Theoretical and Experimental Analysis on Influence of Revolution Radius in Orbital Drilling

Revolution radius is one of the significant parameters in orbital drilling,which has great influence on many factors,such as the cutting area of front and side cutting edge,undeformed chip geometry,delamination and burr at hole exit side,hole surface roughness,cutting tool force and deflection,chip removal and heat transmission.First,the influence of revolution radius on the factors is discussed theoretically in detail.Analysis results show that big revolution radius can reduce axial cutting force,restrain exit delamination and burr,and improve chip removal and heat transmission.Then,single factor test and orthogonal test are utilized in the two processing methods as machining unidiameter holes with several cutting tools and machining different diameter holes with one tool.Finally,the influence of revolution radius on cutting force and hole machining precision is studied.These results provide a profound foundation for future optimization of cutting control parameters.     

跨声速涡轮叶栅激波损失控制方法

为了降低高负荷跨声速高压涡轮激波损失,发展了针对性的涡轮叶栅激波控制方法。针对吸力侧激波,提出可控膨胀设计概念,结合基于曲率的叶型设计方法,通过调整吸力面曲率分布以控制气流膨胀力度,减小了尾缘激波前马赫数,有效减弱了吸力侧激波强度和叶栅出口压力不均匀程度。针对压力侧激波,发展了消波设计方法,在吸力面的激波作用区域设计一鼓包型线,利用鼓包迎风面压缩波的预增压作用和外凸面膨胀波的消波作用,有效抑制了激波/边界层相互干扰,显著削弱了反射激波强度。可控膨胀设计和消波设计对叶栅尾缘两道激波的控制作用相互独立,可单独采用,当两种方法相结合时,吸力侧激波强度降低了29.66%,叶栅出口压力不均匀程度减小了29.28%,总压损失系数减小了12.11%。      

喉部曲率半径对最大推力喷管性能的影响

针对不同喉部结构进行了最大推力喷管型面设计计算,分析了不同曲率半径对喷管流量系数、几何效率、推力系数、扩张损失和分离点位置的影响。结果表明：流量系数随上游曲率半径的增大而增大,推力系数和几何效率随下游曲率半径的增大而减小;下游曲率半径的增大导致扩张损失在小范围内不断减小,分离点位置后移。     

基于NURBS的扩压叶栅非对称前缘设计

前缘对扩压叶栅叶型气动性能具有重要影响,圆弧形或椭圆形前缘吸力面和压力面侧为对称形状,未针对两侧流动差异进行不同设计。为进一步提升扩压叶栅气动性能,发展了一种基于三次非均匀有理B样条(non-uniform rational B-splines,NURBS)曲线的非对称前缘设计方法,在保证曲率连续的前提下,实现吸、压力面两侧非对称的前缘构造。将设计方法应用于两圆弧形前缘叶型改型设计,数值结果表明:与原始叶型相比,总压损失系数可分别降低26.3%和23.5%,提高了整体气动性能;同时与对称曲率连续前缘相比,在51.83°进口气流角下吸力峰强度降低13.4%,前缘转捩位置推后4.6%弦长,在大进口气流角下具有更好的气动性能。      

Data Fusion of Multiple Curvature Mode Shapes for Structural Damage Diagnosis

This study aims to develop a reliable method for locating multiple cracks in a beam using data fusion of multiple curvature mode shapes.The identification of multiple damage in beams based on curvature mode shape has become a research focus in recent decades.However,the curvature mode shape method using a single mode carries limited damage information,and fails to reveal all cracks when multiple damage detection is required.To address this limitation,the curvature mode shape method is further enhanced by a data fusion algorithm to fuse damage information in multiple modes.The effectiveness of the method is proved through a numerical case of a beam with multiple cracks.The applicability of the method is experimentally validated by detecting multiple cracks in a composite laminated beam with mode shapes acquired by a scanning laser vibrometer.The results show that the method of fusing multiple curvature mode shapes carries more complete damage information than the traditional one using a single mode,and can successfully locate all cracks in a damaged beam.     

大落差长度比中介机匣气动性能试验及数值模拟

为了考察中介机匣气动性能水平并验证设计方法,对中介机匣进行了气动性能试验,同时采用NUMECA Fine软件进行了相应的数值模拟。为了准确测量流过中介机匣内涵的气流流量,设计了一种流量测量装置并进行了精度校核,结果表明：测量精度的相对偏差小于1.5%。针对高进口马赫数时在进口平直段上两侧的壁面静压比中间区域小,以及某些涵道比未能调节到目标进口马赫数的情况,进行了相应的数值模拟并提出了解决方案。用单点总压管对内、外涵出口进行了扇面测量,得到了内涵的总性能曲线、总压恢复系数径向变化曲线及内、外涵总压恢复系数云图,并与计算结果进行对比,结果表明：内涵总性能曲线及内、外涵总压恢复系数云图的计算结果与试验结果吻合较好,在设计状态下,内、外涵出口测量截面的总压恢复系数分别为0.992 1、0.986,两数值均高于设计指标,中介机匣具有较好的气动性能。     

小相寨隧道进口段管棚支护参数优化分析

太中银小相寨1号隧道出口段围岩稳定性差,地形坡度大,洞口覆盖层薄,进洞困难,施工中采用大管棚进行超前加固处理.根据初始设计管棚参数,采用二维弹塑性有限单元法,对管棚设置范围、环向间距、注浆浆液扩散半径进行参数优化.优化结果表明:管棚设置范围、环向间距、注浆浆液扩散半径均存在一最优值,当没计参数值超过这一最优值时,设计参数的变化对拱顶下沉量的影响明显减小.因此不能一味地提高没计参数来增加隧道结构的可靠性.     

刀具半径补偿功能在数控加工中的一种应用

介绍了在数控机床中使用刀具半径补偿功能(G41、G42)，实现利用同一段数控程序完成对余量较大的工件进行多次走刀加工的方法。     

离心机大臂动态半径长度的测量

精确测量离心机大臂动态半径长度是离心机研制工作的关键和难点 ,文中不仅介绍了准确测量离心机大臂半径长度的方法 ,同时进行了测量误差的分析。     

直齿锥齿轮的齿面苗率半径和速度分析

根据切齿原理和产形面与被切齿面间的关系推导出直齿锥齿轮的齿面曲率半径和综合曲率半径的表达式，并与当量齿轮法的求解结果进行了比较；在齿面坐标数值计算的基础上，分析了齿面上点的速度，为精确分析直齿锥齿轮的弹流工况及在弹流条件下的接触应力分布提供了依据．