• 한국수소및신에너지학회논문집
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• 제27권3호
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• pp.311-317
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• 2016

This paper presents the flow characteristics of a ball valve used for a gas pipeline. Understanding of the internal flow of a ball valve is an important to analyze the physical phenomena of the valve. Present experimental study was performed by IEC 60534-2-3, the international standard for an industrial control valve testing procedure. Pressure measured at upstream and downstream of the valve, flow-rate and gas temperature passing the inside of the gas pipeline were measured with respect to valve opening rates. Throughout the experimental measurement of the ball valve, empirical equation of the pressure drop between the ball valve according to the mass flow rates is successively obtained using a polynomial curve fitting method. In addition, flow coefficient for determining the valve capacity is also analyzed with respect to valve opening rates using the curve fitting method.

• 자동차안전학회지
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• 제7권3호
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• pp.14-18
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• 2015

Toughened glass is known to have about four times larger external impact resistance than that of original glass. This study is aimed to verify that ceramic-printed toughened glass does not meet of GTR(Global Technical Regulations) No. 6 and its strength is lower than that of original glass through tests. The tests were conducted on the test pieces of original glass, toughened glass, and ceramic-printed toughened glass from five glass manufacturers. In Test 1, a 227g steel ball was dropped from a height of 2 meters, and damage was checked according to the test method of GTR No. 6. In Test 2, a steel ball was freely dropped from different heights and limited damage height was determined. In the result of Test 1 according to the test method of GTR No. 6, while all five test pieces of toughened glasses were not damaged, all the ceramic-printed toughened glass from the five manufacturers were damaged. In the result of Test 2, none of the five test pieces of toughened glass were damaged by a 10m ball drop, meanwhile, the original glasses were damaged by an average of 3m ball drop. And the results of the tests show that the ceramic-printed toughened glass does not have the features of toughened glass due to its very low strength. Therefore, this study contributes to the safety of consumers by considering the GTR No. 6, and by revising the toughened glass test method.

• 한국건설순환자원학회논문집
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• 제8권4호
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• pp.450-457
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• 2020

본 연구에서는 현장 굴착토를 활용한 속경성 유동성 채움재의 배합요인별 유동성, 재료분리 저항성, 재령별 압축강도 등의 공학적 특성을 검토하여 속경성을 발현하는 배합비 및 결합재 조건을 도출하였으며, 이를 토대로 현장 모사 실험을 실시하여 현장에서 적용 가능한 후속공정 개시기 검토 방법의 유효성을 검토하고자 하였다. Kelly ball 낙하시험과 산중식 토양 경도계의 평가결과 유동성 채움재의 후속공정 개시기 확보 가능한 시간은 동일하게 약 3시간으로 나타났으며, 일축압축강도 시험의 결과와 비교하였을 때 Kelly ball 낙하 시험 및 산중식 토양경도계의 현장 적용성에 대한 유효성을 확인할 수 있었다.

• Advances in concrete construction
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• 제5권2호
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• pp.173-182
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• 2017

This paper is aimed at determining the shear and impact strength of waste plastic fibre reinforced concrete. M30 grade of concrete is prepared with waste plastic door fibres cut into 5 mm width and aspect ratios of 30, 50, 70, 90 and 110. Fibres are used in a volume fraction of 0 to 1.5% with an increment of 0.25%. L shaped specimens are cast for shear strength tests and flat plates of size $250{\times}250{\times}30mm$ are used for impact tests. "Drop ball method" is used for checking the impact strength. Shear strength is checked with L shaped specimens under UTM with a special attachment. It was found that up to 1.25% of waste plastic fibres can be effectively used for better strength of concrete both in shear and impact. Shear and impact strength were found to be increasing up to a volume fraction of fibres of 1.25%.

• 한국생산제조학회지
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• 제23권3호
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• pp.237-242
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• 2014

Recently much research are has been done into the compositions of lead-free solders. As a result, there has been a rapid increase in the number of new compositions. In the past, the properties of these new compositions were determined and verified through drop-impact tests. However, these drop tests were expensive and it took a long time to obtain a result. The main goal of this study was to establish an analytical method capable of predicting the impact life-time of a new solder composition for board-level flip chips though the application of drop simulations using LS-DYNA. Based on the reaction load obtain with LS-DYNA, the drop-impact fracture cycles were predicted. The study was performed using a Sn-3.0Ag-0.5Cu solder (305 composition). To verify the reliability of the proposed analytical method, the results of the drop-impact tests and life-time analysis were compared, and were found to be in good agreement. Thus, the new analytical method was shown to be very useful and effective.

• 한국생산제조학회지
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• 제20권2호
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• pp.193-201
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• 2011

Recently, mechanical reliabilities including a drop test have been a hot issue. In this paper, solder balls with new components which are Sn-3.0Ag-0.5Cu and Sn-1.0Ag-0.5Cu-0.05N are introduced, and board level drop test for them are conducted under JEDEC standard in which the board with 15 flip chips is dropped as 1,500g acceleration during 0.5ms. The drop simulations are studied by using a implicit method in the ANSYS LS-DYNA, and modal analysis is made. Through both analyses, the solder balls with new components are evaluated under the drop. It is found that the maximum stress of each chip is occurred between the solder ball and the PCB, and the highest value among the maximum stresses in the chips is occurred on the chip nearest to fixed holes on the board in the drop tests and simulations.

• Advances in concrete construction
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• 제8권4호
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• pp.305-309
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• 2019

Pervious concrete pavements are the need of the day to avoid urban flooding and to facilitate ground water recharge. However, the strength of pervious or porous concrete is considerably less compared to conventional concrete. In this experimental investigation, an effort is made to improve the strength of pervious concrete by adopting fibres and a small amount of fine aggregate. A porous concrete with cement to aggregate ratio of 1:5 and a water-powder ratio of 0.4 is adopted. 30% of the cement is replaced by cementitious material ground granulated blast furnace slag (GGBS) for better strength and workability. Recron fibres at a dosage of 0.5, 1.0 and 1.5% by weight of cement were included to improve the impact strength. Since concrete pavements are subjected to impact loads, the impact strength was also calculated by "Drop ball method" in addition to compressive strength. The effect of fine aggregate and recron fibres on workability, porosity, compressive and impact strength was studied. The investigations have shown that 20% inclusion of fine aggregate and 1.5% recron fibres by weight of cement give better strength with an acceptable range of porosity.

• 마이크로전자및패키징학회지
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• 제18권2호
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• pp.35-41
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• 2011

Recently, board level solder joint reliability performance of IC packages during drop impact becomes a great concern to semiconductor and electronic product manufacturers. The handheld electronic products are prone to being dropped during their useful service life because of their size and weight. The IC packages are susceptible to solder joint failures, induced by a combination of printed circuit board (PCB) bending and mechanical shock during impact. The board level drop testing is an effective method to characterize the solder joint reliability performance of miniature handheld products. In this paper, applying the JEDEC (JESD22-B111) standard present a finite element modeling of the FBGA. The simulation results revealed that maximum stress was located at the outermost solder ball in the PCB or IC package side, which consisted well with the location of crack initiation observed in the failure analysis after drop reliability tests.

• Design & Manufacturing
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• 제13권3호
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• pp.19-23
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• 2019

In the mold industry, CAM software has been introduced to solve the impossible or time-consuming part of the mold industry because the increase in labor costs, the drop in mold price, and the short delivery time are tasks to be solved not only in the manufacturing industry but also in the mold industry as a whole. In order to reduce the processing time and improve the surface roughness, we have been conducting various researches for efficient machining. This study was carried out to compare the ball end mill and radius end mill tools with the Power mill software and NC brain software under the same conditions and to find out the most efficient method of machining the smooth drafting surface and improving the surface roughness. (1) By machining the smooth drafting surface using radius end mill, the machining time is 23.7% faster than when using ball end mill. (2) Surface roughness when machined with radius end mill is smoother than when using ball end mill. Based on these results, it can not be applied to all shapes, but if it is a relatively wide and simple gradient shape, the raster machining method using radius end mill can be more effective in terms of delivery and quality than machining with ball end mill.

• 한국생산제조학회지
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• 제21권2호
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• pp.225-231
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• 2012

Drop simulations of the board level in the flip chips with solder joints have been highlighted for years, recently. Also, through the study on the life prediction of thermal fatigue in the flip chips considering underfill, its importance has been issued greatly. In this paper, dynamic analysis using the implicit method in the Finite Element Analysis (FEA) is carried out to assess the factors effecting on flip chips considering underfill. The design parameters are size and thickness of chip, and size, pitch and array of solder ball with composition of Sn1.0Ag0.5Cu. The board systems by JEDEC standard is modeled with various design parameter combinations, and through these simulations, maximum yield stress and strain at each chip are shown at the solder balls. Modal analysis is simulated to find out the relation between drop impact and vibration of the board system.