Confronto tra metodi di misura delle tensioni residue su un disco estratto da un cilindro autoforzato

La presente memoria analizza i risultati di misure di Tensioni Residue (TR) effettuate su un disco estratto da un cilindro autoforzato eseguite mediante tre tecniche: il metodo della deformazione iniziale (ISD), il metodo del foro cieco (BHD) e il metodo dei raggi X (XRD). Data la geometria e la natura del trattamento di autoforzamento, il campione esaminato presenta un campo di tensioni residue assialsimmetrico che varia solo con la coordinata radiale. Questo permette di confrontare direttamente le tre tecniche di misura che, a tale scopo, sono state applicate in sequenza su diverse aree dello stesso disco. Le tensioni residue ottenute dalle le tre tecniche di misura, vengono presentate e confrontate. In aggiunta vengono tratte alcune conclusioni sulla validità del metodo dell’ISD

Effects of Wire Electrical Discharge Machining and shot peening on the axial High Cycle Fatigue strength of Inconel 718

Nickel-based superalloys are widely used in structural components subjected to fatigue loads at high temperatures. Inconel 718 is probably one of the most used materials, especially for the production of turbine discs. The disc-blade connection is one of the most critical zones due to the simultaneous presence of severe stress cycles, elevated temperature, and high-temperature gradient. Thanks to its low cost, Wire Electrical Discharge Machining (WEDM) can be considered the most effective technology for manufacturing fir-tree slots on turbine discs. However, it is known that WEDM has a detrimental effect on the material fatigue strength. Shot peening is usually used for enhancing fatigue performances. The paper deals with the effects of the WEDM and shot peening treatment on the fatigue strength of Inconel 718 in the range comprehended between 105 and 107 cycles. The investigation has been carried out by determining the Wöhler curve (S-N curve) under pulsed axial loading condition using specifically designed hourglass specimens. Tests were conducted at room temperature and at 1000°F. In order to identify the issues of the fatigue damage process, fractographic analysis has been conducted for each broken specimen using Optical (OM) and Scanning Electron Microscopy (SEM). No significant variation of the S-N curve has been found in the tested conditions, excepted for the reduction of the scatter of the data: shoot peening was seen to reduce the scatter of the fatigue endurance at low-stress amplitudes. The results of the fractographic analysis suggest that this effect can be correlated to a different initial phase of the crack propagation. Moreover, the two tested temperatures were found not to have significant effects on the Wöhler curve, both for the as-built and shot-peened specimens

Multiaxial cyclic plasticity model including elastic modulus variation

In the present work a multiaxial model is proposed to describe the elastoplastic behaviour of a structural steel in the presence of loading-unloading cycles. The activity is a part of a more estensive research carried out in collaboration with Baker & Hughes aimed at developing an accurate model for accurately predicing residual stresses caused by autofrettage processes in thick cylinders and its experimental verification. It has been demostrated that in order to obtain estimates of the residual stress with errors within a few percent, the constitutive behavior of the material has to be reproduced very accurately. To this purpose, both the Bauschinger effect and the variation of the elastic modulus with the accumulated plastic deformation have to be accurately measured and properly included in the constitutive model

Papillary thyroid cancer in a patient with congenital goitrous hypothyroidism due to a novel deletion in NIS gene

Iodide transport defect (ITD) is a rare cause of congenital hypothyroidism (CH) caused by sodium/iodide symporter (NIS) gene mutations. We report a novel NIS gene deletion in a patient with congenital hypothyroidism, goiter and papillary thyroid cancer . The proband was a 40 years old woman affected by CH treated unevenly with levothyroxine (L-T4) since the first year of age. She presented with a recurrence of multinodular goiter containing two indeterminate nodules and lack of iodide uptake by thyroid, salivary glands and stomach one month after L-T4 withdrawal. A second thyroidectomy was performed and one nodule was a papillary thyroid carcinoma (PTC) at histology. One proband’s brother was also affected by CH and developed a large multinodular goiter. After extracting genomic DNA from peripheral white blood cells and total RNA from thyroid tissue, all 15 exons of NIS gene were amplified and sequenced. No amplification band was obtained from the genomic DNA of the patient from exons 8 to 12 suggesting a large deletion. Direct sequencing of cDNA revealed a homozygous deletion producing a protein lacking of 185 amino acids. The same defect was present in the affected brother. We describe the first case of a patient with papillary thyroid carcinoma associated with dyshormonogenetic goiter due to a deletion of the NIS protein. The lack of a functioning NIS raises the question of how to complete the treatment of infiltrative PTC in this patient

Frequency and effect on serum TSH of phosphodiesterase 8B (PDE8B) gene polymorphisms in patients with sporadic nonautoimmune subclinical hypothyroidism.

BACKGROUND: Nonautoimmune subclinical hypothyroidism (NSH) is characterized by elevated serum TSH in presence of normal thyroid hormone levels and absence of anti-thyroid antibodies. As result of a genomic-wide study, a strong association between three polymorphic variants in intron 1 of human PDE8B gene (rs4704397, rs6885099, rs2046045) and serum TSH has been reported in euthyroid subjects. AIM: The aim of this study was to evaluate frequency and effects on serum TSH of PDE8B gene polymorphisms in patients with sporadic NSH and verify if differences in serum TSH levels are associated to these polymorphic variants. SUBJECTS AND METHODS: A total of 58 Italian selected patients affected by NSH, with elevated serum TSH, normal FT3 and FT4 and without TSHr gene mutations, were subjected to genotyping for specific single nucleotide polymorphism of PDE8B gene. RESULTS: In all patients, the integrity of TSH receptor gene was attested. The ancestral allele associated with increased serum TSH was present in 42/58 patients (72.4 %) for rs4704397, in 42/58 patients (72.4 %) for rs6885099 and in 44/58 patients (75.9 %) for rs2046045. However, similar values of serum TSH were detected in patients with minor or major allele for each polymorphism. CONCLUSIONS: A prevalence of the minor allele of PDE8B gene polymorphism associated with elevated serum levels of TSH was demonstrated in patients affected by sporadic NSH; however, significant differences in circulating TSH in patients with minor or major alleles for each polymorphism were not identified demonstrating the lack of association between the polymorphisms and serum TSH levels in these patients

Ipotiroidismo congenito causato da una nuova mutazione omozigote del gene della tireoglobulina

L\u2019ipotiroidismo congenito dovuto a deficit di tireoglobulina (TG) \ue8 una malattia autosomica recessiva con una prevalenza di 1:4000091:100000 nati vivi e caratterizzata da gozzo, bassi livelli sierici di TG, elevati livelli di TSH con bassi livelli di ormoni tiroidei e test al perclorato negativo. La TG umana, una proteina di 2768 aminoacidi, \ue8 codificata da un grosso gene con 48 esoni localizzato su cromosoma 8q24. Mutazioni del gene della TG sono associate a gozzo congenito con ipotiroidismo o eutiroidismo. Ad oggi sono state descritte e caratterizzate 50 mutazioni del gene della TG umana. Lo scopo del nostro studio \ue8 stato quello di eseguire l\u2019analisi del gene della TG in due sorelle nate da genitori consanguinei affette da ipotiroidismo congenito. Le due sorelle sono state identificate allo screening neonatale e trattate dopo la conferma di ipotiroidismo con L9Tiroxina. Alla et\ue0 di 7 anni, una sorella, dopo sospensione della L9tiroxina presentava un franco ipotiroidismo, TG indosabile; alla scintigrafia era presente una tiroide in sede con captazione del 12% dopo 24 ore; la ecografia dimostrava la presenza di una ghiandola in sede di normali dimensioni. La seconda sorella, nonostante il precoce trattamento con L9 tiroxina, era anche affetta da ritardo mentale. La ecografia confermava la presenza di una tiroide in sede di normali dimensioni, e la tireoglobulina era indosabile. Il DNA genomico \ue8 stato estratto dal sangue delle pazienti e da quello del padre, unico genitore in vita, utilizzando un kit commerciale. Tutti i 48 esoni che compongono il gene della TG sono stati amplificati per PCR, sequenziati con BigDye Terminator Kit e analizzati su 3130xl genetic analyzer. Nel sangue di entrambe le pazienti \ue8 stata identificata una mutazione puntiforme omozigote a livello dell\u2019esone 10 del gene della TG (CGA/TGA) che determina la formazione di un codone di stop in posizione 768 (R768X). Il risultato \ue8 quindi la presenza di una proteina precocemente troncata e quindi non funzionante. Erano inoltre presenti varianti alleliche gi\ue0 descritte in letteratura. In conclusione, abbiamo identificato due sorelle con ipotiroidismo congenito e tiroide in sede di normali dimensioni e TG indosabile. L\u2019analisi genetica ha dimostrato una alterazione della Tireoglobulina come causa dell\u2019ipotiroidismo