1、STD-AGMA 94FTfl7-ENGL 1794 W Ub87575 0004587 22T 94FTM7 Allowable Surface Compressive Stresses of Gear Teeth Made of Cast Iron, Tempered Carbon Steels and Tempered Alloy Steels by: Hirofumi Kotorii Mechanical Engineering Laboratory, Japan American Gear Manufacturers TECHNICAL PAPER COPYRIGHT America
2、n Gear Manufacturers Association, Inc.Licensed by Information Handling ServicesAllowable Surface Compressive Stresses of Gear Teeth Made of Cast Iron, Tempered Carbon Steels and Tempered Alloy Steels Hirofumi Kotorii Mechanical Engineering Laboratory, Japan The statements and opinions contained hemi
3、n are those of the author and should not be consmed as an oficial action or opinion of the American Gear Manufacturers Association. ABSTRACT: Load endurance tests have been conducted to obtain dowable surface CompresSiVe stresses for materials required for strength and high reliability of power gear
4、s. The foilowing JIS materiais were used in conducting the tests: spheric graphite cast iron, G5502; carbon steel, G4051 and steel G4502. Using a designed gear with mdde 4 and u) degree pressure ange as a prototype, load endurance tests were conducted and data concerning tooth damage was accumulated
5、. The results of these tests and comparison of the durability of the materials are presented in this paper. Copyright O 1994 American Gear Manufacairers Association 1500 King Street, Suite 201 Aiexandria, Virginia, 22314 October, 1994 ISBN 1-55589-619-7 COPYRIGHT American Gear Manufacturers Associat
6、ion, Inc.Licensed by Information Handling ServicesSTD.AGMA qFTM7-ENGL 1774 Ob87575 0004591 988 Allowable Surface Compressive Stresses of Gear Teeth made of Cast Iron, Tempered Carbon Steels and Tempered Alloy Steels Senior Research Officer Hirofumi Kotorii Mechanical Engineering Laboratory, Japan 30
7、5 Ibaraki-ken Tsukuba-shi Namiki 1-2 Introduction It has been know for long time that clutching surfaces of gear teeth made of steel are damaged by the occurrence of so-called “pitting“ when the gear is operated under load for certain period, and the occurrence of “pitting would occasionally bring a
8、bout the breakages of not only the gear teeth but also the whole system with the increase of vibration noise if operation of the gear is continued under the same conditions. Occurrence of “pitting“ phenomena are also observed in other mechanical elements than gears, in rolling bearings for instance.
9、 Predominant opinion on the cause of “pittingc phenomena basing on the results of researches made for prolonged period is that they are due to the surface fatigue of the materials. Although classifications and causes of “pitting“ phenomena are not discussed in this presentation, “pittingm have been
10、the most serious problem among the damages to be observed on gear teeth surfaces dom to the present time. It has been revealed by the recent research work that the occurence of pitting phenomena was closely related to lubrication. In this connection, one started to have another look at the pitting p
11、henomena, especially from the view point of elastic fluid lubrication. Therefore, it has been urged to change the notion of the durability of tooth surface against pitting, that is, the calculation method of the intensity of gear tooth. circle is frequently compared with the stress of the material i
12、n order to derive the equation for determining the intensity of the teeth surfaces of gear. necessary to obtain the allowable stress of gear teeth surfaces made of various materials beforehand, as in the case of obtaining the bending strength. For this purpose, two test methods, the roller test usin
13、g cylindrical specimens and the test operating a pair of actual gear under load, have been applied for long time. Results obtained by these tests have been adopted as the designing standards. However, it is almost impossible to let the contacting conditions of rollers coincide with those of the toot
14、h surfaces of gears. Therefore, it is theoretically impossible to expect the agreements of the test results obtained by those two test methods respectively since there are several other additional differences between the two in respect to dimensional effects, temperature effects, etc. In this connec
15、tion, it is considered that test results obtained by the gear test should preferably be adopted as the precise designing standard, although those obtained by the roller test may be taken as reference only in case there is no other data available. However, calculated Hertz stress on pitch Standing on
16、 this view point, it should be 1 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling ServicesDue to the above reasons, tests using actual gears were exclusively carried out in this experimental program for obtaining allowable stresses of gear teeth surfaces. exper
17、imental program were compared with the experimental data which has been presented and with the specification limits which had been referred to. Finally, test results obtained by this 1. Running Test 1.1 Test Equipment device was built as a trial. Its profile and specifications are shown in Fig.l and
18、 Table 1 respectively. A recirculation power type gear testing Luricating Device Operating Box Variable Speed Device Fig. 2 The characteristics of this tester are the adoptions of stepless phase adjustable coup1 ing applying harmonic driving mechanism being marketed under the trade name of i* Just 4
19、0“ as loading device and the torque pick-up applying pneumatic signal transmission device (slipringless) as torque measurement devi ce. circulating system, twisting load can be applied even while the tester is at rest. bearings. By setting these devices in the axis of the Both ends of the test gear
20、are supported by Needle bearings are used for the r I I I ia Ei RI A /lest Gear / lorqe Pick Up/ JUST Load Device Fig. 1 Table 1 Recirculation power type gear tester Bearing Distance : 100 I Circular Gear : W,b60.221,29 Spur gear.P.A Zdeg. Max. Trens. Power : 280pS (2051tl) Yax. Trens. Torque : M) I
21、(efi(49Wb)/pinion Max. Tang. driv. force : 1190(1167N) Wpinion : i, , 2000. m. 4o Max. Pitch-line velocity :17.6Us Motor : 22gl Apply load pethod : Applying huwoic driving i.chanim Uust 40) Appearance of this tester is shown in the photographs in Fig. 2. I I I Fie. 3 2 COPYRIGHT American Gear Manufa
22、cturers Association, Inc.Licensed by Information Handling ServicesSTD-AGUA SqFTM7-ENGL 1774 H b87575 17174573 7517 outer ends of the gear box and roller bearings are mainly used for the others. Both gear and bearings are lubricated by the same lubricating oil forcely fed from the same reservoir. The
23、 oil temperature can be controlled at any temperatures within the range of oil temperature to 80C in the accuracy of21“C. Cntrolling diagram of the measurement system is shown in Fig.3. temperature, torque and vibration are recorded on the recorder and rotational frequencies, flow rates of lubricant
24、 and impact loads are read on the indicators. Upper and lower 1 imi t s of operat ional conditions at the necessary parts of the tester can be set and the operation of the tester can automatically be discontinued in emergency including in the case of damage. Changes of oil 1.2 Materials and Specific
25、ations of Test Gear set Typical gear materials selected are cast iron, carbon steel and alloy steel. composition, heat treatment procedure and mechanical characteristics of each gear material. Shown in Table 2 are the chemical Table 2 Mechanical properties Unterials Tention test Yild strength Tensil
26、e Elogation Reduction Charpy or point strength of Area value C 42.5 55. 1 6.2 4.2 o. 4 kf/d %f/3 x x kf/d Ri P 43.4 55.9 5.6 4.9 o. 3 * c) K2 P 45.5 C 46.3 K3 P 47.3 C 54.8 K4 P 68.4 G 55.7 64.7 32.1 62. 5 32.8 74.3 29.6 71.5 30. 9 83. 6 26.2 81.9 27.4 a 58.2 9.3 c 68.2 10.9 - 63.6 7.8 f 66.5 10.1 o
27、 60.5 16.0 “ 63.2 7. 7 K5 P 83.2 95.2 23.9 65.3 20.6 C 76.0 89.2 24.8 67.3 22.5 K6 P 97.6 106.8 21.5 69. 9 15. 1 C 98.3 108.9 22.0 61.8 14.4 P: Pinion c: cear Chemical compositiones %) Heat treatment Hardness and temperature 4 c si Yo p s CU Cr Ni Yo /Hours ,+ 217 3.53 2.91 0.6 0.081 0.014 190 3.63
28、2. OI O. 6 O. O81 O. 014 x c, 2 173 0.340.260.8 0.0160.01 0.060.020.02 rl 166 0.30.230.670.10.0.010.010.02 2 207 O. 4 O. 27 O. 76 0.028 0.013 0.02 O. I3 0.01 O 201 0.45 0.27 0.79 0.026 0.021 0.01 0.12 0.02 o 238 O.MO.3 0.740.02 0.0170.020.130.02 229 O. 65 0.23 O. 76 O. 024 0.014 O. O1 O. 02 O. 02 Pr
29、iq qusmhiiy 85oc 285 /*in. Oil hss. 266 0.38 0.26 0.7 0.012 0.W 0.08 0.I 0.W O. 17 T.iperiu 69Oc/2hr IC 316 Riury Ruichini 8500 316 /Ihin.Oil brs. T.iDsrin# 6u)c/Ur 1. C O. 34 0.24 O. 72 0.026 O. 014 0.01 1.06 0.03 O. I6 O. 4 0.26 O. 8 O. O16 0.02s O. 12 1.02 O. O7 O. 21 O. (2 0.28 0.81 0.916 0.021
30、O. I3 1.08 0.01 0.20 These tables represent the combination of test gears, pinion and gear. made of six different materials respectively. Since each material for making test gears was taken from the same bar lot, the material Characteristics of gear combinations made of same material, Ywhich were us
31、ed for successive tests were regarded identical. Hardness of gear surface and gear core are also included in this table. applied as standard at the stage of design, the actual hardness was measured by applying the unit of Hv as can.be seen in the table. The hardness measurement of each gear tooth we
32、re made at five locations all one can, as per shown in FiR.4 and shown in Table 3. Although the hardness unit of HB was 5k8 30sec Fig. 4 Table 3 Hardness of gear surface (Hv) Points A B CD E Gear KI P 173.7 175.3 179.8 G 186 190 193.5 190 189.5 K2 P 160 157.3 159.7 G 147.5 150.5 155.5 155 151.5 K3 P
33、 216.7 216.2 213.5 G 213.5 215 214.5 215.5 215 G 235.5 234.5 232 237 236 K4 P 252.7 253 254 K5 P 277 277.7 274.7 G 281 281 276 276 279.5 CN F12 - ( I 2 /n (3) Regression Coefficients al and a0 are: $PH /n ( 2 ag = PH - a1 N1 (4 1 10 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by
34、Information Handling Services. STD-AGMA 94FTM7-ENGL 1999 D Ob87575 OOOLibOL b57 m .I n i N1 = ZNl /n Summations of Z equat,ons are made when i=l, 2, , n. preparations of SN diagrams for each material were done over for estimating critical stress of each material at N1=107. Shown in Fig.24 are the es
35、timated critical stresses of various materials obtained by extening each straight line in the direction of the arrow. numerically summarized in Table 8. Basing on the above equations, These estimated critical stresses are relation between critical Hertz stress PHlim(kgf/m) and the hardness of the to
36、oth surface Hv. However, it seems that each material, namely cast iron, carbone steel and alloy steel, indicate different relations respectively. indicating the relation between the critical Hertz stress PHlim(kgf/m) and the hardness of tooth surface Hv was obtained as follows: In case of carbon ste
37、el (7) (8) PHlim(kgf/EId) = O. 17 HV + 61 10 NI In case of alloy steel PH1im(kgf/d) = O. 14 HV + 40 3.2 Comparisons of Allowable Stress of Table 8 Hardness Critical Load SC UV) (kef/&) (kefm2) (Psi) Wa 175 58-54 O. 9177 64932.15 447.808 aterials Surface Fig. 13 Dudley H. P. G. D 2.17- (2.21) PH KI K
38、Z 160 90.9 2.2519 100810.67 695.246 K3 216 94.26 2.4215 104489.87 720.619 ir, 253 99. o1 2.6717 109746.44 756.872 277 88-19 2.1197 97767.67 674.259 g6 310 104.56 2.9796 115952.94 799.675 K5 3.1.2 Hardness of Tooth Surface and Critical Stress and critical stress are shown in Fig.25. As can be seen in
39、 the figure, there is a mutual Relations between hardness of tooth surface 1W ZW 300 Hv 400 Fig. 25 From Fig. 25, an experimental formula Gear Teeth surface made of Various Mater ia1 s There are several calculation methods for determining the intensity of facial pressure. Discussions are still being
40、 made on selecting the best method since different coefficients are adopted to respective method due to difference in the way of thinking. At any rate, it is considered that the most reliable method for determining the intensity of facial pressure should be to adopt the experimental data obtained by
41、 using actual gears. However, ever with thus obtained experimental data, it is hard to put them in order due to differences in dimension of tester and in the ways of application. None the less, various equations are now being recommended and specified by JSME1) and by JGMA2) in JAPAN, by BSS4363) in
42、 England, by AGbA215.014) in USA and by DIN399051 in Germany. 11 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling Services STD-AGUA 74FTfl7-ENGL I994 Ob87575 OOOibOZ 593 Furthermore, experimental data of allowable stress released by Niemann Glaubetz, Niemann Bo
43、tsh and JSME are also available. As mentioned in the above, no summarized conclusion has been made so far regarding the facial intensities of gear teeth made of various materials despite of the fact that many data have been published. Nonetheless, we planned to draw lines in the figure using the tes
44、t data we obtained according to the manner of data arrangements so far applied to the scrutinizations made in the past. .In this connection, data of the critical Hertz stress intensity obtained in this experimental program, which were actually critical Hertz stresses taking hardnesses of respect ive
45、 mat er ia 1 s into consi derat ion, were converted into compressive stress S, (allowable compressive stress being adopted in the formula developed by JSME) using the following equation. E=21000 kgf/m2 S,= P“ii,Z/O. 4182 XE (9) S,s were calculated by substituting values of PHlim shown in Table 8 whi
46、ch were the test results obtained in this experimental program according to the equation. Thus calculated S, s were plotted in S, - Hv figures, which contain many other experimental data as well, with A mark, for cast iron, for carbon steel and alloy steel in Fig.26 respectively. Various specificati
47、on values were also shown in those figures using straight lines (a) (b) and other symbols. 100 200 300 w)soO Hv loo0 100 200 soa iwsoosoo rim Fig. 26 and 12 Test results obtained on samples of cast iron test in this experimental program apparently indicated higher values than the other experimental
48、data groups. Those obtained on samples of carbon steel and alloy steel were also in the data group of Niemann Botsch which were comparatively in high range. At any rate, on applying limited facial stresses of various materials obtained basing on the test results of this experimental program to the a
49、ctual designing of -gears, unavoidable influential factors such as scatters of material characteristics, variations of condition of dynamic load, etc., must be taken into account. Specifically, higher factors of safety than in the above should be adopted in such case. Furthermore, it is preferable to design gears paying attention only to the relative values of allowable stresses among materials without relying entirely on the absolute values of them from the initial stage. 4. Conclusions In order to obtain allowable compressive stress of gear materia
