A non-destructive, contactless technique for the health monitoring of ancient frescoes.

In this paper an innovative non-destructive, contactless technique applied to the health monitoring of ancient frescoes is presented. The problem of the health monitoring of artistic frescoes without a direct interaction with structures and paintings is of great concern in the field of art restoration and preservation. In artistic frescoes, the partial detachment of plaster portions is a typical and serious problem. Both layer-to-layer detachments and delaminations and surface cracks are usually present in ancient wall paintings. At present, the standard procedure of diagnosis consists of manual inspection, but produces only approximate information. This paper describes an acoustic, non-invasive, experimental technique of diagnosis, based on the acoustic-structural interaction which occurs when a fresco wall is excited by a loudspeaker. The analysis of the acoustic pressure field and of its alterations allows the assessment of detachments, since the acoustic modal parameters are affected by the acoustic system boundary conditions, i.e. the portion of analyzed fresco. The reconstruction of the modal behavior of the analyzed portion of the fresco is made by a scanning laser Doppler which measure the velocity field of the observed surface. It is a non-contact measure technique that provides a great accuracy. Experiments carried out on fresco artificial specimens show the potential of the technique

Local anesthetic infiltration vs. nervous blocks in face’s skin lesions: what’s new

Skin tumors are the most common type of cancer. They are localized throughout the body, more frequently in those regions chronically exposed to sun, like face, scalp and neck, compromising aesthetic appearance. The optimization of day hospital surgical procedures is mandatory, to avoid erroneous indications, insufficient intra operative comfort and prolonged recovery. New guidelines should be discussed and shared. Patients were divided in two groups: i. Group A of 50 patients, 21 male and 29 female, age 65 ±9, ASA I – III (10/19/21), weight 68±11 kg, height 160±8, with anesthetic Local Infiltration (LI); ii. Group B of 50 patients, 16 male, 34 female, age 68 ±10, ASA I – III (9/22/19), weight 64 ± 9 kg, height 158 ±11, with nerve block (NB). The purpose of our study is to evaluate the analgesia level, compliance and complication rate after LI or selective NB with alkalinised mepivacaine cloridrate 2%, Guardant®. Demographic data, ASA physical stauts, size of lesions, surgery, anesthesia durations and volume of LA injected were analyzed. Fisher’s exact test and Student’s t test were used; P ≤ 0.05 was considered statistically significant. No differences in age (65 ± 9 vs 68 ± 10 years), weight (68 ± 11 vs 64 ± 9), height (160 ± 8 vs 158 ± 11 cm), size of lesion (23 ± 11 vs 25 ± 14 mm), duration of surgery (47 ± 18 vs 51 ± 23 minutes) were detected in two groups (p > 0.05). Both anesthetic techniques ensured good analgesia, but only nerve’s blocks were be able to determine satisfactory intra operative patient’s comfort, a bloodless wound and weak risk for nervous lesions and toxic reaction to local anesthetic

Microstructure-based RVE modeling of the failure behavior and LCF resistance of ductile cast iron

In this work the failure behavior of ductile cast iron microstructure subjected to tensile and low-cycle fatigue loadings is simulated by a 3-D, FE Reference Volume Element approach. A fully ferritic matrix is considered as representative of the low-hardness, high-ductility material class of nodular cast irons. Plastic flow potential rule, ductile and low cycle fatigue damage models are implemented at the micro-scale for the matrix constituent in conjunction with nonlinear cyclic hardening laws, and periodic boundary conditions are imposed over the RVE at the meso-scale. Different values of triaxiality are imposed. Numerical results confirm experimental findings of the behavior at the meso-scale and correctly predict the LCF lifetime, driving the interpretation of inner strain distribution, voids interaction and triaxiality effects on failure mechanisms

A non-destructive technique for the health monitoring of tie-rods in ancient buildings

A technique is developed to identify in-situ the tensile force in tie-rods which are used in ancient monumental masonry buildings to eliminate the lateral load exercised by vaults and arcs. The technique is a frequency-based identification method that allows to minimize the measurement error and that is of simple execution. In particular, the first natural frequencies of the tie-rod are experimentally identified by measuring the FRFs with instrumented hammer excitation. Then, a numerical model, based on the Rayleigh-Ritz method, is developed for the axially-loaded tie-rod by using the Timoshenko beam theory retaining shear deformation and rotary inertia. Non-uniform section of the rod is considered since this is often the case for hand-made tie-rods in old buildings. The part of the tie-rod inserted inside the masonry wall is also modeled and a simple support is assumed at the extremities inside the walls. The constraints given to the part of the tie-rod inserted inside the masonry structure are assumed to be elastic foundations. The tensile force and the stiffness of the foundation are the unknown. In some cases, the length of the rod inside the masonry wall can be also assumed as unknown. The numerical model is used to calculate the natural frequencies for a given set of unknowns. Then, a weighted difference between the calculated and identified natural frequencies is calculated and this difference is minimized in order to identify the unknowns, and in particular the tensile force. An estimation of the error in the identification of the force is given. The technique has been tested on six tie-rods at the central vault of the famous Duomo of Parma, Italy

Fdm layering deposition effects on mechanical response of tpu lattice structures

Nowadays, fused deposition modeling additive technology is becoming more and more popular in parts manufacturing due to its ability to reproduce complex geometries with many different thermoplastic materials, such as the TPU. On the other hand, objects obtained through this technology are mainly used for prototyping activities. For this reason, analyzing the functional behavior of FDM parts is still a topic of great interest. Many studies are conducted to broaden the spectrum of materials used to ensure an ever-increasing use of FDM in various production scenarios. In this study, the effects of several phenomena that influence the mechanical properties of printed lattice structures additively obtained by FDM are evaluated. Three different configurations of lattice structures with designs developed from unit cells were analyzed both experimentally and numerically. As the main result of the study, several parameters of the FDM process and their correlation were identified as possible detrimental factors of the mechanical properties by about 50% of the same parts used as isotropic cell solids. The best parameter configurations in terms of mechanical response were then highlighted by numerical analysis

modeling the influence of stress triaxiality on the failure strain of nodular cast iron microstructures

Abstract In this study the fracture behavior of different cast iron microstructures subjected to tensile loading under different triaxialities is simulated by a finite element, 3-D Reference Volume Element approach. Three ferritic/pearlitic heterogeneous matrixes are considered which are representative of the class material grades for strength and ductility. Isotropic ductile and shear damage models are considered for the matrix constituents as concurrent damage mechanisms at the microscale, while graphite nodules are considered as voids acting as stress concentrators. Numerical results confirm experimental findings about local strain distribution and damage accumulation, and reproduce the engineering macroscopic behavior. The stress triaxiality is found to play a strong effect on the failure strain, extending the potentialities of this RVE modeling approach

analysis of bistable composite laminate with embedded sma actuators

Abstract The present work is aimed at the development of a finite element model of a composite laminate, to evaluate the possibility to snap between equilibrium configurations by means of shape memory alloy (SMA) wires. The underlying idea is to potentially take advantage of structures which possess multiple equilibrium configurations that can be achieved with a small energy input. Therefore, unsymmetric composite laminates that exhibit bistable response to actuation force are considered. Embedded SMA wires will provide the actuation force by virtue of Shape-Memory Effect i.e. restoring the original shape of a plastically deformed SMA wire by heating it. The Shape-Memory Effect is modelled in a simplified way using the Effective Coefficient of Thermal Expansion concept

Mechanical stress and deformation analyses of pressurized cylindrical shells based on a higher-order modeling

In this research, mechanical stress, static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented. The kinematic relations are developed based on higher-order sinusoidal shear deformation theory. Thickness stretching formulation is accounted for more accurate analysis. The total transverse deflection is divided into bending, shear and thickness stretching parts in which the third term is responsible for change of deflection along the thickness direction. The axisymmetric formulations are derived through principle of virtual work. A parametric study is presented to investigate variation of stress and strain components along the thickness and longitudinal directions. To explore effect of thickness stretching model on the static results, a comparison between the present results with the available results of literature is presented. As an important output, effect of micro-scale parameter is studied on the static stress and strain distributio

influence of material and manufacturing technology on the failure behavior of composite laminate bonded joints

Abstract The purpose of this work is to evaluate the influence of co-lamination vs. co-bonding on the failure behavior, and namely the fracture toughness, of carbon fibre reinforced (CFR) composite laminate joints in order to assess comparatively their performance. Since the strength of the laminate and ply texture are parameters affecting the strength of the joint, the comparison is extended to two different types of CFR pre-preg fibers, a satin T1100 with 2573 Nanoalloy® epoxy resin supplied by Toray and a twill T700 with ER450 toughened epoxy resin supplied by CIT, Toray group, representative of two different fields of application, racing and automotive, respectively

Reconfigurable logic for hardware IP protection: Opportunities and challenges

Protecting the intellectual property (IP) of integrated circuit (IC) design is becoming a significant concern of fab-less semiconductor design houses. Malicious actors can access the chip design at any stage, reverse engineer the functionality, and create illegal copies. On the one hand, defenders are crafting more and more solutions to hide the critical portions of the circuit. On the other hand, attackers are designing more and more powerful tools to extract useful information from the design and reverse engineer the functionality, especially when they can get access to working chips. In this context, the use of custom reconfigurable fabrics has recently been investigated for hardware IP protection. This paper will discuss recent trends in hardware obfuscation with embedded FPGAs, focusing also on the open challenges that must be necessarily addressed for making this solution viable