基于ADAMS的搅拌摩擦点焊机器人动力学仿真分析

ADAMS软件在分析机构的运动学和动力学方面有着强大的功能;针对搅拌摩擦点焊机器人的设计问题,首先建立其动力学模型,然后利用Pro/E软件建立了机器人的三维实体模型,将其导入到ADAMS中进行动力学分析,给各个关节运动副加上相应的轨迹曲线方程,使其按照指定的运动方式运动。通过仿真得到并分析了机器人各关节在运动过程中各阶段的动力学特性,为电机系统的精确选型及控制系统的设计等进一步研发搅拌摩擦点焊机器人设备提供了可靠有力的依据,对于保证其机械系统的性能以及提高其可靠性等具有十分重要的意义。     

红外线加热滚筒式煎饼机的研究与设计

为改进传统煎饼制作工艺,设计一种新型煎饼机械,代替传统手工作业,实现煎饼工业化生产。该机采用滚筒为连续加热面,红外线加热,通过温度控制系统控温,自动进料,可实现自动连续生产。     

Preparation and nucleation of spherical metallic droplet

The preparation and solidification of metallic droplets attract more and more attention for their signifi cance in both engineering and scientifi c fi elds. In this paper, the preparation and characterization of Snbased alloy droplets using different methods such as atomization and consumable electrode direct current arc(CDCA) technique are reviewed. The morphology and structure of these droplets were determined by optical microscopy, X-ray diffraction(XRD) and scanning electron microscopy(SEM). The solidifi cation behavior of single droplet was systematically studied by means of scanning calorimetry(DSC), and the nucleation kinetics was also calculated. In particular, the development of fast scanning calorimetry(FSC) made it possible to investigate the evolution of undercooling under ultrafast but controllable heating and cooling conditions. The combination of CDCA technique and FSC measurements opens up a new door for quantitative studies on droplet solidifi cation, which is accessible to demonstrate some theories by experiments.     

试样尺寸对Al-4.5%Cu合金定向凝固组织和界面稳定性的影响

在传统Bridgeman方法下,利用Al-4.5%Cu合金内外同心嵌套试样,研究了自然对流对凝固过程及组织的影响。试验结果显示,温度梯度和抽拉速率均相同的定向凝固试样,尺寸较大试样的组织呈规则胞状或树枝状时,对应尺寸较小试样组织胞晶尖端发生分叉或杂乱树枝状,表明尺寸较小的试样液-固界面稳定性较差。较小试样尺寸限制了液相中自然对流致使溶质原子液-固界面处大量富集是凝固组织不规则与液-固界面不稳定的主要原因。     

新型铸态高强度珠光体球墨铸铁的研究

采用Cu、Sb合金化元素和余温正火工艺获得铸态高强度和具有良好韧性的珠光体球墨铸铁.该铸铁的珠光体含量≥94%,渗碳体≤6%,抗拉强度可达800MPa,硬度为280～350HBW,伸长率为3%～5%.利用扫描电镜及透射电镜对珠光体组织形态进行分析,结果表明,铸态珠光体中渗碳体的层片间距大小、宽窄、厚薄有很大的差别.当加入0.5%Cu、0.02%Sb时,由于合金元素在相界面上富集,阻止了牛眼状铁素体的出现.     

船用燃气轮机预旋系统增压设计及仿真

为了提高船用燃气轮机进口燃气压力和温度,涡轮冷却空气应当具备更大的压力来满足叶片表面气膜冷却的需求。本文优化现有的预旋系统,通过在供气孔入口布置增压叶轮,减少气流经预旋喷嘴射入盘腔和经盘腔进入供气孔的突扩损失。运用数值计算的方法对预旋系统模型进行研究,所采用的计算模型和冷吹实验与1.0设计工况数据对比具有较好的精度。研究表明：增压预旋系统和常用预旋系统具有相似的流场结构,但预旋腔内形成的涡更小,有效抑制了气流在腔内的总压损失;在增压叶轮和结构改进的作用下,冷气相对总压提高2.90%,绝对总压提高4.59%,同时增压所产生的温升变化较小,提高了冷却空气的冷却能力。     

大豆酱欧姆加热影响因素的初步研究

研究了不同欧姆加热条件对大豆酱电导率、加热速率以及酵母菌杀菌效果的影响.实验结果表明大豆酱的加热速率随着电压、盐含量的增大和固形物含量降低而增大,大豆酱的电导率与温度呈线性关系;正交试验确定最佳杀菌条件65℃、150s、35V;在此条件下,能全部杀灭大豆酱中的酵母菌,电能消耗功率约为785J/kg·s.     

钢筋混凝土梁火灾承载力及等效楼面荷载分析

根据梁截面火灾温度场,将梁截面混凝土分为弹性区和塑性区2部分计算火灾场梁极限承载力,并采用等效楼面活荷载描述火灾场高温对梁极限承载力的削弱,推导了相关的计算公式。通过算例与目前的梁极限承载力计算方法作了对比分析,详细论述了火灾场不同混凝土强度等级简支梁极限承载力和等效楼面活荷载的变化规律。     

Strength distribution at interface of rotary-friction-welded aluminum to nodular cast iron

The morphology, size and composition of intermetallic compound at the interface of AI 1050 and nodular cast iron were studied by electron microprobe analysis（EMPA） and scan electron microscopy （SEM）, respectively. The bond strength of the interface was measured by the tensile tests and the morphology of the fracture surface was observed by SEM. The observation of the interface reveals that there are two distinct morphologies： no interrnetallic compound exists in the central area at the interface; while numbers of intermetallic compounds （FexAly） are formed in the peripheral area due to the overfull heat input. The tensile tests indicate that the distribution of strength in radial direction at the interface is irdaomogeneous, and the central area of the interface performs greater bond strength than the peripheral area, which proves directly that the FexAly intermetallic compounds have a negative effect on the integration of interface. The morphology on the fracture surface shows that the facture in the central area at the interface has characteristic of the ductile micro-void facture. So it is important to restrain the form of the intermetallic compound to increase the bond strength of the AI 1050 and nodular cast iron by optimizing welding parameters and the geometry of components.     

用小型传声器阵列测量环境噪声中简单声源声压级

常规声级计测量到的是目标声和环境噪声的总声压,不具备抑制环境噪声的功能。为此使用以球面波函数叠加逼近理论为基础的声波分离方法,用以提升环境噪声中简单声源声压级的测量精度。该方法以小型传声器阵列探头作为测量前端,近场声全息和声波分离为核心计算方法进行实施。为验证该方法的有效性,在全消声室内对关键参数进行了实验验证。实验结果表明,该方法在500 Hz~2 750 Hz频带内,且探头距目标声源5 cm~12 cm的近场区域,可以在环境噪声中得到较精确的目标声源的声压级。