Vacuum fatigue fracture in titanium alloy plate

Breukvlakonderzoek

In this report an attempt is made to give an overview of the various aspects involved in a fracture surface investigation, stating with a definition of fractography and why it is done. Then the equipment needed is discussed, including stereo-microscopes, optical microscopes, transmission and scanning electron microscopes, and micro-analysis...

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 edge working on the fatigue life under flight-simulation loading

Fatigue tests under flight-simulation loading have been performed on unnotched Alclad 2024-T3, anodised 2.0 mm thick sheet specimens, manufactured according to several machine-shop processes applied in the air craft industry. From the results it appears that milling is preferable to stamping. Rounding off the edges is also advantageous. The...

Residual strength properties of carbon/epoxy composite material

Fatigue tests on unidirectional Ca/ep composite material have been performed to investigate whether previous fatigue loading did influence the residual static strength. Residual strength tests were carried out on (0, ± 45)2s and (± 45)2s laminates, while for the (O, ± 45)2s laminate the influence of previous tensile fatigue loading on the...

Effects of crack plane orientation transitions on flight simulation fatigue crack propagation in a high strength aluminium alloy (7050)

The effects of flat to slant fracture transitions on flight simulation fatigue crack propagation in specimens of 7O5O aluminium alloy forgings are discussed. For specimens containing flat, shearlipped, or full slant fractures at similar crack lengths the crack resistance (R curve) approach appears to provide an explanation for differences in the...

Residual strength of the aluminium alloy 7475-T76 at low temperatures

Residual strength tests have heen performed, on 300 mm wide centrecracked panels of various thicknesses, at room temperature and at -50 C. During the tests, stable crack growth was filmed and recorded with the electric potential method. Fracture toughness was determined using the method of Feddersen.

Application of fracture mechanics in designing built-up sheet structures

Past experience has shown that during the operational life of an aircraft structure cracks or failures may arise in different structural components. In future designs the designer must be able on the one hand to restrict the occurrence of cracks by a careful detail design and on the other hand to guarantee some specified life of the aircraft if...

Residual strength data of riveted panels with different stiffener configurations

Residual strength tests were carried out on center-cracked panels with a 2024-T3 or 7075-T6 skin and provided with eccentric stiffeners of practical design. The stiffeners were riveted to the skin. The material of the stiffeners was 7075-T6. In some cases the stiffeners were combined with Ti-alloy crack stoppers. On the basis of the test results...

Scanning electron microscopy of fracture surfaces of carton composite materials

A microscopic study has been performed on carbon composite fracture surfaces, using the Scanning Electron Microscope (SEM). It appears that the SEM is a useful tool to examine the fracture surface characteristics of composite materials failing under different loading conditions.

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...

Fracture toughness and fatigue properties of the new aluminium alloy 7475-T76

Residual strength tests have been performed on 610 mm wide centre cracked panels. During the tests, stable crack growth was filmed and crack opening displacements were measured. Fracture toughness was determined using the method of Feddersen. Flight simulation fatigue tests were carried out to investigate the crack propagation properties. A...

User's manual of ARREST, a computer routine for prediction of residual strength of cracked stiffened panels

This report gives a detailed description of the computer program ARREST and of the execution of it in determining the residual strength diagram of cracked stiffened panels. The essentials of the computer program are dealt with in chapters 1 through 5, whereas the derivation of the equations together with the program flow charts ajid the program...

An investigation of crack resistance in composite reinforced face sheets of sandwich panels

Aluminium sandwich paaiels provided with carbon-epoxy uniaxial reinforcing strips were fatigued and subsequently tested for residual strength, Although both analysis ajid fatigue tests indicate that the crack tip zone is affected onlywhen the zone is in the immediate vicinity of a stiffener the reinforcement considerably increases crack...

The thickness effect in plane stress fracture toughness

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

An investigation of crack resistance in face sheets of sandwich panels

Sandwich panels provided with a central saw cut in one face layer were fatigue tested to study crack growth up to a predetermined length. Static residual strength was determined subsequently. Crack growth rates and residual strength are compared with similar data for face sheet material. An increased resistance against both stable fatigue crack...