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.     

匹配类型对接头静载下抗断裂性能的影响

本文以造船行业常用的ＺＣＢ钢为研究对象，选用高匹配焊接接头，采用带缺口试样在静拉伸载荷作用下进行试验。试验表明，在本试验条件下，焊缝与载荷垂直时，接头的抗裂性主要取决于焊缝的强度，焊缝强度越高，接头的抗裂性越好。当焊缝与载荷平行时，接头抗裂性主要取决于焊缝塑性，焊缝强度直高的生越差。本文所采用的评定接头抗断裂性能的参量（断列比功Ｗ／Ｆｏ，整体平均应变ε，最小截面收缩率ψｍｉｎ）简单易行，结论可靠，     

铝合金表面状态对搅拌摩擦焊接头组织和性能的影响

研究了铝合金表面状态对搅拌摩擦焊焊接接头组织和性能的影响。试验结果表明:试板表面油污的存在使得焊接接头强度下降为母材的60%左右,同时显著降低接头的塑性;试板表面的氧化膜和油污还会造成焊核区及焊缝前进侧的残余间混结合线缺陷。对焊接接头拉伸断口进行扫描电镜观察发现:拉伸试样的断口中存在油污和A l2O3的聚集物,这些聚集物会成为拉伸时的裂纹源。断口和力学性能综合分析表明:铝合金表面的油污和氧化膜都会降低搅拌摩擦焊接头的强度和塑性。     

海底管线钢焊接接头的安全评定及寿命预测

本研究在给定裂纹尺寸和载荷条件下,根据CTOD(裂纹尖端张开位移)试验结果,采用欧共体提出的结构完整性评定方法SINTAP(Structural Integrity Assessment Procedure),针对API5LX65管线钢焊接接头焊趾处的表面裂纹进行评定.根据拉伸试验结果,建立了X65管线钢焊接接头焊缝和母材的一级、三级评定曲线.评定结果表明,不论是采用一级或是三级评定,各评定点均在评定曲线定义的范围内,说明该结构是安全的.并根据上述评定结果对结构进行疲劳寿命估算,具有实际的工程意义和经济价值.     

B级碳素船体钢焊接接头耐蚀性研究

通过室内腐蚀挂片及电化学测量试验 ,研究了B级碳素船体钢三种常见焊接接头的耐海水腐蚀性能。结果表明 :在海水中 ,接头的焊缝区最易受到腐蚀 ,其次为母材 ,热影响区腐蚀最轻 ;几种接头相比 ,B级碳素船体钢与J4 2 2焊条匹配后焊接接头的综合耐蚀性高于其与J50 7和H0 8MnSi2A两种焊接材料匹配后接头的耐蚀性。     

B级碳素船体钢焊接头接头耐蚀性研究

通过室内腐蚀挂片及电化学测量试验,研究了Ｂ级碳素船体钢三种常见焊接接头的耐海水腐蚀性能,结果表明：在海水中,接头的焊缝区最易到腐蚀,其次为母材。热影响区腐蚀最轻;几种接头相比,Ｂ级碳素船体钢与Ｊ４２２焊条匹配后焊接接头的综合耐蚀性高于其与Ｊ５０７和Ｈ０８ＭｎＳｉ２Ａ两种焊接材料匹配后接头的耐馈性。     

2A21铝合金厚板搅拌摩擦焊接头组织与分层性能研究

采用搅拌摩擦焊焊接19 mm的2A21铝合金,焊后观察并分析了接头不同区域的微观组织,通过接头的拉伸试验和显微硬度测试评定接头的力学性能.结果表明:轴肩影响区和焊核区组织均为细小致密的等轴晶,在靠近焊核区底部的后退侧出现了晶粒大小不一的部分重结晶区;拉伸试验表明上层接头的抗拉强度最高,为348 MPa,达到母材强度的76.5%,断裂位置在后退侧轴肩影响区和热机械影响区分界处;下层接头的抗拉强度最低,断裂位置在部分重结晶区;接头横截面显微硬度分布整体成"W"状,焊核硬度值最高,热影响区硬度值最低,焊缝上部硬度高于焊缝下部.     

2205双相不锈钢焊接工艺及耐腐蚀性能分析

采用不同焊接工艺对2205双相不锈钢进行焊接,分析不同焊接工艺对焊接接头力学性能、微观组织及耐腐蚀性能的影响。结果显示:在晶粒无明显长大时,焊缝及热影响区冲击韧性随奥氏体质量分数的增加而升高;采用熔化极气体保护焊(Gas Metal Arc Welding,GMAW)时,保护气体中加入N2可有效提高焊接接头各区域奥氏体质量分数,从而提高焊接接头力学性能及耐腐蚀性能;2205双相不锈钢母材及焊缝腐蚀速率均明显随腐蚀液质量分数的升高而增加。优化双相不锈钢焊接工艺参数,保证其焊接接头具有良好的综合性能,对于该类材料构件及产品的制造、推广及使用意义重大。     

海洋平台用EQ70高强钢焊接性研究

采用CONARC80焊条手工电弧焊接EQ70钢,研究了焊接工艺对接头性能的影响.结果表明:在焊后热处理的条件下,其接头强度在焊接电流为180 A或200 A时,均能和母材等强;当焊接电流达到220 A时,则接头强度低于母材;EQ70钢焊接接头在室温均具有很好的冲击韧性;在150℃预热、200 A焊接电流和焊后热处理的条...     

铝合金活性TIG焊接接头性能研究

针对6061铝合金,采用自行研制的混合活性剂配方,利用正交设计法进行焊接工艺试验,得到一组性能良好的焊接工艺参数。在此焊接工艺条件下,混合活性剂增加熔深效果显著,可一次焊透10 mm的铝板,实现单面焊双面成形。焊后对焊缝的微观组织进行了观察和分析,并通过力学性能试验分析了活性剂对焊缝力学性能的影响。结果表明：与常规TIG焊相比,活性TIG焊的焊缝组织细密,基本不存在气孔、裂纹、夹杂等焊接缺陷;活性TIG焊接接头的拉伸强度和断裂伸长率均可达到与母材相当的水平,焊缝区的硬度明显提高,焊接接头性能良好。     

A ductile tearing assessment diagram for cracked circular-hollow-section joints under reversed loadings

This paper proposes a ductile tearing assessment diagram (TAD) to predict the load resistance to the crack extension relationship during the stable tearing process of the circular-hollow-section (CHS) joints under the reversed in-plane bending actions. The tearing assessment diagram utilizes the envelope of the load-deformation curve from the fracture test under reversed loadings to build the connection among the fracture resistance, load resistance and crack extension. To verify the proposed approach, this study performs fracture experiments, imposing the reversed in-plane bending on the CHS X-joints, made of Q345 steel, with a surface crack near the weld toe. The experimental investigation reveals the effect of the reversed loading on the fracture resistance and validates the TAD-based assessment for tubular joints. Meanwhile, this study performs the cyclic fracture test on the single-edge-notched-tension [SE(T)] specimen made of Q345 steel and derives the TAD from the experimental record of the SE(T) specimen. The specimen-based assessment successfully predicts the load versus crack extension relation for the reported joints under reversed loadings. The study provides a basic framework to predict the joint response under reversed loadings by integrating the material fracture characteristics.     

锌铝药芯钎焊丝钎焊铝/铜接头性能及组织

采用5种不同成分的锌铝药芯钎焊丝钎焊铝/铜接头,研究钎料成分对接头剪切强度和耐蚀性的影响.研究结果表明：对于同成分的锌铝药芯钎焊丝,采用火焰钎焊的铝/铜接头抗剪强度比炉中钎焊高,Zn80Al20药芯钎焊丝钎焊的铝/铜接头强度最高;随钎料中Al含量降低,铝/铜接头的耐蚀性变差,Zn72Al28药芯钎焊丝钎焊的铝/铜接头耐腐蚀性最好.相同条件下,火焰钎焊铝/铜接头的耐蚀性明显好于炉中钎焊的接头;Zn80Al20药芯钎焊丝钎焊的铝/铜接头钎缝组织呈块状.锌铝药芯钎焊丝中适中的Zn,Al含量有利于使铝/铜接头铜侧界面得到固溶体组织,并避免铝侧母材的过度熔蚀.     

Effects of adhesive type on the mechanical properties of adhesive joints between polyurethane top coats and polyurethane-based adhesives after accelerated atmospheric ageing

The performance of a sealed stainless steel bracket system, adhesively bonded with two polyurethane-based adhesives (flexible adhesive, stiff adhesive) onto a marine polyurethane top coat, is investigated. The investigated joint connections on the coatings exhibited a high mechanical stability even after accelerated ageing (salt spray exposure, cyclic temperature variations, high relative humidity). The aged joints retained up to 81% of their tensile strength and up to 92% of their lap-shear strength. The torsional rigidity of the adhesive joint exceeded the required clamping torque of the designed bolt. A cyclical lifetime of >9·10⁶ load cycles was estimated. Effects of cyclic ageing on the creep performance of the adhesive joint were found to be insignificant. Under tensile loads, the joints with stiff adhesive material exhibited a linear-elastic performance without the capability to deform prior to failure. The joints with the flexible adhesive material, in contrast, exhibited a behavior typically for ductile materials featuring a pronounced yield plateau prior to failure. Failure loads were higher, and displacement was notably lower, for the joints with stiff adhesive material. All joint connections met the requirements for a safety factor for the design for marine applications (11.6 for the flexible adhesive; 14.3 for the stiff adhesive). When the flexible adhesive is applied, the cohesive strength of the adhesive material is the limiting design factor. When the stiff adhesive is utilized, the load carrying capacity is higher, and the interface between priming coat and steel substrate is the limiting design area of the joints. The strength utilization of the adhesive materials depended on the particular structure of the entire joint configuration, particularly on the interface between steel substrate and the coating material. A number of assessment factors, namely stress limit factor, coating adhesion factor and safety factor, are introduced and discussed for tensile and shear loads.     

船体钢焊接接头的韧性要求与控制

在实验室条件下,以ＦＴＰ准则为判据,对潜艇耐压壳体母材韧性进行了测评,并重点就焊接接头性能是否符合壳体抗爆要求的问题进行了小试样实验研究和理论分析,最后根据有关试验结果给出了接头质量控制的合理焊接工艺参数。     

Structural behavior and design of high-strength steel welded tubular connections under extreme loading

The present work is motivated by the increasing need for cost-efficient solutions in offshore structural systems for wind energy production and for improvement of their structural performance. The structural behavior and design of high-strength steel welded tubular connections (yield strength higher than 700 MPa) subjected to monotonic and strong cyclic loading is investigated. In the first part of the paper, an experimental investigation is presented on high-strength steel tubular X-joints subjected to monotonic and cyclic loading far beyond the elastic limit of the material, leading to weld fracture. Two grades of weld metal material are employed in the welding process of the specimens. The experimental results indicate that the weld material grade has a significant influence on the deformation capacity of the welded connection under monotonic loading conditions, and its low-cycle fatigue life. The experimental procedure is simulated using advanced finite element models, elucidating several features of joint behavior and complementing the experimental results. Overall, a good agreement is found between numerical simulations and experimental results, in terms of both global response and local strains at the vicinity of the welds. Furthermore, the structural performance of the welded tubular joints under consideration is assessed using available design methodologies in terms of both ultimate strength and low-cycle fatigue resistance, in an attempt to validate an efficient design methodology for low-cycle fatigue. The results from this research effort are aimed at developing the necessary background for the possible use of high-strength steel in tubular steel lattice structures, particularly in offshore platforms for renewable energy production. They can also be used as a basis for the possible amendment of relevant design specifications and recommendations for including special provisions for high-strength steel structural systems.     

Stress magnification effect of initial deformation on the notch stress field and fatigue strength of thin plate welded joints

Compared with thick plate welded joint, the welding joint of thin plate will produce initial deformation due to its low bending rigidity. The existence of initial deformation will cause the welded structure to produce secondary bending effect, which will produce greater stress magnification effect at the weld toe and seriously affect the fatigue strength of thin plate welded joints. Therefore, based on the correction formula of thick plate, considering the influence of initial deformation and geometric nonlinearity of thin plate, this paper deduces the stress magnification factor formula at the weld toe of T-shaped and cruciform specimens. The accuracy of the revised formula is further verified by comparing the notch stress calculated by the modified formula with the FE results. Finally, the modified formula is applied to the notch stress and fatigue evaluation of typical thin plate welded joints respectively. The results show that the proposed notch stress calculation formula can fully consider the stress amplification effect of thin plate structure, and can be used to quickly evaluate the notch stress field and fatigue strength of thin plate welded joints.     

船用EH36高强钢无缝药芯焊丝焊接接头组织和冲击韧性研究

本文以SRSF501无缝药芯焊丝在船用EH36高强钢中的焊接应用为目的,研究了国产无缝药芯焊丝SRSF501在船用EH36高强钢焊接中的组织和冲击韧性。通过试验表明：SRSF501焊接EH36钢接头各区域的冲击性能均满足船级社要求；多层多道焊时,焊缝组织由粗大的柱状组织和细小的等轴晶组织组成,底层焊缝和末道焊缝柱状晶区域较大；盖面层两侧接头热影响区存在粗晶区,其它位置接头的热影响区不存在粗晶区；焊接接头中熔合线外2mm处,晶粒最细,冲击韧性最好。