• Title/Summary/Keyword: Hardening Effects

Search Result 454, Processing Time 0.028 seconds

Three-dimensional numerical simulation of hydrogen-induced multi-field coupling behavior in cracked zircaloy cladding tubes

  • Xia, Zhongjia;Wang, Bingzhong;Zhang, Jingyu;Ding, Shurong;Chen, Liang;Pang, Hua;Song, Xiaoming
    • Nuclear Engineering and Technology
    • /
    • v.51 no.1
    • /
    • pp.238-248
    • /
    • 2019
  • In the high-temperature and high-pressure irradiation environments, the multi-field coupling processes of hydrogen diffusion, hydride precipitation and mechanical deformation in Zircaloy cladding tubes occur. To simulate this hydrogen-induced complex behavior, a multi-field coupling method is developed, with the irradiation hardening effects and hydride-precipitation-induced expansion and hardening effects involved in the mechanical constitutive relation. The out-pile tests for a cracked cladding tube after irradiation are simulated, and the numerical results of the multi-fields at different temperatures are obtained and analyzed. The results indicate that: (1) the hydrostatic stress gradient is the fundamental factor to activate the hydrogen-induced multi-field coupling behavior excluding the temperature gradient; (2) in the local crack-tip region, hydrides will precipitate faster at the considered higher temperatures, which can be fundamentally attributed to the sensitivity of TSSP and hydrogen diffusion coefficient to temperature. The mechanism is partly explained for the enlarged velocity values of delayed hydride cracking (DHC) at high temperatures before crack arrest. This work lays a foundation for the future research on DHC.

Usefulness Evaluation of Application of Metallic Algorithm Reducing for Beam Hardening Artifact Occur in Typical Brain CT Image (머리 CT영상에서 흔히 발생하는 선속경화인공물 감소를 위한 금속인공물감소 알고리즘 적용의 유용성 평가)

  • Kim, Hyeon ju
    • Journal of the Korean Society of Radiology
    • /
    • v.12 no.3
    • /
    • pp.389-395
    • /
    • 2018
  • The study attempted to use computed tomography images to determine the usefulness of the reduction in the axial reduction algorithm in the event of a metallic artifacts reduction in the image of the beam-hardening effect, which is known as the most effective method of reducing metallic artifact reduction in the image and the reduction of the metal produced in this study. As a result, the result is increased to 140 kVp to reduce the value of the CT value by 0.02 to 0.05 %, resulting in decreased axial effect (P > 0.05). The CT value decreased from 12.4 to 26.9 % when applied to the reduction of the metallic. 12.4 to 26.9 % (p<0.05). In addition, in the qualitative assessment by the clinical trial evaluation, it was assessed as 1.8 points after applying the MAR algorithm, In the resolution of resolution and contrast evaluations, the estimation of the decrease in metallic artifact effects was assessed as the metal was assessed to be scored 7.2 points after the MAR algorithm was evaluated. Therefore, in case of artifacts due to irreversible beam hardening effect, it is useful to reduce artifacts caused by beam hardening effect by using various methods derived from existing researches and scanning by applying the metal artifact reduction algorithm proposed in this experiment.

Effects of processing method and storage temperature and time on the texture of Yaksik(cooked and seasoned glutinous rice) (약식의 제조방법과 저장온도 및 기간에 따른 조직감의 변화)

  • Lee, Hei-Jeung;Lee, Young-Keun;Koo, Sung-Ja;Hong, Sung-Hee;Lee, Cherl-Ho
    • Journal of the Korean Society of Food Culture
    • /
    • v.3 no.4
    • /
    • pp.391-396
    • /
    • 1988
  • The method for the measurement of texture hardening phenomena, which is the limiting factor of shelf-life of Yaksik in the market, was established. The changes in the hardening rate by the processing conditions and the storage temperature and time were examined. The standard sample made by traditional method could be kept at room temperature$(20{\circ}C)$ for 3 days and the multipuncture force measured at the end of marketable quality was 700g. The hardening rate increased rapidly by storing at $5^{\circ}C$ and the ratio of hardening rate constants between room temperature and $5^{\circ}C$ storage reached to $1.3{\sim}3.3$ depending on the processing condition. The largest ratio was observed by the sample made from pressure cooker. The addition of corn syrup retarded the hardening rate. The pressure cooking resulted in making too soft product, which diminished the panel preference, but it extend the shelf-life when products were stored at $5^{\circ}C$ microwave cooking resulted in making too hard texture which was not acceptable. The overall quality preference of Yaksik was decided by the textural preference and the latter showed significant inverse correlation with the maximum force of multipuncture test. Therefore, it was concluded that multipuncture test was useful for the measurement of the quality of Yaksik.

  • PDF

Effects of Al Impurity on Magnetism in bcc Fe by a First-principles Calculation

  • Seo, Seung-Woo;Rahman, Gul;Kim, In-Gee
    • Proceedings of the Korean Magnestics Society Conference
    • /
    • 2009.12a
    • /
    • pp.72-73
    • /
    • 2009
  • First-principles calculations were carried out to investigate the effects of Al impurities on bcc Fe magnetism by considering SOC. No significant solid solution hardening effect was found. Albeit the effects of the SOC by Al on spin magnetic moments were minor, there are sizeable orbital magnetic effects. It is concluded that the orbital magnetism due to the Al impurity is strongly related with the impurity screening of the system as seen in Si impurity case [3], but the effects of Al impurity is stronger than those of Si impurity in terms of orbital magnetism.

  • PDF

EFFECTS OF ALLOYING ELEMENTS ON VARIOUS PROPERTIES OF DENTAL SILVER-PALLADIUM ALLOYS (치과용(齒科用) 은(銀)-파라디움합금(合金)의 합금원소(合金元素)가 제성질(諸性質)에 미치는 영향(影響)에 관(關)한 연구(硏究))

  • Kim, Chun-Jin;Park, Nam-Soo
    • The Journal of Korean Academy of Prosthodontics
    • /
    • v.22 no.1
    • /
    • pp.95-108
    • /
    • 1984
  • Even though the tarnishing and corrosion problems characteristic with dental silver-palladium alloy are not yet fully solved, it is recently widely used because of its low cost. However the effects of major alloying elements on the various properties of this system are not fully understood. The object of this research is to clarify the effects of In and Zn additives on the corrosion and tarnishing resistances and precipitation hardening behavior of this sytem, using electrodynamic polarization, immersion, and Vicker's microhardness test and X-ray diffraction and electron probe micro analysis methods. The obtained results were as follows: I. As indium content is increased, both the corrosion resistance in Cl-solution and microhardness are also increased while the tarnishing resistance is decreased. 2. As Zinc content is increased, the corrosion resistance is decreased, but tarnishing resistance is increased 3. At 70Ag-25Pd-2.5Zn-2.5In composition, the precipitation harding behavior was mot significant. The optimum aging temperature was $450^{\circ}C$ and the time was 2 hrs. The resulting specimen of this work carried 180VHN. 4. Under the heat treatment, the changes in the mechanical property are due to the changes in the shape and composition of dendrite matrix, namely, it is because of the precipitation hardening behavior which has been proved by electron probe micro analysis and optical microscopic finding.

  • PDF

Tensile Mean Strain Effects on the Fatigue Life of SiC-Particulate-Reinforced Al-Si Cast Alloy Composites (SiC입자강화 주조Al-Si복합재의 피로수명에 대한 인장평균변형률의 영향)

  • Go, Seung-Gi
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.23 no.11 s.170
    • /
    • pp.1970-1981
    • /
    • 1999
  • The low-cycle fatigue behaviour of a SiC-particulate-reinforced Al-Si cast alloy with two different volume fractions has been investigated from a series of strain-control led fatigue tests with zero and nonzero tensile mean strains. The composites including the unreinforced matrix alloy, exhibited cyclic hardening behaviour, with more pronounced strain-hardening for the composites with a higher volume fraction of the SiC particles. For the tensile mean strain tests, the initial high tensile mean stress relaxed to zero for the ductile Al-Si alloy, resulting in no influence of the tensile mean strain on the fatigue life of the matrix alloy. However, tensile mean strain for the composite caused tensile mean stresses and reduced fatigue life. The pronounced effects of mean strain on the low-cycle fatigue life of the composite compared to the unreinforced matrix alloy were attributed to the initial large prestrain and non-relaxing high tensile mean stress in the composite with very limited ductility and Cyclic plasticity. Fatigue damage parameter using strain energy, density efficiently accounted for the mean stress effects. Predicted fatigue life using the damage parameter correlated fairly well with the experimental life within a factor of 3. Also, the fatigue damage parameter indicated the inferior life in the low-cycle regime and superior life in the high-cycle regime for the composite, compared to the unreinforced matrix alloy.

Development of Sprayable Strain-Hardening Cement Composite(SHCC) for Joint between Existing R/C Building and Seismic Retrofit Elements (기존 철근콘크리트 건물과 내진보강요소의 접합부 충진을 위한 뿜칠형 섬유보강 시멘트 복합체(SHCC)의 개발)

  • Kim, Sung-Ho;Youn, Gil-Ho;Kim, Yong-Cheol;Kim, Jae-Hwan;Yun, Hyun-Do
    • Journal of the Korean Institute of Educational Facilities
    • /
    • v.19 no.5
    • /
    • pp.29-36
    • /
    • 2012
  • The goals of this study are to develop a sprayable strain-hardening cement composite (SHCC) and to investigate the potential of the sprayable SHCC for packing the joint between existing R/C building and seismic retrofit elements. This paper provides the procedure for the development of a sprayable SHCC, test results of fresh properties required to a sprayable SHCC, and mock-up test results of developed sprayable SHCC. Control mixture of polyvinyl alcohol (PVA) fiber-reinforced SHCC (PVA-SHCC) was predetermined based on available research results. The pumpability and sprayability of the SHCC mixture were depended on the fluid property of fresh SHCC mixture. In this study, the effects of admixtures such as AE agent and fly ash on the rheological and rebound properties of control SHCC mixture were investigated to determine a sprayable SHCC mixture. Flow values and air content during shotcreting procedure of sprayable SHCC were also evaluated. The results show that flow or flowability and amount of air of three SHCC mixtures decreased almost linearly according to shotcreting procedure from mixer to nozzle. And the pumpability and sprayability of mixture with AE agent and low amounts of fly ash were superior to the those of SHCC. Mock-up test result show that developed sprayable SHCC indicates much improved workability and shotcrete construction period than conventional method(nonshrinkage mortar).

Strength Development of High-Strength Concrete in Structure

  • Msuda, Yochihiro
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2000.10a
    • /
    • pp.31-45
    • /
    • 2000
  • Because of the high unit cement content in the concrete mix, major concrete temperature rises are observed in the initial stages of hardening in structural members with large cross-sections made of high-strength concrete. While this temperature rise in the initial stages of hardening contributes to the initial development of the concrete strength, it also causes thermal cracking and obstructs medium to long-term increases of the concrete strength. In the study reports below, investigations were made on the effects of the concrete temperature rise in the initial stages of hardening on the medium to long-term development of the strength of structural concrete between the ages of 28 and 91 days. In the study, comparisons were made, for example, between the compressive strength of a control specimen subjected to standard curing at 28 days and the compressive strength of core specimens taken from structural members, and observations were made on the methods of evaluating the concrete strength in structure, defined here as the compressive strength of core specimens at 91 days. The results obtained indicate that, when the maximum temperature of the concrete is the structure does not exceed $60^{\circ}C$, the concrete strength in structure at the age of long-term will generally be greater than the compressive strength of the standard-curing specimens at 28 days, allowing one to evaluate the strength of the structural concrete in terms of the compressive strength of the 28-days standard-curing specimens. When, on the other hand, the maximum temperature of the concrete in the structure exceeds $60^{\circ}C$, the strength in concrete structure may be smaller than the compressive strength of the 28-days standard-curing specimens, creating risks in the evaluation of the concrete strength in structure by latter.

  • PDF

Kinematics of filament stretching in dilute and concentrated polymer solutions

  • McKinley, Gareth H.;Brauner, Octavia;Yao, Minwu
    • Korea-Australia Rheology Journal
    • /
    • v.13 no.1
    • /
    • pp.29-35
    • /
    • 2001
  • The development of filament stretching extensional rheometers over the past decade has enabled the systematic measurement of the transient extensional stress growth in dilute and semi-dilute polymer solutions. The strain-hardening in the extensional viscosity of dilute solutions overwhelms the perturbative effects of capillarity, inertia & gravity and the kinematics of the extensional deformation become increasingly homogeneous at large strains. This permits the development of a robust open-loop control algorithm for rapidly realizing a deformation with constant stretch history that is desired for extensional rheometry. For entangled fluids such as concentrated solutions and melts the situation is less well defined since the material functions are governed by the molecular weight between entanglements, and the fluids therefore show much less pronounced strain-hardening in transient elongation. We use experiments with semi-dilute/entangled and concentrated/entangled monodisperse polystyrene solutions coupled with time-dependent numerical computations using nonlinear viscoelastic constitutive equations such as the Giesekus model in order to show that an open-loop control strategy is still viable for such fluids. Multiple iterations using a successive substitution may be necessary, however, in order to obtain the true transient extensional viscosity material function. At large strains and high extension rates the extension of fluid filaments in both dilute and concentrated polymer solutions is limited by the onset of purely elastic instabilities which result in necking or peeling of the elongating column. The mode of instability is demonstrated to be a sensitive function of the magnitude of the strain-hardening in the fluid sample. In entangled solutions of linear polymers the observed transition from necking instability to peeling instability observed at high strain rates (of order of the reciprocal of the Rouse time for the fluid) is directly connected to the cross-over from a reptative mechanism of tube orientation to one of chain extension.

  • PDF

Effects of Pre-Aging Treatment on the Corrosion Resistance of Low Temperature Plasma Nitrocarburized AISI 630 Martensitic Precipitation Hardening Stainless Steel (저온 플라즈마 침질탄화처리된 마르텐사이트계 석출경화형 스테인리스강의 내식성에 미치는 시효 전처리의 영향)

  • Lee, Insup;Lee, Chun-Ho
    • Journal of the Korean institute of surface engineering
    • /
    • v.53 no.2
    • /
    • pp.43-52
    • /
    • 2020
  • Various aging treatments were conducted on AISI 630 martensitic precipitation hardening stainless steel in order to optimize aging condition. Aging treatment was carried out in the vacuum chamber of Ar gas with changing aging temperature from 380℃ to 430℃ and aging time from 2h to 8h at 400℃. After obtaining the optimized aging condition, several nitrocarburizing treatments were done without and with the aging treatment. Nitrocarburizing was performed on the samples with a gas mixture of H2, N2 and CH4 for 15 h at vacuum pressure of 4.0 Torr and discharge voltage of 400V. The corrosion resistance was improved noticeably by combined process of aging and nitrocarburizing treatment, which is attributed to higher chromium and nitrogen content in the passive layer, as confirmed by XPS analysis. The optimized condition is finalized as, 4h aging at 400℃ and then subsequent nitrocarburizing at 400℃ with 25% nitrogen and 4% methane gas for 15h at vacuum pressure of 4.0 Torr and discharge voltage of 400V, resulting in the surface hardness of around 1300 HV0.05 and α'N layer thickness of around 11 ㎛ respectively.