Shock and Dynamic Loading in Portable Electronic Assemblies: Modeling and Simulation Results

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
A. F. Askari Farahani ◽  
M. Al-Bassyiouni ◽  
A. Dasgupta
Keyword(s):  
Finite Element ◽  
High Strain Rate ◽  
Strain Rate ◽  
Transient Response ◽  
Material Properties ◽  
Computational Models ◽  
Failure Modes ◽  
High Strain ◽  
Finite Element Models ◽  
Electronic Assemblies

In this study, the transient response of electronic assemblies to mechanical loading encountered in drop and shock conditions are investigated with transient finite element methods. Many manufacturers face design challenges when evolving new designs for high strain-rate life cycle loading. Examples of high strain-rate loading include drop events, blast events, vibration, ultrasonic process steps, etc. New design iterations invariably bring new unexpected failure modes under such loading and costly trial-and-error design fixes are often necessary after the product is built. Electronics designers have long sought to address these effects during the design phase, with the aid of computational models. However, such efforts have been difficult because of the nonlinearities inherent in complex assemblies and complex dynamic material properties. Our goal in this study is to investigate the ability of finite element models to accurately capture the transient response of a complex portable electronic product under shock and drop loading. Finite element models of the system are generated and calibrated with experimental results, first at the subsystem level to calibrate material properties and then at the product level to parametrically investigate the contact mechanics at the interfaces. The parametric study consists of sensitivity studies for different ways to model soft, nonconservative contact, as well as structural damping of the subassembly under assembly boundary conditions. The long-term goal of this study is to demonstrate a systematic modeling methodology to predict the drop response of future portable electronic products, so that relevant failure modes can be eliminated by design iterations early in the design cycle.

scholarly journals Modeling and Simulation of Shock and Drop Loading for Complex Portable Electronic Systems

2008 ◽  
Author(s):  
Farbod Askari Farahani ◽  
Moustafa Al-Bassyiouni ◽  
Abhigit Dasgupta ◽  
Sheldon Tolchinsky
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Transient Response ◽  
Computational Models ◽  
Failure Modes ◽  
High Strain ◽  
Quantitative Agreement ◽  
Design Phase ◽  
Cycle Loading ◽  
Strain Rate Loading

In this study, the transient response of electronic assemblies to mechanical loading encountered in drop and shock conditions are investigated. Many manufactures face design challenges when evolving new designs for high-strain rate life-cycle loading. Examples of high-strain rate loading include drop events, blast events, vibration, ultrasonic process steps, etc. New design iterations invariably bring new unexpected failure modes under such loading and costly trial-and-error design fixes are often necessary after the product is built. Electronics designers have long sought to address these effects during the design phase, with the aid of computational models. However, such efforts have been difficult because of the nonlinearities inherent in complex assemblies and complex dynamic material properties. Our goal in this study is to investigate the ability of finite element models to accurately capture the transient response of a complex portable electronic product under shock and drop loading. While many researchers have shown qualitative ability for such modeling, further work is still needed to demonstrate good quantitative agreement. The product consists of a circuit card assembly in a plastic housing. Dynamic loading, consisting of various shock profiles, is applied using an electrodynamic shaker. Limited number of drop tests are also conducted on a drop tower. The modeling is conducted in ABAQUS/Explicit. In-plane strains and accelerations are the parameters that are compared to assess the agreement between the model and the experimental results. The long-term goal of this study is to demonstrate a systematic methodology to predict failure modes during the design phase of future products.

An Alternate Approach to SHPB Tests to Compute Johnson-Cook Material Model Constants for 97 WHA at High Strain Rates and Elevated Temperatures Using Machining Tests

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Chithajalu Kiran Sagar ◽  
Amrita Priyadarshini ◽  
Amit Kumar Gupta ◽  
Tarun Kumar ◽  
Shreya Saxena
Keyword(s):  
Finite Element ◽  
High Strain Rate ◽  
Strain Rate ◽  
Elevated Temperatures ◽  
High Strain ◽  
Optimization Technique ◽  
Material Model ◽  
Computational Techniques ◽  
Fe Model

Abstract With advances in computational techniques, numerical methods such as finite element method (FEM) are gaining much of the popularity for analysis as these substitute the expensive trial and error experimental techniques to a great extent. Consequently, selection of suitable material models and determination of precise material model constants are one of the prime concerns in FEM. This paper presents a methodology to determine the Johnson-Cook constitutive equation constants (JC constants) of 97 W Tungsten heavy alloys (WHAs) under high strain rate conditions using machining tests in conjunction with Oxley’s predictive model and particle swarm optimization (PSO) algorithm. Currently, availability of the high strain rate data for 97 WHA are limited and consequently, JC constants for the same are not readily available. The overall methodology includes determination of three sets of JC constants, namely, M1 and M2 from the Split-Hopkinson pressure bar (SHPB) test data available in literature by using conventional optimization technique and artificial bee colony (ABC) algorithm, respectively. However, M3 is determined from machining tests using inverse identification method. To validate the identified JC constants, machining outputs (cutting forces, temperature, and shear strain) are predicted using finite element (FE) model by considering M1, M2, and M3 as input under different cutting conditions and then validated with corresponding experimental values. The predicted outputs obtained using JC constants M3 closely matched with that of the experimental ones with error percentage well within 10%.

High Strain Rate Compressive Properties of Soft Tissue

2003 ◽  
Author(s):  
Caleb R. Van Sligtenhorst ◽  
Duane S. Cronin ◽  
G. Wayne Brodland
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Material Properties ◽  
Fiber Orientation ◽  
Soft Tissues ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Strain Rates ◽  
Post Mortem ◽  
Fresh Tissue

High strain rate material properties and constitutive equations are essential for the development of numerical and physical models to assess the performance of soft materials subject to high rate deformation, with potential applications including protective equipment and vehicle crashworthiness. However, these properties are not available for many soft tissues. This is because specialized testing methods must be employed to obtain the necessary data. Fresh bovine tissue from the semimembranosis muscle was obtained and tested using a polymeric Split Hopkinson Pressure Bar. Samples were tested from 1.4 to 200 hours post mortem to observe the effect of rigor and other possible temporal effects on the material properties. Since this muscle had relatively uniform fiber orientation, it was possible to obtain specimens with fiber directions parallel, perpendicular, and at 45 degrees to the compression axis. The stress-strain curves for the muscle were concave upwards, as is typical of soft tissues at high strain rates. Fiber orientation was determined to have negligible effect at the tested strain rates. The testing revealed that the stiffness of the tissue increased with post mortem time until approximately 6 hours. At times greater than 200 hours post mortem, the tissue properties were found to be very similar to the properties of fresh tissue. These findings suggest that properties of fresh tissue might be estimated using more easily obtained post-rigor tissue.

scholarly journals FE Analysis of Critical Testing Parameters in Kolsky Bar Experiments for Elastomers at High Strain Rate

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3817
Author(s):  
Chaudhry ◽  
Czekanski
Keyword(s):  
Finite Element ◽  
High Strain Rate ◽  
Strain Rate ◽  
Pulse Shaping ◽  
High Strain ◽  
Kolsky Bar ◽  
Specimen Geometry ◽  
Strain Rates ◽  
Butadiene Rubber ◽  
Testing Apparatus

The main aim of this research is to present complete methodological guidelines for dynamic characterization of elastomers when subjected to strain rates of 100/s–10,000/s. We consider the following three aspects: (i) the design of high strain rate testing apparatus, (ii) finite element analysis for the optimization of the experimental setup, and (iii) experimental parameters and validation for the response of an elastomeric specimen. To test low impedance soft materials, design of a modified Kolsky bar is discussed. Based on this design, the testing apparatus was constructed, validated, and optimized numerically using finite element methods. Furthermore, investigations on traditional pulse shaping techniques and a new design for pulse shaper are described. The effect of specimen geometry on the homogeneous deformation has been thoroughly accounted for. Using the optimized specimen geometry and pulse shaping technique, nitrile butadiene rubber was tested at different strain rates, and the experimental findings were compared to numerical predictions.

Material Properties as Indicators of Machining Behavior

1999 ◽  
Author(s):  
Robin Stevenson
Keyword(s):  
High Temperature ◽  
High Strain Rate ◽  
Strain Rate ◽  
Deformation Mechanism ◽  
Material Properties ◽  
High Strain ◽  
Temperature Data ◽  
Test Procedures ◽  
High Temperature Data ◽  
Conventional Material

Abstract This paper demonstrates that the material properties developed using conventional material test procedures can be consistent with those developed during machining. However if extensive extrapolation is required to develop the high strain/high strain rate/high temperature data characteristic of machining, it is important to ensure that no change in deformation mechanism occurs over the extrapolation range. If such a mechanism change does occur the extrapolated data will be invalid.

SIF Evaluation Using XFEM and Line Spring Models Under High Strain Rate Environment for Leadfree Alloys

2011 ◽  
Author(s):  
Pradeep Lall ◽  
Mandar Kulkarni ◽  
Sandeep Shantaram ◽  
Jeff Suhling
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Speed ◽  
High Strain ◽  
Strain Rates ◽  
Fracture Properties

In this paper, fracture properties of Sn3Ag0.5Cu leadfree high strain-rate solder-copper interface have been evaluated and validated with those from experimental methods. Bi-material Copper-Solder specimen have been tested at strain rates typical of shock and vibration with impact-hammer tensile testing machine. Models for crack initiation and propagation have been developed using Line spring method and extended finite element method (XFEM). Critical stress intensity factor for Sn3Ag0.5Cu solder-copper interface have been extracted from line spring models. Displacements and derivatives of displacements have been measured at crack tip and near interface of bi-material specimen using high speed imaging in conjunction with digital image correlation. Specimens have been tested at strain rates of 20s−1 and 55s−1 and the event is monitored using high speed data acquisition system as well as high speed cameras with frame rates in the neighborhood of 300,000 fps. Previously the authors have applied the technique of XFEM and DIC for predicting failure location and to develop constitutive models in leaded and few leadfree solder alloys [Lall 2010a]. The measured fracture properties have been applied to prediction of failure in ball-grid arrays subjected to high-g shock loading in the neighborhood of 12500g in JEDEC configuration. Prediction of fracture in board assemblies using explicit finite element full-field models of board assemblies under transient-shock is new. Stress intensity factor at Copper pad and bulk solder interface is also evaluated in ball grid array packages.

Effect of Isothermal Aging and High Strain Rate on Material Properties of Innolot

2013 ◽  
Author(s):  
Pradeep Lall ◽  
Geeta Limaye ◽  
Sandeep Shantaram ◽  
Jeff Suhling
Keyword(s):  
Elevated Temperature ◽  
High Strain Rate ◽  
Strain Rate ◽  
Material Properties ◽  
Isothermal Aging ◽  
High Strain ◽  
Image Correlation ◽  
Lead Free ◽  
Strain Rates ◽  
Full Field

Industry migration to lead-free solders has resulted in a proliferation of a wide variety of solder alloy compositions. The most popular amongst these are the Tin-Silver-Copper (Sn-Ag-Cu or SAC) family of alloys like SAC105, SAC305 etc. Recent studies have highlighted the detrimental effects of isothermal aging on the material properties of these alloys. SAC alloys have shown up to 50% reduction in their initial elastic modulus and ultimate tensile strength within a few months of elevated temperature aging. This phenomenon has posed a severe design challenge across the industry and remains a road-block in the migration to Pb-free. Multiple compositions with additives to SAC have been proposed to minimize the effect of aging and creep while maintaining the melting temperatures, strength and cost at par with SAC. Innolot is a newly developed high-temperature, high-performance lead-free substitute by InnoRel™ targeting the automotive electronics segment. Innolot contains Nickel (Ni), Antimony (Sb) and Bismuth (Bi) in small proportions in addition to Sn, Ag and Cu. The alloy has demonstrated enhanced reliability under thermal cycling as compared to SAC alloys. In this paper, the high strain rate material properties of Innolot have been evaluated as the alloy ages at an elevated temperature of 50°C. The strain rates chosen are in the range of 1–100 per-second which are typical at second level interconnects subjected to drop-shock environments. The strain rates and elevated aging temperature have been chosen also to correspond to prior tests conducted on SAC105 and SAC305 alloys at this research center. This paper presents a comparison of material properties and their degradation in the three alloys — SAC105, SAC305 and Innolot. Full field strain measurements have been accomplished with the use of high speed imaging in conjunction with Digital Image Correlation (DIC). Ramberg-Osgood non-linear model parameters have been determined to curve-fit through the experimental data. The parameters have been implemented in Abaqus FE model to obtain full-field stresses which correlates with contours obtained experimentally by DIC.

Sign in / Sign up

Export Citation Format

Share Document