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Building thin wall tube structures with Trib-Joins

Application Note 3.

Trib-joins will join thin wall tubes to plates or other tubes by asperity cold pressure welding if the parts have a moderate mechanical interference pre-fit. Thin wall tubes can stretch and adjust their diameter as they are forced together hence pre-sizing is not particularly critical. Solid phase cold welds form between asperities between the rubbing surfaces as one tubular part is forced into another after treatment with a Trib-Tool.

Trib-joins are useful for making both decorative and load bearing structures with thin wall tubes. These have significant strength to weight advantage over other structural entities but their use is limited by the practical difficulties of joining them. Welding thin wall tube is prone to thinning, embrittlement and porosity. Heat in the melt zone can cause changes in metallurgy, which reduces fatigue and corrosion resistance. Fusion welds concentrate loads and can crack a thin tube as they cool, to an extent that they are frequently unsafe in tensile loaded structures. Adhesives are more effective at distributing loads but are messy and take time to cure and are not to be trusted in metal to metal structures exposed to high humidity with large temperature variations.

Trib-joins distribute the load evenly over large overlaps and double up at sections of high shear load near joins. There are no known chemical degenerative effects, in fact Trib-joins strengthen over time due to natural diffusion. No expensive assembly equipment is needed. Tubular assemblies are easily made using Trib-joins assembled by simply tapping parts together with a mallet. They showed no deterioration in salt spray tests.

Impressive "push together" structures like space frames can be made with light weight maintenance free stainless or aluminium tube section and rolled channel sections. In its simplest form ornamental fences or gates are made by forcing parts together as shown in the diagram below - made almost with the convenience of a Lego™ toy but with the permanence of a weld. This simple join can become the basis for huge structures like towers, columns, beams and concrete reinforcements that are all easily assembled on site.

In load bearing structures Trib-joins exhibit unique load sharing behaviour. Providing the joins are made slightly less strong than the tube, a formed join within a structure will yield if overloaded but will not lose strength or fail catastrophically. Thus if because of tolerance affects within a structure, one or more joins are overloaded upon first loading, joins yield and optimally redistribute load within a structure.

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Return to list of Application Notes. See Application Note 8 on Built Up Beams.

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The TribTech name derives from  "tribos" - Greek for 'rubbing'. 'TribTech' is a trade name used by Ball Burnishing Machine Tools Ltd. Registered Office 12 Brookmans Av. Hatfield, Herts. AL9 7QJ. United Kingdom;  Company Reg. No. 1408807, VAT Reg. No. 421 6210 04; a knowledge based company that develops, patents and licenses technology based on aspects of  tribology, the science of surfaces. All rights reserved by Ball Burnishing Machine Tools Ltd. Last modified: 29th Sept 2016 copyright © 1999/2016. The information and data provided herein should be considered generally representative for the tools and technologies described. In all cases users should carefully evaluate the tools and technologies to determine their suitability for a particular purpose. Be aware this site uses cookies, your continued use implies you accept these.