Validation of Efficient Welding Technique to Reduce Welding Displacements of Ships using the Elastic Finite Element Method

우동한 해양환경안전학회 2020 海洋環境安全學會誌 Vol.26 No.3

Welding is the most convenient method for fabricating steel materials to build ships and offshore structures. However, welding using high heat processes inevitably produces welding displacements on welded structures. To mitigate these, heavy industries introduce various welding techniques such as back-step welding and skip-step welding. These techniques effect on the change of the distribution of high heat on welded structures, leading to a reduction of welding displacements. In the present study, various cases using different and newly introduced welding techniques are numerically simulated to ascertain the most efficient technique to minimize welding displacements. A numerical simulation using a finite element method based on the inherent strain, interface element and multi-point constraint function is introduced herein. Based on several simulation results, the optimal welding technique for minimizing welding displacements to build a general ship grillage structure is finally proposed.

Validation of Efficient Welding Technique to Reduce Welding Displacements of Ships using the Elastic Finite Element Method

Woo, Donghan The Korean Society of Marine Environment and safet 2020 海洋環境安全學會誌 Vol.26 No.3

Welding is the most convenient method for fabricating steel materials to build ships and of shore structures. However, welding using high heat processes inevitably produces welding displacements on welded structures. To mitigate these, heavy industries introduce various welding techniques such as back-step welding and skip-step welding. These techniques effect on the change of the distribution of high heat on welded structures, leading to a reduction of welding displacements. In the present study, various cases using different and newly introduced welding techniques are numerically simulated to ascertain the most efficient technique to minimize welding displacements. A numerical simulation using a finite element method based on the inherent strain, interface element and multi-point constraint function is introduced herein. Based on several simulation results, the optimal welding technique for minimizing welding displacements to build a general ship grillage structure is finally proposed.

Validation of Efficient Welding Technique to Reduce Welding Displacements of Ships using the Elastic Finite Element Method

Donghan Woo 해양환경안전학회 2020 해양환경안전학회지 Vol.26 No.3

Welding is the most convenient method for fabricating steel materials to build ships and offshore structures. However, welding using high heat processes inevitably produces welding displacements on welded structures. To mitigate these, heavy industries introduce various welding techniques such as back-step welding and skip-step welding. These techniques effect on the change of the distribution of high heat on welded structures, leading to a reduction of welding displacements. In the present study, various cases using different and newly introduced welding techniques are numerically simulated to ascertain the most efficient technique to minimize welding displacements. A numerical simulation using a finite element method based on the inherent strain, interface element and multi-point constraint function is introduced herein. Based on several simulation results, the optimal welding technique for minimizing welding displacements to build a general ship grillage structure is finally proposed.

Optimization of vibratory welding process parameters using response surface methodology

Pravin Kumar Singh,S. Deepak Kumar,D. Patel,S. B. Prasad 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.5

The current investigation was carried out to study the effect of vibratory welding technique on mechanical properties of 6 mm thick butt welded mild steel plates. A new concept of vibratory welding technique has been designed and developed which is capable to transfer vibrations, having resonance frequency of 300 Hz, into the molten weld pool before it solidifies during the Shielded metal arc welding (SMAW) process. The important process parameters of vibratory welding technique namely welding current, welding speed and frequency of the vibrations induced in molten weld pool were optimized using Taguchi’s analysis and Response surface methodology (RSM). The effect of process parameters on tensile strength and hardness were evaluated using optimization techniques. Applying RSM, the effect of vibratory welding parameters on tensile strength and hardness were obtained through two separate regression equations. Results showed that, the most influencing factor for the desired tensile strength and hardness is frequency at its resonance value, i.e. 300 Hz. The micro-hardness and microstructures of the vibratory welded joints were studied in detail and compared with those of conventional SMAW joints. Comparatively, uniform and fine grain structure has been found in vibratory welded joints.

마찰용접에 의한 드릴 생산에서의 AE에 의한 실시간 품질평가에 관한 연구

오세규(Sae-kyoo Oh),윤인진(In-jin Yoon),오정환(Jung-hwan Oh),오명석(Myeong-seok Oh) 한국해양공학회 1993 韓國海洋工學會誌 Vol.7 No.2

A study off riction welding of high speed steel(SKH 51) bar for blade side to carbon steel (STC 3) bar for shank side was carried out experimentally through tensile test, hardness test, microstructure, and acoustic emission(AE) test.<br/> So, this paper deals with optimizing the welding conditions and the real-time quality (strength) evaluation of friction welded joints by acoustic emission technique.<br/> The results obtained are summarized as follows :<br/> (1) For friction welded joints of SKH 51 to STC 3 steel bars, the total upset (U) increases linearly with an increase of heating time (t₁).<br/> (2) The determined optimum welding conditions are heating time (t₁) 7~9 sec, upsetting time (t₂) 5 sec, heating pressure(P₁) 12 ㎏f/㎟, upsetting pressure(P₂) 15 ㎏f/㎟ and rotating speed(n) 2,000 rpm, resulting in a computed relationship between the tensile strength of the joint σ (㎏f/㎟) and the heating time t₁ (sec) as the following : σ=2.39t₁<SUP>1.382</SUP><br/> (3) The quantitative relationship equation between AE cumulative counts(N) and the tensile strength(a) of the welded joints friction-welded under the obove optimal condition is computed as the following : σ=0.07N<SUP>0.61</SUP><br/> (4) From the quantitative relationship between the accumulated AE total count and the welding strength, it was confirmed that the nondestructive real-time evaluation of welding quality(strength) could be possible.

적외선 열화상 기법을 이용한 용접부의 결함 비파괴 측정기법

박수범(Park, Soo-Beom),오진탁(Oh, Jin-Tak),주영규(Ju, Young K.) 대한건축학회 2017 大韓建築學會論文集 : 構造系 Vol.33 No.11

Recently, the Infrared-Thermography Technique is widely used for nondestructive testing (NDT) of structures due to its convenience. In particular, various techniques have been applied to detect imperfections such as surface defects and welding defects of steel structures. This paper is a part of a study to detect defects in weld zone in steel structures using Infrared Thermography techniques. The temperature on steel structures surface depends on the material and thermal properties such as specific heat, thermal conductivity, and thermal diffusion coefficient. In this study, Infrared thermography technique was used to detect the information on the diagnosis of steel structure in welds. Test specimens were prepared with artificial defects, then the passive and active methods were used to determine damages on the steel structures in welds as well to detect the defects. Finally, defects were observed by comparing infrared thermal image and surface temperature data of defected area with the normal area. Furthermore, the defects were measured using the standard deviation of the temperature corresponding to the weld. For normal weld, the standard deviation of the temperature corresponding to the weld zone was low; although the standard deviation of the weld defects zone was high.

대구경 상수관로의 기존 부분 보수보강 기술 성능평가

이호민,배철호,박정수,정기문 대한상하수도학회 2022 상하수도학회지 Vol.36 No.6

In this study, as the proportion of aged pipelines increases rapidly, in the event of an accident caused by corrosion and structural deterioration of metal pipes, appropriate overlay welding is applied in the field to partially repair it. The size of the base steel plate and the selection of a stable welding method were evaluated, and possible problems caused by the overlay welding were identified, and improvement measures were proposed. For the test, a new steel pipe coated with epoxy lining on the inner surface and polyethylene on the outer surface was subjected to a tensile test by processing the repaired specimen through overlay welding with a steel plate after artificial cracking, and structural safety was evaluated after repair. Furthermore, the influences of the size of the throat and the size of the steel plate were analyzed. As a result of the tensile test by dividing the repaired steel plate overlay into a constraint and non-constraint conditions, the tensile load was concentrated in the welded part and damage occurred in the welded part. It was found that the maximum load leading to breakage increases as the size of the welding throat increases. In addition, it was found that the resistance to load increased slightly as the size of the overlaid steel plate increased, but the effect was not significant, confirming the need for repair in consideration of the site conditions. As a result of evaluating the damage to the coating material on the back side of the welding, it was confirmed that the coating material on the opposite side of the welding burned black(epoxy) or was greatly deformed by heat(polyethylene). Therefore, it is necessary to secure structural stability through repainting, etc. in order to prevent damage to the coating material on the opposite side during overlay welding.

Field Inspection of Phase-Array Ultrasonic for PolyEthylene Electrofusion Joints

Kil, Seong-Hee,Jo, Young-Do,Yoon, Kee-Bong The Korean Institute of GAS 2012 한국가스학회지 Vol.16 No.1

Welding and/or fusion in polyethylene(PE) system made on site is focused on the control of the welding or fusion process to follow proper procedure. The process control is important, but it is not sufficient for the long term reliability of a pipe system. To achieve the rate of failure close to zero, Non Destructive Testing(NDT) is necessary in addition to joining process control. For electrofusion joints several non-destructive testing methods are available. The ultrasonic phased array technique is possible to detect various defects including wire deviations and regions with lack of fusion. In this studies, testing was carried to detect the defect after electrofusion joining of polyethylene piping is utilized by the ultrasonic phased array technique. From testing data, ultrasonic phased array technique is recommended as a reliable non-destructive testing method.

Field Inspection of Phase-Array Ultrasonic for PolyEthylene Electrofusion Joints

Seong Hee Kil,Young Do Jo,Kee Bong Yoon 한국가스학회 2012 한국가스학회지 Vol.16 No.1

Welding and/or fusion in polyethylene(PE) system made on site is focused on the control of the welding or fusion process to follow proper procedure. The process control is important, but it is not sufficient for the long term reliability of a pipe system. To achieve the rate of failure close to zero, Non Destructive Testing(NDT) is necessary in addition to joining process control. For electrofusion joints several non-destructive testing methods are available. The ultrasonic phased array technique is possible to detect various defects including wire deviations and regions with lack of fusion. In this studies, testing was carried to detect the defect after electrofusion joining of polyethylene piping is utilized by the ultrasonic phased array technique. From testing data, ultrasonic phased array technique is recommended as a reliable non-destructive testing method.

계장화 압입시험에 의한 SUS316H판재 GTAW용접부의 기계적 물성치 추정

송기남(Kee Nam Song),김성균(Sung Kyun Kim) 대한기계학회 2018 大韓機械學會論文集A Vol.42 No.8

열영향부 및 용융부를 포함하고 있는 금속 구조물의 용접부는 모재부와 다른 금속조직이 형성되며, 따라서 용접부의 기계적 물성치는 모재부의 그것과는 다를 수 있는데 이는 금속조직의 상이함에 기인하는 것으로 알려지고 있다. 별도의 용접후 열처리를 하지 않은 용접구조물이 하중을 받을 때, 용접구조물의 실제 구조적 거동은 용접부의 상이한 미세조직과 용접열에 의한 잔류응력 등에 의해서 균일한 기계적 물성치로 이루어진 구조물의 거동과는 다를 수 있다. 따라서 용접부의 기계적 물성치에 대한 이해는 용접구조물의 구조적 거동을 신뢰성 있게 평가하기 위한 중요한 첫걸음이다. 본 연구에서는 계장화 압입시험법을 이용하여 SUS316H판재 GTAW용접부의 기계적 물성치를 추정하였다. Different microstructures in the weld zone of a metal structure, including a fusion zone and a heat affected zone (HAZ), are formed compared to the base material. Consequently, the mechanical properties of the weld zone may be different from those of the base material to a certain degree owing to different microstructures. When a welded structure without applying any post-weld heat treatment (PWHT) is loaded, the actual structural behavior of the welded structure might be different from that of a structure with homogeneous mechanical properties owing to the different mechanical properties and residual welding stresses. Therefore, understanding the weld mechanical properties is an important first step for evaluating the structural behavior reliably to some extent. In this study, the GTAW weld mechanical properties of SUS316H plate, such as yield stress and ultimate tensile strength, are estimated using an instrumented indentation technique.