Surface Temperature Of Specimens Research Articles

Tension-tension fatigue behavior of a melt-infiltrated SiC/SiC ceramic matrix composites in a combustion environment

An experimental thermo-mechanical facility was developed with conditions towards that of the combustion environments experienced by the hot section components of a jet engine. Two different melt-infiltrated (MI) ceramic matrix composites (CMCs) were evaluated, one containing Hi-Nicalon Type S fibers and the other Tyranno SA fibers. Specimens considered in this study were subjected to fatigue loading with a stress ratio of 0.1, frequency of 1 Hz and a specimen surface temperature of 1200 ± 20 °C. Results indicate that fatigue life in the combustion environment was an order of magnitude lower compared to the furnace environment and is attributed to the hostile environment present with the burner rig. Post-test microscopy was conducted in order to understand the damage mechanisms and oxidation behavior. Polished longitudinal sections of the burner rig specimens revealed longitudinal cracking which could be attributed to the presence of thermal gradient stress. Electrical resistance (ER) was implemented to monitor the damage.

The Influence of Specimen Surface Roughness and Temperature of Steam Injection on Breakaway Oxidation Behavior of Zry-4 Fuel Cladding in Steam at 1273 K

The steam oxidation behavior of Zr-based Zircaloy-4 fuel cladding was studied at 1273 K with two different surface roughness levels. Steam was introduced either at room temperature (RT) or at 1273 K. Weight gain kinetics were evaluated by post-test weight measurement, and the reaction products and alloy microstructure were evaluated using optical microscopy. Hydrogen pick-up was measured by the gas extraction technique. Specimen surface roughness did not affect the oxidation kinetics or the hydrogen absorption. The time to breakaway oxidation was suppressed when steam was introduced at RT, and the oxide was more adherent, suggesting superior mechanical properties. When steam was introduced at 1273 K, an undulated oxide–metal interface formed earlier and a higher amount of hydrogen was absorbed by cladding before the kinetic transition. The alloy grain grew into larger size in the condition when steam was injected at 1273 K compared to the condition when steam was injected at RT, which may affect the observed behavior. After the oxide breakaway, the rate of hydrogen absorption accelerated substantially independent of the temperature of steam injection.

A Novel Thermgoraphic Methodology to Predict Damage Evolution of Impacted CFRP Laminates Under Compression-Compression Fatigue Based on Inverted Weibull Model

A novel thermographic methodology is proposed in this work to predict damage evolution of impacted CFRP laminates under compression-compression fatigue loading based on inverted weibull model. To this goal, the inverted weibull model is firstly mathematically proposed. Then, several specimens are subjected to impact testing, followed by fatigue testing and monitored by infrared thermography. Afterwards, the thermal image and the surface temperature of specimens are analyzed. Finally, taking the surface temperature as damage variables, the inverted weibull model is introduced to predict the damage evolution. The obtained results show that the inverted weibull model can be used for damage evolution prediction with the predicted error less than 10%.

Waterborne Intumescent Coatings Containing Industrial and Bio-Fillers for Fire Protection of Timber Materials.

Flammability and combustion of softwood treated with intumescent coatings were studied in the present work. The formulations applied onto wood surfaces contained different ratios of industrial fillers, titanium dioxide TiO2 and aluminium trihydroxide Al(OH)3, and/or bio-fillers, eggshell and rice husk ash. Combustion behaviours of unprotected and protected wood samples have been examined with the aid of cone calorimetry performed under the varied levels of thermal flux ranging from 30 to 50 kW/m². The char residues obtained after the completion of cone calorimetry test at 40 kW/m² were analysed by the Raman spectroscopy. The fire protective properties of the studied coatings were strongly influenced by the nature of the fillers as well as by the intensity of thermal irradiance. The incorporation of bio-based fillers into the water-based intumescent formulations significantly improved fire resistance of wood substrates. For example, at 30 kW/m², the Effective Heat of Combustion was reduced by more than 40%, whilst the average Peak to Heat Release Rate had dropped from 193.2 to 150.3 kW/m² for the wood sample protected with the formulation incorporating two industrial and two bio-fillers. Moreover, an application of the studied coatings resulted in a notable reduction of the back surface temperature of the wood specimens.

Fly ash-based geopolymer with self-heating capacity for accelerated curing

Geopolymers has gained increasing attentions in recent decades because of its potential for CO2 emission reductions. In order to further increase the curing efficiency and save energy, the self-electrical heating fly ash based geopolymer was developed in this paper. In this work, carbon black and steel fibers were added into the fly ash based geopolymer to increase its electrical property. The feasibility of curing fly ash based geopolymer by using self-electrical heating was investigated. Calorimetry measurements were performed to quantify the effect of curing temperature on geopolymerization process of fly ash-base geopolymer. The three-point bending tests were conducted to investigate the influences of electric-heating on the flexural behaviours of geopolymer specimens. The results showed that the maximum surface temperature of geopolymer specimens under electric-heating reached 67 °C, which proved the feasibility of making conductive geopolymer with self-electrical behaviors. The three-point bending test results showed that the flexural strength for specimen significantly increased after self-electrical heating. With the proper addition of carbon black and steel fiber, the fly ash based geopolymer specimen cured after electrical heating possesses a denser micro-structure and therefore exhibits higher strength and better ductility. Besides, self-electrical heating method can significantly increase the eco-efficiency of geopolymer.

Experimental and Numerical Study of the Impact of a Pulsed Electron Beam on Titanium and Aluminum Targets

The surface temperatures of specimens made of A7 grade aluminum alloy and VT1-0 grade titanium alloy are measured with a high-speed infrared pyrometer during the impact of a pulsed electron beam with different densities of the pulse energy. Numerical modeling of the thermal fields under the same conditions reveals good similarity to the experimental data and confirms that the heating rate of a sample’s surface depends on the basic characteristics of the electron beam.

A 6 MW/m2 High Heat Flux Testing Facility of Irradiated Materials Using Infrared Plasma-Arc Lamps

Assessing the effect of neutron irradiation of plasma-facing materials has been challenging due to both the technical and radiological challenges involved. In an effort to address the radiological challenges, a facility was developed to conduct high heat flux testing (HHFT) of inherently small samples of neutron-irradiated materials. A new line-focus reflector was designed and fabricated at Oak Ridge National Laboratory for a plasma-arc lamp (PAL) to attain a source heat flux of 12 MW/m2. The new reflector was fabricated with two ports for monitoring specimen condition during HHFT. At the same operational conditions for PAL, the absorbed heat flux in tungsten was increased from 1.39 MW/m2 with the uniform irradiance reflector to 5.12 MW/m2 for the line-focus reflector. This fourfold increase in the heat flux, at the same PAL electrode lifetimes, enabled cost-effective facility operation for a high number of cyclic high heat flux tests. Specifically, the test section is confined to a hemispherical dome, and specimens are bolted directly to a water-cooled copper alloy rod. Temperature measurement in the PAL facility was a main challenge due to a limited line of sight. For the first time in a PAL facility operating at high heat fluxes, the specimen surface temperature was directly measured during HHFT with a pyrometer. The HHFT data, which were obtained in this upgraded PAL facility, demonstrated the facility readiness for irradiated materials.

Thermomechanical behavior of adhesively bonded joints under out-of-plane dynamic compression loading at high strain rate

In this study, a new experimental approach in which the deformation, the damage kinetic, and the temperature are measured simultaneously during a high strain rate on adhesively bonded composite joints. Especially, our goal is to quantify the amount heat dissipation during impact and to identify the mechanisms that induce this dissipation. Out of plane dynamic compression tests were conducted on assembled specimens over a range of strain rate from 372 s−1 to 1030 s−1 using the Split hopkinson Pressure Bars technique. The specimen surface temperatures were monitored using an infrared camera. The increase in the strain rate has a dramatic effect on the stress–strain behavior producing a significant heat dissipation in the material. The infrared monitoring provides the spatial distribution of temperature that increase near the adhesive/adherent interfaces of the specimen. The observed temperature increase profiles clearly show that the stress concentration appears in the adhesive area and provide valuable information regarding the damage mechanisms and their role in the heat dissipation during dynamic loading conditions. The dependence of these results on strain rate indicates that there exists a correlation between the thermo-mechanical behavior and the strain rate effect, which might be useful when developping damage models taking into account the energy balance for adhesively bonded joints under impact loading conditions.

Flexural fatigue performance of hybrid composite laminates based on E-glass and polypropylene fibers

An experimental investigation has been conducted to understand the effect of water aging on flexural fatigue performance of unidirectional polypropylene (PP)-glass (G) fiber–reinforced epoxy composites. Test specimens were fabricated using hand lay-up process with a constant total fiber volume fraction. The effects of the reinforcement hybridization, hybrid configuration, and stacking sequences on S–N curves were investigated. Deflection-controlled flexural fatigue tests with a frequency of 25 Hz at zero mean stress have been conducted. A 20% reduction of the initial applied moment was taken as a failure criterion. In the first stage, the flexural fatigue properties of un-aged composite specimens were studied in ambient temperature. In the second stage, flexural fatigue properties were investigated after a preliminary aging step in distilled water for 350 days. The specimen surface temperature rise was measured to ensure that there is no early damage happened in the tested specimens. Results indicated that the hybridization of PP fiber–reinforced composite with G fiber improves its flexural fatigue resistance but increase water uptake. Inter-intraply hybrid laminate with G-fiber layers at the specimen outer faces and PP-fiber layers in the specimen core exhibits the most favorable flexural fatigue behavior, that is, the highest cost ratio and the specific fatigue endurance strength. The water-sorption step induced a significant decrease in fatigue properties of the fabricated specimens. The highest measured temperature rise was observed to be about 9°C for G fiber–reinforced composite.

Combined laser heating and tandem acousto-optical filter for two-dimensional temperature distribution on the surface of the heated microobject

Recently it has been shown that it is possible to measure the two-dimensional distribution of the surface temperature of microscopic specimens. The main component of the system is a tandem imaging acousto-optical tunable filter synchronized with a video camera. In this report, we demonstrate that combining the laser heating system with a tandem imaging acousto-optical tunable filter allows measurement of the temperature distribution under laser heating of the platinum plates as well as a visualization of the infrared laser beam, that is widely used for laser heating in diamond anvil cells.

Emissivity Model of Aluminum 7075 During the Growth of Oxide Layer Over the Temperature Range from 800 to 910 K at a Wavelength of 1.5 μm

The emissivity models of aluminum 7075 were studied during the growth of oxide layer over the temperature range from 800 to 910 K at a wavelength of 1.5 μm. In the experiment, the samples were heated to a certain temperature and kept at that temperature for approximately 6 h. To determine the accurate emissivity, the surface temperature of specimens was measured by the two thermocouples, which were symmetrically welded onto the front surface of samples. The average of their readings was regarded as the true temperature. Eleven models were employed to evaluate the variation of emissivity with temperature or growth of oxide film on the specimen surface at a certain condition. The effect of the number of parameters used in the models on the fitting quality was studied at a certain temperature. The conclusion was obtained as more the number of parameters used in the models, the better the fitting quality became on the whole. The variation of emissivity with temperature was investigated at a certain thickness of oxide layer. The three approximate models of variation in emissivity with temperature and thickness of oxide film were proposed. The strong oscillations of emissivity were observed during the initial heating period, which were affirmed to arise from the interference effect between the two radiations stemming from the oxide layer and coming from the substrate.

Temperature measurement for in-situ crack monitoring under high-frequency loading

A liquid mercury target vessel, composed of type 316L stainless steel and used in a pulsed spallation neutron source, suffers not only from proton and neutron damage but also cyclic impact stresses caused by proton beam-induced pressure waves. In a previous study, we carried out an ultrasonic fatigue test to gigacycles and observed that the specimen surface temperature rose abruptly just before failure. To understand the mechanism of this temperature rise, the temperature distribution of the specimen surface was measured using a thermography instrument during an ultrasonic fatigue test. The result showed that the temperature rose locally, especially at the crack tip, and the peak position moved with crack propagation. Furthermore, nonlinear structural analysis by LS-DYNA was performed to clarify the mechanism of this temperature rise. The analytical results showed that the heat due to plastic deformation at the crack tip is the dominant factor underlying the temperature rise rather than friction between crack surfaces.

Study on infrared differential thermal non-destructive testing technology of the permeability of hot mix asphalt pavements

In order to non-destructive test (NDT) the permeability coefficient of hot mix asphalt (HMA) pavements fast, A methodology for assessing the permeability coefficient was proposed by infrared differential thermal testing of pavement after rain. The relationship between permeability coefficient and air voids of HMA specimen deter-mined. Finite element method (FEM) models were built to calculate the surface temperature difference with different exposure time after precipitation. Simulated solar radiation source and fully saturated plate specimens were set in laboratory, tests verify that the different exposure time the specimen surface temperature difference. Infrared differential thermal detection permeable pavement hardware and corresponding software developed. Based on many test results, the evaluation index and criteria of permeability coefficient of HMA pavements tested by infrared differential thermal were developed. The results showed that: There is correlation between air voids and permeability coefficient of HMA specimen. Permeability coefficient of HMA pavements can be determined by different surface temperature at different exposure time. 9:00 am - 14:00 pm is the best time to detect permeability coefficient by infrared differential thermal NDT. Permeable asphalt pavement permeability can be achieved by infrared detector quickly and continuously, a lane testing; Per the permeable assessment criteria, in-place pavements permeability coefficients can be accurately evaluated.

Effect of Temperature on the Dry Sliding Friction and Wear of Rice Bran Ceramics against Different Counterpart Materials

ABSTRACTIn this study, we investigated the effect of temperature on the friction and wear of rice bran (RB) ceramics, a hard porous carbon material made from rice bran, sliding against alumina, stainless steel, and bearing steel balls under dry conditions. Friction tests were performed using a ball-on-disk-type friction tester wherein a ceramic heater was installed in the rotational stage. The surface temperature of the RB ceramic disk specimens was controlled at 20, 100, 150, or 200°C. The normal load was 1.96 N, sliding velocity was 0.1 m/s, and number of cycles was 20,000. The effect of surface temperature on the friction and wear of RB ceramics substantially differed among the ball material types. The friction coefficient for the RB ceramics sliding against an alumina ball decreased with increasing temperature and exhibited an extremely low value (0.045) at 200°C. The friction coefficient in the case of the RB ceramics sliding against a stainless steel ball exhibited a stable value as the temperature was increased to 150°C and slightly decreased as the temperature was increased further, reaching a low value of 0.122 at 200°C. The friction coefficient for the RB ceramics sliding against bearing steel ball drastically increased with increasing temperature, reaching 0.381 at 200°C. The specific wear rate of the RB ceramics increased with increasing temperature; it was lowest when sliding against alumina and highest when sliding against bearing steel. The wear of the alumina ball was the lowest and that of the bearing steel ball was the highest under all investigated temperature conditions. On the basis of these results, we concluded that alumina is a promising counterpart material for RB ceramics sliding at high temperatures (≤200°C).

Using lightweight cement composite and photocatalytic coating to reduce cooling energy consumption of buildings

Solar reflectance and thermal conductivity are two main factors which affect the heat transfer through opaque building envelope and cooling energy consumption of buildings in tropical countries and other regions in summer season. Effects of a lightweight cement composite (LCC) with hollow cenospheres and a photocatalytic coating with titanium dioxide (TiO2) on the thermal conductivity and solar reflectance were investigated. Individual and combined effects of the LCC and photocatalytic coating on the heat gain and surface temperatures of panel specimens exposed to simulated sunlight were evaluated under controlled experimental conditions in comparison to a conventional concrete of similar 28-day compressive strength.The LCC has a thermal conductivity of 0.39W/m.K, 80% lower than that of the concrete (1.98W/m.K). The photocatalytic coating increases the solar reflectance of the LCC specimen from 0.41 to 0.78without significant effect on the thermal conductivity. The LCC and photocatalytic coating reduce the heat gain in 9h exposure to simulated sunlight by 33% and 54%, respectively, while their combination reduces the heat gain by 69%. The inner surface temperature of the specimens is reduced by 3.7°C, 4.3°C, and 8.0°C after 9h exposure to simulated sunlight due to the use of LCC, photocatalytic coating, and their combination. The results indicate that the energy consumption for cooling building interior can be reduced significantly by the use of the LCC, photocatalytic coating, or a combination of these.

Spectral emissivity model of steel 309S during the growth of oxide layer at 800–1100 K

This work strived to determine the analytical relationships between the spectral emissivity and the wavelength at different temperatures during the growth of oxide layer on the specimen surface of steel 309S. In the experiment, the spectral emissivity was measured at eight wavelengths, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, and 2.1μm, at temperatures from 800 to 1100K in increments of 20K by multispectral radiation thermometry. To accurately measure the normal spectral emissivity, the detector employed in the thermometry should be perpendicular to the surface of specimens as accurately as possible. The temperature of specimen surface was measured by the two thermocouples, which were symmetrically welded onto the front surface of specimens. The average of their readings was regarded as the true temperature. With the spectral emissivity measured here, the variation in the spectral emissivity with wavelength was evaluated at different temperatures and different heating times. Ten emissivity models were evaluated. The effect of number of the parameters used in the models on the fitting accuracy was studied. Both the five-parameter LLWE and LWE models were very suitable for fitting the spectral emissivity and could farthest relieve the effect of heating time on the accuracy of temperature prediction. The uncertainties in the temperature prediction of steel 309S specimens were basically within 10K by thermometry using the two models over the present temperature and wavelength ranges.

Tribological properties of polyamide (PA6) in self-mated contacts and against steel as a stationary and moving body

The time for which each contacting body is exposed to a tribological contact affects its interface temperature, third-body and tribofilm formation, and, as a result, the overall tribological behaviour, which may be particularly relevant with very dissimilar material pairs. This work focuses on the tribological properties of unreinforced polyamide (PA6) in self-mated contacts or against steel (SS) as a stationary (SS/PA6) or a moving contact (PA6/SS) body under dry-sliding conditions. Moreover, the effects of the contact pressure and the sliding velocity were investigated for these contacts. In addition, the contact conditions were carefully controlled with measurements of the specimen's surface temperature using an infrared camera. The results show that the tribological behaviour indeed depends significantly on the contact configuration. The tribological properties of the stationary steel pin sliding against a rotating polymer disc (SS/PA6), as well as of a self-mated PA6/PA6 contact, depended substantially on the contact conditions used. In contrast, the contact configuration of a stationary PA6 pin sliding against a rotating steel disc (PA6/SS) showed only a negligible effect on changes in the sliding speed and the load. Moreover, this was clearly the best-performing contact in the study and the beneficial effect is explained by the ability of a rotating disc to remove the heat from the contact zone and, consequently, to lower the temperatures generated in the tribological contact.

Three-point-bending fatigue behavior of AZ31B magnesium alloy based on infrared thermography technology

The fatigue behavior of the AZ31B magnesium alloy subjected to three-point-bending tests was studied. Real-time recording of the surface-temperature-evolution data of specimens was obtained using the infrared thermography technology during fatigue. The characteristics of heat production and transfer were described, and the correlation between temperature and stress distribution was analyzed. The surface temperature of specimens undergoes four stages: (I) Initial rapid increase stage, (II) Decrease stage, (III) Steady-state stage, and (IV) Abrupt fracture stage during the course of the experiment. The fracture surface of specimens was observed by Scanning Electron Microscope (SEM). The result demonstrates that the AZ31B alloy possess by the quasi-cleavage fracture. The development of twins was analyzed to confirm the reason for temperature changing. An energy model based on the fatigue-damage-accumulation theory was established to predict the fatigue prediction of AZ31B-magnesium-alloy specimens. The fatigue strength of the AZ31B magnesium alloy using the Luong’s method is 128.97MPa, is close to the experimental result of 133.87MPa, the fatigue strength of the prediction model gives 137.33MPa, which is comparable to the experimental results.

Normal Spectral Emissivity Models of Steel 304 at 800–1100 K with an Oxide Layer on the Specimen Surface

This work investigated the normal spectral emissivity characteristics of Steel 304 over a temperature range from 800 to 1100 K and a wavelength range from 1.4 to 2.1 μm. In the experiments, specimens were heated in air for 6 h at a certain temperature. Two platinum–rhodium thermocouples were symmetrically welded onto the front surface of the specimens near the measuring area for accurate monitoring of the surface temperature. The temperatures measured by the two thermocouples had an uncertainty of 1 K. The average of their readings was regarded as the temperature of the specimen surface. The radiance stemming from the specimens were measured at temperatures from 800 to 1100 K in increments of 20 K by multispectral radiation thermometry. Variation in the normal spectral emissivity with respect to wavelength and temperature was studied for different heating times. The effect of surface oxidization on the accurate prediction of the specimen surface temperature was discussed. Similar variation in the normal spectral emissivity for different heating times showed that the emissivity followed a certain rule. Nine emissivity models were examined for accuracy in the temperature prediction. The results showed that the four-parameter log-linear wavelength and line wavelength emissivity models generated best overall temperature prediction. We concluded that the effect of surface oxidization on the emissivity models of Steel 304 could be dismissed; and that the same models could be used to predict its surface temperature from 800 to 1100 K.

Determination of characteristics of erosion wear of grade 15Kh11MF steel with the Cr–CrC ion-plasma sprayed coating

Results of investigations of the influence of a Cr–CrC ion-plasma sprayed protective coating on characteristics and the intensity of erosion wear of grade 15Kh11MF steel at a gas–abrasive flow incidence angle of 30° and an experimental specimen (target) surface temperature of 550°С are presented. The Cr–CrC ion-plasma sprayed coating was formed in a Gefest vacuum installation by magnetron deposition. Investigations of the formed coating were carried out using a research and experimental facility complex that provided the study of the composition and structure of the coating, measurement of its thickness, roughness, microhardness, and determination of its relative resistance at the combined action of the gas–abrasive flow and high temperatures. The Cr–CrC coating with a thickness of 6.5 ± 0.3 μm has a finegrained structure with grains with dimensions of 20–40 nm and contains layers of chromium and chromium carbide. The main coating element is chromium. Its content in carbide layers is 89.4–91.9% at a carbon content of 6.8–9.5%. The coating microhardness is H0.05 = 1350 ± 50 HV. The maximum wear of the 15Kh11MF steel target is observed at the angle of the gas–abrasive flow incidence that is close to 30° (30 7°). With this incidence angle and a target surface temperature of 550°С, the Cr–CrC coating extends the term to the surface failure and the appearance of a clear abrasive trace no less than four times. The coating failure has a local character, i.e., the target surface forms islands with the coating, between which the intensive wear of the base material occurs.