1) Understand the benefit that the extreme number of degrees of
freedom and consistency of optical measurements (ESPI, LDV and
Image Correlation) can give of the dynamic analysis of
complex-shaped components; to increase the accuracy in the
evaluation of dynamic strains and stresses; to assess the fatigue
life of a component due to wide-spectra dynamic loading and enhance
its reliability; to evaluate the sound emission of vibrating
surfaces; to test the materials for defects by means of optical
non-destructive techniques.
2) Formulation of the linearized modal model of complex spatial
mechanisms around all the kinematically compatible positions that
can be explored in the working domain, by means of multibody
techniques, modal analysis and Lagrange multipliers, to be able to
define the boundary and constraint conditions of the problem and
the flexibility of the mechanism components. This study aims at
exploring the kinematics-based variability of the dynamic behaviour
of the spatial mechanisms.
3)Diagnostics and modelling of faults in mechanical components
(gears and bearings);fault identification by means of signal
processing on vibro-acustic signals; rotordynamics.
4) Improvement of the cutting force measurements in milling
machines by means of a filtering of the inertia force components
related to the rigid body motion of the measuring set-up/fixtures
on an instrumented dynamometric table. Rigid body properties
identification
1) Displacement measurement analysis, by means of laser ESPI
technique, for dynamic characterization, modal identification,
stress&strain evaluation, fatigue behaviour analysis and
non-destructive testing of mechanical components.
This topic continues the studies started in the "Speckle
interferometry for industrial needs" project at Dantec
Ettemeyer GmbH, Ulm (Germania), during the European Commission
Marie Curie Post Doctoral Host Fellowship in 2004-2005. The
research first aims at checking the portability of full-field
optical measurement datasets toward the traditional modal analysis
domain (estimation and sharing of Frequency Response Functions).
Then a better insight about the influence of the high degree of
freedom number (100K to 2M dofs) and of the spatially highly
defined displacement fields over modal model estimation and over
dynamic analysis of complex and lightweight structures is searched.
On these latter, the high modal density and eigenshape complexity
result in a difficult set-up for traditional measurement devices,
like accelerometer arrays. From highly defined displacement fields
and object shape-contour description it might also be possible to
evaluate the strain&stress field on the surface directly from
dynamic event measurements: such a full-field based dynamic strain
or modal model might be employed in fatigue and durability
estimation of complex objects.
The usage of full field datasets as input/boundary condition in
sound radiation estimation will be also considered, being this a
part of a wider research, interested in the vibro-acustic modeling
of complex systems: the dynamic signature of the components affects
the emitted sound pressure of the whole system, coming from the
vibrating surfaces.
The high density of spatial information contained in full field
datasets will be also studied for non-destructive testing
procedures, considering techniques deriving from image processing
and compression, beside others computationally suited for the size
of the problem.
Key words:
ESPI, dynamic analysis, light structures, experimental
full-field measurements, stress-strain, fatigue, Non Destructive
Testing.
2) Development of methods for the study of the elastodynamic
behaviour of complex spatial mechanisms, by means of multibody and
modal substructuring approaches.
The research activity aims at an approach for the dynamic
behaviour analysis of spatial mechanisms (from the simple ones to
vehicles, robots, automatic and tooling machines), constituted by
rigid and/or flexible parts coupled together by kinematical
constraints with varying relative dofs and elastic lumped elements.
Linearized modal models of the system will be formulated in the
neighborhood of the kinematically admissible configurations, the
latter being functions of the selected motion laws in the working
domain of the mechanism. The linearized modal model will be
assembled by means of numerical techniques, such as multibody
modeling and Lagrange multipliers, to model the boundary conditions
and the flexibility of the parts (by a modal base, either
experimental or analytical-numerical). A numerical code will result
from this research activity, implementing the above described
procedure with different kinematic and elastic lumped constraints
and able to automatically write and solve the related equations.
Testing on real prototypes should follow for the validation of the
approach.
Key words:
flexible multibody, spatial mechanisms, component mode
synthesis, modal analysis, model optimization
3) Diagnostics of mechanical systems by means of signal
processing.
This activity starts with a literature survey on consistent
diagnostics techniques for complex mechanical systems, focusing in
particular on defect modeling in mechanical components like gears
and bearings, and on damage identification by means of signal
processing techniques on vibro-acustic signals. Non conventional
techniques will be also explored. Experiments to test the fault
identification procedures will be carried on, both in the
laboratory and on field, in industrial environment.
For the diagnosis of rotating machinery, rotordynamics and
fluid-related phenomena in bearings will be investigated by means
of literature readings, construction of a testing rig, acquisition
and analysis software tools, with the aim to prepare an integrated
diagnostic tool.
Key words:
Diagnostics, signal processing, fault diagnosis, gears,
bearings, rotordynamics
4) Development of methodologies to estimate the cutting
forces in tooling machines, by means of an instrumented
dynamometric table.
The first part of the activity was aimed at obtaining the FE
model of the tooling machine Giuliani MT3 C, acquired by DIEM for
researches about active controlled vibrations in industrial
machinery. Useful information, about the dynamic behaviour and
about design guidelines for the dynamometric table, came from the
modal analysis of the frame coupled to the sledges and to the
item-carrying table. The dynamic behaviour of the whole system
induces inertia actions on the instrumented table, due to the rigid
body motion of the latter, even if fixed, through the force
transducers, to the main structure. The procedure, object of this
study, will thus take account for filtering out, from the cutting
force estimation, the inertia forces deriving from the rigid body
constrained motion of the instrumented table. By means of
processing the force and acceleration signals coming from the
table, an equivalent inertia force system is pursued, the latter
having to be subtracted from the force transducer signals to obtain
a more precise estimation of the cutting forces in working
conditions. Rigid body properties of the measurement system will be
evaluated by means of identification algorithms applied to the
available signals coming from the transducers on the instrumented
table.
Key words:
tool-cutting force, inertia forces, filtering, dynamic
analysis
