Coupled effects of axial material gradation and tapered geometry on nanobeam dynamics with uniform square perforations

Effect of material gradation on K-dominance of fracture specimens

Effect of the gradation of binary mixed particle materials on compressive strength and permeability

Effects of Material Gradation on Thermo-Mechanical Stresses in Functionally Graded Beams

This paper is based on a 2D numerical study of crack initiation and growth in ceramic/metal functionally graded materials (FGMs) under mixed mode condition. The finite element method is used for modeling the crack growth trajectory. Two types of ceramic/metal FGMs are considered to explore the effect of the material gradation on the fracture trajectory. The variation of the material properties is declared in a program by defining the material parameters at the center of the elements. After a numerical evaluation of the fracture parameters, the Maximum Tangential Stress (MTS) criterion is used for the prediction of crack propagation direction with respect to the crack axis. The difference in the crack growth trajectory can be related to the influence of the material gradient. In addition, it was found that the easiest way for the crack propagation is when the crack is perpendicular to the material gradation. A crack located on the rigid side of the specimen deviates less compared to the one on the soft side.

The tunneling rock wastes (TRW) have been increasingly generated and stockpiled in massive quantities. Recycling them for use as unbound granular pavement base/subbase materials has become an alternative featuring low carbon emission and sustainability. However, the field compaction of such large-size, open-graded materials remains challenging, thus affecting post-construction deformation and long-term stability of such pavement base/subbase layers. This study conducted a series of proctor compaction and new plate vibratory compaction tests to analyze the compaction characteristics of such TRW materials. A total of six different open gradations were designed from particle packing theory. In addition, the effects of gradation and compaction methods on the compaction characteristics, particle breakage of TRW materials, and the optimal combination of vibratory parameters were investigated by normalizing the curves of achieved dry density versus degree of saturation for various combinations of gradations, compaction methods, and compaction energy levels. The post-compaction characteristics of interparticle contact, pore structure, and particle breakage were analyzed from the X-ray computed topography (XCT) scanning results of TRW specimens with different gradations. The findings showed that the gravel-to-sand ratio (G/S) based gradation design method can effectively differentiate distinct types of particle packing structures. There exists an optimal G/S range that could potentially result in the highest maximum dry density, the lowest particle breakage, and the best pore structure of compacted unbound permeable aggregate base (UPAB) materials. The achieved dry density (ρd) of UPAB materials subjected to vibratory plate compaction exhibited three distinct phases with compaction time, from which the optimal excitation frequency range was found to be 25-27 Hz and the optimal combination of vibratory parameters were determined. The normalized compaction curves of degree of saturation versus achieved dry density were found insensitive to changes in material gradations, compaction methods and energy levels, thus allowing for a more accurate evaluation and control of field compaction quality.

Effect of fine aggregate gradation on the rheology of mortar

This paper describes an experimental investigation carried out to study the load−settlement behaviour and bulge characteristics of granular columns in a soft marine clay bed. The effects of gradation and compacted density of the granular fill material on the load response, bulge length and bulge diameter of granular columns are presented. Granular columns were formed using five kinds of crushed stone aggregates of different gradation, compacted in loose and dense states. The ultimate capacity of the composite ground, bulge diameter and bulge length were more in the case of the densely compacted granular columns than for the loosely compacted granular columns. The relative density and the angle of internal friction of the granular fills, in both loose and dense states, increased with decreasing particle size of the aggregates. Consequently, the load-carrying capacity also increased with decreasing particle size of the aggregates. The percentage increase in the ultimate capacity ranged from 106 to 210% when different aggregates were compacted in their loose and dense states. For a given gradation, the ultimate capacity increased up to an l/d ratio of 11 and decreased thereafter.

ABSTRACTThis paper reports a new research in the field of the timed antenna arrays. It is presented as a novel synthesis of timed antenna arrays for flat-top energy patterns. The synthesis is carried out by optimizing true-time delays and amplitudes of different pulsed antenna arrays. Specially, the study regards the linear array, uniform square array, and uniform concentric ring array geometries. The optimization process is carried out by the well-known sequential quadratic programming. This methodology is compared with the particle swarm optimization algorithm in terms of computational cost and the quality of solution. The results show the performance of different timed antenna arrays with optimum flat energy patterns. The mutual coupling effects are included by a full-wave simulation of Vivaldi elements for the timed linear array in order to verify the proposed method. Important remarks are given for the design of timed antenna arrays for a flat-top energy pattern.

The effects of functionally graded adhesive on failures in socket joint of laminated FRP composite tubes are analyzed in the present research. Various types of failures in the socket joint have been studied using strength of materials and fracture mechanics approach. The critical location in the socket joint has been identified using strength of material approach. Subsequently, the principle of fracture mechanics has been employed with a presumption that a circumferential failure front pre-exist at the critical location in the socket joint. The failure evolution in the functionally graded adhesively bonded socket joint of laminated FRP composite tubes and fracture behaviour of embedded failures have been discussed with respect to the variation of fracture parameters such as the individual modes of strain energy release rates (SERR) along the failure front. The novelty of functionally graded adhesive is introduced with linear function profile in order to improve the failure growth resistance of the socket joint structure. Based on the failure indices, it has been observed that free edges of the coupling region are more vulnerable zones for interfacial failure initiation as failure indices for all the critical surfaces of bond layer are found to be the highest at those locations. Further, the effects of functionally graded adhesive with varied modulus ratios on failure onset are observed for critical surface. It has been observed that the failure onset and its propagation shall be reduced/delayed due to the use of functionally graded adhesive in the joint. Based on the failure growth studies, it has been noticed that interfacial failure propagation is governed by in-plane shearing mode and, other modes are insignificant in propagation. Efforts have been made to enhance the crack/damage growth resistance properties of the bonding material. Series of FE simulations have been carried out for varied interfacial failure length in tubular socket joint with functionally graded adhesive in order to achieve the significant effect of material gradation on SERR. It has been noticed that the effect of material gradation of adhesive on SERR is more predominant for shorter interfacial failure length which leads to delay the failure growth.

Liquefaction resistance and small strain stiffness of silty sand: Effects of host sand gradation and fines content

Multiple surface cracking greatly influences the thermal shock behavior of ceramics and ceramic composites. This work aims to investigate the effects of surface crack morphology coupled with material gradation on the thermal shock damage and residual strength behavior of functionally graded ceramics. We consider a functionally graded plate with an array of periodically spaced surface cracks of alternating lengths subjected to thermal shocks. The coupled strongly singular integral equations for the opening displacements along the long and short cracks are derived using the Fourier transform and a superposition technique. Thermal shock damages (arrested lengths of the long and short cracks) in the specimen and the residual strength are determined using the stress intensity factor criterion. Numerical results for an Al2O3/Si3N4 graded material are presented to examine the effects of initial crack length ratio, crack spacing, and material gradation on the thermal shock damage and residual strength behavior. It is found that surface crack morphology in combination with thermal property gradation significantly influences the thermal shock damage and residual strength behavior of functionally graded ceramics. The specimens with smaller initial crack length ratios suffer severer damages and strength degradation at moderately intense thermal shocks.

This study introduces a model capable of investigating the vibrational response of nanobeams that simultaneously incorporate structural perforations and axially functionally graded materials while being supported by elastic foundations. By using Euler-Bernoulli beam theory with the nonlocal elasticity framework, the model captures nanoscale phenomena often neglected in classical analysis and governing equation of motion is derived. The objective of this study is to examine the coupled effects of axial material gradation, periodic perforations, and elastic foundation parameters on the vibrational behavior of nanobeams, highlighting how variations in perforation geometry and material gradation jointly influence the mode shape and frequency response. The modified equivalent modeling strategy is employed to account for the periodic perforations. The Galerkin method is utilized to handle and extract natural frequencies and mode shapes. The proposed numerical scheme exhibits high accuracy, as verified by comparison with existing results from the literature, with the maximum deviation limited to just 0.081%. Perforation and axial material gradation significantly impact the vibrational characteristics, governed by the nonlocal effects and geometric configuration. Numerical findings highlight the sensitivity of dynamic response to filling ratio, perforation geometry, and foundation interaction across different boundary conditions.

This study examines the nonlinear buckling response of functionally graded shallow circular nano-arches within the framework of the stress-driven nonlocal elasticity theory and Euler–Bernoulli beam kinematics. Geometric nonlinearity is incorporated through von Kármán strain–displacement relations, and the governing equations are discretized using the generalized differential quadrature method (GDQM). A possible equilibrium path, including the post-buckling regime, is traced via the arc-length method to capture potential instability phenomena. A parametric investigation is conducted to explore the influence of boundary conditions, geometric characteristics, nonlocal material length scale, gradation profile, and the extent of a partially applied transverse load on the buckling behavior. The results reveal that shallow nano-arches may exhibit multiple instability patterns, snap-back, and looping—depending on the combined effects of small-scale parameters, material gradation, loading characteristics and boundary conditions (BCs). To the authors’ knowledge, this is the first study to analyze the post-buckling behavior of functionally graded shallow nano-arches subjected to non-uniform partial loading using the stress-driven nonlocal elasticity model in conjunction with an arc-length solution strategy.

This study presents a comprehensive investigation into the free vibration behavior of rotating prismatic sandwich blades with linearly varying thicknesses. The blade structure features an auxetic core and graphene nanoplatelet (GNP)-reinforced composite face sheets. Various GNP dispersion patterns—uniform and functionally graded—are considered along the blade height. Due to the anisotropic and spatially varying nature of the material reinforcement, stress transformation techniques are applied at specific angles to determine the effective material properties. The governing equations of motion are derived using Hamilton’s principle and the variational approach, incorporating the effects of geometric nonuniformity and material gradation. These equations are numerically solved using the generalized differential quadrature method (GDQM), a high-accuracy numerical technique suitable for such complex systems. Parametric studies are conducted to examine the influence of transformation angle, GNP distribution pattern, auxetic geometry, rotational speed, and structural geometry on the natural frequencies. The results provide valuable insights for the optimized design of high-performance rotating structural components.

This paper investigates the buckling behavior of porous PZT-4/PZT-5H smart graded plate resting on the Winkler–Pasternak foundations under the combined thermomechanical and thermoelectric loading conditions. The thermomechanical properties of the material are modeled based on sigmoid variation. The study employs von Kármán nonlinear strain theory coupled with the modified first-order shear deformation theory (FSDT) and variational principles to formulate the equations of motion. A higher-order finite element (HOFE) approach with seven degrees of freedom (DOFs) is utilized alongside modified iterative methods to solve the governing equations. The convergence and accuracy of the proposed methodology have been validated against the existing literature. The simulation results provide a detailed analysis of the effects of temperature changes, thermal gradients, material gradation, applied voltage, porous exponent, porosity distribution, and elastic foundations on the structural behavior of the PZT-4/PZT-5H smart graded plates. The study investigates in detail the effects of porosity distribution, porous exponent applied electrical loading, various temperature profiles (uniform, linear, and nonlinear), material gradient exponent, thickness ratio, elastic foundations, and boundary conditions on the buckling behavior of the PZT-4/PZT-5H smart graded plate. These findings offer critical insights into the design and optimization of thermoelectric and thermomechanical stabilities in smart porous structures, making them more efficient, reliable, and performant for use in engineering systems such as MEMS, biomedical devices, and energy-harvesting technologies.