The poor machinability of Ti-6Al-4V alloy makes it hard to process by conventional processing methods even though it has been widely used in military and civilian enterprise fields. Non-resonant three-dimensional elliptical vibration cutting (3D-EVC) is a novel cutting technique which is a significant development potential for difficult-to-cut materials. However, few studies have been conducted on processing the Ti-6Al-4V alloy using the non-resonant 3D-EVC technique, the effect of surface quality, roughness, topography and freeform surface has not been clearly researched yet. Therefore, the machinability of Ti-6Al-4V alloy using the non-resonant 3D-EVC apparatus is studied in this paper. Firstly, the principle of non-resonant 3D-EVC technique and the model of cutter motion are introduced. Then the tool path is synthesized. The comparison experiments are carried out with traditional continuous cutting (TCC), two-dimension elliptical vibration cutting (2D-EVC), and the non-resonant 3D-EVC method. The experimental results shown that the excellent surface and lower roughness (77.3 nm) could be obtained using the non-resonant 3D-EVC method; the shape and dimension of elliptical cutting mark also relates to the cutting speed and vibration frequency, and the concave/convex spherical surface topography are achieved by non-resonant 3D-EVC in the Ti-6Al-4V alloy. This proved that the non-resonant 3D-EVC technique has the better machinability compared with the TCC and 2D-EVC methods.

Elliptical vibration cutting (EVC) technology has been paid much attention as the unique characteristics of the intermittent cutting and friction reversal, but the residual-height between adjacent trajectories can not be eliminated. In order to solve the problem, we developed a new vibration assisted rotation cutting (VARC) system in this paper. The system has the characteristics of the pseudo-intermittent cutting and friction reversal, which greatly extends the tool-life, reduces cutting forces, and improves the accuracy of the work-piece. The mechanical system based on the parallel kinematic configuration of the two-axis, where the positioning of the tool position has ensured by the rotary motion platform (RMP). The L-shaped flexure hinges are used as the guidance flexure mechanism, to rotate of the RMP. Flexures hinge structure and piezoelectrically actuated are employed positioning in the design. The kinematic analysis of the pseudo-rigid-body model, the matrix-based compliance modeling method is applied for the compliance modeling, and the dynamics characteristic is modeled by using the Lagrangian principle of VARC system. The structural parameters are optimized by the improved differential evolution algorithm, and the theoretical modeling is validated by finite element analysis. Off-machine performance examinations were conducted to evaluate the parasitic motions, resolution, hysteresis, stroke, and frequency of the developed system. The results showed that the motion stroke of the piezoelectric actuator input end could reach up to 26.34 μm with a resolution of 8 nm, moreover, the coupling ration could be effectively decreased within 0.64%. The superior performances and easily achievable structure well facilitate practical applications of the proposed system in micro/nano-machining.

This article focuses on the nonlinear Wiener system identification of three-dimensional elliptical vibration cutting. The developed three-dimensional elliptical vibration cutting device is actuated by four piezoelectric stacks, which have hysteresis nonlinear characteristics. Our research proposes an improved memetic algorithm in order to identify the nonlinear elliptical vibration cutting model. The improved memetic algorithm displays the advantages of both particle swarm optimization and genetic algorithm, while simultaneously overcoming these programs' shortcomings. Moreover, it can quickly and efficiently search for the global optimization. The improved memetic algorithm's identification performance may be compared with the conventional memetic algorithm, particle swarm optimization, and genetic algorithm using two wellknown test functions. Test results demonstrate that the improved memetic algorithm can search the global optimal solution more efficiently than available state-of-the-art algorithms. Based on the input-output data collected from experiments, the accuracy of the identification model can potentially reach 97.55%. This relatively small margin of error verifies the efficiency of the proposed improved memetic algorithm for system identification.

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Machining difficult-to-cut materials has always been a problem to ultraprecision machining due to rapid tool wear. Two-dimensional elliptical vibration cutting (2D EVC) can well alleviate this problem by intermittent cutting motion, but it also has some defects. In this article, a three-dimensional elliptical vibration cutting (3D EVC) apparatus is developed. Four parallel piezoelectric stacks are employed to drive the cutting tool; the tool tip can generate 3D spatial elliptical motions. The spatial positions of generated 3D elliptical motions can be adjusted by varying amplitudes, frequencies, and phase shifts of the actuated signals of piezoelectric stacks; the acting locations of piezoelectric stacks can also be adjusted to satisfy different cutting requirements. Experimental results indicate that the developed 3D EVC apparatus has the feasibility of machining flat surfaces, increasing tool life, and improving machined surface quality compared with conventional cutting and 2D EVC methods.

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In this paper, three-dimensional (3D) elliptical vibration cutting (EVC) method is presented to fabricate optical parts of difficult-to-cut materials, which vibrates the diamond tool at a 3D ellipse trajectory driven by the nonresonant principle. The surface quality of the workpiece is determined by the elliptical motion parameters of the cutting tool. So this paper adopts genetic algorithm (GA) to optimize ellipse parameters to get better surface quality. An optimization model is established to minimize the surface roughness of the workpiece. And the validity of the proposed approach is verified by a numerical example. This research can direct designers to choose the optimum ellipse parameters to machine optical parts in the cutting experiments.

The aerial camera lens largely determines the performance of the camera. It is necessary to further optimize the lens to satisfy the requirements of small-scale and lightweight aircraft camera systems. The optical system design is the primary prerequisite. Therefore, considering the image quality and working environment of the aerial camera, an aspherical aerial camera optical system is developed by studying the aerial camera optical system. The work presented in this paper decreases the overall weight of the aerial camera by using an aspherical lens instead of a spherical lens, which reduces the number of lenses and improves the image quality. The athermalization of the optical system ensures that the camera has good temperature adaptability in the temperature range of −60°C∼60°C. The definition of the aspherical surface shape is detected by a ZYGO digital interferometer. The root mean square (RMS) of the system is 0.0403λ(λ = 632 nm), and the peak value (PV) is 0.354λ, which ensures the image quality of the camera. The research results verify that the aspherical lens can be well applied to the camera optical system, improving the image quality of the system and reducing the weight of the camera.