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Content archived on 2023-01-04

Properties, Performance, Characteristics, and Improvements of Structural Materials: Components and Thermal Fatigue, 1988-1991

Objective

Measurement and modelling of crack propagation in cyclic thermal gradient fields with and without simultaneous irradiation damage and creep to predict component behaviour for non-nuclear and nuclear applications where thermal fatigue life is limited.

Progress to end 1990

LCF tests on 316L stainless steel carried out over various strain ranges at 80 and 350 show good correlation with external data interpolated from tests at other temperatures. Testing to measure growth rates of thorough cracks in centre notched specimens at 80 has started. The out-of-pile test rig for thermal fatigue on tubular test pieces has been constructed,using a 50kW induction heater and a closed loop water cooling system. Careful design and proper selection of heater and cooling parameters have enabled the temperature gradient typical of NET operation conditions to be achieved. Automatic control and monitoring systems of the rig are operational. The D.C.potential drop method to measure crack growth has been calibrated. At the numerical side the line spring method and the weight function method for the determination of the crack growth behaviour of part through cracks were compared. Because the weight function method appears more promising, work to develop a code for the computation of stress intensity factors under arbitrary loading conditions has been initiated.Computer hard- and software to assist with the design calculations of the in-pile (HFR) has been purchased and the software was implemented on the CP 486 and on the Amdahl computer at Ispra.Techniques for monitoring of the crack growth under nuclear irradiation conditions have been assessed and the DC potential drop technique used in the out-of-pile rig was evaluated to determine whether and how it can be adapted to in-pile conditions. Finally, refined thermal and nuclear calculations for the final design of the in-pile rig have started.

Detailed description of work foreseen in 1991 (expected results)

Fracture mechanics data for the 316L material on thorough cracks and on part through cracks will be generated, along with selected data under thermomechanical fatigue conditions simulating the NET cycle.i On the out-of-pile rig, crack growth tests will be performed for different notch geometries using fixed thermal gradients and cycling condtitions. The weight function computer code will be extended to handle 3D configurations of surface cracks. The final design of the in-pile rig will be tackled. The design will be checked by means of tests on a dummy rig to validate the adequate functioning of the mechanical parts necessary for the insertion of the rig in the HFR and of the electronic components for signal measurement. This phase will be followed by the manufacturing of the components and the assembly of the in-pile rig by the commissioning of the rig and by the design and safety report procedures.

Short description of evolution of work in 1992
Extension to examine more complex geometries of defects including simulated natural cracks under a range of cyclic loading conditions in the out-of-pile rig. Elaboration of models to afford improved lifetime prediction methodologies for thermally loaded defective components. Irradiation of the in-pile rig, comparison of the crack growth results with those obtained in the out-of-pile rig and establishment of modifications to the models used to describe out-of-pile rig results in order to take account of the effects of irradiation.

Topic(s)

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Call for proposal

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Funding Scheme

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Coordinator

Joint Research Centre Petten
EU contribution
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Address
Postbus 2
1755 ZG PETTEN
Netherlands

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Total cost
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