Shock bench on mannequins

THE SOLUTION PROVIDED BY LF TECHNOLOGIES

Our client is the French Institute of Transport, Planning and Networks Sciences and Technologies (IFSTTAR). IFSTTAR is a major player in European research in various fields such as transport and infrastructure. Among other things, they study the mechanical behaviour of the human body.

Main functions

Objective

Reproduce the impact of a car crash on dummies or representative samples of limbs or parts of the human body (e.g. bones). The aim is to measure the effects of shocks in order to model them numerically.

PROBLEMATIC ISSUES

Generate a shock at high speed (up to 15 m/s), with great precision and speed regularity despite a high thrust force (up to 20,000 N), corresponding to very high instantaneous power.

Acceleration and braking must be almost immediate.

SOLUTION AND RESULT

The fast-loading machine was custom-designed by LF Technologies to meet the customer’s specifications and guarantee operator safety.

An electric motor drives a flywheel, which is attached to a hydraulic pump that transfers up to 110 cm3 of oil per revolution. The flywheel stores a large amount of energy, enabling instantaneous power of up to 200 kW. The oil is fed symmetrically into a system of adjustable cylinders, to ensure equivalent operation in traction and compression. A system of quick-acting valves ensures very high acceleration and rapid braking.

There are 4 impact cylinders, operating in diagonal pairs. Using one pair of cylinders allows high speeds, while using both pairs allows higher forces. The cylinders are connected by alloy flanges, which are integral with a dual position measurement system (absolute measurement and high-speed incremental measurement). The cylinder assembly can be rotated through 90° around a horizontal axis.

To guarantee operator safety, the machine is equipped with protective covers in several places, a light and sound signal (warning of an imminent shot/impact), and a remote emergency stop button enabling a remote operator to cut off power in an emergency.

The control PC, which can also be remotely controlled, can be used to adjust the height and orientation of the impactor. The cylinders can be used in tension or compression in a number of possible configurations.