• Design & Manufacturing
• /
• 제14권4호
• /
• pp.46-51
• /
• 2020

The purpose of this study was to analyze the change in tensile strength characteristics of the weld when the welding speed and rotational speed of the tool, which are representative variables of the friction stir welding process. The equipment used in the experiment was Machining Center No. 5. The material used in the experiment is an AA6061-T6 alloy, and a rolled plate with a thickness of 2mm was used. Two experimental variables were selected, the welding speed of the tool and the rotational speed of the tool. The experimental conditions were selected in the range in which a healthy weld could be obtained through a preliminary experiment. The welding speed of the tool was increased to 100mm/min, 200mm/min, and 300mm/min, and the rotational speed of the tool was increased to 1000rpm, 2000rpm, and 3000rpm. As a result of the experiment, the tensile strength increased as the rotational speed of the tool changed at each tool welding speed. In addition, as the welding speed of the tool increased, the tensile strength of the weld was increased. The condition with the highest tensile strength of the weld was found to be a tool feed speed of 300 mm/min and a tool rotation speed of 3000rpm.

• Journal of Welding and Joining
• /
• 제16권4호
• /
• pp.55-62
• /
• 1998

While excellent joint quality has been obtained using dry chamber underwater welding methods, the size limitations imposed by this process restrict its use for underwater construction work. The wet underwater shielded metal-arc welding eliminates this restriction but suffers from poor weld properties by the 1-pass bead-on-plate welding due to the excessive diffusible hydrogen. On the other hand, in the wet underwater welding, it is well known that the quantity of diffusible hydrogen in multi-pass welded parts reduce to less than that in 1-pass welded parts. Therefore, in this paper, welding experiments are made the 3-pass bead-on-plate welds by using TMCP and normalized steel plates and E4301 and cellulose coated electrode. After that, The amounts of the hydrogen absorbed into the 3-pass welded area were measured according to the JIS Z 3118 specification. The microstructural changes as well as the microhardness distribution after the underwater 3-pass welding were also investigated using Vickers microhardness tester and S.E.M and O.M. The results indicated that the quantity of diffusible hydrogen in 3-pass welded areas was reduced little less than a half of one of that in 1-pass welded areas at the specific welding condition. As a result, the cold cracking of 3-pass welded areas decreased by reduced effect of diffusible hydrogen. In the underwater 3-pass welding, the micrography of cold cracking fracture surface showed mainly the cleavage of hydrogen embrittlement.

• 한국산업정보학회논문지
• /
• 제19권6호
• /
• pp.25-31
• /
• 2014

GMAW(Gas metal arc welding) 방법은 높은 용착률과 낮은 비용으로 인해 제조 산업분야에서 폭넓게 사용되고 있다. 이 용접방법은 제조 산업분야에서 높은 생산력을 유지하는데 바탕이 되고, 자동화 설비 또는 로봇을 이용한 용접에 적합하다. 용접전압과 전류는 용접비드에 많은 영향을 미친다. 그럼에도 불구하고 용접 전압과 전류는 용접 조건과 사용자 환경에 따라 그 변화가 심하고 예측이 불가능하다. 이 값들을 직접 용접 상태 검출에 사용할 수 없기 때문에 적절한 데이터 분석 기법이 사용되어야 한다. 본 논문에서는 용접 중에 측정된 전압과 전류 데이터에 대하여 이동평균필터를 적용하였다. 그 결과 정상용접 상태의 전압 및 전류의 신호특성과 비정상용접 상태의 전압 및 전류 신호의 특성을 구분할 수 있었으며 이를 통해 용접 상태 검출이 가능하게 되었다.

• 한국산학기술학회논문지
• /
• 제14권4호
• /
• pp.2021-2026
• /
• 2013

냉각법은 용접과 동시에 용접토치로 부터 일정한 거리 떨어져 있는 용접부를 냉각기체를 이용하여 냉각시켜 용접변형을 최소화시키는 기술이다. 냉각기체에 의해 용접부의 온도를 감소시키면 용접부에 발생하는 열응력이 감소되고 그 결과 소성변형이 최소화되어 최종적으로 용접좌굴과 각변형을 방지할 수 있는 기술이다. 이 방법은 용접부 표면을 냉각시키는 방법으로 용접부를 직접 냉각시킴으로서 현장 적용성 면에서 다른 용접변형 방지법 보다 효율적이다. 본 연구에서는 맞대기용접을 대상으로 용접 후면의 냉각조건(폭, 길이)을 변화시켜 열탄소성해석을 실시하여 해석적방법으로 용접 각변형에 미치는 영향을 검토하였다. 그 결과 용접토치와 냉각 선단과의 거리는 25mm, 냉각 길이는 80mm, 냉각 폭은 30mm의 경우가 각변형 저감에 제일 큰 효과가 있었다. 이때 냉각길이는 길면 길수록 각변형을 감소시킨다.

• Journal of Welding and Joining
• /
• 제30권5호
• /
• pp.22-26
• /
• 2012

Butt-joints of A6061-T6 and AZ31 plates were successfully manufactured by using a friction stir welding method. Off-set free joints and off-set joints were fabricated to investigate the effect of the tool plunge position on the mechanical properties of the joints. Hardness test, tensile test and charpy impact test was performed to evaluate the mechanical properties of the joints. Off-set condition resulted in increase of mechanical properties of the joints. The variation of the hardness distribution in the SZ was also stabilized in the off-set condition. Tensile strength of the off-set joint was about 85% against to that of the AZ31 base metal. Impact absorption energy by Charpy-Impact-Test of the off-set joint also increased by almost 2 times against to that of the AZ31 base metal.

• Journal of Welding and Joining
• /
• 제16권3호
• /
• pp.95-101
• /
• 1998

Waveforms of $CO_2$ gas shielded arc welding in short circuit transfer mode was studied with the waveform analysis program, which can calculate various waveform factors such as number of short circuit event, mean and standard deviation of short circuit time and arc time. The calculated values of these factors were correlated independently or in combination with the spatter generation rate to figure out the most reliable index for evaluating spatter generation and further for arc stability. As a result this study, it was confirmed that the spatter generation tends to decrease with the increase of short circuit frequency. Further to this, it was also found that as the short circuit frequency increases the short circuit event becomes more uniform resulting in the decrease of standard deviations ($\sigma$values) of short circuit time and arc time. This result demonstrated that these factors are strongly correlated with each other and thus any one of these factors can be used for the evaluation index. In the discussion, however, short circuit frequency was proposed for the most practical index in evaluating the arc stability of short circuit transfer mode since it is the one which could be monitored in-process condition without any complex caculation process.

• Journal of Welding and Joining
• /
• 제29권6호
• /
• pp.49-55
• /
• 2011

With the development of pre-painted steel sheets for automotive body application, a new joining method is required such as hybrid joining with combination of adhesive bonding and mechanical joining. The objective of this study is to investigate the effect of pre- and post-baking of adhesive bonding on failure mode and strength of hybrid joining of automotive steel sheets. Experiments show that the hybrid joining exhibits better bonding strength and displacement than conventional adhesive joining and mechanical fastening each. Comparison of pre- and post-baked hybrid joining results suggested that baking at $160^{\circ}C$ after mechanical joining was found to have higher joining properties than pre-baking condition. The prebaking condition changed its fracture mode from interfacial to button fracture. The changes in fracture mode with post-baking of hybrid joining was attributed to variation in neck thickness and undercut of joint.

• 한국생산제조학회지
• /
• 제22권1호
• /
• pp.92-99
• /
• 2013

The ratio of mobility handicapped was 12,110,000 in late 2009 about 24.4% of total population. The number of handicapped population is increasing continuously due to traffic accidents and industrial disasters. Therefore, the purpose of this research is to suggest a design for passengers on wheelchairs to get into and off to raise handicapped or elderly people's right of mobility. The scope of this research is mobility handicapped especially wheelchair passengers who use vans, small buses, and trains. The ramp design of vans is module form. The ramp is moved with screw jack and guides are installed on each side to increase stability. Moreover, a bridge was installed for smooth getting in and off of the van. The ramp design for small bus is lowed by 200m in order not to have obstacle such as speed bump when getting in or off. In order to reduce vulnerable environment and administration, air slide cylinder was chosen. Lastly, for the ramp design of train, the principle of link was used that the simpler structure made the weight lighter and installation in the train became easier. If we look at the conjugation condition of heterogeneous materials to produce a ramp, proper welding condition for cold steel plate and stainless plate is 3kW output and 3-5m/min of welding speed using laser beam seems proper.

• Journal of Welding and Joining
• /
• 제23권6호
• /
• pp.87-92
• /
• 2005

It has been well hewn that ductile fracture of steels is accelerated by triaxial stresses. The characteristics of ductile crack initiation in steels are evaluated quantitatively using a two-parameters criterion based on equivalent plastic strain and stress triaxiality. The present study focuses on the effects of strength mismatch, which can elevate plastic constraint due to heterogeneous plastic straining, on the critical condition for ductile fracture initiation usinga two-parameter criterion. Fracture initiation testing has been conducted under static loading using notched round bar specimens which had different notch locations. This study provides the fundamental clarification of the effect of strength mismatching and effect of notch location on the critical condition to ductile crack initiation from notch root using fuite element method and ultrasonic-mechatronics system. The critical condition of ductile crack initiation from notch root of strength mismatched tensile specimens under static loading appeared to be almost the same as those of homogeneous tensile specimens with circumferential sharp notch specimen. Also, the effect of notch location in mismatched specimens was estimated using finite element(FE) analyses.

• Journal of Welding and Joining
• /
• 제14권5호
• /
• pp.113-121
• /
• 1996

The arc sensor has been most widely used for weld seam tracking through welding current or voltage variation. In this work, the relation between the arc light intensity and welding condition is investigated using heat balance in the Plasma for its possible application to seam tracking in the GMAW process. The arc light intensity is derived to be the function of the arc length and welding current Experiments are carried out to verify the proposed heat balance model. Performances of least square and integration methods to process the signals for seam tracking are compared experimentally. Predicted arc light intensity shows reasonably good agreement with experimental results. The weld seam is successfully tracked through the arc light intensity. The least square and integration methods demonstrate almost same performance of seam tracking with $CO_2$gas shielding.