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To explore the evolution mechanism of multistage machining processes and torsional fatigue behaviour based on strain energy for the first time and provide process optimization of axis parts of low-alloy medium-carbon steel for service performance, four multistage machining processes were applied to the 45CrNiMoVA steel, including the rough turning process (RT), RT + the finish turning process (FRT), FRT+ the grinding process (GFRT) and RT+ the finish turning process on dry cutting condition (FRT0). The result showed that the FRT process’s average low-cycle torsional fatigue life increased by 50% when it evolved from the RT process. The lower surface roughness of Ra 1.3 μm caused the total strain energy to increase by 163.8 Pa mm/mm instead of the unchanged strain energy density, and the crack feature evolved from some specific bulges to flat shear plane characteristics. When the GFRT process evolved from the FRT process, its average fatigue life increased by 1.45 times, compared with the RT process. Plastic strain amplitude decreased by 21%, and the strain energy density decreased by 4% due to more considerable compressive residual stress (-249 MPa). Plastic deformation layer depth had a consistent tendency with surface roughness. In this paper, surface integrity evolutions on cyclic characteristics and fatigue behaviour have also been explained. A fatigue life prediction model based on the energy method for machined surface integrity is proposed.

The single crystal scintillating optical fibers acting as the scintillators and light conductors show potential application in scintillating fiber array detectors with high spatial resolution. In this paper we report the growth of 0.2 at% Ce:Y3Al5O12 single crystal fiber. The crystalline phase, surface morphology of the axial-section and cross-section, optical and scintillation properties of the as-grown fiber were investigated. The Ce:Y3Al5O12 single crystal fiber has a pure YAG phase, a uniform distribution of cerium in the axial-section and cross-section surface. Emission spectrum is composed of broad bands ranging from 440 to 700 nm. In addition, the single crystal fiber has a high light yield of 26115 ± 2000 photons/MeV, low energy resolution of 9.44% @662 keV and decay time of a fast component of 78 ns and a slow component of 301 ns. The intensity ratio of fast to slow components is roughly 8:1.

This study proposes a novel micro-deep-hole drill with variable web thickness and flute width to effectively improve the problem of tool breakage and chip clogging during micro-deep-hole drilling. Firstly, the failure form and failure mechanism of micro-drill are explored by performing drilling experiments, and it is found that the torsion fracture and bending fracture are the main premature failure modes of micro-deep-hole drilling tools. The static simulation analysis of micro-drill is further conducted to investigate the influence of geometric parameters on the stiffness and strength of high-aspect-ratio micro-drill, and the results indicate that the web thickness ratio and flute width have significant effects on drill tip stiffness and spiral groove root strength. To balance the rigidity, strength and chip evacuation capability of micro-deep-hole drilling tools, the new micro-drill with variable web thickness and flute width is developed, supplemented by comparative experiments. The results confirm that the new micro-drill has better chip removal ability, greatly reduces the drilling force, torque, drill tip wear and material peeling phenomenon, and significantly enhances the machining quality of hole wall.

Optical mode switch is a key device for reconfigurable mode-division-multiplexing (MDM) technique. Here, an ultra-broadband 1×2 mode switch based on cascaded Mach-Zehnder interferometer and asymmetric Y-branch is proposed. The input E00 or E10 mode will be converted to E00 mode and switched between two output ports by changing the working state of electrode. When E00 mode is launched, the measured insertion loss of fabricated switch is 3.3 dB (off-state)/3.4 dB (on-state), and corresponding crosstalk is −18.8 dB (off-state)/−16.1 dB (on-state) at 1550 nm, respectively. Due to the adoption of polymer with high thermo-optic coefficient as the waveguide material, the measured switching power is 10.3 mW. The captured far-field output mode patterns prove the wavelength independence of proposed mode switch within the range from 1500 to 1630 nm. This broadband operation mode switch has potentials in wavelength-division-multiplexing & MDM complex systems, as well as cost-effective low-end switching applications.

Relative tool sharpness (RTS) is identified as the ratio of undeformed chip thickness to tool cutting edge radius. This paper studies the effects of RTS on the surface generation mechanism of precision turning of electroless nickel-phosphorus (Ni-P) coating. An R-shaped tungsten carbide (WC) tool was adopted for the face turning experiment. The cutting edge radius was 1.84 μm measured by a laser scanning confocal microscope (LSCM). The chip formation behavior, cutting forces and surface morphology were investigated under different RTS values. Results showed that the chip changes from continuous to discontinuous as RTS decreases from 0.54 to 0.27, indicating the transition of the material removal mechanism. The periodical fluctuations with small amplitudes on the machined surface are associated with the high-frequency tool-tip vibration. The low-frequency fluctuations of the cutting forces are related to the material swelling and recovery. The optimal machined surface roughness was obtained at the RTS of 0.38.

Laser Shock Peening (LSP) is a well-established surface treatment commonly used to improve mechanical properties of material's surfaces. To further understand the relationship between tensile property and fatigue life improvement of high strength low alloy steel in the LSP process, LSP treatment of 32CrNi high strength low alloy steel was carried out by YAG laser with pulse energy of 15 J, and tensile property was tested by electronic universal material testing machine. Surface morphology, residual stress and tensile fracture of the specimens before and after LSP were observed by white light interferometer (WLI), X-ray measuring apparatus and scanning electron microscope (SEM). Result shows that LSP did not change tensile strength of 32CrNi steel but cause yield characteristic transform from obvious yield point to no yield phenomenon which is the only factor benefiting fatigue life, indicating that the increment of fatigue life was probably related to the disappearance of yield phenomenon. Formation mechanisms of tensile fractures and yield phenomenon induced by LSP at room temperature were also discussed and completely revealed. Deeper compressive residual stress and flat grains contributed to the transition of yield characteristic and lower elongation rate of 32CrNi steel subjected to LSP.

Developing a mild and efficient method to simultaneously enhance poling efficiency and temporal stability is meaningful and challenging for organic second-order nonlinear optical materials. In this paper, a new poly (aryl ether ketone) and chromophores functionalized with anthracene groups have been designed and prepared. Poling and crosslinking process could be separated by the mild and photo-initiated cycloaddition of anthracene group. As the UV–Vis spectrum, DSC and TGA curves, the networks had formed by 30-min irradiation of the Lower-power UV light which led little decomposition of dipolar chromophores. The maximum electro-optic coefficient (r33) of these polymers is 28.5 pm V−1 (at 1.3 μm), and the order parameter reaches 0.22. Moreover, the depolarization temperature of α peak, related to the dipole relaxation, has been increased to 129 °C after crosslinking, which is 17 °C higher than uncrosslinked ones. All these results indicated that the photo-crosslinking of anthracene exhibited promising potential for improving alignment stability and NLO activity at the same time.

Chatter is one of the challenging topics in the field of metal cutting. The dynamic characteristics of five-axis milling system are complex and variable. Especially in high-speed milling process, the influence of the tool-workpiece interactions and speed effect on milling stability is more obvious. It is necessary to investigate the influence of various interaction effects on milling stability. In this paper, the dynamical model of spindle system was established, and then the model was applied to investigate the influence of gyroscopic effect and centrifugal force on the dynamical characteristics of the tool tip. In order to solve the chatter problem of five-axis flank milling, the extended dynamical model of five-axis flank milling which considers the tool-workpiece interactions and speed effect was established. Based on the established milling dynamical model, the influence mechanism of the spindle system-tool-workpiece interaction effects on five-axis flank milling stability was investigated. The stability lobe diagrams of five-axis flank milling which contains the tool-workpiece interactions and speed effect can be obtained. Experimental results show that the proposed five-axis flank milling dynamical model can predict the milling state more reliable than the traditional ones. The research results are of great significance in preventing five-axis flank milling chatter.

Since cemented carbide has been used as a micro-lens array mold, its processing method and micro-tool is one of the research priorities. In order to achieve high-quality milling of cemented carbide micro-lens array, the design and fabrication of the 0.5-mm diameter polycrystalline diamond (PCD) micro ball-end mill were studied. Based on the space vector, the mathematical model of the plane cutting edge of the PCD tool is established. According to the three processing characteristics of milling, grinding, and milling grinding, the double-edged conical surface micro ball-end mill, spherical micro ball-end mill, and single-edged hemispherical micro ball-end mill were designed respectively. Based on the line-face contact model of the grinding wheel and the movement principle of the CNC tool grinder, the grinding principles and methods of the rake face and the flank face are proposed. The high precision grinding of PCD micro ball-end mills are realized. The micro-groove milling experiment of cemented carbide was conducted; the milling performance of three PCD micro ball-end mills was studied. Considering the surface morphology and roughness of the micro-groove machining, a single-edged hemispherical PCD micro ball-end mill can avoid the phenomenon of chip blocking and depositing and can also fully exert the grinding characteristics of PCD materials to obtain relatively better processing quality.

18Ni maraging steel is normally used to make key components by machining processes. It is necessary to understand the fracture mechanism and behaviour of 18Ni maraging steel for the study and furth...

The chisel-edge axial rake angle has an important effect on the processing performance of helical point micro-drills. In this research, the mathematical modeling for the spiral groove, helical flank, and cross-shaped chisel edge are conducted, and then three types of helical point micro-drills, each having a thinned chisel edge with an unequal axial rake angle, are designed and fabricated. Then, the finite element simulations and processing experiments of micro-drilling are performed separately, and the thrust force, torque, chip morphology, tool wear, and micro-hole machining quality are measured and evaluated. With the rise of the axial rake angle of the chisel edge, the curling degree of the chips and the thrust force were found to decrease owing to the increase of the rake angle along the inner cutting edge. The angle between the tool axis and chip axis was found to gradually decrease due to the reduction of the rake angle gradient along the cutting edge. Additionally, the thickness and width of the uncut chip of the inner cutting edge were found to increase, bringing about the rise in the torque. The wear degree of the micro-drills with a 0° axial rake angle (Type II) was the smallest due to their medium thrust force and torque, and a better micro-hole entrance morphology and minimum roundness were obtained. When drilling to the 30th hole, compared with the micro-drills with a − 10° axial rake angle (Type I) and 10° axial rake angle (Type III), the chisel edge maximum wear width of Type II (δ = 0°) was respectively reduced by 82.43% and 19.69%, and the micro-hole roundness respectively decreased by 26.7% and 11.33%. The thrust force of Type I (δ = − 10°) was the largest, so it caused greater tool wear and poorer micro-hole quality. The larger torque and lower rigidity of the inner cutting edge of Type III (δ = 10°) led to poorer drilling performance. Thus, helical point micro-drills having the 0° chisel edge axial rake angle are suitable for drilling 304 austenitic stainless steel.

Carbon-fiber reinforced silicon carbide matrix (C/SiC) composites are typical difficult-to-cut materials due to high hardness and brittleness. Aiming at the problem of the serious tool wear in conventional milling (CM) C/SiC composite process, ultrasonic vibration–assisted milling (UVAM) and conventional milling tests with a diamond-coated milling cutter were conducted. Theoretical and experimental research on the cutting force during the ultrasonic vibration milling process of C/SiC composites is carried out. Based on the kinematics analysis of tool path during ultrasonic vibration milling process, the cutting force model of ultrasonic vibration milling is established, and the influence mechanism of ultrasonic vibration on the cutting force is revealed. Based on the analysis of the evolution law of tool wear profile and wear curve during the traditional milling and ultrasonic vibration milling of C/SiC, the tool wear forms and mechanism of diamond-coated milling cutters in two processing modes and the influence mechanism of ultrasonic vibration on tool wear are revealed. It is found that the main wear mechanism of the diamond-coated milling cutter is abrasive wear, and the main wear form is the coating peeling. Compared with the traditional milling, the tool wear can be reduced by the ultrasonic vibration milling in machining process. In the range of test parameters, the tool wear decreases first and then increases with the increase of ultrasonic amplitude.

We propose and fabricate a polymeric thermo-optic mode switch based on a Mach-Zehnder interferometer (MZI) by connecting two asymmetric directional couplers formed with a single-mode waveguide (SMW) and a two-mode waveguide (TMW). Thin-film heaters were deposited on the arms of the MZI to realize the switching function. The LP01 mode in the SMW and the LP11a mode in the TMW can be converted to each other by driving the voltage supplied to the heater. Our typical fabricated device with polymer material shows extinction ratios higher than ~11 dB in the C-band. The switching power measured at 1550 nm is lower than 10 mW and the switching rise time and fall time are $540.0~\mu \text{s}$ and $440.0~\mu \text{s}$ , respectively. The device could find applications in reconfigurable mode-division-multiplexing systems.

The micro channel cold plate is very suitable for the application environment of high heat consumption liquid cooling such as PCB plate and multi-layer components. However, at mesoscale, the titanium alloy micro channel cold plate is micro thin-walled structure of cantilever boundary with weak stiffness, which leads to significant deformation and resultant poor machining accuracy during micro milling. To effectively control and reduce micro thin-walled deformation, a 3D FE cantilever model is established to predict dynamic milling deformation of micro thin wall. The constitutive model of titanium alloy (Ti-6Al-4 V) that includes the strain gradient to consider size effect in micro milling, the edge geometry of milling cutter, the thin-walled microstructure, and micro milling parameters is involved in milling modeling of thin wall. Moreover, a series of micro milling experiments for micro thin wall of titanium alloy at different machining parameters were carried out to investigate the law and mechanism of thin wall deformation in milling micro thin wall subjected to dynamic alternating forces. By comparing numerical and experimental deformation of micro thin wall in micro milling, the accuracy and validity of the prediction model based on cantilever boundary are verified, which provides theoretical support and model basis for the deformation control in milling micro channel cold plate at mesoscale.

By exploiting the electro-absorption characteristic of graphene, we proposed and theoretically demonstrated an electro-absorption optical modulator (EOM) based on the graphene-buried polymer waveguides. By burying the graphene layers inside the polymer waveguide, acquiring a strong graphene-light interaction when the graphene layers buried in the center of core, which bring about an important change of the optical mode and effective mode index in the waveguide. The width of the graphene capacitor was also optimized to enhance the bandwidth of the device. Calculations show that the proposed EOM can realize 29 dB extinction ratio, 7 dB modulation depth and 42 GHz bandwidth with an 800 μm-long active region. The required switching voltage form its minimum to maximum absorption state is 1.6 V and 1.55 pJ/bit energy consumption can be achieved. The proposed modulator can remedy the lack of high-speed optical modulator on the passive polymer waveguide and have a potential application for polymer-based photonic integrated circuits.

In this paper, an on-chip electro-optic (EO) modulator with loss compensation based on polymeric active-integrated waveguides was demonstrated. An erbium-doped waveguide amplifier was investigated and integrated with the EO modulator to compensate for signal loss. Polymeric active-integrated waveguides were based on the Mach-Zehnder interferometer structure, which consists of an amplified waveguide formed by two symmetric Y-junction branches and an EO waveguide formed by two decoupled waveguide arms. The dimensions of the polymeric active-integrated waveguides and the modulator were carefully designed and simulated. Moreover, a six-level spectroscopic model pumped at 980 nm was presented. The rate equations and propagation equations were solved, and the gain characteristics were simulated. The internal gain of 4.65 dB was achieved when the signal power was 0.1 mW at 1550 nm, the pump power was 100 mW at 980 nm, the Er3+ concentration was $9.3\times 10^{25}/\text{m}^{3}$ , and the Yb3+ concentration was $8.6\times 10^{26}/\text{m}^{3}$ in one Y-junction branch with a length of 1.5 cm. With the integrated waveguide amplifier, the loss of the EO modulator can be compensated at 9.3 dB in the two symmetric Y-junction branches. The light output intensity was also statistically presented. The proposed device with active-integrated waveguides could be used in polymer-based photonics integrated circuits.

Friction modeling between the tool and the workpiece plays an important role in predicting the minimum cutting thickness during TC4 micro machining and finite element method (FEM) cutting simulation. In this study, a new three-region friction modeling is proposed to illustrate the material flow mechanism around the friction zone in micro cutting; estimate the stress distributions on the rake, edge, and clearance faces of the tool; and predict the stagnation point location and the minimum cutting thickness. The friction modeling is established by determining the distribution of normal and shear stress. Then, it is applied to calculate the stagnation point location on the edge face and predict the minimum cutting thickness. The stagnation point and the minimum cutting thickness are also observed and illustrated in the FEM simulation. Micro cutting experiments are conducted to validate the accuracy of the friction and the minimum cutting thickness modeling. Comparison results show that the proposed friction model illustrates the relationship between the normal and sheer stress on the tool surface, thereby validating the modeling method of the minimum cutting thickness in micro cutting.

A polymer/silica hybrid 3D waveguide thermo-optic (TO) mode switch based on cascaded asymmetric directional couplers (ADCs) is theoretically designed and simulated, where the spatial modes of a few-mode silica waveguide can be switched to various single-mode polymer waveguides placed above the few-mode silica waveguide. A beam propagation method is employed to optimize the dimensional parameters of the mode switch to convert the L P 11 a and L P 11 b modes of the few-mode silica waveguide to the L P 01 mode of two single-mode polymer waveguides using the cascaded ADC 1 and ADC 2. The coupling ratios are higher than 96.4% (93.4%) and 95.1% (92.8%) for the ADC 1 and ADC 2, respectively, under the TE (TM) polarization within the wavelength range from 1530 to 1570 nm, which shows good wavelength independence. Furthermore, the monolayer graphene is introduced as the heating electrode and buried on the surface of the polymer core to increase the heating efficiency and reduce the power consumption. The power consumption for ADC 1 and ADC 2 is 16.69 mW and 17.35 mW, respectively. Compared to the traditional TO switch with an aluminum (Al) heating electrode, the heating efficiency of the presented device can be improved by ∼ 30 % . Moreover, the response speed of the TO mode switch with a 3D waveguide structure was also significantly improved. Compared to the device with Al electrodes, the introduced graphene electrodes can improve the switching speed of the device by ∼ 60 % . The presented TO mode switch with its small size and easy integration should find applications in reconfigurable mode division multiplexing systems.

An organic polymer-based monolithic integrated waveguide device with dual functions of electro-optic (EO) modulation and optical amplification is demonstrated. In this Letter, the dual functions are achieved by employing EO polymer as the waveguide upper cladding and organic optical amplified material as the waveguide core layer. Based on this dual-functional waveguide structure, the waveguide amplifier and the EO switch are successfully designed and fabricated on a S i O 2 -Si substrate. An optical gain of 5.8 dB at the wavelength of 1535 nm is obtained in the dual-functional polymer waveguide, and the EO switch based on the dual-functional polymer waveguide also presents a high-speed response time of ∼ 10 n s .

The construction of a smart city puts forward new requirements for lighting systems, such as variable color temperature adapting to environment and low energy consumption. We introduce a variable color temperature laser lighting system that produces uniform light with minimum energy. The color temperature is controlled by tri-color RGB diode lasers, and uniform lighting is achieved by microlens arrays. Tri-color diode lasers with wavelengths of 650, 556, and 450 nm are used as the lighting sources, and the white light laser output is achieved by combining the three beams. The color temperature is controlled by changing the power ratio of each lighting source. Finally, the homogenization of laser energy is regulated by the microlens arrays, and the energy uniformity reaches 91.1%. Moreover, we do an experiment to compare LED street lighting and laser street lighting, finding that the street lighting system with this design can increase the energy utilization rate by 113.33%, and the color temperature of the car headlamps with this design can be changed according to the environment. Therefore, this laser lighting system is an effective solution for modern smart lighting systems and energy saving, which have vast application.

Single-point diamond cutting is an efficient method to fabricate microlens arrays (MLAs). However, machining MLAs at the microscale with high dimensional accuracy and a smooth surface finish is a difficult task. In this study, a method of profile cutting is proposed to machine MLAs on electroless nickel–phosphorus (Ni–P) plating. To improve the dimensional accuracy of MLAs, a precision tool setting method is introduced, via which the precision of MLA sag can be controlled to within 20 nm. In addition, the formation mechanism of corrugation defects is studied via a finite element (FE) simulation of the wedge nano-cutting process and a cutting experiment of concentric ring grooves. By optimizing the tool settings and the machining parameters, high-quality MLAs with apertures of Φ100 μm can be created.

In five-axis ball-end machining, stability of the milling process is not only determined by the combination of depth of cut and the spindle speed, but also determined by the lead and tilt angles of the milling tool (i.e., the tool orientations). As the degree of freedom increases, five-axis machining machines have more complex dynamic characteristics. Therefore, the influence of the tool-workpiece interactions on the machining performance is more obvious. In this paper, a new five-axis ball-end milling dynamical model which considers the multiple interactions between the tool and workpiece is established for the first time. Based on the established dynamical model, the effects of regenerative effect, structural mode coupling and process damping on the dynamic characteristics of five-axis milling are investigated. In addition, the effects of lead angle and tilt angle on the stability prediction of five-axis milling are investigated. The experimental results show that the proposed five-axis milling dynamical model is more reliable than the traditional one in predicting the stability of five-axis milling.

As a typical single crystal material, the ground surface characteristics of sapphire are influenced by the relationship between machining direction and crystalline orientation. In this paper, the effects of grinding direction on the surface characteristics of the prism-plane sapphire were investigated by a series of sapphire grinding experiments under the orthogonal machining directions. The ground surface topography, surface layer lattice residual stress and degree of lattice distortion were measured. The results show that the grinding force with the grinding direction along the c-axis is greater than the grinding force along the m-axis or the a-axis, and serious damage was generated to the ground surface with grinding direction along the c-axis. The full width at half maximum intensity value of the X-ray rocking curve indicates that the residual stress of the ground surface with machining direction along the c-axis is greater than that along the m-axis or the a-axis, and the molten KOH etching analysis results manifest that the degree of lattice distortion of the ground surface with machining direction along the c-axis is higher than that along the m-axis or the a-axis. Therefore, the grinding direction along the m-axis or the a-axis is better suited to process prism sapphire.

The ultrasonic cavitation and vibration hybrid-assisted micro-drilling method is proposed to improve the micro-drilling performance of difficult-to-machine materials such as stainless steel. The mechanism of ultrasonic cavitation and vibration hybrid micro-drilling is investigated by performing the comparison tests of conventional micro-drilling (CD), ultrasonic vibration micro-drilling (UVD), ultrasonic cavitation micro-drilling (UCD), and hybrid micro-drilling (HD), and the effects of ultrasonic cavitation and vibration on stainless steel during micro-drilling process are analyzed considering the chip morphology, thrust force, tool wear, and micro-hole quality. Experimental results show that both CD and UVD produce strip-shaped chips, and the chips in UVD is much shorter than that in CD. However, the chips in UCD and HD are mostly fragmented short chips with a very small length ranging from tens to hundreds of microns. When drilling to the same number of holes, the thrust force, and micro-hole roundness error in UVD, UCD, and HD are less than that in CD; especially, those in HD are the smallest. Moreover, the tool wear in HD is also smaller than the other three processes. Thus, the HD method can effectively improve the chip breaking ability, greatly reduce the thrust force and extend the tool life, and the best processing quality of micro-hole is obtained by HD. The ultrasonic cavitation and vibration hybrid-assisted micro-drilling is demonstrated to effectively improve the micro-drilling performance of stainless steel.

As an unfavorable factor of machining process, chatter threatens the machined quality of workpiece, which determines the assembly and fatigue performance of the workpiece. During the interaction between machine tool and thin-walled workpiece, the process damping effect, multiple modes response and dynamic changes caused by the material removal of the in-process workpiece (IPW) will make the machining process more complicated and introduce great difficulties to dynamic modeling and performance prediction. In this paper, we considered the process damping determined by the indentation volume between flank face of milling tool and machined surface, and used multi-mode model to describe this behavior. In order to establish the assembled material removal model of the IPW dynamics with multiple modes, the structure dynamic modification (SDM) and finite element method (FEM) were combined together. The updated third-order full discretization method was applied to solve the dynamic equation in modal space. Then, the three-dimensional stability lobe diagrams (SLDs) with and without material removal along the tool path were obtained respectively by enveloping multiple modes of the IPW and milling tool together. Finally, the cutting tests were carried out. The experiments showed that the assembled model could predict the dynamics of IPW accurately, and the proposed stability analysis model was relatively close to experimental results. Besides, the modes of thin-walled workpiece with weak rigidity do not always play a dominant role in the process of machining. Although the material removal rate is limited by considering the multiple modes of the system, the processing quality can be ensured.

There is an increasing demand for microgrooves in optical systems with a pitch at wave length level. Precision glass molding (PGM) is one of the most efficient methods for fabricating microgrooves on glass surface. Nickel–phosphorus (Ni–P) exhibits excellent cutting properties and is developed as the mold material for glass microgrooves. However, the phosphorus in Ni–P mold tends to diffuse into the glass during the PGM process at high temperatures, which may reduce the optical performance of the molded glass microgroove component. In addition, the atomic diffusion increases the interface friction coefficient between the glass and the mold, resulting in the decrease of molding accuracy of the microgroove array. To solve these problems, a rhenium–iridium (Re–Ir) alloy coating is deposited on the surface of the Ni–P microgroove mold by ion sputtering. In this paper, the surface roughness of the mold before and after coating with Re–Ir alloy coating is investigated. The mechanical properties of Ni–P and the Re–Ir alloy coating are obtained using a combination of finite element method (FEM) and experimental tests. The mold deformation after heating to the molding temperature is analyzed. The results show that the mechanical properties of the Ni–P mold surface can be strengthened after being plated with Re–Ir alloy coating, the Re–Ir coating isolates the diffusion of phosphorus from the Ni–P mold, and improve the forming accuracy of glass microgrooves.

The effects of cemented carbide materials on cutting edge fracture mechanism of micro end mills in aluminum alloy 7075 machining are investigated. A series of micro milling experiments on the tool wear were conducted. The surface morphologies of micro end mills were observed, and the end teeth flank wear length and tool total cutting edge length reduction were measured. The results showed that the Co content and WC grain size of cemented carbides have significant effects on tool wear and cutting performance of the micro end mill. With increase of WC grain size, the tool end teeth flank wear length increases and the total cutting edge length reduction of the mill obviously increases. Thus, the micro end mill with finer grain size presents better wear resistance. However, with increase of Co content, the micro end mill exhibits less wear resistance. This can be explained that the adsorption energy between Co atom and Al atom become larger based on first principle calculation of adsorption energy between cemented carbides and aluminum alloy. The Co binder of tool material is dragged off by frequent fall off of built-up edge, resulting in more loss of Co element. Thus, the strength of the tool is decreased.

Compact high-performance electro-optic (EO) modulators are key elements for optical communications. An electro-absorption modulator is theoretically designed. Due to the introduction of graphene film over the silicon slot waveguide, the modulation efficiency is strongly improved. The effect of waveguide dimensions, dielectric insulator thickness, and carrier mobility on performances of the proposed EO modulator have been comprehensively investigated. For the 120-μm-long graphene-on-silicon waveguide modulator, the extinction ratio 28 dB and insertion loss 1.28 dB can be obtained at 1550 nm when drive voltage is 1.91 and 0.59 V, respectively. The 3 dB bandwidth of 117 GHz can be obtained at a small power consumption of 212 fJ/bit. The proposed modulator possesses a high figure-of-merit of 20.5. Its benefits of small size, power saving, and process compatible promises possible applications in on-chip signal processing.

Diamond cutting is a popular method to fabricate microlens array (MLA) on polymethyl methacrylate (PMMA); however, it is limited by brittle fracture, which is formed easily on the surface of MLA during the cutting process. In this paper, the formation mechanism of the brittle fracture is studied via a series of experiments including the slow tool servo (STS) cutting experiment of MLA, surface scratching experiment and sudden-stop cutting experiment. The effects of undeformed chip thickness, feed rate, and machining track on brittle fracture formation are investigated in detail. In addition, based on the fracture formation mechanism, a bi-directional cutting approach is proposed to eliminate the regional brittle fracture of the microlens during diamond cutting. An experiment was then conducted to verify the method; the results demonstrated that bi-directional cutting could eliminate brittle fracture entirely. Finally, a spherical MLA with the form error (vPV) of 60 nm and the surface roughness (Ra) of 8 nm was successfully fabricated.

Precision glass molding (PGM) has been developed and improved to produce various functional lenses in the optical industry. Tungsten carbide (WC) molds have received increasing attention due to the low thermal expansion coefficient and long service time but the molds are difficult to machine using micro-cutting or micro-grinding methods. Electrical discharge machining (EDM) milling is a promising method for the fabrication of WC molds used for microlens arrays but the significant electrode wear results in low machining accuracy. In this paper, a new method is proposed to address the electrode wear by utilizing in situ electrode trimming during EDM milling; the objective is to improve the accuracy of the WC mold used for microlens array fabrication. The feasibility of the proposed in situ electrode trimming method is verified by comparing the surface roughness of the pits on the mold surface fabricated by EDM milling with and without electrode trimming. In addition, the structure of the copper–tungsten electrode is redesigned to improve the electrode stiffness during in situ trimming. Furthermore, an in situ trimming setup is developed and the trimming process of the electrode is optimized.

In this paper, alkyl groups with different lengths are introduced to the two-dimensional spindle-type chromophores as the steric isolators to improve the poling efficiency and long term stability of the poled polymers for second-order nonlinear optical materials. The structure and thermal properties of alkyl functionalized chromophores are characterized by the 1H NMR, FT-IR, UV–Vis, DSC, TGA et al. The chromophores with different alkyl groups present extremely similar maximum absorbance wavelength (480 nm), which means they have very similar first-order hyperpolarizability. Guest-host polymer doped with chromophores has been prepared. Those materials display different glass transition temperatures and good thermal stability. According to the electro-optic coefficients studies and poling efficiency results, chromophores with longer alkyl side chain groups exhibit better poling efficiency and larger electro-optic coefficients. Especially for the chromophores with octyl group, the poling efficiency increases up to 3 times compared to the reference chromophore 2-(3-{2,5-Phenylmethanol-4-[4-(dimethylamino)styryl]-styryl-5,5-dimethylcyclohex-2-enylidene)malononitrile (STC), while the corresponding electro-optic coefficient of the poled polymers increases up to 4 times, indicating a significant effect of the isolate groups on improving the poling efficiency.

Nickel phosphorus (Ni-P) is a promising plating material for the moulds used in the precision glass moulding (PGM) of micropyramid structure components. A transverse planing method for machining Ni-P moulds with a micropyramid array pattern is analysed. Notable defects, including chippings and burrs, are observed on the exit and entry parts, respectively. The defect-forming mechanisms are analysed, and it is confirmed that a large cutting thickness and chip interference in non-free cutting tend to be the most effective methods for eliminating defects. Based on the above analysis, the diamond fly-cutting method is introduced into the micropyramid array Ni-P mould fabrication process. The advantage of the diamond fly-cutting method is revealed through comparison with the transverse planing method. To establish a contrast to the transverse planing method and evaluate the machining quality of the structure in the diamond fly cutting, a maximum effective cutting thickness of the remaining surface is proposed based on theoretical analysis. Finally, an experimental setup of ultraprecision fly cutting is established, and an ultraprecision micropyramid array is fabricated on nickel phosphorus plating.

A new tool strengthening method for micro-tools using pulsed magnetic treatment has been experimentally investigated. Compared with the conventional tool strengthening method, the pulsed magnetic treatment of micro-tools enables effectively reduce tool wear both by improving the mechanical properties of the tool material and changing the tool-chip contact friction mechanism which results in efficient chip removal and good surface quality. On account of this method, the untreated and treated micro-tools and three different magnetic properties of ferromagnetic, paramagnetic, and diamagnetic workpiece materials were used to perform comparative cutting experiments. The tool wear, cutting force, and surface roughness were measured to quantitatively investigate the influence of magnetic treatment on the micro-cutting process. Results showed that wear resistance of micro-tools could be improved when machining ferromagnetic and paramagnetic materials, of which the minor flank wear could be reduced by up to 56%. However, the tool wear increased when machining the diamagnetic materials. On the basis of relationship between micro-tool, micro-chip, and workpiece, the machining mechanism is analyzed in detail in pulsed magnetic treatment for micro-tools.

A broadband polarization-insensitive graphene modulator has been proposed. The dual built-in orthogonal slots waveguide allows polarization independence for the transverse electric (TE) mode and the transverse magnetic (TM) mode. Due to the introduction of metal slots in both the vertical and horizontal directions, the optical field as well as the electro-absorption of graphene are enhanced by the plasmonic effect. The proposed electro-optic modulator shows a modulation depth of 0.474 and 0.462 dB/μm for two supported modes, respectively. An ultra-low effective index difference of 0.001 can be achieved within the wavelength range from 1100 to 1900 nm. The 3 dB-bandwidth is estimated to be 101 GHz. The power consumption is 271 fJ/bit at a modulation length of 20 μm. The proposed modulator provides high speed broadband solutions in microwave photonic systems.

Material property and surface integrity are key parameters that influence the fatigue properties of metallic material, especially residual stress, microstructure, and surface topography. Multiple surface integrity parameters may change simultaneously during the process of surface formation, which makes it difficult to analyze the evolution rule of the individual parameter. In this paper, the influence of surface topography and texture on tensile fatigue properties of ZK61M magnesium alloy was studied. The ball-end milling method was applied to produce workpiece surfaces with three different morphologies and texture directions but ensuring the consistent residual stress, microstructure, and surface roughness in these three cases. The results showed that the fatigue life (14.5 × 104 cycles) of workpiece with surface texture direction parallel to the fatigue loading direction was even larger than the fatigue life (8.8 × 104 cycles) of the samples after polishing, and the fatigue life (3.2 × 104 cycles) of workpiece was the lowest when the angle of the surface texture was 45 degrees obliqued to the fatigue loading direction, which is about 64% lower than the samples after polishing. The surface texture direction can be controlled independently by this method, which provides a new consideration factor for evaluating the influence of surface topography on fatigue life.

We designed and fabricated a Mach–Zehnder interferometer (MZI) thermo-optic switch with an inverted triangular waveguide. The inverted triangular waveguide achieves a fundamental mode in a large waveguide dimension, which can reduce the coupling loss and increase the extinction ratio. The triangular waveguide-based switch was simulated and presented higher heating efficiency and lower power consumption than that of the traditional rectangular waveguide-based switch. Compared with the traditional rectangular waveguide-based device, the power consumption of the proposed device is reduced by 60%. Spacing photobleaching was introduced to fabricate the inverted triangular waveguide and adjust the refractive index to minimize the mode number. The insertion loss of the typical fabricated device with a 2 cm length is about 7.8 dB. The device shows an extinction ratio of ∼ 8.1 d B at 532 nm with a very low power consumption of 2.2 mW, and the switching rise time and fall time are 110 and 130 µs, respectively. The proposed single-mode waveguide and low-power-consumption optical switch have great potential applications in visible optical communication fields such as wavelength division multiplexing and mode-division multiplexing.

Surface-layer defects of M-plane sapphire caused by ultrasonic vibration-assisted cutting were investigated in this paper through comparison cutting experiments. Topography analysis results indicate that when the cutting direction is not along a-axis or c-axis, the spalling defects of conventional cutting groove are asymmetric because the probabilities of activated cleavage/twinning systems vary with machining direction; however, the vibrational cutting groove presents better symmetry and less spalling owning to the propagation of stress wave. The cross-section of cutting groove was obtained by focus ion beam cutting. The cross-section analysis shows that the subsurface defects of conventional cutting groove involve median cracks and lateral cracks, and the main propagating path of cracks is towards downward, which is the cause of the generation of serious spalling; however, lateral cracks are the main defect in the subsurface of the vibrational cutting groove, and they mainly propagate towards the free surface and give rise to material removal. The subsurface quality of cutting groove with ultrasonic assistance is better than that of the conventional cutting groove. It is evident that ultrasonic vibration can prevent the median crack from extending towards bulk material and contribute to improve the uniformity of groove quality.

Bioresorbable polymeric stents have attracted great interest for coronary artery disease because they can provide mechanical support first and then disappear within a desired time period. The conventional manufacturing process is laser cutting, and generally they are fabricated from tubular prototypes produced by injection molding or melt extrusion. The aim of this study is to fabricate and characterize a novel bioresorbable polymeric stent for treatment of coronary artery disease. Polycaprolactone (PCL) is investigated as suitable material for biomedical stents. A rotary 3D printing method is developed to fabricate the polymeric stents. Surface modification of polymeric stent is performed by immobilization of 2-N, 6-O-sulfated chitosan (26SCS). Physical and chemical characterization results showed that the surface microstructure of 3D-pinted PCL stents can be influenced by 26SCS modification, but no significant difference was observed for their mechanical behavior. Biocompatibility assessment results indicated that PCL and S-PCL stents possess good compatibility with blood and cells, and 26SCS modification can enhance cell proliferation. These results suggest that 3D printed PCL stent can be a potential candidate for coronary artery disease by modification of sulfated chitosan (CS).

Precision glass molding (PGM) is an efficient method to mass-produce glass microlens arrays with high-precision, the key to which is the high-quality mold. Silicon carbide (SiC) is considered to be an ideal mold material, but microstructures are difficult to machine in SiC because of its high hardness and strength. In this study, a microcutting-etching method involving the combination of single-point diamond cutting with inductively coupled plasma (ICP) etching is proposed to fabricate microlens arrays on 6H-SiC. The research described in this paper focuses on the use of the proposed method for controllable processing of a microlens array mold made of 6H-SiC. The microcutting process of the mask material and the etching process of the substrate material 6H-SiC are studied. The techniques to control the accuracy of the microlens array on 6H-SiC are managed by studying the cutting process, selectivity ratio and etching condition. In this manner, a ring-shaped microlens array with excellent accuracy and consistency is generated.

We propose a thermo-optic switch based on a symmetric directional coupler formed with two parallel identical two-mode waveguides, where the two modes in one waveguide can be simultaneously switched to the corresponding modes in the other waveguide. We design and fabricate such a device with polymer materials. Our fabricated device has a total length of 22.5 mm and operates at a switching power of 128 mW. The extinction ratios measured across the C-band are higher than ∼18 dB and ∼13 dB for the fundamental mode and the higher-order mode, respectively. The switching time is ∼1 ms. The performance of the device is insensitive to the polarization state of light. Our proposed mode-independent switch could find applications in reconfigurable mode-division-multiplexing transmission systems.

Morphological evolution of ripple on nickel surface induced by temporally shaped femtosecond laser irradiation were studied and compared with titanium. It was revealed that the transformation of single-pulse irradiation into double-pulse irradiation can exert very different influence on ripple morphology evolution for different metals. For nickel, the double-pulse irradiation resulted in the growth in rippled area, ripple period and ripple contrast, compared with the single-pulse irradiation, while double-pulse processing of titanium leads to reductions in in rippled area and ripple period. The contrasted influence of Te on electron-phonon coupling factor (G) for the two metals was the primary factor for the different behaviors of ripple morphology evolution with temporal pulse shaping.

Iron&ndash, nickel based ultra-high strength steel (wt. 18~20% Ni) is characterized by its high strength and low thermal conductivity, and is normally used to make key components by forming and machining processes. The optimization of these processes is based on a deep understanding of the mechanical and dynamic behaviors under high strain, high strain rate, and high temperature. In this paper, the relationship of stress to strain, strain rate, and temperature is systematically investigated by the dynamic compression tests combined with quasi-static compression tests, and the hardening and softening is associated with the transformation in microstructures. According to the analysis, dynamic recrystallization around 600 &deg, C is assumed to be one important influencing factor, hence hot deformation equations are established and the critical strain for dynamic recrystallization and the volume fraction of the dynamic recrystallized grains are defined.

In this work, thermo-optic (TO) lateral shift apodized sampled waveguide grating for 1550 nm wavelength is designed and fabricated by the metal-printing technique based on fluorinated epoxy-terminated polycarbonates (FBPA-PC EP) and fluorinated epoxy resin (FSU-8) materials. The optical characteristics and thermal stability of the FBPA-PC EP and FSU-8 materials are analyzed. To realize periodic wide-spectrum filtering and suppress the side-lobes of grating, a lateral shift apodized sampled waveguide grating is proposed. The 3 dB bandwidth and wavelength spacing can reach 4.8 nm and 9.7 nm. The side-lobe suppression ratio of proposed device can reach 22.6 dB, which is much better than traditional Bragg grating (6.1 dB). Driving electrical powers of 42.4 mW and 87.2 mW can produce blueshifts of 1.8 nm and 3.5 nm in the measured reflection spectrum, respectively. This device realizes the aim of multiple functions, including periodic filtering, wide-spectrum filtering, and high side-lobe suppression. The device is applicable of realizing signal processing and wavelength division multiplexing (WDM )systems.

Cross-shaped chisel edge thinning is an effective method to improve the drilling performance of non-coaxial helical flank micro-drill. In order to study the effect of the cross-shaped chisel edge on drilling performance, the mathematical model of cross-shaped chisel edge is proposed. The rake angle, lip inclination angle, uncut chip thickness, and uncut chip width are calculated by MATLAB software. Finite element models of four kinds of micro-drills with a different thinned chisel edge are established using DEFORM-3D software, and micro-drilling simulations on 304 austenitic stainless steel are carried out. The simulation results show that with a decrease in chisel edge length, the drilling force, tool temperature, tool wear, and curl degree of the chip are clearly reduced. However, for micro-drill without chisel edge, the torque and tool temperature are larger than other micro-drills, and string chips are generated during the drilling process. Furthermore, the non-coaxial helical flank micro-drill with an optimal cross-shaped chisel edge is manufactured by a six-axis CNC grinding machine, and the measurement results indicate that the geometrical parameters meet the designed values. At last, the micro-drill with an optimal cross-shaped chisel edge has a satisfactory drilling performance by the micro-drilling experiment.

The stability of micro-milling has an important influence on the machined surface, and choosing proper machining parameters can effectively avoid machining process instability and dynamic error. The frequency response function (FRF) of micro-milling tool point varies with tool overhang lengths, and it affects stability lobe diagram (SLD) of the machining system. During the micro-milling process, the cutting thickness was divided into the shearing zone and the plowing zone. In the shearing zone, the cutting thickness was calculated with considering cycloidal tool path and dynamic cutting thickness. After the micro-milling force model was established, the receptance coupling substructure analysis (RCSA) and experimental modal analysis (EMA) were used to obtain the FRFs at the micro-milling tool point. The 2 three-dimensional diagrams, SLD and surface location error (SLE), were developed comprehensively by means of frequency domain method, and the flank micro-milling experiments were carried out. The validity of the three-dimensional SLD containing tool overhang length and the prediction model of SLE was verified by the experimental results, and surface topography was characterized to show the actual machining state. The experimental results show that, compared with SLE, the change of tool overhang length had more significant influence on SLD, and the chatter remarks were not very obvious on the bottom of the workpiece no matter whether the machining process was stable or not. In unstable region, chatter caused by cutting tool left marks on the machined surface. Under the condition of stable milling, a machined surface with smaller SLE and better topography was obtained. The 2 three-dimensional diagrams can provide good references for the selection of optimal tool overhang length and machining parameters comprehensively.

In this paper, an integrated processing method was demonstrated to fabricate the polymer-based thermo-optic (TO) switch with low power consumption. The characteristic parameters of the switch were carefully designed and simulated. The air trench structure was exploited to reduce the power consumption, which can be formed with the waveguide simultaneously by the integrated processing method. Moreover, the introduced polymer/silica hybrid waveguide structure can also improve the response time of the device. A typical fabricated switch presented a low switching power of 5.2 mW. The measured switching rise time and fall time are 192.2 and 201.1 μs, respectively.

In this paper, we present and analyze a compact inner-wall grating slot microring resonator (IG-SMRR) with the footprint of less than 13 &mu, m &times, 13 &mu, m on the silicon-on-insulator (SOI) platform for label-free sensing, which comprises a slot microring resonator (SMRR) and inner-wall grating (IG). Its detection range is significantly enhanced without the limitation of the free spectral region (FSR) owing to the combination of SMRR and IG. The IG-SMRR has an ultra-large quasi-FSR of 84.5 nm as the detection range, and enlarged factor is up to over 3 compared with the conventional SMRR. The concentration sensitivities of sodium chloride solutions and D-glucose solutions are 996.91 pm/% and 968.05 pm/%, respectively, and the corresponding refractive index (RI) sensitivities are 559.5 nm/RIU (refractive index unit) and 558.3 nm/RIU, respectively. The investigation on the combination of SMRR and IG is a valuable exploration of label-free sensing application for ultra-large detection range and ultra-high sensitivity in future.

In industrial forming and machining process, the large plastic deformation of material takes place in wide loading ranges of strain-rate and forming temperature. A satisfactory modelling of quasi-static and dynamic material behaviors is of great importance for understanding physical process and processes optimization. A dependence-based integrated methodology, together with an improved weighted multi-objective parameter identification strategy is presented for the development of phenomenological constitutive model and the parameter identification using experimental data from quasi-static and dynamic tests with instantaneous strain rate variations and plastic strain-related temperature changes. The improved multi-objective parameter identification model is reformulated by introducing three weighting factors for valuing different measure errors and fit standard errors in individual objective function corresponding to each test, considering the sampling point number and active material parameter number under different loading conditions, and balancing optimization opportunity of quasi-static and dynamic sub-objective functions. The methodology is verified for feasibility through illustrative constitutive identification for SiCp/Al composites. This may provide a methodology of constitutive modelling for predicting material behaviors in quasi-static and dynamic modes equally well.

Micro ball-end milling is an efficient and feasible method for the fabrication of microlens array molds which are widely applied in the aerospace, mechanical electronics, optics, and optoelectronics fields. The geometric structure of the micro ball-end mill plays an important role in micro dimple milling performance. The relief angle, as one of the major geometric parameters of the micro ball-end mill affects the sharpness of the cutting edge and determines friction between the tool and the workpiece. To investigate effective fabrication of a micro ball-end mill with different relief angles, this paper proposes a practical grinding method for the relief face validated by a grinding experiment, in which micro ball-end mills with relief angles of 10°, 20°, and 30° are fabricated. Furthermore, to analyze the influence of the relief angle on milling performance, micro dimple milling experiments on die steel material H13 with fabricated mills are carried out. The milling force, tool wear, and machining quality are measured and analyzed. The experimental results show that the micro ball-end mill with a 20° relief angle is more appropriate for micro dimple milling compared to the other two mills.