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Shaking table tests of large cross-sectional multi-crack tunnel linings
Get PDFTo study the dynamic response law of large-section cracked lining structures under seismic waves, comparative tests of large-scale shaker tunnel models of non-destructive lining structure (model 1), a crack in the vault of the lining structure (model 2), and two parallel cracks in the vault of the lining structure (model 3) were carried out by applying 0.1-1.0 g progressively increasing the peak acceleration of the input waves. This paper visually showed the distribution of cracks in three groups of the lining structures. In addition, the acceleration response of the lining and surrounding rock, dynamic soil pressure, the dynamic strain on the inner and outer surfaces of the lining, and dynamic internal force variation were obtained, and the seismic performance of three groups of lining structures was discussed. The results showed that the seismic weak positions of model 1 were the arch shoulder and the arch foot, the seismic weak positions of model 2 were the arch shoulder, the arch foot, the initial damage area, and the inverted arch, and the seismic weak positions of model 3 were the positions of the arch foot, the cracks of the vault, the inverted arch, and the arch wall. The soil pressure values at the vault of three groups of models were model 2 > model 1 > model 3 in turn. The surrounding rock amplified the input seismic waves. With the gradual increase of the peak acceleration, the seismic energy was gradually consumed due to plastic damage to the lining structure or the loosening and destruction of the overlying soil, resulting in the acceleration amplification coefficient value of the surrounding rock in the upper part of the lining structure showing a changing trend of first increasing and then decreasing. When the peak acceleration was 0.2 g, the crack propagation phenomenon occurs in the initial crack position of model 2 and model 3. When the peak acceleration was 0.4 g, the cracking phenomenon occurs at the right arch foot of model 1. The above phenomenon confirmed the conclusion that cracks can weaken the seismic performance of the structure. When the peak acceleration was 0.8 g, the peak values of the amplification coefficient of the lining at the inverted arch and near the filled soil surface were about 1.2 and 1.6 respectively. The research results can provide a reference for the seismic performance evaluation of cracked tunnels
Sensitive analysis on added damping of shunted piezoceramic damping: cantilever and simply supported beam
Get PDFThe current research investigates the prediction of piezoelectric damping of resistively shunted beams caused by resistors via joule heating. In order to maximize the extra damping of the piezoelectric shunted beam system, a sensitivity analysis was done. The geometrical impacts on the maximum additional damping simulation are investigated for different length and thickness ratios with the position of the PZT-5H from the base of the cantilever and simply supported beams. Prior to doing sensitivity analysis, a mathematical model for estimating extra damping from voltage produced. Validation experiments are also carried out
Experimental study on continuous firing vibration response of the typical machine guns under different ground conditions
Get PDFIn order to study the influence of ground conditions on the continuous firing vibration response of typical machine gun, and find out under which conditions the machine gun is most stable. A high-speed photography method was used to measure the motion of multiple parts. The motion curve of each part in the shooting process are obtained, and the projectile dispersion are recorded. According to the results, the motion characteristics of each part is analyzed. The pitching and translational quasi-periodic motions of the whole gun under different ground conditions are compared by synthesizing the motion data of various parts. The working modes of gun tripod under different ground conditions are discussed, and are compared according to the corresponding projectile dispersion. The result show that, in quasi-periodic pitching motion, the upward pitching motion response of the gun under the condition of cement ground is large, the ability to restore the initial position is poor, and the corresponding vertical dispersion is the worst. Under the soil condition, the upward and downward pitching motion cycle of the gun is relatively stable, the ability to restore the initial position is strong, and the corresponding vertical dispersion is the best. In terms of quasi-periodic translational motion, the translational motion of the gun mount under the cement ground is the biggest, and the corresponding horizontal dispersion is also the biggest. Under the soil ground condition, the translational motion is the smallest, and the corresponding horizontal dispersion is also the smallest
Longitudinal deformation of Shield tunnel based on construction monitoring data
Get PDFThe rapid development of urbanization has changed the traffic and transportation in the central area. The change of the surrounding rock and structural stress state of the project under construction caused by the tunnel construction in the same period has caused great harm to its safe use and casualties. Shield construction technology can achieve safe excavation and lining, with high degree of automation. And it is a relatively common construction method at present. But its adaptability to section size and section environmental conditions is poor. In view of this, from the analysis of construction monitoring data, the study established a longitudinal model considering lateral effects from the perspective of lateral characteristics. It also achieved stress assessment and improvement through lateral deformation calculation, segment ring bolt calculation and formula correction. The experimental results showed that the opening at the circumferential seam of the right line of the test tunnel under this method is 8.9 mm. The radius of curvature is 758 mm, and the safety assessment level of longitudinal deformation is 3. This method can effectively guarantee the safety of shield tunnel construction and has good guiding value for tunnel management and maintenance
The optimization model of whole process engineering consulting consortium members based on Z-number
Get PDFAt present, there are very few enterprises with whole-process engineering consulting capability and qualification. To carry out consulting work in a consortium is a necessary way to meet the actual situation of the industry and promote whole-process consulting quickly, and the selection of consortium members is the key issue. First of all, this paper summarizes the construction principle of the index system of consortium member selection, and describes the index system. Aiming at the consortium member selection model, on the basis of comprehensive consideration of 9 indicators, the evaluation value of Z-Numbers fuzzy numbers is obtained by using seven-point language terms, the index weight and expert weight are obtained by using the sequential method and entropy weight method, and the data are processed to get the alternative enterprise evaluation matrix. Fuzzy TOPSIS method suitable for Z-Numbers was introduced to solve the positive ideal solution closeness degree of each enterprise, so as to rank the alternative enterprises
Design and analysis of a 4-axis cartesian robot for unloading plastic injection machines in industrial applications
Get PDFIn both industrial and educational settings, efficient handling of products from Plastic Injection Machines is crucial for precise and stable system operation. Enhancements in the design and production processes, achieved through the implementation of a Four Axis (4D) BOM type Cartesian System, lead to significant improvements in cost-effectiveness and product quality. In this study focuses on optimizing system operations, including rotational movements and the operation of the vertical cylinder through forward-backward movements. Finite element analysis is employed to investigate potential issues arising from shape changes in the mechanical structure due to dynamic loads on the plate joint connections. By addressing these concerns during the design phase through simulation, mechanical structure errors are eliminated, resulting in improved system performance
Rigid-flexible coupling modeling of the dual-rotor system for aero-engine
Get PDFThe dual-rotor system is the core component of advanced aero-engine. Establishing a reasonable, accurate, and efficient dynamics model is the key to studying the dynamics and vibration of the rotor system for aero-engine. This manuscript takes a representative aircraft engine dual-rotor system as a prototype, considers the rig-id-flexible coupling characteristics of different stiffness elastic supports and rotor structures, and establishes an analytical dynamic model of the dual-rotor system. Based on the established dynamic model, the natural char-acteristics of the dual-rotor system are analyzed. The model was validated using two different research methods: the rigid-flexible coupling multi-body system dynamics simulation platform ADAMS, and finite element analy-sis. The dynamic model of the dual-rotor system established in this paper can meet the requirements of hierar-chical rigid-flexible coupling of system and structure, overall mass distribution, and stiffness distribution. In particular, it can also effectively realize the simulation of multi-facet and multi-phase unbalanced vibration of the rotor system. The research methods of this paper can further enrich the basic theory of dynamics and vibration of the aero-engine rotor system
Test and application of movable steel barrier with grade SB light composite corrugated beam
Get PDFIn this study, movable steel barrier with grade SB light composite corrugated beam is designed, which addresses the problems of the prior central partition belt portable guardrail in terms of easy mobility, local safety, easy construction, and other indications. This guardrail employs explicit algorithms to conduct a dynamic finite element simulation analysis and a real vehicle crash test, and verifies the guardrails' blocking, guiding, and buffering functions in accordance with the SB level collision conditions listed in the Standard for Safety Performance Evaluation of Highway Barriers (JTG B05-01-2013). According to the results, the safety performance of SB grade lightweight composite corrugated beam movable steel guardrail meets the requirements of the Standard for Safety Performance Evaluation of Highway Barriers (JTG B05-01-2013). In addition, the guardrail can be opened for 12 meters in 1 minute and returned to close in 2 minutes. The opening and restoration of the movable guardrail is superior to the previous central divider movable guardrail. This guardrail has been tried for some high-speed and its safety performance has been verified again in actual high-speed vehicle collisions
Production analysis of manufacturing industry in a single vacation policy under disaster
Get PDFThe disaster in queueing system with second optional service is considered. Arriving customer of this system will receive the essential service and optional second service if needed. When the system is interrupted by the disaster, the server initiates the repair period making all the customer leave the system immediately. The server, when idle, takes single vacation. The disaster cannot happen when server is under vacation or in repair period. The above queueing system is analysed using supplementary variable technique to obtain the probability generating function for various parameters and effects of parameters are explained graphically with numerical illustrations
Research on lightweight pedestrian detection based on improved YOLOv5
Get PDFAiming at the problems of low detection accuracy and the large size of the pedestrian detection algorithm, to improve the edge intelligent recognition capability of the terminal, this paper proposes a lightweight pedestrian detection scheme based on the improved YOLOv5. In this paper, the algorithm first takes the original YOLOv5 as the basic framework and uses the Ghost Bottleneck module to replace the C3 module in the original YOLOv5 network to reduce the number of parameters, eliminate redundant features, and obtain a more lightweight model. Then the attention mechanism CBAM module is added to improve the feature extraction capability and detection accuracy of the algorithm. After experimental verification, the improved lightweight YOLOv5 algorithm significantly reduces the model size and computational cost while guaranteeing accuracy, which is suitable for deployment in edge devices