Physical,mechanical and thermal properties of vacuum sintered HUST-1 lunar regolith simulant

Establishing a base on the Moon is one of the new goals of human lunar exploration in recent years.Sintered lunar regolith is one of the most potential building materials for lunar bases.The physical,mechanical and thermal properties of sintered lunar regolith are vital performance indices for the structural design of a lunar base and analysis of many critical mechanical and thermal issues.In this study,the HUST-1 lunar regolith simulant(HLRS)was sintered at 1030,1040,1050,1060,1070,and 1080℃.The effect of sintering temperature on the compressive strength was investigated,and the exact value of the optimum vacuum sintering temperature was determined between 1040 and 1060℃.Then,the microstructure and material composition of vacuum sintered HLRS at different temperatures were characterized.It was found that the sintering temperature has no significant effect on the mineral composition in the temperature range of 1030-1080℃.Besides,the heat capacity,thermal conductivity,and coefficient of thermal expansion(CTE)of vacuum sintered HLRS at different temperatures were investigated.Specific heat capacity of sintered samples increases with the increase of test temperature within the temperature range from-75 to 145℃.Besides,the thermal conductivity of the sintered sample is proportional to density.Finally,the two temperatures of 1040 and 1050℃were selected for a more detailed study of mechanical properties.The results showed that compressive strength of sintered sample is much higher than tensile strength.This study reveals the effects of sintering temperature on the physical,mechanical and thermal properties of vacuum sintered HLRS,and these material parameters will provide support for the construction of future lunar bases.

The Relation between Mental Workload and Face Temperature in Flight Simulation

In this research, we study the relationship between mental workload and facial temperature of aircraft participants during a simulated takeoff flight. We conducted experiments to comprehend the correlation between work and facial temperature within the flight simulator. The experiment involved a group of 10 participants who played the role of pilots in a simulated A-320 flight. Six different flying scenarios were designed to simulate normal and emergency situations on airplane takeoff that would occur in different levels of mental workload for the participants. The measurements were workload assessment, face temperatures, and heart rate monitoring. Throughout the experiments, we collected a total of 120 instances of takeoffs, together with over 10 hours of time-series data including heart rate, workload, and face thermal images and temperatures. Comparative analysis of EEG data and thermal image types, revealed intriguing findings. The results indicate a notable inverse relationship between workload and facial muscle temperatures, as well as facial landmark points. The results of this study contribute to a deeper understanding of the physiological effects of workload, as well as practical implications for aviation safety and performance.

Elastic-viscoplastic constitutive equations of K439B superalloy and thermal stress simulation during casting process

K439B nickel-based superalloy is a new type of high-temperature material.There is insufficient research on its constitutive equations and numerical modeling of thermal stress.Isothermal tensile experiments of K439B superalloy at different temperatures(20°C-1,000°C)and strain rates(1.33×10^(-3)s^(-1)-5.33×10^(-3)s^(-1))were performed by using a Gleeble-3800 simulator.The elastic moduli at different temperatures(20°C-650°C)were measured by resonance method.Subsequently,stress-strain curves were measured for K439B superalloy under different conditions.The elastic-viscoplastic constitutive equations were established and the correspongding parameters were solved by employing the Perzyna model.The verification results indicate that the calculated values of the constitutive equations are in good agreement with the experimental values.On this basis,the influence of process parameters on thermal stress was investigated by numerical simulation and orthogonal experimental design.The results of orthogonal experimental design reveal that the cooling mode of casting has a significant influence on the thermal stress,while pouring temperature and preheating temperature of shell mold have minimal impact.The distribution of physical fields under optimal process parameters,determined based on the orthogonal experimental design results,was simulated.The simulation results determine separately the specific positions with maximum values for effective stress,plastic strain,and displacement within the casting.The maximum stress is about 1,000.0 MPa,the plastic strain is about 0.135,and the displacement is about 1.47 mm.Moreover,the distribution states of thermal stress,strain,and displacement are closely related to the distribution of the temperature gradient and cooling rate in the casting.The research would provide a theoretical reference for exploring the stress-strain behavior and numerical modeling of the effective stress of the alloy during the casting process.

Numerical simulation of coupling heat transfer and thermal stress for spent fuel dry storage cask with different power distribution and tilt angles

Dry storage containers must be secured and reliable during long-term storage,and the effect of decay heat released from the internal spent fuel on the cask has become an important research topic.In this paper,a 3D computational fluid dynamics model is presented,and the accuracy of the calculation is verified,with computational errors of less than 6.2%.The thermal stress of the dry storage cask was estimated by coupling it with a transient temperature field.The total power remained constant and adjusting the power ratio of the inner and outer zones had a small effect on the stress results,with a maximum equivalent stress of approximately 5.2 kPa,which occurred at the lower edge of the shell.In the case of tilt,the temperature gradient varied in a wavy distribution,and the wave crest moved from right to left.Altering the tilt angle affects the air distribution in the annular gap,leading to the shell temperature being transformed,with a maximum equivalent stress of 202 MPa at the bottom of the shell.However,the equivalent stress in both cases was less than the yield stress(205 MPa).

基于SolidWorks Flow Simulation的PCB测试设备机柜散热仿真分析

为了解决PCB测试设备在机柜中温度过高导致被测产品损坏的问题。根据实际应用场景,设计出一款具有散热高效、结构紧凑、制作成本低的PCB测试设备机柜。结合PCB检测设备整体结构对其所在的机柜进行结构设计和散热仿真分析。主要以4台PCB测试设备满载运行在机柜中散热情况为研究对象。根据实际结构,使用SolidWorks对机柜和测试设备简化仿真模型进行建模,将简化模型导入到SolidWorks Flow Simulation中对机柜进行散热仿真分析。通过分析计算得出散热的分布情况和测试设备关键地方的温升数值,判断机柜散热结构的散热情况是否与预期结果一致。试验结果表明:常温下,在机柜中4台PCB测试设备满载测试时检测区域最高温度达到28℃左右,能够可持续运行状态并保持稳定工作。通过试验验证,机柜的散热实际温度与其散热仿真结果相符,证实了该机柜散热结构设计的合理性以及正确性,并且确定机柜散热结构设计方案。

Quasi-direct numerical simulations of the flow characteristics of a thermal plasma reactor with counterflow jet

Three-dimensional quasi-direct numerical simulations have been performed to investigate a thermal plasma reactor with a counterflow jet. The effects of the momentum flux ratio and distance between the counterflow jet and the thermal plasma jet on the flow characteristics are addressed. The numerical results show that the dimensionless location of the stagnation layer is significantly affected by the momentum flux ratio, but it is not dependent on the distance.Specifically, the stagnation layer is closer to the plasma torch outlet with the increase of the momentum flux ratio. Furthermore, the flow regimes of the stagnation layer and the flow characteristics of the thermal plasma jet are closely related to the momentum flux ratio. The characteristic frequencies associated with the different regimes are identified. The deflecting oscillation flow regimes are found when the momentum flux ratio is low, which provokes axial velocity fluctuations inside the thermal plasma jet. By contrast, for cases with a high momentum flux ratio, flapping flow regimes are distinguished. The thermal plasma jets are very stable and the axial velocity fluctuations mainly exist in the stagnation layer.

Magmatism-Related Thermal Simulation of Volcanic Arcs in the Molucca Sea Bidirectional Subduction System

The bidirectional subduction system,island arc magmatic activities,and thermal structure of the forearc basin in the Molucca Sea are taken into consideration in this study.The active volcanic arcs on both sides of the bidirectional subduction zone in the Molucca Sea are undergoing arc-arc collisions.We applied a finite element thermal simulation method to reconstruct the thermal evolution history of the Molucca Sea Plate based on geophysical data.Then,we analyzed the thermodynamic characteristics of island arc volcanism on both sides of the bidirectional subduction zone.The results showed that at 10Myr,the oceanic ridge of the Molucca Sea Plate was asymmetrically biased to the west,causing this bidirectional subduction to be deeper in the west than in the east.Furthermore,the oceanic ridge subducted under the Sangihe arc at 5.5Myr,causing intermittent cessation of volcanic activities.Due to the convergence of bidirectional subduction,the geothermal gradient in the top 3km depth of the forearc area between the Sangihe and Halmahera arcs decreased from about 60℃km^(−1) at 4Myr to about 38℃km^(−1) today.Finally,within the 45–100 km depth range of the sliding surface of the subduction,anomalously high-temperature zones formed due to shear friction during the bidirectional subduction.

The steady-state and dynamic simulation of cascade distillation system for the production of oxygen-18 isotope from water

Accurate simulation of water distillation system for oxygen-18(18O) isotope separation is necessary to guide industrial practice, since both deuterium(D) and oxygen-18 isotope get enriched and interfere with each other. In the present work, steady-state and dynamic distillation models are established based on a classic method and a cascade distillation system with 5 towers is introduced to test the models. The theoretical expressions of separation factor αH/Dfor protium/deuterium and separation factor α^(16)O/^(18) O.for oxygen-16/oxygen-18 were derived,with the existence of deuterium and oxygen-18, respectively. The results of the steady-state simulation by the classical method proposed in the present work agreed well with the results of the lumping method. The dynamic process could be divided into 5 stages. Impressively, a peak value of product withdraw was observed before the final steady state, which was resulted from the change of ^(16)O/^(18) O separation factor and isotope distribution. An interesting low concentration zone in the towers of T2–T5 existed at the beginning of the dynamic process and it required industrial evidence.

Simulation of Steady-State and Dynamic Behaviour of a Plate Heat Exchanger

The present paper deals with both the steady-state and dynamic simulation of a plate heat exchanger, in counter-flow arrangement. A CFD （computational fluid dynamics） program FLUENT has been used to predict the temperature distribution in steady-state conditions in plate heat exchanger as well as fluid temperatures at exit of flow channels in transient condition. The results are presented for the heat exchanger, which is simulated according to the configuration of the plate heat exchanger used in the experiment. The simulated results obtained by the CFD model have been compared with the experimental data from the literature, which shows that the CFD model developed in this study is capable of predicting the steady-state and transient performance of the plate heat exchangers satisfactorily.

Atomistic simulation of thermal effects and defect structures during nanomachining of copper

Molecular dynamics （MD） simulations of monocrystalline copper （100） surface during nanomachining process were performed based on a new 3D simulation model. The material removal mechanism and system temperature distribution were discussed. The simulation results indicate that the system temperature distribution presents a roughly concentric shape, a steep temperature gradient is observed in diamond cutting tool, and the highest temperature is located in chip. Centrosymmetry parameter method was used to monitor defect structures. Dislocations and vacancies are the two principal types of defect structures. Residual defect structures impose a major change on the workpiece physical properties and machined surface quality. The defect structures in workpiece are temperature dependent. As the temperature increases, the dislocations are mainly mediated from the workpiece surface, while the others are dissociated into point defects. The relatively high cutting speed used in nanomachining results in less defect structures, beneficial to obtain highly machined surface quality.

Analysis and numerical simulation of indoor thermal environments in some university classrooms

In order to study the indoor thermal environments in university classrooms in Tianjin,a field study and a questionnaire survey for a main teaching building are carried out.First,the thermal sensations of participants in the typical classrooms are studied by 180 questionnaires.Then,based on the measured data,the temperature changes in the classrooms during a year are simulated by the DeST software.The results show that the indoor thermal environments in the northern classrooms on the first floor are better than those in other classrooms.And the measurement results accord with the simulation results.These results can be used as a reference for the study of the indoor thermal environments in other seasons.

Selection and thermal physical characteristics analysis of in-situ condition preserved coring lunar rock simulant in extreme environment

With the increasing scarcity of Earth’s resources and the development of space science and technology,the exploration, development, and utilization of deep space-specific material resources(minerals, water ice, volatile compounds, etc.) are not only important to supplement the resources and reserves on Earth but also provide a material foundation for establishing extraterrestrial research bases. To achieve large depth in-situ condition-preserved coring(ICP-Coring) in the extreme lunar environment, first, lunar rock simulant was selected(SZU-1), which has a material composition, element distribution, and physical and mechanical properties that are approximately equivalent to those of lunar mare basalt. Second, the influence of the lunar-based in-situ environment on the phase, microstructure, and thermal physical properties(specific heat capacity, thermal conductivity, thermal diffusivity, and thermal expansion coefficient)of SZU-1 was explored and compared with the measured lunar rock data. It was found that in an air atmosphere, low temperature has a more pronounced effect on the relative content of olivine than other temperatures, while in a vacuum atmosphere, the relative contents of olivine and anorthite are significantly affected only at temperatures of approximately-20 and 200 ℃. When the vacuum level is less than100 Pa, the contribution of air conduction can be almost neglected, whereas it becomes dominant above this threshold. Additionally, as the testing temperature increases, the surface of SZU-1 exhibits increased microcracking, fracture opening, and unevenness, while the specific heat capacity, thermal conductivity,and thermal expansion coefficient show nonlinear increases. Conversely, the thermal diffusivity exhibits a nonlinear decreasing trend. The relationship between thermal conductivity, thermal diffusivity, and temperature can be effectively described by an exponential function(R^(2)>0.98). The research results are consistent with previous studies on real lunar rocks. These research findings are expected to be applied in the development of the test and analysis systems of ICP-Coring in a lunar environment and the exploration of the mechanism of machine-rock interaction in the in-situ drilling and coring process.

Simulation of landslide run-out by considering frictional heating and thermal pressurization

Some of the remarkable characteristics of natural landslides, such as surprisingly long travel distances and high velocities, have been attributed to the mechanisms of frictional heating and thermal pressurization. In this work, this mechanism is combined with a depth-averaged model to simulate the long runout of landslides in the condition of deformation. Some important factors that influence frictional heating and thermal pressurization within the shear zone are further considered, including velocity profile and pressurization coefficient. In order to solve the coupled equations, a combined computational method based on the finite volume method and quadratic upwind interpolation for convective kinematics scheme is proposed. Several numerical tests are performed to demonstrate the feasibility of the computational scheme, the influence of thermal pressurization on landslide run-out, and the potential of the model to simulate an actual landslide.

Numerical Simulation on Thermal Stress of Large-scale Bearing Roller during Heating Process of Final Heat Treatment

hi this paper, the non-linear finite element method had been applied to calculate the thermal stress evolving process of the large-scale bearing roller during heating process of final heat treatment. It was found that two stress peaks appeared during heating process and the second stress peak was higher than the first. If the preheating time was elongated, the second stress peak was reduced distinctly. Therefore, the pre-heating time should be elongated suitably to ensure safety in the practical manufacture process.

Numerical Simulation of Transient Thermal Stress Field for Laser Metal Deposition Shaping

To decrease thermal stress during laser metal deposition shaping(LMDS)process,it is of great importance to learn the transient thermal stress distribution regularities.Based on the“element life and death”technique of finite element analy- sis(FEA),a three-dimensional multi-track and multi-layer numerical simulation model for LMDS is developed with ANSYS parametric design language(APDL)for the first time,in which long-edge parallel reciprocating scanning paths is introduced. Through the model,detailed simulations of thermal stress during whole metal cladding process are conducted,the generation and distribution regularities of thermal stress are also discussed in detail.Using the same process parameters,the simulation results show good agreement with the features of samples which fabricated by LMDS.

Development of thermal simulation system for heavy section ductile iron solidification

A new reliable thermal simulation system for studying solidification of heavy section ductile iron has been developed using computer feedback control and artificial intelligent methods. Results of idle test indicate that the temperature in the system responses exactly to the inputted control data and the temperature control error is less than ±0.5%. It is convenient to simulate solidification of heavy section ductile iron using this new system. Results of thermal simulation experiments show that the differences in nodularity and number of graphite nodule per unit area in the thermal simulation specimen and the actual heavy section block is less than 5% and 10%, respectively.

Study on Thermal Simulation of Solidification in Heavy Section Ductile Iron

Using an artificial intelligent instrument and a computer feedback control method, a new thermal simulation systemis studied. Based on numerical simulation of casting solidification, a sample in the new system successfully simulatedthe solidification of heavy section ductile iron. The results show that the new thermal simulation system is accurateand reliable. Not only cooling curve but also graphite in the center of the thermal sample and the heavy sectionductile iron is identical. Realization of accurate thermal simulation of solidification in heavy section ductile iron willbe helpful for studying formation mechanism and controlling graphite degeneration in heavy section ductile iron.

Effect of t_(8/5) on the microstructure and properties of the HAZ of ASME SA213-T92 steel by thermal simulation

The relationship between the t8/5 and micro-hardness, impact toughness in the heat affected zone （HAZ） of ASME SA213-792 at peak temperature of 1 350 ℃ was studied by thermal simulation. The result shows that the micro-hardness of HAZ rises at the beginning and then decreases with increasing of t8/5 , whereas the impact toughness presents reverse trend. The distribution of precipitates in substrate has great influence on the impact toughness of HAZ. When the t8/5 is 40 s, chain-like precipitates lower the impact toughness of HAZ seriously.

Thermodynamic Analysis,Simulation and Optimization on Energy Savings of Ideal Internal Thermally Coupled Distillation Columns

Internal thermally coupled distillation columns (ITCDIC) are the frontier of distillation energy saving research. In this paper, a novel energy saving model of ideal ITCDIC and a simulation algorithm are presented,upon which a series of comparative studies on energy savings with conventional distillation columns are carried out. Furthermore, we present an optimization model of ideal ITCDIC, which can be used to achieve the maximum energy saving and find the optimal design parameters directly. The binary system of benzene-toluene is adopted for the illustrative example of simulation and optimization. The results show that the maximum energy saving of ITCDIC is 52.25% (compared with energy consumption of conventional distillation under the minimum reflux ratio operation); the optimal design parameters are obtained, where the rectifying section pressure and the feed thermal condition are Pr=0.3006 MPa and q=0.5107 respectively.

SIMULATION OF WELD THERMAL CYCLE USING THE MODEL OF CARBONITRIDE PARTICLES PRECIPITATION

Based on the chasteal nucleation theory, the kinetic precipitation model of carbon - nitride particles in weld HAZ is proposed. Using the model,welding simulation technology and the quantitative metallo- graphic analysis,the precipitation transformation temperatue (PTT) curve is obtained.The data from the simulated welds are in good apreement with the value that the PTT curves predicated.