&lt;title&gt;Determination of the fatigue limit of an austempered ductile iron using thermal infrared imagry&lt;/title&gt;

The quickly identify of fatigue limit of a mechanical component with good approximation is currently a significant practical problem not yet resolved in a satisfactory way. Generally, for a mechanical component, the fatigue strength reduction factor ( i ) is difficult to evaluate especially when it is in service. In this paper, the procedures for crack paths individuation and consequently damage evaluation (adopted in laboratory for stressed specimens with planned load histories) are applied to mechanical components, already failed during service. The energy parameters, proposed by the authors for the evaluation of the fatigue behavior of the materials [1][2][3][4][5], are defined on specimens derived from a flange bolts. The flange connecting pipes at high temperature and pressure. Due to the loss of the seal, the bolts have been subjected to a hot flow steam addition to the normal stress. The numerical analysis coupled experimental analysis (measurement of surface temperature during static and dynamic tests of specimens taken from damaged tie rods), has helped to determine the causes of failure of the tie rods. The determination of an energy parameter for the evaluation of the damage showed that factors related to the heat release of the material (loaded) may also help to understand the causes of failure of mechanical components.

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Fatigue characterization of mechanical components in service

Fargione¹,

Tringale²,

Guglielmino³

et al. 2013

“…From more than 30 years, the authors work on the methodologies based on the energy factors such as the heat development during the fatigue tests (Risitano method) [11][12][13][14][15] in order to define the fatigue curves in a very short time compared to the traditional method (stair case); the results of this method (Risitano method) have been then studied and T analyzed by many other researchers [16][17][18][19][20][21][22][23][24][25][26][27][28] and now this method is quite normal in use. The analysis of the phenomenon of the heat development has highlighted that the material which is subjected to a dynamic stress higher than its fatigue limit, shows the irreversible phenomena already during the first cycle of application of the fatigue loads.…”

Section: Introduction and Aim Of The Workmentioning

confidence: 99%

Definition of the linearity loss of the surface temperature in static tensile tests

Risitano

Fargione

Guglielmino

2014

ABSTRACT. Static tensile tests on material for mechanical constructions have pointed out the linearity loss of the surface temperature with the application of load. This phenomenon is due to the heat generation caused by the local microplasticizations which carry the material to deviate from its completely thermoelastic behavior,. The identification of the static load which determines the loss of linearity of the temperature under stress, becomes extremely important to define a first dynamic characterization of the material. The temperature variations that can be recorded during the static test are often very limited (a few tenths of degree for every 100 MPa in steels) and they require the use of special sensors able to measure very low temperature variations. The experience acquired in such analysis highlighted that, dealing with highly accurate sensors or with particular materials, the identification of the first linearity loss (often by eye) in the temperature curves, can be influenced by the sensibility of the investigator himself and can lead to incorrect estimates. The aim of this work is to validate the above mentioned observations on different steels, by applying the autocorrelation function to the data collected during the application of a static load. This, in order to make the results of the thermal analysis free from the sensitivity of the operator and to make the results as objective as possible, for defining the closest time of the linearity loss in the temperature-time function.

“…n oltre venticinque anni di attività di ricerca condotta dal gruppo di Progettazione Meccanica del DIIM sono state messe a punto nuove metodologie per la caratterizzazione statica e dinamica dei materiali con l'ausilio della termografia, attestati dalle numerose memorie scientifiche [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Il risultato di tali attività è stato fra l'altro un I…”

Section: Introduzioneunclassified

Proposta di utilizzo di metodologie termografiche per il controllo di qualità di componenti meccanici

Clienti

Rosa

Risitano

et al. 2010

Self Cite

RIASSUNTO.In base all'esperienza maturata in anni di sperimentazione sull'analisi delle caratteristiche meccaniche dei materiali mediante indagine termografica, nel presente lavoro è proposta una procedura per il controllo di qualità di componenti meccanici in linea di produzione, che è già stata argomento di brevetto. Lo sviluppo di questo lavoro si colloca nell'ambito del progetto FIRB "Sistemi di produzione intelligenti, flessibili e riconfigurabili". L'attività svolta dal DIIM riguarda il controllo avanzato dell'affidabilità di componenti meccanici per l'industria automobilistica. Viene proposta, quindi, la realizzazione di una cella di controllo in linea di produzione capace di valutare la presenza di eventuali componenti difettosi attraverso l'analisi termica degli stessi, sollecitati secondo un modello predefinito. L'attività, svolta in questa prima fase in laboratorio, è facilmente trasferibile in linea di produzione, considerando la possibilità di realizzare celle di prova in ambiente controllato, con condizioni praticamente identiche a quelle di laboratorio, eliminando gli effetti di disturbo che possono influenzare la risposta dell'indagine termografica in ambiente non strutturato.ABSTRACT. Based on the experience of more than a quarter of century on the analysis of the endurance characteristics of materials using thermographic methodologies, the present paper deals on a proposal of a new procedure for the quality control on mechanical components in processing line. The procedure methodology was already patented by some of the authors. The work described is included in the research programme FIRB Smartflex, particularly regarding the activity of the DIIM about the advanced control of the reliability of automotive elements and systems. A control cell, inside the processing line, able to evaluate the presence of defects in the automotive components by the application of defined cyclic loads and the analysis of the induced thermal maps, is proposed. The results, in this first step found in laboratory, could be easily transferred to the processing line, considering the possibility of realizing a structured environment control cell, with ambient conditions very similar to those created in the laboratory, reducing the noise effects affecting the thermal data in a non-structured environment. PAROLE CHIAVE. Qualità strutturale; C.N.D.; Termografia; Analisi immagini. INTRODUZIONEn oltre venticinque anni di attività di ricerca condotta dal gruppo di Progettazione Meccanica del DIIM sono state messe a punto nuove metodologie per la caratterizzazione statica e dinamica dei materiali con l'ausilio della termografia, attestati dalle numerose memorie scientifiche [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Il risultato di tali attività è stato fra l'altro un I