Weight reduction of a carbon fibre composite wheel

The wheel of a passenger vehicle must be designed to be safe and light. Despite the tremendous potential of carbon fibre as an automotive material due to high strength and low weight, the prevalence of carbon fibre reinforced plastics (CFRPs) in vehicle wheels is limited. Manufacturing and testing CFRP prototypes is expensive. Thus it is advantageous to develop simulation models for composite weight reduction. The simulation models can provide insight into how lighter CFRP wheels can be designed. This study presents the design development of a CFRP wheel for a high-performance roadster; the CFRP wheel is offered by an automotive manufacturer as a high-performance option instead of aluminium wheels. Finite element (FE) simulations were initially conducted assuming an isotropic material. This initial model was used to eliminate stress concentrations and to design and manufacture an initial CFRP wheel. The CFRP wheel weight is 6.8 kg as compared to the original aluminium wheel which weighs 8.1 kg. This initial design passed the dynamic cornering fatigue test (the most stringent strength test for wheels). Thereafter the wheel was instrumented with strain gauges and a bending moment was applied to the hub using a custom-built test rig. The test rig produced a static load equivalent to the dynamic cornering fatigue test (in which the applied bending moment varies sinusoidally). The test rig allowed for the deflection of the load arm to be measured. The comparison of the experimentally measured strains and an FE model which includes the CFRP laminate properties showed good agreement. Two alternative laminate options were simulated using the FE model. These showed both an increase in stiffness and a calculated weight reduction. This study shows that an aluminium wheel for a high-performance roadster can be redesigned using CFRP to be 16% lighter and using a FE model a further 152 g weight reduction is possible (18% weight reduction in total when compared to the aluminium wheel).

ПІДВИЩЕННЯ МІЦНОСТІ ТА НАДІЙНОСТІ БАРАБАНІВ КОЛІС ЛІТАКІВ ЗМІЦНЮВАЛЬНОЮ ОБРОБКОЮ

Technology, equipment, and results of stand tests of plane wheel hubs and flanges strengthened by surface plastic deformation are described. The new method suggested by the authors is called vibrational-centrifugal strengthening treatment. It belongs to the method group of dynamic strengthening of revolutional shape parts. It is based on impact interaction of the part processed with a massive tool which is rolled over the strengthened surface of the part when under vibration. Moreover, the impact contact between the part and the tool occurs through a small number of deformable bodies. This provides formation of compressive residual stress in the contact places in the part material. For magnesium wheel hubs (alloy ML-12) residual compressive stress is within 110 MPa, for aluminium ones (alloy AK6) it is within 250 MPa. The degree of strengthening of outer zone material for magnesium wheel hubs is 45...59 % with surface micro-hardness increasing up to 1150 N/m2 and the thickness of the strengthened layer being 0.9...1.0 mm. When strengthening aluminium wheel hubs and flanges, the thickness of the strengthened layer is to be 0.6...0.9 mm with a degree of cold work being 25...30 %. Fatigue studies of a party of KT-141 type wheel hubs strengthened by the method (magnesium alloy MT-12) demonstrated their service life increasing up to 1000 take-offs and landings at the safety coefficient of n = 3.5. The lifetime of this type of wheel hubs strengthened by roller burnishing did not exceed 750 take-offs and landings; for unstrengthened ones, it made 500 take-offs and landings at lower values of the safety coefficient. Strengthening the wheel hub web KT-150K (aluminium alloy AK6) increases their lifetime by 28...30 % on average. Apart from plane wheel hubs and flanges, the method of vibrational-centrifugal strengthening treatment can be applied for increasing the lifespan of various parts of chassis components of circular section, for strengthening nonferrous metal webs of car wheels, radius blends and steel shaft journals etc.