항복강도에 따른 Zr-2.5Nb 압력관의 Delayed Hydride Cracking Velocity

김영석,최승준,정용무,김인섭,마르켈로프 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.1

The objective of this study is to investigate delayed hydride cracking velocity (DHCV) of Zr-2.5Nb pressure tubes with yield strength. DHC tests were conducted at an initial K_(I) of 15 to 19 MPa √m and 250℃ on the compact tension specimens containing up to 100 ppm hydrogen that were taken from the Zr-2.5Nb tubes with different yield strengths. The crack growth was determined with the direct current potential drop method. A nice correlation of the DHC velocity and the yield strength was obtained at all temperatures by normalizing the DHCV with the terminal solid solubility and diffusion of hydrogen: the DHCV increased exponentially with increased yield strength of the Zr- 2.5Nb tubes. In contrast, the texture and the distribution of the β-Zr phase were found to have a comparatively minor effect on the DHCV of the Zr-2.5Nb tubes. Yield strength of the Zr-2.5Nb tubes determines a plastic zone size with a steep gradient of hydrogen concentration ahead of the crack tip where hydrides can be precipitated. The yield strength effect is analyzed by correlating the plastic zone and the striation spacing observed on the fractured surfaces as a function of the yield strength.

Influence of the connection design and titanium grades of the implant complex on resistance under static loading

Park, Su-Jung,Lee, Suk-Won,Leesungbok, Richard,Ahn, Su-Jin The Korean Academy of Prosthodonitics 2016 The Journal of Advanced Prosthodontics Vol.8 No.5

PURPOSE. The purpose of this study was to evaluate the resistance to deformation under static overloading by measuring yield and fracture strength, and to analyze the failure characteristics of implant assemblies made of different titanium grades and connections. MATERIALS AND METHODS. Six groups of implant assemblies were fabricated according to ISO 14801 (n=10). These consisted of the combinations of 3 platform connections (external, internal, and morse tapered) and 2 materials (titanium grade 2 and titanium grade 4). Yield strength and fracture strength were evaluated with a computer-controlled Universal Testing Machine, and failed implant assemblies were classified and analyzed by optical microscopy. The data were analyzed using the One-way analysis of variance (ANOVA) and Student's t-test with the level of significance at P=.05. RESULTS. The group $IT4_S$ had the significantly highest values and group IT2 the lowest, for both yield strength and fracture strength. Groups $IT4_N$ and ET4 had similar yield and fracture strengths despite having different connection designs. Group MT2 and group IT2 had significant differences in yield and fracture strength although they were made by the same material as titanium grade 2. The implant system of the similar fixture-abutment interfaces and the same materials showed the similar characteristics of deformation. CONCLUSION. A longer internal connection and titanium grade 4 of the implant system is advantageous for static overloading condition. However, it is not only the connection design that affects the stability. The strength of the titanium grade as material is also important since it affects the implant stability. When using the implant system made of titanium grade 2, a larger diameter fixture should be selected in order to provide enough strength to withstand overloading.

Influence of the connection design and titanium grades of the implant complex on resistance under static loading

박수정,이석원,이성복,안수진 대한치과보철학회 2016 The Journal of Advanced Prosthodontics Vol.8 No.5

PURPOSE. The purpose of this study was to evaluate the resistance to deformation under static overloading by measuring yield and fracture strength, and to analyze the failure characteristics of implant assemblies made of different titanium grades and connections. MATERIALS AND METHODS. Six groups of implant assemblies were fabricated according to ISO 14801 (n=10). These consisted of the combinations of 3 platform connections (external, internal, and morse tapered) and 2 materials (titanium grade 2 and titanium grade 4). Yield strength and fracture strength were evaluated with a computer-controlled Universal Testing Machine, and failed implant assemblies were classified and analyzed by optical microscopy. The data were analyzed using the One-way analysis of variance (ANOVA) and Student’s t-test with the level of significance at P=.05. RESULTS. The group IT4S had the significantly highest values and group IT2 the lowest, for both yield strength and fracture strength. Groups IT4N and ET4 had similar yield and fracture strengths despite having different connection designs. Group MT2 and group IT2 had significant differences in yield and fracture strength although they were made by the same material as titanium grade 2. The implant system of the similar fixture-abutment interfaces and the same materials showed the similar characteristics of deformation. CONCLUSION. A longer internal connection and titanium grade 4 of the implant system is advantageous for static overloading condition. However, it is not only the connection design that affects the stability. The strength of the titanium grade as material is also important since it affects the implant stability. When using the implant system made of titanium grade 2, a larger diameter fixture should be selected in order to provide enough strength to withstand overloading.

Influence of the connection design and titanium grades of the implant complex on resistance under static loading

Su-Jung Park,Suk-Won Lee,Richard Leesungbok,Su-Jin Ahn 대한치과보철학회 2016 The Journal of Advanced Prosthodontics Vol.8 No.5

PURPOSE. The purpose of this study was to evaluate the resistance to deformation under static overloading by measuring yield and fracture strength, and to analyze the failure characteristics of implant assemblies made of different titanium grades and connections. MATERIALS AND METHODS. Six groups of implant assemblies were fabricated according to ISO 14801 (n=10). These consisted of the combinations of 3 platform connections (external, internal, and morse tapered) and 2 materials (titanium grade 2 and titanium grade 4). Yield strength and fracture strength were evaluated with a computer-controlled Universal Testing Machine, and failed implant assemblies were classified and analyzed by optical microscopy. The data were analyzed using the One-way analysis of variance (ANOVA) and Student’s t-test with the level of significance at P=.05. RESULTS. The group IT4S had the significantly highest values and group IT2 the lowest, for both yield strength and fracture strength. Groups IT4N and ET4 had similar yield and fracture strengths despite having different connection designs. Group MT2 and group IT2 had significant differences in yield and fracture strength although they were made by the same material as titanium grade 2. The implant system of the similar fixture-abutment interfaces and the same materials showed the similar characteristics of deformation. CONCLUSION. A longer internal connection and titanium grade 4 of the implant system is advantageous for static overloading condition. However, it is not only the connection design that affects the stability. The strength of the titanium grade as material is also important since it affects the implant stability. When using the implant system made of titanium grade 2, a larger diameter fixture should be selected in order to provide enough strength to withstand overloading.

항복강도에 따른 Zr-2.5Nb 압력관의 Delayed Hydride Cracking Velocity

김영석(Kim Young Suk),정용무(Cheong Yong Moo),임경수(Im Kyung Soo),김인섭(Kim In Sup),마르켈로프(V. Markelov) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8

The objective of this study is to investigate the delayed hydride cracking velocity (DHCV) of Zr-2.5Nb pressure tubes with yield strength. DHC tests were conducted at an initial K₁ of 19 ㎫√m and 250℃ on the compact tension specimens containing 100 ppm hydrogen that were taken from the Zr-2.5Nb tubes with different yield strengths. The crack growth was determined with the direct current potential drop method. A nice correlation of the DHC velocity and the yield strength was obtained at all temperatures by normalizing the DHCV with the terminal solid solubility and diffusion of hydrogen: the DHCV increased exponentially with increased yield strength of the Zr-2.5Nb tubes. In contrast, the texture and the distribution of the β-Zr phase were found to have a comparatively minor effect on the DHCV of the Zr-2.5Nb tubes. Yield strength of the Zr-2.5Nb tubes determines a plastic zone size with a steep gradient of hydrogen concentration ahead of the crack tip where hydrides can be precipitated. The yield strength effect is discussed by correlating the plastic and the striation spacing observed on the fractured surfaces as a function of yield strengths.

고온 강구조 압축재의 좌굴 강도에 관한 연구

최현식 한국공간구조학회 2019 한국공간구조학회지 Vol.19 No.2

The high-temperature properties of mild steels were studied by comparing the test results of Kwon and the yield strength, tangent modulus predicted by the design provisions of ASCE and Eurocode(EC3). The column strengths for steel members at high temperatures were determined by the elastic and inelastic buckling strengths according to elevated temperatures. The material properties at high temperatures should be used in the strength evaluations of high temperature members. The buckling strengths obtained from the AISC, EC3 and approximate formula proposed by Takagi et al. were compared with ones calculated by the material nonlinear analysis using the EC3 material model. The newly simplified formulas for yield stress, tangent modulus, proportional limit and buckling strength which were proposed through a comparative study of the material properties and buckling strengths. The buckling strengths of proposed formulas were approximately equivalent to ones obtained from the formulas of Takagi et al. within 4% . They were corresponded to the lower bound values among the buckling strengths calculated by the design formulas and inelastic buckling analysis.

Compressive strength of circular concrete filled steel tubular stubs strengthened with CFRP

Jialing Ou,Yong-Bo Shao 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.2

The compressive strength of circular concrete filled steel tubular (C-CFST) stubs strengthened with carbon fiber reinforced polymer (CFRP) is studied theoretically. According to previous experimental results, the failure process and mechanism of circular CFRP-concrete filled steel tubular (C-CFRP-CFST) stubs is analyzed, and the loading process is divided into 3 stages, i.e., elastic stage, elasto-plastic stage and failure stage. Based on continuum mechanics, the theoretical model of C-CFRP-CFST stubs under axial compression is established based on the assumptions that steel tube and concrete are both in three-dimensional stress state and CFRP is in uniaxial tensile stress state. Equations for calculating the yield strength and the ultimate strength of C-CFRP-CFST stubs are deduced. Theoretical predictions from the presented equations are compared with existing experimental results. There are a total of 49 tested specimens, including 15 ones for comparison of yield strength and 44 ones for comparison of ultimate strength. It is found that the predicted results of most specimens are within an error limit of 10%. Finally, simplified equations for calculating both yield strength and ultimate strength of C-CFRP-CFST stubs are proposed.

템퍼링 열처리 조건에 의한 드라이브샤프트 항복강도 영향성 검증

김형진(Hyeongjin Kim),전현승(Hyeonseung Jeon) 한국자동차공학회 2022 한국자동차공학회 학술대회 및 전시회 Vol.2022 No.11

Drive Shaft requires high strength characteristics for safety reasons. The safety of the Drive Shaft is usually judged on the basis of the fracture strength to prevent the breakage of the Drive Shaft during operation, but the yield strength should also be taken into account. If the input torque greater than yield strength is repeatedly applied to the Drive Shaft, plastic deformation occurs in the bar shaft, which deteriorates fatigue durability. In this study, the application of tempering heat treatment is selected as a method of improving the yield strength. We analyze the tendency of strength according to tempering heat treatment conditions and optimize the conditions for maximum yield strength and fracture strength by using DOE (Design Of Experiments)

테이퍼절삭나사이음을 이용한 고강도 철근(SD500)의 적합성 평가

윤승조 忠州大學校 2010 한국교통대학교 논문집 Vol.45 No.-

In order to evaluate the performance of the taper thread joints suitable for high strength bar(SD500), the yield strength and the tensile strength were tested by changing the material and the length of couplers and the length of threads according to the methods to process threads, and the results have proved the following conclusions. Compared to the tests when the threads were processed after swaging based on the thread processing method, those when threads were processed without swaging showed a sharp decline of weight after the yield load. When the length of couplers and threads were changed, both the tests of processed threads after swaging and those without swaging displayed no big difference in the yield strength and the tensile strength. In addition, in case of the tests when threads were processed after swaging, most parent metals were broken, while the tests when threads were processed without swaging had thread break or the symptom of the fall-out of threads from couplers. It's concluded that processing threads after swaging satisfies .1.25fy suggested in the standard for the architectural structure designing, and taper thread joints can be applied to high strength bars(SD500)

Contiguity as a governing parameter to predict the strength of porous materials

Nam, Kyungju,Park, Hyeji,Choi, Hyelim,Choe, Heeman Elsevier 2018 Materials Letters Vol.214 No.-

<P><B>Abstract</B></P> <P>With increasing demand for porous materials with their popular use in functional applications, there is a strong need to develop a decent strength prediction method for porous materials. The Gibson-Ashby (G-A) model, which is the most common prediction method, has served this purpose. This model is constructed upon a weakly-structured open-cell porous material, thus providing a ‘lower bound’ of yield strength. This study considers ‘contiguity’ as a governing parameter to predict the strength of porous materials and proposes a modified G-A model by incorporating the concept of contiguity. This paper supports preliminary evidence that the new model better describes the strength of selected porous materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> There is strong need for decent strength prediction method for porous materials. </LI> <LI> We consider contiguity as governing parameter to predict porous material’s strength. </LI> <LI> Our new empirical formula yields outstanding predictions for yield strength. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>