Establishment of wear model and life prediction of drum of hot rolling coiler

For the drum of hot rolling coiler is prone to be easily destroyed, the type of MMU-5G abrasion tester was applied to revealing the friction and wear behavior. The morphology observation by scanning electron microscope (SEM) demonstrates the wear mechanism of the drum, and the test data of the influence coefficient of the normal pressure, relative sliding speed and surface lubrication conditions acted on the linear rate of the wear could be obtained by the regression method. A calculation model, which considers the factors of the structure of the drum, coiling tension and coiling strip specifications, was established by the combination method to predict the wear life of the drum. Then the practical production data was applied into this model and the analysis result was in good accordance with that of actual production.

Investigation on tool wear and tool life prediction in micro-milling of Ti-6Al-4V

Short tool life and rapid tool wear in micromachining of hard-to-machine materials remain a barrier to the process being economically viable. In this study, standard procedures and conditions set by the ISO for tool life testing in milling were used to analyze the wear of tungsten carbide micro-end-milling tools through slot milling conducted on titanium alloy Ti-6 Al-4 V. Tool wear was characterized by flank wear rate,cutting-edge radius change, and tool volumetric change. The effect of machining parameters, such as cutting speed and feedrate, on tool wear was investigated with reference to surface roughness and geometric accuracy of the finished workpiece. Experimental data indicate different modes of tool wear throughout machining, where nonuniform flank wear and abrasive wear are the dominant wear modes. High cutting speed and low feedrate can reduce the tool wear rate and improve the tool life during micromachining.However, the low feedrate enhances the plowing effect on the cutting zone, resulting in reduced surface quality and leading to burr formation and premature tool failure. This study concludes with a proposal of tool rejection criteria for micro-milling of Ti-6 Al-4 V.

WEAR AND LIFE OF PCBN TOOLS WHEN DRY-CUTTING BEARING STEEL GCr15

The wear forms and reasons of PCBN tools when dry-cutting bearing steel GCr15are studied systematically. The effect law of the workpiece hardness on PCBN tools is gained andtool wearing with the quickest speed at the workpiece critical hardness is proved. The life equationat two kinds of workpiece hardness demonstrates that the effect of the cutting speed on the PCBNtool life is less than that of carbide tools and ceramic tools.

Influences of Tool Wear on Residual Stress and Fatigue Life of Workpiece in Hard Cutting Process

Tool wear has an important influence on the residual stress distribution on the machined surface.Also,it will influence the fatigue life of finished workpiece. In this research,the hard turning process of hardened die steel Cr12 MoV was studied by using PCBN tool with considering tool wear. Based on the numerical treatment of residual stress,the dispersion and distribution curves of different tool wear were fitted,and the influence mechanism of tool wear on the residual stress distribution of machined surface was analyzed.Based on the theory of fatigue mechanics and mathematical statistics,the mathematical model for difference of stress dispersion and fatigue life was established. The rotating and bending tests were carried out on the standard parts after cutting process for the workpiece. The influence of tool wear on fatigue life was revealed by fracture surface morphology and fatigue life study. The results provide theoretical support for control of residual stress and the fatigue property of the machined surface under the actual working conditions.

An Analysis of the Translation Skills in Life and Death Are Wearing Me Out from the Perspective of Skopos Theory

Skopos Theory is the kernel part of functionalism, holding that the skopos rule is the top-ranking rule that justifies the overall translation process. This paper attempts to make an analysis of the C-E translation of Life and Death Are Wearing Me Out from the perspectives of Skopos Theory, and intends to explore the impact of translating skopos on the translator's choice of translating skills as well as the possible reasons behind them.

New approach based on continuum damage mechanics with simple parameter identification to fretting fatigue life prediction

A new continuum damage mechanics model for fretting fatigue life prediction is established. In this model, the damage evolution rate is described by two kinds of quantities. One is associated with the cyclic stress characteristics obtained by the finite element （FE） analysis, and the other is associated with the material fatigue property identified from the fatigue test data of standard specimens. The wear is modeled by the energy wear law to simulate the contact geometry evolution. A two-dimensional （2D） plane strain FE implementation of the damage mechanics model and the energy wear model is presented in the platform of ABAQUS to simulate the evolutions of the fatigue damage and the wear scar. The effect of the specimen thickness is also investigated. The predicted results of the crack initiation site and the fretting fatigue life agree well with available experimental data. Comparisons are made with the critical plane Smith- Watson-Topper （SWT） method.

Impact of Tooth Surface Loss on the Quality of Life of Patients Seen in a Nigerian Teaching Hospital

Background: Tooth surface loss (TSL) is a progressive process arising from erosion, abrasion, attrition or abfraction. It can affect individuals of any age group: children, young adult, adults or the elderly and can compromise the health of individual tooth or the entire dentition leading to poor quality of life of the affected person. Objective: To evaluate the pattern of TSL among dental patients in a Nigerian Teaching Hospital and to assess the impact of TSL on their quality of life. Subjects and Methods: The study was a cross-sectional study among patients with TSL in a Nigerian Teaching Hospital. The Oral Health Impact Profile-14 (OHIP-14) questionnaire was used to obtain information on the impact of TSL on the quality of life of the participants. Data collected were analysed using IBM SPSS version 20. Chi-square test was used to assess association between types of TSL and quality of life of the patients. Level of significance was set at p ≤ 0.05. Results: One hundred and twenty-five patients (Males = 72;Females = 53) with tooth wear lesions participated in the study. The most common type of tooth surface loss was attrition (40%) followed by abrasion (23.2%). The highest impact of TSL on the quality of life was painful sensation strongly affecting 39 (31.2%) patients. This was followed by problem with chewing. There was no statistically significant relationship between patients’ quality of life and types of tooth surface loss. Conclusion: The most common negative impact of TSL on patient quality of life was painful sensation.

The law of barrel wear and its application

A power function relation between number of rounds and barrel wear amount is created based on the test data from firing of large-caliber barrels. The function is optimized to fully fit the test data. A new concept of diameter change rate of bore is proposed and the law of barrel wear is put forward by means of comparing the diameter change rates for large-caliber barrels with different calibers. It is shown that the law of barrel wear is successful in barrel life prediction.

铣削高温合金GH3039刀具寿命预测及磨损机理

为揭示高温合金GH3039铣削参数对刀具寿命的影响规律,采用正交试验法对其进行铣削试验,运用多元回归法建立刀具寿命预测模型,分析铣削参数对刀具寿命的影响规律,通过观测铣刀后刀面的磨损情况,探究不同主轴转速下铣刀的磨损机理。结果表明:主轴转速对刀具寿命的影响程度最大,最小为轴向切深;当主轴转速为750 r/min时,铣刀磨损区域主要以黏结磨损和磨粒磨损为主;当铣削速度为950 r/min时,氧化磨损与扩散磨损开始增强;当铣削速度为1 180 r/min时,磨粒磨损与黏结磨损开始减弱甚至消失,氧化磨损与扩散磨损占据主导地位。

WC-Co硬质合金冲蚀模型研究及应用

WC-Co硬质合金是制造固定式节流阀阀芯的主要材料,高压天然气携带着井底杂质颗粒在节流阀节流降压的过程中,对节流阀的核心部件阀芯产生冲蚀破坏。因此,以牌号为YG15的WC-Co硬质合金为研究对象,构建室内冲蚀实验平台,以确定YG15硬质合金的冲蚀模型并结合仿真验证。将冲蚀模型进一步应用至固定式节流阀冲蚀仿真中,预测固定式节流阀阀芯的使用寿命。研究结果表明,确定了YG15硬质合金的冲击角函数和在90°冲击角下的速度指数为2.48;当冲蚀角度由30°增加至90°时,YG15硬质合金靶材的冲蚀磨损量由847.1 mg增加至1235.6 mg;固定式节流阀冲蚀最严重的部位位于节流孔处,冲蚀磨损率随颗粒质量流率的增大而增大;对固定式节流阀进行寿命预测,在颗粒质量流较小的情况下,对节流阀固定油嘴保持一年一换;在颗粒质量流较大时,保持半年内更换一次。

自润滑纤维织物复合材料及其在关节轴承中的应用研究现状与展望

自润滑关节轴承是1种球面滑动轴承,因其结构简单、承载能力强、可靠性高以及免维护(不需要润滑油脂)等优异性能受到广泛关注.目前,自润滑关节轴承已广泛应用于飞机发动机、起落架、机体襟副翼以及直升机旋翼系统,其在航天飞行器、汽车、核电和水利水电等领域中的应用也越来越多.随着高端装备极限性能不断提升,对自润滑轴承的服役性能及寿命要求越来越高.因此,自润滑关节轴承寿命提升、损伤失效机制和轴承寿命预测等方面的研究变得尤为重要.本文中从摩擦学视角出发,总结了自润滑关节轴承用自润滑纤维织物复合材料的研究现状,包括织物坯布组织结构、增强纤维、树脂基体、功能增强材料以及纤维-树脂界面改性等内容.此外,文中还介绍了自润滑关节轴承寿命评价方面的研究进展,包括自润滑关节轴承试验规范及产品标准、轴承寿命试验及预测、轴承寿命及可靠性影响因素.最后对关节轴承用自润滑纤维织物复合材料的重点研究方向进行了展望.

基于动态磨损模型的汽车覆盖件模具磨损数值模拟研究

针对某铝合金覆盖件冲模磨损失效问题,为更加准确地预测汽车覆盖件模具的使用寿命,基于Archard磨损模型建立了动态磨损模型。该模型耦合了动态磨损系数和表面硬度变化曲线,其中,磨损系数K转化为随接触压力和相对滑移速度变化的动态磨损系数,表面硬度考虑了磨损深度的变化。利用Python语言对ABAQUS软件进行二次开发,将动态磨损模型耦合到有限元模拟中,实现了考虑磨损系数和硬化层深度变化的汽车覆盖件模具磨损计算。通过对比分析凸凹模典型位置在成形过程中的动态磨损演化规律,并以模具最大磨损深度0.5 mm作为失效判据,得到该铝合金覆盖件冲压模具的使用寿命为635428次。模具主要发生磨损的位置集中在模具合模线附近和大圆角处,在实际生产中需要对这些位置进行修模、调试,从而有效延长模具的使用寿命。

复合运动下冲击活塞杆斯特封磨损寿命预测

磨损是引发密封失效的主要因素之一。针对复合运动的冲击活塞杆斯特封进行磨损寿命预测研究,活塞杆复杂的运动方式导致传统实验方法操作复杂、成本高。基于实际工况建立往复回转密封磨损寿命预测模型,对斯特封密封结构进行有限元分析,得到滑环唇口节点坐标值以及接触压力分布,综合考虑复合运动,模拟唇口轮廓、接触压力和接触长度随磨损时间累加的演化过程,并以密封面接触压力小于最大工作油压作为判断密封圈失效依据,实现斯特封的磨损寿命预测;最后通过实验证明寿命预测的准确性。结果表明:随着磨损时间的累积,磨损速率逐渐减小,最大接触压力表现出先快速降低后缓慢降低的趋势,在该工况下的磨损寿命为64.8~70.2 h。

航空机载设备寿命试验设计

航空机载设备的类型多、故障模式复杂、寿命验证周期长、翻修经费高,且容易集中爆发寿命问题。针对航空机载设备大量存在的“内场考核通过,外场故障频发”的情况,系统总结了寿命试验设计过程中存在的问题,包括施加应力类型不全面、分散系数不够等,针对性提出了基于机载设备耐久性机理分析的寿命试验设计方法,解决全寿命周期敏感应力/耗损性失效机理识别、多应力综合的寿命试验载荷谱制定和基于可靠寿命的试验验证/评估等技术难题,完成了寿命试验规范化设计工作。

基于应变的火炮身管健康监测和剩余寿命评估的可行性研究

火炮发射过程中产生的烧蚀磨损和疲劳使身管性能逐渐衰退直至不能使用,更为严重的是,时而发生的膛炸事故对人员生命和武器装备安全构成威胁,身管发射安全隐患始终存在。传统的身管寿命评估方法,包括基于尺寸、图像、温度和初速变化来预测身管剩余使用寿命的方法,尚不能科学、准确地评估身管健康状态和剩余使用寿命。针对该问题,在深入分析身管内膛损伤物理机制的基础上,提出以发射时身管外壁面应变为损伤特征参数的身管健康监测方法,揭示了应变与弹丸-身管-发射药系统之间的内在映射关系,阐释了该方法的基本原理以及如何用于评估身管剩余使用寿命。火炮实弹射击数据和数值模拟结果均证实了该方法的科学性、可靠性和实用性。

硬质合金铣刀在铣削钛合金过程中的磨损实验研究

针对硬质合金刀具在铣削钛合金过程中容易失效而导致平均寿命低的问题,开发了0.5μm WC颗粒和12%Co配比的新型硬质合金材料刀具,与市场上2种主流刀具进行钛合金湿式铣削磨损对比实验。根据拍摄的刀具前后刀面磨损形貌,分析了3种刀具的失效形式及磨损机理。结果表明,在铣削前期新型刀具圆周后刀面呈现出均匀的磨损带,磨损以粘结磨损和磨粒磨损为主,在铣削后期出现裂纹、崩缺等不均匀磨损;整个磨损过程主要经历初期磨损、稳定磨损和急剧磨损3个阶段。与对比刀具相比,新型材料刀具平均寿命更高、抗崩性能更好、更利于钛合金的加工。

基于双磁盘刀具钝化中磁弹磨粒的磨损及寿命研究

为了探究磁弹磨粒在双磁盘刀具钝化中磨损规律以及使用寿命的长短,通过对磁弹磨粒进行受力分析讨论了其磨损失效的形式,得出了影响磁弹磨粒寿命的主要因素。然后,制备出不同质量配比和不同磨粒相类型的磁弹磨粒,采用双磁盘钝化设备进行钝化实验,分析了磁弹磨粒质量配比和磨粒相类型对磁弹磨粒的磨损规律和对刃口表面粗糙度的变化规律,同时还对钝化前后的磁弹磨粒进行X射线能量色散普(EDS)和激光粒度分析。实验结果表明,以氧化铝为磨粒相的磁弹磨粒在钝化过程中主要发生磨粒相磨钝磨损,以金刚石为磨粒相的磁弹磨粒主要发生磨粒相脱落磨损,两种类型的磁弹磨粒都是在质量配比3:1时使用寿命最好。

地铁车辆车轮磨耗和镟修策略研究

[目的]车轮磨耗对地铁车辆的振动环境有直接影响,异常磨耗严重时引发车辆结构疲劳超限,降低列车运行的安全性,故有必要研究地铁车辆车轮磨耗和镟修策略,以提高地铁车辆车轮运维的水平。[方法]以国内某型地铁车辆作为研究对象,分析了地铁车辆车轮磨耗规律;根据地铁车辆车轮磨耗模型和车轮剩余寿命预测,分析了车轮关键参数在不同运营阶段的变化特征;综合仿真模型和实测数据的结果,提出了运维策略的优化方案。[结果及结论]运营前期车轮损耗量中镟修占比较高,随着轮轨匹配性的改善,轮轨磨耗取代镟修损耗成为轮轨的主要磨耗方式;适当降低轮轨摩擦因数和运营速度有利于降低轮轨磨耗功率;采用小等级镟修方法和灵活进刀量有效降低了车轮径向损耗量,延迟了车轮服役寿命。研究结果可为地铁线路轮轨磨耗的减缓和车轮镟修技术的优化提供应对措施。

数据驱动的动车组车轮剩余寿命预测模型研究及应用

通过对车轮磨耗机理进行分析,研究车轮磨耗的影响因素。基于车轮运用检修数据,结合对车轮镟修流程的分析,采用数据驱动方法,先后建立轮径-轮缘厚的磨耗预测模型、轮径-轮缘厚镟修比例系数、目标轮缘厚确定逻辑的数学模型。再根据动车组车轮的检修情况,提出车轮剩余寿命预测方法,实现对车轮到限情况预测。根据实际应用情况,该成果可以指导生产管理部门提前备品备料、制定预算、安排换轮计划等,提高车轮运用检修效率,节约车轮运维成本。

高压开关用碟簧液压机构活塞杆激光熔覆工艺研究

为提高35CrMo基活塞杆关键部位的耐磨性,防止电镀工艺带来的镀层剥落失效问题。采用激光熔覆技术在35CrMo钢基材上制备不同工艺参数的20%WC/Ni基复合涂层,利用SEM、EDS、维氏硬度计和HRS-2M往复式摩擦磨损测试仪,研究了熔覆层的宏观形貌、微观形貌、显微硬度和耐磨性,最后采用激光熔覆最优工艺参数制备活塞杆并开展10000次机械寿命试验。激光能量密度为63.3 J/mm^(2)能够提高熔覆层组织均匀性、降低晶粒尺寸和提高熔覆层硬度;熔覆层组织越均匀、晶粒越细小有利于硬度、摩擦磨损等性能的提高。最优工艺参数P=1900 W、v=10 mm/s、D=3 mm制备的熔覆层硬度为972(HV0.2),是基材显微硬度的4倍;摩擦系数和磨损失重明显低于基体,磨损形式为磨粒磨损和疲劳磨损结合。熔覆活塞杆精加工后进行着色探伤无明显裂纹等缺陷,进行10000次机械寿命试验后尺寸符合图纸要求,表面粗糙度良好。采用激光熔覆复合涂层能够提高活塞杆的耐磨性,替代电镀铬进行表面防护。