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Growth of short cracks of A5376CL1 steel under fatigue loading in 3.5% NaCL solution
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 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 SW1Y 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 Fatigue s t r e n g t h o f f a r r o c e m e n t in a m a r i n e e n v i r o n m e n t . Ramli, M. J. Ferrocement Oct. 1988 18, (4), 397-404 The fatigue behaviour of ferrocement forms an important characteristic of certain structural elements, especially in civil or mechanical engineering. The material is not only versatile but also possesses a high degree of elasticity and a cracking resistance which is of great value in construction. An experimental study was conducted on ferrocement composite to investigate its fatigue properties in a marine environment. Galvanized wire netting was used as a reinforcing mesh. The effect of corrosion fatigue on the ferrocement composite was considered with particular attention given to fatigue life cycles of the specimen and to cracking and deflection behaviour. The test results indicate a higher fatigue strength for seven layers of 0.71 mm galvanized wire netting under continuous exposure in sea water. The increase in overall stiffness of the composite was due to the wedging effect of salt deposits, thus preventing further crack development. 6 refs.
Fatigue crack growth characteristics o f ARALL-1. Interim Report, A u g u s t 1gT-Januery 1988. Ruschau, J. J. University of Dayton Report No AD-A196 185/3/XAB M a y 1988 Constant-amplitude and spectrum fatigue crack growth rate properties were evaluated for ARALL-1 AI laminate. Testing was performed on M(T) specimens under both laboratory air and high-humidity conditions. Crack length monitoring was performed on each AI ply utilizing electrical potential drop techniques to gain a better insight into the fatigue cracking process. Results indicate an outstanding superiority of ARALL* 1 in terms of fatigue crack growth resistance over conventionally produced 7000 series AI. Fatigue cracking in each of the AI plies was fairly uniform, with no large discrepancies in total crack length or growth rates observed between the various plies. For samples tested under a fighter-type load history, the effect of high humidity was actually beneficial, with fatigue crack growth rates typically onehalf of those developed under laboratory air conditions. Explanations based on increased delamination regions are offered for this behaviour.
Driving forces for c o m p o s i t e interface f a t i g u e cracks. Chan, K. S. and Davidson, D. L. Eng. Fract. Mech. 1989 33, (3), 451-466 The relevant fracture mechanics parameter for representing the crack extension driving force of interface fatigue cracks has been studied both analytically and experimentally. Using the oscillatory stress singularities for open-tip interface cracks, an equivalent stress intensity range, defined in terms of the J-integral and evaluated on the basis of the applied loads, is proposed end shown to correlate fatigue crack growth data of interface cracks in fibre-reinforced composites (eg Mg/AI203; Ti/B). Two complementary procedures for determining the local &K of interface fatigue cracks using experimental crack opening displacements data are presented. Differences between the local and global AK are thought to be due to residual stresses which originated during fabrication. Graphs. 38 refs.
A study on t h e characteristics of creep and fatigue in FRM. h Creep characteristics. Kim, S.-Y., Hyun, C.-Y. and Sung, H.-S, J. Korean Inst. Met, 1989 27, (2), 179-187 (in Korean) The fabrication and creep characteristics of AI-0.65Fe composites reinforced with stainless steel (Fe-0.18C-18.45Cr-8.46Ni-0.73Mn-0.33Mo) fibres have been studied. The Ni-coated, Cu-coated and bare fibres have been tested to examine the effect of fibre surface characteristics. To make various fibre volume fraction composite specimens, the liquid casting method has been applied. Creep characteristics such as the rupture time and the steady-state creep rate have been investigated in the stress range 22.47-72.95 MPa at 537 K. The rupture time was increased with Vf. The stress exponent (n) has been found to be 21.2-114. In the case of Vf 1.6, 2.88%, 100 h rupture stress (~¢) was less than the theoretical value calculated by the ruleof-mixture (RAM). On the other hand, Vf 3.52% showed a ¢rc value close to RaM, and coated composites were even larger than RaM. Several intermetallic compounds such as AINi, AI2Cu, AIsFe3 and AI13Fe4 in the interface were observed by TEM. These improved the wettability of the fibre on the matrix and the creep strength due to obstruction of dislocation movement. Tested specimens showed dislocation cells at the substructure. The dislocation density decreased from interface to matrix. Graphs, photomicrographs. 17 refs.
Int J Fatigue January 1990
Factors influencing t h e f a t i g u e b e h a v i o u r o f ferrous-based l a m i n a t e d composites. (Dissertation). Wittenauer, J. P. Diss. Abstr. Int. M a y 1988 48, (11), Pp 179 Metallic-based laminates offer promise as damage-tolerant materials under conditions of fatigue loading. It has long been known that laminated metals can exhibit improved impact properties due to delaminations and the associated crack arrest phenomena that have been observed to occur at weak interlsminar boundaries, To extend this crack arrest behaviour to conditions of fatigue loading, a broed-bessd experimental programme has been conducted using ultra-high-carbon steel as a base material. In the first phase, a shear test was used to evaluate factors influencing the interleminar bonding strength between adjacent steel plies. A knowledge of bond strength is critical if crack arrest mechanisms are to be optimized. It was found that the bond strength among steel plies remains quite high over s wide range of thermomechanical processing routes. A desire to obtain lower interlaminar bond strengths led to the introduction of secondary metals to be used as weak interleafs between the high-strength ferrous plies. Two meterials--Cu and Fe containing 3% Si--were evaluated and found to be suitable interleaf candidates. In the second phase, a variety of laminates consisting of layers of steel interleaved with Cu or Fe-Si were prepared. The fatigue behaviour of laminates tested in the crack arrest orientation showed that a range of crack growth beheviour is possible, ranging from crack arrest at each interleaf to uninhibited crack propagation. For laminates containing a Cu interleaf, it was shown that crack arrest end life improvement are optimized when ply thickness is increased, when interleaf thickness is decreased, or when ferrous ply yield strength is increased. No life improvement was obtained through use of a ferrous interleaf. Finally, a micromechanical model has been introduced which explains the experimentally observed crack growth behaviour. By seeking an understanding of near-crack-tip stresses as a fatigue crack propagates toward a weak interface, factors influencing local delamination and crack arrest can be fundamentally understood. A previously developed applied mechanics model was used for this purpose. The model used supports the experimental results and has emerged as a potentially useful tool for predicting crack growth behaviour in other materials systems.
Corrosion The microstructuros o f m i l d steels and corrosion fatigue. Xing, Z., Huan~: S., Song, Y. and Tu, M. Acta Metall. Sin. (China) Dec. 1988 24, (6), B398-B403 (in Chinese) The fatigue crack propagation beheviour of two mild steels with various microstructures in 3.5% NaCI solution or atmosphere was studied. It was revealed that the microstructures of the steel and the frequency have a considerable influence on the corrosion fatigue strength. The relation between the crack closure effect and the electrochemical conditions was discussed. Corrosion fatigue mechanisms, which consider the effects of hydrogen embrittlement and anode dissolution, respectively, were proposed. A fracture mechanism map was worked out. 9 refs.
Growth o f s h o r t cracks o f A5376CL1 steel under f a t i g u e loading in 3.5% NaCI solution. Pei, H., Yang, J. and Ke, W. Acta Metall. Sin. (China) Dec. 1988 24, (6), B393-B397 (in Chinese) The effects of environmental media, both in atmosphere and in 3.5% NaCI aqueous solution, on the growth of short cracks, in comparison with long cracks, have been investigated under fatigue loading on specimens with single-edge cracks ranging from 0.05-0.15 mm for A537CL1 steel. The growth rate of short cracks is faster than those of long ones around the threshold stress intensiW. The threshold stress intensity for short crack growth decreases with decreasing crack length. The acceleration effect of salt water, as compared with the atmosphere, on the growth of short cracks under fatigue is much greater than that on the growth of long cracks. 13 refs.
Effect of preloading on corrosion f a t i g u e o f 70/30 brass. Wu. D. Werkst. Korros. May 1989 40, (5), 308-311 The effects of a single tensile overload and precycling load in air on subsequent corrosion fatigue cracking in 70/30 brass exposed to 1M sodium nitrite solution were studied. A single tensile overload caused a decrease in the subsequent corrosion fatigue crack propagation rate. The precycling load also showed retardation
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Composites Fatigue s t r e n g t h o f f a r r o c e m e n t in a m a r i n e e n v i r o n m e n t . Ramli, M. J. Ferrocement Oct. 1988 18, (4), 397-404 The fatigue behaviour of ferrocement forms an important characteristic of certain structural elements, especially in civil or mechanical engineering. The material is not only versatile but also possesses a high degree of elasticity and a cracking resistance which is of great value in construction. An experimental study was conducted on ferrocement composite to investigate its fatigue properties in a marine environment. Galvanized wire netting was used as a reinforcing mesh. The effect of corrosion fatigue on the ferrocement composite was considered with particular attention given to fatigue life cycles of the specimen and to cracking and deflection behaviour. The test results indicate a higher fatigue strength for seven layers of 0.71 mm galvanized wire netting under continuous exposure in sea water. The increase in overall stiffness of the composite was due to the wedging effect of salt deposits, thus preventing further crack development. 6 refs.
Fatigue crack growth characteristics o f ARALL-1. Interim Report, A u g u s t 1gT-Januery 1988. Ruschau, J. J. University of Dayton Report No AD-A196 185/3/XAB M a y 1988 Constant-amplitude and spectrum fatigue crack growth rate properties were evaluated for ARALL-1 AI laminate. Testing was performed on M(T) specimens under both laboratory air and high-humidity conditions. Crack length monitoring was performed on each AI ply utilizing electrical potential drop techniques to gain a better insight into the fatigue cracking process. Results indicate an outstanding superiority of ARALL* 1 in terms of fatigue crack growth resistance over conventionally produced 7000 series AI. Fatigue cracking in each of the AI plies was fairly uniform, with no large discrepancies in total crack length or growth rates observed between the various plies. For samples tested under a fighter-type load history, the effect of high humidity was actually beneficial, with fatigue crack growth rates typically onehalf of those developed under laboratory air conditions. Explanations based on increased delamination regions are offered for this behaviour.
Driving forces for c o m p o s i t e interface f a t i g u e cracks. Chan, K. S. and Davidson, D. L. Eng. Fract. Mech. 1989 33, (3), 451-466 The relevant fracture mechanics parameter for representing the crack extension driving force of interface fatigue cracks has been studied both analytically and experimentally. Using the oscillatory stress singularities for open-tip interface cracks, an equivalent stress intensity range, defined in terms of the J-integral and evaluated on the basis of the applied loads, is proposed end shown to correlate fatigue crack growth data of interface cracks in fibre-reinforced composites (eg Mg/AI203; Ti/B). Two complementary procedures for determining the local &K of interface fatigue cracks using experimental crack opening displacements data are presented. Differences between the local and global AK are thought to be due to residual stresses which originated during fabrication. Graphs. 38 refs.
A study on t h e characteristics of creep and fatigue in FRM. h Creep characteristics. Kim, S.-Y., Hyun, C.-Y. and Sung, H.-S, J. Korean Inst. Met, 1989 27, (2), 179-187 (in Korean) The fabrication and creep characteristics of AI-0.65Fe composites reinforced with stainless steel (Fe-0.18C-18.45Cr-8.46Ni-0.73Mn-0.33Mo) fibres have been studied. The Ni-coated, Cu-coated and bare fibres have been tested to examine the effect of fibre surface characteristics. To make various fibre volume fraction composite specimens, the liquid casting method has been applied. Creep characteristics such as the rupture time and the steady-state creep rate have been investigated in the stress range 22.47-72.95 MPa at 537 K. The rupture time was increased with Vf. The stress exponent (n) has been found to be 21.2-114. In the case of Vf 1.6, 2.88%, 100 h rupture stress (~¢) was less than the theoretical value calculated by the ruleof-mixture (RAM). On the other hand, Vf 3.52% showed a ¢rc value close to RaM, and coated composites were even larger than RaM. Several intermetallic compounds such as AINi, AI2Cu, AIsFe3 and AI13Fe4 in the interface were observed by TEM. These improved the wettability of the fibre on the matrix and the creep strength due to obstruction of dislocation movement. Tested specimens showed dislocation cells at the substructure. The dislocation density decreased from interface to matrix. Graphs, photomicrographs. 17 refs.
Int J Fatigue January 1990
Factors influencing t h e f a t i g u e b e h a v i o u r o f ferrous-based l a m i n a t e d composites. (Dissertation). Wittenauer, J. P. Diss. Abstr. Int. M a y 1988 48, (11), Pp 179 Metallic-based laminates offer promise as damage-tolerant materials under conditions of fatigue loading. It has long been known that laminated metals can exhibit improved impact properties due to delaminations and the associated crack arrest phenomena that have been observed to occur at weak interlsminar boundaries, To extend this crack arrest behaviour to conditions of fatigue loading, a broed-bessd experimental programme has been conducted using ultra-high-carbon steel as a base material. In the first phase, a shear test was used to evaluate factors influencing the interleminar bonding strength between adjacent steel plies. A knowledge of bond strength is critical if crack arrest mechanisms are to be optimized. It was found that the bond strength among steel plies remains quite high over s wide range of thermomechanical processing routes. A desire to obtain lower interlaminar bond strengths led to the introduction of secondary metals to be used as weak interleafs between the high-strength ferrous plies. Two meterials--Cu and Fe containing 3% Si--were evaluated and found to be suitable interleaf candidates. In the second phase, a variety of laminates consisting of layers of steel interleaved with Cu or Fe-Si were prepared. The fatigue behaviour of laminates tested in the crack arrest orientation showed that a range of crack growth beheviour is possible, ranging from crack arrest at each interleaf to uninhibited crack propagation. For laminates containing a Cu interleaf, it was shown that crack arrest end life improvement are optimized when ply thickness is increased, when interleaf thickness is decreased, or when ferrous ply yield strength is increased. No life improvement was obtained through use of a ferrous interleaf. Finally, a micromechanical model has been introduced which explains the experimentally observed crack growth behaviour. By seeking an understanding of near-crack-tip stresses as a fatigue crack propagates toward a weak interface, factors influencing local delamination and crack arrest can be fundamentally understood. A previously developed applied mechanics model was used for this purpose. The model used supports the experimental results and has emerged as a potentially useful tool for predicting crack growth behaviour in other materials systems.
Corrosion The microstructuros o f m i l d steels and corrosion fatigue. Xing, Z., Huan~: S., Song, Y. and Tu, M. Acta Metall. Sin. (China) Dec. 1988 24, (6), B398-B403 (in Chinese) The fatigue crack propagation beheviour of two mild steels with various microstructures in 3.5% NaCI solution or atmosphere was studied. It was revealed that the microstructures of the steel and the frequency have a considerable influence on the corrosion fatigue strength. The relation between the crack closure effect and the electrochemical conditions was discussed. Corrosion fatigue mechanisms, which consider the effects of hydrogen embrittlement and anode dissolution, respectively, were proposed. A fracture mechanism map was worked out. 9 refs.
Growth o f s h o r t cracks o f A5376CL1 steel under f a t i g u e loading in 3.5% NaCI solution. Pei, H., Yang, J. and Ke, W. Acta Metall. Sin. (China) Dec. 1988 24, (6), B393-B397 (in Chinese) The effects of environmental media, both in atmosphere and in 3.5% NaCI aqueous solution, on the growth of short cracks, in comparison with long cracks, have been investigated under fatigue loading on specimens with single-edge cracks ranging from 0.05-0.15 mm for A537CL1 steel. The growth rate of short cracks is faster than those of long ones around the threshold stress intensiW. The threshold stress intensity for short crack growth decreases with decreasing crack length. The acceleration effect of salt water, as compared with the atmosphere, on the growth of short cracks under fatigue is much greater than that on the growth of long cracks. 13 refs.
Effect of preloading on corrosion f a t i g u e o f 70/30 brass. Wu. D. Werkst. Korros. May 1989 40, (5), 308-311 The effects of a single tensile overload and precycling load in air on subsequent corrosion fatigue cracking in 70/30 brass exposed to 1M sodium nitrite solution were studied. A single tensile overload caused a decrease in the subsequent corrosion fatigue crack propagation rate. The precycling load also showed retardation
71