Coupled distance sensor systems for high-accuracy topography measurement: Accounting for scanning stage and systematic sensor errors

Scanning topography measurements using systems of coupled distance sensors suffer from the presence of scanning stage and systematic sensor errors. While scanning stage errors can be estimated for suitably-designed sensor systems, it is usually not possible to simultaneously estimate both scanning stage and systematic sensor errors. Additional angular scanning stage measurements can solve this problem, and potentials and limitations of such a proceeding will be assessed.It is shown that perfect topography reconstruction can be achieved in the presence of systematic sensor and certain scanning stage errors provided that the measurements are noise-free and no further systematic errors emerge. In general, the topography is reconstructed by the application of least-squares, and the uncertainty associated with the reconstructed topography is derived. Resulting topography accuracies are evaluated for different noise levels of the distance sensor and angular scanning stage measurements, and practical considerations are discussed. The gain in accuracy due to accounting for scanning stage and systematic sensor errors can be large, and high accuracies can be reached.     

A simple datum for measurement of the Abbott curve of a profile and its first derivative

The methods used in some recent work to predict boundary friction from surface slopes require that the variation of rms slope with bearing area be calculated: an Abbott curve of the first derivative of the profile. It is shown that this curve can be distorted if a conventional filter is used to set the datum, in the same way as the Abbott curve itself. Better results can be obtained for both the standard Abbott curve and the Abbott curve of slopes if an envelope through the peaks of the profile is used as the datum, rather than a digital filter.     

Does a Manufacturing Execution System reduce the cost of production for bulk pharmaceuticals?

The Manufacturing Execution System (MES) has reduced the cost of production in several discrete manufacturing industries. One pharmaceutical bulk manufacturing facility has evaluated the installation of a full function MES system and the necessary reengineering of its business processes. The potential lifecycle cost and benefits were evaluated.     

A procedure for evaluating the positioning accuracy of reciprocating friction drive systems

The dynamic characteristics of stick-slip motion in reciprocating friction drive systems are investigated under dry contact using a 0.45% carbon steel pair. Based on this dynamic analysis, the stick-slip motion can be eliminated under certain experimental conditions depending upon driver speed, normal load and spring constant. The effects of normal load, driver speed, and spring constant on the positioning accuracy of the reciprocating friction drive system are examined under harmonic oscillation without stick-slip motion. Results show that at very low spring constants, the slip increases with increasing driver speed such that higher normal load has better positioning accuracy or smaller slip than does lower normal load. However, at high spring constants and high normal loads, there exhibits severe wear or peak at two limit positions on the sliding region. As a result, smaller normal loads have a better positioning accuracy than larger normal loads due to severe wear at high normal loads.     

On the performance of integral buckle arrestors for offshore pipelines

This paper presents the results of a study on the effectiveness of integral buckle arrestors for offshore pipelines. A series of full scale experiments were conducted where the pressure at which buckles propagating quasi-statically crossed arrestors of various lengths and thicknesses was established. The crossover pressures were used to establish the parametric dependence of the arresting efficiency (as defined in Kyriakides and Babcock, ASME Journal of Pressure Vessel Technology102 (1980) and Proceedings of Offshore Technology Conference (1979)) of such devices. Buckles penetrated the arrestor in two modes: the flattening mode, where the arrestor and downstream pipe collapse in the same manner as the incoming buckle and the flipped mode, where the sense of collapse of the downstream pipe is orthogonal to the incoming buckle. The mode switch occurred in the neighborhood of efficiency of 0.7.The process of quasi-static engagement of an arrestor by a propagating buckle, the temporary arrest of the buckle and the eventual crossing of the arrestor were simulated through a finite element model. The model is based on finite deformation kinematics, incorporates J₂-type plasticity with isotropic hardening, and allows for contact of the walls of the collapsed section of pipe upstream of the arrestor. The model was verified by simulating each of the 15 physical experiments conducted using the actual geometric and material characteristics of the test specimens. The crossover pressures of the simulations were within 5% from the measured values and the mode of crossover was predicted correctly as well. The model was subsequently used to extend the experimental parametric study of arrestor efficiency. Some limiting values of the parameters were established from the results and several design recommendations are made.     

Optical 3D profilometer for in-process measurement of microsurface based on phase retrieval technique

We have proposed an optical method that can be applied to in-process or in situ measurement of the microsurface profile. The present method is based on optically performed spectral analysis and the phase retrieval technique. Spectral information of a surface profile is obtained by measuring the Fraunhofer diffraction intensity. The phase retrieval technique is used to reconstruct the surface profile from the measured spectrum. We have developed an instrument on the basis of the general principles of the present method, and measured the surface of a reference standard having rectangular pockets 44 nm deep at intervals of 10 μm. The measured surface profile was in good agreement with the nominal dimensions of the specimen as well as the surface profile obtained by atomic force microscopy (AFM).     

A field comparison of two prototype sensors for horizontally on-the-go soil mechanical resistance measurement

Soil compaction is the basis of determining the tillage depth in the precision tillage system. The objective of this study was to compare the performance of two prototypes of measuring systems for horizontally on-the-go soil mechanical resistance measurement including: a vertical single blade equipped with four miniature load cells and a multiple blades system with four independent sensing blades equipped with precision measuring implements and octagonal ring transducers. Results showed that the multiple probes sensor represented closer data to cone penetrometer with correlation coefficient of 0.63, 0.84, 0.83 and 0.80 for the depth of 0–10, 10–20, 20–30 and 30–40 cm, respectively. While these values were 0.23, 0.16, 0.51 and 0.69 for single blade sensor. Some other advantages of multiple blade probes were lower disturbance in the soil, representation of the same failure mode to cone penetrometer at deeper depths, and lower fluctuations in measured data.     

Some issues relating to the construction of materials selection maps for resistance to elevated temperature erosion

In studies of elevated temperature erosion, the performance of various materials has been investigated in a wide range of exposure conditions. Material performance has been shown to be dependent on erosion-corrosion conditions, determined by properties of the impacting particle, the temperature and the composition of the gaseous environment. Changes of the ranking order of wastage rates of various materials, as a function of the process conditions, is a common feature of the results to date. Such observations can make materials selection decisions, for elevated temperature erosion resistance, a fairly arbitrary exercise.In recent years, there has been significant interest in mapping the erosion of materials at elevated temperatures. Such maps demonstrate the transitions between the erosion regimes as a function of the main process parameters. More recently, for erosion of composite materials, they have also been used to identify the magnitude of the wastage rate.The object of this work has been to develop a simple rationale for construction of materials performance maps for exposure of materials to elevated temperature erosion conditions. The results used to construct the maps have been generated from literature on the performance of materials in laboratory simulated fluidized bed conditions. It is shown how ‘materials selection’ maps can be constructed for elevated temperature erosion resistance based on this approach.     

A conceptual development of novel ultra-precision dimensional measurement technology

This research explores the unique physical phenomenon of electrical output versus displacement of a potentiometer with the view of nano-scope. Based on the interesting characters of the phenomenon, a novel conceptual development of ultra-precision dimensional measurement technology is carried out. As an example, a potentiometer and a stack of piezoelectric elements are adopted to build a dual-stage ultra-precision measurement instrument. The theoretical error analysis with the research demonstrates that an instrument developed with this novel ultra-precision dimensional measurement technology is able to achieve low double-digital nanometer absolute measurement accuracy over a large dimensional range.     

Analytical solution for tilted hydrostatic multi-pad thrust bearings of infinite length

Exact solutions are analytically derived for the self-alignment of tilted multi-pad hydrostatic thrust bearings of infinite length. Both capillary and orifice restrictions are considered. Laminar flow condition in the film is assumed. For analysing the hydrostatic multi-pad bearing the equivalent hydraulic network method is used.     

光学传感器星上定标漫射板的特性测量

为了考察星上定标漫射板的光学特性及其在航天环境下的稳定性,对其进行了方向半球反射比(DHR)、双向反射比因子(BRF)、双向反射分布函数(BRDF)等反射特性的测量;同时,进行了系列环境模拟试验.结果显示:星上定标漫射板反射率在可见近红外波段可达0.99,光谱差异＜0.01,在短波红外波段达0.95以上;10～60°BRF变化低于0.1, 0～60°BRDF变化＜0.045,其方向特性与光谱、紫外辐照关系不大;漫射板350 nm反射率在120 h等效紫外辐照下的衰变＜3%,其光学特性受原子氧、质子轰击影响甚微,并通过了航天级力学环境试验.试验研究表明:漫射板具备高反射率、光谱平坦性、朗伯性及其在航天环境下的稳定性,能够满足航天应用要求.     

Analysis of micro-elastohydrodynamic lubrication for engineering contacts

The paper describes methods which have been developed for theoretical analysis of elastohydrodynamic lubrication (EHL) in situations where the nominal oil film thickness is of the same order as the height of roughness asperities on the surfaces in contact. In such contacts the roughness significantly affects the distribution of pressure, and pressures much higher than predicted on the basis of smooth surface theory are obtained even under conditions where a full fluid film is present. This has consequences for surface fatigue processes such as pitting, and the presence of roughness is also considered to be a crucial factor in the occurrence of scuffing in which hydrodynamic film failure leads to adhesion and severe distress of the surfaces. The major aim of the work is to develop a better undertanding of the physics of scuffing based upon models of film failure in the presence of roughness.     

A theoretical model for the prediction of initial growth angles and sites of fretting fatigue cracks

The crack initiation mechanisms under fretting fatigue conditions are investigated. Fretting fatigue tests have been conducted on an aluminium alloy. Two major crack initiation mechanisms are experimentally observed. They are theoretically identified by employing a simple dislocation dipole model and taking into consideration the reverse sliding along dislocation layers and the influence of the distance between these layers. It is shown that cracks may initiate either by an extrusion-intrusion mechanism or a fatigue tensile process. Two parameters respectively linked to each of these initiation mechanisms are proposed to predict crack location. The theoretical crack initial growth directions and locations are shown to correlate very well with the experimental ones. With regards to these initiation processes, a spall detachment mechanism is proposed considering the interaction of microcracks.     

埋入式光纤布拉格光栅传感器封装结构对测量应变的影响

考虑在实际应变测量中传感器封装形式会影响光纤Bragg光栅测得的应变响应,本文研究了测量应变与实际应变之间的关系。针对埋入式光纤Bragg光栅传感器,建立了应变传递函数,并对传递函数的正确性和各个参数对测量应变的影响进行了研究。首先,根据埋入式光纤Bragg光栅传感器的受力特点,提出了多项式形式的剪应力分布,进一步建立了应变传递函数。然后,利用数值方法和实验对该应变传递函数进行验证。最后,分析了传感器长度、胶结层弹性模量、胶结层厚度对测量应变的影响。计算结果表明:该应变传递函数正确;胶结层厚度越薄,弹性模量越大,越有利于应变传递。该应变传递函数计算误差控制在5%以内,完全满足埋入式光纤Bragg光栅测量精度要求,对其实际应用具有指导意义。     

Prototype design and experimental evaluation of wireless measurement nodes for road safety

The paper presents the design and the experimental evaluation of prototypes of measurement nodes that are part of the Wireless Active Guardrail System (WAGS). The WAGS is an innovative infrastructure, allowing increasing traffic safety on roads, by monitoring vehicle speed, proximity between vehicle and guardrail, impact of a vehicle with the guardrail, and several environmental parameters. In particular, in this paper, the designs and prototypes of the nodes dealing with speed and proximity measurements are presented. Then, all the phases of their experimental evaluation are reported and discussed.     

A lower upper-bound solution for shear spinning of cones

The shear spinning process, where the plastic deformation zone is localized in a very small portion of the work piece, is introduced for the manufacturing of large conical shapes. This process seemingly shows a promise for increasingly broader application to the production of axially symmetric parts. This study is to gain a better understanding of the process of shear spinning and to propose a lower upper-bound solution for shear spinning cones. Velocity fields and strain rates are derived from considering the adequate deformation mode and the contact factor is introduced to obtain the lower upper-bound power. The theoretical values are compared with the experimental results of various materials. Al-1100-0, Al-1100-H14, and Al-6061-0. A comparison shows that theoretical prediction is reasonably in good agreement with experimental results.     

Multilevel solution for thermal elastohydrodynamic lubrication of rolling/sliding circular contacts

A fast multigrid approach is presented for the analysis of thermal elastohydrodynamic lubrication (EHL) under rolling/sliding circular contacts at high loads and high slip ratios with low computing time on a personal computer. This fast solver combines directiteration, multigrid, Newton-Raphson, Gauss-Seidel iteration, and multilevel multi-integration methods into one working environment that can reduce the computational complexity from O(n³ to O(nlnn) for the thermal EHL problem under rolling/sliding circular contacts. Since the couped Reynolds and energy equations are simultaneously solved by the Newton-Raphson scheme, the iteration for the convergence solution is less than those of the classical approach. Results show that thermal effects on the pressure profile and film thickness are significant for a wide range of loads, speeds and slip ratios. The maximum midfilm and surface temperature rise in the Hertzian contact region increases with increasing slip ratio, dimensionless speed, and load. The minimum film thickness decreases with increasing load and slip ratio, and decreasing dimensionless speed.     

气固两相流固相浓度电容式传感器优化设计

本文建立了一种螺旋式电容传感器的数学模型,并基于该模型对传感器结构进行了优化设计。优化后的结构可以产生较均匀的灵敏场分布,实测结果表明,优化后的传感器电容值与固相浓度具有良好的线性关系,测量点的线性相对偏差小于0.8%,适用于气固两相流固相浓度的测量。     

Comparative study of electrostatic sensors with circular and probe electrodes for velocity measurement of pulverised coal

This paper presents recent progress on the velocity measurement of pulverised coal in pneumatic pipelines using electrostatic sensors in combination with correlation signal processing techniques.A comparative study of electrostatic sensors with circular and probe electrodes was conducted on a 94 mm bore horizontal pipeline in a 4 MW furnace.The advantages and limitations of both sensors are discussed.Experimental results demonstrate that both sensors are capable of providing pulverised coal velocity measurement with excellent repeatability and dynamic response.     

Experimental validation of non-contacting measurement method using LED-optical displacement sensors for vibration stress of small-bore piping

There have been many reports of fatigue failures of small-bore piping systems such as drain piping, vent piping and instrumentation piping in nuclear power plants that arise from vibration sources such as pumps. To prevent the failures, integrity evaluation of piping is conducted by measuring and analyzing vibration stress in the piping. But, a more efficient and economical measurement method is desirable to evaluate the vibration fatigue in small-bore piping. In this study, a non-contacting measurement method was proposed that is based on optical displacement sensors using light emission diodes (LEDs) to measure the vibration stress. The applicability of the method was discussed based on the vibration experiments using pipe elements and a mock-up piping system. From the experimental results, the proposed method was clarified to be sufficiently applicable and practically useful for the vibration measurement and stress evaluation in small-bore piping systems.