (Equation 2) appositely introduced for aluminium cast alloys is less conservative than Murakami's one.…”

“…The results allow to draw that, although the maximum Feret diameter shows a non-negligible scatter, the endurance limits found in the differently stressed area show a narrow dispersion: σ w is calculated between 75 and 90 MPa, which confirms the evaluations available in literature. 21,23,36,37 In particular, it can be pointed out that Ueno's equation (Equation 2) appositely introduced for aluminium cast alloys is less conservative than Murakami's one.…”

Shape Optimization of Wheel on Fatigue Failure

“…With the rapid development of computer technology, CAD/CAE techniques are widely used in industrial design and manufacturing process [10,11]. Applying the simplified model without considering the effect of circumferential position variation of loads, stress-strain distribution and fatigue life of the wheel can be easily simulated with a computer, which considerably improves the efficiency of product design and reduces the development cost [12][13][14][15]. A precondition for using simulation technique to calculate the fatigue and optimize the structure is that a precise enough stress-strain distribution is required.…”