Lecture 8: Tissue Mechanics
|
|
- Sheila Floyd
- 5 years ago
- Views:
Transcription
1 Computational Biology Group (CoBi), D-BSSE, ETHZ Lecture 8: Tissue Mechanics Prof Dagmar Iber, PhD DPhil MSc Computational Biology 2015/16
2 7. Mai / 57 Contents 1 Introduction to Elastic Materials Hooke s Law Uniform Strain Inside Elastic Materials The Tensor of Elasticity Isotropic Material 2 Tissue as a viscous Fluid 3 Models of Limb Bud Growth
3 Tissue as a visco-elastic material Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
4 Tissue as a visco-elastic material The key differences between the behaviours of solids and fluids lies in how they respond to the application of a force: Elastic Solids Viscous Fluids The deformation is independent of the time over which the force is applied. The deformation disappears when the force is removed. Tissue as visco-elastic material A fluid continues to flow as long as the force is applied A fluid will not recover its original form when the force is removed. Tissue shows a mix of the two extreme properties. We will therefore now discuss the theory of visco-elastic fluids. Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
5 Introduction to Elastic Materials Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
6 7. Mai / 57 Definition of mechanical terms Stress. A coarse-grained description of the forces within a tissue. When a piece of tissue experiences a force from a neighboring tissue region (A), mechanical stress (σ) is defined as the ratio of the force (F ) to the area of contact (A) with that region (B, top equation). Tension and compression correspond to forces pointing respectively outwards from and inwards to the body. Deformation (also called strain ) is the relative change in size of an object subjected to a force. In one dimension, it is a dimensionless number, ɛ (B, bottom equation): the fraction of change in the object length (where L is the new length and L 0 the original length), which would be positive for elongation or negative for contraction.
7 7. Mai / 57 Hooke s Law According to Hooke s law, the force F needed to extend or compress a solid bar (spring) by some distance l is proportional to that distance. That is, F l. (1) The lengthening l of the bar will also depend on its length l. Thus, if the same forces act on each of two blocks that are put together, each will stretch by l. We thus see that we must have F l. (2) l
8 7. Mai / 57 Hooke s Law The force will also depend on the area of the block, and must be proportional to the cross-sectional area A (imagine to blocks side by side that are deformed by l). We then have F = YA l, (3) l where Y is the Young modulus. We can rewrite this as Hooke s Law F A }{{} stress = Y l l }{{} strain, (4)
9 7. Mai / 57 Hooke s Law When one stretches a block of material in one direction, it contracts at right angles to the stretch. We thus have for homogenous, isotropic materials w w = h l = σ, (5) h l where w and h refer to the width and height of the bar, and σ us called Poisson s ratio. Finally, since we are in a linear regime, we can use superposition, i.e. so forces and their effects are additive.
10 7. Mai / 57 Limits of Hooke s Law Hooke s law is only a first-order linear approximation to the real response of springs and other elastic bodies to applied forces. It must eventually fail once the forces exceed some limit, since no material can be compressed beyond a certain minimum size, or stretched beyond a maximum size, without some permanent deformation or change of state. Many materials will noticeably deviate from Hooke s law well before those elastic limits are reached.
11 7. Mai / 57 Uniform Strain Consider a rectangular block exposed to uniform hydrostatic pressure. If we push on the ends of the block with a pressure p, the compressional strain is p/y, and it is negative, l 1 = p }{{} l }{{} Y strain compressional strain (6) If we push on the two sides of the block with pressure p, the compressional strain is again p/y, but we now want the lengthwise strain, which we get according to Eq. 5, by multiplying with σ, l 2 l }{{} strain = l 3 = +σ p }{{} l }{{ Y} strain sideways strain (7)
12 7. Mai / 57 Uniform Strain Combined we have (recognizing that the argument is symmetric in all directions), l l = w w = h h = i l i l = p (1 2σ) } Y {{} strain (8) The change in volume, V = lwh, under hydrostatic pressure is then for small displacements V V = l l + w w + h h = 3 p (1 2σ) } Y {{} strain (9) V V is referred to as volume strain.
13 7. Mai / 57 Uniform Volume Strain The volume stress p is proportional to the volume strain Volume Strain p = K V V, K = Y 3(1 2σ). (10) The coefficient K is called the bulk modulus.
14 7. Mai / 57 Inside Elastic Materials We are now interested in what happens inside an elastic body, i.e. we want to determine the local stress and strain at every point in an elastic body. To this end, we define the displacement vector u = r r (11) of between the location of a point in the original and stretched material.
15 7. Mai / 57 Uniform Stretching We start by considering homogenous strain throughout the material as we would have in case of uniform stretching. Now in x-direction we would have u x x = l (12) l where u x refers to the x-entry of the displacement vector. We can then write u x = ε xx x, ε xx = l. (13) l
16 7. Mai / 57 Non-Uniform Stretch If the strain is not uniform, then the relation between u x and x will vary from place to place in the material and we have ε xx = u x x, ε yy = u y y, ε zz = u z z. (14) For shear-type strains we have ε xy = ε yx = 1 2 ( uy x + u ) x. (15) y For a pure rotation they are both zero, but for a pure shear we get that ε xy is equal to ε yx as required.
17 7. Mai / 57 Symmetric strain tensor We thus have the symmetric strain tensor ε ij = ε ji = 1 2 ( uj i + u ) i, (16) j and u x = ε xx x + ε xy y + ε xz z. (17) In principle, there could also be twisting (rotations), which we will ignore.
18 The Tensor of Elasticity According to Hooke s Law, each component of the stress tensor S ij is linearly related to each of the components of the strain. Here, the i, j component of the stress tensor S ij represents the ithe component of the force across a unit area perpendicular to the j-axis. Since S and ε each have nine components, there are 9 9 = 81 possible coefficients which describe the properties of elastic materials. They are constants if the material itself is homogeneous. If we write these coefficients as C ijkl we have 3 3 S i j = C i j k l ε k l. (18) k=1 l=1 i, j, k, l all take on the values 1,2, or 3. C ijkl is a tensor of the fourth rank, the tensor of elasticity. Since both S i j and ε k l are symmetric, each with only six different terms, there can be at most 36 different terms in C ijkl.there are, however, usually many fewer than this. Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
19 7. Mai / 57 Units 3 3 S i j = C i j k l ε k l k=1 l=1 For continuous media, each element of the stress tensor S is a force divided by an area; it is therefore measured in units of pressure, namely pascals (Pa, or N/m 2, or kg/(ms 2 ). The elements of the strain tensor ɛ are dimensionless (displacements divided by distances). Therefore, the entries of C ijkl are also expressed in units of pressure.
20 7. Mai / 57 Isotropic Material For isotropic media (which have the same physical properties in any direction), C can be reduced to only two independent numbers: the bulk modulus K the shear modulus, that quantify the material s resistance to changes in volume and to shearing deformations.
21 7. Mai / 57 Isotropic Material Isotropic materials are characterized by properties which are independent of direction in space. Physical equations involving isotropic materials must therefore be independent of the coordinate system chosen to represent them. The strain tensor is a symmetric tensor. Since the trace of any tensor is independent of any coordinate system, the most complete coordinate-free decomposition of a symmetric tensor is to represent it as the sum of a constant tensor and a traceless symmetric tensor. In index notation: ε ij = ( 1 3 ε kkδ ij ) }{{} volumetric strain tensor where δ ij is the Kronecker delta. ) + (ε ij 1 3 ε kkδ ij }{{} shear tensor (19)
22 7. Mai / 57 Isotropic Material The most general form of Hooke s law for isotropic materials may now be written as a linear combination of these two tensors: ( ) ) S ij = 3K 1 3 ε kkδ ij + 2G (ε ij 1 3 ε kkδ ij (20) where K is the bulk modulus and G is the shear modulus. Thus, ( ( ) S 11 = 3K 1 3 (ε 22 + ε 33 )) + 2G ε (ε 22 + ε 33 ). (21)
23 Isotropic Material Differently said, for isotropic materials, the components of C must be the same for any choice of coordinate system. This is the case only if C xxxx = C xxyy + C xyxy (22) C xxyy = λ = Y ( ) σ (23) 1 + σ 1 2σ C xyxy = 2µ = Y 1 + σ C xxxx = 2µ + λ = Y 1 + σ ( 1 + σ ) 1 2σ (24) (25) (26) where Y is then Young modulus and σ the Poisson s ratio. We then have ( ) S i j = 2µε ij + λ ε kk δ ij. (27) k Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
24 A Mechanical Feedback Restricts Sepal Growth and Shape in Arabidopsis A stereotypical growth pattern generates tensile stress at the sepal tip A supracellular microtubule alignment forms along maximal tension at the sepal tip The strength of the mechanical feedback can modulate sepal shape The microtubule response to tension acts as an Hervieux et al, Current Biology, 2016 organ shape-sensing mechanism Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil 7. Mai / 57 Lecture 8 MSc 2015/16
25 A Mechanical Feedback Restricts Sepal Growth and Shape in Arabidopsis Computational Biology Group (CoBi), D-BSSE, ETHZ 7. Mai / 57 Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16
26 Mechanical Measurements Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
27 Tissue as a viscous Fluid Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
28 7. Mai / 57 Behaviour of Fluids We are now interested in understanding how external forces affect the behaviour of fluids. Here, we will assume that the fluid behaves as a continuous substance rather than a set of discrete particles. The solution of the Navier-Stokes equations is a flow velocity. The flow velocity is a field, since it is defined at every point in a region of space and an interval of time.
29 7. Mai / 57 Behaviour of Fluids Once the velocity field is calculated, other quantities of interest, such as pressure or temperature, may be found. This is different from what one normally sees in classical mechanics, where solutions are typically trajectories of position of a particle or deflection of a continuum. Studying velocity instead of position makes more sense for a fluid; however for visualization purposes one can compute various trajectories.
30 7. Mai / 57 Navier-Stokes Equation The Navier-Stokes equations are derived from the basic principles of continuity of mass momentum energy. A continuity equation may be derived from conservation principles of mass, momentum, and energy. This is done via the Reynolds transport theorem.
31 7. Mai / 57 The Reynolds transport theorem The Reynolds transport theorem The Reynolds transport theorem is an integral solution relation stating that the sum of the changes of some intensive property (call it φ) defined over a control volume Ω must be equal to what is lost (or gained) through the boundaries of the volume plus what is created/consumed by sources and sinks inside the control volume.
32 Intensive and extensive properties Intensive and extensive properties Intensive property: a bulk property, i.e. it is a physical property of a system that does not depend on the system size or the amount of material in the system, e.g. temperature, T, density, ρ, and hardness of an object, η. Extensive property: is additive for subsystems, i.e. if the system could be divided into any number of subsystems, and the extensive property measured for each subsystem; the value of the property for the system would be the sum of the property for each subsystem (e.g. mass, m, volume, V ). The ratio of two extensive properties of the same object or system is an intensive property. For example, the ratio of an object s mass and volume, which are two extensive properties, is density, which is an intensive property. Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
33 7. Mai / 57 The Reynolds transport theorem The Reynolds transport theorem for an intensive property φ is expressed by the following integral continuity equation: d φ dv = φu n da s dv (28) dt Ω Ω Ω where u is the flow velocity of the fluid and s represents the sources and sinks in the flow, taking the sinks as positive. Ω represents the control volume and Ω its bounding surface.
34 The Reynolds transport theorem The divergence theorem may be applied to the surface integral, changing it into a volume integral: d φ dv = (φu) dv s dv. (29) dt Ω Ω Applying Leibniz s rule to the integral on the left and then combining all of the integrals: φ Ω t Ω dv = (φu) dv s dv (30) Ω ( ) φ t + (φu) + s dv = 0. (31) Ω The integral must be zero for any control volume; this can only be true if the integrand itself is zero, so that: φ + (φu) + s = 0. (32) t Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57 Ω
35 7. Mai / 57 The Reynolds transport theorem φ + (φu) + s = 0. (33) t From this valuable relation (a very generic continuity equation), three important concepts may be concisely written: conservation of mass, conservation of momentum, and conservation of energy. Validity is retained if φ is a vector, in which case the vector-vector product in the second term will be a dyad.
36 7. Mai / 57 Conservation of Momentum A general momentum equation is obtained when the conservation relation is applied to momentum. If the intensive property φ considered is the mass flux (also momentum density), i.e. the product of mass density and flow velocity ρu, by substitution in the general continuum equation: (ρu) + (ρuu) = f (34) t which corresponds to ( ) ( ) ρ u u t + (ρu) + ρ t + u u = f (35)
37 7. Mai / 57 Conservation of Momentum & Mass ( ) ( ) ρ u u t + (ρu) + ρ t + u u = f (36) The leftmost expression relates to the conservation of mass ρ t + (ρu) = S (37) where ρ is the mass density (mass per unit volume), u is the flow velocity. S is a mass source. Typically, S = 0. However, in tissue models S 0 in case of growth. In case of incompressible fluids ρ t = 0 and ρ = 0.
38 7. Mai / 57 Conservation of Momentum & Mass ( ) ( ) ρ u u t + (ρu) + ρ t + u u = f (38) The second term corresponds to the fluid density times its acceleration. Thus, for a velocity v of the fluid, the acceleration at a fixed point in space is v t. However, we also need to take into account velocity changes because of translocations such that the acceleration is given as v t + v v x x + v v y y + v v z z = v t such that the fluid acceleration is given by + (v )v (39) ( ) v ρ t + (v )v. (40)
39 7. Mai / 57 Acceleration ( ) v ρ t + (v )v = m acceleration = F V V = f. (41) According to Newton s law, mass times acceleration is equal to the force on that particular volume element. So what forces f act on the fluid?
40 7. Mai / 57 Hydrostatics: Fluids at Rest We start with fluids at rest. When liquids are at rest, there are no shear forces (not even for viscous fluids). The law of hydrostatics, therefore, is that stresses are always normal to any surface inside the fluid. The normal force per uni area is called the pressure. Since there is no shear in a static fluid, it follows that the pressure stress is the same in all directions. The pressure in a resting fluid may, however, vary from place to place such that we have pressure p at x and pressure p + p dx at x + dx such that the resulting force is given by x F = ( p (p + p ) x dx) dydz = p dv (42) x and the force density per unit volume as f = F V = p. (43)
41 7. Mai / 57 Friction in Moving Fluids == Viscosity When a fluid is set in motion, different parts of the fluid move with different velocities. Just as there is friction when one surface of a solid slides over another, so there is friction when one layer of a fluid slides over another. This friction in fluids is called viscosity.. Imagine a layer of fluid of thickness s between two flat plates. The upper plate moves at velocity v. To maintain the moving plate at a constant speed, it is found experimentally that a force F is required which is directly proportional to the velocity v, inversely proportional to the separation s, and directly proportional to the area of the moving plate A, F = η Av s. (44) The proportionality constant η is called the coefficient of viscosity.
42 Hydrodynamics: Moving Fluids In a dynamic situation, shear stress can build up in a viscous fluid. If the coefficient of dynamic viscosity is constant we have f = p + µ u. (45) In the most general form (for compressible fluids) we have ( ) ( ) ρ u u t + (ρu) +ρ t + u u = p+µ( u+ 1 3 ( u))+f In case of incompressible flow ρ t = 0 ρ = 0 1 ( u) 3 = 0 [ 0 for spatially inhomogenuous mass source] Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
43 7. Mai / 57 Units & Magnitudes Dynamic viscosity µ 1 Pa s for tissue. Density of water ρ 10 3 kg/m 3. Kinematic viscosity is then ν = µ m2 ρ 10 3 s. Reynolds number: Re = L U ν = with characteristic length scale L 10 3 m and characteristic speed U = s m/s = m/s.
44 Models of Limb Bud Growth Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
45 A model of Limb Bud Growth Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
46 Navier-Stokes Model of Limb Bud Growth Navier-Stokes equations: (Motion of a viscous fluid - Tissue as a viscous, incompressible fluid. ) ρ ( ) u t + u u = p + µ( u + 1 ( u)) + F 3 Continuity equation: (Conservation of mass - Volume increases due to proliferation) ρ u = S(c) Boundary Forces: (Forces induced by the Ectoderm) F = f (s, t)δ(x X(s, t)ds Reaction-diffusion-convection: (Signaling Network) Ω c + (uc) = D c + R(c) t Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
47 Signalling-dependent Growth Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
48 Signalling-dependent Growth Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
49 3D Limb Bud Shapes from OPT Computational Biology Group (CoBi), D-BSSE, ETHZ 7. Mai / 57 Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16
50 Shape Changes as the result of proliferation? Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
51 Change in Shape over 6h of development Computational Biology Group (CoBi), D-BSSE, ETHZ 7. Mai / 57 Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16
52 Proliferation Rates in the Limb Bud Computational Biology Group (CoBi), D-BSSE, ETHZ 7. Mai / 57 Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16
53 Proliferation insufficient predictor of shape change Computational Biology Group (CoBi), D-BSSE, ETHZ 7. Mai / 57 Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16
54 Numerical Optimization Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
55 Optimized Rates include Shrinkage Computational Biology Group (CoBi), D-BSSE, ETHZ 7. Mai / 57 Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16
56 SUMMARY OF LIMB BUD GROWTH MODELS Computational Biology Group (CoBi), D-BSSE, ETHZ Prof Dagmar Iber, PhD DPhil Lecture 8 MSc 2015/16 7. Mai / 57
57 7. Mai / 57 Thanks!! Thanks for your attention! Slides for this talk will be available at:
Mechanics PhD Preliminary Spring 2017
Mechanics PhD Preliminary Spring 2017 1. (10 points) Consider a body Ω that is assembled by gluing together two separate bodies along a flat interface. The normal vector to the interface is given by n
More informationGame Physics. Game and Media Technology Master Program - Utrecht University. Dr. Nicolas Pronost
Game and Media Technology Master Program - Utrecht University Dr. Nicolas Pronost Soft body physics Soft bodies In reality, objects are not purely rigid for some it is a good approximation but if you hit
More informationNDT&E Methods: UT. VJ Technologies CAVITY INSPECTION. Nondestructive Testing & Evaluation TPU Lecture Course 2015/16.
CAVITY INSPECTION NDT&E Methods: UT VJ Technologies NDT&E Methods: UT 6. NDT&E: Introduction to Methods 6.1. Ultrasonic Testing: Basics of Elasto-Dynamics 6.2. Principles of Measurement 6.3. The Pulse-Echo
More informationFundamentals of Fluid Dynamics: Elementary Viscous Flow
Fundamentals of Fluid Dynamics: Elementary Viscous Flow Introductory Course on Multiphysics Modelling TOMASZ G. ZIELIŃSKI bluebox.ippt.pan.pl/ tzielins/ Institute of Fundamental Technological Research
More informationMechanics of Earthquakes and Faulting
Mechanics of Earthquakes and Faulting www.geosc.psu.edu/courses/geosc508 Standard Solids and Fracture Fluids: Mechanical, Chemical Effects Effective Stress Dilatancy Hardening and Stability Mead, 1925
More informationSoft Bodies. Good approximation for hard ones. approximation breaks when objects break, or deform. Generalization: soft (deformable) bodies
Soft-Body Physics Soft Bodies Realistic objects are not purely rigid. Good approximation for hard ones. approximation breaks when objects break, or deform. Generalization: soft (deformable) bodies Deformed
More informationChapter 1. Continuum mechanics review. 1.1 Definitions and nomenclature
Chapter 1 Continuum mechanics review We will assume some familiarity with continuum mechanics as discussed in the context of an introductory geodynamics course; a good reference for such problems is Turcotte
More informationPhysics of Continuous media
Physics of Continuous media Sourendu Gupta TIFR, Mumbai, India Classical Mechanics 2012 October 26, 2012 Deformations of continuous media If a body is deformed, we say that the point which originally had
More informationMacroscopic theory Rock as 'elastic continuum'
Elasticity and Seismic Waves Macroscopic theory Rock as 'elastic continuum' Elastic body is deformed in response to stress Two types of deformation: Change in volume and shape Equations of motion Wave
More informationContinuum Mechanics. Continuum Mechanics and Constitutive Equations
Continuum Mechanics Continuum Mechanics and Constitutive Equations Continuum mechanics pertains to the description of mechanical behavior of materials under the assumption that the material is a uniform
More information20. Rheology & Linear Elasticity
I Main Topics A Rheology: Macroscopic deformation behavior B Linear elasticity for homogeneous isotropic materials 10/29/18 GG303 1 Viscous (fluid) Behavior http://manoa.hawaii.edu/graduate/content/slide-lava
More informationPEAT SEISMOLOGY Lecture 2: Continuum mechanics
PEAT8002 - SEISMOLOGY Lecture 2: Continuum mechanics Nick Rawlinson Research School of Earth Sciences Australian National University Strain Strain is the formal description of the change in shape of a
More informationRock Rheology GEOL 5700 Physics and Chemistry of the Solid Earth
Rock Rheology GEOL 5700 Physics and Chemistry of the Solid Earth References: Turcotte and Schubert, Geodynamics, Sections 2.1,-2.4, 2.7, 3.1-3.8, 6.1, 6.2, 6.8, 7.1-7.4. Jaeger and Cook, Fundamentals of
More informationFundamentals of Linear Elasticity
Fundamentals of Linear Elasticity Introductory Course on Multiphysics Modelling TOMASZ G. ZIELIŃSKI bluebox.ippt.pan.pl/ tzielins/ Institute of Fundamental Technological Research of the Polish Academy
More informationLecture 3: 1. Lecture 3.
Lecture 3: 1 Lecture 3. Lecture 3: 2 Plan for today Summary of the key points of the last lecture. Review of vector and tensor products : the dot product (or inner product ) and the cross product (or vector
More informationBasic Equations of Elasticity
A Basic Equations of Elasticity A.1 STRESS The state of stress at any point in a loaded bo is defined completely in terms of the nine components of stress: σ xx,σ yy,σ zz,σ xy,σ yx,σ yz,σ zy,σ zx,andσ
More informationElements of Continuum Elasticity. David M. Parks Mechanics and Materials II February 25, 2004
Elements of Continuum Elasticity David M. Parks Mechanics and Materials II 2.002 February 25, 2004 Solid Mechanics in 3 Dimensions: stress/equilibrium, strain/displacement, and intro to linear elastic
More informationNumerical Heat and Mass Transfer
Master Degree in Mechanical Engineering Numerical Heat and Mass Transfer 15-Convective Heat Transfer Fausto Arpino f.arpino@unicas.it Introduction In conduction problems the convection entered the analysis
More informationViscous Fluids. Amanda Meier. December 14th, 2011
Viscous Fluids Amanda Meier December 14th, 2011 Abstract Fluids are represented by continuous media described by mass density, velocity and pressure. An Eulerian description of uids focuses on the transport
More informationChapter 9: Differential Analysis
9-1 Introduction 9-2 Conservation of Mass 9-3 The Stream Function 9-4 Conservation of Linear Momentum 9-5 Navier Stokes Equation 9-6 Differential Analysis Problems Recall 9-1 Introduction (1) Chap 5: Control
More informationEMA 3702 Mechanics & Materials Science (Mechanics of Materials) Chapter 2 Stress & Strain - Axial Loading
MA 3702 Mechanics & Materials Science (Mechanics of Materials) Chapter 2 Stress & Strain - Axial Loading MA 3702 Mechanics & Materials Science Zhe Cheng (2018) 2 Stress & Strain - Axial Loading Statics
More informationIntroduction to Fluid Mechanics
Introduction to Fluid Mechanics Tien-Tsan Shieh April 16, 2009 What is a Fluid? The key distinction between a fluid and a solid lies in the mode of resistance to change of shape. The fluid, unlike the
More informationChapter 9: Differential Analysis of Fluid Flow
of Fluid Flow Objectives 1. Understand how the differential equations of mass and momentum conservation are derived. 2. Calculate the stream function and pressure field, and plot streamlines for a known
More information3D Elasticity Theory
3D lasticity Theory Many structural analysis problems are analysed using the theory of elasticity in which Hooke s law is used to enforce proportionality between stress and strain at any deformation level.
More informationChapter 1 Fluid Characteristics
Chapter 1 Fluid Characteristics 1.1 Introduction 1.1.1 Phases Solid increasing increasing spacing and intermolecular liquid latitude of cohesive Fluid gas (vapor) molecular force plasma motion 1.1.2 Fluidity
More informationStress, Strain, and Viscosity. San Andreas Fault Palmdale
Stress, Strain, and Viscosity San Andreas Fault Palmdale Solids and Liquids Solid Behavior: Liquid Behavior: - elastic - fluid - rebound - no rebound - retain original shape - shape changes - small deformations
More informationChapter 2: Basic Governing Equations
-1 Reynolds Transport Theorem (RTT) - Continuity Equation -3 The Linear Momentum Equation -4 The First Law of Thermodynamics -5 General Equation in Conservative Form -6 General Equation in Non-Conservative
More informationIntroduction to Marine Hydrodynamics
1896 1920 1987 2006 Introduction to Marine Hydrodynamics (NA235) Department of Naval Architecture and Ocean Engineering School of Naval Architecture, Ocean & Civil Engineering First Assignment The first
More information- Marine Hydrodynamics. Lecture 4. Knowns Equations # Unknowns # (conservation of mass) (conservation of momentum)
2.20 - Marine Hydrodynamics, Spring 2005 Lecture 4 2.20 - Marine Hydrodynamics Lecture 4 Introduction Governing Equations so far: Knowns Equations # Unknowns # density ρ( x, t) Continuity 1 velocities
More informationMechanics of Earthquakes and Faulting
Mechanics of Earthquakes and Faulting www.geosc.psu.edu/courses/geosc508 Overview Milestones in continuum mechanics Concepts of modulus and stiffness. Stress-strain relations Elasticity Surface and body
More informationAgricultural Science 1B Principles & Processes in Agriculture. Mike Wheatland
Agricultural Science 1B Principles & Processes in Agriculture Mike Wheatland (m.wheatland@physics.usyd.edu.au) Outline - Lectures weeks 9-12 Chapter 6: Balance in nature - description of energy balance
More informationNORMAL STRESS. The simplest form of stress is normal stress/direct stress, which is the stress perpendicular to the surface on which it acts.
NORMAL STRESS The simplest form of stress is normal stress/direct stress, which is the stress perpendicular to the surface on which it acts. σ = force/area = P/A where σ = the normal stress P = the centric
More informationChapter 5. The Differential Forms of the Fundamental Laws
Chapter 5 The Differential Forms of the Fundamental Laws 1 5.1 Introduction Two primary methods in deriving the differential forms of fundamental laws: Gauss s Theorem: Allows area integrals of the equations
More informationLecture 7. Properties of Materials
MIT 3.00 Fall 2002 c W.C Carter 55 Lecture 7 Properties of Materials Last Time Types of Systems and Types of Processes Division of Total Energy into Kinetic, Potential, and Internal Types of Work: Polarization
More informationA short review of continuum mechanics
A short review of continuum mechanics Professor Anette M. Karlsson, Department of Mechanical ngineering, UD September, 006 This is a short and arbitrary review of continuum mechanics. Most of this material
More informationIntroduction to Seismology Spring 2008
MIT OpenCourseWare http://ocw.mit.edu 12.510 Introduction to Seismology Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. Stress and Strain
More informationLecture Administration. 7.2 Continuity equation. 7.3 Boussinesq approximation
Lecture 7 7.1 Administration Hand back Q3, PS3. No class next Tuesday (October 7th). Class a week from Thursday (October 9th) will be a guest lecturer. Last question in PS4: Only take body force to τ stage.
More informationChapter 2: Fluid Dynamics Review
7 Chapter 2: Fluid Dynamics Review This chapter serves as a short review of basic fluid mechanics. We derive the relevant transport equations (or conservation equations), state Newton s viscosity law leading
More informationEART162: PLANETARY INTERIORS
EART162: PLANETARY INTERIORS Francis Nimmo Last Week Global gravity variations arise due to MoI difference (J 2 ) We can also determine C, the moment of inertia, either by observation (precession) or by
More informationMechanical Properties of Materials
Mechanical Properties of Materials Strains Material Model Stresses Learning objectives Understand the qualitative and quantitative description of mechanical properties of materials. Learn the logic of
More informationDynamics of the Mantle and Lithosphere ETH Zürich Continuum Mechanics in Geodynamics: Equation cheat sheet
Dynamics of the Mantle and Lithosphere ETH Zürich Continuum Mechanics in Geodynamics: Equation cheat sheet or all equations you will probably ever need Definitions 1. Coordinate system. x,y,z or x 1,x
More informationConstitutive Equations
Constitutive quations David Roylance Department of Materials Science and ngineering Massachusetts Institute of Technology Cambridge, MA 0239 October 4, 2000 Introduction The modules on kinematics (Module
More informationChapter 26 Elastic Properties of Materials
Chapter 26 Elastic Properties of Materials 26.1 Introduction... 1 26.2 Stress and Strain in Tension and Compression... 2 26.3 Shear Stress and Strain... 4 Example 26.1: Stretched wire... 5 26.4 Elastic
More information7 The Navier-Stokes Equations
18.354/12.27 Spring 214 7 The Navier-Stokes Equations In the previous section, we have seen how one can deduce the general structure of hydrodynamic equations from purely macroscopic considerations and
More informationElasticity in two dimensions 1
Elasticity in two dimensions 1 Elasticity in two dimensions Chapters 3 and 4 of Mechanics of the Cell, as well as its Appendix D, contain selected results for the elastic behavior of materials in two and
More informationFluid Mechanics Abdusselam Altunkaynak
Fluid Mechanics Abdusselam Altunkaynak 1. Unit systems 1.1 Introduction Natural events are independent on units. The unit to be used in a certain variable is related to the advantage that we get from it.
More informationMathematical Theory of Non-Newtonian Fluid
Mathematical Theory of Non-Newtonian Fluid 1. Derivation of the Incompressible Fluid Dynamics 2. Existence of Non-Newtonian Flow and its Dynamics 3. Existence in the Domain with Boundary Hyeong Ohk Bae
More informationSurface force on a volume element.
STRESS and STRAIN Reading: Section. of Stein and Wysession. In this section, we will see how Newton s second law and Generalized Hooke s law can be used to characterize the response of continuous medium
More information3.2 Hooke s law anisotropic elasticity Robert Hooke ( ) Most general relationship
3.2 Hooke s law anisotropic elasticity Robert Hooke (1635-1703) Most general relationship σ = C ε + C ε + C ε + C γ + C γ + C γ 11 12 yy 13 zz 14 xy 15 xz 16 yz σ = C ε + C ε + C ε + C γ + C γ + C γ yy
More informationGetting started: CFD notation
PDE of p-th order Getting started: CFD notation f ( u,x, t, u x 1,..., u x n, u, 2 u x 1 x 2,..., p u p ) = 0 scalar unknowns u = u(x, t), x R n, t R, n = 1,2,3 vector unknowns v = v(x, t), v R m, m =
More informationAE/ME 339. Computational Fluid Dynamics (CFD) K. M. Isaac. Momentum equation. Computational Fluid Dynamics (AE/ME 339) MAEEM Dept.
AE/ME 339 Computational Fluid Dynamics (CFD) 9//005 Topic7_NS_ F0 1 Momentum equation 9//005 Topic7_NS_ F0 1 Consider the moving fluid element model shown in Figure.b Basis is Newton s nd Law which says
More informationFluid Dynamics Exercises and questions for the course
Fluid Dynamics Exercises and questions for the course January 15, 2014 A two dimensional flow field characterised by the following velocity components in polar coordinates is called a free vortex: u r
More information3 2 6 Solve the initial value problem u ( t) 3. a- If A has eigenvalues λ =, λ = 1 and corresponding eigenvectors 1
Math Problem a- If A has eigenvalues λ =, λ = 1 and corresponding eigenvectors 1 3 6 Solve the initial value problem u ( t) = Au( t) with u (0) =. 3 1 u 1 =, u 1 3 = b- True or false and why 1. if A is
More information1. The Properties of Fluids
1. The Properties of Fluids [This material relates predominantly to modules ELP034, ELP035] 1.1 Fluids 1.1 Fluids 1.2 Newton s Law of Viscosity 1.3 Fluids Vs Solids 1.4 Liquids Vs Gases 1.5 Causes of viscosity
More information[5] Stress and Strain
[5] Stress and Strain Page 1 of 34 [5] Stress and Strain [5.1] Internal Stress of Solids [5.2] Design of Simple Connections (will not be covered in class) [5.3] Deformation and Strain [5.4] Hooke s Law
More informationINTRODUCTION TO STRAIN
SIMPLE STRAIN INTRODUCTION TO STRAIN In general terms, Strain is a geometric quantity that measures the deformation of a body. There are two types of strain: normal strain: characterizes dimensional changes,
More informationObjectives: After completion of this module, you should be able to:
Chapter 12 Objectives: After completion of this module, you should be able to: Demonstrate your understanding of elasticity, elastic limit, stress, strain, and ultimate strength. Write and apply formulas
More informationFinite Element Method in Geotechnical Engineering
Finite Element Method in Geotechnical Engineering Short Course on + Dynamics Boulder, Colorado January 5-8, 2004 Stein Sture Professor of Civil Engineering University of Colorado at Boulder Contents Steps
More informationSEISMOLOGY I. Laurea Magistralis in Physics of the Earth and of the Environment. Elasticity. Fabio ROMANELLI
SEISMOLOGY I Laurea Magistralis in Physics of the Earth and of the Environment Elasticity Fabio ROMANELLI Dept. Earth Sciences Università degli studi di Trieste romanel@dst.units.it 1 Elasticity and Seismic
More informationComputer Fluid Dynamics E181107
Computer Fluid Dynamics E181107 2181106 Transport equations, Navier Stokes equations Remark: foils with black background could be skipped, they are aimed to the more advanced courses Rudolf Žitný, Ústav
More informationConservation of Mass. Computational Fluid Dynamics. The Equations Governing Fluid Motion
http://www.nd.edu/~gtryggva/cfd-course/ http://www.nd.edu/~gtryggva/cfd-course/ Computational Fluid Dynamics Lecture 4 January 30, 2017 The Equations Governing Fluid Motion Grétar Tryggvason Outline Derivation
More information2. Conservation Equations for Turbulent Flows
2. Conservation Equations for Turbulent Flows Coverage of this section: Review of Tensor Notation Review of Navier-Stokes Equations for Incompressible and Compressible Flows Reynolds & Favre Averaging
More informationSummary PHY101 ( 2 ) T / Hanadi Al Harbi
الكمية Physical Quantity القانون Low التعريف Definition الوحدة SI Unit Linear Momentum P = mθ be equal to the mass of an object times its velocity. Kg. m/s vector quantity Stress F \ A the external force
More informationExplaining and modelling the rheology of polymeric fluids with the kinetic theory
Explaining and modelling the rheology of polymeric fluids with the kinetic theory Dmitry Shogin University of Stavanger The National IOR Centre of Norway IOR Norway 2016 Workshop April 25, 2016 Overview
More informationFurther Applications of Newton s Laws - Friction Static and Kinetic Friction
urther pplications of Newton s Laws - riction Static and Kinetic riction The normal force is related to friction. When two surfaces slid over one another, they experience a force do to microscopic contact
More informationReview of fluid dynamics
Chapter 2 Review of fluid dynamics 2.1 Preliminaries ome basic concepts: A fluid is a substance that deforms continuously under stress. A Material olume is a tagged region that moves with the fluid. Hence
More information1 Hooke s law, stiffness, and compliance
Non-quilibrium Continuum Physics TA session #5 TA: Yohai Bar Sinai 3.04.206 Linear elasticity I This TA session is the first of three at least, maybe more) in which we ll dive deep deep into linear elasticity
More informationChapter Two: Mechanical Properties of materials
Chapter Two: Mechanical Properties of materials Time : 16 Hours An important consideration in the choice of a material is the way it behave when subjected to force. The mechanical properties of a material
More informationCHAPTER 8 ENTROPY GENERATION AND TRANSPORT
CHAPTER 8 ENTROPY GENERATION AND TRANSPORT 8.1 CONVECTIVE FORM OF THE GIBBS EQUATION In this chapter we will address two questions. 1) How is Gibbs equation related to the energy conservation equation?
More informationDifferential relations for fluid flow
Differential relations for fluid flow In this approach, we apply basic conservation laws to an infinitesimally small control volume. The differential approach provides point by point details of a flow
More informationA Study on Numerical Solution to the Incompressible Navier-Stokes Equation
A Study on Numerical Solution to the Incompressible Navier-Stokes Equation Zipeng Zhao May 2014 1 Introduction 1.1 Motivation One of the most important applications of finite differences lies in the field
More informationFlow and Transport. c(s, t)s ds,
Flow and Transport 1. The Transport Equation We shall describe the transport of a dissolved chemical by water that is traveling with uniform velocity ν through a long thin tube G with uniform cross section
More informationFluid Mechanics. If deformation is small, the stress in a body is proportional to the corresponding
Fluid Mechanics HOOKE'S LAW If deformation is small, the stress in a body is proportional to the corresponding strain. In the elasticity limit stress and strain Stress/strain = Const. = Modulus of elasticity.
More informationEntropy generation and transport
Chapter 7 Entropy generation and transport 7.1 Convective form of the Gibbs equation In this chapter we will address two questions. 1) How is Gibbs equation related to the energy conservation equation?
More informationNavier-Stokes Equation: Principle of Conservation of Momentum
Navier-tokes Equation: Principle of Conservation of Momentum R. hankar ubramanian Department of Chemical and Biomolecular Engineering Clarkson University Newton formulated the principle of conservation
More informationStress Strain Elasticity Modulus Young s Modulus Shear Modulus Bulk Modulus. Case study
Stress Strain Elasticity Modulus Young s Modulus Shear Modulus Bulk Modulus Case study 2 In field of Physics, it explains how an object deforms under an applied force Real rigid bodies are elastic we can
More informationABHELSINKI UNIVERSITY OF TECHNOLOGY
ABHELSINKI UNIVERSITY OF TECHNOLOGY TECHNISCHE UNIVERSITÄT HELSINKI UNIVERSITE DE TECHNOLOGIE D HELSINKI A posteriori error analysis for the Morley plate element Jarkko Niiranen Department of Structural
More informationReview of Strain Energy Methods and Introduction to Stiffness Matrix Methods of Structural Analysis
uke University epartment of Civil and Environmental Engineering CEE 42L. Matrix Structural Analysis Henri P. Gavin Fall, 22 Review of Strain Energy Methods and Introduction to Stiffness Matrix Methods
More informationUniversity of Hail Faculty of Engineering DEPARTMENT OF MECHANICAL ENGINEERING. ME Fluid Mechanics Lecture notes. Chapter 1
University of Hail Faculty of Engineering DEPARTMENT OF MECHANICAL ENGINEERING ME 311 - Fluid Mechanics Lecture notes Chapter 1 Introduction and fluid properties Prepared by : Dr. N. Ait Messaoudene Based
More informationBasic Concepts of Strain and Tilt. Evelyn Roeloffs, USGS June 2008
Basic Concepts of Strain and Tilt Evelyn Roeloffs, USGS June 2008 1 Coordinates Right-handed coordinate system, with positions along the three axes specified by x,y,z. x,y will usually be horizontal, and
More information3.22 Mechanical Properties of Materials Spring 2008
MIT OpenCourseWare http://ocw.mit.edu 3.22 Mechanical Properties of Materials Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. Quiz #1 Example
More informationContinuum mechanism: Stress and strain
Continuum mechanics deals with the relation between forces (stress, σ) and deformation (strain, ε), or deformation rate (strain rate, ε). Solid materials, rigid, usually deform elastically, that is the
More informationChapter 13 ELASTIC PROPERTIES OF MATERIALS
Physics Including Human Applications 280 Chapter 13 ELASTIC PROPERTIES OF MATERIALS GOALS When you have mastered the contents of this chapter, you will be able to achieve the following goals: Definitions
More informationChapter 1. Governing Equations of GFD. 1.1 Mass continuity
Chapter 1 Governing Equations of GFD The fluid dynamical governing equations consist of an equation for mass continuity, one for the momentum budget, and one or more additional equations to account for
More informationChapter 2 CONTINUUM MECHANICS PROBLEMS
Chapter 2 CONTINUUM MECHANICS PROBLEMS The concept of treating solids and fluids as though they are continuous media, rather thancomposedofdiscretemolecules, is one that is widely used in most branches
More informationElements of Rock Mechanics
Elements of Rock Mechanics Stress and strain Creep Constitutive equation Hooke's law Empirical relations Effects of porosity and fluids Anelasticity and viscoelasticity Reading: Shearer, 3 Stress Consider
More informationUnderstand basic stress-strain response of engineering materials.
Module 3 Constitutive quations Learning Objectives Understand basic stress-strain response of engineering materials. Quantify the linear elastic stress-strain response in terms of tensorial quantities
More informationENGR Heat Transfer II
ENGR 7901 - Heat Transfer II Convective Heat Transfer 1 Introduction In this portion of the course we will examine convection heat transfer principles. We are now interested in how to predict the value
More informationQuick Recapitulation of Fluid Mechanics
Quick Recapitulation of Fluid Mechanics Amey Joshi 07-Feb-018 1 Equations of ideal fluids onsider a volume element of a fluid of density ρ. If there are no sources or sinks in, the mass in it will change
More information3. BEAMS: STRAIN, STRESS, DEFLECTIONS
3. BEAMS: STRAIN, STRESS, DEFLECTIONS The beam, or flexural member, is frequently encountered in structures and machines, and its elementary stress analysis constitutes one of the more interesting facets
More informationCHAPTER 1 Fluids and their Properties
FLUID MECHANICS Gaza CHAPTER 1 Fluids and their Properties Dr. Khalil Mahmoud ALASTAL Objectives of this Chapter: Define the nature of a fluid. Show where fluid mechanics concepts are common with those
More informationLinear Elasticity ( ) Objectives. Equipment. Introduction. ε is then
Linear Elasticity Objectives In this lab you will measure the Young s Modulus of a steel wire. In the process, you will gain an understanding of the concepts of stress and strain. Equipment Young s Modulus
More informationContinuum mechanics V. Constitutive equations. 1. Constitutive equation: definition and basic axioms
Continuum mechanics office Math 0.107 ales.janka@unifr.ch http://perso.unifr.ch/ales.janka/mechanics Mars 16, 2011, Université de Fribourg 1. Constitutive equation: definition and basic axioms Constitutive
More informationSymmetric Bending of Beams
Symmetric Bending of Beams beam is any long structural member on which loads act perpendicular to the longitudinal axis. Learning objectives Understand the theory, its limitations and its applications
More informationWave and Elasticity Equations
1 Wave and lasticity quations Now let us consider the vibrating string problem which is modeled by the one-dimensional wave equation. Suppose that a taut string is suspended by its extremes at the points
More informationFluid Mechanics II Viscosity and shear stresses
Fluid Mechanics II Viscosity and shear stresses Shear stresses in a Newtonian fluid A fluid at rest can not resist shearing forces. Under the action of such forces it deforms continuously, however small
More information202 Index. failure, 26 field equation, 122 force, 1
Index acceleration, 12, 161 admissible function, 155 admissible stress, 32 Airy's stress function, 122, 124 d'alembert's principle, 165, 167, 177 amplitude, 171 analogy, 76 anisotropic material, 20 aperiodic
More informationAMME2261: Fluid Mechanics 1 Course Notes
Module 1 Introduction and Fluid Properties Introduction Matter can be one of two states: solid or fluid. A fluid is a substance that deforms continuously under the application of a shear stress, no matter
More informationV (r,t) = i ˆ u( x, y,z,t) + ˆ j v( x, y,z,t) + k ˆ w( x, y, z,t)
IV. DIFFERENTIAL RELATIONS FOR A FLUID PARTICLE This chapter presents the development and application of the basic differential equations of fluid motion. Simplifications in the general equations and common
More informationVariable Definition Notes & comments
Extended base dimension system Pi-theorem (also definition of physical quantities, ) Physical similarity Physical similarity means that all Pi-parameters are equal Galileo-number (solid mechanics) Reynolds
More information