Research on fatigue damage and dilatancy properties for salt rock under discontinuous cyclic loading

Étant donné que le stockage de gaz naturel ou d’air comprimé dans des niveaux souterrains constitués de sel joue un rôle essentiel pour assurer l'approvisionnement en énergie sur le long terme, le gouvernement chinois a construit de nombreux lieu de stockage dans ces niveaux géologiques ces dernières années. En raison des variations saisonnières de la pression gaz / air, les entrepôts subissent des chargements cycliques qui provoquent la fatigue des roches et conduisent à des risques de rupture qu’il faut maîtriser pour des raisons liées à la sécurité et à l'environnement. La compréhension des processus de fatigue discontinue du sel sous chargement cyclique est donc très importante et fait l'objet de cette étude, qui se concentre sur des recherches expérimentales et le développement de modèles constitutifs décrivant la déformation sous fatigue. Cette thèse s’articule suivant la méthodologie suivante : ① des essais de chargement cyclique classique pour étudier les propriétés basiques de la fatigue dans le sel. ② des tests de charge cyclique discontinu pour explorer les processus de fatigue discontinue. ③ l’instrumentation pour détecter les émissions acoustiques afin de suivre l'évolution des dommages causés par la fatigue dans le sel. ④ Le développement à la base des résultats expérimentaux obtenus de modèle constitutif pour la fatigue discontinue.Since the salt cavern storage of natural gas and compressed air plays a critical role in ensuring the energy supply and adjusting the seasonal imbalance of power, China government has been constructing numerous new storages in recent years. Because of the seasonal of the seasonal variations of the gas/air pressure, the storages undergo cyclic loading, which causes rock fatigue and induces the associated safety and environmental hazards. The investigation of the discontinuous fatigue of salt under cyclic loading is therefore very important and is the subject of this study, which focuses on the experimental investigations and the development of the constitutive models describing the fatigue deformation. This thesis includes the following principal parts: ① Conventional cyclic loading testing to investigate the basic properties of fatigue in salt. ② Discontinuous cyclic loading tests testing to investigate the discontinuous fatigue. ③ Acoustic emission detecting experimentation to track the evolution of the fatigue damage in the salt. ④ Development of the fatigue life model and constitutive model for the discontinuous fatigue, based on the obtained experimental results

Recherche de propriétés de fatigue dommages et dilatance de roche sous chargement cyclique discontinu

Since the salt cavern storage of natural gas and compressed air plays a critical role in ensuring the energy supply and adjusting the seasonal imbalance of power, China government has been constructing numerous new storages in recent years. Because of the seasonal of the seasonal variations of the gas/air pressure, the storages undergo cyclic loading, which causes rock fatigue and induces the associated safety and environmental hazards. The investigation of the discontinuous fatigue of salt under cyclic loading is therefore very important and is the subject of this study, which focuses on the experimental investigations and the development of the constitutive models describing the fatigue deformation. This thesis includes the following principal parts: ① Conventional cyclic loading testing to investigate the basic properties of fatigue in salt. ② Discontinuous cyclic loading tests testing to investigate the discontinuous fatigue. ③ Acoustic emission detecting experimentation to track the evolution of the fatigue damage in the salt. ④ Development of the fatigue life model and constitutive model for the discontinuous fatigue, based on the obtained experimental results.Étant donné que le stockage de gaz naturel ou d’air comprimé dans des niveaux souterrains constitués de sel joue un rôle essentiel pour assurer l'approvisionnement en énergie sur le long terme, le gouvernement chinois a construit de nombreux lieu de stockage dans ces niveaux géologiques ces dernières années. En raison des variations saisonnières de la pression gaz / air, les entrepôts subissent des chargements cycliques qui provoquent la fatigue des roches et conduisent à des risques de rupture qu’il faut maîtriser pour des raisons liées à la sécurité et à l'environnement. La compréhension des processus de fatigue discontinue du sel sous chargement cyclique est donc très importante et fait l'objet de cette étude, qui se concentre sur des recherches expérimentales et le développement de modèles constitutifs décrivant la déformation sous fatigue. Cette thèse s’articule suivant la méthodologie suivante : ① des essais de chargement cyclique classique pour étudier les propriétés basiques de la fatigue dans le sel. ② des tests de charge cyclique discontinu pour explorer les processus de fatigue discontinue. ③ l’instrumentation pour détecter les émissions acoustiques afin de suivre l'évolution des dommages causés par la fatigue dans le sel. ④ Le développement à la base des résultats expérimentaux obtenus de modèle constitutif pour la fatigue discontinue

Recherche de propriétés de fatigue dommages et dilatance de roche sous chargement cyclique discontinu

Since the salt cavern storage of natural gas and compressed air plays a critical role in ensuring the energy supply and adjusting the seasonal imbalance of power, China government has been constructing numerous new storages in recent years. Because of the seasonal of the seasonal variations of the gas/air pressure, the storages undergo cyclic loading, which causes rock fatigue and induces the associated safety and environmental hazards. The investigation of the discontinuous fatigue of salt under cyclic loading is therefore very important and is the subject of this study, which focuses on the experimental investigations and the development of the constitutive models describing the fatigue deformation. This thesis includes the following principal parts: ① Conventional cyclic loading testing to investigate the basic properties of fatigue in salt. ② Discontinuous cyclic loading tests testing to investigate the discontinuous fatigue. ③ Acoustic emission detecting experimentation to track the evolution of the fatigue damage in the salt. ④ Development of the fatigue life model and constitutive model for the discontinuous fatigue, based on the obtained experimental results.Étant donné que le stockage de gaz naturel ou d’air comprimé dans des niveaux souterrains constitués de sel joue un rôle essentiel pour assurer l'approvisionnement en énergie sur le long terme, le gouvernement chinois a construit de nombreux lieu de stockage dans ces niveaux géologiques ces dernières années. En raison des variations saisonnières de la pression gaz / air, les entrepôts subissent des chargements cycliques qui provoquent la fatigue des roches et conduisent à des risques de rupture qu’il faut maîtriser pour des raisons liées à la sécurité et à l'environnement. La compréhension des processus de fatigue discontinue du sel sous chargement cyclique est donc très importante et fait l'objet de cette étude, qui se concentre sur des recherches expérimentales et le développement de modèles constitutifs décrivant la déformation sous fatigue. Cette thèse s’articule suivant la méthodologie suivante : ① des essais de chargement cyclique classique pour étudier les propriétés basiques de la fatigue dans le sel. ② des tests de charge cyclique discontinu pour explorer les processus de fatigue discontinue. ③ l’instrumentation pour détecter les émissions acoustiques afin de suivre l'évolution des dommages causés par la fatigue dans le sel. ④ Le développement à la base des résultats expérimentaux obtenus de modèle constitutif pour la fatigue discontinue

Numerical modeling of the opening mode fracturing emanating from deformation localization in layered rocks

International audienceIt is known that rock fracture includes inelastic straining or damage that should localize at a certain loading stage and result in fracture initiation. The details of this process are not clear, and it is frequently omitted in the models by imposing the initial microcracks (seeds) with certain lengths and orientations. Here we investigate 2-D systems of three layers in finite-difference models. The layers subjected to the horizontal extension are separated by cohesive-frictional interfaces and have contrasted properties typical of sedimentary piles. Fractures are initiated in a more brittle central layer in the vicinity of the interfaces with the adjacent layers. It starts with the initially distributed inelastic straining, which then localizes into narrow bands. The damage within these bands is strongly accelerated, resulting in complete material failure locally. Short initial fractures corresponding to narrow bands of failed material are normal to the least local stress. They then propagate from the interfaces to the layer center with further extension. We carefully investigate the impact of different regularization procedures, the grid geometry, and structure on all stages of the fracture process and define the optimal conditions that can be applied for fracture modeling in different structural and loading configurations

Fatigue effects of discontinuous cyclic loading on the mechanical characteristics of sandstone

International audienc

National analysis of urinary cadmium concentration and kidney stone: Evidence from NHANES (2011–2020)

BackgroundThe association between urinary cadmium and kidney stone risk is inconsistent in previous studies, which needs further exploration. This study was performed to explore the association between urinary cadmium and kidney stone.Materials and methodsData from the National Health and Nutrition Examination Survey (2011–2020) were included and further analyzed. Urinary cadmium was stratified into quartiles with quartile 1 (Q1: 0.025–0.104 μg/L) and quartile 4 (Q4: 0.435–7.581 μg/L). Further weighted logistic regression was adopted to evaluate the association between urinary cadmium and kidney stone. A subgroup analysis was used to verify the findings. The non-linear association was examined using the restricted cubic spline (RCS) regression.ResultsA total of 9,056 adults aged 20 years and above were included in this study. In the fully adjusted model, an increased risk of kidney stones was identified for quartile 2 (OR = 1.40, 95% CI = 1.06–1.84, P < 0.05), quartile 3 (OR = 1.18, 95% CI = 0.88–1.59, P > 0.05), and quartile 4 (OR = 1.54, 95% CI = 1.10–2.06, P < 0.05). A similar association was found between continuous cadmium increase and OR of kidney stones in the fully adjusted model (OR = 1.13, 95% CI = 1.01–1.26, P < 0.05). The RCS also indicated a non-linear association between urinary cadmium concentration and kidney stone risk (P for non-linear < 0.001).ConclusionIn summary, cadmium exposure is identified as a risk factor for kidney stones in this study. Their non-linear association makes demands on early intervention for the cadmium-exposed population. Medical interventions for kidney stone prevention should take cadmium exposure into account

Research on Strategies and Methods Suppressing Permanent Magnet Demagnetization in Permanent Magnet Synchronous Motors Based on a Multi-Physical Field and Rotor Multi-Topology Structure

In this paper, a permanent magnet synchronous motor (PMSM) with sleeves on the rotor outer surface is investigated. The purpose of sleeves is to fix the permanent magnets and protect them from being destroyed by the large centrifugal force. However, the sleeve material characteristics have a great influence on the PMSM, and therewith, most of the rotor eddy-current losses are generated in the rotor sleeve, which could increase the device temperature and even cause thermal demagnetization of the magnets. Thus, a sleeve scheme design with low eddy-current losses is necessary, and a method suppressing the local temperature peak of permanent magnets is presented. The 3-D electromagnetic finite element model of a 12.5 kW, 2000 r/min PMSM with a segmented sleeve is established, and the electromagnetic field is calculated by using the finite element method. The results show the effectiveness of the presented method in reducing the eddy current losses in the rotor. Using the thermal method, it can be found that the maximum temperature position and zone of permanent magnet will change. Thus, some strategies are comparatively analyzed in order to obtain the change rule of the position and zone. The obtained conclusions may provide a useful reference for the design and research of PMSMs