喷油方式对斜齿轮齿面温度的影响

为探讨喷油方式对齿面温度的影响，以斜齿轮为研究对象，通过CFD仿真和试验研究不同喷油方式对斜齿轮齿面温度的影响。针对斜齿轮喷油润滑过程的特点，分析其齿面摩擦生热量，简化轮齿喷油润滑计算模型，并基于CFX进行齿面对流换热仿真研究，得到了不同喷油方式下的齿面温度；基于功率开放式斜齿轮试验平台，对不同喷油方式下的齿面温度进行了试验测量，与仿真计算结果进行对比分析。结果表明：在高速重载斜齿轮传动系统中，啮出侧喷油润滑的方式比啮入侧喷油润滑方式的冷却降温效果要好。     

ＰＤＣ钻头布齿设计技术

合理的布齿是保证PDC钻头具有优良工作性能的关键。目前常用的PDC钻头布齿设计方法是图解调整法，该方法速度慢，设计工作烦琐，工作量大，效率低，欠灵活，而且有时会出现不必要的误差。讨论了PDC钻头布齿设计的特点，按切削原则设计了钻头冠部形状，并选择了合理的切削结构，为PDC钻头布齿计算机辅助设计软件提供了理论支撑。     

Failure analysis of a broken tooth

Several days after heart surgery, a patient discovered his upper right canine tooth had broken at the root. Such tooth damage, recognized post-operatively, is usually assumed to be caused by blunt mechanical force from an instrument used by the anesthesiologist during placement of a breathing tube at the start of surgery. In this case, the patient had saved the crown portion of the broken tooth, and it was possible to examine the root fracture characteristics. The curvature and direction of the crack path and natural tooth situation suggested that failure could be described through a cantilever beam model. This was confirmed when a whole extracted sample tooth was embedded and broken by a measured force in a manner consistent with the model. The resulting fracture surface matched that of the patient’s broken canine tooth. However, the high load and force direction necessary to fracture the root was inconsistent with forces applied during the anesthesia procedure. The failure analysis and further investigation indicated tooth clenching on the breathing tube during recovery was the likely cause of fracture. This paper presents an alternate explanation for intubation-related dental injury, demonstrates the practicality of fractographic analysis of biological materials, and introduces a methodology for simulating in vitro tooth settings for mechanical testing.     

螺纹钢牙筋长度不足的原因及解决办法

分析了影响螺纹钢牙筋长度的原因，根据铣床的工作原理，利用刀头夹持长度与凸轮工作轨面半径的几何关系，推导出计算各种不同规格螺纹钢牙筋的工艺参数，解决了螺纹钢牙筋长度不足之问题。     

冶金烧结强化盘式钻头齿圈的试验研究

在分析盘式钻头齿圈失效机理的基础上,提出了齿圈表面堆焊耐磨合金强化和镶嵌硬质合金齿圈强化两种方法。通过试验研究和对比分析,确定了采用冶金混合烧结固齿法镶嵌硬质合金齿圈强化盘式钻头。进一步的试验研究表明:采用冶金混合烧结固齿法镶嵌硬质合金齿圈来强化盘式钻头齿圈,其结合情况非常好;硬质合金齿圈的硬度、耐磨料磨损的能力和耐冲击磨料磨损的能力在烧结后都有进一步的提高,说明采用冶金混合烧结固齿法镶嵌硬质合金齿圈来强化盘式钻头齿圈是可行的。     

Distinct Expression Patterns of Cxcl12 in Mesenchymal Stem Cell Niches of Intact and Injured Rodent Teeth

Specific stem cell populations within dental mesenchymal tissues guarantee tooth homeostasis and regeneration throughout life. The decision between renewal and differentiation of stem cells is greatly influenced by interactions with stromal cells and extracellular matrix molecules that form the tissue specific stem cell niches. The Cxcl12 chemokine is a general marker of stromal cells and plays fundamental roles in the maintenance, mobilization and migration of stem cells. The aim of this study was to exploit Cxcl12-GFP transgenic mice to study the expression patterns of Cxcl12 in putative dental niches of intact and injured teeth. We showed that endothelial and stromal cells expressed Cxcl12 in the dental pulp tissue of both intact molars and incisors. Isolated non-endothelial Cxcl12⁺ dental pulp cells cultured in different conditions in vitro exhibited expression of both adipogenic and osteogenic markers, thus suggesting that these cells possess multipotent fates. Taken together, our results show that Cxcl12 is widely expressed in intact and injured teeth and highlight its importance as a key component of the various dental mesenchymal stem cell niches.     

双包络TI-环面蜗杆传动的二次包络分析

在一次包络分析的基础上,着重进行了二次包络齿面接触分析,推导出了蜗杆和蜗轮齿面方程。齿面接触分析表明：齿面呈双线接触,润滑条件好,承载能力大,在重型机械传动装置中具有实用价值。     

过氧化脲牙齿美白剂开发及应用研究进展

过氧化脲可通过持续释放活性氧达到牙齿美白的目的，适用于各种原因引起的着色牙齿的美白。它可同时美白多个牙齿，美白效率高、费用低、使用方便和刺激性小，详细介绍了国内外专利配方及其使用效果；总结了国内外对过氧化脲牙齿美白剂的应用研究和对牙釉质、牙本质的影响；指出了国外研究的发展趋势，结合我国的实际情况对我国开发过氧化脲牙齿美白剂的方向提出了建议。     

斜齿轮高阶传动误差设计与分析

为了改善斜齿轮副啮合传动性能,提出了应用四阶传动误差函数曲线,采用数控加工展成斜齿轮.利用抛物线齿廓的产形齿条与圆柱齿轮啮合推导小轮齿面方程.采用假想小轮的方法推导了四阶齿线修形大轮齿面数学模型.根据两齿面在啮合中连续相切条件,建立了含有误差的轮齿接触分析模型(TCA).仿真结果表明:该设计降低了接触印痕对安装误差的敏感性,相邻两个啮合周期的啮合转换点处,传动误差曲线的切线夹角接近180°,降低振动及冲击.     

刀倾全展成准双曲面齿轮的切齿设计

为提高准双曲面齿轮的啮合性能,对刀倾全展成(HGT)准双曲面齿轮进行切齿设计研究.以局部综合法(Local Synthesis)为基础,并依据格里森准双曲面齿轮的加工原理,得到满足一定啮合性能的加工参数,并采用该参数对齿轮副进行轮齿接触分析(TCA).从齿面印痕和传动误差曲线可以看出,齿轮副重合度大,传动平稳,可通过调整局部控制参数来改变齿轮的啮合性能,验证了切齿设计的正确性.该方法可通过对设计参考点及其领域内的啮合条件进行预控,达到对齿面啮合质量的控制.