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.
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 [1], Gaul et al. [2], Lenz and Gaul [3], and Gaul and Lenz [4].
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[5][6], and Armand et al.[7].
Another variation of such benchmark can be considered a dumbbell oscillator investigated by Segelman[8]. 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.
The Cut Beam Benchmark
Description
The beam is built up with three parts linked by two planar joints. Planar joints assembled by applying normal force, which is applied using screw clamp. Furter, assembled beam clamped to the ground by bolted joints. The benchmark system should be assembled that way, to remain in contact due to the normal pre-load N and the friction between the counter-parts.
The purpose of this benchmark is to measure the damping induced by partial slip and friction in a planar joint.
This benchmark was originally made and investigated by Jean-Luc Dion, Gael Chevallier, and Nicolas Peyret. The design of this benchmark is based on and justified in Peyret et al[9][10]. Detailed description of the experiment and main results are presented in work Dion, Chevallier, and Peyret.
Variations
Currently, there is not known about any variation of this benchmark.
Main features
Main feature of this benchmark is that it allows measuring damping in the pure interface, avoiding the influence of bolts, which ordinary presents in other academic benchmarks.
The benchmark system was designed so that to have nil bending moment over non-zero length. Also, particular attention was given to obtaining the highest frequency for the second bending mode in order to avoid coupling between the first two modes.
Due to that this work requires an accurate method of measurement of nonlinear damping, in the original article the stopped-sine excitation was used as it allows obtaining a single frequency response and studying nonlinear modes with frequency and natural magnitude modulations without other mode couplings.
Reasonable benchmark usage
The shape of the designed benchmark can be used to define contact damping of specimens of several materials, roughnesses, and flatnesses, with or without coating, in order to obtain a library of behaviors for use in the design of jointed structures.
The Ampair 600 Wind Turbine
Description
Variations
Main features
Reasonable benchmark usage
The S4-Beam Beams
Description
Variations
Main features
Reasonable benchmark usage
The Brake-Reuß Beams
Description
Variations
Main features
Reasonable benchmark usage
The New Benchmark
Description
Variations
Main features
Reasonable benchmark usage
Referenses
- ↑ L. Gaul, S. Bohlen, Identification of nonlinear structural joint models and implementation in discretized structure models, in ASME Design Technology Conference – 11th Biennial Conference on Mechanical Vibration and Noise, Boston, MA, 1987
- ↑ L. Gaul et al., Nonlinear vibration damping of structures with bolted joints, in 12th International Modal Analysis Conference (IMAC XII), Honolulu, HI, 1994
- ↑ J. Lenz, L. Gaul, The influence of micro-slip on the dynamic behavior of bolted joints, in 13th International Modal Analysis Conference (IMAC XIII), Nashville, TN, 1995
- ↑ L. Gaul, J. Lenz, Nonlinear dynamics of structures assembled by bolted joints. Acta Mechanica. 169-182 (1997)
- ↑ D. Süß, K. Willner, Multiharmonic balance analysis of a jointed friction oscillator, in ECCOMAS 2012 – European Congress on Computational Methods in Applied Sciences and Engineering, Vienna, 2012
- ↑ D. Süß, K. Willner, Investigation of a jointed friction oscillator using the multi-harmonic balance method. Mech. Syst. Signal Process. 52–53, 73–87 (2015)
- ↑ J. Armand et al., On the effects of roughness on the nonlinear dynamics of a bolted joint: A multiscale analysis.European Journal of Mechanics. 44-57 (2018)
- ↑ D.J. Segalman et al., Handbook on dynamics of jointed structures. Technical Report SAND2009-4164, Sandia National Laboratories, Albuquerque, NM (2009)
- ↑ N. Peyret et al., Non linear dynamic behavior modelling of a planar friction interface in a structure assembly, in ASME International Design Engineering Technical Conferences IDETC/CIE, San Diego, CA, 2009
- ↑ N. Peyret et al., Micro slip induced damping in planar contact under constant and uniform normal stress. Int. J. Appl. Mech. 2, 281–304 (2010)