GB 3323—87标准中环缝一次透照长度的应用

1 问题的提出 按GB 3323—87标准用外透法或双壁单影法透照环焊缝时,一次透照长度L_3的计算方法是用整圈环焊缝的周长除以最少透照次数N求得。一般射线技术中有关外透法或双壁单影法最少透照次数N都是用N=180°/α公式介绍。如果用公式L_3=(π·D)/N就是等分透照长度。在射线技术管理和拍片过程中情况不全一样,我厂环缝射线探伤的圆筒容器在直径φ505～2400mm,厚度6～30mm之间变化的有近20多种。如果都是用N=180°/α和L_3=(π·D)/N公式确定一次透照长度,那么各种圆筒工件有不同的L_3,这样给射线探伤技术管理和拍片工作增加麻烦,往往容易搞错。     

关于三通管焊缝的射线透照方法及最少透照次数的讨论

针对焊接高压三通角焊缝内在质量检测难度大等缺点，简要介绍了三通角焊缝射线检测时的透照方法、角度的确定和最少在照次数的讨论．     

关于三通管焊缝的射线透照方法及最少透归次数的讨论

针对焊接高压这角通角焊缝内在质量检测难度大等缺点,简要介绍了三通角焊缝射检测时的透照方法,角度的确定和最少透照次数的讨论。     

椭圆封头拼接焊缝X射线探伤

讨论标准椭圆封头拼接焊缝Ｘ射线探伤的透照次数及一次透照长度的确定方法。     

冷却器外管环焊缝射线检测工艺探讨

套管工件外管对接环焊缝采用射线检测,对透照布置、透照次数、灵敏度选取等进行分析,采用合适的透照工艺参数,通过工艺验证获得灵敏度、黑度均满足标准要求的射线底片。     

小径管双壁单影透照工艺的探讨

介绍了小径管双壁单影的透照工艺,特别是用黑度确定透照次数的方法,解决了小径管射线检测过程因空间狭小或多次返修不利等因素无法实施双壁双影透照的问题。     

小径管对接环焊缝有效透照厚度的计算

小直径管（直径D≤100mm）对接焊缝无损检测的常用方法是射线检测。但在检测中要准确确定透照厚度较困难，因为小直径管对接焊缝是特殊的变截面工件，其透照厚度在有效透照区域内是连续变化的而且变化很大，无论采用垂直透照法还是椭圆成像法都存在此类问题。透照厚度是射线检测的重要工艺参数，它决定了实际透照管电压和像质指数的选取，还与透照厚度比和有效透照区有关。国内外有关标准虽然近似规定了小直径管对接环焊缝的透照厚度，但不同标准的规定存在差异，这样将导致对同一焊缝检测时，管电压和像质指数等的选取不同，从而引起检测灵敏度不同。     

射线透照几何条件的规范设计

严格执行标准,是保证检测结果可靠性、控制产品质量、保证在役设备安全运行的前提.对于射线检测,除通常考核底片的质量,包括黑度、清晰度、灵敏度等外,对透照的几何条件,还应进一步规范,如对有效透照长度L_3和底片的有效评定长度L_(eff)等.有效评定长度随透照厚度、焦距、焦点大小、环形工件的曲率半径和厚度的不同而变化,而非固定值.在GB3323—87与JB4730—94标准中,穿透厚度差是严格控制的,是控制L_3和L_(eff)的制约条件.在射线质量管理中,L_3和L_(eff)是计算透照比例的重要参数,在实际检测中,采用确定一次透照长度、有效评定长度和一周透照次数来控制.若超过了规定值,则厚度差就失去了控制,影象失真和黑度差增大,满足不了检测质量的要求.平板焊缝透照计算比较简单,而环形工件的L_3与L_(eff)值计算就比较复杂,采用BASIC语言计算其值则迅速准确.下面介绍射线检测中,各种透照方法的L_(eff),L_3及N值计算.     

筒体环缝射线探伤中几个问题的探讨

1 关于横向裂纹检出角θ的计算问题 在许多射线探伤教材中,为了计算最少透照次数和一次透照长度,通常要把对应允许K值的横向裂纹检出角θ计算出来,教材给出的θ计算公式为     

利用胶片长度计算一次透照长度L3和最小焦距F

近年来 ,我们利用射线对3～ 10ｍ ,10～ 30ｍｍ厚的大型压力容器进行 10 0 %探伤 ,在实际探伤中 ,中心透照困难较大 ,只能采用定向透照方法 ,但用片量较大 ,拍片时间也较长。如何确定较大的一次透照长度和最小透照焦距 ,以保证最少曝光次数和最短曝光时间呢 ,实践证明 ,利用胶片长度确定底片的有效评定长度 ,再计算一次透照长度Ｌ3和最小透照焦距Ｆ是可行的。1　纵缝单壁透照ＪＢ 4 730— 1994标准规定 ,透照质量等级为ＡＢ级时 ,透照厚度比Ｋ≤ 1.0 3。根据图 1搭接标记在射线源侧Ａ ,Ｂ点上 ,为使搭接标记能够准确落在底片上 ,取胶片两…     

The influence of positive polarity time on GTAW AC of aluminium

In this work, experiments were carried out to determine the welding behaviour of aluminium 1200 based on an increase in the activation time of the positive polarity for tungsten inert gas AC welding of this metal. To achieve this objective, a series of experiments was developed, in such a way that the intensity of the electrical current in the positive and negative polarities was the same; only the duration times in each polarity were modified. During the experiments, the current and voltage signals were acquired. In this way, the arc voltage and potential could be determined for each condition tested. In terms of the fusion behaviour, an increase in penetration and in welded areas was verified to the extent that longer positive polarity times were used. This behaviour is different from that commonly indicated in the literature about welding processes with non-consumable electrodes, which suggests a reduction in penetration with an increase in the positive polarity activation time. However, this trend grows constantly during the experiments from a determined point, where the positive polarity activity times are greater than 4.0 ms in a total period of 20.0 ms. The use of a minimum positive polarity time (1.3 ms) was shown to be effective for cathode cleaning, as it produced welds with satisfactory fusion characteristics and with minimum wear to the tungsten electrode. The good fusion capacity obtained in welds produced with long positive polarity times was attributed to phenomena arising from the emission of electrons due to the field effect that occurs during the positive electrode phases.     

序列任务下的重构方案组合优化技术研究

针对单元制造系统的长期稳定运行和提高可实施性的问题，提出了一种采用遗传算法的解决方案。在将企业长期计划分解成多个阶段序列任务的基础上，考虑零件加工工艺、设备加工能力、任务交货期等约束，以最低生产成本、最快完工时间、最佳生产线利用率等优化目标为指导，采用遗传算法对不同时间节点下的制造单元重构方案进行组合优化，实现了制造系统的快速合理重构，导出了设备集合和瓶颈解决方案。最后，通过实例验证了算法的有效性。     

Effect of MQL on the tool life of small twist drills in deep-hole drilling

Drilling of deep and small boreholes using twist drills has to be considered as one of the most difficult metal cutting operations. There are many reasons for this, one of them being that the cutting fluid has to be supplied externally. This research work investigates in how far the manner of supplying and the type of minimum quantity lubricant have an effect on the tool life of coated and uncoated high-speed steel twist drills of 1.5 mm diameter. Deep-hole drilling is performed as the holes, drilled into plain carbon steel, had a depth of 10 times the diameter. The feasibility of dry machining as an appropriate alternative to MQL in deep-hole drilling has also been investigated. This work shows that, compared to a continuous supply of the minimum quantity lubricant, a discontinuous supply brings about a significant reduction in tool life, especially in the case of heat-sensitive drills. With respect to the type of minimum quantity lubricant, a low-viscous type with a high cooling-capability gave rise to a notably prolonged tool life. It is also shown that dry drilling is associated with strongly accelerated tool wear for most of the twist drills tested, resulting in a significant reduction in tool life.     

Investigation of non-equilibrium grain boundary segregation on CGHAZ in reactor pressure vessel steel

Abstract

In order to explore the reasons for coarse grained embrittlement, post-weld heat treatment (PWHT) with different times was conducted on the coarse grained heat affected zone (CGHAZ) of A533B steel. The results reveal that the impact toughness of the CGHAZ at room temperature decreases with the prolongation of PWHT time from 0.5?to 4?h. As the PWHT time increases to 4?h, the fracture feature of the CGHAZ presents intergranular cleavage ruptures, and the impact toughness exhibits the minimum value. After PWHT for 4?h, the area of the intergranular cleavage fractures decreases, and the impact toughness gradually increases. Further research reveals that there is phosphorus grain boundary segregation in the CGHAZ. The theory of non-equilibrium grain boundary segregation (NGS) is proposed to explain the phenomenon. It is found that the PWHT time with minimum impact toughness is consistent with critical time of phosphorus NGS.     

Estimating equilibration times and heating/cooling rates in heat treatment of workpieces with arbitrary geometry

Estimation of both equilibration times and heating/cooling rates is very important in heat treatment practices. An improved, practical virtual sphere method recently developed by two of the authors, Gao and Reid, based on the theory of heat conduction in solids, is further examined and evaluated in this article. The method is capable of estimating equilibration times for any workpiece with arbitrary geometry. The requirement of input data for this method is kept to a minimum. The method is simple and cost effective to use and offers much better accuracy than those methods based on rules of thumb. The engineering approach of applying the virtual sphere method for determining both equilibration times and heating/cooling rates at the center is provided in this article. It can be easily implemented in a computer program, and hand calculations are also possible. The test cases presented in this article for evaluating the method include a long cylinder, an infinite plate, and a short cylinder with exact analytical solutions and a H13 die with experimentally measured temperature history for a heat treatment cycle. The method is recommended for engineering applications.     

激光喷丸参数对7075铝合金残余应力分布影响规律的数值分析

为了研究不同激光喷丸参数对残余应力分布的影响规律,较快获取期望的残余应力分布,通过利用有限元软件ABAQUS对激光喷丸过程进行数值模拟,完成了7075航空铝合金靶材在不同冲击波峰值压力、冲击次数、光斑大小及搭接率等工艺参数下的数值模拟。模拟结果表明:随着峰值压力的增加,材料表面残余压应力也增加,当峰值压力增大到一定值时,材料表面残余压应力达到最大;当峰值压力一定时,材料表面及内部残余压应力随光斑大小及冲击次数的增加而增加;随着光斑搭接率的增加,材料表面残余压应力增大,且随着搭接率的增加,表面残余压应力的波动逐渐减小。     

CNTs/Al复合材料搅拌摩擦加工质量的超声衰减评价

针对搅拌摩擦加工法制备的碳纳米管增强铝基复合材料的主要碳纳米管团聚缺陷,提出超声波衰减法对加工质量进行无损评价,通过改变搅拌摩擦加工次数得到不同团聚程度的碳纳米管增强铝基复合材料;根据超声衰减理论分别测量各个试样的衰减系数,从宏观上对团聚缺陷进行评价,最大和最小衰减系数相差50倍,通过超声特征扫描成像检测法验证了评价结果的有效性;同时测量了搅拌摩擦加工次数为3次和6次的纯铝试样的衰减系数分别是0.032、0.029 dB/mm,基本排除了在搅拌摩擦加工后纯铝晶粒变化对试验结果带来的影响;最后又采用超声衰减法从微观角度对团聚缺陷进行评价,随着搅拌次数增加,衰减系数从0.178 dB/mm变化到0.025 dB/mm,每搅拌1次衰减系数降低约1倍,可以得出团聚程度越严重,衰减系数越高。     

磨削深度对42CrMo钢磨削强化层的影响

研究了磨削深度对42CrMo钢强化层组织与硬度的影响。结果表明,在不同磨削深度条件下,强化层的马氏体粗细不均,表层显微硬度随磨削深度先增加后降低,完全强化层显微硬度在720～800 HV0.1之间,比基体硬度提高了2倍。随着磨削深度的增加,强化层厚度最小值也增加,在磨削深度为0.6 mm时强化层厚度可达1.8 mm。     

新型马氏体耐热钢蠕变-疲劳性能与寿命预测

针对P92和G115新型马氏体耐热钢进行了应力控制下蠕变-疲劳性能研究,分析了保载时间和峰值应力对应力控制下蠕变-疲劳性能的影响规律.?结果表明,应力控制下蠕变-疲劳过程中蠕变变形和损伤主导了蠕变-疲劳寿命.?蠕变-疲劳寿命随峰值应力和保载时间的增加而下降,同时相同峰值应力下,G115钢的蠕变-疲劳寿命约是P92钢的8...     

椭圆歧型三通冲蚀磨损数值模拟

目的 解决石油化工行业中高压三通管汇因冲蚀磨损导致失效率高的问题,降低石油化工生产中的不可控成本,提高歧型三通管的使用寿命和管汇区的安全系数。方法 采用 模型,基于固–液两相流冲蚀理论建立椭圆截面歧型三通管冲蚀磨损数值模拟模型,预测椭圆截面歧型三通管在工作时发生冲蚀磨损的几何位置。研究椭圆截面歧型三通管的椭圆形状和方位夹角对管道最大冲蚀率的影响,对比i=0.85时的椭圆截面和i=1时的普通圆截面2种歧型三通管在不同质量流率、颗粒直径、液体流量、流体黏度下对管道最大冲蚀率的影响。结果 夹角为60°时,管道最大冲蚀率最大,夹角为50°和70°时,管道最大冲蚀率比较接近,夹角为40°时,管道最大冲蚀率最小。不同夹角时均满足:当i由0.76增大至1过程中,管道最大冲蚀率先缓慢减小,后迅速增大,在i=0.85附近有最小值,最大值比最小值增大3.66倍;i=1减小至i=0.76过程中,相贯线处冲蚀率逐渐减小,主管中部的冲蚀率逐渐增加,且冲蚀区域逐渐由主管中部转移到主管上部,冲蚀最严重的区域由相贯线处转变为相贯线附近的回旋涡流区(低流速区)。i=1时,在不同固相颗粒质量流率和主管流量下,最大冲蚀率均明显大于i=0.85时的,增大倍数分别为1.9倍和1.93倍;在不同固相颗粒直径和流体黏度下,最大冲蚀率均明显大于i=0.85时的,增大倍数分别为2.74倍和2.36倍。结论 椭圆截面歧型三通管i值由0.76增大到1过程中,最大冲蚀率先减小后增大,且在i=0.85附近有最小值;i=0.85时,最大冲蚀率在不同工况下的变化趋势与i=1时基本一致,但冲蚀率的降低效果十分显著。