Torsion Spring Fracture Analysis

The Failure Analysis of a Torsion Spring

Introduction

Torsion springs are a common component in many mechanical and electronic devices. Torsion springs are used to apply a rotational force to a part, or to store energy in a rotational form. Therefore, it is important that the torsion spring not fail during operation. Failure of a torsion spring can lead to unexpected and costly downtime.

Failures of torsion springs may be due to fatigue, overload, torsion, corrosion, or crack propagation. A thorough failure analysis of a torsion spring must begin with an inspection of the spring and the application in which it is designed to function. In this paper, we will examine a torsion spring that has been found to have failed during a product assembly process.

Case Description

The torsion spring in this case study was found to have failed during a product assembly. The spring had been designed to apply rotational force to a rotating part, which was then assembled into the product. Upon closer inspection, it was discovered that the spring had broken at the point where the coils were closest together.

Failure Analysis

In any failure analysis, the first step is to determine how the torsion spring was being used. In this case, the spring was intended to apply rotational force to a rotating part. It is important to know how the spring was intended to be used, in order to assess the forces the spring was exposed to.

After determining the intended function of the torsion spring, it is necessary to inspect the spring itself. In this case, the spring had broken at the point where the coils were closest together. This indicates that the spring had been subjected to excessive force. When a torsion spring is subjected to excessive force, the coils will compress too far, resulting in the coils being too close together. This can lead to stress concentrations and eventual fracture.

Conclusion

The failure of a torsion spring can have disastrous consequences, leading to costly downtime and potential injury. In this case, a thorough failure analysis revealed that the spring had been subjected to excessive force, leading to a fracture at the point where the coils were closest together. By properly inspecting the application, it is possible to evaluate the forces acting on the spring and take measures to ensure that it is not overloaded. Having an understanding of the forces acting on the spring can also be beneficial in designing a spring that is strong and reliable in its intended application.

In recent years, deep cracks in twist springs have become an increasingly serious problem in the industry. The cause of these cracks is complex. Generally, there are three major causes of failure: incorrect heat treatment process, metallurgical defect, and mechanical overload.

Incorrect heat treatment process is often caused by the improper selection of heating temperature, holding time and cooling speed, which results in a decrease in the strength of the material, resulting in cracks appearing in the twist spring. Metallurgical defects are usually caused by the improper composition of the raw material, as well as porosity and other defects that occur during smelting and pouring into the mold, also resulting in cracks in the twist spring. For most twist spring failures caused by mechanical overload, the spiral springs are subjected to impact forces or pressure during their use which exceeds the design load, causing failure of the twist spring.

To prevent spiral spring failure, operators should pay attention to the selection of raw materials and strictly control the heat treatment technical parameters. In addition, careful attention should be given to the loads imposed on the spiral springs to avoid exceeding the design loads. Last but not least, checks should be carried out regularly on the spiral springs to identify potential risks.