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FEA: What boundary conditions am I missing?

I'm working on a 2D-model (in the xy-plane) in NASTRAN and am getting convergence problems. The main cause of these convergence problems is a "high or negative matrix factor diagonal ratio." I've attached a picture of a setup similar to the one I'm…
anonymouse
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Why is the current that can be drawn from an electric generator constant?

In an answer to this question, for a motor used as a generator, the following was said: The maximum current that can be drawn from a generator is generally a fixed value that is not determined by speed. What equation(s) show this?
Jayy
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How to compare small and large scale model of an IC engine to predict force, torque, rpm etc generated by actual engine?

I have this 6 cylinder radial engine designed in Solidworks. Rendering Blueprint (Source:Inventor Wizards) And I want to perform some motion analysis on this engine to make some prediction about it's feasibility. So by now I have successfully…
Asker
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foam earplugs: what’s the composition of the (non washable) substance that slow down their expansion?

What’s the composition of the (slighlty sticky) substance we find on foam earplugs that allow them to be easily moldable? This substance slows down the expansion of the foam, so it makes the foam a little bit more rigid and help the foam to stick…
Lisa
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How to compare two ANSYS mechanical APDL databases? (.db or .dbb files)

I am new to using ANSYS. I use the student version. Is there a way to find what is the difference between two .db or .dbb files? I have two files say a.db and b.db, which are supposed to be the same exact model for a simple beam structure with one…
Nasser
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Why would a column expand before accepting load through a narrow thunk?

Here's a column top which holds a driveway overbridge. The column is a reinforced concrete cylinder with an inverse truncated cone on top - so it expands sideways at its top. The column top holds some narrow thunk and that thunk holds the driveway…
sharptooth
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Why does paper under pressure become brittle?

In this popular YouTube video, a man attempts to fold a piece of paper more than seven times using a hydraulic press. After the seventh fold was applied pressure from the press, the man shows the audience that the paper became brittle, and breaks…
user01101001
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Deflection of thin plate with 1 free edge and deflection > thickness

I have an thin uniform rectangular steel plate supported on 3 sides and free on one, and supporting a uniform load. I'm trying to determine what thickness of plate I need to keep deflection below a given value, but the deflection may not be "small"…
Stilez
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Viscosity of select species at atmospheric pressure for very large temperatures?

I'm dealing with hot combustion products flowing through heat exchangers and I'd like to perform some calculations regarding the flow properties (velocity, temperature, pressure and density) as it passes trough the heat exchanger. I've a 1D model…
André Almeida
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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. I've found that the heating needed to braze…
Jayy
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Foundation Excavation: How much larger than the RCC footing?

I am trying to estimate the volume of excavation needed for the foundations of a structure from the drawings provided. The drawings clearly give the dimensions of the RC / cement footing but I suppose the actual excavation will need to be larger…
curious_cat
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Why are drill bits always slightly undersized?

I have found that drill bits are always slightly undersized. For example, 10mm bits tend to be more like 9.8mm diameter. And in aluminium, the hole ends up being about 9.9mm. The same seems to be the case for conical stepped drill bits I've found it…
Jayy
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Computer psu to directly power usb port

I'm not an engineer, but I build custom audio equipment and systems as a hobby. My question to you is: from a computer power supply (PSU) which converts AC power into DC of various voltages (12 V-5 V) would it be possible to power a Bluetooth…
user6236
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How does one calculate degrees of freedom in a reactor with parallel reactions?

Some time ago, I was going through some exercises and I came across a odd question, for which my atomic species degrees of freedom did not match my degrees of freedom using molecular species. I showed my lecturer and he couldn't see why this was the…
Ender Delat
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Heat pump driven by a Stirling engine that requires no external work

I was considering some theoretical limits on transferring heat from one system at to another to another. It is well known that if you have two systems at temperatures $T_1$ and $T_2$, respectively, with $T_2> T_1$ then you need to provide work to…
Count Iblis
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