The triply periodic minimal surface lattice structure is innovatively introduced into the design of flexure hinges in this paper. Four types of triply periodic minimal surface lattices are generated by approximate mathematical expressions. The compliance characteristics of these four lattices are simulated by finite element analysis (FEA), and it is found that the primitive lattice (P-lattice) is the most suitable lattice for flexure hinges. Simplified model of single P-lattice and one-dimensional parallel structure composed of several P-lattices are proposed. Finally, the P-lattice is integrated into the beam portion of flexure hinges by Boolean operation, and this new type of flexure hinge is additively manufactured. The FEA and experimental results show that the compliance and compliance ratio of this new type of leaf flexure hinges are greatly improved. 相似文献
Waxy, normal and high-amylose maize starches were subjected to heat-moisture treatment (HMT) and then added to wheat flour (WF) in different ratios (1%, 5% and 10%). The properties of blends and their cooked noodles were studied to investigate the effects of HMT starches. The incorporation of HMT starch in WF led to an increase in swelling power, peak viscosity and breakdown and to a decrease in setback, thus inhibiting retrogradation, hence enhancing resultant noodle softness. Compared to the same addition ratio of native starch to WF, HMT starch led to higher tensile strength and extensibility in resultant noodles. WF with added HMT starch had higher resistant starch than with native starch. This study showed that addition of HMT maize starch has potential to bring nutritional benefits. However, it is necessary to select the proper blending ratio and amylose content of starch to add, in consideration of its effect on noodle quality. 相似文献
Metallurgical and Materials Transactions B - Sintering behaviors of two types of powder compact, i.e., Ti/Al and TiH2/Al, under vacuum were studied using in situ neutron diffraction, in situ... 相似文献
Degenerate pattern is a seemingly disordered morphology but it exhibits the inherently ordered crystal connected with tip-splitting and limited stability which makes it difficult to observe in the metallic system. Here we employ (100)[011] orientated planar-front seeds using directional solidification and reveal the fundamental origins of the degenerate pattern growth in an Al-4.5 wt% Cu alloy. We find that the spacing of the tip-splitting (λ) in the degenerate of the alloys followed a power law, λ∝V−0.5, and the frequency (f) of the splitting was related to the growth velocity (V) by ƒ∝V1.5. The dimensionless growth direction (θ/θ0) increased monotonously and approached 0.6 with faster velocity, attributed to its anisotropy in the interface kinetics. Once growth velocity exceeded a threshold, two types of pattern transitions from degenerate to regular dendrites were proposed. One of them exhibited a random and chaotic mode and the other underwent a rotation in growth direction. 相似文献
Selective laser sintering was combined with reactive melt infiltration to fabricate SiSiC part, and the effects of carbon fiber (Cf) on the properties of the SLS green body, the carbonized and final SiSiC sample were investigated. Results show that the addition of an appropriate amount of Cf (1.59 wt%~2.97 wt%) can increase the bulk density and geometric precision of the sample at all stages, and improve the mechanical properties of green and carbonized samples. The main phases composed of the SiSiC composite were free Si, a-SiC, β-SiC, plus a very small amount of Al–Si alloy. With 1.59 wt% Cf addition, a relatively comprehensive favorable macro-properties of both the green sample and carbonized sample was achieved, and the homogeneous microstructure of the latter favored the decreased free Si content and increased β-SiC content of the final composite. The evolution mechanism of Cf added to the raw material is inferred to be the mutual diffusion of [C] and [Si] that occurred at the Cf/Si melt boundary leading to the formation of the siliconized Cf with relatively large diameter size (24.3 μm) and high aspect ratio (>30). Amorphous C, which derived from the pyrolysis of epoxy resin E12, undergone a dissolution-precipitation mechanism with the formation of fine-grain β-SiC. 相似文献
This paper presents a neural network technique combined with an optical measurement system for the characterization of mechanical vibrations in industrial machinery. In the proposed system, the Gaussian beam of a laser source illuminates on an array of photodetectors. If either the laser source or the photodetector array is coupled with a vibrating system, then the optical powers detected by the photodetectors will vary accordingly, and are expected to reflect the magnitude and frequency of the X–Y planar vibrations of the monitored system. The time-varying optical powers are input to an artificial neural network-based vibration monitoring system which maps the power distributions to the X–Y position of the laser beam center. An experimental setup of the system is built and used for training and testing purposes. The obtained experimental results demonstrate the adequacy of combining optical techniques with neural networks to estimate the vibration frequency and magnitude. Estimated frequencies were within 1% of the actual ones, and the estimated magnitudes were within 29% of the actual magnitudes when using a chirp signal in the training phase. The magnitude estimation percentage error was further reduced below 12% when the neural network was trained with a decaying chirp signal. 相似文献
3D printing offers great potential for developing complex flexure mechanisms. Recently, thickness-correction factors (TCFs) were introduced to correct the thickness and stiffness deviations of powder-based metal 3D printed flexure hinges during design and analysis. However, the reasons for the different TCFs obtained in each study are not clear, resulting in a limited value of these TCFs for future design and fabrication. Herein, the influence of the porous layer of 3D printed flexure hinges on the hinge thickness is investigated. Samples of parallelogram flexure mechanisms (PFMs) were 3D printed using selective laser melting (SLM) and 316L stainless steel powder. A 3D manufacturing error analysis was completed for each PFM sample via 3D scanning, surface roughness measurement and morphological observation. The thickness of the porous layer of the flexure hinge was independent of the designed hinge thickness and remained close to the average powder particle diameter. The effective hinge thickness could be estimated by subtracting twice the value of the porous layer thickness from the designed value. Guidelines based on finite element analysis and stiffness experiments are proposed. The limitations of the presented method for evaluating the effective hinge thickness of flexure hinges 3D printed via SLM are also discussed.