Stress-Concentration Factors of Stepped Shaft of Circular-to-Square Cross-Section under Twisting Moment

摘要

Shaft is a machine element whose main function for power transmission.Shaft is often needed in stepped form (change in cross-section). For a non-smooth shaft (stepped shaft), the elementary stress equations are no longer hold for calculating the actual stress as the stress would be higher than the nominal stress.To relate the maximum stress at the discontinuity with the nominal stress calculated using the elementary stress equations, a factor is needed which is called stress concentration factors (SCF).This paper presents a graph for design purpose of stress concentration factors of stepped-shaft of circular-to-square cross section under twisting moment.The graph was derived from an extensive linear finite element parametric study and presented ini line of the well-known Peterson's graph for stepped-shaft of uniform circular cross section.Finite element parametric study was carried out for every combination of diameter to diagonal ratio,D/d, and radius of fillet to diagonal ratio,r/d. For geometry with particular D/d value, six analyses were done by varying the r/d ratio.Stress distribution shows that maximum shearing stress located at the root of the square, exactly at midside.In general graphical design similar to the well-known Peterson's graph was produced.