SCSC2003 Abstract S6853

Numerical simulation of a piezoelectric engine with progressive wave via a reliability technique.

Numerical simulation of a piezoelectric engine with progressive wave via a reliability technique.

Submitting Author: Mr. Abdelkhalak El Hami

Abstract:
The modelling of the piezoelectric engines with travelling wave implies a large variety of
physical and mechanical phenomena. This variety leads to approaches and models quite as
many and varied, which rest mainly on phenomenological and numerical analyses.
The specifications, increasingly more demanding imposed on the actuators; confine
sometimes the conventional electromagnetic engines with their extreme limits of operation. In
this context, the recent development of a new type of resonant vibromotors, resting on the
principle of the conversion of a mechanical vibration (often ultrasonic) of the stator, in a rigid
movement of body of the rotor, is of unquestionable interest for many industrial applications.
It is at the beginning of the years 1960 that began, with the USA and in the Soviet ex-Union,
the first research in the field of the vibrating stator engines. These original devices were
designed on the basis of theoretical work initially developed by Soviet researchers.
Many sources of energy were explored to ensure the excitation of the vibrations of volume on
the stator element of the engine. The most significant results were recorded with devices
exploiting of the forces of origin electromagnetic or electro-dynamic, magnetostrictive or
piezoelectric. Japan took over this work since the beginning of the years 1980, with
significant means which in particular allowed the design and then the first industrial
developments of piezoelectric engines (driving SHINSEI, engines of Zoom of the apparatuses
auto focus GUN...) are appeared.
Among the many currently studied devices, the engines with travelling wave represent
certainly the most promising way to guarantee soon the manufacture of mass of rotary engines
"extremely couple-low speed" without auxiliary mechanical reducer speed.
The generation of a progressive wave of volume imposes the respect of geometrical
constraints and mechanics relating to the periodicity of the structure of the engine.
The static mechanical behaviour of the rotor and the stator of the engine under loading of prestressing
are modelled by the finite element method. The characterization of the interface of
contact and the radial distribution of the contact pressure which is exerted is our main goal.
Thus, by introducing a risks unit with the mechanical problem, we evaluate the probability
that the constraints of contact in the coating of friction exceed a value threshold safety and
limit the lifespan initially envisaged when designing engine USR 60. The stochastic role of
each parameter of design in the default risk is highlighted. For this analysis of reliability of
the structure, we propose a coupling direct mechanic-reliability between the augmented
Lagrangian method to solve the contact, developed on a computer code by finite elements [3,
4,5], and probabilistic method FORM [6,7,8]. These results are validated by a statistical
procedure of Monte Carlo.
The results obtained then enable us to propose a whole of recommendations to optimize the
reliability of piezoelectric engine USR 60.


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