COBEM99

S24 Mecânica dos Sólidos

Title:

APPLICATION OF ACOUSTOELASTIC TECHNIQUES TO RAILROAD WHEELS STRESSES DETERMINATION

Summary :

ABSTRACT. RAILROAD WHEELS FAILS IN TWO MAIN MODES: ROLLING SURFACE DEFECTS LIKE SPALLING, SHELLING AND WEAR, AND INTERNAL DEFECTS INCLUDING CRACKS PROPAGATING AFTER THE CHANGE IN THE ORIGINAL STRESS PATTERN. ALTHOUGH THE FORMER IS MORE USUAL, THE EFFECTS OF THE LATER ARE ALMOST ALWAYS CATASTROPHIC. THE MAIN METHOD OF VERIFYING HOW DANGEROUS IT IS TO LEAVE A STRESSED WHEEL IN SERVICE IS THE OBSERVATION OF THE CHANGE IN THE RIM COLORS, AND HOW MUCH IT GOES TOWARD THE HUB. SEVERAL RESEARCHERS HAVE CONTESTED THIS METHOD. RECENT RESEARCHES CAME ALONG WITH NEW APPLICATIONS OF THE ULTRASOUND IN THE IDENTIFICATION OF THE DANGEROUS WHEELS, BASED ON ACOUSTOELASTIC PROPERTIES OF THE MATERIALS. TWO METHODS OF GENERATING ULTRASONIC WAVES HAVE BEEN TESTED TO MAP THE STRESSES IN THE WHEELS, ONE USING ELECTROMAGNETIC ACOUSTIC TRANSDUCERS (EMAT) AND THE OTHER USING PIEZOELECTRIC TRANSDUCERS (PZT). THE PROPOSAL OF THIS WORK IS TO REVIEW THE PREVIOUS WORKS, AND DISCUSS THE STATE OF ART IN THIS FIELD. THE BASIC THEORY IS DESCRIBED. THE RESULTS OBTAINED IN THE CURRENT RESEARCH ARE SHOWN AND A COMPARISON BETWEEN THE METHODS IS DONE. THE PERSPECTIVES FOR THE PRACTICAL IMPLEMENTATION OF THESE METHODS IN THE FIELD AND THE DIFFICULTIES IN DOING IT ARE POINTED OUT. KEYWORDS: RAILROAD WHEEL STRESS, ULTRASONIC TECHNIQUES, NONDESTRUCTIVE STRESS MEASUREMENTS.

Author :

Bray, Don E.
Santos, Auteliano Antunes

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