Questions tagged [applied-mechanics]
Questions about using applied mechanics to model engineering problems.
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Derive a Transfer Function from first principles (PID, system identification, statics)
I want to derive a transfer function of my system so I can plug it into MATLAB and use the PID tuner tool.
My system is a balancing beam with a motor on each end of the beam.
My first principles ...
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22 views
Pendulum-like effect
Good morning,
in modelling a wing with finite element, I am asked to consider an engine (approximated as a lumped force and moment) and it’s mass, inertia, prestress and gravity contributions.
So ...
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1answer
35 views
Calculate Rolling Resistance Experimentally
I am trying to calculate the exact rolling resistance ($F_{rr}$) of my car. The approach I am going with is a coastdown test at a low speed so no drag slows down the car. From there I am going to ...
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17 views
Acceleration of the rotation of three gears
Hello, I am trying to solve the question shown in the image but having some doubts in resolving the motion into its different components.
To my knowledge, the problem should be split into 3 or 4 ...
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33 views
Finite Element Code: Convergence issues
I am trying to code a simple FEM problem. A bar is fixed at the bottom edge, and a displacement is applied at the top. I want to apply the displacement gradually , so I have divided it into a number ...
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26 views
Stopping a tall structure from being blown away by a strong wind [duplicate]
I have a 1.5-meter satellite dish, and I wish to have it point directly upwards. Here is what the dish looks like with the feed in place (ignore the wobbliness of the feed, we increased its backplate ...
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16 views
Solving Hertz Impact ODE with Simulink
I have a question about modelling a nonlinear 2nd order ODE for an impact of a sphere on a thin plate in Simulink. Depending on the solver and solver options, my results in Matlab vary a lot. Some are ...
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32 views
Need help with FEA bar analysis problem
I'm trying to solve this
which is to find the total deformation of the bar.
I'm trying to implement the finite element approach, but I am getting way too large of numbers. Here is what I did in ...
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18 views
Distance travelled at articulation point of turning vehicle
Problem outline:
I'm trying to figure out the distance travelled at the articulation point of a turning vehicle with 4 driven wheels (each wheel houses a motor and can all rotate at different RPMs). ...
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2answers
124 views
Statically indeterminate fixed-pinned beam problem
F=32KN; Mf1=60KN-m; Mf2=-58KN-m; g=30KN/m I need to solve this using Force method. Find the reaction at the pinned end.
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1answer
73 views
FEA: Newton-Raphson algorithm for Dirichlet BC non-linear static analysis
I have a standard non-linear static problem to solve with FEA. I am applying displacement boundary conditions only, no external force. The equation to solve look like these:
$K(u)u=R(u)$ Eq(1)
The ...
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31 views
Stopping metallic construction held by a threaded rod from wobbling
I am working on a 1.5m satellite dish with a custom feed. The problem is that the feed is being very wobbly once slightly pushed, as shown here: https://www.youtube.com/watch?v=rAFGbEhhDZ8 (it swings ...
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1answer
23 views
Polarity of a relative angle - Knee joint angle
I'm wondering if it's correct to write:
$$ \alpha = \theta_{lg} - \theta_{th} $$
EDIT: the theta angles are defined positive in counter-clock direcction, instead alpha in clockwise direction. My ...
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0answers
41 views
Need help picking motor to wind a spool
The application is a motor attached to a spool to wind/unwind window blinds.
I would like to operate the motor at $v=0.2\text{ m/s}$, with a max load of 1.5 kg.
I need to know the ideal diameter ...
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1answer
57 views
Installing satellite dish to point to local zenith
After receiving help on my previous post (Stopping/reducing wobbliness in threaded rod), I've decided to come back and ask another question: how can I actually hold the satellite dish into place? I ...
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1answer
90 views
Stopping/reducing wobbliness in threaded rod
I am working on a 1.5-meter satellite dish with a custom receiver cantenna-like feed. The dish didn't come with feed arms, so I need a way to hold the feed into place. What I tried was using a 1-meter ...
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29 views
How to slide 2 small pieces of metal into each other
I'm trying to build a keyboard addon for my smartphone (https://gitlab.com/xengi/mkbd65). The last challenge I'm facing is how the two pieces, namely the smartphone and the keyboard should slide back ...
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1answer
32 views
Soil mechanics-Geotechnical engineering [closed]
Which is more economical to improve or change the soil that is used to build a structure?
my answer is that it depends on each case, but I would like to get more information, or where to search about ...
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1answer
57 views
Moment of Inertia of a Rotor System
I need to settle a discussion on the following question:
Part A:
Find the equivalent spring constant for springs in series
Use equations of motion, sum of torques to find natural frequency of the ...
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2answers
119 views
Rotary to linear motion - how to make upside down “hammer” mechanism?
I’m not an engineer, however I think this place is the best one to find an answer to my question.
So my problem is as follows: I need to create a mechanism, preferably driven by a dc motor, that will ...
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1answer
81 views
Could a spinning permanent magnet's interaction with the Earth's magnetic field propel a boat through the water?
I am wondering if a spinning permanent magnet's interaction with the Earth's magnetic field will produce a propelling force strong enough to propel a toy boat through the water. This propelling force ...
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0answers
59 views
How can I do engineering projects for money at home? [closed]
I am a M.Sc. graduate in mechanical engineering and I have experience with engineering software, like MATLAB, CATIA, and ABAQUS.
I want to know how I can find industrial projects like finite element ...
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1answer
36 views
Calculate surface area and outward normal of each face(non-planar) for a irregular hexahedron.
I am using the vector cross product to calculate each surface area and thus the outward normal. However, this approach fails when the surfaces are non-planar. So what is the best approach to calculate ...
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1answer
110 views
A way to calculate the magnitude of the moment
In my engineering textbook, I didnt understand the example given to explain the magnitude of the moment. It asks to calculate the magnitude of the moment about the base point O of the 600-N force in ...
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1answer
62 views
Approach to solve a frictional problem?
I am having a bar and surface (made of aluminum). I need to attach some material to the end of the bar so that, if I apply any force (25 N-sideways) to bar it has to stick with the surface.
Force ...
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1answer
27 views
Creep / cold flow SS304 vs A514/T1
I made a pallet lift table out of 1/4" SS304 and now have about 5x the deflection that beam calculations predict. I noticed that the machine was shipped supporting a 500lb pallet.
I thinking a few ...
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2answers
144 views
Is strain energy the same as potential energy, or something differen?
Sorry for this stupid, basic question. But I got hung up on it.
We know from Clapeyron's theorem that the strain(internal) energy of an elastically deformed body is equal to half the work
$$
U=\...
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1answer
30 views
Curve-linear vs. Cartesian coordinate systems: linear-elastic & isotropic elasticity tensor
For shell elements, is the elasticity tensor for linear-elastic & isotropic materials the same in a local curve-linear (convected) system vs. a local Cartesian system?
I wonder because ...
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0answers
23 views
Virtual work method for a disk with axisymmetric distributed and concentrated loads
I'm trying to determine all forces/reactions on a disk with a hole in the center.
The disk is loaded with a (known) uniform distributed load from A to C (all around the disk), a concentrated (known) ...
2
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2answers
74 views
Why do we use simple bending equation when bending moment is caused due to shear force?
Simple bending equation is derived assuming pure bending(when a couple is applied onto a beam with no shear stress).We tend to use the above derived equation when moment is caused due to shear stress?...
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1answer
71 views
FBD of folding table leg
I've drawn an FBD of one leg of the table the picture. I've a feeling I'm missing something. Am I?
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1answer
62 views
Reynolds transport theorem and eulerian material derivative
The problem as well as my work so far are in the image.
I begin with equation (2.23) and use the divergence theorem to express the second term as the surface integral part of the problem equation. ...
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1answer
100 views
Eulerian and Lagrangian descriptions of velocity
I feel as if I understand the conceptual difference between Lagrangian and Eulerian descriptions. But I can't seem to follow the math. I have one example that I would greatly appreciate an explanation ...
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1answer
93 views
Difference in Diameter calculation using Solidworks and manually
When I try to create a flat form of a archimedes screw using Solidworks it gives me a diameter different from what is calculated manually basically using a Pythagoras Theorem. Can anyone explain the ...
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2answers
53 views
Polyurethane mix-on-the-spot system
3d printing is a slow process and for my solution I need fast printing. So I print with no infill and I fill inside with a two part, 10 min drying polyurethane resin. I mix them in a disposable cup ...
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0answers
105 views
How to calculate bearing loads in a two stage helical gear box?
Here P, Q, R, S are the bearings and G1, G2, G3, G4 are four helical gears.
The gear forces tangential(Kp), Axial(Ka), Radial(Kn) are known.
All the distances are known. The forces acting on bearing ...
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1answer
108 views
LS DYNA Material Model 163, Modified Crushable Foam
Question is on the meaning of input variable TID within material model 163 of LS-Dyna 971.
Definition of TID variable.
TID: Table ID defining yield stress versus volumetric strain at different ...
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2answers
41 views
What should be the density of a compressed gas while measuring the flow rate using Rotameter?
Say we have a required mass flow rate, in order to have equivalent volume flow rate, we need to consider density of the operating fluid (compressible fluid).
To measure the volume flow rate in LPM, ...
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3answers
132 views
What components are needed to reverse the direction of a belt conveyor using one reversible motor, and how do they change the tension on the belt?
On regular conveyor belts, motors are usually placed on the head shaft where material is discharged, and tension is highest at the entrance of this head shaft. However, if the motor were to be simply ...
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1answer
102 views
Calculate the torque needed to turn a rod it's own axis [closed]
If a rod is turned around it's own axis, force/torque is needed.
Let's assume the rod it self has a diameter $d$, a length $l$, the mass $m$ and should be turned by a motor on one side. The other ...
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1answer
61 views
Analytic expressions of the kinetic and potential energy [closed]
A homogeneous rigid circular disc (radius R, mass ms, center point S) rolls without a slip on a plain with a small angle of inclination alpha against the horizontal. A point mass MG is fixed on the ...
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0answers
108 views
press fit ball joint
I enjoy creating mechanical designs but I am not a trained mechanical engineer.
I have a technical issue with a joint design that needs to be permanently retained using a press (snap) fit. Any idea ...
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1answer
187 views
Calculating the torque requirements of the motor for a specific case
I want to use a DC 12/24V motor to rotate an assembly of glass tubes(image attached) through a hollow shaft of 25mm OD and 22mm ID, the shaft is supported on bearings on both the sides(assume minimum ...
2
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1answer
38 views
Structural mechanics
Ques: I have a question regarding solid mechanics and plate theory,is 2 layer plate means laminated plate or simply refers to as a plate?
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1answer
96 views
What is the maximum deflection and bending moment of a hinged hinged beam? [closed]
It is not a simply supported beam with one end hinged the other end with roller support. I am working on both the ends hinged beam. i.e at the two ends only rotation about z axis is allowed and all ...
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1answer
21 views
A sealed ball is not connected to anything externally, but can have any complex mechanism inside. Can the mass change? [closed]
A sealed ball is not connected to anything externally, but can have any complex mechanism inside (mechanical, chemical, or any other). Can a wireless trigger from a remote or any other wireless ...
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1answer
62 views
Cantilever beam with disc at end (structural mechanics)
I am trying to figure out how I can assemble multiple finite elements to obtain the system mass matrix $\boldsymbol{M}$ and the stiffness matrix $\boldsymbol{K}$.
The situation is depicted in a ...
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1answer
52 views
Rayleigh damping in structural mechanics
In structural mechanics, we often approximate a partial differential equation by a system of ordinary differential equations in matrix form
$$\boldsymbol{M}\ddot{\boldsymbol{q}}(t)+\boldsymbol{B}\dot{...
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359 views
How does Abaqus calculate reaction force?
I wrote a UEL for one element and compared to a reference UEL (FEM), where the results agreed satisfactorily, except the reaction force. The stress, strain, strain energy all were pretty accurate.
I ...
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1answer
49 views
Hinge or similar that breaks at a certain change in acceleration?
Suppose I have a rope that is capable of lifting 100 Kg without breaking. But I would like the rope to break if it is exposed to a sudden change in acceleration (jerk). So if the rope was lifting 10 ...
