14 votes

What is the physical reasoning behind metal becoming stronger and harder if heat treated?

In short the heat treatments in steel change the phase of iron between the following phases: Austenite Cementite Martensite Bainite Ferrite Perlite. (Actually quenching does not allow low ...
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Why does the stress-strain curve decrease?

For the explanation of the loss of stress from E to F, I'll refer you to my answer to another question. Basically, the drop in stress seen in the diagram is a consequence of the fact that we use ...
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11 votes
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How does the strength of a square tube depend on the side size?

Flexural capacity is based on the stress at the extreme fiber (the point farthest vertically from the neutral axis). $$\sigma = \frac{My}{I}$$ Or, rearranging $$M = \sigma \frac{I}{y} = \sigma S$$ ...
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11 votes

Brittle = highly stiff but not very strong

IMHO there is an "misuse" of the words brittle/strong/stiff that the OP is using. My interpretation of brittle has to do with sudden failure during testing with little to none plastic ...
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9 votes

Why does the stress-strain curve decrease?

To add to the other answers: interstitial solutes effectively "lock" dislocations in BCC metals (such as with carbon and nitrogen dissolved in iron), by forming what are called Cottrell atmospheres (...
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9 votes

What is the physical reasoning behind metal becoming stronger and harder if heat treated?

The effects of heating-quenching a metal is explained below Transformation hardening is the heat-quench-tempering heat treatment cycle addressed earlier in this article. It's used to adjust strength ...
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8 votes
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What methods are there to test the flexural, tensile and compressive strength of concrete?

There are two methods to test flexural strength, three point and four point method. Three point method: and the corresponding moment line: four point load: and its moment line: The maximum ...
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8 votes

Increasing torsional-stress resistance of an Auger at its motor-shaft joint

As your construction is 3D printed, increasing the strength at the point of current breaking will more likely transfer the damage to a new location. The obvious and possibly impractical solution is to ...
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6 votes
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Good estimates for torque generated while turning a dial

This a table of a search done on research that was conducted between June 1959 and October 1960 by the Controls Section, Engineering Psychology Branch, Behavioral Sciences Laboratory, 6570th Aerospace ...
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6 votes

What is the physical reasoning behind metal becoming stronger and harder if heat treated?

You are mixing apples and oranges. Many steels harden by rapid cooling, but very few other metals do that; specifically, only aluminum bronze and certain titanium alloys. Many metals will strengthen ...
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6 votes

Brittle = highly stiff but not very strong

These are some great questions to get started thinking about the field of material science! Most of these properties are imao explained very well by looking at a Stress vs strain graph of a material ...
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5 votes

Could a vacuum tank ever be light enough to be boyant in air?

Start out by doing some basic calculations. Air is mostly N2, with a atomic mass of 28, and O2, with a atomic mass of 32. There is more nitrogen than oxygen, so let's say air has a average atomic ...
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5 votes
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Springback after a plastic deformation

When the load is removed, the elastic strain is recovered completely (by definition); the plastic strain is not recovered at all (by definition): If the load is reapplied, the curve picks up where it ...
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5 votes

Which post would be stronger?

The incorrect posts are weaker as it is the dimension perpendicular to the fence which is critical. It sounds like you have a breach of contract here so you should ask them to replace with the ...
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Beginners material science for handling a load

Material Properties For the linear-elastic analysis you describe, the key pieces of material information are the elastic modulus (E) to calculate deflection and the yield stress (Fy) to check if the ...
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Beam buckling criterion?

Shear buckling of beam web happens when the shear at a section of the beam under consideration surpasses the controlling combination of factored shear. The following three equations are the LFRD ...
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5 votes

Increasing torsional-stress resistance of an Auger at its motor-shaft joint

Build the auger around a stronger shaft which has a better connection to the motor shaft. Perhaps a carbon fibre or even a steel centre. But then consider what will be the next breaking point. Or make ...
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5 votes

Increasing torsional-stress resistance of an Auger at its motor-shaft joint

You might consider dealing with it in software. Sense the stepper motor current, and when it exceeds a certain threshold that indicates jamming, perform a high speed reverse rotation for one or more ...
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Mechanics: example of less mass/volume gives more strength

I just found an answear, the keyword is "stress concentration". Sometimes, the material is removed to make a stress relief in an element. Some examples: The origin source I found it: https:/...
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5 votes

What is the physical reasoning behind metal becoming stronger and harder if heat treated?

The other answers describe the "materials science" mechanisms of iron vs. temperature. I'm going to add this: Matter "tries" to reach a minimum energy state whenever possible. In ...
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Definitions of strength?

Strength can mean different things in different contexts and technical definitions can vary significantly from what is commonly understood by the word 'strength'. For structures where actual forces ...
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4 votes

Is strain energy the same as potential energy, or something differen?

This has been asked and answered numerous times before: https://www.quora.com/Why-is-strain-energy-equal-to-1-2*force*displacement-What-about-the-remaining-half basically, it's because you're ...
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4 votes

Increasing torsional-stress resistance of an Auger at its motor-shaft joint

For me a good (compromise of a) solution would be to redesign the shaft with an rectangular slot (although I am still unclear as to the fracture type, so I suspect is torsional). Like so Then you can ...
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4 votes

Stress-strain Curve Interpretation

The stress-strain curve isn't created using a incremental load. Instead what most standards for tensile testing nowadays require a constant displacement rate. I.e. you have a setup similar to the ...
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3 votes

How to provide lateral support for adjacent masonry during installation of steel UC in an old cavity wall?

Disclaimer - No contract exists between us. This post is provided as information and opinion only and does not form "advice" in any way. Although I am a Chartered Civil Engineer I have zero ...
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3 votes

Is it safe to stand on a toilet bowl?

An Australian bar in Hanoi, Vietnam, put up graphic photos in the bathroom of the horrendous injury that a customer who squatted on the bowl got when the porcelain broke suddenly, they fell with it ...
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3 votes

Is it safe to stand on a toilet bowl?

There is another safety issue - the way the bowl is attached to the structure of the building. In the UK, the only structural attachment is by two (large) brass screws passing through cast holes in ...
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3 votes
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Can concrete lose strength during curing?

With the exception of anything extremely unusual: the concrete will continue to gain strength until 28 days. In fact, it will continue to gain strength for something like 50 years, but the main ...
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3 votes
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With which parameter can you specify whether a metal is ductile or brittle

The simplest way to tell if a metal is ductile or brittle is to look at a fracture surface (e.g. from a tensile or impact test). To have either a ductile or brittle metal defines the failure mechanism ...
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Strength of Plastic Underwater Domes with various thicknesses

A shell structure under external pressure is likely to fail in buckling before it reaches the compressive strength of the material. Buckling of curved shells is a complex problem in general, but for ...
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