https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Thu, 12 Mar 2026 11:22:45 GMT 2026-03-12T11:22:45Z http://hdl.handle.net/10985/8062 Very high cycle fatigue of copper: Evolution, morphology and locations of surface slip markings PHUNG, Ngoc-Lam; VALES, Fréderic; MURGHRABI, Haël; RANC, Nicolas; FAVIER, Véronique The surfaces of commercially pure polycrystalline copper specimens subjected to interrupted 20 kHz fatigue tests in the very high cycle fatigue regime were investigated. The stress amplitude needed to form the early slip markings was found twice lower than the stress amplitude required to fracture which confirmed the results obtained by Stanzl-Tschegg et al. (2007). Three types of slip markings were classified according to their morphology and their location in the polycrystalline material. They are compared to slip markings observed during fatigue tests at frequencies lower than 100 Hz and numbers of cycles lower than 107. For 20 kHz fatigue tests, stress amplitudes ranging from 45 MPa to 65 MPa produce straight and long early persistent slip markings located along twin boundaries. Stress amplitudes lower than 45 MPa produce clusters of fine early persistent slip markings mainly located at triple junctions. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/8062 2014-01-01T00:00:00Z PHUNG, Ngoc-Lam VALES, Fréderic MURGHRABI, Haël RANC, Nicolas FAVIER, Véronique The surfaces of commercially pure polycrystalline copper specimens subjected to interrupted 20 kHz fatigue tests in the very high cycle fatigue regime were investigated. The stress amplitude needed to form the early slip markings was found twice lower than the stress amplitude required to fracture which confirmed the results obtained by Stanzl-Tschegg et al. (2007). Three types of slip markings were classified according to their morphology and their location in the polycrystalline material. They are compared to slip markings observed during fatigue tests at frequencies lower than 100 Hz and numbers of cycles lower than 107. For 20 kHz fatigue tests, stress amplitudes ranging from 45 MPa to 65 MPa produce straight and long early persistent slip markings located along twin boundaries. Stress amplitudes lower than 45 MPa produce clusters of fine early persistent slip markings mainly located at triple junctions. http://hdl.handle.net/10985/10495 Very High Cycle Fatigue for single phase ductile materials: slip band appearance criterion PHUNG, Ngoc-Lam; MARTI, Nicolas; BLANCHE, Antoine; RANC, Nicolas; FAVIER, Véronique; CHRYSOCHOOS, André; SAINTIER, Nicolas; GREGORI, Fabienne; BACROIX, Brigitte; THOQUENNE, Guillaume The DISFAT project is a French project financially supported by the French National Agency for Research (ANR). It aims at a deeper understanding of mechanisms leading to crack initiation in metals and alloys under Very High Cycle Fatigue loading (VHCF). The VHCF regime is associated with stress magnitudes lower than the conventional fatigue limit and as a result, numbers of cycles higher than 109. Tests were carried out using an ultrasonic technique at loading frequency of 20 kHz. In the case of pure copper polycrystals, we previously showed that slip band (SB) activity and intrinsic dissipation were closely related. Dissipation and slip band amount increased with the number of cycles. At very small stress amplitudes, no slip band appeared at the specimen surface up to 108 cycles but the material was found to dissipate energy. These results revealed that the material never reached a steady state and so could break at higher number of cycles. In this paper, the morphology and the location of slip bands were characterized. Different types of slip bands depending on the stress amplitudes appeared at the specimen surface. The stress amplitude required to show the first slip bands decreases with the number of cycles. It is twice lower than the stress amplitude required to break the specimen for the same number of cycles. At the smallest stress amplitudes, slip bands were mostly found at twin boundaries. Quasi 3D finite element simulations taking into account the polycrystalline nature of the material emphasized the key role of the elastic anisotropy in slip band initiation. A criterion for slip band appearance was finally proposed. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/10495 2013-01-01T00:00:00Z PHUNG, Ngoc-Lam MARTI, Nicolas BLANCHE, Antoine RANC, Nicolas FAVIER, Véronique CHRYSOCHOOS, André SAINTIER, Nicolas GREGORI, Fabienne BACROIX, Brigitte THOQUENNE, Guillaume The DISFAT project is a French project financially supported by the French National Agency for Research (ANR). It aims at a deeper understanding of mechanisms leading to crack initiation in metals and alloys under Very High Cycle Fatigue loading (VHCF). The VHCF regime is associated with stress magnitudes lower than the conventional fatigue limit and as a result, numbers of cycles higher than 109. Tests were carried out using an ultrasonic technique at loading frequency of 20 kHz. In the case of pure copper polycrystals, we previously showed that slip band (SB) activity and intrinsic dissipation were closely related. Dissipation and slip band amount increased with the number of cycles. At very small stress amplitudes, no slip band appeared at the specimen surface up to 108 cycles but the material was found to dissipate energy. These results revealed that the material never reached a steady state and so could break at higher number of cycles. In this paper, the morphology and the location of slip bands were characterized. Different types of slip bands depending on the stress amplitudes appeared at the specimen surface. The stress amplitude required to show the first slip bands decreases with the number of cycles. It is twice lower than the stress amplitude required to break the specimen for the same number of cycles. At the smallest stress amplitudes, slip bands were mostly found at twin boundaries. Quasi 3D finite element simulations taking into account the polycrystalline nature of the material emphasized the key role of the elastic anisotropy in slip band initiation. A criterion for slip band appearance was finally proposed. http://hdl.handle.net/10985/9824 Evaluating Schmid criterion for predicting preferential locations of persistent slip markings obtained after very high cycle fatigue for polycrystalline pure copper PHUNG, Ngoc-Lam; FAVIER, Véronique; RANC, Nicolas Very high cycle fatigue carried out on pure copper polycrystals promotes early slip markings, labelled as slip markings of types II and III, localized close to grain or twin boundaries. In this work, we focus on whether Schmid criterion can predict the preferential sites of slip markings of types II and III and identify the active slip systems. Combining observations of slip markings and polycrystalline modeling, it is shown that considering pure cubic elastic behavior, maximum resolved shear stress as a criterion for type II slip markings preferential sites is 70% reliable criterion. Concerning slip markings of type III, the reliability falls to 30%. The role of cross slip is highlighted and a scenario rationalizing the stress amplitude conditions and sites to observe early slip markings of type II or III for copper polycrystals is proposed. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/9824 2015-01-01T00:00:00Z PHUNG, Ngoc-Lam FAVIER, Véronique RANC, Nicolas Very high cycle fatigue carried out on pure copper polycrystals promotes early slip markings, labelled as slip markings of types II and III, localized close to grain or twin boundaries. In this work, we focus on whether Schmid criterion can predict the preferential sites of slip markings of types II and III and identify the active slip systems. Combining observations of slip markings and polycrystalline modeling, it is shown that considering pure cubic elastic behavior, maximum resolved shear stress as a criterion for type II slip markings preferential sites is 70% reliable criterion. Concerning slip markings of type III, the reliability falls to 30%. The role of cross slip is highlighted and a scenario rationalizing the stress amplitude conditions and sites to observe early slip markings of type II or III for copper polycrystals is proposed.