Electrochemical drilling inclined holes using wedged electrodes

This paper presents electrochemical machining of inclined holes using wedge-shaped electrodes. Numerical simulation has been carried out to study the initial flow fields of the machining area with and without the wedged tip at different machining inclination angles. Experiments were conducted consequently to study the machining characteristics affected by each flow field distribution mentioned above. Theoretical and experimental analyses indicate that inclined hole machining using wedged electrodes distributes the electrolyte flow more uniformly and hence leads to a more stable machining process. Wedged electrodes could be used in electrochemical drilling to efficiently drill high-quality holes with large inclination angles.     

Quantitative measurement of the hardness profile on carbo-nitriding steel by the hole drilling method

The thrust measured during a drilling test is related to the hardness of the material being tested. When the test is performed on a superficially heat-treated specimen, the results do not correspond exactly to the hardness profile obtained by the standard Vickers micro hardness technique.Because of the extreme hardness of the surface tested and the small diameter required to minimise material damage, a drill is more suitable than a milling cutter. The thrust measured during testing thus integrates heterogeneous resistance along the cutting edge of the drill. Consequently, correspondence between the hardness profile and the measured signal is shown to be non-linear. By discretising the thickness drilled, we have developed an algorithm which yields the hardness of each elemental thickness. Results for carbo-nitriding steel are very close to those obtained by the Vickers technique and the accuracy is also very similar for both methods.     

斜孔钻模测量工艺孔的稳健位置

应用稳健设计原理,对斜孔钻模测量工艺孔的位置设计进行了分析,理论分析表明其位置尺寸对夹具精度和夹具设计的稳健性有重要影响,进而提出了确定工艺孔位置尺寸的具体方法。     

焊接残余应力的小孔法测试

应用小孔释放法对系列手弧焊接接头的焊接残余应力分布进行测试，讨论了焊接残余应力的分布规律及其相关影响因素，对加载法消除焊接残余应力的效果进行了初步的验证。结果表明，焊接接头的应力不均匀性和不确定性是影响钢制压力容器安全性的关键，采用加载法可以有效地改善这种非均匀应力分布状况。     

General approach to residual stresses determination in thin-walled structures by combining the hole drilling method and reflection hologram interferometry

Main questions, which are connected with a determination of residual stresses by combining the hole-drilling method and whole-field displacement measurements, are considered in detail. The relations, which are needed for converting initial experimental data into stress values of interest, are presented for thin-walled plane structures. Required input data are obtained by simultaneous measurements of probe hole distortions in two principal strain directions on opposite sides of thin plane specimen. Emphasis is made on a careful quantitative formulation of the inverse problem, a solution of which is capable of deriving both membrane and bending residual stress components with the highest possible accuracy. It is shown that an availability of two-side initial data is both an essential and a necessary condition of such formulation. Detailed analysis of accuracy of the results obtained is performed proceeding from three different criteria. All presented considerations are supported with a set of high-quality actual interferograms and analogous reference fringe patterns related to weld-induced residual stress fields.     

The effect of plasticity on the ability of the deep hole drilling technique to measure axisymmetric residual stress

Mechanical strain relief covers a class of techniques for measuring residual stress in engineering components. These techniques work by measuring strains or displacements when part of the component is machined away. The assumption is that such strain or displacement changes result from elastic unloading; however, in components containing high magnitudes of residual stress elastic–plastic unloading may well occur. Such elastic–plastic unloading introduces errors into the measurement of the residual stresses and these errors may be large. This paper addresses the performance of the deep hole drilling technique, a mechanical strain relief technique particularly suitable for large section components. First a plane strain analysis is presented that quantifies the errors associated with plasticity for different magnitudes of residual stress. A three dimensional finite element analysis is then carried out that shows larger errors may be obtained than those suggested by the plane strain analysis. A method for reducing the magnitude of the error is investigated. Finally, the results of an experimental measurement of residual stress are presented where substantial plasticity occurs. The work demonstrates the potential vulnerability of mechanical strain relief methods to plasticity and introduces methods for quantifying the resulting errors. It also provides further evidence that modifications to the standard DHD technique can be made to make the technique less susceptible to error when plasticity occurs.     

FEM analysis of plasticity-induced error on measurement of welding residual stress by the contour method

The contour method relies on deformations that occur when a residually stressed component is cut along a plane. The method is based on the elastic superposition principle. When plasticity is involved in the relaxation process, stress error in the resulting measurement of residual stress would be caused. During the cutting the specimen is constrained at a location along the cut so that deformations are restrained as much as possible during cutting. With proper selection of the constraining location the plasticity effect can also be minimized. Typical patterns of longitudinal welding residual stress state were taken to assess the plasticity effect along with constraining locations.     

An experimental and computational method for investigation of residual stresses in two-layer construction members using hole drilling

A technical approach to the evaluation of residual stresses in bimetallic members of spatial constructions, for which stress jump at the interface of heterogeneous materials is peculiar, is presented. It is shown based on the test problem solution that, when up-to-date methods providing the possibility of obtaining significant volumes of experimental information are used to obtain the experimental data, the suggested approach makes it possible to obtain the results with the accuracy necessary for practical use.     

A new mathematical approach to improve residual stress measurement in ring-core method

Journal of Mechanical Science and Technology - III-conditioning at the inverse equation of integral method in ring-core residual stress measurement leads to high stress sensitivity to strain...     

Study on residual stress in viscoelastic thin film using curvature measurement method

Using LSM (laser scanning method), the radius of curvature due to thermal deformation in polyimide film coated on Si substrate is measured. Since the polyimide film shows viscoelastic behavior, i.e., the modulus and deformation of the film vary with time and temperature, we estimate the relaxation modulus and the residual stresses of the polyimide film by measuring the radius of curvature and subsequently by performing viscoelastic analysis. The residual stresses relax by an amount of 10% at 100°C and 20% at 150°C for two hours.     

钻曲轴斜油孔工装工艺参数的实用算法研究

总结了一套钻孔曲轴斜油孔工装工艺参数的实用计算公式，并举例说明。     

钻模钻孔位置误差分析

钻（扩）孔时,孔的尺寸精度主要取决于钻头直径和装夹精度,而孔的位置精度主要靠钻模来保证。图１如图１所示,在钻模上钻孔Ｏ１和Ｏ２时,孔边距的误差计算公式通常为ΔＫＢ＝δＬ１ｊ＋ｅ１２＋ｘ２２＋ｅ２２＋（２ｘ３）２孔Ｏ１与Ｏ２的孔间距误差计算公式为ΔＫｘ＝δＬ２ｊ２＋ｅ１２＋ｘ２２＋ｅ２２＋（２ｘ３）２＋ｅ３２＋ｘ５２＋ｅ４２＋（２ｘ６）２孔与工件底面垂直度误差计算公式（以孔Ｏ１为例）为ΔＫｃ１＝ｘ１ＢＨ各式中δＬ１ｊ———钻模板左底孔中心线与左侧定位面距离的尺寸公差　　ｅ１,ｅ２,ｅ３,ｅ４———…     

孔挤压强化和工艺参数研究

孔挤压强化可以显著提高机械连接的疲劳强度。采用有限元方法建立了孔挤压强化轴对称模型,得到了孔壁残余应力分布状态,建立了孔壁残余应力和孔径、板件厚度、挤压强化过盈量等工艺参数之间的关系曲线。结果表明,周向残余应力和孔径、挤压强化过盈量之间为对数关系,和板件厚度之间为线性关系;径向残余应力和孔径、挤压强化过盈量之间为对数关系,和板厚(以2.5mm为分界线)之间为线性关系,为孔挤压强化效果的定量化认识奠定了基础。     

叠加阀阀体斜孔加工工艺改进

在液压系统的设计制造中，叠加阀以其结构紧凑、体积小、重量轻、占地面积小以及重新组装方便讯速、泄漏小、噪声低等特点越来越受到大家的青睐。叠加阀阀体斜孔多，如果如图1直接在斜面上加工斜孔时，将会出现废品率高、夹具磨损快、维护费用高等问题。     

Failure analysis of rolling bearings by X-ray measurement of residual stress

Residual stress measurements were carried out for the failure analyses of rolling bearings. According to the survey of more than one hundred examples, some change in residual stress was observed in most cases.Compressive residual stresses peak below the surface and if present, represent the position of maximum shearing stress due to normal contact pressure. Unexpected overloading is confirmed by this method.However, bearings often fail without such overloading. Early failures were observed to be associated with the residual stress changes near the surface. The influences of sliding, vibration and surface roughness on residual stress changes are discussed.     

钻孔夹具设计

笔者设计的夹具用于钻床上加工斜孔及倾斜台阶面,是一种摆动式钻床专用夹具。通过分析夹具的结构特点、工作原理,计算定位误差、夹紧力、导向误差,说明该夹具设计新颖、结构合理、效率高,同时,还解决了斜孔和斜面加工精度和位置难保证的难题。     

微孔钻削加工的钻削力监控

对以钻削力为监测对象的微孔钻削实时监测系统进行了研究。建立了一个BP神经网络模型,利用该模型对钻削过程进行监测。有效地避免了微钻头的折断,提高了微钻头的利用率。     

发动机缸体结合面孔位置度测量方法的研究

发动机缸体结合面倒角孔加工和测量时,其基准为底面及其上的2个定位销孔.由于倒角孔及其基准不在同一平面上,混合使用多个线阵及面阵CCD(charge-coupled device)对倒角孔和定位销孔分别成像,提出了用于孔位置度测量的高精度空间坐标转换算法.最终系统测量数据与作为基准的CMM(coordinate measuring machine)测量数据比对,孔位置最大偏差值为0.030 mm,测量相对误差优于0.03％,测量数据标准差误差小于0.015 mm,在95％置信水平下,系统测量不确定度小于±0.035 mm,系统测量时间小于3 min.在工业现场的大量实验结果表明,提出的倒角孔位置度测量方法能够满足生产线上发动机缸体结合面孔组位置度测量的需要.     

Axial curvature and residual stress measurement in thin-walled tubes

The effect of initial curvature in a previously derived expression relating bending moment to beam curvature is discussed. It it proposed that if initial curvature is large compared with elastic orders of curvature some simplification is possible. A method used elsewhere to examine anticlastic bending is extended to provide an analysis of axial bending in thin-walled tubes. The resulting solution is applied to previous experimental data measuring the residual stresses in thin-walled cylindrical tube and good agreement is observed.     

High-speed drilling of small-diameter holes by core flat drills

Examples are presented to illustrate the high-speed drilling of small-diameter holes (up to 10 mm) by core flat drills: holes (diameter 7 mm) in a discharge valve; and the drilling two-part holes consisting of a cylindrical section (diameter 3.8 mm) and conical section (base diameter 10 mm) in a metal housing.