High-quality milling of carbon fiber reinforced polymer (CFRP) composites is of great importance for the high-performance manufacturing of structures made of this hard-to-machine material. In this paper, a multiscale finite element (FE) model, considering the thermal–mechanical coupling effect, was developed to simulate the milling process and reveal its material removal mechanism. The corresponding milling experiments were conducted to validate the simulated cutting forces and temperature, which were in good agreement with the experiment results. In the macroscale model, the Hashin failure criteria were used to estimate the failure of the composites. In the microscale model, the fibers, matrix, and the fiber–matrix interface were modeled separately, to investigate the mechanisms of material removal behavior during milling, among fiber breakage, matrix cracking, and fiber–matrix debonding. Based on the macroscale numerical and experimental results, the higher cutting speed was demonstrated to improve the surface quality of CFRP milling. According to the results from the microscale model, the material removal mechanism varies depending on the orientation of the fibers and can be divided into four stages. The outcome of this work provides guidelines to further investigate optimal manufacturing parameters for the milling of CFRP composites and their cutting mechanisms.

The approach to improve the output power of piezoelectric energy harvester is one of the current research hotspots. In the case where some sources have two or more discrete vibration frequencies, this paper proposed three types of magnetically coupled multi-frequency hybrid energy harvesters (MHEHs) to capture vibration energy composed of two discrete frequencies. Electromechanical coupling models were established to analyze the magnetic forces, and to evaluate the power generation characteristics, which were verified by the experimental test. The optimal structure was selected through the comparison. With 2 m/s² excitation acceleration, the optimal peak output power was 2.96 mW at 23.6 Hz and 4.76 mW at 32.8 Hz, respectively. The superiority of hybrid energy harvesting mechanism was demonstrated. The influences of initial center-to-center distances between two magnets and length of cantilever beam on output power were also studied. At last, the frequency sweep test was conducted. Both theoretical and experimental analyses indicated that the proposed MHEH produced more electric power over a larger operating bandwidth.

Inchworm piezoelectric actuators have the advantage of large strokes, but most of them usually can only carry out linear motion. Some inchworm piezoelectric actuators, composed of multiple piezoelectric stacks, can realize two-degree-of-freedom motion but still fail to simplify the complex structures and struggle to achieve high output speed without backward motion. Here, we design an inchworm piezoelectric actuator that can carry out planar motion with a compact centrosymmetric structure in which only three piezoelectric stacks are used. The amplification mechanisms based on flexure hinges are designed to increase the clamping force and step displacement. A working principle of single-dual mode is designed to effectively utilize the deformations of the driving units, and two steps in one cycle are realized, which improves the output speed of the proposed actuator. Utilizing its center symmetry structure to switch the direction of motion, which enables plane motion. The parameters of the driving units were optimized by theoretical analyses. Then, the finite element method and experiments were employed for the static and dynamic analyses. Experimental results demonstrated the actuator’s capability of point-to-point positioning and tracking a circle within the plane and revealed the maximum speeds of 2085 μm/s along the X-axis and 2407.5 μm/s along the Y-axis without backward motion. Herein, a combination of a simple structure and a good output speed without backward motion is achieved on a planar motion inchworm actuator.

In response to the challenges of difficult energy supply and high costs in ocean wireless sensor networks, as well as the limited working cycle of chemical batteries, a cylindrical wave energy harvester with symmetrically distributed multi-cantilever beams was designed with Galfenol sheet as the core component. The dynamic equation of the device was established, and ANSYS transient dynamic simulations and Jiles-Atherton hysteresis model analysis were conducted to develop a mathematical model of the induced electromotive force of the Galfenol cantilever beam as a function of deformation. Experimental validation demonstrated that the simulated results of the cantilever beam deformation had an average error of less than 7% compared to the experimental results, while the average error between the theoretical and experimental values of the induced electromotive force of the device was around 15%, which preliminarily verifies the validity of the mathematical model of the device, and should be subject to further research and improvement.