All Questions
Tagged with mechanical-engineering solid-mechanics
111
questions
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Design a string
Consider a string with a mass attached. The string is fixed to the support above, and the mass is hanged at the other end. Is it possible to design the string for the following two cases?
The mass is ...
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48
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How to geometrically derive stress transformation equations from Mohr's circle?
Consider the simple case of a 2D stress element with its corresponding Mohr's circle:
Now, for stress transformation using Mohr's circle, we rotate the diameter AB by twice the angle of rotation of ...
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1
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1
answer
37
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Circumferential stress in a toroidal shell
Consider the following formula for circumferential stress (σ2) in a toroidal shell (taken from Roark's Formulae for Stress and Strain):
It seems that it has been derived by using simple force balance ...
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33
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DLC wear resistance
I read that a thickness of one micrometer of DLC coating (which, if I understood correctly, shows similar properties to diamond), increases the lifespan of an item plated with it from a week to more ...
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Shape of a beam that is bowed under compression?
Suppose you have a uniform beam, such as a piece of plywood that is 4 feet long, six inches wide, and half an inch thick. Suppose you cause it to bend by attaching, for example, a string under ...
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Does the magnitude or range of interaction of a force affect which layer dominates the mechanical response of a multilayered structure?
Suppose I have a two-layered material, with a stiff and thin outer layer (high E) and a soft (low E) and thick inner layer.
Intuitively, it feels like the effect of short-ranged forces (e.g., van der ...
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34
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How to calculate the direction of shear stress due to shear force on a circular cross section?
For a circular cross section, we know that the shear stress due to a shear force at the boundary (the radius of the circle) has to be tangent to the curvature. This is so that we have no radial shear ...
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1
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65
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Is it true that there are some principles of mechanical trasmissions and junctions that were known for long but became possible only recently?
Is this true that some parts of mechanisms, such as various types of transmissions or junctions, while were known theoretically for a long time, became possible practically only with advent of 3D ...
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35
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Trying to detach a detachable handle on a meat grinder
I'm trying to detach the handle from my meat grinder. I'm not sure what this kind of lock is called but it had a crescent/half moon shape that locks against the grinding (clockwise) motion. In order ...
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2
answers
281
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What is the difference between maximum principal strain and maximum in-plane principal strain?
For the purpose of answering/explaining this, it does not need to be restricted to strains (i.e., it can be stresses too). I am mainly trying to understand when to use which one (i.e., if I am ...
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Vertically oriented shaft sleeve rubbing against bearing - Calculating side load due to a certain amount of tilt
At some given angle of tilt, we will perceive the pressing of a rotating SS shaft sleeve against a greased bronze journal bearing. How would you compute the side load force on the bottommost bearing ...
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92
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Does gold have elastic behavior?
I know structural steel is considered to have an elastic behavior and after a certain deformation, it has a plastic behavior.
How about gold metal?
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66
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What is the meaning of the traction continuity condition in the generalized momentum balance (continuum mechanics)?
In Nonlinear Finite Elements for Continua and Structures by Belytschko and al. it is stated:
As we have already noted, the strong form, or generalized momentum balance, consists of the momentum ...
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76
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Building Equations of Motion
The following figures represent a model of a building, can someone help me, extract the newton equations of motion and determine the degrees of freedom.
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56
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Which design is most resistant to tipping against 90 degree downward force?
Have a question sort of related to question at (What calculation to find how much force before tipping over?) but with slight modifications.
Trying to weld some tubing together and onto a heavier base ...
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15
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Why are the indices of term of the Cauchy Stress Tensor and Maxwell Stress Tensor opposite to each other?
For CST (https://en.wikipedia.org/wiki/Cauchy_stress_tensor), the first index represents the plane and the second index represents the direction:
For MST (https://en.wikipedia.org/wiki/...
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2
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301
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Why do two simply supported beams stacked on top of each other deflect more than a single beam of twice the thickness?
If the thickness of each beam in the stacked configuration is 't', the thickness of the single beam is '2t'.
Explanations in terms of Euler Bernoulli beam theory, or any other explanation that is ...
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31
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How to find the displacement at each interface of a composite structure subjected to shear force?
Imagine a block made of 3 horizontal layers of 3 different materials (shear moduli S1, S2, S3) and fixed at the bottom surface.
If I apply a displacement 'x1' (or shear stress 'V1') to the top layer, ...
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1
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53
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How to find out the strain distribution of a block in a simple compression test?
I am performing a displacement-controlled compression test on a square block, where the top of the block is attached to a fixed plate, and the bottom of the block is attached to a movable plate that ...
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89
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Thin wall pressure vessels: local stresses in bends
How can I calculate the stresses in corners where different geometries meet?
This image is a quick example of the positions i am referring to.
Additional information
In class we studied the membrane ...
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68
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Why carrom coins have the circular profiles on them?
Why do carrom coins have these circular profiles on them? At first I thought that this will reduce the friction as area reduces, but quickly recalled that friction for solids don't really depend that ...
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2
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210
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Problems in the application of the first theorem of Castigliano for a cantilever beam
I'm having contradictory results while applying the first theorem of Castigliano for the cantilever beam shown in the figure above. Due to P and the restrictions on point $B$, it will have a bending ...
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87
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Thermal Expansion and Stress in a Heated Beam
Consider the case of a beam that is supported in such a way that expansion can occur freely. Suppose that the beam is heated in such a way that the temperature varies with the depth of the beam. Let $...
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51
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Using Strain Tensors to Recover Stress Tensors
Disclaimer:
I am very new to the field of mechanics, my background is in electrical engineering. I apologize in advance if anything is horribly wrong.
My references are:
"First Course in FEM, 4th ...
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52
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Potential Problems of Excessively Hard Shaft
Will there be any issues if we make the shaft too hard?
Hardness being a surface property may prevent surface scratches and wear, could it lead to any problems in general?
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59
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In the context of Beam Deflections If the moment curve has a discontinuity, how do we account for it in the slope and deflection curve?
In reality if we load a beam within the elastic range of the material, it forms a curve that can be represented by a mathematical equation. But if the moment curve has a discontinuity it must mean ...
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2
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191
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Doubt related to S-N curve
S-N curve is drawn from the results of fatigue test and fatigue test is conducted under completely reversed bending stress condition on a standard specimen. Is there any reason for conducting the test ...
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112
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Why does the torsion in a circular bar result in shear stress along the axial direction?
In the case of pure torsion, how does a differential area on cross-section of the cylinder with dx length undergo a shear force that is perpendicular to the cross-section ?
I can understand that a ...
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58
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Which CNC gantry support shape is more ridgid?
I'm in the process of designing a small CNC. There are two styles of side plates for supporting the gantry. The first one has an angled corner cut on the front, while the other has a backslash shape. ...
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How to find Tensile Modulus of a layer of Plain Woven GFRP with GSM of Fabric given
I need to Input "E" the tensile modulus for analysis of a composite layer made from Plain Woven E-Glass Epoxy composite material.
I know the GSM (g/m^2) of fabric is 106.
Using GSM =106, ...
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Is it possible to achieve the same amount of stress for an equal amount of deformation but two different cross sections?
I have a small tube with outer diameter (OD) $R_1$ mm and inner diameter (ID) $r_1$ mm. The tube is bent using a moment $M_1$ to create an angle $\theta_1$ with its plane of origin. The stress can ...
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254
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How does a single point load cell eliminate the inluence of moment/load placement
All descriptions I have been able to find mention some variation of "due to their geometrical design single point load cells are immune to load placement" with no explanation on how is it ...
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2
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1k
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Bending analysis of beams with varying cross section
All problems I solved in MoM class regarding beam bending involved a beam with continuous cross section. But is the process the same for a beam with varying cross section? For 'same process' I mean ...
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33
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Approaching/formulating a problem in solid mechanics
Consider a thin surface and hold it tightly and vertically at a point on its boundary. What it is the shape it assumes?
As a particular example let's take a circular plate clamped on a plane, as shown ...
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58
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How to model flexible plate between two sticks solidworks
I am following a paper on undulatory fin motion and trying to make a model of it in Solidworks.
The problem is stated as having two servo motors with two rays and a flexible rubber membrane between ...
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1
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68
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How holding force is produced in Jacobs taper for holding drill chucks?
How the wedge action produce significant holding force in a Jacobs taper for holding a twist drill chuck.
(Even just sliding the tapered plug inside the sleeve by hand makes a rigid connection that it'...
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1
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53
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Flexure formula insufficient for model
This is just a though experiment that I had.
Two hooks (the hooks are just extrusions of the sketches shown in the pictures below, with both hooks being extruded by the same amount).
If we use the ...
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2
answers
145
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What are the practical solutions to manufacturing this mechanical piece?
My Custom Piece (Measures are in mm)
I'm designing a custom mechanism that needs this piece to be able to function, but when i started thinking about how to manufacture it, I started getting confused ...
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1
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377
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Cauchy stress tensor vs Piola-Kirchoff stress tensors, when to use them?
I'm just reading about the P-K stress tensors, while I've seen Cauchy stress tensor in a course a couple months ago. From a technical point of view, I think it's clear what they represent.
Cauchy ...
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3
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1k
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how to determine the direction of support reactions in a truss?
Hi, I am not sure how to determine the direction of support reactions at point A and K. I know point A has a pin support, therefore, it can take in horizontal and vertical loads and point K has a ...
user38335
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1k
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Determining the angle theta at the Mohr's Circle
I'm having trouble about deciding the initial angle theta before drawing the Mohr's circle.
From what I've learned from the lecture, I need to draw a normal line of indicated plane and find the angle ...
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1
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70
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Ideal design for a long fruit plucking pole
I need to design a long (6-7m) pole for plucking fruits from tall trees.
The following are the requirements:
The pole material needs to be as light as possible.
The pole should not be flexible ...
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2
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86
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Strain energy, Conservative force and Potential energy
What I know:
In general, the work done by a conservative force $F$ is equal to the negative change in a potential energy.
$$\int_1 ^2F.ds = - (U_2 - U_1) $$
A potential energy is always associated ...
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32
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3
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8k
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Why are two wires used in railway overhead equipment?
While watching the train videos, I came across these overhead wires. After searching on the internet, I found that both catenary and contact wires carry the same voltage and are connected by vertical ...
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3
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134
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Work done by a force in a deformable body
Consider a deformable body that is acted upon by several forces at different points of application.
Under these forces, the body remains at rest but deforms and the particles have some displacement. ...
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1
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197
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Constant tension...does angle between rollers matter?
Thank you in advance to anyone with time to take a look at my question here. For anyone interested, this is a question in regards to an open source film scanner project, which can be found here: https:...
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2
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169
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Stress in a L-shaped Beam due to Thermal Expansion
A L-shaped frame $ABC$ (right angle at $B$) consisting of beams $AB$ and $BC$ are fixed at ends $A$ and $C$ to rigid walls. Find the tensile stress at $A$ when the temperature of the frame is raised ...
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82
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Why were handcuffs ever made with a chain between them?
I've noticed that modern handcuffs are always attached directly to each other, without any "chain" of any length in between. I guess I can understand why that make them safer and more robust....
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1
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683
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Relationship between shear moduli in an orthotropic material
I'm confused what the relationship between each of the shear moduli are in an orthotropic material. From what I understand, there are 3 independant major shear moduli, G12, G13, and G23. They each ...
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2
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3k
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How to calculate press load for an interference fit with no friction coefficient between the materials (shaft & hub)
Press-fit load calculation always takes friction into consideration and gives you the load expression as follows,
$$F = µ\cdot PA$$
where µ is the friction coefficient, P (Interference Pressure) is ...
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