• Title/Summary/Keyword: SHPB

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Unilateral, Single Needle Approach Using an Epidural Catheter for Bilateral Superior Hypogastric Plexus Block

  • Baik, Ji-Seok;Choi, Eun-Joo;Lee, Pyung-Bok;Nahm, Francis Sahn-Gun
    • The Korean Journal of Pain
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    • v.25 no.1
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    • pp.43-46
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    • 2012
  • The superior hypogastric plexus block (SHPB) is used for treating pelvic pain, especially in patients with gynecological malignancies. Various approaches to this procedure have been reported due to the anatomic obstacles of a high iliac crest or large transverse process of the $5^{th}$ lumbar vertebra. Here, we report a new technique of superior hypogastric plexus block using a unilateral single-needle approach to block the bilateral superior hypogastric plexus with a Tuohy needle and epidural catheter. We have confidence that this new technique can be another option in performing the SHPB when the conventional bilateral approach is difficult to perform.

Experimental Studies on Tension, Compression JC Constitutive Equation Parameter of Strain Rate Effect for AISI-4340 (AISI-4340 변형률 속도 변화에 따른 인장, 압축형 JC 구성방정식 변수에 관한 연구)

  • Woo, Sanghyun;Lee, Changsoo;Park, Leeju
    • Journal of the Korea Institute of Military Science and Technology
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    • v.20 no.4
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    • pp.520-527
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    • 2017
  • In this study, the experimental methods are compared for obtaining the parameters of the Johnson-Cook constitutive model. The parameters used for numerical simulation are very important in making an accurate estimation of numerical simulation. So, the testing method of obtaining the parameters is also very important. We compared the difference of conventional method, compression method and tensile method of AISI-4340 steel at various strain rate by using MTS, SHPB and SHTB. Taylor impact test and M&S were carried out to compare differences among these three types of JC constitutive parameter.

A Study on the Damage Assesment of Artificial Brittle Materials subjected to Impact Leading (충격하중을 받은 인공취성재료의 손상평가에 관한 연구)

  • Cho, Sang-Ho;Jo, Seul-Ki;Cheon, Dae-Sung;Synn, Joong-Ho;Yang, Hyung-Sik;Kim, Seung-Kon
    • Tunnel and Underground Space
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    • v.18 no.6
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    • pp.457-464
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    • 2008
  • Dynamic fracture mechanism of rock is important to improve rapid excavation method and develop precise damage assesment of rock mass in the vicinity of an excavation. In order to investigate dynamic fracture characteristics and dynamic damage mechanism of brittle materials, this study employed pulse shape-controlled Split Hopkinson Pressure Bar (SHPB) system. The P- and S-wave velocities of the tested samples were measured before and after tests to examine damage of the samples. The decay ratios of the Ultrasonic wave velocities increased with impart velocities and the samples which have lower strength showed higher permanent strain significantly.

Estimation of Dynamic Brazilian Tensile Strengths of Rocks Using Split Hopkinson Pressure Bar (SHPB) System (스플릿 홉킨슨 압력봉 실험장비를 이용한 암석의 동적 압열인장강도 평가에 관한 연구)

  • Yang, Jung-Hun;Ahn, Jung-Lyang;Kim, Seung-Kon;Song, Young-Su;Sung, Nak-Hoon;Lee, Youn-Kyou;Cho, Sang-Ho
    • Tunnel and Underground Space
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    • v.21 no.2
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    • pp.109-116
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    • 2011
  • In this study, we estimated the dynamic tensile strength and strain rate from Brazilian tensile test using Split Hopkinson Pressure Bar (SHPB) system. A pulse shaping technique, which controls the shape of the impactinduce incident waves, was used for achieving the dynamic stress equilibrium and constant strain rate before fracture of rock samples. Three kinds of rock type, Inada granite, Kimachi sandstone and Tage tuff were prepared as 50mm in diameter and 26 mm in thickness. The high-speed videography system was used to observe the fracture processes of the rock samples. As the results of the tests, the ratio of dynamic tensile strength and static tensile strength was 11.9 for Inada granite, 8.5 for Kimachi sandstone and 9.2 for Tage tuff.

Experimental Study on Deformation and Failure Behavior of Limestones under Dynamic Loadings (동적하중 하에서 석회암의 변형 및 파괴거동에 관한 실험적 연구)

  • Kang, Myoung-Soo;Kang, Hyeong-Min;Kim, Seung-Kon;Cheon, Dae-Sung;Kaneko, Katsuhiko;Cho, Sang-Ho
    • Tunnel and Underground Space
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    • v.22 no.5
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    • pp.339-345
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    • 2012
  • Information on the deformation behavior and fracture strength of rocks subjected to dynamic loadings is important to stability analyses of underground openings underground vibration due to rock blasts, earthquakes and rock bursts. In this study, Split Hopkinson Pressure Bar (SHPB) system was applied to estimate dynamic compressive and tensile fracture strengths of limestone and also examine deformation behavior of limestones under dynamic loadings. A micro-focus X-ray CT scanner was used to observe non-destructively inside the impacted limestone specimens. From the dynamic tests, it was revealed that the limestone have over 140MPa dynamic compressive strength and the strain-rate dependency of the strength. Dynamic Brazilian tensile strength of the limestone exceeds 21MPa and shows over 3 times static Brazilian tensile strength.

Dynamic Shear Stress of Tough-Pitch Copper at High Strain and High Strain-Rate

  • Moon, Wonjoo;Seo, Songwon;Lim, Jaeyoung;Min, Oakkey
    • Journal of Mechanical Science and Technology
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    • v.16 no.11
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    • pp.1412-1419
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    • 2002
  • Dynamic shear tests for the tough-pitch copper at high strain and high strain rate was performed. The Split Hopkinson Pressure Bar (SHPB) compression test system was modified to yield a shear deformation in the specimen. Hat-shaped specimens for the tough-pitch copper were adopted to generate high strain of γ=3~4 and high strain-rate of γ= 10$^4$/s. The dynamic analysis by ABAQUS 5.5/EXPLICIT code verified that shear zone can be localized in hat-shaped specimens. A proper impact velocity and the axial length of the shear localization region wert determined through the elastic wave analysis. The displacement in a hat-shaped specimen is limited by a spacer ring which was installed between the specimen and the incident bar. The shear bands were obtained by measuring the direction of shear deformation and the width of deformed grain in the shear zone. The decrease of specimen length has been measured on the optical displacement transducer. Dynamic shear stress-strain relations in the tough-pitch copper were obtained at two strain-rates.

Waveform characterization and energy dissipation of stress wave in sandstone based on modified SHPB tests

  • Cheng, Yun;Song, Zhanping;Jin, Jiefang;Wang, Tong;Yang, Tengtian
    • Geomechanics and Engineering
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    • v.22 no.2
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    • pp.187-196
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    • 2020
  • The changeable stress environment directly affect the propagation law of a stress wave. Stress wave propagation tests in sandstone with different axial stresses were carried using a modified split Hopkinson Pressure bar (SHPB) assuming the sandstone has a uniform pore distribution. Then the waveform and stress wave energy dissipation were analyzed. The results show that the stress wave exhibits the double peak phenomenon. With increasing axial stress, the intensity difference decreases exponentially and experiences first a dramatic decrease and then gentle development. The demarcation stress is σ/σc=30%, indicating that the closer to the incident end, the faster the intensity difference attenuates. Under the same axial stress, the intensity difference decreases linearly with propagation distance and its attenuation intensity factor displays a quadratic function with axial stress. With increasing propagation distance, the time difference decays linearly and its delay coefficient reflects the damage degree. The stress wave energy attenuates exponentially with propagation distance, and the relations between attenuation rate, attenuation coefficient and axial stress can be represented by the quadratic function.

Investigations on the influence of radial confinement in the impact response of concrete

  • Al-Salloum, Yousef;Alsayed, Saleh;Almusallam, Tarek;Ibrahim, S.M.;Abbas, H.
    • Computers and Concrete
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    • v.14 no.6
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    • pp.675-694
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    • 2014
  • Annular and solid concrete specimens with different aspect ratios and static unconfined compressive strengths were studied for impact loading using SHPB test setup. Numerical simulations in LSDYNA were also carried out and results were validated. The stress-strain curves obtained under dynamic loading were also compared with static compressive tests. The mode of failure of concrete specimen was a typical ductile failure at high strain rates. In general, the dynamic increase factor (DIF) of thin solid specimens was higher than thick samples. In the numerical study, the variation of axial, hydrostatic and radial stresses for solid and annular samples was studied. The core phenomenon due to confinement was observed for solid samples wherein the applied loads were primarily borne by the innermost concrete zone rather than the outer peripheral zone. In the annular samples, especially with large diameter inside hole, the distribution of stresses was relatively uniform along the radial distance. Qualitatively, only a small change in the distribution of stresses for annular samples with different internal diameters studied was observed.

Dynamic Behavior of SM45C at High Strain-rate and High Temperature (고온 고변형률속도에서 SM45C의 동적 거동)

  • Yang, Hyun-Mo;Min, Oak-Key
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.11
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    • pp.1093-1099
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    • 2007
  • A compressive split Hopkinson pressure bar (SHPB) technique is used to investigate the dynamic behavior of SM45C at high temperature. A radiant heater, which consists of one ellipsoidal reflector and one halogen lamp, is used to heat the specimen. Specimens are tested from $600^{\circ}C$ to $1000^{\circ}C$ at intervals of $100^{\circ}C$ at a strain-rate ranging from 1100/s to 1150/s. A critical phenomenon occurs between $700^{\circ}C$ and $750^{\circ}C$ in SM45C. This phenomenon results in the drastic drop in a flow stress. In a modified Johnson-Cook constitutive equation, a reducer function is used to take into account for the effect of the drastic drop in a flow stress. A reducer function, which is dependant on the temperature as well as the strain, is introduced and the parameters of the modified Johnson-Cook constitutive equation are determined from test results.