Computational modeling of creep-based fatigue as a means of selecting lead-free solder alloys

The primary aim of this investigation was to understand the effect of temperature fluctuations on a number of various solder materials namely SAC105, SAC305, SAC405 and Sn–36Pb–2Ag. To achieve this objective, three different classic joint assemblies (a ball joint, a test specimen joint and finger lead joint) were modeled which provided the foundation for the creep and fatigue behaviors simulation. Anand’s viscoplasticity as a constitutive … Continue reading Computational modeling of creep-based fatigue as a means of selecting lead-free solder alloys

Constraints Imposed by the Wilshire Methodology on Creep Rupture Data and Procedures for Testing the Validity of Such Constraints: Illustration Using 1Cr-1Mo-0.25V Steel

A new parametric approach, termed the Wilshire equations, offers the realistic potential of being able to accurately life materials operating at in service conditions from accelerated test results lasting no more than 5000 hours. These Wilshire equations contain discontinuities that have in the literature been interpreted either in terms of changing deformation mechanisms or changes in where deformation occurs within a material (i.e., within boundaries or … Continue reading Constraints Imposed by the Wilshire Methodology on Creep Rupture Data and Procedures for Testing the Validity of Such Constraints: Illustration Using 1Cr-1Mo-0.25V Steel

The importance of creep strain in linking together the Wilshire equations for minimum creep rates and times to various strains (including the rupture strain): An illustration using 1Cr-Mo-V rotor steel

This paper highlights the observation that the Wilshire equations for failure times and times to various strains, as reported in the original literature, may not be the most appropriate ones for all materials—including the one selected in this study. Further, such appropriateness can be determined by looking at the consistencies between the parameter estimates obtained using minimum creep rates in comparison to using failure times. … Continue reading The importance of creep strain in linking together the Wilshire equations for minimum creep rates and times to various strains (including the rupture strain): An illustration using 1Cr-Mo-V rotor steel

Accounting for Batch to Batch Variation when Predicting the Safe Life of Materials Operating at High Temperatures: An Application to 1Cr-1Mo-0.25V Steels Using the Theta Methodology

Given the strong reliance on long-term datasets containing multiple heats of the same material (i.e., different bathes), there is a pressing need to obtain reliable predictions of creep properties that are representative of all such batches. This paper presents a new estimation framework for the theta methodology which enables a distribution of creep properties to be predicted which should be representative of any batch of … Continue reading Accounting for Batch to Batch Variation when Predicting the Safe Life of Materials Operating at High Temperatures: An Application to 1Cr-1Mo-0.25V Steels Using the Theta Methodology

The Potential United Kingdom Energy Gap and Creep Life Prediction Methodologies

The United Kingdom faces a looming energy gap with around 20 pct of its generating capacity due for closure in the next 10 to 15 years as a result of plant age and new European legislation on environmental protection and safety at work. A number of solutions exist for this problem including the use of new materials so that new plants can operate at higher temperatures, … Continue reading The Potential United Kingdom Energy Gap and Creep Life Prediction Methodologies

A partial least squares solution to the problem of multicollinearity when predicting the high temperature properties of 1Cr–1Mo–0.25V steel using parametric models

Recently there has been renewed interest in assessing the predictive accuracy of existing parametric models of creep properties, with the recently develop Wilshire methodology being largely responsible for this revival. Without exception, these studies have used multiple linear regression analysis (MLRA) to estimate the unknown parameters of the models, but such a technique is not suited to data sets where the predictor variables are all … Continue reading A partial least squares solution to the problem of multicollinearity when predicting the high temperature properties of 1Cr–1Mo–0.25V steel using parametric models

A new statistical framework for the determination of safe creep life using the theta projection technique

In this article a new estimation framework is put forward for the well-known theta projection technique which enables, for the first time, levels of confidence to be associated with the creep property predictions made using this technique. The predictions made from the resulting model are in the form of distributions, which is a substantial advance on existing life assessment methodologies used in high-temperature applications such … Continue reading A new statistical framework for the determination of safe creep life using the theta projection technique