Fatigue behavior of shot peened aluminum alloys under variable stress conditions

Dissertant

al-Okaidi, Safa Husayn Ali

Thesis advisor

Abd al-Wahhab, Talal Abd al-Jabbar
al-Alkawi, Husayn Jasim Muhammad

University

University of Technology

Faculty

-

Department

Department of Electrical Engineering

University Country

Iraq

Degree

Ph.D.

Degree Date

2012

English Abstract

Many components in the field of mechanical engineering are subjected to cyclic loading such as automobile parts, train wheels, bridges, medical instruments and heavily stressed power plant components (engines and rotors) have to withstand a more than 107 cycles.

Imparting the compressive residual stresses on the surface of the engineering components that experiences repeated loading increases the mechanical properties and fatigue strength and thereby the component life.

Shot Peening has been widely used in the industry for strengthening machine parts against fatigue.

The effect of shot peening time on the mechanical properties and fatigue behaviour of 2024-T351, 7075-T6 and 6063-T6 aluminum alloys were investigated under room temperature and stress ratio R=-1 using Tension-Compression fatigue testing.

The largest increases in ultimate and yield strength were observed in 2024-T351 aluminum alloy were increased using shot peening by 6.7% for ultimate strength and 11.7% for yield strength as a result of compressive residual stresses at 15 shot peening time.

While the mechanical properties of 7075-T6 were increased by 3.23% and 5.45% for ultimate and yield strength respectively under 15 shot peening time.

The increases in the above mentioned mechanical properties for 6063-T6 were observed at 10 shot peening time by 7.2 % and 7 % respectively.

It is found that the magnitude of surface compressive stress and hardness increase with increasing shot peening time up to a limits value and then decreases.

The fatigue behaviour under constant amplitude stresses were studied under different shot peening time conditions for the above three types of aluminum alloys.

It was found that for the 2024-T351, the fatigue strength (fatigue endurance limit at 107 cycles) has increased by 20.87% at 15 minute shot peening time and then a reduction was observed after that, and an increment of 19.07% at 15 minute shot peening time for 7075-T6 while, for 6063-T6 aluminum alloy it was found that the increment was 6 % at 10 minute shot peening time.

A new cumulative damage and fatigue life model was proposed.

It is based on the S-N curve and taking into account the effects of load history and shot peening time.

A comparison between the predications of the proposed model and Miner’s rule life estimation with the experimental results were carried out.

The obtained fatigue lives from this model showed conservative estimation compared to the experimental lives while Miner’s rule estimation was observed to be conservative for some specimens when Dexp.

≥ 1 and non-conservative for other specimen lives Dexp.

< 1.

An instructional program was built depending on Dick and Carey model, to study the effect of shot peening on fatigue behaviour.

It was found that the instructional package has a great effect on learner’s behavior.

Main Subjects

Electronic engineering

Topics

• Temperatures
• Aluminum alloys

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-419375