Transformation plasticity during martensite formation in certain ferrous alloys

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TÜBİTAK MAG Proje01.01.197

Cam takviyeli plastik kompozitlerde yorulma

TÜBİTAK MAG Proje15.07.197

Geri martensitik transformasyonlar

TÜBİTAK MAG Proje01.01.197

Short fatigue crack growth in AL 2024-T3 and AL 7075-T6

Short fatigue crack growth behavior was investigated. The crack growth was monitored using a replica technique for cracks propagating on the specimen notch from an initial length of 40-50 mum to the specimen thickness of 2.3 mm. As part of the AGARD round robin test program Al 2024-T3 and Al 7075-T6 specimens with semi-circular notches on one edge were tested under R-ratios of 0.5, 0, -1 and -2. For each R -ratio several stress levels were used. In order to compare the behavior of short and long cracks, their crack growth rate data were drawn on the same graph. The general conclusion for both aluminum alloys is that the growth rates of short cracks were faster than the rates of long cracks for R-ratios of -1 and -2, no significant differences were observed for R = 0, and the short cracks actually grew more slowly at R = 0.5

Comparison of two non-destructive inspection techniques on the basis of sensitivity and reliability

Two non-destructive inspection (NDI) methods have been used to determine the damage tolerance life prediction of acro-engine turbine discs. For this purpose, low cycle fatigue cracks were examined in the compressor discs of tie bolt holes. The successful implementation of damage tolerance design method strongly depends on the sensitivity and reliability of applied NDI method

Determination of hot crack susceptibility in various kinds of steels

The aim of this investigation was to study the hot crack susceptibility of some Turkish and German structural steel plates with a modified varestraint-transvarestraint test method. Testing was accomplished using a Tungsten Inert Gas (TIG) welding process. The results of this study revealed that total crack length increases as welding current increases or punch radius or welding speed decreases. An attempt is made to provide explanations for these phenomena. (C) 1997 Elsevier Science Ltd

Initiation and early growth of short fatigue cracks at inclusions

In this study, the initiation and early growth behaviour of short fatigue cracks in En7A steel with a high content of elongated MnS inclusions was investigated by generating and evaluating data on the growth of short fatigue cracks under various stress levels and stress ratios for the six principal specimen orientations. Short cracks usually initiated at the debonded interfaces between the matrix and the inclusions. If there was no debonding, cracking sometimes occurred in the inclusions. In the early stages, short cracks propagated by a mechanism of inclusion influenced growth. Under low stress levels, usually one short crack was initiated which dominated most of the fatigue life, while under high stress levels there was multicrack interaction. (C) 1996 The institute of Materials

Hot Cracking Susceptibility of Twin Roll Cast Al-Mg Alloy Welds

The hot cracking susceptibility of two different Al-Mg alloys during welding at various applied strains was investigated. At each strain value, the amount of hot cracking susceptibility increased with increasing magnesium content. Thermal analysis results verified that hot cracking susceptibility indeed call be related to the solidification range. As suggested in the solidification range approach, the results of the present Study confirm that the extent of solidification and liquation cracking depend oil the magnitude of solidification range and the strain imposed during welding. The fracture surfaces of liquation and solidification cracks were investigated with EDS. Liquation crack surfaces were found to have high Mg content whereas solidification crack surfaces revealed iron rich phases. A quench test was designed to observe the effect of mid-plane segregation zone. It was observed that high segregation at the mid-section of the alloy having higher magnesium can increase the liquation cracking susceptibility during welding since it decreases the solidus temperature of the intergranullar liquid