Questions tagged [materials]

Use for questions about designing, manufacturing or synthesizing engineered materials or about the properties of specific materials. Questions concerning common construction materials, such as wood, steel or masonry do not need to use this tag; use the more specific tag instead.

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82
votes
9answers
36k views

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

Glass is fragile and impractical to transport, install and repair. Even worse, glass kills and hurts people when it breaks. Falling to the streets like guillotines during earthquakes and bomb raids. ...
34
votes
10answers
33k views

Is it possible to build a perfectly spherical Prince Rupert's drop?

Prince Rupert's Drops are glass objects created by dripping molten glass into cold water. While the outside of the drop quickly cools, the inside remains hot for a longer time. When it eventually ...
17
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2answers
3k views

Why doesn't epoxy stick to silicone?

Why doesn't epoxy stick to silicone? Is there a type of epoxy that does?
17
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1answer
4k views

How many train passes can railway tracks endure?

I know that the rubber on car and truck tires wear, and the road concrete wears out. I wondered: While steel is hard and elastic, it still causes friction (interaction between molecules) and ...
17
votes
1answer
793 views

Can we change steel properties by application of magnetic field while quenching?

Austenite is non magnetic while $\alpha$-ferrite and pearlite are magnetic. (Magnetic properties of pearlite vary as a function of carbon content) If a strong magnetic field is applied in a ...
15
votes
2answers
11k views

Why do we even use engineering stress?

Surprisingly this hasn't been asked before, so I must be missing something simple. We use engineering stress and engineering strain in this eq. Stress = (Young's modulus) × (strain). This eq. is ...
14
votes
7answers
25k views

Is stainless steel plating possible?

Is there a method for plating steel with stainless steel? If so, is it chemical, electrical, or electrochemical? I did a quick search on the internet but was unable to find a service. I'm ...
14
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1answer
1k views

Why does prestressing in trees make them stronger?

In "Structures: or Why Things Don't Fall Down" James Gordon talks about trees being prestressed with the outside in tension and the inside in compression. Why does it make a tree stronger to have it ...
14
votes
1answer
604 views

What are some cost-effective metal substances that can wet glass?

A highly desirable property of metals like gallium and indium is that they are able to wet glass. Normally, as metals, they wouldn't be able to form an airtight seal when in contact with glass. But ...
14
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3answers
227 views

Looking for best material for a cryogenic ball mill cup and balls

I am working with a set of alloys that must first be ground up in a ball mill at cryogenic temperatures. It is important that no contamination makes it into the material and careful steps are taken to ...
14
votes
1answer
975 views

Can Zinc/Aluminum coated anchor rods be used in concrete?

Bolts and anchor rods that are very high strength ($F_u$ > 150ksi) are not supposed to be galvanized. This is because of concerns about hydrogen embrittlement. This includes ASTM A 490 bolts and ASTM ...
13
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3answers
1k views

Do I need to worry about galvanic corrosion when inserting a steel bar through aluminium?

My design uses a round steel bar inserted through a hole in an aluminium component with a tight fit (no movement). The operating environment is dry, 20-40°C. Do I need to worry about galvanic ...
13
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5answers
3k views

Are there any materials known to be sound-insulating but thermally-conductive?

Are there any materials known to be sound-insulating as well as thermally-conductive? Cost is not an overriding concern, but preferably costing "reasonable amounts" and much less than national ...
12
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6answers
6k views

Why does a gear have extra holes?

In a gear you normally have a center hole for the shaft to be put into. Why do some gears have holes surrounding that center hole? Is it for weight reasons? Does it add stability? Is it so you can add ...
12
votes
1answer
429 views

Is steel relaxation plastic?

Hooke's Law defines a linear-elastic relationship between stress and strain. $$ \sigma = E\epsilon $$ Steel behaves very much like a linear-elastic material, following Hooke's Law closely. It does, ...
11
votes
9answers
2k views

Aluminum weight saving

"Aluminum saves weight! Its 3 times lighter than steel!" Also its 3 times weaker and 3 times softer. When comparing stiffness and strenght to weight ratio, aluminum isnt any better than ...
11
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3answers
1k views

Why do beverage can tabs break when bent?

Most people have had the experience of moving the tab of an aluminum can back and forth until it breaks off. It usually only takes a few complete back and forth motions before the tab breaks off. ...
11
votes
2answers
5k views

What does the steel grade "11SMn30" mean?

I am starting to use steel in some of my designs, and while trying to learn more about this material and its properties I have realized that there is so much more to it than I thought. How does the ...
11
votes
2answers
764 views

Comparing the performance of glass and granite in a heat storage application

Background I am working with a small team on a university project to build a greenhouse heat sink. This will pass warm air at the top of the greenhouse down through a chamber underground filled with a ...
10
votes
4answers
22k views

Why does the stress-strain curve decrease?

This is a stress-strain diagram I have noticed that the curve decreases between points C & D and between E & F. Why does that happen? I expected the curve to always increase since the ...
10
votes
2answers
8k views

What made bronze the first widely used (non-ornamental) metal in human civilization?

I recall learning about the bronze age in school. Why was bronze so important to the technological development of humans? Why not some other metal?
10
votes
1answer
1k views

What kind of metal are eye glasses frames made from?

I've noticed that prescription eye glasses frames are often made from metal that is quite rigid. It's surprisingly difficult to bend the metal, despite how thin it is. And if it does bend, it doesn't ...
10
votes
1answer
2k views

How do I keep my bit from wandering on a drill press?

I punch metals before I start a bit in them, but with small-diameter bits I am finding that they wander inside the material. E.g., drilling a 1/8" hole in 1/2" of aluminum the (titanium-coated HSS) ...
10
votes
2answers
457 views

Are threads machined from high tensile steel more susceptible to damage?

I have an ASTM A311-04 1.25" diameter round 1050 steel bar that exhibits a tensile strength reading of 155,227 PSI. Normally, we receive material in the 13-133,000 PSI range. The bar is machined to a ...
10
votes
3answers
4k views

How do you select the correct area to consiser for first moment of area calculations?

I have just begun studying mechanics of materials and I am struggling to understand intuitively how to select the area in first moment of area calculations. I was hoping someone has a relatively easy ...
10
votes
1answer
1k views

Will a sacrificial anode protect any length of metal that it is connected to?

When using a sacrificial zinc anode, is there a limit to the distance that its protection will extend? The protection works based on electrical conductivity, so distance would seem to affect the ...
10
votes
2answers
347 views

How to calculate permittivity for higher frequencies?

In many books the permittivity of a material is only listed as dielectric constant for one or a couple of frequencies. 1 kHz is used often (for example in the Plastics Technology Handbook, 4th ed, ...
10
votes
1answer
271 views

Developing a stochastic differential equation model for concrete fibers

I am working on modeling concrete fibers (metallic fibers) as a mathematical model. My work is for my thesis. I am a PhD student of numerical analysis, but I am working on a real tunnel project. I ...
9
votes
2answers
3k views

How can a knife cut through butter?

How does anything actually cut anything, since we all know stuff is made up of atoms and molecules, which can't be touched together (It Requires Binding Energy). So how come we see things all around ...
9
votes
6answers
19k views

Steel selection for building a trailer

I'm thinking about building another trailer. I've built lots of smaller trailers in the past, but this time I'd like to build myself a small tandem axle gooseneck rated for 7,500 lbs. I am a ...
9
votes
2answers
157 views

Material selection for weight scale

I am looking to test the FlexiForce sensor in measure force, however for accurate readings the load needs to be disturbed evenly over the sensing area. As such I am having "discs" made to cover the ...
9
votes
4answers
667 views

Can cameras+display screens with window/mirror-like optical behaviour exist?

Display screens connected to cameras are significantly different from windows or mirrors. Looking through a window or mirror, we can focus on infinity, and we can move our vantage point to see a ...
9
votes
1answer
2k views

Stainless steel corrosion resistance in seawater

Stainless steel comes in several qualities. AISI 303 (1.4305) (Stainless Steel A1) approximately 304 but more machinable due to sulfur. AISI 304 (1.4301) (Stainless Steel A2) comprises of 18% ...
9
votes
1answer
556 views

How do I compute the force required to pierce HDPE?

I have a $2\text{ mm}$ sheet of HDPE at $280-320^{\circ}\text{ F}$. I want to pierce the skin of this sheet with a $2\text{ mm}$-high pin with a surface area of $3.33\text{ mm}^2$. The pin is also ...
8
votes
5answers
7k views

How do you attach something temporary to a smooth metal shaft?

I want to attach something small to the smooth metal shaft of a small motor (2-3 mm in diameter), like fan blades, but I want it to be temporary. If I make it too loose, then the fan won't turn at ...
8
votes
3answers
5k views

Is there a mechanical equivalent to a hi/low pass filter (as in electrical engineering)?

I have been wondering if there are certain media (for instance glass, air, foam, etc.) which are peculiar given their chemical composition and/or structure allowing them to filter out mechanical waves ...
8
votes
3answers
633 views

Determining the properties of members of historic structures

From time to time I am tasked with additions or alterations to old buildings or structures. I would need to establish the "as built" structure and from that analysis see how the amended/new structure ...
8
votes
3answers
547 views

Protecting device from microwaves in microwave oven.. but allowing Bluetooth?

I am building a device that needs to be inside of a microwave oven but somehow needs to communicate with another device outside of the microwave. How can I reflect microwaves so they don't come into ...
8
votes
2answers
977 views

Is this railway carriage side likely made of single metal sheet?

A neat image from Wikipedia: Here the railway carriage side looks like it is crafted from a single sheet of metal (if we ignore the doors and the windows and some minor parts like that small thing ...
8
votes
1answer
338 views

Weldability of Pure Tin

The site states that Tin cannot be welded, but after I made some research, I discovered that tin, when alloyed with copper or used as a protective coating for steel, can be welded. My question is why ...
8
votes
2answers
181 views

Can high alloy tool steels be quenched in brine?

It is will known that most of tool steels are quenched in oil to prevent cracking and distortion which appears when quenching in water due to non-uniform cooling caused by formation of insulating ...
7
votes
2answers
2k views

How do suction cups work?

These are suction-mounting hooks. I want to visualize and understand how do they stick on walls. After these hooks stick on wall. Like we compressed them. How? Since gases are compressible up to a ...
7
votes
6answers
13k views

Could a knife blade & shaft be made of 100% diamond?

I am reading a novel set in the future. A planet has been found where there are extensive deposits of diamond. Presumably diamond is mined much like marble is here on earth (there is not a lot of ...
7
votes
3answers
829 views

Can I use a pipe of any material other than copper in a counter-flow heat exchanger?

Why are copper pipes used in counter-flow heat exchangers? Could I enhance heat transfer by using a pipe made of any other material?
7
votes
3answers
9k views

How does the strength of a square tube depend on the side size?

There are two square tubes of the same length, material and wall thickness, one being 40x40mm, the other 20x20mm. How does their strength against bending compare? On the one hand, the cross-sectional ...
7
votes
1answer
10k views

How do train tracks handle really cold weather?

First of all, I'm interested in train track only, not the rolling stock. How are tracks built to cope with really cold weather? An example might be some place in Canada or Siberia. Ice would ...
7
votes
2answers
492 views

Will stainless steel with a #3 finish corrode faster than a #4 finish?

I understand the difference between a #3 finish on a piece of stainless steel compared to a #4 finish being that the surface roughness is different. Specifically, a #4 finish is classified as having ...
7
votes
2answers
504 views

Why do car-seats have an expiration date?

My wife and I are expecting our first child, and therefore are expecting to purchase a car seats. My wife and I have discovered that car seats have "expiration dates": a car seat, no matter how ...
7
votes
2answers
1k views

Questions about making stainless steel boiler

I am currently working on a project (or actually returning to a project) and need to have a heat exchanger boiler made. The hx boiler will be relatively small, a 10" long cylinder around 4" in ...
7
votes
2answers
3k views

Material Properties: Does bending reduce iron rebar's strength?

I'm reading an introduction to structural engineering book and there's a fundamental concept I'm trying to relate to real life: In construction, we regularly bend iron rebar into a variety of shapes ...

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