Questions tagged [applied-mechanics]

Questions about using applied mechanics to model engineering problems.

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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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534 views

Final speed of a truck on a slope?

I have a truck which weighs 190 kg and will travel 100m down a 38° slope. How I can find the trucks speed at the end of the 100m?
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696 views

What is micro-electromechanical systems (MEMS)?

I know definition but how would you explain to complete layik ( as me ) what is MEMS and how it is used. Examples: Silicon nanopore membranes (SNM) have been prototyped from silicon substrates by ...
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2answers
4k views

Force required to rotate an object on a plane - moment of inertia?

I have a rectangular shape with uniform mass, approx 6m x 1m. It rotates around an axis in the centre of its width but 1m from one end. The axis has some friction but this is not known. What I need ...
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2answers
221 views

Thin walled pressure vessel

What is the NORMAL STRESS in a thin walled pressure vessel? I am aware of only 2 types of stresses in thin walled pressure vessels: Longitudinal & Tangential. Is any one of these 2 is ...
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1answer
896 views

How to build a paper ramp for a small car?

I have been assigned to build a ramp for a small car. I have only one A2 sheet of paper, scissors and a stapler. What would be the best slope profile, in order to move the car as far as possible after ...
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40 views

Condition for equilibrium of a rigid body on a horizontal surface

The following question is from a past paper from Further Mechanics and it has been bothering me immensely I have spent hours cracking at a way to make sense of it, the question is in two parts Part ...
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1answer
61 views

Solving for stiffness matrix numerically by a set of measurements

Is it in general possible when you have a mechanical structure (in this case I am referring to the structure in this post) and you want to determine the global stiffness matrix of this structure, to ...
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2answers
40 views

Dimensioning of beam pressed by screw in assembly

I need help dimensioning a screw-beam system of a press. I built one prototype but the beam is bending too much. Below is a sketch of my press. In the middle it has a fixing screw which presses ...
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3answers
1k views

Applications with combination of high friction and low wear?

What would be some common applications involving high friction and low wear rates? for example, gear-driven mechanisms which require high friction between the gear teeth but ideally low wear between ...
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1answer
1k views

How to design a gear escapement like in an old pendulum clock?

I've already got a gear that has its teets as in the picture: I want to create the mechanism from the picture, but it's harder than I expected. I think my gear is not the problem. But I'm not able to ...
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78 views

What mechanisms can be used to move a drum at constant speed without an electrical system?

How could I design a paper spool or drum that is moving at constant speed without electrical system? What mechanisms are available? I know that some paper tracing system was being used in 19th ...
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3answers
649 views

Cantilever with three parallel rods

This is slightly similar to a question I previously asked but now I decided to simplify the question and model it similar to a design I have in mind. I sketched out a slightly simplified model. It is ...
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1answer
116 views

Determine the angular velocity and angular acceleration of the AB bar at the instant shown

Consider a sliding cursor C that is fixed to the disk which has a constant angular velocity counterclockwise at 4 rad/s. Determine the angular velocity and angular acceleration of the AB bar at the ...
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1answer
284 views

How to mechanically attach a compression spring to a flat surface

I am working on a new project right now and I was wondering if anyone had any ideas on how to keep a spring fixed and connected to this flat plastic piece [image shown below]. Our goal is to keep the ...
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3answers
96 views

Torque required to rotate object around axis using Stepper Motor for Kinetic Machine

Hey all, I'm creating a machine to rotate a socket wrench using an arm attached to a motor shaft in order to make clicking sounds from the object therefore I'm trying to choose an appropriate stepper ...
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2answers
132 views

Parallel Axis Theorem for x and y Shift

I have a quick question about the parallel axis theorem. Let's say I have a box-like object rotated about the following pivot point I was wondering, by applying the parallel axis theorem, would the ...
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1answer
289 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
62 views

What kind of positioning holding Hinges do Laptops & Notebook Computers use?

What kind of positioning holding Hinges do Laptops & Notebook Computers use? Is there a set of Mech/ Engineering terms for hinges similar to these and are there a category of them that I can ...
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1answer
741 views

polar moment of inertia for compound shape

I have a shape that I'd like to calculate the polar moment of inertia for: the diameter is 600mm; the hexagon in the middle sides are 70mm each; the holes around the hexagon are 130mm from the center ...
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2answers
137 views

Can buckling failure at the first critical load be avoided by “instantaneous” loading?

Previously, I was told by someone I trust well that a column can avoid buckling at the first critical load by applying the load "instantaneously" with a magnitude between the first and second critical ...
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1answer
1k views

Is there a way rotate a wheel in a single direction but have opposing motions every 180 degrees?

In order to give you a good idea of what I want to accomplish suppose you have a telescope mounted on a single rod extruding from the ground. The telescope is free to move such that you can tilt it to ...
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2answers
110 views

Fixed-Free End Column Design

I am currently working on a problem where I have to design a column. The structure I am currently designing currently takes the following form, When designing the column, I know that I have to ...
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2answers
261 views

How do you find the resultant hydrostatic force on a curved surface which is not exactly semicircle

Assuming this is a pressurized chamber with hydro-static force acting on a semi circle stuck in a surface: To find the resultant force, I would first divide the semicircle into half. Pressure on ...
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1answer
43 views

calculation of tension in curved chain for chain fountain (Mould effect)

https://royalsocietypublishing.org/doi/10.1098/rspa.2013.0689 A chain of some sort goes upwards, turns in a half circle (according to the drawn diagram), and goes back down. Focusing on the half ...
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1answer
313 views

Free pre-processor for Nastran?

I want to do a non-linear analysis (possibly SOL 400) on Nastran. I used PyNastran (python module) to set-up the BDF file for a Linear buckling analysis (sol 105). However I feel like it might be too ...
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1answer
48 views

How could I get the coordinates of the circumscribed circle giving the 3 points coords?

I have the coordinates of 3 points thrgouh which, a circle should pass . Having the coordinates of the points in 3D, how could I have the coordinates of the center of circumscribed circle ? also : if ...
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2answers
72 views

2nd Moment of Area of a ring

This is my first question here. I am having trouble finding the 2nd moment of area of a ring with a thickness 't' and radius 'r'. I seem to be a factor of 2 out. What I do is I consider an area like ...
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1answer
128 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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2answers
333 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
220 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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1answer
200 views

Type of hinge I should use [closed]

Can you please suggest what kind (type) of hinge / pins I should use to make the mechanism in the attached file. I was considering to use the pins shown in the second image. But I am not sure if it ...
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2answers
2k views

Difference between maximum shear stress and absolute shear stress

What is the difference between maximum and absolute shear stress in multi axial stress system?
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2answers
1k views

Maximum torsion shear stress in cylinder

I am trying to figure out am I doing this calculation correctly. To get the maximum shear stress for a solid cylindrical pipe I need two formulas: Moment of inertia = pi/2*r^4 Not sure what this ...
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1answer
224 views

How does friction help a car to turn?

I know that friction helps car to move forward. The engine of the car turns the wheels, and the tyres have to grip the road in order for the car to start moving forward. If there is no friction, tyres ...
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2answers
1k views

Design a trolley with four casters

I need design a trolley with four casters, the four casters are installed on the four corners of a 460mmX405mm metal plane. And the load will be a cubic 380mmX225mmX350mm (Height is 350mm), weight ...
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3answers
154 views

Compound gear system: Finding velocity

In the figure below we have that the gear $A$ is has an fixed axis and has the radius of $R_a = 0,1m$ and, in the instant represented in the figure spins clock-wise with angular velocity $\omega_a = 4\...
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2answers
68 views

Optimizing support board placement on work table wing

I'm currently building a work table that will have "wings" on each side that are fixed to the mid section of the table via a hinge. These wings, in turn, have hinges that fix a support board to them ...
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1answer
42 views

Any idea on how to prove this formula of tension?

The formula is: $$T= \dfrac{\left(\sum (\text{coefficient of tension})_i\right) \cdot g_{effective}}{\sum \frac{(\text{coefficient of tension})_i^2}{m_i}}$$ I tried to prove this formula but not ...
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1answer
125 views

Determine the reactions on supports A and C and write the functions of the internal forces for the beam sections AB

The figure shows a metallic structure composed of two beams $AB$ and $BC$ connected to each other by a pin in $B$, the structure being supported in A and C through fixed supports. In the AB beam, a ...
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1answer
43 views

Reinforce foldable table legs

I'm trying to build a table with 4 swivel legs that can be locked into arbitrary angles so that it can stand over one to three rows of storage crates in my garage: As you can see, the legs aren't ...
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1answer
54 views

What causes an inflated spherical cap to look more like a mountain?

I'm working with bulge tests of materials using biaxial loading (applying pressure from one side through a circular aperture). The materials are clamped on the edges. The diameter of the aperture is &...
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1answer
114 views

If a driver gear has larger radius than a driven gear, will a larger gear ratio result in more torque supplied to the driven gear?

Suppose a driver gear has larger radius than a driven gear. For example, we have a pinion with a main disk, where the main disk is larger than the pinion and the pinion is a follower. This is the case ...
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1answer
135 views

Driving Gearbox in Reverse

https://www.maxongroup.com/maxon/view/product/251601 https://www.maxongroup.com/maxon/view/product/gear/spur/gs45/301171 Consider that this motor-gearbox combination is backdriven so that the motor ...
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1answer
56 views

Unit of Angular velocity of Precession [duplicate]

Since the Equation for the Angular velocity of Precession of a Spinning Disk is: $$\omega _{p}=\frac{m*g*r}{I*\omega _{spin}}$$ Where, m -> Mass of the spinning Disk. [$kg$] g -> ...
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2answers
77 views

Cascaded ball bearings

Around where I live there's these soapbox/gravity kart races (google "carros de rolamentos") in which the wheels are built simply from ball bearings. As I was building my own, I began wondering how I ...
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1answer
33 views

Temperature logging of li-ion cells

I'm looking to measure and log the surface temperature of lithium ion cells (cylindrical and pouch). I tried using LM35 sensors with an Arduino, but, the drift was too much somehow. Any suggestions on ...
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1answer
203 views

Locations of max stresses in a circular beam?

If a torque and axial force is applied to a beam with a circular cross section, where along the cross section of the circular beam is the location of the max shear stress, max bending moment, max ...
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1answer
104 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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1answer
79 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 ...