Keynote Speakers

• Nadine Martin, Senior Researcher CNRS, Gipsa-Lab, Grenoble France
  • Automatic expert condition monitoring: focus on a non-stationary index and the demodulation process
    
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• Eric Bechhoefer, CEO, Green Power Monitoring Systems, Inc., Vermont, USA
  • Improving the Business Case to Expand the Condition Monitoring Market
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• Massimo Ruzzene, D. Guggenheim School of Aerospace Engineering, Georgia Institute of Technology
  
  • Dynamics of Time-Dependent and Spatially Modulated Metamaterials
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• Jérôme Grando, Plasticomnium, France
  • Smart dynamic systems for exterior body panels in automotive industry

Nadine Martin

Automatic expert condition monitoring: focus on a non-stationary index and the demodulation process

Preventive condition monitoring of rotating machines will operate optimally and at a reduced cost if the system is fully autonomous. An autonomous system makes the possibility of a remote system and of a continuous surveillance. “Autonomous” does not mean simple or degraded: the processing should be automatic at an expert level. Without ignoring the physics, signal processing plays a key role in the health assessment of all system components. This talk concerns this challenging strategy and will focus on two specific points.
Firstly, when operating remotely and continuously, a preliminary task should be the data validation, that is the necessity to control the validity of the sensor outputs. Among all possible algorithms, this talk illustrates a time-frequency test that tracks the statistics invariance in the time-frequency plane. It can detect transients or localize nonstationary events in time and frequency. From this test comes out an index which is worthwhile to select not only correct data but also the right data according to the purpose of the system.
Secondly, in the processing chain, the demodulation process is essential for detecting and localizing cracks in gears and bearings. Nevertheless, this operation is troublesome and surprisingly often applied without figuring out the processing in itself. This talk illustrates the Hilbert demodulation by analyzing and comparing real-world measures from a natural wear test and specific models. The variation of the model parameters highlights the interaction between amplitude and phase modulation estimations due to the unicity of the analytic signal. This approach helps for understanding the demodulation of the residual, the residual being the signal where the gearmesh frequencies have been removed.
In any case, the objective being a continuous surveillance, results are given for a sequence of measures
coming from a test bench and from onshore wind turbines.

Eric Bechhoefer

Improving the Business Case to Expand the Condition Monitoring Market

Financial systems track cost. Condition Monitoring reduces cost by providing corrective action before the cost occurs. Because financial systems are not designed to measure opportunity costs of condition monitoring, financial managers cannot get a metric on the cost saving associated with condition monitoring. As most companies require signoff by the Chief Financial Officer for capital expenses, this lack of a business case often scuttles the implementation of a condition monitoring project. As such, it is up to the Condition Monitoring community to develop the business case. By documenting cost saving, financial managers can quantify the cost saving, which can expand the condition monitoring marketplace. This lecture reviews some condition monitoring projects were the cost-benefit documented an used to develop a business case and highlights that some benefits are hard to quantify.

Massimo Ruzzene

Dynamics of Time-Dependent and Spatially Modulated Metamaterials

The presentation describes the effects of two types of property modulations in mechanical waveguides. A first example describes the input-output characteristics of a beam undergoing transverse motion, whose stiffness varies in time at a specified modulation frequency. The modulation produces a frequency-periodic dispersion spectrum, where branches merge at multiple integers of half the modulation frequency and over a finite wavenumber range. In this range, frequency becomes complex, with its real part remaining constant. The vanishing group velocity associated with these flat bands leads to frequency-selective reflection at an interface between a non-modulated medium and a time-modulated one, which converts a broadband input into a narrowband output centered at the half modulation frequency. This behavior is illustrated in an elastic waveguide in transverse motion, where modulation is implemented experimentally by an array of piezoelectric patches shunted through a negative electrical capacitance controlled by a switching circuit. This implementation is suitable for the investigation of numerous properties of time/space modulated elastic metamaterials, such as non-reciprocity and one-way propagation, and can lead to the implementation of novel functionalities for acoustic wave devices operating on piezoelectric substrates.

In a second example, we show that spatial stiffness modulations defined by the sampling of a two-dimensional surface provide 1D elastic lattices with topological properties that are usually attributed to 2D crystals. Cyclic variation of the phase of the stiffness modulation accumulates a phase in the Bloch eigenmodes, which is characterized by integer valued Chern numbers for the associated bands. The resulting non-trivial gaps are spanned by modes whose edge location is determined by the stiffness phase, which can be modulated to drive an edge-to-edge transition. Based on this principle, a topological pump is implemented in the form of a plate whose stiffness varies periodically in one direction, and is adiabatically modulated along a second direction, along which the edge-to-edge transition occurs. The plate configuration effectively implements the stacking and coupling of a family of modulated 1D lattices along a second spatial dimension, along which the adiabatic variation of the stiffness phase drives the transition from a localized state at one boundary, to a bulk state and, finally, to another localized state at the opposite boundary.

J. Grando

Smart dynamic systems for exterior body panels in automotive industry

Automotive industry is moving rapidly towards new challenges with autonomous and low-emission vehicles. Lightweight, aerodynamics, sensitivity, adaptability are strategic drivers for car-makers and tier one suppliers. Exterior body panels and semi-structural parts are directly involved in such evolution as these automotive modules are more and more functional. They can support ultrasonic sensors, cameras, radars, lidars, antennas, motors to become smarter. New sensors and actuators are also developed and embedded in plastics and composites.

Moreover these panels are designed with lower thicknesses and less structural reinforcements to keep acceptable total weight for the next generation of vehicles. As a consequence some technical issues become more critical : vibrations, noises, damages…

In Plastic Omnium, a world leader tier one for body panels, researches and innovations have been conducted in the field of mechanical waves propagation.

Non Destructive Testing is mandatory for obvious safety reasons. Floors, tailgates, doors, roofs, chassis made of composites have to be qualified before delivery to the customers. Defects must be checked and evaluated with short-time cycle constraints, and ultrasonic waves are well-suited for this. Damage mechanism analysis coupled with acoustic emission is also conducted in R&D phases.

In some cases acoustic emission could also be implemented to monitor process steps like composite insert molding.

Lightweighting induces more noise and vibration on or through composite structures. This is not compatible with sound-free electrical vehicles. Standard solutions based on mass-added foams are not suited. Active controlled solutions with piezo-electrics could attenuate considerably acoustic waves and noises. This smart hybridization has been evaluated for several composite materials.

Metamaterials, or structured plastics, may also allow solutions for acoustic and vibration attenuations, or even energy absorption and mitigation during vehicle crashes.

On vehicle outer skins made of thermoplastic materials several wave propagation applications have been developed. Different families of piezo-electrics have been used to generate ultrasonic Lamb waves or to sense specific events like contacts, impacts or climatic conditions. This has led to the design of sensitive plastic skins to get information from the environment or from the plastic part itself.

In some cases it is also possible to send energy with guided waves. Specific piezo-electrics (FSAT) have been designed and manufactured for shear stresses generation.