發(fā)布時間：2018-10-30 15:08

【摘要】：電阻點焊過程伴隨著電、聲、熱等多種能量釋放,與熔核形核生長密切相關(guān)。本文面向鋁合金材料,以研究電阻點焊過程熔核形核生長為目的,利用實時傳感技術(shù)對電阻點焊熔核形核動態(tài)過程的電極電壓、電極電流和結(jié)構(gòu)負載聲發(fā)射信號進行了同步檢測,研究了電阻點焊熔核形核的生長過程、熔核質(zhì)量識別、焊接飛濺及電極損耗對熔核形核特征的影響,以及Ti O_2粉末介質(zhì)介入對熔核形核生長過程的影響。此外還基于ANSYS計算平臺建立了相應(yīng)的數(shù)值模型,研究了熔核形核生長過程的傳熱特征與電勢變化。研究結(jié)果表明,根據(jù)動態(tài)電阻曲線可將熔核形核生長過程劃分為初始階段、生長階段和穩(wěn)定階段,不同階段表現(xiàn)出不同的形核特征。隨著輸出焊接能量的不同,熔核形核動態(tài)過程產(chǎn)生的變化可在動態(tài)電阻曲線中得到體現(xiàn)。與熔核形核相關(guān)的電信號特征參數(shù)與熔核尺寸、焊點承載力表現(xiàn)出良好的相關(guān)性,為通過實時檢測熔核形核動態(tài)信號分析、識別熔核質(zhì)量提供了依據(jù)。根據(jù)動態(tài)電阻和結(jié)構(gòu)負載聲發(fā)射同步信號分析發(fā)現(xiàn),熔核形核過程的飛濺常發(fā)生在熔核穩(wěn)定階段的中后期。隨著電極在點焊中的損耗加劇,熔核形核動態(tài)電阻變異值變化顯著,并影響熔核形核質(zhì)量�？衫秒娮椟c焊過程動態(tài)電阻變異值來評估電極損耗的程度,為電極損耗的實時監(jiān)測提供了理論依據(jù)。Ti O_2粉末介質(zhì)介入改變了待焊工件表面的接觸狀態(tài),顯著提高形核初始階段動態(tài)電阻,得到尺寸更大、承載能力更強的熔核。利用ANSYS通過有限元分析發(fā)現(xiàn),電阻點焊過程溫度隨熔核形核生長過程不斷變化,不同焊接工藝下熔核形核過程溫度變化并不相同。Ti O_2粉末介質(zhì)介入能提高熔核形核過程電極間的電壓,從而提高接觸電阻和熔核形核過程的動態(tài)電阻,使形核電阻熱效應(yīng)增加;還能提高熔核形核過程的溫度梯度,使熔核直徑與焊點承載能力得到顯著提高。
[Abstract]:The process of resistance spot welding is closely related to the nucleation growth with the release of many kinds of energy, such as electricity, sound and heat. In this paper, for the purpose of studying the nucleation and nucleation growth of resistance spot welding process, the electrode voltage of dynamic nucleation process of resistance spot welding is studied by using real-time sensing technology. The current of electrode and the acoustic emission signal of structural load were detected synchronously. The effects of nucleation process, quality identification, splashing and electrode loss on the nucleation characteristics of resistance spot welding were studied. And the influence of Ti O _ 2 powder medium on nucleation and growth process. In addition, the corresponding numerical model is established based on the ANSYS calculation platform, and the heat transfer characteristics and electric potential changes during the nucleation process are studied. The results show that according to the dynamic resistance curve, the nucleation growth process can be divided into three stages: initial stage, growth stage and stable stage, and different stages show different nucleation characteristics. With the variation of the output welding energy, the dynamic process of nucleation can be reflected in the dynamic resistance curve. The electrical signal characteristic parameters related to the nucleation and the size of the nugget and the bearing capacity of the solder joint show a good correlation, which provides a basis for the identification of the quality of the nugget by analyzing the dynamic signals of the nucleation in real time. According to the dynamic resistance and structural load acoustic emission synchronous signal analysis, it is found that the spatter of nucleation often occurs in the middle and late stage of the nucleation stabilization stage. With the increase of electrode loss in spot welding, the variation of dynamic resistance of nugget nucleation varies significantly and affects the quality of nugget nucleation. The dynamic resistance variation value in resistance spot welding process can be used to evaluate the degree of electrode loss, which provides a theoretical basis for the real-time monitoring of electrode loss. The contact state of workpiece surface is changed by the intervention of Ti O 2 powder medium. The dynamic resistance at the initial stage of nucleation can be improved significantly, and the nucleation with larger size and stronger bearing capacity can be obtained. By using ANSYS finite element analysis, it is found that the temperature of the resistance spot welding process changes with the nucleation process. The temperature change of nucleation and nucleation process is different in different welding processes. Ti O\ -2 powder medium can increase the voltage between electrodes in the nucleation process and thus increase the contact resistance and the dynamic resistance of the nucleation process. The thermal effect of nucleation resistance is increased; The temperature gradient of the nucleation process can also be increased, and the nugget diameter and the bearing capacity of solder joint can be improved significantly.
【學(xué)位授予單位】：重慶理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG453.9

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