【作者】

Matti Savolainen,Roger Rabb,Anton Leppaenen

【摘要】

论文已在上海2013年CIMAC大会上发表，论文版权归CIMAC所有。 Component design procedures have developed significantly during the last decades. As a part of the process, the prediction of accurate stresses using the Finite Element Method (FEM) as well as the calculation of fatigue strength with specific codes, have become common practice. Due to ever-increasing computational power, different surface treatments, which contribute to the formation of the local microstructure and stress situation, such as heat treatment or shot peening, can also be integrated in the FE-model. The determination of the fatigue life of a component can be automated to some extent for the sake of decreased design time by using numerical methods. When the outcome of a surface treatment is taken into account in such an analysis, it naturally gives the analyst an opportunity to optimise not only the geometry, but also the desired surface treatment influence on the component. This in turn leads to the fact that the parameters of the surface treatment procedure in manufacturing can be defined more precisely already in the designing phase leading to obvious cost savings. Case hardening is a surface treatment process in which the surface of a metal is hardened by infusing elements into the material. More specifically carburization, where the component is introduced to a carbon-rich environment at an elevated temperature and afterwards quenched so that the car-bon stays in the structure, is a commonly used method for improving the wear and fatigue resistance of several engineering components. The advantage from the fatigue point of view of this procedure is naturally the increase in hardness as well as the compressive residual stresses in the surface of the component. The disadvantage, on the other hand, can be found underneath the surface in a form of balancing tensile residual stresses, which in turn may be a source location for a possible failure initiation. This paper introduces an approach for dimensioning a component, which has been hardened by carburization. The focus of the exercise is on defining the correct case hardening profile in order to meet the required probability of survival. As an example, a gear from a thruster manufactured by Wartsila Netherlands B.V. is investigated, where the teeth of the gear wheels are treated. The examination is conducted through the component surface until a certain depth in order to also take into account the influence of the tensile part of the residual stresses. Those are then combined with the working stresses during operation and based on the result, the fatigue analysis is performed. That is done by adapting existing Wartsila tools including the multiaxial damage models of Findley and Dang Van together with the concept of local fatigue strength, which defines local fatigue limits through depth based on the hardness variation. The material parameters used are obtained by testing and finally the calculated results are compared to available real world data.

【会议名称】

第27届CIMAC会议

【会议地点】

上海

【下载次数】

1

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