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Broek, D. (author), Vlieger, H. (author)
Residual strength tests were carried out on center cracked aluminium alloy panels of various thicknesses. Slow crack growth, crack opening displacements and compliances were recorded. In addition to the test data, the report presents discussions on the residual strength "behaviour, the thickness effect, R-curves and COD and compliance measurements
report 1973
document
Broek, D. (author)
A survey is given of the results of five years electron fractography as conducted at the National Aerospace Laboratory N.L.R. and of the contribution of this work to the comprehension of fatigue cracking, ductile fracture, cleavage and stress corrosion.
report 1972
document
Broek, D. (author)
The growth of fatigue cracks emanating from holes was studied employing 2024-T3 alclad sheet specimens. Both symmetric and asymmetric cases were considered. Crack growth is compatible with the stress intensity factor derived by Bowie and also with the stress intensity factor derived from the simple engineering approach that considers the hole...
report 1972
document
Broek, D. (author)
The topography of the stretched zone was measured from stereo electron micrographs. The stretched zone reflects crack tip blunting preceding fracture. The depth of the stretched zone of fourteen fracture toughness specimens of some Al-Zn-Mg alloys appeared to correlate reasonably with the critioal crack tip opening displacement. The width of the...
report 1972
document
Broek, D. (author)
This report will become part of an AGARD Survey on the application of fracture mechanics in aircraft design. It consists of two parts: PART A BASIC INFORMATION PART B FATIGUE CRACK PROPAGATION IN STRUCTURES. Part C on residual strength of structures will appear as a separate report. Other parts of the fracture mechanics survey will be written by...
report 1972
document
Broek, D. (author), Hartman, A. (author), Nederveen, A. (author)
A few preliminary tests on 2024-T3 material were carried out allowing electron fractographical examination of the fracture features of fatigue crack growth in vacuum. Fatigue striations were generally not formed in vacuum: the fracture surface consists of irregular fine slip steps and coarse slip steps which show a certain periodicity. The...
report 1971
document
Broek, D. (author)
Electron microscopical examination of fracture surfaces and micro-structure of thirteen different aluminium alloys revealed that ductile rupture is initiated at small inclusions. The average dimple spacing is equal to the average inclusion distance. Void initiation is probably the critical event in ductile fracture; it is immediately followed by...
report 1971
document
Broek, D. (author), Bowles, C.Q. (author)
A 1 to 3% strain after quenching introduces many dislocations which act as nucleation sites for precipitates. The result is a smaller precipitate which gives better fatigue and fracture properties. Larger strains introduce too much work hardening and the properties decrease again due to the low ductility. The dimple size in the electron...
report 1969
document
Broek, D. (author), van der Vet, W.J. (author)
An extensive electron fractographical investigation was carried out of a series of fatigue failures in a 4340 type steel. Low tempering temperatures and low stresses promote intergranular fatigue fractures. High stresses and high tempering temperatures promote the formation of striations.
report 1969
document
Vlieger, H. (author), Broek, D. (author)
A brief review is given of the literature dealing with the effect of a stiff ener on the stress distribution in a cracked sheet, Exipting theories for the prediction of the residual static strength of cracked stiffened panels are analyzed. A new approach to this problem is developed, using the residual strength characteristics of the unstiffened...
report 1967
document
Broek, D. (author), van der Vet, W.J. (author)
Numerous measurements of striation spacing were carried out. The relation between striation spacing and crack propagation rate is discussed. The effect of inclusions on fatigue crack propagation is considered and explanations are given for several special features of fatigue fracture surfaces. The mechanism of striation formation is discussed.
report 1967
document
Broek, D. (author)
Results are presented of microscopical investigation on the initiation and growth of cracks in a ductile material under static load. Crack propagation appears to be primarily a slip mechanism. The consequences of this conclusion for establishing a criterion for ductile fracture are briefly discussed
report 1967
document
Broek, D. (author)
Specimens of 2024-T3 and 7075-T6 aluminium alloy sheet containing fine saw cuts appear to have the same residual strength as specimens with fatigue cracks of the same length. The stress level at which the fatigue cracks were grown does not affect the residual strength properties. Stop holes drilled at the crack tip postpone the onset of slow...
report 1966
document
Broek, D. (author)
Results are presented on the effect of thickness on the residual strength of aluminium alloy sheet specimens. It could be explained why a state of plane stress at the crack-tip results in a slant fracture and why a state of plane strain results in a square fracture (flat tensile mode). It could also be explained why a plane strain fracture...
report 1966
document
Schijve, J. (author), Broek, D. (author), de Rijk, P. (author), Nederveen, A. (author), Sevenhuysen, P.J. (author)
Fatigue tests were carried out on full-scale tension skins of a wing center section of 7075-T6 material. Variable-amplitude tests were carried out with the following load sequences: (a) random load, (b) program load, (c) random load with GTAC (ground-to-air cycles) and (d) program load with GTAC. Constant-amplitude tests were carried out with...
report 1965
document
Broek, D. (author), Nederveen, A. (author)
Residual strength tests with a duration ranging from 30 minutes to about 0.4 seconds were carried out on 2024-T3 alclad sheet specimens containing a central transverse saw cut. It turned out that the stress to initiate slow crack growth decreased at increasing loading rate, but in the range of loading rates tested the residual strength did not...
report 1965
document
Broek, D. (author)
Results are given of residual strength tests on specimens of 2024-T3 and 7075-T6 aluminium alloy sheet material. Three types of specimens were used, which had a width of 150 mm, 300 mm or 600 mm. A fracture criterion is developed for a sheet of finite size. This fracture criterion is in reasonable agreement with the test results.
report 1965
document
Broek, D. (author), Jacobs, F.A. (author)
Static tests were carried out on 280 mildly notched specimens of various aluminium alloys. It appears that the nett section fracture stress as a percentage of the ultimate tensile strength is in general higher for materials of lower ductility. This influence of ductility can be reasonably explained on the basis of measured plastic strain...
report 1965
document
Broek, D. (author)
Residual strength tests were performed on 2024-T3 and 7075 " T 6 aluminium alloy sheet specimens of 600 mm width. After the cracks had shown some stable slow growth the specimens were unloaded and then reloaded. Unloading appeared t o have no effect on the residual strength
report 1965
document
Broek, D. (author)
Residual strength tests were performed on 2024-T3 and 7075-T6 aluminium alloy sheet specimens of 600 mm width. After the cracks had shown some stable slow growth the specimens were unloaded and then reloaded. Unloading appeared to have no effect on the residual strength
report 1965
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