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Effect of residual stresses and stress ratio on the fatigue strength of welded components
Joining Fatigue bahaviour of platad staal ahaats and of their weldad structuras. povet P., Granm G. and Maillard-Salin, C. Rev. Meta//., Cah. Inf. Tech. Oct. 1955 85. (10). 909-&l 5 The use of clad steel plates, made up of a C steel base plate associated by co-rolling to a stainless steel sheet, covers various fields of application where the problems of corrosion arise. Therefore. it is necesss~ to check whether the behaviour of these weldments is satisfactory in service. in particular under cyclic loading conditions. The fatigue behaviour of various welded T-joints using clad steel plates with a stainless steel attachment was examined The performance of welded assemblies, made by two different techniques was studied and compared to the results obtained on the welded joints of two solid stainless steel plates 7 refs.
Fatigue of welds in orthotropic bridge deck panels with trapaxoidal stiffanars. Janss, J. J. Constr. Staei Res. 1988 9, (2). 147-l 54 The problem investigated concerns the fatigue resistance, under transverse banding, of the welds between a trapezoidal stiffener and the deck elate in onhotrooic bridae decks. Laboratory tests carried out on small test pieces under l&dings consistent with ihe actual traffic loads. showed that for usual deck panels executed without any particular attention (no preparation of the edges of the stiffeners, lack of penetration of the plate-to-stiffener welds of about Wo thirds of the thickness of the stiffener), the range Au (2 x 1W cycles) of the transverse stresses at the level of the weld root in the stiffener may be adopted equal to BO MPa. The deck plate was Euronorm steel FeSlOD: the stiffener was DIN steel st52-3. 7 refs
Usa of adhasivas in repair of cracks in ship structuraa. A//an, R.C., Bird, J. and Clarke. J.D. Mater. Sci. Technol. Oct. 1995 4, (10). 853-859 The structures of modern warships frequently contain significant quantities of Al alloy: a material especially prone to fatigue induced cracking. The satisfactory repair of such cracks is often vital if the fighting efficiency of a warship is to be maintained properly and would usually be carried out by welding. The welding of Al and its alloys is often diffwlt and onboard IS further complicated by the necessity to remove inflammable linings, cables. and items of equipment to reduce the fire risk and provide access for the repair. Consequently. repair welds are often carried out from the most accessible side and full penetration is seldom achieved. The finished weld is invariably little more than a sealant with a fatigue life Inferior to that of the original plate. Initiation of funher cracking I” the repair weld can be prevented by adhesively bonding a reinforcement awxs the weld to provide a strength at least as good as that of the original plate and a stiffness sufficient to prevent the onset of further cracking. The use of adhesively bonded steel and C fibre patches in tvpical ship applications are described and the factors governing patch design. methods of surface preparation to ensure good bond durability in a marine environment. and choice of adhesives are discussed 13 refs
Stressing and wrvice life of highly pro-strsssad boltad jointr. K/oos, K.H. and Schm W Mater. w&s. We&t. tech. Nov. 1999 19, (11). 349-355 (in German) The loads on bolts in assembly are analysed in terms of the torque. yield point. and angle of rotation methods of tightening. and these are related to the reserve for operation and the operating stresses under symmetrical and asymmetrical loading. Results are sumrnarized of fatigue life of bolts and bolted joints as the factor primarily defining service life of highly stressed joints Results show that plastic deformation on tightening of bolts does not have significant effect on fatigue life in components whose fatigue life is dependent on pre-stress and this method is to be recommended except where high-strength materials have low toughness 24 refs
Defect dataction and signal procassing for cast stainless at&. Shankar, R., Selby, G. and Jeong, P. Int. J. Pressure Vessels Piping 1999 35, (l-4). 57-72 Reliable ultrasow of cast stainless steel components in the primary piping loop of pressurized water reactors (FVJRs) has not been satisfactorily demonstrated to the US utilities. The inspection for flaws is difficult because strong reflections from the grain boundaries could mask the flaw signal response; in addition. the ultrasonic beam can be redirected by the ‘wave guide’ effect of the coarse grain structure. Signal processing approaches that may be relevant to inspection of such materials are described. Specifically. spatial averaging - a proven technique for enhancing signals that exhibit spatial coherency can be useful in enhancing signal-to-noise ratio (SNR) for flaws the length of which are larger than the average grain size Several specimens of PWR main coolant piping. each a cast steel elbow welded to forged steel containing fatigue flaws, were examined with a field usable ultrasonic Imaging system and with a personal computer (PC) based data acquisition and imaging system. both dvelopad under EPRI fundine In addition, Inspection data were examined from a component in a PWR plant during a scheduled outage in 1987 The images produced before and after signal processing showed improvements in flaw detectability 3 refs
Naw developmenta in welding, 1997, Ill. Strength and structuras. Neumann, A., Cottin, D. and Kliemand, W Schweisstechnik (Berlin) 1999 39, (5), 233-240 (in German) This literature review renders an overview of the significant developments in welding in the year 1987. The citations focus on publications accessible to readers in the GDdfor in-depth perusal where of interest. The authors are specialists of the Technical Universities of Magdeburg and Karl-Marx-Stadt. and the Central Institute for Welding Technology of the GDR. Questions of weld strength and fatigue in steel and hght metal weldments are dealt with. Much space is devoted to the fashioning of welded structures including the development of suitable designs, tailored in accordance with the materials of construction. eg steels or light metals. The problems of distonions and stresses during welding are addressed. and a final brief wztion covers brazing. its relevant application, braze strengths and brazed stwctures 41 refs.
Effact of raoidual strasaa and stran ratio on the fatigue strength of waldad componants. Lieurede,MI? Weld. World1999 26, (7-9). 159-197 (in English and French)
Int J Fatigue July 1999
This review paper summarizes the present knowledge on the effects of mean stress (stress ratio) and weldina residual stresses on the in-service behaviour of welded metallic CO(TIDOnents and strutures. The role of a stress-relief heat treatment is analvsed in the various stages of fatigue damage: endurance, crack growth from an initial defect, and crack initiation. The beneficial effect of compressive residual stresses produced by improving techniques is mentioned. 73 refs.
Fatigue strangth charactaristia of 899C/S99C friction waldad tubular butt joints. maws, K.-i., Nakayama, H., Oh-& T1and Haaui A. J. Sot. Mater. Sci., Jpn. Oct. 1999 37, (421). 1209-1215 (in Japanese) By using S35C/S35C friction welded tubular butt joints frabricated under friction welding processes, a series of tests were conducted to determine
five different the effect of
Welding conditions on joint performance. At first, the hardness measurement revealed that. though the extent of the heat affected zones differed from each other depending on the welding conditions. no noticeable difference was observed in the maximum hardness value at the weld interface of the joint. Subsequently the results of monotonic tensile tests indicated that the joint efficiencies of the joints were sufficiently high, with the exception of one joint fabricated under the lowest friction pressure conditions. The results did not necessarily reflect on the fatigue strength of the joints. and their fatigue strength behaviour could be subdivided into two groups as follows: two types of joints showed leer fatigue strength than that of the base material and appeared to have no fatigue limit in the range of this experiment; and in contrast. the fatigue strength of the other three types of joints well exceeded that of the base material and showed a tendency to have a fatigue limit. Such fatigue Strength behaviour seemed to correlate closely to the magnitude of forging pressure in the friction welding process. 12 refs.
Examination of fatigua and cefatigua crack rowth bahaviour of agad typa 347 stainlau staal wald matal at 65%C. Gladwin, D.N., Miller, D.A. and priest R. H. Mater Sci. Techno/. Jan. 1999 5. (1). 40-51 Data are presented from fatigue and creep-fatigue crack growth rate tests carried out at 6WC on an aged type 347 stainless steel weld. Fully reversed tests were carried out under displacement control, with constant displacement hold periods. to simulate closely the thermal induced straining relevant to power plant applications. Tensile hold periods of up to 192 h were used in the creep-fatigue tests, a 1 h hold period was sufficient to induce internal intergranular cracking in the test specimens. In the creepfatigue tests, crack growth occurred during both the cyclic excursions and the hold periods. Cyclic rates were also dependent on hold time, the acceleration in fatigue crack propagation rates being associated with the extent of creep damage produced ahead of the main crack as a result of the hold periods. Such an interaction between fatigue and creep was supported by a sequential creep-fatigue crack growth expsriment. Empirical equations were obtained which describe the total crack growth rates as the sum of a cyclic and a dwell contribution. The cychc contributions were described in terms of a stress intensity factor range. while the dwell components were correlated with a creep crack growth correlating parameter C. It was shown that the reference stress approximation to C accurately predicts measured values as long as creep strain rate data were derived from constant displacement stress relaxation data rather than from forward creep data 18 refs.
Staal castings - a solution to frabrication problems. Marsm, G.J. Steel Technol. Int. 1999 253-259 Large steel material for use follows advantages
castings for structural use have made a comeback and are now a first choice complex heavy-lift and fatigue-critical items in offshore oil platforms, Their a 10yeardevelopment programme. and substantial cost savingsand engineering are being obtained.
Asaaasing design racommandations for waldad joints. Oflkhore Rec. Focus.Oct. 1988 (67). 10. Recent experimental studies indicating a need to modify guidelines concerning the cumulative fatigue of offshore-structure joints by wave forces have prompted a compilation of fatigue-test data designed for use in evaluating design techniques for North Sea structures. Analysis of results for bending and axial loading. inCludinQ the effects of geometry and other variables. indicates that Miner’s cumulative-damage rule appears satisfactory. though its use should be confined to loading spectra with block lengths exceeding 100 cycles For shorter blocks Gurney’s rule. mathematical expressions for which are presented together with those for Miner’s rule. could be applied
A simple procadura for auau@ anvironmantal effactm on fatigue failure of solder joints. Lecey,KG. and Woodford, D.A. SW. Metall Sept. 1999 22, (9). 1543-1545 Some initial results are reported of environmental effects on fatigue lives of a 6OSwlOPb solder in Cu wire. DetaIled analysis of frequency effects on solder layers of this alloy tested I” simple shear. has been reported recently by Solomon. In addition to using a different alloy from that in the previous environnmental study, the procedure involves testing of actual solder joints and surface protection of the sample. It is, of course, not known whether this constitutes an inen environment. although the results are strongly Indicative that full protection is achieved in the room temperature tests. Some precedence for protection against intergranular penetration of oxygen in high temperature alloys by suitable coatings is available. 10 refs
Cavitation in a Pb/low-Sn soldar during low cycle fatigue. Greenwood, P.J.. Rei/ey, T.C., Raman* V. and Tien, J.K. SW. Meta//. Sept. 1999 22, (9). 1495-1499 PbSn solder joints in electronic devices, including computers. are subject to fatigue cycling awing from differential thermal expansion of the materials which are interconnected by the solder For Pb-Sn solder alloys, ambient temperature is at or above one-half the melting temperature Accordingly. mechanical behaviour of Pb-Sn solder at ambient temperature is inherently thermally assisted, and creep related phenomena can be expected. Grain boundary cavitation during low cycle fatigue of a Pb&w Sn alloy is investigated for its own sake. and as a potential signature of plastic damage and residual life assessment. Liquid metal embrittlement (LME) is used to to examine grain boundaries in PMcw Sn specimens after varying number of cycles. LME is applied in a manner similar to that used by Reiley to observe creep cavitation in other systems. The LME agent chosen to embrittle the Pb alloy along the grain boundaries must have very low solubility for the solder constituents. The method and conditions for the application and removal of the
281
Fatigue of welds in orthotropic bridge deck panels with trapaxoidal stiffanars. Janss, J. J. Constr. Staei Res. 1988 9, (2). 147-l 54 The problem investigated concerns the fatigue resistance, under transverse banding, of the welds between a trapezoidal stiffener and the deck elate in onhotrooic bridae decks. Laboratory tests carried out on small test pieces under l&dings consistent with ihe actual traffic loads. showed that for usual deck panels executed without any particular attention (no preparation of the edges of the stiffeners, lack of penetration of the plate-to-stiffener welds of about Wo thirds of the thickness of the stiffener), the range Au (2 x 1W cycles) of the transverse stresses at the level of the weld root in the stiffener may be adopted equal to BO MPa. The deck plate was Euronorm steel FeSlOD: the stiffener was DIN steel st52-3. 7 refs
Usa of adhasivas in repair of cracks in ship structuraa. A//an, R.C., Bird, J. and Clarke. J.D. Mater. Sci. Technol. Oct. 1995 4, (10). 853-859 The structures of modern warships frequently contain significant quantities of Al alloy: a material especially prone to fatigue induced cracking. The satisfactory repair of such cracks is often vital if the fighting efficiency of a warship is to be maintained properly and would usually be carried out by welding. The welding of Al and its alloys is often diffwlt and onboard IS further complicated by the necessity to remove inflammable linings, cables. and items of equipment to reduce the fire risk and provide access for the repair. Consequently. repair welds are often carried out from the most accessible side and full penetration is seldom achieved. The finished weld is invariably little more than a sealant with a fatigue life Inferior to that of the original plate. Initiation of funher cracking I” the repair weld can be prevented by adhesively bonding a reinforcement awxs the weld to provide a strength at least as good as that of the original plate and a stiffness sufficient to prevent the onset of further cracking. The use of adhesively bonded steel and C fibre patches in tvpical ship applications are described and the factors governing patch design. methods of surface preparation to ensure good bond durability in a marine environment. and choice of adhesives are discussed 13 refs
Stressing and wrvice life of highly pro-strsssad boltad jointr. K/oos, K.H. and Schm W Mater. w&s. We&t. tech. Nov. 1999 19, (11). 349-355 (in German) The loads on bolts in assembly are analysed in terms of the torque. yield point. and angle of rotation methods of tightening. and these are related to the reserve for operation and the operating stresses under symmetrical and asymmetrical loading. Results are sumrnarized of fatigue life of bolts and bolted joints as the factor primarily defining service life of highly stressed joints Results show that plastic deformation on tightening of bolts does not have significant effect on fatigue life in components whose fatigue life is dependent on pre-stress and this method is to be recommended except where high-strength materials have low toughness 24 refs
Defect dataction and signal procassing for cast stainless at&. Shankar, R., Selby, G. and Jeong, P. Int. J. Pressure Vessels Piping 1999 35, (l-4). 57-72 Reliable ultrasow of cast stainless steel components in the primary piping loop of pressurized water reactors (FVJRs) has not been satisfactorily demonstrated to the US utilities. The inspection for flaws is difficult because strong reflections from the grain boundaries could mask the flaw signal response; in addition. the ultrasonic beam can be redirected by the ‘wave guide’ effect of the coarse grain structure. Signal processing approaches that may be relevant to inspection of such materials are described. Specifically. spatial averaging - a proven technique for enhancing signals that exhibit spatial coherency can be useful in enhancing signal-to-noise ratio (SNR) for flaws the length of which are larger than the average grain size Several specimens of PWR main coolant piping. each a cast steel elbow welded to forged steel containing fatigue flaws, were examined with a field usable ultrasonic Imaging system and with a personal computer (PC) based data acquisition and imaging system. both dvelopad under EPRI fundine In addition, Inspection data were examined from a component in a PWR plant during a scheduled outage in 1987 The images produced before and after signal processing showed improvements in flaw detectability 3 refs
Naw developmenta in welding, 1997, Ill. Strength and structuras. Neumann, A., Cottin, D. and Kliemand, W Schweisstechnik (Berlin) 1999 39, (5), 233-240 (in German) This literature review renders an overview of the significant developments in welding in the year 1987. The citations focus on publications accessible to readers in the GDdfor in-depth perusal where of interest. The authors are specialists of the Technical Universities of Magdeburg and Karl-Marx-Stadt. and the Central Institute for Welding Technology of the GDR. Questions of weld strength and fatigue in steel and hght metal weldments are dealt with. Much space is devoted to the fashioning of welded structures including the development of suitable designs, tailored in accordance with the materials of construction. eg steels or light metals. The problems of distonions and stresses during welding are addressed. and a final brief wztion covers brazing. its relevant application, braze strengths and brazed stwctures 41 refs.
Effact of raoidual strasaa and stran ratio on the fatigue strength of waldad componants. Lieurede,MI? Weld. World1999 26, (7-9). 159-197 (in English and French)
Int J Fatigue July 1999
This review paper summarizes the present knowledge on the effects of mean stress (stress ratio) and weldina residual stresses on the in-service behaviour of welded metallic CO(TIDOnents and strutures. The role of a stress-relief heat treatment is analvsed in the various stages of fatigue damage: endurance, crack growth from an initial defect, and crack initiation. The beneficial effect of compressive residual stresses produced by improving techniques is mentioned. 73 refs.
Fatigue strangth charactaristia of 899C/S99C friction waldad tubular butt joints. maws, K.-i., Nakayama, H., Oh-& T1and Haaui A. J. Sot. Mater. Sci., Jpn. Oct. 1999 37, (421). 1209-1215 (in Japanese) By using S35C/S35C friction welded tubular butt joints frabricated under friction welding processes, a series of tests were conducted to determine
five different the effect of
Welding conditions on joint performance. At first, the hardness measurement revealed that. though the extent of the heat affected zones differed from each other depending on the welding conditions. no noticeable difference was observed in the maximum hardness value at the weld interface of the joint. Subsequently the results of monotonic tensile tests indicated that the joint efficiencies of the joints were sufficiently high, with the exception of one joint fabricated under the lowest friction pressure conditions. The results did not necessarily reflect on the fatigue strength of the joints. and their fatigue strength behaviour could be subdivided into two groups as follows: two types of joints showed leer fatigue strength than that of the base material and appeared to have no fatigue limit in the range of this experiment; and in contrast. the fatigue strength of the other three types of joints well exceeded that of the base material and showed a tendency to have a fatigue limit. Such fatigue Strength behaviour seemed to correlate closely to the magnitude of forging pressure in the friction welding process. 12 refs.
Examination of fatigua and cefatigua crack rowth bahaviour of agad typa 347 stainlau staal wald matal at 65%C. Gladwin, D.N., Miller, D.A. and priest R. H. Mater Sci. Techno/. Jan. 1999 5. (1). 40-51 Data are presented from fatigue and creep-fatigue crack growth rate tests carried out at 6WC on an aged type 347 stainless steel weld. Fully reversed tests were carried out under displacement control, with constant displacement hold periods. to simulate closely the thermal induced straining relevant to power plant applications. Tensile hold periods of up to 192 h were used in the creep-fatigue tests, a 1 h hold period was sufficient to induce internal intergranular cracking in the test specimens. In the creepfatigue tests, crack growth occurred during both the cyclic excursions and the hold periods. Cyclic rates were also dependent on hold time, the acceleration in fatigue crack propagation rates being associated with the extent of creep damage produced ahead of the main crack as a result of the hold periods. Such an interaction between fatigue and creep was supported by a sequential creep-fatigue crack growth expsriment. Empirical equations were obtained which describe the total crack growth rates as the sum of a cyclic and a dwell contribution. The cychc contributions were described in terms of a stress intensity factor range. while the dwell components were correlated with a creep crack growth correlating parameter C. It was shown that the reference stress approximation to C accurately predicts measured values as long as creep strain rate data were derived from constant displacement stress relaxation data rather than from forward creep data 18 refs.
Staal castings - a solution to frabrication problems. Marsm, G.J. Steel Technol. Int. 1999 253-259 Large steel material for use follows advantages
castings for structural use have made a comeback and are now a first choice complex heavy-lift and fatigue-critical items in offshore oil platforms, Their a 10yeardevelopment programme. and substantial cost savingsand engineering are being obtained.
Asaaasing design racommandations for waldad joints. Oflkhore Rec. Focus.Oct. 1988 (67). 10. Recent experimental studies indicating a need to modify guidelines concerning the cumulative fatigue of offshore-structure joints by wave forces have prompted a compilation of fatigue-test data designed for use in evaluating design techniques for North Sea structures. Analysis of results for bending and axial loading. inCludinQ the effects of geometry and other variables. indicates that Miner’s cumulative-damage rule appears satisfactory. though its use should be confined to loading spectra with block lengths exceeding 100 cycles For shorter blocks Gurney’s rule. mathematical expressions for which are presented together with those for Miner’s rule. could be applied
A simple procadura for auau@ anvironmantal effactm on fatigue failure of solder joints. Lecey,KG. and Woodford, D.A. SW. Metall Sept. 1999 22, (9). 1543-1545 Some initial results are reported of environmental effects on fatigue lives of a 6OSwlOPb solder in Cu wire. DetaIled analysis of frequency effects on solder layers of this alloy tested I” simple shear. has been reported recently by Solomon. In addition to using a different alloy from that in the previous environnmental study, the procedure involves testing of actual solder joints and surface protection of the sample. It is, of course, not known whether this constitutes an inen environment. although the results are strongly Indicative that full protection is achieved in the room temperature tests. Some precedence for protection against intergranular penetration of oxygen in high temperature alloys by suitable coatings is available. 10 refs
Cavitation in a Pb/low-Sn soldar during low cycle fatigue. Greenwood, P.J.. Rei/ey, T.C., Raman* V. and Tien, J.K. SW. Meta//. Sept. 1999 22, (9). 1495-1499 PbSn solder joints in electronic devices, including computers. are subject to fatigue cycling awing from differential thermal expansion of the materials which are interconnected by the solder For Pb-Sn solder alloys, ambient temperature is at or above one-half the melting temperature Accordingly. mechanical behaviour of Pb-Sn solder at ambient temperature is inherently thermally assisted, and creep related phenomena can be expected. Grain boundary cavitation during low cycle fatigue of a Pb&w Sn alloy is investigated for its own sake. and as a potential signature of plastic damage and residual life assessment. Liquid metal embrittlement (LME) is used to to examine grain boundaries in PMcw Sn specimens after varying number of cycles. LME is applied in a manner similar to that used by Reiley to observe creep cavitation in other systems. The LME agent chosen to embrittle the Pb alloy along the grain boundaries must have very low solubility for the solder constituents. The method and conditions for the application and removal of the
281