rods was dealt with in considerable detail by Hanson [2] and Timoshenko [3]. .... ath = CN7. (14). I where ~-- 15(l+m) ' for m = 0.20 ... 0.25, B : 0.56 ... 0.53.
On second-stage blades of FT after 650 h operating time an increase of the normal force from ]26 to 198 N entailed a reduction of wear of the contact surfaces from 0.8 to 0.03 ~ . Thus an effective means of reducing wear of the contact surfaces of shrouding flanges is the increase of the normal force N which, in the final analysis, makes it possible to increase the life of turbines substantially. LITERAT[~E CITED I 9
2.
.
V. Ya. Krivoshei, "Calculation of the shrouding flanges of turbine rotor blades," Probl. Prochn., No. 8, 58-60 (1982). V. N. Chelomei (ed.), F. M. Dimentberg and K. S. Kolesnikov (vol. eds.), Vibrations in Engineering (Handbook) [in Russian], Vol. 3, Vibrations of Machines, Structures and Their Elements, Mashinostroenie, Moscow (1980). R. K. Shidlovskii, A. V. Shavkunov, and M. A. Lavrenova, "Increasing the wear resistance of contact surfaces of shrouding flanges of turbine rotor blades," Vybratsionnaya Prochnost' i Nadezhnost' Dvigatelei i Sistem Letatel'nykh Apparatov, No. 6, 4]-44
(1979). 4.
5.
V. V. Shevelya, A. V. Karasev, I. N. Gorbatov, et al., "Wear resistance of chromium carbide base coatings under conditions of vibration-contact loading," in: Scientific Foundations and Methods of Increasing the Reliability and Life of Gas Turbine Engines [in Russian], Naukova Dumka, Kiev (]979), pp. I09-]13. I. G. Sipukhin, D. S. Elenevskii, R. S. Bekbulatov, and N. G. Gavrilov, "Wear resistance of shrouding flanges of compressor and turbine blades," in: Scientific Foundations and Methods of Increasing the Reliability and Life of Gas Turbine Engines [in Russian], Naukova Dumka, Kiev (1979), pp. 122-126.
EVALUATION OF THE DU~\BILITY OF RODS UNDER CONDITIONS OF TENSION~s
AND BENDING UDC 539.3
G. M. Khazhinskii
The fatigue limit of materials is usually determined from data obtained in tensionscompression tests of specimens. These results are also used for evaluating the durability of structures operaLing under conditions of a state of nonuniform stress, in particular beams. The present approach to the solution of the problem is based on determining the amplitude of the conventional stresses (0~, = Eel) on the surface of the beam and establishing the number of cycles to failure Nf from the corresponding fatigue curve. If the conventional elastic stresses in tension-~:ompression are proportional to the full deformation, then the identification of normal elastic and real surface deformations in bending leads to a substantial error in the calculation of endurance. To eliminate it, it is recommended to carry out elastoplastic calculation Ill. The problem of evaluating the endurance of cyclically bent rods was dealt with in considerable detail by Hanson [2] and Timoshenko [3]. Together with the conventional elastic stresses in the evaluation of durability, especially of notched specimens, fairly wide use is also made of a method of calculation which uses the amplitude of the conventional stresses obtained by Neuber's formula (
