Modeling Stresses in Polyimide Films

1993 ◽  
Vol 308 ◽  
Author(s):  
Michael T. Pottiger ◽  
John C. Coburn
Keyword(s):  
Finite Element Analysis ◽  
Computer Modeling ◽  
Entire Range ◽  
Applied Load ◽  
Narrow Range ◽  
A Priori ◽  
Material Behavior ◽  
Polyimide Films ◽  
Element Analysis ◽  
The Ideal

The trend towards higher density and smaller feature sizes in today's devices, and the increasing costs associated with designing and manufacturing these devices, has placed a greater emphasis on obtaining an a priori understanding of how various materials will perform in a device. A number of manufacturers have turned to computer modeling, utilizing finite element analysis to aid in the design of new devices and reduce the costs associated with preparing prototypes. The use of computer modeling requires a constitutive equation relating the response of a material to an applied load. Polymer behavior is complex and writing an equation or a series of equations that describe the behavior of the polymer over the entire range of possible temperatures and deformations is nontrivial. Instead, series of equations that describe ideal material behavior are used in an attempt to describe the behavior of real materials over a narrow range of temperatures and deformations. For solids, the ideal material response that is generally used to describe real polymer behavior is linear elasticity.

Selecting the Optimum Bolt Assembly Stress: Influence of Flange Type on Flange Load Limit

2008 ◽  
Author(s):  
Warren Brown
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Carbon Steel ◽  
Applied Load ◽  
Hoop Stress ◽  
Elastic Analysis ◽  
Steel Weld ◽  
Element Analysis ◽  
Load Limit ◽  
Stress Influence

In previous papers, practical limits on the maximum applied load for standard ASME B16.5 and B16.47 carbon steel, weld neck pipe flanges were examined. A new code equation for the tangential (hoop) stress at the small end of the hub for a weld neck flange was developed to facilitate calculation of the limits using elastic analysis. The results were verified against elastic-plastic Finite Element Analysis (FEA). In this paper, the work is extended to include other flange configurations, including loose ring flanges, slip-on flanges and flat plate flanges. This paper is a continuation of the papers presented during PVP 2006 and PVP 2007 (Brown [1, 2]) and it extends the scope of the proposed methodology for determining flange stress limits in determining the maximum allowable bolt load for any given flange size and configuration.

Creep Life Simulation and Assessment of High Temperature Piping Systems and Components

2012 ◽  
Author(s):  
Brian Rose ◽  
James Widrig
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Temperature ◽  
Creep Behavior ◽  
Material Behavior ◽  
Piping System ◽  
Remaining Life ◽  
Creep Life ◽  
Element Analysis ◽  
Piping Systems

High temperature piping systems and associated components, elbows and bellows in particular, are vulnerable to damage from creep. The creep behavior of the system is simulated using finite element analysis (FEA). Material behavior and damage is characterized using the MPC Omega law, which captures creep embrittlement. Elbow elements provide rapid yet accurate modeling of pinching of piping, which consumes a major portion of the creep life. The simulation is used to estimate the remaining life of the piping system, evaluate the adequacy of existing bellows and spring can supports and explore remediation options.

Biomechanics of a posture-controlling cervical artificial disc: mechanical, in vitro, and finite-element analysis

2010 ◽  
Vol 28 (6) ◽  
pp. E11 ◽  
Author(s):  
Neil R. Crawford ◽  
Jeffery D. Arnett ◽  
Joshua A. Butters ◽  
Lisa A. Ferrara ◽  
Nikhil Kulkarni ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cervical Spine ◽  
Postural Control ◽  
Range Of Motion ◽  
Computer Modeling ◽  
Mechanical Testing ◽  
Artificial Disc ◽  
Element Analysis

Different methods have been described by numerous investigators for experimentally assessing the kinematics of cervical artificial discs. However, in addition to understanding how artificial discs affect range of motion, it is also clinically relevant to understand how artificial discs affect segmental posture. The purpose of this paper is to describe novel considerations and methods for experimentally assessing cervical spine postural control in the laboratory. These methods, which include mechanical testing, cadaveric testing, and computer modeling studies, are applied in comparing postural biomechanics of a novel postural control arthroplasty (PCA) device versus standard ball-and-socket (BS) and ball-in-trough (BT) arthroplasty devices. The overall body of evidence from this group of tests supports the conclusion that the PCA device does control posture to a particular lordotic position, whereas BS and BT devices move freely through their ranges of motion.

Implosion Analysis of Concrete Cylindrical Vessels

1979 ◽  
Vol 101 (1) ◽  
pp. 98-102
Author(s):  
H. Suzuki ◽  
W. F. Chen ◽  
T. Y. Chang
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Fracture Behavior ◽  
Constitutive Relations ◽  
Analysis Procedure ◽  
Material Behavior ◽  
Ultimate State ◽  
Element Analysis ◽  
Proposed Model ◽  
Effect Of Hydrostatic Pressure

Concrete constitutive relations which can simulate the overall material behavior up to and including its ultimate state under general triaxial loading conditions have been developed. The proposed constitutive relations include: 1) plastic deformation considering the effect of hydrostatic pressure, 2) a dual criterion predicting the fracture of concrete in terms of either stresses or strains, and 3) post-fracture behavior of concrete. Corresponding to the constitutive model, a finite element analysis procedure has also been utilized. Based on the proposed model, implosion pressures and load-deformation responses of several concrete vessels were obtained. The numerical results correlate quite well with the experimental data when the dual criterion was used.

Finite Element Analysis of a Locked Bolt With an Initial Crack

2009 ◽  
Author(s):  
Jean Paul Kabche ◽  
Mauri´cio Rangel Pacheco ◽  
Ivan Thesi ◽  
Luiz Carlos Largura
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Operating Conditions ◽  
Material Behavior ◽  
Isotropic Hardening ◽  
Stress Concentrations ◽  
Engineering Structures ◽  
Element Analysis ◽  
Micro Cracks ◽  
Non Linear

Bolted connections are largely employed in various types of engineering structures to transfer loads from one member to another. In particular, the off-shore industry has made extensive use of these connections, predominantly at the sub-sea level. In spite of their advantages, bolted joints are critical regions and may become sources of structural weakness due to large stress concentrations. Under severe operating conditions, micro-cracks can develop in the bolt, creating regions of elevated stress which may significantly reduce the integrity of the connection and ultimately lead to failure. This paper presents the three-dimensional finite element analysis of a steel locked bolt assembly aimed to assess the effect of micro-cracks on the structural integrity of the assembly using the commercial finite element package ANSYS. Non-linear contact between the bolt and nut threads is considered, where frictional sliding between components is allowed. A bi-linear isotropic hardening model is used to account for non-linear material behavior. The assembly is loaded by applying a pre-load of fifty percent of the yield stress of the material, according to the API-6A Norm. Two geometric models are investigated: a healthy locked bolt assembly with no initial cracks; and a damaged model, where a circular crack is introduced at the root of the bolt threads. The effect of the crack size is studied by modeling the crack with three different radius sizes. The J-Integral fracture mechanics methodology was used to study the stress concentrations in the damaged model.

Fabrication of PDMS Dome-Shaped Membrane and its Performance Analysis Using FEA for Fluidic Based Flow Sensor

2014 ◽  
Vol 699 ◽  
pp. 289-294
Author(s):  
Mohd Norzaidi Mat Nawi ◽  
Asrulnizam Abd Manaf ◽  
Mohd Rizal Arshad ◽  
Othman Sidek
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Performance Analysis ◽  
Fluid Velocity ◽  
Fabrication Process ◽  
Flow Sensor ◽  
Input Flow ◽  
Element Analysis ◽  
Actual Shape ◽  
The Ideal

The dome-shaped membrane was designed for the fluidic based flow sensor for the underwater sensing. It has the diameter of 5mm and thickness within 0.2mm. The simple fabrication process for the dome shaped structure was demonstrated using casting and molding processes. The effect of the fabrication process was investigated by measuring the thickness of the dome-shaped membrane for different sample. For the performance analysis, the actual shape which was the same with the fabricated shaped was simulated and compared with the ideal shape using finite element analysis for the same input flow rate. The membrane sensitivity of the actual shape decreased from 163.4 μm/ms-1 to 133.33 μm/ms-1 compared to the ideal shape based on the displacement of the membrane over input fluid velocity.

Finite Element Analysis on Nitinol Medical Applications

2002 ◽  
Author(s):  
Xiao-Yan Gong ◽  
Alan R. Pelton
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Element Analysis ◽  
Highly Nonlinear ◽  
Device Applications ◽  
Specific Material

Nitinol, an alloy of about 50% Ni and 50% Ti, is a very unique material. At constant temperature above its Austenite finish (Af) temperature, under uniaxial tensile test, the material is highly nonlinear and capable of large deformation to the ultimate strain on the order of 15%. This material behavior, known as superelasticity, along with its excellent biocompatibility and corrosion resistance, makes Nitinol a perfect material candidate for many medical device applications. However, the nonlinear material response also requires a specific material description to perform the stress analysis. The user developed material subroutine from HKS/West makes the simulation of the Nitinol devices possible. This article presents two case studies of the nonlinear finite element analysis using ABAQUS/Standard and the Nitinol UMAT.

INFLUENCE OF THE CONSTITUTIVE MATERIAL BEHAVIOR MODEL ASSIGNED TO THE ANNULUS FIBROSUS AND THE NUCLEUS PULPOSUS ON THE BIOMECHANICAL PERFORMANCE OF A MODEL OF THE CERVICAL SPINE: A FINITE ELEMENT ANALYSIS STUDY

2010 ◽  
Vol 10 (01) ◽  
pp. 151-166 ◽  
Author(s):  
YUAN LI ◽  
GLADIUS LEWIS
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cervical Spine ◽  
Annulus Fibrosus ◽  
Constitutive Models ◽  
Material Behavior ◽  
Elastic Behavior ◽  
Behavior Model ◽  
Element Analysis ◽  
Constitutive Material

One feature of the literature on finite element analysis of models of cervical spine segment(s) is that an assortment of constitutive models has been used for the elastic behavior of the annulus fibrosus (AF) and the nucleus pulposus (NF). The extent to which the model assigned to each of these tissues affects the values of the biomechanical parameters of interest of the model is lacking. This issue was the subject of the present study. We used a three-dimensional solid model of the C4–C6 motion segment units (which comprised the vertebral bodies, the bony posterior elements (transverse processes, pedicles, laminae, spinous processes, and facet joints), the intervertebral discs (IVDs), the endplates, and the five major ligaments) and eight combinations of constitutive models. It was found that (1) the influence of the constitutive material models used depended on the tissue considered, with some, such as the posterior endplate of C5 and the cancellous bone of C6, showing marked sensitivity, while others, such as the cancellous bone of C4 and the cortical bone of C5, were moderately affected; and (2) the biomechanical performance of the spine model is more sensitive to the material behavior model used for the AF than it is to that used for the NF. These results suggest that experimental and computational efforts expended in obtaining the most appropriate constitutive model for the elastic behavior of the two parts of the IVD, in particular the AF, are justified.

scholarly journals A Plastic Load Criterion for Inelastic Design by Analysis

2005 ◽  
Author(s):  
Donald Mackenzie ◽  
Hongjun Li
Keyword(s):  
Finite Element Analysis ◽  
Plastic Deformation ◽  
Finite Element ◽  
Applied Load ◽  
Plastic Response ◽  
Element Analysis ◽  
Alternative Approach ◽  
Salient Points ◽  
Collapse Behavior ◽  
Inelastic Design

The allowable plastic load in pressure vessel Design by Analysis is determined by applying a graphical construction to a characteristic load-deformation plot of the collapse behavior of the vessel. This paper presents an alternative approach to the problem. The plastic response is characterized by considering the curvature of a plot of plastic work dissipated in the vessel against the applied load. It is proposed that salient points of curvature correspond to critical stages in the evolution of the gross plastic deformation mechanism. Application of the proposed criterion is illustrated by considering the elastic-plastic response of a simple cantilever beam in bending and a complex 3-D Finite Element Analysis of a nozzle intersection.

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