What are the failure modes of torsion springs

Torsion springs, as crucial components for mechanical transmission and energy storage, are widely used in various types of mechanical equipment. Stainless steel torsion springs, due to their excellent corrosion resistance and mechanical properties, are the preferred choice for many demanding applications. However, torsion springs inevitably experience various failures over long-term use, impacting the normal operation of the equipment. A deeper understanding of torsion spring failure modes can help improve design rationality, enhance service life, and ensure the stability of mechanical systems.

Fatigue Failure
Fatigue failure is the most common failure mode in torsion springs. Cyclic torsional loads induce alternating stresses within the spring material. Over time, microcracks gradually form and propagate, eventually leading to fracture. Fatigue life is affected by factors such as material properties, surface quality, load magnitude, and frequency. While stainless steel torsion springs offer high fatigue resistance, long-term, high-frequency, or overloaded use can still shorten their service life.

Plastic Deformation Failure
Plastic deformation failure occurs when a torsion spring's torsion angle exceeds its elastic limit, causing permanent deformation and loss of its original elastic recovery capacity. This failure is often caused by design deficiencies or overload. Plastic deformation not only affects spring performance but can also cause equipment loss, posing a safety hazard. Selecting the appropriate material elastic modulus and designing a reasonable working angle are crucial.

Corrosion Failure
Although stainless steel has excellent corrosion resistance, it can still experience localized corrosion or pitting in certain harsh environments, such as media with high chloride ion content. Corrosion reduces the material's cross-sectional area, leading to stress concentration, reducing spring strength, and accelerating the formation and propagation of fatigue cracks. Corrosion failure is common in marine, chemical, and humid environments. Proper material selection and surface treatment are key to preventing corrosion failure.

Stress Corrosion Cracking (SCC)
Stress corrosion cracking (SCC) is a type of cracking that occurs in torsion springs under the combined effects of tensile stress and a corrosive environment. It manifests as elongated, brittle fractures. SCC is common in certain stainless steels, especially in media with specific chemical compositions. This failure is highly insidious and develops rapidly, potentially leading to sudden spring failure, seriously impacting equipment safety. Monitoring the operating environment and properly controlling stress levels are key preventative measures for SCC.

Wear Failure
Wear failure primarily occurs at the contact surface between the spring and adjacent components. Friction causes gradual flaking of the spring's surface material, increasing surface roughness and reducing cross-sectional area, reducing the spring's mechanical strength and lifespan. Long-term wear can also cause spring shape changes, affecting its elastic properties. Proper lubrication and optimized design of springs and contact components can help reduce wear.

Elastic Degradation
Elastic degradation refers to a decrease in the elastic modulus of a spring under long-term stress, resulting in reduced spring stiffness and weakened elastic restoring force. Elastic degradation is often caused by changes in the material's microstructure, such as the increase in lattice defects and the propagation of microcracks. This manifests as a sluggish spring response or an inability to return to its original shape. Reasonable design margins and regular replacement and maintenance are effective measures to address elastic degradation.

Failures Caused by Manufacturing Defects
Defects that may occur during the manufacturing process, such as residual internal stress, surface scratches, poor welding, or uneven heat treatment, can serve as initiation points for fatigue cracks, reducing spring life. Surface defects have a particularly significant impact on fatigue performance. Strict control of the manufacturing process and the use of non-destructive testing techniques can effectively reduce the risk of this type of failure.

Performance Degradation Caused by Temperature
High temperatures can reduce the strength and elastic modulus of the spring material, leading to creep deformation. In severe cases, this can lead to permanent deformation or even fracture. Low temperatures can make the material brittle, increasing the risk of fracture. It is very important to select the appropriate material grade and heat treatment process according to the use environment to ensure that the spring works normally within the expected temperature range.