Effect Of Material Temperature Research Articles

Wear behaviors and plastic deformation mechanisms induced by nano-grinding of indium-doped gallium nitride single crystal

The wear behaviors and plastic deformation mechanisms of indium (In)-doped gallium nitride (GaN) induced by nano-grinding are investigated in this work, which is of great significance for improving the quality and precision of the machined surface of the nitride semiconductor, as well as for elucidating their mechanical properties during the nano-grinding process. A numerical simulation approach based on molecular dynamics (MD) is used to carry out a comparative analysis of the nano-grinding process for the undoped and In-doped GaN by analyzing the machined surface morphology, formation mechanisms of the subsurface damage (SSD) layer, dislocation behaviors, and residual stress. In addition, the effects of material temperature and grinding speed on the nano-grinding process of the In-doped GaN are investigated. Compared to the undoped GaN, indium doping increases the pile-ups and chips on both sides of the abrasive, the roughness of the machined surface, and the coefficient of friction. Moreover, it reduces the thickness of the SSD layer and restricts the occurrence of phase transformations. Indium doping also weakens the dislocation interactions and reduces the generation of dislocation entanglements as well as wall-like dislocations. Furthermore, it decreases the maximum value of the residual stress and increases the area of high residual stress regions. The wear behaviors and plastic deformation mechanisms of In-doped GaN are quite sensitive to material temperature, but not much influenced by grinding speed.

Evolution characteristics of ethyl ether spray explosion process in 20L near-spherical vessel

As a biofuel with a wide range of uses, ethyl ether leakage may cause serious spray explosion accidents during storage and transportation, however, the evolution characteristics and process mechanism of ethyl ether spray explosion have not been thoroughly studied. Therefore, the effects of material temperature and ambient temperature on ethyl ether spray explosion at different concentrations are studied by means of spray explosion experiment system. In this paper, the development of ethyl ether spray explosion with a mass concentration range of 107.1–392.7 g/m3 was studied at different ambient temperature and material temperature. Where the ambient temperature range is 298.15–323.15 K, and the material temperature range is 298.15–323.15 K. Moreover, in this paper, the risk of spray explosion is more clearly understood through the classification of deflagration index, and the explosion characteristics of spray explosion are analyzed comprehensively according to the boiling point as the dividing line. The maximum explosion pressure and its arrival time, the rate of rise of the maximum explosion pressure and its arrival time are used as the basis to evaluate the effect of the explosion process of ethyl ether spray. The results show that when the ambient temperature is lower than the boiling point temperature of ethyl ether, the increase of ambient temperature has little effect on the explosion characteristics of ethyl ether spray. When the ambient temperature is higher than 308.15 K, the maximum explosion pressure and maximum rate of pressure rise of ethyl ether spray explosion increase. At medium and low concentrations(107.1 g/m3, 178.5–249.9 g/m3), the increase of ambient temperature is conducive to the rapid development of spray explosion, and the arrival time of maximum explosion pressure and pressure rise rate both show a decreasing trend. However, under the influence of incomplete combustion at high concentration, the explosion development rate is reduced. At lower material temperature, the maximum explosion pressure and the maximum rate of pressure rise increase with the increase of material temperature. When the material temperature is higher than 303.15 K, the ethyl ether droplet temperature is higher than the ambient temperature, and the heat loss of the droplet has a certain inhibition effect on spray explosion. Especially when the material temperature is high, the inhibition effect is more significant, so when the material temperature rises to 323.15 K, the maximum rate of pressure rise decreases. The effect of ambient temperature on the explosion grade is more obvious than that of the material temperature, and the effect on the explosion characteristics of ethyl ether spray is also greater.

Effects of material temperature on the separation efficiency in a rotary-drum type eddy current separator

Improving the separation efficiency of eddy current separator is of great significance in solid waste recycling. In this study, a three-dimensional transient simulation model of eddy current separator was established based on the finite element analysis. The effects of material temperature on the separation were investigated by combining simulations and separation experiments. New concepts, such as separation index and direction angle, were proposed to clarify the related mechanism. It was found that reducing the material temperature can increase the Lorentz force on conductive non-ferrous particles, so the residual temperature after cryogenic crushing can be used to improve the separation between conductive non-ferrous and non-conductive materials. Reducing the material temperature will also increase the fluctuation of the Lorentz force, which negatively affects the separation between different non-ferrous metals. The results revealed that different optimization indexes should be set for different mixtures in the design and optimization of the eddy current separator.

Effect of Material Temperature on Fabrication Accuracy of Metal Powder Extrusion Additive Manufacturing with Ultrasonic Vibration

Effect of Material Temperature on Fabrication Accuracy of Metal Powder Extrusion Additive Manufacturing with Ultrasonic Vibration

GPU ACCELERATION OF DOPPLER BROADENING FOR NEUTRON TRANSPORT CALCULATIONS1

In radiation transport calculations, the effects of material temperature on neutron/nucleus interactions must be taken into account through Doppler broadening adjustments to the microscopic cross section data. Historically, Monte Carlo transport simulations have accounted for this temperature dependence by interpolating among precalculated Doppler broadened cross sections at a variety of temperatures. More recently, there has been much interest in on-the-fly Doppler broadening methods, where reference data is broadened on-demand during particle transport to any temperature. Unfortunately, Doppler broadening operations are expensive on traditional central processing unit (CPU) architectures, making on-the-fly Doppler broadening unaffordable without approximations or complex data preprocessing. This work considers the use of graphics processing unit (GPU)s, which excel at parallel data processing, for on-the-fly Doppler broadening in continuous-energy Monte Carlo simulations. Two methods are considered for the broadening operations – a GPU implementation of the standard SIGMA1 algorithm and a novel vectorized algorithm that leverages the convolution properties of the broadening operation in an attempt to expose additional parallelism. Numerical results demonstrate that similar cross section lookup throughput is obtained for on-the-fly broadening on a GPU as cross section lookup throughput with precomputed data on a CPU, implying that offloading Doppler broadening operations to a GPU may enable on-the-fly temperature treatment of cross sections without a noticeable reduction in cross section processing performance in Monte Carlo transport codes.

Effect of temperature on early-age properties of self-consolidating concrete equivalent mortar

In this study, the effect of material temperature during casting on fresh properties, hydration kinetics, and early-age compressive strength of self-consolidating concrete (SCC) was evaluated. Concrete equivalent mortars (CEMs) based on SCC mixture designs with water-to-binder ratios of 0.41 and 0.45 were investigated. The SCC mixtures are targeted for infrastructure and building construction and precast applications. The CEMs were prepared at temperatures ranging from 8 to 36°C. Superplasticizer (SP) and air-entraining agent (AEA) demand were evaluated for the CEM mixtures made with different supplementary cementing material (SCM) and limestone filler types. Test results showed that the ambient temperature can significantly affect the SP and AEA demand, hydration kinetics, and compressive strength after 1 d of age. According to the ultraviolet–visible spectrophotometry (UV/Vis) test, the absorption rate of polycarboxylate-based SP decreased with temperature. In contrast, the sensitivity of polynaphthalene sulfonate-based SP to temperature was minimal. Relationships between the variations of different admixture contents, heat flux, and compressive strength with temperature were developed. For a constant slump flow and air content, the demand of the SP and AEA, heat flux, and 1-d compressive strength of CEMs increased linearly with material temperature.

Multiscale simulations of damage of perfect crystal Cu at high strain rates

We use the molecular dynamics code, large-scale atomic/molecular massively parallel simulator (LAMMPS), to simulate high strain rate triaxial deformation of crystal copper to understand void nucleation and growth (NAG) within the framework of an experimentally fitted macroscopic NAG model for polycrystals (also known as DFRACT model). It is seen that void NAG at the atomistic scales for crystal copper (Cu) has the same qualitative behaviour as the DFRACT model, albeit with a different set of parameters. The effect of material temperature on the nucleation and growth of voids is studied. As the temperature increases, there is a steady decrease in the void NAG thresholds and close to the melting point of Cu, a double-dip in the pressure–time profile is observed. Analysis of this double-dip shows disappearance of the long-range order due to the creation of stacking faults and the system no longer has a face centred cubic (fcc) structure. Molecular dynamics simulation of shock in crystal Cu at strain rates high enough to cause spallation of crystal Cu are then carried out to validate the void NAG parameters. We show that the pre-history of the material affects the void nucleation threshold of the material. We also simulate high-strain-rate triaxial deformation of crystal Cu with defects and obtain void NAG parameters. The parameters are then used in a macroscale hydrodynamic simulation to obtain spallation threshold of realistic crystal Cu. It is seen that our results match experimental results within the limit of 20% error.

Effects of Material Temperature on Decomposition and Nitrogen Conversion during Compost Maturing

Effects of Material Temperature on Decomposition and Nitrogen Conversion during Compost Maturing

Stamp forming of carbon fibre/PA12 composites – A comparison of a reactive impregnation process and a commingled yarn system

Two forms of carbon fibre reinforced polyamide 12 (PA12) were compared during non-isothermal stamp forming. The first was a stretch broken commingled yarn woven into a fabric, studied at three initial preconsolidation levels. The second was produced by in situ anionic polymerisation of lactam 12 (APLC12) in a carbon fibre textile, using a thermoplastic resin transfer moulding (TP-RTM) process. A processing window was defined for TP-RTM based upon non-isothermal polymerisation kinetics. For each material form, the effects of stamping parameters on flat plaque properties were examined. For commingled materials, the influence of preheat temperature and the initial preconsolidation level dominated, with preconsolidated materials deconsolidating strongly during the preheat cycle. For CF/APLC12 materials, the effect of material temperature and tool temperature dominated and reduced deconsolidation occurred. Hemisphere forming was enabled by stretch-broken yarn but was possible for both material classes. Over-injection moulding of recompounded CF/APLC12 composite onto stamped CF/APLC12 plate was performed, demonstrating a closed-loop recycling process.

セラミックス成形助剤混合材料のキャピラリー内面のすべりと粘度測定法に関する研究

Capillary flow experiments were performed to evaluate the slip property of injection moldable ceramic compounds of Al2O3, and the following results were obtained. Firstly, slip velocity us was obtained by applying the Mooney method, and the effects of material temperature, particle size and binder composition on the slip velocity were evaluated. Secondly, it was found that the slip velocity changed significantly, when counter pressure was applied at the exit of the capillary. Then, the slip velocity was expressed by an empirical equation considering the pressure effect. Thirdly, an accurate viscosity equation was obtained, based on the pressure dependent slip behavior. Lastly, the flow behavior in a capillary was discussed in consideration of the slip behavior, and the application of counter pressure was found to be effective for realizing high strain rate flow.

Evolutionary Model of Viscoelastic Dampers for Structural Applications

The effects of temperature on the energy dissipation of viscoelastic dampers for seismic mitigation of structures are investigated. To simulate the damper behavior, an evolutionary model is proposed to describe the dependence of the mechanical properties of the damper on the deformation frequency and the temperature increase due to dissipation. Thermorheologically simple materials are considered and the influence of the deformation frequency on the storage and loss moduli is modeled using fractional derivative operators. The effect of material temperature on the force-deformation relation is modeled using the concept of evolutionary transfer function, and the proposed model is implemented using a step-by-step technique in the frequency domain. The predictions of the proposed model in the case of sinusoidal and seismic deformations show good agreement with experimental results. Finally, the response spectra of single-degree-of-freedom structures with added viscoelastic dampers and subjected to seismic excitation are computed using the proposed evolutionary model; the results obtained show that the thermal effect due to energy dissipation is not always negligible.

DYNAMIC SIMULATION AND CONTROL OF CONVEYOR-BELT DRYERS

Abstract The dynamic behavior of conveyor-belt dryers involving externally controlled heat and mass transfer phenomena has been studied via digital simulation. The investigation concerned an industrial dryer used for the moisture removal from wet raisins. The dryer consisted of three drying chambers and a cooling section, all involving the same conveyor belt. For each chamber, perfect temperature control was assumed for the drying air temperature, while its humidity was left uncontrolled. The effect of material temperature and moisture content at the entrance of the dryer and the drying air temperature on material temperature and moisture content at the exit of the dryer and the corresponding drying air humidity, have been explored by step forcing the disturbance and manipulated variables in the non-linear dryer model simulator. Results showed that material moisture content at the exit of the dryer is greatly affected by material moisture content at the entrance as well as by the drying air temperature. R...