THERMAL LOAD EFFECTS ON FATIGUE LIFE OF A CRACKED RAILWAY WHEEL

Abstract

IN THIS PAPER, FATIGUE LIFE OF A CRACKED RAILWAY WHEEL UNDER THERMO-MECHANICAL LOADS IS STUDIED. FOR THIS PURPOSE A FE MODEL OF A WHEEL, WITH TWO BRAKE SHOES AND A PORTION OF RAIL IS CREATED AND SUITABLE LOADS AND BOUNDARY CONDITIONS ARE APPLIED TO THE MODEL. IT IS ASSUMED THAT THE WHEEL HAS CONTAINED AN ELLIPTICAL CRACK IN THE DEFINITE DEPTH OF THE TREAD SURFACE AND THERMAL LOADS ARE DETERMINED BY MODELING THE CONTACT OF THE RAIL-WHEEL AND TWO BRAKE BLOCKS. IN ORDER TO INVESTIGATE THE THERMAL LOADS EFFECT ON THE FATIGUE LIFE OF THE CRACKED WHEEL, ANALYSES ARE PERFORMED IN TWO CASES: MECHANICAL ANALYSIS AND THERMO-MECHANICAL ANALYSIS; WHILE DIFFERENCE BETWEEN THEM, SHOWS THERMAL LOAD EFFECTS AND ITS IMPORTANCE. IN THIS WORK THE WHEEL ROTATION ON RAIL IS MODELED AND A 3D FE MODEL FOR DETERMINATION OF RAIL-WHEEL CONTACT PRESSURE IS USED WHILE IN MANY OF THE PREVIOUS INVESTIGATIONS, EITHER ROLLING WASN'T MODELED OR ITS EFFECT WAS SIMPLIFIED AS A TRANSLATING PRESSURE DISTRIBUTION ALONG THE RAIL-WHEEL CONTACT REGION AND ALSO THE HERTZ CONTACT THEORY HAD USED FOR DETERMINATION OF CONTACT PRESSURE IN WHEEL- RAIL INTERFACE. FINALLY, EFFECTS OF ANGULAR VELOCITY ON FATIGUE LIFE OF A CRACKED WHEEL UNDER -MECHANICAL AND MECHANICAL LOADS ARE SHOWN. THE OBTAINED RESULTS CONFIRM THE IMPORTANT INFLUENCES OF THERMAL LOADS ON THE WHEEL FATIGUE LIFE IN ALL MENTIONED CASES THAT ARE STUDIED IN THIS ARTICLE.