Bulk and plane torsion tests are being used in industry to determine the flow curve of metals up to very high plastic strains. Despite their wide usage the experimental results obtained in torsion tests are still not being evaluated uniformly. Differences arise basically due to the conversion of the measured angle of twist into the corresponding equivalent strain. This paper shows that the often used equivalent strain expression by Nadai and Davis as well as Eichinger is invalid, since the so-called redundant shear during torsion deformation has been ignored. Also, the histories of different stress measures such as the convected and rotated stress tensors are computed to discuss the reasons for differences between the flow curves obtained from torsion and simple tension tests.


Öztürk, Tayfur; EDIZ, T (1994-02-28)
An investigation is carried out into the plane strain deformation of model laminates incorporating a single hard layer. A total of four laminates based on Al alloy(5053)-steels and Cu-W are investigated in which the relative hardness of the constituent layers, r(h), are in the range between 2 and 13. It is found that the deformation is uniform in the initial stages of plane-strain, the strain being partitioned equally between the constituent layers. The regime of uniform deformation is prolonged in samples ...
Experimental investigation of dynamic delamination in curved composite laminates
Uyar, İmren; Çöker, Demirkan; Department of Aerospace Engineering (2014)
In the aerospace industry, high demand for lightweight structures is fostering the use of composite laminates in a wide variety of shapes, as primary load carrying elements. However, once a composite laminate takes a highly curved shape, such as an L-shape, high interlaminar stresses induced in the curved region causes dynamic delamination formation. This thesis discusses the experimental investigation of delamination in L-shaped CFRP composite laminates under quasi-static shear loading. An experimental set...
ECAP processing and mechanical milling of Mg and Mg-Ti powders: a comparative study
Cakmak, Gulhan; Öztürk, Tayfur (2011-08-01)
A study was carried out into the possibility of employing ECAP processing in lieu of mechanical milling for the purpose of developing powder-based hydrogen storage alloys. Mg and Mg-Ti powder compacts were encapsulated in a copper block and were subjected to ECAP deformation to an apparent strain of epsilon = 4. This resulted in the consolidation of the compacts as well as in the refinement of their structures. The values of coherently diffracting volume size were as small as 70-80 nm, quite comparable to t...
Direct pyrolysis mass spectrometry analyses of polyamide-6 containing melamine and boron compounds
Isbasar, Ceyda; Bayramli, Erdal; Hacaloğlu, Jale (2013-08-01)
In this work, the thermal degradation characteristics of polyamide 6 (PA6) containing melamine (Me) and a boron-containing additive, borophosphate (BPO4), zinc borate (ZnB) or a boron and silicon-containing oligomer (BSi) are investigated systematically via direct pyrolysis mass spectrometry. In the presence of boron compounds, not only the release of melamine and its degradation products but also thermal characteristics of PA6 are affected significantly and the interactions between melamine and PA6 are enh...
Measurement of the Isolated Prompt Photon Production Cross Section in pp Collisions at root s=7 TeV
Khachatryan, V.; et. al. (2011-02-01)
The differential cross section for the inclusive production of isolated prompt photons has been measured as a function of the photon transverse energy E-T(Gamma) in pp collisions at root s 7 TeV using data recorded by the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.9 pb(-1). Photons are required to have a pseudorapidity vertical bar eta(gamma)vertical bar 21 GeV, covering the kinematic region 0.006 < x(T) < 0.086. The measured cross section is found to be in agreem...
Citation Formats
A. TEKKAYA, “EQUIVALENT STRAIN AND STRESS HISTORY IN TORSION TESTS,” STEEL RESEARCH, pp. 65–70, 1994, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/63399.