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GMAW process stability evaluation through acoustic emission by time and frequency domain analysis

100%

Huanca Cayo E. , Absi Alfaro S. C.

tom Vol. 34, nr 2

157-164

Purpose: In the present work was made the comparative analysis in time domain and frequency domain to the acoustical pressure generate by the electric arc to determinate which of the two analysis methods is better to evaluates the stability in GMAW process. Design/methodology/approach: Welds had been made with the parameters adjusted to get the highest stability. In these conditions, were simulated instabilities that had been generated by the grease presence in the weld trajectory. In both experimental groups was acquired the acoustical pressure signal produced by electric arc to made analysis based in time domain and frequency domain. Findings: After this comparative study we conclude that the acoustical evaluation of the stability on the GMAW process presents more clarity for the analysis based in the time domain that the frequency domain. Research limitations/implications: In the gotten results, the time domain analysis method could represent adequately the stability and the instability of the process. The stability characterizes for the continuity and minim variation of the statistical parameters, but in the presence of instabilities, these parameters present chaotic changes. In the frequency domain method the variations are imperceptible for steady and unstable regions, but it presents little definite variations in the amplitude of determined bands of frequencies. Originality/value: The stability evaluation in welding is crucial because it is responsible in the weld quality. The non contact methods as the acoustical method have a potentiality extraordinary to monitoring and detect instabilities in welding. The acoustical sensing has the capacity to make an on-line monitoring of the weld process.

The effect of welding fixtures on welding distortions

100%

Vural M. , Muzafferoglu H. F. , Tapici U. C.

tom Vol. 20, nr 1-2

511-514

Purpose: of this paper is to examine the effect of welding fixture used to prevent the distortions during cooling process utilizing a robot controlled gas metal arc welding method on cooling rate and distortions of welded structures. Design/methodology/approach: Using a specially designed welding fixture for a welded steel structure, six different types of AISI 1020 steel specimens are tested in three different welding speeds and two different cooling conditions either at fixture or without using fixture. Findings: designed fixture is reduced amount of distortions. The preheating effect of previous weld on the next weld has increased distortions on the other side of part. Increase in distortions is directly proportional to the increase in welding speed which affects the weld heat input. Research limitations/implications: the study can be repeated on more complex structures and fixtures. Practical implications: the study has shown that the fixture design has an important effect on cooling rate of the welded parts. Originality/value: most of papers in literature is about fixture design methodology, but this paper is an example of demonstration for a practically applied welding fixture.

The effect of welding method on the structure of a welded joint

99%

Ciechacki K. , Szykowny T.

tom Vol. 7, no 3

47-52

This work explains the influence of a local structural heterogeneity and resulting mechanical heterogeneity in welded joints on the location and nature of welded joint failure. Toughened structural steel S355 with a thickness of 7mm, welded using laser beam or gas metal arc welding (GMAW) was used for the purposes of this analysis. Hardness penetration pattern in welded joint cross-section was defined and mechanical properties of a welded joint in static tensile test (Re, Rm, A5, Z) were determined. Microstructure and microfractographic tests of fractures were performed.

Gazy osłonowe do spawania łukowego drutem litym (MAG) stali węglowych i niskostopowych

80%

Niagaj J.

tom nr 9-10

88--92

Omówiono rodzaj i skład gazów używanych podczas spawania stali niestopowych i niskostopowych metodą MAG (GMAW), jak również opisano wpływ poszczególnych gazów na proces spawania i jakość złączy spawanych.

The type and composition of gases used in the MAG (GMAW) welding of carbon and low-alloy steels are discussed, as well as the influence of particular shielding gases on the welding process and quality of welded joints is described.