探伤温度对超声波无损检测缺陷定位、探伤灵敏度的影响

本文通过对超声波探伤过程中斜探头k值、声波扩散角与探伤温度的关系进行定量分析,探讨了探伤温度对缺陷定位、探伤灵敏度的影响,并提出了解决方法.     

利用数字探伤仪实现钢轨防断的新突破

针对钢轨探伤工作中存在的问题及原因进行了深入分析,并从数字探伤仪在实际中的使用及探伤数据回放管理入手,对实施前后的效果进行了比较,对数字化在钢轨探伤中的应用进行了重点阐述,以促进数字探伤仪在铁路钢轨探伤工作中的推广应用。     

建筑钢结构焊缝无损探伤检验若干问题

焊接质量是影响钢结构工程质量的重要因素,对焊缝进行无损探伤检验是确保焊缝质量的重要手段。该文从相关标准规范的角度,对于建筑钢结构焊缝无损探伤检验中普遍采用的超声波探伤、射线探伤、磁粉探伤及渗透探伤等方法进行较全面系统的介绍。     

表面波在预弯机回程缸上的探伤应用

针对JCOE大口径直缝埋弧焊钢管生产过程中预弯机回程缸活塞杆断裂问题,笔者通过实践经验,采用超声表面波与渗透探伤相结合的方法对预弯机回程缸活塞杆进行实时探伤检测,克服了操作空间狭小,工况困难的不利因素,通过理论计算和实际试验数据结合,针对在役使用的活塞杆进行有效监控,提高了生产效率。     

国外无损探伤技术发展概况

无损探伤是应用物理原理无损地检测材料和工件的表面及其内部缺陷的方法。其最终目的是鉴定工件使用的适应性。无损探伤是提高产品质量、保证使用安全、增进产品设计的科学性、加强生产管理、降低成本,以及进行新材料、新工艺、新产品试验研究的重要手段之一。无损探伤并不神秘,广大劳动人民在生产和生活中早已广泛地应用了它。但是,无损     

大跨度钢结构桁架施工焊缝的超声波探伤

本文结合超声波探伤的基本原理和现场超声波探伤工作中的具体情况,对钢结构桁架现场施工焊缝中常见缺陷的产生原因及防止措施进行了分析,并简要介绍了相贯线焊缝的超声波探伤。     

民用飞机静力试验机轮假件加固方案研究

介绍了民用飞机主起落架上用于静力机试验用加载装置机轮组件的设计加固过程,机轮假件是静力试验中传递载荷的起点,具有较高的强度要求。针对试验要求设计了一个主起机轮,在制造过程中出现了影响机轮强度的焊缝裂纹,对焊缝裂纹进行探伤分析,并进行加强方案研究,并且利用试验验证了加强方案的可靠性和安全性。     

论交通安全领域涡流探伤技术的应用

结合交通安全领域对于探伤技术的实际需求,对目前世界上常用的无损探伤方法进行了比对,分析了涡流探伤技术的优缺点。说明了涡流探伤设备的具体工作原理和核心构件,列出涡流探伤设备的应用领域。并针对了我国当下公路、铁路以及桥梁方面的探伤问题给出了相关设计方案。     

焊接检验如何进行?

<正>焊接过程中,首先应按照预定的焊接工艺制成相应焊件,或从构件上切取部分焊接接头,以用于试验。对于焊接问题的检验,未熔合气孔、咬边、焊瘤以及焊接裂纹等表面缺陷可通过肉眼,或借助样板、低倍放大镜等工具观察焊件进行检验。而其他焊接问题则须进行无损检验,即通过不损坏被检查材料或成品的性能和完整性的方法检验焊件,常用的无损检验方法主要包括超声波探伤、射线探伤、磁粉探伤、渗透探伤等,实际施工中应视情况合理选择正确的检测方法。     

轻钢结构焊缝超声波探伤小结

通过对轻钢结构工程中对接焊缝超声波探伤实例的分析,从仪器和试块选择、制作距离—波幅曲线和探伤操作等方面入手,重点介绍了超声波探伤在轻钢结构工程中的应用,并结合轻钢结构焊缝特点进行规范检测,以保证焊缝质量检测的可靠性。     

起重机械钢丝绳EMT智能探伤仪在工程中的应用

简述了EMT智能钢丝绳探伤仪适用范围、检测原理、操作程序及要点,结合工程应用实例,实现了测量起重机械钢丝绳缺陷描述,解决了人工检绳效率低、无法检验内部损伤及人为因素影响等问题,达到了减少和消除钢丝绳安全风险的效果。     

探讨现行超声法检测混凝土缺陷判定准则的不足与完善

本文通过理论分析及工程实例指出了现行超声法检测混凝土缺陷的判定准则中存在的不足之处,当混凝土存在渐变性缺陷时容易出现漏判,进而提出了可以采用伪彩色渲染的声速等值线图加以辅助判别,从而弥补现有判定准则的不足之处。     

Full-field strain evolution and characteristic stress levels of rocks containing a single pre-existing flaw under uniaxial compression

In this study, full-field strain evolution and characteristic stress levels of marble samples containing a single pre-existing flaw were comprehensively studied. The full-field strain was performed by digital image correlation (DIC) method, and the variations of characteristic stress levels with respect to inclination angle were discussed. To compare the experimental results, discrete element method was adopted, and the full-field stress evolution was reproduced to reappraise the localization zones. The results indicate that the presence of pre-existing flaws induces strain localization and degradation of mechanical properties for pre-cracked samples. When the strain localization firstly appeared surrounding pre-existing flaws, the axial stress levels at this moment increase with regard to inclination angle, leading to the increase of peak strength, crack initiation stress, crack damage stress, and normalized crack initiation stress. The normalized crack damage stress obtained by experiments shows flaw independency, and the results were verified by simulation results. Based on the full-field stress evolution, the tensile stress in x direction concentrates around pre-existing flaw and its location moves towards flaw tips with the increase of inclination angle. The compressive stress in y direction around pre-existing flaw is lower than other zones, revealing the upper and bottom surfaces of pre-existing flaw deform to each other. When the numerical models are subjected to same axial loading, the full-field stress around pre-existing flaw decrease as the inclination angle increases, which confirmed the results of full-field strain evolution and elucidated the pre-existing flaw with large inclination angle has less effect on degrading the mechanical properties.

     

The influence of grain size and porosity on crack initiation stress and critical flaw length in dolomites

The influence of rock texture on crack initiation stress (σ_i) and critical flaw length (L_i) is studied by a series of triaxial tests performed on monomineralic dolomites. The critical flaw length, as predicted by analytical models, is shown to be larger than the measured mean grain size (d_m) by two–three orders of magnitude. This discrepancy is explained by rock texture variations, which influence the fracture propagation mode and consequently fracture initiation stress. The quantification of rock texture is accomplished using porosity. Fracture initiation stress is shown to be inversely related to both porosity and mean grain size. When porosity is low, the sensitivity of σ_i to mean grain size is high. This effect is reduced with higher porosity values. A model for initial flaw length is developed by a synthesis of Griffith initiation criteria with our empirical model for fracture initiation stress. Initial flaw length is found to be directly proportional to the elastic modulus, mean grain size and porosity of the rock. When porosity and mean grain size decrease simultaneously, the initial flaw length rapidly decreases and approaches the mean grain size value. Therefore, the classical assumption that grain size scales initial flaw size is shown to be valid only in the very restricted case of low porosity-low grain size rocks. In such textures, where void space is minimal, available crystal faces function as truly initial flaws, and variations in mean grain size influence crack initiation stress significantly. In more porous textures, however, the initial flaw length is shown to be up to two orders of magnitude higher than the mean grain size in the rock, depending upon the porosity and mean grain size values. In such textures crack initiation stress is much less sensitive to variations in mean grain size, indicating that the role of individual grains is less significant.     

膜结构常见疵病、损伤及防治

膜结构是空间结构中充满活力的一种结构体系.近十年来膜结构在我国获得了广泛应用,并呈快速发展势态.然而膜结构工程虽然在形态优美、结构轻盈等方面颇受好评,但工程的局部缺陷、破损乃至整体破坏的事故却时有所闻.本文针对膜结构中存在的常见疵病、损伤与破坏事故进行具体分析,并对其设计、制作及安装中的问题提出相应的防治措施,结论可供膜结构工程参考借鉴.     

盾构管片接头接触面缺陷模型分析

为合理确定盾构管片接头节理单元（goodman单元）法向刚度,首先采用经典弹性接触理论与试验结果进行了对比,在经典弹性接触理论的接触面光滑、弹性假设与试验数据发生背离的背景下,提出了“接触面缺陷”假设,认为计算模型中的节理单元实质上是用来描述物理模型中的因“接触面缺陷”引起的初始非线性位移,而节理单元法向刚度实质上是轴力与接触面初始非线性位移关系的割线刚度。并以此为基础,提出节理单元法向刚度的确定方法以及相应的验证方法。与试验数据的比较和验证表明,以本方法确定的参数进行的反分析结果与实测的管片轴向位移以及弯矩-转角曲线非常吻合,本方法可得到试验数据的有力支持,是可行的。     

浅析集美公铁立交工程桩身混凝土缺陷

厦门市集美公铁立交工程桥梁桩身混凝土缺陷比例偏高。本文介绍桩身混凝土缺陷的原因分析和改进措施。     

公路桥涵混凝土外观质量缺陷分析与防治

通过对公路桥涵混凝土外观质量缺陷病理的分析,提出了相应的预防措施,并总结出各种病害的修补方法,指出要从设计、施工、养护三方面控制公路桥涵的外观质量,以使其达到内实外秀的效果。     

浅谈轻钢结构超声波探伤

在轻钢结构超声波探伤经验的基础上,对此类建筑焊缝探伤的相关问题作出简要的归纳总结。