高压磨料水射流切割工程陶瓷研究

采用高压磨料水切割和工程陶瓷,研究高压磨料水工艺参数对其切割深度的影响.从陶瓷材料力学和高压磨料水流体力学基础出发,建立冲击力和加工参数关系.实验结果表明切割深度与水的压力成正比,与喷嘴移动速度成反比.采用硬质合金和陶瓷两种材料制备了磨料喷嘴,研究了喷嘴磨损量与加工参数的关系,采用SEM分析了喷嘴磨损原因.     

不同结构喷嘴的高压水非定常喷射反推特性

喷嘴作为高压水射流的关键部件,其结构和工作参数对高压水喷射反推性能具有重要影响.以圆柱、圆锥和余弦三种不同结构喷嘴为研究对象,基于CFD对定容积下不同结构喷嘴的高压水非定常喷射过程进行数值模拟,对比分析了不同结构喷嘴的射流反推特性,系统研究了充气压力、出口直径对喷嘴非定常喷射速度和反推力的影响规律.结果表明:相比圆柱喷...     

磨料水喷嘴的优化设计

为提高磨料水射流加工设备中磨料水喷嘴加工性能,通过实验研究了磨料水喷嘴几何形状对喷嘴磨损的影响,并研究了磨料水喷嘴机械结构和加工性能,最终确定优化加工条件.     

前混合磨料射流喷嘴减磨技术综述

从喷嘴的材料、几何形状、结构、加工质量等方面,介绍了前混合磨料射流喷嘴磨损机理及喷嘴减磨技术的研究现状,并从表面涂层技术、纳米技术与高性能陶瓷等方面对磨料射流喷嘴的新技术进行了展望。     

脱硫系统GGH吹灰器高压水喷嘴改进

介绍了通过扩大吹灰器高压水喷嘴口径,增加喷嘴射流流量,提高对脱硫系统GGH(烟气再热器)清洗效果的途径,并实现脱硫系统不开烟气旁路挡板进行GGH波纹板高压清洗的目的。     

磨料水射流喷嘴内流场的数值模拟

该文以后混合磨料水射流水喷嘴为研究对象,基于两相流动的欧拉-拉格朗日和高雷诺数的标准双方程湍流模型,应用FLUENT软件对磨料水喷嘴内部两相流进行仿真,研究了固液两相流在磨料水喷嘴中的流体动态、磨料粒子的速度。通过对磨料水喷嘴磨损和液固混合相流域的权衡和模拟结果分析,得到磨料水喷嘴的锥形收敛角为30°、柱形内孔直径为0.76 mm、聚焦管总长为73 mm时具有较好的切割性能。通过分析不同长度、直径、锥形入口角的磨料水喷嘴,优化了磨料水喷嘴的结构参数。     

提高线切割机床慢走丝切割速度的方法

模具制作中电加工效率的高低是影响模具制作周期的一个重要因素。慢走丝线切割要达到好的尺寸精度和表面粗糙度，通常要采用多次切割，而其中切割速度最慢的是第一遍切割，即粗加工，所以要提高线切割速度关键是提高第一遍切割的速度。下面就瑞士夏米尔（Robofil２９０P）慢走丝线切割机床介绍提高线切割加工速度的一些实用方法。（１）保证上、下高压水工作良好检查回路中的高压泵、高压水阀、旁路水阀、上下喷嘴座、上下喷嘴及水管确保没有任何堵塞和泄露现象。加工时，尽量使上下喷嘴分别贴近工件上下表面（注意防止喷嘴与夹具、横梁碰…     

梯度功能陶瓷喷嘴物理模型设计

在进行磨料喷射喷嘴应力分析和冲蚀磨损试验的基础上,得出喷嘴的冲蚀磨损在入口处最严重、出口次之、中段相对较轻,且该喷嘴冲蚀磨损特点主要由喷嘴入口、出口处承受的高拉应力所致的结论。针对均质陶瓷喷嘴材料的抗冲蚀磨损能力的提高力度有限的现状,提出将陶瓷喷嘴材料设计与喷嘴力学冲蚀磨损机理密切结合,研发新型非均质的陶瓷喷嘴材料的思想。拟订了FGM-1和FGM-2陶瓷喷嘴物理模型,并进行有限元分析,确定了梯度功能陶瓷喷嘴的物理模型。     

高压水射流数值模拟及混凝土路面切割试验研究

探讨了高压水射流的切割机理,并对圆形喷嘴高压水射流垂直冲击水泥混凝土建立了流体动力学模型,进行了数值模拟。通过对模拟结果的分析,得到射流喷嘴最大出口压力和量纲一冲击高度对水泥混凝土在滞止点及其附近压力值的影响。根据结果选取主要参数,设计制造出高压水切割设备并且完成水泥混凝土试块的切割试验。试验达到预期效果,证明此高压水切割设备工作的有效性。     

轧钢生产高压水除鳞系统的设计

叙述了高压水除鳞技术的发展，结合实际重点介绍了高压水除鳞系统中喷嘴的选型和布置设计、水泵的选型设计。     

磨粒流研抛伺服阀阀芯喷嘴的冲蚀磨损分析

为了研究固液两相磨粒流对伺服阀阀芯喷嘴的研抛性能,从冲蚀磨损的角度对比分析了不同磨粒硬度下的磨粒流研抛效果。利用计算流体力学方法,求解分析了磨粒流研抛伺服阀阀芯喷嘴时流场中的冲蚀磨损特性,采用电子显微镜以及扫描电镜仪检测伺服阀阀芯喷嘴零件经磨粒流研抛前后的表面粗糙度和表面形貌。实验结果表明:采用碳化硅磨粒和白刚玉磨粒加工后的伺服阀阀芯喷嘴主干通道、交叉孔以及小孔区域的粗糙度分别由1.1μm、0.823μm、0.743μm降低为0.735μm、0.721μm、0.571μm和1μm、0.747μm、0.696μm。在本试验中碳化硅磨粒的加工效果优于白刚玉磨粒,即具有高磨粒硬度的磨粒研抛效果好。检测结果显示,磨粒流研抛技术可有效改善伺服阀阀芯喷嘴的表面质量;提高磨粒硬度可提高磨粒流的研抛效果;伺服阀阀芯喷嘴的交叉孔以及小孔区域的表面质量要高于主干通道的表面质量。     

喷嘴抗冲蚀磨损研究及梯度模型设计

分析喷嘴冲蚀磨损特点，指出喷嘴的不同部位同时受到不同角度的冲击；磨料颗粒在喷嘴内部加速运动，喷嘴沿长度方向的磨损程度不同，喷嘴人口磨损最严重，出口次之，而中间区域磨损相对较轻。阐述陶瓷喷嘴冲蚀磨损机理，说明陶瓷喷嘴两端承受以高冲击角为主的冲蚀，磨损机理以应力疲劳断裂和脆性断裂为主；喷嘴中部承受低角冲蚀，微切削冲蚀磨损为其主要磨损机理，得到喷嘴磨损属于多冲蚀磨损机理并存的结论。在此基础上，提出均质材料难以适应喷嘴冲蚀磨损特点，不易满足喷嘴高抗冲蚀磨损性能要求的观点。基于梯度功能技术思想首次提出梯度功能喷嘴设计方法，并建立梯度功能喷嘴设计模型。     

不同载荷下水润滑高分子材料磨损机制的试验研究

为了研究载荷对新型水润滑高分子轴承材料磨损机制的影响,在CFT-1型摩擦磨损试验机上对该材料进行不同载荷下的无/有水润滑摩擦磨损试验,通过考察试样的摩擦因数、磨痕和磨损表面形貌,分析该材料的磨损机制。结果表明:在无水润滑条件下,该材料的摩擦因数随着载荷的增加呈现先降低后逐渐上升的变化趋势,磨损表面均出现塑性变形和撕裂脱落现象,磨损机制主要为黏着磨损,其中随着载荷的增大表面塑性变形趋于严重,而表面撕裂脱落在中等载荷下较为轻微,在低载荷和高载荷下较为严重;在水润滑条件下,该材料的摩擦因数随着载荷的增加也呈现出先下降低后急剧上升的趋势,磨损表面未发生塑性变形和撕裂脱落,但出现脱落的磨粒和犁沟,磨损机制主要为磨粒磨损,其中在中等载荷下,表面脱落的磨粒少、犁沟细小而浅,在低载荷和高载荷下表面脱落的磨粒多、犁沟深。     

Correlation between abrasive wear resistance and changes in structure and residual stresses of steels

The connection between the structure and abrasive wear resistance of steels was studied. Samples of AISI 1020, 1040 and 1080 steels were tested. The initial hardness of the samples ranged from HV221 – for annealed steel AISI 1020, to HV868 – for water quenched and tempered at 180°C steel AISI 1080. Two‐body abrasive tests on silicon carbide abrasive paper of grit size 1200–240 were carried out on a friction machine under identical conditions for all specimens. X‐ray studies of the specimens were conducted before and after these tests. It was shown that characteristics such as the integral width of diffraction lines could be used as a universal indicator of abrasive wear resistance for steels, independently of their heat treatment. The compressive residual stresses in the surface layers of the steels were observed. The results showed that there is a correlation between abrasive wear resistance and the sign and magnitude of residual stresses in the surface layers of steels, as well as between abrasive wear resistance and the structural changes in these layers. This revised version was published online in July 2006 with corrections to the Cover Date.     

新型陶瓷喷砂嘴的制备及其应用

分析了喷砂嘴材料和结构的发展情况,采用热压烧结工艺制备出了B4C/(W,Ti)C新型陶瓷喷砂嘴,结果表明随(W,Ti)C含量的增加,陶瓷喷嘴材料的致密度显著增加,晶粒显著细化,保温时间大大缩短,抗弯强度和断裂韧性大大提高;以SiC为冲蚀磨料进行的喷砂冲蚀试验证明了新型陶瓷喷砂嘴的抗冲蚀磨损能力远高于金属、硬质合金和其它陶瓷喷嘴。     

Wear reducing effects and temperature dependence of tribolayer formation in harsh environment

Certain materials show a tribolayer formation especially at enhanced temperatures in abrasive environment, building a wear protection layer with the abrasive on the surface. Three materials with different microstructures were tested in three-body abrasive and impact/abrasive environments at temperatures up to 700 °C to investigate tribolayer formation. Optical and electron microscopical methods were used for wear qualification. Furthermore, hot hardness tests were performed up to 700 °C to investigate the influence of hardness drop on tribolayer formation.It was shown that no significant tribolayer formation occurs on grey cast iron, whereas other materials form tribolayers. Generally, tribolayer formation increases with increasing testing temperature, especially for austenitic and ferritic materials. This entails a self-protecting effect and thus superior wear resistance in abrasive environment.     

Investigations on the influence of graphite filler on dry sliding wear and abrasive wear behaviour of carbon fabric reinforced epoxy composites

In this experimental study, the dry sliding wear and two-body abrasive wear behaviour of graphite filled carbon fabric reinforced epoxy composites were investigated. Carbon fabric reinforced epoxy composite was used as a reference material. Sliding wear experiments were conducted using a pin-on-disc wear tester under dry contact condition. Mass loss was determined as a function of sliding velocity for loads of 25, 50, 75, and 100 N at a constant sliding distance of 6000 m. Two-body abrasive wear experiments were performed under multi-pass condition using silicon carbide (SiC) of 150 and 320 grit abrasive papers. The effects of abrading distance and different loads have been studied. Abrasive wear volume and specific wear rate as a function of applied normal load and abrading distance were also determined.The results show that in dry sliding wear situations, for increased load and sliding velocity, higher wear loss was recorded. The excellent wear characteristics were obtained with carbon-epoxy containing graphite as filler. Especially, 10 wt.% of graphite in carbon-epoxy gave a low wear rate. A graphite surface film formed on the counterface was confirmed to be effective in improving the wear characteristics of graphite filled carbon-epoxy composites. In case of two-body abrasive wear, the wear volume increases with increasing load/abrading distance. Experimental results showed the type of counterface (hardened steel disc and SiC paper) material greatly influences the wear behaviour of the composites. Wear mechanisms of the composites were investigated using scanning electron microscopy. Wear of carbon-epoxy composite was found to be mainly due to a microcracking and fiber fracture mechanisms. It was found that the microcracking mechanism had been caused by progressive surface damage. Further, it was also noticed that carbon-epoxy composite wear is reduced to a greater extent by addition of the graphite filler, in which wear was dominated by microplowing/microcutting mechanisms instead of microcracking.     

Abrasive wear behaviour of bamboo

Abrasive wear of bamboo (Phyllostachys pubescens) against a free abrasive consisting of quartz sand (96.5%-wt) and bentonite (3.5%-wt) was studied on a rotary-disk type abrasive wear tester (a free abrasive wear tester) and the micromorphology of the abraded surfaces were examined by scanning electron microscopy. It was observed that the bamboo fibre (vascular bundle) orientation with respect to the abrading surface had an important influence on the abrasive wear performance. The normally oriented specimens gave much higher abrasion resistance than the parallel-oriented ones, the surface layer than the inner layer, and the vascular bundle than the matrix tissue.     

表面粗糙度对碳/铜载流摩擦副摩擦磨损性能的影响

通过环-块式摩擦磨损试验研究了表面粗糙度对碳/铜载流摩擦副摩擦磨损性能的影响,并分析了磨损形貌及机制。结果表明:其摩擦因数与电弧行为密切相关,无电弧时摩擦因数曲线平滑;对磨环的表面粗糙度越大越容易产生电弧,电弧的烧蚀导致块试样的磨损加剧;不同表面粗糙度下均存在临界起弧法向压力,且随着表面粗糙度的增大而增大;载流摩擦副的磨损机制主要为磨粒磨损、粘着磨损、电弧烧蚀及材料转移。