Questions tagged [applied-mechanics]
Questions about using applied mechanics to model engineering problems.
51
questions with no upvoted or accepted answers
4
votes
1answer
85 views
Determine the aceleration of points B,C and D, angular aceleration of rod and the tension in rope DE when ropes AB suddenly breaks
The solutions are F(DE)=134.38N, a(D)=2.016m/s^2 , α=1.29rad/s^2, a(C)=7.828m/s^2
I agree that the FBD and the KD are these:
Then to solve this problem I've done:
$$\sum M_{c}= I \alpha_{BCD}$$
$<=...
4
votes
0answers
40 views
What is the purpose of the ink delivery disks found in most rollerball pens
See picture.
In most rollerball pens there are those peculiar looking disks near the nib, the purpose of which I have not yet figured out, apart from being some kind of ink reservoir/flow control.
...
4
votes
0answers
75 views
Calculating the bending moment ($M$) of a beam as it relates to stress ($σ$) and strain ($ε$)?
I am trying to learn how to work out the bending moment for progressively complex systems to model a beam. I am assuming only one axis of motion (transverse = $y$).
For the basic equations of motion, $...
4
votes
0answers
72 views
Equation for the spring constant of an orthotropic, rectangular wire spring
I hope I can get some help with this problem as I've been struggling with it for a long time. I have a helical tension spring with radius $R$ and a square wire cross section and made of orthotropic ...
3
votes
1answer
66 views
Differential Equation for: Locking a laser's frequency with a PI controller
I think I have a good understanding of differential equations, so I would like to first try to understand my system in terms of differential equations before transforming my system into the more ...
3
votes
0answers
73 views
Is a Geodesic Dome (fuller dome) that floats possible? What material or engineering effort would it take?
Buckminster Fuller has popularized Geodesic Domes (invented by Dr. Walther Bauersfeld who based it on the use of convex polyhedrons), and thus, making buildings with a very large roofs that don't ...
2
votes
0answers
28 views
Bar released from upright position rotates about a lower hinge before being caught by a steel cable, how to calculate the tension on the cable?
I wish to check the safety factor of a steel cable that I've designed to catch a heavy bar that rotates freely due to the gravitational force acting on it.
From the upright position, I'm assuming that ...
2
votes
0answers
37 views
Magnetic Force - Point of Load
I am using a Magnet like this in an assembly and I am trying to calculate the torque in point P2 (see picture below) resulting from the attraction force F between my magnet and the steel part.
As I ...
2
votes
0answers
56 views
Why funnelling air in order to increase the velocity is a bad idea when generating power
Disclaimer: I’m not trying to violate the conservation of energy here; I know that’s impossible for us mortals. I think I’m either wrong or not considering something, I just want someone to point it ...
2
votes
0answers
24 views
Deformation gradient tensor from particle displacements in an inflating material
I don't have a mechanics background, but am trying very hard to read and understand how to approach this problem. I am struggling with understanding what's "correct" or the basic process of going from ...
2
votes
1answer
81 views
Generating Linear Velocity Movement?
In preparation for a Fluid Mechanics experiment, I am looking for a simple commercial ready made
apparatus to generate a linear velocity trend to prove a new theory:
https://aip.scitation.org/doi/abs/...
2
votes
0answers
44 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
votes
0answers
627 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 ...
2
votes
0answers
184 views
Worm Drive Calculation
I have this setup:
-Pully with a mass attached.
-Worm gear drive to lower the mass with a constant speed. (Section A-A)
Now if we look at the cross-section A-A, we can see the worm gear drive:
...
2
votes
0answers
616 views
IV drip/flow rate controller design
I have a question about intravenous flow rate controllers, which are controlled using microprocessors. For example:
I want to control the IV flow rate, the flow is in range from 0 to 300. So, I just ...
2
votes
0answers
416 views
Impact force with unknown deformations or time duration?
I expected to find more documentation on analytical solutions to determine the contact force between bodies, where deformations ($\delta = \delta_{1} + \delta_{2}$) and impact time ($t = t_{f} - t_{i}$...
1
vote
3answers
53 views
Can I create a whirlpool/vortex around a horizontal axis in a flat bottle using motor?
I am using this flat bottle:
I fixed a motor at the centre of one of the flat sides and attached an impeller. I thought this will create some kind of whirlpool effect but as you can guess, since the ...
1
vote
1answer
65 views
How to generate a repeating semi-circle waveform using a mechanical linkage
How can one, in a smooth way, produce a semicircle wave, as opposed to a sinusoidal wave ?
Imagining the machinery and linkages behind the movement.
I mean the trace. For example a point fixed in ...
1
vote
1answer
51 views
Why this torque is not considered into the virtual work principle equation?
In the picture above you can see a SCARA robot, with its end effector (the point x,y). The torques c_a and c_b are the ones of the motors in the joints, while f is an external force. My teacher has ...
1
vote
0answers
24 views
Pully size, imagine 2 systems A,B both transmitting power, both 1:1 but if OD of pulley is 50mm on A and 100mm on B, How do we choose optimal size?
All searches resulted in ratio calculations, which makes sense, my question relates to creating a servo driven spindle with 1:1 ratio with timing belt. Is increased belt surface engagement important ...
1
vote
0answers
81 views
Understanding compatibility of strains
In mechanics, we have the so called compatibility conditions, which quarantee that when a body deforms, the strains are "compatible" in such a way to no discontinuities or gaps for inside the body as ...
1
vote
0answers
61 views
How is the slip calculated in Abaqus small-sliding interaction?
I’m doing research on the sliding of 2 fracture surfaces.
To do that, I’m trying to understand the Small-sliding deformable interaction in the Abaqus (2018), and I use the Node-to-surface ...
1
vote
1answer
70 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 ...
1
vote
0answers
82 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). ...
1
vote
1answer
110 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 ...
1
vote
0answers
303 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 ...
1
vote
0answers
106 views
Boundary Conditions for a circular clamped plate
I've been trying to find the boundary conditions for a fourth order DE equation for a bending circular plate. I'm assuming angular symmetry and an even pressure distribution.
Displacement Equation
$$...
1
vote
0answers
60 views
Engineering mechanics of cutting blades
There are several machines that have (rotating) cutting blades. For example the kitchen aid Vorwerk Thermomix can cut pieces of Food in hundreds of pieces within a few seconds. But why it is so?
If ...
1
vote
0answers
197 views
Nonlinear simulation in ANSYS workbench
I'm trying to conduct a thermo-mechanical analysis in ansys workbench, I've been able to obtain some results using the transient thermal and static structural modules, however, I would like to perform ...
1
vote
0answers
80 views
Is there a way to construct a self-centering axle?
Suppose I have a flat plate of arbitrary but connected shape.
If I try to connect an axle perpendicular to the plate it is very difficult to align it with the centre of mass, creating wobble when ...
1
vote
1answer
200 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?
0
votes
0answers
26 views
Computing forces and moments acting on the sides of a rectangular shell element from corner forces and moments
I have a FEM program for shell elements implemented through the direct stiffness method. Using this program corner displacements of shell elements due to external loading are obtained through the ...
0
votes
0answers
56 views
Mounting grinding wheels on a threaded rod
I'm trying to mount a set of 6" grinding wheels on an M12 threaded rod. The problem I have is keeping them perpendicular to the rod so that they don't wobble when they turn.
The wheels have a 1&...
0
votes
0answers
32 views
Are there examples of spring-mass-damper system that exhibit increasing growth in an unstable way
Simply, are there examples of spring-mass-damper systems that exhibit unbounded behavior or at least increasing behavior for a period of time. I am trying to do some vibrations research, but I am ...
0
votes
3answers
159 views
Force and the reactions on the supports
Consider the movement in the vertical plane of an $AB$ bar with a mass of $20 kg$, $0.8 m$ long and supported by two cursors: one at the end A and the other at point G coinciding with the center of ...
0
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0answers
36 views
Gear/Mechanics problem: How to design to allow for 2 types of rotation
I am designing a new mowing system that can effectively mow around poles. The machine consists of an arm that is attached to the back of a tractor and runs off its PTO. At the end of the arm is a ...
0
votes
0answers
27 views
how to obtain solution of this bessel equation using Frobenius method
Given this equation:
$$
\frac{1}{r}\frac{d}{dr}\bigg(r \frac{dT}{dr} \bigg) - \bigg(\frac{2h}{bk} \bigg)(T-T_a) = 0
$$
I can let $x=r\sqrt{(2h/bk)}$ and $z=T-T_a$ to obtain the bessel equation using ...
0
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0answers
30 views
Is a pyramid considered axisymmetric? Why so?
I read a source, I will not reference the source on this platform.
They stated a pyramid is axisymmetric. Can you explain why if yes?
0
votes
1answer
94 views
Alternatives to sawstop technology
Sawstop table saw braking system works by putting a low voltage on the blade, and when it detects that voltage shorted to ground, the blade is retracted and slammed into an aluminum block. The claim ...
0
votes
1answer
123 views
Break loose torque calculation of lock nut against rotating/acceleating bolts?
I have a Scenario where my lock nut is tightend using a prevailing torque of 14 Nm (as mentioned by the manufacturer) on to the rotor placed between bearings (But the tightening direction and the ...
0
votes
1answer
44 views
Low-Flow Nozzles for Corrosion Spray Testing
So, for a cyclic corrosion test system, I need a nozzle or arrangement of nozzles that provides a flow rate of 45ml-140ml of salt solution per hour to an area 60cm square. All commercial nozzles I've ...
0
votes
2answers
104 views
How to calculate traction force w.r.t. rotational speed of a shaft mounted at a certain angle on a surface?
I am designing a new mobile robot platform and i need a generic solution for the robot in order to establish a proper mathematical modeling. My question is about calculation of the traction force of ...
0
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0answers
141 views
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 ...
0
votes
0answers
38 views
Pendulum-like effect
In modeling a wing with the finite element method, I am asked to consider an engine (approximated as a lumped force and moment) and it's mass, inertia, prestress and gravity contributions.
So the ...
0
votes
0answers
44 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 ...
0
votes
0answers
69 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 ...
0
votes
0answers
33 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 ...
0
votes
4answers
326 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 ...
0
votes
0answers
33 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 ...
0
votes
1answer
87 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 ...