复合弹模光弹模型中粘结约束应力的消除方法

本文对变弹性模量三维光弹地质体模型中的粘结约束应力进行了分析和讨论。同时,提出了两种消除变弹模光弹模型中粘结约束应力的方法。本文对变弹性模量三维光弹性实验的应用和发展具有一定的参考价值。     

泊松系数对用光弹性法确定应力强度因子的影响

光弹性法确定应力强度因子的概念是 G.RIrwin 在1950年提出的,之后,特别是七十年代以来,许多人进行了这方面的研究,使这一方法由最初提出的求解二维静态 K_1的方法发展成为能解决三维静态 K_Ⅰ,K_Ⅱ,K_Ⅲ和二维动态 K_1,K_Ⅱ的方法。由于工程上常见的复杂三维裂纹体的应力强度因子用计算方法求解的困难,三维光弹性确定应力强度因子的方法就更具有吸引力了。然而,在用三维光弹模型确定工程结构的应力强度因子时还存在一个不符合相似准则的     

3D打印模型在光弹性法教学中的应用研究

本文将3D打印技术引入光弹性法的教学中,解决了传统技术制作光弹模型时成型周期长、试样初始残余应力较大等问题.以圆盘为例,详细介绍了3D打印光弹模型的制备过程.基于光弹系统测量得到了对径受压模型内部的等倾线、等色线相位和条纹值.制备了含不同形状孔隙的教学模型,丰富了课堂内容.展示了数字模型设计、物理模型制备、光弹条纹图采...     

光弹性粘结材料的试验研究

在三维光弹性试验中，为模拟具有软弱夹层或由不同岩土构成的复杂地基问题，需用粘结材料将各种不同弹模的型材粘结成组合模型。本文提出三种新型光弹性粘结材料，并通过试验阐明其光学和力学性能，分析比较了它们的主要特点和差异，同时探讨了其粘结应力的作用与效果。     

应用新型动光弹系统研究某设备受冲击载荷作用

结构受到冲击时,其应力分布与在静荷载作用下完全不同.本丈应用新型动光弹实验系统研究了某设备在冲击载荷作用下其内部动态应力分布情况.该系统由部分传统的动光弹实验装置、高速摄影系统和数字光弹图像处理系统组成,并且采用激光光源、落锤冲击载荷加载装置.加工制作了该设备模型的光弹性模型,应用到冲击载荷作用下的实验研究中,得到了该...     

散斑光弹性干涉法

全息干涉法和普通光弹性法相结合产生了全息光弹性法。与此类似,本文建议将散斑干涉法和光弹性相结合形成具有一定特点的散斑光弹干涉法。近十几年来,散斑干涉法得到了很快的发展,可以获得面内或离面位移,错位散斑干涉法则可获得位移梯度场。本文建议将光弹性透明模型置于双光束散斑干涉光路中,通过两次曝光法可以获得模型的应力条纹图案。但和全息光弹性法相比,只要选择合适的漫反射器,用散斑光弹干涉法可以获得不受等差线干扰的、单纯的等和线条纹图。同样的理由,也可以获得三维应力模型冻结切片的等和线条纹图。更有意义的是采用双光片散光穿透模型的散斑光弹性干涉法将有可能获得整体三维应力模型内部的绝对光程应力条纹图,这将为三维应力分析提供一种新的实验方法。     

一种动光弹模型材料的制作方法及其应用

基于#618环氧树脂、甲基六氢苯酐、促进剂DMP-30、环氧树脂消泡剂四种原料,提出制作光弹性模型的新配方和新方法,并利用单轴压缩实验、电测法和动态光弹法分别测定了制作的光弹模型的动态力学参数。新方法工艺简单,制作周期短,对人体无害。制作的光弹模型初始应力小,表面光洁,质地均匀,透光性好,光学灵敏度高,具有良好的机械加工和切削性能。通过三点弯曲梁冲击实验,得到了清晰的光弹等差条纹图像,验证了该配方和方法制作的模型可以应用于动态光弹性实验。     

一种新的光弹应力分析方法

本方法建立了包括“电光调制器”的光弹性测量装置,用频谱分析的方法可以同时测量光弹模型上各点的主应力方向及主应力差值,测量的灵敏度很高,而且可发展成一种新型的自动光弹仪.     

上尖牙远中移动施力方式的光弹性研究和临床实践

本文利用三维光弹性冻结切片法，研究了在各种不同施力方式下，牙周组织的应力分布规律。研究对象是我国１２～１５岁儿童牙齿。光弹模型采用了牙齿、牙周膜和牙槽骨的组合式模型。得出了施加一个水平力的同时再加一个力偶为最佳施力方式，在正畸矫治中它能使牙齿产生较快整体移动的效果。临床实践证明该方法可行疗效显著。     

三维内埋式弹舱流动特性及形状影响数值分析

采用多块结构化网格生成方法,基于三维雷诺平均 N-S 方程和 SST k-ω湍流模型,模拟了三维内埋式弹舱的流动特性.通过改变弹舱各壁面的倾角及宽深比,分析其对弹舱流动特性的影响,并研究了前缘锯齿对气动特性的影响.计算结果表明,在适当范围内:增大弹舱后壁倾角、减小侧壁倾角、增大宽深比可以改善弹舱流动特性;舱门前缘增加锯齿,有明显的减阻效果.     

The influence of variable stiffness of teeth on dynamic loads in single-gear transmission

Summary In this paper, the influence of the variable stiffness of mating gear teeth on dynamic loads occurring between teeth in a single-gear transmission is investigated using a discrete-continuous model consisting of two torsionally deformable ponderable shafts and four rigid bodies. The stiffness is described by a harmonic function of time. Considerations by means of the wave method enable to determine dynamic loads in steady as well as in transient states. Numerical calculations are concentrated on the determination of the amplitudes of dynamic loads on gear teeth with respect to revolution per minute. Received 4 March 1997; accepted for publication 12 September 1997     

Study on the efficiency of the digging process using the model of excavator bucket

In the first part of the paper, an experimental program is presented investigating the soil cutting problem, with the application of vertical rigid walls at various widths as the working tools. It was found that when the tool width equalled the width of the soil bin, the soil cutting problems might be treated as plane strain processes. For the tools for which no interaction with the sidewalls of the bin was observed, the zone of the plane strain deformations occurred in the central part of the tools. In the second part of this paper a new experimental program of laboratory tests is presented, for a tool model in the shape of an excavator’s bucket equipped with teeth. The experimental verification of the influence of teeth (number of teeth and the position of teeth on the bucket’s inside lip) on the efficiency of the digging cycle is the aim of this paper. For high values of teeth spacing, the superposition of the plane strain deformation mechanism with three-dimensional failure modes within the soil was observed. For the low values of teeth spacing, the teeth did not act as separate three-dimensional objects but as one wide tool built up from several modules. As a consequence, the deformation pattern in front of such an assembly of teeth was again the plane strain deformation pattern.     

Influence of nonlinear stiffness of teeth on dynamic loads in gear transmission

In this paper the influence of the nonlinear stiffness of mating gear teeth on dynamic loads occurring between teeth in a single gear transmission is investigated using a discrete-continuous model consisting of two ponderable shafts torsionally deformed and four rigid bodies. The influence of a weak nonlinearity is discussed for a soft and a hard characteristics of mating gear teeth. Considerations are performed by means of the wave method which enables nonlinear dynamic loads in steady as well as in transient states to be determined.

---

Sommario L'influenza della rigidezza nonlineare di ruote dentate sui carichi dinamici presenti tra i denti di una singola trasmissione a ruote, viene analizzata usando il modello discreto-continuo formato da due alberi ponderabili torsionalmente deformati e quattro corpi rigidi. L'influenza di una debole nonlinearità viene discussa per una caratteristica debole ed una forte di ruote dentate. Vengono fatte alcune considerazioni per mezzo del metodo delle onde che permette di determinare i carichi dinamici nonlineari sia negli stati stazionari che in quelli transitori.

     

不同年龄段天然牙的摩擦磨损行为研究

采用往复滑动摩擦磨损试验台考察了不同年龄段的天然牙同钛合金配副时的摩擦学性能.结果表明:天然牙的摩擦磨损行为同年龄密切相关,早期和中期恒牙的摩擦磨损行为相似,磨损表面主要呈现轻微擦伤迹象,中期恒牙的抗磨性能最佳;乳牙及晚期恒牙的摩擦系数变化波动较大,抗磨性能不佳,磨损表面主要呈现严重犁削和剥落特征.     

斜齿轮弹流润滑下的接触疲劳寿命计算

经典齿轮接触疲劳强度理论是基于光滑表面赫兹干接触理论,而实际齿面具有粗糙度,且啮合轮齿多数处于混合润滑状态.本文基于齿轮润滑接触分析建立了渐开线斜齿轮的接触疲劳寿命计算模型.模型由齿轮润滑接触分析模型和基于次表面应力分布的疲劳寿命模型组成.首先将斜齿圆柱齿轮一对齿的瞬时啮合等效为两反向圆锥的接触问题,建立了齿轮的有限长弹流润滑计算模型,考虑了齿轮啮合周期内瞬时载荷、接触线长、卷吸速度等因素的影响,基于统一雷诺方程方法求得啮合齿对间的润滑压力和油膜厚度分布;在此基础上,计算轮齿接触区次表面的米歇斯应力分布,根据Zaretsky接触疲劳寿命计算模型,对齿轮组的接触疲劳寿命进行模拟预测.针对不同工况参数下接触疲劳寿命计算表明:润滑油黏度、轮齿表面粗糙度等因素对齿面接触疲劳寿命均有显著的影响.     

Dynamic investigations of loads on gear teeth in single gear transmission

Summary In the paper a discrete-continuous model for the analysis of dynamic loads on gear teeth of a single gear transmission is proposed. In this model a constant equivalent mesh stiffness and ponderable shafts deformed by torsion are taken into account. In the discussion a wave method is applied which utilizes the wave solution of the equations of motion. Numerical calculations are concentrated on the determination of amplitudes for dynamic loads on gear teeth with respect to frequencies of external excitation in the first and second resonant regions.

---

Untersuchung der dynanischen Zahnbelastung in einstufigen Getrieben

Übersicht Zur Untersuchung der dynamischen Zahnbeanspruchung in einstufigen Getrieben wird ein Modell aus diskreten und kontinuierlichen Massen mit einer konstanten, äquivalenten Zahneingriffssteifigkeit und massebehafteten, tordierbaren Wellen vorgeschlagen. Die Bewegungsgleichungen werden durch einen Wellenfunktionsansatz gelöst. Numerische Berechnungen werden vorwiegend für die Amplituden der Zahnbelastung bei einer äußeren Erregung im Bereich der ersten und zweiten Resonanz durchgeführt.

     

天然牙和树脂牙体外三体磨粒磨损性能研究

以钛合金作摩擦偶件材料，在往复滑动摩擦磨损试验台上考察了年轻恒牙、老年恒牙以及树脂牙在三体磨粒磨损工况下的摩擦学性能，并与两体磨粒磨损工况下的结果进行了对比．结果表明：天然牙和树脂牙在不同磨损工况下的摩擦磨损行为存在显著差异；在三体磨粒磨损工况下，由于食物浆的润滑和应力分散作用，天然牙的摩擦系数和磨损深度明显比两体磨粒磨损工况下的小，磨损机制主要为擦伤，并伴随剥落I树脂牙的三体磨粒磨损比两体磨粒磨损剧烈，磨损表面呈现犁沟和剥落迹象．     

Study on teeth profile modification of cycloid reducer based on non-Hertz elastic contact analysis

To solve the problem of contact failure for heavy-duty cycloid reducers, the teeth mesh was originally studied as a Non-Hertz elastic contact problem. An analysis method called non-Hertz flexibility matrix method (NHFMM) for the teeth contact was developed for the teeth profile modification of pin gear. The NHFMM analysis shows that the edge concentrated pressure calculated by non-Hertz method is 2.11 times of that by Hertz method on the pin teeth without profile modification. In the end, the analysis results of NHFMM were verified by a specially designed photo-elastic experiment.     

渐开线直齿轮弹流润滑条件下的多轴疲劳寿命预估

本文中基于弹流润滑分析和次表面应力建立了渐开线直齿轮多轴疲劳寿命计算模型.相对于传统的单轴疲劳模型,考虑了齿轮固定点的应力历史和材料属性对疲劳寿命的影响,并可以得到齿轮在完整啮合过程中的寿命分布.首先建立齿轮的有限长弹流计算模型,得到齿轮啮合过程中的油膜压力和油膜厚度,再根据油膜压力计算出次表面的应力分布;通过分析齿轮计算区域随啮合过程移动的关系,得到固定点的应力历史,再根据基于应力历史的多轴疲劳寿命模型对齿轮的完整啮合过程进行寿命预估.计算分析了不同粗糙度幅值对轮齿各点寿命大小和分布的影响.研究表明:齿面粗糙度对疲劳寿命的影响显著,随着粗糙度幅值的增大,表层下最大应力向齿面移动,导致低疲劳寿命区向齿面发展且逐步扩展到整个单齿啮合区;而表面粗糙度降低到一定程度则对疲劳寿命的影响变得不明显.     

Nanoindentation of Teeth-A Review

0Introduction Oneofthemostimportantrolesofteethismastication.Thismasticationprocesscanexertgreat amountofrepetitiveforcesontheteethandaffecttheirstructuralintegrity.Also,intheprocessof consumption,teetharefrequentlyexposedtoallkindsofliquidandthismayagaininfluencetheir mechanicalpropertiesandperformance[1].Certainteeth relateddiseases[2]anddentaltreatmentsuch asbleachingarealsoknowntogreatlyaffectthestructuralintegrityandmechanicalpropertiesof teeth.Assuch,numerousresearchworkshavebeendonetoe…