Editor’s Pick: Tools for Fatigue Analysis Enhanced

By Anthony J. Lockwood

Dear Desktop Engineering Reader:

Years ago I had this car I fancied would help me get a date. Problem was that its engineers glued as many components together as they could. Now, up north in winter, the roads get churlishly lumpy with frost heaves. Every time my love boat bumped, scraped, and jostled across one of these road rapids something jarred loose. The side molding zippered off with a metallic whizzing noise to its gutter grave. Ceiling fabric dangled. The nameplate slunk off the back, embarrassed no doubt, as was I.

That car rolled into my thoughts when I learned about version 8 of HBM’s nCode DesignLife toolbox of fatigue analysis applications. See, while version 8 has been upgraded with all sorts of new and expanded analysis methodologies deserving your attention, one toolset in particular caught my eye: You can analyze the durability of adhesive bonds in lightweight vehicle structures.

When I had that car, adhesive bonding was used to keep costs down and production lines moving as much as anything else. Glues with decent durability were not really high on the agenda, and using them for improved structural rigidity was not a cost-effective option. Glue has come along way since then, and the push to make lightweight, more energy-efficient vehicles has become more urgent. This was a marriage destined to happen.

That’s why adhesive bonding is used more and more to develop lightweight vehicle bodies today. It joins steels, aluminum alloys, and even different materials, and it affords good durability against fatigue even when compared to traditional methods such as spot welding and seam welding. Not that nCode DesignLife disses spot welding and seam welding, I hasten to add. It has robust toolsets for those jobs. It’s simply that HBM is on top of engineering’s evolutionary march.

Of course, adhesive bonding materials have their own set of problems, such as cracking. What the adhesive bonding tools in nCode DesignLife 8 offer you is a fracture mechanics-based method to assess which joints in your structure are most critically loaded. Using your finite-element model, nCode DesignLife 8’s tools determine line forces and moments at the edge of the glued flange. This allows you to get an approximate calculation of the strain energy release rate at the edge of your adhesive. Then, by comparing your strain energy release rate to your crack growth threshold, you can make a safety factor assessment of each joint in your structure then adjust and design accordingly upfront in your development cycle.

Version 8 of nCode DesignLife also offers enhanced tools for thermo-mechanical fatigue and short fiber composite fatigue analysis. And it’s all around faster than earlier versions. You can read more about version 8 in today’s Pick of the Week write-up. Also, tomorrow, February 23, HBM will present a complimentary webinar demonstrating its new adhesive bonding capability. Hit the webinar link after the main write-up for registration details.

Thanks, pal.—Lockwood

Anthony J. Lockwood
Editor at Large, Desktop Engineering

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