Experimental study on fracture properties of dam concrete under post-peak cyclic loading based on DIC and acoustic emission techniques

In order to study the fracture properties of dam concrete under post-peak cyclic loading, wedge splitting tests with three loading rates (0.001 mm/s, 0.01 mm/s, 0.1 mm/s) were performed on notched cubic dam concrete specimens. Meanwhile, the acoustic emission (AE) and digital image correlation (DIC) technologies were used to record the crack propagation process of specimens. Test results show that the fracture of dam concrete has a significant rate effect: with the loading rate increases, the peak load increases, the slope of the post-peak P-CMOD curve gradually decreases and the stiffness degradation of dam concrete becomes more serious. The cumulative AE count shows a step increasing trend and has a Kaiser effect. The Kaiser effect decreases with the post-peak cyclic loading procedure, and with the loading rate increases, the Kaiser effect increases. With the increasing of loading rate, AE energy fluctuates violently and b value fluctuates frequently, indicating the damage of dam concrete becomes more serious. As the loading procedure, the damage of the specimen accumulates gradually, and the strain recovery rate decreases gradually. With the loading rate increases, the strain recovery rate decreases and the permanent crack increases. Based on the fictitious crack model, the effective crack length shows a gradual and steady rising trend. As the loading rate increases, the growth rate of the effective crack length becomes large.

Experimental studies of the energy dissipation processes at the tops of fatigue cracks in the elements of bridge structures

In the article, the authors investigated the possibility of using the thermal control method for diagnosing fatigue cracks in the metal superstructure, determined the necessary parameters for that control method. The studies were conducted during cantilevered steel samples fatigue tests simulating the superstructure beam wall operation, reinforced with stiffening ribs. To carry out the experiments were developed a test setup and a loading procedure at the various intensity of exposure. An electric motor with eccentrics is used as a loading device. The sample surface heating was recorded by thermal imagers with 0.03 K and 0.05 K temperature sensitivities and 60 frames/s and 9 frames/s shooting speed, respectively. Was confirmed the possibility of determining crack presence before its emergence to the surface namely at the stage of its initiation, and also were determined the self-heating zone dimensions at the tip of a crack. The conducting a laboratory experiment technique on the dissipative processes study in the metal superstructure elements is described.

Piroxicam Loading onto Mesoporous Silicas by Supercritical CO2 Impregnation

Piroxicam (PRX) is a commonly prescribed nonsteroidal anti-inflammatory drug. Its efficacy, however, is partially limited by its low water solubility. In recent years, different studies have tackled this problem and have suggested delivering PRX through solid dispersions. All these strategies, however, involve the use of potentially harmful solvents for the loading procedure. Since piroxicam is soluble in supercritical CO2 (scCO2), the present study aims, for the first time, to adsorb PRX onto mesoporous silica using scCO2, which is known to be a safer and greener technique compared to the organic solvent-based ones. For comparison, PRX is also loaded by adsorption from solution and incipient wetness impregnation using ethanol as solvent. Two different commercial mesoporous silicas are used (SBA-15 and Grace Syloid® XDP), which differ in porosity order and surface silanol population. Physico-chemical analyses show that the most promising results are obtained through scCO2, which yields the amorphization of PRX, whereas some crystallization occurs in the case of adsorption from solution and IWI. The highest loading of PRX by scCO2 is obtained in SBA-15 (15 wt.%), where molecule distribution appears homogeneous, with very limited pore blocking.

Estimating Dependence Among Lumber Strength Properties With Copula Models

A copula-based approach is used to estimate the dependence among three lumber strength properties: modulus of elasticity (MOE), modulus of rupture (MOR), and ultimate tensile strength (UTS). MOR and UTS are destructive measurements so they cannot be obtained simultaneously for lumber specimens. The dependence modeling is possible under an appropriate experimental design with i) a shoulder group for rupture, ii) a shoulder group for tension, and iii) other groups proof loaded in either the rupture or tension mode with survivors tested to failure in the mode that was not initially tested. With a fitted copula model based on an assumption of no damage due to the proof loading procedure, we conclude that there is a strong dependence between MOR and UTS conditioning on MOE. To assess the “no damage assumption,” a graphical method with simulated data from the fitted copula model is used. It suggests that there may be some damage to the lumber specimens due to proof loading, especially for weaker lumber specimens. Information from the dependence model can potentially help reduce monitoring costs in the lumber industry.

Management of Loading and Safety Improvement Efforts to Reduce Passenger Accidents on Ships

This study aims to determine the correct loading procedure for ships to reduce the risk of accidents, in accordance with applied operating standards. The study also evaluates the performance of operational officers in the field, to identify when and why they deviate from established protocols, and what risks this poses to passenger safety. The study uses the normative legal method or normative jurisdiction approach, combined with descriptive analysis, drawing on primary data through interviews and observations and secondary data via the study of legislation and books related to this research. The research concludes that one of the greatest risks to passenger safety is inaccurate loading manifestos. To avoid this, each passenger and driver should be required to produce a ticket, to better manage the volume of passengers and ensure ships are not overloaded and the cargo manifests offer clear and accurate information. Keywords: Loading, Passenger, Safety

VARIABLE FORMATION PLASTICITY MATRICES OF A THREE-DIMENSIONAL BODY WHEN IMPLEMENTING A STEP LOADING PROCEDURE

В настоящее время задача создания и совершенствования вычислительных алгоритмов по определению напряженно-деформированного состояния (НДС) техносферных объектов и систем с учетом физически нелинейной стадии работы материала конструкций и их элементов является достаточно актуальной. На основе деформационной теории пластичности представлен вариативный подход к формированию матрицы пластичности на шаге нагружения для трехмерного тела. Рассмотрен вариант получения матрицы пластичности с применением операций дифференцирования ковариантных компонент тензора напряжений по ковариантным компонентам тензора деформаций. В качестве альтернативного ему разработан вариант формирования матрицы пластичности на шаге нагружения, основывающийся на гипотезе пропорциональности компонент девиатора приращений напряжений компонентам девиатора приращений деформаций для трехмерных тел. Использование такого варианта формирования матрицы пластичности на шаге нагружения в вычислительных программных комплексах позволяет значительно упростить процесс программирования и сделать его более понятным потенциальным пользователям вычислительных комплексов при проектировании и реконструкции техносферных объектов и систем.

Two-step polyaniline loading in polyelectrolyte complex membranes for improved pseudo-capacitor electrodes

A two-step polyaniline (PANI) loading procedure has been developed to produce polyelectrolyte complex composite membranes (CPECs) to be used as supercapacitor electrodes. In the first step, CPECs were prepared by co-precipitation of poly(styrene sulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC) mixed with various amounts of PANI as a filler. CPECs were formed by compression molding into 100 micron membranes using NaCl as a plasticizer and characterized for their electrochemical properties. In the second step, the highest capacitance CPEC membranes with 60% PANI loading were further modified and doped by crossflow polymerization of aniline through the composite membranes. By using a two-compartment crossflow reactor containing aniline and ammonium persulfate on each side, the PANI content of the composite membrane was further increased. Cyclic voltammetry showed a doubling in the capacitance of the membranes after the crossflow polymerization. The resulting electrodes were flexible with high capacitance and could be used to improve pseudocapacitor performance.

Decomposition of Energetic Ionic Liquid Over IrCu/Honeycomb Catalysts

The objective of this study is to elucidate the influence of a loading procedure of iridium and copper oxides over cordierite honeycomb support on catalytic performance during the decomposition of a hydroxylammonium nitrate (HAN) solution. Iridium and copper composite oxides were successfully supported on the cordierite honeycomb at the same time by repeating the wash coating process more than 2 times. Through the wash coating process, Cu and Ir were supported up to 43.4% and 4.9%, respectively. The cordierite honeycomb without active metal plays little role as a catalyst to lower the decomposition temperature. It was found that IrCu/honeycomb-2 catalyst, which was prepared by repeating the wash coating procedure twice, is an optimal catalyst for the decomposition of HAN solution. The IrCu/honeycomb-2 catalyst had the effect of lowering the decomposition onset temperature by 27.1°C compared to thermal decomposition.