# Torsion Definition and 237 Threads

In mathematics, specifically in ring theory, a torsion element is an element of a module that yields zero when multiplied by some non-zero-divisor of the ring. The torsion submodule of a module is the submodule formed by the torsion elements. A torsion module is a module that equals its torsion submodule. A module is torsion free if its torsion submodule is reduced to the zero element.
This terminology is more commonly used for modules over a domain, that is, when the regular elements of the ring are all its nonzero elements.
This terminology applies to abelian groups (with "module" and "submodule" replaced by "group" and "subgroup"). This is allowed by the fact that the abelian groups are the modules over the ring of integers (in fact, this is the origin of the terminology, that has been introduced for abelian groups before being generalized to modules).
In the case of groups that are noncommutative, a torsion element is an element of finite order. Contrarily to the commutative case, the torsion elements do not form a subgroup, in general.

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1. ### Calculating torsional stresses in welds that don't fit standard cases

I was required to calculate the torsional stresses on these welds (in green) with the point of rotation G. However this doesn't fit any case in Shigley's so I'm at a loss as to how I should have calculated this. As advised by the teacher, I ended up replacing the keys being welded with full...
2. ### B Torsion Involving an Off Axis Thrust

I have tried to draw a force diagram to illustrate the problem. Suppose I have a 2m, 100kg uniform rod with wheels at the bottom. Center of mass is middle of rod. I want to accelerate this rod horizontally while it remains perfectly vertical (constant angle). But the force is coming from a rod...
3. ### A Problems with the interpretation of the Torsion tensor and the Lie Bracket

Hi, I've been doing a course on Tensor calculus by Eigenchris and I've come across this problem where depending on the way I compute/expand the Lie bracket the Torsion tensor always goes to zero. If you have any suggestions please reply, I've had this problem for months and I'm desperate to...
4. ### I Visualising Torsion Tensor: Is There a Picture?

As I understand it, parallel transport of a vector around a closed loop on a manifold can lead (in the tangent space) to 1) an angular change, given by the Riemann curvature tensor or, 2) a translational defect given by the Torsion tensor. I can see how the looping on the curvature of a 2D...
5. ### Engineering Is this moment a bending or a torsion?

Greetings! As you could see the moment try to make beam to rotate in the support plane with the wall which mean for me this moment is on the Z direction but the longitudinal axis is the X direction and I know that for a moment to be torsion it needs to be in a longitudinal direction, but the...
6. ### Calculating Torsion: Understanding the Role of Force and Distance

Summary:: trying to calculate the torsion but couldn´t understand the solution Greetings I´m trying to understand why the multiplied the Force by a/2 to find the torsion in te point c thank you!
7. ### Prandtl stress function for circular bar in torsion

For a Prandtl stress function to be valid, it must be zero on the boundary. For a circular bar, both of these work: $$\phi_1 = C\left(\frac{x^2}{r^2}+ \frac{y^2}{r^2} - 1\right)$$ $$\phi_2 = C \left(x^2+ y^2- r^2\right)$$ But performing the integration for the internal torque M gives...
8. ### Automotive  Wheel + Trans diff + Torsion bar?

I have a crazy idea to make a 4 motor EV, but ran into an issue: the motors I want to use have a gear reduction (transmission?) That has a differential built into it. I only need to use one side of each, but I don't want to weld or otherwise destroy the other side of it. (That way I can...
9. ### Angle of twist from in-plane displacements in FEA

Hi, solid elements used in FEA don't have rotational DOFs so normally it's not possible to read the angle of twist from simulation involving torsion. Some programs allow the transformation of results to cylindrical coordinate system but it's not always the case. From what I've heard, it's...

18. ### How can I calculate the reaction forces of a torsion spring on a wall?

Hi guys, I am working on design where I am using a torsion spring. And I need make an analysis and see the deflection of the walls. How can I calculate the forces that applied from Spring's legs to walls. Thank you all in advance.
19. ### Integral for the calculation of torque

Hello, I found an integral to calculate the torque from the applied torsional shear stress, and I didn't find an explanation of how this integral is deviated. Where does it come from? Could someone explain? T = ∫τ⋅r⋅dA = ∫τ⋅2πr⋅dr, where T is the torque and τ the shear stress. Thanks a lot!
20. ### Is the Stress in a Twisted Helical Spring Caused by Torsion or Bending?

Let us consider the massless homogeneous helical spring with the infinitesimal wire diameter d and wire length l. We denote the spring radius as R. Now we consider the curvilinear spring section of length dl. We draw radii from the spiral axis to the centers of the end cross-sections of this...
21. ### Engineering Torsion and deflection of a rectangular beam

Hello I would like some feedback about a problem. The idea is to calculate how much the angled bit of this beam moves things to account for are deflection and torsion. Did i miss anything? Underlined with red are the displacements in millimeters. In the picture the dotted line is the axis that...
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### I Christoffel's symbols: symmetry in the two (lower) indices

I have a technical problem. 1. Accordingly to historical E.B. Christoffel’s work (I think year 1869), (Christoffel’s) symbols are symmetric in the two (today writing) lower indices. 2. These symbols have been introduced when studying the preservation of differential forms of degree two. The...
23. ### Torsion of a thick-walled arbitrary open section bar

Hi, I analyzed various open cross-section (I, T, L, C) bars using FEA to find maximum shear stress and twist angle. Now I would like to compare these results with approximate hand calculations. Just out of curiosity. However it's not easy to do it analytically. I know about a method of dividing...
24. ### Solving Torsion Spring Problem with 100 lb Force

I am struggling through a problem in one of my designs and would appreciate some help. Please refer to the image attached. Problem Description: S = Torsion spring F = fixed point T = tire A tire is attached to a torsion spring through an arm as shown in the image. The torsion spring has one...
25. ### Calculate the torsion of a silver thread

Homework Statement The torsion balance shown in the figure consists of a 40 cm long bar with lead balls with a diameter of 2 cm on each end. The rod is hanging by a 100 cm long silver thread with a diameter of 0.5 mm. When two bigger lead balls (density = 11.4 g/cm3) with a diameter of 30 cm...
26. ### Calculate RPM given the force of a torsion spring

Homework Statement I've got a flywheel of Inertia = 0.0019302kg/m^2 (found via solidworks), when a torsion spring is released, a force of 10N acts on the wheel via astring attached 0.065m above and 0.0325m to the right of the wheel's axis at an angle of 40 degrees. Homework Equations What is...
27. ### B Why does a Moebius strip twist unevenly along its length?

A recent article in Smithsonian magazine about knitting geometric forms stimulated the following question: In the above, knitted Moebius strip, there are areas where the material is twisted (seen in front) and areas where the material is flatter/less twisted (seen in back). So far as I can...
28. ### MHB Another Question on Torsion Elements .... D&F Section 10.1, Exercise 8 ....

I am reading Dummit and Foote's book: "Abstract Algebra" (Third Edition) ... I am currently studying Chapter 10: Introduction to Module Theory ... ... I need some help with an Exercise 8(c) of Section 10.1 ... Exercise 8 of Section 10.1 reads as...
29. ### MHB How Can One Show That a Given Example is Not a Submodule?

I am reading Dummit and Foote's book: "Abstract Algebra" (Third Edition) ... I am currently studying Chapter 10: Introduction to Module Theory ... ... I need some help with an Exercise 8(b) of Section 10.1 ... Exercise 8 of Section 10.1 reads as follows...
30. ### Where did torsional shear stress in the x-y plane came from?

Homework Statement Homework Equations maximum torsional shear stress = (Torque*radius)/polar moment of inertia The Attempt at a Solution I am lost on equation(4-14), I looked through the textbook but didn't find a derivation.
31. ### How Can I Ensure My Torsion Spring Is Strong Enough for the Load?

Hi guys, I am working on design where I am using a torsion spring to hold a certain load. How can I calculate if the spring I am designing is strong enough to hold the load and prevent it from slipping down? This is music wire 2mm diam spring, 90deg travel, 60mm legs. Please let me know if I...
32. ### Finding torsion constant of the wire?

Homework Statement A torsional pendulum consists of a disk of mass 450 g and radius 3.5 cm, hanging from a wire. If the disk is rotated through an angle of 45o and released from rest and oscillates with a frequency of 2.5 Hz, what is the torsion constant of the wire? A : 1.7 x 10-3...
33. ### Solving Torsion Direction Homework Statement

Homework Statement Homework Equations Angle of twist = TL/JG The Attempt at a Solution T & L is inversely proportional. But how can i start attempt the question? I think it this way: like moment=L*F, and torsion torque is like force, angle of twist is similar to moment (as TL are also...
34. ### Is the T=2*q*A Formula Valid for Both Open and Closed Thin-Walled Members?

is T=2*q*A formuala valid for both open thin-walled and closed thin-walled members, where T is torque, q is shear flow, and A is the Area.
35. ### Statically indeterminant torsion question

Hi, I'm struggling with this question on an exam pastpaper. I have attached the question and worked solutions below and i am stuck on Q10 c). I'm not sure how they knew that the torque is constant along the whole shaft. I thought a stepped shaft has different torques for its different sections...
36. ### Torsion stress and twist criterion

Hi, below i have attached a exercise sheet question with the solution, however i don't quite understand it. In torsion, the maximum shear stress of a shaft is determined using the max radius of the shaft. Also, when comparing two sections, the one with the larger radius gives a higher shear...
37. C

### Torsion and stress on a beam question

Homework Statement A rectangular Cross-section beam, 20cm deep by 10cm wide, is subjected to a maximum bending moment of 360kNm A) Calculate the second moment of area of the beam cross-section B) what is the maximum stress in the beam under this load C) if the value of E for the beam of...
38. ### Ramachandran plot torsion angles

Can torsion angles were affected by repulsive effect of aminoacid interactions between side chains? Can torsion angles were affected by hydrophilic or hydrophilic interactions between side chains? I know that protein levels were affected by them but torsion angles is suspicious for me
39. ### First natural frequency for bending, axial and torsion modes

Homework Statement We have a rod of length L fixed to a rigid support. At the end of the rod there is a mass, m. Assume that the rod has no mass. Find the first natural frequency for the bending, axial and torsion modes. Homework EquationsThe Attempt at a Solution So I'm reviewing some stuff...
40. ### How a spiral torsion spring works

How spiral torsion spring (used in mechanical watches to store energy) works? physics behind it ? ... I googled it but haven't got a clue. Where should I look for proper and detailed info.
41. ### I Torsion & Non-Closed Rectangle in Feynman & Penrose

In the Feynman Lectures on Physics, Feynman explains the curvature of spacetime by drawing a rectangle in spacetime, see http://www.feynmanlectures.caltech.edu/II_42.html Fig. 42.18 First waiting 100 sec and then moving 100 feet in height on Earth's surface results in a different situation...
42. T

### I Design diameter of transmission shaft

Please bear with me, I am trying to design a shaft that will be under torsion. I do not know the diameter of the shaft and I would like to be able to calculate it by the things that I do know about the system. There's a 15HP 3 Phase motor running at 85RPM [there's a gearbox] This will be...
43. ### I When will metric compatibility hold/not hold?

Hi everyone, I am reading Sean Carroll's note on gr and he mentioned metric compatibility. When ∇g=0 we say the metric is compatible. However from another online material, the lecturer argues ∇ of a tensor is still a tensor, and given that ∇g vanish in locally flat coordinate and this is a...
44. C

### Torsion and the modulus of rigidity

Homework Statement A specimen tested in a simple torsion testing machine , the specimen was 12.5mm in diameter and the angles were read over a gauge length of 0.75m Determine the modulus of rigidity of the material taking the torque T as 4.5Nm and the angle of twist as 4.0 degrees Homework...
45. ### How Do You Calculate the Inside Diameter and Mass Savings for Hollow Shafts?

Homework Statement A solid and hollow shaft of the same material must transmit the same maximum torque. The diameter of the solid shaft is 203mm and the outside diameter of the hollow shaft is to be 216mm. a) Determine the inside diameter of the hollow shaft. (answer = 138.7mm) b) What...
46. ### Can someone confirm my answers on a few torsion problems?

Homework Statement Homework EquationsThe Attempt at a Solution I feel I did something wrong, but not sure where is my problem. I don't feel conformable on number 26 and 27 and 29, can someone please tell me which answer is incorrect and any tip on solving it would be greatly appreciated!
47. ### How do i find the spring constant for a rope torsion spring

I have built a torsion wheel catapult (Mangonel) for an assignment,and I need to do some theoretical calculations about the displacement, velocity and time of the projectile, the problem is I don't know how to calculate the spring constant without the displacement of the spring (x) and i don't...
48. ### I Solving Confusion About Parallelograms in Curved Spacetime

One way to see that spacetime is curved is to try and draw a "rectangle" in spacetime (see the figure in the Feynman lectures, ch 42.7): If I wait for 100 seconds and then move upwards on earth, I end up at a different point in spacetime than when I first move upwards and then wait for 100...
49. ### Torsion in Shafts: Conceptual Doubt Explained

I have some conceptual doubts about shafts subjected to torsion. When studying Strenght of Materials, to find stress and strain in power transmission shafts, we consider that one of the ends of the shaft is fixed, with all degrees of freedom restricted, and the other one is receiving torque. I'm...
50. ### Specifications for elephant-resistant steel poles

This is probably simple for an engineer, but I’m a zoologist and analytical chemist and so I would rather ask those who know. I have camera traps out on the African bush, that are monitoring the responses of leopards to artificial scents. The cameras are in steel boxes to protect them from...