• Title/Summary/Keyword: lack of penetration

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Study on Penetration Performance of Precision Linear Shaped Charge (정밀선상성형장약의 침투·관통 성능에 관한 연구)

  • Lee, Si-Eun;Lee, Juho;Moon, Mi-Ae
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.47 no.6
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    • pp.397-404
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    • 2019
  • Linear Shaped Charge (LSC) that is widely used as separation system in aerospace system has to charge lots of explosives due to lack of uniformity. In addition, it is hard to optimize shape of liner and explosives because of manufacturing process. In order to overcome aforementioned drawbacks, Precision Linear Shaped Charge (PLSC) is currently under development. PLSC is made in two steps: prepare liner independently and charge explosive uniformly. In this study, PLSC is designed to have proper amount of explosives and penetration test of PLSC with different stand-off distance from liner to target is conducted to confirm penetration performance. Based on the penetration test results of PLSC, the numerical analysis method using AUTODYN is established and verified. Penetration mechanism and characteristics of PLSC is analyzed from the numerical and experimental results.

Investigation of Fatigue Strength and Prediction of Remaining Life in the Butt Welds Containing Penetration Defects (블완전용입 맞대기 용접재의 용입깊이에 따른 피로강도특성 및 잔류수명의 산출)

  • Han, Seung Ho;Han, Jeong Woo;Shin, Byung Chun
    • Journal of Korean Society of Steel Construction
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    • v.10 no.3 s.36
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    • pp.423-435
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    • 1998
  • In this paper fatigue strength reduction of butt weld with penetration defect, which can be seen frequently in the steel bridge, was assessed quantitatively. S-N curves were derived and investigated through the constant amplitude fatigue test of fully or partially penetrated welded specimen made of SWS490 steel. The fracture mechanical method was applied in order to calculate the remaining fatigue life of the partially penetrated butt welds. The fatigue limit of the fully penetrated butt welds was higher than that of category A in AASHTO's fatigue design curves, and the slope of S-N curves with 5.57 was stiffer than that of other result for welded part generally accepted as 3. The fatigue strength of the partially Penetrated butt weld was strongly influenced by the size of lack of penetration, D. It decreased drastically with increasing D from 3.9 to 14.7mm. Fracture behaviour of the partially penetrated butt weld is able to be explained obviously from the beach mark test that a semi-elliptical surface crack with small a/c ratio initiates at a internal weld root and propagates through the weld metal. To estimate the fatigue life of the partially penetrated butt weld with fracture mechanics, stress intensity factors K of 3-dimensional semi-elliptical crack were calculated by appling finite elements method and fracture mechanics parameters such as C and m were derived through the fatigue test of CT-specimen. As a result, the fatigue lives obtained by using the fracture mechanical method agreed well with the experimental results. The results were applied to Sung-Su bridge collapsed due to penetration defects in butt weld of vertical member.

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Study for Enhanced Skin Penetration of Cosmetics by Plasma-Sono Stimuli (플라즈마-초음파 자극에 의한 화장품의 피부 침투 증진 연구)

  • Yoonho Hwang;Hyeyoun Cho;Yujin Park;Hwijin Jang;Sanghyo Park;Jaehong Key
    • Journal of Biomedical Engineering Research
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    • v.44 no.4
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    • pp.275-283
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    • 2023
  • The demand for skincare has increased due to the end of the COVID-19 pandemic, leading to a focus on skincare devices and technologies designed to improve the delivery of cosmetics. Among these technologies, skincare medical devices that utilize plasma therapy (Plasma) and sonophoresis (Sono) are commonly used in dermatology clinics. However, there is still a lack of quantitative analysis for transdermal absorption effects of Plasma and Sono skincare medical devices. In this study, we quantified enhanced transdermal absorption effects of Plasma and Sono devices through in-silico and ex-vivo studies. The Sono treatment demonstrated an increased transdermal absorption effect, showing a 10~13% difference in penetration compared to the control group in the in-silico experiment, and 159% and 184% increase in the ex-vivo experiment. The Plasma treatment revealed increased transdermal absorption effects, with a 1.0~2.5% penetration difference in the in-silico experiment, and a 124% increase in the ex-vivo experiment compared to the control group. We also observed a synergistic effect from the combined treatment of Plasma and Sono, as indicated by the highest increases of 197% and 242% in penetration. Furthermore, we have determined the optimal device settings and treatment conditions for Plasma-Sono skincare medical devices. Notably, higher on/off durations (Intensity levels) and longer Sono treatments resulted in greater transdermal absorption effects.

Correlation Analysis between DCPT Value and SPT Value (동적콘관입시험값과 표준관입시험값의 상관성 분석)

  • Lee, Bongjik;Lee, Jongkyu
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.8
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    • pp.23-30
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    • 2014
  • In-situ penetration tests have been widely used in geotechnical engineering for site investigation in support of analysis and design. Standard Penetration Test (SPT) and Dynamic Cone Penetration Test (DCPT) are typical dynamic sounding. DCPT was originally developed as an alternative for evaluating the properties of subgrade soils. The main advantages of DCPT are that it is fast, inexpensive, and it is particularly useful in delineating areas of weak soils overlying stronger strata and in quickly assessing the variability of the soil conditions. But lack of standardization is main reason that this test method has not been advanced more in recent years. In this study, it is clarified the correlation with the SPT blow count, N from DCPT data using big DCP eqipment. Regression analysis and correlationship analysis were conducted with the data from relationship between SPT and DCPT. The analysis results showed that the convert fact are in the range of 1.12~1.31 with variation with soil property.

A Study on Non-contact Penetration and Rebound Measurement Device for Quality Control in Driven Piles (말뚝 시공관리를 위한 비접촉식 관입량 측정장치 활용에 관한 연구)

  • Seo, Seunghwan;Kim, Juhyong;Choi, Changho;Chung, Moonkyung
    • Journal of the Korean Geotechnical Society
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    • v.38 no.11
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    • pp.97-106
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    • 2022
  • The domestic auger-drilled pile method generally manages the driving penetration (set) value with the final stage of construction. The penetration value has been estimated by manual measurement for a long time. The automation technology is yet to be applied due to workability and high-cost limitations, despite safety issues and lack of reliability in measured results. In this study, a non-contact pile penetration measurement device was developed. Further, the field performance was verified by comparing the measurements with a conventional automation device. In addition, the on-site field quality control method was analyzed using the penetration measuring device. The field experiments confirmed that more reliable bearing capacity estimation could calculate the dynamic damping coefficient and the modified Hiley formula with the developed device. Furthermore, it can be used for pile construction management from the bearing capacity viewpoint, even for piles not subjected to dynamic load tests. 

A new rock brittleness index on the basis of punch penetration test data

  • Ghadernejad, Saleh;Nejati, Hamid Reza;Yagiz, Saffet
    • Geomechanics and Engineering
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    • v.21 no.4
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    • pp.391-399
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    • 2020
  • Brittleness is one of the most important properties of rock which has a major impact not only on the failure process of intact rock but also on the response of rock mass to tunneling and mining projects. Due to the lack of a universally accepted definition of rock brittleness, a wide range of methods, including direct and indirect methods, have been developed for its measurement. Measuring rock brittleness by direct methods requires special equipment which may lead to financial inconveniences and is usually unavailable in most of rock mechanic laboratories. Accordingly, this study aimed to develop a new strength-based index for predicting rock brittleness based on the obtained base form. To this end, an innovative algorithm was developed in Matlab environment. The utilized algorithm finds the optimal index based on the open access dataset including the results of punch penetration test (PPT), uniaxial compressive and Brazilian tensile strength. Validation of proposed index was checked by the coefficient of determination (R2), the root mean square error (RMSE), and also the variance for account (VAF). The results indicated that among the different brittleness indices, the suggested equation is the most accurate one, since it has the optimal R2, RMSE and VAF as 0.912, 3.47 and 89.8%, respectively. It could finally be concluded that, using the proposed brittleness index, rock brittleness can be reliably predicted with a high level of accuracy.

The Study on the Performance Prediction of Precision Linear Shaped Charge Using Numerical Analysis Method (수치해석 기법을 이용한 정밀선상성형장약의 성능 예측에 관한 연구)

  • Lee, Sieun
    • Journal of the Korea Institute of Military Science and Technology
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    • v.25 no.3
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    • pp.275-284
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    • 2022
  • Linear Shaped Charge(LSC) is widely used as a separation system in the field of weapon system. However, there are some disadvantages that are charging lots of explosives due to lack of uniformity and having difficulties of the design of liner and explosives because of manufacturing process. In order to solve these problems, Precision Linear Shaped Charge(PLSC) that can design a liner independently and charge explosives uniformly has been developed. In this study, PLSC was designed to have a proper liner shape and amount of explosives, and the penetration test of PLSC with different stand-off distance from liner to target was conducted. On the basis of the penetration test results of PLSC, the numerical analysis method using AUTODYN was established and verified. The penetrative mechanism and characteristics of PLSC with targets of different materials was analyzed from experimental and numerical results.

Skin Friction Properties of SIP Pile through Direct Shear Test (직접전단 시험에 의한 SIP 말뚝의 주면마찰 특성 고찰)

  • 천병식;임해식;김도형
    • Proceedings of the KSR Conference
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    • 2001.10a
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    • pp.558-561
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    • 2001
  • SIP(Soil cement Injected Precast pile) that inserts a precast pile after injecting a cement paste into a boring has been applied rapidly through the change of construction circumstances. But there isnt any logical equation of a bearing capacity fitted to SIP yet. So Meyerhof equation has mainly been used to predict a bearing capacity in a design stage instead. But it has shortcomings such as lack of confidence because it has derived not from a theory but from an experience obtained from the result of SPT (Standard Penetration Test) and because a penetration depth tends to be deeper by an excessive design that depends on an end bearing capacity of a pile more than a skin frictional resistance. In this study, thereupon, a direct shear test in the laboratory was performed to both SM and SC soils in variable conditions to verify skin friction properties for the purpose of presenting some reasons capable of reducing penetration depths. Through the tests, soil to soil of SM in cohesion, rough panel to soil of SM in friction angle and soil to soil of SM in shear strength tended to be high. And a shear strength increased as its total unit weight increased in all cases.

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A study on the technical details of masonry veneer and cavity walls - Focused on the out wyth of clay bricks - (건축물 외부 중공벽의 시공방안에 관한 연구 - 외부 점토벽돌의 사용을 중심으로 -)

  • 양순갑
    • Journal of the Korean housing association
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    • v.8 no.3
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    • pp.219-230
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    • 1997
  • Lack of technical standards, specification and inadequate execution in masonry wall construction in Korea lead to produce serious flaw problems such as crack, efflorescene, and upset etc.. The purpose of this paper is to present the practical details for Masonry cavity wall construction to prevent rain penetration and to accommodate differential movement between the inner and outer wythes of cavity walls. Considering rain penetration and differential movement of both wythes of cavity walls, provision of an adequate air space, an airtight back-up wall, clean cavity with weepholes and vents, properly positioned flashing, tie and shelf angle etc. depend on the cavity wall types will help ensure good performance. The present details included noncorrosive hot dip galvanized steel or stainless steel for metal components, plastic and ultra violet resistant polypropylene Copolymer for other components was taken into account the construction method and several types of cavity walls in Korea

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Fatigue Assessment of Butt Joint with Weld Defect in Steel Bridge (강교 용접 결함부의 피로평가)

  • Juhn, Gui Hyun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.2 no.1
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    • pp.98-107
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    • 1998
  • There are many weld defects such as surface crack, lack of fusion, and imcomplete penetration in the butt joint of the existing steel bridges. The crack-like defects may significantly reduce the fatigue life of the structure. This paper presents the procedure and the results of the fatigue assessment of the butt joints with weld defect in the existing steel girder bridge. The butt joints with imcomple penetration were instrumented with strain gages to determine the stress histogram under normal traffic. Based on the measured stress histogram the crack propagation analyses were performed for the fatigue assesment. By using the suggested procedure and methodology, one can decide the time of periodic inspection and the necessity of repair of the butt joints with serious weld defects in the existing steel bridge.

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