Questions tagged [applied-mechanics]

Questions about using applied mechanics to model engineering problems.

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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 equation of material ...
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4 votes
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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: $$\sum M_{c}= I \alpha_{BCD}$$ $<=...
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4 votes
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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 ...
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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. ...
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3 votes
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233 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 ...
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3 votes
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94 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 ...
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2 votes
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31 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 ...
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2 votes
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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 ...
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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 ...
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2 votes
1 answer
101 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/...
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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) ...
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2 votes
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698 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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2 votes
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236 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: ...
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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 ...
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500 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 ($t = t_{f} - t_{i}$...
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Are there any advantages of using BEM for contact problem over FEM, apart from lesser computational cost?

FEM - Finite Element Method BEM - Boundary Element Method If we had access to "enough" computational resources (to discretize the entire volume domain in FEM to the same degree of fineness, ...
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1 vote
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How to calculate the degrees of freedom, constraints and the generalized coordinates in this dynamic system

The rope lengths are taken to be constant. Solution: $N$ particles with $k$ constraints. . Then the Degree of Freedom (DOF) is $3N-k$. In Figure 1, we have two particles $m_1$ and $m_2$, so $N=2$. But ...
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1 vote
1 answer
89 views

Calculating torque in planetary gearbox

It's my understanding that in a planetary gearbox, force moves through the system via four mechanisms: the ring gear, the planet gears, the planetary carrier, and the sun gear. I'm trying to ...
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1 vote
1 answer
75 views

How to solve this complicated truss system?

Below is a truss I simulated in a truss calculator. I'm just wondering, how to solve for the compression and tension of each member and are there any method that can solve this? My solution is I ...
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1 vote
4 answers
99 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 ...
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1 vote
2 answers
146 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 ...
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1 vote
1 answer
117 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 ...
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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 ...
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116 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 ...
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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 ...
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1 vote
1 answer
80 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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1 vote
0 answers
106 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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1 vote
1 answer
140 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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1 vote
0 answers
358 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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111 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 $$...
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1 vote
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65 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 ...
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1 vote
0 answers
224 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 ...
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1 vote
0 answers
92 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 ...
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1 vote
1 answer
242 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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Does the surface finish of the strings on a musical instrument impact the timbre?

Suppose we are testing out different unwound strings on a piano. Each of the tested strings is made of the same material, has the same length, same diameter, density, etc., the only difference being ...
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2 answers
42 views

Problem of lifting of a body using 4 strings

I have a solid object that has been lifted to a hieght by 4 strings. I know the lifting point and the 4 corners of the object. Also the mass and the center of the gravity location of the object is ...
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0 answers
17 views

how much pounds of pressure does a screw on perfume bottle cap vs a mechanically applied perfume bottle spray mechanism for a bottle exert?

What would be the difference in pressure between a screwed on bottle cap like the ones you see on a refillable perfume bottle screw on top such as this https://www.ebay.co.uk/itm/154178728592?hash=...
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0 answers
29 views

Calculation on gearbox design

I want to design a gearbox of 70hp input motor and speed of 1400rpm. The gearbox ratio is 1:10 of 2 stage parallel arrangements. How do I calculate for the teeth, modules and other requirements ...
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0 votes
1 answer
45 views

I have a question regarding moments and centre of mass

Lets say a plane had 2 engines located 9m ahead of its rear wheels. Give each engine a mass of 7.5 tonnes. A force of 147150N will act 9m ahead of the rear wheels. lets say the aircraft was 133 tonnes ...
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39 views

Modelling a Simple Translational System

I posted this on stack exchange physics, sadly no one has answered so I thought I'd try my luck here. I am trying to model the following translational mechanical system in I/O form, however I am ...
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For pure rolling , Proof for every point on wheel has velocity = vc + wr

There are 2 texts I have seen for every point on wheels finding out the exact velocity of certain points. The theory states for all is that : Every point on wheel has total v = rotational + ...
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2 answers
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Why is velocity of wheel = v0+wr?

The case we have is : A wheel is kept in a box. There are two images given. Given below are conditions of the first image: Velocity at which the wheel is turning. $\frac{d s}{d t}=\frac{d \vec{\...
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36 views

mechanism design for matrix of adjustable direction pointer

I need to construct a matrix of light pointers, each one aims in specific direction, and each pointer direction will be adjusted thousands times, size is flexible could be millimeters or centimeter ...
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1 answer
56 views

Calculate effect of drag on ball in motion

So I’ve been trying to work out the range of a ball that has been projected by two spinning discs please when accounting for drag- This is what I got so far: $V=V\cos\theta$, $T=2V\sin\theta/g$ , and $...
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40 views

Root diameter and the base diameter of gear and pinion

In my design of a spurgear the root diameter in pinion is less than the base diameter but in the gear the base diameter is less than the root diameter. Why?
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64 views

Designing a grabber

I designed a grabber for grabbing strings and yarns. the movement that I need is straight up and down to grab a piece of yarn. I wanted to know if this model (in the video) works in real life or not. ...
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0 answers
40 views

where did the concrete splitting test calculated stress formulat come from?

In compression test of cylindrical concrete sample we get the normal stress easily by dividing failure force by sample cross section, but how we can explain the formulat used to determine tensile ...
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22 views

How to choose contravariant or covariant bases?

I completed an introductory course on continuum mechanics, but we did not delve into curvilinear coordinates with CM. However, when I read some publications I see the stress-strain relationship is ...
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0 answers
40 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 ...
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58 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&...
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