Combined Moisture and Thermal Stresses Failure Mode in a PLCC

1989 ◽  
Vol 111 (4) ◽  
pp. 249-254 ◽  
Author(s):  
Y. Kornblum ◽  
J. C. Glaser
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Failure Mode ◽  
Material Properties ◽  
Thermal Stresses ◽  
High Stress ◽  
The Body ◽  
Free State ◽  
Element Analysis ◽  
Working Model

A finite element analysis has been conducted to provide a new explanation for PLCC cracking during soldering and develop a working model for the cracking phenomena. The model shows that cracking is due to strong moisture, temperature and material properties gradients that are developed in the body of the PLCC and that the moisture is not accumulated in a free state under the pad. Instead it is distributed in three distinct regions in the PLCC encapsulation. The results of this model indicate high stress at points where cracks were reported to occur.

An Efficient Design Optimization Method for Functional Gradient Material Objects Based on Finite Element Analysis

2015 ◽  
Author(s):  
Feng Zhang ◽  
Chi Zhou ◽  
Sonjoy Das
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Optimization Method ◽  
The Body ◽  
Gradient Material ◽  
Material Distribution ◽  
Element Analysis ◽  
Functional Gradient ◽  
Functional Gradient Material

Functional Gradient Material (FGM) is one of the most promising heterogeneous materials for its spatial continuity of material properties and functional flexibility. FGM is a well-studied research topic. In this paper, we utilize Finite Element Analysis (FEA) method to model objects with spatially varying material property. A two-stage optimization framework including Monte Carlo based global optimizer and gradient descent based local optimizer is proposed to achieve the optimal material composition in response to different user defined objectives. An error diffusion based halftoning technique is utilized to convert the continuous material distribution into discrete material distribution for viable manufacturing. The transition of the material properties are governed by predefined equations and only a few coefficients instead of large number of elements are to be optimized, therefore this optimization process is more computationally efficient than traditional techniques. Meanwhile it can automatically guarantee the smoothness of material transition along the body. Such design and optimization method has the potential to enable interactive multiple material modeling and simulation. Several experiments are carried out to demonstrate its efficiency and effectiveness.

Finite Element Analysis of Thermal Stresses in Circumferential Cast Clasps of Removable Partial Dentures

2007 ◽  
Vol 23 ◽  
pp. 229-232
Author(s):  
Liliana Sandu ◽  
Nicolae Faur ◽  
Cristina Bortun ◽  
Sorin Porojan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Stresses ◽  
Element Analysis ◽  
3 Dimensional ◽  
Thermal Changes ◽  
The Finite Element Analysis ◽  
Dimensional Finite Element ◽  
Back Action ◽  
Aggressive Effect

Several studies evaluated the removable partial dentures by the finite element analysis, but none of them evaluated thermal stresses. The purpose of the study was to explore the influence of thermal oral changes induced by hot/cold liquids and food on the circumferential cast clasps of removable partial dentures. A 3-dimensional finite element method was used to explore the temperature distribution, thermal stress and the influence of thermal changes on stresses and displacements of circumferential clasps during functions. Thermal variations induce stresses in dental clasps, high temperatures having a more aggressive effect than lower one. Cold liquids and food induce high stresses in the retentive clasp arms while hot ones in the occlusal rests of the clasps and for the back action clasp also in the minor connector. The study suggests the importance of consFigureidering thermal variations for stress analyses of the cast clasps.

Three Turnaround Heat Treating Studies

2003 ◽  
Author(s):  
Jaan Taagepera ◽  
Marty Clift ◽  
D. Mike DeHart ◽  
Keneth Marden
Keyword(s):  
Heat Treatment ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Stress ◽  
Thermal Stresses ◽  
Heat Treating ◽  
Element Analysis ◽  
Stress Profiles ◽  
Insight Into

Three vessel modifications requiring heat treatment were analyzed prior to and during a planned turnaround at a refinery. One was a thick nozzle that required weld build up. This nozzle had been in hydrogen service and required bake-out to reduce the potential for cracking during the weld build up. Finite element analysis was used to study the thermal stresses involved in the bake-out. Another heat treatment studied was a PWHT of a nozzle replacement. The heat treatment band and temperature were varied with location in order to minimize cost and reduction in remaining strength of the vessel. Again, FEA was used to provide insight into the thermal stress profiles during heat treatment. The fmal heat treatment study was for inserting a new nozzle in a 1-1/4Cr-1/2Mo reactor. While this material would ordinarily require PWHT, the alteration was proposed to be installed without PWHT. Though accepted by the Jurisdiction, this nozzle installation was ultimately cancelled.

Elastic Thermal Stresses in Bimetallic Pipe Welds

1980 ◽  
Vol 102 (4) ◽  
pp. 430-432 ◽  
Author(s):  
R. D. Blevins
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Intensity ◽  
Maximum Stress ◽  
Thermal Stresses ◽  
Simple Expression ◽  
Element Analysis ◽  
Maximum Stress Intensity ◽  
Bimetallic Pipe ◽  
Uniform Change

The elastic thermal stresses in a welded transition between two pipes of the same size but different alloys are explored. A stress-free temperature is postulated and the stress due to a uniform change in temperature is characterized by the maximum stress intensity in the weld. A simple expression for predicting this maximum stress intensity is developed based on the results of finite element analysis.

scholarly journals On the Design of a Biodegradable POC-HA Polymeric Cardiovascular Stent

2012 ◽  
Author(s):  
Joonas Ponkala ◽  
Mohsin Rizwan ◽  
Panos S. Shiakolas
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Three Dimensional ◽  
Polymeric Composite ◽  
Coronary Stent ◽  
Element Analysis ◽  
Material Models ◽  
Solid Models ◽  
Biodegradable Stents

The current state of the art in coronary stent technology, tubular structures used to keep the lumen open, is mainly populated by metallic stents coated with certain drugs to increase biocompatibility, even though experimental biodegradable stents have appeared in the horizon. Biodegradable polymeric stent design necessitates accurate characterization of time dependent polymer material properties and mechanical behavior for analysis and optimization. This manuscript presents the process for evaluating material properties for biodegradable biocompatible polymeric composite poly(diol citrate) hydroxyapatite (POC-HA), approaches for identifying material models and three dimensional solid models for finite element analysis and fabrication of a stent. The developed material models were utilized in a nonlinear finite element analysis to evaluate the suitability of the POC-HA material for coronary stent application. In addition, the advantages of using femtosecond laser machining to fabricate the POC-HA stent are discussed showing a machined stent. The methodology presented with additional steps can be applied in the development of a biocompatible and biodegradable polymeric stents.

Thermal stresses in multilevel interconnections: Aluminum lines at different levels

1997 ◽  
Vol 12 (9) ◽  
pp. 2219-2222 ◽  
Author(s):  
Y-L. Shen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Stresses ◽  
Element Analysis ◽  
Future Studies ◽  
Level Lines ◽  
The Finite Element Analysis ◽  
Staggered Arrangement ◽  
Upper Level ◽  
Different Levels

Numerical results on the evolution of thermal stresses in multilevel interconnects are presented. Two levels of aluminum lines with an aspect ratio of unity, aligned vertically or arranged in a staggered manner, are considered by recourse to the finite element analysis. The stresses are found to be significantly higher in the lower-level lines than in the upper-level lines, for both the aligned and staggered arrangements. The stress magnitudes are generally smaller in lines of staggered arrangement, compared to the case of aligned lines. Implications of the present findings are discussed, with directions of future studies highlighted.

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