Strength of form springs

It is not just a question of cost-effectiveness, but also of sustainability when a high strength of form springs and thus a long service life in continuous operation is expected. A good knowledge of materials is therefore required in order to be able to offer efficient solutions that guarantee maximum functionality in continuous use. The material strength is a central criterion for sustainable solutions in form springs.

What are strength values?

The different materials – carbon steel, stainless spring steel or non-ferrous metals – each have a specific strength that is decisive for the use of the form spring. Strength tells you something about the degree of mechanical resistance that is necessary to bring about, for example, deformation or separation.

Determination of the strength values

Stress-strain diagram is used to determine the strength characteristics. Basically, three areas can be mapped with it:

• Linear-elastic area
  In the linear-elastic range, the strain is proportional to the stress.
• Nonlinear elastic domain
  In the non-linear elastic range, the deformation is still reversible, but no longer proportional to the stress.
• Elastic-plastic area
  Finally, there is the elastic-plastic range, in which the deformation is partially plastic and therefore irreversible. If the elastic limit is exceeded, permanent deformations form in the component.

Influences on the strength of form spring materials

• Load strength
• Load speed
• Type and condition of a material
• Processing temperature

The materials used for form springs are influenced by the above factors. As a rule, it is the first two criteria mentioned that have the greatest influence on the strength of the form spring in the manufacture of form springs. The stress is therefore the essential factor in distinguishing the types of strength.

Types of loading for shaped springs

A distinction is made between static and dynamic loading.

Static load
With respect to time, the load at static strength is dormant.

Dynamic load
The acting force and/or its direction of action change over time.
There is a change in the dynamic load, which is also known as fatigue strength. Here, strength is defined as the deformation and failure behavior of a dynamically loaded material over a certain number of cycles. This fatigue strength is determined using the Wöhler test. This test, also known as the fatigue test, is an important tool for calculating and verifying operational strength and fatigue strength.

The differentiation according to the type of stress is based on three criteria.

• Tensile strenght
  The tensile strength describes the highest mechanical stress in the material during a tensile test.
• Flexural strength
  The flexural strength represents the resistance of a material to bending.
• Compressive strength
  And finally, the compressive strength describes the resistance of the material under pressure.

Competence as a constant

The complexity of shaped springs listed here, which ultimately lead to a sustainable, functional product in continuous use, shows the need for special expertise with the broadest possible practical experience.

These are values that, as a matter of course, result in "durable" solutions at Schaaf. Our competence and experience support your success with products that master even the most special requirements with flying colours. Put your trust in one of the big names in the market: Schaaf!