挖掘机斗齿材料及提高使用寿命的工艺途径

挖掘机斗齿直接与矿石和土壤接触,工作条件恶劣,除正常磨损外,还承受强烈的冲击负荷。影响斗齿使用寿命的因素很多,除矿石结构、爆破情况及使用的合理性之外,斗齿材料与热处理工艺是不可忽视的重要因素。本文就4m~3挖掘机所用斗齿在国内一些矿山的使用情况作了简单介绍,并对今后斗齿的生产提出一些看法。     

一种合金钢新斗齿

挖掘机斗齿是机械工业100项基础件攻关项目之一。机械部规定,到1985年,挖掘机斗齿的攻关目标是,在本溪北台铁矿大顶子采区的条件下,每组斗齿采掘15000吨。长江挖掘机厂根据机械部和城乡建设环境保护部下达的任务,最近研制成一种新的     

会议消息

第一次挖掘机斗齿攻关会议在抚顺挖掘机厂举行一机部第一次挖掘机斗齿攻关会议于1975年7月11日至17日在抚顺挖掘机厂举行。参加会议的有抚顺挖掘机厂、太原重机厂、杭州重机厂、上海建筑机械厂、长江挖掘机厂、江西铸锻厂、韶关铸锻厂、沈阳铸造研究所和天津工程机械研究所等十一个单位。会议还特别邀请了沈阳冶金机械修造厂的代表参加。到会代表充分交流了在提高挖掘机斗齿寿命方面的经验;听取了沈阳冶金机械修造厂的经验介绍,讨论了有关挖掘机斗齿攻关的分工;落实了攻关的具体措施。这次会议对于进一步提高挖掘机斗齿的质量和寿命必将起到积极的促进作用     

斗齿攻关新动向

挖掘机斗齿攻关最近取得了新进展。清华大学与杭州重机厂等单位共同研究试制一种合金铸钢镶铸硬质合金的复合斗齿,在国产第一台斗轮挖掘机和WK-2型单斗挖掘机上作了装机试验,实际使用寿命由原来的60小时提高到186小时。这种斗齿制造工艺简便,耐磨性高,经济效果显著(据估算,每台斗轮挖掘机每年可节约6万元左右)。清华大学机械系为配合斗齿寿命攻关还研制成功一种DM-1型动载磨     

基于逆向工程的挖掘机斗齿动力学分析

斗齿是挖掘机上的重要部件,在挖掘过程中会承受强烈冲击。为保证斗齿在复杂载荷下能够正常工作,在斗齿原始尺寸未知的情况下,通过逆向建模和有限元分析对斗齿进行强度分析。以某型挖掘机斗齿为研究对象,应用三维扫描仪进行逆向扫描获取点云数据,应用Geomagic S tudio软件进行去除杂点、简化数据等预处理,再通过UG进行逆向建模,获取模型的尺寸参数,进而在ANS YS中进行模态分析和瞬态分析,得到斗齿的固有特性以及冲击载荷下的动力学响应,为挖掘机斗齿的设计分析提供了一种新的思路。     

球墨铸铁代替高锰铸钢铸造轻型挖掘机斗齿

我矿装载岩石(硬度f=12～14)主要靠W-1001型、W-501型和 KM-602A 型挖掘机来完成。挖掘机采用高锰钢斗齿。矿党委组织了三结合小组试验以普通浇注球墨铸铁斗齿代用。通过一年多的实践证明,这种斗齿质量接近于高锰钢斗齿。现将铸造工艺简介如下:     

斗齿的焊修

从近几年我厂承接的工程机械修理任务来看,挖掘机、装载机斗齿的修复量较大。斗齿工作条件相当恶劣,磨损非常严重,寿命较短。尤其是挖掘机挖掘含岩石的土壤及挖掘爆破的岩石时,由于坚硬的岩石对斗齿的冲击作用,产生严重的凿削式磨料磨损。斗齿工作部分磨损50％左右时,应及时予以修复。斗齿材料根据生产厂家而异,其焊修特点也不相同。但常用材料一般为高锰钢或中碳低铬钢(碳当量约为0.65～0.75)。判断这两种材     

用复合材质法提高挖掘机斗齿寿命

一、前言矿用挖掘机斗齿,目前国内主要使用高锰钢制造,磨耗十分严重,寿命很短。据1978年北台铁矿统计,在铁矿石硬度f=18～20时,使用W1001挖掘机作清根底挖掘时,一般只能用6～8天,挖掘矿石(5～6)×10~3t,斗齿磨损量约80～90mm,每只斗齿失重约3～7kg。若进行一般性挖掘,则使用寿命可延长至10天左右,可挖矿石(7～8)×10~3t。该矿每台挖掘机每月消耗斗齿约2～3套。备件消耗量大,更换斗齿频繁,影响了整机的使用寿     

大型矿用挖掘机铲斗结构设计综述

铲斗的结构特性对挖掘机的生产效率和可靠性有着决定性的影响。在介绍机械式挖掘机铲斗结构特点及设计要求的基础上,分别从铲斗的形状、斗齿和开斗机构等3个方面,对铲斗结构设计存在的实际问题,国内外研究现状及发展趋势进行分析与讨论,并举例说明离散元、智能控制等先进技术在铲斗设计中的应用,为大型矿用挖掘机铲斗结构的合理设计与性能研究提供参考。     

大型挖掘机斗齿定位监测系统研究

大型挖掘机(电铲、液压铲)作业过程中,易出现斗齿脱落现象,进而引发破碎系统故障。为确保脱落的斗齿被及时发现,设计电铲斗齿定位监测系统,以现有斗齿无线定位监测技术为基础,通过改变信号报警方式及射频信号发射装置固定安装方式,彻底解决了原斗齿防丢预警系统电池续航能力不足,信号强度偏弱,报警信息延迟,射频信号发射装置安装固定不牢等缺点,可对斗齿断裂、脱落进行准确有效报警,确保驾驶员及时发现,有效避免因"卡斗齿"造成破碎站故障停机。     

Heavy metals in human primary teeth: some factors influencing the metal concentrations

Human primary teeth have been used as indicators of heavy metal exposure for several decades, but the knowledge about the influence of factors such as tooth type and the presence of caries and roots on metal concentrations is limited. Samples of tooth powder from more than 1200 Norwegian primary teeth without fillings have been analyzed for lead, zinc and cadmium content, and 554 of them for mercury. The material represents all groups of tooth types (incisors, canines and molars), carious and non-carious teeth, and teeth with and without roots. Here we investigate how tooth group and the presence of caries and roots are related to metal concentrations in the teeth. We find that carious teeth have higher metal concentrations than non-carious teeth; the difference was statistically significant for lead, mercury and zinc. Teeth with roots have higher lead and zinc concentrations than teeth without roots. We find differences in metal concentrations between the tooth groups for lead, mercury and zinc. Significant, positive correlations are found between lead and the three other metals and between mercury and zinc. We conclude that metal concentrations in primary teeth are affected by the presence of caries and roots and by tooth group.     

Do the levels of selected metals differ significantly between the roots of carious and non-carious teeth?

Since the metals deposited in teeth during formation and mineralization processes are to a large extent retained, human teeth receive a considerable attention as the indicators of the heavy metal exposure. The use of permanent teeth is limited because the extraction of healthy permanent teeth just for this purpose is hardly acceptable. As the issue of the loss of elements from a carious lesion in the coronal part of a tooth remains controversial, the valuable material could only be the root of carious and fractured permanent teeth. However, to ensure the validity of the results, it should be ascertained that the levels of certain toxic and essential elements do not differ significantly between the roots of non-carious and carious teeth, and therefore this is the aim of this project. The levels of cadmium, chromium, copper, iron, manganese, lead, zinc, potassium, sodium, calcium and magnesium were determined in the roots of 344 permanent teeth (189 carious and 155 caries-free teeth) from the residents of Ruda Slaska, Poland, aged 18 to 34. No statistically significant difference between the concentration of these metals in the roots of non-carious and carious teeth was found. This finding applies to both the general population and after the grouping by donor's gender and tooth type. The concentration of lead, iron, calcium and manganese in the roots of non-carious and carious teeth exhibited dependence upon tooth type, as well as the concentration of potassium in the roots of carious teeth. Since the mineral composition of the roots of permanent teeth is similar for the non-carious, as well as the carious teeth, they can be indiscriminately selected for the tests required by a research project, as they will produce the comparable results. However, in the case of lead, iron, calcium, potassium and manganese, the comparison should be made after grouping by tooth type.     

弧齿锥齿轮的过载损坏及防护措施

通过工程钻机弧齿锥齿轮的失效分析,提出了提高齿轮承载能力的综合措施,减少了弧齿锥齿轮的过载损坏。     

带齿夹板钢木连接节点受力机理

为解决胶合木网壳螺栓连接节点初始刚度低、木梁螺栓孔易发生劈裂的问题,提出一种带齿夹板钢木连接节点。通过试验研究了带齿夹板节点(JD-2)在单调荷载作用下的力学性能和破坏模式,并与同尺寸下不含钢齿的普通夹板节点(JD-1)进行对比分析。为深入研究带齿夹板节点的受力机理,对带齿夹板节点进行有限元模拟。结果表明:JD-1的破坏模式为木梁沿螺栓孔水平连线方向的横纹劈裂破坏,JD-2的破坏模式为夹板屈服破坏; 与JD-1相比,JD-2的初始刚度提高了47.18%,极限承载力提高了31.4%,延性系数提高了19.83%; 钢齿与木梁之间的机械咬合作用可以有效减少木梁螺栓孔初始间隙对节点刚度的不利影响; 在弯矩与剪力联合作用下,荷载通过钢齿及螺栓共同传递给木梁,减少了木梁螺栓孔的应力,因此延缓了木梁螺栓孔的开裂; 随着夹板翼缘厚度的增加,节点的受弯性能呈现增大的趋势; 增加夹板布齿率,木梁螺栓孔受到螺栓挤压应力减小,钢齿阻止夹板与木梁之间的相对滑动能力增强,建议夹板布齿率取0.46%～0.65%。     

64层螺旋CT全景齿科成像技术在上、下颌骨埋伏牙矫形中的应用

目的探讨64层螺旋CT全景齿科成像技术在上、下颌骨埋伏牙矫形中的临床应用价值。方法对50例上、下颌骨埋伏牙患者均行64层螺旋CT检查,并用Dentascan软件包及多平面重建（MPR）、曲面重建（CPR）、最大密度投影（MIP）、容积再现（VR）及表面遮盖成像（SSD）重建图像,从不同的角度观察牙体断面及三维立体图像,从而获得埋伏牙的牙体形态、唇腭侧位置、开窗的位置、萌出方向、切口方向及与其邻牙关系。结果 50例患者中,上、下颌骨埋伏牙共计65颗。阻生埋伏牙38例,38颗牙;多生埋伏牙12例,27颗牙。多层螺旋CT三维重建图像准确地显示上、下颌骨埋伏牙的数量和牙冠、牙根形态、唇腭侧位置、埋伏牙萌出方向及与邻牙的解剖关系。结论多层螺旋CT全景齿科成像对埋伏牙的诊断具有重要的意义,在临床上可作为埋伏牙外科处理和正畸治疗前的有效的检查手段。     

3种材料修复楔状缺损的疗效观察

目的观察采用不同材料充填修复楔状缺损的临床疗效。方法将500颗需要进行楔状缺损修复的患牙随机分成3组,分别用3M玻璃离子水门汀（1组172颗）,Z350复合树脂（2组195颗）,Dyract复合体（3组133颗）充填修复楔状缺损,随访1年。结果随访1年,1组成功率87.8%,2组成功率94.9%,3组成功率为98.5%。2组和3组之间差异无统计学意义（P〉0.05）,1组与2组、3组之间差异有统计学意义（P〈0.05）。结论 Dyract复合体和Z350复合树脂的临床疗效优于玻璃离子,是较为理想的修复楔状缺损的材料。     

Teeth as biomonitors of selenium concentrations in tissues of beluga whales (Delphinapterus leucas)

Selenium (Se) is an essential element which has been shown to play an important role in protecting marine mammals against the toxic effects of mercury (Hg) and other metals. It has been suggested that metal concentration in marine mammal teeth can potentially be used as bioindicators for body burden. The objective of this study was to investigate the relationship between Se concentrations in beluga (Delphinapterus leucas) teeth and those previously measured in soft tissues (liver, kidney, muscle and muktuk). Tooth Hg concentrations are also measured, and the relationships between Se and Hg in teeth and soft tissues are examined. Se in the teeth of beluga was measured using hydride generation atomic fluorescence spectrometry (HG-AFS) and Hg in beluga teeth was measured by cold-vapour atomic absorption. Tooth Se concentrations ranged from 108 ng/g to 245 ng/g dry weight, and tooth Hg concentrations ranged from 10 to 189 ng/g dry weight. In the soft tissues, Se concentrations were highest in the liver, followed by kidney, muktuk, and muscle. There were significant correlations between tooth Se concentrations and animal age, tooth Se and liver and muscle Se, and between liver Se and animal age. The molar ratio of Hg:Se in the liver was found to be 0.70. This study is the first to measure Se in the teeth of a marine mammal species, and HG-AFS is found to be an effective technique for determining Se in beluga teeth. Tooth Se can be used as predictor for liver and muscle Se, although these relationships may be strongly influenced by the association of Se with Hg in marine mammal tissues. This study contributes to an increased understanding of the storage and metabolism of Se in marine mammals.     

卡脖与冷却部液流结构形态的分析（二）

(接 2 0 0 0年第 4期 )2　冷却部的液流结构冷却部接受经卡脖流入的玻璃液 ,并回流一部分至熔化部 (未完全隔断回流的情况下 )。玻璃液在冷却部进一步均化 ,并冷却至成型要求的温度 ,然后经流道进入锡槽成型。2 .1　冷却部液流的基本形态冷却部的液流结构见图 4。由图 4可见 :(1)由于液流出卡脖的扩流作用和在流道入口急剧的缩流作用 ,会使液流在冷却部窑池四周角部形成基本不动层。(2 )冷却部窑池较宽 ,因液流横向温差造成的横流 (斜流 )在边部形成回旋流 ,并形成一个不很规则、但左右基本对称的半球面。球面之外是受运动特性影响而基本不…     

郑西客运专线旋挖灌注桩成孔施工技术

旋挖灌注桩成孔施工在郑西客运专线三门峡段第四纪Q1地层中遇到难钻进、难卸土问题,通过研究地层工程地质特性,对旋挖钻机不同斗齿刃前角对应的钻进速度进行统计分析,用最小二乘法拟合最佳钻进速度和斗齿刃前角的关系.通过确定斗齿刃前角的合理取值范围,采用单层进土口的旋挖钻斗,加大进土孔,改进钻进施工工艺等措施,克服了旋挖钻机在三门峡段第四纪Q1地层中进尺难、卸土难的问题.     

The occurrence of copper in deciduous teeth of girls and boys living in Upper Silesian Industry Region (Southern Poland)

This work presents the results of a research concerning the copper content in different types of deciduous teeth (incisor, canine, molar) of boys and girls living in the Upper Silesian Industry Region (Southern Poland). The average copper concentration in deciduous teeth was 9.92 microg/g and was significantly higher in the deciduous teeth of boys (12.24 microg/g) in comparison to the deciduous teeth of girls (8.60 microg/g). The concentration of copper was statistically variable depending on the type of tooth (incisor, canine, molar). The results of the correlation analysis and cluster analysis indicate mainly the participation of lead, iron, manganese and chromium ions in the formation of copper content in hard tissue of deciduous teeth.