• Journal of Korean Society of Steel Construction
• /
• v.11 no.3 s.40
• /
• pp.319-327
• /
• 1999

This study makes mechanism of the fatigue strength improvement by the processing of weld toe clear for the vertical cross rib specimens which was made fillet weld joint, also it proposes to the appropriate later processing. As a result of tension fatigue test, the fatigue strength improvement could have been seen in later processed specimens than as-weld specimens. Especially fatigue crack initial life $N_c$ increased in specimens which processed grinder after hammer-peening. Also, fatigue crack propagation life $N_p$ improved more in hammer-peening specimens than as-weld or TIG specimens. It thinks that $N_c$ is because of the geometrical shape of weld toe, i.e. the relaxation of the stress concentration and also that $N_p$ is because the big compression residual stress which was introduced in the surface by hammer-peening is restraining the propagation of fatigue crack.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.10
• /
• pp.1305-1313
• /
• 2013

In this study, a method to apply feature-based simplification to boundary representation models is proposed. For feature-based simplification, a volume decomposition tree is created from a boundary representation model. The volume decomposition tree is represented by regularized Boolean operations of additive volumes, subtractive volumes, and fillet/round/chamfer volumes, and it is generated by stepwise volume decomposition, which consists of fillet/round/chamfer decomposition, wrap-around decomposition, volume split decomposition, and cell-based decomposition. After the volume decomposition tree is transformed to an infix expression, the CAD model can be simplified by reordering the volumes. To verify the proposed method, a prototype system was implemented, and experiments on test cases were conducted. From the results of the experiments, it is verified that the proposed method is useful for simplifying CAD models based on boundary representation.

• Journal of Korean Society of Steel Construction
• /
• v.21 no.1
• /
• pp.55-62
• /
• 2009

Blast cleaning has been applied in steel bridges for cleaning forged surface and increasing adhesive property of applied coating systems. Blasting is the operation of cleaning or preparing a surface by forcible propelling a stream of abrasive metals against it. Blast cleaning may improve surface geometry and induce compressive residual stress, and eventually may increase fatigue life of weld joints. In this paper, fatigue tests were carried out on three types of non-load-carrying fillet welded cruciform joints, as-welded joints, blast-treated joints, and stress-relieved joints after blasting, in order to investigate effect of blast cleaning on fatigue behavior of the weld joints. By Blast cleaning, the weld toe radius was increased by 29% and compressive residual stress was induced near weld toes. Blast cleaning increased fatigue life and fatigue endurance limit of the weld joints. When the applied stress ranges decreased, the increment in fatigue life became larger. About a 150% increase in fatigue limit could be realized by using blast cleaning.

• Journal of Ocean Engineering and Technology
• /
• v.18 no.6 s.61
• /
• pp.79-83
• /
• 2004

The curved blocks which compose the bow and stem of a ship contain many skewed joints that are inclined horizontally and vertically. Most of these joints have a large fitness error and are continuously changing their form and are not easily accessible. The welding position and parameter values should be appropriately set in correspondence to the shape and the inclination of the joints. The welding parameters such as current, voltage, travel speed, and melting rate, are related to each other and their values must be in a specific limited range for the sound welding. These correlations and the ranges are dependent up on the kind and size of wire, shielding gas, joint shape and fitness. To determine these relationships, extensive welding experiments were performed. The experimental data were processed using several information processing technologies. The regression method was used to determine the relationship between current voltage, and deposition rate. When a joint is inclined, the weld bead should be confined to a the limited size, inorder to avoid undercut as well as overlap due to flowing down of molten metal by gravity. The dependency of the limited weld size which is defined as the critical deposited area on various factors such as the horizontally and vertically inclined angle of the joint, skewed angle of the joint, up or down welding direction and weaving was investigated through a number of welding experiments. On the basis of this result, an ANN system was developed to estimate the critical deposited area. The ANN system consists of a 4 layer structure and uses an error back propagation learning algorithm. The estimated values of the ANN were validated using experimental values.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.30 no.2
• /
• pp.131-139
• /
• 2024

In Korea, mackerel is the most preferred red fish commodity and has been increasingly consumed in chillstored fresh state rather than in frozen or salted fish. Modified atmosphere packaging (MAP) technology as a replacement of air with low O₂ and high CO₂ concentration gas was applied in this study to preserve its freshness. Four MAP conditions of CO₂(60):O₂(30):N₂(10), CO₂(60):O₂(5):N₂(35), CO₂(60):O₂(0):N₂(40), and CO₂(30):O₂(0):N₂(70) were compared in quality preservation effect with air package used as Control. Three hundred grams mackerel fillets packaged in gas barrier tray were stored for duration of 10 days at 5℃. Quality was assessed in total aerobic bacterial count, pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid-reactive substances (TBARS), peroxide value (POV), texture, and surface color. High CO₂ concentration MAPs (CO₂(60):O₂(30):N₂(10), CO₂(60):O₂(5):N₂(35), and CO₂(60):O₂(0): N₂(40)) inhibited total aerobic bacteria growth in the fish fillets. MAPs of high CO₂ concentration with O₂ containment (CO₂(60):O₂(30):N₂(10) and CO₂(60):O₂(5):N₂(35)) showed a low TVB-N content through the storage. The treatments containing O₂ above 20% (Control and CO₂(60):O₂(30):N₂(10)) showed more accelerated increases in TBARS and POV than other treatments. The visual appearance was better for fillets in the packages of CO₂(60):O₂(5):N₂(35), CO₂(60):O₂(0):N₂(40), and CO₂(30):O₂(0):N₂(70) than for those of other treatments. The MAPs of CO₂(60):O₂(5):N₂(35) and CO₂(60):O₂(0):N₂(40) are expected to be effective in keeping the freshness of mackerel fillets.

• Journal of Welding and Joining
• /
• v.30 no.6
• /
• pp.86-91
• /
• 2012

Fatigue tests and analyses were carried out to investigate fatigue strength and crack initiation point of load-carrying asymmetric double bevel cruciform welded joints. Mesh-insensitive structural stress approach was adopted to estimate high precise fatigue life and crack initiation point. Two different case material and weld shape were considered in this study. Results of fatigue tests and analyses were compared and discussed in consideration of applicability of structural stress approach as the reliable fatigue assessment method of cruciform welded joints.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.20 no.4
• /
• pp.17-24
• /
• 1983

In this study, it was investigated the distribution of residual stress in the direction of loading between the root and toe the load fillet welds for thick steel plate. Residual stress distributions are measured by sectioning method which is one of stress-relaxation technique in welded joint, and analyzed by two dimensional finite element method on thermo-elasto-plastic theory under plane stress condition. These are compared the results of F.E.M analysis with the experimental result by stress-relaxation techniques. As a results, the following conclusion were obtained. (1) In the no penetration fillet welded joint specimen using mild steel plate with 25mm in thickness, the residual stress of loading direction near the root was about $10kg/mm^2$ tensile. (2) The tensile residual stress has been observed in fillet region of the fillet joint by F.E.M. analysis method. (3) The range of compressive residual stress distribution from the root was largest in the case of 5mm root penetration.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.6 no.2
• /
• pp.9-16
• /
• 2007

The fatigue test of the fillet weldments were executed with different groove angles and porosity. The groove angles of $90^{\circ}$, $45^{\circ}$ and $55^{\circ}$ were compared with fatigue lives. After the fillet weldment failure, the porosity which found at the fractured surface were observed to account the effect on fatigue life. Finite element analysis were performed to correlate the fatigue strength and the size & the location of porosity. The stress-strain field were severely affected by the length of notch and the size & location of porosity. Based on the quantitative analysis of porosity effect, the total volume of porosity was key factor for fatigue strength of the fillet weldment.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2002.04a
• /
• pp.8-11
• /
• 2002

In this study, Automatic design program creates 3D solid models and constructs them. The method of making assembly model is two. One assembles the element made in automatic design program with hand, the other develops the automatic design program for creating assembly model. Automatic design program improves the convenience of user. In creating gears, involute ewe and Trochoidal fillet curve are made by mathematical development.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.10a
• /
• pp.231-231
• /
• 2003

사출성형에서의 지금까지의 에어트랩 문제의 해결법은 사출금형 내에 유동적 관계와 사출성형 기술자의 경험으로 해결했었다. 본 연구에서는 에어트랩 문제를 해결하기 위하여 금형을 설계할 때 미리 에어트랩의 위치를 알고 금형 디자인을 수정하여 사출 시간의 단축과 사출성형의 경제적 효과를 얻고자 한다. 사출성형을 할 때 에어트랩의 불량이 많이 발생하는 특징 형상들을 선정하여 각각의 특징형상들을 다시 해석하여 각각의 특징형상들의 에어트랩의 발생위치와 발생률을 알아내고, 사출금형설계에서 에어트랩불량이 일어날 형상들을 특징형상 변수에 대응시켜 최적의 형상으로 수정절차를 개발하였다. 여기서, 사출속도의 조절, 금형 온도의 조절, 수지온도 조절, 금형내의 압력 조절, 벤트의 설치 등은 최적의 상태로 고정시키고 형상수정 요소로 형상의 두께, 각도, 깊이, 필렛, 모 따기를 선정하여 특징형상 상관관계 모델을 구성하였다.