Testing Under Extreme Conditions: Liebherr Relies on the U10M from HBM for Structural Testing of Excavators and Dump Trucks (ADT)

The Liebherr Development and Demonstration Center is the only one of its kind worldwide. Various testing stations are constructed on the 12 meter by 8 meter testing area. Up to six loading tests are performed here simultaneously. “Our tests provide vital data that allows us to design our components to stand up under high amounts of stress while also being as light as possible, in order to reduce energy consumption and achieve higher efficiency,” says Nils Dippon. “We test a wide variety of different parts here. Often, they are prototypes for a brand new model. With our modular clamping system, we set up a completely new test bench for every part and carry out tests with a variety of force applications. This requires top-notch measurement technology of course, that is capable of optimally covering a wide range of applications.”

In this job set-up, for example, an excavator’s revolving platform is mounted with an extendable arm. Right where the strut would normally meet the excavator shovel, the arm is connected to two hydraulic test cylinders via an adapter. “Our hydraulic cylinders are capable of pulling and pushing with a force of up to 1.2 Meganewtons,” Nils Dippon emphasizes. “This allows us to recreate loads that are likely to impact the excavator later on when it is used on a construction site or used for material handling.” In this case, the force is a decisive measured quantity that the test bench regulates. The component load is set using Y Series strain gauges (DMS) from HBM in order to analyze which loads in the structure originate from specific forces.

“Our U10M force sensor is optimal for the measurements taken during load tests at Liebherr,” says Thomas Kleckers, force sensor technology product manager at HBM. “The sensors are available with a maximum capacity ranging from 1.25 Kilonewtons to 2.5 Meganewtons and achieve very high accuracy, thus allowing for a wide measuring range. Its hermetically welded measuring body ensures long-lasting durability even in demanding industrial environments. For use in harsh industrial environments, there is also a U10M model that meets the requirements for Equipment Protection Class IP68.” Furthermore, the U10M Series sensors are also resistant to shock loads and vibrations.

One unique challenge associated with the tests performed by Liebherr is the mass of heavy test objects such as the big excavator extendable arm. “Bending forces can skew measurement results. That’s why we take measures as early as the test setup phase to stop bending moments from impacting the sensors. One way we do this is by relieving some of the load from the massive hydraulic cylinders and load application dummies by attaching counter loads using control wires. It is often impossible to fully compensate with our very large test objects,” explains Nils Dippon. “Thanks to its rugged measuring body and electrical bending moment compensation, the U10M force sensor provides reliable results even when lateral forces are involved. This allows us to configure very sophisticated job set-ups.” The U10M is tested and optimized in the HBM EMC lab, making it perfect for measuring in environments with strong electromagnetic fields – for electromobility for example.

“With the many options available, such as maximum capacity, adapters, calibration, and various connectors, over 11,000 different models of our U10M force sensors are available on demand and can still be adapted to the measuring task at hand,” says Thomas Kleckers.