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15 votes
Accepted

Unknown metal-piece connected to the case of an iPod Nano 2

It's a naked piezoelectric buzzer. Some piezoelectric crystal grown on a metal circle are the active part and the bottom contact glued on the back cover. The top is then metallised to get the second ...
carloc's user avatar
  • 295
14 votes

Steel expanding in a tight space

The cylinder would expand until constrained by the cylindrical hole. After that it depends on the relative strengths. If the block has thin walls it may be stretched by the expanding cylinder and ...
Transistor's user avatar
  • 10.9k
11 votes

Why does corrosion take place at certain stressed regions?

One of the mechanism that affect corrosion is known in the literature as Stress Corrosion Cracking (SCC). The idea is that tensile stressed regions are prone to crack development. Crack development ...
NMech's user avatar
  • 24.4k
11 votes
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What kind of metal are eye glasses frames made from?

There are many different materials that can be used for modern eyewear. Based on the following table (I put it together from online searches, its not from a single site, although the content is ...
NMech's user avatar
  • 24.4k
10 votes
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Galvanized Steel (Zinc Plated Steel) vs Stainless Steel

Stainless steel can be used up to temperatures of about 1000C. The corrosion resistance of zinc plating decreases rapidly above 100C, and embrittlement can occur above 500C. Zinc plating has lower ...
alephzero's user avatar
  • 12.5k
8 votes
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Do "non-iron steels" exist?

Iron and carbon have an interaction which make them different from most engineering alloys. This is to do with both the relative size of C and Fe atoms and their chemistry. Carbon atoms are just the ...
Chris Johns's user avatar
  • 15.2k
8 votes

Why not build container ships from plastic?

In short, because steel is less expensive on a strength per dollar basis of anything else, and for large structures, it's less expensive to work, again on a strength per dollar basis. That's why ...
TimWescott's user avatar
  • 2,682
7 votes

Why not build container ships from plastic?

Anything is possible and lowering the lightship weight (LS) of ships will save fuel, but the key issue would be any change must not reduce the seaworthiness of ships. This question is very broad. ...
StainlessSteelRat's user avatar
6 votes
Accepted

Why are car bodies not made of titanium?

The bulk price of titanium doesn't tell the whole story. A big chunk of the cost of titanium parts is down to the fact that it is significantly more costly to make things out of titanium than steel. ...
Chris Johns's user avatar
  • 15.2k
6 votes
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Purpose and name of fine pitch marks on a cast metal part

these are part-tracking marks. they indicate which cavity in the mold the part was cast from, in which mold set, in what molding machine, in what year, month, day and shift. this way, a part that ...
niels nielsen's user avatar
6 votes
Accepted

Why did the Soviet Alfa-class submarines have a titanium hull?

the former soviet union had plentiful stores of titanium on hand, so its expense was not an issue. Being nonmagnetic, a titanium hull would be more difficult to detect with magnetometers. Note ...
niels nielsen's user avatar
6 votes
Accepted

Steel expanding in a tight space

Assuming your hypotethical question as what it would be for a difference of 200 degrees celsius and assuming the hole as rigid. The volumetric expansion index of steel is $$ \text{ $9*10^{-6}$ - per 1°...
kamran's user avatar
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5 votes
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Strechable object that can transfer current

First of all, with your 4 inch distance, the propagation time wouldn't be 0.1 seconds. It would be 0.000 000 000 339 seconds. Measuring such short time differences is a significant ...
jpa's user avatar
  • 1,953
5 votes

Strongest brazing materials for titanium?

To give at least some context to this. Titanium is generally considered 'exotic' for welding purposes as it is quite sensitive to both temperature change and contamination by atmospheric gasses, even ...
Chris Johns's user avatar
  • 15.2k
4 votes

Difference between Precipitation Hardening and Tempered Martensite

Summary: Both processes depend on relative solubility of solute between high and low temperature solvent phases. How each process proceeds at sub-microscopic scale is very different. Precipitation ...
do-the-thing-please's user avatar
4 votes

What's the difference between tempering and aging?

Although the time and temperatures may be the same, different things are happening. Tempering generally reduces hardness/strength, but improves toughness. Aging martensite is done for a group of ...
blacksmith37's user avatar
  • 6,154
4 votes

How to create an airtight connection between Stainless Steel and PTFE?

You're going to struggle to get a reliable gas tight fit with that design. For a start it would be better if the two connections were separate so they aren't fighting against each other in terms of ...
Chris Johns's user avatar
  • 15.2k
4 votes
Accepted

What are these metal cylinders often found in the streets of London?

These containers are nitrous oxide canisters https://www.talktofrank.com/drug/nitrous-oxide https://en.wikipedia.org/wiki/Recreational_use_of_nitrous_oxide
D Duck's user avatar
  • 391
4 votes

What mechanism is available to rotate a metal piece on another metal piece?

You have the right idea using a shoulder screw. In between the two pieces, use flat washers and a springy Belleville washer. A Belleville washer, also known as a coned-disc spring, conical spring ...
Mike Waters's user avatar
4 votes
Accepted

Why does corrosion take place at certain stressed regions?

In the real world ,I don't believe I have seen CORROSION at STRESSED areas. Corrosion may be accelerated at STRAINED areas; the strains introduce energy to the microstructure which may promote ...
blacksmith37's user avatar
  • 6,154
4 votes

Can Rotary Friction Welding be used to join metals and ceramics?

Probably not. The friction welding process presupposes a certain level of ductility so the mating surfaces can deform together and completely bond. Ceramics lack the deformation mechanisms that metals ...
niels nielsen's user avatar
4 votes
Accepted

Aluminium Bolt in Titanium Casing: Any Dangers of (Contact-)Corrosion?

Galvanic Compatibility Often when design requires that dissimilar metals come in contact, the galvanic compatibility is managed by finishes and plating. The finishing and plating selected facilitate ...
r13's user avatar
  • 8,202
4 votes

How the choice of etchant can affect the severity of hydrogen embrittlement during pickling and passivation?

The primary cause of hydrogen cracking is a susceptible matrix . Typically a carbon or low alloy steel that is hard ( > HRC 25) untempered is the primary problem. The martensitic chrome steels were ...
blacksmith37's user avatar
  • 6,154
3 votes
Accepted

Is there a drill adaptor or attachment tool for cut a metal solid cylinder

There are cutters that produce circular, slightly tapered plugs, typically 4-12mm diameter. Tapered plug cutter Used in a rigid drill press or milling machine with slow feeds and plenty of lubricant ...
Donald Gibson's user avatar
3 votes
Accepted

Can a Plasma Cutter use for melt metals?

No. Plasma cutters use a jet of air along with the arc to cut they pretty thoroughly oxidise the metal, plus the jet would just spray molten metal everywhere if you tried to contain it. In terms of ...
Chris Johns's user avatar
  • 15.2k
3 votes
Accepted

Pouring aluminum into another block of Aluminum

This is unlikely to work very well. The biggest issue is that you won't get good adhesion between the two surfaces. aluminium has a particularly resilient and inert surface oxide layer so molten ...
Chris Johns's user avatar
  • 15.2k
3 votes
Accepted

Is a metal Prince Rupert's drop possible?

Sort of. This is rendered a bit of a moot point as most metals already have the the sort of hardness and impact resistance that heat treating imparts on glass anyway so you are essentially ...
Chris Johns's user avatar
  • 15.2k
3 votes

Strechable object that can transfer current

Given the theoretical dimensions stated in the question, there would be no measurable difference in the transmission speed of the message. Possible materials include various conductive rubber ...
Donald Gibson's user avatar
3 votes

Do "non-iron steels" exist?

Summary: The Fe-C system, and thus steel, is unique due to a eutectoid transformation from a high-solubility phase to a low solubility phase that allows for a wide variety of microstructures and ...
do-the-thing-please's user avatar

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