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[en] The article Statistical filtering of useful concrete creep data from imperfect laboratory tests, written by Mohammad Rasoolinejad, Saeed Rahimi-Aghdam, Zdenek P. Bazant, was originally published online without Open Access. After publication in volume 51, article ID 153 RILEM decided to grant the author to opt for open choice and to make the article an open-access publication.
[en] Highlights: • Shrinkage of concrete is measured with various temperature and humidity conditions. • The fib MC2010 shrinkage model is accurate for low RH and high T conditions. • The fib MC2010 shrinkage model slightly underestimate for other conditions. • The fib MC2010 creep model conservatively predicts creep strains. - Abstract: Creep and shrinkage of concrete is influenced by many factors including relative humidity and temperature. The combined effect of low relative humidity (<20%) and high temperature (38 °C) on creep and shrinkage of concrete is uncertain as limited tests have been conducted in this domain. Also unknown is the ability of the fib MC2010 model code in predicting the shrinkage and creep at the environment. This paper presents the results of experiments conducted in which concrete was cast and exposed to the aforementioned environmental conditions. The shrinkage and creep behaviour of the concrete was observed for 110 days, and experimental results were compared with predicted values using fib MC2010 model code.
[en] The upsetting of a composite cylinder in frictionless creep is analyzed in energy terms. Three loading programs that lead to upsetting of the cylinder by the same amount in the same time are compared. Variational analysis indicates that the kinematic loading program is best for industrial use.
[en] In the present investigation, creep-rupture behavior of P9 steel in two different product forms of 20-mm plate and 300-mm-thick tubeplate forging has been studied at 793 and 873 K. It has been found that steady-state creep rate and rupture life followed power law dependence on applied stress at low and high stress regimes for both forms of products. At high stress regime, P9 steel plate exhibited better creep strength with respect to tubeplate forging in terms of lower creep rate and higher rupture life at 793 and 873 K. On contrary, both product forms exhibited similar creep rate and rupture behavior in the low stress regime at 873 K. Difference in creep ductility has been found to be insignificant in both product forms. Irrespective of test conditions and product forms, fracture appearance remained transgranular ductile characterized by dimples. The comparative evaluation of creep-rupture properties of both product forms has also been described in terms of creep rate-rupture life relationships of Monkman–Grant type, creep damage tolerance and tertiary creep characteristics at 793 and 873 K.
[en] The recent demand for high-performance vehicles requires the development of vehicle engines with improved output. As the engine becomes more advanced, the exhaust gas temperature increases due to an increase in the rate of heat generation. Thus, to ensure reliability in engine development, an analysis of changes in the mechanical characteristics of the engine exhaust components due to high temperature must be conducted. Especially, for an engine exhaust valve that is operated for long hours at high temperatures, the creep characteristics of its material must be determined. Ni-Cr NCF3015 steel with excellent high-temperature characteristics is under development as an engine valve material. Therefore, it is necessary to study the evaluation of the high-temperature creep characteristics of the material, considering a realistic operating environment. In this study, high-temperature creep tests were performed and the variations in creep rupture life with aging hours were analyzed by observing microstructural changes.
[en] The effect of creep aging parameters on the creep resistance of an Al–Cu–Mg alloy was studied in a temperature of 453 K under a constant stress of 250 MPa. It was found that the creep resistance of alloy decreased with increasing temperature and time, and the alloy was more sensitive to the temperature than to the stress in the present experimental conditions. Microstructural observations revealed that the precipitate phases continuously grow in the creep aging process, which weakens the alloy and leads to large creep strain. Moreover, the increase of PFZ at grain boundary also decreased the creep resistance. This study shows that fine and dispersed precipitate phases contribute to creep resistance of Al–Cu–Mg alloy. Thus the process parameters temperature and stress during creep aging forming should be set reasonably to ensure the long-term use of Al–Cu–Mg alloy in service. (paper)
[en] The effect of gamma-ray irradiation on the cement mortar creep is investigated in this study. The creep investigation is accompanied by the shrinkage measurements and the compressive strength test. The measured creep and shrinkage strains are compared with the values calculated according to the existing models which showed that the creep and the shrinkage of both the control and the irradiated samples lie within the interval predicted by the models. However, creep of the irradiated samples is slightly higher. The gamma-ray irradiation also leads to the significant decrease in compressive strength (20% on average). The physics behind this process is still unclear and demands supplementary porosity and mineral composition investigation. (author).
[en] The effects of 0.5 wt% In as well as 0.5 wt% In and 1 wt% Zn double (In & Zn) additions to eutectic Sn58Bi alloy on the microstructure and mechanical properties were investigated. Newly designed In & Zn-added Sn58Bi alloy showed much finer microstructure than eutectic Sn58Bi and In-added Sn58Bi alloys. The elongation improvements of 36% and 41% before and after 1008 h aging were obtained in In & Zn-added Sn58Bi alloy compared to eutectic Sn58Bi alloy. Nanoindentation tests revealed that In had solid solution softening (SSS) effect on Sn phase. A hardness decrease and a large creep displacement obtained in both In- and In & Zn-added Sn58Bi served as evident of the SSS. The effects of Zn and In were combined responsible for the elongation improvement of In & Zn-added Sn58Bi.
[en] The effect of gamma-ray irradiation on the cement mortar creep is investigated in this study. The creep investigation is accompanied by the shrinkage measurements and the compressive strength test. The measured creep and shrinkage strain are compared with the values calculated according to the existing models which showed that the creep and the shrinkage of both the control and the irradiated samples lie within the interval predicted by the models. However, creep of the irradiated samples is slightly higher. The gamma-ray irradiation also leads to the significant decrease in compressive strength (20% on average). The physics behind this process is still unclear and demands supplementary porosity and mineral composition investigation. (author).
[en] Active faults commonly repeat cycles of sudden rupture and subsequent silence of hundreds to tens of thousands of years, but some parts of mature faults exhibit continuous creep accompanied by many small earthquakes. Discovery and detailed examination of creeping faults on land have been in a rapid progress with the advent of space-borne synthetic aperture radar interferometry. In this study, we measured the spatial variation of the creep rate along the Philippine fault on Leyte Island using ALOS/PALSAR data acquired between October 2006 and January 2011. Prominent creep of mm/year was estimated in northern and central parts of the island except for a locked portion around latitude 11.08–11.20 N. We compared the creep rate distribution along the fault with the slip distribution of the 2017 6.5 Ormoc earthquake which occurred in northern Leyte, estimated from the displacements mapped by ALOS-2/PALSAR-2 interferometric data. The estimated slip of the 2017 earthquake amounted up to 2.5 m and to moment magnitude of 6.49, with the dominant rupture area coinciding with the locked portion identified from the interseismic coupling analysis. Teleseismic waveforms of the 2017 earthquake and another event that occurred in 1947 ( 6.9) exhibit close resemblance, indicating two ruptures of rather similar locations and magnitudes with a time interval of 70 years. .