Forklift Impact Simulation of a Warehouse Guard Rail with Explicit Dynamics FEA

A warehouse safety products manufacturer needed evidence that its anchored double-rail guard rail would stand up to a hit from a loaded forklift. The rail was going to an overseas distributor, who wanted an engineering report on the specific rail span and column combination it planned to sell.

Shirsh Technosolutions ran a full explicit dynamics crash simulation of the forklift striking the guard rail, using stress-strain curves built from the manufacturer's own mill test certificates. The report showed how the rails, posts and base plates take and absorb the impact, part by part, and gave the client a documented basis for the design before any physical crash testing.

A real crash event, not an equivalent load. We modelled the impact as it happens: a forklift carriage and forks moving at speed into the guard rail, solved with explicit time integration so the contact, large deformation and plasticity develop over the duration of the strike.

• Full assembly modelled from the client's general arrangement drawings: formed rails, rail end plates, double-column posts and anchored base plates.

• The forklift impacting face treated as rigid, which is the conservative choice because all of the impact energy has to be taken by the guard rail.

• Base plates restrained at the four anchor bolt holes, rails welded to the end plates and bolted to the posts, as on site.

• Frictional steel-to-steel contact between the parts, and self-weight included from material density.

• A symmetric model to keep run time sensible without losing the behaviour at mid-span or at the posts.

Material curves from the client's own steel. The rails, posts and plates were each given an elastic-plastic true stress-strain curve, built from the yield, ultimate and elongation values in the mill test certificates the client supplied for the actual coil and tube used. The rail steel and post steel behave quite differently past yield, so a single generic curve would have given the wrong answer.

Results read the way a design reviewer needs them. For the full assembly and then for each part, we reported resultant displacement, von Mises stress and effective plastic strain, along with time histories of deformation and stress through the impact. An energy summary showed the forklift's kinetic energy being converted into internal energy in the guard rail, which is the check that the simulation is physically sound.

Common questions

Why use explicit dynamics for a guard rail impact and not a static FEA? A forklift strike lasts a fraction of a second and pushes the steel well beyond yield, with parts sliding and bearing on each other. Explicit dynamics follows that event step by step with contact and plasticity, so the deformation and the energy taken by each part come out directly instead of being guessed from an equivalent static force.

Does a crash simulation replace physical impact testing of a guard rail? Not where a buyer or standard asks for a physical test. The simulation shows where the rail and posts yield, how far they deflect and whether the connections hold, so the design can be settled and documented before the expense of test samples and a crash rig.