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The fatigue performance of adhesively bonded metal joints
Fatigue Abstracts occurred during creep-fatigue tests on a virgin 1Cr-0.5Mo steel. Creep-fatigue cycling led to the fragmentation of M2X needles which were present in the as-received, ex-service steel. Graphs, photomicrographs, 18 ref. Overview of reliability test programme on primary coolant piping of light water reactors. Shibata, K., Isozaki, T., Ueda, S., Kurihara, R., Onizawa, K. and Kosaka, A. Nihon-Genshiryoku-Gakkai Shi (J. Atomic Energy Society of Japan) (Oct. 1993) 35(10), 923-939 (in Japanese) Upon request by the Science and Technology Agency of the Japanese Government, the Japan Atomic Energy Research Institute has conducted the Piping Reliability Test Programme to demonstrate the safety and reliability of light water reactor primary pipings made of stainless steels and carbon steels. The results of the programme are summarized. In the test programme, pipe fatigue tests, leak-before-break (LBB) verification tests and pipe rupture tests were carried out to examine the integrity of pipings, to verify the LBB concept, and to demonstrate the effectiveness of the protective measures against jet impingement and pipe whip under pipe rupture event, respectively. In the pipe fatigue tests, a procedure to predict the fatigue crack growth was developed and the integrity of piping during plant service life was demonstrated. In the LBB verification tests, pipe fracture tests and leak rate tests were performed using cracked pipes. Based on the test results, LBB in the primary pipings was demonstrated. In the pipe rupture tests, the influence of jet impingement on the target plate and the interaction between whipping pipe and restraint were investigated. Using the test results, the effect of jet impingement and the effectiveness of pipe whip restraints were demonstrated. Graphs, 26 ref. On the influence of fatigue on machine part wear. Bulatov, V.P. and Vedernikov, D.N. Wear (1 Dec. 1993) 170(2), 167-173 The main aspects of the relationship between fatigue and machine part wear are considered and the relevant problem is formulated. The results of an investigation of the influence of the fatigue process on machine part wear are given for diesel engine piston rings (of cast iron). As the results show, the solution of the problem could open up new prospects in the development of the theory of machine part cyclic wear and the details of the technology of cyclic straining treatments for increasing fatigue wear resistance. Graphs, 10 ref. A study of thermal fatigue characteristics of explosive clad steels (failure factors). Nishida, M. J. High Temp. Soc. Jpn. (Nov. 1993) 19(6), 264-275 (in Japanese) Factors influencing the lifetime of thermal failure of explosive clad steels have been investigated. Clads used are A1/carbon steel, SUS304 stainless steel/C steel, Cu/C steel and Ti/C steel. By assuming stress equilibrium, interface strain continuity and constitutive equations for the clad metal and the base metal, the stress and strain (elastic and plastic) generated in the clad metal and base metal during thermal cycles were calculated. The calculated stress and strain were compared with the experimental failure life of the explosive clad steels. It was found that the failure life expressed in terms of the number of thermal cycles to failure increased exponentially, as the total strain range resulting from the mismatch at the interface decreased. Graphs, 15 ref. Study on joint strength produced by laser spot welding. Soga, S, lnoue, S. and Asada, H. Nisshin Steel Technical Report (1993) (68), 89-96 Various steel sheets were welded by laser spot welding to investigate the joint strength produced. It was found that both the tensile shear strength and cross-tension strength of laser-spot-welded portions were equal to that of resistance-spot-welded portions having the same nugget diameter as the 'penetration diameter'. To estimate the joint strength produced by laser spot welding, equation are introduced as a function of the 'penetration diameter', thickness, and tensile strength of the base metal. Judging from the results of fatigue tests, the fatigue limit of a joint as formed by laser spot welding is lower than that of a joint formed by resistance spot welding when both joints exhibit equal tensile shear strength. Graphs, photomicrographs, 3 ref. The fatigue performance of adhesively bonded metal joints. Jethwa, J.K. and
Kinloch, A.J. Proc. Conf. Adhesion '93, York, UK, 6-8 Sept. 1993, pp. 197-202 The fatigue performance of aluminium alloy (BS 5083) joints, pretreated using a chromic-acid etch method, and bonded using a rubber-toughened hot-curing paste adhesive, has been assessed. To overcome problems of plastic deformation of the substrates during the fracture tests, the tapereddouble cantilever-beam (TDCB) geometry was selected as the best type of substrate geometry for the fracture tests. First, the experimental and theoretical compliances of the bonded T D C B specimens were determined and confirmed to be in good agreement. Second, the static value of the adhesive fracture energy, GI~, was ascertained and found to be 2.0 kJ m -2. Third, the fatigue behaviour was measured and, as in the static tests, the crack propagated through the adhesive layer. The threshold value, Gth, from the fatigue test was approx 0.4 kJ m -2. Fourth, the fatigue tests were also
$94 Fatigue, 1994, Vol 16, November
conducted in water, and this type of test was found to be an excellent form of accelerated durability test. The crack now propagated along the substrate/ adhesive interfacial regions and the value of Gth decreased by an order of magnitude to approx. 0.4 kJ m -2. Graphs, 2 ref.
Fatigue strength of adhesive/rivetcombined joints. Imanaka, M., Haraga, K. and Nishikawa, T. Proc. Conf. Adhesion '93, York, UK, 6-8 Sept. 1993, pp. 187-192 The strength characteristics of adhesive/rivet combined lap joints in highstrength steel were investigated. To clarify which bonding conditions increase fatigue strength of combined joints, fatigue tests were conducted on rivet, adhesive and adhesive/rivet combined joints with various lap width, where several kinds of adhesives and rivets were used. Moreover, when the fatigue strength was improved through combination with the rivet, fatigue crack initiation and propagation behaviour of the combined joints and those of the adhesive joints were compared. Graphs, 6 ref.
A damage mechanics approach to fatigue assessment in offshore structures. Li, D.L. and Chow, C.L. Int. J. Damage Mech. (Oct. 1993) 2(4), 385-405 This article is intended to describe the development of a fatigue damage model capable of assessing the fatigue damage in offshore structures. This is achieved by formulating a set of damage-coupled constitutive and evolution equations which make the formulation of a unified approach possible under both low- and high-cycle fatigue damage and consistent with the structural dynamic response of the changing/deteriorating material behaviours. The structural analysis for the whole designed period, i.e. approx 30 years, can be carried out with the aid of the proposed analytical procedure, in which the fundamental characteristics of sea wave statistics responsible for the structural dynamic response can be sufficiently considered. An offshore structure subject to complex ocean environment is described by a general stochastic system which embeds a group of stochastic subsystems, each characterizing a duty cycle. An effective analytical method is established by introducing the concept of duty strain range with a clear mathematical definition and its analytical solution which covers all possible spectral parameters. The history-dependent damage is also included in the damage model so that the overload effects can be analysed. It should be pointed out that the whole procedure can be fully computerized such that the practical or engineering significance of varying design variables can be readily highlighted. 35 ref.
Microstructure and mechanical properties of IN 905XL. Lutjering, G.,
Hargarter, H., Becket, J. and Fischer, G. Proc. Conf. Mechanical Alloying for StructuralApplications, Vancouver, BC, Canada, 20-22 Sept. 1993, pp. 313-320 The microstructure and the mechanical properties of the mechanically alloyed aluminum alloy IN 905XL (AI-3.9Mg-I.3Li-I.2C-0.40) were investigated and compared with the conventional ingot alloy AI 8090, both in an identically forged condition. The mechanical properties (tensile, fatigue and fracture toughness) were measured in the short transverse direction. The results showed that the IN 905XL material exhibited at a comparable yield stress level superior ductility and fracture toughness values and a much higher resistance against fatigue crack nucleation (HCF strength) as compared with the Al 8090 material. The fatigue crack propagation behaviour of the two materials was studied both for long cracks (macrocracks), using CT specimens, and for small, self-initiated surface cracks (microcracks), which are often more important for application. While the conventional alloy AI 8090 showed a superior resistance against the propagation of macrocracks, the crack propagation rate of microcracks was more comparable in both materials. The results of the findings are explained on the basis of the microstructure of the two materials. Photomicrographs, graphs, 7 ref.
Gibeling, J.C. and Mercer, M.E. Proc. Col. Mechanical Alloying for StructuralApplications, Vancouver, BC, Canada, 20-22 Sept. 1993, pp. 237-243 Low cyde fatigue of mechanically alloyed aluminum.
The focus of this study is on the mechanisms of cyclic deformation of dispersion-strengthened aluminium alloys produced by mechanical alloying. The materials studied include an AI-Mg alloy (IN-9052) and a lithiumcontaining variant, IN-905XL. The results of plastic-strain-controlledlowcycle fatigue tests are compared with those obtained from a conventional AI-Mg alloy (AA5083-H38). The mechanically alloyed materials exhibit a small amount of cycficsoftening in the firstfew cycles, followed by continuous hardening to failure. These observations suggest that there is some initial rearrangement of the dislocation structure, but that the dispersoids are resistant to shear as expected. This behaviour is in contrast to the usual microstructural instabilities associated with particle shearing in peak-aged precipitation-strengthened materials. The mechanically alloyed materials also exhibit a substantial asymmetry in the tension and compression peak stresses due to the presence of the dispersoids. Of the materials tested, IN-9052 exhibited the longest cyclic lifetime at all plastic strain amplitudes. This result is attributed to the role of the dispersoid particles in promoting homogeneous deformation. Graphs, 14 ref.
Kinloch, A.J. Proc. Conf. Adhesion '93, York, UK, 6-8 Sept. 1993, pp. 197-202 The fatigue performance of aluminium alloy (BS 5083) joints, pretreated using a chromic-acid etch method, and bonded using a rubber-toughened hot-curing paste adhesive, has been assessed. To overcome problems of plastic deformation of the substrates during the fracture tests, the tapereddouble cantilever-beam (TDCB) geometry was selected as the best type of substrate geometry for the fracture tests. First, the experimental and theoretical compliances of the bonded T D C B specimens were determined and confirmed to be in good agreement. Second, the static value of the adhesive fracture energy, GI~, was ascertained and found to be 2.0 kJ m -2. Third, the fatigue behaviour was measured and, as in the static tests, the crack propagated through the adhesive layer. The threshold value, Gth, from the fatigue test was approx 0.4 kJ m -2. Fourth, the fatigue tests were also
$94 Fatigue, 1994, Vol 16, November
conducted in water, and this type of test was found to be an excellent form of accelerated durability test. The crack now propagated along the substrate/ adhesive interfacial regions and the value of Gth decreased by an order of magnitude to approx. 0.4 kJ m -2. Graphs, 2 ref.
Fatigue strength of adhesive/rivetcombined joints. Imanaka, M., Haraga, K. and Nishikawa, T. Proc. Conf. Adhesion '93, York, UK, 6-8 Sept. 1993, pp. 187-192 The strength characteristics of adhesive/rivet combined lap joints in highstrength steel were investigated. To clarify which bonding conditions increase fatigue strength of combined joints, fatigue tests were conducted on rivet, adhesive and adhesive/rivet combined joints with various lap width, where several kinds of adhesives and rivets were used. Moreover, when the fatigue strength was improved through combination with the rivet, fatigue crack initiation and propagation behaviour of the combined joints and those of the adhesive joints were compared. Graphs, 6 ref.
A damage mechanics approach to fatigue assessment in offshore structures. Li, D.L. and Chow, C.L. Int. J. Damage Mech. (Oct. 1993) 2(4), 385-405 This article is intended to describe the development of a fatigue damage model capable of assessing the fatigue damage in offshore structures. This is achieved by formulating a set of damage-coupled constitutive and evolution equations which make the formulation of a unified approach possible under both low- and high-cycle fatigue damage and consistent with the structural dynamic response of the changing/deteriorating material behaviours. The structural analysis for the whole designed period, i.e. approx 30 years, can be carried out with the aid of the proposed analytical procedure, in which the fundamental characteristics of sea wave statistics responsible for the structural dynamic response can be sufficiently considered. An offshore structure subject to complex ocean environment is described by a general stochastic system which embeds a group of stochastic subsystems, each characterizing a duty cycle. An effective analytical method is established by introducing the concept of duty strain range with a clear mathematical definition and its analytical solution which covers all possible spectral parameters. The history-dependent damage is also included in the damage model so that the overload effects can be analysed. It should be pointed out that the whole procedure can be fully computerized such that the practical or engineering significance of varying design variables can be readily highlighted. 35 ref.
Microstructure and mechanical properties of IN 905XL. Lutjering, G.,
Hargarter, H., Becket, J. and Fischer, G. Proc. Conf. Mechanical Alloying for StructuralApplications, Vancouver, BC, Canada, 20-22 Sept. 1993, pp. 313-320 The microstructure and the mechanical properties of the mechanically alloyed aluminum alloy IN 905XL (AI-3.9Mg-I.3Li-I.2C-0.40) were investigated and compared with the conventional ingot alloy AI 8090, both in an identically forged condition. The mechanical properties (tensile, fatigue and fracture toughness) were measured in the short transverse direction. The results showed that the IN 905XL material exhibited at a comparable yield stress level superior ductility and fracture toughness values and a much higher resistance against fatigue crack nucleation (HCF strength) as compared with the Al 8090 material. The fatigue crack propagation behaviour of the two materials was studied both for long cracks (macrocracks), using CT specimens, and for small, self-initiated surface cracks (microcracks), which are often more important for application. While the conventional alloy AI 8090 showed a superior resistance against the propagation of macrocracks, the crack propagation rate of microcracks was more comparable in both materials. The results of the findings are explained on the basis of the microstructure of the two materials. Photomicrographs, graphs, 7 ref.
Gibeling, J.C. and Mercer, M.E. Proc. Col. Mechanical Alloying for StructuralApplications, Vancouver, BC, Canada, 20-22 Sept. 1993, pp. 237-243 Low cyde fatigue of mechanically alloyed aluminum.
The focus of this study is on the mechanisms of cyclic deformation of dispersion-strengthened aluminium alloys produced by mechanical alloying. The materials studied include an AI-Mg alloy (IN-9052) and a lithiumcontaining variant, IN-905XL. The results of plastic-strain-controlledlowcycle fatigue tests are compared with those obtained from a conventional AI-Mg alloy (AA5083-H38). The mechanically alloyed materials exhibit a small amount of cycficsoftening in the firstfew cycles, followed by continuous hardening to failure. These observations suggest that there is some initial rearrangement of the dislocation structure, but that the dispersoids are resistant to shear as expected. This behaviour is in contrast to the usual microstructural instabilities associated with particle shearing in peak-aged precipitation-strengthened materials. The mechanically alloyed materials also exhibit a substantial asymmetry in the tension and compression peak stresses due to the presence of the dispersoids. Of the materials tested, IN-9052 exhibited the longest cyclic lifetime at all plastic strain amplitudes. This result is attributed to the role of the dispersoid particles in promoting homogeneous deformation. Graphs, 14 ref.