Temperature evolution and fatigue life evaluation of AZ31B magnesium alloy based on infrared thermography

The surface temperature of extruded AZ31B alloy plate was measured by infrared thermograph in air during tension and high-cycle fatigue tests. The mechanism of heat production was discussed and the value of critical fatigue damage temperature was calculated according to the P—ΔT curve. Results show that the variation trend of temperature is different between tension and fatigue tests. The temperature evolution in tension test consists of four stages： linear decrease, reverse linear increase, abrupt increase, and final drop. The initial decrease of temperature is caused by thermal elastic effect, which is corresponding to the elastic deformation in tension progress. When cyclic loading is above the fatigue limit, the temperature evolution mainly undergoes five stages： initial increase, steep reduction, steady state, abrupt increase, and final drop. The peak temperature in fatigue test is caused by strain hardening that can be used to evaluate the fatigue life of magnesium alloy. The critical temperature variation that causes the fatigue failure is 3.63 K. When ΔT≤3.63 K, the material is safe under cyclic loading. When ΔT3.63 K, the fatigue life is determined by cycle index and peak temperature.

Robustness optimization for rapid prototyping of functional artifacts based on visualized computing digital twins

This study presents a robustness optimization method for rapid prototyping(RP)of functional artifacts based on visualized computing digital twins(VCDT).A generalized multiobjective robustness optimization model for RP of scheme design prototype was first built,where thermal,structural,and multidisciplinary knowledge could be integrated for visualization.To implement visualized computing,the membership function of fuzzy decision-making was optimized using a genetic algorithm.Transient thermodynamic,structural statics,and flow field analyses were conducted,especially for glass fiber composite materials,which have the characteristics of high strength,corrosion resistance,temperature resistance,dimensional stability,and electrical insulation.An electrothermal experiment was performed by measuring the temperature and changes in temperature during RP.Infrared thermographs were obtained using thermal field measurements to determine the temperature distribution.A numerical analysis of a lightweight ribbed ergonomic artifact is presented to illustrate the VCDT.Moreover,manufacturability was verified based on a thermal-solid coupled finite element analysis.The physical experiment and practice proved that the proposed VCDT provided a robust design paradigm for a layered RP between the steady balance of electrothermal regulation and manufacturing efficacy under hybrid uncertainties.

Integrated Condition Monitoring of Large Captive Power Plants and Aluminum Smelters

Condition monitoring is implementation of the advanced diagnostic techniques to reduce downtime and to increase the efficiency and reliability.The research is for determining the usage of advanced techniques like Vibration analysis,Oil analysis and Thermography to diagnose ensuing problems of the Plant and Machinery at an early stage and plan to take corrective and preventive actions to eliminate the forthcoming breakdown and enhancing the reliability of the system.Nowadays,the most of the industries have adopted the condition monitoring techniques as a part of support system to the basic maintenance strategies.Major condition monitoring technique they follow is Vibration Spectrum Analysis,which can detect faults at a very early stage.However implementation of other techniques like Oil analysis or Ferrography,Thermography etc.can further enhance the data interpretation as they would detect the source of abnormality at much early stage thus providing us with a longer lead time to plan and take the corrective actions.In Large Captive Power Plants and Aluminium Smelters,Integrated Condition Monitoring techniques play an important role as stoppage of primary system and its auxiliaries(boiler,steam turbine,generator,coal and ash handling plants etc.)results into the stoppage of the entire plant,which in turn leads to loss of productivity.From economical and operational point of view,it is desirable to ensure optimum level of system availability.

Effect of undercut defect on deformation behavior TC4 titanium alloy laser welded butt joint under static tensile loading

By measuring and analyzing infrared thermal image of the specimen in static load tensile test process, it was studied that the influence of the undercut defects and double-sided dressing method on the deformation behavior of the laser welded joint specimens of TC4 titanium alloy. The results showed that for the unmodified specimens, the yield phenomenon occurs first in the region of the joint, but the undercut value has an effect on the stress and strain of starting to yield phenomenon, and a great effect on the plastic deformation behavior.When the undercut is less than a certain value, the large plastic deformation occurs in the base metal region and the plasticity of the specimen is comparable to that of the base metal, but the larger undercut defect results in a concentrated plastic deformation in the joint region and rapidly failed in this region. But the double-sided dressing specimen is significantly different. The physical yield is no longer concentrated in the joint region, but at the same time occurs in the several regions including joint and the base metal. And the plastic deformation mainly occurs in the base material area, similar to that of the base material.

Can infrared thermography be used to monitor fatigue during exercise? A case study

Background: Infrared thermographic imaging(IRTG) is a safe and reliable technology used to monitor skin temperature. The main aim of our study was to evaluate the relationship between skin temperature changes and muscle fatigue in order to answer the main research question if IRTG can be used to monitor muscle fatigue.Methods: This was a case study performed on a 23-year-old trained middle distance runner. After warm-up the subject was exercising on the dynamometer for 7.5 min at 120?/s performing only concentric contractions of quadriceps. At the same time IRTG recording of both(exercising and non-exercising) quadriceps was performed.Results: A correlational analysis that was performed in order to quantify the relationship between power and temperature change over time has shown that there is a significant negative correlation between skin temperature increase and power decrease(r = -0.543, p = 0.036) of exercising quadriceps. In linear regression model the exercising quadriceps power could be predicted from skin temperature. No such relationships were noted for the non-exercising limb that served as a control.Conclusion: We believe that correlation between skin temperature change and muscle power output as described in this case study deserves further analysis on the larger sample including subjects of the different ages, health status, and physical abilities in order to create a new tool for monitoring the muscle fatigue.

Thermal Diagnosis of Heat Conduction and Combustion Time of Fruits of the Brazil Nut Tree (<i>Bertholletia excelsa</i>Bonpl.)

The objective of this work was to evaluate the spatial and temporal dynamics of the process of combustion of fruits of the Brazil nut tree (Bertholletia excelsa Bonpl.) using thermographic images in order to characterize the potential of this biomass as an energy source for use in ceramic kilns. Infrared thermography was used as a diagnostic tool, and the trial was conducted in November 2018, in two blocks with two repetitions in each, with the fruits organized so that the cavity was oriented upward and also downward. The thermograms were analyzed using Flir Tools (6.3 v). The temperatures were the highest in the center of the fruits (>160&deg;C), attaining incandescence in 6 min 30 s. Heat was propagated from the center to the edge, and this process was quicker for fruits with their cavities pointed upward. A second order polynomial model explained combustion time with a maximum duration of 7.2 minutes. The thermographic diagnostic has the potential to be used in management strategies for this biomass as an energy source, thus aggregating value to the residuals that are normally left in the forest during harvest by extractivists.

The Maximum Temperatures （Tmax） Distribution on the Body Surface of Sport Horses

The objective of the study was to determine the usefulness of measuring maximum temperatures in designated regions of a healthy horse＇s body surface. Thermographic investigations （Thermovision〉550, FLIR） were carried out on 35 horses from 6 to 16 years old participating in show jumping competitions. The rectal temperatures of the horses were in the range 37.5-38.2 ℃. The research was performed in a stable, the ambient temperature （Tab） of which was 14℃ with a humidity （φ） of 60%. Thermograms of the left and right side of the horses were obtained. Each thermogram consisted of 36 body surface regions （before the competition） and 25 regions （immediately after the competition）. The maximum temperature ranges at rest were 21.8 ℃-31.0℃ and symmetrical regions did not differ statistically （P 〉 0.05）. The highest temperatures were on the head, neck and trunk, the lowest-on the limbs. The hind legs were warmer than the front legs in analogous areas, with the exception of the gaskin and forearm. The warmest body areas had the largest surface area, which is indicative of their crucial role in the thermoregulation of the equine organism. The research results may therefore be useful in veterinary diagnosis. The range of maximum temperatures after the competitions was 25.2℃-34.2℃. The highest increment was observed at the breast, elbow, forearm and gaskin, the lowest-at the head, pastern and hoof （foreand hind limbs）. Research regarding body surface temperature after exercise does not have diagnostic value for veterinarians because ＂warming-up＂ certain parts of body surface masks inflammation.

On the Setup of a Test Bench for Predicting Laminar-to-Turbulent Transition on a Flat Plate

At turbomachinery relevant flow conditions the boundary layers are often transitional with laminar-to-turbulent transition occurring. The characteristics of the main flow can depend highly on the state of the boundary layer. Therefore it can be vitally important for the designer to understand the process of laminar-to-turbulent transition and to determine the position and length of the transitional region. In this paper the flow over a flat plate is experimentally studied in order to investigate and better understand transitional flow. Preston tube measurements as well as a thermographic camera system were performed for two different inlet velocities in order to determine the position of the transitional zone. The results of the experiment are compared to numerical flow solutions using a common transition model to determine its capability. The simulation has been performed with the two commercial codes CFX and Fluent by Ansys and an in-house code called LINARS. As a result of this study, a better understanding of the experimental and numerical methods for determining transition shall be given.

Method for determining effective flame emissivity in a rotary kiln incinerator burning solid waste

Temperature is the most important parameter for the improvement of combustion efficiency and the control of pollutants.In order to obtain accurate flame temperatures in a rotary kiln incinerator using non-intrusive thermographic method,the effective flame emissivity was studied.A combined narrow-and wide-band model and Mie scattering method were used to calculate the radiative properties for gases and fly-ash particles under different combustion conditions.The effects of the air/waste ratio and fly-ash particles on the effective flame emissivity were discussed.The results of numerical calculations showed that the effective emissivity decreased from 0.90 to 0.80 when the air/waste ratio increased from 1.0 to 1.8,and the effect of the fly-ash particles was ignorable under the conditions discussed in this paper.Experimental measurement results indicated that the accuracy of the thermographic temperature measurements improved significantly if the setting of the flame emissivity was adjusted according to the air/waste ratio.

Infrared experiment on the wall temperature distribution for a particle packed channel with constant heat flux

With constant heat flux, wall temperature distribution for a particle filled channel was measured using infrared thermal vision technology. It was found that non-uniform relative high-temperature regions were randomly distributed on the heating wall, possibly due to the lower flow velocity, or even due to the blocked flow near the points where particles contact with the heating wall directly. Not only porosity but also the size and shape of the pores are changed in the wall region of particle-packed structures, because of the limitation of the wall, and the changes affect largely the fluid flow and heat transfer. The transition of the flow pattern in pores can be inferred according to the variation of Nu with Re, where the area weighted wall temperature is adopted to calculate the Nu.