J. Ehrström - Academia.edu (original) (raw)

Papers by J. Ehrström

L'effet d'une exposition en milieu corrosif sur la tenue en fatigue d'alliages destin... more L'effet d'une exposition en milieu corrosif sur la tenue en fatigue d'alliages destines a des pieces structurales automobiles a ete teste. Les alliages sont d'une part l'alliage de moulage A-S7G03 et d'autre part deux alliages de corroyage de la serie 6000 pouvant etre utilises en forge, a savoir les alliages 6082 et 6056 et un alliage experimental contenant du cuivre. Pour les alliages de moulage on compare les proprietes obtenues en conservant ou non la peau de fonderie. Les conditions d'exposition comportent des mises en station pour des durees allant jusqu'a 11 ans et des conditions de laboratoire normalisees. Les resultats montrent un effet negligeable de la corrosion prealable sur la tenue en fatigue de l'alliage A-S7G03. En ce qui concerne les alliages 6000, l'effet de la corrosion est sensible pour des eprouvettes lisses, mais pas pour des eprouvettes entaillees. Ces resultats confirment que les alliages consideres sont globalement ada...

Structural Health Monitoring-an International Journal, 2011

Structural Health Monitoring (SHM) enables the detection of damage via sensors that are placed wi... more Structural Health Monitoring (SHM) enables the detection of damage via sensors that are placed within or onto the structures. SHM technologies are especially considered for the next generation aircrafts as it could reduce maintenance costs and enable significant weight savings by revolutionizing the current aircraft design approach and guaranteeing that a structure is damage-free. Constellium believes that SHM enabling aluminum parts would contribute to such improvements for metallic aerostructures and has thus produced extruded semi-products containing integrated wire-shaped sensors. Optical fibers which are particularly relevant sensors for SHM have been integrated within aluminum extrusions and tested to assess the SHM potential and the feasibility of such a solution. Fatigue crack propagation tests have then been performed, monitoring the optical signal through the optical fibers in parallel. It is demonstrated that a crack can be detected using such embedded optical fibers. Dep...

Résumé The fatigue resistance of an advanced Al-Cu-Li plate alloy (2050) and of conventional allo... more Résumé The fatigue resistance of an advanced Al-Cu-Li plate alloy (2050) and of conventional alloys 7010 and 2024 is characterized on notched samples (Kt=2.15) with and without an added spark eroded 0.3 mm defect. This characterization is performed in laboratory air, at different frequencies and in vacuum. 2050 always shows a higher fatigue resistance than 7010. The fatigue resistance of 7010 is affected by a relatively coarse constituent particles distribution and a relatively fast fatigue crack growth rate of short cracks. 2024 and 2050 have similar fatigue resistance with no added defect. 2024 offer a slow early fatigue crack growth rate, especially under vacuum.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 1994

The mechanical behavior and microstructure of aluminum alloys for high temperature applications, ... more The mechanical behavior and microstructure of aluminum alloys for high temperature applications, prepared by rapid solidification and powder metallurgy techniques, have been observed. These alloys contain high concentrations of transition elements which form thermally stable precipitates. Tensile tests were performed at room temperature, at 77 K and at high temperature. The microstructure is described in terms of precipitation and dislocation structure. Samples deformed at different temperatures were observed. The behavior of alloys of this type is discussed, introducing the effect of an internal stress. Special attention is devoted to the ductility dip frequently observed in such alloys.

13th International Conference on Aluminum Alloys, 2012

Al-Cu-Li alloys are of great interest for aerospace applications due to their good mechanical pro... more Al-Cu-Li alloys are of great interest for aerospace applications due to their good mechanical property balance, excellent corrosion resistance and reduced density. These alloys exhibit an increased resistance to fatigue in particular when compared to 7xxx alloys.

Materials Science and Engineering: A, 2013

ABSTRACT The influence of precipitate microstructure on fracture mechanisms is studied in a recen... more ABSTRACT The influence of precipitate microstructure on fracture mechanisms is studied in a recently developed Al–Cu–Li alloy, AA2198. The intra-granular and inter-granular microstructures are varied independently by changing the quench rate from the solution heat treatment, the amount of pre-stretching and the heat treatment time. Fracture toughness is evaluated by short bar chevron tear tests that make possible to evidence clearly the mechanisms of inter-granular fracture. It is shown that intergranular ductile fracture significantly occurs in all conditions of heat treatment where substantial precipitation has taken place. This mechanism is mainly controlled by the state of inter-granular precipitation and plays a major role to determine the value of transverse fracture toughness, while the strength and ductility of the alloy are mainly controlled by the state of intra-granular precipitation.

Le Journal de Physique IV, 1996

Fracture toughness tests have been carried out on two A1 alloys (7075 and 7475) containing differ... more Fracture toughness tests have been carried out on two A1 alloys (7075 and 7475) containing different amounts of Fe and Si. These materials were tested in T3. T6 and T7 conditions. alone six orientations (LT. LS. TL. TS, SL and ST). Large variations in the fracture toughness (20-60 MP~G were measured. Mechanical tests on notched specimens were also performed to determine the influence of stress triaxiality ratio on ductility. These specimens were calculated by finite element method. Quantitative metallography was largely used to measure the volume fraction of intermetallic particles (Mg2Si and Fe-rich precipitates) and the statistical distribution of these particles. The Gurson potential is used to interpret these test resulls carried out on volume elements and on cracked specimens. It is shown that the ductility of notched specimens and the measured variations in fracture toughness can be interpreted with the Gurson potential provided that the non homogeneous distribution of intermetallic particles is taken into account. A model has been developed to relate the toughness of the alloys to the yield strength, the critical void growth rate calculated on notched specimen from Rice and Tracey equation and to the mean distance between the clusters of second phase particles.

Materials Science and Technology

ABSTRACT

Materials Science and Technology, 2004

... Dr Deschamps and Professor Bréchet are at the LTPCM/ENSEEG, CNRS – UMR 5614, Institut Nationa... more ... Dr Deschamps and Professor Bréchet are at the LTPCM/ENSEEG, CNRS – UMR 5614, Institut National Polytechnique de Grenoble, Domaine Universitaire, BP 75, 38 402 StMartin d'He`res Cedex, France (alexis.deschamps@ltpcm.inpg.fr). ...

Materials Science and Technology, 1996

The recrystallisation behaviour and its effect on the crystallographic texture during solution he... more The recrystallisation behaviour and its effect on the crystallographic texture during solution heat treatment ol'thick aluminium alloy 7010 plates has been studied both on commercially hot rolled plates and on laboratory specimens deformed in plane strain compression. In addition to ...

Metallurgical and Materials Transactions A, 2000

The influence of recrystallization and quench rate after solution treatment on the fracture tough... more The influence of recrystallization and quench rate after solution treatment on the fracture toughness of 7010 aluminum plate has been studied in longitudinal-transverse (L-T) and short-longitudinal (S-L) orientations for T76-type heat treatments. Extensive fractographic analysis was carried out to identify the failure mechanisms, including simultaneous scanning electron microscope (SEM) observation of fracture surfaces and underlying microstructures. A slow quench rate was strongly detrimental because it modified the dominant failure mode from a relatively high energy primary void growth mechanism to lower energy transgranular shear and grain boundary ductile failure in the L-T and S-L orientations, respectively. Low energy failure was associated with coarse precipitation during the quench in both L-T and S-L orientation tests, with intragranular and intersubgranular particles contributing to L-T quench sensitivity, and intergranular particles contributing to S-L sensitivity. Partial recrystallization was generally detrimental, with recrystallized grains being shown to be a preferential crack path. The commonly supposed susceptibility of recrystallized grains to intergranular failure did not explain this behavior, particularly in fast quench materials, as recrystallized grains primarily failed by transgranular void growth from the large intermetallics with which they were intrinsically associated. Exceptional S-L orientation quench sensitivity was observed in unrecrystallized material and attributed to a synergistic interaction between heterogeneous boundary precipitation and the specific location of coarse intermetallics along grain boundaries in the unrecrystallized condition. Quantitative assessment of individual contributions to overall fracture resistance is discussed for cases where multiple failure mechanisms occur, highlighting the importance of interacting and noninteracting mechanisms.

Materials Science and Engineering: A, 2001

ABSTRACT

Journal of Materials Science Letters, 1988

Journal of Materials Science, 1988

Rapidly solidified metal matrix composites have been produced on a laboratory scale either by (1)... more Rapidly solidified metal matrix composites have been produced on a laboratory scale either by (1) melt spinning a composite after introduction of the ceramic phase and extrusion of the flakes obtained, or (2) blending melt-spun powder (basic alloy) with the ceramic phase and subsequent extrusion. AIMg(Si) alloys were used as matrix material while SiC particles with diameters of 3 or 20#m were used as the ceramic phase. For the composites prepared by route 1 it was found that the basic alloy was reinforced by the addition of 3#m particles whereas for the 20#m particles reinforcement was observed only for very ductile matrices. The bond between SiC particles and matrix was good. A diffusion and wetting bond was formed. For the composites prepared by route 2 it was found that reinforcement did not occur and that the bond between particles and matrix was weak. Debonding of the particles took place in the case of tensile fracture. The advantage of a rapidly solidified matrix for these composites is that relatively high ductilities are combined with good reinforcement effects. Prior contact of the ceramic phase and the aluminium melt is needed for a good bond between SiC and the matrix material. It is concluded that route 1 should be preferred for the production of rapidly solidified aluminium matrix composites.

International Journal of Fatigue, 2009

Damage tolerance of aerospace grade aluminum alloys was studied in relation to a new design philo... more Damage tolerance of aerospace grade aluminum alloys was studied in relation to a new design philosophy in skin and stringer geometries. Systematic thickness variations (crenellations) were introduced onto the skin and stringers of the laser beam welded (LBW) stiffened Al2139-T8 large flat panels in order to modify the stress intensity factor (SIF) distribution on center cracked panels in such a way that fatigue life can be improved. Fatigue crack propagation (FCP) tests (on panels with crenellations) with crack growing perpendicular to the welded stringers were conducted under constant amplitude and spectrum loading conditions. Results were compared with the results of "classical" LBW stiffened panels (with no crenellations) having equal weight and tested under the same conditions. The new panel design with crenellations showed substantially longer fatigue lives under constant amplitude loading. This gain significantly improved under spectrum (Mini-Twist) loading fatigue tests. This paper presents the first FCP test results of a comprehensive ongoing program which investigates the benefits and potential role of crenellations on welded Alalloy and steel structures. Further issues including microstructural examinations, numerical investigations, fitness for service analysis and residual strength aspects will be topics of another communication.

ICAF 2011 Structural Integrity: Influence of Efficiency and Green Imperatives, 2011

Materials Science and Technology, 1996

The recrystallisation behaviour and its effect on the crystallographic texture during solution he... more The recrystallisation behaviour and its effect on the crystallographic texture during solution heat treatment ol'thick aluminium alloy 7010 plates has been studied both on commercially hot rolled plates and on laboratory specimens deformed in plane strain compression. In addition to ...

L'effet d'une exposition en milieu corrosif sur la tenue en fatigue d'alliages destin... more L'effet d'une exposition en milieu corrosif sur la tenue en fatigue d'alliages destines a des pieces structurales automobiles a ete teste. Les alliages sont d'une part l'alliage de moulage A-S7G03 et d'autre part deux alliages de corroyage de la serie 6000 pouvant etre utilises en forge, a savoir les alliages 6082 et 6056 et un alliage experimental contenant du cuivre. Pour les alliages de moulage on compare les proprietes obtenues en conservant ou non la peau de fonderie. Les conditions d'exposition comportent des mises en station pour des durees allant jusqu'a 11 ans et des conditions de laboratoire normalisees. Les resultats montrent un effet negligeable de la corrosion prealable sur la tenue en fatigue de l'alliage A-S7G03. En ce qui concerne les alliages 6000, l'effet de la corrosion est sensible pour des eprouvettes lisses, mais pas pour des eprouvettes entaillees. Ces resultats confirment que les alliages consideres sont globalement ada...

Structural Health Monitoring-an International Journal, 2011

Structural Health Monitoring (SHM) enables the detection of damage via sensors that are placed wi... more Structural Health Monitoring (SHM) enables the detection of damage via sensors that are placed within or onto the structures. SHM technologies are especially considered for the next generation aircrafts as it could reduce maintenance costs and enable significant weight savings by revolutionizing the current aircraft design approach and guaranteeing that a structure is damage-free. Constellium believes that SHM enabling aluminum parts would contribute to such improvements for metallic aerostructures and has thus produced extruded semi-products containing integrated wire-shaped sensors. Optical fibers which are particularly relevant sensors for SHM have been integrated within aluminum extrusions and tested to assess the SHM potential and the feasibility of such a solution. Fatigue crack propagation tests have then been performed, monitoring the optical signal through the optical fibers in parallel. It is demonstrated that a crack can be detected using such embedded optical fibers. Dep...

Résumé The fatigue resistance of an advanced Al-Cu-Li plate alloy (2050) and of conventional allo... more Résumé The fatigue resistance of an advanced Al-Cu-Li plate alloy (2050) and of conventional alloys 7010 and 2024 is characterized on notched samples (Kt=2.15) with and without an added spark eroded 0.3 mm defect. This characterization is performed in laboratory air, at different frequencies and in vacuum. 2050 always shows a higher fatigue resistance than 7010. The fatigue resistance of 7010 is affected by a relatively coarse constituent particles distribution and a relatively fast fatigue crack growth rate of short cracks. 2024 and 2050 have similar fatigue resistance with no added defect. 2024 offer a slow early fatigue crack growth rate, especially under vacuum.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 1994

The mechanical behavior and microstructure of aluminum alloys for high temperature applications, ... more The mechanical behavior and microstructure of aluminum alloys for high temperature applications, prepared by rapid solidification and powder metallurgy techniques, have been observed. These alloys contain high concentrations of transition elements which form thermally stable precipitates. Tensile tests were performed at room temperature, at 77 K and at high temperature. The microstructure is described in terms of precipitation and dislocation structure. Samples deformed at different temperatures were observed. The behavior of alloys of this type is discussed, introducing the effect of an internal stress. Special attention is devoted to the ductility dip frequently observed in such alloys.

13th International Conference on Aluminum Alloys, 2012

Al-Cu-Li alloys are of great interest for aerospace applications due to their good mechanical pro... more Al-Cu-Li alloys are of great interest for aerospace applications due to their good mechanical property balance, excellent corrosion resistance and reduced density. These alloys exhibit an increased resistance to fatigue in particular when compared to 7xxx alloys.

Materials Science and Engineering: A, 2013

ABSTRACT The influence of precipitate microstructure on fracture mechanisms is studied in a recen... more ABSTRACT The influence of precipitate microstructure on fracture mechanisms is studied in a recently developed Al–Cu–Li alloy, AA2198. The intra-granular and inter-granular microstructures are varied independently by changing the quench rate from the solution heat treatment, the amount of pre-stretching and the heat treatment time. Fracture toughness is evaluated by short bar chevron tear tests that make possible to evidence clearly the mechanisms of inter-granular fracture. It is shown that intergranular ductile fracture significantly occurs in all conditions of heat treatment where substantial precipitation has taken place. This mechanism is mainly controlled by the state of inter-granular precipitation and plays a major role to determine the value of transverse fracture toughness, while the strength and ductility of the alloy are mainly controlled by the state of intra-granular precipitation.

Le Journal de Physique IV, 1996

Fracture toughness tests have been carried out on two A1 alloys (7075 and 7475) containing differ... more Fracture toughness tests have been carried out on two A1 alloys (7075 and 7475) containing different amounts of Fe and Si. These materials were tested in T3. T6 and T7 conditions. alone six orientations (LT. LS. TL. TS, SL and ST). Large variations in the fracture toughness (20-60 MP~G were measured. Mechanical tests on notched specimens were also performed to determine the influence of stress triaxiality ratio on ductility. These specimens were calculated by finite element method. Quantitative metallography was largely used to measure the volume fraction of intermetallic particles (Mg2Si and Fe-rich precipitates) and the statistical distribution of these particles. The Gurson potential is used to interpret these test resulls carried out on volume elements and on cracked specimens. It is shown that the ductility of notched specimens and the measured variations in fracture toughness can be interpreted with the Gurson potential provided that the non homogeneous distribution of intermetallic particles is taken into account. A model has been developed to relate the toughness of the alloys to the yield strength, the critical void growth rate calculated on notched specimen from Rice and Tracey equation and to the mean distance between the clusters of second phase particles.

Materials Science and Technology

ABSTRACT

Materials Science and Technology, 2004

... Dr Deschamps and Professor Bréchet are at the LTPCM/ENSEEG, CNRS – UMR 5614, Institut Nationa... more ... Dr Deschamps and Professor Bréchet are at the LTPCM/ENSEEG, CNRS – UMR 5614, Institut National Polytechnique de Grenoble, Domaine Universitaire, BP 75, 38 402 StMartin d'He`res Cedex, France (alexis.deschamps@ltpcm.inpg.fr). ...

Materials Science and Technology, 1996

The recrystallisation behaviour and its effect on the crystallographic texture during solution he... more The recrystallisation behaviour and its effect on the crystallographic texture during solution heat treatment ol'thick aluminium alloy 7010 plates has been studied both on commercially hot rolled plates and on laboratory specimens deformed in plane strain compression. In addition to ...

Metallurgical and Materials Transactions A, 2000

The influence of recrystallization and quench rate after solution treatment on the fracture tough... more The influence of recrystallization and quench rate after solution treatment on the fracture toughness of 7010 aluminum plate has been studied in longitudinal-transverse (L-T) and short-longitudinal (S-L) orientations for T76-type heat treatments. Extensive fractographic analysis was carried out to identify the failure mechanisms, including simultaneous scanning electron microscope (SEM) observation of fracture surfaces and underlying microstructures. A slow quench rate was strongly detrimental because it modified the dominant failure mode from a relatively high energy primary void growth mechanism to lower energy transgranular shear and grain boundary ductile failure in the L-T and S-L orientations, respectively. Low energy failure was associated with coarse precipitation during the quench in both L-T and S-L orientation tests, with intragranular and intersubgranular particles contributing to L-T quench sensitivity, and intergranular particles contributing to S-L sensitivity. Partial recrystallization was generally detrimental, with recrystallized grains being shown to be a preferential crack path. The commonly supposed susceptibility of recrystallized grains to intergranular failure did not explain this behavior, particularly in fast quench materials, as recrystallized grains primarily failed by transgranular void growth from the large intermetallics with which they were intrinsically associated. Exceptional S-L orientation quench sensitivity was observed in unrecrystallized material and attributed to a synergistic interaction between heterogeneous boundary precipitation and the specific location of coarse intermetallics along grain boundaries in the unrecrystallized condition. Quantitative assessment of individual contributions to overall fracture resistance is discussed for cases where multiple failure mechanisms occur, highlighting the importance of interacting and noninteracting mechanisms.

Materials Science and Engineering: A, 2001

ABSTRACT

Journal of Materials Science Letters, 1988

Journal of Materials Science, 1988

Rapidly solidified metal matrix composites have been produced on a laboratory scale either by (1)... more Rapidly solidified metal matrix composites have been produced on a laboratory scale either by (1) melt spinning a composite after introduction of the ceramic phase and extrusion of the flakes obtained, or (2) blending melt-spun powder (basic alloy) with the ceramic phase and subsequent extrusion. AIMg(Si) alloys were used as matrix material while SiC particles with diameters of 3 or 20#m were used as the ceramic phase. For the composites prepared by route 1 it was found that the basic alloy was reinforced by the addition of 3#m particles whereas for the 20#m particles reinforcement was observed only for very ductile matrices. The bond between SiC particles and matrix was good. A diffusion and wetting bond was formed. For the composites prepared by route 2 it was found that reinforcement did not occur and that the bond between particles and matrix was weak. Debonding of the particles took place in the case of tensile fracture. The advantage of a rapidly solidified matrix for these composites is that relatively high ductilities are combined with good reinforcement effects. Prior contact of the ceramic phase and the aluminium melt is needed for a good bond between SiC and the matrix material. It is concluded that route 1 should be preferred for the production of rapidly solidified aluminium matrix composites.

International Journal of Fatigue, 2009

Damage tolerance of aerospace grade aluminum alloys was studied in relation to a new design philo... more Damage tolerance of aerospace grade aluminum alloys was studied in relation to a new design philosophy in skin and stringer geometries. Systematic thickness variations (crenellations) were introduced onto the skin and stringers of the laser beam welded (LBW) stiffened Al2139-T8 large flat panels in order to modify the stress intensity factor (SIF) distribution on center cracked panels in such a way that fatigue life can be improved. Fatigue crack propagation (FCP) tests (on panels with crenellations) with crack growing perpendicular to the welded stringers were conducted under constant amplitude and spectrum loading conditions. Results were compared with the results of "classical" LBW stiffened panels (with no crenellations) having equal weight and tested under the same conditions. The new panel design with crenellations showed substantially longer fatigue lives under constant amplitude loading. This gain significantly improved under spectrum (Mini-Twist) loading fatigue tests. This paper presents the first FCP test results of a comprehensive ongoing program which investigates the benefits and potential role of crenellations on welded Alalloy and steel structures. Further issues including microstructural examinations, numerical investigations, fitness for service analysis and residual strength aspects will be topics of another communication.

ICAF 2011 Structural Integrity: Influence of Efficiency and Green Imperatives, 2011

Materials Science and Technology, 1996

The recrystallisation behaviour and its effect on the crystallographic texture during solution he... more The recrystallisation behaviour and its effect on the crystallographic texture during solution heat treatment ol'thick aluminium alloy 7010 plates has been studied both on commercially hot rolled plates and on laboratory specimens deformed in plane strain compression. In addition to ...