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Prediction of fatigue strength of high-speed steel based on estimation of the maximum size of inclusions
this, the fracture surfaces were observed by a SEM. It is pointed out that microcracks produced in elongated MnS inclusions increase daldN for SL specimens but reduce da/dN for ST specimens. Graphs, photomicrographs. 22 refs.
prediction of fatigue stran h of hl h-speed steel based on estimation R atsume, Y., Miyakawa, S., Uemura, yf $;dma;;ra;iJiy of in&ion*. J: Sot. Mater. SL., Jpn. Oct. 1999 38, (4331, 1133-1138
A Monte Carlo simulation of the ropagation of microstructuraliy small fati ue cracks. Akiniwa, Y. and Paneka, K. J. %c. Mater. Sci., Jpn. Oct. 1999 38, /433), 1169-1175 (in Japanese) The continuous distribution of dislocations was used to model the slip deformation ahead of the tip of a small fatigue crack interacting with grain boundaries. The propagation rate of a fatigue crack was assumed to be controlled by the crack-tip opening displacement. A Monte Carlo simulation was conducted for fatigue crack growth by giving the grain size and the frictional stress of each grain as random variables following the two-parameter Weibull distribution. The distributions of the crack propagation rate and the crack propagation life were computed as functions of the crack length and the stress level as well as of the grain size. The results of the simulation agreed at least qualitatively with the experimental results obtained for Al alloy 2026T3. Graphs. 18 refs.
Effect of material structure on statistical scatter of surface fatigue crack ation rata. lshi A &hi Y. and Sasaki SK. T!c%!? Mater. Sci., J&. ‘6ct. 1999 38, (433), 1’163-1166 (in Japanese) In order to clarify the cause of statistical scatter in fatigue lives, crack propagation behaviour was investigated. Three kinds of metals, a low carbon steel fS15C) with four grain sizes, a pure Cu and an austenitic stainless steel ISlJS304). were tested under rotating bending to examine the effect of material structure. To evaluate the characteristics of scatter of crack orooaaation rate. the relationshio between the crack propagation rate da/dN and the &&s intensity factor range AKwas analysed for four ranges of crack length from crack initiation to failure. Statistical properties of a power m and a coefficient C in Paris’ law obtained by a regression analysis for each crack were ewanined in relation to material structure. Furthermore, the crack deflection ratio, Rd. obtained from the measurement of crack length along crack path, which increases with the effect of material structure, was statistically examined and discussed. Graphs. 15 refs.
Effect of notch inclination angia on fatigue strength. Miyazaki, K., Furukawa, T and Watanabe, T. J. Sot. Mater. Sci., Jpn. Oct. 1989 38, (433). 1157-1162 (in Japanese) The effect has been investigated of the notch inclination angle (QP), which is defined as the angle between the centre line of a specimen and the centre line of a Vgroove having a notch opening angle of 90”. on the plane bending fatigue behaviour. This study was conducted to reveal the influences of Q on the plane bending fatigue limit, the fatigue crack initiation and propagation and the behaviour of a nonpropagating crack. The main results obtained are as follows. (1) The fatigue limit was increased and the fatigue life was prolonged with the increase of c. Especially the test soecimen having the notch Shaoe like a steo lin this case, o = 45’) showed the tendency that the fatigue life is much longer than other cases irp = O’, Q = 15”. Q = 30’). (2) In the case of stress level having an inflexion point in the fatigue crack growth curves, the results obtained were independent of the influence of ‘p. The fatigue crack growth rate fdf/dN) decreased with an increase of crack length until it reached the inflexion point of dlldN in the fatigue crack growth curve. Then it increased or the fatigue crack became non-propagating, depending on the level of the applied stress. A similar tendency was found in the relation between dlldN and the stress intensity factor range (AK), when AK was taken as a parameter instead of the crack length. In the increasing range of d//dN, the following equation was experimentally obtained between d//dN and AK: d//dN = 5.92 x lo-” x AK4.‘9. In the decreasing range of dlldN, the relation between dlldk and AK was able to be arranged using the stress concentration factor (a). Graphs, photomicrographs. 13 refs.
Analysis on pooled S-N data of notched specimens from JSMS Data Book. Kikukawa, M., Hatanaka, M. and Misawa, T J. Sot. Mater. Sci., Jpn. Oct. 1989 38, (4331, 1151-1156 (in Japanese) The fatigue strength data of notched specimens of steels has been analysed by distinguishing the fatigue limit for crack initiation, (II, and that for fracture. e_,. with the aid of N&hitani’scritical notch radius w, at the branchpoint, ie at the-&cat point where a non-propagating crack appears. In this study, S-N f&N, S-7’) data of rotary bending tests of sharp (notch radius p 4 so). deep (notch death r >z d p t/5), notched specimens of steels were extracted from the JSMS Data Book and analvsed by fitting a bilinear tv~e S-N curve comorisina inclined and horizontal straight lines on a-log-log diagram, using Nishijima’s method. By taking the stress intensity factor Kof the circumferential crack with notch depth tinstead of the stress P in the S-N curves, and bv using the following correction factor x for low strength steels, ie K = osloc for tensile strength es < dc = 900 MPa, x = 1 for 0s 3 PC, S-N data of sharp, deep notched specimens of both low and high strength steels could bs fitted by a bilinear type curve on a log (KMaps xl-log N diagram, with the coefficient of variation 14.D%, while the coefficient of variation for the log (P Maps o&log N diagram of corresponding smooth specimens was 11.8%. Graphs. 8 refs.
Effects of raphffe shape, size and distribution on the fatigue strength of spheror-1 al graphite cast irons. Endo, M. J. Sot. Mater. Sci., Jpn. Oct. 1969 38, (4331, 1139-1144 (in Japanese) Spheroidal graphite ISG) cast iron is a typical porous material which contains numerous small defects (graphites) in the matrix. In order to clarify the geometrical parameter for the quantitative evaluation of the effect of surface graphite on the fatigue strength of SG cast iron, rotating bending fatigue tests ware carried out on plain and notched specimens of as-cast FClXO-andFCD70. It is concluded from microscopic observations that the fatigue limit is controlled bv the maximum size of surface graphite defined bv the square root of the projected area of graphite (root area*m.l ). The value of root area* mllx in a definite surface area of the specimen can be predicted by the statistics of extreme values. The predicted values of root ere~*~.~ approximately agree with the critical size of an artificial notch which does not act to reduce the fatigue strength. The value of root areatmlx is in general considered to be the controlling geometrical parameter for the prediction of fatigue strength of porous materials. Graphs. photomicrographs. 31 refs.
Int J Fatigue July 1990
(in
Japanese)
The fatigue fracture surface of high strength steels often shows a typical mark like a fish-eye. A non-metallic inclusion is commonly found at the csntra of the fisheye. This implies that the non-metallic inclusion at the centre of the fish-eye of a specimen fractured in e tension-compression fatigue test is the maximum one in the specimen. It was confirmed from experiments on many samples of a high-speed steel that the size (the square root of projected area : root area) of the non-metallic inclusions at a fish-eve followed the statistics of axtreme values. Moreover, it was found that the fatigue fracture stress at these inclusions could be predicted by a previous equation which was proposed on the basis of fatigue data on small artificial defects. The lower limit of a large scattar band of the fatigue strength was also prediaed by combining the statistical distribution of extreme values of root area end the previous equation. It was shown that the prediction was in good agreement with the experimental results. Photomicrographs, graphs. 12 rafs.
Reiationrhip between fati ue proparties and hardness for hi h hardness steels temparad at severaf temperaturea. Konuma, S. and Purukawa, T. J. Sot. Mater. Sci., Jpn. Oct. 1989 38, (433). 1128-1132 (in Japanese) A study was made on the effect of hardness on fatigue properties of high strength steels. Rotating bending fatigue tests were carried out on four different carbon steels tempered at four temperatures. The results are summarizd as follows. (1) The origin and location of fatigue fracture could be classified by hardness. (2) Even for high hardness steel showing fish-eye fracture, the fatigue limit was proportional to hardness under the same tempering conditions. t3)The fatigue limit could be estimated as a function of hardness and tempering temperature. Photomicrographs. graphs. 13 refs.
Effect of he+ generation on the fatlgue strength of a low carbon steai under combmad push-8 ull and .torslonel loading. Ohkawa, L, Takahashi, H., Yanagrsewa, J. an Mrsumr, M. J. Sot. Mater. Sci., Jpn. Oct. 1989 38, (4331, 1122-1127 (in Japanese) Fatigue tests were conducted at a frequency of 20 or 5Hz under push-pull or reversed torsion or a combination of these two loading models. Specimen temperatures rose by heat generation during cyclic stressing at 20 Hz but were kept at room temperature by air-cooling throughout the testing at 5 Hz. The variations of fatigue strength and strain range resulting from heat generation were studied in each loading mode. The heat generation became greater in the order, torsional, combined, push-pull loading, which resulted in shortening of the fatigue life at higher stress amplitude. The-fatigue strength under combined loading ias able to be evaluated by using S-N diagrams derived on the basis of Gough’s ellipse quadrant theory except that the slope in the finite fatigue life region varied departding on temperature rise. Von Mises’ equivalent plastic strain range fAa& increased rapidly at an early stage of fatigue life and decreased durina subseauent stress cvcles~ In the case of heat generation, the change of IA+& v&s amplified and its average in fatigue process was lowered. The relationship between the maximum of (As,& and fatigue life was expressed by a straight line with a narrow scatter bend on a log-log diagram, irrespective of the heat generation. Graphs. 24 refs.
Changes in fatigue strength due to cyclic prestreas: II. Fatigue tests of alummium alloy specimens and evaluation by meens of the sequentlai Wohier curve concept. Pusche, A.C. IfL-Mitt. Mar.-Apr. 1989 28, (2), 43-49 (in German) Fatigue strength as the endurance limit plays an important role in the lightweight constructional dimensioning of component parts subject to cyclic stress. Investigations were made to determine the changes in fatigue strength due to cycle prestress of rod-shaped specimens of Al alloy subjected to rotating bending tests and to evaluate them by utilizing the sequential Wohler curve concept. Graphs. 15 refs.
Fatigue bahaviour of creep-msistant 15Mo3 steal et temperatures to 500 “C. Fleischer, H. and Frank, J. IfL-Mitt. Mar.-Apr. 1969 28, (2), 33-39 (in German)
up
Creep-resistant 15Mo3 steel was subjected to force-controlled and strain-controlled fatigue tests and static tensile and notched bar impact bending tests at temperatures up to 500 “C. At temperatures between 200-35O’C the steel showed signs of deformation ageing involving a marked increase of strength and an associated loss of tenacity. It is considered that the results will allow a better utilization of the material properties and a more economical use of material. Graphs. 9 refs.
Properties and applications of modified PM hi h speed steels in wear resistant situations. Henry, R.J. and Srewin, f. 77 Met. Powder Rep. Nov. 1969 44, (11). 763-767 The results are described of a multi-faceted co-operative research effort to develop PM high-speed steels for wear resistant applications which can be produced by ‘gas’ sintering to close dimensional tolerances. The development is also outlined of abrasive wear tests to generate data comparable to those used by high-speed users and manufacturers, and rolling contact fatigue properties. Graphs. 3 refs.
Restoration of fatigue limit of nitrided shafts after a straightening operation. Zeher, R. and Prummer, f?. Mater.wiss. Werkst.tech. Nov. 1999 20, (ll), 391-396 (in German) It is well known that surface residual stresses influence the fatigue behaviour of machine parts. Compressive residual stresses are of beneficial nature, whereas tensile surface stresses are of detrimental influence. One of the means to improva the service behaviour of components is nitriding. A hard surface layer is created, which is several tenths of a millimeter thick and improves the resistance against wear and fatigue failure. Also, compressive residual stresses improve the service behaviour. As a consequence of the treatment of components by nitriding, a misalignment often has to be taken into account and a certain percentage of the parts have to be straightened. It was observed that parts which undergo such a straightening operation may show a loss in fatigue strength. This was the case for
299
prediction of fatigue stran h of hl h-speed steel based on estimation R atsume, Y., Miyakawa, S., Uemura, yf $;dma;;ra;iJiy of in&ion*. J: Sot. Mater. SL., Jpn. Oct. 1999 38, (4331, 1133-1138
A Monte Carlo simulation of the ropagation of microstructuraliy small fati ue cracks. Akiniwa, Y. and Paneka, K. J. %c. Mater. Sci., Jpn. Oct. 1999 38, /433), 1169-1175 (in Japanese) The continuous distribution of dislocations was used to model the slip deformation ahead of the tip of a small fatigue crack interacting with grain boundaries. The propagation rate of a fatigue crack was assumed to be controlled by the crack-tip opening displacement. A Monte Carlo simulation was conducted for fatigue crack growth by giving the grain size and the frictional stress of each grain as random variables following the two-parameter Weibull distribution. The distributions of the crack propagation rate and the crack propagation life were computed as functions of the crack length and the stress level as well as of the grain size. The results of the simulation agreed at least qualitatively with the experimental results obtained for Al alloy 2026T3. Graphs. 18 refs.
Effect of material structure on statistical scatter of surface fatigue crack ation rata. lshi A &hi Y. and Sasaki SK. T!c%!? Mater. Sci., J&. ‘6ct. 1999 38, (433), 1’163-1166 (in Japanese) In order to clarify the cause of statistical scatter in fatigue lives, crack propagation behaviour was investigated. Three kinds of metals, a low carbon steel fS15C) with four grain sizes, a pure Cu and an austenitic stainless steel ISlJS304). were tested under rotating bending to examine the effect of material structure. To evaluate the characteristics of scatter of crack orooaaation rate. the relationshio between the crack propagation rate da/dN and the &&s intensity factor range AKwas analysed for four ranges of crack length from crack initiation to failure. Statistical properties of a power m and a coefficient C in Paris’ law obtained by a regression analysis for each crack were ewanined in relation to material structure. Furthermore, the crack deflection ratio, Rd. obtained from the measurement of crack length along crack path, which increases with the effect of material structure, was statistically examined and discussed. Graphs. 15 refs.
Effect of notch inclination angia on fatigue strength. Miyazaki, K., Furukawa, T and Watanabe, T. J. Sot. Mater. Sci., Jpn. Oct. 1989 38, (433). 1157-1162 (in Japanese) The effect has been investigated of the notch inclination angle (QP), which is defined as the angle between the centre line of a specimen and the centre line of a Vgroove having a notch opening angle of 90”. on the plane bending fatigue behaviour. This study was conducted to reveal the influences of Q on the plane bending fatigue limit, the fatigue crack initiation and propagation and the behaviour of a nonpropagating crack. The main results obtained are as follows. (1) The fatigue limit was increased and the fatigue life was prolonged with the increase of c. Especially the test soecimen having the notch Shaoe like a steo lin this case, o = 45’) showed the tendency that the fatigue life is much longer than other cases irp = O’, Q = 15”. Q = 30’). (2) In the case of stress level having an inflexion point in the fatigue crack growth curves, the results obtained were independent of the influence of ‘p. The fatigue crack growth rate fdf/dN) decreased with an increase of crack length until it reached the inflexion point of dlldN in the fatigue crack growth curve. Then it increased or the fatigue crack became non-propagating, depending on the level of the applied stress. A similar tendency was found in the relation between dlldN and the stress intensity factor range (AK), when AK was taken as a parameter instead of the crack length. In the increasing range of d//dN, the following equation was experimentally obtained between d//dN and AK: d//dN = 5.92 x lo-” x AK4.‘9. In the decreasing range of dlldN, the relation between dlldk and AK was able to be arranged using the stress concentration factor (a). Graphs, photomicrographs. 13 refs.
Analysis on pooled S-N data of notched specimens from JSMS Data Book. Kikukawa, M., Hatanaka, M. and Misawa, T J. Sot. Mater. Sci., Jpn. Oct. 1989 38, (4331, 1151-1156 (in Japanese) The fatigue strength data of notched specimens of steels has been analysed by distinguishing the fatigue limit for crack initiation, (II, and that for fracture. e_,. with the aid of N&hitani’scritical notch radius w, at the branchpoint, ie at the-&cat point where a non-propagating crack appears. In this study, S-N f&N, S-7’) data of rotary bending tests of sharp (notch radius p 4 so). deep (notch death r >z d p t/5), notched specimens of steels were extracted from the JSMS Data Book and analvsed by fitting a bilinear tv~e S-N curve comorisina inclined and horizontal straight lines on a-log-log diagram, using Nishijima’s method. By taking the stress intensity factor Kof the circumferential crack with notch depth tinstead of the stress P in the S-N curves, and bv using the following correction factor x for low strength steels, ie K = osloc for tensile strength es < dc = 900 MPa, x = 1 for 0s 3 PC, S-N data of sharp, deep notched specimens of both low and high strength steels could bs fitted by a bilinear type curve on a log (KMaps xl-log N diagram, with the coefficient of variation 14.D%, while the coefficient of variation for the log (P Maps o&log N diagram of corresponding smooth specimens was 11.8%. Graphs. 8 refs.
Effects of raphffe shape, size and distribution on the fatigue strength of spheror-1 al graphite cast irons. Endo, M. J. Sot. Mater. Sci., Jpn. Oct. 1969 38, (4331, 1139-1144 (in Japanese) Spheroidal graphite ISG) cast iron is a typical porous material which contains numerous small defects (graphites) in the matrix. In order to clarify the geometrical parameter for the quantitative evaluation of the effect of surface graphite on the fatigue strength of SG cast iron, rotating bending fatigue tests ware carried out on plain and notched specimens of as-cast FClXO-andFCD70. It is concluded from microscopic observations that the fatigue limit is controlled bv the maximum size of surface graphite defined bv the square root of the projected area of graphite (root area*m.l ). The value of root area* mllx in a definite surface area of the specimen can be predicted by the statistics of extreme values. The predicted values of root ere~*~.~ approximately agree with the critical size of an artificial notch which does not act to reduce the fatigue strength. The value of root areatmlx is in general considered to be the controlling geometrical parameter for the prediction of fatigue strength of porous materials. Graphs. photomicrographs. 31 refs.
Int J Fatigue July 1990
(in
Japanese)
The fatigue fracture surface of high strength steels often shows a typical mark like a fish-eye. A non-metallic inclusion is commonly found at the csntra of the fisheye. This implies that the non-metallic inclusion at the centre of the fish-eye of a specimen fractured in e tension-compression fatigue test is the maximum one in the specimen. It was confirmed from experiments on many samples of a high-speed steel that the size (the square root of projected area : root area) of the non-metallic inclusions at a fish-eve followed the statistics of axtreme values. Moreover, it was found that the fatigue fracture stress at these inclusions could be predicted by a previous equation which was proposed on the basis of fatigue data on small artificial defects. The lower limit of a large scattar band of the fatigue strength was also prediaed by combining the statistical distribution of extreme values of root area end the previous equation. It was shown that the prediction was in good agreement with the experimental results. Photomicrographs, graphs. 12 rafs.
Reiationrhip between fati ue proparties and hardness for hi h hardness steels temparad at severaf temperaturea. Konuma, S. and Purukawa, T. J. Sot. Mater. Sci., Jpn. Oct. 1989 38, (433). 1128-1132 (in Japanese) A study was made on the effect of hardness on fatigue properties of high strength steels. Rotating bending fatigue tests were carried out on four different carbon steels tempered at four temperatures. The results are summarizd as follows. (1) The origin and location of fatigue fracture could be classified by hardness. (2) Even for high hardness steel showing fish-eye fracture, the fatigue limit was proportional to hardness under the same tempering conditions. t3)The fatigue limit could be estimated as a function of hardness and tempering temperature. Photomicrographs. graphs. 13 refs.
Effect of he+ generation on the fatlgue strength of a low carbon steai under combmad push-8 ull and .torslonel loading. Ohkawa, L, Takahashi, H., Yanagrsewa, J. an Mrsumr, M. J. Sot. Mater. Sci., Jpn. Oct. 1989 38, (4331, 1122-1127 (in Japanese) Fatigue tests were conducted at a frequency of 20 or 5Hz under push-pull or reversed torsion or a combination of these two loading models. Specimen temperatures rose by heat generation during cyclic stressing at 20 Hz but were kept at room temperature by air-cooling throughout the testing at 5 Hz. The variations of fatigue strength and strain range resulting from heat generation were studied in each loading mode. The heat generation became greater in the order, torsional, combined, push-pull loading, which resulted in shortening of the fatigue life at higher stress amplitude. The-fatigue strength under combined loading ias able to be evaluated by using S-N diagrams derived on the basis of Gough’s ellipse quadrant theory except that the slope in the finite fatigue life region varied departding on temperature rise. Von Mises’ equivalent plastic strain range fAa& increased rapidly at an early stage of fatigue life and decreased durina subseauent stress cvcles~ In the case of heat generation, the change of IA+& v&s amplified and its average in fatigue process was lowered. The relationship between the maximum of (As,& and fatigue life was expressed by a straight line with a narrow scatter bend on a log-log diagram, irrespective of the heat generation. Graphs. 24 refs.
Changes in fatigue strength due to cyclic prestreas: II. Fatigue tests of alummium alloy specimens and evaluation by meens of the sequentlai Wohier curve concept. Pusche, A.C. IfL-Mitt. Mar.-Apr. 1989 28, (2), 43-49 (in German) Fatigue strength as the endurance limit plays an important role in the lightweight constructional dimensioning of component parts subject to cyclic stress. Investigations were made to determine the changes in fatigue strength due to cycle prestress of rod-shaped specimens of Al alloy subjected to rotating bending tests and to evaluate them by utilizing the sequential Wohler curve concept. Graphs. 15 refs.
Fatigue bahaviour of creep-msistant 15Mo3 steal et temperatures to 500 “C. Fleischer, H. and Frank, J. IfL-Mitt. Mar.-Apr. 1969 28, (2), 33-39 (in German)
up
Creep-resistant 15Mo3 steel was subjected to force-controlled and strain-controlled fatigue tests and static tensile and notched bar impact bending tests at temperatures up to 500 “C. At temperatures between 200-35O’C the steel showed signs of deformation ageing involving a marked increase of strength and an associated loss of tenacity. It is considered that the results will allow a better utilization of the material properties and a more economical use of material. Graphs. 9 refs.
Properties and applications of modified PM hi h speed steels in wear resistant situations. Henry, R.J. and Srewin, f. 77 Met. Powder Rep. Nov. 1969 44, (11). 763-767 The results are described of a multi-faceted co-operative research effort to develop PM high-speed steels for wear resistant applications which can be produced by ‘gas’ sintering to close dimensional tolerances. The development is also outlined of abrasive wear tests to generate data comparable to those used by high-speed users and manufacturers, and rolling contact fatigue properties. Graphs. 3 refs.
Restoration of fatigue limit of nitrided shafts after a straightening operation. Zeher, R. and Prummer, f?. Mater.wiss. Werkst.tech. Nov. 1999 20, (ll), 391-396 (in German) It is well known that surface residual stresses influence the fatigue behaviour of machine parts. Compressive residual stresses are of beneficial nature, whereas tensile surface stresses are of detrimental influence. One of the means to improva the service behaviour of components is nitriding. A hard surface layer is created, which is several tenths of a millimeter thick and improves the resistance against wear and fatigue failure. Also, compressive residual stresses improve the service behaviour. As a consequence of the treatment of components by nitriding, a misalignment often has to be taken into account and a certain percentage of the parts have to be straightened. It was observed that parts which undergo such a straightening operation may show a loss in fatigue strength. This was the case for
299