Lifetime prediction in creep-fatigue environment
The creep-fatigue interaction has been studied and innovative mathematical models are proposed to predict the operating life of aircraft components, specifically gas turbine blades subject to creep-fatigue at high temperatures. The historical evolution of the creep-fatigue lifetime prediction is given in order to place the present study in the context. A literature review of the life estimation under creep-fatigue environment is presented.
STRAIN BASED CREEP‐FATIGUE DESIGN RULES
— Although there has been considerable success in the development of design methods for assessment of fatigue and creep fatigue damage there is need for further improvement particularly for creep damage estimation. Strain based creep-fatigue rules have been developed for liquid metal fast breeder reactor technology (LMFBs) which give improved estimation of fatigue and creep damage compared with presently available procedures in commercially available high temperature design codes such as ASME CCN47 and RCC-MR. Presently however their scope is confined to full in-elastic analyses. 
 
 
 
This paper provides a summary of the approach used in the strain based rules in relation to base material and weldments of 316L(N) austenitic steel. The paper examines the application of the strain method to thermal shock tests on long cylinders in which the testing cycle includes periods of constant temperature and some of the test pieces contain circumferential welds. Comparisons are made with time fraction based estimates and those of full cyclic in-elastic analyses. Conclusions are drawn concerning the benefits of the method compared with presently available code procedures. The experience to date shows that the strain based rules give a more realistic interpretation of thermal shock experiments.
Assessment of fractures in endodontically treated teeth restored with and without root canal posts using high-resolution cone beam computed tomography
Background Root fractures are a diagnostic challenge for dentists in endodontic treatment. This study aimed to determine the relationship between the characteristics of tooth fractures and the presence of root canal posts in endodontically treated teeth using high-resolution cone beam computed tomography (CBCT). Material and Methods Fifty high-resolution CBCT scans of endodontically treated teeth with a diagnosis of fracture were obtained, of which 30 were from women and 20 were from men. These scans were acquired with three Veraviewepocs 3D units and one 3D Accuitomo 170 unit, with a 40 × 40-mm field of view and 125 μm voxel size. The variables assessed included the type of fracture, extent of fracture, type of retention, post length, cause of endodontic failure, location of the lesion, and time required to detect the fracture (difficulty score). For data analysis, the chi-squared test, Student’s t-test, and multiple linear regression (α <0.05) were used. Results No association was found between the type of fracture and type of retention or between the type of fracture and its extent (P>0.05). On the other hand, the type of fracture significantly influenced the time required for its detection. Additionally, the most difficult plane for detecting the fracture and the difficulty score were associated, with statistically significant results. Conclusions The type of fracture in endodontically treated teeth was not associated with the type of post used for restoration. All of the CBCT systems used to detect tooth fracture showed the same efficiency. Key words:Cone-Beam CT, Tooth Fracture, Root Canal Post.