Automated measurement of crack length and load line displacement at elevated temperature

Test results reported in the literature show that in creep cracking tests at elevated temperature under steady load, the crack growth rate correlates best with the contour integral C*, also called J*, in comparison to other possible parameters. In the case of fatigue at elevated temperature, the crack growth rate correlates best with C* if...

Heat treatment studies of aluminium alloy type 7050 forgings. Interim report no. 3: Corroded-specimen fatigue tests and SCC propagation tests

The influence of previous corrosion on the fatigue life was investigated. It was foimd that a slight corrosive attack could drastically reduce the fatigue life. The damaging effect of corrosion was greater for the alloy AA 7050 than for AZ 74.61. It could be established that fatigue cracks initiated from various corrosion pits. A second series...

Microscopic study of stress corrosion crack growth in an AlZnMg alloy

The tip of a growing stress corrosion crack was photographed at a magnification of 72 x and at 30 sec. intervals. The crack appeared to grow in a discontinuous manner. Crack reinitiation was preceded or accompanied by gas evolution.

Heat treatment studies of aluminium alloy forgings of the AZ 74.61 type. Interim report no. 3: Fatigue crack propagation performance under manoeuvre spectrum loading

The fatigue crack propagation performance of the alloy AZ 74.61 under manoeuvre spectrum loading was studied. The crack propagation behaviour was also compared with that of the American forging alloy AA 7050, not only for simulated manoeuvre loading but also for simulated gust loading and programme loading. It was found that, at comparable...

Heat treatment studies of aluminium alloy type 7050 forgings. Interim report no. 2: The effect of heat treatment on a variety of engineering properties

The effect of variety of heat treatments on various engineering properties was studied with the aim to derive an optimum heat treatment. The engineering properties comprised Vickers hardness, short-time tensile strength, fatigue crack propagation resistance, fracture toughness and stress corrosion resistance. The test results were compared with...

Rate effects on residual strength of flawed structures and materials

The literature is reviewed with respect to: - tests conducted to investigate crack re-initiation under dynamic load and arrest of a running crack - metallurgical sources of rate effects - available data for aerospace engineering materials - mechanical sources of rate effects, i.e. dynamic crack tip stresses and kinetic energy effects Conclusions...

On the effect of the loading rate on the residual strength of a cracked plate with a hole

Data presented by Branger, and indicating an effect of loading rate on residual strength of aluminium alloys and steels, are analysed using fracture mechanics. It is found that the apparent effect is largely or wholly due to the combination of two causes i.e. - the static data pertain to systematically shorter crack lengths than the dynamic...

Heat treatment and SCC susceptibility of AU4SG type forged material

Material from forgings rejected after cracking in service was given a variety of heat treatments. Material aged to peak hardness was susceptible to SCC at all ageing temperatures. Overageing at temperatures around 160° C imparted a significant increase in SCC resistance while useful strength was retained. An additional one week ageing at 160° C...

Additional studies of the heat treatment of the Al-Zn-Mg-Alloy 7079

Heat treatment studies of Al-Zn-Mg alloy forgings of the DTD 5024 type

Porgings were given a variety of heat treatments after which hardness, static tensile properties, fatigue properties, fracture toughness and stress corrosion resistance were determined. Microstructures were studied in the electron mcroscope using the thinfoil technique. The effect of heat treatment on the microstructure could be explained on the...

Correlations involving properties and microstructures of Al-An-Mg alloy forgings of the 7079 type

Correlation diagrams show that fracture toughness and fatigue crack propagation resistance are closely related properties, while stress corrosion endurance is a crack tolerance property with different characteristics. The heat treatment effects on characteristic dimensions of the microstructure could generally be explained on the basis of...

The repair of fatigue cracks in low-alloy steel sheet

Fatigue cracks were grown in rectangular specimens with a central notch. At a certain crack length, the crack was repaired, using a variety of methods. Fatigue loading was resumed and re-initiation and subsequent growth of the fatigue crack were studied. The repair methods evaluated comprised simple stopholes, brazed straps across the crack,...