• Title/Summary/Keyword: compression damage

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Effects of cold water immersion and compression garment use after eccentric exercise on recovery

  • Maruyama, Tatsuhiro;Mizuno, Sahiro;Goto, Kazushige
    • Korean Journal of Exercise Nutrition
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    • v.23 no.1
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    • pp.48-54
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    • 2019
  • [Purpose] The combined effect of different types of post-exercise treatment has not been fully explored. We investigated the effect of combined cold water immersion (CWI) and compression garment (CG) use after maximal eccentric exercise on maximal muscle strength, indirect muscle damage markers in the blood, muscle thickness, and muscle soreness score 24 h after exercise. [Methods] Ten men performed two trials (CWI + CG and CON) in random order. In the CWI + CG trial, the subjects performed 15 min of CWI (15℃), followed by wearing of a lower-body CG for 24 h after exercise. In the CON trial, there was no post-exercise treatment. The exercise consisted of 6 × 10 maximal isokinetic (60°·s-1) eccentric knee extensions using one lower limb. The maximal voluntary contraction (MVC) and maximal isokinetic (60°·s-1) strength during knee extension, as well as the indirect muscle damage markers, were evaluated before exercise and 24 h after exercise. [Results] The maximal muscle strength decreased in both trials (p < 0.001), with no difference between them. The exercise-induced elevation in the myoglobin concentration tended to be lower in the CWI + CG trial than in the CON trial (p = 0.060). The difference in the MVC, maximal isokinetic strength, muscle thickness, and muscle soreness score between the trials was not significant. [Conclusion] CWI followed by wearing of a CG after maximal eccentric exercise tended to attenuate the exercise-induced elevation of indirect muscle damage markers in the blood.

Finite element analysis of shallow buried tunnel subjected to traffic loading by damage mechanics theory

  • Mohammadreza Tameh
    • Geomechanics and Engineering
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    • v.38 no.1
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    • pp.57-68
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    • 2024
  • Tunnels offer myriad benefits for modern countries, and understanding their behavior under loads is critical. This paper analyzes and evaluates the damage to buried horseshoe tunnels under soil pressure and traffic loading. To achieve this, a numerical model of this type of tunnel is first created using ABAQUS software. Then, fracture mechanics theory is applied to investigate the fracture and damage of the horseshoe tunnel. The numerical analysis is based on the damage plasticity model of concrete, which describes the inelastic behavior of concrete in tension and compression. In addition, the reinforcing steel is modeled using the bilinear plasticity model. Damage contours, stress contours, and maximum displacements illustrate how and where traffic loading alters the response of the horseshoe tunnel. Based on the results, the fracture mechanism proceeded as follows: initially, damage started at the center of the tunnel bottom, followed by the formation of damage and micro-cracks at the corners of the tunnel. Eventually, the damage reached the top of the concrete arch with increasing loading. Therefore, in the design of this tunnel, these critical areas should be reinforced more to prevent cracking.

Development of Compression and Transmission Technology of GIS-based High Resolution Image Data in Flood Disaster Situation (홍수재난 상황에서 GIS 기반의 고해상도 영상데이터의 압축 및 전송 기술 개발)

  • Lee, Seung Hyeon;Lee, Eung Joon;Choung, Yun Jae
    • Journal of Korea Multimedia Society
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    • v.20 no.7
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    • pp.1038-1045
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    • 2017
  • The increase in frequency and scale of natural disasters is the typical negative examples of the global climate change and the change of the human living environment. The damage caused by natural disasters in particular including human and physical damage is directly linked to the safety and properties of citizens. Besides, damage occurs directly or indirectly to the SOC facility, and the damaged SOC facility violates the citizens' safety rights. Therefore, a plan to provide prompt and effective risk map information by linking a 3D disaster information display system, which handles the information of the damage that may occur to SOC facilities at the time of disasters, with an on-site assistance application is suggested in this study. The prompt provision of risk map information is defined as a dynamic expression technology in this study. It also processes and compresses the system to display disaster information, a spreading system that can utilize on-site information, and a module developed to organically link with the DB system that builds information and relationships. Based on the module, the effective disaster information compression plan will be prepared, and the prompt information transmission system will be secured.

Experimental and numerical investigation on post-earthquake fire behaviour of the circular concrete-filled steel tube columns

  • Wang, Yu-Hang;Tang, Qi;Su, Mei-Ni;Tan, Ji-Ke;Wang, Wei-Yong;Lan, Yong-Sen;Deng, Xiao-Wei;Bai, Yong-Tao;Luo, Wei;Li, Xiao-Hua;Bai, Jiu-Lin
    • Steel and Composite Structures
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    • v.38 no.1
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    • pp.17-31
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    • 2021
  • Post-earthquake fire is a common disaster which causes serious safety issues to infrastructures. This study aims to investigate the residual loading capacities of circular concrete-filled steel tube (CFST) columns under post-earthquake fire experimentally and numerically. The experimental programme contains two loading steps - pre-damage cyclic loading at room temperature and transient state tests with constant compression loads. Three finite element models are developed and validated against the test results. Upon validation, a total of 48 numerical results were generated in the parametric study to investigate the effects of thickness and strengths of steel tube, axial compression ratio and damage degree on the fire resistance of circular CFST columns. Based on the analysis on experimental and numerical results, the loading mechanism of circular CFST columns is discussed. A design method is proposed for the prediction of fire resistance time under different seismic pre-damage and compression loads. The predictions by the new method is compared with the newly generated experimental and numerical results and is found to be accurate and consistent with the mean value close to the unity and a coefficient of variation around 1%.

Residual Strength Estimation of Decayed Wood by Insect Damage through in Situ Screw Withdrawal Strength and Compression Parallel to the Grain Related to Density

  • OH, Sei Chang
    • Journal of the Korean Wood Science and Technology
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    • v.49 no.6
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    • pp.541-549
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    • 2021
  • This paper reports a method to evaluate the residual strength of insect-damaged radiata pine lumber, such as the screw withdrawal strength as a semi-destructive method and a compression parallel to the grain test to assess the density changes after exposure to outdoor conditions. The screw withdrawal strength test was used as a semi-destructive method to estimate the residual density of decayed lumber. A compression parallel to the grain test was applied to evaluate the residual density. Three variables, such as the screw withdrawal strength, compression parallel to the grain, and residual density, were analyzed statistically to evaluate their relationships. The relationship between the residual density and screw withdrawal strength showed a good correlation, in which the screw withdrawal strength decreased with decreasing density. The other relationship between the residual density and compression parallel to the grain was also positively correlated; the compression parallel to the grain strength decreased with decreasing density. Finally, the correlation between the three variables was statistically significant, and the mutual correlation coefficients showed a strong correlation between the three variables. Hence, these variables are closely correlated. The test results showed that the screw withdrawal strength could be used as a semi-destructive method for an in situ estimation of an existing wood structure. Moreover, the method might approximate the residual density and compression parallel to the grain if supplemented with additional data.

Brittle rock property and damage index assessment for predicting brittle failure in underground opening (지하공동의 취성파괴 예측을 위한 암석물성 및 손상지수 평가)

  • Lee, Kang-Hyun;Bang, Joon-Ho;Kim, Jin-Ha;Kim, Sang-Ho;Lee, In-Mo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.4
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    • pp.327-351
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    • 2009
  • Laboratory tests are performed in this paper to investigate the brittle failure characteristics of over-stressed rocks taken in deep depth. Also, numerical simulation performed using that the so-called CWFS(Cohesion Weakening Frictional Strengthening) model is known to predict brittle failure phenomenon reasonably well. The most typical rock types of Korean peninsula - granite and gneiss - were used for testing. Results of uniaxial compression tests showed that the crack initiation stress was about 41 % to 42% of the uniaxial compressive strength regardless of rock types, where as, the crack damage stress of granite was about 75%, and that of gneiss was about 97%. Through the damage-controlled test, strength parameters of each rock were obtained as a function of damage degree. After the peak, the crack damage stress and the maximum stress were decreased, The cohesion was decreased and the friction angle was increased with increase of rock damage. Before reaching the peak, the elastic modulus was slightly increased, while decreased after the peak. Poisson's ratio was increased as the damage of rock proceeds. Comparison of uniaxial compression tests and damage-controlled tests shows the crack initiation stress estimated from the damage-controlled test fluctuated within the range of crack initiation stress obtained from the uniaxial compression test; the crack damage stress was less than that estimated from the uniaxial compression test. In order to predict the critical depth that brittle failure occurs, numerical simulations using the CWFS model were performed for an example site. Material parameters obtained from the laboratory tests mentioned above were used for CWFS simulation. Comparison between the critical depth predicted from the numerical simulation using the CWFS model and that predicted by using the damage index proposed by Martin et al.(l999), showed that critical depth cannot be reasonably predicted by the currently used damage index except for circular tunnels. A modified damage index was proposed by the author which takes the shape of tunnels other than circular into account.

Anisotropic damage modelling of biaxial behaviour and rupture of concrete structures

  • Ragueneau, F.;Desmorat, R.;Gatuingt, F.
    • Computers and Concrete
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    • v.5 no.4
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    • pp.417-434
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    • 2008
  • This paper deals with damage induced anisotropy modeling for concrete-like materials. A thermodynamics based constitutive relationship is presented coupling anisotropic damage and elasticity, the main idea of the model being that damage anisotropy is responsible for the dissymmetry tension/compression. A strain written damage criterion is considered (Mazars criterion extended to anisotropy in the initial model). The biaxial behavior of a family of anisotropic damage model is analyzed through the effects of yield surface modifications by the introduction of new equivalent strains.

A Design Guide for Composite Laminates by the Compressive after Impact Tests (충격후 잔류압축강도시험에 의한 복합재료 적층판의 설계)

  • 정태은;박경하;류정주
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.9
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    • pp.2105-2113
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    • 1995
  • The compressive tests under impact conditions were performed to establish a design guide for impact damage tolerance. The composition of layup was selected for the real cases of composite aircraft structure. The energy level of visible of visible damage threshold was determined as 7 Joules. It was found that the normalized bending stiffnesses in the direction of closely fixed boundary affected the area of damage. Graphite/epoxy used in the tests exhibited 60% reduction in compression strength at the energy level of visible damage threshold. Wet-conditioned specimens represented 9% reduction in residual compressive strength in comparison with room temperature ambient specimens. In this study, a design factor of 2.1 was proposed for the low velocity impact damage.

Effects of Sinusoidal Vibration Fatigue on Compression Strength of Corrugated Fiberboard Container for Packaging of Fruits

  • Jung, Hyun-Mo;Kim, Jong-Kyoung;Kim, Man-Soo
    • KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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    • v.16 no.1
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    • pp.1-4
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    • 2010
  • The compression strength of corrugated fiberboard containers for packaging the agricultural products rapidly decreases because of various environmental conditions during distribution of unitized products. Among various environmental conditions, the main factors affecting the compression strength of corrugated fiberboard are absorption of moisture, long-term accumulative load, and fatigue caused by shock and vibration. An estimated rate of damage for fruit during distribution is about 30~40% owing to the shock and vibration. This study was carried out to characterize the durability of corrugated fiberboard containers for packaging the fruits and vegetables under simulated transportation environment. After the packaging freight was vibrated at various experimental conditions, the compression test for the packaging was performed. The compression strength of corrugated fiberboard containers decreased with loading weight and vibration time. The multiple nonlinear regression equation ($R^2$ = 0.9198) for predicting the decreasing rate of compression strength of corrugated fiberboard containers were developed using four independent variables such as input acceleration level, input frequency, loading weight and vibration time.

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A Study on the Threshing Mechanism of Rasp-Bar Type Thresher -Dynamic Analysis of Threshing Process- (줄봉형 탈곡기의 탈곡장치에 관한 연구 -탈곡과정의 역학적 분석-)

  • Park, K.J.;Clark, S.J.;Dwyer, S.V.
    • Journal of Biosystems Engineering
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    • v.18 no.4
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    • pp.371-381
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    • 1993
  • Threshing operation is performed by impact, compression and friction forces inside the thresher. These values should be appropriate to the crop condition to enhance the threshing and separating efficiency and to decrease the grain damage. To analyze the threshing process inside the rasp-bar type thresher, impact, friction and compression forces were measured using transducers with strain gage circuits. To measure the impact forces and friction forces between the rasp-bar and crop, full bridge strain gage circuit was built on the rasp-bar holder. To measure the compression forces and circumferential friction forces between the concave and crop, two sets of full bridge strain gage circuits were built on the T-type concave transducer. Threshing work of wheat crop with 12% of moisture content was performed at 3 levels of compression ratio and with 3 replications. Each transducer could not measure the exact forces continuously because the transducer oscillates with the forces. However they could measure maximum forces and force distribution according to the time. Average friction coefficients between crop and concave was 0.61 not showing any significant difference according to the compression ratio. Average acceleration of the crop in the cylinder appeared from $70.6m/s^2$ to $140.8m/s^2$ according to the compression ratio. The velocity of the crop at the exit of the cylinder appeared from 10.7m/s to 15.0m/s according to the compression ratio.

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