Studies in dynamic design of drilling machine using updated finite element models

The aim of the present work is to develop updated FE models of a drilling machine using analytical and experimental results. These updated FE models have been used to predict the effect of structural dynamic modifications on vibration characteristics of the drilling machine. Two studies have been carried out on the machine. In the first study, modal tests have been carried out on a drilling machine using instrumented impact hammer. Modal identification has been done using global method of modal identification. For analytical FE modeling of the machine, a computer program has been developed. The results obtained using FEM, have been correlated with the experimental ones using mode shape comparison and MAC values. Analytical FE model has been updated, with the help of a program, which has been developed using direct methods of model updating. In the second study, modal testing has been carried out using random noise generator and modal exciter. Global method has been used for modal identification. Analytical FE modeling has been done using I-DEAS software. Correlation of FE results with the experimental ones has been carried out using FEMtools software. Updating of the analytical FE model has also been done using the above software, based on an indirect technique viz. sensitivity based parameter estimation technique. The updated FE models, obtained from both the studies have been used for structural dynamic modifications (SDM), for the purpose of dynamic design and the results of SDM predictions are seen to be reasonably satisfactory.     

Thermostressed state of a pad–disk tribosystem during single braking

The temperature and stress distributions in a disk under single braking have been studied. The finite-element method (FEM) has been used to obtain a numerical solution to the heat-conduction boundary problem for a steadily decelerated rotating disk heated in a local area of the working surface by a frictional heat flow. Given the temperature field, the finite-element method has been used to solve the corresponding quasistatic thermoelasticity boundary problem. The elastostatic boundary problem has been numerically solved separately for a disk loaded with distributed normal and shear stresses in the contact area. The complete field of stresses in the disk has been determined by adding up elastic and thermoelastic components. Numerical analysis has been performed for a cerametallic (FMC-11) pad—cast-iron (ChNMKh) disk friction couple.     

Vibration protection of a power unit by controlled struts with hydroelastic elements

The option of a regulated vibration protection system with a hydraulic transformer has been considered. The possible development of a lower dynamic rigidity within the low-frequency range has been demonstrated. The transient process of the system parameters’ recovery during the changing of a dynamic load has been investigated. The recovery time of the vibration protection properties of the system has been determined.     

Kineto-elastodynamic analysis of mechanisms by finite element method

In the present paper a systematic finite element method for kineto-elastodynamic analysis of high speed mechanisms has been presented. Effects of number of divisions have been investigated and it is found that a certain minimum number of divisions of links is necessary to yield accurate results. A new approach for eliminating the singularity in the stiffness matrices of mechanisms has been developed and it has been shown in this paper that this new approach yields improved results with negligible additional effort. Finite element expressions for the coriolis, tangential and normal components of elastic accelerations have been derived for a moving link and a new geometric stiffness matrix has been developed to include the effects of the rigid body pinforces and the distributed axial rigid body inertia forces on the transverse vibrations of the links. The method has been further extended to take into account the nonlinear elastic axial forces. Several examples have been solved.     

A novel technique of using a thyristor driven pump as the final control element and flow indicator of a flow control loop

In the present paper, design of a flow control loop using a thyristor driven pump as final control element has been described. In this technique, the load current of a thyristor driven pump motor has been utilized as a mass flow sensing parameter of a fluid passing through a pipeline. This thyristor driven pump has been utilized as a final control element of a flow control loop and the speed of the pump has been selected as the manipulated variable. The non-linearity between the thyristor input signal and pump output has been eliminated by using a modified PID control technique with inverse derivative control action. Thus without using any conventional flow meter and control valve only the thyristor driven pump has been utilized both as the final control element and flow indicating device by using the proposed technique. The whole system has been designed, fabricated and tested by using tap water as the flowing liquid through a pipe line. The experimental results along with the theoretical analysis are compared and reported in the paper.     

小孔式动静压轴承的特性分析与试验研究

从理论和试验两方面,对小孔式动静压轴承的性能进行了研究。根据机理和数学模型,推导出计算公式,编制了可在IBM-PC/AT,XT及其兼容机上运算的静、动特性分析计算和优化设计程序,以Auto CAD为图形编辑器,研制成接口软件,实现了参数化绘图,完成从分析计算、优化设计到计算机绘图的CAD全过程。在试验研究方面,设计、制造和调试成一台通用的动静压轴承试验台,对小孔式动静压轴承进行了静、动特性测试,获得一批有价值的试验数据,为这种新型轴承的推广应用提供了可靠的依据。     

A study on enhancement of grinding accuracy by an active tool control

An approach to enhance dimensional accuracy of the grinding process has been presented, and grinding of a glass material with a metal-bonded diamond wheel has been studied. In this study, a grinding tool is suspended flexibly and controlled by an electromagnetic actuator. During grinding, profile error of a ground surface is indirectly measured and fed back to a control system. A model of grinding error has been suggested on which the indirect measurement has been based. An optimal PID control is adopted and effectiveness of the in-process feedback control has been verified experimentally.     

Closed-form solution of axisymmetric contact problem for a viscoelastic base within cycle of increasing and decreasing of load on the indenter

The axisymmetric contact problem for a spherical indenter and viscoelastic base has been considered within a cycle of increasing and decreasing of load. The loading-unloading cycle has been performed at a constant speed of indenter movment. The quasi-static approximation has been used. The study has been carried out according to linear viscoelasticity theory, while the material model allows one to take into account an arbitrary number of relaxation times. The dependence of load on the indenter on time has been defined. Expressions for determining the unknown boundary of the contact area in the loading–unloading process has been given. The hysteretic loop area at different values of the material relaxation time has been analyzed. The applicability of the offered analytical model of elastomer indentation experiments data processing has been discussed.     

A low cost design and development of a reluctance type pressure transducer

Transmission of Bourdon gauge reading to a remote location is very important in industry. This requires a conversion of Bourdon tube displacement into an electrical signal with the help of a suitable transducer. In the present paper, a simple low cost reluctance type pressure transducer has been developed. Its theoretical analysis has been presented in the paper. The transducer has been developed and tested in the laboratory and has been found to follow the theoretical equations. The experimental results of the observed characteristics of the transducer are reported in the paper. A very good linearity and repeatability of the data has been observed.     

Contact Problems for Rolling with Slip for Viscoelastic Solids

The three-dimensional contact problem for rolling of a rigid sphere over a base, which consists of viscoelastic layer bonded to a rigid half-space has been considered. The thin viscoelastic layer simulates the action of a friction modifier. The Kelvin model has been used to describe the layer properties. The method of calculating the distribution of normal and shear stresses within the contact interaction area has been presented, the boundaries of traction have been determined, and the slip subareas have been studied. In addition, the influence of the viscoelastic layer properties on the distributions of contact stresses has been analyzed.     

Optimal industrial robot-calibration policy

The optimal deterministic calibration policy for a robot cyclically performing a single production-integrated activity has been determined analytically. The general solution derived has been analysed numerically, and its sensitivity to changes in the parameters has been established. The model assumptions and the results have been validated on an industrial robot.     

Comparative study on optimum design of rolling element bearing

Long fatigue life is the most important objective in the optimum design of rolling element bearing. In the present study the fatigue life of a radial ball bearing is maximized. The nonlinear constrained optimization problem has been solved using particle swarm optimization algorithm and a hybrid PSO and Teaching Learning based Optimization algorithm. The algorithm uses a ranking method of constraint handling and contact stress has been introduced as a new constraint. The results have been compared with the established available results. A constraint violation study has been carried out to prioritize the constraints. A convergence study has been performed to identify the key design variables. Encouraging results in terms of objective function values and CPU time have been reported in this study.     

Cost based scheduling in a job shop environment

Scheduling is one of the most important issues in operations planning of a manufacturing system. In this paper a new scheduling strategy based on machine cost considerations has been proposed. A scheduling factor based on initial cost of a machine and its running cost has been developed. A scanning procedure has been implemented which prioritizes eligible workstations for each setup of a job based on the scheduling factor. Two measures of performance—idleness factor and idleness cost factor—have been developed. Computer simulation has been used to investigate the impact of various decision parameters on operating behavior of the system.     

Rotor Sealings based on a Metal–Rubber Elastic Porous Material for Turbomachinery

The problems of making efficient rotor seals for turbomachinery has been outlined. A design of a seal with a sealing element made of metal-rubber elastic porous material has been proposed. A model of thermal processes in this seal during contact interactions with the rotor has been developed. The need to determine the range of changes in the parameters of the structure of the metal-rubber material, which makes it possible to use it as a sealing element for rotor seals made using existing technologies for structural damping systems, has been revealed. The results of studies of friction processes have been presented and the types of wear of the metal-rubber material in the rotor seal have been determined.     

Mathematical modeling of the cylindrical grinding process

This paper proposes a dynamic model of cylindrical grinding with a tool owning specified distribution of abrasive grains. Cutting forces have been calculated, the surface geometry formed after a grinding wheel pass has been determined, the influence of the process dynamics on cutting forces and machined surface geometry has been taken into account, and the effects of cutting condit on vibrations being generated in the process of grinding have been investigated.     

Design and construction of an atmospheric or environmental SEM (part 3)

The continuation of the advances in designing and constructing an atmospheric or environmental SEM (ASEM and ESEM, respectively) is reported. A pair of scintillator backscattered electron detectors have been designed and made so that signal processing to enhance topography and Z-contrast can be performed. Optimum shapes and positioning of the detectors have been determined. The light transmittance in the light pipe has been mapped and measured to be 51%. Satisfactory signal-to-noise ratio images of a carbon specimen have been obtained with 5 kV, 2 pA and 50s scan time at 0.1 mbar. With a higher intensity beam, clear images of wool fibres have been achieved at 1 bar pressure. The ASEM and ESEM have been shown to operate both under conditions of a gaseous environment and with detection modes used in other microscopes. Changes and phenomena occurring as the relative humidity varies between 0 and 100% have been recorded.     

Plane strain elastic–plastic bending of a strain-hardening curved beam

Elastic–plastic analysis of plane strain pure bending of a strain-hardening curved beam has been presented. Only a linear hardening case has been analyzed as the nonlinear equations for a general hardening case could not be solved analytically. A numerical scheme for the computation of stresses and displacements in different stages of deformation has been given and limited FEM verifications have been presented.     

高级温控器智能自动化装配机器

对温控器的装配过程进行合理规划,对不同的零件设计相应的拾取夹具,以保证零件唯一的状态在位移过程中不会改变.利用振动送料盘实现自动送料与排料.采用数字点位控制及机器视觉功能对零件的拾取并放入塑件壳体内铆接进行准确的控制.实现温控器装配过程的自动化,提高生产效率.     

A technique for measuring temperature and wind velocity in the ionosphere

A measuring system for studying the temperature conditions and the dynamic characteristics of the lower ionosphere has been developed on the basis of a Fabry-Perot interferometer. The parameters of an I-Pentamax512FT CCD camera, which is a component of the system, have been investigated, and a mathematical model has been created to describe the characteristics of each pixel of the CCD array and reconstruct images of interference rings at low signal-to-noise ratios. An optimal method for reconstructing the spectral line profile from a two-dimensional image of interference rings has been selected. A new algorithm for approximation of measured spectral line profiles has been developed. Using this algorithm, it is possible to find a correct solution to the problem of determining the kinetic temperature and the collective velocity of particles in radiating gas. A software package for semiautomatic data processing has been designed. The temperature and the wind velocities in the auroral zone of the thermosphere have been measured.     

Detection and monitoring of crack in a coast-down rotor supported on fluid film bearings

A Jeffcott rotor with a transverse crack has been considered in the present study. Equations of motion for transient response have been developed and dynamic analysis has been carried out to consider the effects of fluid film bearings. The coast-down phenomenon was analysed by considering the dissipation through the journal film and by evaluating the deceleration for each speed. Characteristic sub-critical response peaks have been found when the cracked rotor decelerates through its critical speed. The continuous wavelet transform (CWT) has been used as a tool to extract the above sub-harmonics from the time domain signals. The use of CWT has been suggested for crack detection and monitoring in a rotor system coasting down through its critical speed.