Effects Of Nonlinear Behavior Research Articles

Fatigue Simulations for Automotive Components undergoing Vibration Loadings: effect of nonlinear behavior

Modern automotive customers are demanding for faster and faster product development, from initial response for quotation (RFQ) to serial production. Finite Element Analysis (FEA) is a powerful tool applied to design validation (DV). In Valeo, FEA and Reliability teams have been working together to establish a robust methodology for the simulation of vibration fatigue at the design validation phase.This paper goes in the framework of using modern simulation tools to routinely validate the goodness of a design.Previous investigations had shown that “simple” DV simulation based on the material's ultimate tensile strength (UTS) tend to be conservative and basically targeting an infinite fatigue life endurance.The present study aims at simulating the design validation of relatively complex systems (multi-materials components, prototype parts, representative system integration) in the high cyclic fatigue domain: the goal is to rely on FEA as early as possible even before official nomination (e.g. RFQ phase).This paper will present an example of a car engine cooling module (ECM) undergoing vibration loadings.The simulated fatigue will be obtained by different calculation methods, such as modal linear and non-linear approaches and time domain methods. A case study will illustrate a practical application of the presented methods. The results of the different methodologies, expressed as predicted time to failure, will be compared and analyzed.The objective of the study is to compare the results obtained from the different approaches when applied to durability design validation of an industrial cooling system undergoing vibration fatigue loadings.

Voltage-Driven Nonlinearity in Magnetoelectric Heterostructures

While the magnetoelectric (ME) resonator is promising for magnetometers, very low-frequency and miniaturized antennas, and energy harvesters, devices based on the converse ME effect in amorphous Metglas alloy face frequency-response nonlinearity issues under high vibrational amplitude. This study aims to resolve this nonlinearity issue, by addressing the dependence of nonlinearity on bias field, driving voltage, mechanical quality factor, and frequency-sweep direction. With magnetic field as a control variable, the effects of nonlinear behavior on a ME antenna's communication distance, bandwidth, and modulation are also presented.

Input-dependence effects in dynamics model calibration

Abstract This paper investigates the use of non-linear structural dynamics computational models with multiple levels of fidelity for the calibration of input-dependent model parameters. Non-linear behavior complicates the calibration of model parameters that are input-dependent (i.e., functions of temperature, loading, etc.). Different types of models may also be available for the estimation of unmeasured system properties, with different levels of physics fidelity, mesh resolution and boundary condition assumptions. To infer these system properties, Bayesian calibration can be used to combine information from multiple sources (such as experimental data and prior knowledge) and comprehensively quantify the uncertainty in the model parameters. Estimating the posterior distributions is done using Markov Chain Monte Carlo sampling, which requires a large number of computations, thus making the use of a high-fidelity model for calibration prohibitively expensive. On the other hand, use of a low-fidelity model could lead to significant error in calibration and prediction. Therefore, this paper pursues a multi-fidelity approach for input-dependent model parameter calibration with a surrogate of the low-fidelity model corrected using higher fidelity simulation data. The effects of non-linear behavior and input-dependence of model parameters and measurements are systematically organized and distinguished using a Bayesian network. The methodology is illustrated with a curved panel, subjected to acoustic and thermal loading, where the damping properties of the panel could be functions of the acoustic loading and temperature magnitudes. Two models (a frequency response analysis and a full time history analysis) are combined to estimate the damping characteristics of the panel. The effect of the temperature on the performance of the strain gages and therefore on the calibration results is also studied.

On-chip capacitive sensing and tilting motion estimation of a micro-stage for in situ MEMS gyroscope calibration

In this paper, we introduce a novel on-chip capacitive sensor design and a motion estimation method for measuring multi-axis out-of-plane tilting motion of a micro-stage that is used for in situ calibration of an integrated MEMS gyroscope. On-chip sensing and motion estimation is critical for this application, since precision in measuring high frequency tilting motion of the micro-stage determines how accurately an on-stage MEMS gyroscope can be calibrated in the field with respect to this motion. To obtain decoupled sensing signals from multi-axis out-of-plane tilting motion, a capacitive sensing layout with high off-axis signal rejection capability is introduced. With the proposed design specifications and range of tilting motion, a dual axis capacitive sensor model is developed, and simulation results show that the sensor is able to reject more than 99.90% of the off-axis signal. The sensor also permits detection of perturbations to stage geometry due to ambient temperature variation through the effects of nonlinear behavior on signal timing. To measure tilting motion with the obtained sensing signal, a motion estimator with extended Kalman Filter (EKF) is also developed. With assistance of a laser Doppler vibrometer (LDV), experiments are performed to identify the parameters of the motion estimator and validate its performance. The experimental results demonstrate a 286 ppm error in scale factor calibration of a commercial MEMS gyroscope by the micro-stage with moderate temperature variation.

Effect of nonlinear behavior of railway structure on derailment limit during earthquake

Effect of nonlinear behavior of railway structure on derailment limit during earthquake

Investigation of Nonlinear Behavior of Concrete on Seismic Performance of an Arch Dam Using Finite Element Method

In this paper the effect of nonlinear behaviour of concrete is investigated on seismic performance of a double curvature concrete dam. The Morrow Point concrete dam has been selected as the case study and dam-reservoir-foundation interaction considered in the model. Finite element method has been used for modelling and analysis of case study by applying the El Centro earthquake components considering nonlinear behaviour of concrete. The obtained results of nonlinear dynamic analysis illustrate the increasing of displacement of dam crest along the river and decreasing of maximum principle stresses in critical points. The results demonstrate the importance of consideration of nonlinear behaviour of material in seismic performance of arch dams to achieve the optimal design of models.

Frequency Domain Analysis of Nonlinear Glucose Simulation Models

Simulation models are frequently used in the development of the artificial pancreas for patients with diabetes. In this paper, frequency domain measurement techniques are used to perform a comparative analysis of widely used nonlinear simulation models of the glucose regulation system in type 1 diabetes. The analysis highlights the main differences between the models under study, based on a nonparametric estimate of their frequency response functions. The underlying linear dynamics, the nature and level of model nonlinearity, and the effect of nonlinear behavior on linear modeling are used as comparison criteria. The analysis shows that, a better understanding of the behavior of such nonlinear systems and the limitations of their linear approximates provides the means to a more careful use in simulations and control design.

Analysis of Nonlinear Structural Dynamics and Resonance in Trees

Wind and gravity both impact trees in storms, but wind loads greatly exceed gravity loads in most situations. Complex behavior of trees in windstorms is gradually turning into a controversial concern among ecological engineers. To better understand the effects of nonlinear behavior of trees, the dynamic forces on tree structures during periods of high winds have been examined as a mass-spring system. In fact, the simulated dynamic forces created by strong winds are studied in order to determine the responses of the trees to such dynamic loads. Many of such nonlinear differential equations are complicated to solve. Therefore, this paper focuses on an accurate and simple solution, Differential Transformation Method (DTM), to solve the derived equation. In this regard, the concept of differential transformation is briefly introduced. The approximate solution to this equation is calculated in the form of a series with easily computable terms. Then, the method has been employed to achieve an acceptable solution to the presented nonlinear differential equation. To verify the accuracy of the proposed method, the obtained results from DTM are compared with those from the numerical solution. The results reveal that this method gives successive approximations of high accuracy solution.

J-Q Characterization of Constraint Effects of a Three-Dimensional Cracked Specimen

Failure assessment of the integrity of a ductile flawed structural component is done currently by a one-parameter fracture mechanics approach. The J-integral is the one-parameter used; it has proven to be useful in order to predict ductile crack initiation. However, when tension loading dominates and/or a fully plastic condition develops around the crack, the J-integral alone does not describe completely the crack-tip stress field and a second parameter is needed. In this work, an accurate modeling of the elastic-plastic stress field around a deep crack in a three-dimensional three-point bend specimen is carried out. Numerical results for the crack-tip stress field are used to evaluate a crack-tip constraint parameter Q, in terms of applied loading, from contained plasticity to large-scale yielding. The parameter Q, measures the degree of stress triaxiality and constraint around the crack-tip. In order to obtain the stresses in the near-crack-tip field with high accuracy, a detailed mesh with higher order three-dimensional finite elements is located around the crack front. The modeling of crack-tip blunting deformation is performed by using a small notch radius in the crack-tip. Large-strain and finite-rotation nonlinear behavior effects around the crack-tip are included. The material, an ASTM A 516 steel, is modeled with incremental theory of plasticity. Numerical results of the Q triaxiality parameter are presented for increasing level loads to obtain an extended yield condition. Additional results of J-integral parameter and crack-tip opening displacement, for different load ratios and for different position across the specimen thickness are shown.

Creep Resistance of Pressure Sensitive Mounting Tapes

The first part of the paper deals with an approach towards a systematic testing procedure to evaluate the creep behavior of single lap shear specimens bonded with PSA mounting tapes under the influence of temperature and humidity. The study includes commercial tapes as well as self-formulated pressure sensitive adhesives based on styrene block copolymers. The second part of the paper relates the obtained data, consisting of the time-dependent sample deformation and time-to-failure, to the observed failure modes. The results show that the creep behavior of a pressure sensitive adhesive is not only dependent on the environmental, conditions but also on the substrate material and its surface composition. The results for the self-formulated adhesives reveal the possibility of enhancing creep resistance of PSA's by adding fillers to the formulation. The paper closes with a modification of the Burgers model that is suitable for describing the creep/creep recovery behavior of tested lap shear specimens. The effect of nonlinear behavior in cyclic loading experiments is described and a thesis for the relation of nonlinear creep behavior to damaging processes in the adhesive bond is presented.

Equilibrium failure processes of granular composites

The macroscopic failure of inhomogeneous media results from damage accumulation on different structural levels. During rigid loading, when given displacements of boundary points are ensured, irrespective of the body's resistance, structural-failure processes of composite materials take place in an equilibrium regime and result in the manifestation of such nonlinear-behavior effects as a descending branch on the strain diagram. the structural elements of a granular composite are homogeneous and firmly connected along the interface. Their geometry and mutual arrangement are given and do not change during deformation and failure of the medium, and the medium itself is macrohomogenous. The strength of isotropic structural elementsis estimated by comparing the second invariant of the stress tensor with its critical value. Nonfulfillment of the indicated strength criterion is associated with loss of ability to resist changes in form; at this point, the positive value of the first invariant corresponds to loss of such ability to resist and increase in volume. The deformation and structural failure of the medium are investigated as a single process that can be described under quasi-static loading by a boundary problem consisting of a closed system of Eqs. (1) and (2) and boundary conditions providing for a macrohomogeneous strain state. A principal feature of the boundary problem under consideration is the possibility of considering in constitutive relationships the states of the inhomogeneous medium, which correspond to partial or complete loss of bearing capacity of the structural elements. The random structural strength constants correspond to three-parameter Weibull distribution (6). The representative volume of a granular composite, which fills a domain in the form of a cube, is modeled by a set of istropic elastobrittle strain diagrams containing a descending branch are obtained as a result of the mathematical modeling of deformation processes and structural failure to realized a representative volume containing 384 structural elements with different strength and similar elastic constants.

Dynamic buckling of nonlinear resin matrix composite structures

A micromechanical approach is combined with a structural analysis in order to investigate the time-dependent response and dynamic buckling of structures composed of nonlinear polymeric matrices (e.g. epoxy) reinforced by elastic fibres. The composite structures considered herein are either plates or cylindrical shells both of which are under cylindrical bending conditions. Results are given which illustrate the effect of nonlinear behaviour on the dynamic response of the composite structure.