维氏硬度修正系数的计算

做维氏硬度试验时,规定试验表面应为平面,但实际工作中常遇到需要在各种曲面上打维氏硬度的情况。由于表面曲率的影响,其硬度值往往与平面的不同,因而必须予以修正,才能正确反映材料的实际硬度值。国外有人在大量试验的基础上制定出实用修正系数表,已在一些国家中广泛使     

球面体与柱面体维氏硬度修正值的计算

压入式硬度计只有在平面体上进行测量才能获得正确的硬度值。若要在曲面体上得到真实硬度值,则必须对实测硬度值进行修正。对于维氏硬度通常采用下式修正:HV=K_vHV′(1)式中,HV-被测体的真实硬度;K_v-修正系数;HV′-被测体实测硬度或称示值硬度。对于维氏硬度的修正系数国际上已有标准,国内有关部门亦推存采用其数值,但尚未见到对这些数值物理意义的阐述。我们曾经提出对于压入式硬度来说,相同硬度值的材料对硬度计压头具有等应力抗力。从这一观点可引伸出曲面体硬度修正值实质上是压头与被测体示值接触面积(按实测     

维氏硬度压痕的形状规律及特殊清况下的测试方法

通过对维氏硬度压痕的各种形状的归纳和总结，找出了其中的规律性及成因，并就其与硬度值的关系和现行曲面维氏硬度值的修正理论进行了研究，更为重要的是解决了平面试验面上曲边压痕的维氏硬度测试难题．     

维氏硬度压痕形状的规律,成因与硬度值关系的研究

通过对维氏硬度压痕的各种形状进行了归纳和总结,找出了其中的规律及成因,并就其与硬度值的关系和现行曲面维氏硬度值的修正理论进行了研究。     

中华人民共和国国家标准 金属维氏硬度试验 第1部分:试验方法

1　范围本标准规定了金属维氏硬度试验的原理、符号及说明、硬度计、试样、试验方法及试验报告。本标准按三个试验力范围规定了测定金属维氏硬度的方法 (见表 1)。表 1试验力范围 /Ｎ硬度符号试验名称Ｆ≥ 4 9.0 3≥ＨＶ5维氏硬度试验1.96 1≤Ｆ <4 9.0 3ＨＶ0 .2～<ＨＶ5 小负荷维氏硬度试验0 .0 980 7≤Ｆ <1.96 1ＨＶ0 .0 1～<ＨＶ0 .2 显微维氏硬度试验本标准规定维氏硬度压痕对角线的长度范围为0 .0 2 0～ 1.4 0 0ｍｍ。特殊材料或产品的维氏硬度试验应在相关标准中规定。2　引用标准下列标准所包含的条文 ,通过在本标准中引用而构成为…     

460 MPa耐火钢高温硬度试验测试研究

为测定材料在高温下的维氏硬度,提出一种间接测试金属材料高温硬度的修正方法。首先,对高温环境下的试件表面进行压头压入实验,待冷却至室温后测量压痕尺寸,得到相应的维氏硬度值。然后,采用有限元方法,考虑材料力学性能的温度依赖性,对高温环境下的压痕形貌进行数值模拟,得到相应的维氏硬度计算值。结果表明,在高温时两者之间的偏差较为明显,例如600℃时相对偏差达14%。结合有限元的分析结果,最后给出维氏硬度偏差修正的计算公式,为较准确地测量460 MPa耐火钢材料在高温时的硬度提供参考。     

维氏硬度计的测量方法及检定中常见故障的处理

1 维氏硬度计的测量方法 1.1 维氏硬度的表示方法 维氏硬度用HV表示,符号之前为硬度值,符号之后按如下顺序排列:(1)选择的试验力值(见表1)(2)试验力保持时间(10～15s一般不标注)示例:640HV30表示在试验力为294.2N下保持10～15s,测定的维氏硬度值为640.640HV30/20表示在试验力为294.2N下保持20s,测定的维氏硬度值为640.     

用Loop细分曲面拟合点云数据的方法

将输入的点云数据进行三角剖分形成三角网格,按参考文献[1]建立求解插值细分曲面控制顶点的线性方程组.将所建立的线性方程组进行变换,使方程组的系数矩阵对称.证明了该系数矩阵正定,给出了矩阵特征值的上下界估计.将三角网格顶点作为迭代的初始控制点,提出了求解插值细分曲面控制顶点的两种迭代算法以及两个相应的盈亏修正公式.实例表明,两种迭代算法收敛速度快,拟合精度高.     

低能原电子下形状因子对金属曲面二次发射系数的影响

提出金属曲面二次电子发射的形状因子概念,并从理论上论述了形状因子对曲面二次电子发射系数的影响。从半经验理论出发,推导出低能原电子入射下,金属曲面二次发射系数与入射角的近似关系,并结合曲面形状,得到形状因子一般表达式,进而求出金属曲面的二次发射系数。以圆柱曲面为例,计算其形状因子和低能入射下其二次发射系数,并用实验数据证明了该理论的正确性,最后对结果进行了讨论,得到如下结论:在低能原电子入射情况下,金属曲面二次发射系数为金属材料二次发射系数与形状因子相乘所得。     

小管径薄壁不锈钢管硬度测试分析

为了保证测试量值的准确可靠,针对小管径薄壁软质不锈钢管硬度测试的特殊性进行分析研究。按照国家标准化的技术要求,分别对洛氏、布氏和维氏硬度测试方法的适宜性进行技术分析和比较,最终选择维氏硬度试验法的HV5级别进行测试和修正。经过标准化验证和五年的质量跟踪,测试质量满足要求。     

硬度值的修正

综合了有关硬度值修正的内容,并增加了按硬度计检定证书修正硬度值的内容,可 硬度试验人员参考。     

New portable hardness testers

This article examines portable hardness testers for real-time determination of the hardness of large parts of complex form in different directions in space, in hard-to-reach places, and on flat and curved surfaces. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 39–41, July, 1997.     

A numerical analysis of free-surface flow in curved open channel with velocity–pressure-free-surface correction

This paper presents a numerical study onfree-surface flow in curved open channel. An improved SIMPLEC algorithm with velocity-pressure-free-surface coupled correction is developed and validated. Such algorithm differs from the traditional SIMPLEC algorithm and includes three correction equations which are named as the velocity correction equation, the free-surface correction equation derived from the continuity equation with the kinematic boundary conditions on the free-surface and the bottom bed, and the pressure correction equation taking the same formulation as the traditional SIMPLEC algorithm does. In this study, the improved method is used to solve the incompressible, three-dimensional, Reynolds-averaged Navier–Stokes equation set combined with the standard k– model and/or the low Reynolds number k– model for free-surface viscous flow in curved open channels. The power law scheme (POW) is used to discretize the convection terms in these equations with a finite-volume method. The practical cases studied are free-surface flow through the 180° curved open channel with different hydraulic discharge rates. The comparisons between computations and experiments reveal that the model is capable of predicting the detailed velocity field, including changes in secondary motion, the distribution of bed shear, and the variations of flow depth in both the transverse and the longitudinal directions. In summary, the improved SIMPLEC algorithm is feasible and effective for numerical study of free-surface viscous flows in curved open channels.Authors acknowledge the financial sponsor of the Strategic Research Grants #7001371 (BC), and 7001463 (BC), City University of Hong Kong, and Research Fund of the State Key Hydraulics Laboratory, Wuhan University, PRC.     

几何约束下曲面场景的立体匹配迭代算法

使用对极约束和同形映射两种几何约束,通过采用面积检测、一致性约束误差检测、概率筛选规则和对称优化等策略,成功地实现了曲面场景图像的特征点匹配.该方法未使用任何与灰度相关的信息和与场景相关的约束,极大地提高了方法的实用性和鲁棒性.整个匹配过程快速有效,并在不同的弱标定关系已知的真实图像数据上成功地得到实现.     

基于Green函数法的Timoshenko曲梁强迫振动分析

该文运用Green函数法求解了Timoshenko曲梁在强迫振动下的解析解,通过分析曲梁截面的力学平衡,建立了Timoshenko曲梁的振动方程。依次采用分离变量法和Laplace变换法,对不同边界的Timoshenko曲梁求解出了相应的Green函数。并且通过引入两个特征参数来考虑阻尼对强迫振动的影响。数值计算中,验证了该解析解的有效性,并对其中涉及的各种重要物理参数的影响进行了研究。研究结果表明:通过将半径R设置为无穷大,可以简化为Timoshenko直梁振动模型,在此基础上,将剪切修正因子κ设置为无穷大,可以退化为Prescott直梁振动模型,最后再把转动惯量γ设置为0,可退化为Euler-Bernoulli直梁振动模型。该文给出的数值结果验证了所得解的有效性。     

The interrelation between hardness and compressibility of substances and their structure and thermodynamic properties

A strong correlation relationship has been established between the structure and specific Gibbs free energy of the substance atomization on the one hand, and the substance hardness and volume compressibility on the other. In the framework of the model proposed hardness is directly proportional to the specific Gibbs free energy per bond in isodesmic crystals. An application of a correction coefficient to the ionic component of chemical bonds allows one to evaluate the hardness of compounds having both the covalent (polar and nonpolar) and ion bonds. In the framework of the suggested approach we have been the first to correctly calculate the temperature dependence of the hardness by the example for diamond and cubic boron nitride.     

与圆弧形曲梁连结的框架柱则移刚度

从悬臂直梁出发，可以推导出线刚度与固定端弯矩及铰支端转角的相互关系，进而通过该关系推导出曲梁的折算线刚度。如果考虑楼板的刚度足够大，利用传统的D值法可以直接计算出相关柱的侧移刚度。如果考虑楼板的刚度是有限的，则可以通过建立平衡方程和协调方程得出曲梁中部柱子的位移与其它柱子位移之间的关系，进而可以对曲梁中部柱子侧移刚度的修正系数进行调整，最终可以求出曲梁中部柱子的侧移刚度。     

On the “Anomalous” hardness of nanocrystalline materials

The present paper is a further contribution on a rule of mixtures approach for the prediction of hardness dependence on grain size for nanocrystalline metals and intermetallics. Different behavior for the “bulk” and the “grain boundary” regions is assumed in order to consider the special features of nanocrystalline materials, such as the arrangement of geometrically necessary dislocations and disclinations. The usual Hall-Peteh (HP) relationship is assumed to describe the hardness dependence for each one of the two regions. A “correction” term is introduced for the HP slope of the boundary region as compared to the grain interior HP slope. An integrated formula for the total hardness H is obtained involving the grain size, the grain boundary width, the hardness characteristics of coarse grain counterparts and an extra parameter describing the arrangement of triple junctions. This formula compares well with a large set of experimental data.     

出租汽车计价器检定时对轮胎修正系数运用的探讨

本文主要对出租车计价器检定时对轮胎修正系数的运用进行了探讨。出租车计价器主要以出租车运行的公里数收取费用，在实际运行中轮胎的宽窄、质地的软硬、花纹的形状深浅、磨损的程度等因素对计价器的使用误差检定有相当大的影响。因此本文就出租车计价器检定时对轮胎的修正系数提出了准确的计算方法。     

Design of lenses with curved Petzval image surfaces

Abstract

Design strategies have been devoted to simplify and miniaturize optical systems. In this paper, by constraining image surface to coincide with the Petzval surface, we achieve a compact f/2.8 lens system design with a curved Petzval image surface. Arc distortion is proposed to accurately measure the distortion relative to a curved image surface. The optical performance of our curved image surface lens is analysed and compared. Results show that modulation transfer function (MTF) of our curved Petzval design over 69% at 100 cycles/mm for entire fields is achievable with 100-mm effective focal length, 40º full field of view, >92.4% edge relative illumination, <0.5% arc distortion. Comparisons with a traditional lens with a planar image plane demonstrate that a curved Petzval image surface is an excellent strategy to simplify and miniaturize optical systems, compensate field curvature and benefit astigmatism correction, increase off-axis illumination and improve MTF. Furthermore, the lens with a curved Petzval image surface has a more uniform optical power distribution and greater degree of lens symmetry.