NDTnet 1998 Aug, Vol.3 No.8

Full-Text - Abstract

Bearings, gears, shafts and many other surface hardened components in modern automotive and aerospace industries form a challenge to design and production engineers. They require special attention in choosing the correct parameters for the heat treatment as well as for the subsequent machining processes. The latter, if carried out inaccurately, may reduce the surface hardness and diminish the favourable compressive surface stresses after surface hardening. Accurate and continuous control of machining processes such as grinding or hard turning is essential in today's production control.

An inspection method based on the analysis of the magnetic Barkhausen noise (BNA) is capable of 100% in-line control of many types of machine components. Proposed by a Finnish - American company, this method has been shown to be more sensitive than the conventional acid etch inspection. It is also superior to the alternative method using eddy current. The sensitivity of the Barkhausen noise method to minute changes in the level of surface residual stress allows detection of grinding damage at its onset.This paper discusses the possibilities of the industrial application of the BNA method and illustrates it with two practical cases.

Table 1 Comparison of methods for detecting grinding burns.

	Nital Etch	Barkhausen Noise	Residual Stress by XRD Surface        Subsurface
No Burns	Class A	20	-700Mpa	-850Mpa
Light burns	Class B	45	200MPa	650Mpa
Heavy Burns	Class D	70	400Mpa	1050Mpa

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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