Modeling and surface texturing on surface roughness in machining LaPO4–Y2O3 composite

In this work, lanthanum phosphate with a 20% yttria (LaPO₄/Y₂O₃) composite prepared by an Aqueous Sol–Gel process is machined using an Abrasive Water Jet Machine (AWJM). The machinability of this composite is studied by varying the input parameters namely Jet Pressure (JP), Stand-Off Distance (SOD), and Traverse Speed (TS) on Surface finish. Garnet of 80 mesh size is used as an abrasive with a flow rate of 85?g/min. The microstructural characterization study reveals the presence of new element YPO₄. This element enhances the machinability and reduced porosity in the composite. Microscopy examinations on the machined surface reveals that partial overlapping at low JP, poor surface finish at high JP and SOD, forged deficiency at maximum SOD and TS. The minimum levels of all input parameters are influenced to obtain acceptable Ra. Atomic Force Microscopy (AFM) on the kerf surface shows micro wear track and peaks. The Multiple Regression Analysis (MRA) is developed for Ra to check the adequacy. From the Analysis of Variance (ANOVA), SOD has a significant effect on Ra with a contribution of 53%. The influence of JP and TS on Ra is found to be 31% and 15%, respectively.     

慢刀伺服车削刀具半径定向补偿的分段逼近求解

复杂曲面的慢刀伺服车削加工过程中，采用刀具法向补偿算法会在各个直线轴产生补偿量，加工法向矢量突变的曲面时，这种算法并非最优，将补偿量只应用于负载较低的直线轴却是更优的选择。提出一种基于线段逼近的刀具半径定向补偿数值求解算法来求解定向刀位点，通过半径细分的策略使法向误差收敛。算法实例验证及与相关算法的对比结果显示，该算法适用于点云构成的曲面或分段曲面的刀具半径补偿。     

基于修正等速运动规律的自由曲面多轴加工刀轴序列优化方法

针对自由曲面多轴加工中起始位置处刀具相对工件速度、加速度不为零导致的一定程度刚性冲击现象,提出了一种基于修正等速运动规律的刀轴序列优化方法,通过控制工件坐标系中决定刀具姿态的两个约束角,使之变化遵循修正等速运动规律,获得了切削行上平稳变化的刀轴序列,避免了由于起始位置处刀具相对工件速度、加速度不为零导致刀具不能精准到达后续加工位置的现象。算例分析表明,该方法能产生平稳且光滑的刀轴序列,可一定程度改善机床运动性能,提高加工表面质量。     

Planetary motion cross bar friction test for application in machining process

This paper describes a new method to evaluate the friction coefficient at the tool-work interface in machining process where high stress and temperature are caused. In order to examine the feasibility of the proposed method, the present report introduces the method and the results obtained only at room temperature. Ti6Al4V, SUS304, AISI1045, FCD 700, FCD 450 and FC300 were used as work materials, while TiN coated carbide tool, TiAlN coated carbide tool and P15 were used as tool materials. The proposed method provided the friction coefficients of different coatings against different work materials, and demonstrated the variability of friction coefficient and the anisotropy of surface roughness.     

松木颗粒热解与高温蒸汽气化半焦产率及形貌特征分析

以成型松木颗粒为原料，进行低温热解，研究了热解温度和升温速率对生成的松木半焦产率及官能团的影响。以试验得到的松木半焦进行蒸汽气化试验，对比分析了温度对半焦重整气化形貌特征、比表面积和平均孔径的影响。研究表明：随着热解温度升高，松木半焦脂肪族结构峰消失转化为烃等小分子物质及气化气，进而降低半焦产率。升温速率升高，半焦产率呈先下降后升高的趋势，在800℃升温速率为30K/min时半焦产率最低。不同温度热解和蒸汽气化对比试验表明，温度相对较低时（500℃）热解和蒸汽气化半焦孔隙结构相近，随着温度的升高，蒸汽气化半焦结构发生明显变化，900°C时出现了更小的孔道结构且比表面积增加明显。蒸汽引入使松木半焦和水蒸气发生热解反应的同时发生了脱氢反应，气化半焦形貌出现熔融和烧结现象。     

Hydrothermal Carbonization of Sewage Sludge: Analysis of Process Severity and Solid Content

Hydrothermal carbonization of sewage sludge was carried out with the aim to evaluate the influence of process severity and initial solid content. Response surface methodology was applied to model yield and C yield responses. Enhanced dewaterability performance was recorded under mild processing conditions. The treatment promoted concentration and immobilization of Pb, Cd, Ni, Zn, and Cu. Variation of the solid content showed a stronger influence than severity on average yield and C yield. Higher heating values (HHVs) and energy retention efficiencies (EREs) of hydrochars obtained at the lowest solid content displayed the lowest values. Hence, the energy requirements of a first dewatering step should be compared with the related improvement in terms of HHV and ERE when sludge is used as feedstock.     

三山岛北部海域金矿大规模海下开采地表岩移预测分析

三山岛北部海域金矿赋存于海平面下,设计生产能力达到12 000t/d,水下开采技术难度大,若矿体开采强度过高、顶柱隔离层保留不足,将可能造成海床沉降变形,引发海水倒灌的风险。根据矿床开采技术条件,在获取有限岩石力学参数条件下,本次采用软件模拟分析了海下矿床上向充填法开采条件下的地表岩移特征。研究结果表明,地表沉降变形最大值分布于矿体上盘区域,随着开采由深部逐渐转入浅部区域,地表沉降变形不断增大,研究建议留设160m顶柱,能够保证海下矿体安全开采。     

Predictive association of metal–organic systems in the solid-state: the molecular electrostatic potential based approach

Designing crystalline solids with improved properties or performances remains a challenging task, despite great strides that have been made within the field of crystal engineering since its birth several decades ago. Herein, we are bringing examples that illustrate recent successes in taking supramolecular synthetic guidelines from the organic crystal engineering and adjusting those to metal-containing systems, particularly to the lower-dimensional ones. The versatility of calculated molecular electrostatic potential (MEP) as a new crystal engineering tool is demonstrated.     

Theoretical and experimental studies of a new aniline derivative corrosion inhibitor for mild steel in acid medium

4-Chloro-N-(pyridin-2-ylmethyl)aniline (CPYA) was synthesized by a simple and inexpensive method and tested as a corrosion inhibitor in acid medium for mild steel by using gravimetric studies and electrochemical measurements. An average maximum efficiency of 96.0% was achieved at 4.59 mmol/L. Corrosion kinetic and thermodynamic parameters were also analyzed. Surface analyses (atomic force microscopy and scanning electron microscopy) show that protection is enabled by adsorption on the metal, forming a film. Quantum chemical calculations were performed to access information regarding the molecular structure in the corrosive medium and to support interpretation of the results obtained by experimental methods.