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.     

Identification of sources of acoustic emission on casting flaws in cast parts

Peculiarities of the estimation of the state of sections with casting flaws in cast parts using acoustic-emission (AE) method are considered. The dynamics of variations in AE parameters for developing flaws during mechanical tests is analyzed. The methods for distinguishing useful information of AE signals from the regions of localization of casting flaws are revealed.     

Nondestructive testing of the quality of blanks for the fabrication of hot-rolled strips using the acoustic-emission method

A method for predicting the quality of hot-rolled strips based on the results of recording acoustic-emission (AE) signals is proposed. Considering the development of flaws in a slab under the effect of technological loads during rolling as a process of the loss of the integrity of the slab material, the AE signals recorded in the course of diagnostic loading of experimental specimens are interpreted from the standpoint of a micromechanical model and the developed methodology for nondestructive testing of the strength of a material and quality estimation. The most informative diagnostic parameters and diagnostic features of the method are determined by comparing the results of the interpretation with the defect level of the obtained strip.     

Clustering of sources of acoustic-emission signals by the leading-edge rise rate

It is shown that the method of clustering by the leading-edge rise rate of the envelope of an acoustic-emission (AE) signal makes it possible to reduce the time of calculation of the coordinates of flaws as compared to the clustering by shape. The developed technique realizes the on-line localization of massive flows of AE signals with an accuracy sufficient for practical application. The practical parameters of using the method for operation on a steel sheet with a simulator obtained for a statically loaded duralumin specimen and for welding of steel specimens with aluminum and titanium inserts are considered.     

交流电磁场检测在空压机中冷器检修中的应用

通过分析裂纹对交流电磁场信号影响的方式和规律,对缺陷和交流电磁场信号响应特征之间的关系进行了分析和研究,介绍了焊缝表面交流电磁场检测技术的原理、方法,制作了对比试样,并进行了测试分析,通过实际检测表明,交流电磁场检测速度快、灵敏度高、测试结果准确.     

Study on the thermo-effect of P-GMAW characterized by structure-borne acoustic emission signals detected in welding on aluminum alloy

According to the structure-borne acoustic emission (AE) signals detected in pulsed gas metal arc welding (P-GMAW), the effects of welding heat input and pulses to the microstructures and the characteristics of AE signals were analyzed. The experiment results showed that the welding arc was the source of most vibration energy in GMAW. The increase of welding heat input caused the growth of grain in weld and the increase of average AE count. The mean grain size was increased with the average AE count increasing, which was attributable to the welding heat input. Both the welding arc and the pulses used in welding were the source of vibration energy in P-GMAW. The mean grain size decreased with the average AE count increasing, which was attributable to the pulses provide additional vibration energy to refine the grain structure. The welding heat input effect played a more important role than the pulses effect to the grain structure in P-GMAW.     

抗氢钢焊缝的声发射检测分析

采用声发射检测方法对抗氢钢焊缝在受载情况下的变化过程进行监测,提取出对应的声发射信号特征并进行了状态的判断。试验表明,无缺陷试样变形过程中所释放的应变能较小,而抗氢钢焊缝内部气孔缺陷在受载后将发生扩展,试样在断裂前会产生大量高幅值声发射信号。经分析后认为,声发射检测方法有望实现抗氢钢焊接构件的监测与整体性能评估。     

Inspection of locomotive bearing rings by the acoustic-emission method

The results of testing the bearing rings (BRs) of a locomotive axle box by the acoustic-emission (AE) method are presented. The small size of the localization zone of BRs leads to a significant spread of the coordinates of flaws even at minimal errors of the time of arrival of AE signals at piezoelectric-antenna probes. To refine the testing technique, the maximum testing load necessary for initializing AE signals is determined. Deformations in BRs are measured with a strain-gauging system related to the AE system. During recording of AE signals, the mechanical stresses are measured, thus allowing rejection of parasitic signals and an increase in the localization accuracy.     

2524-T3铝合金搅拌摩擦焊对接接头的疲劳性能

对2524-T3铝合金母材及三种尺寸搅拌摩擦焊(FSW)对接接头的疲劳性能进行了研究,获得了各试样的S-N曲线并进行了分析。结果表明:在疲劳寿命为1×105周时,小厚度、短焊缝FSW对接接头的疲劳强度约为母材的80.8%,大厚度FSW对接接头的疲劳强度约为小厚度、短焊缝FSW对接接头的80.3%,大焊缝FSW对接接头的疲劳强度约为小厚度、短焊缝FSW对接接头的79.9%。     

高压锅筒集中下降管的焊接

分析了生产高压锅筒中集中下降管焊接易出现的问题,提出了集中下降管埋弧自动焊焊接工艺,减少集中下降管角焊缝焊接缺陷,提高了生产效率。     

Study of fracture of specimens made of fiberglass plastic using acoustic-emission and strain measurements

The crack resistance of specimens made of a fiberglass plastic composite material has been studied. All specimens had approximately the same geometric dimensions. At the center of the specimens, there were 25-mm-long notches on both sides. The specimens were loaded with a static or cyclic load at a frequency f = 5 Hz. The tests were performed using acoustic-emission (AE) and strain gage measurements. The AE technique allowed stable localization of a flaw at an early stage of growth and made it possible to automate the measurement process. The strain gage measuring system was used to find deformations in the zones of localization of AE signals.     

Acoustic Emission Method for Testing Oil and Gas Tanks

Results of practical hydraulic tests of railway tanks owned by Altaivagon Corporation by the method of acoustic emission (AE) are given. A new technique for localization of AE signals and an appropriate software package have been developed to detect with a high certainty both internal and penetrating flaws in tanks under a load of 0.5 atm. A technique for estimating the hazard presented by the flaws in railway tanks based on detection of AE signals is discussed.     

Analysis of variations of the dynamic characteristics of acoustic-emission sources under static loading of metal specimens

Changes in the energy of acoustic-emission (AE) signals and their cross-correlation coefficient for sources of different types have been experimentally studied for statically loaded specimens. The results allow separation of AE signals appearing during irreversible changes in the region of stress concentrators and signals of other types.     

In-process endpoint detection of weld seam removal in robotic abrasive belt grinding process

This paper proposes a novel approach for in-process endpoint detection of weld seam removal during robotic abrasive belt grinding process using discrete wavelet transform (DWT) and support vector machine (SVM). A virtual sensing system is developed consisting of a force sensor, accelerometer sensor and machine learning algorithm. This work also presents the trend of the sensor signature at each stage of weld seam evolution during its removal process. The wavelet decomposition coefficient is used to represent all possible types of transients in vibration and force signals generated during grinding over weld seam. “Daubechies-4” wavelet function was used to extract features from the sensors. An experimental investigation using three different weld profile conditions resulting from the weld seam removal process using abrasive belt grinding was identified. The SVM-based classifier was employed to predict the weld state. The results demonstrate that the developed diagnostic methodology can reliably predict endpoint at which weld seam is removed in real time during compliant abrasive belt grinding.     

基于旋转电弧的机器人角焊缝跟踪建模及仿真

通过对现有旋转电弧传感器采集的焊缝偏差信息和六自由度焊接机器人运动学模型进行研究,结合曲线角焊缝的特点,推导出纠正焊缝偏差后的焊接机器人工具坐标系相对于原工具坐标系的变换矩阵。在此基础上,结合焊接机器人的运动学反解,建立了曲线角焊缝跟踪及焊枪姿态调整模型。输入给定左右偏差及高低偏差信号,利用MATLAB对模型进行仿真验证,结果证明了该模型的有效性与正确性,从而为旋转电弧传感应用于焊接机器人及设计其焊缝跟踪系统提供了理论参考。     

Estimating the possibility of the magnetic detection of microflaws in weld seams of longitudinal electric-welded pipes manufactured by butt high-frequency welding

Fragments of longitudinal electric-welded pipes were inspected in the state after their manufacturing. The presence of flaws, like surface cracks with openings of nearly 10 μm, were detected by means of optical testing in the zone of a weld seam. It was shown that such cracks can be easily detected at the УMД-101M magnetic nondestructive testing station.     

Torque control of friction stir welding for manufacturing and automation

Friction stir welding (FSW) is a solid-state welding process that utilizes a rotating tool to plastically deform and forge together the parent materials of a workpiece. The process involves plunging the rotating tool that consists of a shoulder and a pin into the workpiece and then traversing it along the intended weld seam. The welding process requires a large axial force to be maintained on the tool. Axial force control has been used in robotic FSW processes to compensate for the compliant nature of robots. Without force control, welding flaws would continuously emerge as the robot repositioned its linkages to traverse the tool along the intended weld seam. Insufficient plunge depth would result and cause the welding flaws as the robot’s linkages yielded from the resulting force in the welding environment. The research present in this paper investigates the use of torque instead of force to control the FSW process. To perform this research, a torque controller was implemented on a retrofitted Milwaukee Model K milling machine. The closed loop proportional, integral plus derivative control architecture was tuned using the Ziegler–Nichols method. Welding experiments were conducted by butt welding 0.25 in. (6.35 mm)?×?1.5 in. (38.1 mm)?×?8 in. (203.2 mm) samples of aluminum 6061 with a 0.25 in. (6.35 mm) threaded tool. The results indicate that controlling torque produces an acceptable weld process that adapts to the changing surface conditions of the workpiece. For this experiment, the torque was able to be controlled with standard deviation of 0.231 N-m. In addition, the torque controller was able to adjust the tool’s plunge depth in reaction to 1 mm step and ramp disturbances in the workpiece’s surface. It is shown that torque control is equivalent to weld power control and causes a uniform amount of energy per unit length to be deposited along the weld seam. It is concluded that the feedback signal of torque provides a better indicator of tool depth into the workpiece than axial force. Torque is more sensitive to tool depth than axial force. Thus, it is concluded that torque control is better suited for keeping a friction stir welding tool properly engaged with the workpiece for application to robotics, automation, and manufacturing.     

14NiCrMo10 6V与Q345E钢过渡匹配焊接接头的组织与力学性能

采用E551T1-Ni2药芯焊丝对Q345E钢与14NiCrMo10 6V钢进行焊接,并通过室温拉伸、弯曲、冲击、硬度试验以及金相分析等对焊接接头的力学性能与显微组织进行了研究。结果表明:采用此焊丝可以获得拉伸、弯曲和冲击性能均良好的焊接接头,焊缝硬度在200～250HV之间;焊缝处晶界组织为先共析铁素体、少量无碳贝氏体(从晶界伸向晶内),晶内为针状铁素体与珠光体,个别部位有粒状贝氏体;Q345E钢侧热影响区与焊缝过渡区的组织为沿晶界析出的块状先共析铁素体和向晶内生长的条状铁素体以及少量的珠光体和贝氏体;14NiCrMo10 6V钢侧热影响区与焊缝过渡区的组织为板条状马氏体。