• Journal of Welding and Joining
• /
• 제20권6호
• /
• pp.99-99
• /
• 2002

In order to evaluate the proper fracture strength of microstructures in a steel weldment, smaller size loading ball than used for a conventional small punch(CSP) testing is required due to regional limitation on constitutive structures. In this study, the minimized loading ball(φ 1.5mm) and bore diameter of lower die(φ 3mm) were designed for an advanced small punch(ASP) test. The results obtained from the ASP test were compared with those from a CSP testing for a X20CrMoV121 steel weldment. It was found that the ASP test clearly showed the microstructural dependance on fracture strength and ductile-brittle transition behavior of the weldment. In the ASP test, especially, the cracks tend to initiate for various directions within hemispherical indentation region of an objective structure in SP test. This indicates that the evaluation of more proper fracture strength for F.L+CGHAZ, FGHAZ and ICHAZ can be performed by means of the ASP test in a steel weldment.

• Journal of Welding and Joining
• /
• 제20권6호
• /
• pp.823-829
• /
• 2002

In order to evaluate the proper fracture strength of microstructures in a steel weldment, smaller size loading ball than used for a conventional small punch(CSP) testing is required due to regional limitation on constitutive structures. In this study, the minimized loading ball(${\varphi}1.5mm$) and bore diameter of lower die(${\varphi}3mm$) were designed for an advanced small punch(ASP) test. The results obtained from the ASP test were compared with those from a CSP testing for a X20CrMoV121 steel weldment. It was found that the ASP test clearly showed the microstructural dependance on fracture strength and ductile-brittle transition behavior of the weldment. In the ASP test, especially, the cracks tend to initiate for various directions within hemispherical indentation region of an objective structure in SP test. This indicates that the evaluation of more proper fracture strength for F.L+CGHAZ, FGHAZ and ICHAZ can be performed by means of the ASP test in a steel weldment.

• 한국재료학회지
• /
• 제27권1호
• /
• pp.53-61
• /
• 2017

Magnesium alloys are of emerging interest in the automotive, aerospace and electronic industries due to their light weight, high specific strength, damping capacity, etc. However, practical applications are limited because magnesium alloys have poor formability at room temperature due to the lack of slip systems and the formation of basal texture, both of which characteristics are attributed to the hcp crystal structure. Fortunately, many magnesium alloys, even commercialized AZ or ZK series alloys, exhibit superplastic behavior and show very large tensile ductility, which means that these materials have potential application to superplastic forming (SPF) of magnesium alloy sheets. The SPF technique offers many advantages such as near net shaping, design flexibility, simple process and low die cost. Superplasticity occurs in materials having very small grain sizes of less than $10{\mu}m$ and these small grains in magnesium alloys can be achieved by thermomechanical treatment in conventional rolling or extrusion processes. Moreover, some coarse-grained magnesium alloys are reported to have superplasticity when grain refinement occurs through recrystallization during deformation in the initial stage. This report reviews the characteristics of superplastic magnesium alloys with high-strain rate and coarse grains. Finally, some examples of SPF application are suggested.

• 소성∙가공
• /
• 제18권1호
• /
• pp.67-72
• /
• 2009

This paper covers finite element simulations to evaluate tube bending process of auto chassis component i.e. trailing-arm product. The rear of the auto chassis structure is primarily composed of CTBA and trailing-arm. When a car rolls into a corner, the trailing arm reacts to roll in the same degree as the car body. During the bending process of trailing arm the tube undergoes significant deformation. Thus forming defects such as excessive thinning and flattening of the tube will be formed in the outside of the tube. In this paper, we analyzed the effect of process parameters in rotary draw bending process and searched the optimized combination of process parameters using orthogonal arrays method to minimize the forming defects. In this process we analyzed several parameters which are displacement of pressure die, boosting force, initial position of mandrel bar, dimensions of mandrel in regarding to the thinning and flattening of the tube.

• 한국주조공학회지
• /
• 제24권6호
• /
• pp.331-339
• /
• 2004

Melt-extrusion process, a metallic melt poured and solidified up to semisolid state in the container can be directly extruded through the die exit to form a product of bar shape without other intermediate processes. In this study, the fabrication characteristics of the process were evaluated with various process parameters, such as preheating temperature of extrusion dies, extrusion temperature and extrusion ratio. AI-Cu alloys were successfully extruded after squeezing out of liquid during melt-extrusion with smaller force compared to the solid extrusion. Soundly AI-Cu alloy bar was fabricated at the preheating temperature of $500{\sim}520^{\circ}C$. The range of extrusion temperature for soundly melt-extruded AI-Cu alloy bar was increased with increasing extrusion ratio. Mechanical properties of melt-extruded AI-Cu alloy bars were found change with Cu content of the melt-extruded bars due to the occurrence of segregation. The various extrusion temperature yielded equiaxed structure with a grains size about 200 ${\mu}m$.

• 한국CDE학회논문집
• /
• 제11권4호
• /
• pp.273-288
• /
• 2006

Information integration of heterogeneous digital parts libraries or electronic pars catalogs is one of issues in B2B procurements. We need to provide an integrated view for multiple information sources. Utilization of ontologies as the metadata descriptions of the information sources can provide an integrated view. However, in order to integrate independently developed ontologies, the mismatches among them should be resolved. In this paper, we propose an ontology of meta-concepts, i.e. meta-ontology. The meta-concepts play the role of vocabulary to describe the parts library ontologies and provide well-established ontological semantics that helps the ontology modelers to consistently identify parts library concepts and systematically structure them. Consequently, the meta-ontology reduces the differences in the way the parts knowledge is interpreted and ensures the mismatches are confined to manageable mis matches, so that a software program can merge automatically. Modeling ontologies of mold and die parts libraries for B2B e-commerce is taken as an example to show how to use the meta-ontology. We also discuss how a parts library mediation system can automatically merge the well-structured parts library ontologies.

• 한국정밀공학회지
• /
• 제16권9호
• /
• pp.25-34
• /
• 1999

In spite of the advance of 3D solid modeling technology, there are some distinct areas where 2D CAD S/W are still dominant, and more competent comparing with 3D CAD S/W. For example, in the manufacturing of 2D-shaped electrical parts, most related manufacturing tools have 2D geometric features by nature, and 3D solid models applied to these parts have substantial overheads. Nevertheless, most 2D CAD S/W have no topological inquiry services because they have no such information on their geometrical database inherently. Thus, it is needed to extract such information from 2D CAD database for developing more advanced application such as automated drafting/design S/W. In this paper, the extraction of topological information from 2D CAD has been performed in general way using concept of B-rep. A general extraction algorithm, data structure and meta file format for 2D topological object have been developed and successfully applied to the development of the automated lead frame die design system in Samsung Aerospace. it is also possible to provide a flexible, powerful topology-oriented functionality on any common 2D CAD S/W.

• 한국레이저가공학회지
• /
• 제18권2호
• /
• pp.1-4
• /
• 2015

This study is related to the surface hardening treatment to spheroidal graphite cast iron for die by using high power diode laser. Laser device used in this experiment is capable of real-time laser power control. This is because the infrared temperature sensor (two color pyrometer) attached to the optical system measures the surface temperature of specimen and adjusts the laser power in real time. The surface treatment was carried out with the change of heat treatment temperature at the beam travel speed 3 mm/sec. Hardened width and depth was measured and hardened zone was analyzed by micro vickers hardness test in order to research the optimum condition of heat treatment. The changes in microstructure of the hardened zone also was examined. As a result of hardness measurement and observations on microstructure of hardened zone, hardness increased over three times as compared with base metal because the martensite was formed on the matrix structure.

• 문화기술의 융합
• /
• 제5권4호
• /
• pp.349-354
• /
• 2019

건설현장에서 추락으로 인해 사망하는 근로자는 전체 사망자의 약 40%를 차지하며 사망사고 주요 발생 형태로 나타나고 있다, 또한 우리나라 인구구성이 점차 고령화됨에 따라 건설현장에서도 고령화 비율이 점점 높아지고 있으며 신체기능 저하 인지능력 저하 등에 따른 추락재해가 점점 증가추세에 있다. 이에 따라 고령 근로자 추락에 미치는 요인에 대하여 설문조사를 실시하였으며 재해 당사자인 고령 근로자에 초점을 맞춰 보다 근본적인 추락 예방대책을 제시하고자 한다.

• Design & Manufacturing
• /
• 제15권3호
• /
• pp.26-31
• /
• 2021

In this study, laser-induced periodic surface structure (LIPSS) was fabricated on Ni, Si, and GaAs samples using a flat-top beam with a uniform energy distribution that was fabricated using a Gaussian femtosecond laser with a mechanical slit and tube lens. Unlike the Gaussian beam, the flat-top beam has a uniform beam profile, therefore the center and the periphery of the fabricated LIPSS have similar line periodicity. In addition, LIPSS was obtained not only in metals but also in metalloids and metals and metalloid compounds by using the narrow pulse width characteristic of a femtosecond laser.