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Research on the Influence of Sagging and Continuous Undercut on the Capacity

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Research on the Influence of Sagging and Continuous Undercut on the Capacity
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  International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 07-19 © IAEME   7 RESEARCH ON THE INFLUENCE OF SAGGING AND CONTINUOUS UNDERCUT ON THE CAPACITY OF BUTT-WELDED JOINT Vladimir Stojmanovski 1 , Zoran Bogatinoski 2 , Viktor Stojmanovski 3   1 (Centre for Research, Development and Continuous Education – CIRKO, Inspection Body for Pressure Vessels, Metal Structures and Cableways, Skopje, Macedonia) 2 (Professor, Ss. Cyril and Methodius University in Skopje, Faculty of Mechanical Engineering, Skopje, Macedonia) 3 (Associate Professor, Ss. Cyril and Methodius University in Skopje, Faculty of Mechanical Engineering, Skopje, Macedonia) ABSTRACT The behavior of butt-welded joint with imperfection of the outer contour due to sagging and continuous undercut has been analyzed in this paper. The analysis was done by testing and numerical investigation using Finite Element Analysis. For the testing, the standard probes have been made from material S235JR that is mostly used for the production of welded structures. Sagging and continuous undercut on both sides of the testing plates have been simulated in the welded joint in order to evaluate the imperfection. Research presented in this paper is directed in gaining acknowledgement and experience for analysis of the welded structures and their usage in design, construction, production and testing. In that manner the real picture of stress distribution is going to be acquired and this will contribute in the design of structures with decreased factor of safety leading to less expensive and yet safe structures which is the common interest of the companies that construct, produce and assemble welded structures. The purpose of this paper is to endorse the influence of the sagging and continuous undercut on the capacity of the welded joint in order to make appropriate judgment for the safety. Keywords:  Butt-Weld, Continuous Undercut, FEA, Imperfection, Material Testing, Sagging. I. INTRODUCTION Due to discontinuities from various imperfections found on the outer contour of the welded  joint (such as sagging and continuous undercut), there is irregular stress distribution at the joint with   INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 5, Issue 8, August (2014), pp. 07-19 © IAEME: www.iaeme.com/IJMET.asp Journal Impact Factor (2014): 7.5377 (Calculated by GISI) www.jifactor.com   IJMET   © I A E M E    International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 07-19 © IAEME   8 elevated stress peaks. The influence of these peaks cannot be precisely estimated during the calculation of the joint. In practice, the solution of the problem, in order to prevent the existence of such imperfections, lays in establishment of rigorous criteria prescribed by the regulation. Sometimes there is a question whether these rigorous criteria are reasonable due to the fact that they directly influent the costs of the welded structure. On the other side, in some separate cases as far as there is discontinuity, it is very likely that during the reparation the situation might worsen, particularly if there is a location where the reparation is hard to be made. Considering these facts, in some cases, it is necessary to make judgment whether there is need to make reparation on the discontinuities found on the outer contour during the examination. In this paper has been analyzed the behavior of butt-welded joint with imperfection of the outer contour due to sagging and continuous undercut. The probes used for the tensile, bending and toughness tests are standard and they are produced from the plates [2] made from material S235JR that is mostly used for the production of welded structures. Chemical composition and mechanical properties have been obtained by analyzing the material. Appropriate welding technology for the probes has been adopted according to EN499 and E7018 according to AWSA 5.2. the technology has been verified and appropriate WPQR certificate has been issued. Sagging and continuous undercut on both sides of the testing plates (probes) were simulated at the welded joint. Static examination of the basic material S235JR and the welded joint are made. The joints are analyzed by FEA in their real dimensions of the model and the imperfections with the ALGOR software [4]. Such analysis has shown the stress distribution of the joint. Research presented in this paper is directed in gaining acknowledgements and experience for analysis of the welded structures and their usage in design, construction, production and testing. In that manner is going to be acquired the real picture of stress distribution that will contribute in the design of structures with decreased factor of safety leading to less expensive and yet safe structures that are the common interest of the companies which project, produce and assemble welded structures. II. BASIC MATERIAL Models (probes) analyzed in this paper are produced from material S235JR. The material has been tested in the laboratory and properties of material gained from the test are presented in Table 1 and Table 2. Table 1: Chemical Composition of the material Chemical element (%) C Si Mn P S Cr Ni Al Cu Nb Ti Mo V B C ekv  0,11 0,08 0,58 0,013 0,012 0,03 0,02 0,043 0,03 0,02 0,01 0,01 0,01 0,0 0,213 Table 2:  Mechanical Properties of the material Dimensions F m  (N) Tension Bending Toughness R eh  (Mpa) R m  (MPa) A 5  (%) R eh  /R m   α   (mm) α   ( 0 ) Ρ  (J) 9,5x24,6 L=118 L 0 =90 120980 366 517 31,5 0,71 Ø40 180 112 t= + 20 0 C  International Journal of Mechanical ISSN 0976 – 6359(Online), Volume 5, Tension test graph is presented on Fi Fig. 1: Te From the performed tests, properties, the elongation, bending for the quality of the material S235J III. WELDING TECHNOLOGY Welding of the plates was pe ARC welding procedure for filling a E424 32 X5 according to EN499 an Fig. 2: Welding order: 1. Roo Professionally qualified wel prescribed welding technology was IV. THE PROBES FOR THE TE  From the Basic material u created for the purpose of the te Engineering and Technology (IJMET), ISSN 0 Issue 8, August (2014), pp. 07-19 © IAEME   9 gure 1. sion test graph for material S235JR it can be concluded that chemical composi    and toughness meet the requirements of the st . rformed with TIG welding procedure (141) for nd finish. ARC welding was performed with ba E7018 according to AWSA 5.2 [3]. t -TIG (141), 2. Filling -ARC (111), 3. Finish er who possesses valid certificates performed erified and the WPQR certificate has been issu  TING ing the prescribed welding technology appr st. The characteristic imperfections (sagging 76 – 6340(Print), tion, mechanical ndard EN 10025 the root weld and sic electrode type -ARC (111) the welding. The d priate plates are and continuous  International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 07-19 © IAEME   10 undercut) are simulated at the joint. The imperfection models used in the further tests are presented in Table 3 Table 3:  The Models (probes) used for the tests Probe mark 1. Welded joint with grinded face and root 2.1 2. Weld with significant sagging on one side 2.6. 3. Weld with continuous undercut on both sides 2.7. IV.1. PERMITTED DEVIATION OF THE IMPERFECTIONS The characteristic imperfections according to ISO 6520, depending on the level of quality of the weld are presented in Table 4. Table 4:  Permitted deviation of the imperfections according to ISO 6520 Appearance of the imperfection t (mm) Boundary values of the imperfection for the level of quality D C B 2.6. > 3 Small sizes h ≤ 0,25 t no max 2 mm for probe 2.6 h ≤ 2,375 mm Small sizes h ≤ 0,1 t no max 1 mm for probe 2.6 h ≤ 0,95 mm Small sizes h ≤ 0,05 t no max 0,5 mm for probe 2.6 h ≤ 0,475 mm 2.7. > 3 h ≤ 0,2 t no max 1 mm for probe 2.7 h ≤ 1,9 mm h ≤ 0,1 t no max 0,5 mm for probe 2.7 h ≤ 0,95 mm h ≤ 0,05 t no max 0,5 mm for probe 2.7 h ≤ 0,475 mm IV.2. VISUAL EXAMINATION OF THE WELDED JOINTS Visual examination and dimensional control of the welded joints are performed in order to evaluate the imperfections. The results from the dimensional control of the imperfections are presented in Table 5. Table 5:  Results from the dimensional control Joint with significant sagging 2.6. a 1 (mm) b 1 (mm) a   (mm) b   (mm) c   (mm) 7,6 2 14 1 1 Joint with continuous undercut 2.7. a 1 (mm) b 1 (mm) a   (mm) b   (mm) c   (mm) c 1 (mm) 6,4 2 16,4 2 2 2    t   h   t   h
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