39 votes

From an engineering point of view what are the downsides of a too accurate model?

Beware of overfitting. A more accurate model of gathered data from a system may not be a better predictor of future behavior of a system. The above image shows two models of some data. The linear ...
Scott's user avatar
  • 499
27 votes

From an engineering point of view what are the downsides of a too accurate model?

The most obvious downside is cost, all engineering projects have a finite budget and spending more money than you need to is clearly a bad thing not to mention wasting time. There can also be more ...
Chris Johns's user avatar
  • 15.2k
14 votes

From an engineering point of view what are the downsides of a too accurate model?

There are a few reasons. From a purely pragmatic perspective, it's due to time constraints. The requisite time to solve a model increases far, far faster than the level of precision, and whichever ...
Wasabi's user avatar
  • 13.1k
7 votes

From an engineering point of view what are the downsides of a too accurate model?

An extremely accurate model may require a prohibitive amount of input data. It might be possible to generate an excellent model of weather systems, for example, by taking as input the position and ...
Nuclear Hoagie's user avatar
6 votes

Meshing of complex geometrical domains

While the other guys explained the theoretical framework behind meshing, the practice is markedly different and it is not at all automatic in industries where quality of mesh is of utmost importance ...
m2n037's user avatar
  • 95
6 votes
Accepted

How do you model a real-life truss in structural analysis software?

The most common way to model this structure is as follows (ignore the fact that the proportions are a bit off): So, all of the diagonals are pinned-pinned. You'll notice in the schematic, however, ...
Wasabi's user avatar
  • 13.1k
6 votes

From an engineering point of view what are the downsides of a too accurate model?

"Too accurate" is not monotonic. It can actually create an illusion of fidelity which makes you think it's worth pumping more money into the simulation. This becomes very important when you're ...
Cort Ammon's user avatar
5 votes

Adding a lubricant to an already lubricious material, how is CoF affected?

You can't calculate friction coefficients this way. At the atomic-scale level, the friction coefficient depends on the interactions of the two materials across the interface. If you measure the ...
alephzero's user avatar
  • 12.5k
4 votes

How to define Knurl on drawing?

The (European) standard for knurls is DIN 82. The standard includes a proposed drawing representation as well. Its intention is to describe hand gripping aid knurls. As Ethan48 says, for fitting you ...
Tawhiri Matea's user avatar
4 votes

How to define Knurl on drawing?

It looks to me like your guess was pretty good. The required information is only the type of knurl, the extents of the knurl, and the pitch. It is conventional to show the representative pattern, but ...
Ethan48's user avatar
  • 4,541
4 votes

How I can compute cutting processes with continuum mechanics?

Real-world engineering example To my knowledge there are no simple analytical methods of determining whether an object such as a sword can cut cleanly through any arbitrary object. In manufacturing ...
ConjuringFrictionForces's user avatar
4 votes
Accepted

polar moment of inertia for compound shape

Without looking up all the formula's for you, the approach to this problem is rather simple. Find the polar moment of a solid cylinder, and subtract off the polar moment of the holes. For the off ...
agentp's user avatar
  • 969
4 votes

Matrix Calculation

Your numbers are right. You are just confused about matrix multiplication. See https://en.wikipedia.org/wiki/Matrix_multiplication (or any linear algebra textbook): For matrix multiplication, the ...
Daniel K's user avatar
  • 2,646
3 votes

How to simulate car acceleration

The crucial thing here is that for IC engines torque is some function of RPM and so you need to consult the torque curve for a given engine to do any sort of meaningful modelling. This is also ...
Chris Johns's user avatar
  • 15.2k
3 votes

How do I use FEM to derive the torsional constant of an arbitrary shape?

This is a problem which is usually solved in books on elasticity theory. The underlying math is based on the solution to the Laplace PDE. If you do a Google search for Larry J. Segerlind's book "...
user16622's user avatar
  • 314
3 votes
Accepted

System model for motor controlled inverted pendulum with rotating motor body (used in camera stabilizer application)

There's a couple questions you can ask: Can you control the signal? If not, then it's either a noise or disturbance input. Is it affecting your system (plant), or is it affecting your measurements? ...
Chuck's user avatar
  • 3,565
3 votes
Accepted

How to model a sheet metal nut in SolidWorks?

You might be interested in Smart Components / Smart Features. This technique will associate parts with features. As for the naming, we call those "Press Nuts", or more generically "Press Hardware"
S Barry's user avatar
  • 99
3 votes

What do these sigma subscripts represent?

Wood is anisotropic. Its mechanical properties are different in different directions relative to the grain of the wood. The R, L and T suffixes probably refer to the radial, tangential, and ...
alephzero's user avatar
  • 12.5k
3 votes
Accepted

Two dimensional plasticity with radial return

Let's look at this problem mathematically a la Simo. Let stress tensor ($\boldsymbol{\sigma}$) and its deviator ($\boldsymbol{s}$) in plane stress space be $$ \boldsymbol{\sigma} = \left[\sigma_{11}...
Biswajit Banerjee's user avatar
3 votes

What program to implement mathematical models?

"Numerical Recipes" is probably what you need the most. It contains tons of useful scientific/numerical computation codes. It's a book, but I believe it was also available online. Apart from that, ...
Gürkan Çetin's user avatar
3 votes
Accepted

Failure of N.R.T.L method to model Phenol / Methylcyclohexane / Toluene system in AspenPlus. Why?

At moderate temperatures and pressure NRTL should be a good option provided that the binary interaction parameters are correct. You need to check: Whether the binary interaction parameters for your ...
Toulousain's user avatar
3 votes
Accepted

Modelling gas desorption from a still solution (e.g. a beer)

In perfectly stagnate gas systems, transport of a component through a gas collapses to diffusion of the component through the gas. In this case, $k_L a \propto (D / \delta)^n$ where $D$ is diffusion ...
Jeffrey J Weimer's user avatar
3 votes

Parametric equations for fan blades

For propellers, one usually has blade reference lines called generator lines. They can be parametrically defined in terms of blade number, skew, rake, hub dia, tip dia. If the generator lines are the ...
Phil Sweet's user avatar
  • 4,755
3 votes

Viscoelasticity and Hyperelastic model, history and difference

Let's look at some (very rough) definitions: 1) Viscoelasticity = elastic behavior that changes if the rate of application of the load is changed or, if the load is kept fixed, the change in the ...
Biswajit Banerjee's user avatar
3 votes
Accepted

Viscoelasticity and Hyperelastic model, history and difference

The hyperelastic and viscoelastic material models are both constitutive relations that relate: Stress and strain, in the case of hyperelasticity. Stress, strain and strain rate, in the case of ...
user190081's user avatar
3 votes

Modeling the torque of a real motor

Your general model for an electric motor could be for example, as follows. $$J \phi ''(t)=\text{I} \tau -R \phi '(t)$$ with J as your [kg m^2] inertia, I in [A] amps, and R your friction...at the ...
DrMrstheMonarch's user avatar
3 votes

linearizing a non linear state space equation

The Lagrangian for your 1D pitch system is $\mathcal{L} := T - U$, which is $$ \mathcal{L} = \frac{1}{2}(mb^2 + Ma^2)\dot{\phi}^2 + \frac{1}{2}J\dot{\theta}^2 + (Ma - mb)g\sin\phi $$ The Euler-...
Josh Pilipovsky's user avatar
3 votes

Help understanding this dimension sheet

h11 is the tolerance range. There's a standard shaft/hole chart based on dimension/tolerance. (sorry about the images, I've searched on google but cannot find everything on the same image). h11 is ...
Leafk's user avatar
  • 355
3 votes

a model of a solid using trusses to approximate internal stresses?

Not only can this be done, but it also is done for concrete structures all the time. The shear reinforcement in concrete beams is calculated using Mörsch's truss analogy model: Source The concrete ...
Wasabi's user avatar
  • 13.1k
3 votes

I’m having trouble converting this orthogonal shape to isometric, I’m only a beginner and would really appreciate some help

Now can you draw it? Post your attempt in your question.
Transistor's user avatar
  • 10.8k

Only top scored, non community-wiki answers of a minimum length are eligible