Mahadzir Ishak

In the automotive manufacturing industry, lightweighting has emerged as a key strategy for improving energy efficiency and reducing greenhouse gas emissions. Automobile manufacturers have successively adopted the strategy of replacing steel with aluminum (Al) and using higher-strength steel (HSS) to achieve vehicle weight reduction. However, Al and steel have significant differences in thermophysical properties, which greatly increases the difficulty of joining them. Numerous studies have effectively controlled the thickness of the intermetallic compounds (IMCs) layer at the weld interface by optimizing process parameters, adding filler materials and interlayers, and applying external energy fields. Therefore, this review categorizes Al/steel joining technologies into thermal, mechanical, and composite joining. It systematically discusses and summarizes the latest research findings, current applications, and development trends for each joining method.

The significance of stainless-steel foils, specifically SS304, cannot be overstated in the dynamic field of materials science, given their wide range of industrial applications. A pulsed Nd:YAG laser wobble welding method is considered to be the most effective method of joining these foils, due to its high precision and minimal influence of heat. Despite this, it remains a considerable challenge to determine the complex relationship between heat input and the quality of the weld produced. The purpose of this study was to investigate the effects of three specific heat inputs (0.34, 0.39 and 0.43 J/mm) on the welding of SS304 foil. A methodical approach was employed to employ these distinct heat levels and the resulting welds were rigorously evaluated. Key findings highlighted the peel strength for specimens S1, S2 and S3 as 188.29 N, 363.05 N and 634.10 N, respectively. The maximum penetration depths of these three samples were 0.16 mm, 0.22 mm and 0.18 mm, respectively. Moreover, both vertical and horizontal distortions were measured across the various sections of the weld. The S2 specimen, with a heat input of 0.39 J/mm, displayed pronounced distortions in both axes, while S3, with a heat input of 0.43 J/mm, presented the highest peel strength and volume penetration. There is a delicate balance that welding operations must maintain in order to enhance weld attributes such as strength without inadvertently exacerbating distortions. Taking into account the synthesized insights, it is clear that judicious heat input management is critical. Even though a higher heat input can enhance certain weld qualities, it is crucial to be aware of the consequences of such distortions, thereby requiring a well-calibrated approach. The findings of this research not only contribute to a deeper understanding of welding dynamics, but also lay the foundation for developing future processes that are more nuanced and productive.

Due to the fact that the laser-based cleaning process is quick, efficient, and environmentally friendly, it has been utilized in a various industry, which has increased the number of studies pertaining to this process. In addition to process optimization, the real-time monitoring system was essential in preventing the overexposure of the laser beam to the cleansed surface, which would result in an engraving effect. This article demonstrated the analysis of the acquired sound signal to identify an overexposed laser beam during laser cleaning. In order to accomplish the aim of this work, the corroded boron steel plate was prepared. The laser cleaning procedure involved a four-loop laser scan. Variable scanning speeds between 100 and 1,000 mm s⁻¹ were configured. Concurrently, the acoustic signal within the frequency range of 20 Hz to 10 kHz was acquired. The results indicate that the process with a scanning speed of 1000 mm s⁻¹ recorded the clear surface without morphological change on the cleaned area, whereas an unacceptable deep gouge was formed during the second and third loops of the process with speeds of 100 mm s⁻¹ and 300 mm s⁻¹, respectively. According to an analysis of the acquired sound signal, the trend of the Mel Frequency Cepstral Coefficient (MFCC) was indicative of the existence of the ablated corroded substrate. In addition, the spectral flux can provide important information regarding the formation of a deep groove on a cleansed surface. This research demonstrates the feasibility of using the auditory signal to monitor the laser cleaning process. By characterizing the acoustic signal feature, it is possible to detect the completion of the cleaning process before the morphological change of the cleaned area existed. With further development, it was possible that this method would become the most efficient, resilient, and demanding in the future.