How does thickness affect weld fatigue?

Today ERW tubes are one of the most popular choices for various applications. This is because they can offer excellent strength, low costs, and a wider choice of diameter, shape and wall thickness. However, people will always point to issues like weld fatigue. It can be a problem for some uses, including structural ones. Luckily, high quality tubes can have very strong welds and overcome many limitations.

Why is fatigue a problem?

ERW tubesThe thing to keep in mind is that welds can suffer from fatigue in time. What happens here is they can develop cracks because of the fatiguing that occurs due to cyclic loading. In time the cracking can worsen and eventually cause the tube to fail.

A number of different factors will affect the weld fatigue in ERW tubes and other welded tubing. This includes the design, type of welding, material, surrounding environment, and residual stress from the welding. The level of cyclical stress can also have a big impact. The thing to remember here is that fatigue can happen even if the cyclic stresses are low.

How does wall thickness come into it?

One thing to keep in mind here is that thicker tube walls can have a big impact on fatigue strength. It is naturally trickier to get a good quality weld as you increase wall thickness. This is because more material needs to come together to create a bond. The welding itself also results in higher concentrations of residual stress. As a result, there will be lower strength if a fatigue crack occurs from the weld toe.

What to do?

Interestingly there is so much concern about this problem that there are actually fatigue design rules. They aim to avoid fatigue failures in various welded structures, including those made from ERW tubes. There are some useful recommendations here, including fatigue limits and key factors that have an impact on weld life such as thickness and weld quality. It is a good idea to look at these rules and follow them where possible.

Talk to us about ERW tubes

Union Steel Tubes is proud to be one of the top manufacturers of ERW tubing in the UK. We have our own mills and facilities to offer precise cutting and finishing services. The range of products we can provide is extensive, including a selection of wall thicknesses.

So, if you want to order high quality ERW tube for a variety of projects, speak to us. We can give you plenty of advice about things like weld fatigue strength and more.