Key Engineering Materials Vol. 516

Abstract: Demand for glass Fresnel lenses is increasing in solar panel manufacture in order to increase power efficiency. Glass lenses are usually moulded using a glass moulding method with tungsten carbide moulds. In this study, large Fresnel lens moulds made of tungsten carbide are tested to be ground by a simultaneous 2-axis (Y, Z) controlled grinding method. The resinoid bonded diamond wheel is trued with a rare metal truer to increase the sharpness of the wheel edge. In the grinding test of the tungsten carbide mould, a form accuracy of less than 0.8 μm P-V and surface roughness of 18 nm Rz are obtained, and it is clarified that the proposed grinding method is useful for Fresnel grinding.

Abstract: Modelling and simulation of the micro milling process has the potential to improve tool design and optimize cutting conditions. This paper presents a novel and effective 3D finite element (FE) based method for simulating the micro milling process under large deformations. A tooling model incorporating a helix angle is developed for cutting forces, tooling temperature and chip formation prediction. The proposed approach is experimentally validated and the simulated micro milling performance such as micro chip formation and cutting forces are in reasonable agreement with the measured results in cutting trials.

Abstract: In a variety of practical microscopic imaging applications, many industries require not only lateral resolution improvement but also axial resolution improvement. The resolution in optical microscopy is limited by diffraction and determined by the wavelength of the incident light and the numerical aperture (NA) of the objective lens. The diffraction limit is mathematically described by a point spread function in the imaging system, and three-dimensional (3D) point spread functions describe both the lateral and axial resolutions. Thus, it is useful to focus on exceeding this limit and improving the resolution of optical imaging by the spatial control of structured illumination. Structured illumination microscopy is a familiar technique to improve resolution in fluorescent imaging, and it is expected to be applied to industrial applications. Microscopic imaging is convenient, non-destructive, and has a high-throughput performance and compatibility with a number of applications. However, the spatial resolution of conventional light microscopy is limited to wavelength scale and the depth of field is shallow; hence, it is difficult to obtain detailed 3D spatial data of the object to be measured. Here, we propose a new technique for generating and controlling wide-field 3D structured illumination. The technique, based on the 3D interference of multiple laser beams, provides lateral and axial resolution improvement, and a wide 3D field of view. The spatial configuration of the beams was theoretically examined and the optimal incident angle of the multiple beams was confirmed. Numerical simulations using the finite difference time domain (FDTD) method were carried out and confirmed the generation of 3D structured illumination and spatial control of the illumination by using the phase shift of incident beams.

Abstract: This study focuses on the nonlinear dynamic characteristics of tool vibration in ultra precision diamond turning. Considering the first mode vibration of a tool, the tool is modelled as a one degree of freedom spring-mass-damper system with a developed cutting force model. Numerical simulations were carried out to anlyze the nonlinear dynamics of the system, using bifurcation diagrams, Poincaré maps, phase protraits, time histories and power spectral densities. The results indicated that the dynamic response of the tool is dominantly periodic and harmonic at its natural frequency with a little negligible chaos and its natural frequency, more than its fundamental frequency, is slightly shifted by depth of cut and cutting force.

Abstract: To investigate the maintainability of bulk metallic glasses (BMGs), two Lanthanum base metallic glass were first characterized by using X-ray diffraction and then machined by single point diamond turning (SPDT). With increasing depths of cut (DOC) from 1 um to 5 um, surface finish was improved. However, surface finish is not improved significantly when the DOC is further increased.