材料性能及其结构分析对车门设计的影响

介绍了车身设计中利用先进计算机模拟软件进行模拟分析的重要性.以某型号车门为研究对象,在相同加载情况下,分析了车门关闭和开启状态下的性能.探讨了车门在这两种状态下的能量平衡、门锁处Z向位移以及车门内板应力分布情况.进行模拟分析之后,发现车门变形较大,门板角落处存在应力集中,在铰链处应力集中比较严重.通过深入分析,提出了具体的改进措施,为新车型的开发研究提供了有力支持.     

集装箱装卸冲击力学环境条件研究

分析集装箱装卸冲击特性等环境量值,并结合装卸冲击等力学环境条件对货物的影响,提出安全防护的几点措施。     

行星运动输出机构装配条件的研究

对K—H类NGW型齿轮机构的传动方案、装配条件、偏心距条件及均载进行了分析讨论，得出了这种机构具有较大的增速比度较好的均载、动平衡等重要结论，为这一机构的开发应用提供了必要的理论依据。     

Effect of cyclic loading on the yield surface evolution of 18G2A low-alloy steel

Experimental analysis is presented of the plastic properties of 18G2A steel (notation according to Polish Standards) in the as-received state, and of the same material subjected to cyclic predeformation in different directions of the two-dimensional stress space (σ_xx, τ_xy). The analysis was made by studying the position in stress space and by determination of typical dimensions of the yield surfaces. The initial yield surface has been determined using a number of specimens which were loaded up to the plastic range along different stress directions, and this surface was used as the starting point for comparative studies of yield surfaces of the cyclic prestrained material. Cyclic predeformations were induced by loading at ambient temperature. After predeformation, yield surfaces were determined by the technique of sequential probes of the single specimen. The anisotropic yield condition due to Szczepiński was shown to model the experimental results well. Prior cyclic loading induced the softening effect observed during subsequent monotonic loading of the steel in the plastic strain range considered.     

Effects of sheet thickness and material on the mechanical properties of flat clinched joint

Frontiers of Mechanical Engineering - The flat clinching process is attracting a growing attention in the joining field of lightweight materials because it avoids the geometric protrusion that...     

二维载荷作用对金属橡胶干摩擦阻尼性能的影响

这里研究了金属橡胶隔振器干摩擦阻尼特性在二维载荷作用下的变化情况。作者引入了金属橡胶材料内部接触作用模型,利用宏观滑移和微观滑移的概念来描述金属橡胶材料在振动载荷下的减振机理;通过实验验证了在二维载荷作用下,金属橡胶材料迟滞回线最初加载曲线和完全迟滞回线的变化情况,并针对不同载荷变化情况对金属橡胶干摩擦阻尼特性进行了分析。实验结果及理论分析为金属橡胶材料在航空航天领域的进一步应用提供了依据。     

Study on morphological characteristics and microscopic structure of medicinal organs of Pulsatilla chinensis (Bunge) Regel

Modern clinical studies have found that Pulsatilla radix contains a variety of active ingredients; however, its medicinal parts and microstructure have been controversial. Based on morphological observation and microscopic identification of different structures, we chose Anhui, Henan, Jilin, and Shanxi Province to study Pulsatilla chinensis (Bunge) Regel populations. We specifically addressed different diameters and anatomical structures of different parts of underground organs. We also found that P. chinensis (Bunge) Regel had a “joint point” structure in its underground organ. Above the “joint point” is the rhizome, below the “joint point” is the root. The main medicinal organ is the rhizome. The protective tissues of the endothelial layer of P. chinensis (Bunge) Regel changed in the process of its development. The protective tissues were replaced by epidermis, cortex, endodermis, and phloem. With the secondary growth, the endothelial cells have been radial division. This study showed that morphology and microscopic identification was an important mean of medicinal material identifications, and it had the characteristics of a convenient, fast, and intuitive method to identify the composition and structural characteristics of P. chinensis (Bunge) Regel medicinal parts.     

Influence of part material and sensor adjustment on the quality of digitised point-clouds using conoscopic holography

Conoscopic holography is an interferometric measurement technique commonly used for non-contact surfaces digitising in quality assessment, in-process inspection and reverse engineering. Among other factors, accuracy of measurements provided by this technology is influenced by the surface optical properties. Parameters such as laser power (P) or frequency of acquisition (F) are commonly used to adjust the sensor until a quality indicator of the signal acquired (Signal-to-Noise-Ratio) is maximised. Nevertheless, measurements taken under this adjusting criterion does not necessarily ensure the most accurate results from a metrological point of view. Taking this into account, the present work proposes two additional indicators to analyse the influence of sensor setting parameters on the quality of digitised point-clouds for different metals and polymers. Digitising tests have been performed on flat specimens of each material by means of a conoscopic holography sensor integrated on a Coordinate Measuring Machine. In order to meet an optimal scanning of each material, the study provides a series of recommendations about adjustment of the sensor as well as the most suitable indicator to be used in each case.     

Application of high speed slurry flow finishing method for finishing of inner wall of fine hole die: Effects of the hardness of die material on the polishing characteristics

In order to warrant the quality of drawn metal wires, the inner wall of the hole die which has been used in the drawing of metal wire, has been usually finished by hand work for a long time using a bar daubed the kneaded paste containing diamond powder. High speed slurry flow finishing method which has been recently developed for the finishing of inner wall of capillary has been applied to the finishing of the hole die. It is found that the surface roughness of inner wall of the hole decreases with the increasing number of slurry flow pass in a relatively short finishing time, and that surface roughness reduction rate depends on the hardness of die materials. Experiments show that the bell mouth shape is spontaneously formed in the high speed slurry flow finishing.     

样品状态与装样条件对近红外光谱测定的影响研究

近红外谱区的信噪比较低和测定时的复杂背景，导致近红外光谱易受样品状态和装样条件的影响。本文以2组样品集，考察同一样品集在三种不同的制样状态下的漫反射光谱所建的模型；以及预测时出现装样条件变化时对预测结果的影响及相应的预处理方法研究。试验表明：样品的均匀度越好，则所建近红外模型越优；针对在线分析可能出现的装样疏密度变化，矢量归一化可有效地降低装样稀疏的预测误差。     

柴油机曲轴危险工况的确定及其静强度分析

利用MSC．Patran＆Nastran对柴油机曲轴整体进行三维实体建模、网格划分和静强度有限元分析。采用弹簧单元模拟主轴承支承，使计算模型更接近实际情况。在确定曲轴危险工况时考虑了弯扭的联合作用，以有限元结果为依据，提出了一种更准确地确定曲轴危险工况的方法，证明了曲轴最危险工况并非发生在再进气的上止点或曲柄销受气体力最大时。最后采用了等效应力法对曲轴进行了疲劳强度安全系数校核。     

考虑接触特性的滚动轴承系统建模与仿真分析

根据Hertz接触理论和滚动轴承功能原理,以SKF6208深沟球轴承为参考,在ADAMS/View软件环境下设计建立了基于Impact函数的滚动轴承多体动力学仿真模型。通过实体接触条件下的轴承运转过程动态仿真分析,计算获得了滚珠与内圈、外圈及保持架之间的接触力动态分布规律。指出:轴承系统在启动瞬间(0~0.22 s)存在一定滑动,且接触力变化频率较大;进入滚动阶段(0.22~0.4 s)后,接触力变化频率减小,且呈周期性分布。仿真结果验证了滚动轴承的启动打滑现象,符合实际运行工况。为深入研究滚动轴承系统的接触机理及动态载荷提供了技术参考。     

考虑预压量的橡胶减振件刚度特性及其对动力学性能影响

采用yeoh本构模型拟合应力-应变曲线,对橡胶节点预压量与径向及轴向刚度的关系进行了研究,并分析了刚度对动力学性能的影响.结果表明,适量的预压量既能有效满足橡胶节点各向刚度要求,又能调整橡胶节点的动力学性能,为机车车辆橡胶件的研究提供依据.     

Experimental investigation and analytical modelling of the effects of process parameters on material removal rate for bonnet polishing of cobalt chrome alloy

Cobalt chrome alloys are the most extensively used material in the field of total hip and total knee implants, both of which need highly accurate form and low surface roughness for longevity in vivo. In order to achieve the desired form, it is extremely important to understand how process parameters of the final finishing process affect the material removal rate. This paper reports a modified Preston equation model combining process parameters to allow prediction of the material removal rate during bonnet polishing of a medical grade cobalt chrome alloy. The model created is based on experiments which were carried out on a bonnet polishing machine to investigate the effects of process parameters, including precess angle, head speed, tool offset and tool pressure, on material removal rate. The characteristic of material removal is termed influence function and assessed in terms of width, maximal depth and material removal rate. Experimental results show that the width of the influence function increases significantly with the increase of the precess angle and the tool offset; the depth of the influence function increases with the increase of the head speed, increases first and then decrease with the increase of the tool offset; the material removal rate increases with the increase of the precess angle non-linearly, with the increase of the head speed linearly, and increases first then decreases with the increase of the tool offset because of the bonnet distortion; the tool pressure has a slight effect on the influence function. The proposed model has been verified experimentally by using different Preston coefficients from literature. The close values of the experimental data and predicted data indicate that the model is viable when applied to the prediction of the material removal rate in bonnet polishing.     

等离子堆敷铜-钢异种金属焊接接头性能及结合机理研究

利用光学显微镜观察铜-钢异种金属堆敷接头的显微结构及显微组织构成。对异种金属接头进行剪切强度测试,采用扫描电镜对脉冲等离子弧铜-钢异种金属堆敷接头结合机理进行研究。光学微观金相研究表明：铜-钢异种金属堆敷接头界面平整光洁,接头界面清晰可见,无气孔、裂纹等缺陷,实现了无熔深焊接;距堆敷接头界面28μm外的铜侧没有铁的偏析和渗透现象,故不存在堆敷接头的脆化现象。力学性能试验表明,堆敷接头界面剪切强度大于纯铜的剪切强度。扫描电镜测试表明,铁向铜中的扩散较铜向铁中的扩散明显,室温时在堆敷接头界面扩散过渡区内,形成了铜、铁的过饱和α＋ε固溶体,从而实现了冶金结合。     

Research on the dynamic mechanical characteristics and turning tool life under the conditions of excessively heavy-duty turning

The dynamic mechanical characteristics of excessively heavy-duty cutting were analyzed based on the cutting experiments with 2.25Cr-1Mo-0.25V steel used in hydrogenated cylindrical shells. By investigating the influence of dynamic mechanical characteristics on the tools’ failure in limited heavy-duty cutting processes, the model of dynamic shearing force in the cutting area was established. However, the experimental results showed that the dynamic shear flow stress in the cutting area greatly influenced the tools’ fatigue. The heavy-duty cutting tool was damaged in the form of a shearing fracture. Through a comprehensive analysis of the theory, the critical condition of the tools’ fracture under extreme loading was established.     

A study on friction and wear characteristics of nanometer Al2O3 /PEEK composites under the dry sliding condition

The friction and wear properties of the polyetheretherketone (PEEK) based composites filled with 5 mass% nanometer or micron Al₂O₃ with or without 10 mass% polytetrafluroethylene (PTFE) against the medium carbon steel (AISI 1045 steel) ring under the dry sliding condition at Amsler wear tester were examined. A constant sliding velocity of 0.42 m s⁻¹ and a load of 196 N were used in all experiments. The average diameter 250 μm PEEK powders, the 15 or 90 nm Al₂O₃ nano-particles or 500 nm Al₂O₃ particles and/or the PTFE fine powders of diameter 50 μm were mechanically mixed in alcohol, and then the block composite specimens were prepared by the heat compression moulding. The homogeneously dispersion of the Al₂O₃ nano-particles in PEEK matrix of the prepared composites was analyzed by the atomic force microscopy (AFM). The wear testing results showed that nanometer and micron Al₂O₃ reduced the wear coefficient of PEEK composites without PTFE effectively, but not reduced the friction coefficient. The filling of 10 mass% PTFE into pure PEEK resulted in a decrease of the friction coefficient and the wear coefficient of the filled composite simultaneously. However, when 10 mass% PTFE was filled into Al₂O₃/ PEEK composites, the friction coefficient was decreased and the wear coefficient increased. The worn scars on the tested composite specimen surfaces and steel ring surfaces were observed by scanning electron microscopy (SEM). A thin, uniform, and tenacious transferred film on the surface of the steel rings against the PEEK composites filled with 5 mass% 15 nm Al₂O₃ particles but without PTFE was formed. The components of the transferred films were detected by energy dispersive spectrometry (EDS). The results indicated that the nanometer Al₂O₃ as the filler, together with PEEK matrix, transferred to the counterpart ring surface during the sliding friction and wear. Therefore, the ability of Al₂O₃ to improve the wear resistant behaviors is closely related to the ability to improve the characteristics of the transfer film.