The study of how the properties of matter arise from its structure at all scales and of how processing can be used to modify those properties (often in pursuit of a specific application).

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27 views

Dyson Sphere Structures [on hold]

In a type II civilization we may need to harvest the energy of neighboring stars. Freeman Dyson gave an interesting point of view that we could invent a megastructure to harvest this type of energy. ...
41
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2answers
3k views

Why does sound absorption in oceans depend on the pH?

I was reading "The Sixth Extinction: An Unnatural History", by Elizabeth Kolbert, and there she comments that high level of $CO_{2}$ in the atmosphere lowers the pH of oceans (which makes sense) and, ...
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1answer
31 views

Composite materials [on hold]

I'm reading about brake pad material. The paper said ...according to original equipment manufacturer (OEM) the pads are made by combining five types of materials: binders, abrasive, performance, ...
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0answers
8 views

Chromatic confocal microscopy (CCM) and stylus probe

I read research that compared between chromatic confocal microscopy (CCM) and stylus probe in wear test but the research didn't clearfield what is chromatic confocal microscopy and what is the stylus ...
2
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2answers
41 views

Why alloy have more resistance?

Is there any simple way to understand why alloy have more resistance than metals? My teacher ask this, I answer that, there might be more free electrons in metals than an alloy, but she said you are ...
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0answers
5 views

Liquid metallurgy [on hold]

I want to know more about liquid metallurgy? all i know it is a technique used for fabrication of material. Please help me if you know about this technique. Thank you.
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41 views

Crack pattern of safety glass - what gives rise to spider web-like shape

When (laminated) security or shatter-proof glass fractures, the ensuing crack-pattern is often resembling a spider web, with radial and concentric cracks, see e.g. (Source: http://essentialhommemag....
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2answers
58 views

How do signals go through solid objects? [closed]

So many types of signals pass, or seem to pass I don't know, through solid objects. How do they do this?
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39 views

Speed of sound in solid — temperature dependence

Let $v$ denote the speed of sound in a fixed solid, at a fixed temperature $T$. This will depend on properties of the solid (such as the bulk modulus and density). Given an increase in $T$, does $v$ ...
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1answer
57 views

Why does wood go straight into ignition, while other materials melt first?

Background: I was cooking eggs (very difficult) with a plastic spatula which was not very good, so when I set it on the border of the pan it began melting. In order to keep cooking, I reached for a ...
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3answers
2k views

Why are ceramics good electric insulators?

I know it depends a lot on the composition, so not all are great electric insulators. So what makes it good or bad? And is it different from what makes them good thermal insulators? Power line ...
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1answer
40 views

What is plastic flow?

I read in a book named Introduction To Tribology that when a soft material is in contact with hard material, the soft surface will undergo a plastic flow because it is pressed by the hard asperities ...
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50 views

Derive equation for shear modulus $G=E/(1+2v)$

Shear modulus, G Young's modulus, E and Poisson's ratio, v: $G=E/(1+2v)$ I have always wondered how this relation is derived, but have never found a derivation that I could follow online. I assume ...
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1answer
38 views

why do microscopic cracks happen?

2 weeks ago i asked a question about " Gas permeation through solid metal? " i have got a very good answer here .but microscopic crack was mentioned in the answer. i searched in Internet but i didnt ...
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1answer
37 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 ...
11
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0answers
132 views

Why does temperature change the friction coefficient of my stovetop?

I have a Ceran cooking field at home, it's a glass-ceramic surface with heating coils embedded beneath. When I slide a pan around there's much more friction on a hot plate than on a cool one. Why? ...
3
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1answer
62 views

Sonic boom breaking glass

It's a well known fact that a sonic boom from something such as concord can shatter glass. I'm interested to know why a human is seemingly fine in the presence of the shockwave and yet the glass is ...
9
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1answer
122 views

Why does paper explode when compressed?

Various videos online show paper/card suddenly releasing energy in an explosion like way and transforming into a brittle material when put under sufficient pressure from presses. Examples are shown ...
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1answer
89 views

Gas permeation through solid metal?

if i make a box from aluminum ( 0,5 mm thickness ) and put air in it ( about 2 bar or 3 bar). would the box lose the air over time (10 years period) or not ? assuming the temperature will change ...
3
votes
1answer
34 views

Effectiveness of phase-change materials vs water for heat storage?

I'm trying to understand the benefit of specialized phase-change materials vs. water for absorbing heat in a home during the day. It's my understanding that selecting phase-change materials whose ...
2
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1answer
35 views

High surface area for given volume [closed]

What can be a example similar to mathematical Koch flake that could be found in nature... where for a given enclosed volume its surface area is indefinitely large?
5
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1answer
51 views

Optical Retroreflectors: How Are the Faces So Accurately Righted?

This question is about Optical Retroreflectors (corner cubes) and how the extreme precision in their manufacturing is achieved. I suspect there is interesting basic physics involved, which is why the ...
0
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1answer
47 views

Determining a constant from two equations [closed]

I am an engineering undergraduate taking a materials science module and i am having some trouble with the mathematical execution of the following question: Determine the constant in the equation for ...
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2answers
27 views

P-n junction diode under forward bias configuration

Why there is exponential growth in current with respect to voltage in p-n junction diode under forward bias configuration?
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2answers
37 views

Why chromium is more brittle than iron at room temperature?

Why is chromium more brittle than iron? I understand that both of them are BCC at room temperature. Is it to do with the grain size, and why is it different between the two metals?
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1answer
61 views

Is diamagnetism a static or dynamic effect?

When we put a diamagnetic material in the presence of an external magnetic field $\vec B_0$, the magnetic field inside the material decreases to $$\vec B=(1+\chi_m)\vec B_0,$$ where the magnetic ...
4
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1answer
72 views

Breaking strength of wet paper/cloth

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 ...
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1answer
26 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. $$...
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1answer
76 views

Why a bullet leaves a hole on glass where stone makes scratch?

When we throw a stone it breaks the glass with scratches. But when a bullet hits the glass it leaves a small hole(not always) . I want to know the specific reason behind making hole and scratch.
4
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1answer
46 views

Why does melted agarose in solution appear fully transparent, but become opaque when polymerized?

Agarose gels (hydrogels) are commonly used in molecular biology for electrophoresis of DNA. When a solution of hot agarose is poured, the material is clear: When a gel forms, the material ...
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0answers
12 views

How does one go about designing a substrate heater for PVD? I need to design one that can go till 1000 C in Oxygen.

Can I just use a Kanthal wire and make a pattern on a ceramic base? Wouldn't such an exposed element get shorted when I use substrates like Silicon? But wouldn't a layer of ceramic on top of the ...
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0answers
17 views

Springs and Cantilevers - how linear and repeatable are they under deformation?

I know you guys only deal with the ideal, but in practice how linear and repeatable is the response of a spring or cantilever when deformed under a test mass?
2
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1answer
42 views

Difference between dielectric and insulators

AS per my knowledge - dielectric are insulators which can be polarized in presence of external electric field. Does that mean all Insulators are not dielectrics ? If yes then kindly share example of ...
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0answers
44 views

Lab experiment: hysteresis disappears, reappears and then disappears again. How?

In my college laboratory we were assigned an experiment to measure the hysteresis curves of a certain ferromagnetic material at different temperatures. Sounds simple, right? Well, the block of Monel ...
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3answers
1k views

Why don't metals damp vibrations?

Fluid damps vibrations due to viscous dissipation. Does anyone has any insight on a molecular, microscopic level about the reasons that vibration damping of metals is negligible?
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2answers
61 views

Why an impact exerts so much force? [closed]

If an object of velocity $v$ and mass $m$ moves towards a resting object of mass $M$, then if the object which is hit might break. Why? What is the reason that a collision has more power than a ...
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0answers
21 views

How does the shattering of an amorphous solid change in lower gravity?

This is a question that's been bothering me for a while. If I were to stand on the moon, holding a pane of glass, what would happen if I smashed it? Glass is an amorphous solid, which is why it is ...
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0answers
21 views

Mechanical properties crown cap [closed]

What are the important mechanical properties to look at when designing a crown cork and why? Thank you in advance
14
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4answers
1k views

Are insulators and conductors arbitrary categories?

I have seen charts showing the transition from insulator to semi-conductor is at $10^{-8}~\frac{\text{S}}{\text{cm}}$ and between semi-conductor and conductor is $10^{3}~\frac{\text{S}}{\text{cm}}$. ...
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2answers
29 views

Reason behind heating the substrate in Pulsed Laser Deposition

Why do we need to supply a constant heat to the substrate while depositing thin films in Pulsed Laser Deposition technique?
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2answers
36 views

Can you dent a metal wall with a feather?

I know that theoretically you can only scratch a material with a harder material, but what about denting? While scratching a solid would seem to involve breaking bonds, denting a solid would ...
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0answers
32 views

How strong could a carbon nanotube be?

I was thinking about the limits of flywheel energy storage and wondered about carbon nanotubes. The amount of energy that can be stored per unit mass in a flywheel depends not on tensile strength but ...
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0answers
8 views

Height of a point in a plane given a measure of luminance

Context Assume a left-hand rule coordinate system and X points right, Y points up, Z points out. I have a camera facing perpendicular to the X-Z plane in the negative Y direction. I have 4 ...
7
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2answers
127 views

Why do headphones tangle themselves whereas shoe laces untie themselves?

Why do headphones tangle themselves whereas shoe laces untangle or untie themselves? Why aren't we using the phenomenon to create headphones that tangle less and shoe laces that untie less?
1
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1answer
30 views

Tensile strength of a chain of electromagnets

I was having a discussion about the tensile strengths of various materials. Could something like a chain of electromagnets be made to have a tensile strength proportional to the power applied to it?
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0answers
32 views

Why should we use good conductors as electrodes of a capacitor?

I was asked if and why why should the electrodes of a capacitor should be good electrical conductors. It seemed obvious to me that if I want to form a Helmholtz double layer (because that's what ...
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2answers
47 views

Is there any material that can survive a nuke? [closed]

Is there a material known to man that I can tape to a Tsar-Bomba-yield nuclear warhead and find kilometers away after detonation? This question is quite similar but a nuclear explosion is quite ...
0
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2answers
73 views

What causes tensile stress to decrease after a material/wire reaches its ultimate tensile stress?

I was reading the AQA A Level Physics revision guide by Jim Bretihaupt, and in the Materials chapter in the section to do with plastic deformation, it says: Beyond the ultimate tensile stress, the ...
0
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1answer
27 views

Would a bullet damage a piece of metal the same as a pointy stick?

If you used a materials that would offer zero bending or dulling (the bullet/ pointy stick), would a 10 g bullet traveling at 1000 m/s with a surface area of 1 mm squared damage a piece of metal the ...
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10 views

Does the rate of pressure change matter when measuring the strength of a closed container?

If I had a container that could hold 100 psi, and I increased the pressure to 100 psi instantly would I cause any excess stress on the container, or would it not make a difference from doing it over ...