Relative Influence of Soil Stiffness and Elbow Geometry on Buried Piping Thermal Stresses

2017 ◽  
Author(s):  
Michael P. H. Marohl ◽  
Glenn R. Frazee ◽  
Thomas M. Musto
Keyword(s):  
Thermal Expansion ◽  
Thermal Stresses ◽  
Coefficient Of Thermal Expansion ◽  
Relative Influence ◽  
Element Analysis ◽  
Soil Stiffness ◽  
Piping Systems ◽  
Relative Stress ◽  
Advanced Analysis ◽  
Surrounding Soil

The design of buried piping systems requires special considerations. Historically, buried piping was evaluated for thermal expansion and contraction using simple hand calculations considering the piping to be fully-constrained by the surrounding soil. With the development of analytical software, more advanced analysis of buried piping is possible considering detailed piping routing and the stiffness of the surrounding soil and of the piping itself (in cases of more flexible piping materials). Typically, the areas of highest thermal stress occur at changes in direction (i.e. elbows, etc.) due to the applied moments, and the relative stress magnitude is influenced by the stiffness of the surrounding soil. Due to the relatively high coefficient of thermal expansion of polyethylene, stresses in buried piping due to thermal expansion and contraction are of particular note for high density polyethylene (HDPE) piping. This paper examines the relative influence of the analytical representations of a variety of HDPE piping elbow geometries (e.g. mitered elbows, molded elbows, etc.) and corresponding soil restraint. The study demonstrates that total longitudinal stress calculated in a finite element analysis may be reduced using minor to moderate efforts of refinement.

Role of Out-of-Plane Coefficient of Thermal Expansion in Electronic Packaging Modeling

1999 ◽  
Vol 122 (2) ◽  
pp. 121-127 ◽  
Author(s):  
Manjula N. Variyam ◽  
Weidong Xie ◽  
Suresh K. Sitaraman
Keyword(s):  
Thermal Expansion ◽  
Electronic Packaging ◽  
Thermal Loading ◽  
Coefficient Of Thermal Expansion ◽  
Plane Deformation ◽  
Three Dimensional ◽  
Dissimilar Materials ◽  
3D Models ◽  
Material Behavior ◽  
Element Analysis

Components in electronic packaging structures are of different dimensions and are made of dissimilar materials that typically have time, temperature, and direction-dependent thermo-mechanical properties. Due to the complexity in geometry, material behavior, and thermal loading patterns, finite-element analysis (FEA) is often used to study the thermo-mechanical behavior of electronic packaging structures. For computational reasons, researchers often use two-dimensional (2D) models instead of three-dimensional (3D) models. Although 2D models are computationally efficient, they could provide misleading results, particularly under thermal loading. The focus of this paper is to compare the results from various 2D, 3D, and generalized plane-deformation strip models and recommend a suitable modeling procedure. Particular emphasis is placed to understand how the third-direction coefficient of thermal expansion (CTE) influences the warpage and the stress results predicted by 2D models under thermal loading. It is seen that the generalized plane-deformation strip models are the best compromise between the 2D and 3D models. Suitable analytical formulations have also been developed to corroborate the findings from the study. [S1043-7398(00)01402-X]

Influence of Coating Layer to Reduce Thermal Stresses in Cylindrically Formed Metal Matrix Composites

2000 ◽  
Author(s):  
Fuat Okumus ◽  
Aydin Turgut ◽  
Erol Sancaktar
Keyword(s):  
Thermal Expansion ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Thermal Stresses ◽  
Coating Layer ◽  
Coefficient Of Thermal Expansion ◽  
Aluminum Matrix ◽  
Matrix Composites ◽  
Cylinder Model ◽  
Matrix Layer

Abstract In this study, the use of coating layers is investigated to reduce thermal stresses in the metal matrix composites which have a mismatch in coefficients of thermal expansions in fiber and matrix components. The thermoelastic solutions are obtained based on a three-cylinder model. It is shown that the effectiveness of the layer can be defined by the product of its coefficient of thermal expansion and thickness. Consequently, a compensating layer with a sufficiently high coefficient of thermal expansion can reduce the thermal stresses in the metal matrix. The study is based on a concentric three cylinder model isolating individual steel fibers surrounded with a coating layer and an aluminum matrix layer. Only monotonic cooling is studied.

A General Solution for the Elastoplastic Thermal Stresses in a Strain-Hardening Plate With Arbitrary Material Properties

1962 ◽  
Vol 29 (1) ◽  
pp. 151-158 ◽  
Author(s):  
A. Mendelson ◽  
S. W. Spero
Keyword(s):  
Thermal Expansion ◽  
General Solution ◽  
Strain Hardening ◽  
Material Properties ◽  
Thermal Stresses ◽  
Coefficient Of Thermal Expansion ◽  
Stress And Strain ◽  
Linear Strain ◽  
Hardening Material ◽  
General Method

A general method is presented for obtaining the elastoplastic stress and strain distributions in a thermally stressed plate of a strain-hardening material with temperature-varying modulus, yield point, and coefficient of thermal expansion. It is shown that for linear strain-hardening the solution can often be obtained in closed form. It is indicated that the error due to neglecting strain-hardening may sometimes be appreciable. The assumption that the total strain remains the same as that computed elastically (strain invariance) often leads to smaller errors than the neglect of strain-hardening.

A Finite Element Study of Geometric Modifications to Reduce Thermal Mismatch Curvature in Wafer Bonding

2007 ◽  
Author(s):  
Devasena Duraipandi ◽  
John M. Heck ◽  
Raymond K. Yee ◽  
Sang-Joon J. Lee
Keyword(s):  
Finite Element ◽  
Thermal Expansion ◽  
Wafer Bonding ◽  
Thermal Stresses ◽  
Silicon Wafers ◽  
Geometrical Approach ◽  
Thermal Expansion Mismatch ◽  
Mems Devices ◽  
Element Analysis ◽  
Wafer Curvature

Wafer-level packaging of RF MEMS devices offers an attractive option to reduce packaging cost significantly and ensures hermetic encapsulation of devices. Low-temperature cofired ceramic (LTCC) cap wafers are particularly favorable because they can be pre-patterned with through-wafer vias for integrated electrical contacts and high-density packaging, at a much lower cost than silicon wafers with similar features. However, thermal expansion mismatch between ceramic and silicon wafers at high bonding temperatures induces thermal stresses at the interface, resulting in wafer curvature. For example, a 150 mm silicon wafer 675 μm thick with a ceramic cap wafer 500 μm thick has been measured to exhibit out-of-flatness displacement as severe as of 1.7 mm at the center. While the curvature can be reduced significantly using low-thermal-expansion ceramic, such materials are non-standard and require custom formulation. Furthermore, as the wafer diameter is increased, thermal expansion mismatch becomes more problematic. Therefore, it is desirable to address the problem using a geometrical approach in addition to optimizing the ceramic for wafer bonding applications. The present study applies finite element analysis (FEA) to examine the potential for reducing such curvature by introducing slots in the ceramic cap wafer. Two-level factorial design simulations involving five parameters were conducted to investigate the effect of slot parameters on wafer curvature, using 2-D plane strain simulation of wafer cooling from 300 °C to 25 °C. The five parameters investigated were cap wafer thickness, slot width, slot depth, slot separation, and slot orientation. The nonlinear temperature dependence of thermal expansion was also examined based on test data for the ceramic wafers. Furthermore, a 3-D finite element simulation was conducted to compare the 2-D results to overall impact on wafer distortion. FEA results were compared with experimental curvature measurements on sample wafers measured by coordinate measuring machining (CMM). Simulated results suggest that introduction of slots shows reduction in wafer curvature, and the displacement can be reduced by as much as 25% based on the geometric parameter values for slots in the cap wafer.

scholarly journals Thermal analysis of metal-ceramic bonding using finite element method

2014 ◽  
Vol 3 (2) ◽  
pp. 216 ◽  
Author(s):  
S. Gopinath ◽  
R Sabarish ◽  
R. Sasidharan
Keyword(s):  
Finite Element ◽  
Thermal Expansion ◽  
Thermal Stress ◽  
Bonding Strength ◽  
Coefficient Of Thermal Expansion ◽  
Linear Thermal Expansion ◽  
Processing Temperature ◽  
Element Analysis ◽  
Metal Ceramic ◽  
The Difference

This paper reports a finite element study of effect of bonding strength between metal and ceramic. The bonding strength is evaluated with different processing temperature and holding time. The difference between the coefficients of linear thermal expansion (CTEs) of the metal and ceramic induces thermal stress at the interface. The mismatch thermal stress at the interface region plays an important role in improving bonding strength. Hence, it is essential to evaluate the interface bonding in metal-ceramics joints. The Al/SiC bonding was modeled and analyzed using finite element analysis in ANSYS (v.10). Keywords: Bonding Strength, Coefficient of Thermal Expansion, Thermal Stress, Interface, Al/Sic, FEA.

scholarly journals Thermomechanical finite element analysis of hot water boiler structure

2012 ◽  
Vol 16 (suppl. 2) ◽  
pp. 387-398 ◽  
Author(s):  
Dragoljub Zivkovic ◽  
Dragan Milcic ◽  
Milan Banic ◽  
Pedja Milosavljevic
Keyword(s):  
Thermal Stresses ◽  
Coefficient Of Thermal Expansion ◽  
Strain Analysis ◽  
Nonlinear Effects ◽  
Hot Water ◽  
Reference Object ◽  
Isotropic Hardening ◽  
Stress And Strain ◽  
Element Analysis ◽  
Object A

The paper presents an application of the Finite Elements Method for stress and strain analysis of the hot water boiler structure. The aim of the research was to investigate the influence of the boiler scale on the thermal stresses and strains of the structure of hot water boilers. Results show that maximum thermal stresses appear in the zone of the pipe carrying wall of the first reversing chamber. This indicates that the most critical part of the boiler are weld spots of the smoke pipes and pipe carrying plate, which in the case of significant scale deposits can lead to cracks in the welds and water leakage from the boiler. The nonlinear effects were taken into account by defining the bilinear isotropic hardening model for all boiler elements. Temperature dependency was defined for all relevant material properties, i. e. isotropic coefficient of thermal expansion, Young?s modulus, and isotropic thermal conductivity. The verification of the FEA model was performed by comparing the measured deformations of the hot water boiler with the simulation results. As a reference object, a Viessmann - Vitomax 200 HW boiler was used, with the installed power of 18.2 MW. CAD modeling was done within the Autodesk Inventor, and stress and strain analysis was performed in the ANSYS Software.

Advanced Methodologies for Developing Improved Potted Smart Munitions for High-G Applications

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Nien-Hua Chao ◽  
John A. Dispenza ◽  
Mario DeAngelis
Keyword(s):  
Thermal Expansion ◽  
Thermal Management ◽  
Thermal Stresses ◽  
Coefficient Of Thermal Expansion ◽  
Barrier Properties ◽  
Temperature Cycling ◽  
Circuit Board ◽  
Polymer Layer ◽  
Interference Control ◽  
Protective Polymer

Potted electronics are becoming more common in precision-guided smart munitions designs due to the requirements for miniaturization and structural-robustness. In most of these applications, the potted electronics are inactive for most of their lifetime and may be stored without environmental (temperature and humidity) controls for up to 20 yr. The uncontrolled environment for smart munitions however makes the thermal management task especially difficult due to the coefficient of thermal expansion (CTE) mismatch that can exist between the potting material and the electronic components. In this paper, we will do the following: (1) present a methodology being developed for reducing the thermal stresses to the potted electronics used in uncontrolled environments by encapsulating the circuit board assembly (CBA) with a thin polymer layer which has been precisely formed to conform to the imprecisely shaped, as-populated, CBA. The protective polymer layer will be both flexible and soft enough to protect the CBA components from damage caused by thermal expansion mismatches, but not degrade the structural support that the potting provides during high-g force projectile launches, (2) discuss how the protective polymer layer methodology can also be used to lessen in-circuit board crosstalk, improve shielding from external RF interference, control tin-whisker growth, and enhance moisture barrier properties and thermal management for CBAs, and (3) demonstrate how to improve the smart munitions survivability under extreme high-g applications through the use of syntactic foams and material characterization before and after accelerated temperature-cycling and thermal-aging tests.

Thermal Fracture of Oxidized Polydimethylsiloxane and its Implications in Soft Lithography

2011 ◽  
Author(s):  
Wes W. Tooley ◽  
Shirin Feghhi ◽  
Sangyoon J. Han ◽  
Junlan Wang ◽  
Nathan J. Sniadecki
Keyword(s):  
Soft Lithography ◽  
Thermal Stresses ◽  
Elevated Temperatures ◽  
Coefficient Of Thermal Expansion ◽  
Curing Temperature ◽  
Surface Cracks ◽  
Element Analysis ◽  
Circular Test ◽  
Cte Mismatch ◽  
Cellular Forces

During the fabrication of nanopost arrays for measuring cellular forces, we have observed surface cracks in the negative molds used to replicate the arrays from a silicon master. These cracks become more numerous and severe with each replication such that repeated castings lead to arrays with missing or broken posts. This loss in pattern fidelity from the silicon master undermines the spatial resolution of the nanopost arrays in measuring cellular forces. We hypothesized that these cracks are formed because of a mismatch in the coefficient of thermal expansion (CTE) of PDMS and its oxidized surface layer. To study the fracture of PDMS due to thermal effects, we treated circular test samples of PDMS with oxidizing plasma and then heated them to cause surface cracks. These cracks were found to be more abundant at 180 °C than at lower temperatures. Finite element analysis of a bilayer material with a CTE mismatch was used to validate that thermal stresses are sufficient to overcome the fracture toughness of oxidized PDMS when heated to a curing temperature for PDMS. As a consequence, we have ascertained that elevated temperatures are a significant detriment to the reproducibility of nanoscale features in PDMS during replica molding.

Mitigation of Bending Stress and Failure Due to Temperature Differentials in Piping Systems Carrying Multiphase Fluids: Using CFD and FEA

2005 ◽  
Author(s):  
Philip Diwakar ◽  
Vibhor Mehrotra ◽  
Franklin Richardson
Keyword(s):  
Heat Transfer ◽  
Thermal Stresses ◽  
Initial Stresses ◽  
Piping System ◽  
Atmospheric Conditions ◽  
Element Analysis ◽  
Pipe System ◽  
Piping Systems ◽  
The Dead ◽  
Piping Networks

The bending of large pipes due to temperature differentials between the bottom and top of the pipe is a very serious problem. The temperature differentials can either be caused by extremely cold liquids (such as methane or ethylene flowing from a lateral into a flare header) or hot liquids flowing at the bottom of a piping system (such as in a Vacuum transfer line) while the top is exposed to atmospheric conditions. In some cases liquids may be produced by Joule-Thompson cooling of high pressure cold gas as it expands through a safety-relief or emergency depressurization valve. The liquid so formed can accumulate, for example, on the dead leg side of a flare header. The differential expansion can deform the pipe so that it lifts off its supports. It takes a finite amount of time for the heat transfer by conduction to equilibrate the temperature to a more benign level. The initial stresses induced due to large thermal differential may even cause the pipe to crack in the region of the supports and T-joints to the laterals. This phenomenon has been observed in several industries, most predominantly in the petrochemical industry. This paper recounts the use of Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) to study this important phenomenon. The liquid flowing from the lateral into the main header pipe is multiphase in the dispersed, stratified, slug or annular flow re´gime. Multiphase flows with heat transfer are analyzed using CFD. The temperatures on the walls of the pipe system are then transferred to the FEA and analyzed for heat transfer and thermal stresses. These stresses are compared to ASME standards to see if they are within allowable limits. This paper also recounts efforts to reduce the bending effect by preventing liquid accumulation on the dead leg side. Other methods that provide better supports for bent piping are studied. Further, methods of equilibrating the temperature faster to prevent the bowing of the pipe are also studied. It is hoped that this presentation will benefit people designing piping networks with varying liquid and vapor traffic by providing a safe environment free of cracks and spills.

Evaluation of a New Low Thermal Expansion Creep Resistant Nickel-Based Alloy

2007 ◽  
Author(s):  
Paul D. Jablonski ◽  
Karol K. Schrems
Keyword(s):  
Power Generation ◽  
Thermal Expansion ◽  
Large Scale ◽  
Thermal Stresses ◽  
Coefficient Of Thermal Expansion ◽  
Ferritic Steels ◽  
Chemical Processing ◽  
Large Scale Systems ◽  
Low Thermal Expansion ◽  
Nickel Based Alloy

For many large-scale systems such as land-based power generation and chemical processing facilities, stresses due to thermal expansion can become a significant consideration in system design. Additionally, differential thermal stresses result from materials such as ferritic steels used in conjunction with nickel-based superalloys. An experimental nickel-based alloy designed for low CTE (Coefficient of Thermal Expansion) has been evaluated for creep performance and is compared to other low CTE nickel-based alloys. The creep results of this new alloy compare favorably to other low CTE nickel-based alloys.

Sign in / Sign up

Export Citation Format

Share Document