DOCSLIB.ORG

Rheological Challenges for the Food Industry

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Rheological Challenges for the Food Industry ANNUAL TRANSACTIONS OF THE NORDIC RHEOLOGY SOCIETY, VOL. 20, 2012 Rheological Challenges for the Food Industry Jan Engmann Nestlé Research Center, Vers-chez-les-Blanc, PO Box 44, 1000 Lausanne 26, Switzerland ABSTRACT brings about specific challenges for the Several key challenges for rheologists understanding of rheological behaviour of working in the food industry are presented. foods itself and for interaction with the These range from pure material science different environments they experience problems (complex yield behaviour, fracture during their life time. mechanics of “soft” materials, interfacial rheology) and interactions with solid SEVEN RHEOLOGICAL CHALLENGES surfaces (wall slip) to the probably biggest challenge: the effects of rheology on 1. Characterisation, theory and use of wall processes inside the human body. Finally, slip phenomena the need for enhanced teaching of advanced It is now quite well accepted that slip or rheological concepts in the field is “apparent slip“ phenomena of liquid and highlighted. semi-solid materials near solid surfaces are ubiquitous in food products3. This should INTRODUCTION come as no real surprise, since many food Designing and controlling rheological products are highly concentrated disperse properties of food and nutrition products is a systems (hard or soft suspensions, emulsions key to their commercial success: these or foams), which are known to exhibit this properties crucially affect product type of behaviour. However, the practical manufacture, distribution, convenience and consequence in most cases is that one sensory experience. Since the range of merely tries to eliminate slip phenomena relevant rheological properties can be very when performing rheometry, e.g. by using broad and only well understood through roughened surfaces, vane geometries and advanced physical concepts, it is a challenge other special tools. This in itself is not trivial to achieve this task within the constraints of to do, but even where it is successful, it is the industry. Food structures contain many only a first step. During processing and types of soft matter structures, e.g. consumption of foods (e.g. flow from a amphiphilic molecules, polymers, molecular bottle or tube, use of a spoon to dose a complexes, micelles, colloidal particles, product, in-mouth perception), the slip particulate gels, polymer gels and so forth1,2 characteristics may significantly affect, or and “managing rheology” in foods from a even dominate the perceived behaviour and purely phenomenological (as opposed to thus be vital to successful products. microstructural) perspective not very Likewise, pumping of “slippery” materials promising. The complex microstructure can not be optimally handled by simply 19 ignoring the slip behaviour when choosing potential for improved physical food design and running a pump. For this, we need a seems considerable. methodology to systematically characterise and understand the nature of wall slip (including its transient nature) and how it depends on the structural features (e.g. size and concentration of particles or droplets) of the surface and the food material (see Fig. 1). Figure 2. Yielding of a milk foam under Figure 1. Size of microstructure elements stepwise increased shear stress using vane relative to surface roughness is a key factor geometry. for wall slip. 3. Relation of time-dependent rheological 2. Yield transition in “jammed” systems properties to sensory texture The concept of a yield stress is widely Partially linked to the second challenge used in the food industry. Less appreciated is the question how to relate sensorial is the fact that a “sharp” (singular) yield texture perception and product liking to key transition is a strong idealisation of real rheological properties of food products. This material behaviour and that a more gradual is a formidable challenge because of the (and history-dependent) transition from complexity of human physiology (see also solid-like to liquid-like behaviour with challenge #6) and the psychology of frequent occurence of strongly localised perception, which is a highly non-linear deformation zones (see Fig. 2) is the reality process. However, one may assume that in many food materials. The concept of a substantial ground can be covered by sharp transition (yield point) can be useful adequately characterising time-dependent (for example in describing plug flow pipe properties (linear and non-linear flows), but often results in inconsistencies viscoelasticity, yield and thixotropic and ambiguities when different techniques behaviour) of food products, which is rarely are used to measure it. Apart from done. Two questions always arise beyond measurement artefacts, these issues result the common territory of steady-state from the fundamentally history- and time- viscosity and linear viscoelasticity: dependent nature of yielding. The (a) which rheological material functions idealisation completely fails where the should be measured, i.e. which stress or complex transitional behaviour is actually deformation profile should be imposed and important for the handling and perception of (b) which parameters should be extracted a product (e.g. spreading of butter, perceived from the non-linear response and texture of a dessert or beverage foam). subsequently discussed. Large-amplitude Recent developments and reviews of this oscillatory shear (LAOS) rheometry might area4-7 provide a stronger foundation for be a powerful answer to both questions – it characterisation of these materials naturally covers linear viscoelasticity as well (including the terminology used), and the as the nonlinear domain and more recently, physically meaningful and robust 20 parametrisations of non-linear response in i.e. they can exchange material with the large-amplitude oscillation have been adjoining bulk phases. proposed8-11. Modern rheometer software increasingly provides access to the raw periodic signals needed for this analysis and at least one algorithm (MITLAOS12) for such an analysis is freely available. Fig. 3 shows shear thinning, progressive reduction in shear viscosity and non-linear viscoelastic behavior of a food emulsion tested via LAOS cycling at a maximum shear deformation of 200 %. Figure 4. (a) Size of an air bubble Figure 3. Large-amplitude oscillatory shear evolving due to Ostwald ripening in favour cycles for a food emulsion. of another (larger) bubble, for different emulsifiers (b) description of bubble growth 4. Interfacial rheology and its implications through a model accounting for inerfacial for food structure tension only (model 1) and interfacial Foods are typically “full of interfaces” dilatational modulus (model 2). Van and contain a variety of surface active Hooghten and Verwijlen (2009)15. materials which contribute to microstructure formation and stabilisation. Beverage foams, “Interfacial rheology” is therefore dairy products or mayonnaise are good arguably an even more complex field to examples. To understand and optimise the master than “classical” rheology. A solid formation, stabilisation and breakdown of theoretical framework to describe interfacial food structure, the way these interfaces rheology exisits16,17, but well-defined evolve under specific external conditions techniques allowing to “cleanly” observe needs to be characterised13,14. interfacial kinematics and dynamics and to Real interfaces can have complex separate them from “bulk” behaviour are configurations in three-dimensional space still an emerging field18-20 which is likely to (as well as a finite third dimension, i.e. significantly improve our understanding and thickness) and are naturally open systems, control of disperse food microstructure. 21 5. Solid mechanics and fracture mechanics mastication, swallowing and digestion and Solid mechanics is a well-established our understanding is mostly qualitative24-29. subject in mechanical engineering and The reasons for this are fairly obvious: the classical materials science, but it has found anatomy and physiology of the human body very little application so far in the food are very difficult to characterise industry, although it clearly has applications quantitatively in vivo and even for quite in process as well as in product design21,22. simple aspects (e.g. basic dimensions and One reason is perhaps simply a lack of shape of the tongue and palate), familiarity with solid mechanics in the food characteristic values and natural variations science community. However, both the are not easily established. Similarly, there characterisation and prediction of solid food are few elegant and non-invasive methods to properties are not trivial, even for relatively follow the changes of a food bolus as it “simple” food materials. Unlike liquids, interacts with different parts of the body. solid food materials usually have no Appropriate imaging (e.g. MRI, ultrasound, mechanism to equilibrate towards a X-ray scans) and sensor technologies (e.g. reference state over reasonable (and manometry, impedance measurements) are, therefore useful) timescales. Apart from the however, steadily improving, primarily difficulty of defining a reference state, this driven by medical applications, and we may poses problems for the production of well- be gradually approaching an age in which defined shapes (e.g. cylindrical or many well-posed questions concerning rectangular bars) of appropriate size that are mastication, swallowing and digestion can needed for a well-defined mechanical be answered with justifiable effort and
Load more

Recommended publications
  • Foundations of Continuum Mechanics
    Foundations of Continuum Mechanics • Concerned with material bodies (solids and fluids) which can change shape when loaded, and view is taken that bodies are continuous bodies. • Commonly known that matter is made up of discrete particles, and only known continuum is empty space. • Experience has shown that descriptions based on continuum modeling is useful, provided only that variation of field quantities on the scale of deformation mechanism is small in some sense. Goal of continuum mechanics is to solve BVP. The main steps are 1. Mathematical preliminaries (Tensor theory) 2. Kinematics 3. Balance laws and field equations 4. Constitutive laws (models) Mathematical structure adopted to ensure that results are coordinate invariant and observer invariant and are consistent with material symmetries. Vector and Tensor Theory Most tensors of interest in continuum mechanics are one of the following type: 1. Symmetric – have 3 real eigenvalues and orthogonal eigenvectors (eg. Stress) 2. Skew-Symmetric – is like a vector, has an associated axial vector (eg. Spin) 3. Orthogonal – describes a transformation of basis (eg. Rotation matrix) → 3 3 3 u = ∑uiei = uiei T = ∑∑Tijei ⊗ e j = Tijei ⊗ e j i=1 ~ ij==1 1 When the basis ei is changed, the components of tensors and vectors transform in a specific way. Certain quantities remain invariant – eg. trace, determinant. Gradient of an nth order tensor is a tensor of order n+1 and divergence of an nth order tensor is a tensor of order n-1. ∂ui ∂ui ∂Tij ∇ ⋅u = ∇ ⊗ u = ei ⊗ e j ∇ ⋅ T = e j ∂xi ∂x j ∂xi Integral (divergence) Theorems: T ∫∫RR∇ ⋅u dv = ∂ u⋅n da ∫∫RR∇ ⊗ u dv = ∂ u ⊗ n da ∫∫RR∇ ⋅ T dv = ∂ T n da Kinematics The tensor that plays the most important role in kinematics is the Deformation Gradient x(X) = X + u(X) F = ∇X ⊗ x(X) = I + ∇X ⊗ u(X) F can be used to determine 1.
    [Show full text]
  • Pacific Northwest National Laboratory Operated by Battelie for the U.S
    PNNL-11668 UC-2030 Pacific Northwest National Laboratory Operated by Battelie for the U.S. Department of Energy Seismic Event-Induced Waste Response and Gas Mobilization Predictions for Typical Hanf ord Waste Tank Configurations H. C. Reid J. E. Deibler 0C1 1 0 W97 OSTI September 1997 •-a Prepared for the US. Department of Energy under Contract DE-AC06-76RLO1830 1» DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government, Neither the United States Government nor any agency thereof, nor Battelle Memorial Institute, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. PACIFIC NORTHWEST NATIONAL LABORATORY operated by BATTELLE for the UNITED STATES DEPARTMENT OF ENERGY under Contract DE-AC06-76RLO 1830 Printed in the United States of America Available to DOE and DOE contractors from the Office of Scientific and Technical Information, P.O. Box 62, Oak Ridge, TN 37831; prices available from (615) 576-8401, Available to the public from the National Technical Information Service, U.S.
    [Show full text]
  • Hydrostatic Forces on Surface
    24/01/2017 Lecture 7 Hydrostatic Forces on Surface In the last class we discussed about the Hydrostatic Pressure Hydrostatic condition, etc. To retain water or other liquids, you need appropriate solid container or retaining structure like Water tanks Dams Or even vessels, bottles, etc. In static condition, forces due to hydrostatic pressure from water will act on the walls of the retaining structure. You have to design the walls appropriately so that it can withstand the hydrostatic forces. To derive hydrostatic force on one side of a plane Consider a purely arbitrary body shaped plane surface submerged in water. Arbitrary shaped plane surface This plane surface is normal to the plain of this paper and is kept inclined at an angle of θ from the horizontal water surface. Our objective is to find the hydrostatic force on one side of the plane surface that is submerged. (Source: Fluid Mechanics by F.M. White) Let ‘h’ be the depth from the free surface to any arbitrary element area ‘dA’ on the plane. Pressure at h(x,y) will be p = pa + ρgh where, pa = atmospheric pressure. For our convenience to make various points on the plane, we have taken the x-y coordinates accordingly. We also introduce a dummy variable ξ that show the inclined distance of the arbitrary element area dA from the free surface. The total hydrostatic force on one side of the plane is F pdA where, ‘A’ is the total area of the plane surface. A This hydrostatic force is similar to application of continuously varying load on the plane surface (recall solid mechanics).
    [Show full text]
  • Ch. 8 Deflections Due to Bending
    446.201A (Solid Mechanics) Professor Youn, Byeng Dong CH. 8 DEFLECTIONS DUE TO BENDING Ch. 8 Deflections due to bending 1 / 27 446.201A (Solid Mechanics) Professor Youn, Byeng Dong 8.1 Introduction i) We consider the deflections of slender members which transmit bending moments. ii) We shall treat statically indeterminate beams which require simultaneous consideration of all three of the steps (2.1) iii) We study mechanisms of plastic collapse for statically indeterminate beams. iv) The calculation of the deflections is very important way to analyze statically indeterminate beams and confirm whether the deflections exceed the maximum allowance or not. 8.2 The Moment – Curvature Relation ▶ From Ch.7 à When a symmetrical, linearly elastic beam element is subjected to pure bending, as shown in Fig. 8.1, the curvature of the neutral axis is related to the applied bending moment by the equation. ∆ = = = = (8.1) ∆→ ∆ For simplification, → ▶ Simplification i) When is not a constant, the effect on the overall deflection by the shear force can be ignored. ii) Assume that although M is not a constant the expressions defined from pure bending can be applied. Ch. 8 Deflections due to bending 2 / 27 446.201A (Solid Mechanics) Professor Youn, Byeng Dong ▶ Differential equations between the curvature and the deflection 1▷ The case of the large deflection The slope of the neutral axis in Fig. 8.2 (a) is = Next, differentiation with respect to arc length s gives = ( ) ∴ = → = (a) From Fig. 8.2 (b) () = () + () → = 1 + Ch. 8 Deflections due to bending 3 / 27 446.201A (Solid Mechanics) Professor Youn, Byeng Dong → = (b) (/) & = = (c) [(/)]/ If substitutng (b) and (c) into the (a), / = = = (8.2) [(/)]/ [()]/ ∴ = = [()]/ When the slope angle shown in Fig.
    [Show full text]
  • Topics in Solid Mechanics: Elasticity, Plasticity, Damage, Nano and Biomechanics
    Topics in Solid Mechanics: Elasticity, Plasticity, Damage, Nano and Biomechanics Vlado A. Lubarda Montenegrin Academy of Sciences and Arts Division of Natural Sciencies OPN, CANU 2012 Contents Preface xi Part 1. LINEAR ELASTICITY 1 Chapter 1. Anisotropic Nonuniform Lam´eProblem 2 1.1. Elastic Anisotropy 2 1.2. Radial Nonuniformity 3 1.3. Governing Differential Equations 4 1.4. Stress and Displacement Expressions 5 1.5. Traction Boundary Conditions 6 1.6. Applied External Pressure 7 1.7. Plane Stress Approximation 8 1.8. Generalized Plane Stress 10 References 11 Chapter 2. Stretching of a Hollow Circular Membrane 12 2.1. Introduction 12 2.2. Basic Equations 12 2.3. Traction Boundary Conditions 13 2.4. Mixed Boundary Conditions 16 References 18 Chapter 3. Energy of Circular Inclusion with Sliding Interface 21 3.1. Energy Expressions for Sliding Inclusion 21 3.2. Energies due to Eigenstrain 22 3.3. Energies due to Remote Loading 23 3.4. Inhomogeneity under Remote Loading 25 References 26 Chapter 4. Eigenstrain Problem for Nonellipsoidal Inclusions 27 4.1. Eshelby Property 27 4.2. Displacement Expression 27 4.3. The Shape of an Inclusion 28 4.4. Other Shapes of Inclusions 30 References 32 Chapter 5. Circular Loads on the Surface of a Half-Space 33 5.1. Displacements due to Vertical Ring Load 33 5.2. Alternative Displacement Expressions 34 iii iv CONTENTS 5.3. Tangential Line Load 37 5.4. Alternative Expressions 39 5.5. Reciprocal Properties 43 References 45 Chapter 6. Elasticity Tensors of Anisotropic Materials 46 6.1. Elastic Moduli of Transversely Isotropic Materials 46 6.2.
    [Show full text]
  • Chapter 6: Bending
    Chapter 6: Bending Chapter Objectives Determine the internal moment at a section of a beam Determine the stress in a beam member caused by bending Determine the stresses in composite beams Bending analysis This wood ruler is held flat against the table at the left, and fingers are poised to press against it. When the fingers apply forces, the ruler deflects, primarily up or down. Whenever a part deforms in this way, we say that it acts like a “beam.” In this chapter, we learn to determine the stresses produced by the forces and how they depend on the beam cross-section, length, and material properties. Support types: Load types: Concentrated loads Distributed loads Concentrated moments Sign conventions: How do we define whether the internal shear force and bending moment are positive or negative? Shear and moment diagrams Given: Find: = 2 kN , , Shear- = 1 m Bending moment diagram along the beam axis Example: cantilever beam Given: Find: = 4 kN , , Shear- = 1.5 kN/m Bending moment = 1 m diagram along the beam axis 2 Relations Among Load, Shear and Bending Moments Relationship between load and shear: Relationship between shear and bending moment: Wherever there is an external concentrated force, or a concentrated moment, there will be a change (jump) in shear or moment respectively. Concentrated force F acting upwards: Concentrated Moment acting clockwise Shear and moment diagrams Given: Use the graphical = 2 kN method the sketch = 1 m diagrams for V(x) and M(x) Example: cantilever beam Given: Use the graphical = 4 kN method the sketch = 1.5 kN/m diagrams for V(x) and = 1 m M(x) 2 Pure bending Take a flexible strip, such as a thin ruler, and apply equal forces with your fingers as shown.
    [Show full text]
  • Equation of Motion for Viscous Fluids
    1 2.25 Equation of Motion for Viscous Fluids Ain A. Sonin Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge, Massachusetts 02139 2001 (8th edition) Contents 1. Surface Stress …………………………………………………………. 2 2. The Stress Tensor ……………………………………………………… 3 3. Symmetry of the Stress Tensor …………………………………………8 4. Equation of Motion in terms of the Stress Tensor ………………………11 5. Stress Tensor for Newtonian Fluids …………………………………… 13 The shear stresses and ordinary viscosity …………………………. 14 The normal stresses ……………………………………………….. 15 General form of the stress tensor; the second viscosity …………… 20 6. The Navier-Stokes Equation …………………………………………… 25 7. Boundary Conditions ………………………………………………….. 26 Appendix A: Viscous Flow Equations in Cylindrical Coordinates ………… 28 ã Ain A. Sonin 2001 2 1 Surface Stress So far we have been dealing with quantities like density and velocity, which at a given instant have specific values at every point in the fluid or other continuously distributed material. The density (rv ,t) is a scalar field in the sense that it has a scalar value at every point, while the velocity v (rv ,t) is a vector field, since it has a direction as well as a magnitude at every point. Fig. 1: A surface element at a point in a continuum. The surface stress is a more complicated type of quantity. The reason for this is that one cannot talk of the stress at a point without first defining the particular surface through v that point on which the stress acts. A small fluid surface element centered at the point r is defined by its area A (the prefix indicates an infinitesimal quantity) and by its outward v v unit normal vector n .
    [Show full text]
  • 2 Review of Stress, Linear Strain and Elastic Stress- Strain Relations
    2 Review of Stress, Linear Strain and Elastic Stress- Strain Relations 2.1 Introduction In metal forming and machining processes, the work piece is subjected to external forces in order to achieve a certain desired shape. Under the action of these forces, the work piece undergoes displacements and deformation and develops internal forces. A measure of deformation is defined as strain. The intensity of internal forces is called as stress. The displacements, strains and stresses in a deformable body are interlinked. Additionally, they all depend on the geometry and material of the work piece, external forces and supports. Therefore, to estimate the external forces required for achieving the desired shape, one needs to determine the displacements, strains and stresses in the work piece. This involves solving the following set of governing equations : (i) strain-displacement relations, (ii) stress- strain relations and (iii) equations of motion. In this chapter, we develop the governing equations for the case of small deformation of linearly elastic materials. While developing these equations, we disregard the molecular structure of the material and assume the body to be a continuum. This enables us to define the displacements, strains and stresses at every point of the body. We begin our discussion on governing equations with the concept of stress at a point. Then, we carry out the analysis of stress at a point to develop the ideas of stress invariants, principal stresses, maximum shear stress, octahedral stresses and the hydrostatic and deviatoric parts of stress. These ideas will be used in the next chapter to develop the theory of plasticity.
    [Show full text]
  • Basic Solid Mechanics Other Engineering Titles of Related Interest
    Basic Solid Mechanics Other engineering titles of related interest Automation with Programmable Logic Controllers Peter Rohner Design and Manufacture An Integrated Approach Rod Black Dynamics G.E. Drabble Elementary Engineering Mechanics G.E. Drabble Finite Elements A Gentle Introduction D. Henwood and J. Bonet Fluid Mechanics Martin Widden Introduction to Engineering Materials V.B. John Introduction to Internal Combustion Engines, Second Edition Richard Stone Mechanics of Machines, Second Edition G.H. Ryder and M.D. Bennett Thermodynamics J. Simonson Basic Solid Mechanics D.W.A. Rees Department of Manufacturing and Engineering Systems, Brunei University MACMILLAN ~~:> D.W.A. Rees 1997 All rights reserved. No reproduction, copy or transmission of this publication may be made without written permission. No paragraph of this publication may be reproduced, copied or transmitted save with written permission or in accordance with the provisions of the Copyright, Designs and Patents Act 1988, or under the terms of any licence permitting limited copying issued by the Copyright Licensing Agency, 90 Tottenham Court Road, London W1P 9HE. Any person who does any unauthorised act in relation to this publication may be liable to criminal prosecution and civil claims for damages. The author has asserted his rights to be identified as the author of this work in accordance with the Copyright, Designs and Patents Act 1988. First published 1997 by MACMILLAN PRESS LTD Houndmills, Basingstoke, Hampshire RG21 6XS and London Companies and representatives throughout the world ISBN 978-0-333-66609-8 ISBN 978-1-349-14161-6 (eBook) DOI 10.1007/978-1-349-14161-6 A catalogue record for this book is available from the British Library.
    [Show full text]
  • Arxiv:1909.02884V1 [Physics.Class-Ph]
    Unified discrete approach of acceleration conservation Jean-Paul Caltagirone Université de Bordeaux Institut de Mécanique et d’Ingéniérie Département TREFLE, UMR CNRS nř 5295 16 Avenue Pey-Berland, 33607 Pessac Cedex [email protected] Abstract Discrete mechanics is used to present fluid mechanics, fluid-structure interactions, electromagnetism and optical physics in a coherent theoretical and numerical approach. Acceleration considered as an absolute quantity is written as a sum of two terms, i.e. an irrotational and a divergence-free component corresponding to a formal Hodge-Helmholtz decomposition. The variables of this equation of discrete motion are only the scalar and vector potential of the acceleration, whatever the physical field. These, like the physical properties, are only expressed as a function of two fundamental units, namely a length and a time. The numerical methodology associated with this equation of motion is based on discrete operators, gradient, divergence, primal and dual curl applied to the velocity components of the primal geometric topology. Some solutions resulting from simulations carried out in each domain make it possible to find the results obtained from the Navier-Stokes, Navier-Lamé and Maxwell equations and to show the coherence of the proposed unified approach. Keywords: Discrete Mechanics; Weak Equivalence Principle; Hodge-Helmholtz Decomposition; Navier-Stokes equations; Maxwell equations 1 Introduction The Navier-Stokes, Navier-Lamé and Maxwell equations are fully representative of physical phenomena in the fields of fluid mechanics, solid mechanics and electromagnetism. Continuum mechanics [25], [26] was supposed to unify mechanics but two centuries after their derivation, it turns out that its (Eulerian or Lagrangian) formulations are different; velocity is the variable in fluid media whereas it is displacement in solid media.
    [Show full text]
  • ENGN1750 Advanced Mechanics of Solids
    ENGN1750 Advanced Mechanics of Solids Pradeep R. Guduru Office: Barus Holley& Holley 729; Tel: 863-3362 Email: [email protected] David Henann Office Barus & Holley 604, Tel: 863-2319 [email protected] Course Website http://www.brown.edu/Departments/Engineering/Labs/Gudurulab/E NGN1750/ Tuesday, Thursday; 2:30 – 3:50pm, B&H 159 • Weekly section will be held in the instructional computer lab. Course Outline 1.Introduction 6. Boundary value problems for linear elastic solids 1.1 Scope of the course 6.1 Field equations for plane strain deformation 1.2 Basic concepts of solid mechanics 6.2 Thick walled pressure vessel 1.3 Overview of finite element method in computational solid mechanics 6.3 Field equations for plane stress deformation 2. Mathematical background 6.3 Plate with hole in tension, stress concentration 2.1 Vector algebra 7. Variational methods for elastic solids 2.2 Index notations 7.1 Principle of virtual work 2.3 Matrices and tensors 7.2 Variational statement of governing equations7.3 Work and energy 2.4 Vector and tensor calculus theorems in solid mechanics7.4 Derivations of field equations for thin 3. Stress in a solid plate in bending 3.1 Body forces, surface forces and traction vector at a point on the surface 8.The finite element method for numerical analyses 3.2 Stress tensor at a point 8.1 Finite elements 3.3 Principal stresses at a point 8.2 Element interpolation functions 3.4 Balance of momentum and equilibrium equations 8.3 Element strains, stresses and strain energy density 4. Strain in a solid 8.4 Element Stiffness Matrix 4.1 Displacement field in a deformed solid 8.5 Global Stiffness Matrix 4.2 Strain tensor in a Solid 8.6 Boundary Loading 4.3 Principal strains at a point 9.
    [Show full text]
  • ME 333C - Mechanics/Continuum Mechanics
    ME 333C - Mechanics/Continuum Mechanics Tue/Thu 10:30-11:50, Hewlett 201 Rijk de Rooij ([email protected]) Ellen Kuhl ([email protected]) Summary. Introduction to linear and nonlinear continuum mechanics of solids; Introduction to tensor algebra and tensor analysis; Kinematics of motion; Balance equations of mass, linear and angular momentum, energy, and entropy; Constitutive equations of isotropic and anisotropic hyperelastic solids; Introduction to numerical solution techniques. Although the basic concepts of continuum mechanics have been established more than five decades ago, the 21st century faces many new and exciting potential applications of continuum mechanics that go way beyond the standard classical theory. When applying continuum mechanics to these challenging new phenomena, it is important to understand the main three ingredients of continuum mechanics: the kinematic equations, the balance equations and the constitutive equations. After a brief revision of the relevant equations in tensor algebra and analysis, this class will introduce the basic concepts of finite strain kinematics. We will then discuss the balance equations for mass, linear and angular momentum, energy, and entropy. While all these equations are general and valid for any kind of material, the last set of equations, the constitutive equations, specifies particular subclasses of materials. Grading Homework 30 % three homework assignments, 10% each Final 50 % closed book, closed notes, one single page cheat sheet Project 20 % written evaluation of a manuscript
    [Show full text]