Simulation of Thermal-Structure Interaction

Kyle C. Koppenhoefer, Ph.D. Principal

ALTASIM TECHNOLOGIES

© Copyright 2014 COMSOL. COMSOL, COMSOL Multiphysics, Capture the Concept, COMSOL Desktop, and LiveLink are either registered trademarks or trademarks of COMSOL AB. All other trademarks are the property of their respective owners, and COMSOL AB and its subsidiaries and products are not affiliated with, endorsed by, sponsored by, or supported by those trademark owners. For a list of such trademark owners, see www.comsol.com/trademarks

Shankar Krishnan, Ph.D. Applications Engineer

COMSOL

Agenda

• Introduction to Thermal-Structure Interaction

• Simulating with COMSOL Multiphysics® • Thermal-Structural Examples, Design

Challenges, and Solutions • Live Demo

– Shrink Fitting • Q&A Session • How To

– Try COMSOL Multiphysics – Contact Us

Electric current and heat flow through the contacting surfaces of a switch

Thermal-Structure Interactions

Power generation Electronics and MEMS Automotive

Biomedical Aerospace

Simulating an Application

• Conception and understanding – Enables innovation

• Design and optimization

– Achieve the highest possible performance

• Testing and verification

– Virtual testing is much faster than testing physical prototypes Heating Circuit

Model tree Provides instant access to any part of the model settings • CAD/Geometry • Materials • Physics • Mesh • Solve • Results

The COMSOL Desktop®

Graphics Ultrafast graphic presentation, stunning visualization

COMSOL Desktop Straightforward to use, it gives full insight and control over the modeling process

Poll Question #1

How important is Thermal-Structure Interaction in your simulations?

• Very important - most of my simulations require some form of thermal-

structure interaction

• Important – when it is present, the interaction is important

• Somewhat important – but I don’t tend to work on coupled analysis

• Not important – None involve thermal-structure interaction

Thermal Expansion

l l + Δ l

Δ l = α(T-Tref)l

Heat

α

T-Tref

Δ l/l

Cool

Automatic and Manual Couplings Between Thermal and Structural Simulations

Nonlinear and Anisotropic Material Properties

Plastic, Viscoelastic, Viscoplastic Materials and Creep

Dynamic Effects

σ

ε

Tensile stress cools down Compressive stress heats up

Structural damping manifests as vibration-induced heating

Thermoelastic damping in MEMS devices

Adding More Physical Effects

Electromagnetic Heating and Thermal Expansion

Joule heating in electronics Induction heating furnace RF heating in a waveguide

Customized Multiphysics Interactions

Stress-optics: Thermal-stress-induced difference in refractive index between x and y-directions

Heating circuit: Electrical, thermal, and structural coupling between solid and shell

Thermal-Structure Interaction

Kyle C. Koppenhoefer, Ph.D. Principal

AltaSim Technologies, LLC

Overview

• Thermal-structural interaction examples • Design challenges • Coupling of temperature/deformation • Computational tools necessary for solving • Structural example problem • Shrink fit demonstration

THERMAL-STRUCTURAL EXAMPLES

Thermal-Structural Interaction Electronics

Turbines

Heat Treatment of Metals

Pressure Vessels Shrink-Fitting

THERMAL-STRUCTURAL DESIGN CHALLENGES

Thermal-Structural Design Challenges

• Material damage that is a function of temperature (e.g., yielding, creep)

• Mechanical damage due to constrained thermal growth – Mechanical constraints – Spatial temperature gradients – Material property variations (e.g., CTE)

• Spatial variations • Variations with temperature

Turbines

Constrained Thermal Growth

Δ l = α(T-Tref)l

∆𝒍𝒍

= 𝜶 𝑻 − 𝑻𝒓𝒓𝒓

𝜺𝒕𝒕𝒓𝒓𝒕𝒕𝒍 = 𝜶 𝑻 − 𝑻𝒓𝒓𝒓

𝜺𝒕𝒓𝒎𝒕 = 𝜺𝒕𝒕𝒕𝒕𝒍 − 𝜺𝒕𝒕𝒓𝒓𝒕𝒕𝒍

𝝈 = 𝑬𝜺𝒕𝒓𝒎𝒕

l l + Δ l

Heat

Cool

Thermal strain produces displacement Mechanical strain produces stress

THERMAL-STRUCTURAL COUPLING

Thermal-Structural Interaction

Sequentially Coupled

Turbines

Fully Coupled

Loosely Coupled

Temperature → Deformation Examples: • Pressure vessel w/ different fluids • Beam buckling due to thermal load

Temperature ↔ Deformation Examples: • Forging • Contact changes due to deformation

Examples: • Frictional heating (e.g., disk brakes)

COMPUTATIONAL TOOL – KEY FEATURES

Key Features

• Thermal and structural analysis within same software – Thermal analysis includes conduction, convection, and

radiation – Elastic, plastic structural response – Ability to model phase changes – Solution methods

• Steady state analysis • Transient analysis

– Sequential coupling • Apply temperatures from thermal analysis to structural

– Two-way coupling • Mechanical contact • Thermal contact • Heat source due to plastic strain

Key Features

• Material properties – Thermal

• Thermal conductivity • Density • Specific heat (transient) • Latent heat of transformation (temperature range)

– Structural • Elastic modulus • Poisson’s ratio • Yield Strength

– Temperature dependent material properties

Thermal Contact

• Evaluates heat conduction across two contacting surfaces

• Contact localized at asperities due to surface roughness

• Heat flux on boundaries

Tu

Td

Thermal Contact

• Three components of conductance

– Constriction conductance (hc) – Gap conductance (hg) – Gap radiation (hr) – h = hc+ hg+ hr

• Friction heat , Qfric, is a heat source term that is partitioned between the two surface using the surface roughness term, r – r=0.5 for identical surfaces

Thermal Contact

• Cooper-Mikic-Yovanovich (CMY) Correlation – Isotropic surface roughness – Plastic deformation of the surface asperities

• Mikic Elastic Correlation – Isotropic surface roughness – Elastic deformation of the surface asperities

• User Defined – Define constriction conductance directly

Cooper-Mikic-Yovanovich

• Constriction conductance

THERMAL-STRUCTURAL EXAMPLE

Example Problem – Shrink Fitting

• Railroad wheels assembled via shrink fit onto axle

• Axle critical for railway vehicle safety

• Fretting fatigue at fit interface is significant failure mode

• Safety insured by regular inspection of axels

• High contact stress can accelerate fretting fatigue

Example Problem – Key Features

• Two-way coupled problem due to contact – Mechanical contact – Thermal contact

• Temperature-dependent plasticity • Transient thermal and mechanical analysis • Parametric studies on geometry variations

Live Demonstration

• Please wait while the content is loading • Demonstration of shrink fit problem setup

Poll Question #2

What type of thermal-structure interaction are you interested in simulating?

• Thermal expansion – including thermal stress

• Nonlinear materials – viscoelastic, creep, etc.

• Thermal contact – to account for surface effects

• Other multiphysics – involves electromagnetic heating, convective cooling, etc.

• More than one of the above

Q&A Session

Product Suite – COMSOL 4.4

Try COMSOL Multiphysics

• North America – New York, NY – Ann Arbor, MI – Richland, WA – Fort Worth, TX – East Lansing, MI – Andover, MA – Nashua, NH – Costa Mesa, CA – St John's, NL – Buffalo, NY

• Europe – Paris 11e, France – Grenoble, France – Berlin, Germany – Swansea, United Kingdom – Bristol, United Kingdom – Zoetermeer, Netherlands – Oslo, Norway

• Register for our free hands-on workshops at www.comsol.com/events

Contact Us • www.comsol.com

– Product News – Videos – Model Gallery – User Stories – Discussion Forum – Blog

• info@comsol.com – General inquiries

• support@comsol.com – Technical support