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Processing and mechanical properties of lightweight structural composites
This section contains abstracts of selected articles, technical reports, dissertations and patents concerned with fatigue. The abstracts are prepared in collaboration with Materials Information, a joint service of The Institute of Metals and ASM International. Readers wishing to obtain the full text of articles abstracted here should contact either: The Institute of Metals, 1 Carlton House Terrace, London S W l Y 5DB, UK, or: ASM International, Metals Park, OH 44073, USA (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). Composites Damage initiation and growth in fibre-reinforced M M C a . Saff, C.R., Harmon, D.M. and Johnson, W.S. J. Met. Nov. 1 9 8 8 4 0 , (11), 5 8 - 6 3 Oamage in continuous-fibre-reinforcad metal-matrix (eg B/AI) composites can be quite complex because of the number of constituents (eg fibre, matrix or fibre/matrix interface) that can fail, Multldirectional lay-ups have an even greater number of possible damage orientations, Based on the simplifying assumption of equivalent constituent strain states in the absence of damage, a strain-based failure criterion may be applied to determine when and where initial damage will occur, Depending on the relative fatigue behaviour of the fibre and matrix, and the interface properties, the failure modes can be grouped into four categories: matrix dominated damage; fibre dominated damage; self-similar fatigue damage growth; and fibre/matrix interface failure. 15 refs.
Damage tolerance in discontinuously reinforced metal-matrix composites. Rack, H.J. and Ratnaparkhi, P. J. Met. Nov. 1 9 8 8 4 0 , (11), 5 5 - 5 7 Renewed interest in discontinuously reinforced metal-mattix (eg 6061,2124 AI) composites for primaw structural applications has stimulated further attention to their damage tolerance behaviour, In general, the fatigue and fracture toughness behaviour of particulate-reinforced MMCs can be described utilizing linear-elastic fracture mechanics, However. the generalized use of this methodology for whisker or short fibre-reinforced (eg SiC) MMCs. where reinforcement orientation effects may be paramount, must be approached with caution. 17 refs
Processing and mechanical properties of lightweight structural composites. Lewandowski, J.J. SAMPE Q. Jan. 1989 20, (2), 3 3 - 3 7 The properties of discontinuous metal matrix composites depend sensitively on a variety of processing parameters, including choice of reinforcement and type (eg plate, particulate. whisker), vol.% reinforcement, size and Sizedistribution of reinforcement, and matrix characteristics and properties Techniques available to incorporate reinforcement into potential matrices include casting, powder metallurgy, and spray deposition techniques, In addition, post-processing treatments, such as thermomechanical treatment and heat treatment, may be particularly important in producing optimum properties. Recent work which has focused on structure-properW relationships in AI alloy metal matrix systems is reviewed, 34 refs,
Plane bending fatigue of alumina fibre-reinforced aluminium composites a t t e m p e r a t u r e s ~ n 2 ~ K. Mabuchi, H. and Nakayama, J. Jpn. Inst. Light Met. Oct. 1988 38, (10), 6 0 8 - 6 1 3 (in Japanese) To clarify the fatigue properties of fibre-reinforced metals, four-point bending tests and plane bending fatigue tests were carried out on Al=O~ fibre/AI composites at temperatures between 295673 K. The behaviour of elastic and plastic deformation of this composite was shown by stress-strain curves in the bending tests to be closely associated with that of the matrix. In the cyclic bending stress, stress-strain curves of the loading-unloading tests were accompanied by plastic strain within the ranges which depended on the maximum bending stress and the testing temperature. In the fatigue tests, the relationship between the plastic strain range and fatigue life was expressed well by the Coffin-Manson relation. Microstructural observations suggest that the cyclic plastic deformation in the matrix is a dominating factor in the properties of fatigue for these composites. 7 refs
Corrosion
both frequencies of 0.3 and 30 Hz. (5) Under the freely corroding condition, the crystallographic fracture mode was observed near the threshold for stainless steels, while the fracture surfaces were dissolved for high tensile and C steels. (6) Under cathodic protection, the fracture mode was transgranular at the region of AK < 5 MPa m1/2, while the intergranular cracking was formed at the region of tkK >t 5 MPa m 1/2.
E f f e c t of environments on fatigue behaviour of a dual-phase steel. Ai, S. and Wang, Z Acta Metal/. Sin. (China) J u n e 1988 24, (3) A 1 9 3 - A 1 9 9 (in Chinese) Corrosion fatigue behaviour of an as-rolled dual-phase steel has been investigated in tap water or 3.5% NaCI aqueous solution under fun immersion and intermittent wetting, It was found that in comparison with the data in air, exposure to either tap water or salt water results in a substantial reduction in fatigue life and intermittent wetting later shows the most harmful effects. However, under the same aggressive condition, the corrosion environments become more and more harmful while the stress level decreases. A combined observation of fracture surface with the flat free surface in the SEM shows that corrosion fatigue cracks often initiate at corrosion pits resulting from anodic dissolution. In addition, the interaction between H and crack tips is considered another important factor which controls the crack initiation and propagation in corrosion fatigue. The martensite exhibits a higher resistance to corrosion fatigue than the ferrite matrix 13 refs.
Influence of the lubricant on the pitting capacity of gears. Go/I, S. Antriebstechnik 1987 26, (5), 18, 2 1 - 2 2 , 24 (in German) The pitting fatigue of gears is essentially influenced by the viscosity and the additives of the lubricant used, While decreasing operating viscosity leads to a reduced flank life and wide-area flank spallings, the influence of the additives can only be determined by tests A pitting test was therefore developed on behalf of the German Power Transmission Engineering Research Association (FVA) and appropriate tests carried out. the details of which are reported. A clear operating life differentiation is possible despite the wide spread of the test results. Materials studied include steels 16MnCr5E and 15CrNi6E. 13 refs,
Influence o f s t r e s s r a t i o a n d m a t e r i a l properties on effective s t r e ~ range ratio and crack growth. Kumar, R. and Garg, S.B,L. Eng. Fract. Mech. 1989 32, (2), 1 9 6 - 2 0 2 The influence of stress ratio R and yield strength a v on crack closure and fatigue crack growth were studied. Crack closure and crack growth experiments were performed on 6063-T6 and 6061-T6 AI-alloys of 0, 2, 3 and 6% prestrains Crack closure stresses were measured using a side edge measurement technique with a clip on displacement gauge. The gauge was placed across the side edge notch of the specimen. It was found that. after crack initiation, the crack closure stabilized. The closure load was, however, found to be function of R and <~y, Fatigue crack growth rate is found to be dependent upon R, Uand &K A model Uancl da/dNhas been developed. 12 refs.
The measurement of near-threshold fatigue crack growth. Taylor, D. Eng. Fract. Mech. 1989 32, (2), 177-181 Near-threshold fatigue crack propagation rates have been measured in an AI bronze alloy (BS1400 AB2) using four different test methods: conventional load shedding; load shedding at constant Kmax; stress-relief annealing and the testing of inherent surface defects. All four methods gave the same results, both for the threshold stress intensity factor. AKth, and for crack propagation rates in the near-threshold regime. It has been suggested that experimental results in this regime are strongly influenced by stress history and defect type. The present series of tests shows that this is not the case for this alloy; this provides evidence for the validity of the stress intensity threshold as an engineering parameter. 16 refs.
Near-threshold fatigue crack growth properties and frectogrephic features of various steels in 3% NaCI aqueous solution. Shimodaira, M., Matsuoka, S. and Masuda, H. J. Soc. Mater. ScL, Jpn. Sept. 1988 37, (420), 1 0 9 7 - 1 1 0 3 (in Japanese)
Fatigue strength of aluminium alloys. XX. Takeuchi, K. Kei Kinzoku Yosetsu (J. Light. Met. Weld. Constr.) 1988 26, (12), 5 6 1 - 5 7 0
Near-threshold fatigue crack growth properties and fractographic features in 3% NaCI aqueous solution were studied for high tensile steels SMSOB and HT80. C steel S45C and stainless steels SUS304 and SUS403, under the condition where crack closure did not occur. The results obtained are summarized as follows: (1) In air. fatigue crack growth properties were independent of the type of materials. The threshold values. &K. were equal to about 2.5 MPa m 1/2. (2) Under the freely corroding condition in 3% NaCI solution. fatigue crack growth properties at a frequency of 30 Hz coincided with those in air, when the stress intensity range, AK. was higher than 3 MPa m 1/2. However, the AK~ values were about 1 MPa mr/Tfor high tensile and C steels, and about 1.7 MPa m 1/2 for stainless steels. (3) Decrease in frequency from 30 to 0.3 Hz resulted in a sixfold acceleration of crack growth rate under the freely corroding condition. (4) Under cathodic protection. fatigue crack growth properties including threshold were coincident with those in air at
Studies on the effects of environment and corrosion on the fatigue strength of AI alloys and prevention of corrosion area are reviewed. Effects of vacuum, relative humidity, gases. and organic compound coating on the fatigue strength of alloys such as 1100-H14. 2014T6. 5083-0. 6061-1-6, AZ63-H14. etc. have been investigated. Effects of atmosphere, drinking water, and 3% salt water on the fatigue strength of many AI alloys including 6NO1-T5, 508~Hl12, 7NO1-T5. and 7003-T5 were tested. To prevent corrosion fatigue, various types of surface treatments (lanolin resin coating, AI-2Zn spray, vapour blast, anodic oxidation, etch primer and epoxy resin coating, phenol-based varnish, Alchrome #1200, AI/Zn pigments, shot peening, etc) have been tried and the results are summarized. A cathode anticorrosion method was applied for 7000 series AI alloys. However. the effect was not clear. 28 refs.
Int J Fatigue July 1989
(in Japanese)
279
Damage tolerance in discontinuously reinforced metal-matrix composites. Rack, H.J. and Ratnaparkhi, P. J. Met. Nov. 1 9 8 8 4 0 , (11), 5 5 - 5 7 Renewed interest in discontinuously reinforced metal-mattix (eg 6061,2124 AI) composites for primaw structural applications has stimulated further attention to their damage tolerance behaviour, In general, the fatigue and fracture toughness behaviour of particulate-reinforced MMCs can be described utilizing linear-elastic fracture mechanics, However. the generalized use of this methodology for whisker or short fibre-reinforced (eg SiC) MMCs. where reinforcement orientation effects may be paramount, must be approached with caution. 17 refs
Processing and mechanical properties of lightweight structural composites. Lewandowski, J.J. SAMPE Q. Jan. 1989 20, (2), 3 3 - 3 7 The properties of discontinuous metal matrix composites depend sensitively on a variety of processing parameters, including choice of reinforcement and type (eg plate, particulate. whisker), vol.% reinforcement, size and Sizedistribution of reinforcement, and matrix characteristics and properties Techniques available to incorporate reinforcement into potential matrices include casting, powder metallurgy, and spray deposition techniques, In addition, post-processing treatments, such as thermomechanical treatment and heat treatment, may be particularly important in producing optimum properties. Recent work which has focused on structure-properW relationships in AI alloy metal matrix systems is reviewed, 34 refs,
Plane bending fatigue of alumina fibre-reinforced aluminium composites a t t e m p e r a t u r e s ~ n 2 ~ K. Mabuchi, H. and Nakayama, J. Jpn. Inst. Light Met. Oct. 1988 38, (10), 6 0 8 - 6 1 3 (in Japanese) To clarify the fatigue properties of fibre-reinforced metals, four-point bending tests and plane bending fatigue tests were carried out on Al=O~ fibre/AI composites at temperatures between 295673 K. The behaviour of elastic and plastic deformation of this composite was shown by stress-strain curves in the bending tests to be closely associated with that of the matrix. In the cyclic bending stress, stress-strain curves of the loading-unloading tests were accompanied by plastic strain within the ranges which depended on the maximum bending stress and the testing temperature. In the fatigue tests, the relationship between the plastic strain range and fatigue life was expressed well by the Coffin-Manson relation. Microstructural observations suggest that the cyclic plastic deformation in the matrix is a dominating factor in the properties of fatigue for these composites. 7 refs
Corrosion
both frequencies of 0.3 and 30 Hz. (5) Under the freely corroding condition, the crystallographic fracture mode was observed near the threshold for stainless steels, while the fracture surfaces were dissolved for high tensile and C steels. (6) Under cathodic protection, the fracture mode was transgranular at the region of AK < 5 MPa m1/2, while the intergranular cracking was formed at the region of tkK >t 5 MPa m 1/2.
E f f e c t of environments on fatigue behaviour of a dual-phase steel. Ai, S. and Wang, Z Acta Metal/. Sin. (China) J u n e 1988 24, (3) A 1 9 3 - A 1 9 9 (in Chinese) Corrosion fatigue behaviour of an as-rolled dual-phase steel has been investigated in tap water or 3.5% NaCI aqueous solution under fun immersion and intermittent wetting, It was found that in comparison with the data in air, exposure to either tap water or salt water results in a substantial reduction in fatigue life and intermittent wetting later shows the most harmful effects. However, under the same aggressive condition, the corrosion environments become more and more harmful while the stress level decreases. A combined observation of fracture surface with the flat free surface in the SEM shows that corrosion fatigue cracks often initiate at corrosion pits resulting from anodic dissolution. In addition, the interaction between H and crack tips is considered another important factor which controls the crack initiation and propagation in corrosion fatigue. The martensite exhibits a higher resistance to corrosion fatigue than the ferrite matrix 13 refs.
Influence of the lubricant on the pitting capacity of gears. Go/I, S. Antriebstechnik 1987 26, (5), 18, 2 1 - 2 2 , 24 (in German) The pitting fatigue of gears is essentially influenced by the viscosity and the additives of the lubricant used, While decreasing operating viscosity leads to a reduced flank life and wide-area flank spallings, the influence of the additives can only be determined by tests A pitting test was therefore developed on behalf of the German Power Transmission Engineering Research Association (FVA) and appropriate tests carried out. the details of which are reported. A clear operating life differentiation is possible despite the wide spread of the test results. Materials studied include steels 16MnCr5E and 15CrNi6E. 13 refs,
Influence o f s t r e s s r a t i o a n d m a t e r i a l properties on effective s t r e ~ range ratio and crack growth. Kumar, R. and Garg, S.B,L. Eng. Fract. Mech. 1989 32, (2), 1 9 6 - 2 0 2 The influence of stress ratio R and yield strength a v on crack closure and fatigue crack growth were studied. Crack closure and crack growth experiments were performed on 6063-T6 and 6061-T6 AI-alloys of 0, 2, 3 and 6% prestrains Crack closure stresses were measured using a side edge measurement technique with a clip on displacement gauge. The gauge was placed across the side edge notch of the specimen. It was found that. after crack initiation, the crack closure stabilized. The closure load was, however, found to be function of R and <~y, Fatigue crack growth rate is found to be dependent upon R, Uand &K A model Uancl da/dNhas been developed. 12 refs.
The measurement of near-threshold fatigue crack growth. Taylor, D. Eng. Fract. Mech. 1989 32, (2), 177-181 Near-threshold fatigue crack propagation rates have been measured in an AI bronze alloy (BS1400 AB2) using four different test methods: conventional load shedding; load shedding at constant Kmax; stress-relief annealing and the testing of inherent surface defects. All four methods gave the same results, both for the threshold stress intensity factor. AKth, and for crack propagation rates in the near-threshold regime. It has been suggested that experimental results in this regime are strongly influenced by stress history and defect type. The present series of tests shows that this is not the case for this alloy; this provides evidence for the validity of the stress intensity threshold as an engineering parameter. 16 refs.
Near-threshold fatigue crack growth properties and frectogrephic features of various steels in 3% NaCI aqueous solution. Shimodaira, M., Matsuoka, S. and Masuda, H. J. Soc. Mater. ScL, Jpn. Sept. 1988 37, (420), 1 0 9 7 - 1 1 0 3 (in Japanese)
Fatigue strength of aluminium alloys. XX. Takeuchi, K. Kei Kinzoku Yosetsu (J. Light. Met. Weld. Constr.) 1988 26, (12), 5 6 1 - 5 7 0
Near-threshold fatigue crack growth properties and fractographic features in 3% NaCI aqueous solution were studied for high tensile steels SMSOB and HT80. C steel S45C and stainless steels SUS304 and SUS403, under the condition where crack closure did not occur. The results obtained are summarized as follows: (1) In air. fatigue crack growth properties were independent of the type of materials. The threshold values. &K. were equal to about 2.5 MPa m 1/2. (2) Under the freely corroding condition in 3% NaCI solution. fatigue crack growth properties at a frequency of 30 Hz coincided with those in air, when the stress intensity range, AK. was higher than 3 MPa m 1/2. However, the AK~ values were about 1 MPa mr/Tfor high tensile and C steels, and about 1.7 MPa m 1/2 for stainless steels. (3) Decrease in frequency from 30 to 0.3 Hz resulted in a sixfold acceleration of crack growth rate under the freely corroding condition. (4) Under cathodic protection. fatigue crack growth properties including threshold were coincident with those in air at
Studies on the effects of environment and corrosion on the fatigue strength of AI alloys and prevention of corrosion area are reviewed. Effects of vacuum, relative humidity, gases. and organic compound coating on the fatigue strength of alloys such as 1100-H14. 2014T6. 5083-0. 6061-1-6, AZ63-H14. etc. have been investigated. Effects of atmosphere, drinking water, and 3% salt water on the fatigue strength of many AI alloys including 6NO1-T5, 508~Hl12, 7NO1-T5. and 7003-T5 were tested. To prevent corrosion fatigue, various types of surface treatments (lanolin resin coating, AI-2Zn spray, vapour blast, anodic oxidation, etch primer and epoxy resin coating, phenol-based varnish, Alchrome #1200, AI/Zn pigments, shot peening, etc) have been tried and the results are summarized. A cathode anticorrosion method was applied for 7000 series AI alloys. However. the effect was not clear. 28 refs.
Int J Fatigue July 1989
(in Japanese)
279