The Identification Of The Design Defects Of Structure Processing And Material Selection Of Shaft Parts

Shaft parts are considered as important parts in mechanical system and widely applied to mechanical products. Therefore, failures of shaft parts will have impact on steady work of mechanical equipments or cause significant accident and economic losses. In design process of mechanical products, design work for shaft parts is complicated, their design defects can give rise to failure of mechanical equipments. In this paper, various design defects identification methodologies are employed to identify design defects such as structure processing, material selection for shaft parts.The parts which are designed by inexperienced designers can bring about high processing costs or many manufacturing problems. Based on reasoning strategy of feature element, a design defect identification method for structure processing of shaft parts is presented. Structural features of shaft parts contain all structural design information of parts. The design information of shaft parts is stored in tree of parts information. A knowledge base of feature element is established. A reasoning strategy of feature element is presented. The design defects for structure processing of shaft parts are identified by the reasoning strategy.The traditional calculation method of interference value ignores the stress concentration caused by edge effect. Larger stress could cause crush or fretting wear of the hub. In order to make up disadvantages of traditional calculation method, an identification method for interference design defect of shaft parts is presented, based on the finite element method and support vector machine model. Finite element method is applied to analyze influence factors of the interference fit contact stress. The relationship model between interference and its influencing factors was built by the support vector. The maximum value of interference without causing material yield can be calculated accurately by using the relationship model. Suppose interference value of original design exceed the calculated maximum interference value, design defect of interference fit appear.The traditional anti-overload design method of ball screw overlooks influence of helix angle. In this paper, given the influence of helix angle and ball load distribution uneven, contact model of ball screw is improved. Calculation formula of critical axial load is deduced based on the critical plastic deformation. Structural parameters design defects are identified in term of above theory.Material selection is a multi-objective decision-making process. An indiscreet decision for designer causes material selection dissatisfy design requirements. A design defect identification model for material selection is presented based on improved matter-element model. Calculation method of related degrees in matter-element model is improved. Numerical related degree and range related degree are introduced to overcome disadvantage of matter-element calculation difficulty. Grade membership degree and grade eigenvalues of alternative materials are calculated by using improved matter-element model. The design defects of alternative material are identified by using above two parameters.