Thermal Stresses in Compliantly Joined Materials

1990 ◽  
Vol 112 (1) ◽  
pp. 24-29 ◽  
Author(s):  
J. C. Glaser
Keyword(s):  
Finite Element ◽  
Closed Form ◽  
Thermal Stresses ◽  
Material Interface ◽  
Element Mesh ◽  
Closed Form Solutions ◽  
First Order ◽  
The Past ◽  
Compliant Layer ◽  
Analytical Relations

In the past several years there have been a number of papers published which provide closed-form solutions for the stresses in bonded layers of materials. These closed-form solutions offer a rapid method to obtain first-order stresses for materials which are joined together and the compliant layer between them. However, before using them, it is desirable to have some feeling as to the accuracy of the results from these closed-form equations. Comparisons between these analytical relations and other approaches found in published works on bonding and to finite element solutions for several example problems are given. An attempt is made to qualify these closed-form equations in terms of their accuracy, as compared to other methods of analysis. The effects of finite element mesh refinement on the material interface stress results are also given.

Validation of Nitinol SMA Characteristics Using Finite Element Analysis and Closed Form Solutions

2013 ◽  
Vol 856 ◽  
pp. 147-152
Author(s):  
S.H. Adarsh ◽  
U.S. Mallikarjun
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Closed Form ◽  
Closed Form Solution ◽  
Form Solution ◽  
Fe Analysis ◽  
Element Analysis ◽  
Complex Behaviour ◽  
Closed Form Solutions

Shape Memory Alloys (SMA) are promising materials for actuation in space applications, because of the relatively large deformations and forces that they offer. However, their complex behaviour and interaction of several physical domains (electrical, thermal and mechanical), the study of SMA behaviour is a challenging field. Present work aims at correlating the Finite Element (FE) analysis of SMA with closed form solutions and experimental data. Though sufficient literature is available on closed form solution of SMA, not much detail is available on the Finite element Analysis. In the present work an attempt is made for characterization of SMA through solving the governing equations by established closed form solution, and finally correlating FE results with these data. Extensive experiments were conducted on 0.3mm diameter NiTinol SMA wire at various temperatures and stress conditions and these results were compared with FE analysis conducted using MSC.Marc. A comparison of results from finite element analysis with the experimental data exhibits fairly good agreement.

Jerk Limited Input Shapers

2004 ◽  
Vol 126 (1) ◽  
pp. 215-219 ◽  
Author(s):  
Tarunraj Singh
Keyword(s):  
Time Delay ◽  
Closed Form ◽  
Transfer Functions ◽  
Filter Design ◽  
Limited Time ◽  
Design Technique ◽  
Closed Form Solutions ◽  
First Order ◽  
Damped Systems

The focus of this paper is on the design of jerk limited input shapers (time-delay filters). Closed form solutions for the jerk limited time-delay filter for undamped systems is derived followed by the formulation of the problem for damped systems. Since the jerk limited filter involves concatenating an integrator to a time-delay filter, a general filter design technique is proposed where smoothing of the shaped input can be achieved by concatenating transfer functions of first order, harmonic systems, etc.

A Conical Beam Finite Element for Rotor Dynamics Analysis

1985 ◽  
Vol 107 (4) ◽  
pp. 421-430 ◽  
Author(s):  
L. M. Greenhill ◽  
W. B. Bickford ◽  
H. D. Nelson
Keyword(s):  
Finite Element ◽  
Closed Form ◽  
Cross Section ◽  
Rotor Dynamics ◽  
General Purpose ◽  
Closed Form Expression ◽  
Dynamics Analysis ◽  
Closed Form Solutions ◽  
Analysis Computer ◽  
Rotor Dynamic

The development of finite element formulations for use in rotor dynamics analysis has been the subject of many recent publications. These works have included the effects of rotatory inertia, gyroscopic moments, axial load, internal damping, and shear deformation. However, for most closed-form solutions, the element geometry has been limited to a cylindrical cross-section. This paper extends these previous works by developing a closed-form expression including all of the above effects in a linearly tapered conical cross-section element. Results are also given comparing the formulation to previously published examples, to stepped cylinder representations of conical geometry, and to a general purpose finite element elasticity solution. The elimination of numerical integration in the generation of the element matrices, and the ability of the element to represent both conical and cylindrical geometries, make this formulation particularly suited for use in rotor dynamic analysis computer programs.

An Intelligent System for Spur Gear Design and Analysis

2001 ◽  
Author(s):  
El-Sayed Aziz ◽  
C. Chassapis
Keyword(s):  
Finite Element ◽  
Closed Form ◽  
Intelligent System ◽  
Tooth Profile ◽  
Hertzian Contact ◽  
Design Parameters ◽  
Analysis Model ◽  
Closed Form Solutions ◽  
Gear Teeth ◽  
Gear Design

Abstract A methodology for the analysis of load distribution and contact stress on gear teeth, which utilizes a combination of closed form solutions and two-dimensional finite element methods, within a constraint-based knowledge-based environment, is presented. Once the design parameters are specified, the complete process of generating the analysis model, starting from the determination of the coordinates of the tooth profile, the creation of a sector of the mating gear teeth, automatic mesh generation, boundary conditions and loading, is totally automated and transparent to the designer. The effects of non-standard geometry, load sharing on the contact zone, friction and root stresses are easily included in the model. The Finite Element Method (FEM) based results compare favorably with those obtained from closed form solutions (AGMA equations and classical Hertzian contact solution). The advantage of the approach rests in the ability to modify any of the gear design parameters such as diametral pitch, tooth profile modification etc., in an automated manner along with obtaining a better estimation of the risks of failure of the gear design on hand. The procedure may be easily extended to other types of gearing systems.

An Improved Method for Designing Flexure-Based Nonlinear Springs

2012 ◽  
Author(s):  
Qiaoling Meng ◽  
Giovanni Berselli ◽  
Rocco Vertechy ◽  
Vincenzo Parenti Castelli
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Compliant Mechanisms ◽  
Empirical Equations ◽  
Element Analysis ◽  
Closed Form Solutions ◽  
Nonlinear Springs ◽  
Aspect Ratios ◽  
Analytical Relations ◽  
Flexural Hinges

Monolithic Flexure-based Compliant Mechanisms (MFCM) can functionally act as nonlinear springs by providing a desired load-displacement profile at one point on their structure. Once the MFCM topology is chosen, these particular springs can be conveniently synthesized by resorting to the well-known Pseudo-Rigid-Body approximation, whose accuracy strongly depends on the modeling precision of the flexures’ principal compliance. For various types of flexures, closed-form solutions have been proposed which express the compliance factors as functions of the flexure dimensions. Nonetheless, the reliability of these analytical relations is limited to slender, beam-like, hinges undergoing small deflections. In order to overcome such limitations, this paper provides empirical equations, derived from finite element analysis, that can be used for the optimal design of circular, elliptical, and corner-filleted flexural hinges with general aspect ratios on the basis of both principal compliance and maximum bearable stress. As a case study, a nonlinear spring conceived as a four-bar linkage MFCM is synthesized and simulated by means of finite element analysis. Numerical results confirm that the aforementioned empirical equations outperform their analytical counterparts when modeling thick cross-section hinges undergoing large deflections.

Prediction of the wear profile of a roll groove in rod rolling using an incremental form of wear model

2003 ◽  
Vol 217 (1) ◽  
pp. 111-126 ◽  
Author(s):  
D H Kim ◽  
Y Lee ◽  
S J Yoo ◽  
W Y Choo ◽  
B M Kim
Keyword(s):  
Finite Element ◽  
High Temperature ◽  
Deformation Behaviour ◽  
Ductile Cast Iron ◽  
Wear Model ◽  
Material Interface ◽  
Element Analysis ◽  
Element Mesh ◽  
Bar Rolling ◽  
Incremental Form

A model for predicting the wear profile of the ductile cast iron roll during rod (or bar) rolling is proposed using Archard's wear equation. Archard's wear equation was reformulated as an incremental form and the hardness of the roll was expressed as a function of rolling time under a high temperature. The wear profile of the roll is calculated at each deformation step by consideration of relative sliding velocity and normal roll pressure at contact area. The coefficients required in the proposed wear model have been obtained using the high-temperature wear tester of pin-on-disc type. A three-dimensional finite element analysis coupled with the proposed wear model has been carried out for the oval-round pass rolling sequence widely used in present continuous rod (or bar) rolling mills. To describe the deformation behaviour of material at the roll/material interface better, a contact-searching algorithm that can be applied efficiently to the finite element mesh was also suggested. The results showed that, for an oval groove, the maximum wear occurs at the centre part of the roll and, for a round groove, at the shoulder area of the roll. The wear profiles moves to the spread direction of workpiece (i.e. roll axis direction) as well as the direction of roll centre as the production (tonnage) increases. The proposed wear model might be used for adjusting the gap (pass height) of rolls to set up a suitable rolling schedule for keeping dimensional tolerance of the product and avoid catastrophic failure of rolls after rolling a characteristic tonnage.

Corner-Filleted Flexure Hinges

2000 ◽  
Vol 123 (3) ◽  
pp. 346-352 ◽  
Author(s):  
Nicolae Lobontiu ◽  
Jeffrey S. N. Paine ◽  
Ephrahim Garcia ◽  
Michael Goldfarb
Keyword(s):  
Finite Element ◽  
Closed Form ◽  
Finite Element Simulation ◽  
Analytical Approach ◽  
Flexure Hinge ◽  
Closed Form Solutions ◽  
Flexure Hinges ◽  
Element Simulation ◽  
Model Predictions ◽  
The Right

The paper presents an analytical approach to corner-filleted flexure hinges. Closed- form solutions are derived for the in-plane compliance factors. It is demonstrated that the corner-filleted flexure hinge spans a domain delimited by the simple beam and the right circular flexure hinge. A comparison that is made with the right circular flexure hinges indicates that the corner-filleted flexures are more bending-compliant and induce lower stresses but are less precise in rotation. The finite element simulation and experimental results confirmed the model predictions.

An Algorithm for Reducing the Size of Finite Element Closed-Form Source Code Files

2009 ◽  
Author(s):  
Sara McCaslin ◽  
Kent Lawrence
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Closed Form ◽  
Source Code ◽  
Simple Algorithm ◽  
Higher Order ◽  
Error Estimator ◽  
Element Analysis ◽  
Closed Form Solutions ◽  
Large Source

Closed-form solutions, as opposed to numerically integrated solutions, can now be obtained for many problems in engineering. In the area of finite element analysis, researchers have been able to demonstrate the efficiency of closed-form solutions when compared to numerical integration for elements such as straight-sided triangular [1] and tetrahedral elements [2, 3]. With higher order elements, however, the length of the resulting expressions is excessive. When these expressions are to be implemented in finite element applications as source code files, large source code files can be generated, resulting in line length/ line continuation limit issues with the compiler. This paper discusses a simple algorithm for the reduction of large source code files in which duplicate terms are replaced through the use of an adaptive dictionary. The importance of this algorithm lies in its ability to produce manageable source code files that can be used to improve efficiency in the element generation step of higher order finite element analysis. The algorithm is applied to Fortran files developed for the implementation of closed-form element stiffness and error estimator expressions for straight-sided tetrahedral finite elements through the fourth order. Reductions in individual source code file size by as much as 83% are demonstrated.

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