Wet and Dry Tribological Behaviors of Circular Islandic Protrusion Patterns on M2 Steel Discs under Spinning Condition

Under spinning conditions, lubricant on islandic spot patterned M2 steel disc experiences centrifugal and tangential force components. Depending upon the relative position of the spots and the flow of lubricant, accumulation of lubricant in front of patterned islandic spots creates thrusting to mating part and subsequently reduces contact between the mating couple. Whilst wear debris is likely to be spun off the plateau of the spots to their neighbouring valleys so as to reduce wear. Hence, it gives favorable tribological characteristics. Aiming at verifying such mechanisms, studies were performed on M2 steel disc specimens slid with ASSAB 17 tool steel pin. The M2 steel disc specimens were respectively （i） machined with non-patterned （NP）, （ii） etched to produce in-lined （INE） islandic patterns, and （iii） etched to produce staggered （STE） islandic spot patterns. Results indicated that the INE patterned discs gave most favorable wear characteristics, the NP of the worse characteristics whilst the STE ranged in the middle. However, the actual contact mechanism leads to the descending sequence of favorable friction behaviors nominally as： NP, INE and STE.

Shaking table test and numerical analysis of a 1:12 scale model of a special concentrically braced steel frame with pinned connections

This paper describes shaking table tests of a 1：12 scale model of a special concentrically braced steel frame with pinned connections, which was fabricated according to a one-bay braced frame selected from a typical main factory building of a large thermal power plant. In order to investigate the seismic performance of this type of structure, several ground motion accelerations with different levels for seismic intensity Ⅷ, based on the Chinese Code for Seismic Design of Buildings, were selected to excite the model. The results show that the design methods of the members and the connections are adequate and that the structural system will perform well in regions of high seismicity. In addition to the tests, numerical simulations were also conducted and the results showed good agreement with the test results. Thus, the numerical model is shown to be accurate and the beam element can be used to model this structural system.

Grain growth simulation with the second phase particle pinning for heat-affected zone of microalloyed steel welds

The second phase particle dispersed in microalloyed steel has different effects on grain growth depending on their size and volume fiaction of the second phase particles which will change during welding thermal cycles. The particle coarsening and dissolution kinetics model was analyzed for continuous heating and cooling. In addition, based on experimental data, the coupled equation of grain growth was established by introducing limited size of grain growth with the consideration of the second phase particles pinning effects. Using Monte Carlo method based on experimental data model, the grain growth simulation for heat-affected zone of microalloyed steel welds was achieved. The calculating results were well in agreement with that of experiments.

农用柴油机钢活塞销孔-销的摩擦副润滑特性分析

为解决钢活塞销孔-销摩擦副因同种材料摩擦配副问题以及钢材密度大和导热性能差所带来的润滑特性差的问题,该研究以D25TCIF农用柴油机钢活塞为对象,建立钢活塞连杆组传热模型和热弹性流体动力学模型,并开展钢活塞温度场测试试验与仿真验证。结合单因素扫值法和Box-Behnken多因素优化算法分析了销孔轴承间隙、销孔表面粗糙度和销孔指数型线内外半径增量变化对销孔轴承润滑特性的影响。结果表明:销孔结构对轴承的润滑特性有很大影响,销孔指数型线内半径增量的影响最大,而外半径增量的影响较小。最优参数组合为销孔轴承间隙0.021 mm、销孔表面粗糙度0.798μm、销孔指数型线内半径增量0.008 mm、销孔指数型线外半径增量0.010 mm,此时预测的最小油膜厚度为0.979μm;最大粗糙接触压力为249.406 MPa,与该方案下仿真值的相对误差小于5%。该研究优化方法效果好,且预测准确,可为后续的钢活塞销孔结构设计提供理论依据。

应急钢桁梁桥钢销节点疲劳性能分析

应急钢桁梁作为拼装式结构,反复安拆及倒运过程中可能导致销孔连接位置出现损伤,对其使用寿命产生影响。以某128 m跨应急钢桁梁桥为研究对象,缩短销孔边距,模拟钢桁梁销孔损伤影响,开展疲劳性能试验及仿真模拟,研究钢销节点疲劳性能。结果表明,静力仿真结果与疲劳试验结果具有较好的一致性,验证了模型的可靠性;试验钢销节点损伤后的疲劳寿命仅为16980次,FE-SAFE仿真分析求得疲劳寿命为20592次,两者较为接近,进一步验证了疲劳试验结果的可靠性。考虑销孔损伤的疲劳寿命与正常状态相比差异显著,说明销孔损伤会大幅降低其疲劳寿命。因此应注意应急钢桁梁杆件保护,同时加强钢销节点质量控制。

梁端铰接钢管混凝土框架-核心筒结构的减震研究

梁端铰接钢管混凝土框架-核心筒结构很好地解决了传统双重抗侧体系由于节点焊接而带来的系列问题,但不可避免地对结构抗震性能产生影响,因此,亟需针对此类结构的消能减震研究。本文以30层梁端铰接的钢管混凝土柱-混凝土核心筒结构为研究对象,通过引入不同构造形式的消能黏滞阻尼伸臂形成减震层,利用OpenSees有限元软件对结构进行弹塑性时程分析,优选出最佳构造形式,并据此对比设置一道及两道减震层时,结构在罕遇地震下减震性能及黏滞阻尼器的阻尼系数和速度指数变化对设置一道减震层结构抗震性能的影响分析。研究结果表明:竖向斜撑型减震层对结构顶点位移、层间位移角、基底剪力的控制效果及自身的耗能效果最佳,而两道减震层结构的综合性能要略优于一道减震层结构,但一道减震层结构对减震层位置变化更敏感,且当减震层位于结构1/3 H层高时减震效果最佳;阻尼系数与速度指数过大或过小均会对结构产生不利影响,而速度指数能有效降低结构的层间位移角,但应注意所带来的位移突变和基底剪力增大问题。

Role of coatings and materials of external fixation pins on the rates of pin tract infection:A systematic review and meta-analysis

BACKGROUND Infection at the pin tract is a frequent and feared complication of external fixators(EF).The type of pin material and coatings have been regarded as possibly influencing infection rates.Over the last 20 years,few prospective clinical studies and systematic reviews addressed the role of coated pins on the rate of pin site infection in human clinical studies.AIM To assess the EF literature over the past 20 years on the clinical benefits of pins manufactured from varied materials and coating systems and their possible role in pin tract infection rates.METHODS We performed a systematic review according to the PRISMA and PICOS guidelines using four scientific platforms:PubMed,LiLacs,SciELO,and Cochrane.We searched the literature for related publications over the past 20 years.RESULTS A literature search yielded 29 articles,among which seven met the inclusion criteria.These studies compared stainless-steel pins and pins coated with hydroxyapatite(HA),titanium and silver.The pin tract infection definitions were arbitrary and not standardized among studies.Most studies included a low number of patients in the analysis and used a short follow-up time.Three metaanalyses were carried out,comparing stainless steel vs silver pins,stainless steel vs HA-coated pins,and titanium vs HA-coated pins.None of this analysis resulted in statistically significant differences in pin tract infection rates.CONCLUSION Currently,no clinical evidence supports the advantage of EF pins manufactured with materials other than stainless steel or coated over uncoated pins in reducing the rates of pin tract infections.A standardized definition of pin tract infection in external fixation is still lacking.

广厦大学图书馆钢桁架悬挂体系结构设计

广厦大学图书馆采用钢筋混凝土框架-剪力墙结构体系,为满足建筑功能要求,在屋顶设置悬臂钢桁架,悬臂钢桁架端部设置钢吊柱,吊柱与各层楼面钢梁相连,形成悬挂体系。采用YJK和MIDAS Gen软件,对比分析了小震作用及风荷载作用下结构的内力弹性响应、静力弹塑性分析。考虑钢桁架上下弦楼板协同作用,并指定施工顺序进行施工模拟分析,采用ANSYS有限元分析软件对销轴节点进行验算。结果表明:大震作用下,结构具有较高的承载力和较好的延性,结构具有安全性和合理性;销轴节点具有良好的受力性能,应力水平均符合要求;悬挑位置采用钢-混凝土组合楼盖可以缩短工期,提高建筑装配率。

应急抢修钢桁梁动力响应销孔间隙影响分析

以某128 m跨新型应急抢修钢桁梁为对象,利用ANSYS与UM联合开展车桥耦合分析,选取销孔间隙和钢销直径为关键参数,探究支点存在高差时销孔间隙对钢桁梁结构及车辆响应的影响规律。研究表明:钢桁梁存在支点主桁高差或对角高差,在钢销直径恒定时,钢桁梁和车辆响应均随间隙增大而增大;在销孔间隙恒定时,钢桁梁和车辆响应均随直径增大而降低。相较于主桁高差,当存在对角高差时,销孔间隙对钢桁梁动力响应显著,而对车辆响应影响较小。此外,相较于钢桁梁竖向动力响应,销孔间隙对于横向水平动力响应的影响更为显著,设计与工程应用中应重点关注。

The effect of V-Nb on the growth of austenite grains in 17CrNiMo6 gear steel

This study researches the effect of V-Nb on the growth of austenite grains in 17CrNiMo6 carburized gear steel. Results show that the carbonitride in V and Nb acts as second-phase particles in the steel, which can be used to block the migration of grain boundaries and the thinning of the austenite grains. This causes the crystals in the V-Nb microalloy 17CrNiMo6 steel to coarsen and the temperature to rise, thus reducing the cost of the carbonization that follows processing on the gears.

基于加权Pin-SVM的钢板表面缺陷分类

针对带钢表面缺陷分类问题,提出了一种加权Pin-SVM(WPin-SVM-n)模型。WPin-SVM-n是在Pin-SVM的基础上,结合权重生成算法来解决分类问题。WPin-SVM-n利用Pinball损失函数实现了特征噪声不敏感特性。此外,WPin-SVM-n又引入了样本的权重,实现了标签噪声不敏感特性。另一方面,将WPin-SVM-n与二叉树相结合,解决了钢板表面缺陷的多类分类问题。最后,对六种带钢表面缺陷进行了试验研究。实验结果表明,多类WPin-SVM-n分类器(WPin-SVMs)在分类精度方面取得了令人满意的结果。

万吨米级塔式起重机附墙预埋件方案比选及工艺研究

针对万吨米级塔式起重机附墙预埋件荷载大、附着空间有限的难点,选取代表性预埋件进行比选设计。系统性介绍了锚筋式、爬锥式、盒子式及销棒式4种预埋件的设计计算方法,综合对比了4种预埋件方案的受力特性及优劣,给出了各自的适用条件,选取了万吨米级塔式起重机附墙预埋件的最优方案,并针对该方案进行了施工工艺研究,从施工全流程介绍了销棒式预埋件的工艺要求,同时给出了强风工况下的应对措施。该预埋件的比选设计很好地解决了大吨位塔式起重机附墙预埋件的设计难题。

青浦题学平和学校综合馆结构设计

青浦题学平和学校综合馆由游泳馆和篮球馆组成,下部两层采用钢框架结构,上部屋盖采用格构柱-空间管桁架屋盖体系。对屋盖抗侧力体系及截面选取、格构柱与下部结构连接方式等关键技术进行研究。采用SAP2000软件分别建立屋盖单体模型和结构整体模型,并对两种模型在水平和竖向荷载作用下屋盖的内力和变形进行分析比较;同时针对本项目的受力特点,对屋盖整体稳定及关键节点应力等进行多方面的分析。分析结果表明:关键构件应力比不应大于0.85,屋盖其他构件应力比不大于0.90,屋盖在竖向荷载下挠度及风荷载、地震作用下的位移均满足规范要求,屋盖结构体系安全可行,节点连接可靠,现行的设计能够满足设计目标。

装配式内隔墙板设计与安装的质量控制

我国装配式建筑已经具有一定的规模,但专用于内隔墙的装配式隔墙仍处在研究状态,更未得到人们的普遍认可,其主要原因是装配式内隔墙的成本过高,最关键的还是质量问题,而质量问题主要聚焦在装配式隔墙本体的设计、安装、与结构的有效连接和相邻板缝的处理不合理。笔者单位研发的“装配式坚固类废弃物再生复合轻型隔墙板”就装配式内隔墙的设计与结构的连接和相邻板缝的处理等质量控制方法等,解决了相应问题,现作以介绍,供同行参考。

炮钢销和黄铜盘配副时的摩擦磨损特性研究

在周期性瞬态热载荷和瞬态压力载荷耦合下,机炮弹膛系统中炮弹膛线和炮弹弹头产生的严重磨损会影响弹膛的使用寿命和弹头的命中精度。为研究压力对炮弹膛线和炮弹弹头两者摩擦磨损特性的影响,分别使用炮钢和黄铜加工制作成的销和盘在立式万能摩擦磨损试验机上开展摩擦磨损特性的影响因素实验研究,得到了不同压力下炮钢销和黄铜盘的摩擦系数和摩擦力矩、磨损量、磨面形貌的变化关系。推断表明:摩擦初期,试验力不同,摩擦系数也不同,稳定磨合期,试验力对摩擦系数影响减弱;摩擦力矩与摩擦系数变化基本符合比例关系,增大试验力,摩擦力矩成比例增大;炮钢销和黄铜盘的磨损为粘着磨损,压力越大,磨损量越大。该研究对下一步开展机炮弹膛系统摩擦磨损机理研究具有参考意义。

某定位销断裂失效分析

由40Cr钢制成的定位销在工作过程中多次突然断裂,基于此,文章分析了定位销的化学成分、显微组织、断口形貌等。结果表明,此次断裂为氢致延迟断裂,主要是由于原材料内存在D类非金属夹杂物,同时表面淬火后产生内应力,后续生产过程中的酸洗及电镀工艺致使定位销吸氢,最终在交变应力的作用下发生断裂。改善原材料的冶金质量,表面淬火后增加去应力退火工艺,电镀后增加除氢工序,可有效解决该断裂问题。

改进型钢包加揭盖装置的应用实践

针对原有钢包加揭盖装置在大包浇余或修包过程中易产生铰座销轴积渣而造成钢包盖脱落、铰钩变形或断裂等问题,创新设计出一种改进型钢包加揭盖装置。通过在原有基础上增加横移装置,实现了钢包加揭盖挂钩的南北横向移动;对加揭盖装置中挂钩、导向轮进行改进,减少了铰钩变形、断裂问题的出现,有效提高了钢包加盖率。

考虑局部挤压的盖梁不落地支架牛腿受力分析

后插梢棒式剪力销-分配梁是目前常用的盖梁模板不落地支架结构体系,目前该不落地支架结构体系的受力分析中常将各构件之间视为密贴接触,忽略了牛腿预留孔与后插钢梢棒之间因施工可行性而采用的不等径设计,以及该设计将导致的不等径圆弧面局部挤压接触问题。采用三维有限元分析了不同施工荷载条件下不落地支架牛腿与钢梢棒的局部接触界面和内力分布,并针对整体和局部强度不足的问题提出结构补强建议。

一种模拟热成形工况的高温摩擦试验机的设计及探讨

销-盘摩擦试验机是摩擦学领域的标准摩擦实验设备,但是面对热成形过程中的摩擦过程,销-盘摩擦试验机中的往复摩擦引起磨屑在轨道内快速堆积,与热成形实际工况并不一致。提出一种新的高温滑移摩擦试验机设计方案,该方案控制模具钢销在板料滑条上单向长距离滑移,用以实现对连续热成形摩擦过程的模拟。通过分析销-盘摩擦试验机和高温滑移摩擦试验机的实验结果,发现后者的实验过程更接近热成形的实际工况,利于展开对摩擦磨损机制的定性定量分析。

招商银行总部大厦核心筒偏置超高层结构设计与关键技术研究

招商银行总部大厦是一栋387m高的超高层建筑,采用框架-偏心筒-环带桁架-伸臂桁架结构体系,核心筒偏置于建筑北侧,设5个伸臂桁架加强层。采用合理设计核心筒剪力墙厚度、增设环带桁架等措施,减小了核心筒偏置对结构的不利影响。在伸臂桁架中通过设置屈曲约束支撑(BRB),提高了整体结构的抗震性能。利用屋顶水箱设置调谐液体阻尼器(TLD),减轻了结构风振效应。大跨楼盖跨中增设钢次梁,减小了楼盖人致振动加速度。同时展开了结构整体稳定性、墙体受拉应力控制、长期荷载下的水平位移控制等多项研究,确保了该核心筒偏置的超高层结构的安全,所采取的设计方法和措施可供同类工程参考。