• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.135-140
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• 2001

In metal cutting at the tool-chip interface, friction generates considerable amount of heat. Thus, tile .knowledge of wear properties or the cutting tool material in high temperature has been known as one of tile important factors in need of clarification. The authors presented the wear properties of 5%V-5%Co-1%Nb high speed steel, fabricated by powder metallurgy, in room temperature in a previous article. The objective of this paper is to clarify tile effects of temperature ell its wear properties. Wear tests in sliding conditions under various temperatures have been conducted. The results indicate that tile wear properties of tile tool material in high temperature as well as in room temperature are excellent. It may be deduced that the oxide layer formed on the vol-n surface at high temperature is stable enough to prevent wear due to tile high temperature strength of its matrix.

• Geomechanics and Engineering
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• 제32권2호
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• pp.137-144
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• 2023

The current article studied wave propagation in a nonlocal porous thermoelastic half-space with temperature-dependent properties. The problem is solved in the context of the Green-Lindsay theory (G-L) and the Lord- Shulman theory (L-S) based on thermoelasticity with memory-dependent derivatives. The governing equations of the porous thermoelastic solid are solved using normal mode analysis with an eigenvalue approach. In order to illustrate the analytical developments, the numerical solution is carried out, and the effect of local parameter and temperature-dependent properties on the physical fields are presented graphically.

• Steel and Composite Structures
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• 제15권5호
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• pp.481-505
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• 2013

This paper focuses on thermal post-buckling analysis of functionally graded beams with temperature dependent physical properties by using the total Lagrangian Timoshenko beam element approximation. Material properties of the beam change in the thickness direction according to a power-law function. The beam is clamped at both ends. In the case of beams with immovable ends, temperature rise causes compressible forces and therefore buckling and post-buckling phenomena occurs. It is known that post-buckling problems are geometrically nonlinear problems. Also, the material properties (Young's modulus, coefficient of thermal expansion, yield stress) are temperature dependent: That is the coefficients of the governing equations are not constant in this study. This situation suggests the physical nonlinearity of the problem. Hence, the considered problem is both geometrically and physically nonlinear. The considered highly non-linear problem is solved considering full geometric non-linearity by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. In this study, the differences between temperature dependent and independent physical properties are investigated for functionally graded beams in detail in post-buckling case. With the effects of material gradient property and thermal load, the relationships between deflections, critical buckling temperature and maximum stresses of the beams are illustrated in detail in post-buckling case.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 추계 학술논문 발표대회
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• pp.119-120
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• 2011

Recently, the effects of high temperature and fiber content on the residual mechnical properties of high-strength concrete were experimentally investigated. In this paper, residual mechanical properties of concrete with water to cement (w/c) ratios of 55%, 42% and 32% exposed to high temperature are compared with those obtained in fiber reinforced concretes of similar characteristics with the ranging of 0,05% to 0,20% polypropylene (PP) fibers by volume of concrete, and considered factors include pre-load levels (20% and 40% of the maximum load at room temperature). Outbreak time and water contents were tested and were determined the compressive strength. In the result, it is showed that to prevent the explosive spalling of 50MPa grade concretes exposed to high temperature need more than 0.05Vol.% PP fibers. Also, the cross-sectional area of PP fiber can influence on the residual mechanical properties and the spalling tendency of fiber reinforced concrete exposed to high temperature. Especially, the external loading increases not only the residual mechanical properties of concrete but also the risk of spalling and the brittle tendency.

• 한국농공학회논문집
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• 제55권4호
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• pp.65-72
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• 2013

The physical, mechanical, water purification and temperature properties of fiber reinforced porous hwang-toh green roof concrete have been evaluated in this study. The effect of the depending on replacement ratio of blast furnace slag to cement was investigated such that the replacement ratio is varied to 0 % and 30 %. Also, the replacement ratios of hwang-toh were 0, 20 and 30 %. The polyvinyl alcohol fiber was used for the reinforcing fiber. A series of pH test, unit weight, void ratio, compressive strength, after purification and variation of temperature test have been performed to evaluate the performance, water purification effect and temperature properties of the fiber reinforced porous hwang-toh green roof concrete. The test results indicate that the physical and mechanical properties of fiber reinforced porous hwang-toh green roof concrete is affected by the replacement ratio of the blast furnace slag and hwang-toh contents. Results of purifying water showed that the water purification effect of porous hwang-toh green roof concrete is about 40 %. Also, the temperature properties test results indicate the green roof blocks using fiber reinforced porous hwang-toh green roof concrete have insulation and temperature reduction effect.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.291.1-291.1
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• 2013

We examined the temperature-dependent structural and magnetic properties of HgI2 in the temperature range of 300~400 K. HgI2 is a diamagnetic material and can be used for X-ray or γ-ray detectors. DCmagnetization measurements on HgI2 showed that there is a small but distinguishable change in its diamagnetic properties near 375 K. The magnetic property change is not expected because Hg and I are known as nonmagnetic elements. X-ray diffraction (XRD) measurements revealed a structural transition in the temperature of 350~400 K. Temperature-dependent x-ray absorption fine structure (XAFS) demonstrated that the chemical valence states of both Hg and I did not changed in the temperature range of 300~400 K. However, XAFS revealed that the bond-length disorder was slightly increased in the temperature range, particularly, near Hg atoms. The structural changes of HgI2 are likely related to its diamagnetic property change. We will discuss the relation between the diamagnetic properties and local structural properties of HgI2 in detail.

• 한국농공학회논문집
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• 제46권4호
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• pp.49-55
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• 2004

Properties of concrete using low heat portland cement is different from using ordinary portland cement and temperature of aggregate can be expected to have an important influence on its properties. In this study, experiment by setting up 5 levels (40, 30, 20, 4, $-2^{\circ}C$) by temperature of aggregate for evaluation properties of concrete using low heat portland cement was conducted. The experiments include slump test, air content test, change of slump, change of air content and compressive strength of concrete test. As the result of experiments, slump and air content was decreased by increasing temperature of aggregate. But it was not exceeding it's limit. Change of slump and air content was rapidly decrease by decreasing temperature of aggregate. At early age, compressive strength was influenced by the temperature of aggregate.

• Structural Engineering and Mechanics
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• 제67권4호
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• pp.337-346
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• 2018

The purpose of this study is to investigate thermal post-buckling analysis of a laminated composite beam subjected under uniform temperature rising with temperature dependent physical properties. The beam is pinned at both ends and immovable ends. Under temperature rising, thermal buckling and post-buckling phenomena occurs with immovable ends of the beam. In the nonlinear kinematic model of the post-buckling problem, total Lagrangian approach is used in conjunction with the Timoshenko beam theory. Also, material properties of the laminated composite beam are temperature dependent: that is the coefficients of the governing equations are not constant. In the solution of the nonlinear problem, incremental displacement-based finite element method is used with Newton-Raphson iteration method. The effects of the fibber orientation angles, the stacking sequence of laminates and temperature rising on the post-buckling deflections, configurations and critical buckling temperatures of the composite laminated beam are illustrated and discussed in the numerical results. Also, the differences between temperature dependent and independent physical properties are investigated for post-buckling responses of laminated composite beams.

• 한국전기전자재료학회논문지
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• 제16권12S호
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• pp.1305-1309
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• 2003

To utilize FeCoSiB amorphous films for magnetoelastic sensors, the temperature dependency of magnetization (M-T curve) and the magnetization properties of the amorphous films were investigated in this study. As the amount of cobalt In the films increased, the Curie temperature decreased but the crystallization temperature increased. In addition to this, the crystallization temperature was lower than the Curie temperature in the film containing 20 at% cobalt. The optimized annealing condition was set up by analyzing the H-T curve. And then, the amorphous film that has excellent magnetic properties and uni-axal anisotropy could be prepared for construction of the magnetoelastic sensor devices. The coercive force of the film was below 0.5 Oe and the anisotripic field was about 5 Oe.

• Steel and Composite Structures
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• 제2권4호
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• pp.247-258
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• 2002

The high-temperature material properties of steel are very important to the fire resistance analysis of high-strength bolt connections. This paper reports on the results of the experimental studies on the high-temperature properties of 20 MnTiB steel which is widely used in high-strength bolts, and the friction coefficient of 16Mn steel plates at elevated temperature which is a necessary parameter for bolted frictional connection analysis. The test data includes yield strength, limit strength, modulus of elasticity, elongation and expansion coefficient of 20MnTiB steel at elevated temperature, and the friction coefficients between two 16Mn steel plates under elevated temperatures and after cooling. Based on the data from the tests, the mathematical models for predicting the mechanical properties of 20MnTiB steel and friction coefficients of 16Mn steel plates have been established.