Numerical modelling of power law constants established through impression and micro-Uniaxial creep methods for service exposed A234WPB steel
- Authors: Tembo, Blessed
- Date: 2024-04
- Subjects: Number theory , Numerical analysis , Mechanical engineering
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64852 , vital:73931
- Description: Continuous monitoring of creep life in materials operating at high temperatures and pressures is imperative to prevent catastrophic failures and ensure timely replacement of worn-out components in industrial plants. Small-scale creep testing methodologies offer a valuable means of assessing material creep life while preserving structural integrity. Motivated by the need for reliable methods in creep life assessment, this study aimed to investigate the creep properties of A234WPB material subjected to service conditions using Impression creep and micro-uniaxial creep testing techniques. The research questions focused on establishing power law constants through small-scale creep testing, validating these constants using numerical modelling, and assessing their practical implementation in predicting material creep life. Samples extracted from service-exposed A234WPB steel alloy underwent step-load impression creep tests and step-temperature micro-uniaxial creep tests to derive the power law creep equation. The determined stress exponent of 3.967 indicated that dislocation creep was the dominant creep-controlling mechanism at 520 °C. A numerical model, utilizing the established power law constants, demonstrated a strong correlation with experimental findings in steady-state creep rates. Furthermore, the conventional Monkman-Grant approach was employed to predict the remaining life of the service-exposed material using impression creep data. The predicted remaining life aligned with the scatter band of uniaxial rupture life on a Larson-Miller plot, highlighting the practical utility of impression creep and micro-uniaxial creep testing techniques in assessing creep life. This study contributes to the advancement of small-scale creep testing methods and underscores their potential for practical implementation in industrial settings, thereby enhancing the reliability and safety of high-temperature and high-pressure operations. , Thesis (MEng) -- Faculty of Engineering, the Built Environment, and Technology, School of Engineering, 2024
- Full Text:
- Date Issued: 2024-04
Remarks on formalized arithmetic and subsystems thereof
- Authors: Brink, C
- Date: 1975
- Subjects: Gödel, Kurt , Logic, Symbolic and mathematical , Semantics (Philosophy) , Arithmetic -- Foundations , Number theory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5424 , http://hdl.handle.net/10962/d1009752 , Gödel, Kurt , Logic, Symbolic and mathematical , Semantics (Philosophy) , Arithmetic -- Foundations , Number theory
- Description: In a famous paper of 1931, Gödel proved that any formalization of elementary Arithmetic is incomplete, in the sense that it contains statements which are neither provable nor disprovable. Some two years before this, Presburger proved that a mutilated system of Arithmetic, employing only addition but not multiplication, is complete. This essay is partly an exposition of a system such as Presburger's, and partly an attempt to gain insight into the source of the incompleteness of Arithmetic, by linking Presburger's result with Gödel's.
- Full Text:
- Date Issued: 1975