brittle interference fit parts. Department of Mechatronic Systems, Kalashnikov Izhevsk State. Technical University, ul. Studencheskaya 7, 426069 Izhevsk, Russia.
Coefficient of friction in the design of non-metallic brittle interference fit parts Department of Mechatronic Systems, Kalashnikov Izhevsk State Technical University, ul. Studencheskaya 7, 426069 Izhevsk, Russia
Abramov I.V., Lekomtsev P.V.
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Introduction • Interference fits of brittle non-metallic parts (fixtures of mixing devices in glass chemical reactors, ceramic bearings, impellers, gears, nozzles, etc.) distinct in improved wear- and corrosion-resistance, operated in broad temperature ranges are more and more widely applied in mechanical engineering. • The coefficient of friction of such pair of materials as alumina ceramics and quartz glass, which can be used when evaluating the load capacity of tapered interference fit of parts from the foregoing materials is investigated in this work. Abramov I.V., Lekomtsev P.V.
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Applications Glass tubes joints
Hemispherical Resonator Gyroscope
Glass fixtures
Ceramics bearing and gear
Abramov I.V., Lekomtsev P.V.
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Methods and materials used for research • The coefficient of friction of the pair of materials “alumina ceramics – quartz glass” was investigated in two ways: – directly on the friction machine SRV–III Test System following the testing scheme “discindenter”; – indirectly by measuring the press-in and press-out forces of the tapered interference fit.
Selected physical and mechanical properties of alumina ceramics and quartz glass
Parameter E [MPa]
ВК94-1
КУ-1
380000
72000
K1c [MPa ]
4000
800
HV [MPa]
18000
8000
0,2
0,18
ν
Abramov I.V., Lekomtsev P.V.
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Experiments on the friction machine SRV–III Test System Testing scheme “disc-indenter”
Abramov I.V., Lekomtsev P.V.
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Counterbody and indenter positioning
Abramov I.V., Lekomtsev P.V.
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Obtained dependence
Abramov I.V., Lekomtsev P.V.
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Friction coefficient curve at normal load ranging from 100 to 1000 N (To pre-estimate the interference fits)
Abramov I.V., Lekomtsev P.V.
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Experiments with press-in and pressout forces measuring
Abramov I.V., Lekomtsev P.V.
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Assembling parts
Abramov I.V., Lekomtsev P.V.
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Servo press with PC data acquisition 1
z RS 232 2 3 4
Mechatronic servo press
Fz
Servo press control unit Measuring transducer
1 – servo press crosshead 2 – servo press force measure device 3 – tested sample 4 – base with height adjustable lug
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Appearance of the servo press
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Obtained dependences Press-out forces from the interference for press-fit
Press-out forces from the interference for thermal press-fit Fout, 2500 N
2500 Fout, N
y = 401,68x - 451,3 ± ε R² = 0,9906
2000
2000
1500
1500
1000
1000
500
500
0
y = 398,23x - 500,43 ± ε R² = 0,9562
0 0
2
4
δ, μm 8
6 2500N Fin,
Press-in forces from the interference for press-fit
0
1
2
3
4
5
6
δ, μm 7
y = 431,83x - 450,99 ± ε R² = 0,9568
2000 1500 1000 500 0 0
1
2
3
4
Abramov I.V., Lekomtsev P.V.
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δ, μm 7
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Friction coefficient calculation •during pressing-in Fin fin tg pn S cos
•during pressing-out f out
Fout tg pn S cos
• pn - contact pressure calculated using FEM
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Change in the coefficients of friction from the interference in the tapered fit: - during pressing-in; - during pressing-out of the press fit; - during pressing out of the thermal fit
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Conclusion • As a result of the investigations carried out on the friction machine it was found that the coefficient of friction of the pair of materials “alumina ceramics -quartz glass” changes from 0.2 to 0.16 when the normal force changes from 100 up to 1000 N. • When assembling the trial tapered interference fit with the commensurate contact area, the coefficient of friction decreases from 0.28 to 0.26 when the press-in force changes from 800 up to 2400 N. • Larger value of the coefficient of friction found by the indirect method is conditioned by edge effects in the actual tapered interference fit and geometrical errors of part production. • The coefficient of friction during pressing-out (friction at rest) is less than the coefficient of friction during pressing-in. This phenomenon is not characteristic for traditional fits of metal parts and can be explained by the availability of intermediate layer of abrasive particles, wear as a result of sliding of the contact surfaces during the formation of tapered interference fit, and the emergence of fissured (on microlevel) surface layer of the contact surface. Abramov I.V., Lekomtsev P.V.
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