遥操作工程机器人系统临场感技术研究-6自由度临场运动感觉反馈技术的研究进展

 研究开发出一种遥操作工程机器人系统，可以应用于诸如火灾现场的修复作业等广阔的领域．该系统由伺服控制的工程机器人、2根从远处操纵工程机器人的操纵杆、视频系统和6自由度运动模拟器组成．操作者坐于座椅上，座椅固定于运动模拟器的上方． 该系统需要解决的一个关键问题是如何使操纵者高质量地获得工作现场的临场运动感觉． 提出了一种6自由度临场运动感觉反馈方法，其信号源来自工程机器人上安装的6个加速度传感器． 该方法的有效性已为实验所证明，即应用6自由度运动模拟器不但可以高质量地模拟工程机器人单个自由度的运动：滚动、俯仰、转动以及前后、左右、上下的平移，而且可以高质量地模拟工程机器人的各种复合运动．     

CREEP-FATIGUE CRACK GROWTH AND FRACTOGRAPHY OF A TYPE 304 STAINLESS STEEL AT ELEVATED TEMPERATURE

Abstract— Creep-fatigue crack growth behaviour of a Type 304 stainless steel under four types of reversed loading patterns (P-P, P-C, C-P and C-C) was investigated and the results are discussed in the light of fracture mechanics and fractography. The crack growth rate for all of the four types of loading was successfully correlated in terms of the cyclic integral range λ J. It was unnecessary, for practical purpose, to divide Ay into a fatigue component, λ J _f, and a creep component, λ J _c, as has been done elsewhere. The transition of the correlating fracture mechanics parameter from fatigue to creep was not necessarily associated with the fracture morphology. This was related to the longer transition hold time in morphology in C-C type loading compared to C-P type loading, and was attributed to recovery of grain boundary sliding during the compression hold in the C-C type loading.     

Thermal Shock Behavior of Porous Silicon Carbide Ceramics

Using the water-quenching technique, the thermal shock behavior of porous silicon carbide (SiC) ceramics was evaluated as a function of quenching temperature, quenching cycles, and specimen thickness. It is shown that the residual strength of the quenched specimens decreases gradually with increases in the quenching temperature and specimen thickness. Moreover, it was found that the fracture strength of the quenched specimens was not affected by the increase of quenching cycles. This suggests a potential advantage of porous SiC ceramics for cyclic thermal-shock applications.     

Heavy arsenic doping of silicon grown by atmospheric pressure selective epitaxial chemical vapor deposition

Selective epitaxial Si with a high arsenic concentration of 2.2×10¹⁹ atoms/cm³ was deposited at a high growth rate of 3.3 nm/min under atmospheric pressure. It was confirmed that this method had excellent selectivity and produced films having good crystalline quality, abrupt dopant profiles at the interfaces, and smooth surfaces. The growth mechanism is discussed in terms of the relationship between the effects of arsenic surface segregation and etching by hydrogen chloride.     

Fracture Energies of Tape-Cast Silicon Nitride with β-Si3N4 Seed Addition

The fracture energies of the tape-cast silicon nitride with and without 3 wt% rod-like β-Si₃N₄ seed addition were investigated by a chevron-notched-beam technique. The material was doped with Lu₂O₃–SiO₂ as sintering additives for giving rigid grain boundaries and good heat resistance. The seeded and tape-cast silicon nitride has anisotropic microstructure, where the fibrous grains grown from seeds were preferentially aligned parallel to the casting direction. When a stress was applied parallel to the fibrous grain alignment direction, the strength measured at 1500°C was 738 MPa, which was almost the same as room temperature strength 739 MPa. The fracture energy of the tape-cast Si₃N₄ without seed addition was 109 and 454 J/m² at room temperature and 1500°C, respectively. On the contrary, the fracture energy of the seeded and tape-cast Si₃N₄ was 301 and 781 J/m² at room temperature and 1500°C, respectively, when a stress was applied parallel to the fibrous gain alignment. The large fracture energies were attributable primarily to the unidirectional alignment fibrous Si₃N₄ grains.     

Investigation of the effect of surface phosphate ester dispersant on viscosity by coarse-grain modeling of BaTiO slurry

To understand the role of phosphate ester dispersant, we investigated the rheology of a BaTiO slurry. For the model case, a coarse-grain molecular dynamics (CGMD) simulation was performed with the butyral polymer didodecyl hydrogen phosphate (DHP) in the toluene/ethanol solvent. By systematically analyzing the effect of DHP from an atomic-scale first principle and from all-atom MD to microscale CGMD simulation, we investigated how the adsorption of a DHP dispersant on a BaTiO surface affects the microstructure rheology of a BaTiO slurry. The first-principle and all-atom MD simulation suggests that DHP molecules prefer to locate near the BaTiO surface. CGMD simulation shows a reduction in viscosity with an increase in dispersants, suggesting that the dispersant population near the BaTiO surface plays a key role in controlling the rheology of the BaTiO slurry. In this study, we propose an approach for understanding the BaTiO slurry with molecular-level simulations, which would be a useful tool for efficient optimization of slurry preparation.     

Effect of Agglomeration on Mechanical Properties of Porous Zirconia Fabricated by Partial Sintering

Porous ZrO₂ ceramics were fabricated by compacting a fine ZrO₂ powder, followed by pressureless sintering. Two unidirectional pressures of 30 and 75 MPa were used to prepare the green compacts. The strength and the fracture toughness of porous ZrO₂ specimens sintered from the compacts prepared by 75 MPa were substantially higher than those by 30 MPa, especially for the specimens with low porosity. However, the corresponding Young's moduli were identical. This caused the strain to failure of these porous bodies to increase significantly with increasing compaction pressure. Microstructural analyses showed that a number of voids and small flaws existed in the green compacts prepared by the lower pressure, due to the agglomeration of fine ZrO₂ grains. It was revealed that the ZrO₂ agglomeration resulted in a localized nonuniform shrinkage and degraded the mechanical properties of porous ZrO₂ ceramics.     

Uniformly Porous Composites with 3-D Network Structure (UPC-3D) for High-Temperature Filter Applications

Uniformly porous composites with 3-D network structure (UPC-3D) have been recently developed via a pyrolytic reactive sintering process, which takes advantage of the evolved CO₂ gas from a decomposing carbonate source (e.g., dolomite, CaMg(CO₃)₂) and does not require any additional pore-forming agent nor long-time burning-out process. Through liquid formation via LiF doping, strong necks are formed between constituent particles before completion of the pyrolysis of carbonate, resulting in the formation of a strong 3-D network structure. The pore size distribution is very narrow (with typical pore size: ∼1 μm), and the porosity was controllable (∼30–60%) by changing the sintering temperature. This article presents the development details of UPC-3D, and reports the recent findings in CaZrO₃/MgAl₂O₄ system, which will be one of the more promising systems for practical applications.