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Fatigue behaviour of welded steel tubular structures
offshore coding authorides which are basically for unstiffened joints. The fatigue test results are discussed. ons on internally ring stiffened Anrlytieai and experimental investi stool tubular joints. Murthy, D.S.R., P ao, A.G.M., Gandhr, P., Thandavamoorth T.S., Pant, P.K. and Murty, V.S.R. Conf. &etrgue and Fracture in Steel and Concrete Structures, /SFF ‘91, Madras, India, Dee 1991 Voi 2 (Oxford & IBH Publishing Co. Pvt. Ltd, New Delhi, India, 1991) 715-728 Offshore structures are susceptible lo fatigue failure due to the repetitive action of wave loads. Welded tubular structures commonly used for offshore platforms are subjected lo stress concentration a1 inlersection bf tubulars, in addition to fatigue loads. Internally ring stiffened tubular joints are found to be efficient in reducing stress concentration and increasing fatigue life. Based on finite element analysis of internally ring stiffened steel tubular T and V joints, optimum stiffener parameters have been proposed for reducing stress concentration. Parametric formulae have also been developed for calculating maximum stress concentration factors (SCF) for these joints under different loadhg conditions. Static tests were also conducted on five unstiffened and six internallv rino stiffened steel tubular T end Y ioints. The tests have proved the efficiency of’ring-stiffeners in reducing SCF and ‘increasing ultimate strength of the join&The SCFs predicted by the parametric formulae are found to be in agreement with the experimental values. The analvtical and experimental investigations are discussed. Fatigue khaviour of welded steel tubular structures Gowda, S.S. and Haksla, I. Conf. Fatigue and Fracture in Steel and Concrete Structures, ISFF ‘91, Madras, India, Dee 1991 Vol 2 (Oxford & IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 697-713 Reviewed are the fatigue strength characteristics of many tvpes of welded steel connections used in both onshore and offshore applications. Methods of analysis and factors affecting life of welded structures end the available design standards for the design of such memben are also discussed. The new design aspects, the problems associated with the welds, the use of high-strength steel and the present state of research on steel structures in the European Community of Steel and Coal (ECSC) and ocher organizations are highlighted. In addition, the tesI rasuits of four models of tower crane joints which were tested under constant amplitude loading are included. The stress concentration factors (SCF) obtained by parametric equations end finite element analysis are compared with the measured experimental values. The experimental fatigue lives of joints are compared with standard S-N curves and fracture mechanics analysis. Fsti ue behaviour of unipianar and multiplanar joints of square hollow Bucak, O., Mang, F. and Dutta, D. Conf. Fatigue and Fracture In Steel and Concrete Structures, /SFF ‘97, Madras, India, Dee 1997 Vol 2 (Oxford & IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 683-698
SJens.
A study of the available literature shows that very linle research has been done to determine the fatigue strength of multi-planar joints made of square and rectangular hollow sections. Described are the developments achieved in the field of uniplanar K-type joints and the test series initiated at the Universitv of Karlsruhe to investigate the fatigue behaviour of isolated multi-planar KK-joints of square hollow sections. To determine the influence of combined axial force and in-plane end/or out-ofplane bending moment on the stress concentration in multi-planar KK-join&. static tests with strain measurements bv strain gauge strips and chains were performed. Following the static procedure, fatigue tests on joints with various geometrical parameters were made plotting S, (stress range) vs. N (loading cycles to failure) diagrams. Furthermore, renewed fatigue tests were done on the cracked ioints after repair to find out how they can be efficiently repaired. Dweiopment of a fracture mechanics based ansiysis program for phore structures. Dharmavasan, S., Kam, J.C.P., Ha//, MS. and Kare, C&f. Fatigue and Fracture in S&e/ and Concrete Structures, W-F ‘91, Madras, India, Dee 1991 Vol 1 (Oxford & IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 285-295 Described is the development of a fracture mechanics based analysis package for assessing the fatigue behaviour of offshore structures. The emphasis of this development was 10 encapsulate the results of the various research programmes carried out in Europe and especially the work carried out at University College London over the past ten years in the form that was easily accessible to practising engineers in industv. One of the key features of the philosophy adopted was to incorporate methods that produced results repidlv. Remote sensing of fatigue crack pro gation in CT specimens via strain measurement. Simha, K.R.Y., Rama I?rrshna, D.S. and Arora, P.R. Conf. Fatigue and Fracture m S&e/ and Concrete Structures, /SW ‘91, Madras, India, Dee 1997 Vol 1 (Oxford 81 IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 253-257 Back face strain measurement (BFS) is now well established as an indirect technique 10 monitor the crack length in CT fracture specimens. Developed are empirical correlations between fatigue crack propagation parameters, back face strain and number of cycles for CT specimens subjected to constant amplitude fatigue loading. It is possible to apply these results for either continuous monitoring of fatigue crack propagation or for extracting material parameters controlling crack growth via remote sensing of BFS. (Reference is made to steel.) Spectrum loading fatigue crack growth life prediction. Anandan, K., Dash, P.K. and Brahms, K.K. Conf. Fatigue and Fracture in S&e/ and Concrete Structures, /SW ‘97, Madras, India, Dee 1991 Vol 1 (Oxford & IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 243-252 Prediction of fatigue crack growth life (in 6090 Al) under combat aircraft spectrum loading is made assuming crack closure to be the sole load interaction mechanism. The effect of different crack closure stresses experimentally measured under constant amplitude and spectrum loading on the life prediction accuracy is investigated.
Int J Fatigue November
1992
Crack closure stress is estimated from the load-crack mouth opening displacement records under both types of loading. Constant amplitude crack growth test is carried out at a maximum stress corresponding to the stress at the highesl g level and at a minimum stress corresponding to the lowesi g level of the spectrum. Crack closure stress variation as a function of crack length is used in the life prediction model. Crack closure levels under spectrum loading are seen to be different from thet at constant amplitude loading. Spectrum load crack closure instead of constant amplitude crack closure leads to belter life prediction. Fatioue crack orooaaation behsviour of steel A637 at different temosrature%. Fang, /ii. ahdbuan, M. Conf Fatigue and Fracture in Steel and Concrete Structures, ISFF ‘91, Madras, India, Dee 1991 Vol 1 (Oxford & IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 235-242 Investigated in detail is the fatigue crack propagation behaviour of steel A637 used for tubular ioints of offshore structures in Bohai Oil Comoanv. Bv testina the fatiaue crack propagation of steel A537 at 238, 273 and 303K. it‘was fo;nd thai the fatigue crack propagation of steel A637 was in accordance with Paris law at each tested temperature, and the propagation diagram showed a convergence of the CuNes of fatigue crack growth rate at different temperatures with the increase of stress intensity factor range, AK. These curves intersect at a high growth rata. From the results of the test, as the temperature decreased, the fatigue crack growth rate decreased during most of the crack propagation of steel A537. but the Paris exponent n was increased causing a much higher acceleration of growth rate at low temperatures than at room temperature. Therefore, the growth rate during the later propagation of fatigue crack got higher at low temperatures. Au+ic PInless
emission during fatigue crack growth in AISI type 316 austsnitic steel. Moorthy, V., Jayakumar, T., Bhattacharya, D.K. and Ra/,
Conf. Fatigue and fracture in Steel and Concrete Structures, /SW ‘97, Madras, India, Dee 7991 Vol 1 (Oxford & IBH Publishing Co. Pvt. Ltd, New Delhi, India, 1991) 219-233 Acoustic emission behaviour during crack growth in a ductile AISI type 316 austenitic stainless steel is reported. The two substages in the stage II Paris regime could be distinguished by a change in the rate of acoustic activitv with increase in crack growth rate. The high acoustic activil-y during the substage lla is attributed to largescale irreversible forward and reverse slip with extensive multiplication and annihilation of dislocation taking place between two consecutive crack extensions. The transition from stage Ila to stage Ilb is found lo occur a( a daidn value of approx lo-’ m/cycle which is in agreement with reported value. Presence of carbide precipitates in thermally aged specimens reduces the acoustic activitv bv a factor of two 10 three as compared to solution-annealed specimens. This is explained to be due to reduction in dislocation source length and mean free path which in turn reduce the acoustic activitv. Creep-fstigue crack growth in type 316 stainless steel. Ray, K.K. and Knott, J. F. Conf. Fatigue and Fracture in Steel and Concrete Structures, /SW ‘91, Madras, India, Dee 1991 Vol 1 (Oxford 81 IBH Publishing Co. Pvt. Ltd, New Delhi, India, 1991) 201-218 Reviewed is crack growth behaviour in tvpe 316 stainless steel under creep-fatigue conditions, examining the influence of microstructure, the mechanical and chemical environmenf and the applicabilitv of fracture mechanics. Attention is paid particularly to the classification and analysis of the existing approaches for predicting creepfatigue interactive crack growth in this material. with specific reference to structural integrity analysis of reactor plants. where type 316 steel finds wide application. Fatigue crack growth predictions in pin-loaded iu Narayana, K.B., Dattaguru, B., Ramamurthy, T.S. and &.?ttachmen*. rlayakumar, K. Conf. Fatigue and fracture in Steel and Concrete Structures, /SW ‘91, Madras, /ndia, Dee 1991 Vol 1 (Oxford & IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 193-200 Lug attachments are widely used 10 connect components of a structural assembly. As damage tolerance requirements are becoming stringent for design qualification of high technology industrial structures, the problem of cracks at hole bounderv in such configurations has received practical importance. This kind of design requires prediction of fatigue crack growth IFCG) life and estimation of residual strength of these components. A numerical study of lug attachment with cracks emanating from circular holes filled with push fit pins is presented. The lug is modelled with six-noded quadrilateral elements located at the crack tip end four-noded elements in the remaining regions. A modified crack closure intepral (MCCI) method is used to estimate strain energy release rates (SEMI) from which th corresponding stress infensitv factors (SIFI are derived. A confiouration of steel oin in an Al 2024 lua for which experimental results of FCG life essmations are available in the literatuie is analvsed. FCG is estimated numerically and compared with experimental data. Using early-life measurements for 8 redicting fatigue crock propagation. Alrashidi, H.A., A/-Sugair, H. and rddrqr, G./f. Conf. Fatigue and Fracture in Steel and Concrete Structures, /SfF ‘91, Madras, India, Dee 1991 Vol 1 (Oxford 81 IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 175-182 Fatigue crack propagation (FCP) is one of the major causes of failures in struc(ures and machine components today. Under the effect of repeated stress, cracks prow until they reach a &age when the member can no longe; sustain the applied stress level. and as a result failure occurs. The mathematical modellina of FCP is a subiect of current interest. The uncertaintv in assessmen of the load level that a stru&ure will be subjected to during its lifetime, and the stochastic nature of the environmental conditions which affect the FCP, make it hard to predict, af the outset. the length of a crack over a certain period of time. An attempt is made to include effects of environmenfal and loading conditions. under which a structure operates, to predict FCP. The measurement of ectual crack lengths at different times during the life of a structure are utilized to characterize the crack growth process. A simplified version of the extensively used Paris law is employed 6 develop a mathematical model of FCP.The results indicate that certain earlv life measuremenfs are sufficient to predict the crack growth accurately. The model (6 applied to several sefs of publisheb data.
417
SJens.
A study of the available literature shows that very linle research has been done to determine the fatigue strength of multi-planar joints made of square and rectangular hollow sections. Described are the developments achieved in the field of uniplanar K-type joints and the test series initiated at the Universitv of Karlsruhe to investigate the fatigue behaviour of isolated multi-planar KK-joints of square hollow sections. To determine the influence of combined axial force and in-plane end/or out-ofplane bending moment on the stress concentration in multi-planar KK-join&. static tests with strain measurements bv strain gauge strips and chains were performed. Following the static procedure, fatigue tests on joints with various geometrical parameters were made plotting S, (stress range) vs. N (loading cycles to failure) diagrams. Furthermore, renewed fatigue tests were done on the cracked ioints after repair to find out how they can be efficiently repaired. Dweiopment of a fracture mechanics based ansiysis program for phore structures. Dharmavasan, S., Kam, J.C.P., Ha//, MS. and Kare, C&f. Fatigue and Fracture in S&e/ and Concrete Structures, W-F ‘91, Madras, India, Dee 1991 Vol 1 (Oxford & IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 285-295 Described is the development of a fracture mechanics based analysis package for assessing the fatigue behaviour of offshore structures. The emphasis of this development was 10 encapsulate the results of the various research programmes carried out in Europe and especially the work carried out at University College London over the past ten years in the form that was easily accessible to practising engineers in industv. One of the key features of the philosophy adopted was to incorporate methods that produced results repidlv. Remote sensing of fatigue crack pro gation in CT specimens via strain measurement. Simha, K.R.Y., Rama I?rrshna, D.S. and Arora, P.R. Conf. Fatigue and Fracture m S&e/ and Concrete Structures, /SW ‘91, Madras, India, Dee 1997 Vol 1 (Oxford 81 IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 253-257 Back face strain measurement (BFS) is now well established as an indirect technique 10 monitor the crack length in CT fracture specimens. Developed are empirical correlations between fatigue crack propagation parameters, back face strain and number of cycles for CT specimens subjected to constant amplitude fatigue loading. It is possible to apply these results for either continuous monitoring of fatigue crack propagation or for extracting material parameters controlling crack growth via remote sensing of BFS. (Reference is made to steel.) Spectrum loading fatigue crack growth life prediction. Anandan, K., Dash, P.K. and Brahms, K.K. Conf. Fatigue and Fracture in S&e/ and Concrete Structures, /SW ‘97, Madras, India, Dee 1991 Vol 1 (Oxford & IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 243-252 Prediction of fatigue crack growth life (in 6090 Al) under combat aircraft spectrum loading is made assuming crack closure to be the sole load interaction mechanism. The effect of different crack closure stresses experimentally measured under constant amplitude and spectrum loading on the life prediction accuracy is investigated.
Int J Fatigue November
1992
Crack closure stress is estimated from the load-crack mouth opening displacement records under both types of loading. Constant amplitude crack growth test is carried out at a maximum stress corresponding to the stress at the highesl g level and at a minimum stress corresponding to the lowesi g level of the spectrum. Crack closure stress variation as a function of crack length is used in the life prediction model. Crack closure levels under spectrum loading are seen to be different from thet at constant amplitude loading. Spectrum load crack closure instead of constant amplitude crack closure leads to belter life prediction. Fatioue crack orooaaation behsviour of steel A637 at different temosrature%. Fang, /ii. ahdbuan, M. Conf Fatigue and Fracture in Steel and Concrete Structures, ISFF ‘91, Madras, India, Dee 1991 Vol 1 (Oxford & IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 235-242 Investigated in detail is the fatigue crack propagation behaviour of steel A637 used for tubular ioints of offshore structures in Bohai Oil Comoanv. Bv testina the fatiaue crack propagation of steel A537 at 238, 273 and 303K. it‘was fo;nd thai the fatigue crack propagation of steel A637 was in accordance with Paris law at each tested temperature, and the propagation diagram showed a convergence of the CuNes of fatigue crack growth rate at different temperatures with the increase of stress intensity factor range, AK. These curves intersect at a high growth rata. From the results of the test, as the temperature decreased, the fatigue crack growth rate decreased during most of the crack propagation of steel A537. but the Paris exponent n was increased causing a much higher acceleration of growth rate at low temperatures than at room temperature. Therefore, the growth rate during the later propagation of fatigue crack got higher at low temperatures. Au+ic PInless
emission during fatigue crack growth in AISI type 316 austsnitic steel. Moorthy, V., Jayakumar, T., Bhattacharya, D.K. and Ra/,
Conf. Fatigue and fracture in Steel and Concrete Structures, /SW ‘97, Madras, India, Dee 7991 Vol 1 (Oxford & IBH Publishing Co. Pvt. Ltd, New Delhi, India, 1991) 219-233 Acoustic emission behaviour during crack growth in a ductile AISI type 316 austenitic stainless steel is reported. The two substages in the stage II Paris regime could be distinguished by a change in the rate of acoustic activitv with increase in crack growth rate. The high acoustic activil-y during the substage lla is attributed to largescale irreversible forward and reverse slip with extensive multiplication and annihilation of dislocation taking place between two consecutive crack extensions. The transition from stage Ila to stage Ilb is found lo occur a( a daidn value of approx lo-’ m/cycle which is in agreement with reported value. Presence of carbide precipitates in thermally aged specimens reduces the acoustic activitv bv a factor of two 10 three as compared to solution-annealed specimens. This is explained to be due to reduction in dislocation source length and mean free path which in turn reduce the acoustic activitv. Creep-fstigue crack growth in type 316 stainless steel. Ray, K.K. and Knott, J. F. Conf. Fatigue and Fracture in Steel and Concrete Structures, /SW ‘91, Madras, India, Dee 1991 Vol 1 (Oxford 81 IBH Publishing Co. Pvt. Ltd, New Delhi, India, 1991) 201-218 Reviewed is crack growth behaviour in tvpe 316 stainless steel under creep-fatigue conditions, examining the influence of microstructure, the mechanical and chemical environmenf and the applicabilitv of fracture mechanics. Attention is paid particularly to the classification and analysis of the existing approaches for predicting creepfatigue interactive crack growth in this material. with specific reference to structural integrity analysis of reactor plants. where type 316 steel finds wide application. Fatigue crack growth predictions in pin-loaded iu Narayana, K.B., Dattaguru, B., Ramamurthy, T.S. and &.?ttachmen*. rlayakumar, K. Conf. Fatigue and fracture in Steel and Concrete Structures, /SW ‘91, Madras, /ndia, Dee 1991 Vol 1 (Oxford & IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 193-200 Lug attachments are widely used 10 connect components of a structural assembly. As damage tolerance requirements are becoming stringent for design qualification of high technology industrial structures, the problem of cracks at hole bounderv in such configurations has received practical importance. This kind of design requires prediction of fatigue crack growth IFCG) life and estimation of residual strength of these components. A numerical study of lug attachment with cracks emanating from circular holes filled with push fit pins is presented. The lug is modelled with six-noded quadrilateral elements located at the crack tip end four-noded elements in the remaining regions. A modified crack closure intepral (MCCI) method is used to estimate strain energy release rates (SEMI) from which th corresponding stress infensitv factors (SIFI are derived. A confiouration of steel oin in an Al 2024 lua for which experimental results of FCG life essmations are available in the literatuie is analvsed. FCG is estimated numerically and compared with experimental data. Using early-life measurements for 8 redicting fatigue crock propagation. Alrashidi, H.A., A/-Sugair, H. and rddrqr, G./f. Conf. Fatigue and Fracture in Steel and Concrete Structures, /SfF ‘91, Madras, India, Dee 1991 Vol 1 (Oxford 81 IBH Publishing Co. Pvt. Ltd. New Delhi, India, 1991) 175-182 Fatigue crack propagation (FCP) is one of the major causes of failures in struc(ures and machine components today. Under the effect of repeated stress, cracks prow until they reach a &age when the member can no longe; sustain the applied stress level. and as a result failure occurs. The mathematical modellina of FCP is a subiect of current interest. The uncertaintv in assessmen of the load level that a stru&ure will be subjected to during its lifetime, and the stochastic nature of the environmental conditions which affect the FCP, make it hard to predict, af the outset. the length of a crack over a certain period of time. An attempt is made to include effects of environmenfal and loading conditions. under which a structure operates, to predict FCP. The measurement of ectual crack lengths at different times during the life of a structure are utilized to characterize the crack growth process. A simplified version of the extensively used Paris law is employed 6 develop a mathematical model of FCP.The results indicate that certain earlv life measuremenfs are sufficient to predict the crack growth accurately. The model (6 applied to several sefs of publisheb data.
417