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本文提出三维牙颌光弹模型的制作方法,该方法制作的模型可以满足各种有关牙齿的三维光弹应力分析的需要.同时提出新型的“夹部牙”.临床应用及光弹性实验证明它是设计合理的. 相似文献
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光弹性法是研究结构内部应力分布问题的一个有效方法.光弹性实验中,通常可以方便地得到等色线条纹图.确定了等色线条纹级数以后,为获得平面模型中任意点的应力完全解,需要借助其它方法给出一个补充方程.本文将光弹性法与数字散斑相关法相结合,提出一种用于光弹性法分离主应力的新方法:光弹性-数字散斑相关混合法.在理论研究的基础上,设计了光弹性-数字散斑相关混合法实验系统,并通过相应的三点弯曲实验对该方法和实验系统的有效性做出分析和论证.该研究为光弹全场应力分解以及动态光弹性-数字散斑相关混合法提供了理论和实验基础. 相似文献
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牙齿表面磨损一般通过显微镜进行形貌图像表征分析,而数值化分析牙齿表面磨损形貌的工作相对较少. 本研究中通过白光共聚焦显微镜,Solarmap Universal 软件和Tooth-Frax软件对牙齿咬合前后表面磨损形貌进行数值化分析,建立磨损前后表面尺度敏感曲线. 结果显示:牙齿表面磨损形貌可以通过轮廓分形分析法建立相应的表面尺度敏感曲线,形成表面磨损尺度敏感数字信号. 本工作的主要目的是寻求通过表面磨损数值化分析为研发牙齿磨损动态监测设备提供理论基础和技术支撑. 相似文献
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S. L. Pedersen 《Archive of Applied Mechanics (Ingenieur Archiv)》2005,74(7):489-508
A model of a roller-chain drive is developed and applied to the simulation and analysis of roller-chain drives of large marine diesel engines. Two different ways of modelling the contact between the rollers and sprockets are presented; one using a circular shaped tooth profile and the other using the shape of a real tooth profile. The main components of the roller-chain drive model include the sprockets with different sizes and the chain made of rollers and links, which are represented by rigid bodies, mass particles and spring-damper assemblies, respectively. The contact between the rollers and the sprockets are represented by a continuous contact force. The models proposed effectively represent the polygonal effect always present in this type of drive. The numerical results from the simulations are compared with analytical results, for simplified models. The model with a real tooth profile proves superior to the model with a circular tooth profile.The applications represent the ongoing work that resulted from many fruitful discussions with Per Rønnedal, Mikkel Preem et al. of MAN B&W Diesel A/S, Copenhagen, Denmark. 相似文献
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通过探讨牵张力对甲状旁腺激素相关蛋白(Parathyroid hormone related protein,PTHrP)表达、分布的影响,为深入了解正畸牙齿移动过程的骨改建机理提供参考,本文使用体重200±20g、6~8W龄的健康雄性Wistar大鼠42只适应性喂养1W后随机分为7组,每组6只。选择每只大鼠的左侧上颌第一磨牙作为实验牙,以左侧上颌切牙作为支抗牙,安装正畸用0.012英寸(inch)步镍钛螺旋拉簧,力值为50g(0.49N)。分别于安装牙齿移动装置后1d、3d、5d、7d、14d、21d处死实验组大鼠,取含左侧上颌第一磨牙及其周围牙槽骨的组织块,常规进行HE染色和SABC法免疫组织化学染色。利用图像分析系统(0BI200高清晰度彩色病理图文分析系统),对每张免疫组化染色后的切片做定量分析。SPSS17.0建立数据库并进行统计学分析,显示在张力区牙周膜及牙槽骨组织中的成骨细胞、成纤维细胞以及间充质细胞PTHrP呈阳性表达,且张力区牙周组织中PTHrP的表达在加力第5天达到高峰。表明PTHrP牙周组织的改建有一定的调节作用,使张力区与压力区向不同的方向发展。 相似文献
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行星齿轮磨损会导致齿轮齿侧间隙非线性增大、传动精度下降、齿面冲击力增大, 进而会导致齿轮传动系统振动加剧, 因此需要对行星齿轮的齿面磨损与动力学耦合特性进行研究. 本文构建了齿轮非线性磨损与考虑齿轮齿侧间隙的非线性动力学耦合计算模型, 对行星传动齿轮磨损动力学特性进行了研究. 首先建立齿轮啮合非线性动力学模型, 获得齿轮运行过程中的非线性啮合力; 进一步将非线性啮合力与齿轮齿面磨损模型相结合, 研究齿轮齿面磨损分布规律; 并根据齿轮磨损后的齿侧间隙对齿面重构, 同时对齿轮动力学模型进行更新; 进而得到行星齿轮传动中动态啮合力和磨损特性的变化趋势, 并获得齿轮传动系统齿轮齿向振动响应. 数值计算结果表明, 行星齿轮磨损导致齿轮在单?双齿交替啮合时产生的冲击增大, 同时太阳轮?行星轮啮合齿对对磨损较为敏感, 齿面啮合条件剧烈恶化, 是造成行星齿轮传动性能退化的主要原因, 本文研究结果为行星齿轮传动系统运行状态评估与可靠性预测提供了理论基础. 相似文献
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The anatomical form of the teeth and the density of the base bone differ greatly at different tooth positions. Thus, it is necessary to investigate the effect of tooth position variation on the apical occlusal stress because it would be helpful to understand the mechanism of occusal force transduction along the mandible. Epoxy resin models of seven different occlusal types set up with identical plastic teeth were employed to determine the stress directions and magnitudes in the apical area under 2.0 Kg of vertical load. Both the values and directions of the main stress were measured. Our results indicated that variation of the tooth position had no effect on the directions of principle stress around the apex area in the symmetrical occlusal type. For the asymmetrical occlusal type, the mesio-distal and the lingual-buccal directions of anterior teeth were found to be affected by variations in tooth position. The magnitude of the apical main stress was also apparently altered with changes of tooth position, but the differences were insignificant with occlusal types. Therefore, we conclude that variation in the tooth position could affect the direction of the main apical stress when the symmetry of the occlusion type was also involved. In contrast, the apical stress magnitude was much more related to tooth position than to occlusal symmetry. 相似文献
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For sine movable tooth drive, the movable tooth number must be increased to obtain large speed ratio of the drive which increases largely radial size of the drive. Here, a novel two-step movable tooth drive is proposed. The drive can realize small size and large speed ratio simultaneously. For the two-step movable tooth drive, 3D design was done; the forces and the contact stress in the drive system were investigated; results show that the maximum force on the second step drive depends on radius of the movable teeth, size parameters of the second step drive, and radius of the sine ball track in the first step drive; the contact stresses between the meshing elements change periodically, the contact stress between the movable teeth and cap end is the maximum which can be taken as design factor for the load-carrying ability of the drive system. 相似文献
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The traction characteristics of the grouser, cutting the simulative soil of deep-sea sediment, with different tooth widths, tooth heights, and ground pressures are studied with traction characteristic test apparatus. A traction-displacement model is obtained by combining the analysis of the cutting mechanism. The results show that the traction-displacement curves of grousers with different tooth widths, tooth heights, and ground pressures have the same changing trend, which matches the Wong traction model. Their sensitivity coefficient and shear modulus are slightly fluctuated. Therefore, the average values can be used as the traction model parameters. The maximum traction of the grouser with a two-side edge and a 10mm tooth width increment changing with the tooth height and ground pressure can be determined according to the grousers with different tooth widths. By combining the traction model parameters, the traction-displacement curve of the grouser with a certain group values of tooth width, tooth height, and ground pressure can be predicted. Therefore, the slip of the mining machine can be prevented to improve the mining efficiency. 相似文献
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The orthodontic appliance (“braces”) loads a number of individual teeth; in the case of each tooth, the displacement which results is related to the form of the active force system transmitted from the appliance to the tooth crown. In this paper, a model of a single-rooted tooth together with its support structure, the periodontium, is the subject of a plane-stress study with the objective to correlate crown loading, support reaction and initial tooth-displacement direction. The analytical calculations of the interface-stress components are verified through a photoelastic analysis of the tooth/support-structure model. Center-of-rotation locations are determined as functions of the applied-force system and several interface normal-displacement patterns are included, with the goal of this study being the ability to better predict basic tooth movements from knowledge of the form of the crown loading. 相似文献
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针对RV减速器角接触球轴承承受预紧力、轴向力和径向力等联合外载荷作用的工况,分析得出了内、外圈滚道接触界面的接触区几何参数和接触载荷.在此基础上,综合考虑了角接触球轴承的接触区宏观几何、接触载荷、真实表面粗糙度、瞬态效应等因素,建立了角接触球轴承混合润滑数学模型,分析了在不同工况下角接触轴承的润滑状况及表面以下应力分布.结果表明:随着载荷的不断增加,钢球与内圈沟道之间的油膜厚度会不断减少,导致干接触面积迅速扩大,接触点表面以下最大应力增大;转速的增加会使油膜变厚,干接触面积缩小.该结果对角接触球轴承的实际工程应用具有重要借鉴意义. 相似文献
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This paper is mainly dealing with the stochastic responses of nonlinear vibro-impact (VI) system coupled with viscoelastic force excited by colored noise. By the aid of approximate conversion for the viscoelastic force, the original stochastic VI system is transformed into an equivalent stochastic system without viscoelastic term. Then, the equations of the converted system are simplified by non-smooth transformation, and the stochastic averaging method is employed to solve the above simplified system. A Van der Pol VI oscillator coupled with viscoelastic force is worked out in detail to illustrate the application of the mentioned method, and therewith the analytical solutions fit the numerical simulation results based on the original system. Therefore, the present analytical means of investigating this system is proved to be feasible. Additionally, the exploration of stochastic P-bifurcation by two different ways is also demonstrated in this paper through varying the value of the certain system parameters. Besides, it shows a noteworthy fact that assigning zero or a positive value to the magnitude of viscoelastic force can also lead to the bimodal shape of different degrees in the process of stochastic bifurcations. 相似文献