• Title, Summary, Keyword: recoverable strain

Search Result 8, Processing Time 0.042 seconds

A Study on the Shape Memory Characteristic Behaviors of Ti-42.5at%Ni-10at.% Cu Alloys (Ti-42.5at.%Ni-10at.%Cu합금의 형상기억특성에 관한 연구)

  • Woo, Heung-Sik;Park, Yong-Gyu
    • Journal of the Korean Society of Safety
    • /
    • v.24 no.1
    • /
    • pp.26-30
    • /
    • 2009
  • Shape memory recoverable stress and strain of Ti-42.5at%Ni-10at%Cu alloys were measured by means of constant temperature tensile tests. The alloys' transformation behavior is B2 - B19 by DSC result. The strain by tensile stress were perfectly recovered by heating at any testing conditions but shape memory recoverable stress increased to 66MPa and then slightly decreased. Transformation temperatures from thermal cycling under constant uniaxial applied tensile loads linearly increased by increasing tensile load and their thermal hysteresis are about 110K and their maximum recoverable strain is 6.5% at 100MPa condition.

A Study on the Shape Memory Characteristic Behaviors of Ti-42.5at.%Ni-2.0at.%Cu Alloys in Tension and Compression Condition (Ti-42.5at.%Ni-2.0at.%Cu합금의 인장 및 압축에 따른 형상기억특성에 관한 연구)

  • Woo, Heung-Sik;Cho, Jae-Whan;Park, Yong-Gyu
    • Journal of the Korean Society of Safety
    • /
    • v.24 no.5
    • /
    • pp.1-5
    • /
    • 2009
  • NiTiCu alloys can produce a large force per unit volume and operate with a simple mechanism. For this reasons, it has been widely studied for application as a micro actuator. So in this study, one-way and two way shape memory effects of Ti-42.5at%Ni-2.0at%Cu alloys are studied. In the case of one-way shape memory effects, shape memory recoverable stress and strain of this alloys were measured by means of tension and compression tests under constant temperature. The strains by tension and compression stress were perfectly recovered by heating at any testing conditions also shape memory recoverable stress increased to 116 MPa in tension tests and to 260 MPa in compression tests. In the case of two-way shape memory effects, transformation temperatures from thermal cycling under constant uniaxial applied tension and compression loads linearly increased by increasing external loads and their maximum recoverable strain is 3.8% at 100MPa tensile condition and 2.2% at 125 MPa compression condition.

Fatigue Characterization of NiTiCu Shape Memory Alloys (NiTiCu 형상기억합금의 피로특성)

  • Han, Ji-Won;Park, Sung Bum
    • Journal of the Korean Society of Safety
    • /
    • v.29 no.4
    • /
    • pp.28-33
    • /
    • 2014
  • Recently, the actuator worked by the driving recovery-force of the thermo elastic martensitic transformation of shape memory alloys(SMA) has been studied. This paper presents a study on the fatigue life of shape memory alloy (SMA) actuators undergoing thermally induced martensitic phase transformation under various stress levels. shape memory recoverable stress and strain of Ti-44.5at.%Ni-8at.%Cu alloys were by means of constant temperature tensile tests. Differential scanning calorimetry (DSC) was employed in order to investigate the transformation characteristics of the alloy before the tests. the results were summarized as follows. The martensite inducing stress incerased with the increasing of the Cu-contents. The fatigue life decreased with the increasing of the test load and the Cu-content. The data acquired will be very useful during the design process of an SMA NiTiCu element as a functional part of an actuator.

Stress-Strain Behavior of Clays under Repeated Loading (반복재하(反復載荷)에 의한 점성토(粘性土)의 응력변형특성(應力變形特性))

  • Cho, Jae Hong;Kang, Yea Mook;Ryu, Neung Hwan
    • Korean Journal of Agricultural Science
    • /
    • v.14 no.2
    • /
    • pp.329-344
    • /
    • 1987
  • This paper described the behavior under repeated loading in triaxial compression test on clay. The experiment was conducted to investigate the influence of controlled various over-consolidation ratio and compaction energy, on the stress-strain behavior of clays. 1. The difference of deviator stress during repeated loading was greatly appeared at large strain. And pore water pressure was decreased at initial of unloading, but it was increased again before long. 2. The recoverable elastic strain (${{\Delta}{\varepsilon}e}$) and the slope of un-reloading were decreased with the increment of over-consolidation ratio (OCR). 3. The recoverable elastic strain (${{\Delta}{\varepsilon}e}$) was increased with the increment of strain rate but it was decreased with the increment of strain in strain rate tests. The slope of un-reloading (Eur) tends to increase with the increment of strain rate and it was decreased with the increment of strain. 4. The recoverable elastic strain was greatly increased with the increment of compaction energy and it slightly tends to decrease with the increment of strain on various compaction energy. The slope of un-reloading was not appeared markedly with increment of compaction energy but it tends to decrease with the increment of strain generally.

  • PDF

Approximate Prediction of Soil Deformation Caused by Repeated Loading (반목하중으로 인한 지반의 변형 예측)

  • 도덕현
    • Magazine of the Korean Society of Agricultural Engineers
    • /
    • v.30 no.3
    • /
    • pp.69-81
    • /
    • 1988
  • The Repeated Load Triaxial and Oedometer Tests to the weathered granite & silty clay soil have been fulfilled to investigate their dynarnic characteristics. The results obtained are summarized as follows ; 1. In the relation between the repeated triaxial compression and the oedometer test, the recoverable strain of weathered granite soil showed a tendency to decrease by the increase of the repeated loads number(N), and that of silty clay showed approximately constant values while the total strain increased continuously. 2. The changes of plastic strain was dependent to the level of deviator stress which is the most important element in the calculation of soil deformation under repeated load condition. And there was a significance of 10% between the level of stress and plastic strain. 3. When the soil was aimost dried or saturated to 100%, the deformation by the repeated loads was small. However the deformation showed peak around the saturation of 50%. 4. When the deformation was predicted by the repeated triaxial load tests of a laboratory, it is desirable to introduce the threshold stress concept in the calculation of deformation of subgrade of the pavement. 5. The improved design equation (Eq. 16) introducing the modulus of conversion(Fo), which is based on the Boussineq' s theory, is considered to be rational in the design of flexible pavement. From the above results, the deformation to the repeated traffic loads could be predicted by the repeated triaxial tests on the pavement materials or undisturbed soil layers, therefore it is think that the durable and econornic pavement could be constructed by reflecting that to the design.

  • PDF

Creep Prediction of Chemical Grouted Sands (약액주입 사질고결토의 크리프 예측)

  • Kang, Hee-Bog;Kim, Jong-Ryeol;Kang, Kwon-Soo;Kim, Tae-Hoon;Hwang, Soung-Won
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.8 no.2
    • /
    • pp.195-204
    • /
    • 2004
  • A series of constant creep and repeated creep tests are performed to investigate the behavior of visco-elasto-plastic materials of chemical grouted sands. In the result of constant creep test, the material exhibits three types of shear strain : elastic, plastic, viscoelastic. The elastic, plastic and viscoelastic strains are linear, i.e., the strains are proportional to the stresses for loading. Good agreement is found between the predicted viscoelastic and test results by the power law and the generalized model. In the repeated creep test, the instantaneous recoverable strain is time-independent and the magnitude of accumulated plastic strain increases with number of cycles. Also it is seen that the accumulated plastic strains are approximately proportional to stress. There are no significant differences between test results predicted values for first cycle, and the differences increase relatively insignificantly with number of cycles.

A Basic Study on the Design of the Flexible Keel in the Energy-Storage Prosthetic Foot for the Improvement of the Walking Performance of the Below Knee Amputees (하지 절단환자의 보행 능력 향상을 위한 에너지 저장형 의족의 유연 용골 설계를 위한 기초연구)

  • 장태성;이정주;윤용산;임정옥
    • Journal of Biomedical Engineering Research
    • /
    • v.19 no.5
    • /
    • pp.519-530
    • /
    • 1998
  • In this paper, the basic study on the design of the flexible keel of the energy-storage prosthetic foot was performed in order to Improve the walking performance and Increase the activities of the below knee amputees. Based on the analysis of the anthropometric data and the normal gait on two dimensional sagittal plane available In the literature, we presented a model of the basic structure of the flexible keel of the prosthetic foot. The model of the basic structure was composed of the simple beams, and linear rotational spring and damper. Laminated carbon fiber-reinforced composites were selected as the material of the basic structure model of the flexible keel In order to apply the high strength and light weight materials to the basic structure of the flexible keel of the prosthetic foot. The recoverable strain energy In response to the change of beam shape was calculated bur the finite element analysis and it was suggested that the change of beam shape could be the design variable in flexible keel design. The simulation process was systematically designed by using orthogonal array table in order to design the flexible keel structure which could store the more recoverable strain energy. finite element analysis was carried but according to the design of simulations by using the finite element program ABAQUS and the flexible keel structure of the energy-storage prosthetic foot was obtained from the analysis of variance(ANOVA). The dynamic simulation model of the prosthetic walking using the flexible keel structure was made and the dynamic analysis was carried but during one walk cycle. Based on the above results, an effective design process was presented for the development of the prosthetic fool system.

  • PDF

Identification of Enterococcus faecalis on MSB Medium Selective for Mutans Streptococci

  • Lee, Seung-Hoon;Yoo, So-Young;Kim, Hwa-Sook;Kang, Sook-Jin;Lim, Sung-Hoon;Kim, Kwang-Won;Park, Jung-Min;Shin, Yong-Kook;Shin, Jeong-Hwan;Baek, Dong-Heon;Choe, Son-Jin;Kook, Joong-Ki
    • International Journal of Oral Biology
    • /
    • v.31 no.1
    • /
    • pp.7-10
    • /
    • 2006
  • Mitis-salivarius sucrose bacitracin(MSB) medium is widely used in the selective isolation of mutans streptococci(MS), a designation for a group of oral cariogenic species. Recently, we have isolated three bacterial strains grown on MSB agar from human dental plaques. The three strains exhibited biochemical characteristics similar to those of the biotype IV of MS, with the exception that they manifested a positive reaction for arginine deaminase. The objective of this study was to identify and characterize these three clinical isolates. The bacteria were identified with biochemical tests as well as by 16S rDNA cloning and sequencing. In order to compare the antibiotics susceptibility of the clinical isolates with that of type strain, the minimum inhibitory concentrations of 9 antibiotics were determined using broth dilution assays. The results identified all of our three clinical isolates as Enterococcus faecalis. All E. faecalis strains were found to be susceptible to penicillin G, amoxicillin, augmentin, and vancomycin, but were resistant to ciprofloxacin, cefuroxim axetil, and clindamycin. Our findings indicate that E. faecalis is capable of growing on MSB agar, and suggest that the MSB medium be improved so that only MS should be recoverable on the medium, as originally devised for their selection.