SELECTION OF SHAFT MATERIALS USING A MULTICRITERIA APPROACH

Abstract

The aspiration of modern mechanisms is to achieve the highest possible speed of work. The same requirements apply to transmission shafts, so a precise dynamic analysis of the stability of these elements is very important. It is known that the frequency of oscillation is directly proportional to the elasticity of the body, and inversely proportional to the mass of the body. The essence of the work is in the selection of the optimal shaft material in order to avoid the occurrence of resonance that can lead to different types of shaft destruction. Aluminum and composite carbon fiber shafts in combination with epoxy resin were analyzed. The paper proposes a multicriteria approach (MCDM) for the selection of the optimal transmission shaft material. It is emphasized how suitable this method is for analyzes of this type because it includes the influence of numerous qualitative and quantitative properties of materials in the selection. Metal drive shafts can have mass limitations, low critical speeds, and potentially destructive vibrations. Composite drive shafts, thanks to the nature of composites, in which the specific modulus of elasticity is higher (modulus to density ratio) than in metal, can be a good replacement. Composite drive shafts offer excellent vibration damping, reduced wear of drive assembly components, are less susceptible to the effects of stress concentration, reduce installation time, inventory costs, maintenance, etc. Replacing conventional metal structures with composite structures has many advantages, due to higher specific stiffness and higher specific strength of composite materials. Material has an important role in the design process. Choosing the right material for a particular product is one of the vital tasks for engineers. In order to meet the final requirements of the product, engineers and designers need to analyze the characteristics of different materials and identify the appropriate material. Due to the presence of a large number of materials with different properties, the process of material selection is a complicated and time-consuming task. There is a need for systematization and an efficient approach to select the best alternative material for a given product. The conflicting nature of the material selection evaluation criteria can be resolved using the Multi-Criteria Decision-Making (MCDM) method. The aim of this paper is a multicriteria approach (MCDM) for the selection of the optimal material of the transmission shaft. Aluminum and composite carbon fiber shaft in combination with epoxy resin were analysed, taking into account seven evaluation criteria: Elasticity modulus E1 and E2, sliding modulus, G12, ratio E1/ρ, weight m, natural frequency fs, critical speed nkr.