搅拌摩擦焊接弱结合与未焊透缺陷的检测对比

对搅拌摩擦焊焊缝的弱结合及未焊透缺陷进行超声相控阵检测,并制备拉伸试样,通过声发射检测进行拉伸过程的监测。通过比较弱结合及未焊透缺陷的A、B扫描信号及声发射能量信号的差异,为两种缺陷的信号识别提供依据。分析结果表明:未焊透缺陷较弱结合缺陷更容易检出;垂直型未焊透缺陷的A扫描信号呈单束较高波峰,具有一定曲率的弱结合缺陷的A扫描信号主波峰较低,并存在若干不同角度的反射回波信号;在试样拉伸颈缩断裂前,带有未焊透缺陷的试样较弱结合缺陷释放较大的能量。     

桥式起重机箱形梁异种钢焊接接头疲劳损伤的声发射表征

文中通过声发射技术对桥式起重机箱形梁Q345B/Q235B异种钢焊接接头疲劳损伤过程进行表征,发现了声发射特征参数变化取决于疲劳裂纹扩展不同阶段的特点,得以利用声发射动态监测桥式起重机循环载荷下的疲劳损伤状态,从而实现及早预警的目的。另外,通过对异种钢焊接接头焊缝和热影响区2种不同缺陷位置疲劳实验各阶段典型声发射信号的对比分析,获知热影响区比焊缝位置更易发生疲劳断裂,故箱形主梁在服役过程中应重点关注异种钢焊接接头热影响区位置并及早发现危险。     

压力容器用钢氢致开裂的声发射试验研究

氢致开裂是在役压力容器一种常见的失效形式。声发射技术是监测动态破坏过程的有效手段。为了研究压力容器用钢氢致开裂过程的声发射特征,对电解充氢过程中的20R钢进行了监测。试验结果表明,碳钢表面电解充氢并腐蚀的过程和内部氢致裂纹的产生均会对材料的声发射活动产生影响。氢致裂纹的发展过程可分为孕育期和扩展期两个阶段,随着裂纹的生长,高幅声发射信号的数量明显增多。试验结果为压力容器现场检验提供了参考。     

塔机材料常规缺陷的声发射定位与辨识技术

故障源的实时定位和特性辨识是塔机安全评价及故障预防的关键。试验采用塔机常用材料Q235无缺陷、裂纹及焊接缺陷试件,利用GPS-100高频疲劳试验机和SDAES数字型声发射仪采集在不同载荷下试样的声发射信号,通过结合信号分析技术得出缺陷试件的故障定位、信号的频谱特征和参数特征分析,总结了Q235常规缺陷试样典型声发射信号的主要特征参数的范围。论文研究工作为声发射技术在塔机危险源的检测研究提供了非常重要的学术价值和指导意义。     

基于声发射技术的金属高频疲劳监测

采用声发射技术监测高频疲劳条件下金属材料裂纹的扩展。介绍了如何运用软硬件处理的方法，从采集到的信号中分离出裂纹扩展的声发射信号。从处理后的声发射信号与观察得到的裂纹扩展对比来看，声发射参数的变化能够有效地反映材料疲劳裂纹扩展的过程，并且能更早地发现试样内部微小裂纹的变化。通过试验，得出了紧凑拉伸试样在裂纹稳定扩展阶段声发射信号能量率与应力强度因子幅值之间的关系式。     

基于声发射的Q235钢点蚀过程监测技术研究

以声发射技术为基础,针对油气储运常用材料Q235的点蚀过程,利用试件在模拟溶液中点蚀过程产生的声发射信号为样本,采用参量分析与波形分析相结合,重点研究Q235钢点蚀过程中产生的声发射信号的变化特征,得到了金属点蚀不同阶段的声发射信号特性,并通过声发射信号事件的分布规律,得到了Q235钢早期腐蚀与声发射信号演变的一致性结果。试验证明了声发射技术为基础的Q235钢点蚀过程监测具有良好效果。     

声发射检测起重机的现状与可行性试验

起重机是建筑与工业生产中的重要设备,统计表明起重机事故约占我国全部工业企业伤害事故的20%左右。基于此,文中对目前声发射检测在起重机的应用现状进行了综述,将声发射在线监测方法引入到大型门箱式起重机检测的可行性进行了分析,并在线检测。结果表明,声发射应用于大型门箱式起重机的检测是可行的,能有效识别存在的危险的信号;门箱式起重机两端部的圆弧过渡处角焊缝属于应力集中区,是声发射检测时的重点监测部位。     

一种复杂结构件圆柱面扩散焊缝阵列超声检测方法

航空发动机某高温合金盘构件采用盘体与叶片环进行焊接的方式制备,由于构件结构复杂,在检测圆柱形焊接面缺陷时,采用单晶超声检测换能器检测效率不高,缺陷信号信噪比低。为提高该种结构件的检测能力,研究圆柱面焊缝的阵列超声自动检测方法,分析面积型缺陷和声源的相对位置对缺陷反射声压和波型转换的影响,提出一种基于双阵列换能器的一发一收检测方案。根据高温合金盘结构设计基于双阵列换能器的声束发射-接收方法和圆柱面焊缝全覆盖检测方案;基于时域有限差分方法建立高温合金盘的阵列超声声学响应仿真模型,对检测参数进行设计和优化。对含有人工缺陷的实际试样进行检测试验,结果表明所提出的双阵列超声换能器检测方法能有效检测到圆柱面焊缝区域? 2 mm的当量缺陷。     

基于声发射信号监测的高速准干切削试验研究

声发射信号可以及时地反映出高速切削加工过程中工件和刀具材料的内部缺陷变化和扩展情况.为了对其进行监测和分析,建立了一套基于虚拟仪器的信号采集系统,采集高速切削铝合金加工过程中的声发射信号.对采集到的声发射信号进行小波变换并重构后,发现铝合金切削过程中的声发射信号与切削速度密切相关.随着切削速度的增大,声发射也随着增大.     

基于声发射技术的Q345焊接接头特征信号分析

以Q345为研究对象,基于声发射技术对正常焊接接头和预制缺陷焊接接头的拉伸加载过程进行了动态监测,获得了加载过程中的特征声发射信号,并通过傅里叶变换对信号进行了频谱分析。分析结果表明:信号的撞击计数、能量和幅值与时间之间基本符合线性关系,能够较好地表征试件拉伸过程的各个阶段;预制缺陷引起应力集中,屈服阶段和强化阶段能量与幅值比较突出;Q345试样的拉伸频率主要集中在100kHz~300kHz。     

Studying the correlation of the informative parameters of acoustic-emission signals with the destruction processes in specimens with welding flaws

The results of acoustic-emission (AE) testing of flaws in steel specimens during welding and subsequent loading until destruction in MTS-50 and MTS-250 electrohydraulic machines are presented. Flaws were simulated via faulty fusions or the introduction of titanium and duralumin inserts. During loading, some specimens were broken along the weld seam and the other specimens were broken in the near-seam zone. A comparative analysis of the distributions of the informative parameters of AE signals, which are recorded during different types of specimen fracture, is presented.     

Detecting hazardous sources of acoustic-emission signals using the estimated energy of clusters

A method for detecting hazardous sources of acoustic-emission (AE) signals by the level of their energy activity using clustering by digitized signal shape was considered. The influence of the distance between a source and an AE transducer on the energy of recorded AE signals was analyzed. The energy distribution median of signals in a cluster was proposed for evaluating the hazard of an AE signal source. The application of the developed method was tested based on the example of the analysis of AE inspection data on the welding of steel specimens with incomplete fusion and a crack at the root of a weld seam. This testing confirms the results of the fractographic inspection of a defective weld seam.     

Studying the deformation and temperature distributions in a specimen during acoustic-emission testing of the weld-seam welding and cooling process

The results of experimental studies of the weld-seam welding and cooling process in steel specimens using acoustic emission (AE) and strain gauging are presented. Deformation was measured by high-temperature strain gauges welded to specimens using spot welding. Temperature was measured by chromel-alumel thermocouples. Measurements were performed with measured with an MMTC-64.01 microprocessor strain-gauging system and a C??a?? ?16.10 AE system. Computers of these two systems exchanged information. Residual strain deformations were recorded on a specimen after cooling of a weld seam. Metallographic studies of transverse sections, which were were cut out from the clusterization zones of a weld seam, confirmed the presence of cracks, pores, and faulty fusions.     

Evaluation of fracture behavior of SA-516 steel welds using acoustic emission analysis

The purpose of this study is to evaluate the AE characteristics for the basemetal, PWHT (post-weld heat treatment) and weldment specimens of SA-516 steel during fracture testing. Four-point bending and AE tests were conducted simultaneously. AE signals were emitted in the process of plastic deformation. AE signal strength and amplitude of the weldment was the strongest, followed by PWHT specimen and basemetal. More AE signals were emitted from the weldment samples because of the oxides, and discontinuous mechanical properties. AE signal strength and amplitude for the basemetal or PWHT specimen decreased remarkably compared to the weldment because of lower strength. Pre-cracked specimens emitted even lower event counts than the corresponding blunt notched specimens. Dimple fracture from void coalescence mechanism is associated with low-level AE signal strength for the basemetal or PWHT. Tearing mode and dimple formation were shown on the fracture surfaces of the weldment, but only a small fraction produced detectable AE.     

Studying sources of acoustic emission during the cooling of a weld seam with the use of cluster analysis

Acoustic-emission (AE) signals localized during cooling of a weld seam were analyzed. The hazard degree of flaws (faulty fusions, cracks in the root of a weld seam, etc.) was studied using cluster analysis in the parameters of AE signals. Flaws were simulated via introduction of titanium and duralumin inserts into a weld seam. The results of metallographic investigations of specimens with artificial and actual flaws were analyzed. Localization of AE signals was performed for the specimens studied, and a time distribution taking into account the clustering of the total count and energy of AE signals was constructed.     

核电装备制造中落锤试验的影响因素

落锤试验是核电装备制造中对材料进行检测和评判的一种重要方法.本文分析了试样尺寸、试样焊接、过程控制和结果判定四类影响落锤试验的因素,可在今后的试验过程中进行控制,使测试结果达到稳定准确.     

On the Information Value of the Method of Invariants of Acoustic-Emission Signals in the Diagnostics of Pre-Failure State in Materials

The specific features of using the method of the invariants of acoustic emission (AE) signals for the diagnostics of a pre-failure state are considered. Results of the diagnostics of pre-failure by the amplitude and temporal invariants of AE event stream under mechanic loading of steel specimen are presented. It has been established that the measurement and analysis of amplitude and temporal informative parameters is more pictorial and should be preferred to the direct measurement of invariant relationships. Incorrect application of the method of invariants has been analyzed.     

铝合金焊点疲劳性能及其影响因素分析

研究了铝合金AA5754和AA6111-T4焊点的疲劳性能,获得了不同厚度及试件类型的焊点疲劳数据;研究了试件类型不同时焊点的疲劳失效模式,讨论了焊点疲劳裂纹的扩展形式;分析了铝合金焊点疲劳寿命的影响因素。结果表明:焊点疲劳失效模式主要有两种,分别是母材“眉状”裂纹断裂和焊点熔核界面断裂;母材对焊点疲劳寿命影响不大;循环载荷比对焊点寿命有一定的影响,增大载荷比导致焊点疲劳寿命略有下降;试件类型对焊点寿命有很大的影响,应在设计中避免焊点承受剥离载荷。