Titolo presentazione

sottotitolo Milano, XX mese 20XX

Mechanics of Materials and Structures – DICA

Raffaele Ardito PA

Giuseppe Cocchetti PA

Claudia Comi PO

Alberto Corigliano PO

Massimiliano Cremonesi RTDB

Roberto Fedele PA

Claudio Floris PA

Attilio Frangi PO

Aldo Ghisi RI

Stefano Mariani PA

Giorgio Novati PO

Anna Pandolfi PO

Umberto Perego PO

MMS Permanent faculty members

DICA - MMS

2

• Computational models and methods

• Composites, advanced and complex materials

Domain decomposition and model order reduction

Meshfree and particle methods

Fluid-structure interaction

Boundary element method

Advanced structural mechanics for INFN experiments

Simulation of fracture and fragmentation processes

Damage models for multi-phase materials

Concrete chemo-mechanical interaction

Liquid crystals Biological materials and models

Multi-scale microstructured materials and metamaterials

DICA - MMS

3 MMS Research areas 1/2

• Micromechanics and microsystems

• Inverse analysis, identification and structural optimization

Modelling and simulation

Devices

Characterization and reliability

Inverse procedures

FRP reinforcement of masonry

Advanced experimental techniques: digital image correlation, indentation

DICA - MMS

4 MMS Research areas 2/2

RA Computational models and methods

• Formulation of innovative methods for the simulation of the mechanical reponse

of materials, solids and structures and multi-physics problems.

• Simulation of fracture and fragmentation processes with finite

elements, extended finite element methods, and erosion approaches

• Particle and meshfree methods

• Boundary element method

• Domain decomposition and model order reduction

• Fluid-structure interaction

• Stochastic dynamics

• Complex materials

• Advanced structural mechanics for INFN experiments

• Applications: dams, composite materials, metamaterials, failure and damage of

structures and solids, biomechanis, micro electromechanical systems

DICA - MMS

5

Total time error w.r.t. stag. gain w.r.t. Stag. (%) n° POM

S (ttot=4·10-5) 24370 - - --

S-POD (tsnap=3·10-7) 7121 8,32·10-2 -70,8 35

SD-POD (tsnap=3·10-7) 5587 7,02·10-2 -77,1 35

S-POD (tsnap=2·10-7) 4705 8,33·10-2 -80,7 38

SD-POD (tsnap=2·10-7) 3793 8,32·10-2 -84,4 38

S-POD (tsnap=1.5·10-7) 3639 7,25·10-2 -85,1 34

SD-POD (tsnap=1.5·10-7) 2826 5,86·10-2 -88,4 34

SD-POD updated 2664 9,98 10-2 -89,1 31

Application of the proper orthogonal decomposition technique to the simulation of electro-mechanical vibration of a MEMS plane resonator. Computing time reduced of 90%.

DICA - MMS

6 Proper orthogonal decomposition in MEMS simulations

Structural earthquake and ageing analysis of large concrete dams. Most Italian dams designed several decades ago do not comply with modern earthquake resistance concepts and suffer of various kinds of material degradation. Advanced structural simulation technologies are used to assess their safety.

DICA - MMS

7 Nonlinear FE technology applied to dam engineering

3D simulations performed with an in-house developed Finite Element code using tessellation algorithms for the reproduction of polycrystalline materials, cohesive crack elements for the simulation of fracture processes, domain decomposition techniques for the strong reduction of computing time. Images show a single edge notched specimen subject to tensile loading.

DICA - MMS

8 Fracture and domain decomposition

Cutting of thin-walled structures (plates, foils, sheets, membranes, tissues…) by sharp objects (blades, wedges, splinters…) occurs in many real life instances such as in manufacturing processes, surgery and package opening. In all cases it involves severe nonlinearities: large strains, inelastic deformation, fracture propagation and contact. New finite element and fracture technologies have been developed.

DICA - MMS

9 Cutting of thin walled structures

Simulation of fluid flows and fluid structure interaction problems using a Lagrangian finite element approach based on the Particle Finite Element Method. The technique, based on a continuous re-meshing, guarantees an automatic tracking of the free-surface and of the fluid-structure interfaces.

0.00

0.05

0.10

0.15

0.20

0.00 0.10 0.20 0.30 0.40

free-surface

comparison

0

0.01

0.02

0.03

0.04

0.05

0.06

0 0.1 0.2 0.3 0.4

displacement

comparison

DICA - MMS

10 Particle methods and fluid-structure interaction

Application of the non-Newtonian fluids model to describe the macroscopic behaviour of landslides impinging in water reservoir.

Application of the 3D model to the optimization of the casting procedures.

DICA - MMS

11 Particle method applied to non-newtonian fluids

Max-ent mesh-free approximation and an energy based eigenerosion algorithm to the simulation of quasi-static propagation of fracture in brittle materials in mixed mode I-III. Rendering of the fracture surfaces as produced by the erosion algorithm.

DICA - MMS

12 Simulation of fracture and fragmentation processes

Hybridization of Galerkin approximation and updated Lagrangian approach, to achieve a geometrically exact update in volume for diffusion and advection problems. Interpolation of the incremental transport map through max-ent shape functions.

DICA - MMS

13 Optimal transportation method for diffusion/advection

RA Composites, advanced and complex materials

Formulation of phenomenological and micro-mechanically based constitutive models to

be used in the simulation of the multi-physics behaviour of complex materials under

various loading conditions.

Examples of materials object of research:

• concrete chemo-mechanical interaction

• damage models for multi-phase materials

• elastic-visco-plastic behaviours

• degeneration and damage in composites

• impact induced damage

• fiber reinforced polymers

• soft biological tissues: cornea, arteries, intestine

• structured metamaterials for wave filtering

DICA - MMS

14

Dt = damage in tension

Dc = damage in compression • Bi-dissipative damage

model for concrete

• Ductile damage in steel at high temperature.

Indirect experimental methodologies to assess ductile damage in steel tested at 1100 C: micro-tomography (squares) and ultrasonic wave propagation (diamonds)

DICA - MMS

15 Damage models

472 elements 908 elements

Multiphase chemo-mechanical damage modeling of concrete affected by alkali-silica-reaction (ASR). A multi-phase elastic-damage model was developed for the description of the influence of temperature and humidity on ASR and its structural consequences.

ijggijwwijij pbpb

effective stress

Biot’s coefficients

gel pressure

macro stress

water pressure

DICA - MMS

16

3 years 6 years 60 years

Damage

evolution

Chemo-mechanical interaction

Finite element simulations of mechanical and viscous-electro-mechanical behaviour of soft active biological tissues and organs. Numerical models account for 3D stochastic spatial distributions of the underlying collagen microstructure of the tissue and for strong or weak coupling.

DICA - MMS

17 Biomechanical applications (cornea, artery, intestine)

Human cornea models

Viscous-electro-mechanical coupling

Stochastic distribution of collagen in bio-tissues

Simplified model of the heart

Patient specific model of intestine

Numerical modeling of complex materials behavior. Finite element simulations capture the experimentally observed phase transitions between periodic and homogeneous configurations in a variable thickness thin layer of nematic liquid crystal under the action of uniform electric fields.

DICA - MMS

18 Liquid crystals

DICA - MMS

19 Structured meta-materials for wave filtering

Metamaterials in the form of phononic crystals (PnC): the dispersion diagram shows waves whose propagation is prevented. PnC are used in the creation of resonant cavities in MEMS. Their performance can be boosted through shape optimization, based on finite element simulations

DICA - MMS

20 Structured meta-materials for wave filtering

Metamaterials for full control of 3D waves. The performances of the metamaterial has been predicted by means of finite element simulation and the results have been confirmed by means of experiments

DICA - MMS

21

• Analysis, modelling and simulation, design and reliability assessment of Micro Electro

Mechanical Systems (MEMS)

• Examples:

• design of resonant accelerometers

• design of micro-gyroscopes

• design of magnetometers

• dissipative phenomena: damping, fracture, fatigue, stiction

• accidental drop and impact simulation

RA Micromechanics and microsystems

On-chip fracture-fatigue test device. Microsystem designed for the execution of fracture and fatigue tests at the micro-scale on-chip, by applying and acquiring electric signals only.

Fixed

Notch

Load

Beam

Lever

DICA - MMS

22 Mechanical characterization

THELMATM process

Uniaxial resonant accelerometer. The device was designed, modelled, fabricated and tested. It measures an external acceleration starting from the variation of the vibration frequency of a slender beam.

DICA - MMS

23

external acceleration

spring

spring

resonating beams

inertial mass

Electrodes

for driving

and

sensing

Devices: uniaxial resonant accelerometer

Package

Sensor

Die

Multi-scale procedure for the simulation of non-linear phenomena, e.g., accidental drop events, in microsystems. Three levels of analysis: package, die and sensor.

DICA - MMS

24 Modelling of Micro Electro Mechanical Systems (MEMS)

Maps of probability of rupture in the highly stressed region.

Details of mechanical simulation at the sensor level.

DICA - MMS

25

• Formulation of advanced techniques for the optimal identification of model parameters

through a combined use of laboratory (and in situ) experiments and simulation.

• Advanced experimental techniques:

• Kalman filters

• proper orthogonal decomposition

• digital image correlation

• Indentation

RA Inverse analyses, identification, and structural optimization

1-tonn delamination experiment on CFRP-reinforced ancient masonry. Full-field monitoring of tangential slip by no-contact 2D DIC.

DICA - MMS

26 Inverse analysis, identification, and structural optimization

3D finite element heterogeneous modeling.

Fracture test on an adhesively bonded assembly. Crack propagation monitored by DIC

DICA - MMS

27 Surface measurements by 2D DIC for cohesive model

calibration

Finite element model of the ROI

0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3

0.60.7

0.80.9

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2x [ mm ]

[ mm ]

[ mm ]

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x [mm]

crack front

nT

[MPa]

10t

7t

13t

0n

0n

along the interface

normal traction

cohesive tractions identified by finite element

and kinematic data

uniaxial compression on a polymer sample monitored by X-ray microtomography (20 µm resolution)

DICA - MMS

28 Bulk measurements by 3D Volume Digital Image Correlation

Displacement contour within the bulk provided by 3D-Volume Digital Image Correlation in a finite element framework