Characterization of transition behavior in SA508 Gr.4N Ni–Cr–Mo low alloy steels with microstructural alteration by Ni and Cr contents

Lee, Ki-Hyoung,Park, Sang-gyu,Kim, Min-Chul,Lee, Bong-Sang,Wee, Dang-Moon Elsevier 2011 Materials science & engineering. properties, micro Vol.529 No.-

<P><B>Highlights</B></P><P>► We offer information for determining optimum alloying contents of SA508 Gr.4N steel. ► This study shows improvement of toughness with increasing Ni and Cr contents. ► Ni content is more effective on the impact toughness than on the fracture toughness. ► Cr content is more effective on the fracture toughness. ► We offer detailed information on relationship between toughness and microstructure.</P> <P><B>Abstract</B></P><P>SA508 Gr.4N Ni–Cr–Mo low alloy steel, in which Ni and Cr contents are higher than in commercial reactor pressure vessel (RPV) steels, may be a candidate RPV material with the improved strength and toughness due to its tempered martensitic microstructure. This study aims at assessing the effects of microstructural factors with alloying element contents on the transition properties of Ni–Cr–Mo low alloy steels. Model alloys with different Ni and Cr contents were fabricated and their Charpy impact toughness and fracture toughness were examined in the transition region according to ASTM E23 and E1921 standard procedures, respectively. The test results showed extensive improvements of both impact toughness and fracture toughness with increasing Ni and Cr contents. However, Ni content was more effective on the impact toughness than on the fracture toughness, while Cr content was more effective on the fracture toughness. In order to identify a difference in effects of alloying elements contents on the fracture toughness and impact toughness, the relations between the transition properties and the scale of the microstructural features such as packets and carbides are discussed in detail.</P>

초등학교 축구선수의 성격타입(A/B), 정신력과 운동몰입의 구조적 관계

김인수(Kim In-Soo),최정아(Choi Jeang-a) 한국체육교육학회 2016 한국체육교육학회지 Vol.20 No.4

이 연구는 초등학교 축구선수의 A/B 타입 성격과 정신력, 운동몰입 간에 어떤 인과관계가 있는지를 밝힘으로써 초등학교 축구선수의 경기력 향상에 도움을 주고자 수행되었다. 이러한 연구목적을 달성하기 위해 G광역시와 J도에 소재한 초등학교 축구선수로 등록된 236명과 중학교 축구 선수 110명을 대상으로 A/B 타입 성격척도, 정신력 척도, 운동몰입척도를 사용하여 집단 간 t-test 및 공변량 구조분석을 실시하였다. 변인 간의 구조적 관계분석을 위해 A/B 타입 성격을 외생변인으로 하고, 정신력과 운동몰입을 내생변인으로 한 구조모델을 설정하고 검증하였으며 그 결과 첫째, A/B 타입 성격 간 비교에서A 타입 성격소유자가 B타입 성격소유자에 비해 정신력과 운동몰입이 높은 것으로 나타났다. 입상경력유무집단 간 비교에서 입상경력이 있는 선수는 그렇지 못한 선수에 비해 A 타입 성격, 정신력, 운동몰입이 높았다. 초등학교 축구선수와 중학교 축구선수 간 비교에서는 성격타입, 정신력, 운동몰입에 차이가 없었다. 둘째, 변인 간 상관분석을 실기한 결과 A/B 타입 성격, 정신력, 운동몰입 간에는 서로 유의한(p<.01) 상관이 있었다. 셋째, 변인 간 구조관계를 분석한 결과 완전매개모형이 적합한 것으로 나타났고, A/B 타입 성격을 외생변인으로 하고 정신력과 운동몰입을 내생변인으로 한 구조모형은 이론모델로서 양호한 것으로 나타났으며(χ2=20.13, df=7, Q=2.88, RMR=.01, GFI=.97, TLI=.94, NFI=.96, CFI=.97, RMSEA=.08) 세부 구조경로에서는 A/B타입 성격 → 정신력, 정신력 → 운동몰입의 경로가 유의한(p<.01) 것으로 나타났다. 이를 요약하면 초등학교 축구선수의 경우 A타입 성격 성향이 강할수록 정신력과 운동몰입 수준이 높으며 지방대회 3위 이상의 입상경력을 가진 선수는 그렇지 않는 선수에 비해 A 타입 성격 성향이 강하고, 정신력과 운동몰입 수준이 높다. 또한, A/B 성격 성향은 정신력과 밀접한 관련이 있으며 정신력은 운동몰입과 인과관계가 있는 것으로 나타나 초등학교 축구선수의 운동몰입 수준을 증가시키기 위해서는 정신력의 강화가 필요함을 제시해 주고 있다. Purpose: The Purpose of this study was to define structural relation among A/B type behavior pattern, mental toughness, and sport commitment of elementary school soccer players. Methods: This study set up a structural relation model which was composed of exogenous variables as A/B type behavior pattern and endogenous variables were mental toughness, and sport commitment of soccer players. The participants were 236 elementary school and 110 middle school soccer players who lived in G city and J province. This study used A/B type behavior pattern scale, Mental toughness scale and commitment scale. Results: In analysis of t-test, A type players show higher mental toughness and sport commitment than those of B type. The players who had experienced more 3rd place in province soccer competition show higher A type behavior pattern, mental toughness, and behavioral commitment than those of the others. There were no differences between elementary school players and middle school players in A/B type behavior pattern, mental toughness and sport commitment. In analysis of correlation, there were significant relations between A/B type behavior pattern, mental toughness and sport commitment. In analysis structure equation, this model can be used as theoretical model because general indexes were proved(χ2=20.13, df=7, Q=2.88, RMR=.01, GFI=.97, TLI=.94, NFI=.96, CFI=.97, RMSEA=.08). In analysis details index, there were significant paths of A/B type behavior pattern → mental toughness, mental toughness → sport commitment. Conclusion: In this study define there are causal relationships among A/B type behavior pattern, mental toughness and sport commitment. To approve sport commitment of elementary school soccer players, players kept up A type behavior pattern and make strong mental toughness.

FRACTURE TOUGHNESS OF VARIOUS CORE MATERIALS

Lee Shin-Won,Lee Sun-Hyung,Yang Jae-Ho,Han Jung-Suk,Lee Jai-Bong The Korean Academy of Prosthodonitics 2001 대한치과보철학회지 Vol.39 No.6

This investigation evaluated the fracture toughness($K_{IC}$) of eight currently available core materials, and relate the fracture toughness value to fractography analysis and surface characteristics using a atomic force microscope (AFM). Single-edge notched (SEN) test specimens (n=10) and compact tension (CT) test specimens (n=10) were prepared conforming to the ASTM Standard E-399 for a high copper amalgam, three composite core materials (Core-Max II, Core Paste, Bisfil Core), two reinforced composite core materials (Ti-Core, Ti-Core Natural), a resin-modified glass ionomer core material (Vitremer), and a conventional glass ionomer core material (Ketac-Molar). The specimens were tested with an Instron Universal Testing Machine. The maximum loads were measured to calculate the fracture toughness ($K_{IC}$). Thereafter, fracture surfaces of SEN specimens of each material were investigated for fractography analysis using scanning electron microscope. And, disc-shaped specimens with 1mm thickness were fabricated for each material and were investigated under AFM for surface morphology analysis. The results were as follows: 1. Bisfil Core showed the highest mean fracture toughness regardless of test methods. 2. For the tooth-colored materials, Ti-Core Natural exhibited the highest fracture toughness. 3. Ketac Molar showed a significantly low fracture toughness when compared with the amalgam and the composite resin core materials(p<0.05). 4. The fracture toughness values obtained with the single-edge notched test, except Ketac Molar, were higher than those obtained in the compact tension test. 5. SEM revealed that the fracture surface of high fracture toughness material was rougher than that of low fracture toughness material. 6. AFM revealed that the surface particles of the composite resins were smaller in size, with a lower surface roughness than the glass ionomer core materials.

On the Transferability of Specimen Fracture Toughness Data to a Engineering Component

Yu. G. Matvienko,Young Suk Kim,Hyeon Cheol Jeong 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.8

It was found that the fracture toughness of a material could be a function of test specimen configuration and type of loading. Moreover, the methodology of the cohesive zone model and local fracture criterion clearly demonstrates that the failure assessment diagrams are in general dependent on the type of loading and the elastic stress concentration factor. The transferability of specimen fracture toughness data to engineering components has been discussed from viewpoint of crack-tip constraint. The J-Q theory has been used to analyse the geometry dependent crack-tip constraint of Zr-2.5Nb pressure tube material. The effect of specimen geometry on the crack-tip constraint parameter Q and corresponding fracture toughness of un irradiated and irradiated of Zr-2.5Nb pressure tube material at room and high test temperature has been analysed using material from tubes of low, intermediate and high toughness. The fracture toughness-scaling model was developed for the correction of measured high-constraint toughness values to the fracture toughness of burst test specimens.

체육고등학교 선수의 절실함과 정신적 강인함 및 회복탄력성의 관계

안효연,소영호 한국체육학회 2024 한국체육학회지 Vol.63 No.1

The purpose of this study was to investigate the relationship among julsil, mental toughness, and resilience of physical education high school athlete. The subjects of this study were 249 physical education high school athletes. Participants completed a series of questionnaires on the julsil, mental toughness, and resilience. With the collected data multiple regression and mediation regression analysis were performed by SPSS 23.0. The results of the analysis were summarized as follows. First, the julsil had an positively influenced the prediction of mental toughness of physical education high school athlete. Second, the julsil had an positively influenced the prediction of resilience of physical education high school athlete. Third, the mental toughness had an positively influenced the prediction of resilience of physical education high school athlete. Fourth, the mental toughness was revealed to function as a complete mediating effect on the relationship between julsil and resilience. These results mean that the mental toughness and resilience can be explained through the julsil of physical education high school athlete, and that resilience can be effectively explained by mental toughness. In addition, the julsil had an indirect effect on resilience through the mental toughness as a mediating variable, and the implications and future study directions were presented based on the study results. 이 연구는 체육고등학교 선수의 절실함과 정신적 강인함 및 회복탄력성의 관계를 검증하기 위한 목적으로 수행되었다. 연구대상은 체육고등학교 선수 249명으로 하였고, 설문조사를 통해 절실함, 정신적 강인함, 회복탄력성을 수집하여 SPSS 23.0을 이용한 다중회귀분석과 매개회귀분석을 수행하여 다음과 같은 결과를 얻었다. 첫째, 체육고등학교 선수의 절실함은정신적 강인함을 예측하는 데 긍정적인 영향을 미친다. 둘째, 체육고등학교 선수의 절실함은 회복탄력성을 예측하는 데 긍정적인 영향을 미친다. 셋째, 체육고등학교 선수의 정신적 강인함은 회복탄력성을 예측하는 데 긍정적인 영향을 미친다. 넷째, 체육고등학교 선수의 정신적 강인함은 절실함과 회복탄력성의 관계에서 완전 매개효과를 나타낸다. 이상의 결과는체육고등학교 선수의 절실함을 통해 정신적 강인함과 회복탄력성이 설명될 수 있고, 정신적 강인함에 의해서도 회복탄력성이 설명될 수 있다는 것이 시사되었다. 또한, 절실함은 정신적 강인함을 통해 회복탄력성을 증가시키는 특성이 있다는것이 시사되었으며, 연구결과를 토대로 시사점과 향후 연구 방향이 제시되었다.

Prediction of fracture toughness of ceramic composites as function of microstructure: I. Numerical simulations

Li, Y.,Zhou, M. Pergamon Press 2013 Journal of the mechanics and physics of solids Vol.61 No.2

The evaluation of macroscopic material parameters such as fracture toughness as functions of microstructural attributes is a fundamental issue in material science. The task requires the quantification of both microstructure and material response. Currently, no systematic approach other than experiments exists for establishing microstructure-fracture toughness relations for materials. In this paper, we present a multi-scale computational framework based on the cohesive finite element method (CFEM) for predicting fracture toughness of materials as a function of microstructure. This framework provides a means for evaluating fracture toughness through explicit simulation of fracture processes in microstructures. The approach uses the J-integral, allowing fracture toughness to be calculated for microstructures with random heterogeneous phase distributions and fracture processes with arbitrary crack paths or micro-crack patterns. Calculations carried out concern two-phase Al<SUB>2</SUB>O<SUB>3</SUB>/TiB<SUB>2</SUB> ceramic composites and focus on the effects of constitute behavior, phase morphology, phase distribution, phase size scale, and interphase bonding on fracture toughness. Results show that microstructure and constituent properties can significantly influence fracture behavior and combine to determine the overall fracture toughness through the activation of different fracture mechanisms. In particular, a combination of fine microstructure size scale, rounded reinforcement morphology, appropriately balanced interphase bonding strength and compliance can best promote desirable crack-reinforcement interactions and lead to enhanced fracture toughness.

엘리트 학생선수의 지각된 통제적 코칭행동과 정신적 강인함 및 운동 탈진의 구조적 관계

소영호 한국스포츠심리학회 2024 한국스포츠심리학회지 Vol.35 No.1

목적: 이 연구는 엘리트 학생선수가 지각하고 있는 지도자의 통제적 코칭행동과 정신적 강인함 및 운동 탈진의구조적 관계를 분석하기 위한 목적으로 수행되었다. 방법: 연구대상은 엘리트 학생선수 236명이었으며, 통제적 코칭행동과 정신적 강인함 및 운동 탈진에 대한 설문자료를 수집하여 AMOS 22.0을 이용하여 구조방정식모형분석을 실시하였다. 결과: 첫째, 통제적 코칭행동은 운동 탈진에 정(+)적인 영향을 미친다. 둘째, 통제적 코칭행동은정신적 강인함에 부(-)적인 영향을 미친다. 셋째, 정신적 강인함은 운동 탈진에 부(-)적인 영향을 미친다. 넷째, 정신적 강인함은 통제적 코칭행동과 운동 탈진의 관계에서 부분 매개효과를 나타낸다. 결론: 이상의 결과를 통해엘리트 학생선수가 지각하는 통제적 코칭행동은 운동 탈진을 증가시키고, 정신적 강인함을 감소시키며, 정신적 강인함은 운동 탈진을 예방할 수 있다는 것을 알 수 있었다. 또한, 통제적 코칭행동은 정신적 강인함을 통해 운동탈진을 감소시키는 특성이 있다는 것이 시사되었으며, 연구결과에 대한 시사점과 향후 연구수행을 위한 제언에대해 논의하였다. Purpose: The purpose of this study was to investigate the structural relationship among perceived controlling coaching behavior, mental toughness, and athlete burnout in elite student athletes. Methods: The subjects of this study were 236 elite student athletes. Participants completed a series of questionnaires on the controlling coaching behavior, mental toughness, and athlete burnout. With the collected data structural equation model analysis were performed by AMOS 22.0. Results: First, the controlling coaching behavior impacts positively(+) influence on athlete burnout. Second, the controlling coaching behavior impacts negatively(-) influence on mental toughness. Third, the mental toughness impacts negatively(-) influence on athlete burnout. Fourth, the mental toughness was revealed to function as a partial mediating effect on the relationship between controlling coaching behavior and athlete burnout. Conclusion: These results that increased their athlete burnout through the percetived controlling coaching behavior of elite student athletes, and the reductions mental toughness, but the found that mental toughness can prevent athlete burnout. In addition, the controlling coaching behavior had an indirect effect on athlete burnout through the mental toughness as a mediating variable. And the implications of the research and suggestions for future research were discussed.

Toughness and microscopic pore structure analysis of pasture fiber recycled concrete

Hailong Wang,Lei Wang,Hong Yang Techno-Press 2023 Advances in concrete construction Vol.16 No.3

In order to develop and take full advantage of pasture fiber and waste concrete, this article studied how different amounts of pasture fiber influenced the toughness and pore structure of concrete with different replacement rates of recycled fine aggregate. Pasture fiber recycled concrete constitutive equations were established under idealized stiffness and toughness damage rate, based on fracture energy and damage mechanics theories. The relationship between pore structure and toughness was studied utilizing nuclear magnetic resonance and fractal theory. The toughness of text groups (0% (JZ), 10% (ZS10), 20% (ZS20)) first increased and then decreased with increasing amounts of pasture fiber, based on the damage rate of toughness. The toughness of concrete samples with recycled fine aggregate and pasture fiber is negatively correlated to the fractal dimension of small and medium-sized pores with a pore size of 0-500 nm. At a replacement rate of 10% of the recycled fine aggregate, the fractal dimension of the air voids (r: 500-9000 nm, i.e., Lg(r) ∈ [2.7, 3.9]) shows a gradual decrease with the increase of grass fiber dosage, indicating that with such a replacement rate of the recycled fine aggregate, the increase of pasture fiber can reduce the complexity of the pore structure of the air voids (500-9000 nm).

Bio-Inspired Stretchable and Contractible Tough Fiber by the Hybridization of GO/MWNT/Polyurethane

Kim, Hyunsoo,Jang, Yongwoo,Lee, Dong Yeop,Moon, Ji Hwan,Choi, Jung Gi,Spinks, Geoffrey. M.,Gambhir, Sanjeev,Officer, David L.,Wallace, Gordon G.,Kim, Seon Jeong American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.34

<P>Spider silks represent stretchable and contractible fibers with high toughness. Those tough fibers with stretchability and contractibility are attractive as energy absorption materials, and they are needed for wearable applications, artificial muscles, and soft robotics. Although carbon-based materials and poly(vinyl alcohol) (PVA) composite fibers exhibit high toughness, they are still limited in low extensibility and an inability to operate in the wet-state condition. Herein, we report stretchable and contractible fiber with toughness that is inspired by the structure of spider silk. The bioinspired tough fiber provides 495 J/g of gravimetric toughness, which exceeds 165 J/g of spider silk. Besides, the tough fiber was reversibly stretched to ∼80% strain without damage. This toughness and stretchability are realized by hybridization of aligned graphene oxide/multiwalled carbon nanotubes in a polyurethane matrix as elastic amorphous regions and β-sheet segments of spider silk. Interestingly, the bioinspired tough fiber contracted up to 60% in response to water and humidity similar to supercontraction of the spider silk. It exhibited 610 kJ/m<SUP>3</SUP> of contractile energy density, which is higher than previously reported moisture driven actuators. Therefore, this stretchable and contractible tough fiber could be utilized as an artificial muscle in soft robotics and wearable devices.</P> [FIG OMISSION]</BR>

Evaluation of Fracture Toughness of Paper in Wet State (I)

You Sun Roh,Yung Bum Seo 한국펄프·종이공학회 2016 펄프.종이기술 Vol.48 No.4

Fracture toughness is considered to be a good estimate of the paper breaking tendency of a paper web in a paper machine and press room. Paper breaks are caused by many factors, such as the irregular vibrations of a paper machine, impurities in the fiber furnish, and presence of shive. On a paper machine, the dryness of the paper web changes very rapidly from less than 1% to more than 95%. We tried to measure the fracture toughness of a paper web at different dryness levels in order to acquire a fundamental knowledge of paper breaks. Stretches of wet webs were also measured and compared to the changes in fracture toughness. Four different fiber furnishes were refined to different degrees, and their fracture toughness values were measured at different dryness levels (40%, 60%, 80%, and 95%). Two fracture toughness measurement methods (essential work of fracture and Tryding’s load-widening method) were compared, and found to give identical results. However, Tryding’s method was much easier to implement. The highest stretch was mostly at 80% solid content, where the highest fracture toughness occurred.