Teacher

prof.  Denis BENASCIUTTI

Credits

6 CFU

Language

Italian

Objectives

The course aims to provide a deeper examination to several topics addressed in the courses of Strength of Materials and Machine Design, with particular focus to problems in structural analysis and mechanical design. The course aims to takes a deeper look to beam theory (simple loading cases, deformation of structures, statically indeterminate structures). Furthermore, it aims to address design methods for bolted and welded joints (with reference to design codes) and also to investigate the design methodologies for several topics in mechanical design (e.g. structural durability, low-cycle fatigue, thermal stresses, composite materials), by also providing examples of computer-assisted design (Finite Elements).

Acquired skills

- Understanding of methods for the strength e deformation design of structural elements under different loadings and constraints.
- Design methods for bolted and welded joints.
- Methods for evaluation of the structural integrity of structural elements under different stress conditions.

Lectures and exercises (topics and specific content)

Advanced topics on beam theory: simple loading cases, bending, eccentric normal force, torsion of thin-walled sections, shear in non-symmetric sections; displacements and rotations, kinematic method, Euler-Bernoulli equation, Castigliano's theorem, Principle of Virtual Work; statically indeterminate structures, force method (Müller-Breslau); exercises (20 hours).
Introduction to semi-probabilistic limit state method: variability of loads and strength, probability functions; analysis methods (level IV, III, II, I); characteristic values for loads and strength, design values, partial safety factors (2 hours).
Bolted joints: design of bolted joints under static and fatigue loadings; loading diagram, stiffness of screw and plates, stress distribution among screw threads; strength classes; exercises (10 hours).
Welded joints: introduction, thermal field during welding, microstructure, residual stresses; classification of welded joints; design under static loading, design code methods  for full penetration and fillet welds (directional method, simplified method, method of rotated throat section); design under constant-amplitude fatigue loading, nominal stress approach, FAT class, SN lines; structural stress approach, use of Finite Elements; design under variable-amplitude fatigue loading, cycle counting method (rainflow), cumulative damage (Palmgren-Miner rule); exercises (10 hours).
Thermal stresses and low-cycle fatigues: thermal and mechanical deformation; thermal stresses in simple geometries; material response under cyclic loading (hardening, softening), stabilized stress-strain curve; low-cycle fatigue, Manson-Coffin equation (2 hours).
Design methods for composite materials: classification of composite materials, types and properties of fibres and matrices; lamina, macroscopic approach (anisotropy, material symmetries, coupling effects), microscopic approach ("rule of mixture"); orthotropic plate; damage mechanisms, strength criteria (max. stress, max. strain, Tsai-Hill); laminates (4 hours).
Laboratory exercise of Finite Elements: practical examples of use of commercial Finite Element software (ANSYS, MSC/Nastran) to solve some mechanical and thermo-mechanical load cases (10 hours).
Exercises (15 hours).
Labs (8 hours).
Tutorials / Seminars: seminars given by engineering of local industrial companies on topics of mechanical design (4 hours).

References

- Slides given by the teacher

Type of exam

Oral examination on the main topics addressed in the course