# Questions tagged [stress-strain]

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### Why do we bend a book to keep it straight?

I noticed that I have been bending my book all along, when I was reading it with one hand. This also works for plane flexible sheets of any material. Illustration using an A4 sheet Without bending ...
2answers
14k views

### Why does dry spaghetti break into three pieces as opposed to only two?

You can try it with your own uncooked spaghetti if you want; it almost always breaks into three when you snap it. I am asking for a good physical theory on why this is along with evidence to back it ...
3answers
8k views

### Clarifying the actual definition of elasticity. Is steel really more elastic than rubber?

Yes, I know it's steel. It's everywhere on the web and I did google. But I seek enlightenment. My physics textbook defines elasticity as: Property by virtue of which a material regains its shape. ...
3answers
29k views

### Why is stress a tensor quantity?

Why is stress a tensor quantity? Why is pressure not a tensor? According to what I know pressure is an internal force whereas stress is external so how are both quantities not tensors? I am ...
6answers
130k views

### What is the difference between stress and pressure?

What is the difference between stress and pressure? Are there any intuitive examples that explain the difference between the two? How about an example of when pressure and stress are not equal?
1answer
933 views

### Why does a flat sheet roll back into a cylinder when having rolled it once?

For example, if you were to roll a piece of paper into the shape of a hollow cylinder and then try to return the paper to its original, flat shape, it would naturally roll to the cylinder when you let ...
5answers
4k views

### How is potential energy actually stored in a steel spring at the atomic level?

Elasticity is one the most intriguing phenomena, wiki gives a summary explanation of what happens in a steel spring: the atomic lattice changes size and shape when forces are applied (energy is ...
3answers
103k 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 ...
2answers
241 views

### Dust patterns inside electronic product - what causes this? [duplicate]

(Note: another similar question from a few years ago yielded nought but speculation. I have at provided some detailed observations in the hope that the community can come up with something rigorous as ...
3answers
852 views

### Where does the use of tensors to describe orientation dependence of physical phenomena arise from?

In the context of anisotropy, I have often read that the use of a rank 2 tensor is "a model". But what is the idea behind this choice? Can anyone describe in what sense the use of tensor in this ...
1answer
3k views

### Why does plastic turn white in the area of stress?

There is a phenomenon with plastic in which it changes color to white in areas where stress is applied. When I bend a plastic rod the area in the centre, it turns white or loses colour. Why does this ...
2answers
2k views

### Tearing a piece paper along a crease

Why is it easier to tear paper along a crease? To word it differently: why does a "tear" progress along a crease, if one is present?
7answers
1k views

### What's the biggest cube you could have before gravity rounded it?

I took this question from Quora because it seems interesting and this community would have some fun with it. I would assume that one would use the modulus formulas for force to counteract the gravity, ...
3answers
11k views

### Why is the (non-relativistic) stress tensor linear and symmetric?

From Wikipedia: "[...] the stress vector $T$ across a surface will always be a linear function of the surface's normal vector $n$, the unit-length vector that is perpendicular to it. [...] The ...
3answers
2k views

### Origin of the major symmetry property of the elasticity tensor

In linear elasticity theory the stress tensor $\sigma$ is related to the strain tensor $\epsilon$ via the elastic tensor $C$. Specifically $$\sigma_{ij} = C_{ijkl} \epsilon_{kl}$$ Because $\sigma$ ...
2answers
6k 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 ...
6answers
3k views

### Can any body be uniform in the universe?

If I take any body in the shape of a rod and stretch that, after it reaches breaking stress it breaks at one point. Even though we apply the same the stress on each and every part of the rod it broke ...
4answers
544 views

### Why are stresses of continuum systems described via a tensor?

The tittle pretty much says enough. I have always been told so but no one really motivated it. So, I would like to know why do we use a tensor to describe the stresses in continuum mechanics.
3answers
1k 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 ...
4answers
541 views

### How wide does a wall of ice need to be to stay in place?

Let us say that we have unlimited manpower to construct a huge wall of water ice e.g. 200 m tall (700 feet). -and that the wall is placed in a climate, where the temperature never (for your purpose) ...
2answers
377 views

### Why are springs spiral-shaped? [duplicate]

I've had this question on my mind for quite a while and looking at the web, I couldn't find an answer to this question. I've had a lot of physics experiments involving springs, unintentionally ...
4answers
6k 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.
2answers
68k views

### Will a diamond break if I hit it with a hammer [closed]

I was having this discussion with my friend about the hardness of diamonds. I would like to know if a diamond will break or not if hit with a hammer. Different sources across the internet mention ...
2answers
2k views

### Are Rippled or Wavy Potato Chips Stronger?

I am buying some potato chips. I want to use dip. But half the time I do my chips in the dip, they break apart. Do wavy chips, with the wider bends have a greater strength? Or do the rippled chips, ...
3answers
6k 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 ...
1answer
663 views

### What is the stiffness of a crushed rod or cylinder?

If you are crushing a uniform rod between two plates with a known force, how do I estimate the deflection (and hence the stiffness) of the rod? I am interested in the overall deflection, including ...
2answers
6k views

### Why do chocolate bars usually break at the cleavages?

Why do chocolate bars usually break at the cleavages? The chocolate bar is less thick at cleavages. How can we relate thickness and fracture point of chocolate bar?
1answer
4k views

### Physical meaning of elastic constants of a monoclinic crystal

For the elasticity of a material, Hook's law can be written in tensorial form as: $$\sigma = \mathsf{C}\, \varepsilon$$ where $\sigma$ is the Cauchy stress tensor, $\varepsilon$ is the infinitesimal ...
1answer
323 views

### Why does a wetted cloth get structurally reinforced while paper doesn't?

In the Hollywood movie, Shanghai Knights (pardon me for the non scientific citation), Jackie Chan states that 'wet cloth' does not break easily. How true a fact is this ? We know from common ...
3answers
1k views

### Can we change the volume of a wire by applying force on it in order to stretch it, if yes is there any way to calculate it?

Can we change the volume of a wire by applying force on it in order to stretch it, if yes is there any way to calculate it ??
2answers
794 views

2answers
718 views

### Why does stress need to be described with a tensor?

I understand the idea that stress is basically force per unit area. So let's imagine a force on beam as follows: Notice how the force only occurs in one dimension. But when I look up stress, I ...
5answers
9k views

### What is the difference between traction and stress?

As far as I can tell, stress and traction seem to refer to similar ideas. According to Chapter 8 of Twiss and Moore's Structural Geology, traction is Force per unit area on a surface of a ...
4answers
396 views

### Elastic properties of materials at low temperature

It is common knowledge that materials are more brittle at low temperature. But does it apply also on elastic deformations or is it just matter of plastic deformations? Practically: Is it possible to ...
1answer
1k views

### Hookes law and objective stress rates

Often, in papers presenting updated Lagrangian simulation methods for solid dynamics, the following procedure for updating the (Cauchy) stress tensor is presented: First, the Cauchy stress tensor is ...
2answers
816 views

### First-principles derivation of cutting force

I know that the amount of force required to separate a material from itself is linked to the surface energy of that material. However, looking at just the surface energy laughably underestimates the ...

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