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关键词： Mechanical design   Stress recovery   Contact mechanics   Friction damping   Harmonic balance method   Cyclic symmetry  

摘要： Nonlinear forced response analyses of mechanical systems in the presence of contact interfaces are usually performed in built-in numerical codes on reduced order models (ROM). Most of the cases these derive from complex finite element (FE) models, resulting from the high accuracy the designers require in modeling and meshing the components in commercial FE software. In the technical literature several numerical methods are proposed for the identification of the nonlinear forced response in terms of a kinematic quantity (i.e. displacement, velocity and acceleration) associated either to the master degrees-of-freedom retained in the ROM, or to the slave ones after having expanded the reduced response through the reduction matrix. In fact, the displacement is the quantity usually adopted to monitor the nonlinear response, and to evaluate the effectiveness of a partially loose friction interface in damping vibrations, with respect to a linear case where no friction interfaces exist and no energy dissipation can take place. However, when a ROM is used the engineering quantities directly involved in the mechanical design, i.e. the strains and stresses, cannot be retrieved without a further data processing. Moreover, in the case of a strong nonlinear behavior of the mechanical joints, the distributions of the nonlinear strains and stresses over the structure is likely different than the one obtained as a superposition of linear mode shapes whose definition require a-priori assumptions on the boundary conditions at the contact interface. This means that the mentioned approximation cannot be used to predict the safety margins of a structure working in real (nonlinear) operative conditions. This paper addresses this topic and presents a novel stress recovery algorithm for the identification of the strains and stresses resulting from a nonlinear forced response analysis on a ROM. The algorithm is applied to a bladed disk with friction contacts at the shroud joint, which make t

关键词： Polyphenylene sulfide   Carbon fiber   Graphene oxide   Tribology  

摘要： The aim of this study was the improvement of the thermal conductivity and tribological properties of polyphenylene sulfide (PPS) with carbon fiber (CF) and graphene oxide (GO) fillers. Whereas CF reduce the mechanical strength of PPS, 3-mercaptopropyltrimethoxysilane (MPTMS)-treated CF improve the interfacial adhesion properties of fillers and PPS matrices, which increase the mechanical properties of composites. The improved thermal and mechanical properties of composites were confirmed via diffraction scanning calorimetry, dynamic mechanical analyzer, and wear test. The silane-modified PPS/20M-CF/5M-GO composite has a thermal conductivity of 0.323 W/m.K, which is 175% greater than that of the neat PPS composite. The friction coefficient has decreased from 0.236 to 0.176 and the specific wear rate has decreased from 1200 to 300 E-07 mm(3)/N.m.

关键词： 柔性机械系统   分布参数建模   控制策略   控制方法   振动抑制  

摘要： 近年来，柔性机械系统以其轻量化、低耗能、操作灵活等优势在航空航天、海底勘探、机器人、机械制造等领域得到了广泛应用，其建模和控制问题也成为了当今国内外学者研究的热点问题。在本文中，首先介绍了柔性机械系统的部分应用实例，紧接着汇总了柔性机械系统常见的分布参数建模方法、控制策略、控制方法以及实际工程中常见问题。最后，对柔性机械系统分布参数建模与控制问题进行了总结，并对未来的研究方向进行了展望。

关键词： 微动磨损   微动疲劳   过盈配合   空心轴   有限元  

摘要： 为了分析空心轴与实心轴过盈配合结构微动磨损与疲劳行为的差异,建立了两种过盈配合结构的微动磨损-微动疲劳联合仿真模型。该联合仿真模型基于Archard磨损方程和有限元软件ABAQUS的自适应网格技术实现了循环微动磨损的仿真,基于线性累积损伤理论和修正的SWT临界平面法实现了微动疲劳寿命预测。分析结果表明:空心轴的微动磨损比实心轴严重,微动磨损显著降低了过盈配合边缘附近的应力集中,同时在配合内部引起了新的应力集中,并导致微动裂纹萌生位置出现在配合内部。受到微动磨损的影响,空心轴的微动疲劳寿命仅约为实心轴的40%,但两种结构的微动裂纹萌生位置几乎一致。

关键词： SiC   WS_(2)   树脂基复合材料   核-壳结构   磨损机制  

摘要： 采用粉末冶金法制备了总质量分数为20%SiC与WS_(2)的铜/聚酰亚胺树脂基复合材料,WS_(2)和SiC质量比分别为1:3,3:5,1:1,5:3,3:1,研究了固体润滑剂WS_(2)与增强相SiC质量比对复合材料微观形貌和摩擦磨损性能的影响。结果表明:当WS_(2)与SiC质量比为3:5时,复合材料中开始形成以WS_(2)颗粒为核、SiC颗粒为壳的核-壳结构;随着WS_(2)与SiC质量比的增加,核-壳结构由扁平状变为圆形,且数量增多,面积增大,复合材料的摩擦磨损性能先提高后降低,磨损机制从磨粒磨损转变为疲劳磨损,最后转变为严重的磨粒磨损;当WS_(2)与SiC质量比为5:3时,复合材料的摩擦磨损性能最好。

关键词： SPC技术   船舶零件   加工过程   管理效果  

摘要： 市场大环境竞争激烈,机械制造企业零件加工管理和质量控制,成为当前亟需解决的问题,将SPC技术引入到机械零件加工过程中,可提高生产管理水平,保证零件的精度,大大提升机械制造产品质量。基于此,本文对SPC技术发展情况进行阐述,分析机械制作过程特点,探讨机械制造过程质量控制现状,研究SPC技术在船舶零件加工过程管理中的应用及基于SPC的机械制造质量控制系统相关内容。

关键词： 槽型   高强度钢AF1410   刀具磨损   切削力  

摘要： 采用两种槽型的涂层硬质合金刀具对高强度钢AF1410进行高效铣削试验,研究刀具槽型对刀具磨损和切削力的影响。试验结果表明,在整个切削过程中,两种槽型刀具的磨损主要发生在后刀面;切削前期,负倒棱较窄的刀具磨损较大;在中后期,负倒棱较宽的刀具磨损量较大,负倒棱较宽的刀具各铣削分力均较大;整个切削过程中,两种槽型刀具的切向和轴向铣削分力变化不大,刀具磨损速率对径向力的变化有较大影响,在切削前期径向力增加较大,而在切削中后期,负倒棱宽度较小的刀具径向力的增加较为平缓,负倒棱较大的刀具径向力增加较快。

关键词： CFD-DEM   弯管   涡旋   磨损  

摘要： 为了研究弯管内的二次流、分离流、颗粒分布及预测磨损的位置及变化,本文通过欧拉-拉格朗日法利用CFD-DEM耦合对不同曲率(30、60、90、120°)弯管中的内流场和管壁磨损进行了模拟。结果发现弯管中主要有管道涡和脱落涡两种,涡核开始于弯曲处且向出口阶段延申,随着角度的增大,涡等值面减小;通过分析得出在颗粒进出平衡时,90°弯管内的颗粒数量最多、30°弯管时的颗粒数量最少;对比发现磨损最严重的区域为弯曲管壁,60°弯管时的总磨损量为最大,并利用matlab拟合了四个角度管道的磨损变化公式。本文揭示了不同角度弯管内的流场、磨损等变化,对管道运输、离心泵等机械进出口管道等应用与改进具有特殊的意义。