• Title/Summary/Keyword: 초기크랙길이

Search Result 13, Processing Time 0.026 seconds

A Study on the Interlaminar Fracture Toughness of Hybrid Composites (하이브리드 복합재료의 층간파괴인성치에 관한 연구)

  • Kim, Hyung-Jin;Gwark, Dae-Won;Lee, Hern-Sik;Kim, Jae-Dong;Koh, Sung-Wi
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.40 no.4
    • /
    • pp.328-336
    • /
    • 2004
  • This paper describes the effect of loading rate, specimen geometries and material properties for ModeⅠ and Mode Ⅱ interlaminar fracture toughness of hybrid composite by using double cantilever beam (DCB) and end notched flexure (ENF) specimen. In the range of loading rate 0.2~20mm/min, there is found to be no significant effect of loading rate with the value of critical energy release rate (Gc).The value of Gc for variation of initial crack length are nearly similar values when material properties are CF/CF and GF/GF, however, the value of Gc are highest with the increasing intial crack length at CF/GF. The SEM photographs show good fiber distribution and interfacial bonding of hybrid composites when the moulding is the CF/GF.

A Study on Mode I Interlaminar Fracture Toughness of Hybrid Composites (하이브리드 복합재료의 모드 I 층간파괴인성치에 관한 연구)

  • 김형진;곽대원;김재동;고성위
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.39 no.4
    • /
    • pp.262-268
    • /
    • 2003
  • This paper describes the effect of loading rate, specimen geometries and material properties for Mode I interlaminar fracture toughness of hybrid composite by using double cantilever beam (DCB) specimen. In the range of loading rate 0.2-20mm/min, there is found to be no significant effect of loading rate with the value of critical energy release rate (G_IC). The value of $G_IC$ for variation of initial crack length are nearly similar values when material properties are CF/CF and GF/GF, however, the value of $G_IC/$ are highest with the increasing initial crack length at CF/GF. The SEM photographs show good fiber distribution and interfacial bonding of hybrid composites when the moulding is the CF/GF

A Study On the Rrobabilistic Nature of Fatigue Crack Propagation Life(I) -The Effect of Distribution of Initial Crack Size- (피로크랙 진전수명의 확률특성에 관한 연구 I -초기크랙길이 분포의 영향-)

  • 윤한용
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.14 no.1
    • /
    • pp.138-144
    • /
    • 1990
  • In order to understand the probabilistic nature of fatigue crack propagation, not only the calculation of failure probability and parameter sensitivity, but also the clarification of probabilistic nature of various parameters should be executed. Therefore a method to evalute synthetically the effect of each parameter on the distribution of fatigue crack propagation life is required. In this study, the effects of the initial crack size and other paramaters on the distribution of fatigue crack propagation life are discussed according to the appropriate normalization of the life distribution, the validity of this method is also shown. Such an investigation as the present work may be useful to understand the nature of the life distribution and to utilize the probailistic fracture mechanics.

A Study on the Probabilistic Nature of Fatigue Crack Propagation Life(III) - A Method for Uncertainty Evaluation of Crack Propagation Rate - (피로크랙 진전수명의 확율특성에 관한 연구(III) - 크랙진전속도의 불확정성 평가수법 -)

  • 윤한용
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.15 no.5
    • /
    • pp.1635-1639
    • /
    • 1991
  • 본 연구에서는 제1보에서의 수법을 이용하여 초기크랙길이의 분포를 고려한 재료의 불확정성 평가수법을 제시하고자 한다.

Finite Element Based Edge Crack Analysis of Silicon-Steel Sheet in Cold Rolling (실리콘 강판 압연시 에지크랙 발생에 관한 유한요소해석)

  • Byon, Sang-Min;Lee, Jae-Hyun;Kim, Sang-Rok;Jang, Yun-Chan;Na, Doo-Hyun;Lee, Jong-Bin;Lee, Gyu-Taek;Song, Gil-Ho;Lee, Sung-Jin
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.22 no.6
    • /
    • pp.511-517
    • /
    • 2009
  • In this paper an finite element approach for the edge crack analysis of silicon-steel sheet during cold rolling is presented. Based on the damage mechanics, the proposed approach follows the analysis steps which are composed of damage initiation, damage evolution and fracture. Through those steps, we can find out the initiation instant of crack and resulting propagated length and shape of the crack. The material constants related to fracture is experimentally obtained by tension tests using standard sheet-type specimen and notched sheet-type specimen. To evaluate the prediction accuracy, we performed a pilot rolling test with a initially notched sheets. It is shown that the results obtained by the approach converged to the experimental one concerning about the direction and length of propagated crack. The capability of the proposed one is demonstrated through the application to the actual silicon-steel rolling mill.

Finite Element Analysis of Edge Fracture of Electrical Steel Strip in Reversible Cold Rolling Mill (가역식 냉간 압연기에서 전기강판의 에지 파단에 관한 유한요소해석)

  • Byon, Sang Min
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.36 no.12
    • /
    • pp.1619-1625
    • /
    • 2012
  • An electrical steel strip is commonly used as a core material in all types of electric transformers and motors. It is produced by a cold rolling process. In this paper, a damage-mechanics-based approach that predicts the edge fracture of an electrical steel strip during cold rolling is presented. We adopted the normal tensile stress criterion and the fracture energy method as a damage initiation criterion and a damage evolution scheme, respectively. We employed finite element analysis (FEA) to simulate crack initiation and propagation at the initial notch located at the edges of the strip. The material constants required in FEA were experimentally obtained by tensile tests using a standard and a notched sheet-type specimen. The results reveal that the edge crack was initiated at the entrance of the roll bite and that it rapidly evolved at the exit. The evolution length of the edge crack increased as the length of the initial notch as well as the front tension reel force of the strip increased.

A Study on the Fatigue Strength Evaluation of Sintered Spur Gears (소결치차의 피로강도평가에 관한 연구)

  • Lyu, Sung-Ki;Katsmi, Inoue
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.16 no.8
    • /
    • pp.106-112
    • /
    • 1999
  • It is very important to have exact informations on the properties and characteristics of the sintered steel as a new material of machine elements. The bending fatigue tests are performed for the sintered steel bend specimens of various densities 6.6 to 7.0 g/$cm^3$ and the sintered spur gear to consisted of Fe-Cu-C. The fatigue test at a constant stress amplitude is performed by using an electrohydraulic servo-controlled pulsating tester. Consequently, the S-N curves are obtained. The fatigue strength S for fatigue life N of the specimen with the initial length of crack ai is simulated, and they are shown as N-S-A curves. This study investigate the crack growth characteristics by experiments and present crack growth simulation method for sintered gear

  • PDF

A Study on Mode II Interlaminar Fracture Toughness of Hybrid Composites (하이브리드 복합재료의 모드II 층간파괴인성치에 관한 연구)

  • 김형진;박명일;곽대원;김재동;고성위
    • Journal of Ocean Engineering and Technology
    • /
    • v.16 no.4
    • /
    • pp.42-47
    • /
    • 2002
  • This paper describes the effect of loading rate, specimen geometries and material properties for Mode II interlaminar fracture toughness of hybrid composite by using end notched flexure(ENF) specimen. In the range of loading rate 0.5~2mm/min, there is found to be no significant effect of loading rate with the value of critical energy release rate( $G_{IIc}$). there is no dependence of the interlaminar fracture energy upon the specimen width over the specimen widths examined. The value of $G_{IIc}$ for variation of initial crack length are nearly similiar values when material properties are CF/CF and GF/GF, however, the value of $G_{IIc}$ are highest with the increasing intial crack length at CF/GF. The values of $G_{IIc}$ for variation material properties are higher with the increasing moulding pressure when moulding pressures are 307, 431, 585㎪. The SEM photographs show good fiber distribution and interfacial bonding of hybrid composites when the moulding is the CF/GF.e CF/GF.

An Experimental Study on the Durability and Load Carrying Capacity of RC Structure Repair System Using FR-ECC (고인성 내화보수모르터(FR-ECC)를 활용한 RC 구조물 보수공법의 내구성능 및 내하력에 관한 실험적 연구)

  • Kim, Jeong Hee;Lim, Seung Chan;Kim, Jae Hwan;Kwon, Yung Jin
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.16 no.2
    • /
    • pp.75-86
    • /
    • 2012
  • This paper presents some research results on the shrinkage characteristics and frost resistance before and after cracking of FR-ECC(Fire Resistance-Engineered Cementitious Composite). Also, a waterstop performance and exfoliating resistance of multi-layer lining specimens using FR-ECC and flexural performance of beam member by repaired FR-ECC are estimated in this paper. Experimental results indicate that the plastic shrinkage crack and length change ratio of FR-ECC have been reduced as compared with that of the existing repair mortar, and that its crack resistance on the dry shrinkage is improved under the confining stress. As well as FR-ECC has been great in the frost resistance and its tensile properties under the cracked state have been not reduced by freezing and thawing reaction. In addition, beam member by repaired FR-ECC have been increased in the flexural properties such as initial crack moment, yeild moment, and its crack width has been controled in a stable by the frexural failure.

A study on Twofish Cryptoalgorithm Design for Security in the PC Peripheral devices (PC 주변기기에 대한 보안성을 위한 Twofish 암호알고리즘 설계에 관한 연구)

  • Jeong, Woo-Yeol;Lee, Seon-Keun
    • The Journal of the Korea institute of electronic communication sciences
    • /
    • v.2 no.2
    • /
    • pp.118-122
    • /
    • 2007
  • The previous security system was PCI way which has many difficulties for PC novices to use. Moreover the security programs in use are mostly unverified ones as they are using cracks, and are exposed to attacks such as hackers and viruses. Therefore this thesis describes to design the security system of Twofish cryptographic algorithm using USB, which it can be used in general-purpose computers and users can handle it with ease. Users can easily use the security system by using this USB and it is applicable to various security systems that Twofish cryptographic algorithm used in the security system by having variable key length. Also the efficiency of the system can be enhanced as it can perform both encryption and decryption and it has a benefit of downsizing hardware.

  • PDF