Dynamic Response of Mud in the Field Soil Improvement with Dynamic Drainage Consolidation

The dynamic drainage consolidation (DDC) method is a relatively new technology for soft soil improvement. The method was adopted for the improvement of the mud at a site for the construction of a highway. The in-situ monitoring on the porewater pressures and settlements of the mud were taken for understanding its field dynamic properties. The site original data on the mechanical responses of the mud under dynamic loading were obtained and analyzed. The some important phenomena on pore water pressures were observed. The settlements induced by dynamic tamping and soil fill were also observed. Some basic mechanisms on the behavior of the soft soil under the dynamic loading are discussed. Effect assessment on the improvement is also taken. The in-situ monitoring and analyses show that the dynamic drainage consolidation is more effective than traditional dynamic consolidation in the improvement depth and consolidation rate as well as the application range; the drainage system play an important role

Novel thermally stable segmented solid paraboloid antenna for high surface accuracy

The rapidly growing communication demands in our society require the design of high-performance solid paraboloid antennas with extremely high surface accuracy, which remains a challenge due to the inevitable thermal deformations. This paper proposes a novel design of thermally stable segmented solid surface antenna with high surface accuracy. In this novel design, the antenna reflector is divided into a certain number of segmented pieces, each of which is then individually supported by an innovative thermally stable grid structure. An analytical model based on Sanders improved first-approximation shell theory is developed to predict the thermal deformation of antenna surface, with which the proposed segmenting method in improving the surface accuracy of reflector antenna is theoretically approved. The working mechanism of the proposed thermally stable grid structure that the thermal deformations at the supporting points can maintain a minimum level is verified using finite element analysis. A case study is performed in a practical environment to demonstrate that a segmented antenna supported by thermally stable grid structure can largely suppress the thermal deformation compared with a continuous surface antenna. This study provides a novel and useful engineering solution for paraboloid solid surface antennas to achieve extremely high surface accuracy under various thermal conditions

Advanced nonlinear dynamic modelling of bi-stable composite plates

This paper proposes a novel analytical model to study the nonlinear dynamics of cross-ply bi-stable composite plates. Based on Hamilton’s principle, in conjunction with the Rayleigh-Ritz method, an advanced analytical model with only 17 unknown terms is developed to predict the entire nonlinear dynamic response of bi-stable composite plates, which are excited by an electrodynamic shaker. The coupling between the bi-stable plate and the shaker is considered in the development of analytical model. This work, for the first time, simulates the full dynamics of bi-stable plates using an analytical model, including the prediction of the nonlinear characteristics of single well vibration and cross well vibration. Numerical results on three vibrational patterns of two standard cross-ply composite plates are obtained to study the nonlinear dynamics of bi-stable plates. The prediction accuracy on the dynamic characteristics of different vibrational patterns of bi-stable plates are verified by both finite element analysis (FEA) and experimental results. Large amplitude cross-well vibrations due to the transitions between different stable states of bi-stable plates are also characterized accurately. Applying this 17-term analytical model for the dynamic analysis of bi-stable plates is straightforward, as the mass and stiffness properties are obtained directly from the geometry and material properties. Only the damping coefficients for different plates need to be determined from experiments. Furthermore, this proposed 17-term analytical model has much higher computational efficiency than FEA

A novel bio-inspired design method for porous structures: Variable-periodic Voronoi tessellation

This paper introduces a novel approach, namely Variable-Periodic Voronoi Tessellation (VPVT), for the bio-inspired design of porous structures. The method utilizes distributed points defined by a variable-periodic function to generate Voronoi tessellation patterns, aligning with a wide diversity of artificial or natural cellular structures. In this VPVT design method, the truss-based architecture can be fully characterized by design variables, such as frequency factors, thickness factors. This approach enables the optimal design of porous structures for both mechanical performance and functionality. The varied, anisotropic cell shapes and sizes of VPVT porous structures provide significantly greater design flexibility compared to typical isotropic porous structures. In addition, the VPVT method not only can design micro-macro multiscale materials, but is also applicable for the design of meso-macro scale truss-based porous structures, such as architecture constructions, biomedical implants, and aircraft frameworks. This work employs a Surrogate-assisted Differential Evolution (SaDE) method to perform the optimization process. Numerical examples and experiments validate that the proposed design achieves about 51.1% and 47.8% improvement in compliance performance and damage strength, respectively, than existing studies

Novel rotational motion actuated beam-type multistable metastructures

This work aims to explore and design a family of multistable metastructures, which are actuated by rotational motion. The bi-stability design criteria for a single pre-shaped beam unit are studied firstly using an analytical model and finite element method. Based on this bi-stability study, a typical one-layer of this novel rotational motion actuated bistable structure, which is composed of four pre-shaped beams assembled uniformly inside two circular frames, is proposed and fabricated. The mechanical behaviour of this bistable structure represented in terms of moment-angle curves are analyzed by the finite element method and experiments. A parametric analysis is performed to study the influence of geometric parameters of an one-layer multistable metastructure on its bi-stability performance, which provides the guidance to design multistable structures with more layers. Lastly, multistable structures with two layers and three layers, which can achieve large rotations with controllable angle-step and snapping sequence, are designed and studied. Furthermore, this research demonstrates other as-fabricated beams with bi-stability have prospects to design the rotational multistable metastructures. The multistable metastructures proposed in this work create new opportunities to design advanced reconfigurable structures and devices

Dual-Pulse Mode Control of a High-Speed Doubly Salient Electromagnetic Machine for Loss Reduction and Speed Range Extension

In this paper, a dual-pulse mode control of a high-speed doubly salient electromagnetic machine (DSEM) for efficiency improvement over a wide speed range is investigated and implemented. The dual-pulse mode control method and operation principle are introduced. The influence of excitation angles and field current on the operation performance is analyzed by finite element method (FEM) based on the back-electromotive force (EMF) and inductance characteristics. The loss distribution for various speed and load torque requirement is attained, and the control parameters are optimized. The excitation angle can reduce the back-EMF at high speed through transformer-EMF and flux-weakening armature reaction. A prototype of 12/8-pole DSEM drive system is developed and dual-pulse mode control in high-speed operation under low DC-link voltage is implemented. Both the simulated and measured results show that the torque capacity of the DSEM is improved and the loss is reduced over a wide speed range

A novel understanding of the normalized fatigue delamination model for composite multidirectional laminates

Normalized fatigue delamination models have been widely applied by researchers in the characterization of the fatigue delamination behavior of composite laminates. However, the inherent mechanism of this normalization method has not been explored. This study aims to present a physical understanding on the normalized fatigue delamination model from a viewpoint of energy. The fatigue delamination behavior is considered to be governed by the driving force and delamination resistance, and based on this principle the physical mechanism of the fatigue delamination is studied. A new physics-based normalized fatigue delamination model is proposed in this paper. In order to experimentally validate the proposed fatigue delamination model, mode I fatigue delamination tests are performed on double cantilever beam specimens to obtain the experimental data with different amounts of the fiber bridging. The results show that the normalized model is suitable to accurately characterize the fatigue delamination behavior of the composite laminates by using a single master curve. The master curve is finally employed as a standard approach to predict the fatigue results. Good agreement between the predicted and the experimental results is achieved, therefore it approves the applicability of the proposed fatigue delamination model in characterizing the fatigue delamination growth behavior