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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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 ...
5
votes
1answer
5k views

How do I calculate an estimate for the properties of a composite material?

For a given laminate made of composite material (composed of fibers oriented in a carefully designed sequence coated and embedded in a matrix material), where can I begin estimating the stiffness and/...
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 ...
6
votes
2answers
235 views

Having three heaters on single PCB

I posted this question on electronics SE, but was suggested that I post it here. I basically having three heaters (serpentine pattern) on a PCB (fiberglass board), as the following image shows: The ...
4
votes
1answer
620 views

Why is the Stress vs strain diagram preferable to the Load vs displacement diagram?

I’m really unsure what is the difference between stress vs. strain and load vs displacement graphs and why stress-strain is better. I know that the units are different: stress is in MPa and the load ...
1
vote
0answers
93 views

Is it possible to create a hard slick non-stick non-degradable substance? [closed]

I once read on a web page I can no longer find that corundum is a covalent network. I'm guessing that's because despite the fact that the electronegativity difference between aluminum and oxygen is ...
0
votes
1answer
1k views

Tau max value in torsion calculation [duplicate]

I am going to try and ask this question again. In this formula to calculate shear stress in a solid shaft: τ = T r / J If I want to solve for the radius; I should use the modulus of rigidity ...
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 ...
3
votes
2answers
613 views

What is the strongest known *metallic* material which can be used on Earth?

The discovery of nanotubes and graphene has pushed the limit of material strength high enough that building a space elevator could be managable. But most of the new materials are created from carbon ...
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 ...
6
votes
3answers
2k views

What is the densest ceramic?

I know ceramics are generally considerably less dense than pure metals or alloys but sand is used in barbells for its probably cheapness, user-friendly and easy availability but its a decent density ...
4
votes
1answer
5k views

Does unloading beyond yield point also affect tensile strength?

I know that with strain-hardening you increase the yield and tensile strength. So if you unload at point D, then you also have cold worked it a bit right? So the stress-strain curve will look ...
4
votes
2answers
663 views

6082 Aluminium softened by brazing. How to harden?

I've started playing around with brazing pieces of extruded aluminium sections to join them together for strong joins as an alternative to bolting them. The pieces are made of 6082-T6 aluminium alloy....
4
votes
4answers
3k views

Why 0.2% of strain is considered while taking proof stress?

When a material does not show a distinct yield point then 0.2% of strain is considered and a line is drawn parallel to the elastic line and the corresponding stress is called proof stress. My question ...
0
votes
2answers
289 views

Does a change in specimen dimension affect the measured yield strength and tensile strength?

I am having a hard time trying to understand the effect of geometry on a specimen's yield and tensile strength or if there even is one. If there is an effect or not, why is it so? Thanks in advanced!
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 ...
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
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 ...
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 ...
7
votes
1answer
840 views

How do I compute combined tensile strength?

If I know the tensile strength of a pin, how do I compute the total strength of multiple pins? That is, 2 objects are connected by multiple pins, evenly distributed, each with a height of $2mm$ and a ...
5
votes
1answer
802 views

First principle derivation for torsional constant

For torsional constant, analytical formulas are available for some standard steel sections as shown in this wiki page. But what about arbitrary shapes? How can I obtain the formulas for torsional ...
4
votes
1answer
66 views

Do the steels 1.4404 and 1.4571 look the same?

A contractor delivered three components, all are supposed to be in 1.4571. Part A is actually done in 1.4404 / (X2CrNiMo17-12-2) (according to pretty conclusive documentation). Part B is allegedly ...
3
votes
1answer
744 views

Piezoelectric matching/backing layer materials

To maximize the piezoelectric transducer reception/transmission power we must choose the correct backing/matching layer materials, I'm working on a project to measure a steel tank liquid level (non ...
3
votes
2answers
135 views

What type of failure is this?

The part is a clevis and was insterted in a steering rack . Part was in Tension, torsion and bending. It failed at the end of the threaded bolt part. Is it a common problem for bolted joints ? How can ...
2
votes
2answers
4k views

Why does the yield strength of steel go up if I reduce the thickness of the specimen?

When I look at the yield of one material then you find more than one yield for different thickness. why the yield changes with changing the thickness. is there an equation to prove this ?
1
vote
1answer
37 views

Mirror specification used in Solar Fresnel Collector systems

Im designing a Linear Fresnel collector system, and wanted to know what type of mirrors would be suitable for use as the reflectors. Thickness, type, coating etc. I couldnt find a manufacturer of ''...
1
vote
1answer
165 views

Looking for a formula that states the stiffness of a composite [closed]

I am looking for a formula that states the breaking point of a composite - How much pressure it can withstand before it 'snaps'. Specifically I am looking for a formula that states the materials ...
1
vote
0answers
33 views

Shore durometer type D to brinells

I saw a video where a person was measuring hardness of a material with Shore durometer type D and was comparing it to steel. The screen on durometer showed 96.5 HD and I was just wondering, how much ...
1
vote
2answers
162 views

Trying to shed some weight on my design, any thoughts?

I am trying to design a lifting mechanism and I would love some insight/opinions as to how I can shed some weight off it. The current weight I have for my mechanism is 187.5kg, however, this is ...
1
vote
2answers
10k views

How to calculate the diameter of a transmission shaft from RPM & Torque

If I know the torque and rpm that the shaft need to operate at, can I calculate the diameter of the shaft? A motor operating at 60 rpm applying 1,000 Nm of force on a shaft that has a modulus of ...
0
votes
1answer
43 views

Economical difference with high-pressure vessel design pressures for fixed volume

Suppose space is not an issue and I need a fixed volume of compressed air (for storage), say 1m³. Is it more economical to manufacture a thick-walled vessel but with a smaller volume or a thin-walled ...
0
votes
2answers
211 views

Distribution of energy absorption in inelastic collision

Object A has mass $m_A$, and is travelling west with velocity $v_A$. Object B has mass $m_B$ and is travelling east with velocity $-v_B$. The objects collide in a perfectly inelastic collision so ...
0
votes
1answer
403 views

Strain Energy Problem

A bar of length L and of uniform cross-section area A and second moment of area 1 is subjected to pull P.If the young's modulus of elasticity of the bar material is E,the expression for strain energy ...
-1
votes
1answer
168 views

Is it possible to adapt the design and principle of operation for a tunable microwave photonic notch filter to a visible light photonic notch filter?

I just read the 2015 excellent paper , "Tunable microwave photonic notch filter based on sliced broadband optical source". Is it possible to downconvert a microwave photonic notch filter to a visible ...
-2
votes
2answers
34 views

Suggest a material which can produce heat with DC current

Can anyone please suggest me a material which can produce heat with DC current. I want it to be low of cost. I should be able to turn it into a sheet. And if there no such material. Please tell me how ...