What is Beam: Definition and 1000 Discussions

An I-beam, also known as H-beam (for universal column, UC), w-beam (for "wide flange"), universal beam (UB), rolled steel joist (RSJ), or double-T (especially in Polish, Bulgarian, Spanish, Italian and German), is a beam with an I or H-shaped cross-section. The horizontal elements of the I are flanges, and the vertical element is the "web". I-beams are usually made of structural steel and are used in construction and civil engineering.
The web resists shear forces, while the flanges resist most of the bending moment experienced by the beam. The Euler–Bernoulli beam equation shows that the I-shaped section is a very efficient form for carrying both bending and shear loads in the plane of the web. On the other hand, the cross-section has a reduced capacity in the transverse direction, and is also inefficient in carrying torsion, for which hollow structural sections are often preferred.

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  1. A

    B Pinched plasma inside a neutral beam injector

    Let me start this off with saying I am just a uneducated idiot, But after reading about Zap Energies sheared flow pinch reactor I was wondering if you could use a similar concept in a neutral beam injector? Like could you first compress and heat the plasma inside of a NBI using a pinch, then...
  2. FEAnalyst

    Beam deflection and curvature radius formula doubts

    Hi, I am working with leaf springs and studying the derivation of the formula for the deflection of such a structure. The derivation is shown here: My only doubt is how to obtain the following formula: $$\delta=\frac{L^{2}}{8R}$$ where: ##\delta## - deflection, ##L## - length of the beam...
  3. M

    Concave mirror reflecting a point lamp, that create a wider beam

    I've look if there was any way to get the "image size" or a ratio to use the Mirror Equation to find the focal length, but nothing. I think it's base on some geometry, but I don't see the relation.
  4. IdBdan

    Trailer Frame Beam Design

    I'm building an aluminum tandem axle (7k total capacity) trailer. Boat (18'/1300#) on the rear and a Ryker Can Am 3 wheel (750#) on the front. It's a 23'-6" x 6'-8" bed. Max live load will be approx 2250#. 900# frame weight. 230# axles. I'm testing beam sizes with online calculators and need...
  5. J

    Free Beam moment problem

    Hello all, I'm trying to understand the maximum moment on a free beam. Consider a tail sitter drone that is simplified into being a beam with two motors fitted with propellers on the end of the beam (see the photo below), let the payload be estimated as two, 2 newton loads going downwards. If...
  6. J

    Box Beam stress problem with welding

    Hello All, I'm trying to figure out how to strengthen a box beam that's been welded to another box beam. In the photo on the left is 2 beams welded to each other, they are 2x1" Aluminum 6061-T6, with a 1/8" wall thickness. The yellow lines indicate the location of the weld. A force of 216 lbs is...
  7. Marilyn67

    I Mach-Zehnder interferometer, but with an entangled beam?

    Hello, The Mach-Zehnder interferometer makes it possible to highlight the corpuscular and undulatory aspect of light, (in particular using single photons). By using the "continuous" beam from a coherent source, one is able to visualize directly on two screens E1 and E2, an interference pattern...
  8. Haorong Wu

    I May I treat the light from a star as a light beam?

    Hi. I am studying the wavefront evolution of light from a star. In the papers I have read, the star is often treated as a point source and the light is approximated as a line (geodesics), but this approximation is not very useful when I study the wavefront evolution, so I want to extend the...
  9. greg_rack

    Engineering Calculating shear center for a "skewed" I beam

    Here is the diagram of the cs: As a premise I must say that this topic(shear center and shear flow distributions) is still very hectic in my mind; I aim to clarify it a bit by asking you guys this :) So, in order to identify the SC location, I must compute at what distance a point shear force...
  10. H

    Sign hanging from massless beam attached to hinge supported by string

    Attempted creating equations for zeros of torque and components of forces in x and y as seen in picture. Got lost with having only variables and the d & 2L for the length of the beam. Not sure how to do the question with two points of contact between the beam and the sign. Is the center center...
  11. Philip Koeck

    A Fast electrons passing a beam of slow electrons at a right angle

    I'm wondering what happens when fast electrons (100 - 300 keV) interact with a beam (diameter 1 to 10 μm) of slower electrons (1 to 10 keV), which is at right angles to the trajectories of the fast electrons. The beam of slower electrons is relatively dense with 1 to 10 electrons per μm line...
  12. U

    Engineering Why was the thickness of the beam included in calculating this moment?

    Hi all, Why was the thickness of the beam considered when moment was being calculated and why was the horizontal component of the 600 N force used in calculating the moment? That part is unclear to me. Please explain it. Am I looking for the logic behind using the horizontal comp. and the...
  13. G

    Reactions at the beam supports

    Figure: My attempt at a solution: We know that ##Q=A_T## We calculate ##Q##: $$Q=\dfrac{3\cdot 480}{2}+\dfrac{600\cdot 6}{2}+600\cdot 2=3720\, \textrm{lb}$$ Then we look for the point ##\overline{x}## of the centre of gravity: $$\overline{x_1}=1\, \textrm{ft},\quad...
  14. N

    Engineering An issue with these two curved beam homework problems

    Hi, good evening/morning/night! I have a problem with this 2 homework problems about curved beams. In both I must calculate the stress at points A and B. My procedure is correct, but for some reason in: First problem - the effort in A is very close to that of the teacher, but the effort in B...
  15. K

    A Weird beam behavior in a cavity

    Hello! I am trying to align a bow-tie cavity and I noticed a behavior of the beam spot that I can't explain with my (limited) knowledge of cavities. For reference, I am scanning the current of the laser in order for the laser to follow the cavity. I attached below 3 frames from a video I took of...
  16. sergiokapone

    I Mathematics for dancing laser beam

    Is there a math that describes these shapes at least one frequency?
  17. A

    Light beam fired in a moving train (relativity)

    1) really does not make sense to me. It is not clear to me how light could be reflected in multiple directions if the source is not a tilted mirror or another object with specific properties. I think the thought of the "point" P confuses me. Further, the fact that light travels in the opposite...
  18. C

    A Penetration depth of a ion beam coupled with an EM wave

    A Ion source is a device that allows creating ion beams (e.g. argon ions) and to project them outside the device, for example to be further processed by a particle accelerator, or to irradiate materials or biological tissues etc. Now, suppose the ion beam is coupled with an EM wave, especially...
  19. M

    I Are there currently working colliders with unequal beam sizes?

    I know that for any coliders beams are not exactly the same size but they can be approximated to the same value as the deviation is relatively small, such as LHC. My questions: 1- are there currently working or planned colliders with unequal beam sizes? 2- for coliders of different particles...
  20. J

    I Apparent Weight problem (falling beam)

    Each weight: 2 Kg Hello All, I'm trying to understand an "apparent weight" problem and check my answer. Please use the picture attached. A weightless beam is at first resting over my palm, it has one 2 kg weight on each end of it. It is suspended to the ceiling by a rubber band. I drop it and...
  21. A

    I Does electron beam in empty space generate magnetic fields?

    Does electron beam in empty space generate magnetic fields around them just as with current in conductor. If yes, then is it experimentally proven that two parallel electron beam would attract each other.
  22. link223

    Forces acting on a Walking Beam (oil rig pump) from a pivot pin

    So.. question: - How do I know that only the pin is at work at E and not those 2 beams? my guess: It is because those 2 beams are connected to the pin whilst the pin is the one that exerts a force on that walking beam DEF?
  23. D

    Understanding horizontal shear in beam with vertical load

    In an I-beam, the shear flow is usually shown drawn as on the left, not as drawn on the right. I do not understand why. I do understand: The total horizontal shear force must be zero, consistent with statics.This is satisfied in both images. The vertical direction matches the direction of the...
  24. nuclearsneke

    MCNP5 or MCNPX, parrallel beam

    Hi, I am interested in simulation of parallel beams for neutrons and photons (separately of course). Any ideas on how to simulate them in MCNP5 or MCNPX?
  25. B

    A How to slow down a high energy neutral molecular beam

    Hello! I see that in experiments at facilities like ISOLDE, they produce molecular beams at energies of tens of keV. If I understand it right, they first create the molecule as a positive ion, and using electric fields (and maybe magnetic for mass selection) they take the particle out of the...
  26. M

    How to take a moment into account for deflection of a beam

    Hello! I have to calculate the deflection of a beam at at given point (C). The books says the should be a moment which plays a role in this deflection. How does this moment occur? I have drawn a FBD but couldn't find a moment? Should I divided the beam into separate parts or so? What am I...
  27. yglo98

    Optics. A laser beam is refracted in a piece of glass.

    A red laser with the diameter of 3mm is directed towards a piece of glass. It has the effect, P of 1mW. The angle of incidence is 90 degrees. The glass has refraction index n2= 1,5 and thickness 2 cm. Its front side is convex with a convergence radius,R, of 11 cm. The back side is plane. Whats...
  28. A

    B Wavelength of a laser beam emerging from a prism

    Summary:: If you send a laser beam through a prism, can you measure any shift in wavelength at the other side of it? This sounds like a high school experiment and the concept is simple. I feel the laser should emerge monochromatic and at the same wavelength it went in. Do you get this result...
  29. mechanic667

    Elasticity of a Tubular Cantilever Beam

    I have a problem where I have a metal tube that I am modeling as a cantilever beam which is fixed at one end and has a point load at the other end. The material of this beam is 304 stainless steel, the inner diameter is 0.5mm, the outer diameter is 2mm, and the length of the beam is 4.15mm. With...
  30. M

    I In-flight beam neutralization

    Hello! Someone mentioned to me about about a way to produce in flight neutralization of atomic/molecular beams by making the beam pass through a gas of particles produce through ablation (and not use a neutralization cell as it is often done). From my understanding, basically, one has a region...
  31. L

    Intensity of a laser beam at a certain distance

    I haven't been able to pinpoint a definition of "angular divergence" of a laser so by pure intuition I assumed it would be something like ##\theta=\frac{2R}{D}## and with that I have that the radius of the lase beam is ##R=\frac{D\theta}{2}=90\cdot 5 \cdot 10^{-6} m=450\ \mu m## so...
  32. D

    Lessons with electron beam deflection tube and teltron tube

    Hello, I would like to discuss with my students the deflection of electrons in electric and magnetic fields. For this purpose, I would like to perform the experiments with electron beam deflection tubes and teltron tubes. How would you implement this organizationally in the classroom? There are...
  33. Haorong Wu

    I Could a Gaussian beam be described as parallel at a large distance?

    Hello, there. Suppose a Gaussian beam is sent and is received at a great large distance, i.e., the propagation distance ##z \gg z_R## the Rayleigh distance. The Gaussian beam can be described by $$E_0 \frac {1}{w(z)} \exp \left ( \frac {-r^2}{w(z)^2}\right )\exp\left ( -i\left (kz+k\frac...
  34. Anachronist

    B Beam of air: Extending the range of a fan

    If one Googles for "laminar flow nozzle", one finds many interesting tutorials on creating a nozzle for a laminar water jet; a stream of water that remains coherent over a long distance without breaking up. These typically consist of a large-diameter tube with regions inside (like sponges and...
  35. FEAnalyst

    Leaf Spring Deflection: Calculating Force & Displacement

    Hi, I'm trying to calculate the deflection of a leaf spring. I've found several formulas but the one I'm currently using looks like this: $$f=k \frac{F L^{3}}{6EI}$$ where: ##k## - coefficient depending on the way leaves change their shape in the width direction (in my case it's ##1## because...
  36. D

    Magnitude and average value of energy intensity of light beam

    I tried using the equations above, but I wasn't really able to come up with an intuitive explanation. From my understanding, the electric field vector only varies in the x-y plane while the magnetic field vector only varies in the z-y plane. Also, both vary sinusoidally and both reach extrema...
  37. S

    I Base Motion and Vertical Beam - Basic Reaction Forces?

    So I am trying to understand how to estimate the amount of deflection [D] the vertical beam shown above would experience if the base it is attached to is accelerating at a constant acceleration [a] of 9.81 m/s. I assume the Force [F] would be equal to weight of the vertical beam (mass x...
  38. R

    A Optimum profile of light pipe exit for narrow beam angle

    I am trying to design an acrylic light pipe that has a 3W power red LED input with 60 degree beam angle. I need a reasonably collimated exit light beam or at least a narrow angle output. What I'd like to know is - what is the optimum shape of the exit end of the light pipe to produce the...
  39. S

    Beam current of positrons and electrons

    a) My idea is: 1. Find the energy created by annihilation process, which is ##E=2mc^2## where m is the mass of electron 2. Find the wavelength of photon by using formula E = hf 3. Find the speed of positron by using the formula of de broglie wavelength 4. Find the p.d by using conservation of...
  40. M

    Approach analytical calculation for a beam frame

    Hi all, Currently I am working on a home-project, making a trike. Now just for fun and because I like to calculate things, I calculated the deflection of a frame with a load. The frame is shown in the picture below, I added the force for clarity. With my analytical calculation I found a...
  41. greg_rack

    Engineering Diagram of a beam with distributed load - SOLVED

    Hi guys, I'm wasting much time on this problem but still can't manage to get to a solution; I'll attach my attempt below. I started with drawing the FBD of the beam "sectioned" at point C, in order to find an expression for the internal shear force at that point and then equal that to zero...
  42. M

    A Weird pattern for a laser beam spot

    Hello! I am trying to measure the gaussian profile of a laser beam, which is supposed to be T00. The profile shown in the specifications looks very Gaussian, and the laser is brand new. I am using this camera and I am using 2 of these wedges to guide the laser beam into the camera (mainly to...
  43. N

    Engineering Find the support reactions on a beam

    Hello! in this good afternoon ;). I need some help for this beam and his support reactions. The problem it is done, but my result its different from the teacher`s result. I'm sure my answer is correct, as even the "SkyCivbeam" online software also gives the same results. it appears that the...
  44. greg_rack

    Equivalent system (force+couple moment) of a loaded beam

    Hi guys, I don't really know how to cope with this problem, maybe just because I can't properly understand the data. In the figure we have a beam with its loading(plus a force of 15kN), a pivot O and support at the rightmost point. I would say that in order to find the equivalent system, I...
  45. A

    Klystron beam current, drive frequency, LHC CW example

    First of all I want to ask , do the LHC power klystrons work always in CW or are their frequency shifted to correct for timing of the bunches in the LHC tubes in case something isn't aligned or doesn't that ever happen? Also how do they drive the klystrons at LHC or other CW operation from an...
  46. A

    Statics Question -- Analyzing the forces on this supported beam

    Can someone please tell me why I get two different result of the value of Cy (please see attached image for more detail)? Am I doing a mistake? If yes, what is my mistake?
  47. freddie_mclair

    Calculate the residual stress on a beam after bending

    Hello everyone, I hope you can give me hand with what I will present. I have a beam with cross-section shown below. I considered a simple linear hardening model for predicting the stress and strain developed by bending the beam on the radius ##R_0## around the y-axis, where: The strain...
  48. P

    B Energy loss in the beam of LHC

    Generally, one would expect the beam to lose its content (energy or particles) if it hits anything before its reaching its target. The whole idea of maintaining (conventional) vacuum using pumps or other means is to minimize that loss. But is it possible that there could be a beam loss purely...
  49. D

    I Commutation of Beam splitter operator with Displacement operator

    I have a beam splitter operator (a†)b +(b†)a. Does it commute with exp(αâ†-α*â). Here a and ↠are creation and lowering operator
  50. kimiko333

    Measuring the length of a moving Beam in two different directions

    v_g+v_e=15/t_1 v_g-v_e=10/t_2 v_g=s/(t_1-t_2) But there are too many unknowns. What am I missing?