Shear Direction Research Articles

Interface frictional anisotropy of dilative sand.

Understanding direction-dependent friction anisotropy is necessary to optimize interface shear resistance across soil-structure. Previous studies estimated interface frictional anisotropy quantitatively using contractive sands. However, no studies have explored how sand with a high dilative tendency around the structural surface affects the interface shear response. In this study, a series of interface direct shear tests are conducted with selected French standard sand and snakeskin-inspired surfaces under three vertical stresses (50, 100, and 200kPa) and two shearing directions (cranial → caudal or caudal → cranial). First, the sand-sand test observes a higher dilative response, and a significant difference between the peak and residual friction angles (ϕpeak - ϕres = 8°) is obtained at even a lower initial relative density Dr = 40%. In addition, the interface test results show that (1) shearing against the scales (cranial shearing) mobilizes a larger shear resistance and produces a dilative response than shearing along the scales (caudal shearing), (2) a higher scale height or shorter scale length exhibits a higher dilative tendency and produces a higher interface friction angle, and (3) the interface anisotropy response is more pronounced during cranial shearing in all cases. Further analysis reveals that the interface friction angle and dilation angle are decreased with the scale geometry ratio (L/H). For L/H values between 16.67 and 60, the interface dilation angle varies between 9° and 4° for cranial first shearing and 3.9°-2.6° for caudal first shearing. However, the difference in dilation angle within the same shearing direction is less than 1°.

Development of a double-grating differential interferometer for plasma diagnostics.

A special differential interferometer consisting of two gratings was developed for diagnostics of plasma density. Compared with other differential interferometers, our system has an important advantage that the shear distance, shear direction, and fringe width can be adjusted independently, enabling easy control of the parameters. This feature allows precise tuning of the two probe beams in the interferometer for rigorous differential phase diagnosis and more accurate information of the plasma density can be obtained. The double-grating-based differential interferometer was tested for diagnostics of the laser-produced plasma which was generated by focusing a 1 TW/35 fs Ti:sapphire laser pulse in a gas jet with a 100 μm orifice diameter. It was confirmed that our differential interferometer can provide more reliable and accurate plasma density information, especially for plasmas with a high spatial gradient in density.

Numerical investigation of fluid flowing through rough fractures subject to shear

Comprehending fluid flow in rock masses is essential for modern underground engineering, including chemical energy extraction, nuclear pollutant remediation, and hydrocarbon utilization, complicated by shear-induced and surface roughness effects in fractures. This study employed numerical simulations to investigate the fluid flow behavior in fractures with different surface roughness under shear, where the shear direction is perpendicular to the flow direction. The nonlinear flow of the fluid is observed to have a strong correlation with the confining pressure (Pz), roughness (JRC), and shear displacement (u). The generation of eddy currents is frequently linked to the presence of flow channel intricacies and the velocity of flow at a microscopic scale. The Forchheimer equation could describe the process of nonlinear phenomena accentuation very well. The fracture under Pz caused a reduction in hydraulic transmissivity (T) due to compression. Furthermore, the T changes dramatically as the shear process progresses. Based on the analysis of the Forchheimer coefficient (β) and critical Reynolds number (Rec) parameters used to determine the response of nonlinear flow, it appears that an increase in Pz facilitates the transition of the fluid into a nonlinear flow state. Conversely, shearing has the opposite effect and reduces the tendency toward nonlinear flow.

Bioinspired Integrated Multidimensional Sensor for Adaptive Grasping by Robotic Hands and Physical Movement Guidance

AbstractThe construction of piezoresistive sensors capable of distinguishing multiple mechanical stimuli is important for sensing higher level applications. However, the mutual interference between sensing signals is a technical bottleneck for sensors to recognize multiple mechanical stimuli. Inspired by the structure of human skin and muscle, a multidimensional sensor is designed by integrating three sub‐sensors. Each sub‐sensor is only sensitive to stimulus components in one of the three orthogonal axes, whereas it remains insensitive to others because of its anisotropic sensing properties. Specifically, an omnidirectional gradient wrinkled polyurethane film with MXene‐embedded ZnO nanowire arrays serves as a strain‐insensitive pressure sub‐sensor, while two aligned segmental polyimide/polyurethane films through orthogonal stacking act as two pressure‐insensitive anisotropic strain sub‐sensors. A unique characteristic of multidimensional sensor is its ability to distinguish and measure the type, magnitude, and direction of strain, pressure, and shear. Moreover, multidimensional sensor exhibits maximal gauge factor of 863.7 for strain and highest sensitivity of 187.71 kPa−1 for pressure. Importantly, multidimensional sensor exhibits an unprecedented ability to quantitatively evaluate shear using a library of electrical responses. The adaptive grasping of robotic hands and free‐throw training of players have been demonstrated to initiate the development of robotic object manipulation and physical movement guidance.

Analyzing cyclic shear behavior at the sand–rough concrete interface: An experimental and DEM study across varying displacement amplitudes

AbstractPile foundations frequently endure dynamic loads, necessitating an in‐depth examination of the cyclic shear properties at the pile–soil interface. This study involved a series of cyclic direct shear (CDS) tests conducted on sand and concrete with irregular surface, utilizing varying displacement amplitudes (1, 3, 6, and 10 mm) and joint roughness coefficients (0.4, 5.8, 9.5, 12.8, and 16.7). Discrete Element Method (DEM) models, informed by experimental data, facilitated mesoscopic mechanical response analyses. Findings indicate that the sand–concrete interface undergoes softening, with hysteresis loops' morphology dependent largely on displacement amplitude. A maximum ultimate shear stress corresponds to a specific critical surface roughness, while the initial tangent modulus escalates with increased concrete roughness. Volume variations of the specimen inversely correlate with displacement amplitude and directly with surface roughness. As displacement amplitude expands, there is a reduction in the maximum shear stiffness and an elevation in the maximum damping ratio. Empirical formulas for the surface roughness and normalized shear stiffness were proposed. Larger displacement amplitudes result in more substantial shear bands and heightened energy dissipation, yet the incremental energy ratio remains largely unaffected. Predominant energy dissipation mechanisms include both slip and rolling slip, with the former surpassing the latter in energy dissipation capacity. The anisotropy directions of contact normal, normal contact forces, and tangential contact forces consistently fluctuate with shear direction alterations.

New 2D roughness parameters with geometric and physical meanings for rock joints and their correlation with joint roughness coefficient

Determining the joint roughness accurately will better serve the peak shear strength estimation models of rock joints used for stability assessment of rock masses. Considering the defects of the existing quantitative characterization parameters for two-dimensional (2D) joint roughness, especially the lack of explicit geometric and physical meaning, we proposed two new 2D roughness parameters, θ2D and h2D. The former, θ2D, represents the average inclination angle of all potential contact asperities over the entire joint profile, while the latter, h2D, characterizes their average undulation height. Both parameters are closely related to the shear strength of rock joints. Then, the roughness parameters θ2D and h2D of 102 rock joint profiles digitized at 0.5 mm sampling interval were calculated, and a new nonlinear regression equation for the determination of the 2D joint roughness coefficient (JRC) was established by combining the calculated results of the two roughness parameters. It was verified that the proposed equation could give accurate JRC estimation values of the 10 standard profiles of rock joints. Through the comparative analysis of the experimental data collected from earlier studies for the peak shear strength of 73 rock joint samples and corresponding estimated values, the equation was further verified to be applicable and accurate for estimating the JRC values of rock joints. Furthermore, we discussed the effects of shear direction and sampling interval on roughness and further provided another equation that could be applied to estimate the JRC values of joint profiles at the sampling interval of 1.0 mm.

Investigating the structure under the Pingting Terrace from the co-seismic surface rupture of the 2022 Guanshan earthquake

AbstractOn September 17th and 18th, 2022, shallow earthquakes with magnitudes of 6.6 (ML) and 6.8 (ML) occurred in the eastern Taiwan Longitudinal Valley, which marks the collision zone between the Philippine Sea plate and the Eurasian plate, and led to noticeable surface deformation and ruptures within 70 km. This study primarily focuses on the southernmost section of the rupture zone—the Pingting Terrace. Surface rupture locations and behaviors correspond to changes in topography, providing mutual confirmation that the deformation behavior of Pingting Terrace is complex. Based on the distribution of surface ruptures and topography changes, this study roughly divides the Pingting Terrace into northern and southern segments, using the central concave feature as a boundary. The Riedel shear model analysis results show that the principal shear directions in the northern and southern segments are N–S trending and azimuth 20°, respectively. The maximum principal stress orientations are around 135° for the northern and 155° for the southern segments. These findings align with the fault mechanical investigation of the Lichi Mélange in the northern Muken River area of the Pingting Terrace. This suggests spatial changes in shear zone orientations within the Lichi Mélange, which contribute to developing pressure ridges due to transpressional forces. As a result, the Pingting Terrace experiences rapid uplift, causing the Luliao River to migrate southward into the Beinan River, while the eastern Beinan River turns to the eastward edge of the Pingting Terrace.

Climatology of Dayside E‐Region Zonal Neutral Wind Shears From ICON‐MIGHTI Observations

AbstractLarge vertical shears in the E‐region neutral zonal winds can lead to ion convergences and contribute to plasma irregularities, but climatological studies of vertical shears of horizontal winds in a global scale are lacking due to the limitations of data coverage. The Ionospheric Connection Explorer (ICON) Michelson Interferometer for Global High‐resolution Thermospheric Imaging (MIGHTI) has provided neutral wind observations with an unprecedented spatial coverage. In this study, the climatology of dayside E‐region neutral wind shears has been examined using 2‐years’ data (2020–2021). Specifically, the study focuses on large wind shears with a magnitude larger than 20 m/s/km, since large wind shears are more likely to cause significant perturbation in the ionosphere‐thermosphere (I‐T) system. The results show that the probability of occurrence of large shears is strongly dependent on the altitude, with the vertical profile varying with shear direction, latitude, season, and local time. In general, below 110 km altitude, large negative shears of the eastward wind are most likely to happen during summer at 8–10 LT in 25°N–40°N latitudes, showing a high probability across nearly all longitudes. Meanwhile, large positive shears tend to occur in 10°S–10°N latitudes, with peak probabilities exhibiting roughly consistent longitudinal structures across 8–10 LT in all seasons. The discrepancies between positive and negative large shear distributions underlie different global tidal influences. The large‐shear occurrence probabilities above 110 km are generally small, except in latitudes above 25°N during the winter for positive shears.

The relation between Rossby wave-breaking events and low-level weather systems

Abstract. Rossby wave-breaking events describe the last stage in the life cycle of baroclinic atmospheric disturbances. These breaking events can strongly influence large-scale circulation and are also related to weather extremes such as heat waves, blocking, and extreme precipitation events. Nonetheless, a complete understanding of the synoptic-scale dynamics involved with the breaking events is still absent. For example, it is not clear how well the theoretical life cycle experiments, which use a specified initial perturbation with a single zonal wavenumber and a prescribed simplified initial zonal jet, capture the life cycle of real-atmosphere weather systems. Here we combine a storm-tracking technique together with a wave-breaking detection algorithm to examine how upper-level wave breaking and surface weather systems are related in the North Atlantic during winter. These datasets allow us to examine whether upper-level wave breaking and low-level weather systems always occur simultaneously and if we can identify preferred relations between the surface weather system type (cyclone or anticyclone) and the type of the upper-level breaking event (cyclonic or anticyclonic wave breaking denoted CWB or AWB, respectively). We find that in the North Atlantic, most weather systems are associated with AWB and/or CWB at some point during their lifetime, while only few cyclones and anticyclones do not involve any upper-level wave breaking (roughly 11 % and 15 %, respectively). Our results imply that composites of cyclones and anticyclones involve a mixture of different types of life cycles, depending on whether they involve CWB or AWB, as well as their position relative to the Rossby wave-breaking (RWB) center. Moreover, the system characteristics (including actual and relative positions, intensities, and displacements) differ depending on the associated breaking type. We distinguish between “same-pairing” cases (i.e., cyclone with CWB and anticyclones with AWB) and “opposite-pairing” cases (i.e., cyclones with AWB and anticyclones with CWB). Compositing the cyclones and anticyclones based on this criterion, we find that in similar pairings the surface system is positioned so that its associated upper-level winds would enhance the breaking (the anomalous circulation is in the same direction as the background shear), but, for opposite pairings, the upper-level winds associated with the surface system do not act to enhance the breaking which occurs in the direction of the background shear. A better understanding of the different life cycles of real-atmosphere cyclones and anticyclones and the upper-level breaking they involve is important for exploring the relation between storm tracks and slowly varying weather regimes and how they are mediated by RWB events.

How Fault‐Normal and Shear‐Parallel Stiffness Influence Frictional Sliding Behavior

AbstractThe potential of faults to show earthquake‐generating slip instabilities depends not only on the intrinsic frictional properties of the fault zone, but also on the elasticity of the surrounding material. A velocity‐weakening fault is expected to show increasingly unstable frictional behavior with decreasing local elastic stiffness around the fault zone. Fault zone roughness can cause slip in the shear direction to be accompanied by fault‐normal movement, modulated by fault‐normal elastic properties, however these effects are poorly understood. Here, we systematically vary the stiffness surrounding the fault in both the shear‐parallel and fault‐normal directions, to investigate the origin of slip instabilities and changes in friction constitutive properties. We confirm the transition from stable sliding through slow slip to stick‐slip due to reduced fault‐parallel stiffness, and that the occurrence of different types of slip events can be explained by the ratio between shear and critical stiffness. In contrast, reducing the fault‐normal stiffness produces stick‐slip instabilities under conditions where the conventional critical stiffness criterion predicts stable sliding, and does not produce transitional slow slip events. Our data suggest that: (a) the stability criterion for frictional slip should be modified to incorporate fault‐normal stiffness, and (b) the unexpected slip instabilities may represent wrinkle‐like slip pulses, possibly due to a stiffness asymmetry introduced by lowering the fault normal stiffness on one side of the fault. This implies that earthquakes may occur when the fault‐normal stiffness, or bulk modulus for natural faults, is decreased and/or asymmetric across the fault zone, both of which may be common in nature.

Frictional shear stress-induced incomplete martensitic transformation in mono-crystalline B2-CuZr spherulites

An austenitic B2-CuZr phase, when deformed, can undergo a martensitic transformation (MT) that produces a martensitic B19′-CuZr phase, resulting in remarkable transformation-induced plasticity (TRIP) and shape memory effects in B2-structured alloys. However, the shear mechanism as well as the crystallographic characteristics, which underlie the MT and, in turn, the TRIP and shape memory effects, remain unclear and somewhat controversial. Here we report that a single shear on {110}B2<001>B2, along with {1 1 5.5}B2 being the habit plane, are responsible for the MT in B2-CuZr, where {110}B2 and <001>B2 are the shear plane and the shear direction, respectively. These were revealed by determining unambiguously the orientation relationship between B2 and B19′, co-existing in individual spherulites contained in a B2-CuZr-containing bulk metal glass-matrix composite (BMGC). This exotic microstructure, featuring a core-shell like distribution in each single spherulite in which all the 12 possible martensite (B19′) variants constitute the core and the parent B2 forms the shell, was made from an incomplete MT in originally mono-crystalline B2 spherulites of the as-cast BMGC when subjected to moderately applied frictional shear stresses upon mechanical grinding. Finite element analysis suggests that a core-shell like shear stress distribution inside a B2 spherulite, caused by the confinement of the stiffer glass matrix, may account for it. These results provide direct experimental evidence to elucidate the B2→B19′ MT and its variant selections under various stress states, and pave the way for developing ductile B2-structured alloys, including but not limited to, shape memory intermetallics, high entropy alloys and B2-containing composite materials.

Effects of grain size and dislocation density on thermally-induced martensitic transformation of nanocrystalline NiTi alloys

Nanoscale grain and high dislocation density are the most common microstructures of nanocrystalline NiTi alloy. Although grain size and dislocation density influence the functional properties of NiTi alloy significantly, their effects on martensitic transformation have not been investigated quantitatively. In this work, the effects of grain size and dislocation density on thermally-induced martensitic transformation of nanocrystalline NiTi alloys are studied based on experiment, molecular dynamics simulation and theoretical analysis. Firstly, the drop of martensite-start-temperature and austenite-finish-temperature with decreasing grain size is determined, which is attributed to the increased fraction of grain boundary and the enhanced disordering of austenite near grain boundary via molecular dynamics simulation. Secondly, the positive correlation between dislocation density and transformation temperatures is verified by experiments and molecular dynamics simulations, which is ascribed to the enhanced stability of correspondence variant pair with habit plane of (−0.4138 0.8684 0.2688) and invariant shear direction of [−0.4432 −0.458 0.77706] under the dislocation-induced stress field. At last, a novel thermodynamic model of nanocrystalline NiTi considering grain size and dislocation density is proposed to predict martensite-start-temperature and austenite-finish-temperature. Prediction results accord to experimental data reasonably with the error generally less than 15 K. This study provides a basis for regulating the functional properties of nanocrystalline NiTi alloys through microstructural manipulation.

Conching of dark chocolate – Processing impacts on aroma-active volatiles and viscosity of plastic masses

The conching process plays a key role in determining the sensory and rheological properties of dark chocolate. To further understand this process, changes in the chocolate mass during plastic conching were investigated on a time-resolved basis with varying conching temperature, shear direction, and with or without the presence of residue from previous trials (pre-charge) on the conche vessel wall. Six selected odorants (acetic acid, benzaldehyde, linalool, 2,3,5,6-tetramethylpyrazine, 2-phenylethanol, 2-phenylethyl acetate) were quantified in fat and particle phases of chocolate masses. Particularly at elevated conching temperature, the odorant concentrations were found to decrease (up to 78.0% in the fat phase). The highest concentrations of desired odorants were determined mostly after conching without pre-charge. During conching, odorants were observed to accumulate increasingly in the fat phase (up to 91.7%) with decreasing odorant polarity. Similarly, it was found that conching temperature and the absence of pre-charge had the highest impact on the rheological properties of the chocolate mass, resulting in lowest and highest complex viscosity, respectively. In conclusion, some positive outcomes of conching, namely the retention of desired odorants and the reduction of viscosity, were inversely related at elevated temperature or in the absence of pre-charge, necessitating compromises to achieve optimal flow properties and flavor. Our results contribute to a deeper understanding of the influence of conching on the quality of dark chocolate by providing insights into the complexity of aroma migration and rheological changes during conching.

Misalignment between the propagation direction of the bora wind and its pulsations

AbstractThe bora is a well‐known downslope windstorm that blows at the eastern coast of the Adriatic Sea from inland towards the sea, mainly from the northeasterly direction. One of the notable bora characteristics is the quasi‐periodic gust pulsations. We address their characteristics during strong to severe bora events by applying rotational spectral analysis on 9 months of continuous high‐frequency sonic anemometer measurements in the town of Senj, Croatia. The analysis shows that the orientation of the pulsations' plane of oscillation does not correspond to the measured near‐ground wind direction. In particular, these two directions seem to be negatively correlated. Although the structure of the pulsations is mostly rectilinear, the positive rotational component was larger than the negative one in all except one bora event. The coincidence of the wind shear direction within the lee‐side jet with the orientation of the plane of oscillation leads to a tentative conclusion that its orientation was governed by the Kelvin–Helmholtz instability, at least in the cases presented.

W2AlC: A new layered MAX phase to adjust the balance between strength and ductility

To adjust the balance between the strength and ductility of high-temperature material, we apply the first-principles calculations to explore the structural feature, elastic modulus and brittle or ductile behavior of M2AlC (M = Mo, Cr and W) layered structure MAX phase. In addition, the thermodynamic properties of M2AlC carbides are also discussed. The calculated results show that two novel M2AlC carbides: Mo2AlC and W2AlC are predicted. For M2AlC carbide, the M − C bond in layered structure plays an important role in strength and ductility. In particular, the W2AlC exhibits better ductility in while has high elastic modulus. Naturally, the strength and ductility of W2AlC are related to the bond strength and bond orientation of W–C bond in (W–C)–Al-(W–C) layered structure. The weak bond strength of W–C bond in shear direction improves the slip and then improves the ductility of W2AlC carbide with high strength. In addition, the calculated Debye temperature follows the order of Cr2AlC > Mo2AlC ≈ W2AlC. Therefore, we believe that W2AlC carbide with (W–C)–Al-(W–C) layered structure can optimize the balance between the strength and ductility of this M2AlC MAX phase.

Characteristics structures of the mélange zones in the Ukrainian Carpathians

Mélange is characterized by the block-in-matrix fabric in which rigid blocks of different sizes, lithologies, and ages are distributed in a ductile matrix. Though mélange is a significant component of orogenic belts, in the Ukrainian Carpathians, mélanges of tectonic origin have not been reported. We have described the mélange zones widespread in the Pieniny Klippen Belt, Marmarosh Klippen Zone, and the inner nappes of the Outer Ukrainian Carpathians, as well as the typical deformation structures developed within them.&#x0D; The mélange matrix is characterized by a scaly fabric formed by cleavage surfaces and somewhere arranged in S-C structures. Lenticular clasts within the matrix show their long axis aligned to the tectonic foliation. Rotation of the boudins occurs against the shear direction following the formation of the S-C structures. The rigid clasts somewhere demonstrate sigma-type rotation structures. Some blocks within the mélange are highly fractured up to tectonic breccias.&#x0D; The study of tectonic slicken-sides and other deformation structures within the Pieniny belt demonstrates the presence of regular stress fields correlated with the geodynamics of the Carpatho-Pannonian region. The main stress field indicates the SW-NE regional compression related to the formation of Carpathian nappes and S-N — trending dextral strike-slip faults. Our study in the Priborzhava quarries records the Oash right-lateral strike-slip fault zone. In the Pieniny Klippen Belt some oblique normal faults of the Carpathian direction are related to the Transcarpathian Depression formation. The study showed that the mélange zones in the inner part of the Ukrainian Carpathians were formed largely due to strike-slip movements. In contrast, in the outer part of the Carpathian orogen, they formed mainly due to thrusting.

Theoretical strength of austenite in the presence of a pore or vacancies in the crystal: Molecular dynamics study

The molecular dynamics method was used to study the influence of pores of different diameters, as well as the corresponding concentration of individual vacancies, on the theoretical strength of austenite at different temperatures. The deformation in the model was carried out by shear at a cons­tant rate of 20 m/s. We considered a shear along two directions: [ \(\bar 1\ \bar 1\) 2] and [111]. The computational austenite cell had the shape of a rectangular parallelepiped 14.0 nm long, 14.0 nm high, and 5.1 nm wide. To describe interatomic interactions, the Lau EAM potential was used, which reproduces well the structural, energy, and elastic characteristics of austenite. The stress-strain curves obtained for both considered shear directions had a similar form. In the absence of dislocation sources, plastic deformation was carried out by the formation of dislocation dipoles (dislocations with opposite Burgers vectors). The presence of a pore significantly reduced the yield strength of austenite. In this case, it was found that single vacancies randomly scattered over the volume of the computational cell also lead to a decrease in the yield strength, but, of course, not as much as the pore. The emission of dislocations during deformation occurred by the formation of dislocation loops, as a rule, in two slip planes at once. The effect of pores and vacancies on the yield strength was stronger at low temperatures. As the temperature increased, the effect of defects on the critical stress at which dislocations were formed decreased. With an increase in the pore size, as well as the concentration of vacancies, the yield strength decreased. In this case, the strongest dependence was observed for pores up to 1 nm in diameter. The influence of the concentration of vacancies in the considered range on the yield strength turned out to be comparatively smoother and almost linear.

Two-dimensional (2D) axis-pin force sensor and its characterization on the shear force direction

The characterization of the shear force direction is an imperative technical problem to be solved for the axis-pin force sensor. In the present work, a two-dimensional axis-pin force sensor has been designed. The layout of the sensor is to open horizontal blind holes and vertical blind holes at intervals of 90 degrees along the circular direction on the surface of the axis-pin. Then the variation law of the circumferential strain of blind holes along with the shear force direction is first studied through the FEA simulation. It is found that the sum of the circumferential strains of two horizontal blind holes or vertical blind holes varies in sine and cosine pattern with the shear force direction. On this basis, the mathematical model of shear force direction characterized by circumferential strains of blind holes is derived. Eventually, the prototype of the axis-pin force sensor was made to verify this law. The experimental results showed that the accuracy of the shear force and direction measured by the sensor can reach ± 8% and ± 5% respectively, which meet the requirements of the practical application. This method eliminates the theoretical error caused by the use of correction coefficients and nonlinear model approximation, which provides a theoretical basis for the development of two-dimensional axis-pin force sensors.

Fracture aperture anisotropic effects on field scale enhanced geothermal system thermal performance

The thermal performance of a field-scale Enhanced Geothermal System was investigated, considering anisotropy in fracture aperture distributions. The fracture aperture distribution was treated as an autocorrelated random field with different ranges in the x- and y-directions, defined by geometric anisotropic ratios between 1.5 and 4. To model realistic aperture distributions, constraints were applied to ensure the aperture distributions had Hurst exponents that are typical of fractures observed in nature.The thermal drawdown between the perpendicular and parallel flow configurations was compared, revealing a 60 % likelihood of improved heat transfer in the perpendicular flow configuration. When exploring the impact of geometric anisotropy ratios on thermal performance, aperture distributions with a geometric anisotropy ratio of 2 demonstrated about 70 % better thermal performance in favor of the perpendicular flow direction. This ratio also exhibited aperture distributions with Hurst exponents within the range found in natural faults and fractures, suggesting a 70 % likelihood of improved thermal performance in the perpendicular flow configuration for actual fracture behavior.The perpendicular flow configuration mainly exhibited tortuous flow paths, while the parallel flow direction mostly had near-horizontal flow paths. The tortuous flow paths increased contact between the fluid and fracture surface area, resulting in improved thermal performance.The findings suggest the importance of considering shear direction at the field scale when placing wells. Placing a well perpendicular to the direction of slip or shear may yield enhanced thermal performance compared to placing a well parallel to the direction of slip or shear.

An assessment of PWR fuel assembly spacer grid strength by FEM models

Since Fukushima accident, integrity of fuel assembly for seismic load became very important. This study assesses the structural integrity of mid spacer grid (SG) of PLUS7 fuel assembly (FA) which is the weakest part of fuel assembly structural components. Spacer grid FEM models were developed by 3D solid element and 3D shell element. From the FEM analysis, it was found that the structural strength for normal direction was much larger than for shear direction. At core outlet, the normal stiffness was estimated to 36kN/mm for 3D solid model and 33kN/mm for 3D shell model, and the shear stiffness was estimated to 49 N/mm for 3D solid model and 75 N/mm for 3D shell model. From this result normal stiffness is a lot bigger than shear stiffness, and spacer grid structure is more vulnerable against shear loads. It is recommended to do shear test or analysis of fuel assembly in the development stage.