• Journal of Hydrogen and New Energy
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• v.33 no.2
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• pp.176-182
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• 2022

Since the various characteristics of the polymer electrolyte membrane are not clearly identified, it is difficult to predict and design applications for various conditions. In this study, as a previous study on the aging of the polymer electrolyte membrane, a study was conducted on the change of mechanical properties according to the aging of the polymer electrolyte membrane. Through the tensile test of Nafion 117, the mechanical properties change due to aging was confirmed. As a result of the tensile test, it was confirmed that the aged Nafion 117 had reduced tensile strength. Through DSC measurement, aged Nafion confirmed that the glass transition temperature and enthalpy change were low, which is thought to be the effect of molecular motion and transition due to the lapse of time. The effect is thought to cause a difference in the amount of change in enthalpy, resulting in a difference in mechanical properties during tension.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.68-74
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• 2002

The tensile tests to identify the statistical tensile properties and the acoustic emission characteristics were conducted for STS304 stainless steel at $600^{\circ}C,\;700^{\circ}C$. From tensile tests performed by constant cross head speed controls with 1mm/min, rates at each elevated temperature, the scatters were observed in tensile strength, reduction of area, elongation and the acoustic emission parameters. The effect of temperature on the scatter of tensile behavior was larger at $700^{\circ}C$. The distributions of tensile properties was well followed in 3-parameter Weibull. The AE counts and energy of the $700^{\circ}C$ specimens were smaller than the $600^{\circ}C$.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.787-795
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• 2003

Mechanical properties of the materials used for transportations and industrial machinery under high strain rate loading conditions such as seismic loading are required to provide appropriate safety assessment to these mechanical structures. The Split Hopkinson Pressure Bar (SHPB) technique with a special experimental apparatus can be used to obtain the material behavior under high strain rate loading conditions. In this paper, dynamic deformation behaviors of the aluminum alloys such as A12024-T4, A1606 IT-6 and A17075-T6 under both high strain rate compressive and tensile loading conditions are determined using the SHPB technique.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1358-1362
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• 2005

The Ni-base superalloy GTD-111DS was designed in the 1970s and is widely used as the material of the first stage blade under a severe combination of temperature and pressure in gas turbines. But because GTD-111DS is distributed in the shape of blade and blade has a unique figure and many cooling channels, it is hard to manufacture the test specimen. In this reason, there are little data on the microstructure and mechanical properties of the alloy. Therefore through the microstructure analysis, present paper observed that the shape of $\gamma{'}$ did not change even if aging time was increased but the amount and volume of the deposition of secondary $\gamma{'}\;rose\;and\;secondary\;\gamma{'}\;grew\;among\;primary\;\gamma{'}$. Also, by tensile test for different temperature, there was difference between yield strength and tensile strength in room temperature on heat treatment and extracting region but the more increasing temperature, the more decreasing difference between yield strength and tensile strength.

• Structural Engineering and Mechanics
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• v.46 no.2
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• pp.295-322
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• 2013

Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, toughness, energy absorption capacity and fracture toughness. Modification in the mix design of SCC may have a significant influence on the SFRSCC mechanical properties. Therefore, it is vital to investigate whether all of the assumed hypotheses for steel fiber reinforced concrete (SFRC) are also valid for SFRSCC structures. Although available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates material's mechanical properties. The present study includes: a) evaluation and comparison of the current analytical models used for estimating the mechanical properties of SFRSCC and SFRC, b) proposing new relationships for SFRSCC mixtures mechanical properties. The investigated mechanical properties are based on the available experimental results and include: compressive strength, modulus of elasticity, strain at peak compressive strength, tensile strength, and compressive and tensile stress-strain curves.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1697-1702
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• 2000

This study has been performed to investigate the effects of glass fiber characteristics on the mechanical properties of thermoplastic composite. The surface of glass fiber was coated with the silan e to enhance the bonding strength between fiber and matrix. A micro-droplet pull-off test was performed to investigate the influence of the silane concentration on the bonding strength. The maximum bonding strength was observed around 10.8% silane concentration. In order to examine the influence of the fiber length and fiber content on the properties of the composite, the composite materials involving tile fiber lengths of 5mm, 10mm, 15mm 20mm, and 25mm were tested. The composites used contain 20%, 30%, and 40% by weight of glass fibers. Tension and flexural tests were performed to investigate their mechanical properties of the composites. The tensile strength and tensile modulus of the composite increase with increasing the glass fiber content. The tensile modulus increases slightly with increasing the fiber length. The maximum tensile strength is observed around the fiber length of 15-20mm. The flexural modulus and strength also increase slightly with increasing the fiber length.

• Electrical & Electronic Materials
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• v.10 no.4
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• pp.327-333
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• 1997

Experiments on mechanical fatigue were conducted using the specimens which were cut from hydrogen cooled generator(rated 22kV and 50OMW) stator windings. We have investigated the aged mechanism of mica/epoxy insulation systems under air or hydrogen by both the tensile and compressive loadings. The fracture of generator stator windings is generally affected by mechanical stress. Thus, the tensile strength test were conducted. In this case, the maximum strength and strain are quite different between sound and aged specimens. It is observed that low bonded interface parts of tapes generally have lower strength than those of normal tapes which causes stress. In order to estimate the effects of cyclic load by the electromagnetic forces while the generator starts/stops, the mechanical fatigue test was also conducted. It is confirmed that the equation of expected life depends on stress amplitude and number of cycles. Though the stress amplitude and number of cycles are very tiny, the tensile fatigue of aged specimens under hydrogen atmosphere is bigger than those under air. In the case of hydrogen atmosphere, the tensile stress gives bigger effect than the compressive one.

• Korean Journal of Materials Research
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• v.30 no.12
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• pp.650-654
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• 2020

A combination of Polycarbonate (PC) material and Polymethylmethacrylate (PMMA), fabricated using an injection molding machine, has been investigated to determine its advantages, as studied in Ref. 1). This paper aims to investigate the optimization of PMMA/PC blend for both tensile yield strength and impact strength. Furthermore, interaction effects of process conditions on mechanical properties including tensile yield strength and impact strength of PMMA/PC blend by injection molding process are interpreted in this study. Tensile and impact specimens are designed following ASTM, type V, and are fabricated by injection molding process. The processing conditions such as melt temperature, mold temperature, packing pressure, and cooling time are applied; each factor has three levels. As a result, in comparison with optimization of separated responses, mechanical properties of PMMA/PC are found to decrease when optimizing both tensile and impact strengths simultaneously. The melt temperature is found to be the most significant interaction parameter with the mold temperature and packing pressure. In addition, there is more interaction between the mold temperature and cooling time. This investigation provides a useful understanding of the control of injection molding processing of polymer blends in optical application.

• International Journal of Precision Engineering and Manufacturing
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• v.1 no.1
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• pp.91-97
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• 2000

Anisotropic work hardening of cold rolled low carbon steel sheets is studied. The experiments consist of two stage tensile prestraining and tensile tests. At the first prestraining, steel sheets are streteched along the rolling direction by 3% and 6% tensile strains. The second prestrains are at 0${\cric}$, 30${\cric}$, 60${\cric}$to the rolling directions by varying degrees. Tensile tests are performed on the specimens cut from the sheets after the two stage prestraining. A theoretical framework on anisotropic hardening is proposed which includes Hill's quadratic yield function, ziegler's kinematic hardening rule, and Kim and Yin's assumption on the rotation of orthotropy axes. The predicted variations of R-values with second stage tensile strain are compared with the experimental data.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.190-194
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• 2003

Two different types of nondestructive evaluation (NDE) techniques were employed to investigate the tensile behavior of ceramic matrix composites (CMCs). Two NDE methods, ultrasonic testing (UT) and infrared (IR) thermography, were used to assess defects and/or damage evolution before and during mechanical testing. Prior to tensile testing, a UTC-scan and a xenon flash method were performed to obtain initial defect information in light of UT C-scans and thermal diffusivity maps, respectively. An IR camera was used for in-situ monitoring of progressive damages. The IR camera measured temperature changes during tensile testing. This paper has presented the feasibility of using NDE techniques to interpret structural performance of CMCs.