On-Line Testing of Green-State P/M Compacts Through Active and Passive Thermography

摘要

A complete on-line inspection system of P/M parts, particularly in their pre-sintered state, has always been a challenge that is difficult to achieve in an efficient way. Due to their fragile nature, green-state P/M compacts require a judicious testing approach that cannot involve direct contact of the samples either for energy deposition or imaging. This paper discusses a novel approach that provides a full quality assessment of green-state compacts early in the manufacturing process. The method is based on an active thermography methodology whereby electric energy is deposited into the compact in a contact-less fashion through induction heating. Thermal data is then collected and analyzed in an effort to yield part integrity and process stability information. In this paper we will discuss our design approach and a proof-of-concept instrument with associated data processing software. Toward this end we will first review the underlying physical principles, followed by a brief discussion of the test arrangement, associated software development, and automated defect evaluation. As part of our experimental data processing, we will present results that are collected both in a laboratory setting and in an industrial manufacturing environment. The sample analyses are carried out through a custom-developed software package.