New answers tagged materials
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Ashby method as per 'Material Selection in Mechanical Design' by M Ashby (Butterworth Heinemann) is a powerful method to select material according to functional needs.
The key point of this method is to build a 'performance index' to classify materials. For example, you could classify materials according to their ratio $\frac{E}{\rho}$ (Young modulus over ...
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Apparently Aluminium - Aluminium (clean and dry) has a higher coefficient for kinetic friction than static friction.
The numbers I've found listed are:
Static: 1.05-1.35
Kinetic: 1.4
source source
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Material selection is a crucial step to get your CNC project right. Think of it as assembling a Subway meal based on your diet plan; you add meats if your diet chart asks for more protein, and greens for a vitamin fulfill. Similarly, selected materials must cover your design prerequisites— hardness, rigidity, thermal stability, and chemical resistance just ...
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The best tool is something called a materials engineer but they tend to be very expensive to buy, even on the used market. However, they can be rented. Alternatively, you can get help from a recovering ex-materials engineer (it's part of our 12-step program). It's free, and worth every penny.
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Doesn't a boating cam cleat work in that fashion?
Image source: Schaefer Marine.
The harder the rope is pulled (to the left) the tighter the cleat bites it. If you can do the same with your friction pawl it too will lock onto the plunger even with wear over time.
The other device that comes to mind is the Sprague or one-way clutch.
Image source: SUMA ...
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One method that I have used for mechanical properties is based on the Ashby selection charts. Software exists to apply this approach.
I am not aware whether comparable methods and tools exist for optical properties.
You may to best to start with the base success/fail criteria for mechanical properties, graduate to the maximum/minimum selection criteria for ...
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If you have sampled data at a constant rate (i.e. the time $dt$ between data points is constant), then the average of the temperature will simply be the average of all the temperatures.
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Will it be simple mean of the curve or rms of the curve?
The average temperature will involve a simple mean of the curve multiplied by the total time span of the curve.
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You already mentioned in the question that you want is average, which is mean and not RMS value, use RMS values if the negative sign needs to be treated as positive temperature only.
Here you simply need to calculate the area under the curve (with sign), cummulate it and divide it by the total time period.
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Let's call the horizontal axis m and the vertical axis T.
Consider a very small slice of the temperature curve starting from the time m to time m+dm.
The area of this slice is $A= dm*T$, and its center of geometry is at the $T_{cg}=T/2$.
Then the average temperature of the 1 cycle is,
just using the CG of the different segments and use the following eq i:
$$ ...
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Although as mentioned by others this is not universally accepted, in my opinion the reason that the 0.2% strain was used for proof stress, is that it offers a more straight forward comparison with the yield stress of steel.
Steel has been (and probably still is) the most common material for structural engineering. However, it has distinct differences from ...
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Given the test configuration and the test specimen dimensions I would suspect that the initial gradient slope is due to the gradual engagement of the test specimen.
I.e. the material top and bottom surface will have a roughness associated with it. Something like in the following image.
As a result when this is being compressed initially there is less area ...
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Have you heard of double shot moulding? In this process, the white is a separate molding that is actually embedded behind the black key. This would not show wear and might narrow down your material choices. Nowadays this is done with ABS or PBT. I don't know about your application though.
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And the question you did not ask ;what about shape/crossection . That is, round and rectangular are both very common specimens .And rectangular with a curved crossection- full wall thickness pipe body. They also make very little if any difference. Note specifications often permit round tensile bars or full thickness tests with the same required mechanical ...
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The different mechanical properties for different sheet thicknesses has to do with grain refinement of the material during the rolling process. The following figures show what is happening to the old grain structure.
The new elongated grain are the results of cold working. It is possible through annealing to form new grains (with no bias in direction).
The ...
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Usually no. However, yes in a manner of speaking.
No:
Primarily both properties are material specific. Therefore, no there shouldn't be an effect of the geometry on either the yield or the tensile stress.
yes : (*)
A typical example where geometry appears to have an effect on yield and tensile stress is the effect of thickness of sheet of steels. Usually ...
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The basic method for hardness measurement is using an indender and a standard force on a material surface and then measuring either the depth or the area of the imprint.
However, is happening with almost all hardness scales is that you cannot obtain meaningful results for all types of materials, for a given force and a specific indender. Therefore what you ...
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Different strokes (tests) for different folks. Metal hardness test methods include Rockwell ( A B C D E,etc), Rockwell superficial, brinell 3000 & 500, vickers, knoop, diamond pyramid, Shore ; and the portable variations of most of these methods. I don't know about rubber but there are books written to describe the nuances of difference of the metal ...
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Geick Technical Formulae has tables of common values, but that info is spread across several tables.
One you missed is electrical resistance. The book also contains tables for density etc
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Glass can be very dangerous when it is shattered. Years ago glass on windows should have been banned because it the edges of it could be very sharp like a steak knife. Plexiglass should replace glass especially on windows if someone throws a baseball at a window, so they won't break accidentally.
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I think that neither of your solutions is correct.
a) you are assuming that the volumetric strain is zero. However, if there is a change of volume then the volumetric strain can never be zero.
Also, in that scenario, I am a bit uncertain what is $\varepsilon_d$. Is it deviatoric strain or is it strain perpendicular to the longitudical direction and due to ...
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There is nickel , titanium alloy Nitinol. I don't remember much about it except it has unique mechanical properties.
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First of all a bit of background, the Poisson ratio is calculated from
$$v=-\frac{\epsilon_y}{\epsilon_x}$$
To use the above equation, you need to use a uniaxial loading (axial or compressive). Because at different loads you might have different Poisson ratio usually what happens is that in the elastic region you create a plot of $-\epsilon_y$ vs. $\...
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