• Title/Summary/Keyword: CT 시험편

Search Result 39, Processing Time 0.029 seconds

On the Statistical Properties of the Parameters B and q in Creep Crack Growth Law, da/dt=B(C*)q, in the Case of Mod. 9Cr-1Mo Steel (Mod. 9Cr-1Mo강의 크리프 균열 성장 법칙의 파라메터 B와 q의 통계적 성질에 관한 연구)

  • Kim, Seon-Jin;Park, Jae-Young;Kim, Woo-Gon
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.35 no.3
    • /
    • pp.251-257
    • /
    • 2011
  • This paper deals with the statistical properties of parameters B and q in the creep crack growth rate (CCGR) law, da/dt=B$(C^*)^q$, in Mod. 9Cr-1Mo (ASME Gr.91) steel which is considered a candidate materials for fabricating next generation nuclear reactors. The CCGR data were obtained by creep crack growth (CCG) tests performed on 1/2-inch compact tension (CT) specimens under an applied load of 5000N at a temperature of $600^{\circ}C$. The CCG behavior was analyzed statistically using the empirical equation between CCGR, da/dt and the creep fracture mechanics parameter, $C^*$. The B and q values were determined for each specimen by the least-squares fitting method. The probability distribution functions for B and q were investigated using normal, log-normal, and Weibull distributions. As far as this study is considered, it can be appeared that B and q followed the log-normal and Weibull distributions. Moreover, a strong positive linear correlation was found between B and q.

Mechanical Properties of Fiber-reinforced Cement Composites according to a Multi-walled Carbon Nanotube Dispersion Method (다중벽 탄소나노튜브의 분산방법에 따른 섬유보강 시멘트복합체의 역학적 특성)

  • Kim, Moon-Kyu;Kim, Gyu-Yong;Pyeon, Su-Jeong;Choi, Byung-Cheol;Lee, Yae-Chan;Nam, Jeong-Soo
    • Journal of the Korea Institute of Building Construction
    • /
    • v.24 no.2
    • /
    • pp.203-213
    • /
    • 2024
  • This study delves into the mechanical properties of fiber-reinforced cement composites(FRCC) concerning the dispersion method of multi-walled carbon nanotubes(MWCNTs). MWCNTs find utility in industrial applications, particularly in magnetic sensing and crack detection, owing to their diverse properties including heat resistance and chemical stability. However, current research endeavors are increasingly directed towards leveraging the electrical properties of MWCNTs for self-sensing and smart sensor development. Notably, achieving uniform dispersion of MWCNTs poses a challenge due to variations in researchers' skills and equipment, with excessive dispersion potentially leading to deterioration in mechanical performance. To address these challenges, this study employs ultrasonic dispersion for a defined duration along with PCE surfactant, known for its efficacy in dispersion. Test specimens of FRCC are prepared and subjected to strength, drawing, and direct tensile tests to evaluate their mechanical properties. Additionally, the influence of MWCNT dispersion efficiency on the enhancement of FRCC mechanical performance is scrutinized across different dispersion methods.

Combustive Properties of Medium Density Fibreboards (MDF) Treated with Bis-(Dimethylaminomethyl) Phosphinic Acid and Alkylenediaminoalkyl-Bis-Phosphonic Acids (비스-디메틸아미노메틸 포스핀산과 알킬렌디아미노알킬-비스-포스폰산 유도체에 의해 처리된 중밀도 섬유판의 연소특성)

  • Park, Myung-Ho;Chung, Yeong-Jin
    • Fire Science and Engineering
    • /
    • v.28 no.5
    • /
    • pp.71-79
    • /
    • 2014
  • This study was performed to test the combustive properties of Medium Density Fibreboards (MDFs) treated with chemicals of the bis-(dimethylaminomethyl) phosphinic acid (DMDAP), N,N-dimethylethylenediaminomethyl-bis-phosphonic acid (DMDEDAP), piperazinomethyl-bis-phosphonic acid (PIPEABP), and methylpiperazinomethyl-bis-phosphonic acid (MPIPEABP). MDFs were painted in three times with 15 wt% solution of the bis-(dimethylaminomethyl) phosphinic acid and alkylenediaminoalkyl-bis-phosphonic acids at the room temperature, respectively. After drying MDF treated with chemicals, combustive properties and volatile organic compounds (VOCs) contents were examined by the cone calorimeter (ISO 5660-1), test for flame retardant (NEMA Notice No. 2012034), and gas chromatography (KS M ISO 11890-2), respectively. It was indicated that the MDFs treated with chemicals showed the longer time to combustion time (CT) = (442~492) s than that of virgin plate by reducing the burning rate except for CT treated with DMDAP. In adition, the MDFs treated with chemicals showed both of the higher char area (44.33~61.33) kg/kg and char length (10.33~11.67) cm than those of virgin plate. Especially, the MDFs treated with chemicals showed the higher mean volatile organic compounds (VOCs) (0.188~0.333) g/L than that of virgin plate within the prescribed limits. Thus, It is supposed that the combustion- retardation properties were improved by the partial due to the treated chemicals in the virgin MDF.

Experimental Method to Evaluate Stress Triaxiality near the Crack Tip;Applicability to Various Specimen Configurations (균열선단 응력삼축성의 측정방법;여러 형상 시험편에의 적용성 검토)

  • Kim, Dong-Hak;Kim, Do-Hyung;Kang, Ki-Ju
    • Proceedings of the KSME Conference
    • /
    • 2004.04a
    • /
    • pp.60-65
    • /
    • 2004
  • Kim et al. described and compared other methods of measuring stress triaxiality using the displacements near the side necking, proved the validities of these models and explored the effect of location where the displacements are measured using three-dimensional finite element analysis for a standard CT specimen with 20% side-grooves. In this paper, the applicability of these models to various specimen and materials are examined in detail. To consider the effects of side groove, thickness of specimen, crack length, specimen geometry and strain hardening exponents, three-dimensional finite element simulation has been performed for various specimen geometries. For a case without a side groove, in the whole the difference between the stress triaxilaity analytically evaluated and directly determined is similar. For a case with a 20% side groove the stress triaxiality is measured at the area where ${\theta}$ is smaller than $60^{\circ}$, which excludes a side grooved area.

  • PDF

A Study on the Evaluation of the Fracture Toughness for the Narrow Gap Welding Part of Nuclear Piping (원전배관 협개선 용접재 파괴인성 평가에 관한 연구)

  • Huh, Yong;Park, Soo;Sin, In-Hwan;Seok, Chang-Sung
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.34 no.1
    • /
    • pp.67-72
    • /
    • 2010
  • The fracture toughness for the LBB analysis of piping is generally determined by the J-integral according to ASTM E1820. However, since this evaluates a base metal, the fracture toughness for narrow gap welding can be differently than the real value. This study evaluated the plastic  factor of the narrow gap welding part of a nuclear piping with SA508 Cl.1a and SA312 TP316. Also, it performed the fracture toughness test for the narrow gap welding part and applied the new plastic $\eta$ factor equation by Huh, et al. and then compared the results with those according with the ASTM standard.

Evaluation of tensile strengths and fracture toughness of plain weave composites (평직 CFRP 복합재료의 인장강도 및 파괴저항성 특성 평가)

  • Park, Soon-Cheol;Kang, Sung-Su;Kim, Gug-Yong;Choi, Jung-Hun
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.37 no.8
    • /
    • pp.862-868
    • /
    • 2013
  • The mechanics of woven fabric-based laminated composites is complex. Then, many researchers have studied woven fabric CFRP materials but fracture resistance behaviors for composites have not been still standardized. It also shows the different behavior according to load and fiber direction. Therefore, there is a need to consider fracture resistance behavior in conformity with load and fiber direction at designing structure using woven CFRP materials. In this study, therefore, the tensile strength and resistance for plain-weave CFRP composite materials were investigated under various different angle condition(load to fiber angle: $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$). Tensile strength and fracture toughness tests were carried out under mode I transverse crack opening load by using compact tension specimens.

Fatigue Crack Growth of Welded-Structural Steel under Simple-Variable Loading (단순변동하중(單純變動荷重)을 받는 용접구조용강(鎔接構造用鋼)의 피로균열성장(疲勞龜裂成長))

  • Chang, Dong Il;Bak, Yong Gul;Lee, Bong Hak
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.7 no.4
    • /
    • pp.103-113
    • /
    • 1987
  • Fatigue tests using a single-peak loading and a two-step loading were carried out to examine the fatigue crack growth behaviar and to find the appropriate analysis method. C-T specimens were made using structural steel SWS58 for the tests. From this, just after a single-peak loading acceleration effect was occured and after some times retardation effect was found. And eminent retardation effect was found after High-Low two-step loading. The transition effect of crack growth due to this variable loading was occured owing to the residual stress and the plastic zone size at the crack tip. And the behaviors of these are well explained by Elber's Crack Closure Model. Also I could find that the Wheeler's Retardation Model is a simple and appropriate theory among analysis methods of fatigue crack growth under the variable loading.

  • PDF

The Study on the Confidence Building for Evaluation Methods of a Fracture System and Its Hydraulic Conductivity (단열체계 및 수리전도도의 해석신뢰도 향상을 위한 평가방법 연구)

  • Cho Sung-Il;Kim Chun-Soo;Bae Dae-Seok;Kim Kyung-Su;Song Moo-Young
    • The Journal of Engineering Geology
    • /
    • v.15 no.2 s.42
    • /
    • pp.213-227
    • /
    • 2005
  • This study aims to assess the problems with investigation method and to suggest the complementary solutions by comparing the predicted data from surface investigation with the outcome data from underground cavern. In the study area, one(NE-1) of 6 fracture zones predicted during the surface investigation was only confirmed in underground caverns. Therefore, it is necessary to improve the confidence level for prediction. In this study, the fracture classification criteria was quantitatively suggested on the basis of the BHTV images of NE-1 fracture zone. The major orientation of background fractures in rock mass was changed at the depth of the storage cavern, the length and intensity were decreased. These characteristics result in the deviation of predieted predicted fracture properties and generate the investigation bias depending on the bore hole directions and investigated scales. The evaluation of hydraulic connectivity in the surface investigation stage needs to be analyze by the groundwater pressures and hydrochemical properties from the monitoring bore hole(s) equipped with a double completion or multi-packer system during the test bore hole is pumping or injecting. The hydraulic conductivities in geometric mean measured in the underground caverns are 2-3 times lower than those from the surface and furthermore the horizontal hydraulic conductivity in geometric mean is six times lower than the vertical one. To improve confidence level of the hydraulic conductivity, the orientation of test hole should be considered during the analysis of the hydraulic conductivity and the methodology of hydro-testing and interpretation should be based on the characteristics of rock mass and investigation purposes.

Fracture Mechanics Approach to X-Ray Diffraction Method for Spot Welded Lap Joint Structure of Rolled Steel Considered Residual Stress (잔류응력을 고려한 압연강 용접구조물의 X-ray 회절법에 의한 파괴 역학적 고찰)

  • Baek, Seung-Yeb;Bae, Dong-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.35 no.10
    • /
    • pp.1179-1185
    • /
    • 2011
  • Cold and hot-rolled carbon steel sheets are commonly used in railroad cars or commercial vehicles such as the automobile. The sheets used in these applications are mainly fabricated by spot welding, which is a type of electric resistance welding. However, the fatigue strength of a spot-welded joint is lower than that of the base metal because of high stress concentration at the nugget edge of the spot-welded part. In particular, the fatigue strength of the joint is influenced by not only geometrical and mechanical factors but also the welding conditions for the spot-welded joint. Therefore, there is a need for establishing a reasonable criterion for a long-life design for spot-welded structures. In this thesis, ${\Delta}P-N_f$ relation curves have been used to determine a long-life fatigue-design criterion for thin-sheet structures. However, as these curves vary under the influence of welding conditions, mechanical conditions, geometrical factors, etc. It is very difficult to systematically determine a fatigue-design criterion on the basis of these curves. Therefore, in order to eliminate such problems, the welding residual stresses generated during welding and the stress distributions around the weld generated by external forces were numerically and experimentally analyzed on the basis of the results, reassessed fatigue strength of gas welded joints.