unit for investigating deformation of materials by tension at different temperatures

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  • UNIT FOR INVEST IGAT ING DEFORMATION OF

    MATERIALS BY TENSION AT D IFFERENT TEMPERATURES

    E . A . Sukhodo l ' skaya , B . P . Taran , and M. S. Bres le r

    UDC 620.172.087:620.172.251

    Pract ical experience in the use of modern power equipment and Diesel engines shows that in a number of cases the choice of constructional materials on the basis of the properties determined by standard test methods is insufficient for determining the reliability of parts under conditions of complex thermal and mechanical loads. Therefore, in studying the physical nature of mechanical properties and also the mechanism of deformation and failure of materials under thermal cycling conditions, muchattention is being devoted to such fundamental character ist ics as the work for deformation and the coefficient of deformation strengthening [1].

    These character ist ics may be determined only with the actual current values of stresses and deforma- tions. However, for materials with low ductility the obtaining of the actual current values of deformation on normal tensile machines is impossible. As a result we have created a special unit for investigating the defor- mation of materials by tension over a wide range of temperatures in vacuum or in an inert gas medium.

    The unit consists of a high temperature tensile machine and a system for measuring, recording, and treating the results.

    A somewhaL modified IMASh-5S-65 machine was used as the high temperature tensile machine.

    The nonautomatic ISD-3 instrument was replaced with a specially developed instrument for automatically recording the curve with increased accuracy, the design of the clamps was changed, and a round sample was used instead of a flat one. The gauge length of the sample was made according to All-Union State Standard 1497-- 61, type 3, 18K and an M8 1.5 threadwas machined over the whole length of its heads. However, the use of other types of samples, including flat ones, is possible.

    The measuring system of the unit (Fig. 1) consists of three basic blocks: a) measurement of the load; b) measurement of deformation; c) treatment of the measurement results.

    The load measuring block includes the strain gauge beam 1, the strain gauge amplifier 10, and the type GIB1 compensation recorder 12.

    The deformation measuring block consists of the type 6MKh5S mechanotron 9, the mechanotron power source 11, and the type GIB1 compensation recorder 14.

    The block for treatment of the results consists of the type MN-7 analog computer 16, the type VI~S-1 stabilized recti f ier 13, the type PDS-025 two-coordinate recording potentiometer 15, and the oscil lograph indicator 17.

    Fig. 1. Schematic of the unit.

    Kharkov. Translated from Problemy Prochnosti, No. 9, pp. 121-122, September, 1977. Original article submitted October 10, 1976.

    This material is protected by copyright registered in the name of Plenum Publishing Corporation, 227 West 17th Street, New York, N.Y. 10011. No part I of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or bv any means, electronic, r:leehanical, photocopying, I

    I microfilming, recording or otherwise, without written permission of tile publisher. A cop)' of this article is available from the publisher for $ Z 50. 1

    1147

  • ~ , '+t i~ V stab. ,~OV~

    6.3 V stab.

    F ig . 2 F ig . 3

    F ig . 2. P lan of the connect ion of the 6MKh5S mechanot ron .

    F ig . 3. P lan of the comput ing b lock .

    MB2 ~'~ dOIdt

    The load measur ing b lock operates accord ing to the normal method. The deformat ions are measured in the fol lowing manner . A 6MKh5S mechanot ron [2] is used as the sensor . The bracket 2 with the mechanot ron 9 r ig id ly fas tened on it is located on one of the heads of the sample 5 and the s t r ip 8 with the sc rew- type stop 7 is located on its o ther head. With the help of the stop the pin 6 of the mechanot ron is p laced in its o r ig ina l pos it ion.

    With a change in the sample length under the act ion of the load the s t r ip 8 with the sc rew- type stop 7 moves re la t ive to the bracket 2 and the pin of the mechanot ron 6 def lects in the same d i rec t ion by the cor res - ponding angle with the help of the s l id ing stop 4 under the act ion of the spr ing 3. Th is leads to the occur rence in the d iagonal of the br idge of a cur rent the s ign and amount of which are propor t iona l to the d i rec t ion and angle of deviat ion of the mechanot ron pin. L inear i ty in the read ings is p rov ided by the choice of the res i s - tances R 3 and R 4 (F ig . 2) and a lso by the in i t ia l value of the res i s tances R 1 and R 2.

    In pos i t ion 2 the toggle switch T1 connects the two ca l ib ra ted res i s tances R 6 and R~ to the br idge together with the mechanot ron and if the cur rent in the d iagonal of the br idge is not equal to zero then it is ba lanced with the help of the res i s tance R 6.

    The measur ing l imi ts a re changed by the input d iv ider of the GIB1 recorder .

    To reduce dr i f t and increase measur ing accuracy the f i lament of the mechanot ron is powered with a s tab i l i zed 6 .3 -V vo l tage.

    The f inal purpose of the tests is determin ing the abso lute value of the work with any degree of de forma- t ion a l l the way to fa i lure and a lso the cur rent actua l value of the coef f ic ient of de format ion s t rengthen ing .

    To increase the accuracy and reduce the work for t reat ing the in termed iate va lues the unit uses a com- puting block which uses an MN-7 s imulat ing unit as a base .

    It is known that the work of de format ions is equal to the area of the de format ion curve to a vs e coord i - nates:

    A = i (~de, (1) 0

    and the coef f ic ient of de format ion s t rengthen ing is p resented in the form of the re la t ionsh ip

    drr e = --~-. (2)

    Since the MN-7 unit in tegrates for t ime, having presented the values of a and e in the form of funct ions of t ime, we t rans form Eq. (1) in the fol lowing manner :

    e e d8 t

    o G o (3)

    To ca lcu late the cur rent actua l value of the coef f ic ient of de format ion s t rengthen ing Eq. (2) is conver ted to the form

    1148

  • to:

    d(r 1 o =-~.dt -~.

    The functional circuit of the computing block is shown in Fig. 3.

    1) increase the measuring accuracy;

    2) record the curves to the coordinates

    dff - - t" P- - t , e - - t , (r--e, A- - t , -~ ,

    (4)

    The use of this unit makes it possible

    3) automate and increase the accuracy in treating the measurement results.

    The unit has been used to determine the work for deformation for a number of alloys in the 20-900~ range. In order to protect the mechanotron from direct radiation at test temperatures over 450~ it is neces- sary to install a special screen.

    It should be mentioned that the operating principle of the unit and the measuring circuit are applicable to other tensile machines with an insignificant change in the device for fastening the mechanotron. If it is necessary to subsequently treat the data on a computer in parallel with any of the indicators used an analog- code converter (a digital voltmeter, for example) may be connected with subsequent delivery of the informa- tion to a printer, a perforator, or directly to the memory of the machine.

    1.

    2.

    L ITERATURE C ITED

    Ya. 13. Fridman, The Mechanical Propert ies of Metals [in Russian], Mashinostroenie, Moscow (1974). G. S. 13erlin and S. A. Rozentul, Mechanotron Transducers andTheirUse [in Russian], l~nergiya, Moscow (1974).

    METHOD OF INVEST IGAT ING THE SUPPORTING

    CAPACITY OF MATERIALS WITH PROTECTIVE COATINGS

    B. A . Lyashenko , V. V . R tsh in , V . M. Tovt , l~. S. Umansk i i , and O. V . Tsygu lev

    UDC 620.05.052

    Present service conditions for equipment for new technology are characterized by the simultaneous actio: of high temperatures, aggressive media, andmechanical loads. Investigating the effectiveness of materials used for the production of this equipment on the basis of the individual action of the service factors does not provide reliabil ity in the characterist ics obtained because of the nonaddittve nature of the effect of each of them.

    in the Institute of Problems of Strength of the Academy of Sciences of the Ukrainian SSR we have devel- oped a combination of methods and introduced experimental equipment making it possible to study the suppor- ting capacity and design strength of base-coating systems under conditions close to the actual, with the simul- taneous action of high temperatures, agressive media, and mechanical loads.

    1. The basis of the methods developed for high temperature tensile, creep, and long-term strength tests is radiation heating of the samples, which provides rapid delivery of energy, low inertia, and high clean- liness and correctness in conducting the experiment [1, 2].

    Institute of Strength Problems, Academy of Sciences of the UkraInian SSR, Kiev. Translated from Problemy Prochnosti, No. 9, pp. 123-125, September, 1977. Original article submitted April 8, 1977.

    This material is protected by copyright registered in the name of Plenum Publishing Corporation, 227 West 17th Street, New York, N.Y. 10011. No part [ of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, I microfilming, recording or otherwise, without written permission of the publisher. A copy of this article is available from t