Cyclic loading response of footing on multilayered rubber-soil mixtures

Tafreshi, S.N. Moghaddas,Darabi, N. Joz,Dawson, A.R. Techno-Press 2018 Geomechanics & engineering Vol.14 No.2

This paper presents a set of results of plate load tests that imposed incremental cyclic loading to a sandy soil bed containing multiple layers of granulated rubber-soil mixture (RSM) at large model scale. Loading and unloading cycles were applied with amplitudes incrementally increasing from 140 to 700 kPa in five steps. A thickness of the RSM layer of approximately 0.4 times the footing diameter was found to deliver the minimum total and residual settlements, irrespective of the level of applied cyclic load. Both the total and residual settlements decrease with increase in the number of RSM layers, regardless of the level of applied cyclic load, but the rate of reduction in both settlements reduces with increase in the number of RSM layers. When the thickness of the RSM layer is smaller, or larger, settlements increase and, at large thicknesses may even exceed those of untreated soil. Layers of the RSM reduced the vertical stress transferred through the foundation depth by distributing the load over a wider area. With the inclusion of RSM layers, the coefficient of elastic uniform compression decreases by a factor of around 3-4. A softer response was obtained when more RSM layers were included beneath the footing damping capacity improves appreciably when the sand bed incorporates RSM layers. Numerical modeling using "FLAC-3D" confirms that multiple RSM layers will improve the performance of a foundation under heavy loading.

An analytical solution for nonlinear dynamics of a viscoelastic beam-heavy mass system

Mergen H. Ghayesh,Farbod Alijani,Mohammad A. Darabi 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.8

The aim of this study is to develop an approximate analytic solution for nonlinear dynamic response of a simply-supported Kelvin-Voigt viscoelastic beam with an attached heavy intra-span mass. A geometric nonlinearity due to midplane stretching is considered and Newton’s second law of motion along with Kelvin-Voigt rheological model, which is a two-parameter energy dissipation model, are employed to derive the nonlinear equations of motion. The method of multiple timescales is applied directly to the governing equations of motion, and nonlinear natural frequencies and vibration responses of the system are obtained analytically. Regarding the resonance case, the limit-cycle of the response is formulated analytically. A parametric study is conducted in order to highlight the influences of the system parameters. The main objective is to examine how the vibration response of a plain (i.e. without additional adornment) beam is modified by the presence of a heavy mass, attached somewhere along the beam length.

A hybrid inverse method for small scale parameter estimation of FG nanobeams

Ali. R. Vosoughi,A. Darabi 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.5

As a first attempt, an inverse hybrid numerical method for small scale parameter estimation of functionally graded (FG) nanobeams using measured frequencies is presented. The governing equations are obtained with the Eringen's nonlocal elasticity assumptions and the first-order shear deformation theory (FSDT). The equations are discretized by using the differential quadrature method (DQM). The discretized equations are transferred from temporal domain to frequency domain and frequencies of the nanobeam are obtained. By applying random error to these frequencies, measured frequencies are generated. The measured frequencies are considered as input data and inversely, the small scale parameter of the beam is obtained by minimizing a defined functional. The functional is defined as root mean square error between the measured frequencies and calculated frequencies by the DQM. Then, the conjugate gradient (CG) optimization method is employed to minimize the functional and the small scale parameter is obtained. Efficiency, convergence and accuracy of the presented hybrid method for small scale parameter estimation of the beams for different applied random error, boundary conditions, length-to-thickness ratio and volume fraction coefficients are demonstrated.

R- and Q-mode multivariate analysis to sense spatial mineralization rather than uni-elemental fractal modeling in polymetallic vein deposits

F. Darabi-Golestan,A. Hezarkhani 한국자원공학회 2018 Geosystem engineering Vol.21 No.4

Anomalous patterns from mineralizing processes are very complex associated with their spatial and frequency properties. Determination of how clustering elemental occurrences are and their spatial association within polymetallic veins deposit as a particular geological feature is critical issue for exploration. Fractal (as non-Euclidean geometries) models are uni-elemental and quantitative method, but R-mode and Q-mode analysis corresponding to multivariate techniques could ease quantitative and qualitative interpretations. The R-mode and Q-mode are the two main informative procedures in many multivariate analyses and are useful in order to handle quantitative and qualitative properties. The first and second Dimension of variation from the R-mode and Q-mode analysis explain 77% of the total variance of the polymetallic system at the area. The mineralization trend of Ag≈As≥Au>Pb>Te>Mo>Zn>S>W>Cu indicated from associated large Euclidean distances from R-mode, occurred due to polymetallic samples ID’s of 35, 33, 28, 29, 32, 34, 31, 30, 36, 81, 47 and 80 which resulted from Q-mode analysis. The combination of them is introduced by correspondence analysis (CA) intuitive graphical display to sense and respond to spatial heterogeneity of polymetallic vein deposit.

Experimental and Numerical Investigation of Hydrogen Embrittlement Effect on Microdamage Evolution of Advanced High-Strength Dual-Phase Steel

M. Asadipoor,J. Kadkhodapour,A. Pourkamali Anaraki,S. M. H. Sharifi,A. Ch. Darabi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

The efect of hydrogen on the microdamage evolution of 1200M advanced high-strength steel was evaluated by the combination of experimental and numerical approaches. In the experimental section, the tensile test was performed under diferent testing conditions, i.e., vacuum, in-situ hydrogen plasma charging (IHPC), ex-situ electrochemical hydrogen charging(EEHC), and ex-situ+in-situ hydrogen charging (EIHC) conditions. The post-mortem analysis was conducted on the fracturesurface of specimens to illuminate the impact of hydrogen on the microstructure and mechanical properties. The resultsshowed that under all of hydrogen charging conditions, the yield stress and ultimate tensile strength were slightly sensitive tohydrogen, while tensile elongation was profoundly afected. While only ductile dimple features were observed on the fracturesurfaces in vacuum condition, the results indicated a simultaneous action of the hydrogen-enhanced decohesion (HEDE)and hydrogen enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogenunder the IHPC and EEHC conditions. At the EIHC condition, the HEDE model was the dominant failure mechanism,which was manifested by the HE-induced large crack. In the numerical approach, a fnite-element analysis was developed toinclude the Gorson–Tvergaard–Needleman (GTN) damage model in Abaqus™ software. To numerically describe the damagemechanism, the GTN damage model was utilized in the 3D fnite-element model. After calibration of damage parameters, thepredicted damage mechanisms for two testing conditions, i.e., vacuum and EIHC, were compared with experimental results.

Fabrication of ZnO-doped reduce graphene oxide-based electrochemical sensor for the determination of 2,4,6-trichlorophenol from aqueous environment

Nawaz Muhammad,Shaikh Huma,Buledi Jamil A.,Solangi Amber R.,Karaman Ceren,Erk Nevin,Darabi Rozhin,Camarada Maria B. 한국탄소학회 2024 Carbon Letters Vol.34 No.1

Environmental pollution has become an alarming issue for the modern world due to the extensive release of untreated chemical waste into freshwater bodies. Untreated chemical waste poses significant negative impacts on aquatic life and human health. The phenolic compounds are widely used in different industries for dyeing, as food preservatives, and for the production of pesticides. 2,4,6-Trichlorophenol (TCP) is among the most hazardous phenolic compounds that cause several serious health effects. Thus, it is important to monitor TCP in the environmental samples frequently. In the current work, it was aimed to develop a highly sensitive zinc oxide-doped (ZnO) reduce graphene oxide (rGO) composite-based electrochemical sensor for TCP monitoring in the real samples. In this regard, graphene oxide (GO) was simultaneously reduced and doped with ZnO using a facile microwave-assisted synthesis strategy. The resulting ZnO/rGO composite was successfully utilized to fabricate ZnO/rGO-modified glassy carbon electrode (ZnO/rGO/GCE) for the selective and trace level determination of TCP. The conductivity and electrocatalytic behaviors of ZnO/rGO/GCE were examined through different modes of electrochemical setup. Under the optimal operating conditions such as a scan rate of 80 mV.s−1, PBS electrolyte (pH 7.0), and the concentration range of 0.01–80 µM, the fabricated electrochemical sensor manifested outstanding responses for monitoring TCP. The limit of detection (LOD) and limit of quantification (LOQ) of the ZnO/rGO/GCE for TCP were found as 0.0067 µM and 0.019 µM, respectively. Moreover, the anti-interference profile and stable nature of ZnO/rGO/GCE made the suggested electrochemical sensor a superb tool for quantifying TCP in a real matrix.