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Although the small-scale effect and nonlinear damping on the nonlinear vibration of microbeam electrostatic resonators are important, they have been overlooked by researchers. We use the slender beam model including the small-scale effect and nonlinear damping to investigate the nonlinear vibrations of the electrostatic resonators in the present paper. We apply the Galerkin method on a nonlinear partial differential equation to obtain the nonlinear ordinary differential equations for the first and third modes. The two equations include constant terms. The multiple-scale method is used to obtain the approximate analytical solutions of the two equations. The approximate analytical solutions discover the effects of driving electric field, small-scale effect, and nonlinear damping on structural vibrations. The results suggest that the small-scale effect, the direct current (DC) voltage, and the alternating current (AC) voltage have some critical effects on the vibrations of microresonators.

Based on the generalized nonlocal thermoelastic theory and the memory-dependent differential (MMD) theory, the dynamic response of the inner surface of an infinite hollow cylinder under thermal sho...

Pineapple leave fiber (PALF) can be considered as one of the green materials to the industries, which is the potential to replace the non-renewable synthetic fiber. However, the high disparity in the mechanical properties of PALF becomes an issue in structural composite design. Hence, improved Weibull distribution is utilised to quantify the tensile strength variation of PALF in various gauge lengths. The single fiber tensile test was performed after the fiber surface treatment and fiber diameter scanning. The predicted PALF strength by applying the improved Weibull distribution incorporating with conical frustum model is well compromised with experimental data compared to the traditional Weibull model.

In this manuscript, Electrochemical Micromachining (ECM) is well designed with the important concept called scale effect. The main objective is to evaluate the scale effects that occur when the mac...

Eringen’s nonlocal elasticity theory is one of the most attractive approaches to investigate the intrinsic scale effect of nanoscopic structures. Eringen proposed both integral and differential nonlocal models which are equivalent to each other over unbounded continuous domains. Although the Eringen nonlocal models can be used as very useful tools for modeling the mechanical characteristics of nanoscopic structures, however, several researchers have reported some paradoxical results when they used the nonlocal differential model. In this paper, we develop a well-posed nonlocal differential model for finite domains, and its applicability to predict the static and dynamic behavior of a nanorod is investigated. It is shown that the proposed integral and differential nonlocal models are equivalent to each other over bounded continuous domains, and the corresponding elastic problems are well-posed and consistent. In addition, some paradigmatic static problems are solved the and we show that the paradoxical results disappear by using the present model.

This paper presents the multi-directional vibration behaviors of buckled viscoelastic nanoribbons based on the nonlocal theory containing scale effect, where the Lagrange’s motion equation is introduced to construct the nonlocal viscoelastic governing equation. The first-order transverse vibration mode and the first-order longitudinal vibration mode are considered to study the influences of the scale characteristics on the natural frequency of two different vibration modes. The Kelvin–Voigt model is used to characterize the material viscoelastic property, and an analytical method is presented to solve the nonlocal viscoelastic vibration behaviors of the buckled nanoribbon containing scale effect. Results show that the scale effect could decrease the natural frequency of buckled nanoribbon with viscoelastic behavior, as well as the half bandwidth during forced vibration. The presented results may be taken as a useful reference for the fabrications and applications of buckled nanostructures-based sensors & actuators, electronics, energy harvesters, etc.

The effects of flexoelectricity on thickness-twist waves propagating in the nanoplates are analytically investigated. Detailed calculations are performed for nonpiezoelectric material using the met...

The hydrodynamic performance of a ship with and without a stern flap was comprehensively investigated based on model tests and model- and full-scale simulations. The stern flap led to an increase i...

The interaction between off-road machines and soil is usually a dynamic process of soil shearing. However, in practice, in order to interpret these processes, the empirical modified static Coulomb criterion, which does not take into account the soil strengthening, is commonly used. At Wroclaw University of Technology a proposal for a method for predicting dynamic shear strength in soils was developed. This method takes into account primarily the soil shear velocity, the scale effect of the test device and its kinematics, which include the parameters of the process under investigation in terramechanics. The method will be presented in two parts of the following publication. The first part presents the results of the tests on soil shear strength carried out by the author of the article by means of soil ring shear test device. These results are discussed against the background of the results of soil research performed all around the world. On the basis of the tests conducted by the author, a new dynamic criterion of soil shear strength was formulated and the requirements for the innovative method for predicting dynamic shear strength in soils were established. This experimental method will be presented in the second part of the article.

For the production of seafloor massive sulfides, the ores are expected to be transported as a slurry up to the sea surface. The pipe wear is caused mainly by the collision of the ores against the pipe wall; thus, the evaluation of pipe wear is required for the operation of the production system. The authors conducted a full-scale experiment for evaluating pipe wear due to slurry flow. As the result, the pipe wear resistance of a SUS304 stainless steel is higher than the ultrahigh molecular weight polyethylene. In addition, the pipe wall thickness was measured before and after the experiment to obtain the distribution of the erosion on the pipe wall. The authors confirmed that the wall thickness reduced uniformly along the circumferential direction for vertical pipe, and the erosion occurred mainly along the bottom surface of the pipe for the horizontal and inclined pipes. Also, the authors investigated the relation between the index of rock abrasivity and erosion and proposed a correlation for pipe wear with the index of rock abrasivity. Finally, the authors predicted the pipe wear on the condition of full-scale experiment based on the data obtained in the reduced-scale experiment conducted previously. Then, the authors compared the predicted pipe wear with that measured in the full-scale experiment.

This paper presents three-dimensional analytical solutions for displacement and strain fields near angular corners in plates subjected to in-plane loading. The approach is based on the first-order plate theory, which represents an elementary extension of the classical plane theory of linear elasticity. Utilising the Kontorovich–Lebedev transform, the asymptotic behaviour of the out-of-plane displacement field near the apex is investigated for both Mode I and Mode II loadings. The analytical solutions obtained in the present work correctly predict several three-dimensional effects, such as the order of stress singularity and the intensity of the coupled (local) out-of-plane singular mode under remote in-plane shear loading as well as the scale effect associated with the plate thickness. The developed solutions are more general than many previous analytical results obtained for crack and notch geometries and, essentially, generalise the classical William's solution for angular corners. The analytical predictions compare favourably with three-dimensional finite element modelling and experimental results.

This paper investigates the buckling problem of a multiply connected bar-chain (MCB) system. Unlike the Hencky bar-chain that comprises rigid bars connected to each other by rotational springs, this MCB model has rigid bars connected by both direct and indirect neighbouring rotational springs that simulate the long range interactions between bars. The buckling loads of the MCB with two-neighbour and N-neighbour interactions are analytically obtained for simply supported, clamped-clamped and clamped-free boundary conditions. By continualizing the discrete equations associated with MCB, a nonlocal continuum model is constructed to predict the buckling behavior of nonlocal bars with short and long range interactions. It is shown that this continualized nonlocal model (CNM) is equivalent to a stress gradient type of Eringen's nonlocal media. By comparing the solutions between CNM and MCB, it is shown that CNM is a simple nonlocal continuum model that is able to capture the scale effect of a generalized lattice that includes multiple interactions among its components. The closed form expression of the length scale of CNM is derived in terms of the rotational spring stiffnesses of MCB.

In this study, the mechanical property of copper microwire, a widely used material in our daily life, is investigated by subjecting it to in situ scanning electron microscope twisting based on a self-developed nanorobotic manipulation system. First, copper microwire is assembled on the nanorobotic system inside the scanning electron microscope, and then twisted clockwise and anticlockwise continuously from 0° to 360° until fracture. After that, the mechanical properties of elastic modulus, microhardness, yield stress, and the strain hardening exponent of the twisted sample are investigated by nanoindentation. The change in elastic modulus and indention hardness showed strong indentation size effects, because a large number of geometrically necessary dislocations were generated around the indenter. In addition, the fracture analysis indicated that the smaller the scale of the material, the more sensitive it was to surface cracks or defects. Ductile fracture features of the twisted sample appear due to the nucleation, growth, and coalescence of the microvoids.

The micro-surface asperity scale of grinding metal parts is within several microns. When two grinding surfaces are in contact, the unevenness of the plastic deformation of the asperities at the micro-scale leads to greater plastic hardening strength of the material. The results of the nano-indentation experiment conducted in this paper confirmed this phenomenon. Based on conventional mechanism-based strain gradient (CMSG) plasticity theory, the micro-scale plastic constitutive equation of materials is given and then is verified by the nano-indentation experiment. Finite element software abaqus and the user-defined element (UEL) subroutine are used to build three-dimensional rough surface elastoplastic contact models. By calculating the grinding rough surface contact in the macro-scale constitutive model based on J2 theory and in the CMSG plasticity constitutive model, the influence law of plastic micro-scale effect on contact performance is obtained.

An electrothermal microgripper is an important actuator in microelectromechanical and micro-operating systems, and its temperature field analysis is the core problem in research and design. Because of the small size of an electrothermal microgripper, its microscale heat transfer characteristics are different from those of the macrostate. At present, only a few studies on the heat transfer scale effect in electrothermal microgrippers have been conducted, and the heat transfer analysis method under the macrostate is often used directly. The temperature field analysed and simulated is different from the actual situation. In the present study, the heat transfer mechanism of an electrothermal microgripper in the microscale was analysed. The temperature field of a series of microscale heating devices was measured using microthermal imaging equipment, and the heat transfer parameters of the microscale were fitted. Results show that the natural convective heat transfer coefficient of air on the microscale can reach 60–300 times that on the macroscale, which is an important heat transfer mode affecting the temperature field distribution of the electrothermal microgripper. Combined with the finite element simulation software, the temperature field of the electrothermal microgripper could be accurately simulated using the experimental microscale heat transfer parameters measured. This study provides an important theoretical basis and data support for the optimal design of the temperature controller of the electrothermal microgripper.

SiC-fibers are subjected to a predictable premature failure, consequence of a slow crack growth mechanism. This has chiefly been studied through static fatigue testing of multifilament tows. The discrepancy existing between experimental results, broadly dispersed, and the bundle theory (solely considering the filament strength distribution) has been interpreted by discrete stochastic phenomena. In this work, the uncertainty on applied stress caused by fiber misalignment (slack) was rather investigated through Monte Carlo simulation, ascribing to each filament of the tow a strength and a stress among established distributions. If a coherent lifetime range could this way be obtained, a scale effect on stress exponent was also revealed: equal to 12.6 on filament it falls to 8.4 on bundle, in agreement with experimental results. The same would apply to larger scale (woven tow).

Masonry columns often exhibit a lack of load-carrying capacity that is due to overloads and do not provide any ductility or dissipation capacity under seismic forces. Column confinement has been extensively studied as an effective technique, which could mitigate these structural vulnerabilities. The confinement of masonry columns will be studied in this paper, by considering fabric-reinforced cementitious matrix (FRCM) materials as external jackets. Due to the lack of information in the scientific literature, a new analysis-oriented model (AOM) for the prediction of the axial stress-strain law will be presented and discussed in this paper. The proposed AOM consists of a system of equations that make several assumptions: crossing the predicted peak point (strength and relative strain), crossing the ultimate point (80% residual strength and relative strain), and the horizontal tangent at the peak point and the initial (linear elastic) slope derived from the geometry and mechanical properties of the materials involved. The AOM was demonstrated to be simple and accurate, based on Pearson's test (χ2); therefore, the proposed approach could be considered for future design equations. In addition, this paper will illustrate and discuss the validation of two available design-oriented models (DOMs), which could predict the axial strength of FRCM jacketed columns, by comparing the theoretical results with a database of experimental results that is available in the scientific literature. Novel formulas for the computation of both the peak and ultimate axial strains will be further proposed, as the basis for a design procedure. Their accuracy was demonstrated by considering an experimental versus theoretical comparison.

An investigation was made into the performance and scale effect of birdlike flapping wing aircraft in short landing. A flapping mechanism is proposed to transform a powered shaft rotation to an optimal kinematics of wing motion combining up-and-down stroke, pitching, and fore-and-back swing. An unsteady aerodynamic method (UAM) was developed based on potential flow theory, including the leading- and trailing-edge vortices generated by a flapping wing. After validation based on computational fluid dynamics (CFD) results, the method is used to calculate the aerodynamic forces of flapping wings. The flight dynamics model of the aircraft is built using Automated Dynamic Analysis of Mechanical Systems (ADAMS) software version 2012 interfacing with the UAM coded in Python. The coupling between the inertial force of the body motion and the aerodynamic forces from flapping wings and tailplane is incorporated into the numerical simulation of the aircraft landing. Taking a 0.196-kg birdlike aircraft model with a prescribed kinematics of flapping wing motion as an example, a parametric study was carried out in a small range of initial tailplane angles and subsequent flapping frequencies. Optimal parameters were obtained to reduce the forward and descending velocities of the aircraft to a minimum value for safe and short landing performance. The study is then extended to aircraft of different geometric scales in a range of 0.5–10 associated with a weight scale of 0.1–1,000. Based on the study, a method is developed to determine the required flapping frequency for birdlike aircraft of different scales to achieve a short landing target with the descending velocity reduced to a specified value. For the aforementioned example aircraft (geometric scale of 1), the flapping frequency is 4 Hz to reduce both descending and forward velocities to 50% of the landing performance in fixed-wing mode, while a birdlike aircraft on a geometric scale of 10 and landing weight of 196 kg requires a minimum flapping frequency of 1.25 Hz to achieve a 50% reduction of the descending and forward velocities compared with the same aircraft landing in fixed-wing mode.

This chapter introduces the thermoelectric technologies for harvesting energy from pavements. It starts by presenting the basic principle of thermoelectric effect known as “Seebeck effect.” It then explains the temperature characteristics of road surface, ambient air, and subgrade. Based on this, pavement-ambient thermoelectric system and pavement-subgrade thermoelectric system are introduced, including system composition, material design, and energy output of indoor and outdoor tests. And the influence of external environment, traffic load, scale effect, thermoelectric generator, etc., on the energy output of pavement thermoelectric system is explained. Then, the effect of the thermoelectric system on the pavement temperature is analyzed. By the end of the chapter, the problems and development of pavement thermoelectric technologies are analyzed and discussed.

This work deals with the prediction of the maximum efficiency achievable by turbines for Organic Rankine Cycle (ORC) systems by means of similarity principles. At present, this is a key topic in the preliminary design optimization procedures of these systems. The dimensional analysis applied to the most general ORC turbines scenario helps obtain the functional relationship between maximum turbine efficiency and the most relevant design variables within the general framework of the flow similarity. Aim of the work is to search for the less wide and more convenient set of independent similarity parameters to increase the accuracy of turbine efficiency data in the optimization of ORC systems. Results show that the strict flow similarity does not hold if the same design is used for different working fluids, because real gas compressibility effects cannot be disregarded for most of the fluids usually adopted in ORC systems. On the other hand, a “quasi-similarity” approach can be applied to the design of low volume expansion ratios ORC turbines using the size parameter (SP), volume expansion ratio (VR) and the compressibility factor (Z) as predictors of turbine efficiency. Accordingly, two original correlations for the SP-VR-Z map of optimized axial turbine stages are suggested.

This paper deals with the study of the actual progression of the damage in the 90 degrees lamina of a composite. It has been proved and observed that isolated debondings between fibres and matrix are the first manifestation of damage in the weakest lamina, the 90 degrees lamina in a [0,90]S laminate. It was also numerically supported that this first phase was independent of the thickness of the 90 degrees lamina, not being then affected by the “scale effect”. The continuation of this first phase of damage is the objective of the present paper. To this end, a multiscale model is created involving the debonding between fibre and matrix and studying the kink of this crack, abandoning the fibre-matrix interface and entering into the matrix to produce a meso-transverse crack in the 90 degrees ply. The study is based on the application of Fracture Mechanics to an incipient kinked crack that starts from a debonding between fibre and matrix. It is concluded that this second phase of damage, playing with the thickness of the 90 degrees lamina, is not affected by the scale effect, as the variation of the energy release rate of the kinked crack is not significantly influenced by the variation of the thickness of the lamina.

A microstructure-dependent plate model for bending of orthotropic functionally graded micro-plates was proposed on the basis of a re-modified couple stress theory. The proposed model contributed a ...

This paper compares the results of experimental fatigue life tests for two types of materials. For each of them, fatigue tests taking into account both the size effect and stress or strain gradient were considered. Two different materials were selected for the analysis: 16Mo3 steel and 6082-T6 aluminum alloy. In the case of 6062-T6 aluminum, both the scale effect and the gradient effect are small, which is probably due to the fact that the material behaves elastically to a very large extent. On the other hand, this effect is noticeable for the tests of 16Mo3 steel, where the material is to a large extent a material in the elastic–plastic state. The analysis shows that the stress gradient obtained in fatigue bending of 16Mo3 steel and 6082-T6 aluminum produces a similar effect as that of small specimens, i.e., an increase of the fatigue life compared to standard tension–compression tests. Therefore, the bending stress gradient of specimens without geometric notch can be considered as a different type of size effect.

The economic impact of industrial agglomeration has been examined by many studies. However, few has focused on its environmental consequences partly due to data availability. Applying decomposition method to a newly constructed industrial-level CO2 emissions dataset of 286 Chinese prefectural and above (PAA) cities over the period 2004–2013, this paper examines the mechanism of how industrial agglomeration impacts urban CO2 emissions through three components, scale, composition and technique effects. We find that industrial agglomeration pushed up CO2 emissions through the scale effect, but reduced CO2 emissions through both the technique and composition effects. At the regional level, the effect of agglomeration on CO2 emissions was dominated by the scale effect in the central and western cities. However, in the eastern cities, the scale effect was almost offset by the technique and composition effects. China’s regional development programs tend to relocate economic activities from the more agglomerated eastern cities towards the more dispersed western cities. This relocation may have reduced the environmental efficiency gains from industrial agglomeration.

An approach for probabilistic prediction of fatigue crack initiation lifetime of structural details and mechanical components is presented. The methodology applied is an extension of the generalized local model (GLM) to the fatigue case using the fatigue Weibull regression model proposed by Castillo-Canteli. First, the primary failure cumulative distribution function (PFCDF) of the generalized failure parameter is derived from experimental results for a given reference size, taking into account the non-uniform distribution of the generalized parameter (GP) the specimens are submitted to. The adequacy of the GP is presumed, ensuring uniqueness of the derived PFCDF as a material property, irrespective of the specimen shape and size, and the test chosen to this end. Next, the GP distribution is obtained by a finite element calculation and the PFCDF is applied to each finite element, considering the scale effect, to derive the probability of failure for the whole component. The suitability of the proposed approach is illustrated twice: first, assessing simulated data in a theoretical example, and second, evaluating experimental fatigue life results for riveted joints from the historical Fao Bridge. The PFCDF for the puddle iron from the bridge is calculated from standard tensile specimens, from which the initiation fatigue lifetime of the riveted connections is predicted and compared with the experimental results. In this way, the transferability from standard tests to real components is demonstrated.

The micro-scale effect occurs because of the gas flows in shale reservoirs containing small organic pores. In this study, based on a lattice Boltzmann model incorporating the bounce-back and specular-reflection boundary conditions, the gas flow through two parallel plates driven by differential pressures is simulated, which in turn verifies the model. Considering the effects of the slippage, surface diffusion, and adsorption, the gas flow in the organic channels is simulated based on the proposed lattice Boltzmann model. It is shown that the micro-scale effect is significant in the gas flows in the micro-scale channels. The compression effect leads to a nonlinear distribution of pressures along the centreline of the flow channels, and the nonlinearity increases with an increase in the pressure difference between the two sides of the flow channel. In case of gas flows in organic pores, the adsorption effect decreases the free-gas velocities, and with a decrease in pore sizes, the average free-gas velocity is reduced owing to the increased adsorption effect. The slippage effect and surface diffusion have a significant impact on the free-gas velocity of the mass flow. Compared to the slippage effect, surface diffusion contributes more to the mass flow of gas in organic pores. An increase in the Knudsen number intensifies the slippage effect and surface diffusion and enhances the mass flow.

Against the background of global warming, China faces the dual pressures of economic structural transformation and carbon emission reduction. While promoting economic development, the development and construction of transportation infrastructure has contributed to urban carbon emissions. Using an improved STIRPAT model, we examine panel data for 283 cities between 2003 and 2013 to explore the effects of transportation infrastructure on urban carbon emissions. The results show that transportation infrastructure increases urban carbon emissions and intensity. In addition, while the population scale effect of transportation infrastructure is conducive to decreasing carbon emissions, the economic growth and technological innovation effects of transportation infrastructure increase carbon emissions. Results also demonstrate that in large and medium-scale cities, construction of transportation infrastructure increases carbon emissions. In small cities, this relationship is not significant. Robustness tests support all findings. These results indicate that the effective development of carbon-abatement policies requires an examination of the effects of transportation infrastructure.

The paper presents the experimental and numerical investigations of a novel design of a pneumatic life raft in calm water conditions. Two main issues were considered: the life raft performance under tow and its resistance in calm water conditions. The experiment and CFD simulations were performed by using the full scale prototype to eliminate the scale effect. The towing tank tests confirmed the results of numerical computations. The compatibility of the results of numerical and experimental tests was high mainly because the new life raft does not deform under the hydrodynamic and aerodynamic loads. The characteristics similar to rigid body behaviour result mainly from a new construction and materials used for manufacturing the life raft.

This paper deals with free vibration analysis of nanosize rings and arches with consideration of surface effects. The Gurtin-Murdach model is employed for incorporating the surface effect parameters including surface density, while the small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. An analytical Navier solution is presented to solve the governing equations of motions. Comparison between results of the present work and those available in the literature shows the accuracy of this method. It is explicitly shown that the vibration characteristics of the curved nanosize beams are significantly influenced by the surface density effects. Moreover, it is shown that by increasing the nonlocal parameter, the influence of surface density reduce to zero, and the natural frequency reaches its classical value. Numerical results are presented to serve as benchmarks for future analyses of nanosize rings and arches.

This paper reviews the relationship between mechanical properties and scale effect of coal specimens containing gas in stress condition. Firstly, the scale effect stress–strain model of coal was established based on Weibull theory and modified Terzaghi equation. And then, the scale effect stress–strain model of coal containing gas was proposed considering the effect of interfacial friction and expansion force of gas. Lative parameters of the model were obtained through experiments. The mechanical properties of coal specimens containing gas were analyzed, and the correctness of the theoretical model was validated. The results indicate that the theoretical curve of the coal specimens’ compressive strength varying with height–diameter ratio shows consistency with experimental curve. The theoretical scale effect stress–strain curve of coal containing gas agrees well with the experiment at the pre-peak. With the increase in the height–diameter ratio, the coal specimens’ compressive strength decreases and the elastic modulus increases. The coal specimens’ compressive strength and elastic modulus decrease with the gas pressure.

Classical continuum models are unable to capture the response of a microstructured solid when the scale effect is relevant. In vibration analysis, this limitation appears when the solid undergoes vibrations of wavelength that approaches the characteristic length of the microstructure. A discrete model may be formulated to account for this effect, but this comes at the expenses of high computational costs. For example, scale effects are relevant in strings employed in sensing applications which often rely on information gathered in the nonlinear dynamic regime. In this work, we study the dynamic behavior of a taut string modeled as a lattice of particles linked to first neighbors by linear springs. We develop an inertia-gradient generalized continuum model of the chain, which undergoes nonlinear vibrations. Unlike the corresponding classical continuum model, enrichment of the kinetic energy density with the characteristic length of the microstructure permits the model to capture short-wavelength vibrations. Comparison of the response predicted by the continuum models highlights that the generalized model provides better estimations of the dynamic response of the considered microstructured string in the nonlinear regime and at short wavelengths. Program during academic year 2017-18. This work was supported by the Ministerio de Economía y Competitividad de España (grant numbers DPI2014-57989-P and BES-2015-073720). Publicado

Plint (IMechE 182 (1):300–306,1967) reported a reduced coefficient of friction with increasing roller sizes in EHL traction measurements. In this study, a similar scale effect has been observed when comparing measured traction curves at the same operating conditions between a ball-on-disc rig and a twin-disc machine of different geometrical sizes. This scale effect has been studied numerically for point contacts of different radii of curvature Rx based on thermal EHL simulations. Results show that the reduced friction for large Rx is caused by an increase in film thickness and the enhanced thermal effects. The mechanisms are: (1) heat is hard to conduct across a thicker EHL film due to bad thermal conductivity; (2) shear is mainly localized in the middle film.

International audience; This article presents the application of a thermo-hydro-chemo-mechanical (THCM) model to a real complex structure of reactor confinement (mock-up VERCORS from EDF) by taking into account the specificities of the construction (construction consequences), the distributed reinforcements and the material heterogeneity of massive structure. The experimental campaigns were conducted during and after the construction of VERCORS. The early-age behavior of concrete is first modelled based on a multiphasic hydration model to ensure the thermal evolution. Then a 3D mechanical model is used to predict the consequences of hydration, temperature and water variations on mechanical behavior. An alternative approach to consider the structural effect of distributed reinforcement without explicit meshing of reinforcements is implemented and is able to reproduce the influence of reinforcement on the crack patterns. Moreover, the " Weakest link localization " method is also adapted to deal with a probabilistic scale effect due to the material heterogeneity of massive structure. It permits to assess directly the most likely tensile strength which can treat the first crack in softening part of the loaded volume of structures.

Replica scaled impact experiments with unconfined ceramic targets have shown that the transition velocity, i.e., the impact velocity at which interface defeat ceases and ceramic penetration occurs, decreased as the length scale increased. A possible explanation of how this scale effect is related to the formation of a cone crack in the ceramic has been presented by the authors in an earlier paper. Here, the influence of confinement and prestress on cone cracking and transition velocity is investigated. The hypothesis is that prestress will suppress the formation and growth of the cone crack by lowering the driving stress. A set of impact experiments has been performed in which the transition velocity for four different levels of prestress has been determined. The transition velocities as a function of the level of confining prestress is compared to an analytical model for the influence of prestress on the formation and extension of the cone crack in the ceramic material. Both experiments and model indicate that prestress has a strong influence on the transition from interface defeat to penetration, although the model underestimates the influence of prestress.

The aim of this experimental study is to investigate the effects of hydraulic parameters on the formation of air-entraining vortices at horizontal intake structures without approach flow induced circulation. Six intake pipes of different diameters were tested in the study. The intake pipe to be tested was horizontally mounted to the front side of a large reservoir and then for a wide range of discharges experiments were conducted and critical submergences were detected with adjustable approach channel sidewalls. Empirical equations were derived for the dimensionless critical submergence as a function of the relevant dimensionless parameters. Availa- ble data is also checked for the possible scale effect. Then, these obtained equations were compared with the similar ones in the literature which showed a quite good agreement.

Twin-disc tests have been conducted to study the initiation of local rolling contact fatigue (LRCF) observed on high-speed railway wheels. The tested wheel and rail discs, being about 60 mm in diameter, are extracted from ER8 wheel tires and U71MnG rail heads, respectively. Since indentations have been identified as the main cause of LRCF in practice, artificial defects are applied on the contact surfaces of wheel discs before tests using three different methods, namely, the Vickers hardness tester, electric discharge machining (EDM) and indenting of M10 tap tips (TT). Test results have shown that significant cracks and LRCF can indeed initiate under fully lubricated conditions at TT indentations deeper than approximately 0.15 mm and 0.2 mm, respectively, but not at Vickers indentations or EDM defects. Larger plastic flow and sharper geometries at relatively deep TT indentations, the influencing depth of the normal contact load and the detachment of wear debris should be the dominating factors, based on which a mechanism is proposed for the initiation of LRCF. Care should be taken, when applying the above thresholds into practice, to take into account the scale effect of the test rig, and dry load cycles and various types of indentations present in the field.

The response of fibrous materials to complex mechanical, hygroscopic and thermal loadings is a relevant research question in many engineering fields. In the literature, the behaviour of fibrous networks is typically investigated by assuming uniform loading conditions at the micro-structural level and by developing homogenization schemes that provide structure-property relations. However, in a number of situations, for instance in paper media used in digital ink-jet printing applications, the length scale of the applied loading (in this case of the moisture distribution) may be comparable to the characteristic length scale of the micro-structure. Therefore, a homogenized description may not be adequate for capturing the response of the fibrous network, even in an average sense. Indeed, the response of the network may depend on the ratio between the typical length scale of the loading and that of the micro-structure. The goal of this paper is precisely to investigate the scale effect on the network response due to the application of hygroscopic (or thermal) loads, which may rapidly fluctuate over the micro-structure. To this aim, a two dimensional fibrous network model is exploited. This model properly represents several network level features, such as the fibre's hygro-elastic properties and geometry, orientation, areal coverage, etc. The model is subjected to different moisture profiles, ranging from slow to fast oscillations. This reveals a pronounced size effect in the network deformation: the faster the moisture fluctuation, the higher the network's average strain. By exploring the dependence of the size effect on different micro-structural parameters, it is shown that the size effect is strictly related to the accommodation of fibre swelling by the voided network regions, and that therefore it is governed by the average size of the voids.

In this article, the eigenfrequency responses of a nanoplate structure are evaluated numerically via a novel higher-order mathematical model and finite-element method including nonlocal ela...

In this paper we study the coupled axial-transverse nonlinear vibrations of a kind of one dimensional structured solids by application of the so called Inertia Gradient Nonlinear continuum model. To show the accuracy of this axiomatic model, previously proposed by the authors, its predictions are compared with numeric results from a previously defined finite discrete chain of lumped masses and springs, for several number of particles. A continualization of the discrete model equations based on Taylor series allowed us to set equivalent values of the mechanical properties in both discrete and axiomatic continuum models. Contrary to the classical continuum model, the inertia gradient nonlinear continuum model used herein is able to capture scale effects, which arise for modes in which the wavelength is comparable to the characteristic distance of the structured solid. The main conclusion of the work is that the proposed generalized continuum model captures the scale effects in both linear and nonlinear regimes, reproducing the behavior of the 1D nonlinear discrete model adequately. The authors are indebted to the Ministerio de Ciencia e Innovación de España (Project DPI/2014-57989-P) for the financial support.

In this paper, considering the small scale effect, the linear free vibration in pre/post-buckled states and nonlinear dynamic stability of lipid tubules with in-plane movable ends are studied. The small scale effect is characterized by nonlocal elasticity theory. The vibration in pre/post-buckled regions is solved by the differential quadrature method (DQM), and the nonlinear dynamic stability is solved by incremental harmonic balance method (IHBM). In numerical results, the effects of small scale parameter, types of lipid tubule on vibration in pre/post-buckled states and nonlinear dynamic stability are discussed.

In this paper, dynamic spherical cavity expansion model is developed for rate-dependent concrete material described by modified Drucker-Prager Cap plasticity model incorporated with size effect. Penetration resistance components are computed accordingly with static resistance dependent on projectile diameter scale. Saturated region is introduced to investigate the response of concrete target under high impacting velocity. The validation of the proposed model is conducted by modelling a rigid projectile with full-scale and 1/10-scale diameter penetrating a semi-infinite concrete target. Depth of penetration numerically obtained is also compared with some widely recognized empirical penetration formulae, and better agreement is achieved by the proposed model for penetration tests with various striking velocities.

This paper conducts calibration tests on the shallow-water maneuverability of 1:100 ship models for the typical navigation fleets in Three Gorges Reservoir. Major influential factors for the maneuverability similitude between models and prototypes and for scale effect were identified. A correction method for model scale was also established through model tests. Test results indicate that, by correcting the model scales of various fleets based on scale effect, the maneuverability indexes K’ (dimensionless of K) and T’ (dimensionless of T) of ship models are suitable for shallow-water tests, and properly reflect the maneuvering characteristics of prototypes. The findings provide an experimental basis for the navigation safety in Three Gorges Reservoir.