Institut de Mécanique et d'Ingénierie (i2M)-DUMAS
http://hdl.handle.net/10985/185
2018-02-20T13:30:16ZA method to determine composite material residual tensile strength in the fibre direction as a function of the matrix damage state after fatigue loading
http://hdl.handle.net/10985/12048
CAOUS, Damien; BOIS, Christophe; WAHL, Jean-Christophe.; PALIN-LUC, Thierry; VALETTTE, Julien
Composites Part B: Engineering
The phenomenon of residual strength in composite laminates after fatigue loading has been studied for decades but is generally expressed as a function of the number of cycles applied to the specimens. henomenological laws deduced from these tests are therefore loading dependent and identifying a valid model for any loading condition of a given laminate requires long fatigue testing campaigns. To overcome this difficulty, a testing procedure is proposed to express the residual tensile strength of a unidirectional ply in the fibre direction, as a function of its matrix damage. The resulting behaviour is then independent of the imposed loading and can be etermined by only a few fatigue tests. Experimental results obtained on glass-epoxy non-crimp fabric laminates are presented and analysed.
2017-01-01T00:00:00ZCAOUS, DamienBOIS, ChristopheWAHL, Jean-Christophe.PALIN-LUC, ThierryVALETTTE, JulienThe phenomenon of residual strength in composite laminates after fatigue loading has been studied for decades but is generally expressed as a function of the number of cycles applied to the specimens. henomenological laws deduced from these tests are therefore loading dependent and identifying a valid model for any loading condition of a given laminate requires long fatigue testing campaigns. To overcome this difficulty, a testing procedure is proposed to express the residual tensile strength of a unidirectional ply in the fibre direction, as a function of its matrix damage. The resulting behaviour is then independent of the imposed loading and can be etermined by only a few fatigue tests. Experimental results obtained on glass-epoxy non-crimp fabric laminates are presented and analysed.Fatigue behaviour of two-phase titanium alloy in VHCF regime
http://hdl.handle.net/10985/12047
NIKITIN, Alexander; SHANYAVSKIY, Andrey; PALIN-LUC, Thierry
This paper is focused on fatigue crack initiation and early growth in two-phase titanium alloy VT3-1 (similar to Ti-6Al-4V) under VHCF loads. The material was produced by two different processes: forging and extrusion. Each kind of material was investigated under three different loading types (push-pull, pull-pull and fully reversed torsion). Fracture surfaces of the tested specimens were analyzed by scanning electron microscopy (SEM) for getting information on crack initiation sites and surrounded fracture surface zones. The results of such analysis were compared with microstructure of the titanium alloy for establishing a crack initiation and early crack growth mechanisms. It was found that crack initiation in this alloy is caused by single or an agglomeration (“cluster”) of alpha-platelets. Under fully reversed tension the fatigue life seems to depend on the geometry of alpha-platelets clusters whereas under tension tension loading such dependence was not observed. However, materials with larger alpha-platelets clusters (macro-zones) have a lower VHCF resistance. The comparison of tension and torsion VHCF test results show a higher slop of the S-N curve under torsion than under tension for both forged and extruded titanium alloys. Nonetheless, some similarities in crack initiation and propagation scenarios were outlined between tension and torsion loadings.
2017-01-01T00:00:00ZNIKITIN, AlexanderSHANYAVSKIY, AndreyPALIN-LUC, ThierryThis paper is focused on fatigue crack initiation and early growth in two-phase titanium alloy VT3-1 (similar to Ti-6Al-4V) under VHCF loads. The material was produced by two different processes: forging and extrusion. Each kind of material was investigated under three different loading types (push-pull, pull-pull and fully reversed torsion). Fracture surfaces of the tested specimens were analyzed by scanning electron microscopy (SEM) for getting information on crack initiation sites and surrounded fracture surface zones. The results of such analysis were compared with microstructure of the titanium alloy for establishing a crack initiation and early crack growth mechanisms. It was found that crack initiation in this alloy is caused by single or an agglomeration (“cluster”) of alpha-platelets. Under fully reversed tension the fatigue life seems to depend on the geometry of alpha-platelets clusters whereas under tension tension loading such dependence was not observed. However, materials with larger alpha-platelets clusters (macro-zones) have a lower VHCF resistance. The comparison of tension and torsion VHCF test results show a higher slop of the S-N curve under torsion than under tension for both forged and extruded titanium alloys. Nonetheless, some similarities in crack initiation and propagation scenarios were outlined between tension and torsion loadings.Experimental and Theoretical Study of Multiscale Damage-Failure Transition in Very High Cycle Fatigue
http://hdl.handle.net/10985/12046
BETEKHTIN, V.I.; KADOMTSEV, A.G.; NARYKOVA, M.V.; BANNIKOV, M.V; ABAIMOV, S.G.; AKHATOV, I. S.; PALIN-LUC, Thierry; NAIMARK, O.B.
Physical Mesomechanics
Multiscale mechanisms of failure of metals (Armco iron, titanium, aluminum) are studied for high cycle and very high cycle fatigue. By correlating with the results of structural studies, a theoretical approach is developed to describe fatigue crack kinetics in damaged material under high cycle and very high cycle fatigue loading conditions. Stages of crack nucleation and propagation are analyzed using the profilometry data from the fracture surface. The scale invariance of fracture surface roughness is established, which allows an explanation of the self-similar nature of fatigue crack kinetics under high cycle and very high cycle fatigue. Variation of elastic-plastic properties of Armco iron under very high cycle fatigue is studied using an acoustic resonance method. It is found that the material density decreases during fatigue damage accumulation, with the minimum of the material density in the bulk of the specimen.
2017-01-01T00:00:00ZBETEKHTIN, V.I.KADOMTSEV, A.G.NARYKOVA, M.V.BANNIKOV, M.VABAIMOV, S.G.AKHATOV, I. S.PALIN-LUC, ThierryNAIMARK, O.B.Multiscale mechanisms of failure of metals (Armco iron, titanium, aluminum) are studied for high cycle and very high cycle fatigue. By correlating with the results of structural studies, a theoretical approach is developed to describe fatigue crack kinetics in damaged material under high cycle and very high cycle fatigue loading conditions. Stages of crack nucleation and propagation are analyzed using the profilometry data from the fracture surface. The scale invariance of fracture surface roughness is established, which allows an explanation of the self-similar nature of fatigue crack kinetics under high cycle and very high cycle fatigue. Variation of elastic-plastic properties of Armco iron under very high cycle fatigue is studied using an acoustic resonance method. It is found that the material density decreases during fatigue damage accumulation, with the minimum of the material density in the bulk of the specimen.A new ultrasonic fatigue testing device for biaxial bending in the gigacycle regime
http://hdl.handle.net/10985/11535
BRUGGER, Charles; PALIN-LUC, Thierry; OSMOND, Pierre; BLANC, Michel
International Journal of Fatigue
A new fatigue testing device has been developed to test specimens under biaxial loading at 20 kHz. The specimen is a flat smooth disc. It is placed on a torus frame and cyclically loaded in compression at the center of its upper face. Consequently disc bending generates a biaxial proportional stress state at the center of the specimen lower face. Any positive loading ratio can be applied. This device has been tested and is well functioning on specimens made of a cast aluminum alloy used to produce cylinder heads. Preliminary results in VHCF regime are compared with literature results obtained under similar stress state but in HCF regime and at 20 Hz only.
2017-01-01T00:00:00ZBRUGGER, CharlesPALIN-LUC, ThierryOSMOND, PierreBLANC, MichelA new fatigue testing device has been developed to test specimens under biaxial loading at 20 kHz. The specimen is a flat smooth disc. It is placed on a torus frame and cyclically loaded in compression at the center of its upper face. Consequently disc bending generates a biaxial proportional stress state at the center of the specimen lower face. Any positive loading ratio can be applied. This device has been tested and is well functioning on specimens made of a cast aluminum alloy used to produce cylinder heads. Preliminary results in VHCF regime are compared with literature results obtained under similar stress state but in HCF regime and at 20 Hz only.Special Issue on ‘Multiaxial fatigue 2016: Experiments and modeling’: Selected papers from the 11th International Conference on Multiaxial Fatigue and Fracture (ICMFF11), held in Seville, Spain, on 1–3 June 2016
http://hdl.handle.net/10985/11534
CARPINTERI, Andrea; FATEMI, Ali; PALIN-LUC, Thierry; VANTADORI, Sabrina
International Journal of Fatigue
This Special Issue of the International Journal of Fatigue contains selected papers presented at the International Conference on Multiaxial Fatigue and Fracture held in Seville, Spain, on 1–3
June 2016.
2017-01-01T00:00:00ZCARPINTERI, AndreaFATEMI, AliPALIN-LUC, ThierryVANTADORI, SabrinaThis Special Issue of the International Journal of Fatigue contains selected papers presented at the International Conference on Multiaxial Fatigue and Fracture held in Seville, Spain, on 1–3
June 2016.Mechanical characterization of composite materials from curved structures
http://hdl.handle.net/10985/11383
CROZATIER, Mathilde; TEREKHINA, Svetlana; DAU, Frederic; GUILLAUMAT, Laurent
Mechanical behavior of composite laminates depends strongly on the manufacturing process. It is necessary to use representative samples of the material, and therefore of the process. In the case of filament winding, specimens are necessarily cylindrical or barrel extracted. In our case, a full-scale fiberglass composite structure is used for radial compression and axial cuts experimental performances. This work aims to estimate the elastic properties of composite laminate from a curved structure taking into account the manufacturing process. An inverse approach using an optimization process is adopted. By coupling a radial compression experiment with a 3D model obtained by Finite Element Method (FEM), a mechanical characterization becomes possible. Furthermore, these identifications combined with experiments of axial cuts enable the estimation of residual manufacturing stresses.
2016-01-01T00:00:00ZCROZATIER, MathildeTEREKHINA, SvetlanaDAU, FredericGUILLAUMAT, LaurentMechanical behavior of composite laminates depends strongly on the manufacturing process. It is necessary to use representative samples of the material, and therefore of the process. In the case of filament winding, specimens are necessarily cylindrical or barrel extracted. In our case, a full-scale fiberglass composite structure is used for radial compression and axial cuts experimental performances. This work aims to estimate the elastic properties of composite laminate from a curved structure taking into account the manufacturing process. An inverse approach using an optimization process is adopted. By coupling a radial compression experiment with a 3D model obtained by Finite Element Method (FEM), a mechanical characterization becomes possible. Furthermore, these identifications combined with experiments of axial cuts enable the estimation of residual manufacturing stresses.Reevaluation of the diametral compression test for tablets using the flattened disc geometry
http://hdl.handle.net/10985/11248
MAZEL, Vincent; GUERARD, Sandra; CROQUELOIS, Benjamin; KOPP, Jean-Benoit; GIRARDOT, Jérémie; DIARRA, Harona; BUSIGNIES, Virginie; TCHORELOFF, Pierre
International Journal of Pharmaceutics
Mechanical strength is an important critical quality attribute for tablets. It is classically measured, in the pharmaceutical field, using the diametral compression test. Nevertheless, due to small contact area between the tablet and the platens, some authors suggested that during the test, the failure could occur in tension away from the center which would invalidate the test and the calculation of the tensile strength.
In this study, the flattened disc geometry was used as an alternative to avoid contact problems. The diametral compression on both flattened and standard geometries was first studied using finite element method (FEM) simulation. It was found that, for the flattened geometry, both maximum tensile strain and stress were located at the center of the tablet, which was not the case for the standard geometry. Experimental observations using digital image correlation (DIC) confirmed the numerical results. The experimental tensile strength obtained using both geometries were compared and it was found that the standard geometry always gave lower tensile strength than the flattened geometry. Finally, high-speed video capture of the test made it possible to detect that for the standard geometry the crack initiation was always away from the center of the tablet.
2016-01-01T00:00:00ZMAZEL, VincentGUERARD, SandraCROQUELOIS, BenjaminKOPP, Jean-BenoitGIRARDOT, JérémieDIARRA, HaronaBUSIGNIES, VirginieTCHORELOFF, PierreMechanical strength is an important critical quality attribute for tablets. It is classically measured, in the pharmaceutical field, using the diametral compression test. Nevertheless, due to small contact area between the tablet and the platens, some authors suggested that during the test, the failure could occur in tension away from the center which would invalidate the test and the calculation of the tensile strength.
In this study, the flattened disc geometry was used as an alternative to avoid contact problems. The diametral compression on both flattened and standard geometries was first studied using finite element method (FEM) simulation. It was found that, for the flattened geometry, both maximum tensile strain and stress were located at the center of the tablet, which was not the case for the standard geometry. Experimental observations using digital image correlation (DIC) confirmed the numerical results. The experimental tensile strength obtained using both geometries were compared and it was found that the standard geometry always gave lower tensile strength than the flattened geometry. Finally, high-speed video capture of the test made it possible to detect that for the standard geometry the crack initiation was always away from the center of the tablet.An energy based criterion for high cycle multiaxial fatigue
http://hdl.handle.net/10985/11237
PALIN-LUC, Thierry; LASSERRE, Serge
European Journal of Mechanics - A/Solids
In spite of the great number of high cycle multiaxial fatigue in the literature, none predicts the difference that exist between the endurance limits in tension, four point rotative bending and four point plane bending. An enerdy based criterion based on a new concept using the strain energy density is proposed in the paper. This new calculation method explains the previous differnces by taking into account the volumic distribution of the strain energy density around the considered critical point in fatigue. This method, available now under fully reversed mutiaxial loadings, also takes into account the stress state triaxiality. Under combined plane bending and torsion the predictions of the new proposal lead to Gough and Pollard's ellipse quadrant for ductile materials and lead to a curve close to an ellipse arc for brittle materials. Under other multiaxial loadings, predictions are always close to an ellipse quadrant dependent on the loading mode. This method has been tested on smooth cylindrical specimens with several materials; calculations are in very good agreements with multiaxial experimental data.
1998-01-01T00:00:00ZPALIN-LUC, ThierryLASSERRE, SergeIn spite of the great number of high cycle multiaxial fatigue in the literature, none predicts the difference that exist between the endurance limits in tension, four point rotative bending and four point plane bending. An enerdy based criterion based on a new concept using the strain energy density is proposed in the paper. This new calculation method explains the previous differnces by taking into account the volumic distribution of the strain energy density around the considered critical point in fatigue. This method, available now under fully reversed mutiaxial loadings, also takes into account the stress state triaxiality. Under combined plane bending and torsion the predictions of the new proposal lead to Gough and Pollard's ellipse quadrant for ductile materials and lead to a curve close to an ellipse arc for brittle materials. Under other multiaxial loadings, predictions are always close to an ellipse quadrant dependent on the loading mode. This method has been tested on smooth cylindrical specimens with several materials; calculations are in very good agreements with multiaxial experimental data.A non-local theory applied to high cycle multiaxial fatigue
http://hdl.handle.net/10985/11236
MOREL, Franck; PALIN-LUC, Thierry
Fatigue & Fracture of Engineering Materials & Structures
The stress gradient effect on the fatigue limit is an important factor which has to be taken into account for an efficient transfer of fatigue data from laboratory tests to design of industrial components. A short review of some multiaxial high cycle fatigue criteria considering this effect is presented. On the basis of the two local mesoscopic approaches of Papadopoulos, two new non-local high cycle multiaxial fatigue criteria are developed. These proposals are based on the concept of volume influencing fatigue crack initiation. Their predictions are compared with experimental multiaxial fatigue data on four materials (a mild steel, two high strength steels and a spheroidal graphite cast iron). The accuracy of the two local Papadopoulos criteria and of the non-local proposals are compared and discussed together with the physical interpretation of the threshold defining the volume influencing fatigue crack initiation.
2002-01-01T00:00:00ZMOREL, FranckPALIN-LUC, ThierryThe stress gradient effect on the fatigue limit is an important factor which has to be taken into account for an efficient transfer of fatigue data from laboratory tests to design of industrial components. A short review of some multiaxial high cycle fatigue criteria considering this effect is presented. On the basis of the two local mesoscopic approaches of Papadopoulos, two new non-local high cycle multiaxial fatigue criteria are developed. These proposals are based on the concept of volume influencing fatigue crack initiation. Their predictions are compared with experimental multiaxial fatigue data on four materials (a mild steel, two high strength steels and a spheroidal graphite cast iron). The accuracy of the two local Papadopoulos criteria and of the non-local proposals are compared and discussed together with the physical interpretation of the threshold defining the volume influencing fatigue crack initiation.Experimental Investigation on the Significance of the Conventional Endurance Limit of a Spheroidal Graphite Cast Iron
http://hdl.handle.net/10985/11235
PALIN-LUC, Thierry; LASSERRE, Serge; BERARD, J-Y.
Fatigue & Fracture of Engineering Materials & Structures
Fatigue tests were performed on a spheroidal graphite cast iron in four point plane bending under constant stress amplitude and block loading conditions. The microstructure of this material has a ‘bull’s eyes’ appearance, i.e. the spheroids of graphite are surrounded by ferrite and these nodules and ferrite zones are included in a pearlitic matrix. Scanning electronic microscope observations were carried out at different fractions of life for constant stress amplitude loadings above and below the conventional endurance limit. Non-propagating micro-cracks were observed at a stress level equal to the conventional endurance limit. These observations showed that another limit can be defined below the conventional endurance one, i.e. one below which micro-cracks were not observed to initiate in the matrix. These cracks were found to arrest at the ferrite/pearlite interface when the material was tested below this new limit. This concept was used to rationalize fatigue results from tests with loading in blocks above and below the conventional endurance limit.
1998-01-01T00:00:00ZPALIN-LUC, ThierryLASSERRE, SergeBERARD, J-Y.Fatigue tests were performed on a spheroidal graphite cast iron in four point plane bending under constant stress amplitude and block loading conditions. The microstructure of this material has a ‘bull’s eyes’ appearance, i.e. the spheroids of graphite are surrounded by ferrite and these nodules and ferrite zones are included in a pearlitic matrix. Scanning electronic microscope observations were carried out at different fractions of life for constant stress amplitude loadings above and below the conventional endurance limit. Non-propagating micro-cracks were observed at a stress level equal to the conventional endurance limit. These observations showed that another limit can be defined below the conventional endurance one, i.e. one below which micro-cracks were not observed to initiate in the matrix. These cracks were found to arrest at the ferrite/pearlite interface when the material was tested below this new limit. This concept was used to rationalize fatigue results from tests with loading in blocks above and below the conventional endurance limit.