Calibration of saturated liquid helium weir flowmeter at Fermilab

The flow of saturated liquid helium at 4.2 K was studied in a unique weir flowmeter mounted inside a duct. The objective was to develop a calibration for helium flow rate in the weir, and thereby, making it a viable flowmeter. The weir flowmeter was tested in a liquid helium system at Fermi National Laboratory used for cooling the superconducting magnets in the experimental areas of the site. Unlike for open channel weir devices, the calibration of this flowmeter was influenced by both the liquid flow through the weir notch and the vapor flow over it. The results of this study and the calibration are presented taking into account effects of both liquid and vapor.     

Experimental investigation of an oscillating circular piston positive displacement flowmeter: II – Leakage flows and wear tests

Experimental data from an oscillating circular piston positive displacement flowmeter are described which focused on leakage flows and wear. This is the second part of a two part paper on the experimental tests, the first part concerned piston movement and pressure loss. In this paper the leakage across the meter is reported for key parameters including: flow rate, liquid density and viscosity, mass of circular piston, surface coating and length of connection pipes. In addition to the average leakage over a period of time, the leakage past a stationary circular piston was measured during a simulated oscillation. Wear tests were run for both stainless steel and carbon pistons to identify the affected areas of piston and chamber.     

提高数控机床主轴组轴承性能特性的方法

轴承预紧是提高数控机床主轴等组性能特性的一种有效方法,文章从提高回转精度,增强刚度,等方面进行了阐述。并对预紧力大小,预紧力调整,测量和预紧后锁紧等方面进行了较系统的讨论。     

Accuracy Optimisation for Mould Surface Profile Milling

In the profile milling process for mould surfaces, for any type of curve combination, when implementing the milling process on a CNC machine, the surface can be produced from straight lines or curves in a piecewise or continuous milling process. This work employs the features of a CNC machine: 1. To divide the various sizes of curve at different slopes. 2. To use with different milling spindle speeds. 3. To use cutting feeds for actual milling experimentation. The results of the profile dimension accuracy and profile surface roughness from these experiments are then used in a neural network to establish an experiment result and a model for the milling variables. The neural network is composed of a number of functional nodes. Once the milling parameters (spindle speed, feed speed and milling angle) are given, the milling processing performance (the surface roughness, the surface profile-error) can be accurately predicted by the net-work developed. The optimal milling processing parameters can be searched for by a simulation annealing (SA) optimis-ation algorithm with a performance index to obtain a satisfactory mould surface. The experiment is then used to show that improved conditions for mould profile processing can indeed be obtained.     

涡轮流量传感器测量水平泡状流数学模型研究

对涡轮流量传感器测量水平泡状流的数学模型进行了研究,提出了水平环形通道内混合流体的虚拟速度剖面指数,分析了混合流体中气泡对叶片的阻力影响,得出虚拟速度剖面指数随体积含气率变化的规律.在气液两相流实验装置上,通过理论计算与实验结果的比较,验证了数学模型的有效性.     

Efficient determination of stability lobe diagrams by in-process varying of spindle speed and cutting depth

The experimental determination of stability lobe diagrams (SLDs) in milling can be realized by either continuously varying the spindle speed or by varying the depth of cut. In this paper, a method for combining both these methods along with an online chatter detection algorithm is proposed for efficient determination of SLDs. To accomplish this, communication between the machine control and chatter detection algorithm is established, and the machine axes are controlled to change the spindle speed or depth of cut. The efficiency of the proposed method is analyzed in this paper.The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-018-0225-x.pdf     

中大口径电磁流量计无液校准技术的应用研究

基于电磁流量计测量原理,在建立了包含相关物理量的微分方程及边界条件基础上,提出了一种电磁流量计无液校准技术,设计了一套无液校准设备。采用逐点测量管壁磁感应强度及测量传感器结构尺寸的方法,获得确定的边界条件,用数值方法求解微分方程,获得传感器的灵敏度系数,并对2台口径200 mm电磁流量计进行了无液和实流的对比试验,两者所获得的灵敏度系数相对误差不超过0.5%。     

一种新型并联动力头动力学参数辨识方法研究

以一种一平动两转动自由度的新型三坐标并联动力头为对象,研究这类系统的动力学参数辨识方法。在运动学和刚体动力学分析的基础上,提出一种通过在运动构件上设置特征点构造适合参数辨识的动力学模型。根据不同工况下负载力矩的特点,提出一种具有分层递阶格式的动力学参数辨识策略。该策略可通过选择适当轨迹,有效消除或抵消库仑摩擦力矩的影响,进而可有效提高运动构件的动力学参数。通过不同工况下的试验验证了所提出辨识策略的正确性和有效性。     

Thermo-mechanical model of spindles

This paper presents a Finite-Element-method-based thermo-mechanical model of spindles with rolling bearings. The heat generated in the bearings and the motor is transferred to the ambient air, the motor coolant and the spindle structure, and causes thermal expansion of spindle parts. The experimentally validated thermo-mechanical spindle model predicts temperature distribution and thermal growth, as well as bearing stiffness and contact loads, under specified operating conditions. Transient changes in temperatures, deformations, viscosity of the lubricant, and bearing stiffness are considered in the solution. The predicted bearing properties are used to estimate the changes in the dynamic behavior of spindles.     

滚齿机静压工作台设计

开发研制了数控高精度双蜗杆蜗轮消隙静压工作台,该工作台具有高效、高精度、高刚度的特点.