Development and performance analysis of new spade bit designs

The purpose of this work is to present the development and experimental performance assessment of a new generation of spade drill bits. Rigorous point geometry and drilling force models that describe the topology of the drill and its cutting behaviour have guided the development of these new drills with unique topological features. It is shown, both analytically through simulations and through a systematic experimental study, that the performance of the newly developed topologies exceeds that of the commercially available designs. The new spade bits yield lower thrust and torque over the whole range of pragmatic operating conditions.     

盘型件宽槽双面辗压的实验研究

利用自行研制的双面辗压实验机和铸造纯铅圆盘毛坯进行了盘型件宽槽双面辗压试验研究。实验发现,盘型件双面辗压与其他局部成形的明显区别在于双面辗压的沟槽深度小于辗压头的压痕深度(即压下量),将给此差值命名为“甩高”,并用甩高、槽深、压痕深度描述沟槽的基本几何形态。通过实验给出了辗压头转速、沟槽位置对沟槽几何形态的影响;此外还给出了多遍次宽槽辗压过程中径向材料堆积的高度和影响区大小的试验数据。     

A new thermomechanical model of cutting applied to turning operations. Part I. Theory

In this paper, an analytical approach is used to model the thermomechanical process of chip formation in a turning operation. In order to study the effects of the cutting edge geometry, it is important to analyse its global and local effects such as the chip flow direction, the cutting forces and the temperature distribution at the rake face. To take into account the real cutting edge geometry, the engaged part in cutting of the rounded nose is decomposed into a set of cutting edge elements. Thus each elementary chip produced by a straight cutting edge element, is obtained from an oblique cutting process. The fact that the local chip flow is imposed by the global chip movement is accounted for by considering appropriate interactions between adjacent chip elements. Consequently, a modified version of the oblique cutting model of Moufki et al. [Int. J. Mech. Sci. 42 (2000) 1205; Int. J. Mach. Tools Manufact. 44 (9) (2004) 971] is developed and applied to each cutting edge element in order to obtain the cutting forces and the temperature distributions along the rake face. The material characteristics such as strain rate sensitivity, strain hardening and thermal softening, the thermomechanical coupling and the inertia effects are taken into account in the modelling. The model can be used to predict the cutting forces, the global chip flow direction, the surface contact between chip and tool and the temperature distribution at the rake face which affects strongly the tool wear. Part II of this work consists in a parametric study where the effects of cutting conditions, cutting edge geometry, and friction at the tool–chip interface are investigated. The tendencies predicted by the model are also compared qualitatively with the experimental trends founded in the literature.     

A new thermomechanical model of cutting applied to turning operations. Part II. Parametric study

In Part I of this work, Molinari and Moufki [Int. J. Mach. Tools Manufact., this issue], an analytical model of three-dimensional cutting is developed for turning processes. To analyse the influences of cutting edge geometry on the chip formation process, global effects such as the chip flow direction and the cutting forces, and local effects such as the temperature distribution and the surface contact at the rake face have been investigated. In order to accede to local parameters, the engaged part in cutting of the rounded nose is decomposed into a set of cutting edge elements. Thus each elementary chip, produced by a straight cutting edge element, is obtained from an oblique cutting process defined by the corresponding undeformed chip section and the local cutting angles. The present approach takes into account the fact that for each cutting edge element the local chip flow is imposed by the global chip movement. The material characteristics such as strain rate sensitivity, strain hardening and thermal softening, the thermomechanical coupling and the inertia effects are considered in the modelling. A detailed parametric study is provided in this paper in order to analyse the effects of cutting speed, depth of cut, feed, nose radius and cutting angles on cutting forces, global chip flow direction and temperature distribution at the rake face. The influence of friction at the tool–chip interface is also discussed.     

Nacl—Bacl2—Srcl2三元熔盐相图的计算

本文运用作者提出的从三个对应的二元系的热力学性质预示三元溶液的热力学性质的新对称几何模型,推导得到三元溶液中三个组元的偏摩尔热力学性质的数学表达式。进而将这一结果应用于NaCl-BaCl_2-SrCl_2三元熔盐相图的计算中,得到此三元系的液相析出面及若干等温截面。计算所得结果与实测结果偏差小于5℃,说明此模型在一些熔盐体系中有较好的适用性。     

Computing Minimum Area Homologies

Calculating and categorizing the similarity of curves is a fundamental problem which has generated much recent interest. However, to date there are no implementations of these algorithms for curves on surfaces with provable guarantees on the quality of the measure. In this paper, we present a similarity measure for any two cycles that are homologous, where we calculate the minimum area of any homology (or connected bounding chain) between the two cycles. The minimum area homology exists for broader classes of cycles than previous measures which are based on homotopy. It is also much easier to compute than previously defined measures, yielding an efficient implementation that is based on linear algebra tools. We demonstrate our algorithm on a range of inputs, showing examples which highlight the feasibility of this similarity measure.     

双球面投影几何可量测全景模型的构建

针对全景影像难以提供空间度量的问题,提出一种基于双球面投影几何的可量测立体全景模型构建方法.该方法依据球面全景投影关系与多视几何原理,采用对应变换与本质变换求取旋转及平移参数,并推导出双球面核线约束;在此基础上,建立起双球面投影几何的立体全景模型,解决了球面全景的量测问题.实验结果表明,文中方法可使全景影像在真实呈现户外场景的同时,提供满足一定应用需求的量测分析功能.     

利用标志点多视图约束实现结构光扫描高精度粗拼接

在采用标志点拼接的结构光扫描系统中,两两相邻视图拼接存在累积误差,导致拼接精度会随拼接次数下降,为此提出一种利用标志点多视图几何约束的高精度拼接方法.首先利用两两视图拼接的方式在扫描过程中构建标志点多视图网络,并利用光束法平差技术优化多视图网络得到高精度全局控制点;在此过程中保存每个视局部坐标系下三维点云,然后将各局部坐标系下点云和全局控制点进行拼接,得到物体表面完整的三维数据.该方法克服了传统拼接过程中累积误差,提高了多视角三维扫描拼接精度;并通过实验证明了所提出算法的有效性.     

基于信息几何的图像去噪

提出一种基于信息几何的图像去噪方法,与传统的欧氏空间中去噪方法不同,基于信息几何的图像去噪方法是在流形上利用两点间的测地线距离的大小来衡量图像中两像素点之间的相似性。流形中的点是通过图像中某区域构建的高斯模型,模型间的测地线距离表示两图像区域平均灰度强度和细节丰富程度的差别。这样将区域的平均灰度强度和细节丰富程度的差别作为像素点间的相似性,能够更加准确地衡量像素点间相似性的差异。实验表明,该算法提高了图像去噪效果,能够很好地保持图像细节。     

An introduction to the Information Display Measurement Standard 1, the first display measurement standard from the International Committee for Display Metrology

On June 1, 2012, the Information Display Measurement Standard version 1 was released. This is the first standard from the worldwide standard group, the International Committee for Display Metrology, a standards committee within SID, and it culminates several years worth of development from many contributors at various levels. It has 26 top‐level chapters and a total over 450 sections of all parts, including over 200 measurement sections and 8 appendices that cover 133 topics of display metrology, tutorials, technical discussions, and references. Herein is an overview of the Information Display Measurement Standard version 1, including the structure of the document, tips, tricks, and hidden features, how it is maintained, support material, a breakdown of its contents, and finally, a sampling of four of the over 200 measurements. The standard is available as a free download and can be found on the International Committee for Display Metrology home page — http://www.icdm‐sid.org .