It is a machine element that shows large amounts of deformation under the influence of force and accumulates energy during this deformation. Springs have a wide range of uses.
Springs undertake many tasks in the system, such as applying force, controlling movement, damping, changing frequency, measuring force and torque. Because of these features, they are indispensable elements of many products produced. They are made of many types of materials, from metal to plastics. The shape and loading characteristics of the springs vary according to the application areas in which they are used.
First of all, springs are elements used to accumulate mechanical energy when they are deformed. For this reason, a good spring should be able to undergo significant deformation and return to equilibrium without any dimensional change.
The Importance of Spring Design
Designers serving in the field of engineering often need spring design in their professional lives. However, most of the time, the spring design is not given the necessary importance in the design processes. However, the spring is one of the most important elements to be considered in the design process.
If the spring used does not work as desired, a good result will not be obtained from the product. For this reason, it is important to design the spring correctly before designing the product. This process will reduce the cost of the product, increase its efficiency and provide a long working life for the product.
If the spring design is considered late in the product design process, there may be trouble in supplying the spring that will perform the desired function in the product and may cause extra cost and complexity.
All designers will agree that spring reliability is crucial to the life of any machine. Statistics have shown that a correct spring design is the most important factor in assuring a long life for the product. A spring with correct technical features provides maximum performance and optimum life where it is used. In order to realize a very good design, information and support can be obtained from experts and organizations. In creating a product, opinions can be exchanged from these people and organizations during the process from the conceptual ideas at the beginning of the design to the acquisition of the product.
Necessary design modifications can be made more quickly and more efficiently with the help of spring specialists. Early dialogue with these people during the design process will save time and redesign costs.
Spring materials are the strongest materials used in the industry (Figure 2.). Springs are generally designed considering that they are subject to more stress than other elements.
For example, helically wound compression springs can be subjected to tension at a value of 70% or even more of the breaking strength. In addition, the spring materials should be able to work in places where there are high and low temperatures, where there are corrosive solutions, where there is sudden and dynamic loading. Not only the mechanical properties of spring materials, but also their electrical and magnetic properties are important.
There are several factors that guide the material selection for helical springs. These can be counted as loading condition, operating voltage range, weight, operating limit dimensions, fatigue life, temperature, corrosion, production method (cold and hot winding) and material properties.
When the load applied to the springs is increased and the space used is limited, the springs should be made of materials with higher tensile strength. If the stress value acting on the spring is high and the loading situation is dynamic, materials with high fatigue strength should be preferred this time.
The subject of spring materials is an important and deep subject. This study is a small introduction to this subject and provides spring designers with confidence in their material selection.
In this study, five main groups of spring materials are discussed. These are high carbon spring steels, alloy spring steels, stainless spring steels, copper alloys and nickel alloys. A summary material reference table is given in Table 1. This table is not the entire spring material list. For the sake of brevity, many have not been taken.
WHAT IS SPRING RATE?
To indicate the softness or hardness characteristic of a spring, it is the ratio defined as the result of a certain amount of weight applied on it (x gr.) decreases by a certain distance (y mm). This rate is called the spring rate and is expressed as g/mm or lbs/inch. For a better understanding of the subject, if we accept g/mm as the measurement unit, the x number is variable, but the y number, which indicates how much the spring will drop, is fixed and 1mm. is Let's give an example if you want:
Suppose we have 2 different springs with different spring rates. Let one of them have a spring rate of 345 g/mm and the other 480 g/mm. This means that if you apply a weight of 345 grams to the first spring, this spring is 1mm. shortens, the second spring is only 480 gr. When we apply weight, this spring is 1mm. shortens. Accordingly, the second spring is a stiffer spring than the first.
From here, we can conclude: springs with a low spring rate are soft springs, while springs with a high spring rate are hard springs.
High Carbon Spring Steels
For general purpose work, these spring steels are the best choice for spring designers. They are also durable materials that spring designers can choose from. The steel materials used in the construction of the springs vary according to the stress conditions of the springs such as tension, compression, bending and torsion.
Spring wires are produced from hot rolled bars, cold drawn from carbide dies. Thus, the desired size, surface smoothness, dimensional accuracy and mechanical properties are obtained. In addition, the performance of the springs depends on the mechanical properties of the material used and the properties gained as a result of heat treatments such as annealing, cold drawing, pre-tempering applied to the material. SAE J271 special quality cold drawn carbon steel, which is given in the standard for springs with dimensions less than 2 mm, is the most durable. These materials are ideal materials in terms of surface treatment and strength. They are used where wire tolerances are limited and where high voltages are present. Some steels in this group are obtained by pre-drawing with Zn or Al–Zn. These normally have adequate corrosion protection. Otherwise, some treatment will be required for corrosion protection.
On the other hand, in oil tempered SAE J316 carbon steels, the martensitic structure obtained as a result of tempering is more resistant to softening, that is, to loosening, under constant or variable loads. These steels are also more suitable for precision forming. J113 cold drawn wires in this group withstand more deformation than oil tempered J316 steel. In addition, cold drawn wires are used where static loads, low stresses and stress repetitions are low.