• Journal of Welding and Joining
• /
• 제12권1호
• /
• pp.59-72
• /
• 1994

This paper presents an on-line quality monitoring and control method to obtain a uniform weld quality in gas metal arc welding (GMAW) processes. The geometrical parameters of the weld pool such as the top bead width and the penetration depth plus half back width are utilized to assess the integrity of the weld quality. Since a good quality weld is characterized by a relatively high depth-to-width ratio in its dimensions, the second geometrical parameter is regulated to a desired one. The monitoring variables are the surface temperatures measured at various points on the top surface of the weldment which are strongly related to the formation of the weld pool The relationship between the measured temperatures and the weld pool size is implemented on the multilayer perceptrons which are powerful for realization of complex mapping characteristics through training by samples. For on-line quality monitoring and control, it is prerequisite to estimate the weld pool sizes in the region of transient states. For this purpose, the time history of the surface temperatures is used as the input to the neural estimator. The control purpose is to obtain a uniform weld quality. In this research, the weld pool size is directly regulated to a desired one. The proposed controller is composed of a neural pool size estimator, a neural feedforward controller and a conventional feedback controller. The pool size estimator predicts the weld pool size under growing. The feedforward controller compensates for the nonlinear characteristics of the welding process. A series of simulation studies shows that the proposed control method improves the overall system response in the presence of changes in torch travel speed during GMA welding and guarantees the uniform weld quality.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
• /
• pp.329-334
• /
• 1987

The purpose of this study is to monitor and control the back bead width in arc welding with consumable electrode for reduction of the occurrence of weld defect. The temperature of a point on the weldment surface is selected, as a monitoring parameter, and measured by an optical infra-red sensor. The correlation between the back bead width and the surface temperature is experimentally obtained for various thicknesses of the weldment. The welding travel speed and the surface temperature are taken, respectively, as an input and an output of the welding process under the stable condition of arc. A PI control scheme to maintain the surface temperature at the desired level is proposed by the experimental study.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
• /
• pp.545-550
• /
• 2002

In order to ensure the signal could be transported cocrrectly, the microwave devices made of Aluminmn alloys must be assembled and brazed flaw-freely. In this paper, a new approach of using contact reactive brazing (CRB) process to realize the compact brazing of Aluminum alloys was put forward. The reason for this is that CRB, which realizes bonding depending on the liquid alloy produced by metallurgy reaction between the materials to be joined, overcomes the limitation of traditional brazing that the macroscopically disorganized filling flow of liquid filler metal would result in defects in brazed seam. Joint ofLF21 (AA3003) with the compactness of over 95% was brazed by the method of CRB using Si powder as an interlayer. At last, the influence of the physical parameter related to the Si powder interlayer on the compactness of the joints was investigated in detail.

• Journal of Welding and Joining
• /
• 제16권1호
• /
• pp.77-87
• /
• 1998

This paper deals with the effect of laser welding parameters on the weld formation. Thin steels for automotive application were prepared so as to be welded with high power carbon dioxide laser system. Major process parameters were position of focus and travel speed. The effect of shielding gas was also discussed by employing the high speed photometry. Test results showed that the optimal position of focus varied in accordance with the joint configuration; bead-on-plate, butt or lap welding. It was recommended that the position of focus for the lap welding be located at slightly inner part of the material to be welded. In this case, however, it was noticeable that the weld penetration ratio, d/t$_{0}$ dropped drastically at the critical region. Results also demonstrated that both the bead width and penetration reduced as the travel speed increased. The penetration ratio showed two distinct regions; stabilized zone at the lower range of the travel spped and sudden drop zone at the higher range of travel speed. Lower limit of the penetration for acceptable weld was proved to be about 90% of the parent metal thickness based on the physical properties of the weld. Mixed gas application for both the shielding of molten metal and laser induced plasma control was recommended as far as the penetration was concerned.d.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2000년도 특별강연 및 춘계학술발표대회 개요집
• /
• pp.251-255
• /
• 2000

Recently, the improvement of computer capacities and artificial intelligence ware caused to employ for prediction of residual stresses and strength evaluation. There are a lot of researches regarding the measurement and prediction of residual stresses for weldment using a neural network in the advanced countries, but in our country, a neural network as a technical part, has only been used on the possibilities of employment for welding area. Furthermore, the relationship between residual stress and process parameters using a neural network was wholly lacking. Therefore development of a new technical method for the optimized process parameters on the reduction of residual stress and applyment of real-time production line should be developed. The objectives of this paper is to measure the residual stress of butt welded specimen using strain gage sectioning method and to apply them to a neural network for prediction of residual stresses on a given process parameter. Also, the assessment of the developed system using a neural network was carried out

• Journal of Advanced Marine Engineering and Technology
• /
• 제32권4호
• /
• pp.570-577
• /
• 2008

Magnesium alloys are potentially useful as structural materials due to higher strength/weight ratio, heat conductivity and recyclability compared to other alloys. These alloys have attracted the interest of modern manufacturing such as the automobile, computer, communication and consumer electronic appliances industries. Hence welding techniques are required to be developed for these applications. Laser are known to be an excellent tool for them. This paper presents the laser weldability of AZ31 magnesium alloy with CW Nd:YAG laser. The low viscosity and surface tension of the melt pool make magnesium more difficult to weld than steel. As a result of this study, optimal process parameters could be obtained without weld defects. Also it was certain that cutting methods had influence on butt weldability.

• 한국기계가공학회지
• /
• 제20권3호
• /
• pp.24-32
• /
• 2021

The size of container ships is increasing to increase the cargo loading capacity. However, container ships are limited in terms of the hull longitudinal strength. To overcome this limitation, brittle crack arrest steel can be used. This study was aimed at examining the influence of the heat input on the welding procedures of flux cored arc welding and submerged arc welding. In the experiment, the crack tip opening displacement test, which pertains to a parameter of fracture mechanics, was performed, and a 3-point bending tester was adopted. Based on the results, the crack measurement method was presented, and the stress expansion coefficient value for the pre-fatigue crack length was derived according to the heat input after the pre-cracking length was measured. It was noted that the heat input affected the crack tip opening displacement of brittle crack arrest steel.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제17권2호
• /
• pp.143-149
• /
• 2017

Purpose: In recent years, weight reduction for improving fuel efficiency of the vehicle and cost reduction have been developed. The structure of suspension link is widely used as a single plate press structure which can reduce process and weight compared to existing pipe welding method. However, it was found that the lifetime of a single plate press structure is determined by initial defects that occurred during initial manufacturing rather than fatigue damage caused by driving. Methods: I research the mechanism of failure phenomenon of the single plate press assist arm of rear wheel. In addition, I investigate durability effect parameters to determine the link lifetime in inserting bush into single plate press process through durability test. Conclusion: I discover significant durability effect parameter in inserting bush into single plate press process. It is expected that the durability can be improved by suggesting a bush inserting process inspection guide for similar suspension link like single plate press structure.

• 한국마린엔지니어링학회:학술대회논문집
• /
• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
• /
• pp.29-30
• /
• 2006

나이모닉 일체형으로 사용되고 있는 선박용 2 행정 저속엔진의 배기밸브 스핀들을 고온, 고압, 배기가스 및 반복 충격 하중에 노출된 스핀들의 Head부분은 기존의 나이모닉 소재를 적용, 기존 재질의 우수한 성질을 유지하고 설계적으로 나이모닉 소재의 적용이 불필요한 Stem부는 오스텐나이트 계열의 SNCrW 소재를 사용하여 관성마찰 용접 방식으로 접합하여 제품을 제작하고, 접합부의 미세조직 관찰, 성분분석, 인장, 경도, 피로시험 등의 기계적, 금속적 특성평가를 통해 마찰용접제품에 대한 신뢰성을 확인하고 양산 생산을 위한 기술적 토대를 마련하였다.

• 대한기계학회논문집A
• /
• 제41권4호
• /
• pp.321-327
• /
• 2017

본 연구에서는 수평 자세에서의 TIG 용접 시 반응표면법(RSM)을 이용하여, 최적의 이면비드 형상을 구하는 연구를 진행하였다. 입력변수로는 베이스 전류, 피크 전류, 용접속도를 선정하였고, 이면비드 폭을 용접품질에 관한 출력변수로 하여 목표값을 5.4 mm로 설정하였다. Box-Behnken 실험계획법에 따라 실험을 진행하였고, 비드 폭에 관한 2차 회귀모형을 구한 후, F-테스트를 이용하여 회귀모델을 검정하였다. 그리고 망목특성의 호감도 함수를 사용하여 이면비드 형상을 평가함으로써 최적화를 수행하였다. 이렇게 도출된 최적의 용접조건은 코드화된 값으로 베이스 전류; 0.9204, 피크 전류; 0.8676, 용접속도; 0.3776이었다. 검증실험 결과 목표값에 근접한 5.38 mm의 이면비드 폭을 얻을 수 있었다.