轻钢承重墙用硅酸钙板热工参数模型及墙体耐火极限变参数模拟研究

根据冷成型钢承重组合墙墙体足尺耐火试验及墙用硅酸钙板内部粉末热工参数测试结果,利用ANSYS软件,对立柱控制截面建立传热模型。通过对比耐火试验结果,给出了硅酸钙板的热工参数模型。通过参数分析发现,改变C型龙骨规格、拼接方式对耐火极限没有显著影响;改变墙板厚度及火源模型则有显著影响。提出了单侧受火双拼C型龙骨墙体内龙骨截面温度分布模型,分析了火源模型降温段引起的墙体截面不同位置降温滞后现象。

High temperature deformation behavior and optimization of hot compression process parameters in TC11 titanium alloy with coarse lamellar original microstructure

The high temperature deformation behaviors of α＋β type titanium alloy TC11 （Ti-6.5Al-3.5Mo-1.5Zr-0.3Si） with coarse lamellar starting microstructure were investigated based on the hot compression tests in the temperature range of 950-1100 ℃ and the strain rate range of 0.001-10 s-1. The processing maps at different strains were then constructed based on the dynamic materials model, and the hot compression process parameters and deformation mechanism were optimized and analyzed, respectively. The results show that the processing maps exhibit two domains with a high efficiency of power dissipation and a flow instability domain with a less efficiency of power dissipation. The types of domains were characterized by convergence and divergence of the efficiency of power dissipation, respectively. The convergent domain in a＋fl phase field is at the temperature of 950-990 ℃ and the strain rate of 0.001-0.01 s^-1, which correspond to a better hot compression process window of α＋β phase field. The peak of efficiency of power dissipation in α＋β phase field is at 950 ℃ and 0.001 s 1, which correspond to the best hot compression process parameters of α＋β phase field. The convergent domain in β phase field is at the temperature of 1020-1080 ℃ and the strain rate of 0.001-0.1 s^-l, which correspond to a better hot compression process window of β phase field. The peak of efficiency of power dissipation in ℃ phase field occurs at 1050 ℃ over the strain rates from 0.001 s^-1 to 0.01 s^-1, which correspond to the best hot compression process parameters of ,8 phase field. The divergence domain occurs at the strain rates above 0.5 s^-1 and in all the tested temperature range, which correspond to flow instability that is manifested as flow localization and indicated by the flow softening phenomenon in stress-- strain curves. The deformation mechanisms of the optimized hot compression process windows in a＋β and β phase fields are identified to be spheroidizing and dynamic recrystallizing controlled by self-diffusion mechanism, respectively. The microstructure observation of the deformed specimens in different domains matches very well with the optimized results.

Hot deformation behavior of extruded AZ80 magnesium alloy

The hot deformation behavior of extruded AZ80 magnesium alloy was studied through hot compression tests performed at temperatures ranging from 250 to 450 ~C with strain rates varying from 0.001 to 10 s-1. The flow stress was corrected due to the deformation heating. The Zener-Hollomon parameter （Z parameter） and processing map were established to describe the hot deformation behavior. The results indicate that the applicable deformation should be conducted at the strain rate of 0.1 s-~ and the temperature range of 350-400 ~C. Besides, the relationship between the microstructure evolution and Z parameter was also discussed. High temperature and low strain rate result in a low Z parameter, which leads to full dynamic recrystallization （DRX） and large DRX grain size in the microstructure. Considering processing map and microstructure, the hot deformation should be carried out at the temperature of 400 ~C and the strain rate of 0.1 s 1.

Prediction of mechanical properties of A357 alloy using artificial neural network

The workpieces of A357 alloy were routinely heat treated to the T6 state in order to gain an adequate mechanical property.The mechanical properties of these workpieces depend mainly on solid-solution temperature,solid-solution time,artificial aging temperature and artificial aging time.An artificial neural network（ANN） model with a back-propagation（BP） algorithm was used to predict mechanical properties of A357 alloy,and the effects of heat treatment processes on mechanical behavior of this alloy were studied.The results show that this BP model is able to predict the mechanical properties with a high accuracy.This model was used to reflect the influence of heat treatments on the mechanical properties of A357 alloy.Isograms of ultimate tensile strength and elongation were drawn in the same picture,which are very helpful to understand the relationship among aging parameters,ultimate tensile strength and elongation.

Modified constitutive model and workability of 7055 aluminium alloy in hot plastic compression

To obtain flow behavior and workability of 7055 aluminium alloy during hot deformation,hot compression tests at different temperatures and strain rates are conducted.True stress?strain curves of 7055 aluminium alloy under different conditions are obtained and the flow stress increases with ascending strain rate and descending temperature.For Arrhenius constitutive equation,each material parameter is set as a constant,which will bring forth large error for predicting flow behavior.In this work,material parameters are fitted as a function of temperature or strain rate based on experimental results and a modified constitutive equation is established for more accurate prediction of flow behavior of 7055 aluminium alloy.The effects of temperature and strain rate on power dissipation and instability are analyzed to establish a processing map of 7055 aluminium alloy.The dominant deformation mechanism for microstructure evolution at different deformation conditions can be determined and high efficiency of power dissipation may be achieved from power dissipation map.Meanwhile,proper processing parameters to avoid flow instability can be easily acquired in instability map.According to the processing map,optimized processing parameters of 7055 aluminium alloy are temperature of 673?723 K and strain rate of 0.01?0.4 s^?1,during which its efficiency of power dissipation is over 30%.Finite element method(FEM)is used to obtain optimized parameter in hot rolling process on the basis of processing map.

Experimental research on oxidation of phenol by activated persulfate

In this paper, the optimum process parameters were obtained through treating phenol of simulated semi-coking wastewater using heat, Fe2＋, Fe^0 and semi-coke to catalyze persulfate. The results of phenol decomposition using PS catalyzed by heating, Fe2＋, Fe^0 and semi-coke were compared for selecting a better activating way. The article investigated the effects of temperature, catalyzer dosage, pH value and reaction time. The experiment showed the four methods can all catalyzed the process. Under the experimental conditions of heating, Fe2＋, Fe^0 and semi-coke degradation rate could reach to 20.7%, 75.1%, 94.5% and 40.0%, respectively. On this basis, this study established an Lt6（45） table to analyze the main influencing factors in semi-coke/Fe^0 catalyzing system. Under the optimum conditions, the degradation rate of Phenol reached to 93.6%. However, the PS dosage was reduced by 14.4%.

Process forces and heat input as function of process parameters in AA5083 friction stir welds

AA5083 friction stir welds were produced using systematic experimental design, the process forces and heat input with varying parameters were studied. Helpful empirical models were developed in designing friction stir welding （FSW） tools and FSW welders. These models may be further helpful for making process parameter choice for this sort of alloy, defining welding program and control of process parameters by using computer numerical control friction stir welding welders. The results show that tool rotational speed, welding speed and tool shoulder diameter are most significant parameters affecting axial force and heat input, while longitudinal force is significantly affected by welding speed and probe diameter.

Country-level meteorological parameters for building energy efficiency in China

Accurate basic data are necessary to support performance-based design for achieving carbon peak and carbon neutral targets in the building sector.Meteorological parameters are the prerequisites of building thermal engineering design,heating ventilation and air conditioning design,and energy consumption simulations.Focusing on the key issues such as low spatial coverage and the lack of daily or higher time resolution data,daily and hourly models of the surface meteorological data and solar radiation were established and evaluated.Surface meteorological data and solar radiation data were generated for 1019 cities and towns in China from 1988 to 2017.The data were carefully compared,and the accuracy was proved to be high.All the meteorological parameters can be assessed in the building sector via a sharing platform.Then,country-level meteorological parameters were developed for energy-efficient building assessment in China,based on actual meteorological data in the present study.This set of meteorological parameters may facilitate engineering applications as well as allowing the updating and expansion of relevant building energy efficiency standards.The study was supported by the National Science and Technology Major Project of China during the 13th Five-Year Plan Period,named Fundamental parameters on building energy efficiency in China,comprising of 15 top-ranking universities and institutions in China.

A CFD model for predicting the heat transfer in the industrial scale packed bed

Compared to the traditional lumped-parameter model, computational fluid dynamics （CFD） attracted more attentions due to facilitating more accurate reactor design and optimization methods when analyzing the heat transfer in the industrial packed bed. Here, a model was developed based on the CFD theory, in which the heterogeneous fluid flow was resolved by considering the oscillatory behavior of voidage and the effective fluid viscosity. The energy transports in packed bed were calculated by the convection and diffusion incorporated with gaseous dispersion in fluid and the contacting thermal conductivity of packed particles in solids. The heat transfer coefficient between fluid and wall was evaluated by considering the turbulence due to the packed particles adjacent to the wall. Thus, the heat transfer in padded bed can be predicted without using any adjustable semi-empirical effective thermal conductivity coefficient. The experimental results from the literature were employed to validate this model.

A Brief Report of Graphic Explanations for Generalized Potential Temperature in the Non-Uniformly Saturated Atmosphere

Compared to potential temperature （θ） in the dry atmosphere and equivalent potential temperature （θc） in the saturated atmosphere, generalized potential tem- perature （θ＂） has already proven a better thermodynamic parameter in describing the non-uniformly saturated real atmosphere. To add otherwise absent graphic explanations, this paper first presents the physical definition of θ through a tephigram. Then, the utility of the measurement in identifying and forecasting the locations of precipita- tion maxima and heat wave areas with diagnostic com- parison studies and traditionally used thermodynamic parameters is shown.

Effect of working parameters on performance characteristics of hydrostatic turntable by using FSI-thermal model

Effects of working parameters on performance characteristics of hydrostatic turntable are researched by applying the fluid-structure-thermal coupled model.Fluid-structure interaction(FSI)technique and computational fluid dynamics(CFD)method are both employed by this new model,and thermal effects are also considered.Hydrostatic turntable systems with a series of oil supply pressures,various oil recess depth and several surface roughness parameters are studied.Performance parameters,such as turntable displacement,system flow rate,temperature rise of lubrication,stiffness and damping coefficients,are derived from different working parameters(rotational speed of turntable and exerted external load)of the hydrostatic turntable.Numerical results obtained from this FSI-thermal model are presented and discussed,and theoretical predictions are in good agreement with the experimental data.Therefore,this developed model is a very useful tool for studying hydrostatic turntables.The calculation results show that in order to obtain better performance,a rational selection of the design parameters is essential.

Study on the resistance spot welding technology of 22MnMoB hot stamping quenched steel

In this paper, the spot welding technology of a new kind of 22MnMoB hot stamping quenched steel sheet was systematically studied by power frequency spot welder. Through a series of technology and test experiments, we have obtained the optimal spot welding technological parameter condition. According to the results, the relations among spot welding technological parameter, welding nugget, mechanical property and fracture mode were discussed. The effects of all the welding parameters such as welding current, welding time and electrode force on the quality of joint can be boiled down to one thing--the diameter of welding nugget. The experimental results showed that welding nugget diameter determines the mechanical property of spot welding joint and the relation between welding nugget diameter and the mechanical property of joint presents a kind of linear mathematic representation. There are two typical fracture models of 22MnMoB hot stamping quenched steel sheet, i.e., interracial fracture and nugget pullout. Other than mild steel or normal high strength steel, in the shearing tensile test, hot stamping quenched steel has a great tendency to fail in interfacial mode due to the effects of high strength matrix structure, welding soft zone and the porosity level of fusion zone.

Response Surface Optimization for Process Parameters of LiFePO_4/C Preparation by Carbothermal Reduction Technology

A statistically based optimization strategy is used to optimize the carbothermal reduction technology for the synthesis of LiFePO4/C using LiOH,FePO4 and sucrose as raw materials.The experimental data for fitting the response are collected by the central composite rotatable design(CCD).A second order model for the discharge ca-pacity of LiFePO4/C is expressed as a function of sintering temperature,sintering time and carbon content.The ef-fects of individual variables and their interactions are studied by a statistical analysis(ANOVA).The results show that the linear effects and the quadratic effects of sintering temperature,carbon content and the interactions among these variables are statistically significant,while those effects of sintering time are insignificant.Response surface plots for spatial representation of the model illustrate that the discharge capacity depends on sintering temperature and carbon content more than sintering time.The model obtained gives the optimized reaction parameters of sinter-ing temperature at 652.0 ℃,carbon content of 34.33 g?mol-1 and 8.48 h sintering time,corresponding to a dis-charge capacity of 150.8 mA·h·g-1.The confirmatory test with these optimum parameters gives the discharge ca-pacity of 147.2 and 105.1 mA·h·g-1 at 0.5 and 5 C,respectively.

A New General Equation of State

A new general equation of state is presented, which can be used to express not only common cubic equations of state, but also quartic equations of state and so on. Main advantage of the new equation over the previous general equations is that it is in simple form, and is easy to manipulate mathematically.

Influence of the Main Technological Variables of Cyclical Mechanic-Thermal Processing on the Strain Hardening of Steel Parts

The main objective of the present work was to determine the influence of the most important technological variables of CMTP （cyclical mechanic-thermal processing） on the strain hardening in the surface layers of steel parts. For this, it was designed a full factorial plan at two levels of five independent variables that include the whole processing in two and three cycles, the cold-forming degree and force during the plastic deformation （burnishing）, and the temperature and time at the given temperature during the aging. Each cycle is composed of plastic deformation at room temperature plus aging. As dependent variables, the degree and penetration depth of strain hardening were evaluated. Based on the appropriately used set of experimental data, it had been fitted an exponential model for each dependent variables and also a two-degree polynomial fitting of in-depth evolution of microhardness profile was obtained. The amount of cycles and the cold-forming degree are the technological variables of CMTP that influence the most on strain hardening, although other variables also are significant. The microhardness profile highlights that during the CMTP, the strain hardening decreases from the outer bound to the transition zone of the surface layers, where it disappears.

Effects of process parameters on warpage of rapid heat cycle moulding plastic part

The effects of process parameters in rapid heat cycle moulding （RHCM） on parts warpage were investigated. A vehicle-used blue-tooth front shell （consisting of ABS material） was considered as a part example manufactured by RHCM method. The corresponding rapid heat response mould with an innovational conformal heating/cooling channel system and a dynamic mould temperature control system based on the Jll-W-160 type precise temperature controller was proposed. During heating/cooling process, the mould was able to be heated from room temperature to 160 ~C in 6 s and then cooled to 80 ~C in 22 s. The effects of processing conditions in RHCM on part warpage were investigated based on the single factor experimental method and Taguchi theory. Results reveal that the elevated mould temperature reduces unwanted freezing during the injection stage, thus improving mouldability and enhancing part quality, whereas the overheated of mould temperature will lead to defective product. The feasible mould temperature scope in RHCM should be no higher than 140 ~C, and the efficient mould temperature scope should be around the polymer heat distortion temperature. Melt temperature as well as injection pressure effects on warpage can be divided into two stages The lower stage gives a no explicit effect on warpage whereas the higher stage leads to a quasi-linear downtrend. But others affect the warpage as a V-type fluctuation, reaching to the minimum around the heat distortion temperature. Under the same mould temperature condition, the effects of process parameters on warpage decrease according to the following order, packing time, packing pressure, melt temperature, injection pressure and cooling time, respectively.

Processing map and hot working mechanisms of Cu-Ag alloy in hot compression process

For Gu-Ag alloy, an important parameter called workability in the forming process of materials can be evaluated by processing maps yielded from the stress-strain data generated by hot compression tests at temperatures of 700-850 °C and strain rates of 0.01-10 s-1. And at the true strain of 0.15, 0.35 and 0.55, respectively, the responses of strain-rate sensitivity, power dissipation efficiency and instability parameter to temperature and strain rate were studied. Instability maps and power dissipation maps were superimposed to form processing maps, which reveal the determinate regions where individual metallurgical processes occur and the limiting conditions of flow instability regions. Furthermore, the optimal processing parameters for bulk metal working are identified clearly by the processing maps.

Effect of Operating Parameters on Composition of Dry Gas Obtained During Gasoline Cracking Process

The influence of operating parameters on ethylene content in dry gas obtained during catalytic cracking of gasoline was investigated in a pilot fixed fluidized bed reactor in the presence of the MMC-2 catalyst. The results have shown that the majority of dry gas was formed during the catalytic cracking reaction of gasoline, with a small proportion of dry gas being formed through the thermal cracking reaction of gasoline. The ethylene content in dry gas formed during the catalytic cracking reaction was higher than that in dry gas formed during the thermal cracking reaction. The ethylene content in dry gas formed during catalytic cracking of gasoline with a higher olefin content was higher than that in dry gas formed during catalytic cracking of gasoline with a lower olefin content, which meant that the higher the amount of carbonium ions was produced during the reaction, the higher the ethylene content in the dry gas would be. An increasing reaction temperature could increase the percentage of dry gas formed during thermal cracking reaction in total dry gas products, leading to decreased ethylene content in the dry gas. An increasing catalyst/oil ratio could be conducive to the catalytic cracking reactions taking place inside the zeolite Y, leading to a decreased ethylene content in the dry gas. A decreasing space velocity could be conducive to the catalytic cracking reactions taking place inside the shape-selective zeolite, leading to increased ethylene content in the dry gas.

A Generalized Equation of State for High-Pressure Liquids

An equation of state （EOS） for high-pressure liquids, i.e., Tait EOS, is deduced according to isothermal 1 3V compressibility KT= -1/V· （2V/2p）T·.Based on the equation, a generalized EOS for high pressure-liquids is established by using the reduced state principle and introducing a characteristic parameter-configuration factor ξ. Reasonably satisfactory P-V-T data for many organic compounds, including some polar components, were calculated by using the equation.

Optimizing Geothermal Energy Resource

Unlike other types of renewable energy resources, geothermal energy provides a stable source of energy as it can be exploited regardless of meteorological conditions. Using organic cycle, geothermal energy can be utilized for power generation. In such systems, the heat is exchanged between the surrounding rock mass and transport fluid. Consequently, the temperature of extracted geofluid from the well decreases with the time in accordance with the working parameters. Those parameters includeenergy extraction rate, temperature difference between inlet and outlet of the well, and the thermal conductivity of the ground. Current work, aims to develop a reliable computer model to specify the optimal working parameters so that the geofluid temperature will not reach a low value that is not acceptable for electricity generation, and the energy availability of geothermal resource is maximized. In the current study the ground thermal properties, the geothermal gradient and well dimensions are based on realistic data in Qatar and neighboring countries. The proposed model was developed for different heat extraction rate, different ground thermal properties, and for varied temperature difference between inlet and outlet of the well. Simulation shows that selecting the optimal working parameters can increase the availability of geothermal resource significantly.