基于磁记忆的建筑钢结构焊接试件弯曲试验研究

发布时间：2018-11-12 21:04

【摘要】：在建筑钢结构领域中,主要连接方式有焊缝连接、螺栓连接与铆接连接,焊缝连接是其中一种极为重要连接方式。但由于焊接工艺非常复杂,操作难度很高,在对试件焊接过程中,不可避免会在焊缝处产生一些焊接缺陷或者应力集中,这会使结构构件的安全性和可靠性都大大降低,使用寿命也会随之减小,故而,能够提前发现这些焊接缺陷或试件损伤,能够对结构构件的早期健康进行有效检测,对我们社会生活的影响至关重要。金属磁记忆无损检测技术不仅是一种新型无损检测技术,更是二十一世纪最有发展前景的无损检测技术之一。它的作用原理是利用了金属材料内部应力集中区在地磁场作用下表面散射磁场的特性,在发现材料早期损伤或缺陷方面具有巨大的潜力。该检测技术对焊缝的检测具有独特优势,不仅能够检测出已经存在的宏观缺陷,对于存在应力集中或损伤区域的检测也非常有效。本文将理论与试验相结合,重点研究基于材性的建筑钢结构焊接试件三点受弯试验,通过使用厦门某电子公司生产的智能磁记忆检测仪EMS-2003型,测量含有缺陷试件表面焊缝处的漏磁场法向分量。由于检测的磁记忆信号非常弱(属于弱磁场信号),很容易受到外界环境干扰信号的干扰,影响试验结果分析,所以本文先通过小波包法对测得磁信号进行降噪处理,以将信号从噪声中分离出来,然后对不同应力作用下磁记忆信号的变化规律进行分析,以提出适用于建筑钢结构焊接试件的损伤判定方法。试验结果表明,磁记忆信号强度Hp(y)在应力集中部位出现“波峰”或者“波谷”现象,且随着荷载逐渐增大,yHp)(具有先减小,进入塑性阶段后发生反转,再逐渐增大的规律;磁记忆信号梯度K在应力集中部位出现“峰-峰”值变化且具有极大值,且K值在此处变化最为剧烈;区域信号极大值与极小值差值的绝对值“峰-峰值”Hpp(y)的最大值常常出现在试件预制缺陷附近区域;Hp(y)~F曲线在试件所加荷载由弹性进入塑性的界限附近出现“拐点”。这些规律表明用磁记忆无损检测方法发现焊接弯曲试件损伤是有效可行的。
[Abstract]:In the field of building steel structure, the main ways of connection are weld joint, bolt connection and riveting connection. Weld joint is one of the most important connection modes. However, the welding process is very complicated and the operation is very difficult. In the welding process of the specimen, some welding defects or stress concentration will inevitably occur in the weld, which will greatly reduce the safety and reliability of the structural members. The service life will also be reduced. Therefore, it is very important to detect these welding defects or specimen damage in advance, and to detect the early health of structural members effectively, which is of great importance to our social life. Metal magnetic memory nondestructive testing is not only a new nondestructive testing technology, but also one of the most promising nondestructive testing technologies in the 21 century. The principle of its action is to utilize the characteristics of surface scattering magnetic field in the stress concentration region of metal materials under the action of geomagnetic field, and it has great potential to discover the early damage or defect of materials. This technique has a unique advantage in weld detection. It can detect not only the existing macroscopic defects, but also the detection of stress concentration or damage zone. In this paper, the theory and test are combined to study the three-point bending test of welded specimens of building steel structures based on the material properties. By using the intelligent magnetic memory detector (EMS-2003) produced by an electronic company in Xiamen, this paper focuses on the research of the three-point bending test of welded steel structures based on the material properties. To measure the normal component of magnetic flux leakage at the weld seam on the surface of the specimen containing defects. Because the detected magnetic memory signal is very weak (which belongs to the weak magnetic field signal), it is easy to be interfered by the external environment interference signal, which affects the analysis of the test results, so the wavelet packet method is adopted to reduce the noise of the measured magnetic signal in this paper. In order to separate the signal from the noise and analyze the variation of the magnetic memory signal under the different stress, the damage determination method suitable for the welding specimen of the building steel structure is put forward. The experimental results show that the magnetic memory signal intensity (Hp (y) appears "wave peak" or "trough" phenomenon at the stress concentration, and with the increasing of the load, the, yHp) (decreases first, and then reverses after entering the plastic stage. The law of increasing gradually; The magnetic memory signal gradient K has a "peak-peak" change in the stress concentration and has a maximum value, and the K value changes most intensely here. The maximum value of the absolute "peak-peak" Hpp (y) of the difference between the maximum and the minimum of the regional signal often appears in the region near the precast defect of the specimen. The "inflection point" appears in the Hp (y) ~ F curve near the limit of elasticity into plasticity. These results show that it is effective and feasible to detect the damage of welded bending specimens by magnetic memory nondestructive testing.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU391

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