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2
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2answers
101 views

Is it possible that Cauchy stress be asymmetric?

According to conservation of linear momentum and angular momentum, one can derive that Cauchy stress tensor is symmetric and hence has only 6 independent components. Is it possible that, when breaking ...
8
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3answers
19k views

Hollow Tube Stronger than Solid bar of same Outside Diameter (O.D.)?

I was listening to some co-workers talking about problems meeting stiffness requirements. Someone said that even with a solid metal rod (instead of the existing tube) we could not meet stiffness ...
0
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0answers
44 views

Types of semiconductor relaxation

Ok, so you've basically got tensile and compression strain in a lattice mismatched material right? So as you're epitaxially layering the material, the strained material is deforming more and more ...
0
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1answer
263 views

Maximum Weight Sustained by wire / Breaking limit of wire [closed]

I know that breaking stress depends on material of wire, not on the diameter or the length of wire. and also that Breaking load depends on the area of cross section of wire. But still i have a ...
3
votes
1answer
65 views

in Science materials, what is difference b/w E and G?

I'm studying Science Materials on Callister's Materials Science and Engineering: An Introduction. I've never studied Mechanics (except for basic Physics courses), so I was wandering: when talking ...
2
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0answers
81 views

Stress calculations in a perforated paper

You have a sheet of paper (torn out of a good quality foolscap notebook) as shown above, and you start pulling it apart with both your hands (forces indicating by the blue arrows). Its difficult to ...
0
votes
0answers
233 views

Caculating thermal stresses in a composite rod

The Question Between two rigid walls separated by a distance $l_1+l_2$, two rods of equal cross-section area $A$, and length, coefficient of linear expansion and Young's modulus $l_1, ...
0
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2answers
84 views

Can stress be observed directly?

Strain can be directly observed using e.g. a ruler. Can (internal) stress be directly observed?
0
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1answer
155 views

Why does the pure shear term / strain deviator tensor have non-zero entries on the main diagonal?

In a textbook of mine an operation is performed, of which I think the goal is to get zeros on the main diagonal of a matrix (the matrix represents strain). But im not sure that is the goal and Im also ...
1
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0answers
23 views

Solid state diffusion as a function of shear stress

I am hoping to get some clarification on the impact of shear stress or shear strain on atomic diffusion in a metallic solid. More specifically, will the kinetics for the dissolution of secondary phase ...
2
votes
2answers
351 views

It would take an elephant, balanced on a pencil, to break through a sheet of graphene the thickness of Cling Film

I'm currently doing some work on a presentation about graphene, and have come across numerous articles which claim something along the lines of It would take an elephant, balanced on a pencil, to ...
0
votes
2answers
140 views

Stretching a rod? [closed]

The stress applied on a rod is linearly proportional to its strain. But shouldn't the opposite be true? I mean if you pull particles further apart doesn't the force they apply on each other decrease ...
4
votes
3answers
455 views

Does zero strain always imply zero stress?

In solid mechanics, can I always assume that if an object undergoes no strain, then no stress is applied to it? I think it's true only because I can't seem to find a counter-example.
3
votes
2answers
2k views

How does the energy in a standing wave travel beyond a node?

In a standing wave, how does energy travel past a node? It should just get reflected. Assume the case of first overtone and you strike the string at a place. How will energy distribute itself? If it ...
2
votes
2answers
336 views

What is the motivation for Mohr's circle?

I am very puzzled by the motivation for Mohr's circle in Wikipedia here. Please, explain why we need something called "Mohr's circle". Use as little words as possible and be precise. Helper questions ...
2
votes
1answer
69 views

stress work of uniformly deforming continuum

I have a volume which is deforming (using explicit time-integration scheme) uniformly with velocity gradient $L$ and stress tensor $\sigma$. I would like to determine work done by the volume ...
1
vote
1answer
3k views

Calculating force absorbed by compression of a material (i.e. rubber)

Say I was trying to design padding to absorb impacts using polymers or similar materials, such as rubber. I have a good understanding of any relevant physics, most likely, but I wouldn't know where to ...
1
vote
1answer
548 views

Where I can find a torsional stiffness table for different types of stainless steels?

I am trying to comparing the torsional stiffness of different types of stainless steels. I googled the keywords but I could not find any useful information. Would anyone please give me some links ...
2
votes
0answers
58 views

If I roll an elastic plate into a cylinder, does it shrink?

Suppose I start with a rectangular elastic (to keep things simple, zero Poisson's ratio) sheet of length $2\pi R$, thickness $h$, and (immaterial) width $W$. I roll it up into a cylinder of radius ...
-1
votes
1answer
104 views

What is the $n$ in the formula in Solid Mechanics? [closed]

The formula is about the critical force for the elastic beam that is supported by its joints: $$ P_{cr} ~=~ n^2 \pi^2 \frac{EI}{ L^2} $$ It should be based on the book Parnes - Solid ...
0
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0answers
37 views

Photoelasticity and existence of stress

Shall we consider photoelasticity a non-mathematical, or purely visual, proof of the existence of stresses in mechanical structures undergoing external loading?
0
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0answers
56 views

What is the relationship between strain and electric current?

Strain or stress can be caused by different sources. I categorized theses sources as mechanical, thermal and electrical loads and formulated the total stress as follows: $$ \epsilon_{total} = ...
3
votes
1answer
1k views

What causes stress concentration (aka stress risers/raisers) at corners?

I've read a few explanations about why stress concentration occurs at sharp corners but I don't find the explanations intuitive. Can anyone explain it perhaps using an analogy such as atoms "holding ...
0
votes
0answers
21 views

Estimating the fatigue life of elastomer diaphragm [duplicate]

Disclaimer: I have asked this question before, but it got put on hold because it was judged as off-topic. I happened to disagree and explained my reasons in the comments, but they have been ignored, ...
-3
votes
1answer
7k views

Neutral axis of T shaped beam? [closed]

I am not a mechanics or physics student but a computer science student. I came across a question related to find neutral axis of figure but I do not have slightest idea of what it is and how to find ...
2
votes
2answers
100 views

Do all impacts create a wave-like disturbance in the medium through which they travel?

There is a scene in the first Matrix movie, where a helicopter strikes a skyscraper. The most interesting part is the 'slow-motion' bit where, as the helicopter strikes the building, a wave first ...
2
votes
2answers
2k views

Stress in a thick-walled pressure vessel

I can find many references that give the stress in the walls of a pressure vessel for spheres and tubes, but they all seem to be limited to a thin-wall approximation. I'll limit my writing here to ...
2
votes
1answer
64 views

Potential collapse during an earthquake? [closed]

I was asked to determine the shear forces on 12" diameter table legs supporting a few hundred pounds of static weight. How does one calculate or determine the potential force on the legs and/or ...
2
votes
0answers
294 views

Stress analysis of a cantilever beam using FDM

I am a CSE researcher with a not so in depth background of physics. As a part of my research in object modelling, I am trying to computationally figure out the stress for various objects by using ...
2
votes
1answer
323 views

Equivalent of the Kirsch Equations for an elliptical rather than circular hole

Is there an equivalent set of closed form equations to the Kirsch Equations but for an elliptical hole rather than a circular hole?
1
vote
1answer
135 views

Why can we analyse force balance on a dislocation?

Dislocation (like screw or edge dislocation) is not a 'real' thing, while Newton's laws only apply to a real object (no matter macroscopic, like stars, or microscopic, like atoms). In the derivation ...
5
votes
1answer
239 views

What happens when a piezo crystal is exposed to a vacuum?

Application of mechanical stress to a piezo crystal generates a charge. Quoting from wikipedia, a 1 cm3 cube of quartz with 2 kN (500 lbf) of correctly applied force can produce a voltage of 12500 ...
1
vote
1answer
138 views

Strain and stress tensor

I have problem by definition of strain and stress. From Gockenbach's book that our reference for FEM, we have $$\epsilon=\frac{\nabla u+ \nabla u^T}{2},$$ that $u$ is vector displacement, and ...
3
votes
1answer
208 views

Decomposition of deformation into bend, stretch and twist?

I'm wondering is there any way to decompose the deformation of an object into different components? For example, into stretching, bending and twisting part respectively? The decomposition could be ...
2
votes
0answers
51 views

What diameter is used to calculate stress in an elastomer whose cross sectional area changes continuously when streched?

Consider a cylindrical rope of rubbery elastomer with a radius (in inches) equal to the square root of the inverse of $\pi \rightarrow \sqrt \frac{1}{\pi} $ so that the cross sectional area is $1 \, ...
0
votes
1answer
107 views

Hollow stone columns provide more support?

In history class in elementary school I remember learning that the Greeks would build their stone columns hollow because they thought this provided more support. Is it true that a hollow column is ...
1
vote
4answers
1k views

What is a strain gauge and how do I use one?

As the title says, I have no idea what these things are or how to get or use one. Can I receive a simple explanation or links to one? I'm a computer engineer so I have very little physics/mechanical ...
2
votes
1answer
162 views

Why is $dL = L d\epsilon$?

Let's say there's a random elastic material. It's length is $L$ and it's tensile strain $\epsilon= (L-L_0)/L_0$ Now, when one pulls on it the following is true: $dW_{tot}=FdL =\sigma AdL=\sigma A L ...
0
votes
0answers
41 views

How do I minimize the the stress created by fore-aft forces?

My friends and I are designing a bench press spotter. Essentially, when the user needs help lifting the barbell due to muscle fatigue, an arm on each side of the user raises to provide assistance. ...
0
votes
0answers
463 views

Whats the contact area for elastic contact between a cylinder and a plane surface?

I am trying to determine the contact area between a cylinder and a plane surface of two different materials so that the plane lies tangent to the cylinder. There is elastic contact between the two ...
2
votes
3answers
546 views

Glass pipe cutting

I want to know how to quickly create the straightest possible breaks in glass pipes I apologise if this is only borderline suitable for a physics forum - I just hope experts with a lot of experience ...
3
votes
1answer
263 views

Material strain from spacetime curvature

Let's say that you moved an object made of rigid materials into a place with extreme tidal forces. Materials have a modulus of elasticity and a yield strength. Does the corresponding 3D geometric ...
0
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0answers
115 views

Continuum mechanics and effects of stress

Going to word this question a bit more straightforward than I may have before. Also, I'm trying to use baby formulas so I can grasp exactly what's going on. Object A has an elasticity of ...
2
votes
1answer
183 views

Is shear elasticity the same as shear modulus?

I've encountered both the terms "shear elasticity" and "shear modulus". Are these the same?
3
votes
1answer
635 views

Why does glass break at the line where you score it?

Why does it take such a small incision for the glass to break at that spot? Why is the structural strength of the material influenced by such a small imperfection?
2
votes
1answer
342 views

What is the two dimensional equivalent of a spring?

I'm trying to model isotropic linear elastic deformation in two dimensions. In one dimension, I know that a linear elastic material can be thought of as a spring which obeys Hooke's law $F=-k\Delta ...
2
votes
0answers
281 views

Free body diagram of stresses governing fracture propagation in a solid material

Reading this, I can intuitively understand that fractures propagate along the path of least resistance, creating "width in a direction that requires the least force". However, it is less intuitive ...
3
votes
1answer
1k views

Formulas for compressibility of solids

I am taking a course in mechanics this semester, as well as a course in reservoir physics. Both courses have sections devoted to pressure/compressibility of solids, but the formulas look slightly ...
1
vote
1answer
333 views

Euler's buckling formula applicable for impact calculations?

$$F = \frac{\pi^2 EI}{(KL)^2}$$ Is Euler's buckling formula applicable for impact calculations, considering speeds relevant for a car or aircraft crash? If there is a level where the formula ...
2
votes
1answer
387 views

Poisson effect formula for large deformations

English Wikipedia in the Poisson's ratio article gives an equation for large deformation: $$ \frac{\Delta d}{d}=-1+\frac{1}{\left(1+\dfrac{\Delta L}{L}\right)^\nu} $$ I couldn't find any reference ...