Effects of Linear Hysteric Material Damping and Shock Pulse Shapes for Uniform Board Response

2016 ◽  
Author(s):  
Sharan Kallolimath ◽  
Jiang Zhou
Keyword(s):  
Test Performance ◽  
Strain Distribution ◽  
Computational Models ◽  
Numerical Solutions ◽  
Flexural Rigidity ◽  
Interpolation Method ◽  
Computational Time ◽  
Stress Concentrations ◽  
Stress Strain ◽  
Test Board

Validation of surface mounted electronic devices for drop test performance is considered as one of the most challenging tasks for researchers to search for key dynamic parameters either by experimentation or by numerical simulation. It has not only become challenging task to capture some of the important parameters that affect board flexural rigidity, stiffness, dynamic stresses and strains, but also avoid stress concentrations near undesired locations resulting in non-uniform strain distribution throughout the test board. There is a requirement to simulate exact drop condition that quantifies high impact energy on the board and also control drop to improve the board surface stress/strain distribution measured should be independent from standoff stress region. In this paper, an effort to find the importance of viscous and linear hysteric damping characteristics on uniform board response has been made. The influence of damped responses during no ring impact has been analyzed. Two different types of computational models are developed and an approximate FEA numerical solutions are obtained to compare current JEDEC test board and alternative hexagonal boards at reduced computational time and challenging experimental cost. The effect of board responses with two types of linear damping models are considered to study the effect. An approach towards finding key parameters that affect stress/strain distribution under both free as well as constrained model has been made, with including different pulse shapes parameters into effect. Maximum board strains are validated and compared using Global FEA model and maximum stresses on the components are evaluated using cut boundary interpolation method. Comparative to empirical results data, an effort to improve uniform stress strain distribution of package solder joints has been made and results are correlated.

A Study on the Dynamic Response in Standardized Drop Test

2012 ◽  
Author(s):  
Sharan Kallolimath ◽  
Jiang Zhou
Keyword(s):  
Solder Joint ◽  
Strain Distribution ◽  
Input Pulse ◽  
Surface Strain ◽  
Drop Test ◽  
Analytical Models ◽  
Time Duration ◽  
Stress Strain ◽  
Impact Pulse ◽  
Test Board

For past several years, industries are carrying out board level drop tests to calibrate JEDEC board and improve on simulation in order to quantify the solder joint reliability performance of their products. It has not only become a difficult to simulate exact drop condition but also a challenging task to capture some of the important parameters such as board flexural rigidity, stiffness, resulting in non-uniform strain distribution throughout the test board. Previous simulations reveal unreliable stresses on all 15 components during predominate mode, which resulted in grouping of the components by location for performing reliability analysis. In addition, current experimental test procedures are not only expensive but also time consuming. In order to reduce cost and time, predictive analytical models were developed to understand drop behavior and also the key factors effecting solder joint failures. The drop impact simulation was performed using the different pulse time duration input function by analytical Method and evaluate response characteristics of the JEDEC board system. In this paper parametric study is done in order to bring more realistic drop condition and to quantify stress /strain distribution throughout the test board independent from standoff region by analyzing the system as simplified continuous beam system with sine impact pulse with the consideration of singular value (predominate mode) of the natural frequency. In addition, FEA simulation is also performed by developing JEDEC global/local model to simulate the realistic drop test condition. Direct acceleration method is adopted and no ring phenomenon is validated. By adjusting the input pulse period from 1.0 to 2.5 times the system period reveal further increase in the maximum peeling stress and board surface strain due no ring effect. In order to match the current test case, the magnitude of board input acceleration is reduced to the current drop conditions to understand and improve in the efficiency of the test and to capture more stress strain data in all the components. Close forms of theoretical and analytical results were correlated with the results of current JEDEC finite element global model.

Computational Models for Multilayered Composite Shells with Application to Tires

1996 ◽  
Vol 24 (1) ◽  
pp. 11-38 ◽  
Author(s):  
G. M. Kulikov
Keyword(s):  
Type Theory ◽  
Computational Models ◽  
Geometrical Nonlinearity ◽  
Higher Order ◽  
Stress Strain ◽  
Strain Fields ◽  
First Order ◽  
Timoshenko Type ◽  
Joint Influence ◽  
Discrete Layer

Abstract This paper focuses on four tire computational models based on two-dimensional shear deformation theories, namely, the first-order Timoshenko-type theory, the higher-order Timoshenko-type theory, the first-order discrete-layer theory, and the higher-order discrete-layer theory. The joint influence of anisotropy, geometrical nonlinearity, and laminated material response on the tire stress-strain fields is examined. The comparative analysis of stresses and strains of the cord-rubber tire on the basis of these four shell computational models is given. Results show that neglecting the effect of anisotropy leads to an incorrect description of the stress-strain fields even in bias-ply tires.

Normal form method in search for periodic solutions of ordinary differential equations. Case of the fourth order

2018 ◽  
pp. 24-34
Author(s):  
V. F. Edneral ◽  
O. D. Timofeevskaya
Keyword(s):  
Normal Form ◽  
Differential Equations ◽  
Ordinary Differential Equations ◽  
Periodic Solutions ◽  
Fourth Order ◽  
Numerical Solutions ◽  
Numerical Calculations ◽  
Computational Time ◽  
Resonant Normal Form ◽  
Normal Form Method

Introduction:The method of resonant normal form is based on reducing a system of nonlinear ordinary differential equations to a simpler form, easier to explore. Moreover, for a number of autonomous nonlinear problems, it is possible to obtain explicit formulas which approximate numerical calculations of families of their periodic solutions. Replacing numerical calculations with their precalculated formulas leads to significant savings in computational time. Similar calculations were made earlier, but their accuracy was insufficient, and their complexity was very high.Purpose:Application of the resonant normal form method and a software package developed for these purposes to fourth-order systems in order to increase the calculation speed.Results:It has been shown that with the help of a single algorithm it is possible to study equations of high orders (4th and higher). Comparing the tabulation of the obtained formulas with the numerical solutions of the corresponding equations shows good quantitative agreement. Moreover, the speed of calculation by prepared approximating formulas is orders of magnitude greater than the numerical calculation speed. The obtained approximations can also be successfully applied to unstable solutions. For example, in the Henon — Heyles system, periodic solutions are surrounded by chaotic solutions and, when numerically integrated, the algorithms are often unstable on them.Practical relevance:The developed approach can be used in the simulation of physical and biological systems.

scholarly journals Energy Minimization Scheme for Split Potential Systems Using Exponential Variational Integrators

2021 ◽  
Vol 2 (3) ◽  
pp. 431-441
Author(s):  
Odysseas Kosmas
Keyword(s):  
Numerical Solutions ◽  
Oscillatory Behavior ◽  
Lagrangian Function ◽  
Computational Time ◽  
Variational Integrators ◽  
Weighted Sum ◽  
Lagrange Equations ◽  
Exponential Functions ◽  
Intermediate Time ◽  
Definition Of

In previous works we developed a methodology of deriving variational integrators to provide numerical solutions of systems having oscillatory behavior. These schemes use exponential functions to approximate the intermediate configurations and velocities, which are then placed into the discrete Lagrangian function characterizing the physical system. We afterwards proved that, higher order schemes can be obtained through the corresponding discrete Euler–Lagrange equations and the definition of a weighted sum of “continuous intermediate Lagrangians” each of them evaluated at an intermediate time node. In the present article, we extend these methods so as to include Lagrangians of split potential systems, namely, to address cases when the potential function can be decomposed into several components. Rather than using many intermediate points for the complete Lagrangian, in this work we introduce different numbers of intermediate points, resulting within the context of various reliable quadrature rules, for the various potentials. Finally, we assess the accuracy, convergence and computational time of the proposed technique by testing and comparing them with well known standards.

An Improved Assembling Algorithm in Boundary Elements With Galerkin Weighting Applied to Three-Dimensional Stokes Flows

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Sofia Sarraf ◽  
Ezequiel López ◽  
Laura Battaglia ◽  
Gustavo Ríos Rodríguez ◽  
Jorge D'Elía
Keyword(s):  
Boundary Element Method ◽  
Linear System ◽  
Boundary Element ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Boundary Integral ◽  
Computational Time ◽  
Creeping Flows ◽  
Order Of Magnitude ◽  
Element Method

In the boundary element method (BEM), the Galerkin weighting technique allows to obtain numerical solutions of a boundary integral equation (BIE), giving the Galerkin boundary element method (GBEM). In three-dimensional (3D) spatial domains, the nested double surface integration of GBEM leads to a significantly larger computational time for assembling the linear system than with the standard collocation method. In practice, the computational time is roughly an order of magnitude larger, thus limiting the use of GBEM in 3D engineering problems. The standard approach for reducing the computational time of the linear system assembling is to skip integrations whenever possible. In this work, a modified assembling algorithm for the element matrices in GBEM is proposed for solving integral kernels that depend on the exterior unit normal. This algorithm is based on kernels symmetries at the element level and not on the flow nor in the mesh. It is applied to a BIE that models external creeping flows around 3D closed bodies using second-order kernels, and it is implemented using OpenMP. For these BIEs, the modified algorithm is on average 32% faster than the original one.

scholarly journals A Computational Model to Assess Poststenting Wall Stresses Dependence on Plaque Structure and Stenosis Severity in Coronary Artery

2014 ◽  
Vol 2014 ◽  
pp. 1-12
Author(s):  
Zuned Hajiali ◽  
Mahsa Dabagh ◽  
Payman Jalali
Keyword(s):  
Coronary Arteries ◽  
Computational Models ◽  
Strong Dependence ◽  
Internal Stresses ◽  
Shear Stresses ◽  
Stress Concentrations ◽  
Opening Pressure ◽  
Fibrous Cap ◽  
Stent Restenosis ◽  
Von Mises

The current study presents computational models to investigate the poststenting hemodynamic stresses and internal stresses over/within the diseased walls of coronary arteries which are in different states of atherosclerotic plaque. The finite element method is applied to build the axisymmetric models which include the plaque, arterial wall, and stent struts. The study takes into account the mechanical effects of the opening pressure and its association with the plaque severity and the morphology. The wall shear stresses and the von Mises stresses within the stented coronary arteries show their strong dependence on the plaque structure, particularly the fibrous cap thickness. Higher stresses occur in severely stenosed coronaries with a thinner fibrous cap. Large stress concentrations around the stent struts cause injury or damage to the vessel wall which is linked to the mechanism of restenosis. The in-stent restenosis rate is also highly dependent on the opening pressure, to the extent that stenosed artery is expanded, and geometry of the stent struts. The present study demonstrates, for the first time, that the restenosis is to be viewed as a consequence of biomechanical design of a stent repeating unit, the opening pressure, and the severity and morphology of the plaque.

Routes towards Novel Active Pressure Sensors in SOI Technology

2011 ◽  
Vol 276 ◽  
pp. 145-155
Author(s):  
Benoit Olbrechts ◽  
Bertrand Rue ◽  
Thomas Pardoen ◽  
Denis Flandre ◽  
Jean Pierre Raskin
Keyword(s):  
Finite Elements ◽  
Strain Distribution ◽  
Pressure Sensors ◽  
High Sensitivity ◽  
Stress Strain ◽  
Pressure Transducers ◽  
Active Devices ◽  
Active Pressure ◽  
Soi Technology

In this paper, novel pressure sensors approach is proposed and described. Active devices and oscillating circuits are directly integrated on very thin dielectric membranes as pressure transducers. Involved patterning of the membrane is supposed to cause a drop of mechanical robustness. Finite elements simulations are performed in order to better understand stress/strain distribution and as an attempt to explain the early burst of patterned membranes. Smart circuit designs are reported as solutions with high sensitivity and reduced footprint on membranes.

AFM-Based Nanoindentation Process: A Comparative Study

2012 ◽  
Author(s):  
Rapeepan Promyoo ◽  
Hazim El-Mounayri ◽  
Kody Varahramyan
Keyword(s):  
Md Simulation ◽  
Computational Models ◽  
Surface Deformation ◽  
Experimental Results ◽  
Computational Time ◽  
Machined Surface ◽  
Indentation Force ◽  
Subsurface Deformation ◽  
Different Types ◽  
Copper Aluminum

Atomic force microscopy (AFM) has been widely used for nanomachining and fabrication of micro/nanodevices. This paper describes the development and validation of computational models for AFM-based nanomachining. Molecular Dynamics (MD) technique is used to model and simulate mechanical indentation at the nanoscale for different types of materials, including gold, copper, aluminum, and silicon. The simulation allows for the prediction of indentation forces at the interface between an indenter and a substrate. The effects of tip materials on machined surface are investigated. The material deformation and indentation geometry are extracted based on the final locations of the atoms, which have been displaced by the rigid tool. In addition to the modeling, an AFM was used to conduct actual indentation at the nanoscale, and provide measurements to which the MD simulation predictions can be compared. The MD simulation results show that surface and subsurface deformation found in the case of gold, copper and aluminum have the same pattern. However, aluminum has more surface deformation than other materials. Two different types of indenter tips including diamond and silicon tips were used in the model. More surface and subsurface deformation can be observed for the case of nanoindentation with diamond tip. The indentation forces at various depths of indentation were obtained. It can be concluded that indentation force increases as depth of indentation increases. Due to limitations on computational time, the quantitative values of the indentation force obtained from MD simulation are not comparable to the experimental results. However, the increasing trends of indentation force are the same for both simulation and experimental results.

scholarly journals Stress-Strain State of a Cylindrical Shell of a Tunnel Using Construction Stage Analysis

2019 ◽  
Vol 21 (3) ◽  
pp. 72-76
Author(s):  
Sergey B. Kosytsyn ◽  
Vladimir Y. Akulich
Keyword(s):  
Cylindrical Shell ◽  
Comparative Analysis ◽  
Static Analysis ◽  
Strain State ◽  
Computational Models ◽  
Stress Strain ◽  
Construction Stage ◽  
Stress Strain State ◽  
Slurry Shield ◽  
Stage Analysis

The work is aimed at research of the stress-strain state of a cylindrical shell of a tunnel using the non-linear static analysis and construction stage analysis. Research is carried out on the example of determining the stress-strain state of the tubing (shells) of the main line tunnel, constructed using a tunnel powered complex (slurry shield). Based on obtained results, a comparative analysis of the computational models with the corresponding conclusions is presented.

Sign in / Sign up

Export Citation Format

Share Document