Benchmarks

One of the major aims of the committee is promoting the development and improvement of the technics of measurement and modelling of jointed structures behaviour, which often is nonlinear due to its intrinsic structure. The benchmark systems are aimed to help researchers to test their developed technics of jointed structure behaviour measurement and prediction. In other words – benchmarks serve as a reference system for verification. The benchmark system must have the following qualities:

• Well-controlled and understood boundary conditions to avoid uncertainties during experiment and modelling;

• Simple experimental setup to be easily repeatable and commonly used.

In this section several benchmarks, including its variations, pretended to be such reference systems, are described.

The Gaul Resonator

Description

The Gaul resonator consists of two massive parts, connected to each other by the single lap joint, one of which is designed to have an elastic element in the foundation of the connection interface.

The resonator is designed in a way, that has a relatively low natural frequency, corresponds to the tangential movement in the joint. It allows achieving quite heavy dynamic tangential loadings by exciting the system around an axial resonance frequency.

Experimental setup with Gaul Resonator from original work

The original resonator was developed by professor L. Gaul's research group and was made from round steel stock. This resonator is investigated by Gaul and Bohlen , Gaul et al. , Lenz and Gaul , and Gaul and Lenz .

Variations

There are two similar systems developed at the University of Erlangen–Nürnberg. The first one is similar to the original resonator. The second one is an improved version made of flat stock material and a different orientation of the lap joint. This has the advantages that sensors can be attached in an easier manner, mechanical post-processing or rejuvenation of the contact interface is possible, and accessibility for microscopic surface measurements is given. The detailed investigation of these systems given by Süß and Willner, and Armand et al..

Another variation of such benchmark can be considered a dumbbell oscillator investigated by Segelman. This oscillator consists of two rigid steel cylindrical parts, which represent two masses, connected by a lap joint.

Main features

The main features of the Gaul Resonator -like systems are caused by its massive structure:

• Insensibility to the way/place sensor is attached and load is applied
• Better controllability of the boundary conditions
• Ability to store a large amount of energy for extensive ring-down testing
• Can be accurately simulated with a low-order model, which provides high performance of simulations

Reasonable benchmark usage

In spite of being a very academic structure, this system is an ideal benchmark for measuring the transfer behavior of a bolted lap joint and also delivers the opportunity to perform hysteresis measurements, which establishes a bridge between the two round-robin challenges.