The effectiveness of different wear indicators in quantifying wear on railway wheels of freight wagons

Railway infrastructure relies on the dynamic interaction between wheels and rails;thus,assessing wheel wear is a critical aspect of maintenance and safety.This paper focuses on the wheel-rail wear indicator T-gamma(Tγ).Amidst its use,it becomes apparent that Tγ,while valuable,fails to provide a comprehensive reflection of the actual material removal and actual contact format,which means that using only Tγas a target for optimization of profiles is not ideal.In this work,three different freight wagons are evaluated:a meter-gauge and a broad-gauge heavy haul vehicles from South American railways,and a standard-gauge freight vehicle operated in Europe,with different axle loads and dissimilar new wheel/rail profiles.These vehicles are subjected to comprehensive multibody simulations on various tracks.The simulations aimed to elucidate the intricate relationship between different wear indicators:Tγ,wear index,material removal,and maximum wear depth,under diverse curves,non-compensated lateral accelerations(A_(nc)),and speeds.Some findings showed a correlation of 0.96 between Tγand wear depth and 0.82 between wear index and material removed for the outer wheel.From the results,the Tγis better than the wear index to be used when analyzing wear depth while the wear index is more suited to foresee the material lost.The results also show the low influence of A_(nc)on wear index and Tγ.By considering these factors together,the study aims to improve the understanding of wheel-rail wear by selecting the best wear analysis approaches based on the effectiveness of each parameter.

DEM Numerical Simulation of Abrasive Wear Characteristics of a Bioinspired Ridged Surface

This paper presents numerical investigations into a ridged surface whose design is inspired by the geometry of a Farrer’sscallop.The objective of the performed research is to assess if the proposed Bioinspired Ridged Surface (BRS) can potentiallyimprove wear resistance of soil-engaging components used in agricultural machinery and to validate numerical simulationsperformed using software based on the Discrete Element Method (DEM).The wear performance of the BRS is experimentallydetermined and also compared with a conventional flat surface.Different size of soil particles and relative velocities between theabrasive sand and the testing surfaces are used.Comparative results show that the numerical simulations are in agreement withthe experimental results and support the hypothesis that abrasive wear is greatly reduced by substituting a conventional flatsurface with the BRS.

Simulation of wheel and rail profile wear:a review of numerical models

The development of numerical models able to compute the wheel and rail profile wear is essential to improve the scheduling of maintenance operations required to restore the original profile shapes.This work surveys the main numerical models in the literature for the evaluation of the uniform wear of wheel and rail profiles.The standard structure of these tools includes a multibody simulation of the wheel-track coupled dynamics and a wear module implementing an experimental wear law.Therefore,the models are classified according to the strategy adopted for the worn profile update,ranging from models performing a single computation to models based on an online communication between the dynamic and wear modules.Nevertheless,the most common strategy nowadays relies on an iteration of dynamic simulations in which the profiles are left unchanged,with co-simulation techniques often adopted to increase the computational performances.Work is still needed to improve the accuracy of the current models.New experimental campaigns should be carried out to obtain refined wear coefficients and models,while strategies for the evaluation of both longitudinal and transversal wear,also considering the effects of tread braking,should be implemented to obtain accurate damage models.

Erosion wear at the bend of pipe during tailings slurry transportation:Numerical study considering inlet velocity,particle size and bend angle

Pipeline hydraulic transport is a highly efficient and low energy-consumption method for transporting solids and is commonly used for tailing slurry transport in the mining industry.Erosion wear(EW)remains the main cause of failure in tailings slurry pipeline systems,particularly at bends.EW is a complex phenomenon influenced by numerous factors,but research in this area has been limited.This study performs numerical simulations of slurry transport at the bend by combining computational fluid dynamics and fluid particle tracking using a wear model.Based on the validation of the feasibility of the model,this work focuses on the effects of coupled inlet velocity(IV)ranging from 1.5 to 3.0 m·s^(-1),particle size(PS)ranging from 50 to 650μm,and bend angle(BA)ranging from 45°to 90°on EW at the bend in terms of particle kinetic energy and incidence angle.The results show that the maximum EW rate of the slurry at the bend increases exponentially with IV and PS and first increases and then decreases with the increase in BA with the inflection point at 60°within these parameter ranges.Further comprehensive analysis reveals that the sensitivity level of the three factors to the maximum EW rate is PS>IV>BA,and when IV is 3.0 m/s,PS is 650μm,and BA is 60°,the bend EW is the most severe,and the maximum EW rate is 5.68×10^(-6)kg·m^(-2)·s^(-1).In addition,When PS is below or equal to 450μm,the maximum EW position is mainly at the outlet of the bend.When PS is greater than 450μm,the maximum EW position shifts toward the center of the bend with the increase in BA.Therefore,EW at the bend can be reduced in practice by reducing IV as much as possible and using small particles.

Application of simulated annealing algorithm to improve work roll wear model in plate mills

Employing Simulated Annealing Algorithm (SAA) and many measured data, acalculation model of work roll wear was built in the 2 800 mm 4-high mill of Wuhan Iron and Steel(Group) Co. (WISCO). The model was a semi-theory practical formula. Its pattern and magnitude werestill hardly defined with classical optimization methods. But the problem could be resolved by SAA.It was pretty high precision to predict the values for the wear profiles of work roll in a rollingunit. After one-year application, the results show that the model is feasible in engineering, and itcan be applied to predict the wear profiles of work roll in other mills.

Atomistic simulations on adhesive contact of single crystal Cu and wear behavior of Cu-Zn alloy

Atomistic simulations are carried out to investigate the nano-indentation of single crystal Cu and the sliding of the Cu-Zn alloy.As the contact zone is extended due to adhesive interaction between the contact atoms,the contact area on a nanoscale is redefined.A comparison of contact area and contact force between molecular dynamics(MD)and contact theory based on Greenwood-Williamson(GW)model is made.Lower roughness causes the adhesive interaction to weaken,showing the better consistency between the calculated results by MD and those from the theoretical model.The simulations of the sliding show that the substrate wear decreases with the mol%of Zn increasing,due to the fact that the diffusion movements of Zn atoms in substrate are blocked during the sliding because of the hexagonal close packed(hcp)structure of Zn.

Numerical simulation of temperature field in laser-arc hybrid welding of wear-resistant steel

Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-flux- attenuation function, a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300TP wear-resistant steel is proposed. The proposed model considers convection, radiation, molten pool flow, and heat conduction effect on temperature. A comparison of the simulation and actual welding test results confirms the reliability of the model. This welding heat-process model can provide the cooling rate at any position in the heat affected zone （HAZ） and can be used as a reference for the analysis of material properties and for process optimization.

基于骨料运移的高浓度充填管道磨损机制

高浓度充填管道磨损威胁矿山安全,但磨损机制尚不明析。采用CFD-DEM模拟高浓度充填管道磨蚀、骨料运移、骨料与管壁接触,结合理论分析和现场实测揭示管道磨损机制。结果表明:料浆承载力充足时,固液两相在管内呈柱塞流,骨料向管道中心运移,管壁处形成减磨滑移层,管道四周磨损较均匀;反之,骨料在管底呈滑动床,管底磨损最严重。滑动床对管壁的作用力是柱塞流时的2.46~2.76倍,管底磨损是柱塞流时的1.48倍。骨料在管壁附近的运动轨迹类似波形线,以小角度接触管壁并滑滚,对管壁的切向力是法向力的27.44~30.84倍,管壁磨损受骨料切向刮擦主导。非稳态输送、粗糙管壁和过高浓度会劣化滑移层的减磨效果。根据模拟结果提出六条磨损防控措施,可供相关矿山借鉴。

实测轮轨蠕滑曲线对钢轨磨耗影响分析

轮轨蠕滑曲线会影响轮轨动态相互作用,进而影响钢轨磨耗,为研究实测轮轨蠕滑曲线对钢轨磨耗的影响,首先,基于最小二乘法获得适用于Polach模型和修改FASTSIM算法的参数,模拟40~400 km/h行车速度范围内的实测蠕滑曲线;随后,在SIMPACK软件中建立车辆系统动力学模型,并通过Polach模型测得实测蠕滑曲线;最后,采用Kik-Piotrowski模型和修改的FASTSIM算法进行轮轨非赫兹滚动接触计算,并结合USFD磨耗模型预测钢轨磨耗,对比了理想与实测蠕滑曲线条件下钢轨磨耗的差异.研究表明:理想蠕滑曲线条件下钢轨磨耗深度明显大于实测蠕滑曲线下的结果,随着车辆通过次数的增加,理想条件下钢轨磨耗分布范围更大,内外轨磨耗分布范围分别为实测蠕滑曲线的1.5倍和1.3倍;摩擦系数和磨耗率显著影响钢轨磨耗大小及磨耗分布情况,故在车辆动力学仿真和钢轨磨耗计算中有必要考虑实测轮轨蠕滑曲线;形成了确定实测蠕滑曲线参数的前处理程序,可服务于车辆动力学仿真和钢轨磨耗计算,可以有效指导现场进行钢轨打磨等养护维修工作.

复合纳米自润滑金刚石砂轮磨削SiC陶瓷的试验研究

提出一种复合纳米自润滑金刚石砂轮的制备方法,并对制备的砂轮进行SiC陶瓷的磨削试验,分析砂轮表面不同质量分数的复合纳米颗粒对磨削性能的影响。使用MoS2、TiO2纳米颗粒作为自润滑砂轮基底的填充材料,采用复合纳米自润滑金刚石砂轮和传统金刚石砂轮进行磨削对比试验,研究复合纳米自润滑金刚石砂轮的润滑机制。研究结果表明,复合纳米自润滑金刚石砂轮自释放的纳米颗粒有效地参与了磨削区间的润滑,砂轮的法相力、切向力降低,提升了工件表面质量。在磨削深度为2~8μm内,复合纳米自润滑金刚石砂轮的具体表现为法向磨削力降低18.6%~38.7%、切向磨削力降低11.2%~28.6%,工件表面粗糙度降低13.9%~41.5%。根据本试验所得数据,当砂轮表面复合纳米颗粒质量分数为8%时,润滑性能和工件表面质量最佳。

基于CFD-DPM模型的高浓度矿浆输送90°弯管冲蚀磨损特性研究

在工况条件较为复杂的矿浆输送管道中,造成管道失效的主要原因是冲蚀磨损。管道中的冲蚀主要发生在典型弯管、变径管等流向或结构发生变化的位置。本文基于CFD-DPM耦合模型,模拟研究了复杂工况下液固两相流中的固体颗粒粒径、矿浆流速、矿浆浓度对某选矿厂矿浆输送管道的90°弯管冲蚀磨损的影响。结果表明:弯管的冲蚀磨损最为严重,90°弯管处的冲蚀磨损速率与矿浆浓度呈线性关系;流速达到5 m/s时90°弯管处的冲蚀磨损速率变化幅度较大;粒径在0.0374~0.0750 mm范围时,90°弯管处的冲蚀磨损速率无明显变化,粒径达到0.150 mm后90°弯管处的冲蚀磨损速率变化幅度较大。研究结果可实现矿浆输送管道冲蚀磨损区域和磨损速率的有效评估,为管道安全运维和寿命预测提供技术依据。

基于EDEM的砂卵石地层盾构刀具磨损特征研究

为揭示砂卵石地层土压平衡盾构典型刀具的磨损特征,指导该地层中盾构刀具的设计、布置等关键问题。采用室内三轴试验及数值离散元软件(EDEM)仿真分析,标定了颗粒-刀具磨损接触参数。依托北京新机场“磁各庄-1号风井”砂卵石盾构工程,构建了砂卵石地层EDEM数值盾构模型,可视化了砂卵石地层土压平衡盾构中典型刀具(楔犁刀、刮刀)的磨损特征,通过实际工程对模型进行了验证。研究表明:(1)以犁松原状砂卵石土为目的的楔犁刀具是掘进主切削刀具,表现为刀头合金表面以及刃角处连续的摩擦磨损形式,磨损量较大;(2)以剥落输排为目的刮刀主要表现为刀身迎土面以及刀头合金表面随机的点蚀磨损,磨损量较小;(3)刀盘径向刀具的磨损量随轨迹半径及刀体高度的增加而增大,同轨迹上高刀的磨损系数高于低刀,高刀对低刀的磨损有保护作用;刀盘径向刀具和环向刀具的“梯次化”布置可延长盾构单次连续掘进距离。

电连接器高温振动失效仿真研究

应用Ansys软件对电连接器整体模型在高温振动环境下的动态响应进行仿真,深入分析接触件尾部线缆质量、温度、分离力、应力松弛等指标对微动幅值的影响。基于仿真得出原设计在高温振动中会发生失效的结论,优化设计接触正压力和尾部线缆质量。结合仿真分析结果和计算,得到电连接器在指定高温振动条件下不发生失效的设计指标范围,即分离力应尽量接近上限值2.5 N,每个接触件尾部线缆质量应尽量控制在1.2 g以内。通过试验验证了仿真和优化的正确性,研究结果可为电连接器抗高温振动提供设计与优化思路。

基于DPM模型的变径管冲蚀磨损分析与结构改进

针对变径管冲蚀失效的问题,基于DPM模型、Realizeble k-ε模型和颗粒磨损方程对变径管进行数值模拟计算,分析流速、颗粒直径、质量流量、过渡倾角、改进后过渡圆角对变径管的冲蚀磨损规律和改进后变径管的性能。结果表明:过渡段与小径管相贯处冲蚀磨损最为严重;随流速、质量流量的增大和颗粒直径的减小,最大冲蚀速率逐渐增大,其中受流速的影响最大。过渡倾角由5°增加至35°,最大冲蚀速率在9.32×10^(-5) kg/(m^(2)·s)上下波动;由35°增加至85°,最大冲蚀速率整体上升、后大幅度下降;80°~85°时,最大冲蚀速率较小且受各因素的影响很小,尤其等于85°时,其最大冲蚀速率降低了23.5倍。结构改进后过渡圆角7.5~15 mm变径管的最大冲蚀速率小于改进前变径管,且冲蚀分布比较均匀;随过渡倾角的增大,结构改进后过渡圆角2.5~15 mm变径管与改进前变径管相比,管内最大压力相差逐渐减小,且改进后管内最大压力及应力均低于改进前变径管,管内压力最大降低了2.25倍。该结果可为实际作业中变径管的选用及结构设计与优化提供参考。

表面圆形凹坑微织构对DC53模具钢的摩擦学性能影响

为了探究微织构对DC53冷作模具钢表面摩擦学性能的影响,基于有限元法研究了模具钢表面圆形凹坑微织构的最优深度,采用飞秒激光加工了不同面密度的圆形凹坑微织构模具钢试样,并通过开展摩擦磨损实验研究了不同润滑状态下面密度对模具钢摩擦学性能的影响规律。结果表明,DC53冷作模具钢表面的圆形凹坑微织构在直径为Φ140μm,织构深度为50μm时表现出最大油膜承载力与最小摩擦因数;随着圆形凹坑微织构面密度的增加,充分润滑时模具钢表面的摩擦因数先减小后增大,面密度为20%时平均摩擦因数最小,相较于无织构模具钢降低了51.35%;少油润滑与干摩擦时,模具钢表面摩擦因数随着面密度的增加逐渐降低;面密度为30%时,模具钢表面平均摩擦因数最小,较无织构模具钢分别降低了35.84%与15.02%。微织构的存在提升了模具钢表面不同润滑状态下的减摩性能;充分润滑时效果最好,干摩擦时也明显改善了模具钢表面的黏着磨损。

仿生扇贝花生挖掘铲的设计与试验

农机挖掘部件作为重要的耐磨部件,其耐磨性能的好坏关系到收获机械的使用寿命及能耗的高低。在挖掘部件的结构优化设计中,仿生学在提高农机挖掘部件性能上提供了新的设计思路。为此,通过扇贝壳轮廓曲线拟合,研制出一种仿生扇贝挖掘铲。基于EDEM仿真软件,对仿生挖掘铲和普通挖掘铲进行运动仿真分析,结果表明:在0.4、0.6、0.8m/s 3种不同运动速度下,仿生挖掘铲受力明显小于普通挖掘铲,其减阻性能较普通挖掘铲可提高5%~7%;对比两种挖掘铲造成的土壤颗粒运动变化,仿生挖掘铲对土壤颗粒的速度变化影响较小,分布更为均匀。

Ni含量对CrN涂层抗磨蚀性能的影响研究

目的探究在模拟海洋环境下,Ni的掺入对CrN涂层耐磨性能的影响,研究不同Ni含量的CrNiN涂层的磨蚀行为。方法采用磁控溅射方法对CrNiN涂层中的Ni含量进行调控,制备CrN涂层、Ni掺杂含量分别为15.85%(原子数分数)和39.06%的CrNiN涂层。通过干摩擦试验和模拟海水磨蚀试验,对3种涂层的力学性能和磨蚀行为进行研究对比,并分析其摩擦损伤机理。结果在干摩擦试验条件下,CrNiN涂层的摩擦学性能主要由涂层的力学性能决定,Ni原子数分数为15.85%的CrNiN涂层兼具高硬度和良好韧性,磨痕最浅,其磨损率在3种涂层中最低,为9.1×10^(-7)mm^(3)/(N·m),而在模拟海洋磨蚀的开路电位(OCP)下,Ni原子数分数为15.85%的CrNiN涂层的磨损率大于CrN涂层,CrN涂层具有最低的摩擦因数以及最低的磨损率。3种涂层在正电位(+0.6 V)时的磨损率显著大于开路电位(OCP)下的磨损率,说明腐蚀降低了涂层的耐磨性。通过对腐蚀产物进行分析,表明CrN的腐蚀产物主要是CrO_(2)以及Cr_(2)O_(3),具有一定的润滑作用,而含Ni的CrNiN涂层在腐蚀过程中产生了NiO,对涂层的耐磨性产生了不利影响。结论在干摩擦试验条件下,CrNiN涂层的摩擦学性能主要由涂层的力学性能决定,Ni原子数分数为15.85%的CrNiN涂层兼具高硬度和良好韧性,从而更耐磨。在模拟海洋磨蚀试验条件下,CrNiN涂层的腐蚀产物严重影响其磨蚀性能。

考虑间隙的起落架收放机构运动精度可靠性分析

随着飞机起落架收放机构的复杂度不断提升,多关节间隙耦合对机构运动精度的影响更加显著。复杂机构的运动精度可靠性问题呈现出非线性程度高、影响参数多、样本量少的特点,研究难度极大。针对该问题,提出了一种结合理论分析、动力学联合仿真以及间隙磨损的机构运动精度可靠性分析方法。首先,建立考虑7处关节间隙的收放机构动力学模型,研究各关节间隙对机构收放精度的独立影响及耦合影响。然后,建立关节磨损量随收放次数增加的分析模型,获取间隙的变化规律,进而建立收放机构运动精度随收放次数变化的可靠性分析模型。最后,基于自适应Kriging代理模型对起落架收放机构的可靠性进行分析,给出可靠性随机构收放次数的变化规律。研究结果表明,各处结构间隙对机构收放运动精度都有不同程度的影响,机构失效概率呈现先平稳后急剧上升的趋势。所提方法为起落架复杂机构运动可靠性评估提供重要的分析手段。

出砂油井潜油电泵叶轮结构优化

潜油电泵应用于出砂油井时,砂粒对离心泵叶轮磨损严重,导致增压性能降低,甚至机组失效。为了明确叶轮磨损规律,优化叶轮结构参数,开展了含砂条件叶轮磨损特性仿真分析。建立了全尺寸离心泵几何模型,利用六面体结构化网格进行网格划分,基于CFD数值模拟技术,优选RNG k-ε湍流模型和离散相模型模拟固-液两相流场,以冲蚀磨损率为评价指标,通过SIMPLEC算法进行求解。实验采用正交设计方法,解决多因素敏感分析的交互影响。结果表明:出口宽度对叶轮磨损影响最大,叶包角、入口宽度和叶片数次之,出口宽度越大,冲蚀磨损率越小。最优叶轮结构参数为出口宽度21.1 mm、叶包角90°、叶片数10、入口宽度13.6 mm,相比于原泵型叶轮结构,新叶轮几何形态更发散。研究成果对同类油井泵型选择提供了参考依据,也为潜油电泵制造商开展防砂优化设计提供了理论支撑。

高压隔膜泵单向阀阀隙流场的冲蚀磨损特性分析

目的探究高压隔膜泵单向阀阀隙流场冲蚀磨损产生的原因及主要影响因素。方法基于固液两相流基本理论和冲蚀模型,考虑颗粒保护效应及磨蚀效应,采用计算流体力学(CFD)方法模拟单向阀阀隙流场的冲蚀磨损行为,探究矿粉颗粒体积分数、颗粒粒径、单向阀半锥角、胶垫突出高度等参数对单向阀冲蚀磨损特性的影响。结果矿粉颗粒紧贴阀芯壁面的剪切运动是造成阀芯发生冲蚀磨损失效的主要原因。当矿粉的体积分数由0.1增大到0.5时,由冲蚀造成的最大冲蚀磨损速率随之减小,由磨蚀造成的平均冲蚀磨损速率随之增大。当矿粉粒径为0.025~0.048 mm时,随着矿粉粒径的增大,平均冲蚀磨损速率随之增大。当矿粉粒径超过0.048 mm时,平均冲蚀磨损速率逐渐减小。当单向阀半锥角由30°增大到45°时,阀隙流场的最大流速由12.23 m/s减小至9.19 m/s,矿粉颗粒对阀芯壁面的最大冲蚀磨损速率减小了41.16%。阀隙流场的最大流速和冲蚀磨损速率随着胶垫突出高度h的增大而增大,同时位置也发生了相应变化。结论矿粉颗粒体积分数的增加会加重粒子对阀芯壁面的损伤程度,随着粒径的增加,泵阀的最大冲蚀磨损速率先增大后减小,增大半锥角可以缓解颗粒对壁面的冲蚀磨损,增大胶垫突出高度会导致冲蚀磨损区域逐渐向胶垫突出位置集中。