络合滴定法测定低压流体输送用镀锌焊接钢管镀锌层重量

介绍了利用络合滴定法测定低压流体输送用镀锌焊风管镀锌层重量的方法，试样用稀硫酸溶解，在ＰＨ１．５￣２．０的弱酸性介质中，以磺基水杨酸钠为指标剂，用ＥＤＴＡ滴定铁，调ＰＨ为５．５，以ＰＡＮ为指示剂，用ＥＤＴＡ滴定锌，由ＥＤＴＡ用量求出锌的重量，用ＧＢ／Ｔ３０９１－９３方法比较，试验结果满意。     

Dispersion and attenuation by transmission,reflection, and mode conversion in welded pipes

Torsional wave dispersion and attenuation in an open empty welded pipe are determined from a multi-receiver position reflection experiment. The fundamental torsional wave is dominantly reflected at the free end and the converted non-axisymmetric flexural modes are naturally attenuated. The resulting phase velocity contours are in agreement with theoretical predictions. The transmission losses are quantified and compared to those reflective elements associated with end and weld reflection. At any reflective node, the incident wave is split between back and forward preserved mode scattering (“reflection/transmission”), conversion to other modes plus energy lost by absorption. The ratios for each element are quantified.     

焊接接头和U型试样中的氢分布

本文作者利用自行研制的激光测氢装置,测量了焊接接头和U型试样中的氢分布,并且推导了U型试样弯曲部分(塑性变形区)的应变、残余应力计算公式。结果表明:在焊接接头中,1.沿熔深方向上,氢分布是不均匀的。最高氢含量在熔合线附近;2.氢的具体分布情况,取决于焊缝金属和母材原始含氧量,以及金相组织。在U型试样中,1.计算应变的公式和应力公式可以用来计算无明显反弹的U型试样弯曲部分的应变量和残余应力值。1Cr18Ni9Ti(C.R.)钢的F=990MPa、n=0.146;2.氢分布明显受应力和应变的影响。应力、应变值愈大,含氢量愈高。     

Characteristics of deep penetration laser welding of dissimilar metal Ni-based cast superalloy K418 and alloy steel 42CrMo

Experimental trials of autogenous deep penetration welding between dissimilar cast Ni-based superalloy K418 and alloy steel 42CrMo flat plates with 5.0 mm thickness were conducted using a 3 kW continuous wave (CW) Nd:YAG laser. The influences of laser output power, welding velocity and defocusing distance on the morphology, welding depth and width as well as quality of the welded seam were investigated. Results show that full keyhole welding is not formed on both K418 and 42CrMo side, simultaneously, due to the relatively low output power. Partial fusion is observed on the welded seam near 42CrMo side because of the large disparity of thermal–physical and high-temperature mechanical properties of these two materials. The microhardness of the laser-welded joint was also examined and analyzed. It is suggested that applying negative defocusing in the range of Raylei length can increase the welding depth and improve the coupling efficiency of the laser materials interaction.     

A Categorical Structure for the Virtual Braid Group

This article gives a new interpretation of the virtual braid group in terms of a strict monoidal category SC that is freely generated by one object and three morphisms, two of the morphisms corresponding to basic pure virtual braids and one morphism corresponding to a transposition in the symmetric group. This point of view makes many relationships between the virtual braid group and the pure virtual braid group apparent, and makes representations of the virtual braid groups and pure virtual braid groups via solutions to the algebraic Yang–Baxter Equation equally transparent. In this categorical framework, the virtual braid group has nothing to do with the plane and nothing to do with virtual crossings. It is a natural group associated with the structure of algebraic braiding.     

焊接薄板中S0兰姆波对槽型缺陷响应特性的数值研究*

采用数值仿真方法,就焊接薄板中S_0兰姆波对槽型缺陷的响应特性以及焊缝对S_0兰姆波槽型缺陷检测灵敏度的影响开展了数值研究。数值仿真结果表明,S_0_R信号(经槽型缺陷反射的S_0兰姆波回波信号)的反射比率随槽型缺陷深度的增大而单调增加;S_0_R信号的反射比率随槽型缺陷宽度的变化呈非单调变化关系,可将S_0_R信号的反射比率及其持续时间一并加以考虑,以评价槽型缺陷宽度的变化。随着焊缝余高的增加,S_0兰姆波对槽型缺陷的检测灵敏度将降低;随着焊缝宽度的增加,S_0兰姆波对槽型缺陷检测灵敏度的影响并不明显;相比之下,焊缝余高是影响S_0兰姆波槽型缺陷检测灵敏度的主要因素。研究结果表明,将S_0兰姆波用于检测隐藏于焊缝背后的槽型缺陷,是具有可行性的。所得结果对于发展焊接薄板的超声兰姆波无损检测技术,具有一定的理论指导意义和实际参考价值。     

Plane waves at an imperfectly bonded interface of two orthotropic generalized thermoelastic rotating half-spaces with two relaxation times

The present paper concentrates on the study of reflection and refraction characteristics of plane waves at an imperfectly bonded interface of two orthotropic generalized thermoelastic rotating half-spaces with different elastic and thermal properties. In this type of problem of orthotropic thermoelastic rotating medium, there are three types of plane waves quasi longitudinal (QL-) wave, quasi thermal (T-mode) wave and quasi transverse (QT-) wave, whose velocities depend on the angle of incidence, imperfection and rotation. The amplitude ratios of reflected waves to that of incident one in each case have been derived. Some special cases of boundaries, i.e. normal stiffness, transverse stiffness, thermal contact conductance, slip boundary and welded contact boundary have been deduced from an imperfect one. Effect of rotation on the amplitude ratios of different reflected and refracted waves with respect to incident QL-wave at different boundaries have been studied graphically. It is observed that thermal properties, imperfect boundary and rotation have significant effect on the propagation of waves.     

Accumulative damage near crack tip for welded bridge members: fatigue life determination

The behavior of crack growth for the fatigue damage accumulation near tip where damage is most severe is analyzed. Fatigue life is assessed for the welded members of bridges under traffic loading. Two parts are considered. They consist of the development of a fatigue damage accumulation model for welded bridge members and a method for calculating the stress intensity factor that is needed for evaluating the fatigue life of welded bridge members with cracks. Based on the concept of continuum damage accumulation and fatigue and fatigue crack growth relations, results are obtained to describe the relationship between the cracking count rate and the effective stress intensity factor. Crack growth and fatigue life are found for two types of welded members assisted by using fatigue experimental results. The stress intensity factors are modified by correcting for the geometric shape of the welded members in order to reflect the influence of the weldment and geometry. This is accomplished via the stress intensity factor. The calculated and measured fatigue lives were generally in good agreement for the initial cracking conditions of two types of welded members widely used in steel bridges.     

焊接波纹管在热声机械中的应用

焊接波纹管是近年来国内外兴起的一种新型元件 ,它有两突出的优点 :变形量大 ,寿命长。利用其改进热声机械 ,有可能解决许多重大问题。文中介绍了焊接波纹管的结构 ,总结了其在热声机械中可能的几点应用 ,对其寿命也做了初步讨论。     

Fatigue growth prediction of elliptical cracks in welded joint structure: Hybrid and energy density approach

A hybrid weight function approach (HWFM) is presented for the fatigue life prediction of infinite body and welded joint structure containing elliptical cracks. A self-containing computer code has been developed for this purpose. Numerical computations were first conducted on cracked infinite body showing a physical fact, that the elliptical shape of the crack becomes circular during its evolution. The prediction of the fatigue crack growth shows that the present results are in perfect concordance with those reported in the literature. Then, numerical tests were carried out on two types of specimens of welded joint structure. The present results were compared to the experimental and predicted ones of other authors, demonstrating that the hybridization method is a powerful numerical technique, and that the SEDF approach (using the Sih’s law) is more valid for the critical cases of welded joints than the SIF approach (using the Paris law). A parametric study has been conducted on the stress ratio “R” showing that the fatigue life to failure decreases with the increase of “R”.