ANSYS FEM Research Articles

Crack Detection in Shaft Using Lateral and Torsional Vibration Measurements and Analyses

Cracking of cylindrical shafts is an important area for research, since the changes observed in their vibration characteristics even during large-sized cracking are much smaller than those observed for rectangular beams; hence early identification of crack existence becomes essential to prevent sudden failures in rotating shafts. In this paper experimental and numerical investigations are carried out to identify the presence of a crack in a cylindrical overhanging shaft with a propeller at the free end. In the experimental study, cracks of different depths are located at the (un-cracked) maximum bending moment position. Shaft response parameters for lateral (using an accelerometer) and torsional vibrations (using shear strain gages fixed at three different locations) are obtained using the modal analysis software, LMS Test LabTM. The experimental results are used to validate the numerical results obtained using the three-dimensional isoperimetric elements available in the ANSYS FEM program; the open crack is embedded in the shaft and the mesh generation is suitably modified to incorporate the stress intensity effects present at the crack tip. The results indicate that the use of the rate of change of frequencies, modal amplitudes (of displacements, velocities and accelerations) as a function of crack depth ratio will indicate the presence of crack in the shaft from a crack depth ratio of 0.2. Also the use of the rate of change of torsional frequency will indicate the presence of a crack in the shaft from the initiation of the crack. The approach indicated in this paper will provide a sound and robust procedure for a first level of damage assessment by using vibration techniques.

Crack Detection in Shafts Using Mechanical Impedance Measurements

In this study, experimental and analytical investigations are carried out on an overhanging cylindrical shaft carrying a propeller at the cantilever end, in order to identify the crack existence in shafts using the mechanical impedance approach. Also the experimental study uses the modal analysis software, LMS Test LabTM, for measuring and analyzing the response results from un-cracked and cracked shafts. In the numerical study, both the un-cracked and the cracked shafts (with varying crack depths) are modeled by finite element procedure. 3-D iso-parametric elements (element types 186 and 187), available in the ANSYS FEM program, are utilized to model the system. The impedance and velocity frequency response functions are used to identify the crack depth in the shaft system. Impedance and mobility were measured and simulated in the vertical direction for the resonant frequencies and anti-resonant frequencies. The experimental results are used to validate the numerical results. A better crack detection procedure was obtained by the plot of the slope of the non-dimensional frequency ratio (in the resonant and anti-resonant regimes) vs. the non-dimensional crack depth ratio. By this method crack presence could be definite detected when the non-dimensional crack ratio is greater than 0.20 to 0.25. In addition monitoring of the lower torsional frequency indicated the crack presence even from the beginning stages.

Optimal Design of an Ultrasonic Transducer in Rotary Ultrasonic Machining

In this paper, an ultrasonic transducer is designed and optimized in order to reduce the error of resonance frequency and maximize the amplitude of the radiating tip. In order to get the basic dimensions of an ultrasonic transducer easily, resonance frequency equations are derived by using the traditional analytic method. Using ANSYS FEM software, we analyzed the vibration model of the transducer, including Modal Analysis and Harmonic Response Analysis. Studied how the length of two resonance rods affects the resonance frequency. By optimizing the dimensions of the ultrasonic transducer, the error of resonance frequency is reduced to 0.03%; the amplitude of the vibrating tip is up to 6.20μm. The optimal results show that the transducer designed in this paper has superior performance parameters and meets the requirements of machining.

Effects of Mining Excavation on Surface Structures

In order to study the effect of mining excavation on planed structure on ground surface, the effect of certain mining excavation on ground stabtility was calculated by use of the advanced Ansys FEM computation program. The recults can not only provide ground deformation parameters for planned structure, but also give light for understanding the deformation mechanism of mining excavation.

Tall Building Structure’s Heightening Reform and Elasto-Plastic Analysis

Aim at one tall building structure model, which is a nonlinear three-dimensional finite element model. ANSYS FEM software is used to set up the structure model, proceeding modal analysis on natural vibration period and vibration model; ANSYS FEM software is used to import El Centro and Taft acceleration time-travel curves, which are used in 7 degree film, proceeding elasto-plastic analysis, and compared with the result of PKPM software earthquake static effect, the layer displacement calculation results contrast between two software shows it is consistent, but contrary results occurs in ISDA. So for the similar project design auxiliary FEM analysis is needed; Seven degree rarely met earthquake acceleration time-travel data and larger seismic peak acceleration time-travel imported to research the plastic development.

The effects of electro slag welding on material properties of box column plates

The effects of electro slag welding (ESW) on the material properties of box column plates, which is ASTM A572 Gr. 50 steel, were investigated experimentally and numerically. The material properties of the column plates before and after ESW were evaluated by macro-etching observation, micro-structural observation, and CVN impact tests. The temperature distribution of the column plates, with the ESW heat cycle as the heat input, was simulated by using the ANSYS FEM software. It was found that: (1) The CVN values in the through thickness direction of the base metal can be as low as 14J, 8.1J, and 8.1J at 0°C for plate thicknesses of 32, 40, and 50 mm respectively; (2) During the ESW process, the measured peak temperature for a 25×50 mm column plate surface was as high as 1033, 880 and 744°C for plate thicknesses of 32, 40 and, 50 mm respectively; (3) After the ESW heat cycle, the through thickness CVN value decreased by 68% for the coarse grain heat affected zone (HAZ) of the column pate; (4) The FEM thermal conduction model developed was able to simulate the temperature distribution of the steel plate during the ESW process with reasonable accuracy; (5) To avoid welding penetration due to ESW, a minimum plate thickness is suggested; (6) The impact of ESW heat cycle is more significant for thin column plates compared to thick ones.

VD Vacuum Furnace Shell’s Buckling Numerical Analysis Based on Ansys

Take VD furnace’s shell as research object, using ANSYS FEM study its stability character. The furnace body and cover’s 3D and FE model were established separately. Model’s eigenvalue buckling were analyzed at 20°C and 200°C , on the basis of this, considering structure’s initial disfigurement and material’s nonlinearity, furnace body and cover’s double non-Linear Buckling Load under external pressure were calculated. The result shows that furnace body’s double non-Linear Buckling Load are 1.44 MPa and 0.96 MPa at the normal temperature and 200°C separately, and its appeared 7 wave-number’s lateral instability; The furnace cover’s double Non-Linear Buckling Load are 2.07MPa and 1.23 MPa at the normal temperature and 200°C separately, maximum displacement on the roof and near vacuum duct position. The furnace body and cover’s stability under 20°C and 200°C satisfied design requirements. The calculate results provide the theory basis for VD vacuum furnace’s physical design.

Determination of Flux linkage Characteristics and Inductance of a Submersible Switched Reluctance Motor using Software Tools

Problem statement: The Switched Reluctance Motor (SRM) is an old member of the Electric Machines Family. It’s simple structure, ruggedness and inexpensive manufacturing capability make it more attractive for Industrial applications. Now, the applications of switched reluctance motors in various industrial fields are tried by many engineers. However, switched reluctance motors are not used so far in submersible underwater motor for agriculture purposee. The torque developed by an SRM is dependent on the change of flux-linkage and rotor position. The flux linkage characteristic of the motor is required to make the control circuit. Since the SRM is non-linear in nature, estimation and calculation of the flux linkage characteristics is very difficult. Approach: With the flux tube method concept a simple algorithm is being developed in a MATLAB. ANSYS Software is used to determine the flux distribution at various rotor positions. Results: The aligned and unaligned flux linkage values for theoretical calculation at a current of 7 A is 72.7 mwb and 13.79 mwb respectively. With FEA simulation the obtained value is 92.73 mwb and 19.175. Conclusion: In this and, a simplified method for the determination of flux linkage characteristics of submersible SRM using MATLAB has been presented. The obtained value has been validated with the ANSYS FEM method. the calculated unaligned and aligned inductance values of a 4- phase, 3 hp, 220 V Submersible SRM using simplified MATLAB method very much matches with the ANSYS FEM Method.

Initiation of Bulges in a Coke Drum Subjected to Cyclic Heating and Cooling, also Cyclic Mechanical Loads

Coke drums are equipments of an oil refinery system used to separate petroleum coke from lighter oils. During operations, a coke drum is subjected to cyclic heating and cooling also cyclic mechanical loads. Thus, the useful life of a coke drum is much shorter than the other equipments in the refinery. Bulges are commonly problems found in a coke drum. The initiation mechanisms of the bulges are not clear yet. However, there are two postulates have been proposed. First is that bulges are caused by contact stresses due to differential expansion between solid coke and steel. Second is that they are caused by thermal stresses due to presence of hot and cold spots in the coke drum wall. The present paper tends to agree with the second one. The main objective is to demonstrate that thermal stresses are sufficient to initiate the bulges. A coke drum with overall length, diameter, and thickness of 25.46 m, 6.4 m, and 42 mm, respectively has been taken into analysis. In order to provide actual temperature boundaries, operational temperatures of the coke drum have been measured and collected while it is operating. A cycle which shows the most severe operational temperature has been selected to be analyzed. Two-dimensional axisymmetric model was developed and stresses analysis upon the model was carried out by using ANSYS FEM commercial code. The equivalent stresses and the yield strength as a function of time are plotted. The results show that the maximum equivalent stress can reach the yield strength of the coke drum material. This concludes that the bulges are mainly initiated by thermal stresses.

A theoretical and experimental study of the BCB thin-film cap zero-level package based on FEM simulations

This paper presents the investigation of the behaviour of the BCB thin-film package based on the ANSYS FEM analysis. The residual stress of the BCB cap was determined by comparison between experimental data and ANSYS simulation. The pressure load–deflection method modified to be suitable to the BCB thin-film package was used to find the residual stress of it after the packaging process. Thin gold film was sputtered on the perimeter of the BCB cap to keep the interior of the package at lower pressure than the exterior of the BCB cap, and hence ambient pressure was applied to the top of the BCB cap. It was found that the well-matched BCB cap profiles from experiment and FEM simulation gave the residual stress of 28 MPa when Young's modulus of BCB was 3 GPa. With these actual material properties, the behaviour of the BCB thin-film package was parametrically investigated in terms of BCB cap deformation and device chip deformation. The parameters of concern are the BCB sealing ring width, BCB membrane height and BCB sealing height. It was found that the critical parameters on the package deformation are the BCB sealing ring width and BCB membrane height. In addition, the effects of different device substrates such as Si and GaAs are presented.

An Advanced Creep Model Allowing for Hardening and Damage Effects

Abstract: In this work an original creep prediction model is presented with a unified comprehensive formulation with primary, secondary and tertiary stages for variable stresses and temperature fields. The creep model is implemented in the ANSYS FEM code, using the Fortran subroutine usercreep, specifically suited for the cases examined, in order to assess the material behaviour more accurately than that provided by the mono‐dimensional approach. Furthermore, the residual stresses that arise from thermo‐mechanical loading and unloading cycles, under the temperature‐dependent bilinear elastic–plastic hypothesis, are considered. In order to validate the model proposed, an investigation into the final stages of turbine blade is presented and discussed. The nonlinear properties of the material are taken from an industrial context and the literature. In addition to the temperature dependence of the properties of the material, geometric nonlinearities are also considered. The material adopted for model calibration is a polycrystalline Ni‐based superalloy. Load conditions used in the simulations are obtained using a computational fluid dynamics (CFD) analysis under working conditions provided by industrial research and the constraints modelled are representative of the real joining condition of the blade. Finally, the simulation results are compared with those obtained by the Norton–Bailey prediction model.

Non-Linear Indentation Law for Lightweight Sandwich Beam

Indentation law is the relationship between force and deflection under the load on a sandwich beam in a fully backed state (on rigid ground). In the classical method, the Winkler model, which is based on analysing a beam on elastic foundation, is used for verifying the indentation law and for measuring core compression yielding load. This load is assumed to be the same as the one in the three-point bending (3PB) state. The typical formula of indentation is F= Kα n, where K and n are determined by an indentation test and α is the sandwich compression. In the present article, the sandwich beam is analysed by the higher order sandwich panel theory (HOSPT), and the indentation law is determined for fully backed and 3PB states separately. The effect of contact width on non-linearity of the indentation law is investigated, and the contact width is determined for cylindrical indentors. Foam, laminate, and sandwich beam contact pressure profiles are presented, and the indentation law is obtained in accordance to the radius of the indentor and contact width. It presents an analytical solution for the factors K and n in the indentation problem for simply supported and fully backed states. It is shown that the core compression in the 3PB state is lower than fully backed indentation. However, the classical theory predicts lower value for it than experimental value. It is shown that K increases as the indentor radius increases in the indentation law. Results are compared with the Winkler foundation method, ANSYS FEM software, and the previous article. Good agreements are found between HOSPT, ANSYS, and the previous work.

Design and Analysis of a Dual-Mode MEMS Micromirror

In this paper, the design and simulation of a dual-mode Aluminum MEMS micromirror device are proposed. The dual-mode micromirror can work in either torsional or piston modes, depending on the voltage scheme applied to the bottom driving electrodes. The working principle and performance of the micromirror are analyzed. Based upon the analysis, a set of optimized micromirror design parameters is suggested, and the corresponding performance of the micromirror design is reported. According to the analysis, the mirror can deflect for a maximum controllable displacement of 1.3μm in its piston mode, and rotate for a maximum controllable angle of ±3.6° in its torsional mode. If the micromirror works in digital operation in its torisional mode, a maximum rotation angle of ±7.8° can be achieved. ANSYS FEM method is used to simulate the first five vibrational modes and the corresponding resonant frequencies of the micromirror. The micromirror is to be fabricated with thick photoresist sacrificial layer technique. The proposed micromirror can be used to modulate the phase as well as the direction of the incident light due to its dual-mode modes. Keywords: Microelectromechanical Systems (MEMS), Spatial Light Modulator (SLM), micromirror, piston mirror, torsional mirror

Creep characteristic simulation of deep soft rock roadway and long-term mechanical analysis of lining support

By the generalized Kelvin creep model, rheological characteristics of deep soft rock and long-term mechanical behaviors of support structures were simulated. Mechanical deformation characteristics of support structures under different lining circumstances were also analyzed on the basis of deducing the relationship between the generalized Kelvin creep model and implicit creep equations in ANSYS FEM software. The results show that high stress of deep tunnels is the main factor in creep damage; the surrounding rock’s deformation binding effect due to lining increases as the thickness increases but the effect becomes very weak when it increases to a certain value; contact pressure on the lining decreases as its thickness decreases.

Weight and cost oriented multi-objective optimisation of impact damage resistant stiffened composite panels

In this paper, a multi-objective optimisation procedure, based on the adoption of genetic algorithms, is presented. The optimal configuration with minimum weight and minimum cost of a damage resistant stiffened, composite panel with buckling constraints has been determined. The numerical procedure is based on an in-house optimisation code used in conjunction with the ANSYS FEM code. The presence of both continuous and high sensitivity discrete design variables, suggested for GA the adoption of a special bit-masking data structure able to increase the overall computational efficiency. Optimal configurations of the stiffened panel, are finally analysed and discussed focusing on the influence of the damage resistance constraint on the overall costs.

Electromechanical coupling analysis for MEMS featured by stepped-height structure and concentrated load

A method is presented for MEMS’s electromechanical coupling analysis after a discussion about the limitation of traditional methods. Models for stepped-height beam subjected to arbitrary concentrated force or moment, and models for stepped-height circular plate subjected to central concentrated force are developed. Deflections and pull-in voltages obtained from the new method are in good agreement with Ansys FEM simulation results. The new method is also applicable to beam and circular plate with unvaried or smoothly varied height and under distributed load, with an obvious calculation speed advantage over finite difference method when strict convergence criterion is demanded. As same as a numerical method, it can replace finite difference method in electromechanical coupling analysis of beam or circular plate with more functions and better performance.

THERMAL BEHAVIOUR OF HOLLOW CASTINGS CAST IN CO2-SAND MOULDS BY USING FINITE ELEMENT METHOD TECHNIQUE

Prediction of solidification time is one of the very important parameters used for assessing the properties of the material. Knowledge of solidification behavior of hollow cylindrical castings and the thermal behaviour of associated moulds and cores would be of immense value to a foundrymen in the production of sound castings. In the present study, experimental investigation is carried out to measure the solidification time in a cylindrical hallow casting cast in CO2-Sand moulds and the same has been compared with the Analysis made through finite element method Technique. Finite Element Analysis was carried out by using ANSYS FEM Package. Standard physical properties were taken from ASTM metal handbook. Latent heat evolution was incorporated by enthalpy method. The solidification problem for hollow cylindrical casting was assumed to be a 2-Dimensional transient Heat Conduction flow. Convective Heat losses were considered. Aluminum-4.5% copper alloy has been used. The results shows that the solidification time obtained by experimental study compares well with the one predicted by the analysis made with the help of FEM technique.

Research on a Novel Vibration System for Dynamic Balancing Measurement Based on Flexure Hinge Mechanism

A novel vibration system for dynamic balancing measurement is presented based on flexure hinges mechanism. A kinetics modeling for this novel vibration system is established, and its equivalent stiffness and natural frequencies are analyzed in depth. Finally the obtained simulation results by ANSYS FEM validate the correction of the theoretical analysis and provide advantageous conclusions for optimal design of vibration system.

Numerical Analysis of Electromagnetic Field of Solid Rotor Asynchronous Permanent Magnetic Coupling by Finite Element Method

A new-type of solid rotor asynchronous magnetic coupling which works on the principle of electromagnetic induction is researched by ourselves. This kind of asynchronous magnetic coupling can solve the problem effectively that the permanent magnets on its inner rotor is demagnetized if its temperature is too high, because its inner rotor need not the permanent magnets. in order to study the transmission capability of the new-type magnetic coupling, its magnetic field should be analyzed. Because of its magnetic field variety, it is extremely complicated and a precision result is difficult to be got by the analytic method of the magnetic field calculation. Here the software ANSYS FEM is used to analyze its magnetic field. And some formulas were deduced and used to calculate its torque. The experimental and calculational results indicate that this design is practicable.

Analysis and experiment for the deflection of a shear-mode PZT actuator

The analytical closed-form solution for the deflection of a novel beam-shaped shear-modePZT actuator is derived. The actuator can be applied in a microfluidic system. Its activeregion possesses two oppositely poled segments separated by one non-poled segment. Thedeflections in four cases of segment dimensional designs are compared between theanalytical solution and the ANSYS FEM solution. The two solutions show good agreement.And the maximum deflection of the case with a symmetrical design is the largest.Moreover, an experiment for the sample with symmetrical design is performedand the actual shear piezoelectric coefficient is obtained. Based on the actualcoefficient, the experimental result agrees with the analytical solution very well.