Study crack propagation rate in stainless steel weldment by cyclic load

Dissertant

Abd al-Wahhab, Asjad

University

University of Technology

Faculty

-

Department

Department of Production Engineering and Metallurgy

University Country

Iraq

Degree

Master

Degree Date

1999

English Abstract

In this work, a study is made into fatigue crack propagation behavior in austenitic stainless steel type AISI 3I6L under constant amplitude loading at room temperature with load ratio (R = 0.2) for two loads levels (7 and 8.5 KN).

The results have been compared with those of base metal The study includes two techniques , automatic submerge arc welding (SAW) and manual arc welding (MAW) from crack propagation point of view ; two cases of crack propagation have been considered, longitudinal and perpendicular to the rolling direction of the base metal.

The phase transformation that took place in the structure of the weld metal (as cast), due to welding heat s was considered as well.

The effect of -ferrite which is formed during solidification, on crack behavior has also been taken into account. A compact - tension, C (T) specimens were prepared at the different conditions of base metal, weld and HAZ (heat affected zone).

They were tested at 4 Hz frequency on hydraulically powered testing machine " Dartec " in tension-tension case-From the log-log relation between fatigue crack propagation rate (da / dN) and the stress intensity factor range (AK), the material constant: c , m have mathematically been calculated using Paris law equation , the following results were obtained at AP equal 7 KN 1- da / dN = 4.92468-10 ∆ K 3.9309 for base metal L.

R.

D 2- da / dN = S.27679-9 ∆ K3.16508 for base metal T.

R.

D 3- da/dN =1.151 OS-8 ∆ K3.09971 for through weld (Y1) 4- da / dN = 6.56287-10 ∆ K4.16513 for HAZ 5- da / dN = 2.1S924-8 ∆ K2.52193 for automatic weld the notch is ┴ 6- da / Dn = 7.73316 -11 ∆ K4.35576 for manual weld the notch is ┴ da / dN = 1.28463-13 ∆ K6.39274 for automatic weld the notch is ┴ star in weld From the results obtained it could be noticed the successful fatigue test appearance which is clear in the base metal fracture surface that was examined by SEM (Scanning Electron Microscope), The results of the base metal were compared with those of the weld ments which have different crack propagation rates, the4case where the notch is in middle of the weld region. Fast fatigue crack has been noticed in heat affected zone (HAZ), through weld zone that may be due to the change in structure and the applied load direction. However when the crack propagation is perpendicular (┴) to the weld line, the results shows that the propagation rate is lower, specially when the crack starts in the weld zone. The HAZ shows high rate of propagation, compared with that of base metal.

This may be due to change in structure, grain growth and the direction of the applied load, still the appearance of the fracture surface shows the fatigue characteristic.

Main Subjects

Materials Science , Minerals

Topics

• Stainless steel

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-306325