Nominal Plane Research Articles

Anisotropy in shear failure of shale: An insight from microcracking to macrorupture

Anisotropic shear failure in shale is crucial to wellbore instability and hydraulic fracturing. While previous studies have examined bedding angles ranging from 0° to 90°, the intermediate angles have not been thoroughly investigated, with limited quantitative analysis from microcracking to macrorupture. To address this gap, we conducted direct shear tests on cubic shale samples with seven bedding angles (α = 0°, 15°, 30°, 45°, 60°, 75°, and 90°) using an innovative combination of acoustic emission (AE) and digital image correlation (DIC) techniques. This approach allowed us to gain a comprehensive understanding of the cracking damage process from the interior to the surface. Under various normal stresses, the minimum peak shear strengths occurred at α = 0°, while the maximum values were observed at α = 45° or 60°, rather than remaining constant. The internal friction angle peaked at α = 45°, not at α = 30° as previously reported. Furthermore, the shear failure pattern was influenced by complex interactions among nominal shear plane, bedding structure, and normal stress. The primary strain concentration zones and microfractures formed not only along the nominal shear plane but also along the bedding planes. Notably, microcracking damage initiated most readily at α = 0°, where the b value in AE events was higher and the fractal dimension was lower. At α = 30°–60°, the b value reached its minimum, while the fractal dimension peaked. The more random distribution of larger-scale microcracks was associated with an increase in the shear strength. These findings provide critical insights into the anisotropy of shear failure in shale and demonstrate the potential of microcracking analysis in predicting critical macrorupture and shear resistance. The identification of three distinct shear failure mechanisms further enhances our understanding of shale anisotropy.

Deterministic Trajectory Design and Attitude Maneuvers of Gradient-Index Solar Sail in Interplanetary Transfers

A refractive sail is a special type of solar sail concept, whose membrane exposed to the Sun’s rays is covered with an advanced engineered film made of micro-prisms. Unlike the well-known reflective solar sail, an ideally flat refractive sail is able to generate a nonzero thrust component along the sail’s nominal plane even when the Sun’s rays strike that plane perpendicularly, that is, when the solar sail attitude is Sun-facing. This particular property of the refractive sail allows heliocentric orbital transfers between orbits with different values of the semilatus rectum while maintaining a Sun-facing attitude throughout the duration of the flight. In this case, the sail control is achieved by rotating the structure around the Sun–spacecraft line, thus reducing the size of the control vector to a single (scalar) parameter. A gradient-index solar sail (GIS) is a special type of refractive sail, in which the membrane film design is optimized though a transformation optics-based method. In this case, the membrane film is designed to achieve a desired refractive index distribution with the aid of a waveguide array to increase the sail efficiency. This paper analyzes the optimal transfer performance of a GIS with a Sun-facing attitude (SFGIS) in a series of typical heliocentric mission scenarios. In addition, this paper studies the attitude control of the Sun-facing GIS using a simplified mathematical model, in order to investigate the effective ability of the solar sail to follow the (optimal) variation law of the rotation angle around the radial direction.

Optimal Trajectories of Diffractive Sail to Highly Inclined Heliocentric Orbits

Recent literature indicates that the diffractive sail concept is an interesting alternative to the more conventional reflective solar sail, which converts solar radiation pressure into a (deep space) thrust using a thin, lightweight highly reflective membrane, usually metalized. In particular, a diffractive sail, which uses a metamaterial-based membrane to diffract incoming solar rays, is able to generate a steerable thrust vector even when the sail nominal plane is perpendicular to the Sun–spacecraft line. This paper analyzes the optimal transfer performance of a diffractive-sail-based spacecraft in a challenging heliocentric scenario that is consistent with the proposed Solar Polar Imager mission concept. In this case, the spacecraft must reach a near-circular (heliocentric) orbit with a high orbital inclination with respect to the Ecliptic in order to observe and monitor the Sun’s polar regions. Such a specific heliocentric scenario, because of the high velocity change it requires, is a mission application particularly suited for a propellantless propulsion system such as the classical solar sail. However, as shown in this work, the same transfer can be accomplished using a diffractive sail as the primary propulsion system. The main contribution of this paper is the analysis of the spacecraft transfer trajectory using a near-optimal strategy by dividing the entire flight into an approach phase to a circular orbit of the same radius as the desired final orbit but with a smaller inclination, and a subsequent cranking phase until the desired (orbital) inclination is reached. The numerical simulations show that the proposed strategy is sufficiently simple to implement and can provide solutions that differ by only a few percentage points from the optimal results obtainable with a classical indirect approach.

Orientation distribution and deviation behaviors of dislocation loops in a quenched Al-Cu alloy

Dislocation loops in quenched aluminum alloys are usually seen deviating from their nominal habit planes, while the orientation distribution and deviation mechanism are far from understanding. Based on the method of tomographic crystallography of dislocations and correlative in-situ heating experiments in transmission electron microscopy (TEM), we revisit the three-dimensional (3D) characteristics and deviation behaviors of dislocation loops in a quenched Al-Cu alloy with an aim to fully unravel the relationship between dislocation crystallography and deviation behaviors. The results show that all the dislocation loops exhibit approximately circular shapes and have a/2 < 110>-type Burgers vectors, with loop orientations deviating from their pure edge orientation {110} of 0°-17.8° and distributing mainly close to the [101]-[001] and [101]-[111] edges of the standard stereographic triangle. Three types of deviation behaviors of dislocation loops are then defined, which are characterized by loop rotation around 〈100〉, 〈110〉 and irregular axes, respectively. Theoretical calculations of strain energy variation with increasing deviation angle indicate that the relatively low energy barrier may account for a high frequency of loop deviation in the low angle range. Detailed in-situ TEM heating experiments and correlative tomographic crystallography analyses strongly demonstrate the specific roles of dislocation gliding and climbing at elevated temperatures in the shrinkage, polygonization and deviation processes of dislocation loops, and the competitive and cooperative motion of dislocation segments close to slip planes {111} are the fundamental reasons for the formation of three types of deviated dislocation loops.

Circular Orbit Flip Trajectories Generated by E-Sail

An Electric Solar Wind Sail (E-sail) is a propellantless propulsion concept that extracts momentum from the high-speed solar wind stream to generate thrust. This paper investigates the performance of such a propulsion system in obtaining the transition from a prograde to a retrograde motion. The spacecraft is assumed to initially trace a circular heliocentric orbit of given radius. This particular trajectory, referred to as Circular Orbit Flip Trajectory (COFT), is analyzed in a two-dimensional mission scenario, by exploiting the capability of a medium-high performance E-sail to change the spacecraft angular momentum vector during its motion in the interplanetary space. More precisely, the paper describes a procedure to evaluate the E-sail optimal performance in a set of COFTs, by calculating their minimum flight times as a function of the sail reference propulsive acceleration. It is shown that a two-dimensional COFT can be generated by means of a simple steering law in which the E-sail nominal plane has a nearly fixed attitude with respect to an orbital reference system, for most of the time interval of the interplanetary transfer.

Optimal interplanetary trajectories for Sun-facing ideal diffractive sails

A diffractive sail is a solar sail whose exposed surface is covered by an advanced diffractive metamaterial film with engineered optical properties. This study examines the optimal performance of a diffractive solar sail with a Sun-facing attitude in a typical orbit-to-orbit heliocentric transfer. A Sun-facing attitude, which can be passively maintained through the suitable design of the sail shape, is obtained when the sail nominal plane is perpendicular to the Sun–spacecraft line. Unlike an ideal reflective sail, a Sun-facing diffractive sail generates a large transverse thrust component that can be effectively exploited to change the orbital angular momentum. Using a recent thrust model, this study determines the optimal control law of a Sun-facing ideal diffractive sail and simulates the minimum transfer times for a set of interplanetary mission scenarios. It also quantifies the performance difference between Sun-facing diffractive sail and reflective sail. A case study presents the results of a potential mission to the asteroid 16 Psyche.

Solar Sail Orbit Raising with Electro-Optically Controlled Diffractive Film

The aim of this paper is to analyze the transfer performance of a spacecraft whose primary propulsion system is a diffractive solar sail with active, switchable panels. The spacecraft uses a propellantless thruster that converts the solar radiation pressure into propulsive acceleration by taking advantage of the diffractive property of an electro-optically controlled (binary) metamaterial. The proposed analysis considers a heliocentric mission scenario where the spacecraft is required to perform a two-dimensional transfer between two concentric and coplanar circular orbits. The sail attitude is assumed to be Sun-facing, that is, with its sail nominal plane perpendicular to the incoming sunlight. This is possible since, unlike a more conventional solar sail concept that uses metalized highly reflective thin films to reflect the photons, a diffractive sail is theoretically able to generate a component of the thrust vector along the sail nominal plane also in a Sun-facing configuration. The electro-optically controlled sail film is used to change the in-plane component of the thrust vector to accomplish the transfer by minimizing the total flight time without changing the sail attitude with respect to an orbital reference frame. This work extends the mathematical model recently proposed by the authors by including the potential offered by an active control of the diffractive sail film. The paper also thoroughly analyzes the diffractive sail-based spacecraft performance in a set of classical circle-to-circle heliocentric trajectories that model transfers from Earth to Mars, Venus and Jupiter.

Optimal Circle-to-Ellipse Orbit Transfer for Sun-Facing E-Sail

The transfer between two coplanar Keplerian orbits of a spacecraft with a continuous-thrust propulsion system is a classical problem of astrodynamics, in which a numerical procedure is usually employed to find the transfer trajectory that optimizes (i.e., maximizes or minimizes) a given performance index such as, for example, the delivered payload mass, the propellant mass, the total flight time, or a suitable combination of them. In the last decade, this class of problem has been thoroughly analyzed in the context of heliocentric mission scenarios of a spacecraft equipped with an Electric Solar Wind Sail as primary propulsion system. The aim of this paper is to further extend the existing related literature by analyzing the optimal transfer of an Electric Solar Wind Sail-based spacecraft with a Sun-facing attitude, a particular configuration in which the sail nominal plane is perpendicular to the Sun-spacecraft (i.e., radial) direction, so that the propulsion system is able to produce its maximum propulsive acceleration magnitude. The problem consists in transferring the spacecraft, which initially traces a heliocentric circular orbit, into an elliptic coplanar orbit of given eccentricity with a minimum-time trajectory. Using a classical indirect approach for trajectory optimization, the paper shows that a simplified version of the optimal control problem can be obtained by enforcing the typical transfer constraints. The numerical simulations show that the proposed approach is able to quantify the transfer performance in a parametric and general form, with a simple and efficient algorithm.

Effect of chemical disorder on the magnetic anisotropy in L10 FeNi from first-principles calculations

We use first-principles calculations to investigate how deviations from perfect chemical order affect the magnetocrystalline anisotropy energy (MAE) in $L{1}_{0}$ FeNi. We first analyze the local chemical environment of the Fe atoms in various partially ordered configurations, using the orbital magnetic moment anisotropy (OMA) as proxy for a local contribution to the MAE. We are able to identify a specific nearest neighbor configuration and use this ``favorable environment'' to successfully design various structures with MAE higher than the perfectly ordered system. However, a systematic analysis of the correlation between local environment and OMA using smooth overlap of atomic positions indicates only a partial correlation, which exists only if the deviation from full chemical order is not too large, whereas in general no such correlation can be identified even using up to third nearest neighbors. Guided by the observation that the identified favorable environment implies an Fe-rich composition, we investigate the effect of randomly inserting additional Fe into the nominal Ni planes of the perfectly ordered structure. We find that the MAE increases with Fe content, at least up to 62.5% Fe. Thus, our paper shows that the perfectly ordered case is not the one with highest MAE and that an increased MAE can be obtained for slightly Fe-rich compositions.

Predicting instabilities of a tunable ring laser with an iterative map model

Simple mathematical models have been unable to predict the conditions leading to instabilities in a tunable ring laser. Here we propose a nonlinear iterative map model for tunable ring lasers. Solving a reduced nonlinear Schrödinger equation for each component in the laser cavity, we obtain an algebraic map for each component. Iterating through the maps gives the total effect of one round trip. By neglecting the nonlinearity, we find a linearly chirped Gaussian to be the analytic fixed point solution, which we analyze asymptotically. We then numerically solve the full nonlinear model, allowing us to probe the underlying interplay of dispersion, modulation, and nonlinearity as the pulse evolves over hundreds of round trips of the cavity. In the nonlinear case, we find that the chirp saturates and the Fourier transform of the pulse becomes more rectangular in shape. Finally, for a nominal plane in the parameter space, we uncover a rich, sharp boundary separating the stable region and the unstable region where instabilities degrade the pulse into an unsustainable state.

Modeling Adhesive Hysteresis

When an elastomer approaches or retracts from an adhesive indenter, the elastomer’s surface can suddenly become unstable and reshape itself quasi-discontinuously, e.g., when small-scale asperities jump into or snap out of contact. Such dynamics lead to a hysteresis between approach and retraction. In this study, we quantify numerically and analytically the ensuing unavoidable energy loss for rigid indenters with flat, Hertzian and randomly rough profiles. The range of adhesion turns out to be central, in particular during the rarely modeled approach to contact. For example, negligible traction on approach but quite noticeable adhesion for nominal plane contacts hinges on the use of short-range adhesion. Central attention is paid to the design of cohesive-zone models for the efficient simulation of dynamical processes. Our study includes a Griffith’s type analysis for the energy lost during fracture and regeneration of a flat interface. It reveals that the leading-order corrections of the energy loss are due to the finite-range adhesion scale at best, with the third root of the linear mesh size, while leading-order errors in the pull-off force disappear linearly.

Experimental study of internal forces and moments generated by strut injection in a supersonic cross-flow in a C-D nozzle

An experimental investigation was conducted to obtain wall pressure distribution in a convergent divergent nozzle with a strut inserted through the diverging wall and to find out the possible generation of side force. The strut inserted through the nozzle wall represented an active control method for thrust vector control. Laboratory tests were carried out to examine whether this type of strut injection would be effective and serve as an alternative thrust vector control method for the other widely used such as secondary injection thrust vector control. The nozzle model used in the experiments had a design Mach number of 1.84 with a corresponding area ratio of 1.48. The solid strut which was inserted through the diverging wall of the nozzle had a square cross section. Experiments were conducted for identifying three different strut positions from the nozzle throat, i.e. at Ld/3, Ld/2, and 2Ld/3, where Ld was the length of the diverging section of the nozzle. At each strut position, the strut height was varied and the maximum strut height corresponded to the radius of the local cross section where the strut was inserted. The nozzle was operated at overexpansion conditions such as nozzle pressure ratios of 3.4 and 5. The strut side and the opposite side of the nozzle wall had eight wall pressure tappings each and the wall pressure data were obtained using a pressure scanner. The asymmetrical pressure distributions of the strut side and the non-strut side (opposite side) of nozzle wall were used for the calculation of side force and pitching moment in the nominal plane through the wall pressure ports of both sides. The calculated two-dimensional side force, axial force, and pitching moment coefficients were plotted against strut height at each strut position from the nozzle throat. From the experimental data and calculations, it was found that the axial force varied more or less linearly with strut height irrespective of the strut position. However, the side force and pitching moments varied nonlinearly with strut height and the nature of variation of the two was similar. Both the side force and pitching moment exhibited maximum and minimum values at two specific values of the strut height. The change in the strut position did not alter the nature of the above variations and the strut height values for maximum and minimum. The magnitude of the side force was found to be 1–10% of the axial force generated as a fluid dynamic pressure drag. Both positive and negative side force and pitching moments were produced with increase in the strut height.

ДОСЛІДЖЕННЯ ВПЛИВУ НЕРІВНОМІРНОСТІ ЦЕМЕНТОВАНОГО ШАРУ НА НЕСУЧУ ЗДАТНІСТЬ БАЗОВИХ ТА ОПОРНО-КОРПУСНИХ ДЕТАЛЕЙ УНІВЕРСАЛЬНО-ЗБІРНИХ ПРИСТОСУВАНЬ

The article contains analysis of the uneven cemented layer effect upon the bearing capacity of the base and supporting parts of versatile prefabricated welded work tools. The issue was studied as there is a lack of data on contact deformations, which are necessary for further calculation of assembly errors due to thermal deformations. Fluctuations of the cemented layer depth along the base part surface negatively affect the contact of the tool base surfaces. This issue is especially acute when expanding the scope of application of reconfigurable reusable technological equipment, which would be cost-effective in terms of serial multi-item production of welded structures.The relation between microhardness and the value of the polished cemented layer was determined during testing of 12 ХН3А steel samples, cemented to a depth of 2.4 mm and hardened to a hardness of HRC 60-62. Obtained relation between the microhardness and polished layer thickness has shown that with increasing polished layer, the microhardness decreases. This leads to a decrease in the critical load, under which recoverable deformations of irregularities transit into plastic deformations. The ratio of the actual planes of contact, where the recoverable deformation of microroughnesses appoears when approaching and penetration of harder irregularities into soft ones occurs, will be proportional to the ratio of the nominal planes of the cemented and raw layers.As a result of processing the test data, the relation between critical pressure and cemented layer thickness has been got. Microroughnesses at lower loads will be deformed plastically, reducing the bearing capacity of base surfaces, which is unacceptable for parts of tools and affects their service life. It follows from the above that the unevenness of the cemented layer depth of the front surfaces of the base and supporting parts is a negative phenomenon that impairs their performance. It is necessary to use a process that ensures minimal distortion of the part during heat treatment and a stable depth of the cemented layer.

Yielding, rigidity, and tensile stress in sheared columns of hexapod granules.

Granular packings of nonconvex or elongated particles can form freestanding structures like walls or arches. For some particle shapes, such as staples, the rigidity arises from interlocking of pairs of particles, but the origins of rigidity for noninterlocking particles remains unclear. We report on experiments and numerical simulations of sheared columns of "hexapods," particles consisting of three mutually orthogonal sphero-cylinders whose centers coincide. We vary the length-to-diameter aspect ratio, α, of the sphero-cylinders and subject the packings to quasistatic direct shear. For small α, we observe a finite yield stress. For large α, however, the column becomes rigid when sheared, supporting stresses that increase sharply with increasing strain. Analysis of x-ray microcomputed tomography (micro-CT) data collected during the shear reveals that the stiffening is associated with a tilted, oblate cluster of hexapods near the nominal shear plane in which particle deformation and average contact number both increase. Simulation results show that the particles are collectively under tension along one direction, even though they do not interlock pairwise. These tensions comes from contact forces carrying large torques, and they are perpendicular to the compressive stresses in the packing. They counteract the tendency to dilate, thus stabilizing the particle cluster.

Fundamental differences between plane strain bending and far-field plane strain tension in ductile plate failure

The objective of this paper is to investigate the ductile fracture behavior of thin metal plates under nominally plane strain conditions, with an emphasis on the differences between far-field plane strain tension and plane strain bending. Recent experimental results show that the fracture strain obtained using far-field plane strain tension tests is significantly lower than that obtained under plane strain bending conditions. Investigating the source of these differences is of critical importance for multiple industries since it affects formability, crashworthiness and ductile failure of thin metal plates. The present work provides critical insights into this issue based on the results of a detailed numerical investigation of both tests to failure, using the micro-mechanics based Gurson material model. The numerical simulations reveal many similarities between plane strain bending and far-field plane strain tension until the onset of localization. In the far-field plane strain tension case, after Considère thinning, a through-thickness shear localization occurs, followed by a micro-crack formation in the center of the plate. This is accompanied by an increase of the stress triaxiality well above the nominal plane strain tension level (i.e., ~ 0.57 for thin plates). In contrast, the absence of thinning in plane strain bending yields a stress triaxiality that equals nominal plane strain tension, which results in a significantly lower void growth rate (in reference to far-field plane strain tension). A surface instability (undulations) eventually forms on the tension side of the plate in plane strain bending, followed by multiple shear bands. The crack initiates inside the dominant shear band and propagates from the surface into the plate. These differences in the localization mechanisms and local stress states are responsible for the difference in the macroscopic fracture strain obtained under far-field plane strain tension and plane strain bending.

Impact of Nonlinear Kerr Effect on the Focusing Performance of Optical Lens with High-Intensity Laser Incidence

The rapid development of high-energy and high-power laser technology provides an important experimental means for the research of extreme physical state in the laboratory and for the design of large laser facilities for realizing inertial confinement fusion. However, when the incident laser field is very strong, the Kerr effect of materials affects the nominal performance of optical elements. In this work, the impact of Kerr effect on the focusing performance of an optical lens is studied by calculating and comparing the filed patterns of focal spots for three different incident laser beams together with three different levels of light intensities. The traditional transfer function of an optical lens is firstly modified according to the theory of nonlinear Kerr effect. We use the two-dimensional fast Fourier transform algorithm and angular spectrum algorithm to numerically calculate the field distributions of focal spots in the nominal focal plane of lens and its adjacent planes based on the Fresnel diffraction integral formula. The obtained results show that the Kerr effect affects the focusing characteristics of lens, especially for the incidence of high-order Gaussian beams, such as Hermite-Gaussian beams and Laguerre-Gaussian beams. At the same time, the focal length and refractive index of lens also change the field patterns of focal spots. The presented methodology is of great value in engineering applications where the practical problem with beam size up to 100 mm can be calculated using a common laptop computer. The work provides an efficient numerical technique for high-intensity incident laser beams focused by lens that takes Kerr effect into consideration, which has potential applications in high energy density physics and large laser facilities for inertial confinement fusion.

Optimal steering law of refractive sail

The interaction between electromagnetic waves and matter is the working principle of a photon-propelled spacecraft, which extracts momentum from the solar radiation to obtain a propulsive acceleration. An example is offered by solar sails, which use a thin membrane to reflect the impinging photons. The solar radiation momentum may actually be transferred to matter by means of various optical phenomena, such as absorption, emission, or refraction. This paper deals with the novel concept of a refractive sail, through which the Sun’s light is refracted by crossing a film made of polymeric micro-prisms. The main feature of a refractive sail is to give a large transverse component of thrust even when the sail nominal plane is orthogonal to the Sun-spacecraft line. Starting from the recent literature results, this paper proposes a semi-analytical thrust model that estimates the characteristics of the propulsive acceleration vector as a function of the sail attitude angles. Such a mathematical model is then used to analyze a simplified Earth-Mars and Earth-Venus interplanetary transfer within an optimal framework.

Radial Shearing Interferometer Based on a Cosinusoidal Zone Plate

A simple and compact radial shearing interferometer (RSI) based on a cosinusoidal zone plate (CZP) is proposed. The CZP can modulate both phase and amplitude, it has two foci, so as the nominal plane beam under test passes through the CZP, it is diffracted into two parts, i.e., a converging beam and a diverging beam. Then, the two beams can be considered as the compressed beam and the expanded beam in the RSI, respectively. A charge-coupled device detector located in the vicinity of the CZP records the interference pattern. This RSI needs only a single zone plate and therefore can be made very compact. The experiment validates the correctness of the proposed method. With the compactness and stability, the presented interferometer is expected to be used in the detection of moving objects and dynamic processes.

Numerical Understanding of Free Surface Vortex Driven by Rotational Field Inside Viscous Liquid

The present study established the genesis of free surface vortex inside a viscous liquid using a rotating cylindrical disc immersed in the liquid. The longitudinal axis of the disc is kept normal to the nominal interfacial plane and its rotation is characterized in terms of Froude number (1.50–4.49). This configuration is simulated using a grid-based volume of fluid technique in the air and high viscous polybutene pair. A dip in nominal interface profile is observed at low disc rotations (Froude number ≈ 1.50), however, the gradual progress of the rotational inertia (Froude number > 1.50) has resulted in elongation of the interface in the form of a free surface vortex progressing inside the liquid. The transient progress of vortex depicts bullet nose like interface tip during the early stages, which grows in the outward radial direction along with its downward motion due to the centrifugal effect of the surrounding liquid. The initial submergence ratio of the disc and its radius are shown as the important parameters governing the entrainment rate and shape of the vortex profiles. The physical understanding behind the formation of the vortex is revealed using axial and crosswise circulations of the surrounding liquid.

Network Effects and Handling of the Geocenter Motion in Multi‐GNSS Processing

AbstractBoth, the network configuration and the way of terrestrial reference frame (TRF) realization, affect the global geodetic products delivered from the Global Navigation Satellite Systems (GNSS) data processing. The purpose of this study is to analyze the differences in GNSS products, such as station coordinates, Earth rotation parameters, geocenter coordinates (GCC), and satellite orbits delivered from the double‐difference multi‐GNSS (GPS, GLONASS, and Galileo) processing, which may arise from (1) using a homogeneous and inhomogeneous network of multi‐GNSS stations, (2) different approaches to the TRF realization using minimum constraint conditions, and (3) different approaches to handling of GCC in GNSS global processing. The questionable quality of GCC delivered from the global GNSS solutions is described with a special attention to network effects and system‐specific parameters. We found that Galileo can provide GCC, whose quality corresponds to the GPS series. Moreover, the GCC from Galileo is of a better quality than those based on GLONASS data, despite the same number of nominal orbital planes and a much lower number of active satellites. When the No‐Net‐Translation constraint is not applied on the GNSS network, the station coordinate repeatability is worsened by about 70%, 55%, and 25% for the north, east, and up components, respectively, compared to the solution when applying No‐Net‐Translation and when having the network origin consistent with the international TRF. We thus infer that the No‐Net‐Translation condition is mandatory in global GNSS solutions.