• International Journal of Korean Welding Society
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• 제2권1호
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• pp.29-32
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• 2002

In previous study, the decrease and recovery of total stiffness in welded structure was discussed on the basis of experimental examination through tensile loading and unloading test of welded specimen. The recovery of structure stiffness was caused by the release of welding residual stress through mechanical loading. In this study, analysis model that is indispensable for the effective application of MSR method was established on the basis of test and measurement result. Thermal elasto-plastic analysis for welding process was performed by non- coupled analysis. Analysis results of welding process were transfer to elasto-plastic model for tensile loading & unloading by restart technique. In elasto-plastic analysis model for mechanical loading & unloading, hardening appearance of weld metal was considered by rezoning technique and tying technique was used for JIG condition of test machine.

• 복식
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• 제58권1호
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• pp.1-8
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• 2008

The purpose of this study was to investigate the mechanical properties and hand values of polypropylene knit and to analyze its color-fastness for light, laundering and abrasion, comparing to nylon and polyester knits. The results of this study were as follows: 1. Polypropylene stretched more with less force than nylon and polyester and its elastic recovery and shape stability were better than nylon and polyester. 2. Polypropylene was more flexible than nylon and polyester. 3. Polypropylene stretched more easily for shearing but its recovery from shearing was less than nylon and polyester. 4. Polyester had smoother surface than nylon and polyester. 5. Polypropylene was compressed more easily than polyester with less force but less than nylon. Its recovery from compression was more than nylon and polyester. 6. Polypropylene had lower KOSHI and SHARI values and higher FUKURAMI value than nylon and polyester. It had better T.H.V. value than nylon but less than! polyester. 7. Color fastness of polypropylene for lanudering, light, and abrasion in wet and dry conditions was good except polypropylene dyed with red color.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.75-79
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• 1995

A cutting experiment using diamond tool was performed to make the die cabity which is composed of micro groove with mirror surface. Fine cutting depth was generated by the elastic recovery of the modified tool holder on the conventional M/C. Surface roughness and profile were investigated with cutting speed and depth and through the low cutting speed of 10mm/min, Rmax 0.005 .mu. m or less of machined surface could be achieved.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 추계학술대회논문집
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• pp.53-56
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• 1997

The multistage precision forming process for aperture of electronic guns consists mainly of drawing and swaging operations. The multistage forming sequence is analyzed in view of production industry, and based on the industrial investigation. The processes are simulated by the finite element code MARC. The elastic recovery, strain and stress distribution, and the die forces are summarized.

• 대한치과보철학회지
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• 제41권5호
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• pp.551-564
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• 2003

Statement of problem : Magnesium oxide may increase pH of alginate, and supply magnesium ions to the polymerization reaction of alginate. Purpose : This study was designed to evaluate the influence of incorporation of magnesium oxide to alginate composition. Material and Method : Seven kinds of experimental alginates were prepared and used for the experiments. Components with unchanging concentrations were sodium alginate 15%, calcium sulfate 14%, sodium phosphate 2%, and zinc fluoride 3%. Contents of magnesium oxide were varied as 0%, 1%, 2%, 3%, 4%, 5%, 6%. Diatomaceous earth were added to each experimental groups as balance to be 100%. Control group was a MgO 0% group. Working time, setting time, elastic recovery strain in compression, compressive strength and tear resistance were measured were measured. Sample size for each groups were 10. Arithmetic means were used as each groups representative values. Regression test between MgO contents and results, Duncan's multiple range test, and One-way ANOVA test were done between groups at level of 0.05. Results : 1 Magnesium oxide made the working time and setting time as longer(p<0.0001). 2 Magnesium oxide did not alter the elastic recovery(p>0.05). 3. Magnesium oxide contents between 2% and 4% exhibited the lowest strain in compression on alginates(p<0.0001). 4. Magnesium oxide made the compressive strength and the tear resistance stronger(p<0.0001). Conclusion : These results mean that setting time of alginate maybe controlled and that mechanical properties maybe improved by the incorporation of magnesium oxide into alginate, without any reduction of elasticity.

• 한국의류학회지
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• 제33권5호
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• pp.701-710
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• 2009

This study was conducted to develop excellent insole with good thermal insulation using new materials. We investigated that aerogel/fiber composite can be used as padding materials of shoes by comparing surface shape, moisture regain, water vapor permeability, thermal insulation and compression rate of insole materials tried with nonwoven fabric padding materials and insole sold in market. The results are as follows. Surface shapes were shown that the most appropriate material for sealing aerogel/fiber composite was high density fabric as per size of particle of aerogel. Moisture regain of aerogel/fabric composite was better than nonwoven fabric padding samples. However, when compared to insole sold in market, its moisture regain was worse than those of insole merchandises. Water vapor permeability was higher in material padded with nonwoven fabric than materials padded with aerogel/fiber composite in all three kinds of sealing fabrics. Thermal conductivity of aerogel/fabric composite was lower than nonwoven fabric material regardless of sealing fabrics. Thermal insulation of aerogel/fiber composite was higher than padding material of nonwoven fabric regardless of sealing fabrics. Compression rate of nonwoven (SP1) was higher than that of aerogel/fiber composite (SP2). Compressive elastic recovery rate of SP1 was also higher than that of SP2, which its compression rate and compressive elastic recovery rate were both poor. As the above result, ultra porous aerogel/fiber composite were proved to be material of good thermal insulation with lower thermal conductivity and also compression rate was proved to be low. Therefore, we can say that aerogel/fiber composite have high possibility to be used as insole materials for cold winter shoes requiring good thermal insulation protection.

• 한국기계가공학회지
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• 제20권12호
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• pp.113-122
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• 2021

Complicated residual stress distributions occur in the vicinity of a deposited region via directed energy deposition (DED) process owing to the rapid heating and cooling cycle of the deposited region and the substrate. The residual stress can cause defects and premature failure in the vicinity of the deposited region. Several heat treatment technologies have been extensively researched and applied on the part deposited by the DED process to relieve the residual stress. The aim of this study was to investigate the residual stress characteristics of a specimen fabricated by DED and a quenching process using thermomechanical analyses. A coupled thermomechanical analysis technique was adopted to predict the residual stress distribution in the vicinity of the deposited region subsequent to the quenching step. The results of the finite element (FE) analyses for the deposition and the cooling measures show that the residual stress in the vicinity of the deposited region significantly increases after the completion of the elastic recovery. The results of the FE analyses for the heating and quenching stages further indicate that the residual stress in the vicinity of the deposited region remarkably increases at the initial stage of quenching. In addition, it is observed that the residual stress for quenching is lesser than that after the elastic recovery, irrespective of the deposited material.

• 한국재난정보학회 논문집
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• 제15권2호
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• pp.249-258
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• 2019

연구목적: 본 연구에서는 서울 경기지역의 화강암을 대상으로 시추조사 시 채취된 암석 시료에서 측정된 물리적 특성 중 탄성파속도와 탄성계수로부터 암석의 일축압축강도와의 상관성을 분석하여 암석의 일축압축강도를 추정하는 것을 목적으로 한다. 연구방법: 119개의 화강암 시추 코아 시료를 대상으로 탄성파 속도와 탄성계수 그리고 일축압축강도와의 상관관계를 도출하기 위하여 실내 암석 실험을 실시하였다. 연구결과: 화강암에 대하여 탄성파속도와 일축압축강도 그리고 탄성계수와의 상호 관계를 단순회귀와 다중회귀로 분석한 결과는 전반적으로 관계식에 나타난 것처럼 신뢰도가 낮음을 확인하였다. 이는 화강암의 구성 입자가 균질하지 못하여 탄성파속도와 탄성계수를 이용한 압축강도 추정에 대한 활용성이 낮은 원인으로 사료된다. 결론: 본 연구에서 암석의 탄성파속도와 탄성계수로부터 일축압축강도를 추정하기 위한 상관관계를 분석하기 위하여 단순회귀분석과 다중회귀분석 방법을 이용하였다. 단순회귀분석은 결정계수($R^2$)가 0.61~0.67 이었으며, 다중회귀분석은 0.71로 나타났다. 따라서 다중회귀분석을 이용하여 암석의 일축압축강도를 추정할 때 다소 신뢰성이 높아질 수 있다. 또한, 향후 탄성파 속도와 탄성계수를 이용한 암석의 일축압축강도를 추정할 때 다양한 통계분석 기법(회귀분석, 인공신경망, 빅데이터 분석 등)을 활용하면 보다 신뢰성이 높은 결과를 얻을 수 있을 것으로 본다.

• 한국정밀공학회지
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• 제9권3호
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• pp.110-116
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• 1992

Electromgnetic joining of aluminum alloy tubes to high toughness polyurethane rubber cores is studied in order to estimate the joining strength and to analyze the effect of the process variables. The equation which can estimate the joining strength is proposed under considering the elastic recovery of the polyurethane core and the radial shrinkage of the core by pulling it axially. The obtained results are as follows : 1) The joining strength is mainly dependent on the magnitude of residual elastic strain of the polyurethane core. 2) The radial shrinkage (residual strain reduction) of the core during the axial pulling causes the joining strength to decrease severely. The equation for the reduced axial strength is proposed and it is found that the estimated values agree well with experimental results. 3) The magnitude of radial shrinkage could be reduced for the smaller value of ratio l/r. 4) The joining strength in metal/polymer joining increases as the friction coefficient increases. But its effect of friction coefficient is insignificant in comparison with the case of metal/metal joining.

• Steel and Composite Structures
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• 제9권3호
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• pp.191-208
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• 2009

Observations from experiments and real fire indicate that restrained steel beams have better fire-resistant capability than isolated beams. Due to the effects of restraints, a steel beam in fire condition can undergo very large deflections and the run away damage may be avoided. However disgusting damages may occur in the beam-to-column connections, which is considered to be mainly caused by the enormous axial tensile forces in steel beams resulted from temperature decreasing after fire dies out. Over the past ten years, the behaviour of restrained steel beams subjected to fire during heating has been experimentally and theoretically investigated in detail, and some simplified analytical approaches have been proposed. While the performance of restrained steel beams during cooling has not been so deeply studied. For the safety evaluation and repair of steel structures against fire, more detailed investigation on the behaviour of restrained steel beams subjected to fire during cooling is necessary. When the temperature decreases, the elastic modulus and yield strength of steel recover, and the contraction force in restrained steel beams will be produced. In this paper, an incremental method is proposed for analyzing the behaviour of restrained steel beams subjected to cooling. In each temperature decrement, the development of deformation and internal forces of a restrained beam is divided into four steps, in order to consider the effect of the recovery of the elastic modulus and strength of steel and the contraction force generated by temperature decrease in the beam respectively. At last, the proposed approach is validated by FE method.