# Investigating the Welding Parameters in Friction Stir Welding of Yellow Brass 405-20
## 5 Conclusions  
In this work, novel brass 405-20 was friction stir welded using two weld factors, namely rotational speed and traverse speed. Both empirical and numerical studies were conducted using brass 405-20 for the first time. Full factorial design of experiments (DOEs) was implemented for both numerical and empirical research works. Three response parameters were focused on, namely thermal distribution at HAZ, joint strength, and joint hardness at the HAZ. Two numerical FEA studies were performed, transient thermal analysis (FEA_A) and static structural analysis (FEA_B). Thermal outputs of FEA_A were input to the FEA_B to find the shear stress at the joint resulting in numerical values of joint strength. Moreover, well temperature was numerically confirmed using FEA_A. Empirical values of weld strength and weld temperatures were also found to validate the numerical results. Weld hardness was only studied experimentally due to its direct involvement in the healthy discussion on finding optimal weld factor levels, which were found for DOE4. The main findings during the current numerical and empirical investigations actings include a good agreement of numerical studies with the empirical work. Optimal FSW factor levels were found to be 1450 rpm and 60 mm/min for DOE4 in full factorial settings. The maximum temperature was found to be 598 \({}^{\circ}\)C, which is well below the melting point of brass. So, successful friction stir welding of brass was validated in terms of its basic definition of solid-state welding. This temperature was found for DOE4. Maximum joint strength was found to be 228 MPa, again at DOE4, which is 83.00% of base brass strength. Microscopic examination revealed crucial clues as to the reasons for lower weld strength as compared to that of the parent brass material strength. Weld hardness was found to be the lowest for DOE4, i.e., 73 HR, validating further that DOE4 carries an optimal combination of both rotational speed and traverse speed for FSW of brass 405-20.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13042433/s1](https://www.mdpi.com/article/10.3390/app13042433/s1)]([https://www.mdpi.com/article/10.3390/app13042433/s1](https://www.mdpi.com/article/10.3390/app13042433/s1)), Figure S1: Coupling Thermal Transient Analysis (FEA_A) with Static Structural Analysis (FEA_B), Figure S2: Electric Saw Equipment for cutting sides of testing strips; Figure S3: A sample Cut by Electric Saw Equipment; Figure S4: Customized FSW using CNC Machining Centre; Figure S5: Thermal Imager; Figure S6: An example of Thermal Image  
Figure 19: SEM micrographs of welded specimen for DOE4.  
from Testo 868 Imager; Figure S7: Hounsfield Tensometer for measuring Friction Stir Weld Strength (FSWS); Figure S8: Rockwell Hardness Tester.  
**Author Contributions:** S.F.R.: conceptualization, data analysis, resources, methodology, writing--original draft, M.A.: methodology, data analysis, writing, investigation, M.S.H.: writing, investigation, review and editing, N.A.: methodology, data analysis, F.R.: resources, review and editing, data analysis, and curation. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data related to experimental findings are reported within the paper, and can be made available from the corresponding author upon a reasonable request.  
**Acknowledgments:** The authors are highly indebted to the University of Engineering and Technology, Lahore, Pakistan for the research facilities and Abu Dhabi University, UAE for partial funding. A preprint of this manuscript is presently online at the research square platform.  
**Conflicts of Interest:** The authors state that they have no conflict of interest or personal relationships that could have appeared to influence this work.