**3.1 Highlights of the works of the last 5 years**

An analysis of the works in the field of stability in the last 5 years was made and allowed to find the following trends. There is a considerable increase in the study and application of works in pulsed GMAW (**Figure 19**). This increase is caused by the known improvements in quality and productivity with respect to regular metal gas arc welding (GMAW).

Another trend that could be identified is the increase in research that integrates classical statistics techniques and novel machine learning algorithms. It is well known that with the increase of the computing processing capacities, the data analysis, big data, and machine learning have had a significant boom since 2009. The welding area has not been oblivious to the use of such techniques, although it should be noted that in the area of stability, classical statistics is more commonly used as demonstrated in the present study.

Already in recent years, some interesting solutions have been presented. Alizadeh and Omrani [41] integrate successfully the Taguchi method with back-propagation neural network (BPNN) technique for controlling quality in offline mode. Gyasi et al. [42] are employing an artificial neural network (ANN) to predict geometric characteristics of the welded cord. Wan et al. [43] integrate multiple linear regression analysis and back-propagation neural network to estimate the weld quality. Yue-zhou et al. [44] use sound monitoring and develop a classification algorithm with SVM (support vector machine). Sumesh et al. [45] use machine learning algorithms for weld quality monitoring, acoustic signature, and the perform classification use J48 and random forest algorithms.

In addition, there has been an increase in the use of artificial intelligence algorithms and sensorial fusion. Two powerful techniques have enabled the monitoring and control of welding processes in real time. Also, and as expected, we already find in the literature novel proposals for applications of artificial intelligence and robotics.

Another area that has been highly developed in recent years and future perspectives is image processing. A great number of algorithms have been created for high performance in this subject. Thanks to these advances, the monitoring of the weld bead in real time is now a reality.

## **3.2 Innovative techniques**

It is known that metal transfer has a direct influence on the stability of the process and on the final quality of the welding. Consequently, it has been widely studied as demonstrated in the present review of the literature.

But innovative techniques continue to appear in this field with future prospects of great interest. In this case, they were identified as laser-enhanced gas metal arc welding (GMAW), a modification of GMAW, used to control the metallic

**Figure 19.** *Number of publications for years in the area of pulsed GMAW.*

Note that the highest percentage of investigation is aimed at the study of metal transfer stability. It is also evident that the main processing techniques to develop the indexes were the mathematical formulation and statistical methods. Although in the case of metal transfer, image processing is widely used, mainly to define the

**Figure 18** shows a taxonomy that details the methods used to measure the stability of the welding process and the techniques associated with them. The techniques used were divided according to Weglowski [40] into traditional and

Finally, to find a trend and a possible vision of the direction of future studies, the

transfer mode and drop size.

*Classification of the main methods used for monitoring.*

nontraditional.

**20**

**Figure 18.**

**Figure 17.**

*Welding - Modern Topics*

*Techniques used to develop the indexes classified by groups.*

following was analyzed:

transfer. A low power laser helps to obtain greater strength in the detachment of the drop. It was also determined as a newly developed arc welding method and ultrasonic-wave-assisted arc welding. This new technique uses power ultrasound energy to radiate the arc and weld pool, modifying the speed with which the plasma heats and cools. According to Fan et al. [46], it allows increasing the stability of the process.

**Acknowledgements**

*Stability on the GMAW Process*

**Conflict of interest**

**Author details**

**23**

Physics, La Habana, Cuba

have no conflict of interest.

research CAPES foundation and CNPQ.

*DOI: http://dx.doi.org/10.5772/intechopen.90386*

This work has been supported by the Brasilia University (UnB), the government

Elina Mylen Montero Puñales and Sadek Crisótomo Absi Alfaro declare that they

Elina Mylen Montero Puñales1,2\* and Sadek Crisóstomo Absi Alfaro3

1 University of Brasilia, Campus Darcy Ribeiro, Brasilia, DF, Brazil

\*Address all correspondence to: mylen88a@gmail.com

provided the original work is properly cited.

2 Department of Automatic Control, Institute of Cybernetics, Mathematics and

3 Department of Mechanical, Mechatronic Engineering, Faculty of Technology, University of Brasilia, Campus Universitario Darcy Ribeiro, Brasilia, DF, Brazil

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,
