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Central Alborz Zone (CAZ) is one of the most important zones in Iran, which comprises a wide variety of carbonate rocks such as limestone, dolomite, and their compounds. Therefore, determining engineering geological characteristics of carbonate rocks is essential for proper use in civil, mining, and geotechnical engineering. The purpose of this work was to investigate the relationships between the uniaxial compressive strength (UCS) and the point load index (PLI), Schmidt hammer rebound (SHR) value, and Brazilian tensile strength (BTS). In addition, the UCS value was predicted based on the young modulus (UCS-E) and sample size factors in terms of length, length to diameter (L/D), and volume. In this study, samples were collected from the type section of 12 formations of the CAZ, and all of them were classified based on the petrographic study as carbonate rocks (Limestone, dolostone, etc.). The results showed significant positive linear equations within the 95% prediction bands for correlating UCS to PLI, BTS, SHR, and E. A conversion factor of carbonate rocks in the linear regression without intercept for UCS–PLI, UCS–BTS, UCS–SHR, and UCS-E was observed as 14.32, 7.26, 1.71, and 3.52, respectively. This study concentrated on the carbonate rocks; therefore, the results compared to previous studies were conducted on carbonate rocks. Also, the relation between the modulus ratio (MR), UCS, and maximum axial strain (εa max) studied for all rock samples and results showed that the UCS has a partial effect on MR and εa max has a strong correlation with MR. Concerning the sample size, results showed that with an increase in the length, L/D, and volume of the specimens, the UCS values are decreased. This reduction is because of an increase of internal defects (increase in length and diameter), end effects, and lateral deformation. The decrease of the UCS value is more sharply in the L/D ratios between 2 and 2.5, and for more than 2.5, the reduction rate is much lower. [ABSTRACT FROM AUTHOR]

In the study, fracture tests on three-point bending beams and wedge-splitting specimens with different sizes suggested by RILEM technical committee TC265-TDK were conducted. Factors that may affect the determination of the double-K fracture parameters, such as the methods to obtain the initial cracking load, the loading rate arrangement, specimen size and geometry, were investigated. Results show that (1) the digital image correlation method can be used for not only the observation of crack propagation on specimen surfaces qualitatively, but also the determination of the crack initiation time. (2) The size effect and the loading rate effect are coupled with each other. For a series of specimens with proportional dimensions, there is a lower limit of the loading rate. If the loading rate is smaller than that of the lower limit, the arrangement for the loading rate to be proportional to the specimen size will not be reasonable. (3) The T-stress has limited contribution in the mode-I fracture tests when the specimen dimension is chosen properly. (4) The initial cracking toughness is of size and geometry independence. While the unstable fracture toughness KIcun is related with the crack propagation length. After specimen depth reaches 300 mm, i.e. the ligament length is eighteen times the maximum aggregate size, the calculated elastic modulus Ea and KIcun for WS specimens can be approximately regarded as a constant. [ABSTRACT FROM AUTHOR]

Double-K fracture criterion is comprised of two fracture parameters: initial cracking toughness and unstable fracture toughness. Both parameters are derived from linear-elastic fracture mechanics principles and can be obtained through experiments in laboratories conveniently. A RILEM recommendation is put forward to standardize the testing method for determination of double-K criterion. To validate the clarity of the proposed standard, a round-robin testing campaign is proposed. The results of round-robin testing, for determination of double-K criterion for crack propagation in concrete, are presented and discussed in this paper. [ABSTRACT FROM AUTHOR]

The shock-induced ignition and detonation wave propagation in reactive elliptic premixed bubbles are numerically studied. Close attention is paid to the bubble geometry effect on the ignition pattern and the ensuing bubble behavior. Five elliptic bubbles with different aspect ratios are examined. According to the numerical results, three typical ignition patterns are identified under the same incident shock strength and the underlying mechanisms are interpreted. The difference in ignition pattern shows that, comparing with the inert shock-bubble interaction, the geometry effect in reactive shock-bubble interaction (RSBI) has more implications. In addition to the aspect ratio, the ignition location and the distance from the ignition spot to the nearest/farthest bubble surface should also be considered as elements of the geometry effect in RSBI. In the present investigation on reactive shock-elliptic bubble interactions, three typical ignition patterns are identified. The difference in ignition pattern shows that, comparing with the inert shock-bubble interaction, the geometry effect in reactive shock-bubble interaction (RSBI) has more implications. In addition to the aspect ratio, the ignition location and the distance from the ignition spot to the nearest/farthest bubble surface should also be considered as elements of the geometry effect in RSBI. [ABSTRACT FROM AUTHOR]

Up to now, several methods have been proposed to determine the mode I fracture toughness of rocks. In this research, different cylindrical and disc shape samples, namely: chevron bend (CB), short rod (SR), cracked chevron notched Brazilian disc (CCNBD), and semi-circular bend (SCB) specimens were considered for investigating mode I fracture behavior of a marble rock. It is shown experimentally that the fracture toughness values of the tested rock material obtained from different test specimens are not consistent. Indeed, depending on the geometry and loading type of the specimen, noticeable discrepancies can be observed for the fracture toughness of a same rock material. The difference between the experimental mode I fracture resistance results is related to the magnitude and sign of T-stress that is dependent on the geometry and loading configuration of the specimen. For the chevron-notched samples, the critical value of T-stress corresponding to the critical crack length was determined using the finite element method. The CCNBD and SR specimens had the most negative and positive T-stress values, respectively. The dependency of mode I fracture resistance to the T-stress was shown using the extended maximum tangential strain (EMTSN) criterion and the obtained experimental rock fracture toughness data were predicted successfully with this criterion. [ABSTRACT FROM AUTHOR]

In this paper, the effects of specimen size and geometry on the apparent mode I fracture toughness ( K) of an Iranian white marble (Neyriz) are studied. A number of fracture tests were conducted on center-cracked circular disk (CCCD) specimens with different radii to investigate the size effects on K. The experimental results demonstrate that the apparent fracture toughness increases in bigger specimens. In order to explain the experimental results, the modified maximum tangential stress (MMTS) criterion is used, where higher order terms of the Williams' series expansion are included in the maximum tangential stress criterion. It is shown that the MMTS criterion provides good estimates for the apparent fracture toughness of Neyriz marble, obtained from fracture tests of edge-cracked triangular specimens. It is, therefore, concluded that the proposed criterion is able to account for the size and geometry effects on the fracture resistance of rocks simultaneously. [ABSTRACT FROM AUTHOR]

Mixed mode fracture experiments were conducted on Harsin marble using two disc-shape samples namely the Brazilian disc (BD) and the semi-circular bend (SCB) specimens. For each specimen, a complete fracture toughness envelope ranging from pure mode I to pure mode II was obtained. The experimental results indicate that the mixed mode fracture toughness depends on the geometry and loading conditions such that for any similar mode mixture, the BD test data were significantly greater than the SCB fracture toughness results. Therefore, the conventional fracture criteria which present a unique mixed mode fracture curve, fail to predict the test results. It is shown that a generalized criterion, which takes into account the effects of geometry and loading conditions, is able to provide individual fracture curves for theses specimens with very good estimates for the test results obtained from both BD and SCB specimens. The BD and SCB specimens can be suggested as appropriate specimens for obtaining typical upper bound and lower bound envelopes for mixed mode fracture toughness of rocks. [ABSTRACT FROM AUTHOR]

Ternary IrO-SbO-SnO anode has shown its superiorities over IrO and many other electrocatalysts for O evolution, in terms of electrochemical stability, activity and cost. The performance of IrO-SbO-SnO anodes is affected by its electrochemical properties and operating conditions. In this paper, the electrochemical stability and activity of the Ti/IrO-SbO-SnO anodes prepared with three different geometries were investigated under different operating conditions. It was found that anodes with large mean curvature have high electrochemical stability. Although increasing temperature results in a decrease in the stability of Ti/IrO-SbO-SnO, the anode with a mean curvature of 200 m still shows acceptable service life even at 70 °C. This tolerance of high temperature was attributed to the thermal expansion difference between the substrate and the coating layer, the redox window for Ir(V)/Ir(IV) conversion, and the redox reversibility of Sb and Sn species in the coating layer. [ABSTRACT FROM AUTHOR]

Effects of solder ball geometry on lap shear creep deformation were investigated using the three-dimensional (3-D) finite element method (FEM). The meridian of the solder ball before creep, calculated using the energy principle, was very close to the circular arc which was assumed for subsequent calculations. As solder with a given volume and pad area was varied in geometry from convex to concave, lap shear strain rates increased by two to three orders of magnitude, implying that the solder geometry effect must be taken into account for accurate assessment of lap shear results. Finally, a simple method which can handle the solder geometry effect is proposed. [ABSTRACT FROM AUTHOR]

Shielded Active Gas Forge Welding is a robust and efficient solid state welding method applicable to offshore and oilfield applications. The mechanical or fracture performance of the welded connection may be influenced by the forge weld shape. In this paper the main focus is on the geometry effect of weld shape and defects on forge weld mechanical performance and fracture behavior. The potential impact of variables on the undercut description is parametrically analyzed by finite element calculation. As for the undercut located in the transition region between weld and base material, our studies show that the outer undercut of more than 0.3 mm has a significant impact on mechanical behaviour of welded pipe. When the undercut is located in the fusion plane, its impact on mechanical performance of welded pipe is negligible. Weld caps are beneficial since they contribute to weakening the driving forces for crack propagation. Even if the effect of undercut is considered, the beneficial contribution of weld cap still exists. [ABSTRACT FROM AUTHOR]

This paper describes the influence of some geometric parameters on aerodynamics performance of a low-aspect-ratio turbine blading designed by a novel method developed at the Institute of Engineering Thermophysics, Chinese Academy of Sciences. This is a part of the study on aerodynamics optimization of turbomachinery. It follows the development of the basic ideas in the turbomachinery aerodynamics research project at the institute. The present paper concentrates mainly on the effects of geometry, such as stagger angle, leading and trailing edge thickness, maximum thickness and its location on adiabatic efficiency, total pressure ratio and mass flow rate. The study was performed and assessed for a low-aspect ratio turbine nozzle using 3D steady Reynolds-averaged N.S. solver. Using the knowledge of the flow physics analysis an optimized turbine nozzle was obtained. [ABSTRACT FROM AUTHOR]