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"Abbasi, Mahmoud"
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Numerical analysis of vibration effect on friction stir welding by smoothed particle hydrodynamics (SPH)
A numerical analysis is improved to study the effect of vibration on temperature history, heat generation, and mechanical properties during the friction stir welding process with different welding speeds. In this investigation, smoothed particle hydrodynamics (SPH) was applied to improve the 3D numerical analysis for simulation of the friction stir welding (FSW) process and friction stir vibration welding (FSVW) under different welding speeds. According to the experimental analysis, the grain size of the FSVW-ed sample is finer compared with that of the FSW-ed sample. The analysis was validated through a comparison of the simulated thermal cycles with the experimental results. There was a close agreement between FEM and experimental values. The results indicated that the vibration increased the mechanical properties such as von Misses stress and also thermal properties of the FSW-ed sample. The vibration in the FSW process can lead to an enhanced plastic material flow and also improve the weld quality by enhancing the plastic material flow near the tool. The shear zone volume (SZV) develops from 289.56 mm
3
for the FSW process to 367.34 mm
3
for the FSVW process. It was found that the axial forces, traverse force, and tool torque with respect to different steps (plunging, preheating, or dwelling time and traveling) in FSVW is lower than those in the FSW.
Journal Article
Advanced Approach to Modify Friction Stir Spot Welding Process
Nowadays, friction stir spot welding (FSSW) is used in automotive, rail vehicle construction, the aerospace industry, and electrical industry. In the current research, a modified version of the FSSW process entitled friction stir spot vibration welding was introduced to join Al5083 specimens. The joining specimens were vibrated normal to the tool movement direction, while the joint position cooled by passing coolant through the fixture. Different characteristics of developed joint namely microstructure, mechanical properties, corrosion behavior were studied. The results showed that stir zone grain size decreased significantly as the vibration was employed and the joint position was cooled. It was found that vibration enhanced the dynamic recrystallization and coolant decreased the grain growth. Both led to enhanced grain refinement in the stir zone. The results also indicated that shear strength and hardness of the weld region increased as the modified version of FSSW was applied. Corrosion tests revealed that corrosion resistance increased as the modified method was applied.Graphic Abstract
Journal Article
Numerical analysis of cooling and joining speed effects on friction stir welding by smoothed particle hydrodynamics (SPH)
This current work considers the utilization of the completely Lagrangian technique, smoothed particle hydrodynamics to improve the 3D finite element model for numerical analysis of the friction stir welding (FSW) in the air and underwater conditions. This technique was primarily applied to simulate fluid motion because of various advantages compared to conventionally grid-based methods. Newly, its usage has been developed to analyze the metal-forming analysis. The temperature history, strain and stress distributions during the FSW process in the air, as well as underwater, were considered. Besides the cooling influence, the effect of traveling speed, friction coefficient, mesh size and the mass scaling technique to find the converged model and decrease the CPU time were studied. The improved model is confirmed by comparing the numerical welding temperature with experimental outcomes. There was close compatibility between finite element analysis and experimental results. The conclusions indicated that the lower peak temperature was achieved due to higher cooling effect in underwater welding in comparison with conventional welding. Moreover, the peak temperature and strain rate decreased as traveling speed increased for both welding conditions, while stress values increased.
Journal Article
Microstructure and mechanical characteristics of AA6061-T6 joints produced by friction stir welding, friction stir vibration welding and tungsten inert gas welding: A comparative study
This study compared the microstructure and mechanical characteristics of AA6061-T6 joints produced using friction stir welding (FSW), friction stir vibration welding (FSVW), and tungsten inert gas welding (TIG). FSVW is a modified version of FSW wherein the joining specimens are vibrated normal to the welding line during FSW. The results indicated that the weld region grains for FSVW and FSW were equiaxed and were smaller than the grains for TIG. In addition, the weld region grains for FSVW were finer compared with those for FSW. Results also showed that the strength, hardness, and toughness values of the joints produced by FSVW were higher than those of the other joints produced by FSW and TIG. The vibration during FSW enhanced dynamic recrystallization, which led to the development of finer grains. The weld efficiency of FSVW was approximately 81%, whereas those of FSW and TIG were approximately 74% and 67%, respectively.
Journal Article
A comparative study between friction stir processing and friction stir vibration processing to develop magnesium surface nanocomposites
Friction stir processing (FSP) can be used to improve surface composites. In this study, a modified method of FSP called friction stir vibration processing (FSVP) was applied to develop a surface composite on AZ91 magnesium alloy. In this technique, the workpiece is vibrated normal to the processing direction. The results illustrated that compared with the FSP method, the FSVP caused a better homogeneous distribution of SiC particles in the microstructure. The results also showed that matrix grains of friction stir vibration processed (FSV-processed) samples ((26.43 ± 2.00) µm) were finer than those of friction stir processed (FS-processed) specimens ((39.43 ± 2.00) µm). The results indicated that the ultimate tensile strength (UTS) of FSV-processed specimens (361.82 MPa) was higher than that of FS-processed specimens (324.97 MPa). The higher plastic strain in the material during FSVP, due to workpiece vibration, resulted in higher dynamic recrystallization, and consequently, finer grains were developed. The elongation and formability index of the FSV-processed specimen (16.88% and 6107.52 MPa%, respectively) were higher than those of the FS-processed sample (15.24% and 4952.54 MPa%, respectively). Moreover, the effects of FSVP were also found to intensify as the vibration frequency increased.
Journal Article
Impact of teaching, learning, and assessment of medical law on cognitive, affective and psychomotor skills of medical students: a systematic review
Background
It is necessary to improve medical students’ legal cognitive, affective, and psychomotor skills to prevent further legal issues in the medical profession. Choosing the proper teaching and assessment methods is crucial in this matter. This study aimed to investigate the impact of teaching, learning, and assessment of medical law on the cognitive, affective, and psychomotor skills of medical students.
Methods
A systematic review was conducted in PubMed, Embass, and Web of Science databases, and Google Scholar search engine using MECIR and PRISMA, AMEE Guide 94 for 1980 to 2022.12.30. Nineteen articles met the inclusion criteria. MERSQI checklist was used to assess the quality of the articles, and URSEC (theoretical underpinning of the development, resources required, setting, educational methods employed, and content) used to assess the risk of educational bias.
Results
Internship courses called Medical Education Humanities and Society (MESH), clinical scenario design, seminars and small group discussions, web-based interactive training, legal training courses, PBL, and mind maps have been used to improve the medico-legal knowledge of medical students. MESH clerkship, simulation of a legal event, medico-legal advocacy program based on interdisciplinary education, group discussion, integration, and court-based learning used to improve student attitudes. Multidisciplinary training, small group discussions after the seminar, mock trial competition, and interdisciplinary education are used to teach psychomotor skills. All studies, except one on knowledge, reported positive effects of legal education on students’ knowledge, attitudes, and legal performance. Written assessments were used for cognitive and affective domains, while performance was assessed by OSCE, simulated court, and evaluation of patient referrals.
Conclusion
There are few studies to examine the cognitive, affective, and legal psychomotor skills of medical students. The texts have not yet fully explored the high level of affective and psychomotor domains, which is evidence of a gap in this sector. Recognizing that medico-legal problems are prevented through proper education and assessment, it is recommended that this area be considered a research priority and that effective educational policies are adopted.
Journal Article
Thermal analysis of friction stir welding process and investigation into affective parameters using simulation
Friction stir welding (FSW) as an efficient solid state joining process has numerous applications in industries. Temperature distribution analysis through simulation not only brings the possibility to characterize the microstructure of different zones, but also enables one to save cost and energy as optimum welding variables are obtained with less concern. In the present study, the temperature distribution during the friction stir welding (FSW) process of AA6061-T6 was evaluated using finite element method (FEM). Since experimental measurements cannot be readily made in the weld region, it is difficult to understand physics in the stir zone of the welds without simulation. Abaqus software was applied to model the parts and simulate the process of welding, while Johnson-Cook law utilized to evaluate the effect of strain rate and generated heat. FE-results were verified by experimental results. The comparisons revealed a good compatibility between the results. The effect of probe shape on temperature distribution was also studied. It was found that spherical pins result in the highest temperatures at workpieces with respect to cylindrical and tapered pins. Additionally, it was concluded that more heat is generated in workpieces as pin angle increases.
Journal Article
Effects of Predefined Thermomechanical Procedure on the Microstructure and Mechanical Properties of the Two-Way Shape Memory Effect in the NiTi Alloy
In the current paper, a predefined thermomechanical procedure has been applied to the two-way shape memory effect (TWSME) in a NiTi alloy to study the effect of two different applied load conditions on the induced martensitic state. The microstructure of the strips was studied using optical microscopy (OM), scanning electron microscopy (SEM) fitted with an EDS microprobe, and microhardness tests at the end of both the training and thermal cycles. Inducing internal stresses along specified directions during training cycles results in the formation of oriented martensitic variants rather than expected twinned martensitic variants upon cooling. It was found that the microstructure is made up of interlocking martensitic lathes, including the fine martensite colony next to the coarse martensite lathes. Furthermore, the results of the average hardness tests for bending at one point and three points were 241 and 247 HV0.2, respectively. It was shown that only the cubic austenitic phase (B2) and the martensitic monoclinic phase (B19′) experience transformation. The results reveal that homogeneous bending in three locations leads to achieving the best difference between high- and low-temperature curvatures after training.
Journal Article
Ethical considerations from the viewpoint of headquarters experts on HIV/AIDS prevention and control strategic program
Background: The HIV control and prevention program is one of the Public Health programs that confronts with many ethical challenges. This study aimed to explore ethical considerations from the viewpoint of headquarters experts on HIV and AIDS prevention and control strategic plan. Methods: In this qualitative study with content analysis design, focus group discussion method was utilized. After purposeful introduction of the experts and previous coordination about subject and time, two discussion sessions were held with the participation of six ministry and university headquarters experts of HIV control program. After frequent reviews of the data and using deductive content analysis, main themes and subthemes were categorized. In order to transformability of the findings to similar situations, the data were checked by three external reviewers. Results: The participants agreed that HIV/AIDS control requires focusing on prevention, treatment, and support services, and considering the general population and all vulnerable groups. In this study, five main themes were emerged: informing and empowering to make autonomous decisions, observing confidentiality, prohibiting stigma and discrimination, and being accountable. Conclusions: The viewpoint of participants indicates on the more need to pay attention the mentioned ethical considerations when compiling and finalizing the program. Moreover, in addition to instructing moral norms in PH programs with a special look to HIV/AIDS and how to apply them in the formulation and implementation of program, systematic evaluation of the program by an ethical framework is recommended to ensure the achievement to the goals of program.
Journal Article