A damage tolerance study conducted with structure relevant specimens

A preliminary investigation is reported of the development of a Structure Relevant (SR-) specimen, which maintains the essential features of a stiffened panel configuration, in order to study damage growth behavior at limited cost. Several SR-specimens were fabricated, damage was applied, either through impacts or by the insertion of artificial...

The B2000 linear buckling processor

In many practical problems of plate and shell buckling, the pre-buckling state is linear and can be obtained from the linearized equations of elasticity. The computation of the buckling load and mode in such cases correponds to a linear eigenvalue problem that can easily be formulated and implemented in a finite element code. This report...

A CAD-system for the design of stiffened panels in wing box structures

In this paper the CAD system DESTIP is described. DESTIP is developed at the NLR for designing compression panels in wing box structures. Application of the system yields optimal panels in the sense that they meet all the requirements imposed by the designer and have minimum weight per unit width. Weight reductions ranging from 0 to 10% have...

Flight simulation environmental fatigue crack propagation in 2024-T3 and 7475-T761 aluminium

Flight simulation fatigue crack propagation tests on 202U-T3 and 7475-T761 aluminum alloy sheet were carried out using a gust spectrum representative of the load history of an under wing skin in a transport aircraft. The investigation included tests at several design stress levels and in environments of laboratory air and air plus water spray....

Evaluation of non-destructive inspection methods applied to milled step-down areas

The present report describes how fatigue cracks were produced in 102 specimens. After cracking these specimens were inspected non-destructively by means of eddy currents, ultrasonics. X-rays and penetrants, and the indications were recorded. Successively the specimens were exposed to corrosion whereafter the inspections were repeated. Upon...

Effects of flight load spectrum variations on fatigue life of riveted specimens and crack propagation in sheet made of Alclad 7075-T6

Riveted specimens that are considered representative for F-27 type wing structure were subjected to comparative flight simululation test in which the gust load severity and Ground-Air-Ground cycle were systematically varied. The effect of these variations on crack propagation behaviour was studied by means of crack growth tests on 2 mm sheet...

Aluminium alloys for advanced structural applications in transport aircraft

This paper concisely reviews and discusses (1) metallurgically cleaner alloys like -2124, 2048 and 7475, (2) potential application of 7000 series alloys in tension panels, (3) development of high strength stress corrosion resistant thick section materials like 7010, 7049 and 705O, (4) powder metallurgy 7000 series alloys with high strength and...

The effect of sheet thickness on flight simulation fatigue crack propagation in 2024-T3, 7475-T761 and mill annealed Ti-6A1-4V

Flight simulation fatigue crack propagation tests were carried out on 2024-T3, 7475-T761 and mill annealed Ti-6A1-4V sheet in thicknesses up to 3 nim and representative for traJisport aircraft lower wing skin stiffened panels of end load capacities 1.5 and 3 MN/m. There was a significant effect of sheet thickness on crack propagation. Thinner...

Flight simulation fatigue crack propagation evaluation of candidate lower wing skin materials with particular consideration of spectrum truncation

Flight simulation fatigu-e crack propagation tests were carried out on 2024-T3, 7475-T761 and mill annealed Ti-6A1-4V sheet in thicknesses up to 3 miri and representative for transport aircraft lower wing skin stiffened panels of end load capacities 1.5 and 3 MN/m. The performance of 2024-T3 was much superior, owing mainly to greater retardation...