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Heading of a small bi-metallic components for electric contacts

100%

Presz W. , Cacko R.

Computer Methods in Materials Science

2018

tom Vol. 18, No. 2

41--48

Electrical connectors mostly have silver contacts joined to the supplying and discharging electric current elements by riveting. In order to reduce costs, the rivet core of the contact can be replaced with a cheaper material such as copper. There is a wide range of commercially offered bi-metallic, silver-copper rivets available for the production of contacts. This generates a new situation in the riveting process, as the bi-metallic rivet is to be formed. In the analyzed example it is a small-sized object that places it near the limits of micro-forming. The riveting process was originally designed by classical upsetting. It was based on the results of FEM simulation taking into account the deformation of three materials included in the joint: two materials for rivet and sheet material. The FEM results were verified by the results of experimental studies indicating high compliance. The elimination method of the elastic deformations of the load system impact on the process forces was elaborated and it was used for comparative analysis with the force run obtained from FEM. The model simulating the working conditions of the connector was developed. Based on the joint load modeling results, the cause of possible delamination of constituent materials was determined. It was also defined the desired silver distribution in the connector head to eliminate the risk of separation of both materials during exploitation.

New approach of friction AlN ceramics metallization with the initial FEM verification

80%

Cacko R. , Chmielewski T. , Hudycz M. , Golański D.

Archives of Civil and Mechanical Engineering

2020

tom Vol. 20, no. 3

385--395

Although, the friction method is well known for metals surface modification, the novelty of the article is based on the new idea of ceramics surface treatment with metal. The paper describes AlN ceramic metallization process by titanium coating deposition, obtained in friction surfacing method, which has been developed by the authors. The friction energy is directly transformed into heat and delivered in a specified amount precisely to the joint being formed between the metallic layer and the ceramics substrate material. The stress and temperature fields (as factors promoting the formation of diffusion joints) induced in the joint during the metallization process were qualitatively determined with the finite element method analysis and these results were verified experimentally. Finally, obtained structures of the metallic coatings were investigated and the results are discussed in the paper. As a novelty it was found, that the conditions of frictional metallization can favour the formation of a coating-substrate bond based on diffusion phenomena and atomic bonds of the coating components with the components of the substrate, despite the fact that it happens for metal–ceramics pairs. This type of connection is usually associated with long-term heating/annealing in chamber furnaces, because for diffusion in a solid state the most effective factor is time and temperature. It was shown that other components of the chemical potential gradient, such as temperature gradient, gradient and stress level, load periodicity and configuration of pairs of elements with high chemical affinity may play an important role in friction metallization. As a result, the relatively short time of operation (friction) is compensated.