On the induction plasma deposition of tungsten metal

The central particle injection and long residence time characteristics of induction plasma have given rise to the complete melting of tungsten particles injected into an Ar- H₂ plasma under soft vacuum conditions. The influences of process variables such as power level, chamber pressure, and spray distance on splat morphology, apparent density, and deposition efficiency have been studied. Dense tungsten deposits with no oxidation have been obtained. Scanning electron microscopy (SEM) micrographs reveal a well-flattened lamellar structure in deposits. Radiative cooling is observed to play a significant role in the plasma spraying of this refractory metal.     

Determination of the optimum conditions for ion nitriding of AISI 5140 steel

AISI 5140 low alloy steel was ion nitrided under different process parameters including time (1, 4, 8 and 12 h), temperature (400, 450, 500 and 550 °C) and gas mixture ratio (0.05, 0.33, 1 and 3 N₂/H₂). By determining the fatigue strength, surface hardness, compound layer thickness and case depth, the optimum working conditions were determined by using a Taguchi design of experiment. After ion nitriding process, it is aimed to maximize fatigue strength, surface hardness and case depth as well as to minimize compound layer thickness. While the optimum conditions were determined, due to the goals (above aims) more than one being, the trade-off among goals was considered. First of all, each goal was optimised, separately. Then, all the goals were optimised together, considering the priority of the goals, and the optimum results were obtained at 0.05 N₂/H₂ gas mixture ratio, at the temperature of 450 °C and for 12 h process time.     

Analytical and experimental study of shear localization in chip formation in orthogonal machining

A simplified theory of instability of plastic flow is applied to analyze the formation of shear localized chips in orthogonal machining. A flow localization parameter is expressed in terms of associated cutting conditions and properties of the workpiece material. The analysis, which indicates the important parameters in the cutting process, is used to investigate the effect of cutting conditions on the onset of shear localization and the formation of adiabatic shear banding in metal cutting. Comparisons are made between the analysis and experiments in which the flow localization parameter is obtained for several workpiece materials. The results of this investigation seem to support the analysis and its potential benefits in analyzing and/or remedying problems associated with chip formation and temperature generated in metal cutting. Presently at Advanced Technology Center, Valenite, Inc., Madison Heights,MI 48071, USA     

New attachment for controlling gas flow in the HVOF process

During the decade, the high-velocity oxyfuel (HVOF) process proved to be a technological alternative to the many conventional thermal spray processes. It would be very advantageous to design a nozzle that provides improved performance in the areas of deposition efficiency, particle in-flight oxidation, and flexibility to allow deposition of ceramic coatings. Based on a numerical analysis, a new attachment to a standard HVOF torch was modeled, designed, tested, and used to produce thermal spray coatings according to the industrial needs mentioned above. Performance of the attachment was investigated by spraying several coating materials including metal and ceramic powders. Particle conditions and spatial distribution, as well as gas phase composition, corresponding to the new attachment and the standard HVOF gun, were compared. The attachment provides better particle spatial distribution, combined with higher particle velocity and temperature. The original version of this article was published as part of the ASM Proceedings, Thermal Spray 2003: Advancing the Science and Applying the Technology, International Thermal Spray Conference (Orlando, FL), 5–8 May, 2003, Basil R. Marple and Christian Moreau, Ed., ASM International, 2003.     

锥形凹模板料不起皱条件和极限拉深系数

本文通过分析锥形凹模拉深变形过程，利用试验数据，列出了板料不起皱的条件；并运用主应力法和板料弯曲的外力功等于内力功的原理以及摩擦理论，推导出加工硬化时变形区危险断面最大拉应力计算公式和无压边装置锥形凹模的圆筒件极限拉深系数计算公式；均由实例进行验证。拉深系数为０．３９的两种零件，从试制到生产，证明了锥形凹模是可以实现深拉深的模具。     

Determination of waviness decrease rate by measuring the frequency characteristics of the grinding force in centerless grinding

In centerless grinding, it is difficult to optimize the grinding conditions for minimizing the workpiece roundness error because of the high number of process parameters such as center height angle, blade angle, and stock removal rate. We had previously proposed a function for evaluating grinding conditions, i.e., the waviness decrease rate, in order to automatically select the optimum process parameters. In order to build a closed-loop control system for the process parameters, however, it is necessary to find a practical way to determine the waviness decrease rate. In this paper, the relationship between the waviness decrease rate and the dynamic components of the grinding force was investigated analytically. It was found that the frequency characteristics of the waviness decrease rate show a similar tendency to those of the grinding force. A grinding force measurement system was built and experiments for measuring the frequency characteristics of the grinding force were carried out. As a result, it was confirmed that the waviness decrease rate can be determined by measuring the frequency characteristics of the grinding force.     

2014年灵丘春玉米生育期气象条件分析

根据灵丘县2014年4月下旬到9月下旬的气象观测资料和玉米获得高产所需的农业气象条件,对灵丘县春玉米生育期的气象条件进行了综合分析,得出2014-04—09的综合气象条件能满足春玉米生长发育的需求。其中,有3个时段的气象条件与春玉米生育阶段的需求不吻合,即5月上旬出现冷害、7月中下旬降水偏少、9月出现阶段性低温和阴雨寡照天气,这些不利气象条件都会对春玉米的发育造成不同程度的影响。     

Optimisation of specimen temperature and pulse fraction in atom probe microscopy experiments on a microalloyed steel

This paper details the effects of systematic changes to the experimental parameters for atom probe microscopy of microalloyed steels. We have used assessments of the signal-to-noise ratio (SNR), compositional measurements and field desorption images to establish the optimal instrumental parameters. These corresponded to probing at the lowest possible temperature (down to 20 K) with the highest possible pulse fraction (up to 30%). A steel containing a fine dispersion of solute atom clusters was used as an archetype to demonstrate the importance of running the atom probe at optimum conditions.     

Controllability results for damped second-order impulsive neutral integrodifferential systems with nonlocal conditions

In this paper, we establish a set of sufficient conditions for the controllability of damped second-order impulsive neutral integrodifferential systems with nonlocal initial conditions in Banach spaces. The approach used is the Sadovskii fixed point theorem combined with a noncompact condition on the cosine family of operators. An example is presented to illustrate the result.     

分布式仿真系统的数据监控软件的实现

文中以高速列车数字化仿真平台为研究背景,设计并实现了基于Oracle数据库的分布式仿真系统数据监控软件。该系统采用VisualC++和LabWindows/CVI混合编程的方式以及多线程技术,实现了对分布式仿真系统中仿真工况的状态查询及监控,仿真工况模型的下载及图形化显示,待监测工况参数的灵活配置及多通道数据曲线动态显示,报警提示等功能。能及时、直观、有效地展示出仿真系统中各仿真工况的仿真过程及结果,使系统操作人员能及时了解分布式仿真系统中各工况的工作状态。