Effect of friction stir welding and process parameters on the mechanical properties of 2024-T3 aluminum alloy weldments

Dissertant

Hammudi, Numayr Abd al-Rasul

Thesis advisor

al-Sadi, Munir Hamid
Hasan, Shakir Sakran

University

Mutah University

Faculty

Faculty of Engineering

Department

Mechanical Engineering Department

University Country

Jordan

Degree

Ph.D.

Degree Date

2011

English Abstract

-This thesis is concerned with the study of friction stir welding and process for the aluminum alloy 2024-T3, from which 5 mm sheets were chosen for the experimental work, a threaded pin with a diameter of 6 mm and a shoulder of 18 mm was used.

The welding process was performed at different rotational speeds and variable feeding rates.

A conventional milling machine was used to perform the welding processes, the specimens were tested to determine the best ultimate tensile strength ( ult) and the maximum elongation and compared with the as received metal.

The microhardness distribution and microstructure were also investigated during this research and were found to be similar to results of previous studies on the same subject in both orientation and distribution.

In addition to friction stir welding (FSW), another phase of welding called friction stir process (FSP) was also used.

The best specimens from the first welding process conditions were selected, and the optimum rotation speed and feeding speed in the feeding direction were determined.

It was found that the best result is in forward welding travel and counter clockwise tool rotation.

For the second process (FSP), the microhardness and microstructure were again investigated, and the distribution of the microhardness was found to be similar to that of the first welding process.

The tensile properties was studied for the different welding processes, and from the results, it was found that the maximum tensile strength reached in stir welding process was 72% of the base metal and didn’t improve in the FSP process significantly (about 3%).

On the other hand, when the applied bending stress was 185 MPa , the fatigue life didn’t exceed 1.3x106 cycle in the best conditions with a single pass FSW while it exceeded 107 cycle in double pass process (FSW and FSP) , and this is regarded as a dramatic improvement in the fatigue lives under the dynamic conditions.

A simulation system was constructed by using a neural network (Elman’s method), and it is consisted of two parts, the first one is the system identification, from which a mathematical representation for the FSW system was derived.

In the second part, a control system was designed by using a neural network for controlling the variables in the welding process to reach the required tensile strength.

In both parts of the simulation system, Matlab version 6.5 was adopted for solving the system equations.

The results of the mathematical representation for FSW showed that it was an accurate representation of the FSW and with percentage of error reaching approximately to zero.

In addition, the control system proved effective with a rapid response in correcting any disturbance during the welding process.

Main Subjects

Mechanical Engineering

Topics

• Mechanical properties
• Aluminum alloys
• Welding

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-305039