• Journal of Korea Foundry Society
• /
• v.22 no.1
• /
• pp.17-25
• /
• 2002

Recently, many studies have been carried out to process on the purpose of lightness in a transport parts because of the saving energy, the environmental problem. The cast-forging process can be expected to lower costs without decreasing the mechanical properties. So, the finest microstructure is needed to get for applying the cast-forging process with Al-Si alloy because the microstructure affects to the cast-forging process. For refinement treatment of eutectic Si and Al solid-solution phase, Sr and TiB were added in Al-Si alloys. The finest microstructure could be observed when 0.075 wt.%Sr and 0.1 wt.%TiB were added respectively. In this case, tensile strength and elongation much more increased than as casting. After high temperature deformation simulation test with grain refinement specimens was carried out, about 70N per unit $area(mm^2)$ of specimen was confirmed. After hot forging, tensile strength and elongation were increased. It was considered because casting defect was removed by compressive working.

• Journal of Korea Foundry Society
• /
• v.22 no.1
• /
• pp.26-34
• /
• 2002

For application of cast-forging process with Al-Si alloys, casting experiments are carried out by adding Sr and TiB to Al-Si alloys for grain refinement treatment. We experimented on the mechanical properties according to microstructural changes, forging ability test and also investigated the mechanical properties after forging. The finest microstructure could be observed respectively when 0.05 wt.%Sr and 0.1 wt.%TiB were added. In this case, tensile strength and elongation increased much more than as casting. After high temperature deformation simulation test with grain refinement specimens was carried out, about 60N per unit $area(mm^2)$ of specimen was confirmed. After hot forging, tensile strength and elongation were increased. It was considered that casting defect was removed by compressive working.

• Journal of Korea Foundry Society
• /
• v.19 no.1
• /
• pp.47-53
• /
• 1999

Squeeze casting process has been used in the field of a commercial manufacturing method, in which metal is enforcedly solidified under pressure enough to prevent the cast defects such as either gas porosity or shrinkage defect. In this paper, to clarify the relationship between applied pressures and macro ${\cdot}$ microstructural behaviors in gravity and direct squeeze casts, specimens were cast by various squeezing pressures during solidification of 7000 series Al wrought alloy in the metal die designed specially. The applied pressures used in this study were 0, 25, 50, and 75 MPa. The microstructural morphologies of squeeze cast were more fine and dense with increasing the applied pressures, because of the greater solidification rate of billet resulting from the applied pressure. A normal segregation phenomenon of an increasing in amount of eutectics towards the center of the billet was observed for squeeze casts, whereas gravity cast showed an inverse segregation phenomenon of an increasing in amount of eutectics towards the edge in the billet. This change in segregation pattern which is normal or inverse is due to a higher radial temperature gradient and reduced time in the semi solid state for squeeze casting.

• Journal of the Korean Ceramic Society
• /
• v.36 no.11
• /
• pp.1252-1260
• /
• 1999

The defect chemistry and electrical characteristics of the grain boundaries of semiconducting SrTiO3 ceramics synthesized with wet-chemically surface-coated powders were investigated. The starting powders were separated into groups of 1-10${\mu}{\textrm}{m}$ 10-20${\mu}{\textrm}{m}$ etc by sedimentation and sieving methods. Na+ ions were absorbed on the powder surfaces by wet chemical-treatment method. The width of the grain boundary ranged up to several nm and the intergranular materials was amorphous. The additives coated on the surface of the powders were observed to be present at the grain boundaries of the ceramics. The diffusion depth of the additives into grains was about 30nm for the SrTiO3 ceramics synthesized with 5w/o coated materials, The threshold voltage grain boundary resistance and boundary potential barrier of the ceramics increased from 0.67V/cm 2.27k$\Omega$ and 0.05eV to 80.9V/cm 13.0k$\Omega$ 1.44eV with increasing the amount of the additives from 0 to 5 w/o respectively .

• Journal of Institute of Control, Robotics and Systems
• /
• v.22 no.1
• /
• pp.59-65
• /
• 2016

As modern electronic devices get smaller and smaller, high-resolution, large Field-Of-View (FOV), fast, and cost-effective 3-dimensional (3-D) measurement is requested more and more. In particular, defect inspection machines using machine-vision technology nowadays require 3-D inspection as well as the conventional 2-D inspection. Phase Measuring Profilometry (PMP) is one of the fast non-contact 3-D shape measuring methods currently being extensively investigated in the electronic component manufacturing industry. The PMP system is well known and is successfully applied to measuring complex surface profiles with varying reflectance properties. However, for highly reflective surfaces, such as Ball Grid Arrays (BGAs), it has difficulty accurately measuring 3-D shapes. In this paper, we propose a new fast optical system that can eliminate the highly reflective saturated regions in BGA ball images. This is achieved by utilizing four Low Intensity Grating (LIG) images together with the conventional High Intensity Grating (HIG) images. Extensive experiments using BGA samples show a repeatability of under ${\pm}20um$ in standard deviation, which is suitable for most 3-D shape measurements of BGAs.

• Journal of Welding and Joining
• /
• v.34 no.6
• /
• pp.16-19
• /
• 2016

Needs for structural integrity procedure such as BS 7910, the nuclear industry document R6 Rev.4 and the European FITNET procedure are being increased in industry. Especially, BS 7910 allows metallic structures to be assessed on the basis of fracture mechanics analysis rather than strict adherence to design and fabricated codes. This study is to propose the flaw assessment to judge the toughness level of welding consumables at the development stage. The FCA welding consumables with YP 690MPa and CTOD over 0.25 mm have been developed and its allowable weld flaw size considering actually applied environment has been evaluated. Since the estimated allowable defect size is sufficiently detectable in nondestructive testing, the toughness of the developed material is judged to be appropriate and no problem in securing the structural integrity.

• Structural Engineering and Mechanics
• /
• v.61 no.1
• /
• pp.1-13
• /
• 2017

The effectiveness of the repair scheme for the damaged captive-columns with CFRPs (Carbon Fiber Reinforced Polymer) was investigated in terms of response quantities such as strength, ductility, dissipated energy and stiffness degradation. Two 1/3 scale, one-story one-bay RC (Reinforced Concrete) frames were designed to represent the substandard RC buildings in Turkish building stock. The first one, which is the reference specimen, is the bare frame without infill wall. Partial infill wall with opening was constructed between the columns of the second frame and this caused captive column defect. Severe damage was observed with the concentration of shear cracks in the second specimen columns. Then, the damaged members were repaired by CFRP wrapping and retested. For the three test series, similar reversed cyclic lateral displacement under combined effect of axial load was applied to the top of the columns. Overall response of the bare frame was dominated by flexural cracks. Brittle type of shear failure in the column top ends was observed in the specimen with partial infill wall. It was observed that former capacity of damaged members of the second frame was recovered by the applied repair scheme. Moreover, ultimate displacement capacity of the damaged frame was improved considerably by CFRP wrapping.

• Journal of the Semiconductor & Display Technology
• /
• v.10 no.3
• /
• pp.15-19
• /
• 2011

The performance of the DRAM is strongly dependent on the purity and surface roughness of the TIT (TiN/Insulator/ TiN) capacitor electrodes. Hence, in the present study, we evaluate the effects of organic contamination and change of surface roughness on the cylindrical TIT capacitor electrodes during the wet cleaning process by various analytical techniques such as TDMS, AFM, XRD and V-SEM. Once the sacrificial oxide and PR (Photo Resist) are removed by HF, the organic contamination and surface oxide films on the bottom Ti/TiN electrode become visible. With prolonged HF process, the surface roughness of the electrode is increased, whereas the amount of oxidized Ti/TiN is reduced due to the HF chemicals. In the 80nm DRAM device fabrication, the organic contamination of the cylindrical TIT capacitor may cause defects like SBD (Storage node Bridge Defect). The SBD fail bit portion is increased as the surface roughness is increased by HF chemicals reactions.

• Journal of the Semiconductor & Display Technology
• /
• v.11 no.2
• /
• pp.45-51
• /
• 2012

Multilayer co-extrusion blown film construction is a popular technique for producing plastic films for various packaging industries. Automated detection of defective films can improve the quality of film production process. In this paper, we propose a film inspection system that can detect and classify film defects robustly. In our system, first, film images are acquired through a high speed line-scan camera under an appropriate lighting system. In order to detect and classify film defects, an inspection algorithm is developed. The algorithm divides the typical film defects into two groups: intensity-based and texture-based. Intensity-based defects are classified based on geometric features. Whereas, to classify texture-based defects, a texture analysis technique based on local binary pattern (LBP) is adopted. Experimental results revealed that our film inspection system is effective in detecting and classifying defects for the multilayer co-extrusion blown film construction line.

• Journal of the Semiconductor & Display Technology
• /
• v.12 no.2
• /
• pp.67-72
• /
• 2013

Temperature is a critical parameter in yield improvement for wafer manufacturing. In chemical vapor deposition (CVD) equipment, crack defect in ceramic heater leads to yield reduction, however, there is no suitable ceramic heater fault detection system for conventional CVD equipment. This paper proposes a short-time zero-crossing rate based fault detection method for the ceramic heater in CVD equipment. The proposed method measures the output signal ($V_{pp}$) of RF filter and extracts the zero-crossing rate (ZCR) as feature vector. The extracted feature vectors have a discriminant power and Gaussian mixture model (GMM) based fault detection method can detect fault in ceramic heater. Experimental results, carried out by measured signals provided by a CVD equipment manufacturer, indicate that the proposed method detects effectively faults in various process conditions.