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IMPROVEMENT OF THE RESISTANCE OF HIGH PROPERTY ALLOYS ADVANCED MECHANICAL STRUCTURES TO FRETTING

Objective


THE OBJECTIVE OF THE PROJECT IS TO DEVELOP AN EXPERIMENTAL METHODOLOGY AND A MECHANICAL MODEL OF FRETTING AND OF ITS RELATIONSHIP WITH FATIGUE RESISTANCE, IN ORDER TO BETTER RATIONALIZE THE SELECTION OF MATERIALS AND SURFACE CONDITIONS ACCORDING TO THE CONTACT PARAMETERS.

Critical parts life-limited by fretting, and their operating condition have been identified and selected.
A mechanical model of crack propagation in fretting fatigue for one and multiple, perpendicular or inclined cracks has been developed. A parametric study of interactions between cracks and numerical simulation for multilayered structures have also been developed.
Fretting and fretting fatigue tsting adaptations have been manufactured and test specimens have been machined.
Fretting, fatigue and fatigue fretting tests (95%) on different materials (Ti alloys, Ni alloys, high strength steels), with and without different coatings (self lubricating varnishes, plasma spray or electrolytic deposits), and associated metallurgical analyses have been carried out. The synthesis of all the results: mechanisms, influence of load, displacement, fretting frequency, materials coatings, influence of fretting on low cycle or high cycle fatigue strength has commenced.

Fretting tests and their analyses have led to the identification and understanding of different damage mechanisms. There are 2 types of fretting damage depending on the contact parameters only, fretting wear and fretting fatigue. With tests made under different conditions, fretting maps can be drawn from which the material response can be predicted. The governing parameters have also been clarified as have their modes of interaction.

2 solid mechanics models have been developed which allow the calculation of thermal and mechanical response of a multilayered medium submitted to thermomechanical loading, as well as the prediction of the propagation of cracks present in a sliding contact.

THIS PROPOSAL IS BASED ON A MECHANICS/MATERIAL COOPERATION WHICH HAS BEEN VERY PRODUCTIVE IN THE PAST. THIS PLURIDISCIPLINARY APPROACH CAN FOCUSSES DAMAGE ANALYSIS AROUND THE PROPERTIES OF INTERFACIAL FILMS OR THIRD BODIES WHOSE COMPOSITION ON THE ONE HAND AND FLOW (WHICH IS A MEASURE OF WEAR) ON THE OTHER ARE STUDIED SIMULTANEOUSLY USING TOOLS WHICH BELONG TO BOTH SUBJECTS.
THE PROJECT INCLUDES THE MAIN FOLLOWING PHASES:
- IDENTIFICATION AND SELECTION BY THE INDUSTRIAL PARTNERS OF THE MAIN MECHANICAL COMPONENTS LIFE-LIMITED BY FRETTING AND THEIR OPERATION CONDITIONS (MATERIALS, STRESSES, FREQUENCIES, TEMPERATURE).

- FRETTING TESTS ON THE MATERIALS AND COATINGS OF THE CRITICAL COMPONENTS (TITANIUM ALLOYS, NICKEL BASE ALLOYS AND HIGH STRENGTHENED STEELS) TO UNDERSTAND THE MECHANISMS, AND EXPLIAN THE INFLUENCE OF COATINGS.

- FRETTING-FATIGUE TESTS ON THE SAME CONFIGURATIONS TO ASSESS THE LOSS OF FATIGUE LIFE DUE TO FRETTING.

- IN PARALLEL, A SOLID MECHANIC ANALYSIS WILL BE DEVELOPED IN ORDER TO TAKE INTO ACCOUNT THE FRETTING PROBLEMS IN THE LIFE CALCULATION OF PARTS.
- THE ANALYSIS OF THE RESULTS WILL PERMIT TO SELECT REMEDIES ADAPTED TO EACH CASE, AND CAPABLE OF INDUSTRIAL DEVELOPMENT, AND TO COMPARE MODELLING AND EXPERIMENTS.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Société Nationale d'Études et de Construction de Moteurs d'Aviation (SNECMA)
Address
2 Boulevard Du Général Martial Valin
75724 Paris
France

Participants (2)

Institut National des Sciences Appliquées de Lyon (INSA)
France
Address
20 Avenue Albert Einstein
69621 Villeurbanne
KHD Luftfahrttechnik GmbH
Germany
Address

61440 Oberursel