Methodology to assess integrity with application to collector copper lamellas

Abstract The performance of engineering components and structures is strongly influenced by the interaction between design, manufacture and materials. A methodology to assess the integrity of a circular collector is presented by investigating the failure of copper lamellas. The investigated circular collector, having 315 copper lamellas, is one of the main parts of an electric motor. The fracture of the copper lamellas was observed in normal operation. This unexpected fracture required an investigation of the fracture origin, in order to improve the initial design. The numerical results of the finite element analysis on the stress field in the copper lamellas for the operating regimes, and the stress concentration effects are shown. Failure assessment diagram, based on notch stress intensity factor, was considered in order to estimate if crack initiation can occur. Finally a study of crack propagation will present comparatively the numerical obtained crack path against the one observed in-service.

[1]  Paolo Lazzarin,et al.  A unified approach to the evaluation of linear elastic stress fields in the neighborhood of cracks and notches , 1996 .

[2]  S. Cunningham,et al.  Stress intensities at notch singularities , 1997 .

[3]  M. Kanninen,et al.  A finite element calculation of stress intensity factors by a modified crack closure integral , 1977 .

[4]  Roberto Tovo,et al.  Developments of some explicit formulas useful to describe elastic stress fields ahead of notches in plates , 2002 .

[5]  A. Kifani,et al.  Fracture toughness of high strength steel using the notch stress intensity factor and volumetric approach , 2003 .

[6]  G. Pluvinage.  Fracture and Fatigue Emanating from Stress Concentrators , 2003 .

[7]  Paolo Lazzarin,et al.  A generalized stress intensity factor to be applied to rounded V-shaped notches , 2006 .

[8]  Paul C. Paris,et al.  Elastic field equations for blunt cracks with reference to stress corrosion cracking , 1967 .

[9]  G. Sih.  Strain-energy-density factor applied to mixed mode crack problems , 1974 .

[10]  Roberto Tovo,et al.  Stress field parameters to predict the fatigue strength of notched components , 1999 .

[11]  G. C. Sih,et al.  Sharp notch fracture strength characterized by critical energy density , 1991 .

[12]  G. Sih.  Mechanics of fracture initiation and propagation , 1990 .

[13]  F. Erdogan,et al.  On the Crack Extension in Plates Under Plane Loading and Transverse Shear , 1963 .

[14]  Filippo Berto,et al.  Stress distributions in notched structural components under pure bending and combined traction and bending , 2005 .

[15]  Steven J. Zinkle,et al.  Fracture toughness of copper-base alloys for fusion energy applications , 1999 .

[16]  Guy Pluvinage,et al.  The use of notch stress intensity factor as a fatigue crack initiation parameter , 1995 .

[17]  M. Williams,et al.  Stress Singularities Resulting From Various Boundary Conditions in Angular Corners of Plates in Extension , 1952 .

[18]  M. N. James,et al.  Design, manufacture and materials; their interaction and role in engineering failures , 2005 .

[19]  C.H.A. Townley,et al.  The effect of defects on structural failure: A two-criteria approach , 1975 .

[20]  Paul A. Wawrzynek,et al.  Quasi-automatic simulation of crack propagation for 2D LEFM problems , 1996 .

[21]  David Taylor,et al.  A mechanistic approach to critical-distance methods in notch fatigue , 2001 .