A multi-level model for the analysis and prediction of creep and creep fracture of 2.25Cr–1Mo steel tubes

The creep and creep rupture properties of 2.25Cr–1Mo steel tubes have been analysed using the Wilshire equations. The observed behaviour patterns are then discussed in terms of the dislocation processes governing creep strain accumulation. A suitable statistical framework for analysing both the single and multi batch data available on this material is then specified. It is shown that ignoring the hierarchical nature present in many … Continue reading A multi-level model for the analysis and prediction of creep and creep fracture of 2.25Cr–1Mo steel tubes

A Novel Approach to the Prediction of Long-Term Creep Fracture, with Application to 18Cr-12Ni-Mo Steel (Bar, Plate, and Tube)

Designers of new power-generation plants are looking to make use of new and existing high-strength austenitic steels so that these plants can operate with much higher steam and, therefore, metal temperatures. However, this article shows that the Wilshire–Scharning methodology is incapable of producing accurate long-term-life predictions of these materials from short-term data. This article puts forward a modification of this approach that should enable existing … Continue reading A Novel Approach to the Prediction of Long-Term Creep Fracture, with Application to 18Cr-12Ni-Mo Steel (Bar, Plate, and Tube)

A generalisation of the Wilshire–Scharning methodology to creep life prediction with application to 1Cr–1Mo–0.25 V rotor steel

Wilshire–Scharning have recently developed a new methodology that has been demonstrated to deliver accurate longer term creep life predictions, and so offers the prospect of cost-effective acquisition of long-term creep design data. This methodology differs from existing approaches to creep life prediction by normalising the applied stress through the appropriate tensile strength. This article develops a generalisation of this Wilshire–Scharning model that has the potential … Continue reading A generalisation of the Wilshire–Scharning methodology to creep life prediction with application to 1Cr–1Mo–0.25 V rotor steel

Alpha-Case Kinetics and Surface Crack Growth in the High-Temperature Alloy TIMETAL 834 Under Creep Conditions

Investigations of Timetal 834 crept specimens showed that a uniform alpha-case layer was developed at the surfaces of all specimens tested in air at 823 K to 923 K (550 °C to 650 °C). The formation of this alpha-case was a result of the inward diffusion of oxygen, which is an alpha stabilizer, and other elements promoting the transformation of the beta matrix into an alpha phase and, thus, … Continue reading Alpha-Case Kinetics and Surface Crack Growth in the High-Temperature Alloy TIMETAL 834 Under Creep Conditions

Mechanical characterisation of a fibre reinforced oxide/oxide ceramic matrix composite

Monotonic tension, fatigue and creep experiments were conducted on an oxide/oxide ceramic matrix composite over the range of temperature 20–1200°C. The role of continuous fibre reinforcement, differential thermal expansion, stress redistribution interactions between fibres and matrix and the influence of inherent processing defects are all considered when describing the deformation and ultimate mechanical failure of these systems.   D.T. Di Salvoa, E.E. Sacketta, R.E. Johnstona, … Continue reading Mechanical characterisation of a fibre reinforced oxide/oxide ceramic matrix composite

25 Year Perspective Recent developments in analysis of high temperature creep and creep fracture behaviour

Over many decades, the creep and creep fracture properties of metals and alloys have commonly been described using power law relationships. However, with this approach, controversies still surround the mechanisms proposed to account for the stress and temperature dependencies of the minimum creep rate and rupture life. Similarly, power law and related expressions do not allow extrapolation of short term data sets to predict the … Continue reading 25 Year Perspective Recent developments in analysis of high temperature creep and creep fracture behaviour

An Analysis of Small Punch Creep Behaviour in the Gamma Titanium Aluminide Ti-45Al-2Mn-2Nb

Previous literature on gamma titanium alumindes(γ-TiAl) have found that this family of alloys offer significant potential for replacing more conventional nickel and titanium based alloy systems in future designs of gas turbine engines. Despite the inherent brittle nature of such materials, γ-TiAl typically exhibits considerable ductility at elevated temperatures and a demonstrable uniaxial creep response. Until now, the creep properties of γ-TiAl have primarily been sourced from conventional uniaxial approaches, … Continue reading An Analysis of Small Punch Creep Behaviour in the Gamma Titanium Aluminide Ti-45Al-2Mn-2Nb

Elevated Temperature Creep Deformation of a Single Crystal Superalloy through the Small Punch Creep Method

Small punch testing is now a widely recognised approach for obtaining useful mechanical property information of critical structural components, particularly in the nuclear industry. However, to date the utilisation of this method has been limited to isotropic materials such as aluminium alloys and steels.This paper will look to utilise the small punch(SP) test to assess the creep response of 〈001〉-orientated CMSX-4 at temperatures above 950°C. An orthogonal rafting … Continue reading Elevated Temperature Creep Deformation of a Single Crystal Superalloy through the Small Punch Creep Method

Creep Lifing Methodologies applied to a single crystal superalloy by use of small scale test techniques

In recent years,advances in creep data interpretation have been achieved either by modified Monkman–Grant relationships or through the more contemporary Wilshire equations, which offer the opportunity of predicting long term behaviour extrapolated from short term results. Long term lifing techniquesprove extremely useful in creep dominated applications, such as in the power generation industry and in particular nuclear where large static loads are applied, equally a reduction in … Continue reading Creep Lifing Methodologies applied to a single crystal superalloy by use of small scale test techniques

Development and Assessment of a New Empirical Model for Predicting Full Creep Curves

This paper details the development and assessment of a new empirical creep model that belongs to the limited ranks of models reproducing full creep curves.  The important features of the model are that it is fully standardised and is universally applicable. By standardising, the user no longer chooses functions but rather fits one set of constants only.  Testing it on 7 contrasting materials, reproducing 181 … Continue reading Development and Assessment of a New Empirical Model for Predicting Full Creep Curves