The life of today's turbochargers is primarily determined by the life of the aluminium compressor wheel. The damage mechanism is based on Low Cycle Fatigue (LCF). Aerodynamic and structural design optimisation for stress reduction of the compressor wheel are described in this paper. To use compressor wheels close to the limits BorgWarner developed a tool to analyse and judge cyclic loading by using Miner's Damage Accumulation Rule and statistical cycle counting using the Rainflow Method. Material and component properties e.g. spin test and cyclic pull test results, are taken into account. Examples for different load cycles and corresponding lifetime predictions are given. To meet the highest demands in relation to loading and lifetime, titanium compressor wheels were developed. Lifetime is increased compared against Aluminium wheels by more than a factor of 13. A 5-month spin test was completed without a failure.
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