Object-Oriented Software for Fitness-For-Service Assessment of Cracked Cylinder Based on API RP 579

Fitness-for-service assessment of a cracked component intends to evaluate its remaining strength and remaining life to support the implementation of a maintenance plan. This research aims to develop a fitness-for-service assessment software to facilitate the task. The software development process included identifying the software specifications, designing the software structure, manipulating the information from the standard for programming, the graphical user interface design, and finally verification of the software. The assessment procedure employed in this study was the third edition of the standard API RP 579. The software structure was designed using an object-oriented concept. The software can perform integrity assessment levels 1, 2, and 3 option B, leak-before-break assessment, and remaining life assessment for a cracked cylinder that has a through-thickness crack or semi-elliptical surface crack oriented in an axial or circumferential direction. The applied loads could be a nominal axial force, bending moment, and internal pressure, as well as stress profiles perpendicular to the crack plane due to mechanical, thermal, and residual stresses. Accuracy of the software was demonstrated by applying it to example problems. Some aspects of the software extensibility were conceptually discussed

Finite Element Analysis of the Mechanical Behaviors of Endodontic Nickel–Titanium Rotary Files: A Review

An endodontic rotary file is a special instrument used in the treatment of dental pulp and surrounding tissues. They are available in a wide range of sizes and configurations, specifically tailored to accommodate the narrow and curved root canals of the teeth. Consequently, dental rotary files are slender, flexible, and generally made of a nickel-titanium alloy. The investigation of mechanical behaviors of dental files can be effectively conducted using computational approaches, such as the finite element method. This numerical tool is widely used in many engineering applications, especially for solid mechanics and structural problems. With the finite element method, the reliability and safety of dental files can be preliminarily assessed in a short period of time. This report reviews applications of the finite element analysis method to investigate the mechanical responses of endodontic rotary files. Both the finite element modeling of the files and applications of the method to rotary file problems are included in the study. This review includes the stress distribution, flexibility and stiffness, and fatigue life of the files. There have been a variety of approaches to model files under flexural and torsional loads. Static analysis with simple loading conditions was adopted in most of the studies. The analytical approach can be improved so that files under working conditions are accurately modelled. Moreover, there is a need for verification of the finite element solutions with experimental or clinical studies

Effect of Different Mechanical Properties of Core Build-up Materials on the Root Furcation of A Severely damaged Primary Molar: A Finite Element Analysis

Objectives: To assess the von Mises stress and stress distribution pattern on the root furcation of a severely damaged primary molar restored with different core build-up materials and stainlesssteel crown (SSC). Materials and Methods: The finite element analysis was used to investigate stresses induced in the tooth structures included a sound primary molar and severely damaged primary molars restored with four different core-build up materials, including flowable composite core build-up, bulkfill resin composite, RMGIC and nano-RMGIC. The maximum von Mises stress was used to representthe internal load induced in the model. Results: Overall maximum von Mises stresses was the highest in the sound tooth. However, when focusing on apico-cervical aspect, all restored primary molars showed higher maximum von Mises stress than the sound tooth. The stress distribution pattern of each group was similar, except for the nano-RMGIC group that showed high stress concentrated at the tooth furcation and the buccal aspect of the root furcation. From the ratio of its tensile strength and the maximum von Mises stress, the nano-RMGIC possessed the highest fracture resistance, followed by bulk-fill composite, RMGIC and flowable composite core group, respectively. Discussion: Although nano-RMGIC possessed the highest fracture resistance, it showed an unfavorable stress distribution pattern, which caused high stress at the root furcation. The bulk-fill composite possessed not only high fracture resistance but also favorable stress distribution. Conclusion: The present study introduces crucial information that could lead to an alternative treatment for severely damaged primary molar. Our findings recommend bulk-fill composite as a potential core build-up material. > ว.ทันต.มศว ปีที่ 16 ฉบับที่ 1 พ.ศ. 2566 หน้า 62-77. > SWU Dent J. 2023;16(1): 62-77

Reference Stress Approach for Fracture Assessment of Extrados Circumferential Through-Wall Crack at the Interface between Elbow and Pipe Subjected to Internal Pressure

The fracture assessment of a cracked component can provide a technical support for an effective maintenance and a prevention of catastrophic accident. The present study applies the reference stress method to extend the J-integral solution from the finite element analysis for the Ramberg-Osgood stress-strain relationship to other types of stress-strain relationship. The problem in this study is an extrados circumferential through-wall crack at the interface between elbow and pipe subjected to internal pressure. The finite element results from the literature were analyzed to determine the optimized reference pressure. The reference-stress-based failure assessment curve which incorporated with the obtained reference pressure can be used to estimate the finite-element-based failure assessment curve with a sufficient accuracy in fracture assessment. The failure load predicted from the reference-stress-based failure assessment curve deviated from that predicted from the finite-element-based failure assessment curve within the range of -7% to 11%