反向钻孔法应用于工件内表面残余应力测量的研究

针对现有应力测试难以准确获得工件内壁应力的问题,该文提出于内壁贴片测应变,由外壁钻入的反向钻孔法。应用有限元数值模拟反向钻孔过程,借助生死单元技术获得反向钻孔法测试所需要的应变释放系数a,b;对比反向钻孔法、盲孔法和X射线衍射法对不同厚度钢板的同一测点测得的残余应力结果,以验证反向钻孔法的可行性和可靠度。模拟结果发现,a,b系数与样品壁厚、孔径、剩余钻深均有关系,对此进一步归纳出适用于标准ASTM E837中A、B型应变片的a,b系数赋值表。实验结果显示,不同测试方法间虽由于测试范围不同而存在差异,但大部分测试结果保持一致。综合模拟与实验结果,通孔法可以改善原先工件内壁应力测试难的问题,并提高内壁应力的测试精度。     

基于传递矩阵的钻孔应变法测量薄板残余应力

针对ASTME837标准中钻孔应变法测量薄板工件残余应力计算精度低、计算过程复杂的现状,引入弹性力学应变传递矩阵,根据应力叠加原理推导出残余应力与测量应变关系的解析表达式,进而实验研究采用应变传递矩阵计算残余应力的精度.结果表明:与标定值相比,采用传递矩阵计算的残余应力相对误差绝对值均值小于2％,采用ASTM E837...     

铝合金材料非均匀表面应力的逐层构建与还原

铝合金板坯加工后表层应力呈现非均匀性,且强度高、深度浅.本文运用逐层钻孔应力释放-还原机理,通过积分法和逐层钻孔力学模型构建了材料表层加工应力-变形函数,在考虑材料各向异性条件下,用ANSYS仿真计算标定了5阶校准系数矩阵.同时,对加工表面进行逐层钻孔,孔径尺寸1.8 mm、深度20μm,使孔周围应力释放,并测量释放后应变,最后将实验应变值代入函数求得表面应力分布.计算结果表明:在材料表层100μm的深度范围,计算应力与仿真结果、XRD逐层测试结果均吻合较好,其中计算与实验结果偏差小于10 MPa,说明计算模型能较好地还原材料表层非均匀应力分布.     

ASTM 防火标准E2768延长表面燃烧特性试验时间

ASTM E84建筑材料表面燃烧特性检测方法是ASTM制定的最早的一项防火标准,它规定了表面火焰蔓延和烟浓度的测量方法。ASTM国际标准组织技术委员会E05防火标准技术委员会对一项普通建筑规范要求做出了响应,将ASTM E84标准中所规定的试验时间由10分钟增加到了30分钟,并将修订版本制定成为新标准ASTM E2768建筑材料表面燃烧特性延时检测方法     

金属材料仪器化冲击试验方法国内外标准比较

对EN ISO 14556:2015,GB/T 19748-2005,ASTM E2298-15仪器化冲击试验方法标准的主要区别进行了对比,特别是各标准的仪器设备要求、适用的试样尺寸及类型、力-位移曲线类型的判定、韧性断面率的评价等,对正在修订国标中新增的内容也予以了说明。结果表明:ASTM标准在仪器设备方面要求更高,但ISO及GB的可行性更好;ISO及ASTM标准覆盖了小夏比V型缺口试样(MCVN试样)的试验部分,使得试验内容更加丰富,但实际试验情况显示小尺寸试样的力-位移特征曲线稳定性不如10mm×10mm×55mm尺寸标准试样的;利用各标准中提供的计算公式对韧性断面率进行评价时,计算公式及特征系数K值的选择对试验结果有很大影响;正在修订国标中加入了裂纹形成能Wi及裂纹扩展能Wp的概念,使得在力-位移特征曲线Fm的后段部分进一步得到细化,具有一定的理论研究价值。     

ASTM金属材料拉伸试验方法介绍

介绍了ASTM E8(E8M)标准中的金属材料屈服强度、屈服点伸长率、均匀伸长率、抗拉强度、伸长率和断面收缩率的测量方法，并与我国相应的标准试验方法进行了比较。     

5XXX铝合金晶间腐蚀质量损失试验标准内容差异分析

为了更好地理解及执行5XXX铝合金晶间腐蚀质量损失试验新版标准ASTM G67-2018,从适用范围、试验装置、试剂浓度、温度要求、取样及试样处理、方法验证、控制样品、报告内容、精密度要求等方面对ASTM G67-13、ASTM G67-2018和GB/T 26491-2011 3份5XXX铝合金晶间腐蚀质量损失试验标准进行差异性分析,重点比对了ASTM G67-13和ASTM G67-2018的差异。     

美标和中国检定规程的试验机同轴度测试方法对比

采用美国标准(ASTM)ASTM E1012-2014和中国检定规程JJG 475-2008,JJG 556-2011对试验机同轴度进行测试,并对测试方法和测试结果进行了对比.结果表明:ASTM和中国检定规程在定级标准、装置(试样棒)、操作方法及计量溯源等方面都有所不同.ASTM采用应变片试样棒,中国检定规程采用双引伸...     

航空金属材料平均晶粒尺寸检测标准研究

为制定更适合我国民航行业的金属材料平均晶粒尺寸的检测标准,从标准评级图、面积法计算公式、断口晶粒尺寸法以及其他影响平均晶粒尺寸精确度的因素4个方面,比较分析ASTM和GB检测标准的主要的差异。结果表明:ASTM和GB的标准评级图相同,但给出的金属材料适用范围、放大倍数换算表格不同,导致评级结果精度差异;面积法中,ASTM标准中的圆形法和矩形法分别有Jeffries,Saltykov的研究成果作为支撑,更为科学,而GB使用的测量网格规定和计算公式有待改进;ASTM和GB对于晶粒尺寸等相关概念、检测方法使用规定等方面的表述和理解存在差异,对平均晶粒尺寸的精度存在影响;断口晶粒尺寸法为ASTM独有。在制定我国民航行业的金属材料平均晶粒尺寸检测标准时,相比GB/T 6394——2002,ASTM E112——2012标准更加详细、规范,实用性高,更符合我国民航行业行情。     

3种金属材料夏比冲击试验方法标准分析及对比

从试验原理、试样要求、试验设备、试验程序、冲击试验结果处理及报告等方面对GB/T 229-2007,EN ISO 148-1:2016,ASTM E23-18等3个金属材料夏比冲击试验方法标准进行了分析和对比.结果表明:GB/T 229-2007和EN ISO 148-1:2016的内容基本相同;ASTM E23-18...     

Error and Uncertainty Analysis of the Residual Stresses Computed by Using the Hole Drilling Method

Abstract: The hole‐drilling method is one of the most used techniques for the experimental analysis of the residual stresses in mechanical components. For both through‐thickness uniform and non‐uniform residual stress distributions, its application is standardised by the ASTM E837‐08. In accordance with the ASTM limitations, the analysis of uniform residual stresses, to which the present work deals with, leads in general to results with a maximum bias of about 10%. Unfortunately, in general the user does not have appropriate procedures to estimate the actual stress error; consequently, if one or more of the experimental influence parameters fall out of the corresponding standard limitations, the computed residual stresses have to be considered as qualitative results. In order to overcome such drawbacks as well as to permit in general the estimation of the stress uncertainty, in the present work the procedures for the correction of the effects of the main error sources and for the stress uncertainty estimation, are proposed. The practical application of such procedures is carried out by using a simple calculation code properly implemented in Matlab environment. Also, the use of this tool allows the user to highlight the relative error and the stress uncertainty contribution of each influence parameter.     

ASTM E381-01标准简介及与国内相关标准的对比

简要介绍了ASTM E381-01标准的使用范围、试样的选取与制备、侵蚀剂的配制及标准评级图的概况。与GB／T1979-2001，YB／T4002-991，YB／T4003-1991和YTB／T153-1999标准在使用中的共性和差别进行了比较。     

Measurement of residual stresses in vvelded steel joints using hole drilling method

Abstract

An experimental investigation of the residual stresses in three types of welded structural steel joint is presented. A total of twelve specimens was tested. In this investigation, the blind hole-drilling method of ASTM E837 was used–adapted and improvedfor determination of residual stresses.To accountfor the effect of local plasticity due to stress concentration near the drilled hole, new calibration coefficients were obtained by carrying out a series of calibration tests. Then, the residual stresses in the welded joints were determined using the new coefficients. The improved hole drilling method presented in this paper was found to be much less time consuming than the conventional sectioning (saw cutting) method for residual stress measurement. The final results obtained in this study showed good agreement with the residual stresses obtained by previous researchers using the sectioning method.

MST/1486     

Effects of plasticity on residual stresses measurement by hole drilling method

Since the fundamental relationships of hole drilling method are derived based on elastic behavior of materials (ASTM E837), there are some limits in determination of high residual stresses (higher than half of yield stress). These limits due to the plastic deformations around the hole were caused by high stresses and their concentrations. In this study the effects of plasticity and mechanical behavior of materials on measured residual stresses were investigated. The results show that the errors of measurements are considerable when the behavior of materials is close to elastic-perfectly plastic. Magnitude and direction of high residual stresses also have some effects on the results. We defined weighted mean stress and used in conjunction with effective stress. The results in different cases show that using this method with proper correction coefficients significantly decreased the errors.     

ASTM力学性能试验总则标准与分项试验方法标准的技术比较

对美标钢制品力学性能试验总则标准（ASTMA370—2010）与分项试验方法标准（ASTMES／E8M-2009,ASTME10—2010,ASTME18—2008b,ASTME23—2007a^ε1和ASTME384—2010^ε2等）分别从标准的适用范围、环境温度的定义、采用的单位制、对试样和试验设备的要求、尺寸测量精确度、拉伸试验的速率、不同硬度标尺间的相互转换以及试验结果的处理与修约等方面进行了系统的对比分析。结果表明：ASTM力学性能试验总则标准和与其相对应的ASTM分项试验方法标准之间存在着一定的技术差异,其中尤以拉伸试验和冲击试验方法标准与总则标准之间的差异居多,实际使用中应注意区分和选择。     

Study on ASTM E399 and ASTM E1921 standards

Costs of ASTM E399 and ASTM E1921 tests, which were developed to determine the fracture toughness (K_Ic) and the ductile–brittle transition temperature of ferritic steels, respectively, are considered high and the procedures are also very complicated. In this study, a method, which is more cost‐effective and easier to carry out, is proposed.     

Ultrasonically aided laser drilling of particle reinforced aluminium based composites

Abstract

An ultrasonically aided laser drilling technique has been developed to raise the performance of traditional laser drilling on metal matrix composite materials. In the process, the workpiece is rigidly attached on top of a transducer which vibrates at a frequency of 20 kHz. Ultrasonic vibration has significantly increased liquid expulsion in laser drilling. For blind hole drilling of an aluminium alloy 2124/SiC composite, the thickness of the recast layer was reduced greatly by about 30–80% at different segments of the hole. In the recast layer the size and the amount of carbides were reduced when vibration was employed. Moreover, the depth of drill can be increased by as much as 20% when vibration was used. In through hole drilling of some 0'6-1'2 mm thick materials the recast layer was virtually removed and a reduced heat affected zone was obtained with no apparent depositionfound at either end of the hole. Also the diameter of the through hole became more uniform.     

Effect of machining parameters on edge-chipping during drilling of glass using grinding-aided electrochemical discharge machining (G-ECDM)

The problem of eliminating edge-chipping at the entrance and exit of the hole while drilling brittle materials is still a challenging task in different industries. Grindingaided electrochemical discharge machining (G-ECDM) is a promising technology for drilling advanced hard-to-machine ceramics, glass, composites, and other brittle materials. Edge-chipping at the entrance of the hole can be fully eliminated by optimizing the machining parameters of G-ECDM. However, edge-chipping at the exit of the hole is difficult to eliminate during the drilling of ceramics and glass. This investigation suggests some practical ways to reduce edge-chipping at the exit of the hole. For this purpose, a three-dimensional finite element model was developed, and a coupled field analysis was conducted to study the effect of four parameters, i.e., cutting depth, support length, applied voltage, and pulse-on time, on the maximum normal stress in the region where the edgechipping initiates. The model is capable of predicting the edge-chipping thickness, and the results predicted by the model are in close agreement with the experiment results. This investigation recommends the use of a low voltage and low pulse-on time at the hole entrance and exit when applying G-ECDM to reduce the edge-chipping thickness. Moreover, the use of a full rigid support in the form of a base plate or sacrificial plate beneath the workpiece can postpone the initiation of chipping by providing support when the tool reaches the bottom layer of the workpiece, thereby reducing the edge-chipping thickness.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-017-0194-5     

GB/T 229-2007金属材料夏比摆锤冲击试验方法简介

介绍了新修订的GB/T 229—2007规定的金属材料夏比摆锤冲击试验方法,并与ASTM E23—2007进行了比较,分别从适用范围、试样要求、设备要求、试验过程及试验结果评定等主要技术要求方面进行了对比说明。结果表明:GB/T 229—2007较修订前的旧版本与ASTME23—2007的差异有所缩小,但两标准仍存在较大的差别。