【摘要】：激光熔化沉積技術(shù)借助大功率激光技術(shù)及CAD/CAM技術(shù)可以實現(xiàn)復雜結(jié)構(gòu)金屬零部件的快速無模近成形,不僅能大幅縮減產(chǎn)品開發(fā)周期還能最大程度上節(jié)約原材料。然而由于缺乏規(guī)范的工藝標準,成形件常出現(xiàn)內(nèi)部孔隙、裂紋等缺陷,嚴重制約了其在更廣泛領(lǐng)域的應(yīng)用。交變磁場能在其附近導體內(nèi)產(chǎn)生感應(yīng)電磁力,使導體發(fā)生塑性變形。這一原理已被廣泛應(yīng)用在金屬成形領(lǐng)域。本文借鑒電磁成形的工藝技術(shù),旨在利用感生的電磁力使工件產(chǎn)生塑性變形,抵消工件因冷卻收縮產(chǎn)生的拉伸應(yīng)變,從而達到降低殘余應(yīng)力幅值,抑制熱裂紋生長的目的。主要完成工作如下:(1)從理論方面系統(tǒng)分析了激光熔化沉積殘余應(yīng)力產(chǎn)生的機理以及電磁優(yōu)化激光熔化沉積的機理,包括降低殘余應(yīng)力和細化枝晶組織的機理。(2)基于ANSYS平臺,模擬了電磁輔助激光熔化沉積過程。研究了單一激光熔化沉積的殘余應(yīng)力在時間和空間上的分布,并分析了固定電磁力對殘余應(yīng)力的影響以及不同電磁力大小的影響規(guī)律。(3)搭建試驗裝置,并開展了激光熔化沉積單道單層試驗,制備了金相樣件,對制造件內(nèi)部晶粒組織進行了觀察分析。(4)在激光熔化沉積單道單層的基礎(chǔ)上,進行了多道多層試驗。使用X射線衍射法測量工件表面殘余應(yīng)力,并結(jié)合電解腐蝕的方法對深度方向的殘余應(yīng)力進行了測量。本文通過APDL編程語言實現(xiàn)了溫度場、應(yīng)力場和電磁場的三場耦合。利用該仿真模型不僅研究了殘余應(yīng)力的分布情況,而且分析了電磁場對殘余應(yīng)力的影響規(guī)律,仿真結(jié)果與后期試驗取得了較好的一致性,為后期進一步的工藝研究奠定了基礎(chǔ)。
[Abstract]:Laser melting deposition technology can realize the rapid formability of metal parts with complex structure by means of high power laser technology and CAD/CAM technology. It can not only greatly reduce the product development cycle but also save the raw materials to the greatest extent. However, due to the lack of standard process standards, defects such as internal pores and cracks often occur in forming parts, which seriously restrict its application in a wider field. The alternating magnetic field can produce inductive electromagnetic force in the nearby conductor, which causes plastic deformation of the conductor. This principle has been widely used in the field of metal forming. Using the technology of electromagnetic forming for reference, the purpose of this paper is to make use of the induced electromagnetic force to make the workpiece produce plastic deformation, to counteract the tensile strain caused by cooling shrinkage of the workpiece, so as to reduce the amplitude of residual stress and restrain the growth of hot crack. The main works are as follows: (1) the mechanism of laser melt deposition residual stress and the mechanism of electromagnetic optimization of laser melting deposition are analyzed theoretically, including the mechanism of reducing residual stress and refining dendrite structure. (2) based on ANSYS platform, The electromagnetic assisted laser melting deposition process was simulated. The distribution of residual stress in time and space of single laser melting deposition is studied, and the influence of fixed electromagnetic force on residual stress and the influence of different electromagnetic force are analyzed. (3) A test device is built. The single channel single layer experiment of laser melting deposition was carried out and the metallographic sample was prepared. The grain structure in the fabrication part was observed and analyzed. (4) on the basis of laser melting deposition single channel monolayer, multichannel and multilayer tests were carried out. The residual stress of workpiece surface was measured by X-ray diffraction method and the residual stress in depth direction was measured by electrolytic corrosion method. In this paper, the coupling of temperature field, stress field and electromagnetic field is realized by APDL programming language. The simulation model is used not only to study the distribution of residual stress, but also to analyze the influence of electromagnetic field on residual stress. The simulation results are in good agreement with the later test results, which lays a foundation for further technological research in the later stage.
【學位授予單位】：南京航空航天大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG665

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本文編號：2203531