噴涂機(jī)器人的結(jié)構(gòu)設(shè)計(jì)
噴涂機(jī)器人的結(jié)構(gòu)設(shè)計(jì),噴涂機(jī)器人的結(jié)構(gòu)設(shè)計(jì),噴涂,機(jī)器人,結(jié)構(gòu)設(shè)計(jì)
噴涂機(jī)器人的結(jié)構(gòu)設(shè)計(jì)
中文摘要：
英文摘要
目錄
1.前言
2電動機(jī)的設(shè)計(jì)
（1）大臂電動機(jī)的設(shè)計(jì)
（2）基座電動機(jī)的設(shè)計(jì)
3軸的設(shè)計(jì)和校核
（1）基座傳動軸的設(shè)計(jì)
（2）軸的強(qiáng)度校核
（3）基座傳動軸上零件校核
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前言
首先我介紹一下機(jī)器人產(chǎn)生的背景，機(jī)器人技術(shù)的發(fā)展，它應(yīng)該說是一個科學(xué)技術(shù)發(fā)展共同的一個綜合性的結(jié)果，同時(shí)，為社會經(jīng)濟(jì)發(fā)展產(chǎn)生了一個重大影響的一門科學(xué)技術(shù)，它的發(fā)展歸功于在第二次世界大戰(zhàn)中各國加強(qiáng)了經(jīng)濟(jì)的投入，就加強(qiáng)了本國的經(jīng)濟(jì)的發(fā)展。比如說日本，戰(zhàn)后以后開始進(jìn)行汽車的工業(yè)，那么這時(shí)候由于它人力的缺乏，它迫切需要一種機(jī)器人來進(jìn)行大批量的制造，提高生產(chǎn)效率降低人的勞動強(qiáng)度，這是從社會發(fā)展需求本身的一個需求。另一方面它也是生產(chǎn)力發(fā)展的需求的必然結(jié)果，也是人類自身發(fā)展的必然結(jié)果，那么人類的發(fā)展隨著人們逐漸的這種社會發(fā)展的情況，人們越來越不斷探討自然過程中，在改造自然過程中，認(rèn)識自然過程中,來需求能夠解放人的一種奴隸。那么這種奴隸就是代替人們?nèi)ツ軌驈氖聫?fù)雜和繁重的體力勞動，實(shí)現(xiàn)人們對不可達(dá)世界的認(rèn)識和改造，這也是人們在科技發(fā)展過程中的一個客觀需要。但另一方面，盡管人們有各種各樣的好的想法，但是它也歸功于電子技術(shù)，計(jì)算機(jī)技術(shù)以及制造技術(shù)等相關(guān)技術(shù)的發(fā)展而產(chǎn)生了提供了強(qiáng)大的技術(shù)保證。
機(jī)器人有三個發(fā)展階段，那么也就是說，我們習(xí)慣于把機(jī)器人分成三類，一種是第一代機(jī)器人，那么也叫示教再現(xiàn)型機(jī)器人，它是通過一個計(jì)算機(jī)，來控制一個多自由度的一個機(jī)械，通過示教存儲程序和信息，工作時(shí)把信息讀取出來，然后發(fā)出指令，這樣的話機(jī)器人可以重復(fù)的根據(jù)人當(dāng)時(shí)示教的結(jié)果，再現(xiàn)出這種動作，比方說汽車的點(diǎn)焊機(jī)器人，它只要把這個點(diǎn)焊的過程示教完以后，它總是重復(fù)這樣一種工作，它對于外界的環(huán)境沒有感知，這個力操作力的大小，這個工件存在不存在，焊的好與壞，它并不知道，那么實(shí)際上這種從第一代機(jī)器人，也就存在它這種缺陷，因此，在20世紀(jì)70年代后期，人們開始研究第二代機(jī)器人，叫帶感覺的機(jī)器人，這種帶感覺的機(jī)器人是類似人在某種功能的感覺，比如說力覺、觸覺、滑覺、視覺、聽覺和人進(jìn)行相類比，有了各種各樣的感覺，比方說在機(jī)器人抓一個物體的時(shí)候，它實(shí)際上力的大小能感覺出來，它能夠通過視覺，能夠去感受和識別它的形狀、大小、顏色。抓一個雞蛋，它能通過一個觸覺，知道它的力的大小和滑動的情況。
那么第三代機(jī)器人，也是我們機(jī)器人學(xué)中一個理想的所追求的最高級的階段，叫智能機(jī)器人，那么只要告訴它做什么，不用告訴它怎么去做，它就能完成運(yùn)動，感知思維和人機(jī)通訊的這種功能和機(jī)能，那么這個目前的發(fā)展還是相對的只是在局部有這種智能的概念和含義，但真正完整意義的這種智能機(jī)器人實(shí)際上并沒有存在，而只是隨著我們不斷的科學(xué)技術(shù)的發(fā)展，智能的概念越來越豐富，它內(nèi)涵越來越寬。
機(jī)器人有三個發(fā)展階段，那么也就是說，我們習(xí)慣于把機(jī)器人分成三類，一種是第一代機(jī)器人，那么也叫示教再現(xiàn)型機(jī)器人，它是通過一個計(jì)算機(jī)，來控制一個多自由度的一個機(jī)械，通過示教存儲程序和信息，工作時(shí)把信息讀取出來，然后發(fā)出指令，這樣的話機(jī)器人可以重復(fù)的根據(jù)人當(dāng)時(shí)示教的結(jié)果，再現(xiàn)出這種動作，比方說汽車的點(diǎn)焊機(jī)器人，它只要把這個點(diǎn)焊的過程示教完以后，它總是重復(fù)這樣一種工作，它對于外界的環(huán)境沒有感知，這個力操作力的大小，這個工件存在不存在，焊的好與壞，它并不知道，那么實(shí)際上這種從第一代機(jī)器人，也就存在它這種缺陷，因此，在20世紀(jì)70年代后期，人們開始研究第二代機(jī)器人，叫帶感覺的機(jī)器人，這種帶感覺的機(jī)器人是類似人在某種功能的感覺，比如說力覺、觸覺、滑覺、視覺、聽覺和人進(jìn)行相類比，有了各種各樣的感覺，比方說在機(jī)器人抓一個物體的時(shí)候，它實(shí)際上力的大小能感覺出來，它能夠通過視覺，能夠去感受和識別它的形狀、大小、顏色。抓一個雞蛋，它能通過一個觸覺，知道它的力的大小和滑動的情況。
那么第三代機(jī)器人，也是我們機(jī)器人學(xué)中一個理想的所追求的最高級的階段，叫智能機(jī)器人，那么只要告訴它做什么，不用告訴它怎么去做，它就能完成運(yùn)動，感知思維和人機(jī)通訊的這種功能和機(jī)能，那么這個目前的發(fā)展還是相對的只是在局部有這種智能的概念和含義，但真正完整意義的這種智能機(jī)器人實(shí)際上并沒有存在，而只是隨著我們不斷的科學(xué)技術(shù)的發(fā)展，智能的概念越來越豐富，它內(nèi)涵越來越寬。
我設(shè)計(jì)的噴吐機(jī)器人主要運(yùn)用于房屋墻壁的噴漆，汽車表面噴途等用途。我
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本論
2.2.1電動機(jī)的設(shè)計(jì)
假設(shè)手腕的最大負(fù)荷重量3kg，初估腕部的重量3kg，最大運(yùn)動速度V=1.5m/s
功率P=fv=mgv=6×10×1.5=90kw
取安全系數(shù)為1.2，
考慮到傳動損失和摩擦，最終的電機(jī)功率P=110W。
查表選擇75BF004型號反應(yīng)式步進(jìn)電動機(jī)。
具體參數(shù)如下表
型號
相數(shù)
步距角
最大精轉(zhuǎn)矩
安裝外徑
長度
軸徑
重量
75BF004
3
1.5
0.882NM
75mm
75mm
6mm
1.58kg
小臂減速比的確定
求角速度 W＝==3.75r/s
其中W為角速度（r/s）
V為運(yùn)動速度（m/s）
R為小臂連桿的長度（400mm）
在求實(shí)際轉(zhuǎn)速
N＝=36r/min
最后求得總傳動比：i=
步進(jìn)電動機(jī)轉(zhuǎn)速為 n＝
其中為步距角
f為控制脈沖頻率
由電動機(jī)型號查表求得f＝2500hz
則 n＝==625r/min
則i==17.3
取i整＝17
查表采用行星齒輪結(jié)構(gòu)的 諧波減速器具體機(jī)構(gòu)及參數(shù)如下所示
：
行星齒輪減速器
自齒
輸出端軸承
滾珠軸承
最大 允許軸向載荷
150N
最大允許安裝力
300N
推薦輸入速度
800rpm
減速比
17：1
輸出最大轉(zhuǎn)矩
15N.M
允許瞬間輸出轉(zhuǎn)矩
22.5N.M
具體安裝尺寸見下圖所示：
2.2.2機(jī)座電動機(jī)和大臂電動機(jī)的結(jié)構(gòu)設(shè)計(jì)同小臂采用相同原理
大臂電動機(jī)的設(shè)計(jì)：
初步估計(jì)大臂電動機(jī)的 負(fù)載為16kg 最大運(yùn)動速度為1.5m/s
同理求得P=288W
查相關(guān)手冊選步進(jìn)電動機(jī)的型號為：90BF003
具體參數(shù)如下：
電動機(jī)型號
相數(shù)
步距角
最大靜轉(zhuǎn)矩
最大啟動功率
90BF003
3
1.5
1.96
1500HZ
質(zhì)量
外徑
長度
軸徑
最大運(yùn)行頻率
4.2kg
90mm
125mm
9mm
8000hz
由以上數(shù)據(jù)可得步進(jìn)電動機(jī)的轉(zhuǎn)速為
由公式n＝==2000r/min
又由W===2.14r/s
實(shí)際轉(zhuǎn)速n’==20r/min
由公式得 i總＝==100
查表采用行星齒輪結(jié)構(gòu)的諧波減速器，具體參數(shù)如下表
：
行星齒輪減速器
直齒
輸出端軸承
滾珠軸承
最大允許軸向載荷
250N
最大安裝力
410N
推薦輸入速度
8000rpm
減速比
100：1
輸出最大轉(zhuǎn)矩
26N.M
允許瞬間輸出轉(zhuǎn)矩
36N.M
具體安裝尺寸見下圖：
2.23機(jī)座電動機(jī)的設(shè)計(jì)
初步估計(jì)電動機(jī)最大載荷重量為m=30kg 最大運(yùn)動速度V＝1.5m/s
功率P＝FV=mgv=30×10×1.5＝450W
取安全系數(shù)為1.2
則P’＝P×1.2＝540W
考慮到傳動損失和摩擦，最終的電動機(jī)功率確定為P額=560W
查表找出電動機(jī)的具體參數(shù)如下表
電動機(jī)型號
相數(shù)
步距角
最大靜轉(zhuǎn)矩
最大啟動功率
90BF001
4
1.8
3.92
2000HZ
質(zhì)量
外徑
長度
軸徑
最大運(yùn)行頻率
4.5kg
90mm
145mm
9mm
8000hz
求基座電動機(jī)的諧波減速比：
由公式n＝==2400r/min
又由基座傳動軸與噴槍幾乎處在 同一直線的特殊位置故：
W===15r/s
實(shí)際轉(zhuǎn)速n’===143
最后求得總傳動比
i總＝==16.7
取i整＝17
基座電動機(jī)也采用同諧波減速器相聯(lián)一體的結(jié)構(gòu)。具體參見下圖，安裝尺寸見下：
行星齒輪減速器
直齒
輸出端軸承
滾珠軸承
最大允許軸向載荷
250N
最大安裝力
410N
推薦輸入速度
8000rpm
減速比
17：1
輸出最大轉(zhuǎn)矩
26N.M
允許瞬間輸出轉(zhuǎn)矩
36N.M
3.軸的設(shè)計(jì)和校核
軸的結(jié)構(gòu)決定與受力情況，軸上零件的布置和固定方式，軸承的類型和尺寸，軸的毛坯和制造，裝配工藝，以及運(yùn)輸，安裝等條件，軸的結(jié)構(gòu)，應(yīng)使軸受力合理，避免或減輕應(yīng)力集中。
3.1基座傳動軸的設(shè)計(jì)
取軸的材料為45鋼。調(diào)制處理。
a.軸經(jīng)同電動機(jī)輸出軸相同大小故d=9mm
b. 各段軸徑的確定
初估軸徑后，就可按照軸上零件的安裝順序從出開始逐段確定軸徑，上面是軸段1的直徑。
軸段1上 用套筒開通鍵和電動機(jī)輸出軸相連。由于套筒幾乎不受軸向力故在套筒上開一緊盯螺釘螺釘采用。
軸段2上安裝套筒。右端用軸肩固定，考慮到軸的強(qiáng)度取軸徑＝18mm
軸段3上要安裝軸承，其直徑應(yīng)該便于軸承安裝，，故取軸段3的直徑為d=30mm
軸段4左端用軸肩固定軸承，有軸承的安裝尺寸可得＝40mm。根據(jù)尺寸結(jié)構(gòu)和便于控制軸段4末端采用圓孔型結(jié)構(gòu)。具體尺寸見圖。
C. 各段長度的確定
根據(jù)套筒及箱體結(jié)構(gòu)的尺寸?。?0mm
考慮到套筒長及箱體的長度?。?8mm
根據(jù)軸承寬度取＝34mm
由機(jī)器人的噴涂范圍及基座總長等因素?。?26mm
軸的結(jié)構(gòu)見下圖所示：
3.2軸的強(qiáng)度校核
軸在初步完成結(jié)構(gòu)設(shè)計(jì)后，進(jìn)行校核計(jì)算，計(jì)算準(zhǔn)則是滿足軸的強(qiáng)度或剛度要求，進(jìn)行軸的強(qiáng)度校核計(jì)算時(shí)，應(yīng)根據(jù)軸的具體受載及應(yīng)力情況，采取相應(yīng)的方法，并恰當(dāng)?shù)剡x取其許用應(yīng)力。
a 計(jì)算軸上的轉(zhuǎn)矩T
主軸上的傳遞功率
＝==0.7kw
T=9.55**
=9.55**=4.67*N
b 軸的受力分析
軸傳遞的轉(zhuǎn)矩：=4.67*N=9.55**
c 按彎矩合成強(qiáng)度校核軸的強(qiáng)度
（1）。繪制軸受力簡圖。見圖a
（2）。繪制垂直面彎矩圖b
軸承支撐力
=mg=32*10=320
又有*L=*
=
計(jì)算彎矩
截面C右側(cè)彎矩 NM
截面C左側(cè)彎矩 NM
d 繪制水平面彎矩圖
由于軸承水平面幾乎不受外力?？梢院雎圆凰?。
e 繪制彎矩圖
NM
NM
f 繪制轉(zhuǎn)矩圖
轉(zhuǎn)矩產(chǎn)生的扭剪應(yīng)力按脈動循環(huán)變化
?。?.6 截面C處的當(dāng)量彎矩為
g 校核危險(xiǎn)截面C的強(qiáng)度
故滿足強(qiáng)度要求
3.3基座傳動軸上零件的校核
3.31鍵的校核：
根據(jù)軸徑的大小選擇鍵的類型，
由GB1096-79查表取鍵的規(guī)格：b*h=3*3 取鍵的系列長度L=12mm
鍵的材料選用45剛
校核擠壓強(qiáng)度：
又有L=12-3=9mm
。
查表求得許用擠壓應(yīng)力＝(120－150)MP
故
擠壓強(qiáng)度足夠
3.3.2傳動軸上軸承的校核
滾動軸承的主要失效形式為疲勞點(diǎn)蝕和塑性變形。滾動軸承的計(jì)算準(zhǔn)為
針對疲勞點(diǎn)蝕進(jìn)行壽命計(jì)算，針對塑性變形進(jìn)行靜強(qiáng)度計(jì)算，對于轉(zhuǎn)速較承
除進(jìn)行壽命計(jì)算外還需要計(jì)算軸承的極限轉(zhuǎn)速。
課題中選用的軸承規(guī)格為：30206型。
具體參數(shù)如下表：
型號
D
d
T
B
C
額定動載荷
額定靜載荷
30206
62
30
17.5
16
14
41.2KN
29.5KN
如下圖所示：
a. 求當(dāng)量動載荷P:
對于只受徑向載荷為主的軸承，當(dāng)量動載荷為：
其中＝3340N
查表得＝1.2
根據(jù)公式計(jì)算：=1.2*3340=4008N
軸承的壽命計(jì)算公式為： 查表得到：C=41200N
對于球類軸承=3
則有 ：＝＝116×1086＝125998>20000h
故滿足壽命要求。
b.軸承的精強(qiáng)度校核：
求當(dāng)量精載荷
由于軸承只承受徑向載荷，由于則
=17668.6
靜強(qiáng)度選擇軸承的計(jì)算公式為：
查表=2
則=3533.7N 查表后得到：=505*N
故滿足要求。
3.4大臂軸的結(jié)構(gòu)設(shè)計(jì)
軸的材料選擇45號剛，調(diào)制處理。
各段軸徑的確定
軸段1由于和電動機(jī)配合故＝9mm
考慮到在軸段2上裝上套筒故取軸徑d=20mm
軸段3上安裝軸承，其直徑因該便于軸承的安裝，又因該符合軸承的內(nèi)徑系列。即軸段3的直徑和軸承型號的選則同時(shí)進(jìn)行，軸承型號為6..6型的深溝球軸承，故＝30mm
軸段4的右端固定軸承故取＝35mm
各段長度的確定
各段長度主要根據(jù)軸上零件的配合部分長度確定，還和箱體及軸承蓋等零件又關(guān)。
考慮到套筒長取軸段1＝30mm
軸段2上安裝套筒，取長為26mm
根據(jù)軸承的尺寸取軸段3＝14mm
根據(jù)機(jī)器人的整體結(jié)構(gòu)取軸段4＝83mm
3.4.1 軸的強(qiáng)度校核
大臂傳動軸式一個傳動力矩的軸如下圖所使的結(jié)構(gòu)：
a 軸上轉(zhuǎn)矩
主軸上傳遞的功率
又公式代入d＝9mm c=110
則
NM
b 畫出垂直面彎矩圖（如下圖）
水平面的支撐反力：
軸承支撐反力，由
則軸承
支撐反力為：
計(jì)算彎矩，取截面C處研究對象。
經(jīng)計(jì)算：
C 繪制水平面彎矩圖
由于水平面幾乎不受力的作用，故不予考慮。
d 繪制合成彎矩圖
e 繪制轉(zhuǎn)矩圖：如下圖所示
轉(zhuǎn)矩T＝9.55×＝5250NM
f 繪制當(dāng)量彎矩圖
轉(zhuǎn)矩產(chǎn)生的扭剪應(yīng)力按脈動循環(huán)變化
?。?.6 截面C處的當(dāng)量彎矩為：
＝3150NM
g 校核危險(xiǎn)截面強(qiáng)度
完全滿足要求。
3.5大臂上零件的校核
3.51軸段1上鍵的校核
由軸的直徑確定鍵的類型，根據(jù)GB1096-79選取鍵的類型
B*h=3*3 其中L=12mm
校核擠壓強(qiáng)度：
，又有L=12-3=9mm
又由轉(zhuǎn)矩T=5.25*
故
故強(qiáng)度滿足要求
3.5．2軸承的校核。
滾動軸承的計(jì)算準(zhǔn)為
針對疲勞點(diǎn)蝕進(jìn)行壽命計(jì)算，針對塑性變形進(jìn)行靜強(qiáng)度計(jì)算，對于轉(zhuǎn)速較承
除進(jìn)行壽命計(jì)算外還需要計(jì)算軸承的極限轉(zhuǎn)速。
大臂傳動軸選用的軸承規(guī)格為：6006型。
求當(dāng)量動載荷
式中為徑向載荷
為軸向載荷
為載荷系數(shù)
由于軸承主要承受徑向載荷故當(dāng)量動載荷為：
其中＝424.7N又根據(jù)工作條件查表得到＝1.2
則＝1.2×424.7＝509。64N
根據(jù)公式計(jì)算壽命：
查表C=10200N 對于球類軸承＝3
則＝66790.6>20000h
故滿足要求。
靜強(qiáng)度校核：
求當(dāng)量靜載荷
軸承主要承受徑向載荷，?。?
則＝293.04
靜強(qiáng)度校核選用公式: 查表?。?
則有：
查表得到=50500N 則可得到：。符合靜強(qiáng)度要求。
箱體的設(shè)計(jì)
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結(jié)論
》。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。
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謝辭
在此我要特別感謝我們的指導(dǎo)教師常主任給我的無盡的幫助，對我的指導(dǎo)，陪伴我們做畢業(yè)設(shè)計(jì)，使我們能夠按時(shí)保質(zhì)的完成畢業(yè)設(shè)計(jì)，同時(shí)我還要感謝我同組的同學(xué)對我的幫助和大力支持，使我能夠盡可能在短的時(shí)間完成畢業(yè)設(shè)計(jì)。
參考文獻(xiàn)
〈〈機(jī)械設(shè)計(jì)基礎(chǔ)〉〉
〈〈機(jī)械制造技術(shù)基礎(chǔ)〉〉
〈〈機(jī)械制圖〉〉
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附錄：六張圖紙
噴吐機(jī)器人的裝配圖
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Simulation of the Effect of Process Parameters on Particle Velocity in Cold Spray Using Laval Nozzle with Nine Holes Chuanshao Liua, Yaohui Jinb and Jianxin Zhengc Henan Polytechnic University, Jiaozuo 454003,P.R.China , , Keywords: Cold spray; Simulation; Laval nozzle with nine holes; Particle velocity. Abstract. Simulations of the supersonic flow field inside and outside of the Laval nozzle with single hole and nine holes were carried out based on the computational fluid dynamics method. The effects of different standoff distance and particle diameter on impact velocity of Cu particle spraying from single hole and nine holes were investigated firstly. The results show that the particle velocity obtained with the nine holes nozzle is higher than that of the single hole nozzle under the same standoff distance, and the smaller the standoff distance, the higher the particle velocity may be obtained with the nine holes, and the higher particle velocity may be obtained with smaller particle diameter for particles with diameters of 1 15 m. Furthermore the effects of different spraying pressure and temperature on particle velocity of Cu particle spraying from the nine holes nozzle were also studied. And the simulations indicate that the higher the spraying pressure and temperature may make the particle spraying with greater velocity. Introduction The standoff distance (SoD) between the nozzle and the substrate is one of the important parameters in the cold spray process, and which influences the particle impact velocity directly. Many scholars have focused on this problem. Pattison 1 found that a bow shock was formed at the impingement zone between the supersonic jet and the substrate when the SoD was small, and the bow shock was detrimental to the process performance as it reduced the particle impact velocity. His study also showed that the deposition efficiency was closely related to the SoD, and the bow shock reduced deposition efficiencies by as much as 40% under the SoD is less than 60mm when using a custom-made helium nozzle, operating at 2.0 MPa and 20oC. Alkhimov 2 found that the thickness of the compressed layer which formed between the bow shock and substrate depended on SoD when spraying air and helium, and the smaller the SoD, the thicker the compressed layer. His research also showed that aluminum particles less than 5m in diameter could be decelerated obviously in the compressed layer. Gilmore 3 and Dykhuizen 4 also found that the particles less than 5m in diameter could be decelerated and even deflected away from the substrate by the bow shock. The Laval nozzle with nine holes was used in this study in order to reduce the adverse effects of bow shock on particle impact velocity so as to obtain the better spraying effects under the same conditions of the nozzle exit area compared with the Laval nozzle with single hole. Theoretical Models Mathematical model. Compressible flow is a very complex and comprehensive phenomenon, and the actual flow of the nozzle is non-constant isentropic flow in the actual conditions. The flow inside of the nozzle is considered as a steady isentropic flow in theory so as to simplify the simulation. The governing equations used to describe the process are as follows 5. Continuity equation: 0)( =+ ut ; Momentum equation: +=+ puuut )()( ; Advanced Materials Research Vols. 314-316 (2011) pp 78-81 Online available since 2011/Aug/16 at (2011) Trans Tech Publications, Switzerland doi:10.4028/ All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, . (ID: 222.88.196.201-26/08/11,01:28:10) Energy equation: )()( Tkupete D +=+ ; Equation of state: p=RT Where u, p, and T represent the flow velocity, pressure and temperature; , , and k represent the flow density, viscous stress tensor and thermal conductivity, respectively; e, D are the stagnation internal energy per unit volume and viscous dissipation, respectively. Particles can be considered as discrete phase in the continual gas flow, and the acceleration of a spherical particle by the gas flow can be expressed by the following equation when the interaction between the particles and gravity is ignored 6: pp pp Dp uuuu d C dt du = )( 4 3 Where up, dp, p represent particle velocity, diameter and density; CD is drag coefficient and expressed for a smooth spherical particle by eeD RaRaaC / 321 += and a1, a2, and a3 are constants, Re is the Reynolds number and defined by: /uudR ppe = and is the fluid dynamic viscosity and this equation can be practically applied to a Re 50000. Geometrical model. The jet flow region in cold spray process is made up of the internal flow of the nozzle and free jet flow region. Due to the use of nine holes nozzle, a three-dimensional model is built up in this study. Fig.1 shows the exit section diagram of the nine holes nozzle, and there are eight small holes with diameter of 1.67 mm uniformly distributed and a center hole with diameter of 2.6mm in the circular face with diameter of 6.4mm. The distance L (as shown in Fig.1) between the small hole and center hole is 2.25mm, the total area of the nine holes equals the exit area of the single hole with diameter of 5.4mm. Other dimensions of the Laval nozzle with nine holes are identical to the single hole nozzle, Fig.2 shows the section diagram of the Laval nozzle with single hole and computational domain, and its main dimensions are shown in table 1. Boundary conditions and solving method Gas inlet Outlet SoDAxis Wall Exit Divergent sectionConvergent section Substrate Fig.2 Section diagram of Laval nozzle with single hole and computational domain Inlet diameter(mm) 8 Convergent length(mm) 23 Divergent length(mm) 40 Throat diameter(mm) 2.7 Exit diameter(mm) 5.4 SoD(mm) 20 L Fig.1 Exit section diagram of the Laval nozzle with nine holes Table 1 Main dimensions of the Laval nozzle with single hole Advanced Materials Research Vols. 314-316 79 Gas inlet as shown in Fig.2 is selected for the pressure inlet boundary condition, and outlet is selected for the pressure outlet boundary condition which is atmosphere pressure and room temperature. And the air is selected as the accelerating gas. The standard k- turbulence model is utilized to disperse turbulence flow of gas, and standard wall functions are used to deal with the near wall region. Second-order upwind discretization scheme is used for governing equations. The computation of discrete phase follows the continuous phase flow field. Results and discussion Effect of SoD on particle velocity. The impact velocities of Cu particles with diameter of 2m sprayed by the Laval nozzle with the single hole and the nine holes are shown in Fig.3 with different SoD when spraying pressure P is 2.5MPa and spraying temperature T is 700K. It is seen clearly that the particle velocities obtained by the Laval nozzle with nine holes is higher than that of by the Laval nozzle with the single hole in the same simulation conditions. And the smaller the SoD, the higher the particle velocity may be obtained by the Laval nozzle with nine holes. It is also seen that the optimum SoD is 40mm when the Laval nozzle with single hole operates at P=2.5MPa and T=700K. 400 500 600 700 800 10 20 30 40 50 Pa rti cle ve loc ity (m /s) SoD (mm) Single hole Nine holes 300 400 500 600 700 800 0 5 10 15 Pa rti cle ve loc ity (m /s) Particle diameter (m) Single hole Nine holes Fig.3 Effect of SoD on particle velocity Fig.4 Effect of particle diameter on particle velocity When using the Laval nozzle with single hole, a series of compress waves are produced by the supersonic gas flow due to sharp compression before the substrate. And the shock wave will occur when the compression waves stacking with each other. Supersonic gas flow becomes subsonic gas flow when it goes through the shock wave, and the pressure, density, temperature of the gas flow rises sharply, while Mach number drops rapidly. The particle velocity decreases continuously owing to shock waves effect. The intensity of shock wave before the substrate also increases consequently with the decreasing of SoD, so does the influence on particle velocity. The gas flow tends towards stability, and so is the particle velocity when using the Laval nozzle with nine holes. Effect of particle diameter on particle velocity. Fig. 4 shows the effect of particle diameter on particle velocity when the Cu particles pass through the Laval gun to the substrate at the simulation conditions of SoD=40mm, P=2.5MPa and T=700K. It is seen clearly that the higher particle velocity may be obtained with the smaller particle using different Laval nozzle, while the particle velocity obtained by the Laval nozzle with nine holes is higher than that of the Laval nozzle with single hole at the same conditions. The particle velocity decreases rapidly by the effect of shock wave before the substrate because the small particle has much low mass, low inertia and influenced by the gas easily. While using the Laval nozzle with nine holes, particle velocity has a little change as the intensity of shock wave is diminished. The greater particle has higher weight, higher inertia and can not be accelerated easily by the gas, so the variation of the particle velocity is not apparent by the effect of shock wave before the substrate. Therefore the Laval nozzle with nine holes is appropriate for the small particles. Effect of pressure on particle velocity. Fig. 5 shows the effect of pressure on particle velocity when the Cu particles pass through the Laval gun with nine hole to the substrate at the simulation conditions of SoD=40mm, T=700K and the diameter of the Cu particle is 2m. The distance x as shown in Fig.5 80 Advanced Manufacturing Technology is from nozzle inlet to the substrate. It is seen clearly that the particle velocity has a little change and tends towards stability between the exit of nozzle and the substrate. With the increment of spray pressure, the particle velocity also has little change inside of the nozzle and small increase outside of the nozzle. Therefore there is little effect of the pressure on particle velocity. 0 100 200 300 400 500 600 700 800 900 0 0.02 0.04 0.06 0.08 0.1 0.12 Pa rti cle ve loc ity (m /s) x (m) 2.5 MPa 2.0 MPa 1.5 MPa 0 100 200 300 400 500 600 700 800 900 0 0.02 0.04 0.06 0.08 0.1 0.12 Pa rti cle ve loc ity (m /s) x (m) 700K 500K 300K Fig.5 Effect of pressure on particle velocity Fig.6 Effect of temperature on particle velocity Effect of temperature on particle velocity. Fig. 6 shows the effect of temperature on particle velocity when the Cu particles pass through the Laval gun with nine hole to the substrate at the simulation conditions of SoD=40mm, P=2.5 MPa and the diameter of the Cu particle is 2m. It is seen clearly that the effect of the spray temperature on particle velocity is large, and the higher the temperature, the higher the particle velocity. Furthermore, the massive plastic deformation occurs easier in both the incident particles and the substrate with the higher temperature. Conclusions (1) The particle velocity obtained by the Laval nozzle with nine holes is higher than that with the single hole at the same standoff distance, and the smaller the standoff distance, the higher the particle velocity may be obtained by the Laval nozzle with nine holes. (2) The higher particle velocity may be obtained with smaller particles using the Laval nozzle with nine holes at the same conditions. (3) The higher the spraying pressure and temperature may make the particle spraying with greater velocity using the Laval nozzle with nine holes. References 1 J. Pattison, S. Celotto, A. Khan. Surface & Coating Technology, Vol. 202 (2008), p. 1443-1454. 2 A. P. Alkhimov, S. V. Klinkov, et al. Journal of Applied Mechanics Technical Physics, Vol. 38, No. 2 (1997), p. 324-330. 3 D. L. Gilmore, R. C. Dykhuizen, et al. Journal of Thermal Spray Technology, Vol. 8, No. 4 (1999), p. 576-582. 4 R. C. Dykhuizen, M. F. Smith. Journal of Thermal Spray Technology, Vol. 7, No. 2 (1998), p. 205-212. 5 Hidemasa Takana, Kazuhiro Ogawa, Tetsuo Shoji. Powder Technology, Vol. 185 (2008), p. 116-123. 6 Wen-Ya Li, Hanlin Liao, G. Douchy. Materials and Design, Vol. 28 (2007), p. 2129-2137. Advanced Materials Research Vols. 314-316 81 Advanced Manufacturing Technology doi:10.4028/ Simulation of the Effect of Process Parameters on Particle Velocity in Cold Spray Using Laval Nozzle with Nine Holes doi:10.4028/
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