Gravitational Stress Research Articles

Investigating the variation of the fields of elastic stresses in the rock mass when developing the Peschanskoye deposit

Research aim is to study parameter variations in the stress state of the rock mass to ensure safe and efficient mining of the Peschanskoye magnetite deposit (Northern Ural) to the full depth, which has been carried out by Severopeschanskaya mine since 1958 in a complex of hard rock at a depth of 200 to 700 m. Blind, thick, and steep ore bodies are developed by a block-caving method with ore breaking to a clamped medium. From a depth of 400 m, the field is classified as rock burst hazardous. The first rock burst was recorded in 1981 at a depth of 450 m. Research methodology includes full-scale experimental measurements of the rock and ore mass stress state at accessible depths and horizons of the deposit, establishing patterns of stress growth with depth, as well as long-term (since 1990) geo-deformational monitoring of an untouched rock mass stress level in time. Research results analysis has allowed to establish the patterns in stress-strain state changes during mining. Gradients of gravitational and tectonic stresses growth with depth are determined. Alternating (astrophysical) stresses are highlighted in a special line, the extreme values of which are linked chronologically with various information factors. Conclusions. The determined values of rock mass natural stress state variation parameters in combination with the established stresses around the workings and goafs (technogenic impact) make it possible to take into account the main tempo-spatial factors of the impact made by the mentioned loads when selecting rockburst-safe and effective mining parameters for underground geotechnology both at the top horizons when applying controlled collapse of overlying blind deposits and in the prevention of rockburst hazard in the lower horizons of the developed field

EFFECT OF ORIGINAL STRESS STATE OF THE ROCK MASS ON DISTRIBUTION OF DISPLACEMENTS AND STRESSES IN THE VICINITY OF SUPPORTED MINE WORKING IN UNSTABLE ROCKS

The statement of the problem of finding the stress-strain state of support and rocks surrounding the mine working in case of cushioning with phenol resins is used to determine the peculiarities of its formation under the influence of gravitational and hydrostatic original stress fields. It is found that maximum vertical compressive stresses arise in vertical support units at gravitational field, which exceed by half their values for a hydrostatic field. However, as the height in the mine roof filled with phenol resins increases, maximum vertical stresses for both options become comparable. In arch support units at hydrostatic original state of the rock mass, the values of horizontal tensile stresses are by half less than at gravitational original field.

Lower body negative pressure: a novel remedy for preserving the cerebrovasculature from gravitational stress.

Lower body negative pressure: a novel remedy for preserving the cerebrovasculature from gravitational stress.

Gravitational Transitions Increase Posterior Cerebral Perfusion and Systemic Oxidative-nitrosative Stress: Implications for Neurovascular Unit Integrity

The present study examined if repeated bouts of micro- and hypergravity during parabolic flight (PF) alter structural integrity of the neurovascular unit (NVU) subsequent to free radical-mediated changes in regional cerebral perfusion. Six participants (5♂, 1♀) aged 29 ± 11 years were examined before, during and after a 3 h PF and compared to six sex and age-matched (27 ± 6 years) normogravity controls. Blood flow was measured in the anterior (middle cerebral artery, MCA; internal carotid artery, ICA) and posterior (vertebral artery, VA) circulation (duplex ultrasound) in-flight over the course of 15 parabolas. Venous blood was assayed for free radicals (electron paramagnetic resonance spectroscopy), nitric oxide (NO, ozone-based chemiluminescence) and NVU integrity (chemiluminescence/ELISA) in normogravity before and after exposure to 31 parabolas. While MCA velocity did not change (P > 0.05), a selective increase in VA flow was observed during the most marked gravitational transition from micro- to hypergravity (P < 0.05). Increased oxidative-nitrosative stress defined by a free radical-mediated reduction in NO and elevations in glio-vascular GFAP and S100ß were observed after PF (P < 0.05), the latter proportional to the increase in VA flow (r = 0.908, P < 0.05). In contrast, biomarkers of neuronal-axonal damage (neuron-specific enolase, neurofilament light-chain, ubiquitin carboxy-terminal hydrolase L1 and tau) did not change (P > 0.05). Collectively, these findings suggest that the cumulative effects of repeated gravitational transitions may promote minor blood–brain barrier disruption, potentially related to the combined effects of haemodynamic (posterior cerebral hyperperfusion) and molecular (systemic oxidative-nitrosative) stress.

Lower body negative pressure protects brain perfusion in aviation gravitational stress induced by push-pull manoeuvre.

Rapid alterations of gravitational stress during high-performance aircraft push-pull manoeuvres induce dramatic shifts in volume and pressure within the circulation system, which may result in loss of consciousness due to the rapid and significant reduction in cerebral perfusion. There are still no specific and effective countermeasures so far. We found that lower body negative pressure (LBNP), applied prior to and during -Gz and released at the subsequent transition to +Gz, could effectively counteract gravitational haemodynamic stress induced by a simulated push-pull manoeuvre and improve cerebral diastolic perfusion in human subjects. We developed a LBNP strategy that effectively protects cerebral perfusion at rapid -Gz to +Gz transitions via improving cerebral blood flow and blood pressure during push-pull manoeuvres and highlight the importance of the timing of the intervention. Our findings provide a systemic link of integrated responses between the peripheral and cerebral haemodynamic changes during push-pull manoeuvres. The acute negative (-Gz) to positive (+Gz) gravity stress during high-performance aircraft push-pull manoeuvres dramatically reduces transient cerebral perfusion, which may lead to loss of vision or even consciousness. The aim of this study was to explore a specific and effective counteractive strategy. Twenty-three healthy young male volunteers (age 21±1year) were subjected to tilting-simulated push-pull manoeuvres. Lower body negative pressure (LBNP) of -40mmHg was applied prior to and during -Gz stress (-0.50 or -0.87Gz) and released at the subsequent transition to +1.00Gz stress. Beat-to-beat cerebral and systemic haemodynamics were continuously recorded during the simulated push-pull manoeuvre in LBNP bouts and corresponding control bouts. During the rapid gravitational transition from -Gz to +Gz, the mean cerebral blood flow velocity decreased significantly in control bouts, while it increased in LBNP bouts (control vs. LBNP bouts, -6.6±4.6 vs. 5.1±6.8cms-1 for -0.50Gz, and -7.4±4.8 vs. 3.4±4.6cms-1 for -0.87 Gz, P<0.01), which was attributed mainly to the elevation of diastolic flow. The LBNP bouts showed much smaller reduction of mean arterial blood pressure at the brain level than control bouts (control bouts vs. LBNP bouts, -38±12 vs. -23±10mmHg for -0.50 to +1.00Gz, and -62±16 vs. -43±11mmHg for -0.87 to +1.00Gz, P<0.01). LBNP applied at -Gz and released at subsequent +Gz had biphasic counteractive effects against the gravitational responses to the push-pull manoeuvre. These data demonstrate that this LBNP strategy could effectively protect cerebral perfusion with dominant improvement of diastolic flow during push-pull manoeuvres.

Characteristics of in-situ stress and its controls on coalbed methane development in the southeastern Qinshui Basin, North China

In-situ stress is a key reservoir parameter to evaluate reservoir permeability, hydraulic fractures, coal seam deformation and coalbed methane (CBM) recovery. With limited CBM test wells in the Zhengzhuang field, southeast of the Qinshui basin, North China, the in-situ stress data is inadequate for CBM exploration and development. It is necessary to find a method to predicate in-situ stress through other exploration data such as geophysical well loggings. In this study, we provide a new well-logging data-based model to predicate the in-situ stress based on 17 sets of well test data and comprehensive logging data. As a distinguished characteristic of this model, different structural compartmentalization of CBM reservoirs was considered. A regional adaptive residual strain index was introduced to the model. Based on the model, the in-situ stress distribution in the Zhengzhuang field were evaluated systematically, and the influences of in-situ stress on permeability and the propagation of hydro-fractures were discussed. Results indicate that the magnitude of the maximum (SHmax,14.19–45.40 MPa) and minimum horizontal stresses (Shmin, 10.62–28.38 MPa) and the gravitational stress (Sv, 9.58–30.82 MPa) all show positive correlations with burial depths. The in-situ stress fields in the study area are characterized by 1) SHmax > Sv > Shmin in shallow layers (<700 m), indicating a dominant strike-slip faulting stress regime; 2) Sv ≈ SHmax > Shmin and SHmax > Sv > Shmin in the depth of 700–1050 m, suggesting a transformed regime; and 3) SHmax > Sv > Shmin in deep layers (>1050 m), indicating a strike-slip faulting stress regime. The SHmax in the study area is orientated by NE-SW, with a trend of 40°–49°. Resulted from the change of the in-situ stress regimes from shallow (500 m) to deep layers (∼1000 m), the reservoir permeability variation shows a typical increase followed by decrease. The presence of natural fractures significantly affect the propagation pattern of hydraulic fractures, and the length difference between the major and branch fractures increases with increasing stress anisotropy in the Zhengzhuang field.

Between a beam and catenary: Influence of geometry on gravitational stresses and stability of natural rock arches

The self-weight of freestanding natural arches imparts stresses on the lintel and abutments, setting the conditions for rock fracture and erosion. Rock is weak in tension, therefore an ideal arch form is one that minimizes tensile stresses and supports the weight of the lintel in compression, e.g. an inverted catenary. However, rock mass structure, including bedding, cross-bedding and other discontinuities, often imparts strong control on the geometry of arches, leading to forms that are less favorable from a stress perspective. Here we analyze a suite of nineteen arch models created from ground- and drone-based photogrammetry to assess the three-dimensional static stress field under gravitational loading. The models represent a range of arch lengths from 4 to 88 m, as well as a variety of forms, and use material properties previously calibrated from dynamic analysis of ambient vibrations. Our results demonstrate that arches shaped like beams have relatively high tensile stresses and a nearly symmetrical statistical distribution of principal stresses, while those with convex forms have comparably lower tensile stresses and statistical distributions favoring compressive stresses. In-situ observations of tensile cracks frequently correspond to the location of predicted tensile stresses in our models. We calculated the ratio of mean principal stresses for each arch, which is theoretically 1 for a flat prismatic beam and approaches infinity for an ideal inverted catenary. We found several arches with mean principal stress ratio around 1 and that values increased with lintel convexity. These results indicate that while self-sculpture might attempt to create ideal stress-based forms, discontinuities can control lintel geometry and natural arches evolve with forms that may be less favorable for long-term stability. The mean principal stress ratio is a simple metric to classify and compare arches, useful for assessment of arch stability supporting conservation and hazard analyses.

Strain and retrogression partitioning explain long-term stability of crustal roots in stable continents

Abstract Away from tectonically active regions, the continental crust has an average thickness of 40 ± 1 km. Yet, it shows a remarkable variability from 25 to 65 km, comparable to that of the most tectonically active regions. Here, we consider the problem of the formation and preservation of anomalous deep crustal roots in stable intracontinental regions. Using two-dimensional thermomechanical experiments, we show that the interplay between partial melting, the formation of garnet-pyroxene-bearing rocks, and their strain rate–dependent retrogression result in the preservation of thick and strong crustal roots. We argue that it is the partitioning into narrow regions of strain, retrogression, and weakening coupled into a positive feedback loop that explains why strong high-grade crustal roots remain largely immune to gravitational stresses and are able to persist over hundreds of millions of years.

Experimental study of coal burst risk prediction using fractal dimension analysis of AE spatial distribution

The sustainable and clean mining of coal is essential for Australia and the world as coal is a key energy source. However, with the increase of mining depth, many coalmines are facing potential coal burst hazards as deep mining always associated with high gravitational stress and complicated geology. More recently, the coal burst risk is highlighted by accidents happened at Austar and Appin coalmines in Australia. Assumedly due to long time mining history with relatively shallow mining depth, coalmines in Australia has no coal burst history and corresponding risk controlling plans, technics and equipment. This paper proposes a novel method for coal burst risk prediction based on fractal dimension analysis of AE spatial distribution. Besides, this paper introduces the mathematical analysis method of fractal dimension based on dimension calculation formula and MATLAB coding. Finally, obvious fractal dimension decrease of AE spatial distribution is observed in experimental study of coal samples with high burst propensity, which promises the feasibility of coal bursts prediction through AE monitoring.

Ground Reaction Forces generated by a Lower Body Negative Pressure Exercise Device for Space Flight

Loss of bone and muscle are leading concerns among astronauts during prolonged space flight. Lower body negative pressure (LBNP) chambers generate gravitational and cardiovascular stresses to maintain musculoskeletal strength and fitness by means of suction pressure. Ground reaction forces (GRFs) generated underneath the user’s feet are directly proportional to the level of negative pressure applied. However, the exact mechanism of GRF generation remains unresolved. We hypothesize that increasing the cross‐sectional area (CSA) of the user’s waist in contact with a flexible waist seal will increase the GRFs generated at a given vacuum pressure. To test our hypothesis, we collected GRFs generated by 6 healthy subjects under two conditions: original (unchanged) CSA of their waist and a greater waist CSA using expanded cushioning around waist of the same subjects. GRFs were measured with LBNP levels ranging from 0 (ambient pressure) to 50 mmHg with subjects lying in supine position to simulate microgravity. The original CSA of 467.7 cm2 ± 69.0 cm2 generated 118 % ± 31 % body weight at −50 mmHg. However, the larger CSA of 1,451.0 cm2 ± 331.0 cm2 generated a mean GRF of 146 % ± 31% body weight at −50 mmHg. A one‐way ANOVA test resulted in p‐values &lt; 0.05 for all pressures, denoting statistically significant increases in larger compared with original CSA GRF. The GRF generated with larger CSA followed this equation GRF = −1.8211 (LBNP) + 0.7899 while the GRF generated with original CSA followed the equation: GRF = −1.5079 (LBNP) + 0.3995. These data support our hypothesis that GRFs generated by LBNP are directly proportional to the waist CSA. Using this new concept, astronauts may generate GRFs at lower LBNP levels to prevent pre‐syncopal symptoms during exercise in space.Support or Funding InformationSupported by NASA grants NNX13AJ12G and NSSC19K0409.Average weight measurements with varying pressures for six volunteers; red is original CSA of subject's waist and blue is larger CSA.Figure 1

Geomechanical aspects of formation of natural stresses in a concrete mount of a shaft shaft

In the presented studies, the laws of the formation of natural stresses in the rock mass are confirmed, which are the sum of gravitational, static tectonic and variable components that have a variable value as a result of uniform periodic volume expansion and contraction of the Earth. The problem of trunk stability is due to the need to solve problems to determine the level of stress-strain state and strength properties in concrete supports. The stress parameters in the lining of the shafts and the monitoring of their changes are determined using a new method for measuring unloading strains. When comparing the stresses obtained experimentally by analytical methods in the concrete support of mine shafts from 2013 to 2019 at experimental test sites in the support having the lengths of bases of 1600 and 70 mm, provided that the number of geoblock ranks at this base is two, a connection with the results of measurements in an array of rocks based on 50 m with an average size of structural blocks of 0.5 m and an investment coefficient of l = 5, which corresponds to three ranks of geoblocks. In practice, it is proposed to use the main identified provisions, namely: the stress state of the mine shaft lining, which is formed as a function of their structural parameters, the full tensor of gravitational tectonic stresses acting in the rock mass at the time of the start of research and time variables, which are determined by natural and analytical methods.

The effects of high gravitational stress on the expression of stress response genes in Arabidopsis thaliana

As humans venture farther into space, we are increasingly interested in how plants respond to the unique conditions of spaceflight. This experiment focuses on how gene expression in the model plant Arabidopsis thaliana is affected by high-gravitational stress that is comparable to the amount experienced on a small model rocket. The genes chosen have been studied previously for their roles in mechanical stress and pathogen response. Our results showed an increase in expression of the genes TCH2, TCH3, and MPK3, no change in the expression of CBP60g, and a decrease in the expression of RCI3 and ICS1. These results are largely consistent with spaceflight data and warrant further investigation into the effects of rocket launch on plant growth.

Space explorers need to be space farmers: What we know and what we need to know about plant growth in space

Space exploration will require life support systems, in which plants can provide nutrients, oxygen, moisture, and psychological well-being and eliminate wastes. In alien environments, plants must adapt to a different gravity force, even the zero gravity of spaceflight. Under these conditions, essential cellular and molecular features related to plant development are altered and changes in gene expression occur. In lunar gravity, the effects are comparable to microgravity, while the gravity of Mars produces milder alterations. Nevertheless, it has been possible to develop and reproduce plants in space. Current research seeks to identify signals replacing gravity for driving plant growth, such as light. Counteracting gravitational stress will help in enabling agriculture in extraterrestrial habitats.

Back Analysis of the Initial Geo-Stress Field of Rock Masses in High Geo-Temperature and High Geo-Stress

In a high geo-temperature environment, it is rarely reported that geo-temperature has been considered during a back analysis. This may cause the initial geo-stress field that is obtained by a back analysis to be wrong. In this study, according to the theory of elasticity, the theoretical solution of the hydraulic fracturing equation is obtained in a high geo-temperature environment. Since the vertical stress that is obtained by the hydraulic fracturing method is calculated using the density of overlying strata, this vertical stress lacks the thermal stress that is caused by geothermal gradients. Therefore, in a high geo-temperature environment, inverting the initial geo-stress field of rock masses directly using the stress that is measured by the hydraulic fracturing method can cause serious errors. We propose that the regression coefficient of a gravitational stress field should be set to one during a back analysis if stresses are measured by the hydraulic fracturing method, and this regression coefficient should not be equal to one if stresses are measured by overcoring methods. We also propose a workflow for the back analysis of the initial geo-stress field of rock masses that considers geo-temperature, and this workflow is applied to the Sangzhuling tunnel in China.

Microscopic precursors of failure in soft matter.

The mechanical properties of soft matter are of great importance in countless applications, in addition of being an active field of academic research. Given the relative ease with which soft materials can be deformed, their non-linear behavior is of particular relevance. Large loads eventually result in material failure. In this Perspective article, we discuss recent work aiming at detecting precursors of failure by scrutinizing the microscopic structure and dynamics of soft systems under various conditions of loading. In particular, we show that the microscopic dynamics is a powerful indicator of the ultimate fate of soft materials, capable of unveiling precursors of failure up to thousands of seconds before any macroscopic sign of weakening.

Incommensurate Crystallization of Neutron Matter in Neutron Stars

The composition of the neutron stars from its surface region, outer-core, inner-core, and to its center is still being investigated. One can only surmise on the properties of neutron stars from the spectroscopic data that may be available from time to time. A few models have suggested that the matter at the surface region of the neutron star is composed of atomic nuclei that get crushed under extremely large pressure and gravitational stress, and this leads to the creation of solid lattice with a sea of electrons, and perhaps some protons, flowing through the gaps between them. Nuclei with high mass numbers, such as ferrous, gold, platinum, uranium, may exist in the surface region or in the outer-core region. It is found that the structure of the neutron star changes very much as one goes from the surface to the core of the neutron star. The surface region is extremely hard and very smooth. Surface irregularities are hardly of the order of 5 mm, whereas the interior of the neutron star may be superfluid and composed of neutron-degenerate matter. However, the neutron star is highly compact crystalline systems, and in terrestrial materials under pressure, many examples of incommensurate phase transitions have been discovered. Consequently, the properties of incommensurate crystalline neutron star have been studied. The composition of the neutron stars in the super dense state remains uncertain in the core of the neutron star. One model describes the core as superfluid neutron-degenerate matter, mostly, composed of neutrons , and a small percentage of protons and electrons More exotic forms of matter are possible, including degenerate strange matter. It could also be incommensurate crystalline neutron matter that could be BCC or HCP. Using principles of quantum statistical mechanics, the specific heat and entropy of the incommensurate crystalline neutron star has been calculated assuming that the temperature of the star may vary between to . Two values for the temperature T that have been arbitrarily chosen for which the calculations have been done are and . The values of specific heat and entropy decrease as the temperature increases, and also, their magnitudes are very small. This is in line with the second law of thermodynamics.

Dynamic behaviors of sedimenting colloidal gel materials: hydrodynamic interactions

It is a highly nonlinear poromechanics phenomenon that colloidal gel materials that are exposed to a gravitational stress greater than their yield stress undergo elastic compression. Here, we resolve theoretically the dynamic behaviors of colloidal gel settling in a closed cylindrical tube of finite height. We develop an extended phenomenological model by considering the hydrodynamic interactions between the backflow of the interstitial fluid and the sedimenting gel columns. We address the hydrodynamic signature by assembling a cylindrical streamer channel into pure Darcy's flow regime, and therefore our continuous model enables us to explore how geometric confinement exerted by the wall affects the colloidal gel sedimentation in a closed tube, which extends beyond the conventional poroelastic model. The results suggest a dynamically propagating strain rate from the gel bottom towards the settling gel front, which demonstrates the duality characteristics of fluidity and solidity for all gel types in our calculations. Our results confirm the vital role that geometric confinement has in association with hydrodynamic interactions in speeding up the sedimentation in gels because the average velocity of the settling front and the bulk sedimentation velocity of the gel particle (cluster) increase significantly under confinement. Furthermore, an analytical model we derive identifies the functional correlation of the velocity ratio to concentration in the compressive sedimentation regime of the gel. The numerical and analytical results collaboratively elucidate a signature that the compressive regime in the settling gel can be suppressed by the confinement, but strengthened again as the confinement increases to exceed a threshold. This threshold is shown to highly depend on the gel softness and initial particle loadings. Our systematic investigations benefit desirable strategies to manage the sedimentation dynamics of colloidal gel materials for application in various fields.

Manufacturing and Control of a Robotic Device for Time-averaged Simulated Micro and Partial Gravity of a Cell Culture Environment

Gravity is omnipresent for all objects on Earth. However, in an environment of different gravitational stress (e.g., microgravity or partial gravity), cells and organs show different biological responses. So, researchers have attempted to achieve micro- or partial gravity on Earth through various approaches, such as parabolic flight or free fall. However, the duration of such ground experiments is highly limited, making it very difficult to conduct time-consuming tasks, such as cell culture. Thus, a three-dimensional (3D) clinostat is utilized as an alternative for experiments on the International Space Station. It provides time-averaged simulated micro- and partial gravity by using mechanical frames with two rotating actuators. This study proposes novel control algorithms for simulating micro- and partial gravity and validates them by applying it to the control of a manufactured 3D clinostat. First, the novel algorithm for time-averaged simulated microgravity (taSMG) provided a more uniformly distributed gravity field by reducing two poles the gravity-concentrated areas. The taSMG with reduced poles provides isotropic gravitational patterns, from which it is possible to minimize the unnecessary effect due to nonuniformity of the gravity vector direction. Second, the other suggested novel algorithm for time-averaged simulated partial gravity (taSPG) controls the pole sizes asymmetrically to generate the intended size of partial gravity. The suggested algorithms are based on mathematical models rather than totally randomized motions. Therefore, the convergence of gravity values, in the rotating frame over time, can be analytically predicted with improved accuracy compared with previously reported algorithms. The developed 3D clinostat hardware and algorithms will effectively provide well-validated taSMG and taSPG for cell growth experiments in future studies for space medicine.

RNAseq Analysis of the Response of Arabidopsis thaliana to Fractional Gravity Under Blue-Light Stimulation During Spaceflight.

Introduction: Traveling to nearby extraterrestrial objects having a reduced gravity level (partial gravity) compared to Earth’s gravity is becoming a realistic objective for space agencies. The use of plants as part of life support systems will require a better understanding of the interactions among plant growth responses including tropisms, under partial gravity conditions.Materials and Methods: Here, we present results from our latest space experiments on the ISS, in which seeds of Arabidopsis thaliana were germinated, and seedlings grew for six days under different gravity levels, namely micro-g, several intermediate partial-g levels, and 1g, and were subjected to irradiation with blue light for the last 48 h. RNA was extracted from 20 samples for subsequent RNAseq analysis. Transcriptomic analysis was performed using the HISAT2-Stringtie-DESeq pipeline. Differentially expressed genes were further characterized for global responses using the GEDI tool, gene networks and for Gene Ontology (GO) enrichment.Results: Differential gene expression analysis revealed only one differentially expressed gene (AT4G21560, VPS28-1 a vacuolar protein) across all gravity conditions using FDR correction (q < 0.05). However, the same 14 genes appeared differentially expressed when comparing either micro-g, low-g level (< 0.1g) or the Moon g-level with 1g control conditions. Apart from these 14-shared genes, the number of differentially expressed genes was similar in microgravity and the Moon g-level and increased in the intermediate g-level (< 0.1g), but it was then progressively reduced as the difference with the Earth gravity became smaller. The GO groups were differentially affected at each g-level: light and photosynthesis GO under microgravity, genes belonged to general stress, chemical and hormone responses under low-g, and a response related to cell wall and membrane structure and function under the Moon g-level.Discussion: Transcriptional analyses of plants under blue light stimulation suggests that root blue-light phototropism may be enough to reduce the gravitational stress response caused by the lack of gravitropism in microgravity. Competition among tropisms induces an intense perturbation at the micro-g level, which shows an extensive stress response that is progressively attenuated. Our results show a major effect on cell wall/membrane remodeling (detected at the interval from the Moon to Mars gravity), which can be potentially related to graviresistance mechanisms.

The dimensional stability assessment of the composite honeycomb panel for the conditions of thermal and gravitational loading in a Near-Earth Orbit

The results of the numerical determination of the stress-strain state of the composite honeycomb panel under gravitational and thermal loads of varying intensity in a near-earth orbit are presented. As a simulation model of the structure under study, a typical structure of a composite cell panel with a known type of cell arrangement of honeycomb aluminum filler and reinforcement schemes for layers of carbon fiber material for upper and lower plates with known thermomechanical properties was chosen. To solve the problems of thermoelasticity, we used the finite element method in mathematical formulations for stationary thermal and quasistatic thermomechanical analysis. The distribution of the values of von Mises equivalent stresses in the structural elements of the honeycomb panel under thermal loads in the temperature range from -80 to +80 is determined. The longitudinal and transverse deflections of the honeycomb from the action of thermal loads of various intensities in the near-earth orbit are found. The limiting value of the temperature difference between the outer surfaces of the plates, which ensures the thermal stability of the composite honeycomb panel, has been established. The maximum deflections of the honeycomb have been found out from gravitational and thermal stresses in the near-Earth orbit.