Questions tagged [structural-beam]

A structural element whose length greatly exceeds both its width and height, which are of the same order of magnitude.

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What will happen if I bombard electron beam on metalloid?

I know when we bombard electron beam on metals it gives out X rays, but my question is that what will happen if I bombard electron beam on metalloids?? please give answer
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How Gaussain beam exaclty be after diffraction between two mediums?

How it will be the refraction of the Gaussian beam, does one of its sides will go in distortion, and which equations can predict this distortion? Sure I have to use Snell's law to know the angle but ...
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Writing a two variable function$ f(x,t)$ in terms of Dirac-Delta $δ(x)$ function and a function $P(t)$?

How to write a two variable function $f(x,t)$ in terms of Dirac-Delta $\delta(x)$ function and a function $P(t)$? For example; I read something in a book. You can find the following picture. But ...
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In a beam, when there is a UDL present on a small portion, why do we add a UDL above and below of the remaining beam?

In the above image, I need to find the deflection at point C and D of the simple supported beam. Macaulay's method is to be used. To solve this, on part BC a UDL of 1 kN/m is introduced both above ...
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How the length, flexural rigidity and position of attached mass affects the period of oscillaion of cantilever?

Hey everyone, I'm a highschool student from New Zealand and can someone please explained to me with physics principles in words: Why increasing the length of cantilever increases the period of ...
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113 views

Understanding positive and negative shear strength sign

Shear strength is a force that tries to keep stuff in equilibrium, when another force tries to break/bend/modify a structure. This "another force" (external force) may also produce a moment. In the ...
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57 views

Moment on a body and on a simply supported beam

Consider a body on a frictionless floor being acted upon by a force F as shown in figure. Force acts on its centre of mass. (Centre of mass and centre of gravity coincide in this case, ie, both lie on ...
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Finding Shear Force in a Beam [closed]

I have the following question: The question is asking for the shear force at point C. To work this out, I've determined the reaction force at point A. To find the shear force, the book then sums the ...
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Simple beam deflection of cantilever beam

Recently I had need to prove the beam deflection equation for a simple cantilever beam with a point load at the end. The equation would be in reference to the Euler-Bernoulli theory taught in most ...
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47 views

Poisson's ratio in analytical beam deflection equations

After looking at some of the analytical expressions for analyzing beams, I noticed that none of the equations depend on the material's Poisson ratio. Some analytical expressions can be found in https:/...
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Why is a force omitted when calculating shear force in this structure?

Here is a picture from an example problem I found in my lecture notes. The problem is to find an expression for the shear force at point C. My attempt to solve this was: If we split the beam into ...
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Positron beams and crystallography

I wad mainly reading about impact and uses of positron beam to determine conductivity and the structure of material . Do can anyone just describe how positron beams can determine conductive of ...
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20 views

What component of the strain tensor is a strain gauge measuring in a bend test?

I am studying a bend test of a beam. The beam is set up like a 4 point bend. The force is applied at 2 locations on the top surface, and 2 locations on the bottom surface are fixed in place. It is ...
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94 views

Why are there no vertical normal compressive stresses when a horizontal beam has a vertically applied load?

In a beam with a a single vertically applied load and a single vertical reaction force, as well as a reaction moment, for example, this one: We would typically consider the normal stress ($\tau_{xx}(...
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143 views

Is the Young's modulus the same for compressive and tensile test?

I want to know the Young's modulus for a compressive test, but I have just a tensile test. Are they of the same value?
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Does the resonance frequency of a cantilever beam depend on whether it is bending in-plane?

What is the in-plane resonance frequency equation for a single-beam cantilever of rectangular cross-section that is fixed on one end and has a mass M attached to the other end? Below are the only ...
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106 views

Why it is better to have two legs than four?

I cite from the available on internet book "Structures or why things don't fall down" written by J.E.Gordon. ...from the structural point of view two legs are better than four, and the centripede is ...
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Why is beam forming more energy efficient than a straight up omnidirectional signal?

Someone tried to explain the process of beam forming to me, and how beam forming is far more efficient than an omnidirectional signal of similar amplitude. This seemed obvious at the time: the power ...
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Is electron in a beam (SLAC and/or CERN) a classical or Quantum Particle?

Electron and Positron beams collide at SLAC and CERN for high energy experiments. Electron beam is produced by thermionic emission from tungsten filament and then launched in the Electric field to ...
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34 views

Stopping a spinning object with a flexible gripper

I would like to know how deformation of the contact surface affects friction of a spinning object. In the image below I have a 2D problem of a spinning circle with two elastic "fingers" pinching it ...
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Explain cantilever dynamics of first mode

I would like to implement the time-dynamics of the first mode of a homogeneous cantilever, $w_1(x, t)$. I have found the equation for the first mode in wikipedia: https://en.wikipedia.org/wiki/Euler%...
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140 views

Model of an Elastic Rod

For an electrical design, i am having a cable modeled as a perfect elastic static rod, fixed at both ends, as i have depicted how should it be for different given reference lengths. I've studied ...
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What stresses should be considered to determine the effective stress and FOS?

This question I tried to solve by considering the torsional shear and transverse shear and axial loading. But the answer is not clear. But the answers that I got by different trial and error method ...
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1answer
714 views

Why frictionless joints are assumed in pin-joint truss analysis?

In pin-jointed truss analysis, we consider some assumptions. One of them is that they have friction-less joints. Why do we have this assumption? What would happen if the joints were to have ...
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Consistency in length in beam theories

From my understanding, the Euler Bernoulli Beam theory is mostly used for small angle displacements, and an implication of this assumption is that the length of the beam is subject to distortion and ...
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87 views

Curvature of a beam when subjected to an axial force

How do you calculate the curvature of a beam due to any forces acting parallel to the beam? Intuitively, a beam in real life would bend perpendicular to the force to form an arc. How is this ...
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81 views

How does a beam splitter split a reflected beam? (experiential data)

Modtager = receiver. Prøve = sample. An beam is emitted from the emitter send to the beam splitter and is devided into two as shown in the figure. From the sample (prøve) the beam is reflected and ...
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266 views

Truss analysis how to calculate for a single beam?

Suppose I want to calculate the tension/compression force only in 4. Is there an easier way to calculate it or do I have to calculate everything with the joint method? I don't immediately see zero-...
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72 views

Beams versus Cables

It seems obvious that when a beam deforms under a point load, it deforms into a U-shape and when a cable deforms, it deforms into a V-shape. Is there any graphical method of understanding this beyond ...
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233 views

Euler-Bernoulli equation for a cantilever strained by a force

I'm trying to model an experiment where a cantilever, fixed at one end, is oscillating under an applied force at the free end. Specifically, I'm focusing a laser on a rectangular cantilever and ...
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102 views

Paraxial diffraction

I got some work to do at a lab, but I am quite stuck with this task: Gaussian beam at a plane $z=0$ is $f=\exp[-(x^2+y^2)/d]$. Evalute the formula at a plane $z=z_0$ using paraxial diffraction theory. ...
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76 views

Dumping term in equation

I want to know the physical interpretation of the term $$\int\limits_0^\infty {g(s){\psi _{xx}}(x,t - s)ds}$$ in some equation. This term is called infinite memory and the function $g$ is called ...
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51 views

Why conceptually cut a beam or else? (method of sections)

This question is related to structural design, and statics: When studying a beam, for example using the sections method, why do we make a conceptual cut?
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125 views

What is the stress distibution in a cantilever non-slender beam?

I recently had a discussion with another engineer about shear walls and the check that are necessary to establish their capacity to resist horizontal loads. He was arguing that the walls should be ...
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1answer
109 views

For a tall skyscraper, what are the requirements for young/shear modulus?

I am teaching physics 101 for the first time and am discussing stress/strain. As an illustrative example to students, I'd like to make the broad statement, "The primary supports in skyscrapers need a ...
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1answer
98 views

Solution of Euler-Bernolli differential equation for a simple beam

I'm trying to solve the Euler-Bernolli differential equation for an homogeneous rectangular beam without load: $$ EI{\frac {\partial ^{4}w}{\partial x^{4}}}+\mu {\frac {\partial ^{2}w}{\partial t^{...
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118 views

Linear momentum density of light in general case

If I am given a photon wave function of the form: $\vec{A} = \hat{x} \;u(r,\phi,z)\; e^{-ikz}$ where $u(r,\phi,z)$ is a distribution of the field amplitude (linear polarization). Then the linear ...
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588 views

Find the 'rigidity per mass' of beam profiles from second moment of area, length and density? [closed]

Calculate the “rigidity per mass”, i.e. the ratio of the second moment of area and the mass of a beam (length 𝐿, density 𝜌) for the following cross-sections: I know how to get the second ...
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359 views

Why are truss members two force members and why are the forces directed along the axis of the member?

In Hibbeler's book, Engineering Mechanics: Statics, on pages 264-265 it is mentioned that two assumptions are made in the design of a truss: All loadings are applied at the joints The members ...
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167 views

Ratio of reaction force - Principle of moments

I am having difficulties figuring out how I can determine the ratio of the reaction force at B to the reaction force at A: I am also asked to justify which reaction force on the plank is greater; I ...
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What is the role of pillars in bridges?

As I can see in the picture, there are so many pillars which are holding the bridge. This picture gave a question to me that what are these pillars doing below the bridge?? An appripriate answer ...
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1answer
47 views

Fixed rectangular structure and gravitational force

Suppose I have rectangular structure hanging from the ceiling. It has dimension of height $H$, and square area $A$. The top is fixed to the ceiling, and gravitational force is pulling the structure ...
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1answer
534 views

How to calculate the beam size of a laser from the end of a fibre?

I need to calculate the beam size of the laser beam after a distance $z = 2$ mm from the fibre tip. I know the numerical aperture NA = 0.59, half angle $\theta = 36$ degrees, and core diameter $d_\...
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1answer
54 views

Does it make sense to compute moment of force about any axis?

This Wikipedia article gives that If the unit vector along the axis is $e$, the moment of force about the axis is defined as $$M=e \cdot M = e \cdot (r \times F)$$ Then gives an example which I ...
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2answers
474 views

Bending moment as product of thickness and deflection?

I'm reading a book on shape optimization and in p.3. the author gives an example of optimizing the thickness of a vertical beam represented by the interval $I=[0,1]$ (so it's a line) and under a ...
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225 views

Dispersion of Gaussian Beams

I'm new to optics, especially Gaussian beam optics. I'm curious about things that I've been reading in Daniel Steck's textbook, and how they compare with my common sense intuition. Guassian beams are ...
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Is the light emitted by a laser a 'beam' or a 'ray'? [closed]

In English, the light generated by a laser is almost always referred to in technical texts as a 'laser beam'. However, in French, Spanish, Portuguese and Italian, forms that correspond to laser beam ...
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Sun light collimation

Is it possible to make sun light collimated in such a way, to increase energy density and keep it more less parallel? like on the Earth we have intensity of sun approximately 1300 watt/m2. If we use ...
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1answer
103 views

Why is shear force indeterminate at a section where point load acts

Why is shear force indeterminate at a section where a point load acts, i understand it from the mathematical point of view, since the left and right hand limits would not agree and would lead to ...
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Fermi-Pasta-Ulam for the beam equation

The Fermi-Pasta-Ulam numerical experiment is based upon the discrete wave equation, with a small non-linearity added to the forcing term. Does anybody know of similar research performed on the beam ...