35MN水压试验机插销油缸漏油的分析与处理

某公司35 MN水压试验机安装使用以来,一直存在插销油缸频繁漏油的现象,分析原因是插销油缸O型密封圈损坏所致.通过将原水压试验机插销油缸换向阀由二位四通阀改为带有O型中位机能的三位四通阀,并利用O型中位机能的隔断油路的功能,避免了水压试验机挡料装置受管时对插销油缸无杆腔的压力冲击,有效杜绝了插销油缸漏油事故的发生.     

Potential mechanism involved in removal of hydrophobic pesticides from vegetables by hydrostatic pressure

In our previous study, we found that the removal rate of hydrophobic pesticide on cherry tomatoes shows the maximum by hydrostatic pressure treatment (HPT) around 75 MPa. The objective of this study was to investigate the causes of reduction in the removal rate above 75 MPa HPT. Separating cuticle from flesh of the cherry tomatoes after HPT and examining the pesticide residues in each part the following was found: the detectable pesticide amount in the flesh part showed little change from the non-treated samples. Ethanol was applied as the surrounding solution during pressurization so as to prevent the reattachment of pesticide and decrease water solubility, and removal efficiency declined little. The effect of HPT on removal rate time indicated no significant difference at 0.1 MPa, the optimum level to be at 75 MPa for a comparatively short time, and at 400 MPa removal rate increased with time.     

Analysis of the strengthening mechanism based on stress-strain hysteresis loop in short fiber reinforced metal matrix composites

The strengthening mechanism of short fiber or whisker reinforced metal matrix composites has been studied by a continuum mechanics treatment utilizing finite element analysis (FEA). To assess the tensile and compressive constitutive responses, a constraint-unconstraint comparative study based on stress-strain hysteresis loop has been performed. For analysis procedures, the aligned axisymmetric single fiber model and the stress grouping technique have been implemented to evaluate the domain-based field quantities. Results indicate that the development of significant triaxial stresses within the matrix both for the tensile and compressive loading, due to the constraint imposed by reinforcements, provide an significant contribution to strengthening. It was also found that fiber stresses are not only sensitive to the fiber/fiber interaction effects but also substantially contribute to the composite strengthening both for the tensile and compressive loading.     

Effect of pressure on photocatalytic water splitting performance of Z-scheme RP/CH3NH3PbI3 perovskite heterostructure

Energy is an extremely important strategic material basis for socio-economic development. Here, we have investigated the structural, electronic, optical, charge transfer and photocatalytic mechanism of red phosphorus RP/CH₃NH₃PbI₃ heterostructure under hydrostatic pressure by density functional theory (DFT) calculations. Ab initio molecular dynamics (AIMD) prove RP/CH₃NH₃PbI₃ is thermodynamically stable. Interestingly, direct band gap of RP/CH₃NH₃PbI₃ decreases linearly with increase of pressure. The band gap is 1.43 eV at 1.5 GPa, which can enhance the absorption of visible light and generate redshift in absorption edge. Interface charge redistribution makes valence/conduction band edge positions of RP monolayer and CH₃NH₃PbI₃ (010) surface vary with Fermi level, forming an internal electric field have ability to separate electron-hole pairs. Typical Z-scheme heterostructure is formed and supposed to have resulted strong redox ability. The theoretical results hope to provide a possibility for the future experimental preparation of CH₃NH₃PbI₃-based photocatalysts.     

The vibration and buckling of freely supported non-homogeneous orthotropic conical shells subjected to different uniform pressures

The paper examines the vibration and stability of freely supported orthotropic truncated and complete conical shells with non-homogeneous material properties under uniform lateral and hydrostatic pressures. First, the basic relations have been obtained for orthotropic truncated conical shells, Young's moduli and density which vary continuously in the thickness direction. By applying the Galerkin method, the buckling pressures and lowest cyclic frequencies of truncated and complete conical shells are obtained. To verify the accuracy of the results, comparisons are made with results available in the open literature. This study also examines in detail the effects of the variations of conical shell characteristics, the effects of the non-homogeneity and the orthotropy on the critical pressures and lowest cyclic frequencies of truncated and complete conical shells.     

Effects of ionizing irradiation and hydrostatic pressure on Escherichia coli O157:H7 inactivation, chemical composition, and sensory acceptability of ground beef patties

A randomized complete block design with three replications was utilized to determine the effects of ionizing irradiation and hydrostatic pressure on the inactivation of Escherichia coli O157:H7, volatile composition, and consumer acceptability (n = 155) of frozen ground beef patties. E-beam and X-ray irradiation (2 kGy) inactivated E. coli O157:H7 below the limit of detection, while hydrostatic pressure treatment (300 mPa for 5 min at 4 °C) did not inactivate this pathogen. Solid-phase microextraction (SPME) was used to extract volatile compounds from treated ground beef patties. Irradiation and hydrostatic pressure altered the volatile composition (P < 0.05) of the ground beef patties in respect to radiolytic products. However, results were inconclusive on whether these differences were great enough to use this method to differentiate between irradiated and non-irradiated samples in a commercial setting. Irradiation did not affect (P > 0.05) consumer acceptability of ground beef patties when compared to untreated samples, but hydrostatic pressure caused decreased acceptability (P < 0.05) when compared to other treatments.     

FORCE ANALYSIS AND DYNAMIC SIMULATION OF THE PLAIN FLOWDISTRIBUTION PAIR IN A RADIALPISTON HYDRAULIC

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偏载工作台静压圆导轨相关参数分析

根据TH6918落地镗铣床的工作台液压支承结构方案,研究偏载工况下,4 000 mm×5 000 mm工作台与滑座之间的静压圆导轨相关参数的影响,分析得出了各油腔的压力和油膜厚度随偏载位置的变化曲线,确定了工件摆放的合理位置,为工作台的进一步受力分析及动态性能研究奠定了基础。     

Study on lubrication performance of hydrostatic clearance oil film considering multi-factor coupling

The lubricating performance of the clearance oil film determines the machining accuracy of the hydrostatic thrust bearing and the stability of the oil film. From the perspective of working parameters and cavity structure, based on tribological principles and lubrication theory, the clearance oil film temperature rise equation, pressure equation, and viscosity-temperature equation are deduced, and the relationship between load-rotating speed-oil film thickness for different cavity shapes is matched. Through the combination of simulation and experiment, the multi-factor coupling influences on the lubricating performance of the clearance oil film are studied. The study found that the degree of influence on the clearance oil film temperature is in order: rotational speed, hydraulic oil viscosity, load, and cavity depth, and the degree of influence on the clearance oil film pressure is in order: load, hydraulic oil viscosity, rotational speed, and cavity depth. This work provides a theoretical basis for the research and optimization of the lubrication performance of hydrostatic thrust bearings, and provides a research direction for the machining accuracy and running stability of high-speed and heavy-duty CNC equipment.     

无周向回油液体静压轴承优化设计

介绍以总功耗最小为目标函数、主轴系统刚度为主要约束条件的无周向回油液体静压轴承优化设计方法,与普通设计方法相比,其总功耗可大幅度降低。