本文選題：多層單道GMA增材制造 + 成形形貌　； 參考：《哈爾濱工業(yè)大學(xué)》2014年博士論文

【摘要】：熔化極氣體保護(hù)電弧(Gas Metal Arc， GMA)增材制造(AdditiveManufacturing，AM)采用電弧作為熱源、焊絲作為填充材料，根據(jù)零件三維模型逐層堆敷直至形成金屬零件。當(dāng)前對(duì)GMA-AM過程的研究主要集中在成形工藝的可行性、成形件組織和力學(xué)性能上，對(duì)成形過程穩(wěn)定性、成形件表面質(zhì)量和尺寸精度的研究比較匱乏。本文以多層單道GMA-AM為研究對(duì)象，以提高成形過程穩(wěn)定性和成形精度為目標(biāo)，深入研究了GMA直接成形金屬零件過程的工藝特性、成形件表面質(zhì)量，并在此基礎(chǔ)上對(duì)成形尺寸的視覺傳感檢測(cè)及閉環(huán)控制等關(guān)鍵問題進(jìn)行了系統(tǒng)研究，為確保成形過程質(zhì)量、成形尺寸精度奠定了基礎(chǔ)。 首先研究了不同熔敷工藝參數(shù)下單層單道成形形貌，得到了單層單道良好成形形貌的工藝規(guī)范區(qū)間。接著探索了熔敷電流、堆積速度、熱輸入對(duì)多層單道成形形貌的影響。研究表明，熔敷電流是影響多層單道成形形貌的決定性因素，電流大于200A時(shí)，通常在第二到四層出現(xiàn)熔池表面嚴(yán)重失穩(wěn)、甚至流淌，成形件形貌呈現(xiàn)坍塌；多層單道獲得良好成形形貌的電流區(qū)間為100~180A；隨熔敷電流的增大，得到良好成形形貌的最大熱輸入減小。 采用二次回歸旋轉(zhuǎn)組合設(shè)計(jì)的方法建立了熔敷工藝參數(shù)與熔敷層尺寸的模型關(guān)系。該模型可預(yù)估不同工藝參數(shù)下的熔敷層層寬和層高尺寸，為三維模型分層切片提供了依據(jù)。 針對(duì)GMA-AM過程起弧端熔敷尺寸高且寬、熄弧端高度低的特點(diǎn)，提出了相應(yīng)的控制策略。封閉路徑成形時(shí)，相同層間采用起弧和熄弧端搭接的方式彌補(bǔ)高度尺寸缺陷。對(duì)非封閉路徑零件，一種策略是相鄰層間采用交錯(cuò)式堆積方式；另一種策略是相鄰層間采用同向式堆積方式，起弧點(diǎn)增大堆積速度、減小送絲堆積速度比，熄弧點(diǎn)降低熔敷電流、堆積速度、增大送絲堆積速度比。 進(jìn)一步研究了多層單道GMA-AM表面質(zhì)量影響因素。激光視覺傳感系統(tǒng)對(duì)多層單道表面質(zhì)量進(jìn)行測(cè)量，，建立了成形件表面質(zhì)量評(píng)價(jià)體系。考察了層間溫度、定送絲堆積速度比、變送絲堆積速度比等因素對(duì)成形件表面質(zhì)量的影響。結(jié)果表明，熔敷層表面質(zhì)量是層間溫度、層高、電流、堆積速度多重因素作用的結(jié)果。相同熔敷工藝參數(shù)下，層間溫度越高，表面質(zhì)量越差。送絲堆積速度比為定值時(shí)，隨電流增加，表面質(zhì)量下降。保持電流和層間溫度不變，堆積速度增加，表面質(zhì)量提高；保持堆積速度和層間溫度不變，電流增加，表面質(zhì)量下降。 為實(shí)時(shí)檢測(cè)GMA-AM過程熔敷層尺寸，設(shè)計(jì)了一套用于熔敷尺寸控制的雙被動(dòng)視覺傳感系統(tǒng)，可同時(shí)獲得熔敷層寬度和焊槍到熔敷層表面的高度圖像。采用高斯濾波去噪、邊緣提取、Hough變換擬合等圖像處理技術(shù)，開發(fā)了GMA-AM熔敷層尺寸實(shí)時(shí)處理算法，實(shí)現(xiàn)了熔敷層寬度、高度參數(shù)的在線準(zhǔn)確檢測(cè)，為過程建模和控制器設(shè)計(jì)打下基礎(chǔ)。 采用單變量階躍響應(yīng)傳遞函數(shù)方法建立了工藝參數(shù)與熔敷層尺寸的單輸入單輸出動(dòng)態(tài)模型，分析了系統(tǒng)的時(shí)域響應(yīng)特點(diǎn)。成形過程存在非線性、時(shí)滯等特點(diǎn)，簡(jiǎn)單的數(shù)學(xué)模型難以精確描述。隨機(jī)試驗(yàn)數(shù)據(jù)辨識(shí)了堆積速度與熔敷層尺寸的非線性Hammerstein模型，該模型可用于控制系統(tǒng)仿真。 針對(duì)GMA-AM過程多變量、多干擾的特點(diǎn)，以熔敷層寬度為被控變量，堆積速度為控制變量，設(shè)計(jì)了單神經(jīng)元自學(xué)習(xí)(Proportional SummationalDifferential，PSD)控制器。仿真結(jié)果和干擾試驗(yàn)驗(yàn)證了控制器性能。參數(shù)自學(xué)習(xí)PSD控制器在熔敷層定寬度和變寬度控制中均可以獲得良好的控制效果。同時(shí)為了滿足熔敷層高度的穩(wěn)定性要求，對(duì)熔敷層上表面到焊槍噴嘴的距離進(jìn)行了宏觀監(jiān)測(cè)和自適應(yīng)控制。 最后，應(yīng)用GMA-AM技術(shù)成形了航天發(fā)動(dòng)機(jī)燃燒室殼體、環(huán)形機(jī)匣、液體火箭發(fā)動(dòng)機(jī)推力室等模擬件，成形件表面質(zhì)量良好。雙視覺傳感系統(tǒng)檢測(cè)和PSD控制器控制結(jié)果表明，熔敷層寬度控制精度小于0.4mm。
[Abstract]:In order to improve the stability and the precision of the forming process , the paper studies the process characteristics and surface quality of the forming process by using the multi - layer single GMA - AM as the research object , and then studies the key problems such as the visual sensing and closed - loop control of the forming process .

In this paper , the morphology of single - layer single - channel formed by different melting process parameters is studied . The influence of welding current , deposition rate and thermal input on the morphology of multi - layer single - channel forming is obtained . The results show that the welding current is the decisive factor affecting multi - layer single - channel forming topography .
the current range of the multi - layer single track to obtain the good forming topography is 100 - 180A ;
With the increase of the welding current , the maximum thermal input of good forming topography is reduced .

The model relationship between the parameters of the welding process and the size of the cladding layer is established by the method of quadratic regression rotation combined design . The model can predict the width and height dimension of the cladding layer under different process parameters , and provide the basis for the layered slicing of the three - dimensional model .

In the process of GMA - AM , a corresponding control strategy is proposed for the characteristics of high arc end cladding size and low arc end height . When the closed path is formed , the arc - extinguishing and arc - extinguishing ends of the same layer are used to make up for the height - dimensional defects .
the other strategy is that the adjacent layers adopt the same - direction stacking mode , the arc - starting point increases the stacking speed , the wire - feeding stacking speed ratio is reduced , the arc - quenching point reduces the deposition current and the stacking speed , and the wire - feeding stacking speed ratio is increased .

The influence factors of the surface quality of multi - layer single - channel GMA - AM are studied . The effect of laser vision sensing system on the surface quality of the multi - layer single - channel GMA - AM is studied . The results show that the surface quality of the layer is the result of multiple factors such as inter - layer temperature , high - layer , current and stacking velocity .
the bulk speed and the interlayer temperature are kept unchanged , the current is increased , and the surface quality is reduced .

In order to detect the size of the cladding layer of GMA - AM process in real time , a set of dual passive vision sensing system is designed to control the width of the cladding layer and the height of the welding gun to the surface of the cladding layer . The real - time processing algorithm of GMA - AM is developed by using Gaussian filter denoising , edge extraction , Hough transform fitting and so on . The online accurate detection of the width and height parameters of the cladding layer is realized , which lays the foundation for the process modeling and controller design .

A single - input single - output dynamic model of the process parameters and the size of the cladding layer is established by a single - variable step - response transfer function method , and the time - domain response characteristics of the system are analyzed . The nonlinear and time - delay characteristics of the forming process are difficult to accurately describe . The stochastic test data identifies the nonlinear Hammerstein model of the stacking velocity and the size of the cladding layer , and the model can be used for the control system simulation .

Based on the characteristics of multi - variable and multi - interference in GMA - AM process , a single neuron self - learning ( PSD ) controller is designed with the width of the cladding layer as the controlled variable and the stacking velocity as the control variable . The simulation results and the interference test have verified the controller performance .

Finally , by using GMA - AM technology , the simulation parts such as combustion chamber shell , annular casing and liquid rocket engine thrust chamber are formed by GMA - AM technology . The surface quality of the former is good . The results of the double vision sensing system and the control of PSD controller show that the control accuracy of the width of the cladding layer is less than 0.4mm .
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TH16

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