关于焊接残余应力消除原理的探讨_王者昌
关于焊接残余应力消除原理的探讨
王者昌
(中国科学院金属研究所,沈阳 110015)
摘 要: 介绍了机械拉伸法、温差拉伸法、滚压法和低应力无变形焊接技术消除应力原理的传统观点,认为焊接时焊缝产生压缩塑性变形,消除应力的原理在于用拉伸塑性变形抵消、补偿压缩塑性变形。本文提出新的应力应变发展过程,指出焊缝不存在压缩塑性变形,一直受拉伸,熔合线附近处于脆性温度时承受较大的纵向拉伸应变,随着远离熔合线,应变值陡降。焊缝消除应力的原理在于用塑性应变减少甚至抵消弹性应变,在一般情况下是用拉伸塑性应变减少甚至抵消拉伸弹性应变。本文还阐述了各种消除应力工艺的原理并很好地解释了横向液化裂纹分布在熔合线附近和裂纹很短的现象。关键词: 焊接残余应力;应力消除;塑性应变;弹性应变;液化裂纹
中图分类号: TG404 文献标识码: A 文章编号: 0253-360X(2000)02-55-
04王者昌
0 序 言
焊接应力和变形一直是焊接界关注的重要问题之一。尼古拉也夫ГА院士、关桥院士、田锡唐教授等在此领域作了卓有成效的工作。机械拉伸法、温差拉伸法和焊缝滚压法等也是消除焊接残余应力和变形的有效方法。上述方法消除应力的原理虽有报道,但有互相矛盾之处,载入《机械工程手册》、《焊接手册》中的一些权威性提法尚有商榷之处。因此搞清楚焊接残余应力消除原理是必要的。
1 问题的提出
1.1 机械拉伸法消除应力
文献[1,2]指出:“对焊接结构进行加载,使焊接压缩塑性变形区得到拉伸,可减少由焊接引起的局部压缩塑性变形量,使内应力降低。”文献[3]指出:“通过一次加载拉伸,拉应力区在外载的作用下产生了拉伸塑性变形,它的方向与焊接时产生的压缩塑性变形相反。因为焊接残余应力正是由于局部压缩塑性变形引起的,加载应力越高,压缩塑性变形就抵消的越多,内应力也就消除的越彻底。”
1.2 温差拉伸法消除应力
文献[1,2]指出:“两侧的金属受热膨胀对温度较低的焊缝区进行拉伸,使之产生的拉伸塑性变形以抵消原来的压缩塑性变形,从而消除内应力。”
1.3 滚压法消除应力和变形
文献[4]指出:用适当的压力滚压焊缝或近缝
收稿日期:1999-01-12区,“造成与焊接压缩塑性变形完全相等而方向相反的延伸塑性变形(见图1),这样在薄板构件上就可以达到既消除应力又消除变形的目的。”文献[5]指出:“在窄轮压力的作用下,焊缝区产生相应延伸塑性变形,用以补偿焊后残余的压缩塑性变形(即不协调应变量)。
”
图1 滚压法消除应力原理示意图
Fig.1 Schematic diagram of principle of relieving
residual stress by rolling metho d
1.4 低应力无变形焊接技术
关于动态低应力无变形焊接法消除应力的原理,文献[6]指出:“刚凝固的焊缝区中,已受到压缩但仍处于高温的金属,由于强迫冷却射流热沉作用,在温度低谷中受到极大的温差拉伸的作用,随即得到拉伸塑性变形的补偿。”文献[7]指出:“焊缝受冷急剧收缩,产生很强的拉伸作用,使仍处于高温状态焊缝区的压缩塑性变形量得到补偿。”
第21卷 第2期2000年6月
焊接学报
TR ANSACTIONS OF THE CHINA WELDING INSTITUTION
Vol.21 No.2
June2000
上述文献都认为焊接时焊缝产生压缩塑性变
形,消除应力的原理在于设法使焊缝产生拉伸塑性变形以抵消、补偿已产生的压缩塑性变形。焊缝是否存在压缩塑性变形?文献[3]提出另一种观点,认为“对于焊缝金属来说,并不存在加热阶段。在冷却过程中除相变外,都受到拉伸。”也就是说不存在压缩,更不会出现压缩塑性变形。看来,焊接时焊缝是否存在压缩塑性变形以及随之而来的消除应力原理问题尚待研究。
2 焊接应力应变发展过程
尼古拉也夫ГА院士分析了焊接应力应变发展过程,原理图见图2[8]。在600℃最宽截面即I -I 截面,钢板中心区为压应力和压应变区,而板的两侧
为拉应力和拉应变区。在大约200℃以上的区域产生压缩塑性变形,在600℃以上的区域,压缩塑性变形为常量,其值为α·600℃,式中α为线膨胀系数。尼古拉也夫ГΑ在文献[9]中将α·600℃改为α·T ,式中T 为温度,应力应变图则改为图3。文献[2]引用了后一观点
。
图2 低碳钢板焊接纵向应力应变分布Fig .2 Longitudinal stress and strain distributio n
patterns in mild steel welded joint
在图2和图3中,作者忽略了一个最基本的事实,即板中心区(焊缝及近缝区)处于冷却过程,而不是加热过程,在这两个过程中,应力应变发展过程是不同的。
下面分析一下薄板焊接应力应变发展过程。温度场分布如图4a 所示。虚线将焊接板材分为升温
区和降温区两部分,以焊接方向为准,虚线前为升温
图3 低碳钢板焊接纵向应力应变分布
Fig .3 Lo nitudinal stress and strain distribution patterns
in the mild steel welded joint
图4 低碳钢板中心堆焊纵缝时横截面应力应变的变化Fig .4 C hange of stress and strain distribution pattern of cross section of surfacing on center of mild steel sheet
区,虚线后为降温区,可以看出,焊缝处在降温区。现取三个典型截面,分析应力应变发展过程。截面I 取自熔池前沿。此截面全部在升温区,中心区升温很高,两边升温很低,中心区膨胀受阻产生压缩塑性应变,应力应变分布见图4b ,这与图3类似。截面II 取自熔池最宽处。截面III 取自熔池尾部后不远处,其最高温度约为1450℃,在图4c 中同时画出
截面II 和III 的温度分布。焊缝降温将产生收缩,两侧的金属阻碍其收缩,结果将产生拉伸应变,温度高于力学熔点处,不会有应力存在,因此没有弹性应
变,全部拉伸应变为塑性应变,其大小相应于图4c 斜阴影高度,在熔合线处拉伸塑性应变出现最大值。离焊缝稍远处将引起升温,它的膨胀受阻,将产生压应变和压应力,板边则出现与压应力平衡的拉应力,应力应变分布如图4c 所示。在随后的降温过程中,焊缝一直承受拉伸应变,在温度降到力学熔点以前,这种应变一直是拉伸塑性应变。当温度降到力学熔
56 焊 接 学 报
第21卷
点以后,焊缝开始出现弹性拉伸应变和拉应力。可以看出,焊缝从凝固温度降到室温的全过程中不存
在压应力和压应变,更不存在压缩塑性变形。至于熔池前沿升温膨胀产生的压缩塑性应变和变形,因为焊缝尚未形成,故不能算作焊缝的压缩塑性变形。
3 讨 论
3.1 应力应变分布
从尼古拉也夫ГΑ院士给出的图2、3所示的应力应变分布可知,焊缝存在压缩塑性变形,这种传统的观点一直被焊接界接受,从而也形成了消除应力的原理在于设法使焊缝产生拉伸塑性变形以抵消、补偿已产生的压缩塑性变形的传统观点。图2、3的根本错误在于没有分清加热过程还是冷却过程,若是加热过程,图2、3显然是正确的。但是对焊缝而言,只有冷却过程。在冷却过程中,焊缝收缩受阻将产生拉应力和拉伸变形,不存在压缩塑性变形,因此前述文献[3]的观点是正确的。焊接应力应变分布是消除残余应力原理的基础,基础变了,消除应力的原理需要重新论述了。3.2 应变曲线出现拐点的原因
图4c 中应变曲线在熔合线处出现拐点,这是由于局部熔化所致。熔化时温度分布出现拐点,这引起应变分布出现拐点。如果加热温度未达熔化温度,金属未熔化,则温度分布和应变分布都不会出现拐点,也不会出现图4c 所示的应变分布。此时的应变分布应该是如图3所示。看来图3与图4c 中相反符号的塑性应变的出现是由于是否考虑金属熔化现象造成的。
3.3 焊件纵向变短的原因
焊件沿焊接方向缩短是持有焊缝受压缩观点的一个理由,即焊缝受压缩,产生压缩塑性变形,因此变短了。从上述分析可知,焊缝沿纵向不存在压缩塑性变形,并且一直受拉伸,并产生明显的拉伸塑性变形。那么焊件沿焊缝方向为什么会变短呢?焊缝受拉伸,不等于此处的金属一直受拉伸,在熔池前沿的金属受热产生明显的压缩塑性变形,见图4b 。这种压缩塑性变形量与焊缝冷却拉伸变形量相当。此外,熔池凝固还会产生大约3%收缩。三项合在一起,总的结果是产生了收缩变形,焊件变短了。可以说焊件变短主要是由于金属局部熔化随后凝固收缩造成的。3.4 液化裂纹形成机制
某些高强钢焊接时,在熔合线两侧容易产生横
向微裂纹,长度一般不足0.5mm ,具有晶间特征,示
意图见图5[10],属于液化裂纹,是热裂纹的一种。拉应力和拉应变是产生热裂纹的必要条件。从图2和图3给出的应变分布可知,在高温阶段,焊缝及近缝区存在压缩塑性变形。如果放弃力学熔点的假设,还会存在少量的压应力。这样,图5所示的液化裂纹就失去了产生的条件。
图5 液化裂纹示意图
Fig .5 Schematic illustration of liquation cracks
按照作者给出的应力应变分布(图4c ),能够很好地解释图5所示的液化裂纹形成机制。当熔合线附近处于脆性温度时,存在拉应力和拉应变,并且熔
合线处应变值最大,产生微裂纹。随着远离熔合线,不管是焊缝一侧还是热影响区一侧,应变值陡降,裂纹难以扩展。这就容易解释液化裂纹分布在熔合线附近和裂纹很短的现象。
4 焊接残余应力消除原理
4.1 机械拉伸法
焊缝及近缝区纵向残余拉应力一般为屈服应力σs ,相应的弹性应变为εs ,加上拉伸载荷将产生工作应力σp 和应变εp 。因为原来的残余应力已达屈服点,故εp 全部为拉伸塑性应变,卸载后焊缝和近缝区的弹性应变为εs -εp ,最终的残余应力为E (εs -εp )。显然E (εs -εp ) 4.2 温差拉伸法和低应力无变形焊接法 低应力无变形焊接法,不管是“静态”还是“动态”的,都是在焊接过程中建立一种焊缝温度低于两侧的温度场,与焊后进行的温差拉伸效果是一样的,其原理在此一并叙述。 在建立两侧的温度高于焊缝及近缝区的温度场时,两侧高温区的金属膨胀引起焊缝及近缝区拉伸应力σT 和拉伸应变εT ,σT 与原来的残余应力叠加,引起材料屈服,若原来的残余应力达到屈服应力 第2期王者昌:关于焊接残余应力消除原理的探讨57 σs,则产生的应变εT全部为拉伸塑性应变。最终残余应力为σs-σT,残余应力减少了。若σT=σS,则残余应力全部消除,若σ T>σS,则焊缝出现压应力。也就是说,此法不仅可消除残余拉应力,还可产生残余压应力。 温差拉伸法和低应力无变形焊接法消除应力的原理可以这样描述:在建立两侧温度高于焊缝的温度场时,焊缝产生拉伸塑性应变,这与机械拉伸起到类似作用,使应力降低。其原理也可这样描述:在建立两侧温度高于焊缝的温度场后,在随后的均温过程中,两侧高温区的降温收缩将对焊缝及近缝区沿纵向进行压缩,抵消原来的拉应力,使残余应力降低。 4.3 滚压法 滚压前焊缝的残余拉伸应力为σ S,弹性应变为εs,焊缝滚压时产生拉伸塑性变形和拉伸塑性应变εp,滚压后剩余的弹性应变为εs-εp,相应的残余应力为E(εs-εp),显然E(εs-εp) 可以看出,上述消除残余应力原理中,有一个共同点,即产生拉伸塑性应变,消除应力的过程实质就是将拉伸弹性应变转变为拉伸塑性应变的过程。 推而广之,所有消除残余应力的过程都是将弹性应变转变为塑性应变的过程。例如,整体和局部高温消除应力处理是利用金属屈服点的降低和保温过程中应力松驰,使弹性应变转变为塑性应变的。锤击和爆炸消除应力分别是用锤击和爆炸的冲击力使残余拉应力区产生拉伸塑性应变,若这一应变小于εs,则应力降低,若等于εs,则应力全部消除,若大于εs,则产生压应力。振动消除应力时,振动产生的交变载荷与残余应力叠加,交变载荷中的拉伸载荷与机械拉伸起到类似的作用,引起构件相应部位拉伸塑性应变,残余应力降低。 5 结 论 (1)根据作者提出的应力应变分布(图4c)可知,焊缝不存在压缩和压缩塑性变形,而是受到拉伸和产生拉伸塑性变形。在接近熔点温度,熔合线处拉应变出现最大值,在熔合线两侧,随着到熔合线距离的增加,拉应变激剧减少。 (2)焊接时焊缝不存在压缩塑性变形,消除焊接残余拉应力的原理不是设法产生拉伸塑性变形来抵消、补偿焊缝产生的压缩塑性变形,而是产生塑性应变抵消弹性应变。在一般情况下,焊缝和近缝区产生拉伸塑性应变,抵消此处的拉伸弹性应变,从而减少焊缝及近缝区残余拉应力。 (3)用传统的焊缝和近缝区存在压应变的观点无法解释横向液化裂纹形成机制,用作者提出的图4c中应变分布则能很好的解释,并且由于高应变区很窄,所以液化裂纹很短。 参考文献: [1] 机械工程手册编辑委员会.机械工程手册(第二版)[M].北京: 机械工业出版社,1996,6～20. [2] 中国机械工程学会焊接学会.焊接手册(第三卷)[M].北京:机 械工业出版社,1992. [3] 田锡唐.焊接结构[M].北京:机械工业出版社,1997. [4] 关桥.推广应用焊接滚压工艺的几个问题[J].航空工艺技术, 1980,(2);21～26. [5] 关桥.飞行器薄壳结构变形控制与焊接力学的发展[C].第八 次全国焊接会议论文(第一册)北京:机械工业出版社,1997,51 ～57. [6] 关桥,等.动态控制的低应力无变形焊接新技术[J].焊接学报, 1994,15(1):8～14. [7] 关桥,等.航宇薄壳结构的低应力无变形焊接新技术[J].航空 工艺技术.1996,4;4～7. [8] НиколаевГА,расчетсварныхсоединенииипрочностьсварных Консирукции[M].ИЗДАТЕЛЬСТВО,1965,155～158. [9] НиколаевГА,др,Сварныеконструкции[M].МОСКВА,1982, 194～195. [10] Savage W F.A mechanism for crack formation in Hy-80s teel weld- ments[J].Welding J ournal,1967,46(2):94s～96s. 作者简介: 王者昌,男,1938年出生,研究员。兼任中国焊接学会IXb专业委员会、中国宇航学会材料工艺专业委员会和中国空间科学学会机械专业委员会委员,中国水机磨蚀中心理事。主要从事钛合金焊接、焊接气孔、焊接热裂纹、堆焊材料和水轮机抗磨蚀用钢的研究。研究成果曾获全国科学大会奖和国家特等奖各1项、科学院二等奖2项、航天部二等奖1项、水利部一等奖1项。申请五项国家发明专利。参与《机械工程手册》、《焊接手册》和《材料大词典》的编审,发表论文80余篇。 58 焊 接 学 报第21卷 crack of stainless steels,namely the,stress-s train field in the trail of molten-weld pool.Firs tl y,the effect of the deformation in the mol ten-weld pool was eli minated after the element rebirth met hod was adopted.Secondl y,the influ-ence of solidification s hrinkage was considered by increasing thermal expan-sion coefficients of the steels at elevated temperature.Finally,the stres s-strain distributions of different conditions have been got and anal yz ed.Fur-thermore,the driving force curves of the s olidification crack of the steels have been obtained by converting strain-pos ition curves into s train-temperature ones which found a bas is for predicting welding solidification crack. K ey words:welding s olidification crack;wel ding s ol idificati on crack driving force;s tress-strain field;numerical simulation A Direct Ass essing Method of Heated Widths During Local PWH T WA NG J ian-hua(Shanghai Jiao tong University,Shanghai,China),LU Hao, Hidekazu Muraka wa.p39～42 Abs tract:Local postweld heat treatment(l ocal PWHT)is usually per-formed for tempering and relaxation of res idual stress es.Many factors have an influence on PWHT procedures and the heated widt h is the most important pa-ra meter controlling the effectiveness of local PWHT.However,the determina-tion rules of this para meter are very different in the different codes.In this study,a direct method to assess the effectiveness of l ocal PWHT was used based on the thermal-visco-elas tic-plastic FEM wit h t he consideration of creep phenomena.This method clearly s hows the whole history of s tress relief during PWHT and a critical heated width can be obtained.The pipe with original welding residual stresses is anal yzed under different conditions of PWHT.In-ves tigations s how that the maxi mum res idual stress after PWHT decreases when the heated width increases.When the heated width becomes large e-nough,the res idual s tress after PWHT changes very slo w l y and a critical heat-ed width can be found which gives a residual s tress close t o the value obtained from th uniform PWHT.A series of different PWHT conditions are studied to find the critical heated width by us ing this method.It is found that a heated area of5rq centered on weld s ee ms res onable from the vie w of stress re-lief. K ey words:post weld heat treat ment;res idual s tress;heated width;finite ele ment method Influence of Proces sing Parameters on G eometrical Featu res of Powder Feedi ng Laser Cladding ZHANG Qing-mao(The Quartermaster Univer-sity of PLA,Changchun,China),LIU Xi-ming,WANG Zhong-dong,GUA N Zhen-z hong.p43～46 Abs tract:The influences of las er proces sing parameters with auto-feed-ing on the geometrical features of cladded coating by cladding Ni60A powders on steel Q235plate have been investi gated.The rul es of the combined param-eters(s uch as laser energy dens ity P w,interaction time T,powder feeding rate and scanning speed V s)on the s izes of the coatings have been amphati-call y discuss ed.In order to express the rel ations hip bet ween the processing pa-ra meters and the macroqualit y of cladded coating,the equation express ing the relationship bet ween the covering rate and the process ing parameters was de-ri ved.By varying the powder feeding rate and scanning s peed under definite laser po wer and beam s pot di mens ions,coatings with different thicknes s were obtained.The covering rate was calculated approximatel y based on metallo-graphical measurement.The results s how that the cross-secti on S,width vari-able and contact angle are mainly c ontrolled by the laser energy density and interaction ti me,they all become larger with the increase of laser energy den-s ity and interaction time. K ey words:metallographical measurement;las er energy density;cover-ing rate J-integral of Surface Crack in Overmatched Joint LI J i-hong(The Ins tit ute of Welding,Xi'an Jiaotong University,Xi'an,China),ZHANG J ian-xun,PEI Yi.p47～50 Abstract:The part-through surface cracks exist widel y in practical weld-ed structure,and the inves tigation of the el as tic-plastic fracture mec hanics parameters(eg.J-integral)of this three-di mens ional mechanical heterogene-ity is not enough.In this paper,the J-integral of s urface crac ks in over-matched weldment with different matching ratios has been investigated by us-ing direct evaluation method.The influences of matching ratio of joints on the crack driving force(J-integral,crack mouth opening dis placement CMOD) and strain distributions along the contour have been dis cuss ed in detail.The results indicate that the comprehens ive effect of crack position and the match-ing ratio of welded j oint dominate t he dis tribution of strain.With the increas-ing of load,the obvious strain c oncentration may be produced in the parent metal zone close to weld.Moreover,with the decreas ing of the matching ra-tio,the degree of the s train concentration grows,the deformation of weld met-al decreases to a certain extent,and the crack driving force increases. K ey words:wel ded joint;s urface crack;J-integral Analysis of Metal Transfer and Usability of H igh Cellu lose Electrode LIU Hai-yun(Taiyuan Univers ity of Technology,Taiyuan,China),WANG yong,WANG Bao.p51～54 Abstract:By us ing high-speed photographic method and usabil ity exper-iments,the metal transfer form and usabil ity of hi gh cellul os e electrode have been analyzed.The res ults s how that the metal trans fer forms of high cellulose electrode contain spray trans fer,explosive trans fer and short circuiting trans-fer.The spatter forms include big and s mall droplet spatters.The transfer and s patter of bi g droplets s ho w obviousl y periodic characteristic,and the s mall droplet s pray trans fer and s patter exist through whole welding.Strong and reg-ular s pray trans fer form is advantageous to the us ability.The bi g dropl et spat-ter is the main reason for bad usabil ity,e.g.low depos ition efficiency,unsta-ble arc etc,.and it should be anal yz ed and prevented further. K ey words:high cell ulose electrode;metal transfer;usabilit y Discuss on Princip le of Relieving Welding Residual Stress WANG Zhe-chang(Institute of M etal Research,Chines e Academy of Sciences, Shenyang,China).p55～58 Abstract:According to traditional viewpoint,for the mechanical stres s rel ieving method,the low temperature stress rel ieving method,the rolling s tress relieving method and Low-Stres s Non-Distortion Wel ding Technology, 2000,Vol.21,No.2 TR ANSAC TIONS OF THE CHINA WELDI NG I NSTI TUTI ON Ⅴ the res idual s tress relieving principle is to c ompensate the co mpressive pl as tic strain in the weld with tensile plastic s train which is produced in the welding process.In this paper,a new s tress and strain devel oping process is gi ven. The weld metal al ways bears tens il e stres s and there is no co mpressive pl as tic strain being produced in the welding process.In the brittle temperature z one, the maxi mum tensile stres s appears in the fusing line and it decreas es s harpl y far from t he fusing line.The s tress-relief principle is to reduce or eli minate e-lastic strain with plas tic s train.In general case,the principle is to reduce or eli minate t he original tens ile elastic strain with tens ile pl as tic s train.In this paper,the principle of all kinds of residual stress relieving methods is als o discus sed.It also is satisfact orily interpreted why the trans verse liquation crack appears in the adjacency to fusing line and it is very s hort. K ey words:welding residual s tress;s tress rel ieving;pl as tic strain;el as tic strain;liquation crack Investigation of an Engineering Simplification Approach for LOP's J-integral Calculation MENG Xiang-feng(Ocean Universit y of Qingdao, Qingdao,China),WANG Wei-qiang,ZHAN G Xua-li,GU O Jian-zhang.p59～62 Abs tract:The lack of penetration(L OP)is a very c ommon t ype of dis-continuities in welds,s o that how to simplify it more scientificall y and reason-able and therefore to conduct its fracture anal ys is are a problem continuousl y interested to engineering and academic circles.In this paper,several common root shapes were chos en among the photos of LOP's root profiles and five t yp-ical sorts of notches with regular root s hapes were obtained after so me extent simplification to the LOP's root s hapes.Bas ed on t his,the el as tic-plastic finite ele ment method was adopted in the paper.The finite el ement calc ulations were conducted by taking the geometrical shapes and sizes of not hch root as param-eters and a s eries of J-L r c urves were gotten.Through analyzing the curves,the main factors influencing the value of J-integral can be found,they were the notch wedth or the notch root curvature and the s hapes of notch,and finall y the root s hape with the maximum J-integral value was deri ved to be the flat end s hape.Therefor,the values of L OP's J-integral can be calculated si mpl y and cons ervativel y by adopting the notch with a flat end proposed in this pa-per,and furthermore the engineering calculati ons of L OP's J-integral values can be realiz ed. K ey words:l ack of penetration;J-integral;finite element anal ysis;engi-neering simplification method New Model Cu-Ni Alloy PTA Surfacing Material and I ts Corrosion Re-sistance J I Jie(Tianjin Univers ity,Tianj in,China),ZHANG Wen-yue, ZHANG Shu-s heng,LIU Li.p63～66 Abs tract:By putting some alloy elements into white copper B30,through weldabilit y examination,static corros ion trial and polarized curve test,a kind of c orrosi on resis tance alloy powder to be used for plasma s urfacing has been studied and prepared.The reason of reducing the corros ion-res isting property of the white copper alloy B30after adding all oy ele ments has been al so inves-tigated by means of SEM,AES,XPS. K ey words:Cu-Ni alloy;powder plas ma arc s urfacing;corrosion Infrared Telecontrol of IG BT Arc Welding Inverter PI You-guo(The Automation Engineering E/R Center of Guangdong Academy,Guangz hou, China),HU Dao-ming,HU ANG Shi-sheng.p67～69 Abstract:The design of infrared telecontrol IGBT converting wel der is presented in t his paper and the des igns of the s ys tem,power circuit,infrared s ys tem hardware and s oftware are presented in detail als o.The controlled dis-tance is as far as10meters and the control scope is as wide as±45°.The wel der has its output current250A,both good static and dynamic characteris-tics and can stably work in wel ding workshop K ey words:infrared telecontrol;c onverting welder;IGBT Switching Welding Power Source Controlled by Microcomputer WU Wan-hua(Shanghai Jiaotong U niversit y,Shanghai,China),Y AO Shun,YU Hai-liong.p70～73 Abstract:The paper introduces the real value of t he s witching power s ource designed by authors and the systemic analysis of the principl e and con-s titution of the po wer s upply including the microcomputer controlling s ys tem. The authors put forward some viewpoints about the ne w welding po wer s ource .The power s ource which is controlled by the microcomputer s ystem in t his paper adopts the giant trans is tor(GTR),and have it work in bot h the condi-tion of“on”and“off”.Therefore,it overwhel ms l ower efficienc y of analogue transis tor power s ource,and keeps a s table operation state.In the meanti me, the power source makes use of single chip microcomputer controlling technolo-gy and realiz es the function of previous setting up the welding parameters. This power can als o modify the welding voltage U f through feedback control-l ing so that gets cons tant voltage characteristic. K ey words:microcomputer control;s witching t ype;pulse width modula-tion Meas uring Normal Deformation Produced by Res idual-s tress i n Friction Weldi ng Joint Usi ng Double-expos ure Holography LIU Xiao-wen (Northwes tern Polytec hnical Univers ity,Xi'an,China),DU Sui-geng,LIU Xiao-z hong,WANG Guo-z hi.p74～76 Abstract:The principle of meas uring normal deformation of the s urface of friction welding j oint is anal yzed.When the experimental s ys tem meets s ome conditions,the interfero metric fringe obtained from double-exposure hol ogram reflects the amplitude of normal deformation.In experi ment,a Q-s witched ruby laser is us ed as light source,and a double-exposure hologram of friction welding j oint is obtained.In this paper,the hol ographic interferomet-ric fringe is collected through a CCD image process s yste m and stored into computer.After using computer to process these data,the amplitude of nor-mal deformation of the s urface of friction welding j oint is obtained. K ey words:double-exposure hol ography;friction welding joint;normal deformation Rotational Regres sion Experimental Study on H igh Velocity Arc Sprayed Stainless S teel Coatings TIAN Bao-hong(Surface Engineering R es earch Ins tit ute,CMES,Beij ing,China),XU Bin-shi,MA Shi-ning,LIA NG Xiu- Ⅵ MAI N TOPI CS,AB STRACTS&KEY WORDS 2000,Vol.21,No.2