本文選題：激光散斑 + 激光散斑圖像測量法　； 參考：《西南交通大學(xué)》2017年碩士論文

【摘要】：激光焊接的過程中,會產(chǎn)生不完全焊接,孔隙,裂縫等缺陷,這些缺陷如果沒有被檢測出來會造成非常大的影響,因此需要針對焊接窄縫進行缺陷檢測。可是傳統(tǒng)的檢測方式針對這種焊接方式不是特別的適用,因此需要一種新型的檢測方式來對激光焊接的過程進行監(jiān)測。激光散斑圖像測量法(LSP:Laser speckle photometry)是一種新型的、非接觸、快速的光學(xué)無損檢測方法。它的原理是通過觀察和分析熱能傳過物體或應(yīng)力拉伸時所引起的物體表面的動態(tài)散斑變化來對檢測物體進行監(jiān)測。當(dāng)熱能在傳播中或應(yīng)力拉伸過程中,物體的表面會由于原子細微的變化產(chǎn)生一個肉眼不可見的微小變化,這是由于物體各個局部不同程度的熱/機械膨脹引起的。這個微小的變化會使得激光散斑在時間軸上發(fā)生變化,也可以說激光散斑的動態(tài)變化受到熱/機械膨脹的影響。通常情況下這個微小的變化是有規(guī)律可循的,但是如果在待檢樣本的近表面有缺陷,那么這個變化將會無規(guī)律,這種無規(guī)律的現(xiàn)象是由于缺陷使得樣本在局部有著不同于其他地方的熱/機械擴張,因而導(dǎo)致了這種不同尋常的現(xiàn)象。在分析視頻后,通過記錄激光散斑的運動變化,缺陷可以被檢出來。通過使用一種特殊的相關(guān)函數(shù)將散斑強度的變化和局部時間域的空間梯度進行連接,這是激光散斑圖像測量法技術(shù)原理。在目前的工作中,我們的目標(biāo)是通過激光散斑圖像測量法對于在激光焊接過程中產(chǎn)生的缺陷進行檢測。在本文中,第1章介紹了這項工作的目的。第2章介紹了與激光散斑圖像測量法及相關(guān)技術(shù)的發(fā)展現(xiàn)狀,重點介紹了激光散斑和激光散斑圖像測量法的原理。第3章中闡明了當(dāng)前工作的目標(biāo)和范圍。第4、5、6章對整個實驗過程進行詳細的描述,給出了實驗結(jié)果,得到了實驗結(jié)果,最后對實驗的結(jié)果進行了分析。本文提出了針對激光焊接檢測的新方法,將激光散斑圖像測量法與多重激光焊接技術(shù)進行結(jié)合,通過理論的論證,在大量實驗后,證明了檢測方法的可行性,將激光散斑圖像測量法應(yīng)用到了新的領(lǐng)域。改進了激光散斑圖像測量法的算法,把激光散斑圖像測量法從靜態(tài)測量引到動態(tài)測量,通過實驗證明了新算法的可行性,從舊算法的不能檢測到新算法的可以檢測。在目前的研究階段,通過大量的實驗,對整個實驗裝置進行調(diào)整,對實驗數(shù)據(jù)進行分析,證明了激光散斑圖像測量法可以對激光焊接的過程進行監(jiān)測,同時對缺陷進行識別與檢測。目前可以通過激光散斑圖像測量法可以識別出焊接過程中產(chǎn)生的缺乏融合缺陷和細孔缺陷。
[Abstract]:In the process of laser welding, defects such as incomplete welding, pores, cracks and so on will be produced. If these defects are not detected out, they will have a great impact, so it is necessary to detect the defects of the welding narrow seam. However, the traditional detection method is not especially suitable for this kind of welding, so a new type of detection method is needed to monitor the process of laser welding. Laser Speckle Image Measurement (LSP: laser speckle photometry) is a new, non-contact, fast optical nondestructive testing method. Its principle is to monitor the detected object by observing and analyzing the dynamic speckle changes on the surface of the object caused by the heat energy passing through the object or when the stress is stretched. When the heat energy is propagating or the stress is being stretched, the surface of the object will have a small invisible change due to the subtle change of the atom, which is caused by the different degrees of thermal / mechanical expansion of the body. This slight change will cause the laser speckle to change on the time axis, and it can be said that the dynamic change of laser speckle is affected by thermal / mechanical expansion. Normally, this small change is regular, but if there is a defect in the near surface of the sample to be tested, then the change will be irregular. This irregular phenomenon is due to the fact that the defect causes the local thermal / mechanical expansion of the sample to be different from that of other places, which leads to this unusual phenomenon. After analyzing the video, the defects can be detected by recording the motion changes of laser speckle. The change of speckle intensity is connected with the spatial gradient of local time domain by using a special correlation function, which is the principle of laser speckle image measurement. In the present work, we aim to detect the defects in laser welding by laser speckle image measurement. In this paper, chapter 1 introduces the purpose of this work. In chapter 2, the development of laser speckle image measurement and its related techniques are introduced, and the principle of laser speckle and laser speckle image measurement is emphasized. Chapter 3 describes the objectives and scope of the current work. In chapter 4, chapter 5, the whole experiment process is described in detail, the experimental results are given, and the experimental results are obtained. Finally, the experimental results are analyzed. In this paper, a new method of laser welding detection is proposed. The laser speckle image measurement method is combined with the multiple laser welding technology. The feasibility of the detection method is proved by a large number of experiments. Laser speckle image measurement is applied to a new field. The algorithm of laser speckle image measurement is improved and the laser speckle image measurement method is introduced from static measurement to dynamic measurement. The feasibility of the new algorithm is proved by experiments, and the new algorithm can be detected from the old algorithm. In the current research stage, through a large number of experiments, the whole experimental device is adjusted and the experimental data are analyzed. It is proved that the laser speckle image measurement method can monitor the process of laser welding. At the same time, the defects are identified and detected. At present, laser speckle image measurement method can be used to identify the defect of fusion and fine hole produced in welding process.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG441.7;TP391.41

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本文編號：2099965