Springs, how they work, their coiled structure

In summary, the conversation discusses the amazing properties of springs and how they are able to compress or extend a finite length due to their coiled shape. The spring wire is stressed in torsion and can be either prestressed or not, depending on the manufacturing process. The conversation also mentions two books, "Fundamentals of Spring Design" and "Mechanical Springs," as definitive sources on spring design and internal stress. The latter book, written by A.M. Wahl, is available in the public domain.
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fog37
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Understand how a spring really works
Hello!

Springs are amazing devices: we take a straight piece of metal wire, we change its shape and get something that can compress or extended a finite length. We could not do that with the straight wire (too difficult to move atoms apart or close to each other in a significant way).

Why does the spring work the way it does? The coil/helical shape is key to the design. But I am not sure what the explanation is. Is the spring, in the coiled shaped, a prestressed material? If we pull it along its axis, does that longitudinal pull translate in torsional motion of the spring section? Is that what happens? Why would the torsion be helpful?

Thanks
 
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The wire in coil springs loaded in tension or compression is stressed in torsion. The spring wire may be either prestressed or not, depending on the manufacturing process.

A good discussion of spring stresses is in Fundamentals of Spring Design, by Spring Manufacturers Institute: https://smihq.org/store/ViewProduct.aspx?id=8088348. This should answer your questions. From an earlier edition of Fundamentals of Spring Design:

Springs.jpg


If you want to know more, the definitive source on spring design and internal stress is Mechanical Springs, by A.M. Wahl: https://smihq.org/store/viewproduct.aspx?id=8088306.

Interestingly, both of these books are well known, but neither is available from Amazon.
 
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fog37 said:
Springs are amazing devices: we take a straight piece of metal wire, we change its shape and get something that can compress or extended a finite length. We could not do that with the straight wire (too difficult to move atoms apart or close to each other in a significant way).
Wire can be stretched but can't easily be compressed. When the "strings" on a steel-string guitar are tightened, they produce a tone that is higher in pitch. If you tighten them too much, they break -- they can be lengthened only so much.

Springs don't have to be helical. There are many types of springs that aren't, such as leaf springs on trucks and some kinds of cars. All of them are based on the elasticity of the material used to make the spring.
 
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Ok, so let's take a mathematical helix, a curve which has both constant curvature and torsion.

1) The more curvature a curve has, the less straight it is. The more torsion the curve has, the less planar it is. When we elongate a helix, I guess its torsion increases and its curvature decreases.

2) When I think of torsion, I think of twisting something using shear stress to deform it permanently or temporarily.
Back to springs, elongating a spring produces more torsion. I see how torsion increases given the mathematical definition of torsion: the piece of the spring get more distant from each other...still the straight metal wire making the spring that we started with has the same material and same overall length as the spring. Having deformed it into the helical shape, we have essentially convert it into something with very different properties...
 
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FAQ: Springs, how they work, their coiled structure

1. How do springs work?

Springs work by storing potential energy in their coiled structure. When a force is applied to the spring, it compresses or stretches, storing energy in the form of potential energy. When the force is released, the spring returns to its original shape, releasing the stored energy.

2. What is the purpose of the coiled structure of springs?

The coiled structure of springs allows them to compress and stretch easily without permanently deforming. This makes them ideal for absorbing and storing energy, as well as providing a flexible and durable support.

3. How are springs made?

Springs are typically made by coiling a long piece of wire around a cylindrical object, such as a rod or tube. The wire is then cut to the desired length and the ends are often flattened or bent to provide a secure attachment point. Springs can also be made by stamping or shaping metal sheets into a coiled shape.

4. What factors affect the strength of a spring?

The strength of a spring is affected by several factors, including the material it is made of, the diameter and length of the wire, and the number of coils. The type of coil, such as a tight or loose coil, can also impact the strength of the spring.

5. What are some common uses for springs?

Springs have a wide range of uses in everyday objects, such as in car suspensions, door hinges, and ballpoint pens. They are also used in more specialized applications, such as in watches, mattresses, and shock absorbers. Springs are also commonly used in industrial machinery and equipment.

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