Nanoindentation response analysis of TiN-Cu coating deposited by magnetron sputtering

To investigate the change of the mechanical properties of soft metals doped PVD(Physical Vapor Deposition)coatings after the migration of soft metal to the surface, TiN-Cu coating was deposited on Si(100) by magnetron sputtering. The microstructure and mechanical properties at room temperature and after vacuum heat treatment at 300 ℃ were investigated. The results showed that the grains were clustered and the microstructure was porous for TiN-Cu coating at room temperature, while many micro-and nano-sized Cu particles were observed on the surface after vacuum heat treatment at 300 ℃. The elastic properties of the TiN-Cu coating after vacuum heat treatment at 300℃ degraded compared with that at room temperature. The hardness and elasticity modulus of TiN-Cu coating kept constant(3.7 GPa and 125.0 GPa, respectively) with the increase of nano-indentation depth, while the hardness and elasticity modulus of TiN-Cu coating after vacuum heat treatment at 300 ℃ increased gradually.     

含位形权重的磁流变液孤立链流变剪应力模型

为降低采用标准孤立链理论模型计算高体积分数磁流变液流变剪应力时的计算误差,提出一种通过距离权重系数评价磁链间相互作用的流变模型.编写Monte Carlo仿真程序计算颗粒位置与磁矩方向矢量、同时输出与系统颗粒间距有关的距离权重系数.按标准和距离权重这两种链结构模型计算磁流变液剪切应力数值,并和4种磁流变液(30.58%~44.79%)的流变仪剪应力测试数据进行比较,结果显示,权重模型在磁场全范围内具有更高的计算精度,并且和流变试验实际结果基本符合,证实了磁链微观结构间的相互作用力是影响磁流变液流变特性的主要因素之一.     

面向球头铣刀多轴铣削加工的铣削力系数辨识

提出了一种适用于球头铣刀多轴铣削加工的铣削力系数辨识方法.首先,将剪切力系数考虑为轴向位置角κ的多项式函数,推导了基于平均铣削力的铣削力系数辨识模型.然后,设计了多组刀具轴线与工件表面夹角不同的槽切铣削实验来实现铣削力系数辨识,以保证通过实验辨识得到的铣削力系数包含了球头铣刀不同姿态切削对铣削力的影响因素.最后,通过实验验证了该方法的正确性和可靠性.实验结果表明,该辨识方法相比于基于瞬时铣削力的辨识方法具有更好的抗干扰能力和更高的辨识精度,适用于球头铣刀多轴铣削加工的铣削力预测.     

铝锡轴承合金的摩擦磨损机理与性能

铝锡轴承合金对大型载重汽车、坦克、高速汽车、拖拉机等的高速高压柴油机的发展有重要的意义。提高铝锡合金的耐摩擦磨损性能可节省大量能源并延长零件的使用寿命,如何取得具有优良的耐摩擦磨损的铝锡合金成为研究的重点。本文介绍了提高铝锡合金的耐摩擦磨损性能的措施及其影响因素,总结铝锡合金中锡元素含量改变、合金元素的添加、热处理与制备工艺的改变对铝锡合金的显微组织以及耐摩擦磨损性能的影响。     

Engineering a Cu‐MOF Nano‐Catalyst by using Post‐Synthetic Modification for the Preparation of 5‐Substituted 1H‐Tetrazoles

A new nano scale Cu‐MOF has been obtained via post‐synthetic metalation by immersing a Zn‐MOF as a template in DMF solutions of copper(II) salts. The Cu‐MOF serves as recyclable nano‐catalyst for the preparation of 5‐substituted 1H‐tetrazoles via [3 + 2] cycloaddition reaction of various nitriles and sodium azide in a green medium (PEG). The post‐synthetic metalated MOF were characterized by FT‐IR spectroscopy, powder X‐ray diffraction (PXRD), atomic absorption spectroscopy (AAS), and energy dispersive X‐ray spectroscopy (EDX) techniques. The morphology and size of the nano‐catalyst were determined by field emission scanning electron microscopy (FE‐SEM).     

Cooling Characteristics During Bath Quenching of Test Probe Using Inverse Heat Transfer

It is of engineering importance to accurately predict the surface cooling characteristics in bath quenching of metals and alloys. In this investigation, the surface cooling characteristics in quenching of Wolfson probe are estimated with reasonable accuracy by solving an inverse heat conduction problem. Regularization method is used for smoothening the input temperature measurements at probe center, for superior inversion estimates. The reverse pool-boiling curve is captured on bath quenching characteristic, plotted as cooling velocity versus surface temperature. The prime advantage is the bypassing of convection coefficients, which are uncertain in pool boiling.     

On the nature and the practical relevance of the molecular modifications induced in wheat proteins by high pressure treatment

Abstract

Modifications induced by the combined application of pressure (up to 800 MPa) and temperature (up to 80° C) were studied on wet and dry semolina, and on fresh pasta as such and after cooking. Rheological and immunochemical properties of the treated products were investigated, along with parameters indicating the extent of protein denaturation. No modification occurs in semolina treated at less than 45% water, below 60°C/800MPa for 10min. Egg noodles prepared from pressure/heat treated semolina had increased protein digestibility and low recognition by anti-gliadin antibodies either before or after cooking. The same effects were observed in heat/pressure treated pasta, but were lost upon subsequent cooking, although we found decreased immunochemical reactivity after heat/pressure treatment of cooked pasta. No sensory difference was found between cooked and pressure-treated semolina products.     

The effective ionization coefficients and electron drift velocities in gas mixtures of CF3I with N2 and CO2 obtained from Boltzmann equation analysis

The electron swarm parameters including the density-normalized effective ionization coefficients(α-η)/N and the electron drift velocities V e are calculated for a gas mixture of CF3I with N2 and CO2 by solving the Boltzmann equation in the condition of a steady-state Townsend(SST) experiment.The overall density-reduced electric field strength is from 100 Td to 1000 Td(1 Td = 10-17V·cm2),while the CF3I content k in the gas mixture can be varied over the range from 0% to 100%.From the variation of(αη)/N with the CF3I mixture ratio k,the limiting field strength(E/N) lim for each CF3I concentration is derived.It is found that for the mixtures with 70% CF3I,the values of(E/N) lim are essentially the same as that for pure SF 6.Additionally,the global warming potential(GWP) and the liquefaction temperature of the gas mixtures are also taken into account to evaluate the possibility of application in the gas insulation of power equipment.     

Thermal Resistance Measurement across a Wick Structure Using a Novel Thermosyphon Test Chamber

A novel system is developed for measuring the thermal resistance across thin layers of sintered copper wicks of varying porosity. Wicks to be tested are integrated into a passive vertical thermosyphon system, and the resistance is measured for a series of input power levels. The wicks are sintered to a thermally conducting pedestal above a pool of deionized water and heated from below. The apparent thermal resistance across the wick (from the pedestal/wick interface to the vapor space) under the evaporative operating conditions encountered in heat pipes is measured using thermocouples. The apparent thermal resistance across the wick is measured to be as low as 0.01°C/W, corresponding to an evaporative heat transfer coefficient of greater than 128,000 W/m²K.     

A quasi‐dynamic procedure for coupled thermal simulations

This paper outlines the development and adaptation of a coupling strategy for transient temperature analysis in a solid via a conjugate heat transfer method. This study proposes a quasi‐dynamic coupling procedure to bridge the temporal disparities between the fluid and the solid. In this approach, dynamic thermal modeling in the solid is coupled with a sequence of steady states in the fluid. This quasi‐dynamic algorithm has been applied to the problem of convective heat transfer over, and transient conduction heat transfer within, a flat plate using the severe thermal conditions of a solid propellant rocket. Two different coupled thermal computations have been performed. In the first one—referred to as the reference computation—the coupling period is equal to the smallest solid time constant. In the second one, a very large coupling period is used. The results show that the procedure can predict accurate transient temperature fields at a reasonable computational cost. The simulation CPU time is approximately reduced by up to 90%, while maintaining a very good accuracy. All the details of the numerical test case are given in the paper. This application illustrates the capabilities and the overall efficiency of this coupled approach in a solid transient problem using long term simulations of time dependent flows. Copyright © 2013 John Wiley & Sons, Ltd.