Studies on the Correlation between Mechanical Properties and Ultrasonic Parameters of Aging 1Cr-1Mo-0.25V Steel

Seok Chang-Sung,Kim Jeong-Pyo The Korean Society of Mechanical Engineers 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.2

Mechanical properties of in-service facilities are required to evaluate the integrity of power plants and chemical plants. Non-destructive technique can be used to evaluate the mechanical properties. To investigate the mechanical properties using ultrasonic technique, the four classes of thermally aged specimens were prepared using an artificially accelerated aging method. Ultrasonic tests, tensile tests, fracture toughness tests, and hardness tests were performed for the specimens. Then the mechanical properties were compared with ultrasonic parameters such as attenuation and non-linear parameter. From the investigation, we confirm that the ultrasonic parameter can be used to evaluate the mechanical properties.

최소 자승법에 의한 현무암 섬유의 성분 - 인장성 해석

이현욱,임정호,허유,Lee, Hyun U.,Lim, Jung H.,Huh, You 한국섬유공학회 2016 한국섬유공학회지 Vol.53 No.4

Properties of material consisting of several components are dramatically influenced by the portion distribution and structural array of the components. In particular, mineral fibers contain several natural components and have significant variations in mechanical properties, as the portions of the components vary in each spinning process. This research aims at providing information on the influence of the components on the mechanical properties of basalt fibers, which is adopted as the experimental material, through experiments. For this purpose, the mechanical properties of the multi-component material are expressed in terms of linear combinations of the weight portions of the ingredients. By melting basalt rocks and spinning them into fibers, we prepared specimens to measure the amounts of the components and the tensile strength, tensile strain at breakage, and the tensile modulus. As the basalt ingredients cannot be controlled arbitrarily, the effects of individual components on the tensile properties of basalt fibers could not be easily separated. In this research, the contribution of each component to the tensile properties was expressed in terms of a linear model with multi-variables. Then, the model coefficients were obtained by applying the least square method to a loss function that was defined in terms of the errors between the estimated values of the tensile properties from the model and the measured values from the experiments. Results show that Ca had the most significant positive influence on the tensile properties with relative model coefficients of 16 (strength), 10 (strain at break), and 6 (modulus); while K and Si had the most significant negative influence on the tensile properties. Si showed the greatest negative effect on the tensile strength with a relative model coefficient of 10, and on the strain at break with a relative model coefficient of 6, while K had the most negative effect on the tensile properties in an absolute sense.

A basic research on correlation analysis of electrical-chemical-mechanical characteristics for estimating mechanical properties

Yong-Seok Lee(이용석) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

The materials properties are very important not only for research but also for industries that use various materials. Many industries and researchers have tried to measure materials properties. However, most of the research on materials properties have been conducted by focusing on only one characteristic. In hence, it is difficult to discover the correlation between each characteristic of the material. The electrical-chemical-mechanical properties of materials appear characteristics based on the atomic structure of materials. If the atomic structure is changed, the electrical, chemical, and mechanical properties will be effected and are expected to correlation among them. Therefore, we propose basic experiments that can analyze the correlation among electrical-chemical-mechanical properties for predicting mechanical properties of new materials in this research.

Effects of manufacturing process and surface treatments on mechanical properties of PLA/SCF composites using extrusion printing

Zhiyong Ma,Zheng Qian,Jiabin Cai 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5

Short carbon fiber (SCF) reinforced polylactic acid (PLA) composites were fabricated by extrusion printing, and the effects of process parameters and surface treatments on the mechanical properties of composites were studied. Based on the rheological properties of composites and the extrusion process simulation, pure PLA specimens and PLA/SCF specimens were manufactured under different printing parameters. Three kinds of surface treatment were adopted to improve the mechanical properties. The experimental results show that SCF can effectively improve the tensile strength and bending strength, but the compressive strength decreased. The specimen had the best mechanical properties when the layer height was 0.1 mm and the nozzle diameter was 0.6 mm. The mechanical properties can be further improved by coupling agent coating method, and the compressive strength was even higher than that of pure PLA specimen. The research in this paper can provide a reference for the fabrication of thermoplastic composites with excellent mechanical properties by extrusion printing.

Wood Physical and Mechanical Properties of Clonal Teak (Tectona grandis) Stands Under Different Thinning and Pruning Intensity Levels Planted in Java, Indonesia

( Gama Widya Seta ),( Fanny Hidayati ),( Widiyatno ),( Mohammad Na’iem ) 한국목재공학회 2023 목재공학 Vol.51 No.2

The objective of this study was to reveal the impact of thinning and pruning regimes on the physical and mechanical properties of clonal teak wood planted in Java. In this study, a 15-year-old clonal teak plantation was carried out and the obtained data were evaluated with analysis of variance (ANOVA). The results showed that different thinning intensities had a significant impact on the alteration of heartwood volume development (F = 25.63; p < 0.0001). Meanwhile, the impact of different thinning treatments in several physical properties depends on the pruning treatment levels [moisture content (F = 12.18, p < 0.0001); tangential shrinkage (F = 15.60, p < 0.0001); T/R ratio (F = 7.17, p < 0.0001); and volumetric shrinkage (F = 10.81, p < 0.0001)]. However, different thinning intensities had no significant impact on wood basic density alteration (F = 0.72, p = 0.486), while pruning intensities affect the differences between radial (F = 3.52, p = 0.030) and volumetric shrinkage (F = 3.13, p = 0.044). In mechanical properties, thinning intensity levels did not promote any significant differences [modulus of elasticity (F = 1.41, p = 0.248); modulus of rupture (F = 0.94, p = 0.392); compressive strength parallel to grain (F = 0.21, p = 0.813); and compressive strength perpendicular to the grain (F = 0.41, p = 0.669)]. Meanwhile, different pruning treatments and combination treatments were not significantly altered all mechanical properties. These results indicated that the thinning and pruning regimes can enhance the mechanical properties without having a serious alteration in the physical properties of clonal teak wood.

3D 프린팅 된 탄소 단섬유강화 복합재료의 후처리 효과가 재료의 기계적 성능에 미치는 영향

차가락 ( Jia-le Che ),장승환 ( Seung-hwan Chang ) 한국복합재료학회 2022 Composites research Vol.35 No.6

상용 FFF (Fused filament fabrication) 3D 프린터로 제조된 탄소 단섬유강화 나일론 복합재료 구조의 내부 채움 패턴(Infill pattern)의 높은 공극률은 프린팅 된 구조의 기계적 성능을 결정한다. 본 연구는 프린팅 된 구조의 내부 채움 패턴의 공극률을 줄여서 기계적 특성을 개선하기 위해 사각형 내부 채움 구조로 제작된 Onyx 복합재료 시편의 열압밀 조건에 따른 시편의 기계적 성능을 실험적으로 평가하고, 가장 우수한 기계적 물성을 유도하는 열압밀 공정 조건(145℃, 4 MPa, 12 min)을 찾았다. 현미경 관찰결과 열압밀 후처리를 겪은 복합재료 시편의 내부 채움 공극률이 효과적으로 줄어듦을 확인하였다. 후처리된 시편의 기계적 성능을 확인하기 위해, 후처리를 하지 않은 대조군 시편과, 후처리 후 밀도와 치수를 동일하게 설정하여 출력한 시편과 함께 인장시험 및 3점 굽힘시험을 수행하여 기계적 물성을 비교한 결과 열압밀 후처리를 수행한 경우 기계적 물성이 효과적으로 개선되는 것을 확인하였다. The high porosity of the infill pattern of carbon chopped fiber-reinforced Nylon composite structures fabricated by the fused filament fabrication (FFF) type 3D printers determines the mechanical performance of the printed structures. This study experimentally evaluated the mechanical performance of Onyx composite specimens fabricated with a rectangular infill structure under the hot-pressing condition to improve the mechanical properties by reducing the porosity of the infill pattern of the printed structure, and evaluated the best mechanical performance. The hot-pressing conditions (145℃, 4 MPa, 12 min) that induce the most appropriate mechanical properties were found. As a result of microscopic observation, it was confirmed that the infill porosity of the composite specimens subjected to post hot-pressing treatment was effectively reduced. In order to confirm the mechanical performance of the post-treated specimen, a tensile test and a three-point bending test were performed with a control specimen without post-treatment and a specimen printed with the same density and dimensions after post-treatment to evaluate the mechanical properties. As a result of comparison, it was confirmed that the mechanical properties were effectively improved when the post-treatment of hot-pressing was performed.

Integrated Graphical Presentation of Fabric Sound and Mechanical Properties

Cho, Gil-Soo,Lim, Nam-Kyoo,Yang, Yoon-Jung 한국섬유공학회 2010 FIBERS AND POLYMERS Vol.11 No.3

This paper proposes a new model capable of predicting frictional sounds of woven fabrics, knitted fabrics and vapor permeable water repellent fabrics by measuring the relationships between their sound parameters and mechanical properties. We conducted an experiment in which fabric frictional sounds were recorded and analyzed. A total of 217 specimens consisting of woven fabrics, knitted fabrics, and vapor permeable water repellent fabrics were sampled, and their frictional sounds recorded using a Sound Quality System. Sound parameters of fabrics including SPL (Sound Pressure Level), Loudness (Z), Sharpness (Z), and mechanical properties by Kawabata Evaluation System (KES) were obtained. The relation between sound parameters and mechanical properties were analyzed by multiple regressions. Specimens were divided into 3 clusters using mechanical properties selected by stepwise selection method, and the mechanical properties of each cluster were investigated. Specimens were classified into clusters having high level of SPL and Loudness (Z), high level of Sharpness (Z), and middle level of Loudness (Z) and Sharpness (Z), which means that sound parameters are well verified by mechanical properties of the specimens. Mechanical properties relevant to each sound parameter were mapped on two dimensional spaces by integrated graphical presentation. SPL showed high positive correlation coefficients with MMD and LT. Loudness (Z) was well predicted by 2HG5 and Sharpness (Z) by MIU.

Tencel 직물의 역학특성과 Seam Puckering 에 관한 연구

조차,박채련,신지혜 한국의류학회 1999 한국의류학회지 Vol.23 No.1

For this study, It was measured the seam puckering based on the mechanical properties of tencel under the proper condition of needlework and machine sewing, analyzed the mechanical properties which are influenced to the seam puckering, and estimated the seam puckering based on the mechanical properties. The results of this study are as follows : There are three types of the seam puckering for each step which is caused by repeated washing and press. Concerning the seam puckering with the number of washing, the more the number of washing is increased, the less the seam puckering is decreased. Concerning the mechanical properties of the sample with the seam puckering, the seam puckering is related to LT positively, B, 2HB, T, W negatively. Among the mechanical properties LT, B, 2HB, T, W are most influenced to the seam puckering. Judging from the result of estimating seam puckering based on mechanical properties, the estimate-formula is satisfied in this study.

고온 및 냉각조건에 따른 콘크리트의 역학적특성에 관한 실험적 연구

김규용,강연우,이태규,최경철,윤민호 한국건축시공학회 2012 한국건축시공학회지 Vol.12 No.3

Since the 1970s, the mechanical properties of concrete at high temperature, such as compressive strength, elastic modulus, thermal strain, etc. have been investigated. Internal and external factors should be effect to concrete elevated temperature. In particular, the thermal properties of aggregate and cooling conditions are most important to estimate residual mechanical properties. This study evaluates the mechanical properties of concrete with aggregate type and cooling methods. We use normal and light aggregate for different thermal properties, and also test mechanical properties to use Ø100×200 mm cylinder specimen according to target temperature, slow cooling and water cooling. We found that normal aggregate concrete that uses is more highly influenced by cooling conditions than concrete that uses light aggregate concrete. In addition, the residual mechanical properties of concrete increase as cooling velocity lowers. 1970년대부터 고온을 받은 콘크리트의 압축강도, 탄성계수, 열응력 등 콘크리트에 영향을 미칠 수 있는 내적,외적 인자들의 역학적 특성은 조사되어 왔다. 특히, 골재의 열적 특성이나 냉각 방법은 잔존 역학적 특성을 평가하는데 가장 중요하다. 본 연구에서는, 골재 종류와 냉각방식에 따른 콘크리트의 역학적 특성에 대해 평가했다. 본연구에서는 열적특성이 다른 일반 골재와 경량골재를 사용했다. 또한, Ø100×200mm 원주형 공시체를 사용하여목표 온도, 서냉 및 급냉조건 후에 역학적 특성을 평가하였다. 결과적으로, 보통 골재를 사용한 콘크리트는 경량골재를 사용한 콘크리트보다 냉각조건이 미치는 영향이 큰것으로 나타났다. 그리고 냉각 속도가 빠르지 않을수록 콘크리트의 잔존 역학적 특성이 크게 나타났다.

Evaluation of interfacial and mechanical properties of glass fiber and <i>p-</i>DCPD composites with surface treatment of glass fiber

Kim, Jong-Hyun,Kwon, Dong-Jun,Shin, Pyeong-Su,Park, Ha-Seung,Baek, Yeong-Min,DeVries, K. Lawrence,Park, Joung-Man Elsevier 2018 Composites Part B, Engineering Vol.153 No.-

<P><B>Abstract</B></P> <P>Optimum interfacial conditions are important in the fabrication of glass fiber (GF)/<I>p-</I>DCPD composites to enhance mechanical and impact properties. In this study, different GFs were used in the manufacture of <I>p-</I>DCPD composites and their interfacial and wetting properties compared. Interfacial properties of different GFs and <I>p-</I>DCPD were compared using interfacial shear stress (IFSS). IFSS was determined using a fragmentation test of dual fiber composite (DFC) and cyclic loading tensile tests. The CR-212 GF/<I>p-</I>DCPD composite was the best IFSS to 60.2 MPa than others and cyclic loading tensile strength decreased the slightest than others. Wetting properties were obtained from dynamic contact angle measurement and the variation of static contact angle. The <I>p</I>-DCPD wetted the quickest to CR-212 GF in 2 s than others. Surface energy and work of adhesion of different GFs and <I>p-</I>DCPD were calculated using the dynamic contact angle. The CR-212 GF/<I>p-</I>DCPD was the best work of adhesion than others. Sizing agent of different GFs was extracted using an acetone extraction method and compared using FT-IR spectra. The CR-212 GF exhibited the most hydroxyl group than others. Mechanical properties of different GFs and <I>p-</I>DCPD composites were compared using tensile, flexural and Izod impact test at room and low temperature. The CR-212 GF/<I>p-</I>DCPD composites exhibited the most tensile, flexural and Izod impact test at room and low temperature than other composites. The relationship between interfacial properties and mechanical properties was determined and optimum fiber sizing conditions were obtained using these all results. The GF/p-DCPD composites will be applied to external material of heavy vehicle and military field because of high impact properties at room and low temperature.</P>