Mechanical springs are used in mechanical components to exert force, provide flexibility, and absorb or store energy. This article provides an overview of the operating conditions of mechanical springs. Common failure mechanisms and processes involved in the examination of spring failures are also discussed. In addition, the article discusses common causes of failures and presents examples of specific spring failures, describes fatigue failures that resulted from these types of material defects, and demonstrates how improper fabrication can result in premature fatigue failure. It also covers failures of shape memory alloy springs and failures caused by corrosion and operating conditions.

This article discusses the common causes of failures of springs, with illustrations. Design deficiencies, material defects, processing errors or deficiencies, and unusual operating conditions are the common causes of spring failures. In most cases, these causes result in failure by fatigue. The article describes the operating conditions of springs, common failure mechanisms, and presents an examination of the failures that occur in springs.

This article discusses the failure mechanism of springs. It describes the critical application factors that affect spring fatigue performance. These include: material type and strength; stress conditions; surface quality; manufacturing processes; rate of application of load; and embrittlement or cracking. The article summarizes the methods of statistical analysis of S-N data for general comparisons of fatigue strength of spring steels. The fatigue performance of springs is illustrated by Goodman diagrams. The article also exemplifies the examination of failed springs.

Steel springs are made in many types, shapes, and sizes, ranging from delicate hairsprings for instrument meters to massive buffer springs for railroad equipment. The primary focus of this article is small steel springs that are cold wound from wire. Wire springs are of four types: compression springs (including die springs), extension springs, torsion springs, and wire forms. Chemical composition, mechanical properties, surface quality, availability, and cost are the principal factors to be considered in selecting steel for springs. Both carbon and alloy steels are used extensively. The three types of wire used in the greatest number of applications of cold formed springs are hard-drawn spring wire, oil tempered wire and music wire. Residual stresses can increase or decrease the strength of a spring material, depending on their direction. Steel springs are often electroplated with zinc or cadmium to protect them from corrosion and abrasion. Although some hot-wound springs are made of steels that are also used for cold-wound springs, hot-wound springs are usually much larger, which results in significant metallurgical differences. All spring design is based on Hooke’s law; charts and formulas are available to aid in the design of springs.