Design of an Orthodontic Torque Simulator for Measurement of Bracket Deformation

The design and testing of an orthodontic torque simulator that reproduces the effect of archwire rotation on orthodontic brackets is described. This unique device is capable of simultaneously measuring the deformation and loads applied to an orthodontic bracket due to archwire rotation. Archwire rotation is used by orthodontists to correct the inclination of teeth within the mouth. This orthodontic torque simulator will provide knowledge of the deformation and loads applied to orthodontic bracket that will aide clinicians by describing the effect of archwire rotation on brackets. This will also impact that design on new archwire\bracket systems by providing an assessment of performance. Deformation of the orthodontic bracket tie wings is measured using a digital image correlation process to measure elastic and plastic deformation. The magnitude of force and moments applied to the bracket though the archwire is also measured using a six-axis load cell. Initial tests have been performed on two orthodontic brackets of varying geometry to demonstrate the measurement capability of the orthodontic torque simulator. The demonstration experiment shows that a Damon Q bracket had a final plastic deformation after a single loading of 0.022 mm while the Speed bracket deformed 0.071 mm. This indicates that the Speed bracket plastically deforms 3.2 times more than the Damon Q bracket for similar magnitude of applied moment. The demonstration experiment demonstrates that bracket geometry affect the deformation of orthodontic brackets and this difference can be detected using the orthodontic torque simulator.     

个性化正畸弓丝曲线交互调整方法研究*

数字化医疗技术是口腔正畸领域发展的必然趋势,临床上开始使用正畸弓丝弯制机器人技术辅助弯制正畸弓丝,而正畸弓丝的数字化表达是机器人弯制的前提。由于人类牙齿排列的个性化,弓丝形状设计的复杂性,难以实现精确地个性化正畸弓丝曲线数字化表达。提出一种个性化正畸弓丝曲线交互调整的设计方法,根据托槽上的基准点坐标,定义了正畸弓丝曲线的托槽直线段和过渡曲线段,过渡曲线段由3阶Bezier曲线数学模型构建。参考手工弯制正畸弓丝的过程,基于离散和组合的方式建立了正畸弓丝特殊功能曲的参数化数学模型及数学模型库。通过对托槽直线段的位置调整、过渡曲线段的形状改变、选择插入特殊功能曲的位置和类型的方式,进行了个性化正畸弓丝曲线交互调整方法的研究。基于LABVIEW软件平台设计了交互调整的软件,并进行调整实验,其结果证明个性化正畸弓丝曲线交互调整的方法具有可行性和有效性。     

Self-lubricating coatings containing fullerene-like WS2 nanoparticles for orthodontic wires and other possible medical applications

Uneven malaligned teeth are a problem afflicting large numbers of people, having significant economic and societal repercussions. Sliding a tooth along an archwire during orthodontic treatment involves a frictional type of force which resists this movement, causing a number of adverse effects. First, using excessive orthodontic force, leads to unwanted movements of the anchor teeth and increasing the risk of damage to the roots of the teeth. Furthermore, the frictional force is distributed unevenly between the archwire and the brackets interface, leading to strong adhesion between the wire and the bracket’s corner. This force-asymmetry causes lengthening of treatment and frequent visits for fine-tuning of the orthodontic appliances. Despite numerous efforts to lower the friction, no satisfactory solution to this issue has been obtained. In the present work a self-lubricating metal coating containing fullerene-like WS₂ (IF) nanoparticles is demonstrated. Such coatings significantly reduce archwire friction, and may alleviate the adverse complications. Moreover, a number of other medical applications of the self-lubricating coatings are foreseen.     

基于有限点展成法的正畸弓丝成形控制点规划

错颌畸形是目前常见的口腔疾病,固定矫治是治疗错颌畸形的有效方法,其中固定矫治技术的关键是正畸弓丝的精确化弯制。机器人利用其位姿的精确控制能力可以实现精确化的弓丝弯制,其中弓丝成形控制点的规划决定了机器人弯制正畸弓丝的成形精度。基于分段式的正畸弓丝数学模型,提出采用有限点展成法实现正畸弓丝成形控制点的位置规划,对基于有限点展成法的正畸弓丝成形控制点位置规划方案进行实验验证,对不同弦弧围成面积下弦弧差值对控制点数目和面积误差的影响规律,以及控制点数目和面积误差之间的关系进行了讨论,并提出基于斜率法的正畸弓丝成形控制点角度规划策略。基于患者临床口腔数据,利用自行设计的正畸弓丝弯制机器人实验系统,通过正畸弓丝弯制实验验证了正畸弓丝成形控制点位置和角度规划策略的有效性。     

含内阻的拉杆组合转子双稳态振动特性

为揭示含内阻组合转子复杂的双稳态振动特性,基于拉格朗日方程推导了含轮盘接触、非线性油膜力及内阻的组合转子非线性运动控制方程.采用升速和降速相结合的方法研究了组合转子跨2阶临界转速的非线性动力学行为及内阻机理.研究结果表明:组合转子双稳态振动特征显著,内阻导致出现双稳态现象的转速区间明显向低转速方向移动,在分析组合转子振...     

Measurement of developing turbulent flows in a 90-degree square bend with spanwise rotation

Mean flow and turbulence properties of developing turbulent flows in a 90 degree square bend with span-wise rotation are measured by a hot-wire anemometer. A slanted wire is rotated into 6 orientations and the voltage outputs from them are combined to obtain the mean velocity and the Reynolds stress components. Combined effects of the centrifugal and Coriolis forces due to the curvature and the rotation of the bend on the mean motion and turbulence structures are investigated experimentally. Results show that the two body forces can either enhance or counteract each other depending on the flow direction in the bend.     

Springback Mechanism Analysis and Experiments on Robotic Bending of Rectangular Orthodontic Archwire

Fixed-appliance technology is the most common and effective malocclusion orthodontic treatment method, and its key step is the bending of orthodontic archwire. The springback of archwire did not consider the movement of the stress-strain-neutral layer. To solve this problem, a springback calculation model for rectangular orthodontic archwire is proposed. A bending springback experiment is conducted using an orthodontic archwire bending springback measurement device. The springback experimental results show that the theoretical calculation results using the proposed model coincide better with the experimental testing results than when movement of the stress-strain-neutral layer was not considered. A bending experiment with rectangular orthodontic archwire is conducted using a robotic orthodontic archwire bending system. The patient expriment result show that the maximum and minimum error ratios of formed orthodontic archwire parameters are 22.46% and 10.23% without considering springback and are decreased to 11.35% and 6.13% using the proposed model. The proposed springback calculation model, which considers the movement of the stress-strain-neutral layer, greatly improves the orthodontic archwire bending precision.     

机器人弯制正畸弓丝成形控制点规划及实验研究

错颌畸形是目前危害人类健康的第三大口腔疾病,固定矫治是一种常用且有效的正畸治疗手段,其中矫治弓丝的弯制是重要部分。机器人以其精确的位姿控制和刚性保持能力可以克服弓丝的超弹性实现弓丝弯制。基于幂函数模型建立了分段式的正畸弓丝数学模型,提出采用增量法实现正畸弓丝成形控制点的规划,进行了增量法实现正畸弓丝成形控制点规划策略的研究。通过正畸弓丝成形控制点规划实验,分析不同等分数下初始精度值对控制点数目和面积误差的影响规律,以及控制点数目和面积误差之间的关系。基于正畸弓丝弯制机器人实验系统,针对一例患者的口腔参数,进行了正畸弓丝弯制实验研究,结果验证了正畸弓丝成形控制点规划策略的有效性。     

轮齿压力角对齿轮强度的影响分析

运用赫兹接触理论,分析了轮齿压力角对齿轮接触强度的影响,得出了轮齿强度随压力角的变化规律.发现轮齿压力角的增大,齿面接触正应力和工作剪应力均减小,同时齿根的弯曲强度提高,对提高齿轮强度和防止齿面点蚀极为有利,为重载齿轮的设计提供了理论依据.     

磨前加工内燃机车齿轮用圆弧头滚刀的设计

基于齿轮的齿根倒圆可增大轮齿抗弯强度,应采用圆弧头滚刀加工渐开线齿廓和槽底圆滑过渡曲线。分析了三种类型圆弧滚刀的特点及使用范围,计算并绘制了Ⅱ型圆弧滚刀的刀齿廓形,给出了滚刀齿顶是否切除齿轮有效渐开线齿形的验证方法,计算了滚刀齿顶圆弧头的运动轨迹坐标,最后得出了确定齿槽高度的条件。     

Effects of self-ligating brackets on the surfaces of stainless steel wires following clinical use: AFM investigation

In orthodontic treatment, the frictional force between the archwire and bracket reduces the effectiveness of orthodontic treatment. The frictional force is affected not only by the geometry of the self‐ligating brackets but also by physical changes between the bracket slots and archwire surfaces during sliding movement. This study examined quantitatively the effect of self‐ligating treatments on the surfaces of stainless steel (SS) archwires during tooth movement in vivo by atomic force microscopy. Orthodontic 0.019″ × 0.025″ SS archwires after clinical use with the first bicuspid‐extraction treatment were employed using the Damon 3MX^® SS self‐ligating brackets, Clippy‐C^® ceramic self‐ligating brackets, and Kosaka^® SS brackets. Intact SS archwires were used as the control group. All SS archwires after clinical use showed severe scratches and significantly higher roughness caused by frictional interactions between the brackets and archwires (p < 0.0001 vs. control). The descending order of surface roughness was the SS archwires treated, with ceramic self‐ligating brackets, with conventional SS brackets, and with SS self‐ligating brackets (p < 0.001). These findings suggest that an orthodontic treatment with SS self‐ligating brackets may require smaller orthodontic forces than that with ceramic self‐ligating brackets or conventional SS brackets.     

Development of a method to calculate the strength reliability of tooth gears based on the fatigue resistance when the teeth bend

A verified method is discussed regarding how to calculate the strength reliability of tooth gears when they bend and thus resist fatigue. It is based on the computer simulation of random values and the mathematical apparatus of nonparametric statistics. The effective and tolerable bending stresses are described with samples generated by nonparametric sensors. It allows for the correct assessment of the probability of the failure-free performance of tooth gears under any loading conditions.     

骨架折弯进行直齿轮建模及其齿廓逆变形曲线

本文讨论了用骨架折弯进行直齿轮建模方案的可行性 ,并对折弯前平板基件上的齿廓线即所谓变形曲线参数方程进行了推导 ;最后还以一个定尺寸参数齿轮为例 ,演示了按此方案建模的全过程。     

PRO-E中的直齿锥齿轮骨架折弯建模方案

本文讨论了在PRO_E中用骨架折弯进行锥齿轮建模方案的可行性 ,并给出了一套锥齿轮折弯前平板基件上的齿廓线亦即所谓展平渐开线逆变形曲线参数方程 ;最后 ,以一个定尺寸参数的锥齿轮为例 ,演示了按此方案建模全过程     

同向啮合共轭齿廓副参数化建模及特性分析

针对同向啮合共轭齿廓建立了以中心距、螺棱直径、螺槽直径及螺棱系数为参数的啮合线方程,并基于啮合线反转法建立了同向共轭齿廓副构造模型。通过仿真系统分析了同向啮合共轭齿廓副的啮合特性：自清洁楔角随啮合位置变化,瞬时啮合点处圆弧切线垂直于两螺杆中心连线,啮合点的瞬时相对运动速度最大且恒等于转速乘以中心距。研究结果为系统研究同向啮合共轭齿廓设计理论提供了新的途径。     

微段渐开线齿轮的原理及齿廓参数选择计算

介绍微段渐开线齿轮齿廓形成原理及形成过程中影响其啮合点相对曲率为零数量的因素是初始压力角和压力角增量 ,影响齿廓弯曲程度的因素是初始基圆半径和基圆半径的变化规律 ,给出相关计算的图表和一个轮齿变尖的齿轮 ,给出选择有关参数的参考范围 ,提出需对这些因素进行优化设计 ,给出一优化计算结果。讨论微线段齿轮的几何尺寸的计算     

A parametric study on oil/air lubrication of a high-speed spindle

The ball-bearing is widely used on many high-speed spindles due to its low starting friction and high load capacity. However, heat generation and dynamic loading caused by high-speed rotation have been obstacles for increasing the speed limit in many high-speed ball-bearing applications. Applying an appropriate lubrication and preload cannot be overemphasized. Recently, oil/air lubrication has been used on high-speed spindles because of its accuracy in oil quantity control and high cooling efficiency. However, an oil/air supply with inadequate parameters is undesirable. In this study, the performance of a high-speed spindle under different lubrication parameters and preloads was investigated. The Taguchi method was applied to study the effects of design parameters on the lubrication efficiency. This method can also be used to obtain the optimum lubrication conditions. The optimum operating conditions that create the smallest temperature increase were established. The effects of preload on the temperature increase, the thermal deformation and the static stiffness of an oil/air lubricated spindle were studied. The results provide a useful tool in designing a high-speed spindle with a small increase in temperature and sufficient static stiffness.     

齿面磨损对齿轮系统动态特性的影响

为研究齿面磨损对齿轮系统动态特性的影响,综合考虑齿轮齿侧间隙、传输误差、齿面磨损,采用集中参数法建立齿轮平移-扭转非线性动力学模型,分析齿轮的转速、运行次数对含有齿面磨损的齿轮传动系统动态特性的影响。结果表明:在啮合区域内,齿根处的齿面磨损量呈减小趋势,在节点处理论磨损量为零,齿顶处的齿面磨损呈增加趋势,齿面磨损量减小趋势大于增加趋势,整个过程中齿面磨损会造成啮合刚度的减小;存在齿面磨损时,过大或过小的转速都会使齿轮系统的振幅波动变大,幅值减小;当转速一定时,含有齿面磨损的系统随着运行次数的增加,振幅幅值会逐渐减小,传动的波动会加剧。     

个性化正畸弓丝成形规划方法及实验研究

传统手工弯制正畸弓丝弯制效率低、弯制精度不高，使用正畸弓丝弯制机器人弯制正畸弓丝能够克服上述缺点。根据临床上正畸医师常用的牙位标识方法对牙位进行了标识，使用贝塞尔曲线量化正畸弓丝在三维空间内的形状、位置和约束关系，采用插补的方式以离散的运动形式表达连续的状态，以实现正畸弓丝空间曲线的弯制，提出了基于有限点展成法的成形控制点的规划方法以及基于投影面角度合成的空间角度规划方法。通过对一例临床患者一组上颌的三维节点信息进行正畸弓丝弯制实验研究，证明了正畸弓丝机器人弯制方法的有效性。     

数控成形砂轮磨齿机在机测量研究

提出了利用数控机床的回转运动（C轴）和径向进给运动（X轴）形成理论渐开线，实现齿形误差的在机测量方法。通过使用Num数控系统的YK73125数控成形磨齿机上的渐开线直齿轮齿形误差的在机测量实验验证了该方法的可行性。