Prüfung des plastischen Verhaltens metallischer Werkstoffe in Torsionsversuchen

Pöhlandt, K.; Tekkaya, A. Erman; Lach, E.

doi:10.1002/mawe.19830140605

Cited by 6 publications

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References 11 publications

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“…It can be shown that this uncertainty does not strongly affect the shape of the calculated flow curve; for flow curves deviating from equation (2), the uncertainty of the coefficient fJ in equation (10) has little effect on the shape of the flow curve.…”

Section: ·5mentioning

confidence: 96%

Torsion testing – plastic deformation to high strains and strain rates

Pöhlandt¹,

Tekkaya²

1985

Materials Science and Technology

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A new method of calculating stress-strain curves from torsion measurements is .described. Contrary to the usual calculation of stress and strain at the surface of the specimen -where the material properties are distorted by microcracks, notch effects, etc. -stress and strain are determined at a 'critical radius' inside the specimen. For this purpose an initial approximation for the flow curve of the type (Jf""" ¢o¢m is improved by calculating a 'correction function' from the test results. This calculation is based on a Taylor series expansion which converges more strongly if tubular specimens are used instead of solid ones. Tubular specimens are therefore used if the flow curve appears to deviate strongly from the exponential law. The new method of test evaluation makes use of the fact that contrary to tensile and upsetting tests, in torsion tests the measured curve gives an almost undistorted linear projection of the flow curve. In fact the test evaluation consists only of 'calibrating' the measured torque and angle of twist in terms of yield stress or equivalent strain, respectively. MST/94 . cP. equivalent strain ¢ time derivative of ¢ a radius of solid or tubular specimen at inner radius of tubular specimen B constant defined by equation (30) C constant in equation (8) Dij deformation rate tensor f mean value of fey, y) defined by equation (20) fey, y) 'correction function' for shape of flow curve f2(yp, Yp) second approximation of fey, y), for r = rp F force h height of upsetting test specimen jk(a, at) parameter defined by equation (19) 10 length of cylindrical section of specimen m strain rate sensitivity index M torque Mo calculated torque assuming zero approximation for flow curve n strain hardening exponent p abbreviation (p = n +m) P normalized torque r distance from axis of specimen distance) r p critical radius R notch radius x relative variation of dimension z axial coordinate (distance from median plan of specimen) f3 constant defined by equation (10) y shear strain (finite Lagrangian strain tensor component) y shear strain rate Ya shear strain at radial distance r = a (surface) Ya time derivative of Ya Yat shear strain at inner radius r = at of tubular specimen Yat time derivative of Yat Yp shear strain at critical radius rp Y P time derivative of Yp Yr shear strain at radial distance r Yr time derivative of Yr e angle of twist e time derivative of e (J f yield stress O"t constant in equation (1) O"rt constant in equation (2) TO zero approximation for shear stress T 2 second approximation for shear stress

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Section: ·5mentioning

confidence: 96%

Torsion testing – plastic deformation to high strains and strain rates

Pöhlandt¹,

Tekkaya²

1985

Materials Science and Technology

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Über die Wechselwirkung von Werkstoff und Umformung und ihre Erfassung in Versuchen

Pöhlandt

1984

Materialwissenschaft Werkst

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Es werden Versuche beschrieben und diskutiert, in denen Werkstoffeigenschaften vor dem Umformvorgang, Verfahrensparameter während der Umformung sowie Werkstoff‐ und Werkstückeigenschaften nach der Umformung erfaßt werden können. Zur Bestimmung von Werkstoffeigenschaften vor der Umformung stehen zahlreiche genormte oder sonstwie vereinheitlichte Prüfverfahren zur Verfügung. Dies ist bei Versuchen während und nach der Umformung nicht in gleichem Maße der Fall. Insbesondere muß nach der Umformung der Einfluß der Geometrie auf die Werkstückeigenschaften berücksichtigt werden, wodurch sich veränderte Bedingun‐gen für Versuche zur Erfassung von Werkstoff‐ und Werkstückeigenschaften ergeben.

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