Effect Of Specimen Temperature Research Articles

The effect of specimen temperature on the fretting wear behaviour of a non-nitrided against nitrided high strength alloy steel contact pair

The fretting wear performance of the heterogeneous non-nitrided against nitrided contact pair of the high strength alloy steel, SCMV was investigated in the gross slip regime at ambient and elevated temperatures (120 and 150 °C). The tests were performed with displacement amplitudes of 25 and 100 μm at an applied normal load of 250 N using a cylinder-on-flat configuration. As the fretting contact temperature increases, the energy dissipation and total wear volume decreases for the same applied normal load irrespective of the displacement amplitude. The energy dissipation increases with increase in displacement amplitude for the same applied normal load. During fretting at ambient temperature, a substantial loss of material as wear debris was observed in the contact, whereas the overall loss of material from the contact significantly reduces with an increase in temperature. The variation in the tangential force coefficient and the total wear volume at elevated temperatures may be attributed to the sintering of oxide particles in the contact to form a protective debris bed. The worn surface morphology of the fretted specimen investigated using a scanning electron microscope shows the presence of wear debris in the wear track, oxide patches, delamination cracks, delamination cavities and discontinuities, scale like topography and plate-like wear debris. The abrasive action of the particles in the contact interface promoted wear at ambient temperature whereas at elevated temperatures, the compaction of the oxide particles reduced the wear.

High Resolution Magnetic Resonance Imaging of Excised Atherosclerotic Carotid Tissue: The Effects of Specimen Temperature on Image Contrast

Previous Magnetic Resonance (MR) studies of carotid endarterectomy (CEA) specimens have been directed at interpreting image contrast to determine plaque composition and stability. Such studies may give misleading results since it is believed that the acquired MR data is affected by the conditions used to store the excised tissue. This has been investigated in a high-resolution imaging study of the changes in contrast occurring with a change in specimen temperature. MR images were acquired from 20 CEA specimens. The initial MR examination was made within four hours of excision in tissue maintained and imaged at body temperature. Specimens were subsequently cooled and then re-examined at different times. The MR data was interpreted by comparison with histology obtained from equivalent sections. With the exception of signals arising from blood, changes in MR image contrast occurring in the 24-hour period after the CEA were relatively slight. Plaque lipid T2-weighted image intensity was initially relatively hyperintense in some samples and decreased with time on cooling reflecting a decrease in the lipid transverse (T2) relaxation time. High-resolution imaging allowed a detailed description of plaque calcification and showed that clot retraction was probably responsible for the marked change in the distribution of signals assigned to intraluminal blood. The use of high-resolution MR imaging to examine freshly excised specimens at body temperature showed previously unreported image features. This is important in the design of in vivo MR studies directed at assessing plaque stability by identifying the composition of the atheromatous tissue.

On the energetics of flickering contrast observed in TEM images of an aged 53Cu45Mn2Al damping alloy

Video imaging techniques were applied to transmission electron microscope images in order to investigate the motion of the spatially consistent and repetitive contrast variations (termed flickering) observed in an aged CuMnAl dampig alloy. A fiber optic light sensing probe was coupled with a spectrum analyzer to determine the frequency characteristics of the flickering activity directly from a video screen connected to the TEM. The effects of specimen temperature and TEM beam current were studied. Certain flickering sites exhibit peaks in the magnitude of contrast change at specific frequencies. The peaks in the frequency spectrum vary in amplitude and, to a lesser extent, in frequency, with specimen temperature and with TEM beam current. Detailed examination of the real-time behavior at the flickering sites suggests that the underlying mechanism which produces the contrast change is a gradual crystallographic transition, typical of a second order phase transition. As well, the patterns of change which comprise the flickering contrast display many of the characteristics of “chaotic vibrations”.

Mass Loss is Reduced at Liquid Helium Temperature

Since mass loss is a fundamental limitation in electron microscopy and microanalysis of biological materials it is very valuable to understand the effect of specimen temperature on the mass loss process. An electron energy loss spectrometer has been added to the Duke University Cryomicroscope (fig. 1) to allow a general study of radiation damage effects in specimens held at liquid helium temperature.The reduction of specimen mass is measured by recording a long series of electron energy loss spectra with a Tracor-Northern TN-5400 analyzer, using the region integration feature of the analyzer to report the number of counts in the zero-loss and inelastic scattering regions of the spectrum.

Effect of specimen temperature on the breaking point for splitting-off in AMG-6 aluminum alloy

The investigation of the temperature dependence of the strength of constructional materials under intense shock loads, including breaking loads, is of considerable practical interest. There are certain technical difficulties involved in loading the materials and making the required measurements in such experiments. Hence, the number of papers devoted to this problem is extremely limited. In [1, 2] data is given on the elastic-plastic properties of a number of metals at normal and high temperatures, obtained by investigating the parameters of elastic waves excited by an explosion. In [3, 4] investigations were carried out of the temperature dependence of the breaking point for splitting-off in steel and copper. In the present paper we investigate the effect of the specimen temperature on the breaking point for splitting off in widely used AMG-6 aluminum alloy in the temperature range from 0°C to 550°C, i.e., practically up to the temperature at which the alloy begins to melt.

Effect of cooling on fatigue strength of metastable austenitic 30Kh10G10 [30Cr10Mn10] steel in relation to specimen length

This investigation was concerned with the kinetics of phase transformations in metastable austenitic 30Kh10G10 steel specimens fatigued in rotating bending and with the effect of specimen temperature on the fatigue strength of this steel in relation to the specimen length. It was shown that spray cooling produces substantial changes in the kinetics of phase transformations, increases the fatigue strength of the steel in question and substantially inhibits the manifestation of the size factor.

Deposition of Zirconium Coatings from the Vapour of the Iodides

A review is given on techniques for deposition of Zr coatings with data on equipment and procedures using thermal decomposition of the iodides. The effects of specimen temperature, Zr sponge temperature, and iodine vapor pressure on the deposition rate were investigated. Comparison was made of the coatings on Mo and stainless specimens with consideration to the problem of interdiffusion of Zr and steel or stainless steel. (Rev. Metal Lit., 19: No. 12, Dec. 1962)

Le spectro-lecteur automatique comme instrument de recherche

The author describes briefly the principles of the direct-reading apparatus made by the Cie Radio-Cinéma and then outlines a number of uses in spectrochemical research in addition to its purely analytical purpose. In particular, he describes how the indicating unit can be used to check the uniformity of a source, and the degree to which line-pairs are homologous. Specimen shape and surface condition have been examined, and the value of different types of graphite as counter-electrodes, also the effect of specimen temperature.