謝建華，陳學(xué)庚，孫超偉

（1. 新疆農(nóng)業(yè)大學(xué)機(jī)械交通學(xué)院，烏魯木齊 830052；2. 新疆農(nóng)墾科學(xué)院，石河子 832000）

·農(nóng)業(yè)裝備工程與機(jī)械化·

桿齒式殘膜回收機(jī)卸膜過程分析及高速攝像試驗(yàn)

謝建華1，陳學(xué)庚2，孫超偉1

（1. 新疆農(nóng)業(yè)大學(xué)機(jī)械交通學(xué)院，烏魯木齊 830052；2. 新疆農(nóng)墾科學(xué)院，石河子 832000）

為解決殘膜回收中卸膜不可靠、卸膜率低的問題，基于MB（Majumdar-Bhushan）接觸分形理論，分析桿齒式殘膜回收機(jī)卸膜工作過程中拾膜桿齒和卸膜刮板間的接觸載荷與形變量的關(guān)系及其動(dòng)力學(xué)影響因素。運(yùn)用ANSYS 軟件對(duì)拾膜桿齒和卸膜刮板的接觸過程進(jìn)行仿真分析，并通過高速攝像試驗(yàn)追蹤了拾膜桿齒末端的運(yùn)動(dòng)軌跡，測(cè)量卸膜過程中拾膜桿齒與卸膜刮板前端的最大形變量。結(jié)果表明，當(dāng)拾膜機(jī)構(gòu)轉(zhuǎn)速為36 r/min時(shí)，拾膜桿齒和卸膜刮板前端的最大形變量分別為15.741、49.733 mm；當(dāng)機(jī)具行進(jìn)速度為0.85 m/s且機(jī)具行進(jìn)速度與拾膜桿齒軸線速度比為1.5時(shí)，機(jī)具有較高生產(chǎn)效率，能保證可靠卸膜。該研究結(jié)果可為拾膜、卸膜機(jī)構(gòu)的運(yùn)動(dòng)參數(shù)優(yōu)化提供參考。

攝像；變形；膜；殘膜回收；拾膜機(jī)構(gòu)；卸膜機(jī)構(gòu)；接觸分析

謝建華，陳學(xué)庚，孫超偉. 桿齒式殘膜回收機(jī)卸膜過程分析及高速攝像試驗(yàn)[J]. 農(nóng)業(yè)工程學(xué)報(bào)，2017，33(10)：17－24.

doi：10.11975/j.issn.1002-6819.2017.10.003 http://www.tcsae.org

Xie Jianhua, Chen Xuegeng, Sun Chaowei. Unloading film process analysis and high-speed photography experiment of pole-tooth residual plastic film collector[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017,33(10): 17－24. (in Chinese with English abstract) doi：10.11975/j.issn.1002-6819.2017.10.003 http://www.tcsae.org

0 引 言

農(nóng)用地膜覆蓋栽培技術(shù)自20世紀(jì)70年代引入中國(guó)后得到大力推廣[1-2]。地膜用量不斷增加，由于不能及時(shí)有效回收，致使農(nóng)田殘膜堆積越來越多[3-5]。為了解決地膜使用后造成的“白色污染”問題，國(guó)內(nèi)科研工作者針對(duì)殘膜回收技術(shù)展開了大量研究并制造出多種殘膜回收機(jī)具[6-8]。婁秀華等[9]設(shè)計(jì)了一種殘膜回收起膜器，并運(yùn)用Matlab軟件對(duì)其參數(shù)進(jìn)行了優(yōu)化。侯書林等[10]根據(jù)撿膜彈齒工作軌跡的要求，建立了拾膜機(jī)構(gòu)和脫膜機(jī)構(gòu)的運(yùn)動(dòng)學(xué)模型，利用計(jì)算機(jī)輔助程序模擬了控制桿和推膜板的運(yùn)動(dòng)軌跡。陳發(fā)等[11-12]對(duì)固定凸輪殘膜撿拾機(jī)構(gòu)進(jìn)行了優(yōu)化設(shè)計(jì)，得到一種減少凸輪磨損、提高可靠性的新方法。趙海軍[13]分析了伸縮桿齒滾筒和弧型桿齒滾筒的受力情況，得出弧型桿齒能夠改善撿拾機(jī)構(gòu)受力的結(jié)論。

殘膜回收機(jī)具根據(jù)拾膜機(jī)構(gòu)的結(jié)構(gòu)可以分為彈齒式、伸縮桿齒式、鏈齒式、夾持式和氣吸式等幾種[14-16]，其中，彈齒式、伸縮桿齒式和鏈齒式可統(tǒng)稱為桿齒式。對(duì)于桿齒式殘膜回收機(jī)的拾膜、卸膜機(jī)構(gòu)自身來說，桿齒末端的運(yùn)動(dòng)姿態(tài)和桿齒與卸膜部件的接觸作用關(guān)系直接影響機(jī)構(gòu)的拾膜率和卸膜率。目前，桿齒式殘膜回收機(jī)的研究主要集中在拾膜過程如何提高拾膜率方面，而卸膜機(jī)構(gòu)性能在實(shí)際工作中影響機(jī)組可靠性和殘膜最終回收率的問題更加突出。受研究手段和研究水平的制約，對(duì)于卸膜過程的工作機(jī)理研究較少[17-26]。為了深入研究卸膜過程的工作機(jī)理，本文針對(duì)桿齒式殘膜回收機(jī)，對(duì)拾膜、卸膜機(jī)構(gòu)進(jìn)行 MB（Majumdar-Bhushan）接觸分形理論分析，通過卸膜工作過程的有限元仿真和高速攝像試驗(yàn)，觀察拾膜桿齒與卸膜機(jī)構(gòu)作用后的接觸形變情況，分析桿齒式殘膜回收機(jī)可靠卸膜的條件，為該機(jī)具的優(yōu)化提供依據(jù)。

1 桿齒式殘膜回收機(jī)的結(jié)構(gòu)及工作原理

圖 1所示為桿齒式殘膜回收機(jī)的結(jié)構(gòu)，其主要由懸掛架1、拾膜機(jī)構(gòu)2、地輪3、鏈傳動(dòng)系統(tǒng)4、卸膜機(jī)構(gòu)6、集膜箱7和機(jī)架8等組成。機(jī)具工作時(shí)，拖拉機(jī)通過三點(diǎn)后懸掛方式牽引機(jī)具前進(jìn)，地輪帶動(dòng)拾膜機(jī)構(gòu)轉(zhuǎn)動(dòng)，卸膜機(jī)構(gòu)由拾膜機(jī)構(gòu)上的鏈傳動(dòng)帶動(dòng)，并與桿齒式拾膜機(jī)構(gòu)同向轉(zhuǎn)動(dòng)。在凸輪滑道的約束下，固定在桿齒軸上的桿齒逆時(shí)針旋轉(zhuǎn)低頭入土，將地表殘膜挑起，向上升運(yùn)，再平移回收。在拾膜桿齒平移回收過程（卸膜階段）中，卸膜機(jī)構(gòu)的卸膜刮板與桿齒接觸，將桿齒上的殘膜捋下并拋送至集膜箱，機(jī)具完成收膜。

圖1 桿齒式殘膜回收機(jī)Fig.1 Pole-tooth type residual plastic film collector

2 拾膜桿齒與卸膜機(jī)構(gòu)的接觸分析

接觸過程一般存在彈性變形、彈塑性變形及塑性變形。為了保證拾膜機(jī)構(gòu)和卸膜機(jī)構(gòu)的性能，在卸膜過程中，應(yīng)盡可能使拾膜桿齒與卸膜刮板變形均在彈性范圍內(nèi)，以免拾膜桿齒、卸膜刮板產(chǎn)生塑性變形影響其拾膜性能和卸膜性能。由于拾膜機(jī)構(gòu)與卸膜機(jī)構(gòu)的結(jié)構(gòu)、相對(duì)位置關(guān)系及機(jī)構(gòu)轉(zhuǎn)速與拾膜桿齒和卸膜刮板間的作用力、變形情況密切相關(guān)，因此，有必要研究卸膜過程拾膜桿齒與卸膜刮板接觸機(jī)理，確定影響機(jī)構(gòu)卸膜的關(guān)鍵參數(shù)。

在卸膜過程中，卸膜機(jī)構(gòu)上的卸膜刮板通過刮和捋的動(dòng)作將拾膜桿齒上挑起的殘膜回收至集膜箱。如圖 2所示，機(jī)具以速度v行駛，卸膜刮板隨卸膜機(jī)構(gòu)以2w的速度勻速轉(zhuǎn)動(dòng)，拾膜機(jī)構(gòu)的桿齒軸以1w的速度轉(zhuǎn)動(dòng)，拾膜桿齒在拾膜機(jī)構(gòu)曲柄滑道的控制下水平后移。此時(shí)，在卸膜刮板與拾膜桿齒的接觸面上，桿齒受法向力FN和與切向力FT作用。

圖2 桿齒式殘膜回收機(jī)卸膜機(jī)構(gòu)示意圖Fig.2 Schematic diagram of unloading film mechanism of pole-tooth type residual plastic film collector

單個(gè)微凸體在彈性接觸變形階段的法向力[27]為

式中FeN為單個(gè)微凸體法向力，N；E*為復(fù)合彈性模量，Pa。.E1和E2為兩接觸材料的彈性模量，Pa；ν1和ν2為兩接觸材料的泊松比；D為分形維數(shù)；A為微凸體接觸面積，mm；δ為微凸體形變量，mm。

δ與A的關(guān)系式[28]為

由式（2）可得

式中G為分形粗糙度參數(shù)。

由式（1）、（2）和（3）可得桿齒與卸膜刮板在彈性接觸變形階段所受法向力為

式中δc為彈性臨界形變量，mm。δc可用下式[29]計(jì)算：

式中K為硬度系數(shù)，K=0.454+0.41νs（νs為較軟材料的泊松比）；H為軟材料的硬度（卸膜刮板），H=2.8σs（σs為較軟材料的屈服強(qiáng)度）；R為刮板與桿齒接觸部分微凸體的曲率半徑，mm。

將式（5）代入式（4）即可求得法向力與形變量的關(guān)系：

微凸體的曲率半徑[30]為

微凸體臨界接觸面積[31]Ac為

卸膜過程中，桿齒與卸膜刮板間存在切向滑動(dòng)，若桿齒與卸膜刮板間滑動(dòng)摩擦系數(shù)為μ，則桿齒與卸膜刮板在彈性接觸變形階段的切向力FT為

為了使卸膜刮板能從桿齒上捋下殘膜，卸膜刮板對(duì)殘膜的切向作用力要大于殘膜與桿齒之間的摩擦力，則保證卸膜時(shí)的必要條件為

式中μ￠為桿齒與殘膜之間的摩擦因子；m為被桿齒挑起的地膜質(zhì)量，g；r為被挑起的地膜距瞬心的距離，mm；

兩彈性體接觸，根據(jù)動(dòng)力學(xué)基本控制方程可得

根據(jù)動(dòng)量守恒定律，對(duì)式（11）從接觸開始時(shí)刻 0到接觸結(jié)束時(shí)刻tn時(shí)間積分，得到

對(duì)于式（12），兩彈性體速度不一樣時(shí)，接觸過程通常會(huì)持續(xù)一段時(shí)間。在此接觸過程中，接觸體的材料特性、幾何特性和運(yùn)動(dòng)特性都會(huì)對(duì)接觸情況產(chǎn)生影響。在拾膜機(jī)構(gòu)和卸膜機(jī)構(gòu)結(jié)構(gòu)和材料確定的情況下，包括機(jī)構(gòu)轉(zhuǎn)速在內(nèi)的運(yùn)動(dòng)特性對(duì)拾膜桿齒與卸膜刮板變形的影響尤為重要。

采用顯示中心差分法求解式（11），已知0，t1，t2，…，tn時(shí)刻節(jié)點(diǎn)的位移、速度與加速度，可以解出tn+1(t+Δt)時(shí)刻的結(jié)構(gòu)響應(yīng)。對(duì)速度、加速度的導(dǎo)數(shù)采用中心差分代替，有

求解線性方程組（13），可獲得t +Δt時(shí)刻的節(jié)點(diǎn)位移向量Ut+Δt。根據(jù)接觸動(dòng)力學(xué)算法，將Ut+Δt代回對(duì)應(yīng)的幾何方程和物理方程中，得到t +Δt時(shí)刻的單元應(yīng)力和單元應(yīng)變，再將單元應(yīng)力與單元應(yīng)變集合即可求出彈性體總體應(yīng)力和變形[32]。

3 卸膜過程的接觸仿真

針對(duì)卸膜過程中拾膜桿齒與卸膜刮板的接觸過程運(yùn)用ANSYS Workbench軟件進(jìn)行分析，觀察拾膜桿齒和卸膜刮板的變形情況，以確定機(jī)構(gòu)的運(yùn)動(dòng)速度，為優(yōu)化機(jī)構(gòu)的運(yùn)動(dòng)參數(shù)匹配提供依據(jù)。

3.1 有限元模型的建立

采用Unigraphics（UG）軟件對(duì)拾膜桿齒和卸膜刮板進(jìn)行三維建模及虛擬裝配，為了簡(jiǎn)化運(yùn)算的復(fù)雜程度，以單個(gè)桿齒及所對(duì)應(yīng)的卸膜刮板為分析對(duì)象。桿齒長(zhǎng)230 mm，直徑5 mm，兩拾膜桿齒間距72 mm，一組桿齒作用的卸膜刮板寬度取200 mm。將裝配好的模型保存為.stp格式導(dǎo)入 ANSYS Workbench軟件，拾膜桿齒材料為55SiMnVB彈簧鋼，材料密度7 860 kg/m3，泊松比為0.3，彈性模量1.96′1011Pa，屈服極限1 225 MPa。卸膜刮板采用丁腈橡膠，其材料密度1 300 kg/m3，泊松比為0.49，彈性模量7.8′106Pa。模型導(dǎo)入后進(jìn)行網(wǎng)格劃分，圖3所示為劃分網(wǎng)格后的拾膜桿齒和卸膜刮板有限元接觸模型，共含有20 866個(gè)實(shí)體單元和8 577個(gè)節(jié)點(diǎn)。

圖3 網(wǎng)格劃分后的接觸模型Fig.3 Contact model after meshing

3.2 約束與加載

按照卸膜刮板與拾膜桿齒的實(shí)際接觸情況，對(duì)有限元模型添加約束。卸膜刮板限制沿相對(duì)坐標(biāo)的移動(dòng)約束為TX=TY=TZ=0和繞相對(duì)坐標(biāo)軸的轉(zhuǎn)動(dòng)方向RX=RY=0；拾膜桿齒限制沿相對(duì)坐標(biāo)的移動(dòng)約束TX=TZ=0和繞相對(duì)坐標(biāo)軸的轉(zhuǎn)動(dòng)方向RX=RY=RZ=0。設(shè)定桿齒外圓柱面為目標(biāo)面，卸膜刮板弧形端外側(cè)為接觸面，根據(jù)機(jī)具行進(jìn)速度（0.6～1.2 m/s），分別對(duì)拾膜機(jī)構(gòu)施加18和36 r/min 2種轉(zhuǎn)速。

3.3 結(jié)果與分析

通過ANSYS Workbench對(duì)建好的有限元模型進(jìn)行顯式動(dòng)力學(xué)求解。圖 4為卸膜刮板變形圖和桿齒變形圖，從圖中可以看出隨著拾膜機(jī)構(gòu)轉(zhuǎn)速的增加，卸膜刮板和拾膜桿齒的形變量都增大。當(dāng)拾膜機(jī)構(gòu)轉(zhuǎn)速為 36 r/min時(shí)，卸膜刮板最大形變量為55.966 mm，桿齒最大形變量為 20.228 mm。拾膜桿齒的最大形變量發(fā)生在桿齒桿末端，卸膜刮板的最大形變量出現(xiàn)在刮板兩側(cè)，且靠近刮板軸，這與實(shí)際工作情況一致。為了保證刮板與桿齒的接觸力，在刮板軸和刮板連接處加裝寬度為8 cm的硬質(zhì)膠板以增大刮板靠近刮板軸部分的剛度，使刮板最大變形前移。

圖4 不同拾膜機(jī)構(gòu)轉(zhuǎn)速下卸膜刮板及拾膜桿齒變形Fig.4 Deformation of unloading film scraper and picking up film pole-tooth under different rotation speed of picking up film mechanism

4 桿齒式殘膜回收機(jī)卸膜過程高速攝像試驗(yàn)

桿齒式殘膜回收機(jī)作業(yè)時(shí)，桿齒末端的軌跡是否符合設(shè)計(jì)要求對(duì)于卸膜刮板在卸膜段、拾膜桿齒水平回抽時(shí)能否卸下殘膜至關(guān)重要。卸膜過程中，卸膜刮板與拾膜桿齒間的接觸力是保證殘膜卸下的關(guān)鍵因素。接觸力過大，使卸膜刮板磨損嚴(yán)重，從而影響卸膜機(jī)構(gòu)的工作壽命；接觸力過小，會(huì)使卸膜刮板對(duì)桿齒上殘膜施加的切向作用力小于殘膜與桿齒之間的摩擦力，此時(shí)殘膜不能被順利卸下。由于卸膜刮板與拾膜桿齒接觸位置不便于安裝測(cè)量接觸力的傳感器，直接精確測(cè)量卸膜刮板與拾膜桿齒間的作用力較為困難。通過高速攝像可以觀察卸膜刮板與桿齒的變形情況，進(jìn)而了解卸膜過程中接觸力變化的情況。因此，對(duì)桿齒式殘膜回收機(jī)的拾膜機(jī)構(gòu)和卸膜機(jī)構(gòu)進(jìn)行高速攝像試驗(yàn)，觀察桿齒式殘膜回收機(jī)能否在預(yù)定軌跡脫膜段可靠卸膜及卸膜過程中桿齒與卸膜刮板的接觸變形情況，驗(yàn)證機(jī)構(gòu)理論分析及仿真結(jié)果的正確性。

4.1 試驗(yàn)條件與試驗(yàn)設(shè)備

4.1.1 試驗(yàn)條件

選取厚度為0.008 mm的聚乙烯農(nóng)用舊地膜，地膜鋪設(shè)與實(shí)際菜地種植模式一致，壟寬60 cm（白蘿卜種植壟寬）、壟高20 cm、將邊膜壓入壟高下2/3～3/4處。

根據(jù)田間工作的實(shí)際情況和桿齒式殘膜回收機(jī)設(shè)計(jì)要求，選取3種工況：工況Ⅰ為機(jī)具速度0.60 m/s、機(jī)具行進(jìn)速度與拾膜桿齒軸線速度比為1.0；工況Ⅱ?yàn)闄C(jī)具速度0.85 m/s、速比為1.5；工況Ⅲ為機(jī)具速度1.20 m/s、速比為1.5。為了保證可靠卸膜，卸膜過程中桿齒被卸膜刮板連續(xù)刮捋2次，即卸膜輪轉(zhuǎn)速與桿齒軸轉(zhuǎn)速比為8/3。

4.1.2 試驗(yàn)設(shè)備

試驗(yàn)在自制的行走式土槽試驗(yàn)系統(tǒng)上進(jìn)行，該試驗(yàn)系統(tǒng)組成如圖 5所示。試驗(yàn)系統(tǒng)主要由土槽車、機(jī)架、桿齒式拾膜機(jī)構(gòu)、卸膜機(jī)構(gòu)、控制元件等組成。土槽車由路陽(yáng)紅 404輪式拖拉機(jī)牽引，變頻器控制拾膜機(jī)構(gòu)和卸膜機(jī)構(gòu)轉(zhuǎn)速。試驗(yàn)土壤為黏性土壤，土壤含水率為50%～70%。選用精度為0.1 g的FA2104-N型電子分析天平稱質(zhì)量。快門范圍最快為0.2μs/幀，視頻以.hsv格式輸出。錄制完成的影像通過配套軟件i-SPEED Suite和i-SPEED Viewer圖像分析軟件進(jìn)行分析處理。

圖5 卸膜過程高速攝像試驗(yàn)Fig.5 High-speed photography test of unloading film process

4.2 試驗(yàn)標(biāo)定

高速攝像時(shí)，保證拍攝角度、焦距、像素容量及像素基準(zhǔn)坐標(biāo)相同。為了得到卸膜刮板和拾膜桿齒末端的實(shí)際形變量，需要把像素值轉(zhuǎn)換為實(shí)際值。通過機(jī)構(gòu)的標(biāo)準(zhǔn)尺寸LS與圖像上機(jī)構(gòu)的像素尺寸L的比值得出基準(zhǔn)比例值k，即

圖6所示，采用i-SPEED Suite的分析功能標(biāo)記卸膜過程視頻圖像中的拾膜桿齒和卸膜刮板。像素坐標(biāo)原點(diǎn)選取桿齒芯軸中心。桿齒發(fā)生最大形變時(shí)，標(biāo)記桿齒末端為 1點(diǎn)；與卸膜刮板分離后、桿齒回復(fù)原始位置時(shí)，標(biāo)記桿齒末端為2點(diǎn)，1、2兩點(diǎn)之間的距離為桿齒末端形變量的像素值LP，則桿齒實(shí)際形變量LSP為k·LP，同理，可測(cè)得卸膜刮板的形變量LSS。

圖6 試驗(yàn)標(biāo)定Fig.6 Experimental calibration

4.3 結(jié)果及分析

圖7為拾膜桿齒末端的高速攝像追蹤軌跡和UG仿真軌跡。如圖7所示，桿齒末端的高速攝像追蹤軌跡與UG軟件仿真軌跡吻合；拾膜桿齒末端在卸膜段基本上保持水平回抽，滿足卸膜要求。

圖7 高速攝像追蹤軌跡與Unigraphics (UG) 仿真軌跡Fig.7 Tracking trajectories of pole-tooth end for high-speed photography and UG simulation

表1所示是高速攝像分析軟件測(cè)定的3種工況下拾膜桿齒和卸膜刮板變形結(jié)果。工況Ⅰ中拾膜桿齒末端形變與仿真分析結(jié)果較接近；工況Ⅱ中拾膜桿齒末端形變量為15.741 mm，較仿真結(jié)果20.228 mm明顯減小，這是由于受實(shí)際拾膜桿齒排布和卸膜刮板材料的影響，相鄰桿齒的疊加作用和卸膜刮板材料的超彈性減小了桿齒的形變量。

表1 3種工況下拾膜桿齒和卸膜刮板前端形變結(jié)果Table 1 Deformation results of pole-tooth and scraper front end under 3 working conditions

如圖8所示，通過i-SPEED viewer軟件，將3種工況卸膜過程以等時(shí)間間隔剪影各成4張照片。

圖8 不同工況下卸膜機(jī)構(gòu)卸膜過程Fig.8 Working process of unloading residual plastic film mechanism under different working conditions

圖8a所示卸膜過程工況Ⅰ中，卸膜刮板前端形變量較小，根據(jù)式（6）和式（9）可知，卸膜刮板前端與桿齒相互作用力較小。在圖8b和圖8c所示工況Ⅱ、Ⅲ中，隨著機(jī)具速度、機(jī)具速度和拾膜桿齒軸線速度比增大，則拾膜桿齒、卸膜刮前端板的變形程度也增大，同理可知，卸膜刮板前端與拾膜桿齒間的作用力也增大。Ⅰ、Ⅱ工況下，在卸膜過程中卸膜刮板前端可以較好地貼合桿齒，且刮板不會(huì)發(fā)生折疊，對(duì)桿齒的刮捋范圍較大，能最大程度地刮捋桿齒進(jìn)行卸膜。工況Ⅲ中（圖8c），卸膜過程中存在桿齒上地膜不能及時(shí)脫下，且卸膜刮板前端彎曲處會(huì)將脫下的殘膜揚(yáng)起至卸膜輥后上方的情況。

通過高速攝像試驗(yàn)得出在卸膜過程中，臺(tái)車(機(jī)具)行進(jìn)速度與拾膜機(jī)構(gòu)的轉(zhuǎn)速對(duì)卸膜機(jī)構(gòu)的性能有影響，臺(tái)車（機(jī)具）行進(jìn)速度、拾膜機(jī)構(gòu)的轉(zhuǎn)速與卸膜刮板和桿齒接觸間作用力及形變量成正比。在工況Ⅰ中（圖8a），由于拾膜機(jī)構(gòu)轉(zhuǎn)速較低，桿齒拾起地膜、向上升運(yùn)過程中存在地膜滑落現(xiàn)象；工況Ⅱ中（圖 8b），不存在地膜滑落現(xiàn)象。增大機(jī)具行進(jìn)速度（工況Ⅲ，圖8c），拾膜、卸膜機(jī)構(gòu)轉(zhuǎn)速相應(yīng)提高，機(jī)具工作效率提高，但是，卸膜刮板和拾膜桿齒作用時(shí)間短，不利于殘膜脫卸和收集。

5 結(jié) 論

1）根據(jù)接觸分形理論和 MB（Majumdar-Bhushan）接觸分形模型，得出卸膜刮板與桿齒的接觸過程中接觸載荷和形變量的關(guān)系，通過動(dòng)力學(xué)接觸分析得到影響動(dòng)態(tài)接觸載荷的材料特性與運(yùn)動(dòng)特性的關(guān)系。

2）運(yùn)用ANSYS Workbench對(duì)卸膜刮板與拾膜桿齒的接觸過程進(jìn)行了有限元分析，得出滿足在卸膜段可靠卸膜的條件下，拾膜機(jī)構(gòu)轉(zhuǎn)速為36 r/min時(shí)，卸膜刮板最大變形出現(xiàn)在后部?jī)蓚?cè)，最大形變量為55.966 mm；拾膜桿齒最大變形在桿齒末端，最大形變量為20.228 mm。

3）為了觀察桿齒末端運(yùn)動(dòng)軌跡和桿齒末端與卸膜刮板前端在卸膜過程中的變形程度，搭建試驗(yàn)系統(tǒng)進(jìn)行了高速攝像試驗(yàn)。試驗(yàn)結(jié)果表明，桿齒末端的實(shí)際工作軌跡與仿真分析結(jié)果一致；機(jī)具行進(jìn)速度、拾膜機(jī)構(gòu)的轉(zhuǎn)速與卸膜刮板前端和桿齒接觸間作用力及形變量成正比。機(jī)具行進(jìn)速度為0.85 m/s、機(jī)具行進(jìn)速度與拾膜桿齒軸線速度比為1.5時(shí)，該桿齒式殘膜回收機(jī)具在滿足生產(chǎn)效率較高的情況下能保證可靠卸膜。

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Unloading film process analysis and high-speed photography experiment of pole-tooth residual plastic film collector

Xie Jianhua1, Chen Xuegeng2, Sun Chaowei1
(1.Department of Mechanical and Traffic, Xinjiang Agricultural University, Urumqi830052,China;2.Xinjiang Academy of Agricultural Reclamation, Shihezi832000,China)

In order to solve the problem of “white pollution” caused by the residual plastic film, researchers has carried out a lot of researches on residual film recovery technology and produce a variety of residual film recycling equipments. Lots of residual plastic film collectors have been designed to address “how to pick up” in recent years, however, the problem of “how to unload” is often overlooked. This study was to investigate the uploading process of a pole-tooth residual plastic film collector that was designed to efficiently collect and unload residual plastic film. Based on the MB (Majumdar-Bhushan)contact fractal theory, the relationship between the contact load and the deformation during the contact between the unloading blade and the rod was obtained, and the relationship between the material and the motion characteristics of the dynamic contact load was also obtained by the dynamic contact analysis. The contacting payload and contacting deformation and dynamic influencing factors between picking-up pole-tooth and unloading film scraper in the process of film uploading were analyzed and simulated using a finite-element analysis software, ANSYS. A high-speed camera was used to track the trajectory of the picking-up pole-tooth, and the maximum deformation of picking-up pole-tooth and unloading film scraper front end was observed during the process of film unloading. The resulted showed that, to satisfy reliable unloading films, the maximum deformation of picking-up pole-tooth and unloading film scraper front end were 15.741 and 49.733 mm, respectively when the rotation speed of the picking-up film mechanism was 36 r/min. The pole-tooth plastic film residue collector could reach the higher production efficiency and ensure unloading film reliably when the speed of the machine was 0.85 m/s, and the speed ratio of machine to pole-tooth was 1.5, the pole-tooth residual film recovery machine could ensure reliable unloading of film in the case of high production efficiency. When the speed of the machine was 0.60 m/s, and the speed ratio of machine to pole-tooth was 1.0, because the speed of picking-up film mechanism was low, the film picked up by pole-tooth could be slipped off in the process of moving up. When the speed of the machine was 1.20 m/s, and the speed ratio of machine to pole-tooth was 1.5, the rotation speed of the picking-up film mechanism and unloading film mechanism were improved, and the working efficiency of the machine was improved. However, the contacting time of the film and the picking-up rod got shorter, which was harmful to the unloading and collection of the residual film. Through the finite element simulation and high-speed camera test of the unloading process, the contact deformation of the rod-splicing tooth and the unloading mechanism was observed, and the conditions of reliable unloading of the rod-type residual film recovery machine were analyzed, and the optimization of the equipment was provided, the experimental result was consistent with the simulation result. The results can provide the support for motion parameter optimization of picking-up and uploading residual film mechanisms in design of a pole-tooth residual film collector.

photography; deformation; films; residual plastic film collector; picking-up film mechanism; unloading film mechanism; contact analysis

10.11975/j.issn.1002-6819.2017.10.003

S223.5

A

1002-6819(2017)-10-0017-08

2016-10-06

2017-04-10

國(guó)家自然科學(xué)基金資助項(xiàng)目（51465057）；公益性行業(yè)（農(nóng)業(yè)）科研專項(xiàng)（201503105）；新疆自治區(qū)自然科學(xué)基金項(xiàng)目（2016D01A039）

謝建華，女，副教授，博士，主要從事農(nóng)業(yè)機(jī)械設(shè)計(jì)與研究。烏魯木齊 新疆農(nóng)業(yè)大學(xué)機(jī)械交通學(xué)院，830052。Email：xjh199032@163.com