轧机伺服液压缸内泄漏故障诊断研究

针对目前轧机伺服液压缸故障诊断过程中,故障特征提取困难,信号非线性变化,数据量大的问题,提出了一种基于深度置信网络的轧机伺服液压缸故障诊断的方法。根据轧机系统工作原理,建立轧机系统仿真模型,对轧机内泄漏故障状况进行模拟。利用深度置信网络在智能故障诊断的优越性,将信号归一化处理后放入深度置信网络进行训练,然后通过反向传播学习,优化网络各参数,提高诊断精度。深度置信网络模型由多层玻尔兹曼机以及顶层BP神经网络组成。与传统BP神经网络方法进行比较,结果表明,在训练样本数据足够的条件下,深度置信网络模型在伺服液压缸内泄漏故障诊断具有更高的诊断精度。     

Risks and safety level of composite cylinders

The increasing amount of composite transport systems for hydrogen leads to new and therefore unknown potential hazards for general public. Due to lack of experience, risks of new technologies tend to be rated higher than existing familiar applications. An approach for probabilistic safety assessment of technologies or products requires the definition of minimal acceptable reliability levels. This ensures that the probability of a critical failure with a certain consequence is limited to an acceptable risk. But what is the acceptable risk and which risk results from specific probabilities of occurrence and consequences? This is always a very complex question. The following example is based on a probabilistic approach for safety assessment of composite cylinders developed at the BAM (Federal Institute for Materials Research and Testing).     

发动机密封面漏油问题分析

某发动机试验发现缸体与框架之间的密封面残存的密封胶变为褐色,且该区域发生轻微漏油问题。为了解决该问题,建立了漏油原因分析鱼刺图,并根据鱼刺图中可能的原因逐一排查。通过模拟试验和CAE计算确定出四个主要原因,制定出三个相应的优化方案,并建立了相应的控制标准。根据实施周期的长短分步实施和验证,确认了各方案均有明显的改进。三个方案一起实施以后,通过反复的工程测试,确认了漏油问题得以解决。     

A closed-form solution for elastic buckling of thin-walled unstiffened circular cylinders in pure flexure

To date, despite the significant development in the field of structural mechanics, there still remains a paradox in the solutions available for a classical shell buckling problem. The difference in strength between a cylindrical shell under uniform axial compression and that under pure bending is not quite well investigated. This lack of research is reflected in the wide variations in the elastic bending strength and the slenderness limits given in current international design standards. The discrepancies in the available classical solutions and hence the design rules have initiated the current research. The main aim of this paper is to present a closed-form solution for the elastic buckling strength of unstiffened circular cylinders under pure bending using a new simplified energy approach employing the well-known Ritz method. Two types of analyses are presented for cylinders with large (D/t>200) and medium (100<D/t<200) diameter-to-thickness ratios. A unique testing rig was used to experimentally verify the new theory using a Moiré fringe film. The theoretical results are compared against the available and present test results and the existing classical solutions. The current design rules for thin-cylinders in international steel specifications are also compared, and the newly derived design curve is proposed which was found in a good agreement with the available test results.     

Annular axisymmetric stagnation flow on a moving cylinder

Fluid is injected from a fixed outer cylindrical casing onto an inner moving cylindrical rod. Using similarity transform, the Navier-Stokes equations reduce to a set of nonlinear ordinary differential equations, which are integrated numerically. Asymptotic solutions for large and small cross-flow Reynolds numbers and small gap widths are also found. Drag, torque and heat transfer on the moving rod are determined. The problem is particularly important in pressure-lubricated bearings.     

Modeling of program, erase and retention characteristics of charge-trap gate all around memories

This paper describes the effect of geometry in charge-trap (CT) memory devices. We first theoretically analyze the impact of the curvature radius on the behavior of the gate current in Gate-All-Around devices, and then describe the change to make to planar model in order to fit the cylindrical devices characteristics. This model is used to simulate Nanocrystal and SONOS program, erase and retention behaviors. The dynamics enhancement during program/erase due to the bending of the active region in such cylindrical devices is explained. The scaling perspectives conclude this paper.     

各国压力容器标准中外压圆筒的计算及数值计算屈曲和弹塑性分析

通过比较GB150-1998、ASMEⅧ-1、ASMEⅧ-2(2007)、EN13445-3(2009)、AD-2000和гост14249中外压圆筒的计算,利用Ansys软件做屈曲和弹塑性分析。结果表明,GB150-1998中外压圆筒的计算方法偏于保守。     

R108A型柴油机的开发研制

本文就由R105系列柴油机经扩缸、加长行程为R108A系列柴油机的研制开发过程作了介绍,较为详细的说明了零部件的结构设计及整机的性能和可靠性。     

Effect of a Magnetic Field on a Micropolar Fluid Flow in the Vicinity of an Axisymmetric Stagnation Point on a Circular Cylinder

The effect of a magnetic field on a micropolar fluid flow in the vicinity of an axisymmetric stagnation point on a circular cylinder is studied numerically. The governing conservation equations of continuity, momentum and angular momentum are partial differential equations which are transformed into a system of ordinary differential equations by using the usual similarity transformations. The resulting system of coupled non‐linear ordinary differential equations is solved numerically by using the shooting method. The numerical results indicate the velocity, angular velocity and pressure distributions for different parameters of the problem including Reynolds number, magnetic parameter and dimensionless material properties, etc. In addition, the effect of the pertinent parameters on the local skin friction coefficient and the couple stress are discussed numerically and illustrated graphically.     

皮带助卷器液压回路原理设计及故障诊断

通过对冷轧后处理机组皮带助卷器的结构和运动特点的分析,进行了液压回路的设计;利用仿真软件对该液压回路进行动态仿真验证。在现场调试过程中,发现该液压回路不能保压。经排查,最后通过实验的方法找到问题原因。通过该问题的解决过程得知:在设计液压原理时,不但要选择合理的液压回路及阀件,还必须充分考虑油缸的内泄漏对系统的影响,并应提出油缸内泄漏的要求和减小内泄漏的措施。