• 제목/요약/키워드: dynamic stress intensity factors

검색결과 41건 처리시간 0.025초

등방성체용 동적 광탄성 하이브리드 법 개발에 관한 연구 (A Study on the Development of the Dynamic Photoelastic Hybrid Method for Isotropic Material)

  • 신동철;황재석
    • 대한기계학회논문집A
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    • 제24권9호
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    • pp.2220-2227
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    • 2000
  • In this paper, dynamic photoelastic hybrid method is developed and its validity is certified. The dynamic photoelastic hybrid method can be used on the obtaining of dynamic stress intensity factors and dynamic stress components. The effect of crack length on the dynamic stress intensity factors is less than those on the static stress intensity factors. When structures are under the dynamic mixed mode load, dynamic stress intensity factor of mode I is almost produced. Dynamic loading device manufactured in this research can be used on the research of dynamic behavior when mechanical resonance is produced and when crack is propagated with the constant velocity.

X방향의 선형함수구배인 재료에서 전파하는 균열의 동적응력확대계수 $K_{IIID}$ (Dynamic Stress Intensity Factor $K_{IIID}$ for a Propagating Crack in Liner Functionally Gradient Materials Along X Direction)

  • 이광호
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 추계학술대회논문집A
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    • pp.3-8
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    • 2001
  • Dynamic stress intensity factors (DSIFs) are obtained when a crack propagates with constant velocity in rectangular functionally gradient materials (FGMs) under dynamic mode III load. To obtain the dynamic stress intensity factors, it is used the general stress and displacement fields of FGMs for propagating crack and the boundary collocation method (BCM). The stress intensity factors and energy release rates are the greatest in the increasing properties $(\xi>0)$, next constant properties $(\x=0)$ and decreasing properties $(\xi<0)$ under constant crack tip properties and crack tip speed.

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길이방향의 전단응력을 받은 직교이방성 원판에 내재된 외부균열의 등속전파 응력확대계수 $K_{III}$ (Dynamic Stress Intensity Factor $K_{III}$ of Crack Propagating with Constant Velocity in Orthotropic Disk Plate Subjected to Longitudinal Shear Stress)

  • 최상인
    • 한국자동차공학회논문집
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    • 제4권2호
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    • pp.69-79
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    • 1996
  • Dynamic stress intensity factors are derives when the crack is propagating with constant velocity under longitudinal shear stress in orthotropic disk plate. General stress fields of crack tip propagating with constant velocity and least square method are used to obtain the dynamic stress intensity factor. The dynamic stress intensity factors of GLV/GTV=1(=isotropic material or transversely isotropic material) which is obtained in out study nearly coincides with Chiang's results when mode Ⅲ stress is applied to boundary of isotropic disk. The D.S.I.F. of mode Ⅲ stress is greater when α(=angle of crack propagation direction with fiber direction) is 90° than that when α is 0°. In case of a/D(a:crack length, D:disk diameter)<0. 58, the faster crack propagation velocity, the less D.S.I.F. but when crack propagation velocity arrive on ghear stress wave velocity, the D.S.I.F. but when crack propagation velocity arrive on shear stress wave velocity, the D.S.I.F. unexpectedly increases and decreases to zero.

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스트레인게이지법을 이용한 동적응력확대계수 평가 (Evaluation on dynamic stress intensity factor using strain gage method)

  • 이현철;김덕희;김재훈;문순일
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 추계학술대회논문집A
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    • pp.304-309
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    • 2000
  • Strain gage method is used to evaluate the mode I dynamic stress intensity factor of marging steel(18Ni) and titanium alloy(Ti-6A1-4V). To decide the best strain gage position on specimen, static fracture toughness test was performed. Then instrumented charpy impact test and dynamic tensile test was performed by using strain gage method for evlauating dynamic stress intensity factor. Strain gage signals on the crack tip region are used to calculate the stress intensity factors. It is found that strain gage method is more useful than method by using load which is obtained from impact tup to assess dynamic characteristics such as dynamic stress intensity factor.

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Dynamic Interface Crack Propagating Along a Line Between Two Holes

  • Lee, Ouk-Sub;Park, Jae-Chul;Yin, Hai-Long;Byun, Kwi-Hwan
    • Journal of Mechanical Science and Technology
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    • 제15권2호
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    • pp.172-179
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    • 2001
  • The effects of the interface and two holes located near the crack path in the hybrid specimen on the dynamic crack propagation behavior have been investigated using dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system. The dynamic stress field around the dynamically propagating interface crack tip in the three point bending specimens under a dynamic load applied by a hammer dropped from 0.6m high without initial velocity are recorded. The complex stress intensity factors for the dynamically propagating interface crack are extracted by using a overdeterministic least square method. Theoretical dynamic interface isochromatic fringe loops generated by using the numerically determined complex stress intensity factors are compared with the experimental results. Furthermore, the influence of the hole to the dynamic interface crack velocities has been investigated experimentally.

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Dynamic stress intensity factors for two parallel cracks in an infinite orthotropic plate subject to an impact load

  • Itou, Shouetsu
    • Structural Engineering and Mechanics
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    • 제33권6호
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    • pp.697-708
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    • 2009
  • Stresses are solved for two parallel cracks in an infinite orthotropic plate during passage of incoming shock stress waves normal to their surfaces. Fourier transformations were used to reduce the boundary conditions with respect to the cracks to two pairs of dual integral equations in the Laplace domain. To solve these equations, the differences in the crack surface displacements were expanded to a series of functions that are zero outside the cracks. The unknown coefficients in the series were solved using the Schmidt method so as to satisfy the conditions inside the cracks. The stress intensity factors were defined in the Laplace domain and were inverted numerically to physical space. Dynamic stress intensity factors were calculated numerically for selected crack configurations.

이방성비가 큰 직교이방성체의 반 무한 균열에 대한 동적 응력확대계수에 관한 연구 (Dynamic Stress Intensity Factors of the Half Infinite Crack in the Orthotropic Material Strip with a Large Anisotropic Ratio)

  • 백운철;황재석
    • 대한기계학회논문집A
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    • 제24권6호
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    • pp.1557-1564
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    • 2000
  • When the half infinite crack in the orthotropic material strip with a large anisotropic ratio(E11>>E22) propagates with constant velocity, dynamic stress component $\sigma$y occurre d along the $\chi$ axis is derived by using the Fourier transformation and Wiener-Hopf technique, and the dynamic stress intensity factor is derived. The dynamic stress intensity factor depends on a crack velocity, mechanical properties and specimen hight. The normalized dynamic stress intensity factors approach the maximum values when normalized time(=Cs/a) is about 2. They have the constant values when the normalized time is greater than or equal to about 2, and decrease with increasing a/h(h: specimen hight, a: crack length) and the normalized crack propagation velocity( = c/Cs, Cs: shear wave velocity, c: crack propagation velocity).

Calculation of dynamic stress intensity factors and T-stress using an improved SBFEM

  • Tian, Xinran;Du, Chengbin;Dai, Shangqiu;Chen, Denghong
    • Structural Engineering and Mechanics
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    • 제66권5호
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    • pp.649-663
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    • 2018
  • The scaled boundary finite element method is extended to evaluate the dynamic stress intensity factors and T-stress with a numerical procedure based on the improved continued-fraction. The improved continued-fraction approach for the dynamic stiffness matrix is introduced to represent the inertial effect at high frequencies, which leads to numerically better conditioned matrices. After separating the singular stress term from other high order terms, the internal displacements can be obtained by numerical integration and no mesh refinement is needed around the crack tip. The condition numbers of coefficient matrix of the improved method are much smaller than that of the original method, which shows that the improved algorithm can obtain well-conditioned coefficient matrices, and the efficiency of the solution process and its stability can be significantly improved. Several numerical examples are presented to demonstrate the increased robustness and efficiency of the proposed method in both homogeneous and bimaterial crack problems.

WL-RDCB 시편의 동적 균열전파속도와 동적 응력확대계수 (Dynamic Stress Intensity Factors and Dynamic Crack Propagation Velocities in Polycarbonate WL-RDCB Specimen)

  • 정석주;한민구
    • 한국안전학회지
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    • 제11권3호
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    • pp.3-9
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    • 1996
  • Dynamic fracture characteristics of Polycarbonate WL-RDCB specimen were investigated. The dynamic crack propagation velocities in these specimens were measured by using both high speed camera system and silver paint grid method developed and justified in the INHA Fracture Mechanics Laboratory. The measured crack propagation velocities were fed into the INSAMCR code(a dynamic finite element code which has been developed in the INBA Fracture Mechanics Laboratory) to extract the dynamic stress intensity factors. It has been confirmed that both dynamic crack arrest toughness and the static crack arrest toughness depend on both the geometry and the dynamic crack propagation velocity of specimens. The maximum dynamic crack propagation velocity of Polycarbonate WL-RDCB specimen was found to be dependent on the material property, geometry and the type of loading. The dynamic cracks in these Polycarbonate WL-RDCB specimens seemed to propagate in a successive manner, involving distinguished 'propagation-arrest-propagation-arrest' steps on the microsecond time scale. It was also found that the relat-ionship between dynamic stress intensity factor and dynamic crack propagation velocities might be represented by the typical '$\Gamma$'shape.

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스트레인측정에 의한 응력확대계수 결정 (Determination of Stress Intensity Factors by Strain Measurement)

  • 이억섭;나경찬
    • 한국정밀공학회지
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    • 제12권8호
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    • pp.147-155
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    • 1995
  • Recent experimental studies have been shown that strain gages can be employed to determine either static or dynamic stress intensity factors $K_{I}$ wiht relatively simple experiments. However, it does not usually provide a reliable value of stress intensity factor because of local yielding and limited regions for strain gage placement at the vicinity of the crack tip. This paper attempted to define a valid region and to indicate procedures for locating and orienting the strain gage to determine static toughness $K_{Is}$ accurately form one strain gage readings with respect to varying loadings. The strain gage methods was used for compact tension specimens made of Polycarbonate and PMMA(polymethyl methacrylate). Series expansions of the static and dynamic strain fields are applied. Strain gage orientation and location are then studied to optimize the strain response. Especially, in the dynamic experiment, the specimen employed is an oversized Charpy V-notch specimen which has been modified to provide significant constraint with a large elevation of the flow stress. The impact behavior of the specimen is monitored by placing strain gage near the crack tip. The dynamic toughness $K_{Id}$ is determined from the strain time traces of this gage.e.

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