铝硅合金表面激光Cr／WC梯度层组织及抗微动磨损性能研究

利用5kWCO2激光器对铸造铝硅合金表面进行两次激光辐照,先后将不同成分的预置合金粉末和基体材料一起熔化后迅速凝固,在其表面获得Cr/WC激光表面梯度层,并对它们的显微组织进行分析,发现在表面梯度层中存在大量的Al/Cr化合物Al9Cr4。在激光表面梯度层中自表及里显微硬度基本呈连续变化趋势,而单次激光表面合金化层与基体之间的显微硬度值有一突变,在基体和激光表面改性层的微动磨损试验中发现,激光改性后的表面抗微动磨损的能力增强,磨损机制不同于铝硅合金基体,而表现出较好的抗粘着损伤性能。     

316L不锈钢微动磨蚀过程力学化学交互作用研究

采用球－平面接触微动设备,对３１６Ｌ不锈钢在不同ＮａＣｌ溶液中微动过程力学化学交互作用进行了研究,并解析了材料微动损伤速率与溶液腐蚀特性之间的关系。结果表明,材料微动过程力学化学作用相互促进,力学损伤在微动损伤过程中占居主导作用。强碱性、强酸性及溶液富含Ｃｌ＾－的情况下,都可导致材料严重微动损伤,而在中性条件下,力学因素对化学损伤促进作用最为明显。     

1045钢在部分滑移区和滑移区内的高温微动磨损性能研究

从室温到400℃，对GCr15钢与1045钢组成的摩擦副进行了微动摩擦拭验。法向载荷变化范围为100—300N、位移幅值为15—60μm。通过摩擦动力学分析，结合显微观测，发现1045钢的高温微动行为与微动区域特性密切相关。在滑移区内，随着温度的升高，摩擦系数与磨损降低，但在部分滑移区内，温度对微动行为影响很小。     

Fretting cracking behaviour on pre-stressed aluminium alloy specimens

A new testing rig has been developed which enables fretting tests on pre-stressed specimens to be carried out. Three aluminium alloys, Al-Li 2091, Al-Cu 2024 and Al-Zn 7075, were used in the tests. The imposed amplitude D ranged from ± 10 to ± 75 μm and normal load F_n from 500 to 1000 N. The static external stress σ_S was set as σ_D/10, σ_D/2 and σ_D (σ_D is the fatigue limit). The tests were carried out with a frequency of 1 or 5 Hz up to 10⁶ cycles. In this paper, analysis of fretting behaviour has been carried out using the fretting map concept. The effect of the axial load (pre-stress) on fretting cracking is emphasized.     

Design effects on the fretting wear behaviour of ball bearings

A change in design of a ball bearing is described based on the results of numerical and experimental analysis to reduce fretting wear. Increasing the radii of curvature of the inner and outer races by a small amount reduces the product of the relative slip δ and the tangential traction τ at the contact region, both of which are caused by Heathcote slip. This results in the consequent reduction in fretting wear because there is a good correlation between the amount of fretting wear and τδ. This prediction is confirmed experimentally by increasing the groove radius of the inner race from 4.02 to 4.21 mm for a ball of radius 3.97 mm.     

GCr15轴承钢的复合微动磨损行为研究

对GCr15轴承钢球/平面接触方式,在倾角分别为30°和45°进行复合微动磨损试验。分析了该微动接触条件下的动力学特性;利用光学显微镜、轮廓仪和扫描电子显微镜对磨痕进行了分析,根据复合微动运行的三个阶段,提出了GCr15钢的复合微动磨损的物理模型。     

Processing and mechanical properties of network ceramic/steel composites by pressureless infiltration

A new style Ni-containing alumina ceramic foam based continuous three-dimensional interconnected skeleton was prepared by impregnating a polymeric sponge with aqueous ceramic slurry.Subsequently,alumina ceramic foam/steel metal matrix composites（MMCs） were prepared successfully by sand mold casting technique.The microstructure and mechanical properties of MMCs were investigated by SEM,EDS and compressive test.The results show that the depth of infiltration is about 40 μm to the bonding interface of ceramic/steel and the fracture strength σmax and plastic strain limit εp of composite are 520 MPa and 11.2%,respectively.The fretting wear mechanism of MMCs is mainly performed at the oxidative wear mode with lower load/friction frequency and the predominant oxidation wear together with slight adhesive wear and abrasive wear multiple mode with higher load/ friction frequency.Moreover,the infiltration bonding and continuous three-dimensional interconnected ceramic skeleton play a vital role in the stability of the bonding interface and excellent mechanical properties.     

U型波纹管的扭转刚度计算

就EJMA标准关于U型波纹管扭转刚度的计算公式进行探讨。用钱伟长关于旋转壳扭转刚度的积分公式给出了U型波纹管扭转刚度妁计算公式,分析了EJMA标准计算出的扭转刚度较小的原因,并就其公式建议提出修改,用新的等效半径来代替EJMA的等效半径可以得到满足工程计算精度要求的简化公式。所有结果都通过有限元分析来验证。     

压电石英晶片扭转效应理论研究与验证

从各向异性弹性理论和麦克斯韦电磁理论出发,较系统地探讨了圆形压电石英晶片扭转效应理论,得出了扭转应力场与非线性极化电场分布规律,并采用有限元法求得了极化电荷电场在压电片内的分布。根据理论分析,用分割电极法有效地在压电片表面布置了检测电极,理论与试验结果均表明电极检测的极化电荷量与外转矩成线性关系,理论与试验基本符合。这些研究为新型转矩传感器与测力仪的开发奠定了必要的理论基础。     

齿轮减速器特性参数识别

通过对二级齿轮减速器进行实验测定和参数识别，提出了用三质量弹簧简化模型代替复杂齿轮减速器的方法，并对其简化模型的特性参数进行了识别，进而得到了系统的固有特性，这为复杂齿轮系统的简化计算和动态分析奠定了基础。