Study of features in weld root formation under double-sided synchronized arc welding of vertical joints of steel tanks

It is shown that increase in the welding productivity of vertical joints of storage tanks for oil and oil products can be achieved due to the double-sided synchronized formation of the X-shaped groove. To minimize various disturbances, including variation of gap size and root face dimension, computer engineering analysis is performed, which showed that the formation of root pass during welding with the movement of the electrode down (vertical down) with increased dimension of the root face leads to lack of penetration, but during groove filling with the movement of the electrodes up (vertical up) deep penetration is achieved given the considerable root face dimension. It is defined that during welding of 30 mm thickness plates with root face dimension range from 6 to 8 mm, it is necessary to ensure the root gap dimension range from 1.5 to 3 mm along the entire length of the seam. In this case, the remaining unfilled cross-sectional area of the groove is small, which makes it possible to fill it in during single pass under two-arc double-sided welding. There is area of double-sided synchronized welding modes in which the occurrence probability of typical defects during the formation of the weld root is minimal.

Analisis Sifat Mekanik Hasil Pengelasan SMAW dengan Akar Las Tig dan Las SMAW pada Pipa API 5L

The purpose of this research is to know the mechanical properties of the welds due to the current variation of welding joint API 5L using TIG and SMAW welding root methods. Preparation of specimens of pipe API 5L PSL1 grade X56 (Ø 177.8 mm, length 200 mm, width 7 mm), then specimens preparation were made in a single V 600, root gap 2mm, root face 2mm. Filling the welding roots with TIG welding and SMAW using electrodes E7018 with a current variation 70A, 80A, 90A. Mechanical tests consist of tensile, bending and hard test. The results showed that the quality of a good TIG root weld at 70A, the highest tensile strength of the weld joint 52.27 kgf/mm2 (70A), the highest hardnest 164,217 HRB (90A), the bending strength 1.123,061 N/mm2 (70A) using face bend method and 1,172,959 N/mm2 with root bend. In SMAW root welding, the highest tensile strength 54.27 kgf/mm2 (70 A) , the highest hardnest 158.717 HRB (70 A), the highest bending strength 1.115,611 N/mm2 (70 A) using face bend method, and 1.161,748 N/ mm2 with root bend.

Influence of Process Parameters of 316LN Hot Wire Filling Laser Welding on the Blunt Edge Layer Forming Quality

Laser welding with hot wire addition is a new type of welding method. In order to search for appropriate laser welding technological parameters, main technological parameters have ran orthogonal optimization tests, root face layers have ran orthogonal experiments, impacts on root face forming qualities of technological parameters have been analyzed. Experimental results show that, the most influential technological parameter of weld width is welding speed, by lowering welding speed heat heat input in per unit of time will be increased, weld width decreases with the increase of defocusing amount and decrease of density of power.

A Generic Method for Bijections between Blossoming Trees and Planar Maps

This article presents a unified bijective scheme between planar maps and blossoming trees, where a blossoming tree is defined as a spanning tree of the map decorated with some dangling half-edges that enable to reconstruct its faces. Our method generalizes a previous construction of Bernardi by loosening its conditions of application so as to include annular maps, that is maps embedded in the plane with a root face different from the outer face.The bijective construction presented here relies deeply on the theory of $\alpha$-orientations introduced by Felsner, and in particular on the existence of minimal and accessible orientations. Since most of the families of maps can be characterized by such orientations, our generic bijective method is proved to capture as special cases many previously known bijections involving blossoming trees: for example Eulerian maps, $m$-Eulerian maps, non-separable maps and simple triangulations and quadrangulations of a $k$-gon. Moreover, it also permits to obtain new bijective constructions for bipolar orientations and $d$-angulations of girth $d$ of a $k$-gon.As for applications, each specialization of the construction translates into enumerative by-products, either via a closed formula or via a recursive computational scheme. Besides, for every family of maps described in the paper, the construction can be implemented in linear time. It yields thus an effective way to encode or sample planar maps.In a recent work, Bernardi and Fusy introduced another unified bijective scheme; we adopt here a different strategy which allows us to capture different bijections. These two approaches should be seen as two complementary ways of unifying bijections between planar maps and decorated trees.

Optimization of Welding Parameters by Regression Modelling and Taguchi Parametric Optimization Technique

There are many welding parameters In welding process, the major factors whose selection contributes to the welded product as they all affect the strength and quality to a larger extent are weld design (edge preparation), Root face, and Root gap. The purpose of this paper is to efficiently determine the optimum welding operation parameters for achieving the highest ultimate strength in range of parameters. In order to meet the purpose in terms of both efficiency and effectiveness, this study will utilize the Taguchi parameters design methodology. The study includes selection of parameters, utilizing an orthogonal array, conducting experimental runs, data analysis, determining the optimum combination, finally the experimental verification and comparison by regression modelling.

Biology and Management of Dogfish Sharks

Abstract.—Squaliform sharks constitute a monophyletic group of predominantly deep-water neoselachians. Their fossil record mainly consists of isolated teeth; complete skeletons or skeletal remains are very rare. The quality of the fossil record of squaliform sharks is analyzed using a phylogenetic hypothesis based on a supertree to establish the timing of cladogenetic events, those related to descent from a common ancestor, and gaps in the fossil record. The supertree is the most inclusive estimate of squaliform interrelationships that has been proposed to date and contains 23 fossil and extant members of all major groups. In addition, the simple completeness metric is used to examine the quality of the fossil record of squaliforms as an independent measure. Although different (48% and 61%, respectively), both measures indicate that the fossil record of squaliforms is very incomplete considering that most living and extinct squaliforms are deep-water sharks and corresponding sediments are very scarce. Gaps in the fossil record range from 5 to 100 million years. The most basal and stratigraphically oldest group within Squaliformes consists of <em>Squalus </em>and †<em>Protosqualus</em>¹<em>. </em>The phylogenetic hypothesis indicates a gap in the fossil record of <em>Squalus </em>spp. of about 25–30 million years. Our results show a postJurassic origination of squaliforms in the shallow waters of the northern Tethyal margin. The hypothetical ancestor of squaliforms is characterized by two dorsal fin spines and absence of dignathic heterodonty (the morphology of upper and lower teeth differs significantly). Lower teeth are characterized by a slightly oblique basal root face and overlapping upper teeth. Although disappearance and appearance of organisms is a fact of life, the very long geologic range and success of <em>Squalus </em>highlights the need for very careful management of its current population crisis, which is due to causes that never occurred before in Earth’s history–the anthropogenetic impact.

Fracture Analysis of Thick Plate for Partial Penetration Multi-Pass Weldment Using Ĵ-Integral

Partial penetration welding joint defines the groove welds that applies the one side welding which does not use steel backing and both side welding without back gouging, that is, the partial penetration welding joint leaves an unwelded portion at the root of the welding area. In this study, we analyzed the residual stress and fracture on the thick metal plates that introduced the partial penetration welding method. We performed the fracture behavior evaluation on the partial penetration multi pass welding with 25.4mm thick plate by using the Ĵ-integral, which finally led us the conclusion that the partial penetration multi-pass welding method is more applicable and effective in handling the root face with less than 6.35mm.