FEM Simulation Results Research Articles

Development of capacitive-type MEMS microphone with CMOS amplifying chip

In this study, we reported the fabrication of a capacitive MEMS microphone packaged with an analog amplifying chip. The MEMS device and the amplifying chip were made using a micromachining technique and an IC Multi-Project Chip (MPC) service, respectively. The MEMS device consisted of a low stressed SiNx membrane that is sensitive to sound and the rigid Si back plate. The membrane and the back-plate parts fabricated separately on two wafers were bonded through a eutectic bonding process. Finally, the MEMS device and the amplifying chip were packaged on a single PCB for measuring. The evaluation results of the packaged microphone devices showed similar characteristics compared to FEM simulation results. The sensitivity of the microphone was about −37.4 dB in audio frequency bandwidth.

Hierarchical Metamodeling: Cross Validation and Predictive Uncertainty

At Esaform 2013 a hierarchical metamodeling approach had been presented, able to combine the results of numerical simulations and physical experiments into a unique response surface, which is a “fusion” of both data sets. The method had been presented with respect to the structural optimization of a steel tube, filled with an aluminium foam, intended as ananti-intrusion bar. The prediction yielded by a conventional way of metamodeling the results of FEM simulations can be considered trustworthy only if the accuracy of numerical models have been thoroughly tested and the simulation parameters have been sufficiently calibrated. On the contrary, the main advantage of a hierarchical metamodel is to yield a reliable prediction of a response variable to be optimized, even in the presence of non-completely calibrated or accurate FEM models. In order to demonstrate these statements, in this paper the authors wish to compare the prediction ability of a “fusion” metamodel based on under-calibrated simulations, with a conventional approach based on calibrated FEM results. Both metamodels will be cross validated with a “leave-one-out” technique, i.e. by excluding one experimental observation at atime and assessing the predictive ability of the model. Furthermore, the paper will demonstrate how the hierarchical metamodel is able to provide not only an average estimated value for each excluded experimental observation, but also an estimation of uncertainty of the prediction of the average value.

A microstructure-sensitive constitutive modeling of the inelastic behavior of single crystal nickel-based superalloys at very high temperature

The prediction of the viscoplastic behavior of nickel-based single crystal superalloys remains a challenging issue due to the complex loadings encountered in aeronautical engine components such as high pressure turbine blades. Under particular in-service conditions, these materials may experience temperature cycles which promote the dissolution of the strengthening γ′ phase of the material on (over)heating, and subsequent precipitation on cooling, leading to a transient viscoplastic behavior.Within this context, a model was recently developed by Cormier and Cailletaud (2010) to fulfill the effects of fast microstructure evolutions occurring upon high temperature non-isothermal loadings. New internal variables were introduced in the crystal plasticity framework to take into account microstructure evolutions such as γ′ dissolution/precipitation and dislocation recovery processes which are known to control the creep behavior and life. Nevertheless, this model did not consider the γ′ directional coarsening, one of the main microstructural evolutions occurring specifically at high temperature. In addition, no kinematic hardening was considered to describe the mechanical behavior, leading to a poor description of cyclic loadings.This paper details the development of a new model by introducing new internal variables for both modeling the γ′ directional coarsening and the evolutions of isotropic and kinematic hardening under complex loading paths.This model was calibrated using monotonous and cyclic experiments performed on [001] oriented single-crystal samples and both under isothermal and non-isothermal conditions. Thereby, it is able to predict microstructural evolutions for complex thermal and mechanical loadings as well as internal stress evolutions whatever the thermomechanical history. The model efficiency was highlighted by comparing FEM simulation and experimental results of a non-isothermal creep test on a notched sample (i.e. under complex mechanical stress state).

Design of Plane Magnetic Field Image Drawing System Based on PLC Motion Control

The image of magnetic field is traditionally obtained by spreading magnetic powder manually or by sparse arrays of magnetic needles, obtaining the images of the magnetic field in different permanent magnet shapes and do repeated tests on the permanent magnet are in need. Based on programmable logic controller (PLC) motion control, the servo control and mechanical system have been built, the control strategy is discussed and the software is programmed. 2D FEM model of a test permanent magnet bar is built. Compared with the FEM simulation results, the system has achieved the goal that spreading magnetic powder quickly and evenly in the appointed area.

Material Characterization for FEM Simulation of Sheet Metal Stamping Processes

Sheet metal forming is an important technology in manufacturing, especially in the automotive industry. Today, engineering simulation tools based on the finite elements method are employed regularly in the design of stamping dies for sheet metal parts. However, a bad material model choice or the use of nonaccurate enough parameters can lead to imprecise simulation results. This work uses ANSYS LS-DYNA software to analyze several material models and the influence of their parameter values in FEM simulation results. The main tool to solve these problems is an application designed to assist die stamp designers. The program allows a procedure to be defined to obtain the values of the properties of an unknown material, which combines finite element simulations with real experimental results. Results obtained for the simulation of a real automotive part are analyzed and compared with the real experimental results. Parameters involved in each material model have been identified, and their influence in final results has been quantified. This is very useful to fit material properties in other simulations. This paper fulfils an identified need in the manufacturing industry. In fact, the proposed application is currently being used by a manufacturer of automotive components.

Modeling of ray paths of head waves on irregular interfaces in TOFD inspection for NDE

The TOFD (Time of Flight Diffraction) technique is a classical ultrasonic inspection method used in ultrasonic non-destructive evaluation (NDE). This inspection technique is based on an arrangement of two probes of opposite beam directions and allows a precise positioning and a quantitative evaluation of the size of cracks contained in the inspected material thanks to their edges diffraction echoes. Among the typical phenomena arising for such an arrangement, head waves, which propagate along the specimen surface and are chronologically the first waves reaching the receiver, are notably observed. Head wave propagation on planar surfaces in TOFD configurations is well known. However, realistic inspection configurations often involve components with irregular surfaces, like steel excavated specimens.Surface irregularity is responsible for numerous effects on the scattering of bulk waves, causing the melting of surface and bulk mechanisms in the head wave propagation. In order to extend the classical ray approach on these complex cases, a generic algorithm of ray tracing between interface points (GIRT) has been designed. With respect to time of flight minimization (i.e. the Generalized Fermat’s Principle), ray paths can be computed by GIRT for different natures of waves scattered by the complex surfaces or by flaws. The head wave fronts computed by GIRT are notably in good agreement with FEM simulated results. This algorithm, based on pure kinematic analysis of waves propagation, represents a first step in the future development of a complete ray theory for head waves simulation on irregular interfaces.

Optimal Design and Experimental Investigations of Aluminium Extrusion Profiles for Lightweight of Car Bumper

The present study aimed at developing an aluminium car bumper unit to replace the steel ones by using optimization based on experimental and FEM simulation results. The topology optimization method and response surface methodology (RSM) were applied in order to achieve an optimized design for the cross section of the crossbeam and the crash box, respectively. The three-points bending test and crash test for bumper unit were simulated to evaluate the optimization processes. The 6061 and 6063 aluminium alloy bumper unit has a weight reduction of 67% compared to the steel ones. The new extrusion dies were manufactured to produce profiles for the crossbeam and the crash box, respectively. Then the optimized extrusion profiles of crossbeam and crash box were verified by experimental studies. The performance tests were arranged to validate the experimental product. The mechanical properties of extruded aluminium crossbeam and crash box can satisfy the design requirements of products. The results indicate that the new designed unit can change the whole design of automotive parts for crash energy absorption, and definitely contribute to drastic weight reduction of steel parts.

Estimation of Flow Stress of Zinc-Titanium Strip during Reverse Rolling

Due to some specific features (high corrosion resistance and long-life durability in particular) as well as interesting aesthetic appeal, zinc-titanium strips are widely used as roof coverings, facade panels and rain gutters. The Zn-Ti strips are manufactured either in the hot rolling lines or in the reverse rolling mills at elevated temperatures. A problem of determination the average flow stress of zinc-titanium strip in the latter mentioned technology and in the actual rolling conditions is discussed in the paper. The analysis is based on the results of plastometric compression tests, FEM simulations and industrial practice.

Novel mathematical approaches for analyzing time dependent creep deformations in reinforced metals

The objective of this paper is to present some novel insights for solving a second stage creep problem in metal matrix composites. First, a new analytical approach is developed for obtaining some unknowns in second stage creep of short fiber composites under an applied axial load. The unknowns are the radial, circumferential, axial, shear and equivalent stresses, which are determined by approximation of creep constitutive equations and using proper assumed displacement rates. A nonlinear differential equation is solved employing suitable and correct approximate assumptions. Then, the difference of the stress components utilizing creep constitutive equations and assumed displacement rates is determined. Finally, the axial stress behavior in matrix is predicted by linear and nonlinear boundary value approaches, as well as displacement rates in matrix. For the purpose of the analysis, the steady state creep behavior of matrix material is described by an exponential law. As an important application, factor of safety n will be determined for fibers in order to have a good composite design. Based on the results, the aforementioned methods such as general boundary value approaches can be used to simply determine the approximate behavior of unknowns. These analytical results are then verified by the results of FEM simulation and other available research works. Interestingly, good compatibilities are found among the original mathematical approaches, numerical modeling and also previous available results.

The Effect of Inclusions on Internal Cracks for 20Mn5N Steel Ingot after Forging

The heavy forging ingots of steel 20Mn5N have been extensively used to fabricate the hydropower shaft steel, which plays as an extremely important part in industry. However, the quality of the heavy ingots has been commonly affected by various inner defects. One of the most typical defects is internal cracks, which has been found to be always accompanied by inclusions. In order to effectively analyze the formation of internal cracks, a 30-ton 20Mn5N ingot has been cut along the axle plane. Exceeding macroscopic cracks can be found in macro-segregation area gathered many large and grid inclusions (Al2O3). Based on the experimental results and FEM simulation method we have investigated that large and grid inclusions accompanied by other macro-visible defects such as banded structure could lead to the forging cracks easily. FEM simulation result shows that the stress concentration resulting from the large and grid inclusions (Al2O3) is relatively large. These large and grid inclusions accompanied by banded structure are the fundamental cause of cracks.

Efficient Oxyhydrogen Mixture Determination in Gas Detonation Forming

Oxyhydrogen is a mixture of Hydrogen (H2) and Oxygen (O2) gases. Detonative mixtures of oxyhydrogens with various combinations of these two gases were used in Gas Detonation Forming (GDF) to form sheets of mild steel. In die forming experiments, three types of conical dies with apex angles of 60, 90 and 120 degrees were used. Pressure of mixtures inside the chamber before detonation was varied from 3 Bar to 5 Bar to investigate the effect of pre-detonation pressure in the forming process. On each conical die, several experiments with different percentages of Hydrogen were carried out to determine the optimum gaseous mixture. According to our results the best forming process occurred when approximately 50-70%. Hydrogen was employed in the mixture. Furthermore, the experimental results were compared to the ones from FEM analysis. The FEM simulation results of thickness strain, hoop strain, thickness variation and deformed geometry are promising. method is used to investigate the deformation mechanisms and examine the effect of detonation pressure on the work piece (7). The FE computations are based on three-dimensional explicit dynamics formulations (8). The strain rate effects are incorporated using Johnson-Cook material model (9). In this paper results of experimental tests obtained from GDF apparatus are presented. The experimental tests reported in this paper are divided into two groups: Die forming of clamped circular mild steel sheets; and efficient combination determination by varying the percentage of Hydrogen in the mixture. Also, the effect of the primary variables including pre-detonation pressure of oxyhydrogen mixture inside the chamber, the effect of die angles, and percentage of Hydrogen in mixture, on the amount of deformation and strain distribution are discussed. Furthermore, a FEM model is used to simulate this process and obtained numerical results are compared with the experimental data.

Complex Numerical Analysis of the Tube Forming Process Using Diescher Mill

Abstract This paper presents the results of FEM simulations of the rotary piercing process in which disc guiding devices of the Diescher type are used. During this process the material is formed by means of two skew rolls, two guiding devices, and the piercing plug mounted on the mandrel. The aim of the analysis was to determine the effect of the plug diameter, the plug advance, the feed angle and the diameter reduction on the piercing process. Nine cases of piercing with three different plugs used were analyzed. The effects of the basic process parameters on the tube shell diameter and the tool load were analyzed. The numerical results obtained using Simufact.Forming 10.0 were verified under experimental conditions in which the tube shell made from 100Cr6 bearing steel was pierced. The results of the FEM calculations show agreement with the experimental results.

Improving mesh stiffness calculation of cracked gears for the purpose of vibration-based fault analysis

For the purpose of vibration-based condition monitoring and to prevent occurrence of catastrophic gear failures it is important to improve the simulated dynamic response of the studied gear model. The time-varying gear mesh stiffness will contribute to the dynamic response of a geared system. Some previously applied methods for stiffness calculation, described in the literature, show good agreement with the results obtained with FEM simulation for smaller crack sizes. However, when larger crack sizes are reached, these methods show an increasing deviation from FEM simulation results. A reduction in the gear mesh stiffness can be considered to assess the status of tooth damage and, therefore, by increasing the accuracy of the calculated mesh stiffness, dynamic simulations of a gear can be improved. In this paper a new method is presented for calculating the gear mesh stiffness for a propagating crack in the tooth root. The influence of gear mesh stiffness on the vibration-based fault detection indicators, the RMS, kurtosis and the crest factor, is investigated. Different crack sizes are examined by using this new method for sizes up to around 50% of the total tooth root thickness. When compared to FEM simulations, the presented method shows more accurate results for calculations of the gear mesh stiffness (for the studied model) than the previously suggested methods.

Study on Influence of the Load Path on Formability of Variable Cross-Section Y-Shaped Tube Hydroforming

Based on the analysis of now available evaluation indexes to estimate the formability of Variable cross-section Y-shaped tube hydroforming, an aggregative indicator is proposed. The effect of load path on the formability of Variable cross-section Y-shaped tube is discussed by FEM simulation, and validity of the evaluation index and simulations are proved by experiment. Results show that with the broken line load path of 0-30-30-40, the value of aggregative indicator is the greatest and the formability is the best. The optional parameters are testified by experiment and the results are in agreement with the FEM simulation results.

Rectifying Process Problems in Production of Thin Sheets of Special Alloys

The paper deals with solutions to particular process problems in production of thin sheets of special nickel and iron-based alloys. Experiments were focused on trial operation of a new melting furnace, on hot rolling of feedstock from experimental heats and on fine-tuning hot and cold rolling processes with the aid of numerical modelling in DEFORM 3D software. The paper also gives description of results of FEM simulation of cold rolling of strips. A FEM model of the cold rolling process with front and back tension was developed. In order to describe the behaviour of nickel alloys in the FEM simulation, a specific material model was proposed. This material model combines the material data obtained from Rastegaev compression test and the results of thermodynamical calculation from JMatPro software.

Research on Piezoelectric Tube Stack for Radial Vibration Mode

According to electro-mechanical equivalent principle, piezoelectric tube stack electro-mechanical equivalent circuit is derived by the admittance of single piezoelectric thin tube. The resonance frequency of piezoelectric tube stack for radial vibration mode is also calculated. The relationship between resonance frequencies and average radius, thickness and height with radial vibration mode are obtained through analytical calculation. And radial vibration mode is simulated by FEM .Analytical calculation and FEM simulation results are compared. They coincide well with each other.

Effects of Draw-Bending Characteristics on Concave Wall Feature in Rectangular Deep-Drawn Parts

In recent years, the requirements on the complicated deep-drawn parts with the high dimension precision are increasingly. As the major defect, the concave wall feature which commonly encounter in the complicated deep-drawn parts of the difficult-to-deep draw material is focused. In this research, the effects of draw-bending characteristics on concave wall feature during deep-drawing process are clearly identified. The mechanism of concave wall feature related to the draw-bending characteristic was investigated and clearly identified by using the finite element method (FEM) and the experiments were also performed to validate the FEM-simulation results. On the basis of stress distribution, the effects of draw-bending characteristics on the concave wall feature could be clearly identified via the changes of stress distributions on the wall, convex feature and spring-go feature on the bottom surface, and spring-back feature on the top surface. However, comparing with U-draw bending model, the effects of draw-bending characteristics was decreased and the concave wall feature in the case of deep-drawing model was smaller than that in the case of U-draw bending model. The experiments were carried out in both cases of the deep-drawing and U-draw bending models to validate the FEM-simulation results. The FEM-simulation results showed a good agreement with the experimental results with reference to the distribution of material thickness.

Investigation of the cold orbital forging process of an AlMgSi alloy bevel gear

Orbital forging is a metal forming process in which one of the dies performs a complex rocking motion. It ensures reduction in required load and allows for the cold forming of a workpiece. One of the mechanical parts formed by means of this technology is a bevel gear. However, a numerical analysis of orbital forging bevel gears is very difficult to perform due to the complex rocking motion of the die, which is confirmed by numerous works investigating the orbital forging process. In the present work, investigation results of the cold orbital forging of aluminum alloy bevel gears are presented. In contrast to other works devoted to the process, this study proposes a new procedure for forming bevel gears and the workpiece used has a shape which is different from the previously applied ones. The obtained results apply to both theoretical and technological aspects of orbital forging. The FEM simulation results have been successfully verified in laboratory conditions using the industrial PXW-100A press.

Force Sensor for Laparoscopic Tool of RobIn Heart Robot

The design of a force sensor prototype as an equipment of a control system with force feedback to be used in the RobInHeart [1,2, telemanipulator system is presented. The main problems with placing the sensor on the laparoscopic tool are discussed. The method of decoupling impact of the gripper actuation force from the measurement is described. Also, the results of computer FEM simulations are shown.

A New Application of Bimetallic Thin Film

To perform the temperature compensation, a bimetallic thin film with different thermal expansion coefficients is deposited on the surface of the crystal plate. The thermal stress generated in the crystal and the thin film will cancel each other when temperature changes, thus improve the frequency stability of the crystal oscillator. In this paper, a finite element simulation was carried out for the crystal plate with bimetal, and then an experiment was performed to verify the FEM simulation results. The result shows that this approach achieves good temperature - frequency characteristics and reduces the frequency shift of crystal oscillator.