M A C H I N E FOR M E A S U R I N G F R I C T I O N A N D R E S I S T A N C E TO W E A R IN A G G R E S S I V E M E D I A A T H I G H S L I D I N G S P E E D S V. V, Polotai F i z i k o - K h i m i c h e s k a y a Mekhanika Materialov0 Vol. 1, No. 8, pp. 808-804, 1965 Machines designed for testing friction pair materials should be c a p a b l e of reproducing the service conditions of modern engineering equipment, which often operates at high speed, temperatures, and pressures, while at the same t i m e exposed to the action of aggressive media~ The construction of a machine of this type is described in the following paragraphs. The e x p e r i m e n t a l friction pair comprises a stationary ring test piece, one of the end faces of which is pressed against the end face of another ring of the same size rotating at a predetermined speed, provision being made for carrying out the tests in an aggressive m e d i u m . The main characteristics of the m a c h i n e are as foilows: 1) m a x i m u m torque on the test piece: i0 k g . cm: 2) motor power rating: 2 kW 3) m a x i m u m motor speed: 24 000 rmp; 4) m i n i m u m motor speed: 1000 rmp; 5) compressive load on the test piece: 0-10 kg: 6) normal pressure at the contact interface: 0-2 kg/cm2; 7) sliding speed: 2-50 m / s e c ; 8) test p i e c e dimensions: o . d . = 40 ram; i . d . , = S0 mm; height = 10 ram. (For tests at higher normal pressures test pieces with a reduced cross-sectional area are used.) Tests can be carried out in any aggressive medium, which will not attack the stainless steel used in the construction of the machine. Provision has been m a d e for measuring and recording the extent of wear, frictional torque, and temperature in the contact zone. Th~ 7~achine consists of a frame, a stand, an e l e c t r i c control drive, a friction unit, a loading system, a d e v i c e for feeding the aggressive medium, and measuring instruments. The test p i e c e is rotated with the aid of a h i g h - f r e quency asynchronous motor whose speed can be varied (by varying the frequency) between 1000 and 24 000 rmp. The various subassemblies are mounted on a weldedconstruction frame incorporating a stand which carries the e l e c t r i c motor and loading system.
Schematic representation of friction unit of testing m a c h i n e . 1) Lower test piece, 2) spherical bearing, 3) upper test piece, 4) hinged lever, 5) spring with a tensometer.
The position of the e l e c t r i c motor can be adjusted by moving it along special guides with the aid of a winch and a rope: an indicator with a scale value of 0.01 m m is used for fine adjustment. A d i a p h r a g m - t y p e chuck to hold the test p i e c e is fitted onto the motor shaft.
As shown in the figure, the lower test p i e c e is secured to the inner face of a spherical ball bearing, mounted in such a way that its oscillation center is in the plane of the specimen contact interface. The aggressive m e d i u m is fed through a hollow bushL'lg fitted into the lower test piece, the rotating upper test p i e c e acting as a seal. The aggressive m e d i u m is contained in a h e r m e t i c a l l y sealed tank and fed to the friction zone under the pressure of an inert gas, controlled with the aid o f a manometer: the rate o f flow of the aggressive m e d i u m is regulated by a valve, The bearing with the lower test p i e c e is mounted at one end of a d o u b l e - a r m lever, the other end o f which carries 417
a weight; by moving this weight along the lever the load exerted on the test p i e c e can be varied between 0 and 10 kgf. The total wear of both test pieces is indicated by the deflection of the d o u b l e - a r m lever, which is recorded by an inductive sensing e l e m e n t . The extent of wear of each individual test p i e c e is determined g r a v i m e t r i c a l l y or by a meth od involving artificial bases. The friction torque is transmitted to a spring attached to which is a wire resistance strain gage, whose signal is amplified and fed to a self-recording instrument. The machine is provided with a special friction d e v i c e which switches the motor off if the test pieces seize. The temperature at a distance of 0 . 9 - 0 . 5 m m from the contact interface is measured with the aid of a c h m m e l alumel thermocouple (0.2 m m diam.) placed in a hole in the lower test piece. The bearings of the high-speed motor are lubricated by an oil spray; a special control panel is incorporated in the m a c h i n e . The machine is o f simple design, safe to use, and easy to control; it provides a means of accurately measuring the degree of wear, friction coefficients, and temperature in the contact zone of friction pairs. 15 October 1964
418
Kiev Institute of Materials Science AS UkrSSR
