GH3039真空扩散焊接工艺研究

对GH3039合金进行了真空扩散焊接试验,分析了焊接工艺参数对焊接接头拉伸强度的影响。结果表明:接头拉伸强度随着焊接温度的升高和保温时间的增长先升高而后降低;接头拉伸强度随着焊接压力的提高而升高。在本次试验中,最佳焊接工艺条件为:焊接温度,1100℃;保温时间,45Min;焊接压力,20MPa。     

低强匹配焊接接头匹配特性研究

焊接接头的屈服强度匹配方式对接头的设计、制造工艺、裂纹敏感性以及破坏行为有重要影响,焊缝金属、母材、焊接接头强度以及焊接接头强度匹配系数的分布是焊接结构强度、寿命和可靠性计算的基础.文章介绍了对12Ni3CrMoV钢焊接接头屈服强度匹配系数的分布进行的研究,并给出了分析结果.作者认为控制母材和焊缝金属的屈服强度分布的标准差,是降低失配概率的主要途径.     

00Cr21Ni14Mo2Mn5N钢焊接接头晶间腐蚀性能研究

通过对00Cr21Nil4Mo2Mn5N不锈钢焊接接头晶间腐蚀性能试验研究,利用低倍检测、扫描电镜能谱分析和金相显微镜对晶间腐蚀斯口进行观察、检测和分析,确定晶间腐蚀试验发生断裂并不是由晶间腐蚀引起．而是母材与焊接材料的强度差距太大所致。研究为焊接接头晶问腐蚀试验的检验及判定提供了理论依据,从多个方面分析了影响焊接接头晶间腐蚀性能的原因,并就提高不锈钢焊接接头抗晶间腐蚀的能力进行探讨。     

基于压条拘束的薄板接头焊接失稳控制

将焊接试验与数值模拟相结合，对采用压条拘束控制的2种典型焊接接头失稳变形机理进行了研究。基于热-弹-塑性有限元方法，分别再现5mm厚对接接头和T型接头在常规自由态和压条拘束下的焊接过程，将2种接头计算得到的面外变形与焊接试验后测量的面外变形进行对比，从而验证所采用的有限元计算方法的准确性。分别计算对接接头与T型接头在不同压条拘束距离下的面外变形，并分析拘束距离对2种接头焊接失稳变形的控制效果；比较不同拘束距离下接头的焊接温度场及固有变形，阐明压条拘束控制2种焊接接头失稳变形的机理。结果表明：施加压条拘束使对接接头的纵向固有收缩和横向固有弯曲均减小，从而控制其焊接失稳变形；T型接头施加压条拘束后，几乎不影响纵向固有收缩，但使得横向固有弯曲显著减小，从而达到控制焊接失稳变形的效果。     

钢铝过渡接头的应用研究

为降低船舶的质量重心、提高航速,某型船上层建筑首次采用铝合金材料。以往铝合金材质的上层建筑与钢质主船体采用铆钉连接,现已逐渐被钢铝过渡接头所替代,其优点为采用焊接工艺、水密性好、耐腐蚀,还使得建造工艺大为简化,但在实际建造中出现了钢铝过渡接头分层的质量问题,直接影响船舶质量。对此,阐述如何从钢铝过渡接头特性出发,对钢铝过渡接头分层的原因进行分析,对钢铝过渡接头之间的焊接接头连接形式以及钢铝过渡接头与钢质主船体、铝合金上层建筑的连接形式进行优化;控制钢铝过渡接头焊接时焊点的厚度,焊接时不超过钢铝复合界面,且焊接点与钢铝复合界面的距离>3mm;控制复合界面临界温度,焊接过程中界面温度应低于临界温度,并留有安全裕度。通过优化钢铝过渡接头连接结构形式及焊接工艺规则,掌握了解决钢铝过渡接头分层原因的关键技术。     

钢铝过渡接头的应用研究

为降低船舶的质量重心、提高航速,某型船上层建筑首次采用铝合金材料。以往铝合金材质的上层建筑与钢质主船体采用铆钉连接,现已逐渐被钢铝过渡接头所替代,其优点为采用焊接工艺、水密性好、耐腐蚀,还使得建造工艺大为简化,但在实际建造中出现了钢铝过渡接头分层的质量问题,直接影响船舶质量。对此,阐述如何从钢铝过渡接头特性出发,对钢铝过渡接头分层的原因进行分析,对钢铝过渡接头之间的焊接接头连接形式以及钢铝过渡接头与钢质主船体、铝合金上层建筑的连接形式进行优化;控制钢铝过渡接头焊接时焊点的厚度,焊接时不超过钢铝复合界面,且焊接点与钢铝复合界面的距离>3mm;控制复合界面临界温度,焊接过程中界面温度应低于临界温度,并留有安全裕度。通过优化钢铝过渡接头连接结构形式及焊接工艺规则,掌握了解决钢铝过渡接头分层原因的关键技术。     

船舶十字焊接接头在不同位错精度下应力集中系数的有限元计算

研究了船舶十字焊接接头在不同位错精度上的力学性能。建立了船体十字焊接接头有限元应力分析的力学模型，利用增量法，对由２１．５ｍｍ，２５ｍｍＢ级船用钢组成的船体十字焊接接头进行了平面应变的有限元应力弹塑性分析；研究了不同位锚精度下十字焊接接头的应用力集中系数，并分析了不同焊角尺寸对十定焊接接头应力集中程度的影响，这将对制订更为合理的船舶结构十字接头位错精度标准提供了可靠的依据。     

S32750超级双相不锈钢管钨极氩弧焊焊接工艺研究

通过焊接工艺评定试验,对S32750超级双相不锈钢无缝钢管的焊接接头做力学性能测试及金相试验,检测接头的点腐蚀性能,从而对钨极氩弧焊的焊接工艺进行评定,以保证焊接接头的力学性能和耐腐蚀性能满足要求。     

焊接热输入量对E36高强度钢接头金相组织及机械性能的影响

针对E36高强度钢,通过对不同焊接参数下焊接接头金相组织的变化和机械性能的影响进行分析研究,结果发现若焊接参数选择不当,焊接过程过大的热输入会造成焊接接头金相组织的变化,碳化物在晶界聚集偏析,从而极大降低了接头的冲击性能,导致冲击值极低,而抗拉强度和弯曲无明显影响.     

铝合金填充式搅拌摩擦点焊工艺试验

文章对5A06铝合金进行了填充式搅拌摩擦点焊,对焊接接头进行了力学性能试验和金相试验。通过观察焊缝的微观组织,分析了不同焊接工艺参数对填充式搅拌摩擦点焊接头力学性能和截面成形的影响。结果表明:焊接时间对摩擦点焊接头的抗剪切性能和抗拉性能影响最大;点焊工具旋转速度增加对接头的抗拉性能有增强作用。     

超声冲击处理对高强钢焊接接头残余应力影响的数值模拟

超声冲击处理(UIT)是一种有效的焊后改善焊接接头疲劳性能的工艺措施,其借助机械撞击和超声振动的共同作用,使焊趾表面产生塑性变形从而引入有益的压缩残余应力。为评价UIT技术对焊接接头残余应力的影响,该文提出了一套新的数值分析方法,包括焊接数值模拟及随后的超声冲击处理过程的动态弹塑性有限元分析。在有限元模型中考虑了实际的工艺参数和超声促成的材料软化效应。以船用高强钢AH36非承载十字焊接接头为研究对象,将预测的超声冲击处理前后的残余应力分布与实验结果进行对比,两者有较好的吻合。在此基础上,探讨了静态预载荷对超声冲击处理态残余应力再分布的影响。     

打磨处理改善焊缝疲劳性能的试验研究

由于高强度钢的使用，船舶结构许用应力水平的提高，船舶结构的疲劳强度越来越受到关注。船舶结构的疲劳寿命取决于其焊接结构的疲劳寿命。因此，了解焊缝几何参数对焊件疲劳强度的影响以及采用经济实用的方法改善船舶结构的疲劳性能是十分重要的。本文首先对焊缝几何参数对焊件疲劳寿命的影响进行了分析，在此基础上用ABS钢和945钢两种钢板做试件，分别进行了简单拉伸实验及打磨和未打磨条件下对接接头的疲劳试验。试验结果表明焊件的疲劳寿命可以通过打磨焊缝得到改善；尤其对于高强度钢焊件。试验还说明手工打磨焊缝和机械磨削焊缝对焊件疲劳强度的改善效果差别很大，疲劳寿命的分散性也很大。因此，应当对改善焊件疲劳寿命的工艺进行更详细的研究。     

A design method of tensile triangles and low transformation temperature weld metal for reduction of stress concentration and residual stress of welded joints

Stress concentration and residual stress have a significant influence on fatigue life of welded joints. In order to reduce the stress concentration of welded joints, a mathematical design method of tensile triangles (MTT) based on bionics was applied to weld shape design. Accordingly, the stress concentration of various weld beads in the corner boxing welded joint and the fillet welded T-joint was dissected using our in-house FEM software JWRIAN. It was found that there existed a large stress concentration in the conventional welded joints, whereas those welded joints with elongated weld bead were accompanied by a lower stress concentration, especially for elongated weld bead with MTT design. Furthermore, among the weld shapes of the corner boxing fillet welded joint, the rectangle shape of weld bead had the minimum stress concentration factor (1.05). For the fillet welded T-joint with MTT design, the stress concentration of weld toe decreased dramatically with the increase of the index of designed shape, but there was a minor difference of stress concentration at weld root between the weld beads with MTT design. In addition, application of low transformation temperature (LTT) weld metal utilizing martensitic transformation to the fillet welded T-joints can produce compressive residual stress at weld toe.     

对接接头焊趾应力集中有限元分析

研究焊缝几何参数对应力集中的影响,对于提高焊接结构疲劳强度有重要的意义.本文采用有限元方法,计算了双侧对称加强高和单侧加强高的对接接头焊趾处的应力集中系数,分析了几个主要参数,包括焊趾倾角、焊趾过渡圆弧半径和板厚对于应力集中系数的影响,研究了焊趾处应力集中沿板厚方向的变化情况,在分析大量计算结果的基础上给出了估算两种形式的对接接头应力集中系数的经验公式.结果表明,减小焊趾倾角,增大过渡圆弧半径,可以减缓焊趾处截面形状的变化,改善焊趾处的应力集中;板厚的增加使得应力集中系数增大.并且单侧加强高的对接接头应力集中系数小于双侧对称加强高对接接头的,其减小幅度只与θ有关.     

焊趾表面裂纹应力强度因子简化计算的比较研究

对接、T型接头与十字接头是船舶与海洋结构的典型结构形式,其大部分疲劳失效是由于焊趾引起的.各种表面裂纹的应力强度因子计算是船舶与海洋结构基于断裂力学安全评定和疲劳寿命预测的基础.Bowness等人提出了T型接头焊趾表面裂纹应力强度因子计算式,作者对其复杂的计算式进行了简化.BS7910针对对接、T型接头与十字接头提出了两套焊趾应力强度因子表达式,一是针对二维表面裂纹提出的,一是针对三维表面裂纹提出的.本文对作者给出的简化表达式以及BS7910的两套表达式进行了比较.结果表明作者给出的简化表达式不仅可以用来计算T型接头的焊趾表面裂纹应力强度因子,而且可以用来计算对接与十字接头焊趾表面裂纹的应力强度因子.同时发现在a/T＜0.05处三者的差别比较大,因此用有限元法进行了验证,结果证明作者给出的简化表达式比其他表达式更加合理.     

Size effect on residual stress in low transformation temperature welded joints

It has been reported that low transformation temperature (LTT) weld metals are beneficial to generation of compressive residual stress around weld zone. In this study, the relationship among residual stress, size effect of LTT welded joints with different plate width and thickness as well as martensite start (Ms) temperatures was investigated by experimental and finite-element analysis. It was found that heat dissipation and thermal expansion coefficient of LTT weld metal had a significant impact on residual stress. Welded joint with a small plate width led to greater compressive residual stresses in the LTT weld, which was due to the lower heat dissipation and smaller thermal expansion coefficient of the LTT weld metal in due course of cooling process. Additionally, the finite-element analysis revealed that increasing plate width mainly affected the longitudinal residual stress, while increasing the plate thickness influenced all the residual stress components in the LTT weld. Furthermore, the LTT weld with a lower Ms temperature of 191 °C resulted in greater compressive residual stresses, and was less sensitive to the LTT joint size, as against the Ms temperature of 398 °C.     

热喷铝对船体钢焊接接头疲劳性能影响试验研究

通过对390MPa级船体钢焊接接头热喷铝与不喷铝疲劳对比试验，结果表明：在相同疲劳交变应力条件下，热喷铝焊接接头疲劳寿命大于不喷铝焊接接头的疲劳寿命。     

不同强度匹配10CrNi3MoV船体钢焊接结构的安全评定

为了研究不同强度匹配对焊接接头安全性能的影响,基于"欧洲工业结构完整性评定程序(SINTAP)"提供的失效评定图FAD方法,针对不同强度匹配的10CrNi3MoV船体钢焊接接头,建立了对应的失效评定曲线。根据母材与焊缝的拉伸试验及CTOD(裂纹尖端张开位移)试验结果,对比分析了3种匹配条件下的接头安全评定结果。研究表明,对于选定的评定级别,不同强度匹配系数对FAD图形状的影响很小;焊缝强度较高时,接头对塑性失稳的抵抗能力取决于母材性能;接头韧度水平相似时,低匹配接头对塑性失稳及脆性断裂的抵抗能力均稍差,弱于等匹配与高匹配;焊缝强度稍高于母材的"等强匹配"安全裕度最大,安全性最佳。     

Geometric stress distribution along the weld toe of the outer brace in two-planar tubular DKT-joints: Parametric study and deriving the SCF design equations

Regarding the research efforts expended so far on the calculation of stress concentration factors (SCFs) in tubular joints, two major shortcomings can be noted: (a) significant effort has been devoted to the study of SCFs in various uni-planar connections. Nevertheless, for multi-planar joints which cover the majority of practical applications, very few investigations have been reported due to the complexity and high cost involved; (b) majority of these research works focused on the study of SCFs at certain positions such as the saddle, crown toe, and crown heel, and they have ignored the hot-spot stress (HSS) at other positions along the weld toe. In the present paper, effects of dimensionless geometrical parameters on the SCF distribution along the weld toe of main (outer) braces in the axially loaded right-angle two-planar tubular DKT-joints are investigated. In order to study the multi-planar effect, SCF distribution in two-planar joints is compared with the distribution in a uni-planar joint having the same geometrical properties. A complete set of SCF database is constructed based on the two-planar DKT-joint Finite element models which are verified against experimental results and the predictions of Lloyd’s Register (LR) equations. The FE models cover a wide range of geometrical parameters. Six new SCF parametric formulae are developed through nonlinear regression analyses for the accurate and reliable fatigue design of two-planar DKT-joints under axial loads. An assessment study of these equations is conducted against the experimental data, the original FEM database and the acceptance criteria recommended by the UK Department of Energy.     

定位焊顺序对单面埋弧焊接头残余应力和变形的影响（英文）

Submerged arc welding(SAW) is advantageous for joining high thickness materials in large structure due to high material deposition rate. The non-uniform heating and cooling generates the thermal stresses and subsequently the residual stresses and distortion. The longitudinal and transverse residual stresses and angular distortion are generally measured in large panel structure of submerged arc welded fillet joints. Hence, the objective of this present work is to quantify the amount of residual stress and distortion in and around the weld joint due to positioning of stiffeners tack. The tacking sequence influences the level of residual stress and proper controlling of tacking sequences is required to minimize the stress. In present study, an elasto-plastic material behavior is considered to develop the thermo mechanical model which predicts the residual stress and angular distortion with varying tacking sequences. The simulated result reveals that the tacking sequence heavily influences the residual stress and deformation pattern of the single sided fillet joint. The finite element based numerical model is calibrated by comparing the experimental data from published literature. Henceforth, the angular distortions are measured from an in-house developed experimental set-up. A fair agreement between the predicted and experimental results indicates the robustness of the developed numerical model. However, the most significant conclusion from present study states that tack weld position should be placed opposite to the fillet weld side to minimize the residual stress.