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Structural instability motion and optimization of the demolition and blasting scheme for complex continuous multi-span frame-shear structure
Get PDFDue to challenges faced during demolition and blasting processes such as conducting prototype monitoring tests on large continuous multi-span structures or carrying out full-area dynamic monitoring of overall structural stress; This paper takes the demolition of the Ruzhou Unicom building as the background, optimizes the design of the demolition and blasting program through theoretical analysis and simulation monitoring, and also studies the form of structural instability movement and the deformation of the key parts of the damage and internal force characteristics, and obtains the following conclusions: the axial force reaches the maximum value when the building is not deflected; when the first-order derivative of the shear force is 0, the maximum shear stress occurs at the position of 2/3 of the height of the building; When the first-order derivative of bending moment is 0, the maximum bending moment occurs at 1/3 of the building height. In Mushroom Pavilion incision formation, the support part of the main structure produces a downward force, exacerbating the disintegration of the main part of the damage; the main structure of the collapse process, the back row of columns are mainly presented as bending shear damage, the upper side beams are mainly presented as tensile damage, the central and lower side beams are mainly presented as compression shear damage. Notably, the bidirectional notch configuration results in a forward displacement of 9.5 meters and a subsequent recoil of 4.6 meters, providing effective shielding for the military fiber-optic cables positioned at the forefront and the adjacent deep excavation pits. Additionally, this configuration facilitates the rapid establishment of a stable collapse pattern between the Mushroom Pavilion structure and its main body, ultimately accelerating the disintegration of the overall building structure during the collapse event
Optimal control of lane changing problem of intelligent vehicle
Get PDFLanes changing is one of the basic behaviors of vehicle driving, which has a significant impact on road traffic safety and stability. Aiming at the problem of slow convergence rate in solving the optimal control problem of vehicle lane changing, an optimal lane changing control method based on hp adaptive pseudospectral method is proposed. By establishing a vehicle kinematic model, boundary constraints, and path constraints, combining with the physical process of vehicle lane changing the proposed method discretizes the control and state variables to transform the multi constraint optimal control problem into a nonlinear programming problem and the minimum vehicle lane changing time is set as the performance objective function. And also, the proposed method is compared with traditional solving methods. The simulation results show that the proposed method can effectively solve the optimal feasible lane changing trajectory and complete the lane changing maneuver process in the shortest possible time
Almaty ankle exoskeleton: comparative analysis and structural improvements of versions V.1 and V.2
Get PDFThis paper presents a comparative analysis of the V.1 and V.2 versions of the Almaty Ankle Exoskeleton. The main objective of the study is to identify the structural and functional shortcomings observed in the first version (V.1) and to develop an improved prototype in the second version (V.2) by addressing these issues. The paper compares the kinematic schemes, CAD models, and physical prototypes of both versions, highlighting their structural differences and technical advancements. In addition, the results of a static structural analysis performed on the V.2 prototype using the Finite Element Analysis (FEA) method are presented. This analysis allowed for the evaluation of stress, strain, and displacement distribution within the structure. The results demonstrated that the exoskeleton can effectively handle applied loads, although additional reinforcement is required in certain critical regions. Overall, the findings provide a foundation for engineering solutions aimed at enhancing the functional performance of the ankle exoskeleton and its application in rehabilitation processes
Improved CEEMD-based correction method for low-frequency shock response spectrum in large dual-wave shock tester devices
Get PDFThe shock response spectrum (SRS), calculated from a shock acceleration signal, is a critical indicator of shock environments. However, under intense loads, acceleration sensors are prone to trend term errors that can cause significant drift in the low-frequency spectral lines of large dual-wave shock tester devices. To address this issue, the complementary ensemble empirical mode decomposition (CEEMD) method was employed to decompose acceleration signals and restore the actual shock environment. Intrinsic mode functions (IMFs) were cross-correlated and compared to a predefined threshold to identify the effective IMF components required to reconstruct the signal. K-means clustering was employed to further validate the effectiveness of the IMFs for enhanced selection accuracy. Finally, the reconstructed acceleration signal was used to calculate a corrected SRS. The proposed approach demonstrated significant improvements over the traditional CEEMD algorithm. The corrected SRS exhibits a 5.6316 dB/oct slope in the low-frequency band, reflecting an equal displacement trend. The maximum error at the corresponding frequency was less than 6 % in comparison to the relative displacement response measured by low-frequency spring oscillators. This improved CEEMD correction method can effectively restore the actual shock environment of a dual-wave shock tester device, offering a valuable reference for evaluating shock resistance in onboard equipment
Coupling dynamics modeling and vibration characteristics analysis of TBM main drive system under complex tunnelling conditions
Get PDFIn order to ensure the reliable operation of TBM excavation process, it is particularly important to analyze the vibration characteristics in complex surrounding rock environments. The coupling dynamics model of the TBM main drive system proposed in this article considers the structural characteristics of distributed support and multi-source inputs, as well as nonlinear internal excitations such as bearing dynamic stiffness, gear meshing error, and tooth side clearance, which can more accurately calculate the dynamic characteristics of the main drive system. Based on the TBM scale test-bed, the modeling method and the vibration response of the main components were compared and verified. Based on the coupled dynamic model of the main driving system, the vibration characteristics of the driving system were analyzed under different excavation penetrations and different proportions of soft and hard surrounding rocks. The analysis results show that during the process of penetration from 5 mm to 6 mm, the average vibration increase speed is the highest, reaching 0.1493 g/mm. As the proportion of soft surrounding rock increases, the lateral unbalanced load and torque of the cutterhead significantly increase. Meanwhile, as the proportion of soft surrounding rock increases, the corresponding rate of load increase significantly increases. Within the range where the proportion of soft surrounding rock increases from 21 % to 35 %, its lateral overturning vibration RMS value increases by 13.08 %. Within the range where the proportion of soft surrounding rock increases from 35 % to 50 %, its lateral overturning vibration RMS value increases by 32.18 %. This can easily cause safety accidents such as the fracture of key load-bearing components of the system during the excavation process
Effect of Si addition on phase structure and wear resistance of CoCrFeMoNi alloy coatings
Get PDFCoCrFeMoNi high entropy alloy coating was prepared on Q235 substrate by plasma cladding method. The phase structure, morphology characteristics, element distribution, microhardness, and wear resistance for this alloy without and with Si doping were investigated by XRD, OM, SEM, EDS, microhardness tester, and friction-wear tester, respectively. The results show that CoCrFeMoNi alloy is composed of a single FCC phase, while Si-containing alloy is composed of FCC main phase and HCP phase. Both alloys have a typical dendritic structure. There is a layer of isotropic fine-grained region near the fusion line, and a columnar crystal region away from the fusion line. After adding Si element, the enrichment of Mo element in the interdendrite region and Co element in the dendrite region significantly decreased, which is related to the Si-containing alloy can provide a liquid environment with longer duration, lower viscosity, and greater fluidity. The change of Cr element enrichment from interdendrite region to dendrite region is the result of comprehensive competition of mixing enthalpy, atomic radius difference, electronegativity, density, and melt flowability between alloying elements. The friction coefficients of the two alloys show a rapid increase first and then gradually stabilize with the increase of time. After adding Si element, the hardness and wear resistance of the alloy are greatly improved, which is mainly related to the increase of the lattice distortion of FCC phase, the formation of high-strength HCP phase and the reduction of internal defects
Vibration damping and interfacial adhesion behavior of steel-UHMWPE composite structures
Get PDFHybrid structures combining steel and polymer layers are widely used in engineering systems where vibration reduction and mechanical durability are required. In this study, a composite structure consisting of a low-carbon steel substrate and an ultrahigh molecular weight polyethylene (UHMWPE) coating was investigated in terms of vibration damping capacity, adhesion strength, and thermal behavior. The UHMWPE coating was applied to the steel surface through a thermal pressing technique under optimized temperature and pressure conditions. The vibration damping performance was analyzed using a modal analysis method and accelerometer-based measurements within the frequency range of 100-1000 Hz. Interfacial adhesion was evaluated via shear and peel tests according to ASTM D1002 standards. Results show that the steel-UHMWPE composite exhibits up to 35-40 % improvement in damping ratio compared to bare steel specimens. The optimal adhesion strength was achieved at a processing temperature of 190 ℃, where the interfacial energy balance between the polymer and steel substrate minimizes delamination. Thermal stability analysis using DSC and TGA confirmed the material’s operational range up to 120 ℃, making it suitable for automotive and mechanical vibration isolation applications. These findings demonstrate that the combination of steel’s stiffness and UHMWPE’s viscoelastic damping behavior offers a promising approach to lightweight vibration control components. Further optimization of interface modification and filler reinforcement is planned to enhance tribological and thermal resistance properties
Theoretical assessment of the mechanical properties of fiber concrete using the dispersion analysis method
Get PDFThis paper examines how the type of fiber and the amount of fiber in concrete impacts the mechanical characteristics of fiber-reinforced concrete (FRC) by both experimental testing and statistical modelling. Basalt, polypropylene, and steel fiber reinforced concrete specimen were cast at different percent ratios (0, 0.1, 0.2 and 0.3) and subjected to laboratory conditions to measure compressive strength. At every dose and fiber type, three specimens were tested, and average values of the strengths were computed. OriginPro was used to fit the data in polynomial regression models (second degree) to quantify the connections between the parameters of this fiber and compressive strength. The most important statistical indicators provided in the assessment of the model accuracy were coefficients of determination (R2), adjusted R2, F-statistics, p-values, and residual analysis. The results revealed that the models were all characterized by high predictive accuracies (R2= 0.72, 0.93) and found to be significant using ANOVA (p< 0.0001). Results validated that the type of fiber along with the dosage were critical in the effectiveness of strength with optimal amount enhancing performance and loads beyond or below those levels decreasing the matrix bonding. The produced models offer a predictive predicting model that would be helpful in FRC mixture optimization. The study presents significant information in the field of structural engineering where a newly established structure will be needed to have superior durability, dependability, and load capacity
Influence of angular speed of tedder on kinematic parameters of linter machine drive
Get PDFThis article investigates the influence of the tedder’s angular speed on the kinematic and power characteristics of the drive system of the 5LP linter machine. The linter machine is a complex technological unit used to remove residual fibres from the surface of cotton seeds. One of the key factors determining linting efficiency is the interaction between the tedder and the seed roller inside the machine’s working chamber. A detailed kinematic and force analysis is presented, taking into account the resistance forces generated by the seed roller during its movement and processing. Particular attention is given to the development of a calculation model that describes the interaction between the tedder blades and the seed roller. In this model, each blade is treated as a cantilever beam subjected to variable loads resulting from the non-uniform mass and density distribution of the seed material. The analysis demonstrates that variations in the mass and density of the seed roller significantly affect the load transmitted to the drive and the stability of the saw cylinder. The obtained results enable more accurate selection of drive parameters and optimisation of the operating modes of the linter machine. These findings are crucial for improving the productivity and reliability of the equipment, as well as for accounting for both transient and steady-state operating conditions in real industrial environments
Neural network-based ANC algorithms: a review
Get PDFActive Noise Control (ANC) technology is of great value in the field of noise mitigation. Recently, traditional linear adaptive control methods, represented by the FxLMS algorithm, are structurally simple and computationally efficient but often suffer from performance degradation or even failure in practical applications due to nonlinear system factors. For this reason, neural network-based ANC methods have attracted significant research interest for their strong nonlinear processing capabilities and have gradually emerged as a focal point for addressing nonlinear ANC problems. This paper systematically reviews the research progress of neural networks in the field of nonlinear ANC, focusing on two key dimensions: network architecture and training methods. In terms of architecture design, existing studies primarily enhance performance through topology optimization, improvements to functional link artificial neural networks, and innovative hidden layer designs. Advancements in training methods focus on the optimization of loss functions, innovation in weight update algorithms, and the introduction of other training strategies. In the future, neural network-based ANC algorithms will continue to deepen, with potential development paths including the integration of advanced network architectures such as Generative Adversarial Networks (GANs), optimization of utility functions, pruning of hidden layers, improvement in loss function design, and the adoption of more efficient training strategies. These efforts will further improve algorithm performance and ultimately provide robust support for achieving more precise and efficient active noise control