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Increasing tool life in cold forging through advanced design and tool manufacturing techniques
T. t m t a t h m •Mater. u iEvsl. t •t~#aofquso. m n kM~cLellan, d m ' lp.m Oct.
o f • metal m a t r i x oompo~lte using m n d e r d
1992 SO (10) 1148-1154
Standard ultrasonic tests were performed on a metal-matrix composite (MMC) between machenicel cyclings in an attempt to detect the initiation and propagation of damage. The MMC, SCS-6/TI-24AI-11Nb, was subjected to an isothermal 650"C modified fatigue test with en impoaed hold time of 20 000 s at maximum stress. At the end of each correaponding cycle, two different types of ultrasonic methods - reflector plate and backacatmring - were performed in an attempt to determine the degree of damage incurred by the specimen. Modulus values for the specimen were also gathered, using corresponding load-displacement data after each cycle. The goal was to determine whether standard uitrelonic techniques could be used to detect the initiation and propagation of damage in MMCs. Photomicrographs, graphs, 3 raf. Ultimate limit state o f slender steel w e b s subject t o (i) constant and (ii) repeated partial edge loading. Kutmanova, L and Skaloud, M. J. Construct. Steel Res. 1992 2 1 ( 1 - 3 ) 147-162 The first stage of the research dealt with the performsnca of steel webs under the action of constant patch loading. Altogether 184 experimental girders were tested, with the following geometrical characteristics of the test girders being varied from girder to girder: (i) the depth:thicknses ratio of the web; (it) the flange size; (iii) the position of the longitudinal rib; (iv) its dimensions; and (v) the length of load. In conclusion, formulae were established for (i) the optimum rigidity of the longitudinal rib and (it) the predicted ultimate loads of webs subject to partial edge loading and stiffened by a longitudinal rib. The aim of the other pert of the Prague experimental research was to look into the effect of the repeated character of patch loading on the ultimate limit state of steel plate girder webs fitted with longitudinal ribs. Eighty experimental panels were teated, the flange size, snd the position and dimensions of the longitudinal ribs being varied. During the tests, the 'breathing' of the girder webs under the action of a cyclic patch load, the initiation and propagation of cracks in the most heavily stressed areas of the webs, and their influence on the 'erosion' of the plsstic failure mechanisms of the test girders were carefully studied. Final analysis of the data obtained made it possible to establish the limit fatigue loads, PI=~of longitudinally stiffened steel plate girders whose thin webs are subject to a repeated partial edge toad. Graphs, 4 raf. Threshold s t , ms criterion in n e w w h s o l / r a i l Interaction f o r limiting rail damage under heavy axle loads. Kumar, S. and Singh, S. P. J. Eng. Ind. (Trans. ASME) Aug. 1992 114 (3) 284-288 A qualitative discussion of the effects of increasing new (initial) wheal-rail contact stresses on the degree of damage to the rail due to heavy axle loads is presented. The importance end need for heavy axle loads and their relationship to rail damage as a result of the increasing whsel-rail contact stresses are discussed. Various mechanisms of energy absorption/losses due to free rolling and modes of rail damage are presented. These modes include surface and internal damage due to wear, contact shear, plasticity, fatigue, shelling, and crack formation. The concept of threshold stress observed in frea-rolling friction much earlier by Drutowski is discussed and snslysed. It is believed that the threshold stress is a material property. This concept of threshold stress, based on shsrply increased rates of wear in freeroiling contact, is then presented and anslysed. Consideration of increased plesticityregion development, due to increasing COntact stresses and their relationship to increased rates of wear seen in experiments, is utilized to determine an upper bound of contact stresses for new wheel and rail under heavy axle load conditions. it is indicated that new wheal-rail profiles, which will achieve COntact stresses below the threshold stress, will enable the US railroads to carry heavy axle loads without serious future damage to the rails. It is concluded that a satisfactory solution for maintaining rail integrity under heavy axle loads is possible with proper design accompanied with laboratory experimentation for the new steels as they may be used in the rails. Graphs, 24 raf.
tension loads. However, tensile residual stress had a significant influence on the fatigue strength under alternating cyr,Jic loads. The weld end toe was associated with a stress concentration factor of el)Proximately 3 end was the most critical factor in initiating fatigue cracks. Weld defects, such as slag inclusions, lack of fusion, and porosity were found to significantly affect the fatigue strength of a welded joint when the load magnitude or mean atrsse was low. An equivalent crack concept, based on linear elastic fracture mechanics theory, was introduced to quantify ths weld toe stress concentration effect. This concept was shown to be effective for fatigue design and fatigue life prediction of welded structures. Ststisticel modal f o r fatigue crack propagation s t t h e w e l d toe. Zheng, Y. and Wang, L. Jixie Gongcheng Xuebao (Chinese Journal of Mechanical Engineering) 1992 35 (2) 22-25 (in Chinese) The fatigue crack propagation beheviour at the weld toe of a welded joint of A131 steel was obtained from a test programme. A statistical model for fatigue crack propagation at the weld toe was proposed by means of s probebillatlc method. The statistical nature of fatigue crack propagation at the weld toe was invsetigated. Graphs, 3 raf. international recommendations f o r t h e fatigue strength of w e i d m e n t s (Internationals Empfehlungen zur Schwtnghlstigkelt G e l d m f e b s t e r Bauteila) Hobbacher, A. Schweiesen und Schneiden Fob. 1992 44 (2) 82-87 (in German; in English pp E39-E34) Standards defining the fatigue strength of weldments in terms of dimension and defect evaluation are discussed. The adverse effects of manufacturing imperfections, volumetric and plate discontinuities on the fatigue strength could arise from increasing stress level or generation of local notch effects in the welded joint. Imperfections are to be evaluated by measuring edge miselignment and angular distortion, weld undemutting, slag inclusions and pores and formation of cracks or similar plane defects derived from fracture mechanics. Graphs, 14 raf. Increasing t o o l life in cold forging t h r o u g h advanced design and t o o l manufactudng tsohnlques. Lange, K., Hettig, A. and Knoerr, M. J. Mater. Proc. Technol, Oct. 1992 35 ( 3 - 4 ) 496-513 Results of two investigations concerned with the evaluation and prediction of fatigue failure and the improvement of tool service life in cold forging are presented. The first study presents an integrated approach to tool stress analysis and shows its possible application for s punch failure case provided by industry. The second study experimentally investigates measures that can be taken during design and tooling manufacture to reduce fatigue failure. Both studies clearly indicam the value of performing a tool stress analysis during the process and tool design phase. Steel developments f o r Improved fatigue resistance in suspension springs. Smart, E., Cook, W. 7", and Ellis, A. Ironmaking and Steelmaking 1992 19 (4) 285-289 The parabolically tapered steel leaf spring is the main method of suspension used on heavy commercial vehicles in western Europe, and the Teperlite product made by Tinsiey Bridge Ltcl is s market leader in this type of spring. These springs are designed to high stresses and are manufactured to achieve high levels of fatigue durability using conventional spring steels. Techniques of 'alternative metallurgy" have been examined to establish whether lighter springs could be designed to operate at even higher stress levels. This work involved the use of a lower carbon base steel and a different method of alloying than the conventional spring steal, heat treatment to a much higher strength level, end the development of an enhanced compressive residual stress profile below the surface of the steel. Trials were carried out on three sizes of tapered leaf spring and, in each case, the alternative metallurgy springs exhibited fatigue properties superior to those of the conventional springs.
Heat treatment, microstructures, and residual stresses In cerburizad
steels, Kraues, G. Proc. Conf. Quenching and Distortion Control, Chicago, Illinois, USA, 22-25 Sept. 1992 (ASM International, Materials Park, OH 44073-0002, USA) 1992 pp 181-191 The evolution of microstructure and residual stress during the heat treatment processing of gas carburized steels is reviswed and these factors ere related to fetigus resistance. The tempered martensite-rateined suatenito microstructure produced by quenching and tempering, end the prior microstructurs produced by carbudzing at temperatures where austenite is stable, are described. Austenitizing affects grain growth, segregation of phosphorus, carbide formation, and surface oxidation. Factors which sffact the development of surface residual stresses, ie quenching, refrigeration, oxide formation, tempering, shot peening, and straininduced trsnaformation of auatenite, are discussed. The microstructure and residual stresses sre relatedto fatigue crack initiation mechanisms sad fatigue performsnce. Effects of residual stress, w e l d t o e notch and w e l d defects on fatigue
of welded ~ struct~Jrce. Shen. W. Diss. Abstr. Int. Sept. 1992 53 (3) 232 pp in studying the fatigue behaviour of fillet-welded railroad tank car shell structures, the effects of welding residual stress, weld toe notch and weld defects on the fatigue of fillet-welded A515 steal specimens were evaluated. Both hole-drilling and sectioning measurement techniques were used to obtain residual stress information. Pad-on-plate weld spelomens were designed to simulate the tank car structure for measurement of welding residusl stress. Simple bead-on-plate end fillet weld specimens, which have similar welding residusl stresses near the weld end toe to the peal-on-plate specimens, were designed to be as compact ss possible for fatigue testing. As-welded and stress-relieved simple weld specimens were tssted under pulsed tension and siternating cyclic load conditions to determine stress life and fatigue crack propagation properties. Weld toe stress concentration effects were determined by strain gauge measurement. Fracture surface features and crack initiation sites were studied by visual analysis, scanning electron microscopy and optical microscopy. Welding residual stresses were found to be biaxial tension-compression near the weld end toe end biaxial tension-tension near the weld centre toe. Longitudinal tensile residual stress was significantly relieved when the applied longitudinal tensile cyclic load w e s > 14 ksi. Test results did not show a consistent effect of tensile residual stress on the fatigue strength under pulsed
442
Corrosion fatigue bebeviour of t h e austunitic steel XGCrNIMoTi17 12 2 in 3% NaCI solution under rotating bending load (Schwingungsrieskorrosionsverhaitso des Austenitieshso Stshlce X6 CrNiMoTI 17 12 2 in 3% Iger NaCI-Lceung U n t e r Umlaufblegebelsotung)
Roeder, E., Bassler, H.-J., Huber, M. and Vollmar, J. Werket. Korros. Sept. 1992 43 (9) 426-431 (in German) The fatigue beheviour of steel X6CrNiMoTi17 12 2 (German material-number 1.4571, comparable to AISI 316 Ti) is investigated under rotating bending load with a frequency of 50 Hz. The fatigue strength in inert medium (thermostat oil) at room temperature is 315 N/mm 2, In 3% NaCI solution of pH 7 at the same temperature, the corrosion fatigue limit for N = 107 reached only 94% of the mentioned value. A higher temperature (70°C) caused • further reduction to 89% and an additional decrease of the pH value (pH 3) lowers the dynamic strength to 88% of the reference value. The free COrrosion potential, recorded during all COrrosion fatigue tests, remains in the passive region for all specimens, which do not fail under the machanicel-corrosive load. The potential of specimens, which fail under a higher mechanical load, announces their rupture by s sudden decrease to negative values, which starts at least 3 x 104 cycles (10 mini before. Graphs, 11 raf. Study of fatigue charactsdstlc of 3SaM ultra-high-strength steel corn-
ponents. Liu, J. J. Mater. Eng. (China) 1992 (3) 20-23 (in Chinese)
The axial tension and flaxurel fatigue beheviour of 300M uitre-high-strongth smel was examined by using lugs, bolts, and circular tubes at room temperature in an air medium. The effect on fatigue beheviour of surface integrity, various stress ratios R, heat treatment and load spectre are discussed, and the difference in fetigue property between the Chinese materials and the American materials is studied. Graphs, 4 rsf. Effect of prsioadlng on short fatigue crack g r o w t h at a notch. Xu, K.,
He, J. and Zhou, H. Chinese J. Met. Sci. TechnoL 1992 8 (2) 79-83
Results of tests on samples of 42CrMo4 steal indicate that under cyclic tension the growth rate of short fatigue cracks from notch roots will be lowered greatly by
Int J Fatigue September 1993
o f • metal m a t r i x oompo~lte using m n d e r d
1992 SO (10) 1148-1154
Standard ultrasonic tests were performed on a metal-matrix composite (MMC) between machenicel cyclings in an attempt to detect the initiation and propagation of damage. The MMC, SCS-6/TI-24AI-11Nb, was subjected to an isothermal 650"C modified fatigue test with en impoaed hold time of 20 000 s at maximum stress. At the end of each correaponding cycle, two different types of ultrasonic methods - reflector plate and backacatmring - were performed in an attempt to determine the degree of damage incurred by the specimen. Modulus values for the specimen were also gathered, using corresponding load-displacement data after each cycle. The goal was to determine whether standard uitrelonic techniques could be used to detect the initiation and propagation of damage in MMCs. Photomicrographs, graphs, 3 raf. Ultimate limit state o f slender steel w e b s subject t o (i) constant and (ii) repeated partial edge loading. Kutmanova, L and Skaloud, M. J. Construct. Steel Res. 1992 2 1 ( 1 - 3 ) 147-162 The first stage of the research dealt with the performsnca of steel webs under the action of constant patch loading. Altogether 184 experimental girders were tested, with the following geometrical characteristics of the test girders being varied from girder to girder: (i) the depth:thicknses ratio of the web; (it) the flange size; (iii) the position of the longitudinal rib; (iv) its dimensions; and (v) the length of load. In conclusion, formulae were established for (i) the optimum rigidity of the longitudinal rib and (it) the predicted ultimate loads of webs subject to partial edge loading and stiffened by a longitudinal rib. The aim of the other pert of the Prague experimental research was to look into the effect of the repeated character of patch loading on the ultimate limit state of steel plate girder webs fitted with longitudinal ribs. Eighty experimental panels were teated, the flange size, snd the position and dimensions of the longitudinal ribs being varied. During the tests, the 'breathing' of the girder webs under the action of a cyclic patch load, the initiation and propagation of cracks in the most heavily stressed areas of the webs, and their influence on the 'erosion' of the plsstic failure mechanisms of the test girders were carefully studied. Final analysis of the data obtained made it possible to establish the limit fatigue loads, PI=~of longitudinally stiffened steel plate girders whose thin webs are subject to a repeated partial edge toad. Graphs, 4 raf. Threshold s t , ms criterion in n e w w h s o l / r a i l Interaction f o r limiting rail damage under heavy axle loads. Kumar, S. and Singh, S. P. J. Eng. Ind. (Trans. ASME) Aug. 1992 114 (3) 284-288 A qualitative discussion of the effects of increasing new (initial) wheal-rail contact stresses on the degree of damage to the rail due to heavy axle loads is presented. The importance end need for heavy axle loads and their relationship to rail damage as a result of the increasing whsel-rail contact stresses are discussed. Various mechanisms of energy absorption/losses due to free rolling and modes of rail damage are presented. These modes include surface and internal damage due to wear, contact shear, plasticity, fatigue, shelling, and crack formation. The concept of threshold stress observed in frea-rolling friction much earlier by Drutowski is discussed and snslysed. It is believed that the threshold stress is a material property. This concept of threshold stress, based on shsrply increased rates of wear in freeroiling contact, is then presented and anslysed. Consideration of increased plesticityregion development, due to increasing COntact stresses and their relationship to increased rates of wear seen in experiments, is utilized to determine an upper bound of contact stresses for new wheel and rail under heavy axle load conditions. it is indicated that new wheal-rail profiles, which will achieve COntact stresses below the threshold stress, will enable the US railroads to carry heavy axle loads without serious future damage to the rails. It is concluded that a satisfactory solution for maintaining rail integrity under heavy axle loads is possible with proper design accompanied with laboratory experimentation for the new steels as they may be used in the rails. Graphs, 24 raf.
tension loads. However, tensile residual stress had a significant influence on the fatigue strength under alternating cyr,Jic loads. The weld end toe was associated with a stress concentration factor of el)Proximately 3 end was the most critical factor in initiating fatigue cracks. Weld defects, such as slag inclusions, lack of fusion, and porosity were found to significantly affect the fatigue strength of a welded joint when the load magnitude or mean atrsse was low. An equivalent crack concept, based on linear elastic fracture mechanics theory, was introduced to quantify ths weld toe stress concentration effect. This concept was shown to be effective for fatigue design and fatigue life prediction of welded structures. Ststisticel modal f o r fatigue crack propagation s t t h e w e l d toe. Zheng, Y. and Wang, L. Jixie Gongcheng Xuebao (Chinese Journal of Mechanical Engineering) 1992 35 (2) 22-25 (in Chinese) The fatigue crack propagation beheviour at the weld toe of a welded joint of A131 steel was obtained from a test programme. A statistical model for fatigue crack propagation at the weld toe was proposed by means of s probebillatlc method. The statistical nature of fatigue crack propagation at the weld toe was invsetigated. Graphs, 3 raf. international recommendations f o r t h e fatigue strength of w e i d m e n t s (Internationals Empfehlungen zur Schwtnghlstigkelt G e l d m f e b s t e r Bauteila) Hobbacher, A. Schweiesen und Schneiden Fob. 1992 44 (2) 82-87 (in German; in English pp E39-E34) Standards defining the fatigue strength of weldments in terms of dimension and defect evaluation are discussed. The adverse effects of manufacturing imperfections, volumetric and plate discontinuities on the fatigue strength could arise from increasing stress level or generation of local notch effects in the welded joint. Imperfections are to be evaluated by measuring edge miselignment and angular distortion, weld undemutting, slag inclusions and pores and formation of cracks or similar plane defects derived from fracture mechanics. Graphs, 14 raf. Increasing t o o l life in cold forging t h r o u g h advanced design and t o o l manufactudng tsohnlques. Lange, K., Hettig, A. and Knoerr, M. J. Mater. Proc. Technol, Oct. 1992 35 ( 3 - 4 ) 496-513 Results of two investigations concerned with the evaluation and prediction of fatigue failure and the improvement of tool service life in cold forging are presented. The first study presents an integrated approach to tool stress analysis and shows its possible application for s punch failure case provided by industry. The second study experimentally investigates measures that can be taken during design and tooling manufacture to reduce fatigue failure. Both studies clearly indicam the value of performing a tool stress analysis during the process and tool design phase. Steel developments f o r Improved fatigue resistance in suspension springs. Smart, E., Cook, W. 7", and Ellis, A. Ironmaking and Steelmaking 1992 19 (4) 285-289 The parabolically tapered steel leaf spring is the main method of suspension used on heavy commercial vehicles in western Europe, and the Teperlite product made by Tinsiey Bridge Ltcl is s market leader in this type of spring. These springs are designed to high stresses and are manufactured to achieve high levels of fatigue durability using conventional spring steels. Techniques of 'alternative metallurgy" have been examined to establish whether lighter springs could be designed to operate at even higher stress levels. This work involved the use of a lower carbon base steel and a different method of alloying than the conventional spring steal, heat treatment to a much higher strength level, end the development of an enhanced compressive residual stress profile below the surface of the steel. Trials were carried out on three sizes of tapered leaf spring and, in each case, the alternative metallurgy springs exhibited fatigue properties superior to those of the conventional springs.
Heat treatment, microstructures, and residual stresses In cerburizad
steels, Kraues, G. Proc. Conf. Quenching and Distortion Control, Chicago, Illinois, USA, 22-25 Sept. 1992 (ASM International, Materials Park, OH 44073-0002, USA) 1992 pp 181-191 The evolution of microstructure and residual stress during the heat treatment processing of gas carburized steels is reviswed and these factors ere related to fetigus resistance. The tempered martensite-rateined suatenito microstructure produced by quenching and tempering, end the prior microstructurs produced by carbudzing at temperatures where austenite is stable, are described. Austenitizing affects grain growth, segregation of phosphorus, carbide formation, and surface oxidation. Factors which sffact the development of surface residual stresses, ie quenching, refrigeration, oxide formation, tempering, shot peening, and straininduced trsnaformation of auatenite, are discussed. The microstructure and residual stresses sre relatedto fatigue crack initiation mechanisms sad fatigue performsnce. Effects of residual stress, w e l d t o e notch and w e l d defects on fatigue
of welded ~ struct~Jrce. Shen. W. Diss. Abstr. Int. Sept. 1992 53 (3) 232 pp in studying the fatigue behaviour of fillet-welded railroad tank car shell structures, the effects of welding residual stress, weld toe notch and weld defects on the fatigue of fillet-welded A515 steal specimens were evaluated. Both hole-drilling and sectioning measurement techniques were used to obtain residual stress information. Pad-on-plate weld spelomens were designed to simulate the tank car structure for measurement of welding residusl stress. Simple bead-on-plate end fillet weld specimens, which have similar welding residusl stresses near the weld end toe to the peal-on-plate specimens, were designed to be as compact ss possible for fatigue testing. As-welded and stress-relieved simple weld specimens were tssted under pulsed tension and siternating cyclic load conditions to determine stress life and fatigue crack propagation properties. Weld toe stress concentration effects were determined by strain gauge measurement. Fracture surface features and crack initiation sites were studied by visual analysis, scanning electron microscopy and optical microscopy. Welding residual stresses were found to be biaxial tension-compression near the weld end toe end biaxial tension-tension near the weld centre toe. Longitudinal tensile residual stress was significantly relieved when the applied longitudinal tensile cyclic load w e s > 14 ksi. Test results did not show a consistent effect of tensile residual stress on the fatigue strength under pulsed
442
Corrosion fatigue bebeviour of t h e austunitic steel XGCrNIMoTi17 12 2 in 3% NaCI solution under rotating bending load (Schwingungsrieskorrosionsverhaitso des Austenitieshso Stshlce X6 CrNiMoTI 17 12 2 in 3% Iger NaCI-Lceung U n t e r Umlaufblegebelsotung)
Roeder, E., Bassler, H.-J., Huber, M. and Vollmar, J. Werket. Korros. Sept. 1992 43 (9) 426-431 (in German) The fatigue beheviour of steel X6CrNiMoTi17 12 2 (German material-number 1.4571, comparable to AISI 316 Ti) is investigated under rotating bending load with a frequency of 50 Hz. The fatigue strength in inert medium (thermostat oil) at room temperature is 315 N/mm 2, In 3% NaCI solution of pH 7 at the same temperature, the corrosion fatigue limit for N = 107 reached only 94% of the mentioned value. A higher temperature (70°C) caused • further reduction to 89% and an additional decrease of the pH value (pH 3) lowers the dynamic strength to 88% of the reference value. The free COrrosion potential, recorded during all COrrosion fatigue tests, remains in the passive region for all specimens, which do not fail under the machanicel-corrosive load. The potential of specimens, which fail under a higher mechanical load, announces their rupture by s sudden decrease to negative values, which starts at least 3 x 104 cycles (10 mini before. Graphs, 11 raf. Study of fatigue charactsdstlc of 3SaM ultra-high-strength steel corn-
ponents. Liu, J. J. Mater. Eng. (China) 1992 (3) 20-23 (in Chinese)
The axial tension and flaxurel fatigue beheviour of 300M uitre-high-strongth smel was examined by using lugs, bolts, and circular tubes at room temperature in an air medium. The effect on fatigue beheviour of surface integrity, various stress ratios R, heat treatment and load spectre are discussed, and the difference in fetigue property between the Chinese materials and the American materials is studied. Graphs, 4 rsf. Effect of prsioadlng on short fatigue crack g r o w t h at a notch. Xu, K.,
He, J. and Zhou, H. Chinese J. Met. Sci. TechnoL 1992 8 (2) 79-83
Results of tests on samples of 42CrMo4 steal indicate that under cyclic tension the growth rate of short fatigue cracks from notch roots will be lowered greatly by
Int J Fatigue September 1993