Search results for "Fatigue"

Fatigue resistance: is it possible having a unique response?

2012

The mechanical characterisation of the asphalt concrete in terms of both the fatigue resistance and the stiffness modulus is necessary to use any design method of the flexible road pavements. Different kinds of test are usually used in experimental work such as bending tests, uniaxial tests, etc., but sometimes they do not give the same answer. In this paper mechanical characterization was carried out by means of fatigue tests undertaken with two most used testing machines for asphalt material: two point bending (2PB) test at IFSTTAR in Nantes (France) and four point bending (4PB) test at University of Palermo, in Palermo (Italy). Different strain controlled tests were undertaken for the sa…

Rubberised stone mastic asphalt mixtures: a performance-related evaluation

2022

The binder content of rubberised asphalt mixtures is usually increased compared to that used in conventional asphalt. This increase is deemed important to compensate for the reduction in the actual bitumen due to the existence of rubber particles. This study presents the results of performance evaluation conducted on different rubberised Stone Mastic Asphalt (SMA) mixtures produced using different types and contents of rubberised bitumen. The energy ratio (ER) computed from Superpave Indirect Tensile (IDT) tests was used to evaluate the cracking resistance of asphalt mixtures while the rutting behaviour was evaluated using the Repeated Load Axial Test (RLAT). The indirect tensile stiffness …

RESISTENZA STATICA E A FATICA DI NUOVI LAMINATI BIOCOMPOSITI RINFORZATI CON FIBRE DI AGAVE

2018

L’obiettivo di ridurre l’inquinamento legato alla produzione ed allo smaltimento dei materiali sintetici ha portato recentemente alla messa punto di normative di protezione ambientale che impongono l’uso crescente di materiali ecocompatibili e/o rinnovabili, e conseguentemente Ad un notevole interesse verso i cosiddetti biocompositi, materiali innovativi ottenuti attraverso il rinforzo di polimeri ecocompatibili o rinnovabili con fibre naturali quali lino, juta, canapa, agave ecc. Nonostante numerosi lavori di ricerca siano stati indirizzati a tali materiali, allo stato attuale pochi lavori hanno riguardato lo sviluppo di biocompositi ad elevate performance per applicazioni strutturali. Al …

Effect of residual stresses and their redistribution on the fatigue crack growth in cold-worked holes

2009

The cold-expansion process is widely used to enhance the fatigue life of structures with fastener holes. Various studies assert that the cold-expansion improves the fatigue strength of fastener holes; however, the improvement of fatigue life is difficult to quantify. The influence on fatigue life of cold-worked hole in a 6061-T6 alluminum allosy was studied by numerical and experimental tests. Fatigue crack growth tests were carried out to find the crack length and growth rates of crack propagating from hole edge. Thus, the cold-expansion process was modeled with a Lagrangian implicit code for metal forming to obtain the residual stress field. Progressive crack growth along the observed fat…

Fatigue behavior of self-piercing riveting of aluminium blanks and carbon fiber composite panels

2012

Evaluation of residual stress during fatigue test in a FSW joint

2007

At present, friction stir welding (FSW) represents one of the most interesting techniques in the field of welding. The process is has been implemented in industrial practice for joining aluminium alloys, while the welding of the titanium alloy and the steels is still primarily in a developmental stage. The thermo-mechanical action of the tool causes a residual stress field in the FSW joint. Although, the peak temperatures of the process are relatively low; residual stresses similar to the traditional welding technique may develop in the FSW joint. Moreover, the restraints of clamps, which are used for fixing the plates during the process, impede the relief of the heated zones that causes lo…

DETERMINAZIONE DELLA DURATA A FATICA DI COMPONENTI SOGGETTI A SOLLECITAZIONI SCHEMATIZZABILI COME PROCESSI ALEATORI A BANDA STRETTA

2016

In questo lavoro sono state sviluppate le espressioni analitiche per la determinazione della durata a fatica di componenti soggetti a svariate tipologie di sollecitazione aleatorie a banda stretta (con parametro di irregolarità 0.9<aX≤1), in particolare: processi non stazionari di tipo separabile, tensione normale monoassiale con tensione media costante, sollecitazione biassiale con tensioni normali agenti in fase, sollecitazione di sforzo normale e tensione tangenziale agenti in fase, propagazione della frattura. In this paper the analytical equations for the determination of the fatigue life of components subjected to various types of narrowband random processes of stress (having irregula…

Influence of custom-made and prefabricated insoles before and after an intense run

2017

[EN] Each time the foot contacts the ground during running there is a rapid deceleration that results in a shock wave that is transmitted from the foot to the head. The fatigue of the musculoskeletal system during running may decrease the ability of the body to absorb those shock waves and increase the risk of injury. Insoles are commonly prescribed to prevent injuries, and both custom-made and prefabricated insoles have been observed to reduce shock accelerations during running. However, no study to date has included a direct comparison of their behaviour measured over the same group of athletes, and therefore great controversy still exists regarding their effectiveness in reducing impact …

Assessment of Fatigue Effects Induced by Fast Beam Transients in the IFMIF-DONES Li Target

2020

One of the crucial steps toward the commercial exploitation of fusion energy is the availability of a high-intensity neutron source able to test and qualify structural materials to be used in future fusion power reactors. The International Fusion Materials Irradiation Facility-DEMO Oriented NEutron Source (IFMIF-DONES) facility, which is currently being designed within the framework of the EUROfusion Consortium, represents the European effort to develop such a neutron source. It employs a liquid lithium target struck by an accelerated deuteron (D+) beam to produce fusion-like neutrons used to irradiate materials samples. So far, a detailed investigation of the thermomechanical behavior of t…

Quantitative thermoelastic stress analysis by means of low-cost setups

2020

Abstract A low-cost Thermoelastic Stress Analysis (TSA) experimental setup is proposed which uses an ordinary micro-bolometer and in-house developed signal processing scripts. The setup is evaluated by analysing the thermoelastic signal from a tensile and a SENT specimen made of stainless steel AISI 304L, and the bolometer performances are compared with those of a state of the art photon detector. Signal processing is based on off-line cross-correlation, using a self-reference signal which is retrieved from the acquired thermal data. Procedures are in particular developed to recognise, quantify and correct errors due to spectral leakage and loss of streamed frames. The thermoelastic signal …