Objective
Determining by experiment and modelling of the mechanical performance of advanced structural materials; experimental validation of the models.
Experimental work is being carried out on the measurement of specific mechanical properties and on the identification and analysis of the modes and mechanisms of deformation and failure of 2 highly advanced engineering materials: firstly, coated, single crystal nickel base alloys for application in blades of aero gas turbines which are being tested under thermomechanical fatigue conditions; and secondly, 2-dimensional continuous fibre reinforced ceramic matrix composites, which are being characterized with respect to their creep and cyclic fatigue behaviour. Appropriate routes to model the mechanical performance of both materials are under survey.
Multiaxiality and fracture mechanics concepts are applied to model the behaviour of various steels under simulated service conditions. Tubular components of a ferritic steel and of an austenitic steel are used for benchmark testing, measuring multiaxial creep and crack growth, and crack propagation in cyclic thermal gradient fields respectively. In the former project, modelling is based on continuum damage mechanics and C* approaches. In the latter project linear elastic and elastoplastic fracture mechanics are applied to predict the useful life of the components. A computer code to simulate crack growth numerically has been extended to handle 3-dimensional configurations on surface cracks.
A project on the design methodology of ceramic heat exchangers has been initiated.
The last project is concerned with the development of a methodology to quantify the microstructural defect state in creep damaged materials. In an AMCR steel it was shown that ultrasonic wave velocity measurements provide a sensitive means for creep damage detection. Similar measurements on a ferratic steel and on an oxide dispersion strengthened (ODS) alloy have been made. On the basis of theoretical considerations, an improved relationship between metallographic results and mechanically defined damage parameters has been established. Finite ele ment analysis for the assessment of damage in structures has begun.
Progress to end 1991
The projects under this heading have advanced to various degrees along the line measurement-modelling-validation.
Experimental work has started on the measurement of specific mechanical properties and on the identification / analysis of the modes and mechanisms of deformation and failure of two highly advanced engineering materials, i.e.:
- coated, single crystal nickel base alloys for application in blades of aero gas turbines which are being tested under thermomechanical fatigue conditions;
- 2D continuous fibre reinforced ceramic matrix composites are being characterised with respect to their creep and cyclic fatigue behaviour.
Appropriate routes to model the mechanical performance of both materials are under survey.
Multiaxiality and fracture mechanics concepts are applied to model the behaviour of various steels under simulated service conditions. Tubular components of a ferritic steel and of an austenitic steel are used for benchmark testing, measuring multiaxial creep and crack growth, and crack propagation in cyclic thermal gradient fields respectively. In the former project, modelling is based on continuum damage mechanics and C* appraoches. In the latter project linear elastic and elasto- plastic fracture mechanics are applied to predict the useful life of the components. A computer code to simulate crack growth numerically has been extended to handle 3D-configurations of surface cracks.
The effect of neutron irradiation on crack growth will be measured in an in-pile rig in the HFR and subsequently modelled. The detailed design of the in-pile rig is nearly completed and the problems relating to the quantitative measurement of crack advance under neutron irradiation have been evaluated.
A project on the design methodology of ceramic heat exchangers has been initiated by collecting the parameters enabling the design of the necessary test facility.
The last project is concerned with the development of a methodology to quantify the microstructural defect state in creep damaged materials. In an AMCR steel it was shown that ultrasonic wave velocity measurements provide a sensitive means for creep damage detection. Similar measurements on a ferritic steel and on an ODS alloy are ongoing. On the basis of theoretical considerations, an improved relationship between metallographic results and mechanically defined damage parameters has been established. Finally finite element analyses for the assessment of damage in structures has begun.
Detailed description of work foreseen in 1992
The research area addresses applications in the transport, energy and (petrol) chemical industrial sectors, working both on advanced materials with a highly anisotropic microstructure and on isotropic materials exposed to extreme conditions of temperature, stress and environmental degradation. Materials investigated include coated single crystal and ODS superalloys, monolithic and continuous fibre reinforced ceramics, steels, MMC's and surface treated Al alloys.
The experimental work will focus on:
- the development and implementation of appropriate techniques for the measurement of the mechanical properties of damage by means of US waves, quantitative metallography and non-intrusive optical techniques and of the behaviour of components during verification testing. In the area of NDE it is planned to start with the development of a multi-purposes US inspection system aimed at sizing small defects. The whole activity has a strong spin-off towrads prenormative work;
- measuring and analysing the mechanical and fracture mechanics behaviour of the materials under investigation and the modes, mechanisms and mechanics of strain and damage accumulation and of failure;
- validating models for the prediction of performance by means of complex mechanical tests on samples and on components.
The modelling will concentrate on:
- the evaluation of existing models for performance prediction in terms of their aplicability to anisotropic and composite materials and to transient loading conditions; initiate the development of new model concepts where existing models fail;
- implementation of the models in computer codes for numerical treatment purposes and their application to the materials/loading conditions under investigation.
Short description of evolution of work in 1993
- the basic equipment for most of the projects in the research area is installed and commissioned and the experimental activity for all the projects is scheduled to start in 1992. In 1993 sufficient results will become available to start applying the selected models.
Topic(s)
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1755 ZG PETTEN
Netherlands