1100℃以上高温连铸板坯表面缺陷的模拟在线无损检测

高温状态下连铸板坯表面缺陷的在线无损检测在现代化的连铸坯热送－直轧工艺中对于保证铸坯的质量有着极其重要的意义。本文介绍了连铸坯高温探伤技术和相应的试验装置。采用涡流方法成功地模拟了１１００℃以上铸坯表面缺陷的动态检测，所用探头及检测设备均可在高温状态下长时间连续工作，能检测出深度为１．５ｍｍ，宽度为０．３ｍｍ，长为１０ｍｍ的表面缺陷，并能有效地抑制铸坯表面振动斑痕所产生的噪声影响。借助于计算机信号     

Detection of multiple cracks using frequency measurements

A method for detection of multiple open cracks in a slender Euler-Bernoulli beams is presented based on frequency measurements. The method is based on the approach given by Hu and Liang [J. Franklin Inst. 330 (5) (1993) 841], transverse vibration modelling through transfer matrix method and representation of a crack by rotational spring. The beam is virtually divided into a number of segments, which can be decided by the analyst, and each of them is considered to be associated with a damage parameter. The procedure gives a linear relationship explicitly between the changes in natural frequencies of the beam and the damage parameters. These parameters are determined from the knowledge of changes in the natural frequencies. After obtaining them, each is treated in turn to exactly pinpoint the crack location in the segment and determine its size. The forward, or natural frequency determination, problems are examined in the passing. The method is approximate, but it can handle segmented beams, any boundary conditions, intermediate spring or rigid supports, etc. It eliminates the need for any symbolic computation which is envisaged by Hu and Liang [J. Franklin Inst. 330 (5) (1993) 841] to obtain mode shapes of the corresponding uncracked beams. The proposed method gives a clear insight into the whole analysis. Case studies (numerical) are presented to demonstrate the method effectiveness for two simultaneous cracks of size 10% and more of section depth. The differences between the actual and predicted crack locations and sizes are less than 10% and 15% respectively. The numbers of segments into which the beam is virtually divided limits the maximum number of cracks that can be handled. The difference in the forward problem is less than 5%.     

Defect classification using a new feature for pulsed eddy current sensors

The objective of this study is to identify defects such as surface cracks, subsurface defects and metal losses using feature based pulsed eddy current sensors. A new feature, termed as the rising point, related to the propagation time of electromagnetic waves in metallic targets is proposed for defect classification. Experimental studies of the validation, robustness of the new feature of rising time are reported. In addition to other features, defects can be detected and quantified robustly and lift-off can also be derived from the rising time. Conclusion and further work are derived on the basis of the findings.     

陶瓷材料的无损检测技术

综述了无损检测在陶瓷材料领域的应用，简略介绍了用于陶瓷无损检测的几种主要方法。     

门座起重机疲劳裂纹扩展寿命分析研究

门座起重机存在大量因疲劳裂纹导致结构破坏的现象,所以进行疲劳裂纹扩展寿命分析,预测起重机剩余安全使用期的研究就显得非常必要.先对疲劳裂纹扩展寿命进行理论推导,在此理论基础上,制定疲劳裂纹扩展寿命分析的流程;接着以某台100t门座起重机的一处裂纹为研究对象,通过无损探伤确定裂纹尺寸和位置,获取准确的应力谱,在各种典型工况下,对该裂纹进行疲劳裂纹扩展寿命分析研究.定性分析结果表明该裂纹为安全裂纹.该方法能较真实地反映门座起重机的剩余寿命状况,为解决剩余寿命分析问题提供参考.     

钢管端部横向裂纹的漏磁检测方法

针对目前钢管自动检测过程中普遍存在的检测盲区问题,提出采用管内部磁化器固定,管外部扫描的漏磁检测新方法。介绍了无盲区检测钢管端部横向裂纹的原理,并从磁化器到检测探头的设计等多方面介绍了整个检测装置的结构,通过大量的实验分析验证了该检测方法的适用性与可靠性。     

基于科赫雪花图形激励装置的涡流传感器工作原理分析

首次提出并设计了一种基于分形理论自相似结构的科赫雪花图形激励装置涡流传感器,对这种传感器的工作原理和物理模型进行了深入的分析,分析表明,基于分形结构激励线圈的涡流传感器,在多处具有涡流叠加效应,随着科赫雪花图形阶次的提高,这种涡流叠加效应越来越明显,分布密度不断增加,可以显著提高涡流传感器激励效果和检测灵敏度,从而提高对微小裂纹缺陷的检测能力.研制了实际装置,通过实验证了这一结论.     

Applications of non-destructive testing techniques for post-process control of additively manufactured parts

This paper presents an overview on the principle of operation for post-process inspection non-destructive testing (NDT) techniques. The techniques include visual inspection, liquid penetrant testing, magnetic particle testing, eddy current testing, ultrasonic testing, and radiography. The applications of these NDT techniques in additive manufacturing (AM) and their suitability for defects detection of additively manufactured parts are reviewed. The sensitivity, and the advantages and disadvantages of each technique are evaluated. The types of defect, and the detectability of these defects by NDT techniques are assessed. The applicability of each NDT technique for different categories of AM process is discussed. The categories of AM are, namely, material extrusion, powder bed fusion, vat photopolymerisation, material jetting, binder jetting, sheet lamination, and directed energy deposition.     

Effects of microstructural heterogeneity on very high cycle fatigue properties of 7050-T7451 aluminum alloy friction stir butt welds

In this study, the very high cycle fatigue (VHCF) properties of 7050-T7451 aluminum alloy and its friction stir welding (FSW) butt welds have been investigated. The results show that the failure of FSW joints still occurs at 7.0 × 10⁸ cycles. The fatigue properties of the FSW joints are superior to those of the base material, especially in the super long life regime. Most fatigue cracks initiate at the thermo-mechanically affected zone and heat affected zone on the advancing side of the FSW joints, and the susceptibility of these zones to fatigue is attributed to the metallurgical heterogeneity.     

地质雷达在边坡稳定性检测和预警中的应用

西南科技大学老校区某处边坡处在特殊的地质环境中,存在潜在的滑坡危害。为了给其安全防治工作提供有效的科学依据,采用SIR-20型地质雷达进行了无损检测并分析所得数据,发现坡体原始结构层均遭受了一定的破坏,存在多处裂缝,坡体内存有积水,影响了其地层结构的稳定性,遇雨水长期浸润,极易出现整体滑坡现象。根据检测结果提出了相应的排水沟网和抗滑桩支挡的预警措施。