Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Journal of Achievements in Materials and Manufacturing Engineering

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

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

Huanca Cayo E., Absi Alfaro S. C.

Journal of Achievements in Materials and Manufacturing Engineering

2009

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.

Weld transference modes identification through sound pressure level in GMAW process

Cayo E. H., Absi Alfaro S. C.

Journal of Achievements in Materials and Manufacturing Engineering

2008

Vol. 29, nr 1

57-62

Purpose: One of the most used processes in the industry is GMAW, in this welding process there is physical phenomena such as the temperature, electromagnetic field, luminosity and sound pressure. It is known that GMAW weld specialized techinicisian combine visual and sound at the work to garantee the process stability. It is important to improve the final weld quality; therefore, the quantification of electrical and acoustical behaviour-within the audible bands, offer an information that is important to comprehend his impirical rules. Design/methodology/approach: With these he can identify the transfer mode, instabilities in the process, determine defects and evaluate the weld quality along the weld bead. The sound signal is captured simultaneously with the arc voltage and current signals. Was proved that first derived from the instantaneous power of the electrical arc presents a behaviour similar to the acoustical with a delay, because the measured sound is airborne. Findings: This relation was corroborated by the comparison between the sound pressure level calculated by electrical signals and by acoustical signals. This relation presented a similarity between the calculated signals greater than that between the sound and the power first derived. Practical implications: Besides that, with the sound pressure level it is possible to identify process instabilities that is not so trivial to realize with the sound pressure signal. In spite of it, the identification of instabilities for the globular and spray tranfer modes displays greater difficulty than that for the short circuit transfer mode. It was shown that the acoustical weld sensing offers information about the behaviour of the tranfer mode and the process stability. Originality/value: The sound quantification would be applied as a control variable for the weld process. Thus, it would be possible to develop similar control strategies as those applied by specialized workers.