The microplastic deformation of TiAl alloys during nano-scratching is synergistically governed by geometrically necessary dislocations (GNDs), statistically stored dislocations (SSDs), and back stress. However, conventional standalone experimental methods struggle to quantitatively characterize the strain-rate sensitivity of these underlying microscopic deformation mechanisms. To address this challenge, a strain-rate-dependent crystal plasticity finite element method (CPFEM) was developed to capture the coupled evolution of GNDs, SSDs, and back stress. The accuracy of the constitutive model was verified via nano-scratch experiments conducted on both γ and α2 grains. The simulated scratch forces exhibit an excellent agreement with the experimental data, yielding a peak load deviation of merely 2.13%. The results indicate that the intrinsic crystallographic heterogeneity between the two phases leads to distinct strain-rate-induced GND accumulation behavior, which consequently renders a higher scratch resistance in the α2 phase than in the γ phase. Furthermore, a comparative analysis between simulations with and without GNDs quantitatively demonstrates that strain-rate-induced GNDs trigger strong localized internal stress fields. This mechanism elevates the predicted hardness by 15% compared to the benchmark model incorporating only SSD hardening. These findings confirm that the strain rate effectively enhances the strain-hardening capacity while simultaneously improving the microplastic flowability through the stimulated co-proliferation of GNDs and SSDs, thereby achieving concurrent material strengthening and processing damage mitigation.
Laser self-mixing interferometry (SMI) and its derivative, self-mixing grating interferometry (SMGI), offer compact, self-aligned, single-channel architectures for nanoscale displacement metrology. Built on a Cr atom-lithography grating (ALG) whose period, d = (212.7779 ± 0.0021) nm (k = 1), is directly traceable to an atomic transition frequency with picometre-level accuracy, an SMGI acquires a length scale anchored in this traceable standard. In this grating-based configuration, however, the limited diffraction efficiency keeps the SMGI under weak feedback, where the direction-dependent fringe asymmetry is subtle, making phase reconstruction near motion turning points susceptible to noise, and direction misjudgement. This paper proposes a direction-constrained phase reconstruction (DCPR) method: Hilbert analytic phase provides continuous phase increments; a direction function constructed from piecewise integration of the differential envelope's midline imposes a physical constraint on phase increments; and piecewise cubic Hermite interpolating polynomial (PCHIP) interpolation suppresses spurious increments near turning points. Validated on a Cr-ALG-based SMGI system against a Fabry–Pérot reference, the DCPR reconstruction yielded cycle-wise forward–return RMS deviations relative to the reference of 8.4 ± 1.7 nm and 12.4 ± 0.6 nm for the nominal 8- and 12.5-μm motion datasets, respectively. DCPR converts weak directional asymmetry into a cumulative physical constraint, providing a robust phase-reconstruction scheme for compact SMI/SMGI displacement sensing.
Electron beam lithography (EBL) pattern fidelity is strongly affected by electron scattering, energy deposition, and resist development, yet the geometry-dependent influence of point spread function (PSF) parameters remains insufficiently quantified. This study develops a PSF-driven EBL modeling workflow combining Monte Carlo electron scattering, analytical PSF fitting, exposure convolution, and threshold-based contour prediction. A hybrid scattering model is selected by balancing computational cost and PSF-fitting accuracy. The workflow is validated using isolated-square, tuning-fork, rectangular-array, and L-shaped patterns, yielding IoU values of 95.8%, 92.7%, 92.1%, and 93.1%, respectively. For the L-shaped pattern, Monte Carlo perturbation and Bootstrap resampling give mean edge-placement errors of 6.69 and 6.52 nm. Global sensitivity analysis shows that the effects of the forward-scattering length α, backscattering length β, and backscattering energy weight η depend strongly on geometry and spatial scale. Retrospective sample-size analysis confirms stable first-order and total-order Sobol estimates using 500 model evaluations. Pairwise second-order analysis further reveals that α−β and β−η interactions dominate in H-shaped, dense LSB, and two-plane iISO geometries, whereas α−η is the largest pairwise contribution for isolated ISO patterns. The results provide a quantitative basis for geometry-aware PSF calibration and test-pattern design.
This paper presents the first laser diode-based raster scanning imaging system using self-mixing interferometry (SMI) for in-process inspection of directed energy deposition (DED) additive manufacturing. The prototype achieves high-fidelity surface imaging at 20 μm spatial resolution, offering flexible region-of-interest scanning. Validation includes detecting 87 μm defects on DED components. A core innovation is its inherent ambient light immunity, critical in high-stray-light DED environments. This immunity stems from synergistic spectral filtering, temporal photon gating via galvanometric scanning with 5 μs dwell time, and adaptive feedback control (AFC) stabilizing signal-to-noise ratio (SNR) under intense 240 klux illumination. The open-source design with non-customized components, outputs standardized 8-bit grayscale bitmaps up to 3000 × 3000 pixels, requiring no preprocessing for AI-driven quality monitoring. Experimental studies show scanning frequency governs stability, with 83.3 kHz being optimal. They also reveal that increased detection distance degrades contrast, and resolution affects image detail quality but is capped by the 200 μm optical spot size. The system's compactness and feasibility for dual-view integration demonstrate transformative potential for real-time, closed-loop DED process control.
We propose and demonstrate a novel fiber-bundle-type polarization-based rotary encoder that integrates a reflective optical configuration with four-directional wire-grid polarizers (WGPs). A four-directional WGP chip was fabricated using electron beam lithography and a lift-off process, and subsequently bonded to the end face of an optical fiber bundle. By combining this chip with a reflective polarizing element, photodiodes, and signal processing circuits, we constructed a compact rotary encoder with optical fiber transmission. Transmission measurements confirmed that the fabricated WGP chip functions as a polarizer with extinction ratios of up to 17.5 dB at 850 nm. Performance evaluation of the prototype showed an angle detection error ranging from −0.67° to 0.61° and a resolution of 12,585 pulses per revolution, ensuring stable angle detection over a 180° range. These results verify the potential of the proposed configuration as a miniaturized, high-resolution, and noise-robust rotary encoder for precision positioning applications.
In secondary assembly of machine tool linear guideways, a small assembled straightness error does not necessarily ensure stable straightness retention after a disturbance loading–unloading cycle. This study investigates how the first preassembly response affects the straightness drift error after secondary assembly. A nonlinear finite element model is developed by considering the initial geometric error, equivalent residual stress, bolt preload, and contact states at the joint interfaces. The first preassembly response is described by local vertical deformation, contact pressures at the guideway-shim and shim-bed interfaces, effective contact state, and bed rebound. To introduce this response into the assembly process, the detrended vertical displacement component is projected into a scalar correction term for the secondary support height. A contact support compatibility index is then defined to evaluate pressure nonuniformity, pressure mismatch between the two support interfaces, and effective support continuity. The results show that the assembly scheme with the smallest assembled straightness error does not necessarily produce the smallest unloading drift error. Under the baseline numerical model, the response-transfer correction scheme reduces the unloading drift from 1.44 μm for geometric shim compensation to 0.94 μm, while maintaining effective support at all 12C2/C3 support pairs. The study provides a finite element framework for evaluating response transfer, contact support compatibility, and straightness retention after unloading in secondary assembly of linear guideways.
In response to poor milling tool stability under large overhang conditions, a simulation-based analysis of tool system rigidity was conducted. A Timoshenko cantilever beam model of the large overhang tool system was first established to identify the main factors affecting toolholder deformation. Based on this model, a three-dimensional finite element model was developed, and three modified toolholder designs were proposed through material and geometric changes. The FE simulation outputs, including maximum total deformation, maximum equivalent elastic strain, and the nominal interface-stress indicator, were used to compare the static deformation response and relative sensitivity to interface loading among the evaluated toolholder designs. The modified toolholders were then manufactured and compared with the original toolholder through milling experiments under different machining parameter combinations. The results show that the modified toolholders improved tool life, while their effects on surface quality depended on the machining condition under the tested conditions. Toolholder 3, featuring two equal-length cylindrical reinforcement sections, achieved the best overall performance by reducing tool deformation while maintaining a relatively low nominal interface-stress indicator and manufacturing cost. Within the tested parameter combinations, higher feed rate combined with reduced axial engagement consistently prolonged tool life, whereas its effect on surface roughness depended on the cutterhead and toolholder configuration. For Toolholder 3 with the D100 cutterhead under the higher-feed/lower-axial-engagement condition, tool life increased by 50% and surface roughness Ra decreased by approximately 46% relative to Toolholder 1 under the same machining condition.
Grazing-incidence X-ray mirrors constitute the pivotal optical elements for next-generation space-based astronomical observation and synchrotron radiation facilities; their manufacturing accuracy directly governs the focusing efficiency and imaging resolution of high-energy radiation. Consequently, extremely stringent specifications are imposed on both the surface figure (peak-to-valley, PV < 1 μm) and the surface roughness (Ra < 1 nm). To address the high cost and limited flexibility of conventional large-scale gantry optical machining platforms, as well as the insufficient stiffness and challenging force regulation associated with industrial robots, this work develops a pneumatic constant-force polishing system based on a robotic manipulator that integrates “macroscopic trajectory generation” with “microscopic contact-force sensing and active control.” The proposed system exhibits excellent and stable material removal performance in the polishing of single-crystal silicon. Beyond mitigating the longstanding force–position coupling issue in robotic polishing, this study provides an enabling theoretical foundation and a practical technological paradigm for the deterministic fabrication of large-aperture, freeform optical surfaces.
Micromanipulation technology has been widely applied in advanced fields such as biomedical detection and precision assembly, and is particularly suitable for semiconductor chip packaging and precision assembly of microelectronic devices. To address the insufficient stability of conventional two-jaw microgrippers when gripping three-dimensional microdevices such as spheres and cylinders, this paper develops a piezoelectrically actuated three-jaw microgripper based on compliant mechanisms. The main structure of the microgripper consists of a spatial bridge-type mechanism and a parallelogram-type lever mechanism, enabling two-stage amplification of the input displacement and synchronous centripetal motion of the jaws. A loop-shaped integral structure is adopted for the main body, which effectively improves the structural compactness of the device and the motion consistency of the jaws. The kinematic, static, and dynamic characteristics of the microgripper are analyzed using the pseudo-rigid-body method and finite element simulation, and its key dimensional parameters are optimized. To reduce the influence of hysteresis, model uncertainty, and external disturbance on the tracking accuracy of the piezoelectric actuation system, a disturbance-observer-based (DOB) PI composite closed-loop control method, referred to as DOB-PI control, is further developed, in which equivalent disturbance estimation and input compensation are realized using a low-frequency nominal model. Experimental results show that the proposed microgripper achieves a displacement resolution of 0.1 μm, a force resolution of 0.2 mN, a displacement response time of 36 ms, a force response time of 16 ms, and a resonant frequency of 938 Hz. Compared with conventional PI control, DOB-PI control exhibits better disturbance rejection under both step and sinusoidal reference inputs, effectively reducing the output deviation caused by disturbance. The microgripper can stably grip various three-dimensional microdevices, including cylinders, spheres, and complex hexagonal prisms.
To simultaneously enhance the surface polishing quality of workpieces and reduce processing costs, this study proposes a fabrication method for Pore-Confined Free Abrasive Polishing Disc (PC-FAPD) using water-soluble shell Diamond@Na2SO4 core-shell abrasives. During polishing, the Na2SO4 shell dissolves to form pore-confined free abrasives, which act in a three-body friction mode under pore constraints to enable high-efficiency, high-quality polishing while ensuring high abrasive utilization. Diamond@Na2SO4 core-shell abrasives were synthesized via evaporative crystallization, and the influence of different Diamond/Na2SO4 mass ratios on coating thickness was systematically investigated, followed by an evaluation of the polishing performance of PC-FAPD with core-shell abrasives of varying coating thicknesses. Results show that as the Diamond/Na2SO4 mass ratio decreases, the Na2SO4 coating becomes thicker and denser; at a 1:3 mass ratio, the C atomic percentage in the abrasives drops from 92.690% to 12.628%, the particle size increases from 4.3 μm to 6.3 μm, and the diamond coating thickness reaches 1 μm. Polishing tests on single-crystal SiC indicate that the uncoated abrasive disc achieves the highest material removal rate (MRR) of 2968.06 nm/h, while the 1 μm-thick coating disc yields the lowest surface roughness (Sa = 1.31 nm). As the coating thickness of the core-shell abrasives increases, the material removal mode of the abrasives on the workpiece becomes closer to that of free abrasives. This reduces the MRR to a certain extent but enables better surface quality, with the performance of repeated polishing remaining relatively stable. Friction and wear experiments confirm that thicker coatings transition the removal mode from two-body plowing to three-body rolling and scratching. This research provides a novel strategy for ultra-precision machining.
Micro/nanostructured surfaces are widely applied in drag reduction, optical, and medical fields. The machining accuracy and quality of micro/nanostructured surfaces directly determine the operational performance of functional devices. In this study, a one-degree-of-freedom ultrasonic vibration generator was carefully developed, and the ultra-precision sculpturing process was proposed to enable efficient and precision machining of micro/nanostructured surfaces. Firstly, by integrating one-dimensional longitudinal vibration theory with finite element simulation optimization, an ultrasonic vibration generator was designed. Then, impedance analysis and sweeping frequency testing confirmed the resonance characteristics and vibration stability of the system. The measured resonant frequency deviated by only 2.5% from the designed value, and the vibration amplitude remained stable at 1.6 μm. Finally, cutting experiments demonstrated the high performance fabrication of micro/nanograting spacing of 460 nm and 700 nm, with the workpiece surface exhibiting distinct red and blue structural colors and well-defined boundaries. The results validated the structural reliability and superior machining performance. The machined surface was dominated by residual compressive stress, which increased as the microstructure spacing decreased. Therefore, this study provides a theoretical foundation and technical support for the manufacturing of functional micro/nanostructured surfaces.
