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Ti-6A1-4V composites
Fatigue Abstracts This section contains abstracts of selected articles, technical reports, dissertations and patents concerned with fatigue. It is prepared in collaboration with Materials Information, a joint service of The Institute of Materials and ASM International. Readers wishing to obtain the full text of articles abstracted here should contact either: The Institute of Materials, 1 Carlton House Terrace, London SW1Y 5DB, UK, or: ASM International, Metals Park, OH 44073, U S A (not International Journal of Fatigue). The fees charged for photocopying articles are £7.00 for the first ten pages and £3.00 per additional ten pages (UK office), or $10.00 for the first ten pages and $4.00 per additional ten pages (US Office).
Short fatigue crack growth and J - R curve behavior of particulate A1203reinforced A1(2014) alloy. Wang, Z. and Zhang, J. Mater. Sci. Eng. A (1 Nov. 1993) AI71 (1-2), 85-94
The characteristics of short fatigue crack growth from a sharp notch and the behaviour of the J-R curve of 10% A1203 particulate-reinforced A1(2014) alloy were studied through three-point bend tests. A new single-specimen method for using this method were similar to those obtained from conventional testing. By considering the results of optical observations, scanning electron microscopic fractography and microhardness measurements, it was found that there are several regimes of crack growth behaviour, and each regime shows distinct crack-extension mechanisms. Graphs, photomicrographs, 34 ref. Structural analysis of boraluminium fatigue damage. Aphanasov, V.N. and Karimbaev, T.D. Sci. Eng. Compos. Mater. (1993) 2(4), 227-235 A structural model for estimating fatigue strength in composite materials (CM) is suggested. It is based on a structural theory of CM deformation and strength now being developed as well as on the results of numerous experimental studies on the fatigue strength of metallic CM (MCM) beams. To clarify this issue, following is a brief description of (i) the abovementioned structural model of CM deformation and strength, (ii) testing technique and character of beam fatigue damage for aluminium beams reinforced with boron fibres, (iii) calculation of the stress-deformed state of beams while vibrating, according to the first bending mode with fixed vibration amplitude, and (iv) a structural model of fatigue strength evaluation. Photomicrographs, 8 ref. Effects of microstructure on the strain-controlled fatigue behavior of an aluminum-alloy/ceramic-particlecomposite. Srivatsan, T.S. and Lavernia, E.J. Compos. Sci. Technol. (1993) 49(4), 303-313
A study has been made to understand the cyclic fatigue and cyclic fracture characteristics of a cast aluminium alloy (A356) metal matrix discontinuously reinforced with particular silicon carbide. The A1/SiCp composite was strained to failure over a range of strain amplitudes giving lives of < 104 cycles to failure. The specimens were cycled by using tension--compression loading under total strain control. In the as-cast condition, the A1 aHoy/ceramic composite displayed combinations of cyclic hardening and softening to failure at higher cyclic-strain amplitudes, and progressive softening to failure at low cyclic-strain amplitudes. The spray-atomized and deposited composite exhibited softening to failure at the higher cyclic-strain amplitudes and combinations of softening and hardening behaviour at the lower strain amplitudes. The observed hardening and softening behaviour is a mechanical effect and attributed to concurrent and competing influences of interactions between cyclic deformation and composite microstructurc during cyclic straining. The processed microstructure exhibited better cyclic ductility and cyclic-strain resistance than the as-cast composite microstructure. The cyclic fatigue behaviour of the alloy is briefly interpreted in the light of composite microstructural effects, plastic strain amplitude, and concomitant response stress. Graphs, photomicrographs, 55 ref. Oxidative thermal fatigue of SCS-6/Ti-6A1-4V composites. Thomin, S.H.
and Dunand, D.C. Proc. Conf. Mechanisms and Mechanics of Composites Fracture, Pittsburg, PA, USA, 17-21 Oct. 1993, pp. 221-234 A titanium alloy (Ti-6A1-4V) reinforced with continuous SiC fibres (SCS-6) was subjected to up to 2000 thermal cycles between 200 and 700°C in air. The mechanical properties measured in bending deteriorate with an increasing number of cycles, as a result of cracks emanating from the surface of the specimens. These cracks are caused by the cyclically varying internal stresses (resulting from the temperature cycles and the mismatch of thermal expansion between fibres and matrix) and oxygen (leading to oxide formation and matrix embrittlement). The microstructure and properties of the air-cycled composites are compared with those of as-received, air-aged, and argon0142-1123/94/080585-10 (~) 1994 B u t t e r w o r t h - H e i n e m a n n L t d
cycled composites. The state of stress in the composite is determined using an analytical three-shell model considering elastic stresses and stress relaxation by matrix creep at high temperature. These results are used to estimate the crack progagation rate which can only be accounted for if the O embrittlement of the matrix is considered. Graphs, photomicrographs, 37 ref. Mechanisms of fatigue damage and failure of a SCS-6/Ti-15-3 comlmsite.
Majumdar, B.S. and Newaz, G.M. (Battelle) Proc. Conf. Mechanisms and Mechanics of Composites Fracture, Pittsburg, PA, USA, 17-21 Oct. 1993, pp. 77-90 The fatigue fracture mechanisms and their sequence were evaluated for a 0 ° SCS-6/Ti-15-3 MMC at room temperature (Ti-15-3 is Ti-15V3Cr-3AI-3Sn). In the intermediate life regime (Regime 2), the dominant damage mechanism was matrix fatigue cracking. Experiments with MMCs having different volume fraction of fibres confirmed that in this regime the fatigue life was controlled by the imposed strain range. Additionally, in Regime 2, MMC life was comparable to matrix life, and the important role of matrix fatigue in MMC failure was metallurgically confirmed through observation of channel-type dislocation structures in the MMC, that are characteristic of persistent slip bands in b.c.c, metals. Reaction-zone cracks played the role of preferred slip nucleation sites, those slip bands finally evolving into persistent slip bands and matrix cracks. In the low-life regime (Regime 2), matrix cracks were not observed, and fractography revealed overload fracture. Additionally, extensive debonding was observed when tested sampled were polished metallographically. A mechanism of debonding is provided, and it is suggested that rubbing following debonding may have been responsible for fibre damage and MMC failure after a limited number of cycles, at cyclic maximum stresses below the monotonic tensile strength. Graphs, photomicrographs. 26 ref. Fatigue crack initiation and growth characteristics of SIC whisker reinforced aluminum ahoy composites. Toda, H. and Kobayashi, T. Proc. Conf. Mechanisms and Mechanics of Composites Fracture, Pittsburgh, PA, USA, 17-21 Oct. 1993, pp. 55-63
Short fatigue crack tests and long fatigue crack propagation tests were carded out. The results indicate that short cracks initiate and grow under the threshold stress intensity range for long fatigue cracks as generally reported in unreinforced alloys. In addition, many cracks tend to initiate and grow simultaneously and interact with each other in metal-matrix composites (such as alumnium base alloy 6061 reinforced with SiC whiskers). Further, statistical scatter in crack growth rate of considerably short cracks, for example, < approx. 200 ttm for underageing condition, is discussed, taking interaction between a plastic zone and whiskers into account. On the other hand long crack progagation behaviour is characterized by premature fracture of whiskers ahead of the crack tip. Therefore, crack closure from asperity wedging and diminished crack driving force caused by crack deflection become remarkable with extension of the plastic zone size; fatigue crack growth resistance thereby increases with increasing plastic zone size. Graphs, photomicrographs, 12 ref. Thermo-mechaniral fatigue behavior of a cross-ply SCS-6/Ti-15-3 metalmatrix composite. Mall, S. and Schubbe, J.J. Compos. Sci. Technol. (Jan 1994) 50(1), 49-57
The thermomechanical fatigue behaviour of a cross-ply laminate of a siliconcarbide-fibre-reinfored titanium-matrix composite, SCS-6/Ti-15-3 (Ti-15V-3A1-3Sn-3Cr), has been investigated. Two sets of tests involving in-phase and out-of-phase thermal-mechanical fatigue from 149 to 427°C at different stress levels, which were below and above the static first ply failure strength of the laminate, were conducted. Fatigue damage originated at the fibre-matrix interface of 90~ fibres, and progressed as transverse cracking in the matrix. However, final damage modes were dependent on stress level and test conditions. Furthermore, fatigue lives were also found to be dependent on test conditions at a given stress level. Graphs, photomicrographs, 11 ref.
Fatigue, 1994, Vol 16, November 585
Short fatigue crack growth and J - R curve behavior of particulate A1203reinforced A1(2014) alloy. Wang, Z. and Zhang, J. Mater. Sci. Eng. A (1 Nov. 1993) AI71 (1-2), 85-94
The characteristics of short fatigue crack growth from a sharp notch and the behaviour of the J-R curve of 10% A1203 particulate-reinforced A1(2014) alloy were studied through three-point bend tests. A new single-specimen method for using this method were similar to those obtained from conventional testing. By considering the results of optical observations, scanning electron microscopic fractography and microhardness measurements, it was found that there are several regimes of crack growth behaviour, and each regime shows distinct crack-extension mechanisms. Graphs, photomicrographs, 34 ref. Structural analysis of boraluminium fatigue damage. Aphanasov, V.N. and Karimbaev, T.D. Sci. Eng. Compos. Mater. (1993) 2(4), 227-235 A structural model for estimating fatigue strength in composite materials (CM) is suggested. It is based on a structural theory of CM deformation and strength now being developed as well as on the results of numerous experimental studies on the fatigue strength of metallic CM (MCM) beams. To clarify this issue, following is a brief description of (i) the abovementioned structural model of CM deformation and strength, (ii) testing technique and character of beam fatigue damage for aluminium beams reinforced with boron fibres, (iii) calculation of the stress-deformed state of beams while vibrating, according to the first bending mode with fixed vibration amplitude, and (iv) a structural model of fatigue strength evaluation. Photomicrographs, 8 ref. Effects of microstructure on the strain-controlled fatigue behavior of an aluminum-alloy/ceramic-particlecomposite. Srivatsan, T.S. and Lavernia, E.J. Compos. Sci. Technol. (1993) 49(4), 303-313
A study has been made to understand the cyclic fatigue and cyclic fracture characteristics of a cast aluminium alloy (A356) metal matrix discontinuously reinforced with particular silicon carbide. The A1/SiCp composite was strained to failure over a range of strain amplitudes giving lives of < 104 cycles to failure. The specimens were cycled by using tension--compression loading under total strain control. In the as-cast condition, the A1 aHoy/ceramic composite displayed combinations of cyclic hardening and softening to failure at higher cyclic-strain amplitudes, and progressive softening to failure at low cyclic-strain amplitudes. The spray-atomized and deposited composite exhibited softening to failure at the higher cyclic-strain amplitudes and combinations of softening and hardening behaviour at the lower strain amplitudes. The observed hardening and softening behaviour is a mechanical effect and attributed to concurrent and competing influences of interactions between cyclic deformation and composite microstructurc during cyclic straining. The processed microstructure exhibited better cyclic ductility and cyclic-strain resistance than the as-cast composite microstructure. The cyclic fatigue behaviour of the alloy is briefly interpreted in the light of composite microstructural effects, plastic strain amplitude, and concomitant response stress. Graphs, photomicrographs, 55 ref. Oxidative thermal fatigue of SCS-6/Ti-6A1-4V composites. Thomin, S.H.
and Dunand, D.C. Proc. Conf. Mechanisms and Mechanics of Composites Fracture, Pittsburg, PA, USA, 17-21 Oct. 1993, pp. 221-234 A titanium alloy (Ti-6A1-4V) reinforced with continuous SiC fibres (SCS-6) was subjected to up to 2000 thermal cycles between 200 and 700°C in air. The mechanical properties measured in bending deteriorate with an increasing number of cycles, as a result of cracks emanating from the surface of the specimens. These cracks are caused by the cyclically varying internal stresses (resulting from the temperature cycles and the mismatch of thermal expansion between fibres and matrix) and oxygen (leading to oxide formation and matrix embrittlement). The microstructure and properties of the air-cycled composites are compared with those of as-received, air-aged, and argon0142-1123/94/080585-10 (~) 1994 B u t t e r w o r t h - H e i n e m a n n L t d
cycled composites. The state of stress in the composite is determined using an analytical three-shell model considering elastic stresses and stress relaxation by matrix creep at high temperature. These results are used to estimate the crack progagation rate which can only be accounted for if the O embrittlement of the matrix is considered. Graphs, photomicrographs, 37 ref. Mechanisms of fatigue damage and failure of a SCS-6/Ti-15-3 comlmsite.
Majumdar, B.S. and Newaz, G.M. (Battelle) Proc. Conf. Mechanisms and Mechanics of Composites Fracture, Pittsburg, PA, USA, 17-21 Oct. 1993, pp. 77-90 The fatigue fracture mechanisms and their sequence were evaluated for a 0 ° SCS-6/Ti-15-3 MMC at room temperature (Ti-15-3 is Ti-15V3Cr-3AI-3Sn). In the intermediate life regime (Regime 2), the dominant damage mechanism was matrix fatigue cracking. Experiments with MMCs having different volume fraction of fibres confirmed that in this regime the fatigue life was controlled by the imposed strain range. Additionally, in Regime 2, MMC life was comparable to matrix life, and the important role of matrix fatigue in MMC failure was metallurgically confirmed through observation of channel-type dislocation structures in the MMC, that are characteristic of persistent slip bands in b.c.c, metals. Reaction-zone cracks played the role of preferred slip nucleation sites, those slip bands finally evolving into persistent slip bands and matrix cracks. In the low-life regime (Regime 2), matrix cracks were not observed, and fractography revealed overload fracture. Additionally, extensive debonding was observed when tested sampled were polished metallographically. A mechanism of debonding is provided, and it is suggested that rubbing following debonding may have been responsible for fibre damage and MMC failure after a limited number of cycles, at cyclic maximum stresses below the monotonic tensile strength. Graphs, photomicrographs. 26 ref. Fatigue crack initiation and growth characteristics of SIC whisker reinforced aluminum ahoy composites. Toda, H. and Kobayashi, T. Proc. Conf. Mechanisms and Mechanics of Composites Fracture, Pittsburgh, PA, USA, 17-21 Oct. 1993, pp. 55-63
Short fatigue crack tests and long fatigue crack propagation tests were carded out. The results indicate that short cracks initiate and grow under the threshold stress intensity range for long fatigue cracks as generally reported in unreinforced alloys. In addition, many cracks tend to initiate and grow simultaneously and interact with each other in metal-matrix composites (such as alumnium base alloy 6061 reinforced with SiC whiskers). Further, statistical scatter in crack growth rate of considerably short cracks, for example, < approx. 200 ttm for underageing condition, is discussed, taking interaction between a plastic zone and whiskers into account. On the other hand long crack progagation behaviour is characterized by premature fracture of whiskers ahead of the crack tip. Therefore, crack closure from asperity wedging and diminished crack driving force caused by crack deflection become remarkable with extension of the plastic zone size; fatigue crack growth resistance thereby increases with increasing plastic zone size. Graphs, photomicrographs, 12 ref. Thermo-mechaniral fatigue behavior of a cross-ply SCS-6/Ti-15-3 metalmatrix composite. Mall, S. and Schubbe, J.J. Compos. Sci. Technol. (Jan 1994) 50(1), 49-57
The thermomechanical fatigue behaviour of a cross-ply laminate of a siliconcarbide-fibre-reinfored titanium-matrix composite, SCS-6/Ti-15-3 (Ti-15V-3A1-3Sn-3Cr), has been investigated. Two sets of tests involving in-phase and out-of-phase thermal-mechanical fatigue from 149 to 427°C at different stress levels, which were below and above the static first ply failure strength of the laminate, were conducted. Fatigue damage originated at the fibre-matrix interface of 90~ fibres, and progressed as transverse cracking in the matrix. However, final damage modes were dependent on stress level and test conditions. Furthermore, fatigue lives were also found to be dependent on test conditions at a given stress level. Graphs, photomicrographs, 11 ref.
Fatigue, 1994, Vol 16, November 585