• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.59-60
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• 2015

In this study, stress-strain, thermal expansion strain, total strain and high temperature creep strain of ultra-high-strength concrete with compressive strengths of 80, 130, and 180MPa were experimentally evaluated considering elevated temperature and loading condition. Also, transient creep strain has been calculated by using the results of experiment. Experimental coefficient K was proposed with application of non-steady state creep model. It is considered that the experimental results of this study could be baseline data for deformation behavior analysis of ultra-high-strength concrete.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.755-761
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• 2014

Internal or external restraint of concrete strain due to drying shrinkage and creep in concrete structures causes mechanical strain and becomes a source of persistent change in creep-causing stress conditions. Mathematical modeling to incorporate the persistent change of creep-inducing stress is generally achieved with consideration of the ages of concrete and concrete properties at the times of loadings, and stress history. This paper presents an incremental format of creep model based on parallel creep concept to depict the creep under time-varying stress history in developing creep strain. Laboratory experiments are carried out to validate the performance of the presented creep model. Typical creep phenomena are addressed through the comparisons between the measured and predicted creep strains.

• Asian-Australasian Journal of Animal Sciences
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• v.31 no.12
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• pp.1956-1962
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• 2018

Objective: This experiment was carried out to determine the effects of different creep feed types on suckling performance and further adjustments to solid feed after weaning. Methods: A total of 24 multiparous sows and their litters were allotted to one of three treatment groups: i) provided highly digestible creep feed (Creep), ii) provided a pig weaning diet (Weaner), and iii) provided sow feed (Sow) as creep feed until weaning. After weaning, a total of 96 piglets were selected for evaluation of post-weaning performance. Results: For pre-weaning performance, the Creep treatment led to a significantly higher feed intake from 14 to 28 d (p<0.05) and higher body weight gain from 21 to 28 d than piglets that were provided other diets. However, after weaning, the Weaner treatment yielded a significantly higher feed intake and average daily gain than other treatments from 0 to 14 d after weaning (p<0.05); Creep treatment tended to generate lower villus heights in the duodenum than the other treatments (p = 0.07). Conclusion: Highly digestible creep feed improved pre-weaning performance, but feed familiarity and grain-based creep feed improved post-weaning performance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.45-54
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• 2006

To obtain realistic stress-strain relation in concrete, it is necessary to improve the constitutive model for creep and shrinkage of concrete. This study is made up with predicting model of creep using rheological approach and mathematical development which is solution for phenomenon of concrete creep. Long-term deformation components are combined based on traditional 4-parameters model. Creep deformation is obtained adequately using 4-parameters determined by considering aging effect and microprestress among gels. And coefficient of effective viscosity is able to represent both basic creep and total creep included drying creep. This study attempt to establish mathematical model considering effects of aging, hydration, and variations of pore humidity. It can predict both basic creep and total creep. Values of result between prediction and experiment have greater than correlation factor 99%. Additionally experimental results report bad consentaneity with highway design specification adopting FIB MC 90. Rather than those are similar to FIB MC 90 rev.99.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.2
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• pp.21-28
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• 2010

Creep behaviors of the solder balls in a flip chip package assembly during thermal cycling test is investigated.. A material models used in the finite element analysis are viscoplastic model introduced by Anand and creep model called partitioned model. Experiment of two temperature cycles using moir$\acute{e}$ interferometry is conducted to verify the reliability of material models for the analysis of thermo-mechanical behavior. Bending deformations of the assemblies and average strains of the solder balls due to temperature change and dwell time are investigated. The results show that time-dependent shear strain of solder by the partitioned model is in excellent agreement with those by moir$\acute{e}$ interferometry, while there is considerable difference between results by Anand model and experiment. In this paper, the partitioned model is employed for the time-dependent creep analysis of the FC-PBGA package. It is also shown that the thermo-mechanical stress becomes relaxed by creep behavior at high temperature during temperature cycles.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.1
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• pp.237-246
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• 2001

This study is to measure the creep coefficient by 3 days, 7 days and 28 days in the age when loading for the quality assessment of $350kgf/cm^2$ in the high-strength concrete. And it is to analyze the behavior of creep coefficient by applying the experimental data though the compressive strength test, the elastic modulus test and the dry shrinkage test to the ACI-209, AASHTO-94 and CEB/FIP-90, the prediction mode, and the basis of concrete structural design. Also it is to analyze the behavior of short-term creep coefficient during 91 days in the age when loading through the experiment by using the regression analysis, the statistical theory. As applying it to the long-term behavior during 365 days and comparing with the creep prediction mode and examining it, the result from the analysis of the quality of the concrete is as follows. As the result of comparison and analysis about the ACI-209, AASHTO-94 and CEB/FIP-90, the prediction mode, and the basis of concrete structural design, the normal Portland cement class 1 shows the approximate value with the prediction of GEE/PIP-90 and the basis of concrete structural design, but in case of the prediction of ACI-209 and AASHTO-94, there would be worry of underestimation in the application.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.11
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• pp.1540-1546
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• 2009

One hundred and forty-four piglets with an average birth weight of 1,672${\pm}$13.4 g were used to evaluate different feeding strategies for piglets reared from birth on a dummy sow. A 3${\times}$2 factorial experiment compared three nursing frequencies (1, 3 or 6 h intervals) and two feeding regimes (milk only, or milk combined with access to creep feed and water). The piglets which were nursed at one hour intervals had the lightest body weights at all days, and the poorest combined milk and creep feed dry matter conversion efficiency to piglet body weight gain in the second week. Piglets which were nursed at 3 h intervals had the heaviest body weight at day 15 and 22, but those nursed at 6 h intervals achieved similar body weight by days 29 (milk withdrawal) and 36. Piglets offered creep feed were observed to wean themselves before cessation of milk availability, and the timing of this self-weaning depended on the nursing frequency. The piglets nursed at one hour intervals weaned themselves between day 22 and day 29, those nursed at 3 h intervals weaned themselves between day 15 and day 22, whilst those nursed at 6 h intervals weaned themselves between day 8 and day 15. The piglets which were nursed at 6 h intervals had the highest total dry matter intake in weeks 3 and 4 when fed with milk, creep feed and water but not when fed milk only. They consequently had the poorest dry matter conversion efficiency in the fourth week and overall when fed with milk, creep feed and water, but not when fed milk only. It is concluded that the optimal management routine under these conditions is a 3 h nursing cycle with provision of supplementary creep feed and water.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.6
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• pp.383-390
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• 2000

The static creep behaviour of AlSl 420F stainless steel was investigated over the temperature range of $540{\sim}585^{\circ}C$ and the stress range of $13{\sim}19kg/mm^2$ (127.4~186.2MPa). Constant stress creep tests were carried out in the experiment. Measured stress exponent, n, for the creep deformation of the alloy under the given conditions was found to vary at the range of 9.59, 9.15, 8.78, and 8.53 for the temperature of 540, 555, 570, and $585^{\circ}C$ respectively. The activation energy, Qc, for the creep deformation was 106.42, 102.58,97.81, and 94.58 kcal/mole for the stress of 13, 15, 17, and $19kg/mm^2$, respectively. Lason-Miller parameter, P, for the crept specimens for AlSl 420F stainless steel was measured as $P=T(log\;t_T+21)$. The empirical static creep rate obtained by the regression analysis was as follows. $${\varepsilon}={\exp}[(3.79{\times}10^{-2}{\sigma}+2.722)T-3.0747{\sigma}+28.109]{\times}{\sigma}^{(-2.367{\times}10^{-2}T+22.33)}{\exp}\left[-\frac{(-2.015{\sigma}+132.580){\times}10^3}{RT}\right]$$ The failure plane were observed, intergranular fracture was dominated by r (round) type crack over the experimental range.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.4
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• pp.395-402
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• 1985

The apparent activation energy Q$_{c}$ and the applied stress exponent n have been determined during creep of Al 7075 alloy over the temperature range of 90.deg. C to 320.deg. C (0.4-0.65T$_{m}$) and stress range of 1.85 kgf/mm$^{2}$ to 21 kgf/mm$^{2}$, respectively in order to investigate the creep behavior. Constant load creep tests were carried out in the experiment. At round the temperature of 200.deg. C-240.deg. C and under the stress level 8.13-9.55kgf/mm$^{2}$ and again at around the temperature of 280.deg. C-320.deg. C and under the stress level of 1.85-2.55kgf/mm$^{2}$, the creep behavior obeyed for the creep deformation was nearly equal to that of the volume self diffusion of pure aluminum (34kcal/mole). But at around the temperature of 90.deg. C and under the stress level of 10-21kgf/mm$^{2}$, the creep behavior did not obey a simple power-law relation and the apparent activation enrgy, Q$_{c}$ was 26.01 kcal/mole. From the above facts, at around the temperature of 200.deg. C-240.deg. C and 280.deg. C-320.deg. C, the creep deformation for Al 7075 alloy seemed to be controlled by dislocation climb but at 90.deg. C, by cross slip over the range of experimental stress conditions.tions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.77-86
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• 1989

A modified $C^{*}$ integral as load parameter in creep fracture is proposed considering the effect of crack growth. It is shown that the parameter does not depend on crack velocity. By performing experiment using STS 304 stainless steel at 600.deg.C the validity of the parameter is investigated. The results show that the parameter is a good measure as a load parameter in creep fracture and the rate of crack tip opening displacement can also be a creep load parameter for STS 304 at 600.deg. C.C.