The Experts below are selected from a list of 171 Experts worldwide ranked by ideXlab platform
Rainer Johe - One of the best experts on this subject based on the ideXlab platform.
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Tensile Testing of Nitinol Tubes and Wires with Higher Strain Rates
Journal of Materials Engineering and Performance, 2009Co-Authors: Rainer JoheAbstract:During tensile testing of superelastic Nitinol material, the Specimen Temperature increases as result of the exothermic Austenite-to-Martensite phase transformation. The increase in Specimen Temperature has great influence on the stress-strain response—in particular, upper and lower plateau values—and limits the strain rate of the tensile test, so that for larger Specimen dimension, the strain rate has to be reduced. A special setup of the tensile testing equipment has been developed using a fan to improve the heat exchange between the Specimen and the ambiance to allow much higher strain rates as well as even gradient of the upper and lower plateau. It could be shown that the strain rate of the first loading and unloading cycle could be two to four times higher as recommended in ASTM F 2516-07 without any negative impact on the determined values. The needed time for tensile testing of Nitinol products could be reduced considerably. The improved heat exchange gives a better comparability and reproducibility of the tensile test data.
Adam Lipski - One of the best experts on this subject based on the ideXlab platform.
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change of Specimen Temperature during the monotonic tensile test and correlation between the yield strength and thermoelasto plastic limit stress on the example of aluminum alloys
Materials, 2020Co-Authors: Adam LipskiAbstract:This paper presents an attempt to generalize the description of the course of Specimen Temperature changes during the tensile test and to connect the value of the thermoelasto-plastic limit stress with the value of a clear (physical) or proof strength (offset yield strength) on the example of tests of the following aluminum alloy sheets used in Poland for airplane structures: 2024-T3 and D16 in three grades: D16ATV, D16CzATV, and D16UTV. A thermographic camera was used for Specimen surface Temperature measurement during the tensile test. The Portevine-Le Chatelier effect (the so-called PLC effect) was observed for tests of Specimens cut from sheet plates, which was strongly reflected in the Temperature fluctuations. The course of Temperature change during tensile tests was divided into four characteristic stages related to the occurrence of a clear or offset yield strength. It was found that if there is a clear yield strength, the value of the thermoelasto-plastic limit stress was greater than this yield strength. If there was an offset yield strength, the value of the thermoelasto-plastic limit stress was lower than this yield strength. The differences in the aforementioned values of individual yield strengths did not exceed several percent. Thus, it can be concluded that the thermoelasto-plastic limit stress determined on the basis of the course of Specimen Temperature changes during the tensile test is well correlated with the value of the yield strength of the material.
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Proposition of Low-Cycle Fatigue Test Termination Criterion Based on Specimen Temperature Change
Solid State Phenomena, 2016Co-Authors: Adam Lipski, Zbigniew LisAbstract:This paper presents proposition of the low-cycle fatigue test termination criterion based on Specimen Temperature change. The tests were performed using Specimens made of G-X12CrMoVNbN9-1 (GP91) martensitic cast steel under axial tension-compression conditions with strain controlled at the total strain amplitude levels amounting to eac = 0.25%, 0.5% and 0.6%. Very good compliance of the proposed criterion with the criterion used so far was obtained. The discrepancy for the tested material has not exceeded 2% in the eac stress range not exceeding 0.5%.
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variations of the Specimen Temperature depending on the pattern of the multiaxial load preliminary research
Materials Science Forum, 2012Co-Authors: Adam Lipski, Dariusz SkibickiAbstract:This paper provides the results of research on Temperature changes of cylindrical Specimens depending on the pattern of the multiaxial load. The research were made by using passive infrared thermography. It was found out that the average Temperature value is significantly dependent on the plastic strain energy and that the Temperature change amplitude depends on the nominal normal stress (except for torsion).
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Variations of the Specimen Temperature Depending on the Pattern of the Multiaxial Load – Preliminary Research
Materials Science Forum, 2012Co-Authors: Adam Lipski, Dariusz SkibickiAbstract:This paper provides the results of research on Temperature changes of cylindrical Specimens depending on the pattern of the multiaxial load. The research were made by using passive infrared thermography. It was found out that the average Temperature value is significantly dependent on the plastic strain energy and that the Temperature change amplitude depends on the nominal normal stress (except for torsion).
Mark Aindow - One of the best experts on this subject based on the ideXlab platform.
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Temperature calibration of TEM Specimen heating holders by isothermal sublimation of silver nanocubes
Ultramicroscopy, 2018Co-Authors: Sriram Vijayan, Mark AindowAbstract:Abstract Micro electro mechanical systems (MEMS) based TEM Specimen heating holders exhibit excellent thermal stability and minimal Specimen drift, which allows thermally-activated processes to be studied dynamically at high spatial resolution. The advantages of MEMS-based devices arise from the very small thermal masses of the sample studied, but this poses particular challenges for the precise measurement of Specimen Temperature. Previously, it has been proposed that the size-dependent sublimation behavior of Ag nanoparticles could be used to measure the Specimen Temperature by applying the Kelvin equation, but the effects of the capping ligands used in the nanoparticle synthesis and of electron beam heating have limited the application of such approaches. Here it is shown that for an appropriate choice of experimental parameters (nanoparticle size, loading, intermediate holding Temperature, and illumination conditions) the sublimation of Ag nano-cubes can be used to measure the Specimen Temperature to an accuracy of ±5 °C, over the range 700–850 °C. The measurements are reproducible from area to area on the same MEMS chip, and from chip to chip of the same type. The values of Specimen Temperature obtained are consistently lower than the calibrated MEMS heater plate Temperatures, and it is shown that this cannot be explained on the basis of random errors in the experimental measurements or systematic errors in the materials parameters used for the Kelvin equation analysis. It is proposed that this is instead due to the low thermal conductivity of the electron-transparent amorphous silicon nitride support membrane on the chip. As further evidence for this, it is shown that for a thicker crystalline Si support with a higher thermal conductivity, the magnitude of the difference is smaller. This approach could be extended to other Temperature ranges by using nanoparticles of other metals with different vapor pressures and sublimation Temperatures.
Craig L Slingluff - One of the best experts on this subject based on the ideXlab platform.
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Shipping blood to a central laboratory in multicenter clinical trials: effect of ambient Temperature on Specimen Temperature, and effects of Temperature on mononuclear cell yield, viability and immunologic function
Journal of Translational Medicine, 2011Co-Authors: Walter C Olson, Mark E Smolkin, Erin M Farris, Robyn J Fink, Andrea R Czarkowski, Jonathan H Fink, Kimberly A Chianese-bullock, Craig L SlingluffAbstract:Background Clinical trials of immunologic therapies provide opportunities to study the cellular and molecular effects of those therapies and may permit identification of biomarkers of response. When the trials are performed at multiple centers, transport and storage of clinical Specimens become important variables that may affect lymphocyte viability and function in blood and tissue Specimens. The effect of Temperature during storage and shipment of peripheral blood on subsequent processing, recovery, and function of lymphocytes is understudied and represents the focus of this study. Methods Peripheral blood samples (n = 285) from patients enrolled in 2 clinical trials of a melanoma vaccine were shipped from clinical centers 250 or 1100 miles to a central laboratory at the sponsoring institution. The yield of peripheral blood mononuclear cells (PBMC) collected before and after cryostorage was correlated with Temperatures encountered during shipment. Also, to simulate shipping of whole blood, heparinized blood from healthy donors was collected and stored at 15°C, 22°C, 30°C, or 40°C, for varied intervals before isolation of PBMC. Specimen integrity was assessed by measures of yield, recovery, viability, and function of isolated lymphocytes. Several packaging systems were also evaluated during simulated shipping for the ability to maintain the internal Temperature in adverse Temperatures over time. Results Blood Specimen containers experienced Temperatures during shipment ranging from -1 to 35°C. Exposure to Temperatures above room Temperature (22°C) resulted in greater yields of PBMC. Reduced cell recovery following cryo-preservation as well as decreased viability and immune function were observed in Specimens exposed to 15°C or 40°C for greater than 8 hours when compared to storage at 22°C. There was a trend toward improved preservation of blood Specimen integrity stored at 30°C prior to processing for all time points tested. Internal Temperatures of blood shipping containers were maintained longer in an acceptable range when warm packs were included. Conclusions Blood packages shipped overnight by commercial carrier may encounter extreme seasonal Temperatures. Therefore, considerations in the design of shipping containers should include protecting against extreme ambient Temperature deviations and maintaining Specimen Temperature above 22°C or preferably near 30°C.
A. F. Emery - One of the best experts on this subject based on the ideXlab platform.
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Contact thermal shock test of ceramics
Journal of Materials Science, 1992Co-Authors: W. P. Rogers, A. F. EmeryAbstract:A novel quantitative thermal shock test of ceramics is described. The technique employs contact between a metal cooling rod and hot disc-shaped Specimen. In contrast with traditional techniques, the well-defined thermal boundary condition allows for accurate analyses of heat transfer, stress, and fracture. Uniform equi-biaxial tensile stresses are induced in the centre of the test Specimen. Transient Specimen Temperature and acoustic emission are monitored continuously during the thermal stress cycle. The technique is demonstrated with soda-lime glass Specimens. Experimental results are compared with theoretical predictions based on a finite element method thermal stress analysis combined with a statistical model of fracture. Material strength parameters are determined using concentric ring flexure tests. Good agreement is found between experimental results and theoretical predictions of failure probability as a function of time and initial Specimen Temperature.