RMZ â MATERIALI IN GEOOKOLJE

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334 Kugler, G., Terčelj, M., Peruš, I., Turk, R.Figure1. Dimension of specimen’s for tensile testing.(a)(b)Figure2. Schematic representation of temperature control (left), andshaping of contour (right) during hot tensile testing of Alloy201.The hot tensile tests were carried outon Gleeble 1500D thermomechanicaltesting machine. The samples were deformedbetween 8 mm and 11 mm attemperatures from 800 °C to 1000 °Cunder prescribed constant strain ratesbetween 10 –3 s –1 and 10 –1 s –1 assumingthat deformation was homogeneous onentire working length. The temperatureas a function of time during tensile testsis shown on Figure 2a, and specimenduring testing is shown on Figure 2b.Essentially the deformed shape-ofthe-rodafter tensile testing representsthe history of traveling of the crosssectionthat separates the elastic andplastic state of material. [3, 4] The portionof material that in a given momentleft the plastic state preserves its shapeuntil the end of the experiment.Basedon this fact, in what follows, the newmodel for description of evolution ofspecimen’s contours during tensiletesting will be introduced.Description of the mathematical approachModel for description of contour oftensile specimenA cylindrical rod of radius, r, maintainsits rotational symmetry aroundthe longitudinal axis, z, during a tensiletest, and thus its shape at giventime, t, is determined by the rotationalcurve r = r(z, t), which forms its sur-<strong>RMZ</strong>-M&G 2012, 59
Calculation of stress-strain dependence from tensile tests at high temperatures using ...335 = (, face after rotation around longitudinal elastic parts of the rod. These )twoaxis, z, of the rod. Before the test this points were moving along the () curvecurve is a cylinder r(z, 0) = r 0, where r = r(z, t k), during tensile test. Thus,r 0is the initial radius of the rod. After the rod may be () at = any = time divided (, ) = (, )the test is finished this curve must be into three partscarefully measured to obtain results () in () ()()the form() = = (, ) = ( (, ) + (, ) + = (, )(1)() () ()where t kis the duration of the experi- = = ( Initial (, volume (, ) ) + of the rod (, ) of + (, ))(3)( (), ) = ( (), )() = ment.length, l o, is V 0= πr 2 l 0. The volume is () () ()0conserved during plastic deformation, = (, )and ()thus volume ( for (), ()an arbitrary ) = ( time (), The ) first and last sections belong to, ) + can be expressed (, ) as + = (, ) ()(, ))the elastic part and the middle section ()to the plastic part of the rod. The final ()() ()( (), ) = ( (), ) = ( (), ) = (, )shape of the rod represents the line( (2) of movements of the points which (),() ) =( = (), ) (, ) (, )separate plastic and elastic = (, state () = (, ))of the material. The portion () of the curve () () ( (), ) = ( (), ) = ( (), ) () ()where l(t) is the length of the rod at r = r(z, t k), that lies left of the minimal) cross-section is a monotonically = (, ) = time t. By ()()(, )(, )( (, ) + comparison (, )between + final (, )(, )shape ()of the rod andits shape= (, () = ) = (, )at arbitrarymoment after occurrence of neck, the right is a () monotonically increasing = (, decreasing function )and () the portionon () () () () ()(), ) =but( before(), )the= (end (),ofthe ) ( test, we ascertainthat both shapes differ only in of l lfunction. Thus for the prescribed value (), ) (, = () (), )(t) the value of l d(t) can be calculated ()(, ) the middle, = (, but = (, () ()()) () = (, ) = ( () the end () ()= (, ) = + (, (, )) + (, ))parts are the from the () condition () () same. () Namely, the rod () at the intermediate = time is shorter (, ) () () ()()and it has a smaller(4)(, ) neck. = Thus, (, we () )can conclude that the = ( (, (, ) () = (), ) = ( (), ) = ( (, (, ) ) + ) parts () of the rod, which () have the same From those two +1 + ) ) () () () values the () volume ( (),shape)as=it(is at(),the)end= (of the (),test, )were which is at given time in plastic stateat that ()moment in an elastic state and can be calculated(, ) () = the part, which (, = ) is (, different, )( was in plastic ) = = = (, )( (, ) (, ) (), ) = ( (), ) ()state. Consequently, 1 + () on deformed() () ()( ( (), ) = ( (), ) ) = ( (), ) rod there are always two points that at(5)(,given )moment = separate (, = (, ))the plastic and = ( (, ) + (, )) (, ) (, ) ( 1 + () ) = (, ) () = (, ()) <strong>RMZ</strong>-M&G 2012, 59 () () ( (), ) = ( (), ) = ( (), ) () ( ) = ( (, ) + (, )) (, () = ) (, ))() () ()
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384 Sunmonu, L. A., Adagunodo, T. A
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392 Shemetov, P. A., Bibik, I. P.in
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394 Shemetov, P. A., Bibik, I. P.
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k =1.05+Dλ = 1+k =( s )396 Shemeto
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398 Shemetov, P. A., Bibik, I. P.si
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у 3 b400 D = f eShemetov, P. A., B
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V4BEK Q σBEad = ,commQрσV 01 +
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404 Shemetov, P. A., Bibik, I. P.wh
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thrмR iλ = 2 λ= 100⋅exp[ −(
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qLevel of average technical (theore
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.6670.05=0.35k1,05+D avet( s3≥ Kt
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414 Adewale, A., Olawale, O. O., Ma
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430 Kos, A., Dervarič, E.novega ve
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432 Kos, A., Dervarič, E.diamond w
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434 Kos, A., Dervarič, E.chines to
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436 Kos, A., Dervarič, E.the best
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438 Kos, A., Dervarič, E.Before th
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440 Kos, A., Dervarič, E.nally to
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444 Lajovic, A.disc brakes, further
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446 Lajovic, A.Slika 2. Izrez iz Si
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448 Lajovic, A.Livne lonce smo na n
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450 Lajovic, A.Ingersol pa je bil z
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452 Lajovic, A.Med delavci, ki so b
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454 Lajovic, A.imel vsak delavec na
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456 Lajovic, A.Slika 5. Izdelki Že
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458 Lajovic, A.pa se ni najbolje iz
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460 Lajovic, A.za delo. Promet na z
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462 Lajovic, A.Sredi osemdesetih le
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464 Lajovic, A.njem delu forme. Na
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466 Lajovic, A.Enourni film je mars
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470 Medved, J., Rosina, A., Vončin
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472 Author’s IndexAuthor`s Index,
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Contents476Phase contrast method fo
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Contents47859/4Calculation of stres
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Instructions to authors481Compositi
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Instructions to authors483NAVODILA
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Instructions to authors485Knjige:Ro
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Template487TEMPLATEThe title of the
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Template489References (Times New Ro
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