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The influence of sample geometry on various measured physical properties (including the magneto-Seebeck effect, Nernst effect, magnetoresistance effect, Hall effect, and thermal conductivity) in the presence of a magnetic field was examined using a polycrystalline Bi-Sb sample. The sample, consisting of polycrystalline Bi88Sb12, was prepared through spark plasma sintering and subsequent annealing. Measurements of the physical properties were conducted under a magnetic field of 5 T, and the obtained values were compared with simulated results derived using the finite element method for different sample geometries. Distinct shapes were found to be necessary for accurate measurements, with each physical property requiring a specific aspect ratio of sample length (l) to width (w). These ratios were determined to be l/w > 0.57, 2.9, 4.2, 1.2, and 3.1 for the magnetoresistance, Hall, two-wire magneto-Seebeck, four-wire magneto-Seebeck, and Nernst effects, respectively. Additionally, to achieve a minimal error of less than 2% in thermal conductivity measurement, a thermal conductance ratio of Ks/Kw > 27 was necessary, where Ks and Kw denote the thermal conductance of the sample and lead wire, respectively. [ABSTRACT FROM AUTHOR]

The metal supported catalysts are emerging catalysts that are receiving a lot of attention in CO2 hydrogenation to C1 products. Numerous experiments have demonstrated that the support (usually an oxide) is crucial for the catalytic performance. The support metal oxides are used to aid in the homogeneous dispersion of metal particles, prevent agglomeration, and control morphology owing to the metal support interaction (MSI). MSI can efficiently optimize the structural and electronic properties of catalysts and tune the conversion of key reaction intermediates involved in CO2 hydrogenation, thereby enhancing the catalytic performance. There is an increasing attention is being paid to the promotion effects in the catalytic CO2 hydrogenation process. However, a systematically understanding about the effects of MSI on CO2 hydrogenation to C1 products catalytic performance has not been fully studied yet due to the diversities in catalysts and reaction conditions. Hence, the characteristics and modes of MSI in CO2 hydrogenation to C1 products are elaborated in detail in our work. [ABSTRACT FROM AUTHOR]

In the present study, experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores. The high velocity impact tests were carried out using a compressed air gun. A sharp conical nosed projectile was impacted normally and with some offset distance (20 mm and 40 mm). The deformation, failure mode and energy dissipation characteristics were obtained for both kinds of loading. Moreover, the explicit solver was run in Abaqus to create the finite element model. The numerically obtained test results were compared with the experimental to check the accuracy of the modelling. The numerical result was further employed to obtain strain energy dissipation in each element by externally running user-defined code in Abaqus. Furthermore, the influence of inscribe circle diameter and cell wall and face sheet thickness on the energy dissipation, deformation and failure mode was examined. The result found that ballistic resistance and deformation were higher against offset impact compared to the normal impact loading. Sandwich panel impacted at 40 mm offset distance required 3 m/s and 1.9 m/s more velocity than 0 and 20 mm offset distance. Also, increasing the face sheet and wall thickness had a positive impact on the ballistic resistance in terms of a higher ballistic limit and energy absorption. However, inscribe circle diameter had a negative influence on the ballistic resistance. Also, the geometrical parameters of the sandwich structure had a significant influence on the energy dissipation in the different deformation directions. The energy dissipation in plastic work was highest for circumferential direction, regardless of impact condition followed by tangential, radial and axial directions.

In this article, four different structural epoxy adhesives such as SPABOND™ 820HTA (non-toughened), SPABOND™ 840HTA (toughened) adhesives, and their two hybrid combinations are fabricated using a manual mixing method. Quasi-static tensile experiments are conducted at standardized and high strain rates using ASTM D638-22 Type II specimens to investigate the strain rate effects on the tensile properties. Tensile-tensile fatigue experiments are performed using ASTM D638-22 Type I and Type II specimens to evaluate the impact of specimen geometry and toughening on fatigue life. The digital image correlation technique is utilized to obtain full-field strain data in these experiments. Technical data analysis, plotting, smoothing, filtering, and averaging are carried out using Origin ProⓇ and MATLAB R2021bⓇ. The obtained S-N curve data can be used to develop fatigue failure criteria and predict the behavior of wind turbine blade adhesive joints through finite element modeling.

In the present study, experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores. The high velocity impact tests were carried out using a compressed air gun. A sharp conical nosed projectile was impacted normally and with some offset distance (20 mm and 40 mm). The deformation, failure mode and energy dissipation characteristics were obtained for both kinds of loading. Moreover, the explicit solver was run in Abaqus to create the finite element model. The numerically obtained test results were compared with the experimental to check the accuracy of the modelling. The numerical result was further employed to obtain strain energy dissipation in each element by externally running user-defined code in Abaqus. Furthermore, the in- fluence of inscribe circle diameter and cell wall and face sheet thickness on the energy dissipation, deformation and failure mode was examined. The result found that ballistic resistance and deformation were higher against offset impact compared to the normal impact loading. Sandwich panel impacted at 40 mm offset distance required 3 m/s and 1.9 m/s more velocity than 0 and 20 mm offset distance. Also, increasing the face sheet and wall thickness had a positive impact on the ballistic resistance in terms of a higher ballistic limit and energy absorption. However, inscribe circle diameter had a negative influence on the ballistic resistance. Also, the geometrical parameters of the sandwich structure had a significant influence on the energy dissipation in the different deformation directions. The energy dissipation in plastic work was highest for circumferential direction, regardless of impact condition followed by tangential, radial and axial directions. [ABSTRACT FROM AUTHOR]

A prominent example of unwanted accumulation in production plants is particulate fouling, which has been subject of many studies in apparatuses. However, pipe fittings have attracted little attention despite their large number in production plants. Here, the influence of process parameters and geometry factors on the fouling in pipe fittings is investigated under isothermal conditions that aims to an improved understanding of their fouling behavior. The variation of fitting type and size, the run time and particle mass fraction have the greatest impact on the fouling mass while the temperature does not influence the result. [ABSTRACT FROM AUTHOR]

Asymmetrical single-edge notched beam (ASENB) specimen is among the suitable specimens for measuring full mode I/II fracture parameters. However, in lack of a standard or common method, researchers used this specimen with different geometers, which have proven can affect the results. This research evaluated the effect of ASENB's geometry on fracture parameters numerically and experimentally. First, the finite element method determined the geometry factors (Y I and Y II) and non-singular (T -stress) fracture parameters. Then, the experimental fracture tests were conducted using ceramic material. Results show it is more reasonable to express the Y I and Y II based on S 1 / L and S 2 / H , instant S 1 / L, and S 2 / L. In other words, the geometry factors can be expressed better based on the height of the specimen and not length. So, for ASENB specimens tested in conventional S 1 / L of 0.7 to 0.9, the pure mode-II condition was generated in 0.05 < S 2 / H < 0.14. The modeling showed that the non-singular term of fracture (T -stress) was significant compared to fracture toughness, so the Biaxiality was measured as 0.5 to −2.5, more significant for pure mode-II and almost regardless of the a / H ratio. As experimental tests show, the relative length of the ASENB specimen has an insignificant effect on measured fracture toughness, so a more compact specimen with L / H of about 2 to 4 can suggested for tests. [ABSTRACT FROM AUTHOR]

• Modified maximum tangential strain (MMTSN) criterion is proposed for fracture analysis of quasi-brittle materials. • MMTSN criterion considers both stress intensity factors and T-stress in strain components near the crack tip. • MMTSN criterion can be used for investigating both geometry and size effects in rocks. • Fracture test data related to a limestone are used to validate the MMTSN criterion. In this paper, a new strain-based criterion is suggested for assessing the effects of size and geometry of specimen on the fracture resistance of rocks under mixed-mode (I/II) loading. The new approach named the modified maximum tangential strain (MMTSN) criterion is based on the classical maximum tangential strain (MTSN) criterion, in which the first non-singular term (T) of Williams series expansion is considered in addition to the singular terms (K). Furthermore, to provide more coherence, the critical distance (r c) from the crack tip is defined according to a new strain-based failure model. Unlike similar strain-based fracture models available in the literature, the critical distance r c in the MMTSN criterion is assumed to be size-dependent and a semi-empirical formulation is utilized for describing this size-dependency. To assess the ability of MMTSN for considering the size and geometry effects, the experimental data existing in the literature for a number of cracked Brazilian disk (CBD) and semi-circular bend (SCB) specimens manufactured from Guiting limestone are taken into account. It is demonstrated that the MMTSN criterion can predict the experimental data very well by taking into consideration the size and geometry effects without needing to calculate the other higher order terms. [ABSTRACT FROM AUTHOR]

Structural epoxy adhesives modified with short-glass fiber and core-shell rubber particles are used in wind turbine rotor blade assembly. This work aims at investigating the hybrid effects of these adhesives on their fatigue performance. The effect of ASTM D638-22 Type I and Type II specimen geometry on fatigue life is also examined. Competing damage mechanisms are identified with scanning electron microscopic images. These mechanisms result in similar S-N curve slopes for the examined adhesives when Type II specimens are used. All adhesive materials can endure at least 106 cycles at the maximum applied stresses of nearly 35% of their static strength, confirming the strength-life equal rank assumption. Nevertheless, Type I specimens exhibit an increased S-N curve slope of 7.32%–15.56% than Type II specimens.

This paper proposes a novel creep‐fatigue life estimation method considering the effect of non‐uniform stress state, through the comprehensively experimental and numerical investigation. Conventional and digital image correlation (DIC) based in‐situ creep‐fatigue tests were performed on thin‐walled plates with various types of holes at 850°C. DIC measurements and scanning electron microscope (SEM) analysis show that tensile stress plays the dominant role in the creep‐fatigue failure of plate with holes, and the crack initiated at the maximum stress position of the end hole. An equivalent stress was defined to describe the complex stress state between the adjacent holes. The stress factor was proposed to account for the holes‐related stress concentration and multi‐axial stress state. Moreover, a novel weight function was proposed to assess the damage contribution of non‐uniform stress in the damage zone. Creep‐fatigue life model was developed by introducing this proposed weight function, and was validated based on test data. Highlights: An equivalent stress is defined to describe the complex stress state in the high stress zone between adjacent holes.A new weight function is proposed to evaluate the damage contribution of non‐uniform stress in the damage zone.Creep‐fatigue life estimation method was developed by introducing the novel weight function. [ABSTRACT FROM AUTHOR]

Membrane absorption (MA) has a great prospect for CO2 capture. In MA modeling, conventional one‐dimensional (1D)‐ and two‐dimensional (2D)‐models make simplification of membrane contactor (MC) geometry. Geometry simplification allows an easy process modeling and numerical solution, however, is only reasonable for particular MCs. Here, efforts are underway to quantify the geometry effect on the MA‐CO2 performance. First, we proposed a rigorous 3D model without geometry simplification for simulating the MA‐CO2 process in real MCs and then validated it with experimental data. More importantly, we highlighted a preferable hybrid model in which two correction factors were introduced to a 2D model to make the simulation results approximately equal to the 3D simulation values. The correction factors were correlated with dimensionless fluid dynamic parameters for characterizing the geometry effects on flowing fluids. Such hybrid modeling contributes to characterizing the influence of geometry on the MA‐CO2 performance and improving computation accuracy‐efficiency combinations. [ABSTRACT FROM AUTHOR]

Accurate retrieval of land surface temperature (LST) over urban areas is of great significance for urban thermal environment monitoring. In previous studies, most of the urban LST retrieval methods were developed based on the assumption of a flat surface without considering the influence of urban 3-D geometry structure, which has a significant impact on the retrieval accuracy of LST over urban areas. In this study, a radiative transfer equation (RTE)-based single-channel method was developed to retrieve LST with urban geometry effect correction from the Landsat 8 thermal infrared (TIR) data in band 10. The increase in adjacent radiance from the surrounding pixels and the decrease in atmospheric downwelling radiance caused by urban geometry structure were taken into account in this method. Because it is difficult to directly validate the retrieval accuracy of LST over urban areas using in situ LST measurements, the performance of the RTE-based LST retrieval method was evaluated via comparing brightness temperature (BT) at the top of the atmosphere (TOA) simulated by the discrete anisotropic radiative transfer (DART) model and the urban RTE over three subregions. There is a good agreement between BT at the TOA simulated by the DART model and the urban RTE, with a root-mean-squared error (RMSE) of less than 0.25 K. The variations in LST retrieved with urban geometry effect correction over different local climate zones (LCZs) were analyzed. In general, built-up LCZs have relatively higher LST than land cover LCZs. The differences between LST retrieved without/with urban geometry effect correction over different LCZs are greater than 0.2 K. The largest average LST difference over built-up LCZs is approximately 0.9 K, whereas that over land cover LCZs is approximately 0.65 K. LST retrieved without/with urban geometry effect correction was used to calculate urban heat island intensity (UHII) in terms of the LCZ-based method. The results indicate that UHII calculated from LST with urban geometry effect correction is lower than that calculated from LST without urban geometry effect correction, with an average difference of approximately 0.5 K. [ABSTRACT FROM AUTHOR]

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]

A double cantilever beam geometry has been chosen in order to investigate the importance of the higher-order terms of the Williams power expansion for the crack path estimation. The crack propagation has been tested experimentally on a brittle polymethylmethacrylate (PMMA) specimen and although the mode I loading conditions were applied, the crack kinked from its original plane immediately and propagated towards the bottom side of the specimen. It has been shown that this phenomenon is connected to the magnitude and sign of the T-stress and to the level of the constraint generally. In this work, the influence of the third and higher terms of the Williamsᒒ series on the crack propagation is investigated. The generalized form of the well-known maximum tangential stress fracture criterion for determination of the crack propagation angle has been tested and discussed. The observed differences in the crack trajectory of different specimens have been found to be related to the magnitude of the higher-order terms of the stress tensor components at the crack tip.

An experimental study was carried out to investigate the effects of entrance length on the main characteristics of rectangular liquid jets discharged into the stagnant atmosphere. Six rectangular nozzles, all with the same aspect ratio of 3 but with different entrance length ratios ranging from 3.3 to 60 were constructed. The physics of the fluid flows was visualized by the aid of backlight shadowgraph technique and high speed photography. Flow visualizations revealed that in the mid-range of Weber numbers, the perturbations induced over the liquid surface remarkably depended on the entrance length ratio. Moreover, the characteristics of the axis-switching instability of rectangular liquid jets were measured. It was found that axis-switching wavelength was independent of the entrance length, while the amplitude of axis-switching was directly influenced. For entrance length ratios smaller than 10, the amplitude was increased with increase of entrance length, whereas for entrance length ratios higher than 10, this trend was reversed. Measurements of breakup length also showed that the transition of flow regimes was not perceptibly affected by the entrance length. [ABSTRACT FROM AUTHOR]

The effects of geometrical constraints on the fracture initiation location and the fracture strength are evaluated in U‐notched specimens using theoretical and experimental analyses. It is proven that high geometrical constraints in pure mode I loading of geometrically symmetric U‐notched specimens can result in occurrence of the maximum tangential stress (MTS) at two symmetric points on both sides of the notch bisector line. The experiments also indicated that the fracture takes place from a direction that is not along the notch bisector line. The experimental results are then examined theoretically through a stress‐based brittle fracture criterion. Because the conventional MTS criterion was poor to predict the onset of fracture properly, an attempt is made to use the generalized MTS (GMTS) criterion by considering the higher order terms in the fracture model. It is shown that the GMTS criterion gives very good predictions for experimentally obtained values of crack initiation angle and notch fracture resistance. [ABSTRACT FROM AUTHOR]

The metal supported catalysts are emerging catalysts that are receiving a lot of attention in CO 2 hydrogenation to C1 products. Numerous experiments have demonstrated that the support (usually an oxide) is crucial for the catalytic performance. The support metal oxides are used to aid in the homogeneous dispersion of metal particles, prevent agglomeration, and control morphology owing to the metal support interaction (MSI). MSI can efficiently optimize the structural and electronic properties of catalysts and tune the conversion of key reaction intermediates involved in CO 2 hydrogenation, thereby enhancing the catalytic performance. There is an increasing attention is being paid to the promotion effects in the catalytic CO 2 hydrogenation process. However, a systematically understanding about the effects of MSI on CO 2 hydrogenation to C1 products catalytic performance has not been fully studied yet due to the diversities in catalysts and reaction conditions. Hence, the characteristics and modes of MSI in CO 2 hydrogenation to C1 products are elaborated in detail in our work., (© 2024 Wiley-VCH GmbH.)

The cryogenic performance of multinanoscale CMOS transistors with a standard 55-nm Si-bulk technology is systematically investigated by dc measurements. In contrast to 300 K, the cryogenic drain saturation current (Idsat) gain significantly enhances from 54% to 167% with the increasing channel length and has a relatively weak response to width change. In addition, the degraded subthreshold swing (SS) due to the short channel effect is alleviated at lower temperatures. The merits of a typical nMOS transistor (W/L = 0.6 μm/60 nm) worked at 4.2 K are associated with an improved Idsat (~1.3 times), decreased drain leakage current with three orders of magnitude, and 2/3 reduced SS. However, the cryogenic Idsat tends to saturate below 10 K and the threshold voltage increases, as well as barrier lowering induced by drain voltage, starts to deteriorate. The detailed analyses on these MOSFET (deep) cryogenic characteristics are implemented based on the comprehensive semiconductor physics images, including energy band change, temperature/geometry-dependent scattering, band-to-band tunneling process, and depletion width influence. Our findings will be beneficial for the community to design ultralow temperature-integrated circuits. [ABSTRACT FROM AUTHOR]

Mode I fracture resistance of two asphalt mixtures (control and modified with low‐density polyethylene [LDPE] as binder additive) was studied experimentally and theoretically. The fracture toughness experiments were conducted on edge notch disc bend, edge notch disc compression and semi‐circular bend configurations under two loading rates and two low temperatures. The fracture resistance was increased by increasing the loading rate, reducing the test temperature and adding the LDPE additive. A discrepancy due to the influence of specimen geometry and its loading type was also observed on the measured critical stress intensity factors, demonstrating the effect of specimen type on mode I fracture behaviour. By considering the maximum normal strain value as constant material property and taking into account the effect of T‐stress, the fracture toughness value for any of the investigated mode I samples was estimated in terms of the fracture results of the other specimens. [ABSTRACT FROM AUTHOR]

Gas-solids flow structures between a circular fluidized bed and a square fluidized bed were compared by differential pressure drops and solids holdups. The flow regime transition from bubbling to turbulent fluidization in the fluidized bed was studied by the standard deviations of pressure drop and solids holdup. The geometry effect on the regime transition was also discussed by comparing the local solids holdup profiles and instantaneous solids holdup signals between the circular and square beds. The frequency and duration time of the changeover between the dilute and dense phases around the transition progress were also studied by statistically analyzing the solids holdup signals in both the square and circular beds. Unlabelled Image • Comparison of the flow structures between a smaller circular bed and a larger square bed. • Study on the local transition around the turbulent fluidization regime. • Scale-up and geometry effects on BFB to TFB transition progress. • Dynamic bubble behavior and dilute-dense phase changeover during regime transition. [ABSTRACT FROM AUTHOR]

The geometry effect is one of the effective methods to modulate the photoelectric properties of photovoltaic units. Herein, we investigate the geometry effect on the optical absorption and photoelectric conversion properties of nanosheet array-based tilted/horizontal MoS2/WSe2 van der Waals heterostructures based on the bond relaxation consideration and detailed balance principle. We find that the tilted/horizontal heterostructures exhibit excellent photoelectric properties compared to those of horizontal/horizontal cases owing to the small light reflectivity in the nanosheet array. Especially, the MoS2/WSe2 heterostructure with type-B is the optimal structure for energy harvesting as the optimal power conversion efficiency (PCE) can be further achieved by modulating the sheet size and tilt angle, and its PCE can be up to 12.60% at θ = 62° and D1 = 9.7 nm in the case of L1 = D2 = 100 nm. Our results provide insights into optimizing the nanodevice performances of TMDs-based heterostructures. [ABSTRACT FROM AUTHOR]

Creep crack growth is accompanied by strong nonlinear deformation and stress relaxation. Finding an appropriate parameter to characterize the crack tip fields, as well as the fracture resistance, has long been a challenge. Most previous studies were performed within the framework of the C (t)-integral, which is limited to the assumptions of small deformation and simple proportional loading. By using the crack tip opening displacement (CTOD), we propose a new creep stress intensity factor K δ (t) -Tz consisting of the time-dependent CTOD, δ (t) and the out-of-plane stress constraint factor T z to characterize the three-dimensional creep crack tip fields. Four typical specimens, single-edge cracked tension specimens, compact specimens, centre-cracked tension specimens and single-edge-notched bending specimens under three-point bending are comprehensively analysed using the power-law creeping model and three-dimensional finite element analyses. It is found that under both small-scale and large-scale creep conditions, the change in K δ (t) -Tz along the thickness direction for different specimens is within 8.6%, whereas the change in C (t) can exceed 400%, showing that K δ (t) -Tz is a stable parameter that governs the creep crack tip fields. With the exception of the centre-cracked tension specimens under large-scale creep conditions, good agreements are obtained between the two-parameter description δ (t) -T z of crack border stress fields with the three-dimensional finite element results under small-scale and large-scale creep conditions. These results indicate that the CTOD-based two-parameter description δ (t) -T z can be taken as the basis of creep fracture criteria. [ABSTRACT FROM AUTHOR]

• A novel method was proposed to determine the damage zone of structures. • A geometrical feature factor was defined to represent the stress concentration. • LCF and creep weight functions were proposed to assess the effect of stress gradient. • A systematic method was developed to estimate the creep-fatigue life of structures. This paper develops a novel weight function modified critical distance method to estimate the creep-fatigue lives of geometrically complex structures. A geometrical feature factor was defined to account for the geometry-induced stress gradient, namely the average normalized stress gradient. The conventional weight function was modified using this concept to assess the weight effect of stress distribution on the low-cycle fatigue (LCF) and creep lives, respectively. The weight function modified critical distance methods were verified by the LCF and the creep test data of the specimens with significantly different geometries. Furthermore, creep-fatigue experiments on the full-scale hollow and solid turbine blades were conducted. The creep-fatigue lives of turbine blades were predicted using the systematical weight function modified methodology. The predicted results showed a good agreement with the experimental lives. Compared with other models, this novel method achieves a significantly better accuracy in the case of LCF, creep and creep-fatigue life predictions. [ABSTRACT FROM AUTHOR]

Numerical simulations are conducted to investigate the impacts of airfoil thickness, the angle of attack and camber on the airfoil-gust interaction noise in transonic flows where locally supersonic regimes and terminating shocks are present. The conclusions about the geometry effects based on the extensively studied subsonic cases are revisited. With the increase of airfoil thickness, the sound generation is reduced in the downstream direction as in subsonic flows. More sound is produced in the upstream direction for thicker airfoils due to the non-uniform mean flow and shocks in the near field. The compensative effect makes the overall sound reduction by the airfoil thickness less than the subsonic cases despite the significant difference in the radiation patterns. The acoustic responses to the single frequency gusts are sensitive to the airfoil angle of attack in transonic flows. However, the overall differences are reduced when multiple wavenumber components are superposed in isotropic turbulence, and the sound pressure levels are therefore close as in subsonic flows. Similarly, the significant variations in single frequency acoustic responses by airfoil camber are averaged by the superposition of various wavenumber components. However, apparent variations are still found in the upstream direction, especially for the turbulences with small integral length scales. [ABSTRACT FROM AUTHOR]

Strained silicon-on-insulator (SSOI) is a promising platform for 5G, which will require both high-performance and low-power complementary metal–oxide–semiconductor (CMOS) devices. Hence, it is important to understand the behavior of strain in SSOI at deeply scaled dimensions. We thus present a simulation study of SSOI technology, where the strain profiles of “fins” with different dimensions and layer thicknesses are analyzed. We discover, for the first time, that a buried oxide (BOX) as thin as 10–15 nm is able to effectively memorize the strain. It is also able to retain the strain under annealing up to 1000 °C, a result verified by the Raman measurements. Such a thin BOX enables a good back-gate control for dynamic threshold voltage (${V}_{\text{t}}$) tuning of SSOI transistors. The ability to have a good performance enhancement (from strain), and dynamic ${V}_{\text{t}}$ tunability (from thin BOX) makes SSOI favorable for 5G mixed-signal applications. [ABSTRACT FROM AUTHOR]

A double cantilever beam geometry has been chosen in order to investigate the importance of the higher-order terms of the Williams' power expansion for the crack path estimation. The crack propagation has been tested experimentally on a brittle polymethylmethacrylate (PMMA) specimen and although the mode I loading conditions were applied, the crack kinked from its original plane immediately and propagated towards the bottom side of the specimen. It has been shown that this phenomenon is connected to the magnitude and sign of the T-stress and to the level of the constraint generally. In this work, the influence of the third and higher terms of the Williams' series on the crack propagation is investigated. The generalized form of the well-known maximum tangential stress fracture criterion for determination of the crack propagation angle has been tested and discussed. The observed differences in the crack trajectory of different specimens have been found to be related to the magnitude of the higher-order terms of the stress tensor components at the crack tip. [ABSTRACT FROM AUTHOR]

When the tunnel is excavated in the granite stratum, the surrounding rock will deform and fail, and the failure modes of the surrounding rock are mostly rockburst, slab cracking, landslide, etc. The macroscopic mechanical parameters of the granite and the progressive failure model can be obtained by indoor uniaxial and triaxial compression tests. The indoor compression test can analyze the failure nature of granite on macroscopic scale, while the failure process of granite under uniaxial and triaxial compression on microscopic scale can be simulated by PFC2D soft codes. By taking the Nanwan tunnel engineering along the Hong Kong-Zhuhai-Macao bridge connecting line as the study background, the macro-microscopic mechanical parameters, fracture mechanism and their shape effect of granite sample were analyzed by employing both of laboratory test and numerical simulation of discrete element. Research results show that: (1) The results of numerical simulation are similar as the results form laboratory test in not only the macro scale mechanical parameters but also the final failure pattern. With the increase of confining pressure, the peak strength of rock increases accordingly, while the elastic modulus varies little. With the increase of specimen ratio between length and diameter L/D, the peak strength of rock decreases accordingly, while the elastic modulus increases. (2) The statistical method based on the comparative strain and crack number per some area is more effective to analysis the micro scale progressive failure mechanism with the increasing of specimen ratio between length and diameter L/D, the final failure pattern changes from shear to tensile progressively. The final crack number per some area will be largest when the L/D is equal to 1.0. The percent of shear cracks will be largest when L/D is equal to 2.0. (3) With the increase of the aspect ratio of rock specimens L/D, the peak strength decreased and the influence of confining pressure was obvious. The elastic modulus also increased obviously but the relationship was not significant with confining pressure. (4) By statistically comparing the relationship between the number of fractures and the strain, the number of cracks inside the rock increases with the increase of axial deformation like the "S"curve under different confining pressure conditions. When the axial deformation is close to the peak strain, the crack grows abruptly, and the number of final cracks tends to converge only when the confining pressure is small. (5) With the increase of the length-to-diameter ratio of the specimen L/D, the number of cracks per unit area decreases gradually when the rock fractures, and the speed of decreasing will increase. In general, the shape change of rock sample has significant influence on the whole peak strength and elastic modulus of granite. Therefore, the shape of the granite sample should be rationally designed in order to get the real parameters and strengths of rock during indoor test. [ABSTRACT FROM AUTHOR]

The violent fires undergone by many cultural-heritage masonry buildings during their history are the starting point of this work, whose objective is to investigate the effect of high-temperature on building stones at the block scale. The effects of geometry and particularly of the thickness-to-side on the behaviour of square and rectangular limestone blocks subjected to high temperatures were studied. Six French limestones with compressive strengths ranging from 9.4 to 74.5 MPa and total porosity varying from 11 to 31% were selected for this study. The limestone blocks with different shapes and dimensions were subjected to unidirectional heating with a heating rate of 9 °C/min. The results give information on the influence that the geometry and the size of the blocks have on the crack pattern and on the damage extent at high temperature. Among the various physical and mechanical properties of the stones, the tensile strength and the fracture toughness (i.e., the material's resistance to breaking or fracturing when subjected to stress), play a sizeable role in the thermal sensitivity of the stones, as the higher the toughness and the tensile strength, the lower the damage at high-temperature. • The high temperature sensitivity of stone blocks is related to the tensile strength and toughness of the stone. • The geometry and slenderness of stone blocks seriously affects their thermal stability. • The colour change allows a good evaluation of the temperature experienced in the thickness of the limestone block. [ABSTRACT FROM AUTHOR]

There are numerous analytical solutions in order to take into account the geometry effect on the fracture toughness and the fracture load of the cracked specimens. However, due to the complexities of the mentioned criteria it is practical to have an engineering method which can be used for fracture prediction in cracked samples of various shapes and loading conditions. In this paper, the fracture behaviors of five different testing samples made of various brittle and quasi-brittle materials have been studied using an energy based criterion namely the Average Strain Energy Density (ASED) criterion. According to the formulation of the ASED criterion, all the stress terms around the crack tip were taken into account and the brittle fracture of different samples with various geometry constraints were well predicted. [ABSTRACT FROM AUTHOR]

In the present paper, convective boiling heat transfer results of R134a for circular, square and triangular tubes are presented. The evaluated channels present the same external perimeter and equivalent diameters of 1.100, 0.977 and 0.835 mm, respectively. Experiments were performed for mass velocities ranging from 200 to 800 kg/m 2 s, heat fluxes from 15 to 85 kW/m 2 , saturation temperatures of 31 and 41 °C, and vapor qualities from 0.05 to 0.95. In order to perform reasonable comparisons among the test sections, the tests were run under similar mass velocities for the three geometries. The experimental data were carefully analyzed and discussed focusing on the effect of the cross-sectional geometry. It was found that for low heat fluxes, the heat transfer coefficient for the circular channel is higher. While for high heat fluxes, the heat transfer coefficient for the triangular channel is higher than for circular and square channels. Subsequently, the experimental data were compared with predictive methods from literature which are usually developed based only on data for single circular channels. Statistically, Kanizawa et al. [24] and Kim and Mudawar [34] provided reasonable predictions of the overall database. However, none of the methods captured adequately the experimental trends for the triangular channel. [ABSTRACT FROM AUTHOR]

Several studies have dealt with the application of the generalized stress intensity factor (GISF) on the failure load prediction of adhesive joints. However, the effect of geometry on the critical value of the GSIF (Hc) is complex and limits its application. Due to the effect of multiple geometrical features and the limited success in the field of adhesive joints, a statistical analysis is a possibility. This paper investigates the impact of different geometrical features on theHcin single lap adhesive joints. To achieve this, the statistical response surface methodology (RSM) was used to design the experiments and for the statistical analysis. According to the RSM, 31 arrangements of single lap joints were manufactured and tested. In this analysis, the adhesive thickness, adherend thickness, overlap length and also the free length, each in five different levels, were considered. The effect of linear, quadratic and two-way interactions of the geometrical parameters on theHcand failure load were also studied. It was shown thatHcis most affected by the overlap length. Variation ofHcin term of the free length is by far higher at lower adhesive thicknesses. Also, the effect of substrate thickness onHcis more considerable for thinner bondlines. The interactions of overlap length/free length and overlap length/adhesive thickness affect the failure load more considerably than the other studied interactions. The effect of free length on the failure load increases with the bondline thickness, while the effect of substrate thickness is stronger for a lower adhesive thickness. [ABSTRACT FROM PUBLISHER]

This study presents a direct numerical simulation of the geometry effect on fluid flow and heat transfer characteristics in the transitional flow over backward and forward facing steps. A computer program of FORTRAN code is used to solve the governing equations according to finite volume method. The effects of the bottom wall length and the step height are investigated. With the increase of bottom wall length, a fundamental frequency of flow fluctuation appears at L b = 10 h and then disappears at L b = 14 h. This fundamental fluctuating frequency decreases with the increase of step height. The fact that the heat transfer performance is better in the reattachment region at L b = 12 h and S = h indicates that the periodic flow fluctuation with a larger fluctuating velocity has positive effects on heat transfer enhancement. The results of the relationship between flow fluctuation and heat transfer enhancement are significant for certain practical applications of energy conversion. [ABSTRACT FROM AUTHOR]

An investigation was conducted on the effects of fluid refrigerant and channel geometry on the frictional pressure drop during two-phase flow inside microchannels. Experimental results for two-phase frictional pressure drop were obtained for the refrigerants R134a, R1234ze(E), R1234yf and R600a in a circular channel and for R134a in square and triangular channels. The experiments were performed for mass velocities from 100 to 1600 kg m −2  s −1 , saturation temperatures of 31 and 41 °C, and vapor qualities from 0.05 to 0.95. The experimental data have been analyzed focusing on the effects of the geometry and fluid on the two-phase pressure drop. Then, the data were compared with the most quoted predictive methods from the literature. Based on the broad database obtained, a new method for prediction of the two-phase frictional pressure drop was proposed. The new method provided accurate predictions of the database, predicting 89% of the results within an error band of ±20%. [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]

The liquid atomization process relies on the disturbance of the liquid surface by various forces. In the case of "flow-blurring" (FB) atomization, this is achieved by inducing flow instabilities near the liquid channel exit. In this study, we analyze the underlying dynamics of these coherent turbulent structures and their role in the primary atomization within the FB regime. For that purpose, Smoothed Particles Hydrodynamics (SPH) simulations have been conducted using alternative FB nozzle geometries at different operating conditions. An in-house developed visualization and data exploration platform (postAtom) was used to capture the time-resolved Lagrangian coherent structures (LCSs) via the finite-time Lyapunov exponent (FTLE) fields. Simulations were conducted at different gas/liquid momentum ratios at the nozzle exit by changing the mass flow rate of the gas phase and/or changing the position of the liquid injector. The effect of outer chamber design on the atomization performance is further assessed. The results indicate that the design of the mixing chamber can trigger an oscillatory behavior at the nozzle exit, which has a direct impact on the evolution of the micro-ligaments and the consecutive primary atomization. Comparisons between different operating points further reveal that FB atomization may not be achieved if the gas momentum is below a certain threshold value. • Flow structures developed during flow-blurring atomization are analyzed numerically. • Lagrangian coherent structures were extracted from two phase simulations. • Cases cover different gas to liquid ratios, h/d ratios and 4 different nozzle designs. • h/d ratio or GLR alone was not sufficient enough to categorize atomization process. • The transition between flow regimes is correlated with gas velocity at the interface. [ABSTRACT FROM AUTHOR]

Stress concentration around nanosized defects such as cavities always leads to plastic deformation and failure of solids. We investigate the effects of depth, size, and shape of a lotus-type nanocavity on onset plasticity of single crystal Al during nanoindentation on a (001) surface using a quasicontinuum method. The results show that the presence of a nanocavity can greatly affect the contact stiffness (Sc) and yield stress (σy) of the matrix during nanoindentation. For a circular cavity, the Sc and σy gradually increase with the cavity depth. A critical depth can be identified, over which the Sc and σy are insensitive to the cavity depth and it is firstly observed that the nucleated dislocations extend into the matrix and form a y-shaped structure. Moreover, the critical depth varies approximately linearly with the indenter size, regarding the same cavity. The Sc almost linearly decreases with the cavity diameter, while the σy is slightly affected. For an ellipsoidal cavity, the Sc and σy increase with the aspect ratio (AR), while they are less affected when the AR is over 1. Our results shed light in the mechanical behavior of metals with cavities and could also be helpful in designing porous materials and structures.

The present study is an attempt to introduce the method for optimizing the geometry of the unit process. The comprehensive unit process performances are generated by a CFD engine. The CFD engine can simulate the unit process performances at what ever conditions. Both design geometry and operating variables weree used on the CFD simulation. The burden on a simplified process was taken out from CFD simulation. A complex geometry of a unit process is represented by a secondary reformer. A secondary reformer has a conical volume as a space to undergo the combustion reaction before entering the catalyst bed. This complexity is added by the boundary of the porous solid surface as the top surface of catalyst bed. The spread angle affect the flow pattern in side the conical volume having a porous solid surface as a base. The spread angle above 65o results the disappearing of the recirculation flow. The inlet distance from the porous solid surface also can exhibit different characteristics of recirculation flow. The closer the distance to the porous solid surface, the stronger the recirculation is. The inlet velocity values have no significant effect on the flow pattern. The introduction of a solid volume inside the geometry creates the distortion of the flow pattern. In the application, the inserted solid volume is equivalent to a burner. It means that the use of the burner inherently produces some problems of the flow distribution

A mathematical model for slug (finite liquid volume) motion in not-fully-wettable capillary tubes with sinusoidally varying cross-sectional areas was developed. The model, based on the Navier-Stokes equation, accounts for the full viscous terms due to nonuniform geometry, the inertial term, the slug's front and rear meniscus hysteresis effect, and dependence of contact angle on flow velocity (dynamic contact angle). The model includes a velocity-dependent film that is left behind the advancing slug, reducing its mass. The model was successfully verified experimentally by recording slug movement in uniform and sinusoidal capillary tubes with a gray-scale high-speed camera. Simulation showed that tube nonuniformity has a substantial effect on slug flow pattern: in a uniform tube it is monotonic and depends mainly on the slug's momentary mass/length; an undulating tube radius results in nonmonotonic flow characteristics. The static nonzero contact angle varies locally in nonuniform tubes owing to the additional effect of wall slope. Moreover, the nonuniform cross-sectional area induces slug acceleration, deceleration, blockage, and metastable-equilibrium locations. Increasing contact angle further amplifies the geometry effect on slug propagation. The developed model provides a modified means of emulating slug flow in differently wettable porous media for intermittent inlet water supply (e.g., raindrops on the soil surface). [ABSTRACT FROM AUTHOR]

Boundary layer transition over isolated roughness elements is investigated in the incompressible flow regime using tomographic PIV. Four different geometries (cylinder, square, hemisphere and micro-ramp) are considered maintaining constant height and span of the element. The main target is to compare the different flow topologies and study the effect of the element shape on accelerating boundary layer transition. The measurement domain encompasses the full transition process until the turbulent regime is established. The flow behavior is described by means of vortex topology and by statistical analysis of the velocity fluctuations. The instantaneous flow topology elucidates the mechanism of transition along its stages. A main distinction is observed between the bluff front elements that induce a horseshoe vortex due to upstream flow separation, leading to more rapid transition and the slender micro-ramp. The later geometry requires significant longer distance for transition onset. The mechanism of sideward propagation of the turbulent non-turbulent interface features a continuous convection and generation of hairpin-like vortices and remains the common denominator among all elements considered. [ABSTRACT FROM AUTHOR]

An elliptical ring test method is proposed to replace the circular ring test recommended by ASTM and AASHTO for faster and more reliable assessment of cracking tendency of concrete. Numerical models are also established to simulate stress development and crack initiation/propagation in restrained concrete rings. Cracking age, position and propagation in various rings are obtained from numerical analyses that agree well with experimental results. Elliptical thin rings of certain geometry can shorten the ring test duration as desirable. In thin rings, crack initiation is caused by external restraint effect so that a crack occurs at the inner circumference and propagates towards the outer one. In thick rings, crack initiation is mainly due to the self-restraint effect so that a crack occurs at the outer circumference and propagates towards their inner one. Therefore, thick elliptical concrete rings do not necessarily crack earlier than circular ones as observed from experiment. [ABSTRACT FROM AUTHOR]