The Use of Infrared Thermography for Maintenance Purposes in the Production Process of Components for Automotive Alternators

摘要

This work reports an investigation concerning the employment of infrared thermography in the production environment of claw pole alternators, aimed for early detection of anomalies during the stamping stage at the press. The investigated process consists of a number of steps, starting from a raw workpiece in the form of a star, sheared from a low carbon steel plate, is brought to its final shape through bending and coining operations, using a progressive die. The process is characterized by a high production rate since the component is destined for the automobile market, therefore the controlling of both the die conditions as well as the mechanical press is crucial in order to reduce unexpected stops of the process. After having analysed each production stage, a series of experimental tests have been carried out and a series of thermal snapshots were taken during the normal production run and analyzed in order to detect any process signature which were capable of giving information concerning the process conditions. An FEM model has also been developed for each step of the process in order to characterize the material flow and, in addition, the thermal field related to the transformation of the mechanical energy into heat, due to plastic deformation of the material and frictional effects. Correlations between the geometry resulting from material flow and thermal maps detected in the production environment have allowed to address of the maintenance activity in order to eliminate defects which can affect significantly the functionality of the product as well as the die life.