Corso di laurea: Ingegneria meccanica Programmazione per l'A.A. 2020/2021

XPERIMENTAL AND NUMERICAL ADVANCED MECHANICAL DESIGN

Course Teacher: G. Mirone, room 30, floor 6, building 3 “Polifunzionale”;

gmirone@dii.unict.it

Objectives and organization

This course aims at delivering the skills to perform the mechanical design and the integrty assessment of structures and components according to the most advanced modern procedures.
Extensive training about finite elements modeling (FEM) will be ensured, for enabling the students to predict the structural response within the frameworks of elastoplasticity, dynamics, structural integrity and damage tolerance.
In order to achieve such objective, notions of material mechanics and experimental characterization will be delivered from a pragmatical viewpoint, respectively addressing the latest models of material behavior (static/dynamic plasticity, material damage/failure), and the most recent laboratory procedures for calibrating such models.
The students will assist to laboratory experiments for static and dynamic testing (motor driven and hydraulic testing machines, Hopkinson bar equipment, data acquisition and image analysis); they will then use the experimental data for calibrating some selected material models which, then, will be implemented within the FEM platform MSC-MARC through user subroutines simulating the overall mechanical response of specimens/components/structures.
A section of the course will also aim at the thermal methods for fatigue asessment; this section will train the students at acquiring infrared imagery data and at processing data from thermal acquisitions, aimed at determining the fatigue response of components/structures subjected to cyclical loads.
Contents of the course (C = classes, L = lab., E = exercitation).

I) Elastoplasticity

- C1) Introduction to plasticity - Normality rule and consistency condition – hardening – associate plasticity and yield surface – von Mises plasticity –Path dependence of plastic straining – Pressure and Lode dependent yield surfaces – Experimental determination of the hardening curve – Necking – Experimental characterization – Engineering, True and Flow curves – MLR and MVB methods for round and rectangular section specimens - Practical notions for Finite Elements (FEM) modeling and anaysis;

- L1) Laboratory experiments for characterization and flow curve validation: 3-4 specimen shapes (e.g. smooth/notched, round/flat) of the same material for as many groups;

- E1) - Finite elements implementation of tensile tests by round/flat, smooth/notched specimens;

II) Damage mechanics and ductile failure

- C2) Triaxiality factor and Lode angle – Rice-Tracey introductory model - Phenomenological damage models (Bao-Wierzbicki, Xue-Wierzbicki etc.) –Problems of mesh dependence for failure propagation in finite elements;

- L2) Lab. experiments with simple components / special specimens made of the characterized materials;

- E2) Calibration of damage models by data from L1, L2, E1 – Implementation of damage models via user subroutines – Prediction of failure by FEM simulations of L2;


III) Dynamics and High Strain Rate effects

- C3) Strain rate effect and models of dynamic hardening – Plastic work dissipation and selfheating in dynamics – Experimental procedures for high strain rate testing – Elastic waves propagation in rods – Split Hopkinson Bar equipment;

- L3) Lab. Experiments with Split Hopkinson Tensile Bar (SHTB);

- E3) Evaluation of dynamic stress-strain curves – Calibration and implementation of a dynamic hardening model via User Subroutine – FEM simulation of dynamic SHTB tests;

IV) Thermal methods for fatigue assessment - Prof. G. Fargione

- C4) Review of fatigue concepts – random loading and multiaxial fatigue – staircase method - infrared (IR) detection of heat – Training on Thermocamera Flir model…. commands and software – Procedure for determination of the fatigue limits by thermocamera – Laboratory activity tests.

- L4) thermocamera acquisition from static/fatigue tests;

- E4) Postprocessing of experimental IR data;


EXAM: ORAL COLLOQUIUM;

REFERENCES:
- Lecture notes provided by the course teacher;
- Selected papers from recent literature;
- MSC MARC user manuals
- FLIR user manuals

- Lecture notes provided by the course teacher;
- Selected papers from recent literature;
- MSC MARC user manuals
- FLIR user manuals

A) Teoria

1a.Tecniche di Manifattura Additiva per materiali polimerici: Manifattura Additiva per Estrusione (FFF, FDM); Stampa 3D mediante polimerizzazione di resina (DLP; LCD; LCA; InkJet Printing); Sinterizzazione Laser (SLS).

2a. Processi di lavorazione dei materiali polimerici: Estrusione, Stampaggio ad Iniezione, Stampaggio per Soffiaggio, Stampaggio per compressione.

3a. Miscelazione reattiva dei polimeri

4a. Reologia e cinetica di reazione dei materiali termoindurenti

5a. Processi di produzione dei materiali compositi.

B) Esperienze di Laboratorio

1b) Esercitazioni di manifattura additiva: Impostazione del processo di stampa mediante software dedicati; Esperimenti di stampa 3D su geometrie semplici; Esempi di stampa 3D su geometrie complesse (casi studio)

2b) Esercitazioni di estrusione: Preparazione di una miscela polimerica binaria; Preparazione di una compound polimerico rinforzato.

3b) Esercitazione di stampaggio ad iniezione: preparazione di campioni ad "osso di cane" o altra geometria semplice utilizzano le formulazioni preparate al punto 2b).

4b) Esercitazioni di realizzazione manufatti in materiale fibrorinforzato: preparazione di pannelli, o geometrie semplici, utilizzando la tecnica del Hand Lay Up o del VARTM.

C) Caso Studio: Lo studente selezionerà almeno un caso studio da realizzare autonomamente