横向交变磁场作用下的等离子体弧特性分析

第31卷第1期2010年1月
焊　接　学　报
T RANS ACTI O NS OF T HE CH I N A W E LD I N G I N STI T UTI O N
Vol .31　No .1January 2010
收稿日期:2008-09-03
基金项目:国家自然科学基金(50775019)
横向交变磁场作用下的等离子体弧特性分析
孟建兵,　徐文骥,　王续跃,　宋文庆
(大连理工大学精密与特种加工教育部重点实验室,辽宁大连　116024)
摘　要:以外加横向交变磁场作用下的等离子体弧为研究对象,建立了等离子体弧摆动幅度和热流密度分布的数学模型.对横向交变磁约束下的等离子体弧射流特性进行理论研究,并分析工艺参数和励磁强度对横向交变磁约束等离子体弧形态和特性的影响规律.结果表明,横向交变磁场可有效控制等离子体弧形态和位置,等离子体弧在横向交变磁场作用下,分布范围增大、热流密度梯度减小.其摆动幅度随磁场强度的增加而增大,但过高的磁场强度会使等离子体弧变得不稳定;相同励磁强度下,气流量和弧电流越小、喷嘴到工件的距离越大,则摆动幅度越大;而工件表面的等离子体弧热流密度分布随励磁强度的增强趋于平坦化;相同励磁条件下,热流密度峰值随气体流量和弧电流的增大而增大、随喷嘴到工件距离的增大而减小.
关键词:横向交变磁场;等离子体弧;摆动幅度;热流密度分布
中图分类号:TG403 文献标识码:A 文章编号:0253-360X (2010)01-0075-
05
孟建兵
0　序 言
近年来,、切割、喷涂等材料
加工领域得到广泛应用,其射流特性直接影响着上述工艺的加工效果.由于气体放电的雪崩效应和等离子体弧柱的自磁压缩,可使能量集中在很小的区域内,且弧柱中的电流密度和温度分布具有较大的
梯度变化.对于等离子体弧清洗[1]
、等离子体弧柔性成形、大面积表面改性处理等工艺来说,则不希望热源过分集中,而是需要形态和位置(加热区域宽度)可控的等离子体弧来获得较高的工艺质量和效率.为此,一些学者尝试引入外加横向磁场,通过扩展等离子体弧柱横截面、使弧柱内电流密度和温度的分布平坦化,以获得热流密度和加热区域可控的等离子体弧(“软”等离子体弧).文献[2]通过定量分析阳极弧根随励磁强度变化而变化的轨迹方程,给出横向磁场作用下的焊弧不是直线形状而是弯弧状的结论;文献[3]通过试验发现横向磁约束下等离子体弧存在加速和偏转减速两个阶段,并分析了产生偏转减速的原因;文献[4]通过数值模拟的方法分析了外加横向恒定磁场作用下电弧气动力学特性,发现偏转角度与射流长度成正比,与弧电流成反比.
可见,目前对“软”等离子体弧的研究工作主要侧重于采用外加横向恒定磁场作用方式,而对横向交变磁场作用方式下的等离子体弧研究鲜有报道.文中在上述研究的基础上,通过分析横向交变磁场作用等离子体弧的原理和特点,分别建立等离子体弧摆动幅度和热流密度分布的数学模型,为分析横向交变磁场作用下弧电流、气体流量、悬距等相关工艺参数和励磁强度对等离子体弧形态和特性的影响规律提供有效途径.
1　基体原理
当如图1所示的试验装置工作时,平行的两个线圈在电流的激励下产生横向交变磁场(励磁电流取正弦波形),而喷嘴与工件间的转移型等离子体弧受磁靴导入的垂直横向交变磁场作用,以同样的频率作往复摆动.其原理为:与外加磁场具有可作用性的等离子体弧是由大量带电粒子组成的,因而通过研究单个带电粒子在外加横向交变磁场中的运动,就可推断宏观上即等离子体弧在相应磁场中的摆动规律.忽略粒子间的相互作用以及粒子运动所产生的自感应磁场,则带电粒子在横向交变磁场中受到洛伦兹力作用而做回转运动,其回转半径为
r =m v QB
(1)
式中:m 为粒子质量(kg );v 为粒子速度(m /s );Q 为
76
　焊　接　学　报第31卷
粒子电量(C );B 为磁感应强度(T )
.
图1　横向交变磁约束等离子体弧发生装置
F i g 11　Gene ra t o r de vi ce o f p l a sm a a rc i n ET AM F
2　数学模型
2.1　摆动幅度模型
设等离子体从喷嘴出口运动到工件表面所需时间为t,当励磁频率f <1/2t 时,等离子体弧的摆动幅度与励磁频率无关.交变磁场的方向平行与图2中的“y ”轴,由于带电粒子受洛伦兹力作用而发生回转,使得等离子体弧在横向交变磁场作用下作同样频率的往复摆动,此时任意一段等离子体弧的电磁力可表示为
F =B Id
(2)
式中:I 为等离子体弧电流(A );d 为任意一段等离子体弧长度(m ).由牛顿第一定律可知,电磁力F 也可表示为
F =m d a sin α
(3)
式中:m d 为此段等离子体弧的质量(kg );a 为此段
等离子体弧的加速度(m /s 2
).
t 时刻等离子体弧对应质量m d 结合式(1),式
(2)并考虑α较小时α≈sin
α,则回转半径表示为r =
m d a sin αB I α=ρqta 60B I =
ρqv
60B I
(4)
式中:q 为气体流量(L /m in ).
设横向交变磁场频率为f,等离子体从喷嘴喷射到工件表面的时间为t 0,当1/2f µt 0时,则任意时刻,横向交变磁场作用下等离子体弧在工件表面的摆动幅度可表示为
l =r -r 2
-D
2
(5)
式中:D 为喷嘴到工件表面间的距离(m ).当回转半径r <D 时,等离子体弧将变得不稳定,为了使交变磁场作用下等离子体保持稳定,回转半径r µD.
当r ≥D 即tg α≈sin α时,通过上述公式联立,则等
离子体弧在工件表面摆动的最大幅度可近似表示为
l 0=
60I BD
2
ρQ
v
(6)图2　横向交变磁场作用下摆动幅度示意图
F i g 12　Mo vem en t o f p l a sm a a rc i n e xte rna l T AM F
2.2　热流密度分布模型
为建立工件表面热流密度分布数学模型,对施
加横向交变磁场前后的等离子体弧作如下假设:扣除对流、辐射散热的影响(约占10%),则工件表面等离子体弧有效热量W (W )全部转移到工件中;无外加磁场作用时,投射在工件表面上的等离子体弧近似为圆状分布,分布半径为R 0;施加横向交变磁场,等离子体弧在工件表面的形态近似为椭圆,其短轴为R 0、长轴为(R 0+l 0),如图3所示;此外,d
R 、d x 环面上等离子体弧热流密度均匀分布.
图3　工件表面等离子体弧形态分布近似图
F i g 13　Fo r m d is tri bu ti o n o f p l a sm a a rc o n ano de su rfa ce
则工件表面等离子体弧平均热流密度分布可表示为
J r =W
πR 20
(7)
设摆动等离子体弧在工件表面上的一点到弧中
心O 的距离为R ,则d t 时刻,d S 面积微元流过的热
第1期孟建兵,等:横向交变磁场作用下的等离子体弧特性分析77
　量为
d Q J=J[πR0(R+d R)-πR0R]d t(8)
励磁电流波形为正弦波形,则横向交变磁场作用下,
等离子体弧在工件表面上任一点移动位移为
x=l0sinωt+R(9)
分别对式(9)两边求关于时间t的导数,把d t代入
式(8)并联立式(9),则Q
J
可表示为
Q J=∫∫WωR0・d R・d x
l20-(x-R)2
(10)
定义等离子体弧摆动的1/2周期内,单位时间
内工件表面等离子体弧流入工件的热量为W′,并
考虑工件表面等离子体弧热流密度与热功率存在如
下关系,即
J=W′
S
=
d W′
πR
(x+d x)-πR0x
(11)
通过上述公式的联立,则横向交变磁场作用下,在1/2个摆动周期内,阳极工件表面上等离子体弧从(-l
-R0)运动到(l0+R0),其中任意x点处的热流密度分布数学模型为
当-l
-R0<x<-l0+R0时
J(x)=
W
(πR
)2
π
2
+arcsin
R0+x
l0
(12)
当-l
+R0≤x≤l0-R0时
J(x)=
W
(πR
)2
arcsin
R0-x
l0
+arcsin
R0+x
l0
(13)
当l
-R0<x<l0+R0时
J(x)=
W
(πR
)2
arcsin
R0-x
l0
+
π
2
(14)
3　计算结果与分析
整个系统包括等离子体弧发生装置和横向交变磁场励磁装置,如图1所示.其中前者的工艺参数如表1所示,后者的磁感应强度由HT102交直流特斯拉计测得.实际采用的励磁频率50Hz,半个励磁周期所用时间10m s,远大于等离子体运动到工件表面的最长时间0.78m s,即上述试验条件下的等离子体弧摆动幅度与励磁频率无关.
3.1　工艺参数对摆动幅度的影响
3.1.1　气体流量对摆动幅度的影响
当其它试验参数保持不变,即I=15A,D= 7mm,在不同氩气流量作用下(q=4,5,6L/m in),等离子体弧摆动幅度的变化规律如图4所示.等离子体弧摆动幅度随励磁磁场强度的增加而增加,当磁场强度达到临界值后,摆动幅度将达到极大值.
表1　等离子体弧发生装置的工艺参数Tab l e1　P a ram e te rs o f p l a sm a a rc gene ra t o r de vi ce 工作电流
I/A
氩气流量
q/(L・m in-1)
喷嘴悬距
D/mm
弧速度
v1/(mm・s-1) 155712.5
205725.8
255736.3
15478.95
156713.3
155611.9
155813.2
而在相同励磁强度位置处(B=10mT),等离子体弧摆动幅度随氩气流量的增大而减小.这是因为:其它工艺参数不变,工作气体流量的增加导致喷嘴出口处等离子体速度升高,而速度的升高将缩短等离子体经过横向交变磁场区域的时间,从而使得等离子体弧的摆幅随之减小.
图4　氩气流量对摆动幅度的影响
F i g14　Effe c t o f q o n o sc ill a ti ng am p litude
3
.1.2　工作电流对摆动幅度的影响
当其它试验参数保持不变,即q=5L/m in,D= 7mm时,不同弧电流作用下(I=15,20,25A),等离子体弧摆动幅度的变化规律如图5所示.在相同励
图5　弧电流对摆动幅度的影响
F i g15　Effec t o f Io n o sc ill a ti ng am p litude
78　焊　接　学　报第31卷
磁强度位置处(B =15mT ),等离子体弧摆动幅度随
弧电流的增大而减小.这是因为:其它工艺参数不变时,一方面等离子弧电流的增加有使摆动幅度加大的趋势;另一方面,等离子弧电流的增加导致喷嘴出口处等离子体速度急剧升高,而速度剧增导致等离子体弧摆动幅度减小的趋势要强于工作电流增加所引起的摆动幅度增大的趋势,最终使得等离子体弧的摆幅随弧电流的增大而减小.3.1.3　喷嘴悬距对摆动幅度的影响当其它试验参数保持不变,即I =15A ,q =5L /m in,则不同喷嘴出口与工件间距离下(D =6,7,8mm ),等离子体弧摆动幅度的变化规律如图6所示.在相同励磁强度位置处(B =15mT ),等离子体弧摆动幅度随喷嘴出口到工件悬距的增加而增大.这是因为:喷嘴出口到工件间悬距的加大,意味着弧长的增加.一方面,弧长的增大对出口处的等离子体速度影响很小;另一方面,弧长的增大使得横向交变磁场作用下的等离子体从喷嘴运动到工件表面的时间增加,移动轨迹的长度变大,在工件表面上的投影变长,即摆动幅度随喷嘴出口到工件距离的加大而显著增加
.
图6　喷嘴悬距对摆动幅度的影响
F i g 16　Effe c t o f D o n o sc ill a ti ng am p litude
3.2　工艺参数对热流密度的影响3.2.1　气体流量对热流密度的影响
当其它试验参数不变,即I =15A,D =7mm ,B =15mT,R 0=2mm ,在不同氩气流量(q =4,5,6L /m in )下,横向交变磁场作用下等离子体弧在工件表面上的热流密度分布情况如图7所示:随气体流量的加大,等离子体弧在工件表面的热流密度分布半径减小,而弧柱中心的热流密度随之增大;并且弧中心附近区域的热流密度分布随气流量的增加而越来越集中.3.2.2　工作电流对热流密度的影响
当其它试验参数不变,即q =5L /m in,D =7mm
,
图7　气体流量对热流密度的影响
F i g 17　Effe c t o f q o n d is tri bu ti o n o f hea t fl ux de n s ity
B =15mT,R 0=2mm ,在不同弧电流(I =15,20,25
A )下,横向交变磁场作用下等离子体弧在工件表面
上的热流密度分布情况如图8所示:随弧电流的增
大,等离子体弧在工件表面的热流密度分布半径减小,在弧中心的热流密度随之增大;并且弧中心附近区域的热流密度分布随电流的增加而越来越集中
.
图8　弧电流对热流密度的影响
F i g 18　Effec t o f I o n d is tri bu ti o n o f he a t fl ux den sity
3.2.3　喷嘴悬距对热流密度的影响
当其它试验参数不变,即q =5L /m in,I =15A,B =15mT,R 0=2mm ,则不同悬距(D =6,7,8mm ),横向交变磁场作用下等离子体弧在工件表面上的热流密度分布情况如图9所示:
随喷嘴出口与工件间
图9　喷嘴悬距对热流密度的影响
F i g 19　Effec t o f D o n d istri bu ti o n o f he a t fl ux de n s ity
第1期孟建兵,等:横向交变磁场作用下的等离子体弧特性分析79
　距离的增大,等离子体弧在工件表面的热流密度分布半径增加,在弧中心处的热流密度随之减小;并且弧中心附近区域的热流密度随悬距的增大而越来越平坦化.4　试验验证
当I =15A,q =5L /m in,D =6mm 时,施加横向交变磁场作用前后的等离子体弧形态见图10.其中,B =15mT 时,等离子体弧摆动幅度的试验测量值为3.0mm ,与上述条件下的摆动幅度模型计算值2.8mm 相比,误差小于7%.上述试验条件下,施加横向交变磁场作用前后,等离子体弧在工件表面的热流密度分布见图11.其中,B =0时的热流密度模型计算峰值95.5W /mm 2
,与无励磁作用的热流密
度高斯分布[5]的理论峰值101.6W /mm 2
的误差小
于6%.而B =15mT 时的热流密度分布,与无励磁作用下的高斯分布值和模型计算值相比,其分布范围更广,内部热流梯度较小,即热流密度分布更加均匀.
5　结 论
(1)建立了等离子体弧摆动幅度和热流密度分
布模型,从而掌握了气体流量、弧电流等参数对横向交变磁场作用下等离子体弧特性的影响规律.
(2)随横向交变励磁强度的增大,等离子体弧的摆动幅度增加.当磁感应强度相同时,摆动幅度随弧电流和气体流量的增加而减小,随喷嘴悬距的增大而增大.
(3)弧电流和气流量越大,热流密度分布半径越小,而内部梯度和中心处的热流密度值增加;增大喷嘴出口到工件的距离,则工件表面上的热流密度分布半径随之加大,而中心处的热流密度值和内部梯度减小,即等离子体弧内的热流密度分布随悬距的增加而更加平坦化.参考文献:
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作者简介:孟建兵,男,1978年出生,博士研究生.主要研究方向
为大气常压等离子体弧特性及应用方面的研究.发表论文7篇.
Em a il :
jianbing meng@
ⅣMA I N T OP I CS,ABSTRACTS&KEY WORDS2010,Vol.31,No.1
Abstract:　Experi m ental study and ther mal elastic2p lastic finite ele ment method(FE M)of p late surfacing were carried out for304L stainless steel,and rati onality of assu med material p r operties under high te mperature in calculati on was verified by consistency of experi m ental results and nu merical si m ulati on re2 sults.On this basis,ther mal elastic2p lastic FE M was app lied t o welding of dome and cylinder shell of independent liquid tank of 304L stainless steel LNG carrier,and structural welding defor m2 ati on was p redicted successfully.
Key words:　304L stainless steel;material p r operties un2 der high te mperature;ther mal elastic2p lastic FE M;welding de2 for mati on;large comp licated structure
W eld i n g behav i or of two curren t pha se rel a ti on s for tw i n2 w i re pulsed M AG weld i n g W E N Yuan mei1,2,HUANG Sh2 isheng1,WU Kaiyuan1,LAO Zhengp ing1(1.School ofM echan2 ical Engineering,South China University of Technol ogy,Guang2 zhou510640,China;2.Faculty of I nf or mati on Engineering, Guangdong University of Technol ogy,Guangzhou510006,Chi2 na).p59-62,66
Abstract:　Based on the high2s peed video system with e2 lectrical signals analyzer in synchr onous,the electrical signals and the phot ographs of molten dr op let under certain welding pa2 rameters were collected,the electrical arc shape and dr op let transfer pattern of welding p r ocess in t w in2wire pulsed MAG welding were studied.It is observed that when the pulse current exerted on the fr ont wire and rear wire by turns,the shape of arcs p resents the cl ock cover f or m,and has no influence on each other.W hen the pulse current exerted on the fr ont wire and the rear wire in phase,the arcs attract each other and the arc is in2 cor porated as a peach.The weld appearance of the synchr onous pulse current is good and the concom itant is great noise and s mog.The weld appearance of the alternating pulse current is t olerable.
Key words:　pulsed MAG welding;t w in2wire;dr op let transfer;shape of arc
I n terpol a ti on a lgor ith m and si m ul a ti on of auto2weld i n g s ad2 dle2shaped nozzle of heavy pressure vessels DUAN Tiequn1,SH I Guangyuan1,Y U Dan2,Y ANG Kefei2(1.Harbin University of Science and Technol ogy,Harbin150080,China;
2.Harbin W elding I nstitute,Harbin150080,China).p63-66
Abstract:　According t o the welding p r ocesses of nozzle of heavy p ressure vessels,this paper intr oduced the structure and p rinci p le of the aut omatic welding machine,and als o p resenteed the math metical model and si m p lified inter polati on algorith m which used t w o collaborative axis t o f or m a s pace fitting saddle2 shaped welding bead.The si m ulati on results indicate that the t w o2axis inter polati on algorith m can meet the require ments of the aut omatic welding.
Key words:　heavy p ressure vessels;aut omatic welding machine;inter polati on algorith m;si m ulati on M i crostructure and m echan i ca l property of Ag2Cu2T i f illers added w ith rare earth l an thanu m Y ANG Changyong,XU J iuhua,D I N G W enfeng,F U Yucan,CHE N Zhenzhen(J iangsu Key Laborat ory of Precisi on and M icr o2manufacturing Technol o2 gy,Nanjing University of Aer onautics&A str onautics,Nanjing 210016,China).p67-70,74
Abstract:　The effect of lanthanu m(La)on the m icr o2 structure,m icr ohardness of Ag2Cu2Ti filler app lied in brazed CBN t ools and the shear strength of brazed j oint bet w een Ag2Cu2 Ti filler and0.45%C steel substrate were researched.The re2 sults indicated that the additi on of La could accelerate the all o2 ying of filler all oy,i m p r ove the m icr ohardness of Ag2Cu2Ti filler all oy and shear strength of brazed j oint bet w een Ag2Cu2Ti filler and0.45%C steel substrate.The content of La added in Ag2Cu2 Ti all oy filler should be less than0.5wt%.
Key words:　rare earth La;Ag2Cu2Ti filler;m icr ostruc2 ture;mechanical p r operty
Effects of appli ed long itud i n a l magneti c f i eld on pl a s ma arc hardfac i n g m i crostructure and property L I U Zhengjun, S ONG Xingkui,SHAO Da wei,ZHAO Q ian,ZHANG Shixin, CHE NGM inghua(Materials Science and Engineering Acade my, Shenyang University of Technol ogy,Shenyang110023,China). p71-74
Abstract:　T o contr ol the shape and distributi on of hard phase,l ongitudinal magnetic field was app lied during p las ma hardfacing of Fe5all oy.The hardness,wearing,m icr ostructure and X2ray diffracti on analysis of the hardfacing layer were tested as well as the structure and p r operty of the handfacing layer of the powder.The results showed that the layer had higher hard2 ness and better wearing with magnetic field than the layer for med without magnetic field.The p r operties of hardfacing layer were op ti m u m when the magnetic field current was3A and the m icr o2 structures of all oy hardfacing layer obtained ideal hard phase such as Cr7C3,Cr B ect and s olid s oluti onαandγwere refined sufficiently.
Key words:　p las ma arc surfacing welding;magnetic field;hard phase
Perfor mance of DC pl a s ma arc i n externa l tran sverse a lter2 na ti n g magneti c f i eld M E NG J ianbing,XU W enji,WANG Xuyue,S ONG W enqing(Key Laborat ory f or Precisi on and Non2 traditi onal Machining Technol ogy of M inistry of Educati on, Dalian University of Technol ogy,Dalian116024,L iaoning,Chi2 na).p75-79
Abstract:　T wo mathe matical models are devel oped t o de2 scribe the oscillating a mp litude of the p las ma arc al ong the metal surface and the heat fl ow density distributi on of p las ma arc on the metal surface res pectively.The behavi or of p las ma arc jet under an external transverse sinus oidal alternating magnetic field i m2 posed per pendicular t o the p las ma current is analyzed theoretical2 ly,and the effect of p r ocess para meters such as gas fl ow rate, arc current,magnetic fl ow density and the distance fr om the noz2 zle outlet t o the anode workp iece on the f or m and distributi on of
2010,Vol.31,No.1T RANS ACTI O NS OF T HE CH I N A W ELD I N G I N STI T UTI O NⅤ
p las ma arc are als o in vestigated.The results show that it is fea2 sible t o contr ol the shape and heat fl ow density of the p las ma arc for the transverse alternating magnetic field,which can expand the area of p las ma arc ther mal treat m ent and flat the heat fl ow density upon the workp iece.Further more,the oscillating amp li2 tude of p las ma arc increases and the heat fl ow density gradient upon the workp iece decreases with the magnetic fl ow density en2 hancing.However,an overly str ong magnetic field coil results in the p las ma arc unstable.Under the same magnetic fl ow density, less gas fl ow rate and arc current,l onger distance fr om the nozzle outlet t o the anode causes the oscillating a mp litude t o increase. Contrarily,the more gas fl ow rate and arc current,the more heat fl ow density peak increases.Moreover,l onger distance fr om noz2 zle outlet t o workp iece descends the heat fl ow density peak.
Key words:　transverse alternating magnetic field(T A MF); p las ma arc;oscillating a mplitude;heat fl o w density distributi on
Exper i m en t a l i n vesti ga ti on on i m pact toughness i n h i gh2te m2 pera ture of BH W35steel welded jo i n t WANG Xian2 gyun1,2,WANG W enxian1,L I J ie mu2,WANG Baodong3(1. College ofM aterials Science and Engineering,Taiyuan University of Technol ogy,Taiyuan030024,China;2.Taiyuan Boiler Gr oup Co.L td.,Taiyuan030021,China;3.Shanxi Zhongt ong High2 Technol ogy Co.,Taigu030008,Shanxi,China).p80-84 Abstract:　Aut omatic submerged2arc welding and shielded metal arc welding were e mp l oyed by H10M n2N i M oA welding wires,E70152D2electr ode foll owed by the post w eld heat2treat2 ment syste m s of nor malizing,dra wing te mper and stress relief an2 nealing.I m pact tests on welded j oint and base metal at20℃、100℃、200℃and350℃were carried out.Further more,SE M fract ograph,metall ograph and che m ical compositi ons of welding sea m were analyzed.The results indicate that the highest hard2 ness of HAZ was:270.5HV in S AW;235.2HV in S MAW,the t oughness increases greatly compared with conditi ons at r oom te mperature.Peak value of i m pact t oughness of S AW is at100℃,S MAW is at200℃,which is cl ose t o that of base metal. The i m pact t oughness in HAZ is better than that in welding sea m,and it is better in S MAW than that in S AW.The i m pact t oughness of welded j oint is upward96.33J at r oom te mperature, it is upward120J in welded j oint at350℃,and186J in base metal,which indicate that the t oughness of welded j oint and base metal ars in their best at r oom and high2te mperature.SE M frac2 t ograph indicates that all i m pact fractures exhibit ductile di m p le, the better t oughness,the more obvi ous tearing feature of ductile di m p le.The larger the ductile di m p le is,the more obvi ous non2 unif or m distributi on is.
Key words:　BH W35steel;welded j oint;metall ograph and hardness;i m pact t oughness;fract ograph
Fuzzy P I speed con trol for weld i n g w i re feed syste m ba sed on st a te observer and feedforward DU Hong wang1,3,L I U Zheng2,ZHAO Yanan1,XU J ian wei1,L I U Gang1(1.College of Mechanical and Electrical Engineerin,Harbin Engineering Uni2 versity,Harbin150001,China;2.College of Computer Science and Technol ogy,Harbin Engineering University,Harbin 150001,China;3.College of Aut omati on,Harbin Engineering University,Harbin150001,China).p85-88
Abstract:　W elding wire feeding device is an i m portant component of welding r obot,stabilizati on and reliability of weld2 ing wire feed is the essential for welding quality.The resistance was highly nonlinear and both wire feed rate and welding quality are severely affected by the resistance.A state observer was a2 dop ted t o evaluate the resistance,and then the observed resist2 ance was for ward fed in order t o increase s peed res ponse and e2 li m inate the i m pact of resistance on the welding wire feed sys2 te m.Because of DC mot or da mp ing,the steady2state characteris2 tics can be i m p r oved and the steady2state err or can be inhibited when conventi onal P I contr ol is adop ted.The fuzzy contr ol and P I contr ol arc organically intr oduced by means of dyna m ic re2 s ponse of fuzzy contr ol and steady2state perfor mance of P I con2 tr ol,it is reliable t o achieve stable weld wire feeding.The si m u2 lati ons indicate that there are fast s peed res ponse,s mall over2 shoot and str ong r obustness with state observer and f or ward feed, the dyna m ic and static characteristics of fuzzy P I contr ol are bet2 ter than P I contr ol.
Key words:　wire feed device;sub merged2arc welding; state observer;feedfor ward;fuzzy P I contr ol
Effect of hybr i d2pulse square2wave curren t frequency on m i2 crostructure and m echan i ca l properti es of5A06a lu m i n u m a lloy welds CONG Baoqiang,Q I Bojin,ZHOU Xingguo, LUO Jun(School of Mechanical Engineering and Aut omati on, Beihang University,Beijing100191,China).p89-92 Abstract:　A novel ultrafast2convert hybrid2pulse square2 wave variable polarity arc welding technol ogy f or alu m inu m all oy is devel oped.Based on the hybrid2pulse variable polarity TI G welding technique,the effect of hybrid2pulse square2wave current frequency on the m icr ostructure and mechanical p r operties of 5A06welds is researched.The experi m ental results show that, compared with no hybrid2pulse current,the weld mechanical p r operties are decreased when the pulse current frequency is less than20kHz.Under the conditi on of pulse current frequency up t o40kHz,the size of crystal grains and degree of welds s often2 ing are decreased,tensile strength of weld j oints is i m p r oved ob2 vi ously.The rates of weld tensile strength and percentage el onga2 ti on t o base metal are95.8%and84.8%,res pectively.
Key words:　ultrafast convert;hybrid high2frequency pulse;pulse frequency;variable polarity;alu m inu m all oy
W avelet detecti on a lgor ith m of short2c i rcu it si gna l i n CO2 arc weld i n g ba sed on D SP TI A N Songya,G U Haitao,F U W eiliang,SH I Rusen,XU Huizhe(College ofM echanical&E2 lectrical Engineering,Hohai University,Changzhou213022, J iangsu,China).p93-96
Abstract:　According t o algorith m a’tr ous and analysis of CO2arc voltage characteristic byW avelet Toolbox in M atlab,the wavelet algorith m which is suitable for detecti on of short2circuit signal in p ractical CO2welding p r ocess is derived.D ifferent。