• Title/Summary/Keyword: Testing Temperature

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The Method of Determining Stress Levels Regarding the Electrical ALT through Optical Temperature Sensor

  • Ryu, Haeng-Soo;Han, Gyu-Hwan;Yoon, Nam-Sik
    • Journal of Electrical Engineering and Technology
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    • v.3 no.2
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    • pp.184-191
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    • 2008
  • Electrical endurance is the critical characteristic of Magnetic contactors(MCs), which are widely used in such power equipment as elevators, cranes, and factory control rooms in order to close and open control circuits. Testing time, however, is not short in typical cases in which some method of reducing the testing period is required. This study shows the method of determining the stress level of electrical ALT(Accelerated Life Test) through optical temperature sensor and the relationship between 0.05 s and 0.1 s for on-time. The tool used for analyzing the test result is MINITAB. I will propose the method of determining the optimized stress level through optical temperature sensor, which will contribute to minimize the testing time and development period and also raise the product reliability.

The Effects of the Testing Temperatures on the Mechanical Properties of the Carbon Tool Steel(SK4M) for Flat Spring (박판 스프링용 탄소공구강재(SK4M)의 시험온도에 따른 기계적 특성)

  • 류태호;원시태;박상언;임철록
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.10a
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    • pp.693-696
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    • 2002
  • This study examined the effects of the testing temperature on the mechanical properties of the carbon tool steel (SK4M) for flat spring. Hardness test and fatigue test were performed at room temperature ($20^{\circ}C$). Tensile test and creep test were performed at temperature range $20^{\circ}C$ ~$160^{\circ}C$. The micro-vickers hardness values of SK4M was Hv=584. The Elastic modulus, tensile strength and yield strength of SK4M at 160t test temperature were decreased 0.92 time, 0.97 time and 0.82 time those of SK4M at 2$0^{\circ}C$ test temperature, respectively. The maximum creep strain for 100hr at creep temperature ($80^{\circ}C$ ~$160^{\circ}C$) and creep stress ($37.4Kgf/\textrm{mm}^2$ ~$93.6Kgf/\textrm{mm}^2$) was 0.572%. The fatigue limit of SK4M was $94Kgf/\textrm{mm}^2$.

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Infrared Thermographic Monitoring for Failure Characterization in Railway Axle Materials (철도차량 차축 재료의 파괴특성 적외선열화상 모니터링)

  • Kim, Jeong-Guk
    • Journal of the Korean Society for Nondestructive Testing
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    • v.30 no.2
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    • pp.116-120
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    • 2010
  • The wheelset, an assembly of wheel and axle, is one of important parts in railway bogie, directly related with the running safety of railway rolling stock. In this investigation, the tensile failure behavior of railway axle materials was investigated. The tensile coupons were prepared from the actual rolling stock parts, which were operated over 20 years. The tensile testing was performed according to the KS guideline. During tensile testing, an infrared camera was employed to monitor temperature changes in specimen as well as demonstrate temperature contour in terms of infrared thermographic images. The thermographic images of tensile specimens showed comparable results with mechanical behavior of tensile materials. In this paper, the failure mode and behavior of railway axle materials were provided with the aid of infrared thermography technique.

Stepped Isothermal Methods Using Time-Temperature Superposition Principles for Lifetime Prediction of Polyester Geogrids

  • Koo Hyun-Jin;Kim You-Kyum;Kim Dong-Whan
    • Proceedings of the Korean Reliability Society Conference
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    • 2005.06a
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    • pp.69-73
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    • 2005
  • The failure of geogrids used for soil reinforcement application can be defined as an excessive creep strain which causes the collapse of slopes and embankments. Accordingly, the lifetime is evaluated as a time to reach the excessive creep strain using two accelerated creep testing methods, time-temperature superposition(TTS) and stepped isothermal methods(SIM). TTS is a well-accepted acceleration method to evaluate creep behavior of polymeric materials, while SIM was developed in the last ten years mainly to shorten testing time and minimize the uncertainty associated with inherent variability of multi-specimen tests. The SIM test is usually performed using single rib of geogrids for temperature steps of $14^{\circ}C$ and a dwell time of 10,000 seconds. However, for multi-ribs of geogrids, the applicability of the SIM has not been well established. In this study, the creep behaviors are evaluated using multi-ribs of polyester geogrids using SIM and TTS creep procedures and the newly designed test equipment. Then the lifetime of geogrids are predicted by analyzing the failure times to reach the excessive creep strains through reliability analysis.

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Temperature-Dependency of Tensile Properties of GFRP Composite for Wind Turbine Blades (풍력 발전 블레이드 복합재 GFRP의 인장 특성의 온도 의존성)

  • Huh, Yong-Hak;Kim, Jong-Il;Kim, Dong-Jin;Lee, Gun-Chang
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.9
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    • pp.1053-1057
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    • 2012
  • In this study, the temperature-dependency of the tensile properties of a glass fiber reinforced plastic (GFRP) used in wind turbine blades was examined. The tensile strength, elastic modulus, and Poisson's ratio of the tensile specimen manufactured from uniaxial ($0^{\circ}$) and triaxial ($0/{\pm}45^{\circ}$) laminate composite plates were measured at four different testing temperatures-room temperature, $-30^{\circ}C$, $-50^{\circ}C$, and $60^{\circ}C$. It was found that the tensile strengths and elastic moduli of the uniaxial laminates were greater than those of the triaxial laminates over the testing temperature range. The tensile strength of the two laminates was significantly dependent on the testing temperature, while the dependency of the elastic modulus on the temperature was insignificant. Furthermore, it could be considered that the Poisson's ratio changed slightly with a change in the testing temperature.

A Study on the Accelerated Life Test for Evaluating the Reliability of Nickel-Cadmium Batteries

  • Kwon, Soo-Ho;Huh, Yang-Hyun;Lim, Tae-Jin
    • International Journal of Reliability and Applications
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    • v.1 no.1
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    • pp.89-104
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    • 2000
  • Accelerated testing consists of a variety of test methods for shortening the life of products or hastening the degradation of their performance. This paper presents practical, modern statistical methods for evaluating the reliability of Nickel-Cadmium batteries at their design temperature of 2$0^{\circ}C$ by accelerated life test. Batteries have been life tested at three high temperature conditions, 50, 60, 7$0^{\circ}C$, respectively to yield failures quickly. The failures have been observed and judged by means of charge and discharge current integration. Analyses of life data from those conditions resulted in the Weibull distribution, which has been verified on the ground of the Kolmogorov-smirnov test and the pairwise t-test. Life data are modeled according to the Arrhenius life-temperature relationship. The mean life of tested batteries is assessed at about 590 cycles, and the activation energy of this chemical reaction is concluded to be 0.39eV as results. This study provides procedures for estimating the reliability of batteries in a short period, which has little been possible in domestic industries. The results can be applied in many fields such as proof testing, acceptance testing, and estimating assurance periods.

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Thermal Inspection of GFRP using Liquid Crystal (액정을 이용한 GFRP의 열적시험법에 관한 연구)

  • Kim, Y.H.;Kwon, O.Y.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.10 no.2
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    • pp.50-55
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    • 1990
  • Flaws in GFRP(Glass Fiber Reinforced Plastics) were thermally detected using cholesteric liquid crystals. Presence of flaws changes the thermal conductivity of GFRP, and disturbs heat flow. When a uniform heat source is applied, the surface temperature of flawed region is different from that of sound region. The surface temperature distributions were measured by thermo-optic properties of liquid crystal. Since the colors of liquid crystal indicate temperature distribution of GFRP surface, the thermal disturbance by flaws could be detected. The locations of flaws in GFRP could be determined from the distribution of liquid crystal colors.

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Characterisation of Tensile Deformation through Infrared Imaging Technique

  • B. Venkataraman, Baldev Raj;Mukhophadyay, C.K.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.22 no.6
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    • pp.609-620
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    • 2002
  • It is well known that during tensile testing, a part of the mechanical work done on the specimen is transformed into heat energy. However, the ultimate temperature rise and the rate of temperature rise is related to the nature of the material, conditions of the test and also to the deformation behaviour of the material during loading. The recent advances in infrared sensors and image/data processing techniques enable observation and quantitative analysis of the heat energy dissipated during such tensile tests. In this study, infrared imaging technique has been used to characterise the tensile deformation in AISI type 316 nuclear grade stainless steel. Apart from identifying the different stages during tensile deformation, the technique provided an accurate full-field temperature image by which the point and time of strain localization could be identified. The technique makes it possible to visualise the region of deformation and failure and also predict the exact region of fracture in advance. The effect of thermal gradients on plastic flow in the case of interrupted straining revealed that the interruption of strain and restraining at a lower strain rate not only delays the growth of the temperature gradient, but the temperature rise per unit strain decreases. The technique is a potential NDE tool that can be used for on-line detection of thermal gradients developed during extrusion and metal forming process which can be used for ensuring uniform distribution of plastic strain.

Lifetime Prediction of Automotive Airbag Fabrics (자동차 에어백용 원단의 수명예측)

  • Koo, Hyun-Jin;Cho, Hang-Won;Chang, Gap-Shik
    • Journal of Applied Reliability
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    • v.9 no.4
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    • pp.319-329
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    • 2009
  • The airbag module is an inflatable restraint system that inflates within 0.05 seconds automatically in a collision to protect the occupants. The airbag fabrics used in the module are required to have the good resilience and strength and also to have retained at least 80% of mechanical properties after using longer than 10 years. In this study, we develop an accelerated test method in order to predict the lifetimes of airbag. In this test, we select temperature and humidity as environmental stresses by analyzing the failure mechanisms of coated and uncoated nylon 66 fabrics. It is found that the degradation of airbag fabrics is effectively accelerated under the combined conditions of high temperature and humidity. Analyzing the results of the accelerated test, the lifetimes of airbag fabrics are predicted to be longer than 10 years.

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A New Compressive Testing Specimen for Linerboard and Corrugating Medium (ECT를 응용한 라이너지의 압축강도 측정시편 개발)

  • Youn, Seuk-Ki;Seo, Yung-Bum;Jeon, Yang
    • Korean Journal of Agricultural Science
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    • v.35 no.1
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    • pp.19-24
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    • 2008
  • A new compressive strength test specimen for linerboard and medium was developed, and tested for its agreement with conventional testing methods such as RCT and STFI. The new specimen enables compressive testing under the changing humidity and temperature. Experimental results showed that the new specimen gave equivalent compressive strengths as the other conventional methods at a constant temperature and humidity. We'll apply the methods under the cyclic humidity and temperature conditions.

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