Southern Springs & Pressings Ltd
enquiries@southernsprings.co.uk
+44 (0)1425 611517
  • Home
  • About
  • Products
  • Services
  • Who we work with
  • News
  • Blog
  • Careers
  • Contact
  • Gallery

16th March 2018
What factors should be considered when manufacturing springs to avoid fatigue performance


​One of the key factors that a spring user requires is reliability, there has been much research into the behaviour of springs under fluctuating loads to ensure a spring is long-lasting.

If a spring will only be operated for less than 10,000 cycles during its lifespan then fatigue does not need to be taken into account. Any spring that will be performing for more than 10,000 cycles can be affected by fatigue and this needs to be factored in during the design process.

​The factors that can affect the fatigue performance in springs include working stress, material surface quality and wear.
 
Working stress
When in operation, springs will generally work between two fixed positions. In order to predict the working life of the spring the working stress at these positions can simply be calculated.

A common cause of failure in an extension spring is when the loop of the spring breaks off in the area where the hook meets the body of the spring, this is the area of highest stress. Loops are subjected to bending and torsion stress, when they are formed in extension springs small tooling marks are unavoidable. These marks can increase the likelihood of a failure at this point, sometimes loops are formed using bends that are too small and a small radius can increase stress. Different fatigue performance can be caused by different types of end loop, this can be solved by using a loop with a transition radius between the spring body and the end loop of approximately the body radius.

​When an extension spring is required to work dynamically, it must be noted that an extension springs can have around 20% lower performance with regard to fatigue than compression springs.

​Material surface quality
The material surface quality is very important when trying to avoid the risk of spring failure, fatigue cracks generally originate from the surface of the material, so the greater the surface quality the more chance of improved fatigue performance.

There are a number of methods that can improve the surface quality, the most popular of these is shot-peening. This involves firing small rounded beads of material at the surface of the spring which will lead to a small residual compressive stress this then lowers the chance of a fatigue crack appearing.

The process of shot-peening is generally carried out only on compression springs and large leaf springs, otherwise the shot could become trapped in the coils of close wound torsion and extension springs. Also, the inside face of the coils would not be peened and this would eliminate the benefits of the process.
 
Wear
The wear of springs can be caused in a manner or ways, when operating it’s important that the maximum deflection of the spring should not exceed 85% of the available deflection. If a spring is working close to its solid (coil bound) length, the number of active coils will reduce due to coils coming into contact with each other and there is a chance that this could cause wear to the contacting faces.
 
Another cause of wear is when a spring works over a shaft or in a bore, if a spring is able to contact either the shaft or the wall of the bore then the wear can lead to early fatigue. If the inside diameter of the spring is worn this can increase the failure as this is where the working stresses are at their greatest.
 
Torsion springs have a lower fatigue performance in comparison to compression and extension springs, mainly due the friction and wear between the spring and that shaft. It’s hard to eliminate this with torsion springs however it can be reduced with an effective design.
 
There are other factors that can affect the fatigue performance such as corrosion, material cleanliness and speed of operation. 

Call our Sales Team NOW: +44 (0)1425 611517 or send us an email

Legal Notices   |   Download Quality Accrediation  | 
Picture
Keep up-to-date with SSP
NEWSLETTER SIGN-UP


​Website by THE VIVIDESIGNER
  • Home
  • About
  • Products
  • Services
  • Who we work with
  • News
  • Blog
  • Careers
  • Contact
  • Gallery
Picture
Picture
Southern Springs & Pressings Ltd
​Stem Lane, New Milton

Hampshire BH25 5NE
tel: +44 (0)1425 611517
enquiries@southernsprings.co.uk​
© Southern Springs & Pressings Ltd 
Copyright © 2016
Cookies Policy. ​
​Privacy Policy
Company Registration Number: 00452833
Place of Registration United Kingdom
VAT Registration Number: 188 5778 89
Picture
Find out about our ISO 9001 accreditation

The VIVIDesigner
SSP manufacture a wide range of springs, wire forms, flat strip components and tailor made metal products to meet your needs. We also provide specialist services such as tooling, assembly and design solutions to help deliver your products to market.
SSP, Southern Springs & Pressings, design, manufacture, assemble, wire forms, flat strip components, tailor made metal products, tooling, sample batches, prototypes, large production run, custom assembly service, extension springs, torsion springs, compression springs, tension springs, press production line, construction, IT, medical, electronics, military, avionics.