基于卤素灯激励的红外热成像裂纹无损检测研究

钢轨安全状态的监测对保证列车的安全运行至关重要,针对钢轨裂纹的检测,本文阐述了几种不同的裂纹检测技术.重点分析了红外热成像检测技术在钢轨裂纹检测中的应用,该检测技术包括外激励加热、红外图像采集以及图像处理三部分.本文将常用激励方式进行了介绍和对比,详细阐述了卤素灯作为激励在裂纹检测中的应用;其次,搭建了基于卤素灯激励的...     

一种测定钢表面裂纹深度的涡流检测技术

采用涡流法检测钢表面的缺损状况和裂纹深度.设计和制作了双线圈涡流传感器和检测电路.并确定了裂纹深度与响应电压的关系曲线.     

基于卷积模块注意力机制深度学习模型的激光熔覆裂纹识别

为改进传统人工方法对熔覆区域裂纹检测耗时、准确率低的现状,提出了一种融合注意力模型的熔覆区裂纹自动识别方法,以便对裂纹进行标识和检测.基于U-net网络构造的熔覆裂纹语义分割网络存在对局部小特征提取能力不足的问题,而通过增加注意力模型(CBAM)层,提取特征空间和特征通道的权重信息,就可以对激光熔覆区微观裂纹进行实时的像素级标注和检测.实验结果表明:引入注意力模型的深度学习模型可使熔覆裂纹的识别和检测准确率提升2.7个百分点;融合注意力模型的网络在熔覆区域裂纹测试集上的准确率为79.8％.深度学习模型标注的准确度和速度均已超过人工标注,为激光熔覆裂纹的识别提供了有效方法.     

测量技术与设备

1610 测量总论0325852钢杆裂纹定量检测的研究[刊]/罗成汉//传感器技术.-2003,22(5).-10-12阐述了钢杆裂纹缺陷的定量检测原理。设计了钢杆裂纹缺陷漏磁的计算机辅助定量检测系统,并对钢杆裂纹缺陷进行模拟实验,获得裂纹缺陷信号波形,并对实验数据进行曲线拟合,初步建立检测系统的数学模型,从而验证了该方法的可行性,并得出相关的结论。参2     

航空发动机涡轮叶片焊接裂纹故障表现及修改方法

某航空发动机出现了焊接裂纹故障,在进行修理的过程中使用荧光渗透探伤并没有检验出来.在分析裂纹的性质后发现该裂纹主要是由残余应力造成的延时裂纹,进行荧光探伤后没有发现开口.采用金相分析裂纹性质后,证明裂纹主要是因为残余应力造成的.综合分析后研究决定使用X射线进一步进行探伤检测,并对修理工艺流程进行优化,消除残余应力的影响,有效解决了裂纹故障.     

基于涡流热成像的铁磁材料近表面微裂纹检测

采用涡流热成像技术,对铁磁材料近表面微裂纹进行了检测研究。提出了平行激励热传导方式检测近表面微裂纹的检测方法;数值计算模拟了涡流激励下裂纹处的生热过程,分析了裂纹处的温度分布及其对检测结果的影响;采用平行激励方式对含近表面微裂纹的铁磁材料进行了检测实验,通过提取试件表面温度分布数据,获取其变化速率曲线,实现了对裂纹的检测和识别。结果表明:涡流热成像平行激励方式能够准确地检测到铁磁材料近表面的微裂纹缺陷;选择适当的涡流激励时间有助于提高裂纹处与非裂纹处温度对比,增强检测效果。该方法的研究为近表面微裂纹的检测和定量识别奠定了基础。     

超声红外热成像技术在航空发动机叶片裂纹的对比研究

由于航空发动机叶片具有复杂的曲面结构,对服役过程中形成的微小裂纹检测带来了困难,文中采用超声红外热成像技术对航空发动机叶片裂纹实施检测,开展了超声红外热成像技术研究,搭建了超声红外热成像实验平台,并对实际服役过程中产生裂纹的航空发动机工作叶片进行检测.超声红外热成像结果与渗透检测、金相检测进行了对比;实验结果表明,对于...     

高铁摩擦片表面裂纹检测方法研究

摩擦片的裂纹数目和长度是衡量高铁制动性能的核心评定标准之一,有效的裂纹检测对高铁的安全运行具有重要意义.提出基于CSPDarkNet53主干网络架构的改进算法,实现摩擦片裂纹的在线自动检测.一方面融合双路特征提取网络以增强对于裂纹特征检测的敏感度,有效提高摩擦片裂纹检测的准确率;另一方面在YOLO检测模块预测框的去冗余计算环节中,采用目标框加权融合算法(weighted fusion algorithm of target box,WBF)降低误检率.实验结果表明,相较于当前最具有代表性几类目标检测算法,本文采用的方法准确率显著提高,平均精度提升7.64％.     

路面破损图像实时检测方法研究

提出一种路面破损图像实时检测的实现方法.对高速采集的路面图像去模糊后再进行裂纹特征分析,设计了一种基于邻域像素灰度值比较的特征快速提取方法,利用邻域相关及连贯性等知识智能去除虚假裂纹,从而提取真实裂纹信息.大量采集的图片的处理结果表明,该方法可实时快速检测路面破损信息,具有较强的鲁棒性和实际应用性.     

基于激光红外检测信号的表面裂纹定量重构

激光红外检测方法作为一种新型的远距离无损检测技术,对于表面裂纹的检测具有很高的效率。本文基于频域叠加法和数据库策略实现了激光激励下表面温度的快速数值模拟,研究了裂纹尺寸与温度分布间的关系,在时域与空域验证了快速数值方法的有效性。为基于红外检测信号实现裂纹尺寸的定量重构,选取合适的特征量并且建立了基于确定论方法的裂纹重构算法。最后,搭建了红外检测实验系统,进行了平板试件裂纹红外检测实验,基于实验信号实现了裂纹的定量重构,验证了重构算法的有效性。     

基于CNN的金属疲劳裂纹超声红外热像检测与识别方法研究

传统超声红外热像检测与识别金属疲劳裂纹主要是通过图像处理算法提取红外热图像的相关热特征,并与裂纹特征进行匹配,其过程过于繁琐,识别率较低且需要人工筛选有效特征。结合主动红外热成像技术以及卷积神经网络（Convolutional Neural Network,CNN）在金属结构无损检测与缺陷自动识别中的优势,提出了一种基于CNN的金属疲劳裂纹超声红外热像检测与识别方法。通过超声红外热成像装置对实验对象（文中为金属平板试件）进行检测,获取红外热图像并制作图像数据集。运用设计的卷积神经网络对不同尺寸裂纹的超声红外热图像进行特征提取与识别分类。此外,对所提出的方法与两种常见图像分类网络模型以及支持向量机的分类结果进行对比。实验结果表明,设计的卷积神经网络在该数据集上识别分类准确率为100%,优于其他网络模型和支持向量机的识别分类,可以有效检测与识别金属疲劳裂纹。     

铝合金疲劳裂纹振动红外热成像检测研究

航空铝合金经过多次使用存在紧密闭合型裂纹严重威胁飞行安全,以带有疲劳裂纹的7075铝合金为检测对象,利用超声振动做为振动红外热成像技术的激励源,通过多次调节功率、焊枪与平板之间预紧力和激励位置实现对铝合金板缺陷的识别,实验结果表明,振动热成像技术能检测出紧密闭合裂纹,同时发现检测效果受控于激励功率的影响,功率大振幅显著检测效果好,且功率较大的情况下预紧力对检测效果影响较大,功率较低时预紧力对检测效果小,最后发现在功率一定的情况下合理的调节预紧力和激励位置能使缺陷成像结果更加清晰。     

A modified 4-point bend delamination test

The 4-point bend delamination test is widely used to study the adhesive properties in thin film structures. The analysis of such tests is commonly based on assumption that symmetry conditions are appropriate to describe crack length and loading. These conditions are, however, rarely fulfilled, and it is common that only a single crack is being propagated. This fact is especially of concern in fatigue crack growth studies. Solutions for energy release rates for asymmetric 4-point bend delamination specimens are presented. A semi-articulated test fixture is described. The experiments conducted with this fixture and the additional energy release rate equations allow that cracks to both sides of the specimen are being propagated. In toughness testing this provides two values for the critical energy release rate from a single test. In fatigue testing, it is demonstrated that near symmetric crack growth was obtained, and remaining asymmetry effects can be quantified.     

Fatigue and thermal fatigue damage analysis of thin metal films

In this paper, we summarize several testing methods that are currently available for the characterization of fatigue properties of thin metal films. Using these testing methods, a number of experimental investigations of the fatigue and thermal fatigue of metal films with thicknesses ranging from micrometers to sub-micrometers are described. Extensive experimental observations as well as theoretical analyses reveal that the damage behavior, i.e. typical fatigue extrusions and cracking, are quite different from that of bulk materials, and are controlled by the length scales of the materials. Due to the high surface to volume ratio of thin films interface-induced and diffusion-related damage are prevalent in these small length scale materials. As a result, interfaces pose a serious threat to the reliability of thin films.     

激光喷丸强化中材料表面残余应力的优化控制

激光喷丸强化是一项新型的表面处理技术,在这个处理过程中会产生残余应力,从而有效抑制材料疲劳裂纹的萌生以及减缓裂纹扩散速率,有效提高材料的疲劳寿命.为有效地控制金属表面残余应力,结合激光喷丸技术的特点,利用神经网络强大的非线性映射能力,将金属材料主要的力学性能参数和激光参数作为网络输入,金属材料表面残余应力作为网络输出,建立金属材料表面残余应力的优化控制模型.最后选用7050Al、A304不锈钢和AM50镁铝合金这三种金属材料对此模型进行验证,验证结果表明此模型可以有效地控制金属材料表面的残余应力.     

Superior Fatigue Resistant Bioinspired Graphene‐Based Nanocomposite via Synergistic Interfacial Interactions

Excellent fatigue resistance is a prerequisite for flexible energy devices to achieve high and stable performance under repeated deformation state. Inspired by the sophisticated interfacial architecture of nacre, herein a super fatigue‐resistant graphene‐based nanocomposite with integrated high tensile strength and toughness through poly(dopamine)‐nickel ion (Ni²⁺) chelate architecture that mimics byssal threads is demonstrated. These kind of synergistic interfacial interactions of covalent and ionic bonding effectively suppress the crack propagation in the process of fatigue testing, resulting in superhigh fatigue life of this bioinspired graphene‐based nanocomposite (BGBN). In addition, the electrical conductivity is well kept after fatigue testing. The proposed synergistic interfacial interactions could serve as a guideline for fabricating high‐performance multifunctional BGBNs with promising applications in flexible energy devices, such as flexible electrodes for supercapacitors and lithium batteries, etc.     

频率共振法在飞机结构疲劳损伤预测中的可行性研究

用不同振动周期数时的相位偏移角来表征结构的疲劳状态,通过无孔样品在共振法测试后不同应力区表现的相似性,以及有孔样品在共振法测试后裂纹产生处的疲劳损伤情况,研究频率共振法在飞机结构疲劳损伤预测时的可行性,研究结果为飞机结构安全检测提供理论依据.     

Design and Control of a Piezoelectric Driven Fatigue Testing System for Electronic Packaging Applications

Failure of solder joints for electronic packaging is an important issue for controlling the reliability of semiconductor devices. However, the complicated coupling between mechanical stressing and temperature and time dependent material properties makes it difficult to explore the fundamental failure control mechanisms using the existing accelerated thermal cycling methods. In addition, the testing speed is also severely restricted by the thermal time constant of the characterization system. In order to decouple the mechanical stress effect from other factors as the first step toward exploring the control mechanisms of failure, a piezoelectric-based fatigue characterization system is developed to replace the thermal cycling and provide fast and purely mechanical stressing cycles. A self-tuning based (STR) adaptive controller is also developed to provide accurate process control during experiments for compensating stiffness variation due to fatigue crack growth. It is found that this STR regulator is more robust than the traditional PID controller. The bandwidth of the system is approximately 70 Hz and is currently restricted by the equivalent time constant of the piezoelectric material. Nevertheless, this speed is sufficient for conducting a successful fatigue testing of solder joints. Finally, preliminary fatigue experiments have been performed on Sn₆₃Pb ₃₇ solders and the reduction of stiffness due to crack growth is clearly visible while the actuation performance is consistent and stable during the entire testing period. In the future, it is possible to operate in conjunction with a temperature control unit and a creep testing scheme to explore both the temperature and time dependent nature of solders in order to fully understand the failure control mechanisms of packaging     

激光冲击强化对TC17钛合金高周疲劳性能的影响

为了研究激光冲击强化对TC17钛合金高周疲劳性能的影响,对TC17钛合金进行激光冲击强化处理,并对处理前后的试样进行了高频疲劳试验,对疲劳断口和形貌用扫描电镜和透射电镜进行了观察。7J能量激光冲击2次后,材料在300MPa下的疲劳寿命相比未处理的材料提高了近2倍;相比于母材试样,强化试样的裂纹源位于次表层深处,扩展区的疲劳条带排列更加紧密。结果表明,激光冲击强化后,试样表面强化区域产生高密度位错和位错缠结。这些缺陷能有效地阻止疲劳裂纹的萌生和扩展,进而改善TC17钛合金的高周疲劳性能。     

A fast test technique for life time estimation of ultrasonically welded Cu–Cu interconnects

In this research the quality of the interconnects of the ultrasonically welded Cu terminals to the Cu substrate in the IGBT-module has been investigated. An ultrasonic resonance fatigue system in combination with a laser Doppler vibrometer and a special specimen design was used for shear fatigue testing of these large ultrasonic Cu–Cu welds (about 0.5 cm²). Fatigue life curves up to 10⁹ loading cycles were obtained in a very short period of time. Using this technique it was possible to evaluate the fatigue strength of these interconnects for the first time. The microstructural features of the interconnects were characterized and their crack growth behaviour was studied. Fracture analysis of the fatigued specimen shows that failure occur due to the propagation of the crack beneath the welding interface into the copper substrate. Additionally performed finite element simulations offer an insight into the stress and strain concentrations during the mechanical fatigue tests. As this method is not restricted to the welding geometry, material joints with larger interconnects can be tested likewise. Thus this new technique can be used as a practical and valid fatigue testing method for evaluation of various interconnects.