Do Springs Lose Tension Over Time?

How tension is created in springs

Most of us go about our daily lives without giving much thought to the springs which are vital for the operation of so many household objects and manufacturing procedures we benefit from. From deckchairs to car suspension systems and everything in between, springs are used in all manner of ways to make our lives easier. 

But how do springs work, and how is tension created? 

Springs use tension to store and release energy, providing a means to absorb shock, maintain force, or return to a specific position. When a force is applied to a spring, it either compresses (compression spring) or stretches (extension spring). This deformation stores potential energy within the spring's material. The stored energy creates a force that attempts to return the spring to its original shape. The force of the energy is proportional to the degree of deformation and so tension is vital for springs to work as intended. 

Temporary vs. permanent loss of spring tension

When a spring loses its tension, it is less able to store and use energy by compressing or stretching when a load is applied. A spring can lose its tension when the spring loses its ability to retain its original shape and strength under force. Sometimes this tension loss can be temporary, but in other cases it is permanent. 

Causes for Springs Temporarily Losing Tension 

Temporary tension loss occurs when a spring temporarily loses some of its tension due to short-term factors but can recover its original tension once these factors are removed.

Common causes include;

• Temperature Fluctuations: Springs can temporarily lose tension when exposed to high temperatures as the heat can cause the metal to expand and become less stiff. Once the temperature returns to normal, the spring often regains its original tension.
• Overloading: When a spring is subjected to loads within its elastic limit, it may temporarily deform and lose some tension.
• Cyclic Loading: Repeated loading and unloading can cause temporary changes in tension due to minor shifts in the material's internal structure. Given time to rest, the spring can often regain its initial tension.

Reasons for Permanent Tension Loss in Springs

Permanent tension loss is more concerning than temporary tension loss, as it indicates irreversible changes in the spring's structure and a permanent decrease in its ability to store and release energy. 

• Material Fatigue: Over time, repeated cycling of a spring can lead to material fatigue. Micro-cracks and dislocations within the metal structure accumulate, eventually leading to a permanent loss of tension as the spring can no longer return to its original shape.
• Overstretching or Overcompressing: Exceeding the elastic limit of a spring by applying a load that is too great can cause deformation. This results in permanent elongation or compression, irreversibly reducing the spring's tension.
• Corrosion and Wear: Environmental factors such as moisture, chemicals, and abrasive particles can corrode or wear down the spring material. This degradation weakens the spring and results in a permanent loss of tension.

Creep: When a spring is subjected to a constant load over an extended period, it can slowly deform due to creep, particularly at high temperatures. This leads to a gradual yet permanent loss of tension.

Factors influencing spring tension loss over time

Several factors can influence the tension loss of springs over time and understanding the causes is crucial for maintaining their performance. The following factors can impact the spring's ability to maintain its original tension and overall functionality.

• Material Quality

The type of metal or alloy used in the spring affects its strength and durability. High-quality materials like stainless steel or high-carbon steel typically offer better resistance to fatigue and corrosion. The method of manufacturing is also a vital part of this, including heat treatment and surface finishing. This can significantly impact the spring’s durability to wear and fatigue and help a spring resist tension loss.
 

• Load Stress

Springs subjected to higher loads, especially those close to or exceeding their design limits, will experience greater stress and a higher likelihood of tension loss. Likewise, repeated loading and unloading cycles can lead to material fatigue, gradually reducing the spring's ability to return to its original shape and tension and prolonged application of a load can cause creep, leading to permanent deformation and spring tension loss.

• Environmental

Exposure to extreme temperatures can affect the material properties of the spring. High temperatures can cause the metal to soften, while low temperatures can make it brittle. Exposure to moisture, chemicals, and other corrosive elements can degrade the spring material, leading to pitting, rusting, and a reduction in tensile strength.

Regular inspection, proper usage within design limits, and protection against environmental factors can help mitigate these issues, ensuring springs remain reliable and effective in their applications.

Testing and measuring spring tension

Testing and measuring tension in a spring is essential for ensuring its performance and longevity. Various methods can be employed to assess the tension, depending on the precision required and the spring's application.

• Load testing is one method of measuring the tension in a spring. To do this, you apply a known load to the spring and measure the resulting displacement to determine if the spring is performing within its specified parameters.
  
  
• The spring rate (or stiffness) is a measure of how much load is required to compress or extend the spring by a certain distance. You can also stretch the spring to measure the force required for a specific extension; this is called tensile testing. 
  
  
• Dynamic testing evaluates the spring's performance under cyclic loading conditions, simulating real-world usage and is vital in our manufacturing process.

Preventing tension loss in springs

Preventing tension loss in springs is paramount to not only increase their longevity but also to ensure you don’t fall foul to the hazards involved in using faulty springs. 

Proper use and maintenance

Never overload a spring, and ensure that it is kept within the parameters of the recommended temperature for optimum performance. If you are repeatedly using a sprung mechanism, be sure to make regular checks to assess its functionality and maintenance. 

Storage and handling tips

Store springs in a clean, dry environment to prevent contamination by dust, dirt, or moisture which can lead to corrosion. Maintain a consistent temperature and humidity level in the storage area. Avoid extreme temperatures and high humidity, which can cause material degradation or corrosion. Do not stretch or compress springs beyond their design limits during handling to avoid permanent deformation or damage.

Material selection and design considerations 

Material selection and design considerations are crucial for ensuring the optimal performance, durability, and reliability of springs in their intended applications. For example, high tensile strength materials can withstand greater forces without deforming, whilst materials with a higher elastic modulus provide better stiffness and resistance to deformation. 

How tension works in different types of springs

Depending on the intended use, different types of springs use different types of tension. By carefully selecting the right material and considering the specific design requirements, engineers can ensure that springs meet the performance, durability, and safety standards necessary for their applications.  

• Compression Springs: Designed to resist compressive forces. Important to consider solid height (fully compressed length) and buckling. 
• Extension Springs: Designed to resist pulling forces. Ensure proper end hook or loop design to avoid stress concentrations.
• Torsion Springs: Designed to resist rotational forces. Pay attention to the direction of the wind and arm positioning.

Conclusion 

Whilst springs can and do lose tension over time, careful selection, proper use, and ongoing maintenance can ensure that you minimise the risk of this happening. If you have ever wondered ‘Do springs lose tension over time?’ we hope that our concise exploration of tension spring loss has answered your questions and will help you to be able to better maintain your own spring mechanisms. If you have any questions about springs losing tension, please do get in touch with our engineering team who will be only too happy to help.