Hydrogen degradation of steel 12X1MΦ and its estimation by the acoustic emission method

The acoustic emission method for estimating damage to specimens made of thermally resistant steel is described as applied in air and in a gaseous hydrogen medium. Acoustic diagrams (AD) of steel cracking and their interpretation are presented. It is shown that thermal cycling of the steel in air and in a hydrogen medium leads to an increase in bulk damage to the steel. It is shown that the exploited material is more subject to micro- and macrocracking under the influence of temperature and the working environment.     

Bayesian Analysis on Deming’s Model with Consideration of Inspection Errors

This paper studies an extension to Deming’s model for inspection sampling. This new model is more useful in practice since it takes into account the two inspection errors (i.e. accepting out of tolerance components or rejecting in tolerance components) with the goal of minimising the expected total cost. Mathematical formulae corresponding to the model are derived based on the Bayesian approach. A computer program of this model is available for industry. Some numerical analysis of the effects due to model factors, such as inspection errors, component quality, and k₂ /k₁ ratio, is also presented. As a result, we conclude that a model that involves the two types of inspection error will lead to a looser inspection policy and higher expected total cost than a model without inspection errors. This method can be used to select the best suppliers when the total cost of the product is the main concern of the producer. ID="A1" Correspondence and offprint requests to: Dr C.-C. Chyu, Department of Industrial Engineering and Management, Yuan-Ze University, Chung-Li, Taiwan 320. E-mail: iehshsu@saturn.yzu.edu.tw     

Machine of testing the ceramic’s bending strength properties at high temperature and ultra-low speed

According to the established rules for testing ceramic’s bending strength, the falling velocity of the pressure head of the machine should be more than 0.5 mm/min. For the machine of testing the ceramic’s bending strength properties, most designs adopt the lowest falling velocity as 0.5 mm/min. In the fields such as aerospace and deep-ocean exploration, the utilization of ceramic materials that work at normal temperature, low temperature, or even high temperature and bend at an ultra-low velocity is increasing; thus, the intense requirements for the machine of testing the ceramic’s bending strength properties at high temperature and ultra-low speed (MTCBSP) and its experimental basis are put forward. This research developed an MTCBSP suitable for normal temperature and high temperature with the lowest falling velocity of 0.05 mm/min, and manufactured a drive reducer for ultra-low speed and high-temperature working condition. In the test, equipment includes a high-temperature furnace, bending die for four-point bending, and protection system of inert gas, which was placed in the high-temperature furnace to prevent the ceramic sample from being oxidized to diminish its effects. The results show that the lowest falling velocity of the pressure head of this new machine is 0.05 mm/min, and the mechanical properties of silica glasses are noticeably different at the same high temperature and the different falling velocities of 0.5 mm/min and 0.05 mm/min.     

Modeling of fatigue crack growth closure considering the integrative effect of cyclic stress ratio, specimen thickness and Poisson’s ratio

Key components of large structures in aeronautics industry are required to be made light and have long enough fatigue lives.It is of vital importance to estimate the fatigue life of these structures accurately.Since the FCG process is affected by various factors,no universal model exists due to the complexity of the mechanisms.Most of the existing models are obtained by fitting the experimental data and could hardly describe the integrative effect of most existing factors simultaneously.In order to account for the integrative effect of specimen parameters,material property and loading conditions on FCG process,a new model named integrative influence factor model(IIF) is proposed based on the plasticity-induced crack closure theory.Accordingly to the predictions of crack opening ratio(γ) and effective stress intensity factor range ratio(U) with different material under various loading conditions,predictions of γ and U by the IIF model are completely identical to the theoretical results from the plane stress state to the plane strain state when Poisson’s ratio equals 1/3.When Poisson’s ratio equals 0.3,predictions of γ and U by the IIF model are larger than the predictions by the existing model,and more close to the theoretical results.In addition,it describes the influence of R ratios on γ and U effectively in the whole region from-1.0 to 1.0.Moreover,several sets of test data of FCG rates in 5 kinds of aluminum alloys with various specimen thicknesses under different loading conditions are used to validate the IIF model,most of the test data are situated on the predicted curves or between the two curves that represent the specimen with different thicknesses under the same stress ratio.Some of the test data slightly departure from the predictions by the IIF model due to the surface roughness and errors in measurement.Besides,based on the analysis of the physical rule of crack opening ratios,a relative thickness of specimen is defined to describe the influence of material property,specimen thickness and so forth on FCG characteristics conveniently.In conclusion,the relative thickness of specimen simplifies the expression of FCG characteristic and provides a general parameter to analyze the fatigue characteristics of different materials with various thicknesses under different loading conditions.The IIF model describes the integrative effect of existing influence factors explicitly and quantitatively,and provides a helpful tool for fatigue property estimation of practical component and experiment design.     

The prediction technology study of fatigue life for key parts of a tracked vehicle’s suspension system

In allusion to fatigue life of a tracked vehicle torsion bar, a virtual prototype model of the tracked vehicle suspension system including a flexible torsion bar was built based on dynamic simulation software ADAMS. Node force and stress results of the torsion bar from last step simulation were acquired; taking into account the material characteristics and influential factors, fatigue life of the flexible body of the torsion bar was predicted. Engineering results can be acquired through the contrast of the result of virtual test and statistical fatigue.     

Reconstruction of emission coefficients for a non-axisymmetric coupling arc based on MALDONADO’s method

The reconstruction of emission coefficient is a key factor for the calculation of temperature field.However,most of the researches for determining arc plasmas are based on axisymmetric sources,little has been done to study non-axisymmetric arc plasmas.In order to reveal temperatures of a non-axisymmetric coupling arc,the distribution of emission coefficients must be reconstructed in advance.In this paper,the argon atomic line intensities of the coupling arc are obtained by using the imaging system that involves a high speed camera in conjunction with a neutral and a narrow-band filter.The converted programme between emission coefficients and emitted intensities is programmed based on MALDONADO’s method.A displaced Gaussian model is used for evaluating the validity of the converted programme.Then,the emission coefficients of a free burning arc are reconstructed by MALDONADO’s method and an Abel inversion,respectively,and good agreement is obtained.Finally,the emission coefficient profiles of the coupling arc are achieved.The results show that the distribution of emission coefficient for the coupling arc is non-axisymmetric.The emission coefficient profile is similar to an ellipse,and the short axis of the ellipse is in the direction that the two electrodes are arranged along.The peak temperature of the coupling arc is in the middle of both electrodes.There is a strong interaction between both arcs within the coupling arc.The proposed research solves difficulties for determining asymmetric arcs and enlarges the application scope of spectroscopic techniques.     

Static and dynamic pull-in instability of multi-walled carbon nanotube probes by He’s iteration perturbation method

A continuum model is utilized to extract the nonlinear governing equation for Carbon nanotube (CNT) probes near graphite sheets. The van der Waals (vdW) intermolecular force and electrostatic actuation are included in the equation of motion. Static and dynamic pull-in behavior of the system is investigated in this paper. To this end, a new asymptotic procedure is presented to predict the pull-in instability of electrically actuated CNTs by employing an analytic approach namely He’s iteration perturbation method (IPM). The effects of basic non-dimensional parameters such as initial amplitude, intermolecular force, geometrical parameter and actuation voltage on the pull-in instability as well as the fundamental frequency are studied. The obtained results from numerical simulations by employing three mode assumptions verify the strength of the analytical procedure. The qualitative analysis of the system dynamics shows that the equilibrium points of the autonomous system include stable center points and unstable saddle nodes. The phase portraits of the carbon nanotube actuator exhibit periodic and homoclinic orbits.     

Dynamics and Wheel’s Slip Ratio of a Wheel-legged Robot in Wheeled Motion Considering the Change of Height

The existing research on dynamics and slip ratio of wheeled mobile robot (WMR) are derived without considering the effect of height, and the existing models can not be used to analyze the dynamics performance of the robot with variable height while moving such as NOROS-Ⅱ. The existing method of dynamics modeling is improved by adding the constraint equation between perpendicular displacement of body and horizontal displacement of wheel into the constraint conditions. The dynamic model of NOROS-Ⅱ in wheel motion is built by the Lagrange method under nonholonomic constraints. The inverse dynamics is calculated in three different paths based on this model, and the results demonstrate that torques of hip pitching joints are inversely proportional to the height of robot. The relative error of calculated torques is less than 2% compared with that of ADAMS simulation, by which the validity of dynamic model is verified. Moreover, the relative horizontal motion between fore?hind wheels and body is produced when the height is changed, and thus the accurate slip ratio can not be obtained by the traditional equation. The improved slip ratio equations with the parameter of the vertical velocity of body are introduced for fore wheels and hind wheels respectively. Numerical simulations of slip ratios are conducted to reveal the effect of varied height on slip ratios of different wheels. The result shows that the slip ratios of fore?hind wheels become larger?smaller respectively as the height increases, and as the height is reduced, the reverse applies. The proposed research of dynamic model and slip ratio based on the robot height provides the effective method to analyze the dynamics of WMRs with varying height.     

Surface roughness and roundness of bearing raceway machined by floating abrasive polishing and their effects on bearing’s running noise

As the two most important indexes of bearing raceway, surface roughness and roundness have significant influence on bearing noise. Some researchers have carried out studies in this field, however, reason and extent of the influence of raceway surface geometric characteristics on bearing running noise are not perfectly clear up to now. In this paper, the raceway of 6309 type bearing＇s inner and outer ring is machined by floating abrasive polishing adopting soft abrasive pad. Surface roughness parameters, arithmetical mean deviation of the profile Ra, the point height of irregularities Rz, maximum height of the profile Rmax and roundness fof raceways, are measured before and after machining, and the change rules of the measured results are studied. The study results show that the floating abrasive polishing can reduce the surface geometric errors of bearing raceway evidently. The roundness error is reduced by 25%, Rm~x value is reduced by 35.5%, Rz value is reduced by 22% and Ra value is reduced by 5%. By analyzing the change of the geometrical parameters and the shape difference of the raceway before and after machining, it is found that the floating abrasive polishing method can affect the roundness error mainly by modifying the local deviation of the raceway＇s surface profile. Bearings with different raceway surface geometrical parameter value are assembled and the running noise is tested. The test results show that Ra has a little, Rmax and Rz have a measurable, and the roundness error has a significant influence on the running noise. From the viewpoint of controlling bearings＇ running noise, raceway roundness error should be strictly controlled, and for the surface roughness parameters, R,n~x and Rz should be mainly controlled. This paper proposes an effective method to obtain the low noise bearing by machining the raceway with floating abrasive polishing after super finishing.     

System and prospects of China’s intercity rail transit technology

City clusters and metropolitan areas in China are flourishing in the midst of the deepening urbanization in the country, thereby resulting in the emergence of intercity rail transit. Intercity railways connect mainline and urban railways for an integrated regional transportation system that underpins and leads the development of city clusters and metropolitan areas. This study explores the development mode and service characteristics of intercity rail transit, as well as proposes overviews on this system and prospects of its future technology in China.     

Coordinating the Operation of a Robot’s Manipulator and Vision System

Russian Engineering Research - The effectiveness of autonomous service robots may be improved by coordinating the operation of the manipulators and the robot’s built-in vision system in the...     

Physical simulation of the action of atomic oxygen and vacuum ultraviolet radiation on polymer materials in the earth’s ionosphere

A procedure of the physical (bench) simulation of the long-term interaction of polymer materials with flows of atomic oxygen and vacuum ultraviolet radiation in the earth’s ionosphere is designed. The efficiency of the bench measurements of mass losses of kapton-H and PM-1E polyimides, polyethylene, and FEP Teflon is confirmed by results of satellite measurements. The dependences of degradation of polymer films on the fluence of atomic oxygen are determined. They allow one to forecast time changes of mass and geometric characteristics of polymers during the whole operating period in the ionosphere. The synergetic effect of the action of the near-satellite environment on the ablation of the polymer films characterizes threshold ratio values of the vacuum ultraviolet energy flow to the atomic oxygen flow.     

Precise volume fraction prediction in oil–water–gas multiphase flows by means of gamma-ray attenuation and artificial neural networks using one detector

Artificial neural network (ANN) is an appropriate method used to handle the modeling, prediction and classification problems. In this study, based on nuclear technique in annular multiphase regime using only one detector and a dual energy gamma-ray source, a proposed ANN architecture is used to predict the oil, water and air percentage, precisely. A multi-layer perceptron (MLP) neural network is used to develop the ANN model in MATLAB 7.0.4 software. In this work, number of detectors and ANN input features were reduced to one and two, respectively. The input parameters of ANN are first and second full energy peaks of the detector output signal, and the outputs are oil and water percentage. The obtained results show that the proposed ANN model has achieved good agreement with the simulation data with a negligible error between the estimated and simulated values. Defined MAE% error was obtained less than 1%.     

Development of free vibration analysis algorithm for beam structures by combining Sylvester’s inertia theorem and transfer stiffness coefficient method

A new free vibration analysis method, which is called the Sylvester-transfer stiffness coefficient method (S-TSCM), is developed by combining Sylvester’s inertia theorem and the transfer stiffness coefficient method. In this paper, the free vibration analysis algorithm of a straight-line beam structure is formulated by S-TSCM. From the computation results of the free vibration analysis for the three types of beam structures, we confirm that S-TSCM is a very effective method. In particular, S-TSCM is superior to both the transfer stiffness coefficient method and the transfer matrix method in terms of computational accuracy and time. In the free vibration analysis for the beam structure with a large number of degrees-of-freedom, S-TSCM is superior to the finite element method in terms of computational time and storage.     

Developing techniques for testing magnetic properties of electric steels. I. Epstein’s apparatus (Review article)

The review briefly describes the history of development of techniques measuring magnetic parameters of one of the materials which are of vital importance for energy generation, electric engineering, radio engineering, and other branches of industry, i.e., electric steel, whose quality determines operational characteristics of numerous devices, such as generators, transformers, electric motors, magnetic conductors of relay switches in various automated systems, etc. The development of techniques for measuring its magnetic parameters is reviewed starting with the advent of Epstein’s apparatus, which was designed at the turn of the century [1] and has remained an instrument used in resolving controversies between suppliers and consumers of electric steels, and ending on contemporary methods of testing roll steels using complex electronic circuits incorporated in automatic control systems of factories. In connection with the spread of magnetic parameters of electric steels (in sheets, rolls, and batches), the issues of standardization and selection of measures for more reliable characterization of steels are discussed. Instruments and facilities for classification and distribution of steels in batches with uniform characteristics are also described. Sheet-testing instruments for measuring steel parameters, which are designed to replace Epstein’s apparatus, are described. Problems of on-line testing of electric steel in rolls and instruments for such tests developed by this time are discussed. In this connection, the issues of steel tests based on indirect characteristics [those not specified in GOSTs (State Standards)], which could be more easily conducted on production lines, alongside the methods and facilities for nondestructive measurements of magnetic parameters are broached. Part I of the review is dedicated to conditions of magnetic measurements using Epstein’s apparatus, and this paper was written exactly one hundred years after its invention in 1900.     

Analysis of singularized motion equations of latticed vibroimpact 2D systems in renouncing Newton’s hypothesis

Mathematical models of a 2D latticed structure colliding with a fixed catcher are considered. Consideration of these models is relevant in connection with the development of scientific bases for the design and calculation of machines and structures. The system is analyzed by time–frequency analysis and singularization methods. The calculation techniques of resonant modes are presented and the defining relations are derived.     

Modeling of surface hardness in hot chamber die casting using Buckingham’s π approach

Hot chamber die casting (HCDC) process is designed to achieve high dimensional accuracy and surface hardness (SH) for industrial applications (like machine tool components). In the present study, outcome of Taguchi model has been used for developing a mathematical model for SH; using Buckingham’s π-theorem for HCDC process. Three input parameters namely pressure at 2^nd phase; metal pouring temperature and die opening time were selected to give output in form of SH. This study will provide main effects of these variables on SH and will shed light on the casting hardness mechanism in HCDC process. The comparison with experimental results will also serve as further validation of model.     

A study on the variation of the performance and the cost of power generation in a combined heat and power plant with the change of the user facility’s return temperature

Journal of Mechanical Science and Technology - A combined heat and power (CHP) system generates electricity from thermal energy and generates heat by utilizing the remaining thermal energy. The...     

Experimental model and analytic solution for real-time observation of vehicle’s additional steer angle

The current research of real-time observation for vehicle roll steer angle and compliance steer angle（both of them comprehensively referred as the additional steer angle in this paper） mainly employs the linear vehicle dynamic model, in which only the lateral acceleration of vehicle body is considered. The observation accuracy resorting to this method cannot meet the requirements of vehicle real-time stability control, especially under extreme driving conditions. The paper explores the solution resorting to experimental method. Firstly, a multi-body dynamic model of a passenger car is built based on the ADAMS/Car software, whose dynamic accuracy is verified by the same vehicle＇s roadway test data of steady static circular test. Based on this simulation platform, several influencing factors of additional steer angle under different driving conditions are quantitatively analyzed. Then ε-SVR algorithm is employed to build the additional steer angle prediction model, whose input vectors mainly include the sensor information of standard electronic stability control system（ESC）. The method of typical slalom tests and FMVSS 126 tests are adopted to make simulation, train model and test model＇s generalization performance. The test result shows that the influence of lateral acceleration on additional steer angle is maximal （the magnitude up to 1°）, followed by the longitudinal acceleration-deceleration and the road wave amplitude （the magnitude up to 0.3°）. Moreover, both the prediction accuracy and the calculation real-time of the model can meet the control requirements of ESC This research expands the accurate observation methods of the additional steer angle under extreme driving conditions.