Arises

This article is in the course of transfer and of rewriting on Wikilivres. For the moment only certain parts were written, with many complements and an iconography much more complete.

We advise you to take note of it while following this bond, before approaching below the part relating to calculations.

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A arises is a body or machine element which uses the elastic properties some Matériau X to absorb mechanical energy, to produce a movement, or to exert a effort or a couple.

For a simpler but limited sight springs, to see: ideal Spring

Cave paintings attest that the man has invented this part for more than 10.000 years, in the form of the arc, constituted primarily of a part curves flexible formant arises; the spring thus played a determining role in the rise of the Civilization S.

An ideal spring is perfectly elastic and regains its shape of rest, or one of its forms of rest if it has some several, after having undergone a Déformation.

Attention at the end “deformation” ! One should not confuse the deformation of an element of infinitely small volume, such as one conceives it in resistance of materials, and the total deformation of a spring, i.e. a change in form which is translated, in the simplest cases, by the displacement of one of his ends compared to the other.

One can distinguish several main categories of springs according to the materials used, which can be metals, elastomers, composite materials or of gases.

Association of spring

According to the assembly of the springs:

• in parallel:
• the total arrow: $f\_\; \{early\}\; =\; f\_1\; =\; f\_2\; =\; f\_3\; =\; \backslash \; ldots\; =\; f\_n$
• the total force: $F\_\; \{early\}\; =\; F\_1\; +\; F\_2\; +\; F\_3\; +\; \backslash \; ldots\; +\; F\_n$
• total stiffness: $k\_\; \{early\}\; =\; k\_1\; +\; k\_2\; +\; k\_3\; +\; \backslash \; ldots\; +\; k\_n$
• in series:
• the total arrow: $f\_\; \{early\}\; =\; f\_1\; +\; f\_2\; +\; f\_3\; +\; \backslash \; ldots\; +\; f\_n$
• the total force: $F\_\; \{early\}\; =\; F\_1\; =\; F\_2\; =\; F\_3\; =\; \backslash \; ldots\; =\; F\_n$
• total stiffness: $\backslash \; frac\; \{1\}\; \{k\_\; \{early\}\}\; =\; \backslash \; frac\; \{1\}\; \{k\_1\}\; +\; \backslash \; frac\; \{1\}\; \{k\_2\}\; +\; \backslash \; frac\; \{1\}\; \{k\_3\}\; +\; \backslash \; ldots\; +\; \backslash \; frac\; \{1\}\; \{k\_n\}$

Metal springs

If the design of a spring of quality requires solids knowledge in the fields of the analysis of the constraints and the mechanics, the concretization of a project raises questions of choice of materials (natural, treatments), of working and especially of surface quality (structure, residual stresses, roughnesses) since one works on a mechanism moving.

Although many springs are requested at rather high or very high frequencies, we will limit ourselves here to a static or quasi-static study. When the deformations take place at low speed, the radial forces are reflected without time lag in all the mass of the spring. On the other hand, in the case of a high frequency dynamic operation, the loads applied at an end of a spring are not transmitted instantaneously until the other; this delay generates vibratory phenomena which one can sometimes make profitable but which is generally undesirable. The motor mechanics, for example, hardly appreciate the “dance” within the competences of valves.

The springs, obviously intended to become deformed under load, are basically different from the other machine elements which one wishes usually as not very deformable as possible. We will use despite everything the traditional formulas of the beams studied in resistance of materials, although they are applicable in any rigor only in the case of small deformations. In any case, the precision brought to the calculation of the springs has direction only if one has materials allowing to obtain and especially to preserve in the duration the adequate characteristics.

Materials and treatments

Without entering in detail, let us say that a good material to produce springs has a resistance lives elastic R_e²/2.E as large as possible, R_e being the Limit elastic and E the Modulus Young of this material. However, a high elastic limit is not enough, it is necessary that it is accompanied by good a impact strength and of good a endurance with respect to the alternate efforts.

Among the steels , a first family is that of mangano-siliceous steels containing from 1,5 to 2% of Silicium, 0,6 to 0,7% of Manganèse, 0,4 to 0,6% of Carbone, with a possibly little chromium, Tungstène, Molybdène or Vanadium. Let us quote the following nuances: 45S7 (leaf springs), 55S7, 45SCD6, 60SC7, (torsion bars), 45SW8. One finds also chrome steels, with vanadium, manganese or silicon-molybdenum, for example: 45C4, 50CV4. (Opinion of the manufacturer of springs: These materials exist only in large Øfil dimensions higher than 6mm, blade thickness higher than 4mm)

ELINVAR (“steel” with 33% from nickel, chromium 12%, manganese 1,2%) has a YOUNG modulus independent of the temperature. It is used with manufacture of springs intended for apparatuses as precision (Galvanomètre S, Sismographe S, Chronomètre S, Diapason S, etc). (Opinion of the manufacturer of springs: this matter is almost unknown, and its employment is conscutif provisioning by the customer)

The elastic limit of steels drops quickly when the temperature rises. The alloys of the INCONEL type containing Nickel (45 to 75%), of chromium (15%), of Cobalt, Molybdenum, Tungsten, Titanium, Iron, and Aluminum preserve correct properties up to 400-500 °C. (Opinion of the manufacturer of springs: these matters are very expensive and are seldom used, but one can find them without too much problem)

The piano wire is (in theory) a steel wire with 0,8 - carbon 1%, of which polished surface is of defects or notable imperfections likely to start ruptures of tiredness. One reaches limit normally R_e an elastic = 1.210 MPa for the wire of 0,5 mm and R_e = 1.125 MPa for the wire of 13 Misters However, it is necessary to be wary of the “piano wire” bought with the do-it-yourself department of the supermarket of the corner, because it high risk not to approach these performances… (Opinion of the Manufacturer of springs: this matter is to be preferred for its low costs.)

Stainless AISI 302 (Z12 CN 18-8) /AISI 316 (Z11 NDT 17-6) these matters very close in use compared to steel above have an advantage of being not very sensitive to rust. Its cost is slightly higher than that of steel above, but becomes more economic in the case of small quantities having to be protected from rust. (Opinion of the Manufacturer of springs: this matter is a good alternative to steel, its price being very reasonable)

A material too little known but largely used in electrical engineering is the Cuivre with beryllium (1 to 2%). It makes it possible to produce springs very good drivers of electricity and heat. Its elastic limit reaches 100 MPa, with a very good Endurance. (Opinion of the manufacturer of springs: this matter requires a heat treatment of quality after use, and often revètement of tinning type to facilitate the welding of it)

The memory-shape alloys (for example, Nitinol, alloy of Nickel, Titanium and Copper) constitute an interesting solution when the relaxation of the spring must be differed in time. They present several very special properties, inter alia the Ratchet effect simple direction which makes it possible alloy to find its initial form after a deformation mechanical or thermal and the ratchet effect double direction which makes it able after “education” to have two stable positions below and above a certain “critical temperature”. Springs can thus remain “at rest” with room temperature and become “active” if their temperature increases. They have extremely interesting applications in Orthodontie, in the systems of mechanical Assemblage, the equipment of safety, etc (Opinion of the manufacturer of springs: these materials remain very discrete as-with their use)

At the very low temperatures (- 150 to -200 °C), steels are almost all extremely fragile but one can use other metals like… the Plomb ! Of course, a lead spring should never be brought back under load to the room temperature.

It is not in our intention to enter here in detail of the manufactoring processes. Let us announce simply that all the serious springs undergo mechanical treatments which, putting in compression the surface layers of metal, minimize the formation and the propagation of the fatigue cracks. These treatments can be the Galetage (torsion bars) or the Grenaillage of prestressed (in English shot peening ). The preconformation of the springs is also a solution to create, at the most requested places, the Residual stress of adequate compression or shearing.

General characteristics of the springs

Although the linear behavior most frequently is evoked or sought, by facility or for technical imperative truths, the laws which connect the overall deformations of the springs to the efforts which are applied to them are varied much than than one generally thinks; all the art of the originators and the manufacturers of springs consists in adapting them the best possible one to the needs!

In the case of the linear behavior, the curve which represents the result of its overall deformation (translation or rotation of an end compared to the other) according to the effort applied (force or moment) is a line. The arrow F or rotation θ is then proportional to the force P or the couple C which caused it.

The stiffness of a spring is defined like the quotient: $k\; =\; \backslash \; frac\; P\; F\; (N/m)$ or $k\; =\; \backslash \; frac\; C\; \backslash \; theta$ (Nm/radian). A stiffness independent of the load corresponds to the linear behavior described by the Loi of Hooke. The reverse of the stiffness, 1/k, is the flexibility or compliance.

Foot-note: not to confuse the two terms stiffness and rigidity. Even if they are more or less interchangeable in the language running, from the technical point of view the stiffness applies at piece-rates while rigidity characterizes materials.

This paragraph was entirely rewritten in the wikilivre.

Springs whose matter works in torsion

See also: Bar of torsion

See also: helicoid Spring

Related springs

Instead of a round wire, one can use other forms, elliptic, rectangular,… Parfois, the springs with rectangular wire are obtained by cutting in a tube.

The conical springs are rolled up with constant step (on the spring in a free state, one rises of the same quantity to each turn) or with constant slope (the whorls are increasingly tight as one approaches the end of small diameter). - in the first case, one can progressively obtain an increasingly strong stiffness of compression (the whorls of stronger diameter are most flexible and compress “with block” the first) or an obstruction minimal once compression carried out. - in the second case, one minimizes the variation of stiffness, the whorls are crushed in order to little close simultaneous but once completely flattened, the wire takes the aspect of an increasingly loose spiral as one moves away from the center. Let us note that all the conical springs cannot be put “flat”.

For the springs in volute one does not use any more of the wire but bands of special sheet cut out according to various profiles. If a variable stiffness is wished, then it is necessary to adopt a constant width so that the whorls of largeer diameter subside the first. If on the contrary it is wished that the stiffness remain constant, then it should be made so that the section is increasing interior towards outside. It is also possible to produce springs in double volute as that which (badly) is drawn below.

In addition to their a little special mechanical characteristics, the springs in volute have the characteristic to have a closed structure, limiting the risks of blocking by foreign bodies. The spring in double volute, for example, is very often used to draw aside the two branches of the shears. The gardeners do not like much the shears provided with ordinary helical springs, because the brushwood is wedged there easily! (This type of spring is also called arises Comtois)

Springs whose matter works in inflection

See also: Leaf spring

See also: spiral Spring

See also: Spring of torsion

Various metal springs

See also: Rondelle arises

Diaphragms

Various manufacturers propose standardized parts which function like the Belleville spring washers but in much less stiff. It is necessary to consult their catalogs for more information.

One sees below a arise-diaphragm in cup with multiple blades used in particular in certain clutches, a Ringspann disc and a conical diaphragm Borrelly:

Annular springs

One carries out elastic systems with variable height by piling up conical rings. Such systems, subjected to an axial loading, decrease length because of the dilation of the rings external and the contraction of the interior rings. The interior rings “male” penetrate in the external rings “females”:

Very important frictions which occur between the rings are such as the thrust load provided at the time of the relaxation of stacking is very largely lower than that which was applied at the time of loading. They cause a considerable loss of energy which corresponds to the shaded zone of the diagram representing the cycle compression-relaxation. One can make profitable this characteristic in certain mechanisms like the plugs of railway rolling stock, where they contribute to absorb the shocks.

By replacing one or more complete interior rings by split rings, one can give to this spring very an other behavior: it becomes “soft more and more” at the beginning of its deformation, then “hard”:

Corrugated discs

There are multiple types. Are used they for example to adjust for wear or to replace the spiral springs like return springs. It is the Borrelly Company which developed for a Lyons client the first leaf spring or corrugated cup spring. This corrugated cup spring often known under the name of Rondelle Borrelly is intended to adjust for wear internal of the rolls of the dice. A broad standard range of these discs was created by Mr Albert Borrelly in the years 1970 to meet the needs for the manufacturers of electrical motors for bearings of diameter 10 to 400 millimetres. These springs make it possible to bring mechanical solutions when one wishes to store an energy in a volume diametrically opposed to the spiral spring. The characteristic of this spring being to use the place in diameter and not in height. he knows of this fact many other applications: multipin electric connectors, sealing packings, industrial valves and fittings,… Many materials are used according to specificities. A new disc undulated with a whorl or multi whorls having different characteristics was developed in France in the years 1990 per Mr Dominique Borrelly. This corrugated disc named disc ONDUFIL is quite different from its elder since it is manufactured starting from a flat wire what confers a resistance in fatigue static and dynamic to him higher of share a direction of circular fiber drawing. This advantage however is often inhibited by the difficulties of automatic feeding generated by its open geometry. Moreover it is delicate to use when it is put in rotation (deformation of geometry due to the centrifugal force). A multiturn disc ONDUFIL makes it possible to increase the arrow by the number of whorls what makes it possible to obtain an arrow and a force identical to a spring of compression roll in a third of the space of this last.

Here some examples of application (Doc. BORRELLY)

(SKETCH UNDER DEVELOPMENT)

http://www.borrelly.fr

Here some industrial examples (Doc. SMALLEY):

The figure of left represents the use of cup springs in a flow control valve. The stronger the pressure of fluid at the entry is, the more the piston moves towards the line and the more the openings of exit of the fluid are narrowed. The drawing of right-hand side shows a quick action coupling of piping with a restraint system by balls. The discs ensure the locking of the balls which retain the male part (not represented).

Various elastic parts

There exist innumerable elastic parts playing the part of springs in much of mechanisms, with specific characteristics and thus in-outside standardized production. Here for example a part in bent wire:

The seals Ball-Seal have springs with flattened whorls which give them radial elasticity necessary for a good interior and external contact on the parts to be sealed:

Many springs are produced starting from strip iron says “sheet blue” cut out and formatted at the request. For the electrical material, when one needs at the same time elastic and good parts conducting, one makes call under the same conditions with copper with beryllium:

Let us announce finally the possibility of carrying out more complex parts by cutting, stamping and forming:

Elastomer springs

In addition to the fact that it is much weaker than that of metals, the modulus of elasticity of rubbers varies with the shape of the elastic element, which varies itself much with the load applied. It is thus practically impossible to obtain linear characteristics, especially in the case of the springs of compression.

In fact, this characteristic is often made profitable to damp out the vibrations between the two elements connected by the spring. Indeed, the energy brought by the sinusoidal vibration of an element will be distributed, at the exit, between the fundamental frequency and its harmonics, which are multiples. However, it is known that the more one vibration has a high frequency and the easier it is to deaden.

If the rubber springs have a very good resistance to the dynamic stresses, they also undergo, to differing degree, the effects of the mechanical hysteresis which makes that the resumption of their initial form is not instantaneous after they underwent a deformation. This is due to the viscoelastic behavior always more or less of these materials. Let us not forget that the phenomenon of hysteresis is before a whole phenomenon of delay of an effect on a cause.

This hysteresis causes the transformation into heat, inside even of the viscoelastic material , part of provided energy. Rubber being bad conductive of heat, it results a likely internal heating from it, for badly studied mechanisms, to involve the degradation or the destruction of rubber. Also let us announce that the modulus of elasticity varies with the temperature, with the rate of load application, and that it evolves/moves during time because of the ageing of material.

All these factors interact and under these conditions, one understands easily that the characteristics of a rubber spring cannot be defined with the same precision that those of a metal spring. On the other hand, it is relatively easy to obtain moduli of elasticity and very variable damping capacities, while exploiting the nature and the proportions of the components of the mixture to be used.

Composite material springs

Springs with gas

Use

The springs are very widespread today in all kinds of Machine S and equipment. Their functions are very diverse. One can quote, without precise order:

• recall of an isolated part of its position of balance (beating doors standard “saloon”, measuring devices),
• maintenance of a tightening (clothes pins),
• fast opening (flick knife, Hand-left three-pronged fork),
• suspension of a vehicle (helical spring, leaf springs, hydropneumatic system),
• emission of sounds (tuning forks, musical boxes, “locusts” of recognition),
• distribution of loads (diagrids and spring mattress),
• accumulation of energy (engines of toys, watches) driving Spring,
• damping of the shocks (plugs of railway material),
• measurement and/or fixing of the value of an effort (torque wrenches),
• compensation of a load or a weight (forage ladders back of car, doors of dishwasher),
• application of an effort with a therapeutic aim (apparatuses orthodontic),
• use as toys or objects decorative (the long very flexible springs “Slinky” which descend the staircases).

See too

Related articles

• Système mass-arises. Studied the period of oscillation of a mass suspended with a spring.
• Shock absorber

External bonds

• a video explanatory on the relieving of a spring

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