Date of Award
5-2022
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Mechanical Engineering
Committee Chair/Advisor
Dr. Hongseok Choi
Committee Member
Dr. Gang Li
Committee Member
Dr. Cameron Turner
Abstract
The growing demands on reducing the harmful emissions from automobiles have forced automakers to reduce the weight of the vehicle. The increasing demands on improving the fuel economy also has challenged automotive manufacturers to make the vehicle as lightweight as possible. However, the challenge is also to ensure that the vehicle meets safety standards. For the vehicle to meet these standards, it needs to be of adequate strength as well. Automotive manufacturers have adopted a strategy of using multi-material construction to achieve the target. But with multi-material construction comes the requirement of advanced joining techniques that are capable of joining dissimilar materials. The requirement of the advanced techniques is due to the difference in physical and chemical properties of the dissimilar materials to be joined. The conventional methods are either unable to join the dissimilar material or form a joint with defects and of poor quality. Friction Element Welding (FEW) is one of the advanced joining techniques capable of joining dissimilar materials effectively. The process is based on the concepts of friction welding technique where the materials to be joined are heated to the temperature below their melting temperatures. In FEW, a friction element is used to form a friction weld. It has been found that the FEW process although has a low processing time, it is still higher than a few of its competitors. Most of the processing time of the FEW process is taken by the second step of the process, i.e., the cleaning step. Cleaning step parameters are the dominating factors that affect the processing time of the process. The cleaning step involves removing the coatings/impurities present on the bottom sheet of the materials to be joined while also pre- iii heating the friction element. The removal of coatings/impurities, however, can be accelerated with the use of abrasive particles. This study focuses on the effect of abrasive particles on the cleaning time and processing time of FEW. Silicon carbide abrasive particles have a high hardness and provide higher wear rates. The higher wear rates promote the wearing off of coatings from the surface of the materials. Silicon carbide abrasive particles were placed in a pre-drilled pocket in an aluminum top sheet. Design of Experiments (DOE) involved two levels of pocket size, pocket depth, abrasive particle size, and volume fraction of abrasives. The results show that abrasive particle size and volume fraction of abrasive particles were the dominating factors in determining the cleaning step time and overall processing time. Lower particle size and volume fraction of abrasives resulted in a reduction of cleaning time and processing time. Cross-tension strength (CTS) tests were performed, followed by microscopy analysis and hardness testing to study the effect of abrasives on the joint quality. The best case was observed for 6 mm pocket size, 0.2 mm pocket depth, 5 μm abrasive particle size, and 50% volume fraction of abrasives. The best case with abrasives was compared with the FEW sample which does not involve pocket and abrasives. The comparison showed that the inclusion of abrasives results in a reduction in cleaning time by 39.93% and processing time by 14.28%. The CTS of the joints formed with abrasives was slightly higher than the case without abrasives. Both the cases showed a button pull-out failure when subjected to CTS loading conditions. Microstructural analysis showed a presence of hard SiC and wider martensite phase, which is a probable reason for an increase in the joint strength for the joints that involved iv abrasives. The Microhardness tests further supported the CTS results. For the joints involving abrasives, a marginally higher hardness was observed along the cross-section. The significance of this study lies in the opportunities to reduce the processing time of the joining process using abrasive particles.
Recommended Citation
Awate, Gaurav, "Investigating the Effects of SiC Abrasive Particles on Friction Element Welding" (2022). All Theses. 3743.
https://open.clemson.edu/all_theses/3743