Questions related to the Continuum Mechanics Division of Elasticity. The bending of beams, deflection of rods, or in general, applications of Hooke's Law generalized to three dimensions.

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1answer
24 views

Particle attached in equilibrium to two elastic strings

The question I'm trying to answer is this: This is the solution: The only part of the solution I have a problem with is $x_{ps} + x_{qs}=l$, where $x_{ps}$ is the extension of the string from $P$ ...
4
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1answer
21 views

Which weapon can transfer more energy to a projectile: sling or slingshot?

Which weapon can transfer the most energy to a projectile, a sling or slingshot? Each is totally powered by a person, one stores energy in elastic the other kinetically. Which can store and transfer ...
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0answers
13 views

Interpretation of Evanescent Elastic Waves for Material Damage

In elastodynamic theory, when the slowness vector is imaginary, the resulting elastic waves are called evanescent. I have read that this corresponds to exponential decay. I have also read that complex ...
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2answers
29 views

Is it possible a linear compression to result in rotational movement? [on hold]

I am looking for a spring or elastic mechanism that I will compress linearly; and when I let it go, it will rotate. Is there such a mechanism or spring?
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4answers
142 views

Will a tennis ball go further if i hit it with the side of the racket?

If i hit a tennis ball 'properly' on the stringing, does it go further than if i rotate the racket 90 degrees in my hand and hit the ball with the same force, but on the side of the frame? I'm ...
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1answer
416 views

Fundamental frequency of a material and its Young's modulus

I wonder if there is a connection between fundamental frequency and Young's modulus of a material. For example, how to calculate the Young's modulus of a glass bar by knowing its frequency spectrum?
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0answers
37 views

Parabola or Catenary in this case?

Exhibit A: the flexible film sinks into the box due to lower internal pressure inside the box. question is, does the film form a paraboloid or a 3D catenary or neither? this is the usual method used ...
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2answers
35 views

Rubber on atomic scale during bending

When you compare rubber with steel whats the difference on the atomic scale when you bend it?
108
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3answers
4k views

Why is the vibration in my wire acting so oddly?

I was soldering a very thin wire today, and when I had one end firmly soldered, I accidentally bumped the wire diagonally with my tweezers. What I'd expect to happen is that the wire oscillates for a ...
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1answer
1k views

Inflating a balloon (expansion resistance)

I am doing a quick calculation on how to calculate the pressure needed to inflate a perfectly spherical balloon to a certain volume, however I have difficulties with the fact that the balloon (rubber) ...
0
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1answer
16 views

How does linear elasticity deal with Heaviside forces?

For a particular elastic material with prismatic geometry, I observed a linear relationship between stress and strain but the forces applied to the material are given by a step function where the ...
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0answers
14 views

relationship between creep and hysteresis

For a particular material that's suspected to be viscoelastic, I observe a hysteresis curve where the difference in elongation between the loading and unloading curves ranges between 5% and 10% for a ...
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2answers
42 views

theoretical explanation for smaller Young's modulus of silicone foam

I measured the Young's modulus of a rectangular silicone foam sample which is equivalent in material constitution to silicone rubber except that it is 80% empty. The Young's modulus for this foam was ...
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1answer
39 views

Marsden and Hughes Mathematical Foundations of Elasticity Derivation

in the beginning of the book they discuss transformation between coordinate systems and they use this to show that the velocity of a point transforms into that coordinate system;, in terms of the ...
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1answer
42 views

necessary and sufficient conditions for linear elasticity

If it's experimentally observed that a particular elastic isotropic material has a linear relationship between stress and strain for a certain range of stresses and strains, does it follow that a ...
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2answers
70 views

Estimating Young's Modulus

In order to measure the Young's modulus of a rectangular sample of elastic material I subject it to a vertical load along its major axis using weights of gradually increasing importance and measure ...
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3answers
66 views

the poisson ratio and conservation of volume

In order to measure the Poisson ratio of a rectangular sample of elastic material I subject it to a vertical load along its major axis using weights of gradually increasing importance and measure the ...
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2answers
60 views

Impulse in perfectly elastic collision

I am implementing this simplified model at the moment, and I am trying to get my head around the physics concepts behind this model. Event-Driven Simulation So the model has two parts, first is ...
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0answers
10 views

stress concentration and geometry of elastic sample

If a rectangular sample of rubber and a cylindrical sample of rubber are both stretched along their major axes I am told that there will be less uniform stress concentration in the rectangular sample. ...
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0answers
9 views

Bending and elastic torques origin problem

In the picture, the sheet of metal is hinged and rotated with angular acceleration alpha, bending is quite small. Problem I'm facing is, where is the origin for torque due to elastic forces (M), what ...
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2answers
557 views

Determining flexural modulus by performing 3 point bending test using hollow cylindrical tube

I would like to decide the flexural modulus of the material of plastic tube by performing 3 point bending test according to the ASTM D 790 procedure. In ASTM D 790, the form of the specimen is ...
0
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1answer
17 views

ultimate tensile strength for elastomers

I'm doing experiments with an elastomer and I'd like to know how I should determine tensile strength in practice. Is this the point where I begin to observe tears in the elastomer or where the ...
4
votes
1answer
203 views

What equation predicts at what point a stretched object comes apart?

I am creating a simulation and am interested in pulling stretchy things and when they break, like taffy. I imagine this is a bit tougher then a simple equation like gravity, but I have no idea. Is ...
0
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1answer
40 views

Understanding stress-strain calculations

I'm trying to compute the stress-strain curve for an elastic material with cylindrical geometry subject to an increasing uniaxial load. I understand that this requires: stress = $F/A_0$ where $A_0$, ...
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1answer
28 views

Understanding stress-relaxation for viscoelastic materials

I'm studying a viscoelastic material with a cylindrical geometry and I read that for fixed strain(i.e. fixed elongation), I should observe decreasing strain over time. Given that stress $= F/A_0$ ...
1
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1answer
23 views

Modeling rubber foams

Are there any good papers/texts on the subject of modeling the dynamics of rubber foams? So far I haven't found any good papers/texts that cover this particular subject and I've done some searching. ...
2
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1answer
109 views

Mathematical expression of energy storage

I'm trying to develop an idea which is as follows. Put simply, imagine a flat sheet of material which, when distorted (I.e. curved in the third dimension) stores energy. Now, by calculating the ...
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1answer
43 views

Studying dynamic elasticity for finite deformations

this is not a question asking for help with a problem but one asking for help where to begin serious study of elasticity, particularly that applied to dynamic systems. Most textbooks about elasticity ...
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11answers
13k views

Why is filling a balloon from your mouth much harder initially?

Why is it that when you first fill up a balloon, it's hard to get air through, but after inflating it a bit, it becomes much easier to further inflate the balloon?
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votes
2answers
309 views

Relationship of the volume of a plumbing system to pressure

How does the volume of water a plumbing system holds vary with water pressure? I know the ratio would include the modulus of elasticity of the plumbing material, the total surface area of the plumbing ...
2
votes
1answer
51 views

Are hardness, strength and toughness of materials not the same thing in a way?

I had to look through several videos and re-read Wikipedia statements about these material properties several times before I could even begin to differentiate them. However, now that I have found out ...
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1answer
33 views

“Poynting vector” for transverse waves in elastic solid

What is the expression or name for the vector that gives the direction and intensity associated with the energy flux or momentum flux carried by transverse waves in an elastic solid?
0
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0answers
33 views

derivation of elastic moduli in terms of compliance tensor, and reference textbook

I recently learned that the elastic modulus, namely Young's modulus and shear modulus can be written as in terms of compliance tensor, or elastic constants. The equations for cubic system are $$ \...
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1answer
25 views

Does silicone rubber have a fundamental frequency?

I'm wondering whether impulse excitation techniques may be used to derive the Young's Modulus and Poisson Ratio of Silicone rubber.
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0answers
17 views

Linear elasticity: can “extremal” strain tensors be in the interior of the body?

i am new to elastic theory. I have a question about linear elasticity. In each point $p$ of a body $\Omega$, the strain tensor has three eigenvalues $\lambda_1(p)\geq \lambda_2(p)\geq \lambda_3(p)$. ...
0
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1answer
39 views

About elongation produced in a body, when 2 forces of equal magnitude but opp. in direction are applied on a body

When 2 oppositely- directed forces are applied on the same body , they act at the body's center of mass(com). The vector sum of the forces thus becomes 0(zero). How do the forces then bring about ...
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0answers
11 views

Standard Minimal Reference Set of Poroelastic Parameters

I am coding a poroelastic reservoir simulator which requires the input of poroelastic parameters of the reservoir rocks. Detournay and Cheng, "Fundamentals of Poroelasticity" (1993) state that: ...
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1answer
35 views

Young's modulus and geometry of test material

When measuring Young's modulus in a material, does the geometry of the material actually matter? I have seen several references recommend that I use cylindrical pieces. But, wouldn't the tests work ...
0
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1answer
38 views

Poisson's ratio and change in volume

The Poisson's ratio $\nu$ is always less than $0.5$. A traction force ($\Delta L >0$) can cause an increase in volume, while a compression force ($\Delta L <0$) can only decrease the volume. $$...
0
votes
1answer
46 views

Why does a bungee jumper continue to move downwards beyond the equilibrium position of the jumper and cord?

When a bungee jumper jumps, ignoring the mass of the bungee cord, the jumper initially falls in freefall before an inelastic collision occurs between the jumper and cord, and the cord extends as the ...
1
vote
1answer
24 views

Hooke's Law in 3D and in plane stress problems

Using Lame's constants, the Hooke's law of isotropic materials in 3-dimensions can be written as: $$ \begin{aligned} \sigma_{ij}&=\lambda \varepsilon_{kk}\delta_{ij}+2\mu\varepsilon_{ij}=c_{ijk\...
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votes
2answers
37 views

Illustrating the definition of Young's modulus from spring factor

The relationship between Young's modulus $E$ and the spring factor $k$ from Hooke's law is $k=\frac{E A}{L_0}$ where $L_0$ is the initial length of the stretched material and $A$ the cross-...
3
votes
2answers
155 views

Derivation of elastic energy per unit volume

So I basically asked this question a little while back and didn't get much help, but I really need help, so I'm coming back and asking again. Looking at the section on Continuum Systems on the ...
1
vote
2answers
47 views

Speed of Sound in matter

So basically when it comes to the speed of sound, it is said that speed of sound in media is based on two main factors - 1)elasticity and 2)density from the formula V= $\sqrt{E/\rho }$ where E is ...
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2answers
600 views

Range of poissons ratio

I know the range of poisson's ratio is -1 to 0.5 but how do you arrive at this expression? I am a 11th grade student and I am not too familiar with advanced physics
1
vote
1answer
301 views

A moving brush on a vibrating surface

Hi group, I am a HS student in China preparing for a regional Young Physicist Tournament even. We are very puzzled about why would there be such movement. We would be grateful to see any inspiring ...
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2answers
95 views

Why does a ball eventually stop?

I was wondering, if the force of friction with the ground does not make any work on the ball and just give it the necessary torque to rotate (hence the consideration of static friction coefficient in ...
0
votes
2answers
136 views

Difference between stiffness and damping?

I understand stiffness as the extent to which an object (e.g. a mass spring) resists deformation from an applied force, or the rigidity of an object. And I understand damping as the energy ...
0
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0answers
18 views

Derivation of expression for sagging of a beam [duplicate]

I read in my physics textbook that: A bar of length $l$, breadth $b$ and depth $d$ when loaded at the centre by a load $W$ sags by an amount given by the expression $Wl^3/(4bd^3Y)$ where $Y$ ...
0
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1answer
19 views

What are the assumptions made when analysing a stretched elastic string from a thermodynamic aspect?

Consider a stretched elastic string. Then conducting a thermodynamic analysis of the elastic string. The approach is very similar to that used for $(P, V, T)$ systems, with the pressure and volume ...