【摘要】：在建筑鋼結(jié)構(gòu)領(lǐng)域中,主要連接方式有焊縫連接、螺栓連接與鉚接連接,焊縫連接是其中一種極為重要連接方式。但由于焊接工藝非常復(fù)雜,操作難度很高,在對試件焊接過程中,不可避免會在焊縫處產(chǎn)生一些焊接缺陷或者應(yīng)力集中,這會使結(jié)構(gòu)構(gòu)件的安全性和可靠性都大大降低,使用壽命也會隨之減小,故而,能夠提前發(fā)現(xiàn)這些焊接缺陷或試件損傷,能夠?qū)Y(jié)構(gòu)構(gòu)件的早期健康進(jìn)行有效檢測,對我們社會生活的影響至關(guān)重要。金屬磁記憶無損檢測技術(shù)不僅是一種新型無損檢測技術(shù),更是二十一世紀(jì)最有發(fā)展前景的無損檢測技術(shù)之一。它的作用原理是利用了金屬材料內(nèi)部應(yīng)力集中區(qū)在地磁場作用下表面散射磁場的特性,在發(fā)現(xiàn)材料早期損傷或缺陷方面具有巨大的潛力。該檢測技術(shù)對焊縫的檢測具有獨(dú)特優(yōu)勢,不僅能夠檢測出已經(jīng)存在的宏觀缺陷,對于存在應(yīng)力集中或損傷區(qū)域的檢測也非常有效。本文將理論與試驗(yàn)相結(jié)合,重點(diǎn)研究基于材性的建筑鋼結(jié)構(gòu)焊接試件三點(diǎn)受彎試驗(yàn),通過使用廈門某電子公司生產(chǎn)的智能磁記憶檢測儀EMS-2003型,測量含有缺陷試件表面焊縫處的漏磁場法向分量。由于檢測的磁記憶信號非常弱(屬于弱磁場信號),很容易受到外界環(huán)境干擾信號的干擾,影響試驗(yàn)結(jié)果分析,所以本文先通過小波包法對測得磁信號進(jìn)行降噪處理,以將信號從噪聲中分離出來,然后對不同應(yīng)力作用下磁記憶信號的變化規(guī)律進(jìn)行分析,以提出適用于建筑鋼結(jié)構(gòu)焊接試件的損傷判定方法。試驗(yàn)結(jié)果表明,磁記憶信號強(qiáng)度Hp(y)在應(yīng)力集中部位出現(xiàn)“波峰”或者“波谷”現(xiàn)象,且隨著荷載逐漸增大,yHp)(具有先減小,進(jìn)入塑性階段后發(fā)生反轉(zhuǎn),再逐漸增大的規(guī)律;磁記憶信號梯度K在應(yīng)力集中部位出現(xiàn)“峰-峰”值變化且具有極大值,且K值在此處變化最為劇烈;區(qū)域信號極大值與極小值差值的絕對值“峰-峰值”Hpp(y)的最大值常常出現(xiàn)在試件預(yù)制缺陷附近區(qū)域;Hp(y)~F曲線在試件所加荷載由彈性進(jìn)入塑性的界限附近出現(xiàn)“拐點(diǎn)”。這些規(guī)律表明用磁記憶無損檢測方法發(fā)現(xiàn)焊接彎曲試件損傷是有效可行的。
[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.
【學(xué)位授予單位】：西安科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU391

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