Analysis on the Wear Performances of Cemented Carbide Tools Containing Ti in the Coatings When Machining Ti⁃6Al⁃4V Alloys

Because of the high affinity of the same element Ti,cemented carbide tools containing Ti seem to be non⁃optimal in machining titanium alloys.However,in practice,cemented carbide tools containing Ti are still widely used in machining titanium alloys.Cutting experiments were conducted in order to systematically explain the contradictions between the practice and theory.The diffusion process between titanium alloys and the cemented carbide tools was analyzed by auger electron spectroscopy detecting the cutting regions.It was also analyzed by Ti/Co diffusion behavior simulated by molecular thermodynamics.The experimental results and the simulation results showed that the mutual diffusion of Ti/Co atoms was the major reason for the diffusion wear.The dissolution⁃diffusion wear was one of the main wear mechanisms for the cemented carbide tools containing Ti in the coatings.Moreover,four types of cemented carbide tools and two other types of cermet tools were used to machine the Ti⁃6Al⁃4V alloys at different cutting speeds to further verify the high affinity of cutting tools containing Ti in the substrate/coating.The verification experiments results showed that the cemented carbide tools containing Ti generally cannot be used for machining titanium alloys,but could show less affinity in the cutting regions with reasonable cutting conditions.

Thermodynamic Study on the Catalytic Partial Oxidation of Methane to Syngas

the catalytic partial oxidation of methane to syngas (CO + H_2)has been simulated thermodynamically with the advanced processsimulator PRO/II. The influences of temperature, pressure, CH_4/O_2ratio and steam addition in feed gas on the conversion of CH_4selectively to syngas and eat duty required were investigated, andtheir effects on carbon formation were also discussed. The simulationresults were in good agreement with the literature data taken from aspouted bed reactor.

Mathematical modeling and analysis of thermodynamic processes in a twin-rotor piston engine

In order to study the major performance indicators of the twin-rotor piston engine(TRPE), Matlab/simulink was used to simulate the mathematical models of its thermodynamic processes. With consideration of the characteristics of the working processes in the TRPE, corresponding differential equations were established and then simplified by period features of the TRPE. Finally, the major boundary conditions were figured out. The changing trends of mass, pressure and temperature of working fuel in the working chamber during a complete engine cycle were presented. The simulation results are consistent with the trends of an actual working cycle in the TRPE, which indicates that the method of simulation is feasible. As the pressure in the working chamber is calculated, all the performance parameters of the TRPE can be obtained. The major performance indicators, such as the indicated mean effective pressure, power to weight ratio and the volume power, are also acquired. Compared with three different types of conventional engines, the TRPE has a bigger utilization ratio of cylinder volume, a higher power to weight ratio and a more compact structure. This indicates that TRPE is superior to conventional engines.

Thermal-hydraulic modeling and analysis of hydraulic system by pseudo-bond graph

To increase the efficiency and reliability of the thermodynamics analysis of the hydraulic system, the method based on pseudo-bond graph is introduced. According to the working mechanism of hydraulic components, they can be separated into two categories: capacitive components and resistive components. Then, the thermal-hydraulic pseudo-bond graphs of capacitive C element and resistance R element were developed, based on the conservation of mass and energy. Subsequently, the connection rule for the pseudo-bond graph elements and the method to construct the complete thermal-hydraulic system model were proposed. On the basis of heat transfer analysis of a typical hydraulic circuit containing a piston pump, the lumped parameter mathematical model of the system was given. The good agreement between the simulation results and experimental data demonstrates the validity of the modeling method.

SIMULATED RESEARCH ON HOT FORMING MECHANISM OF 35CrMo STEEL

The significance of this paper lies in the application of bending-upsetting 35CrMo steel in train crack-shaft. The hot deforming tests of 35CrMo steel have been done on the Gleeble-1500 testing machine with the deformation temperature at the range of 900癈-1250癈, a strain strain of 0.05 s-1, 0.5 s-1, 1.0 s-1 and compress degree of 15%-80%. Through respectively analyzing and studying the microstructure of the specimen and getting the data from the testing, the results obtained are as follows: the model of flow stress and the stress-strain relationship of material hot deformation, the model of dynamic and static re-crystallization and the correlative references of hot forming parameters and changes of microstructure. The hot deforming stress-strain curses and relevantly re-crystallized micro-structure of 35CrMo steel are drawn at the deformation temperature of 1250 and the strain rate of 1.0 s. Through analyzing and regressive calculating the grain size of the deformation specimen of 35CrMo steel at different locations under the large-deformation and high-temperature conditions, the hot-deforming model of grain calculation is verified. The experimental results and the model of grain calculation can provide scientific basis for analyzing the hot deformation processes and controlling quality.

Synthesis of Sintered Galaxite Clinker for Chrome-free Bricks

Galaxite clinker as refractory starting material has been fabricated using chemically pure MnO2 and Al2O3 as starting materials at various processing atmospheres and temperatures under the guidance of thermodynamic simulation. A dense galaxite clinker can be synthesized at low cost under 0. 04% -99. 98% CO partial pressure created by coke bed in sealed sagger.

Efficiency analysis of trilateral-cycle power systems for waste heat recovery-to-power generation

Numerous innovative heat recovery-to-power technologies have been resourcefully and technologically exploited to bridge the growing gap between energy needs and its sustainable and affordable supply.Among them,the proposed trilateral-cycle(TLC) power system exhibits high thermodynamic efficiency during heat recovery-to-power from low-to-medium temperature heat sources.The TLCs are proposed and analysed using n-pentane as working fluid for waste heat recovery-to-power generation from low-grade heat source to evaluate the thermodynamic efficiency of the cycles.Four different single stage TLC configurations with distinct working principles are modelled thermodynamically using engineering equation solver.Based on the thermodynamic framework,thermodynamic performance simulation and efficiency analysis of the cycles as well as the exergy efficiencies of the heating and condensing processes are carried out and compared in their efficiency.The results show that the simple TLC,recuperated TLC,reheat TLC and regenerative TLC operating at subcritical conditions with cycle high temperature of 473 K can attain thermal efficiencies of 21.97%,23.91%,22.07% and 22.9%,respectively.The recuperated TLC attains the highest thermodynamic efficiency at the cycle high temperature because of its lowest exergy destruction rates in the heat exchanger and condenser.The efficiency analysis carried out would assist in guiding thermodynamic process development and thermal integration of the proposed cycles.

A MATHEMATICAL MODEL FOR POWER PLANT HEATERS

This paper studies the modelling and simulation for all forms of hcaters.The assumption of former days that the temperature of condensation is the saturationtemperature corresponding to heater pressure in steam side is no longer used.On the basisof the laws of conservation of mass,energy and momentum,the mathematical model ofheaters is established and the simulation calculation of a 125MW unit is made.The rcsultshows that the model is applicable for various kinds of steam-water heater in power plant.

Selective laser melting 3D printing of Ni-based superalloy： understanding thermodynamic mechanisms

A mesoscopic model has been established to investigate the thermodynamic mechanisms and densification behavior of nickel-based superalloy during additive manufacturing/three-dimensional （3D） printing （AM/3DP） by numerical simulation, using a finite volume method （FVM）. The influence of the applied linear energy density （LED） on dimensions of the molten pool, thermodynamic mechanisms within the pool, bubbles migration and resultant densification behavior of AM/3DP-processed superalloy has been discussed. It reveals that the center of the molten pool slightly shifts with a lagging of 4 ktm towards the center of the moving laser beam. The Mar- angoni convection, which has various flow patterns, plays a crucial role in intensifying the convective heat and mass transfer, which is responsible for the bubbles migration and densification behavior of AM/3DP-processed parts. At an optimized LED of 221.5 J/m, the outward convection favors the numerous bubbles to escape from the molten pool easily and the resultant considerably high relative density of 98.9 % is achieved. However, as the applied LED further increases over 249.5 J/m, the convection pattern is apparently intensified with the formation of vortexes and the bubbles tend to be entrapped by the rotating flow within the molten pool, resulting in a large amount of residual porosity and a sharp reduction in densification of the superalloy. The change rules of the relative density and the corresponding distribution of porosity obtained by experiments are in accordance with the simulation results.

Carbide precipitation and element distribution in high Co-Ni secondary hardening steel

As the increasing need of the steels with both high strength and hydrogen embrittlement resistance ability, carbide precipitation and element distribution in high Co-Ni secondary hardening steel were concerned. Carbide precipitation and element distribution in M54 were observed using carbon replicas method. Both simulation and observation results showed that MC and M2C formed in the steel. MC was round particle, which would act as grain refiners. And MzC was needle-like phase, which would be remarkable strengthening phases. Nb and V were main metallic elements in MC phase. Mo and Cr were main metallic elements in MzC phase. W, Co, and Ni were probably mainly dissolved in the matrix. As the carbide precipitation in AerMetl00 was M2C, which had similar size and shape with M2C in M54, the tensile strength and yield strength of AerMetl00 and M54 were similar. Compared with traditional high Co-Ni secondary hardening steel, M54 had higher hydrogen embrittlement resistance ability, probably because of element W in the matrix.

Finite time thermodynamic analysis and optimization of water cooled multi-spilit heat pipe system(MSHPS)

This study focuses on the heat transfer characteristics of the evaporation terminal,the cool distribute unit(CDU)and refrigerant flow distribution of a water cooled multi-spilit heat pipe system(MSHPS)used in data center.The finite time thermodynamic analysis,the exergy method and the software SIMULINK was employed to build the simulation model of the combined system.The results show that the IT servers should concentrate on arranging at the location below 1.3 m.The CDU has a heat transfer of about 74 J in a period of 6 s.And the optimum flow rate of the CDU is 0.82 kg/s.The flow distribution characteristic of a CDU which connect 2 heat pipe evaporator terminals of 6 kW was calculated,and the working fluid is R22.Then the free cooling time,part time free cooling and energy saving potential in major cities of China were analysised.The energy saving potential is from 61%to 25%.The results are of great significance for the operational control and practical application of a MSHPS and other pipe-net systems.