scholarly journals A Unified Creep-Fatigue Equation with Application to Engineering Design

Creep ◽  
2018 ◽  
Author(s):  
Dan Liu ◽  
Dirk John Pons
Keyword(s):  
Engineering Design ◽  
Creep Fatigue ◽  
Fatigue Equation

scholarly journals The Unified Creep-Fatigue Equation for Stainless Steel 316

Metals ◽  
2016 ◽  
Vol 6 (9) ◽  
pp. 219 ◽  
Author(s):  
Dan Liu ◽  
Dirk Pons ◽  
Ee-hua Wong
Keyword(s):  
Stainless Steel ◽  
Creep Fatigue ◽  
Stainless Steel 316 ◽  
Fatigue Equation

Development of a stress-based creep-fatigue equation: Accommodating pure-fatigue to pure-creep for the high-cycle loading regime

2017 ◽  
Vol 27 (9) ◽  
pp. 1397-1415 ◽  
Author(s):  
Dan Liu ◽  
Dirk J Pons
Keyword(s):  
Fatigue Damage ◽  
Full Range ◽  
Creep Condition ◽  
Fatigue Behaviour ◽  
Reference Condition ◽  
Good Ability ◽  
Creep Fatigue ◽  
Cycle Loading ◽  
Casting Steel ◽  
Fatigue Equation

Background The creep-fatigue damage in low-cycle regime has been described by a strain-based creep-fatigue equation through integrating creep effect into fatigue damage. Need There is a need to develop a creep-fatigue equation which describes the stress-controlled creep-fatigue behaviour in high-cycle regime. Approach This stress-based creep-fatigue equation was developed through superposing a fatigue mechanism with a creep mechanism. This creep-fatigue equation was then validated on GP91 casting steel. The creep-fatigue data were transformed to the reference condition and collapsed into one power-law curve with good quality. Outcomes This result verified the formulas of the fatigue component and the creep component, and demonstrated the method of extracting the coefficients. The full-range characteristic of this creep-fatigue equation is discussed. In addition, the introduction of the compatibility presents a better description of the reference condition. Originality A new creep-fatigue equation is provided with demonstrably good ability to cover the full range of conditions from the pure-fatigue condition to the pure-creep condition for the high-cycle regime. The method of extracting the coefficients is also provided.

scholarly journals An Explicit Creep-Fatigue Model for Engineering Design Purposes

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 853 ◽  
Author(s):  
Dan Liu ◽  
Dirk John Pons
Keyword(s):  
Fatigue Life ◽  
Engineering Design ◽  
Creep Behavior ◽  
Design Method ◽  
Full Range ◽  
Diffusion Creep ◽  
Explicit Model ◽  
Element Analysis ◽  
Fatigue Model ◽  
Creep Fatigue

Background: Creep-fatigue phenomena are complex and difficult to model in ways that are useful from an engineering design perspective. Existing empirical-based models can be difficult to apply in practice, have poor accuracy, and lack economy. Need: There is a need to improve on the ability to predict creep-fatigue life, and do so in a way that is applicable to engineering design. Method: The present work modified the unified creep-fatigue model of Liu and Pons by introducing the parameters of temperature and cyclic time into the exponent component. The relationships between them were extracted by investigating creep behavior, and then a reference condition was introduced. Outcomes: The modified formulation was successfully validated on the materials of 63Sn37Pb solder and stainless steel 316. It was also compared against several other models. The results indicate that the explicit model presents better ability to predict fatigue life for both the creep fatigue and pure fatigue situations. Originality: The explicit model has the following beneficial attributes: Integration—it provides one formulation that covers the full range of conditions from pure fatigue, to creep fatigue, then to pure creep; Unified—it accommodates multiple temperatures, multiple cyclic times, and multiple metallic materials; Natural origin—it provides some physical basis for the structure of the formulation, in its consistency with diffusion-creep behavior, the plastic zone around the crack tip, and fatigue capacity; Economy—although two more coefficients were introduced into the explicit model, the economy is not significantly impacted; Applicability—the explicit model is applicable to engineering design for both manual engineering calculations and finite element analysis. The overall contribution is that the explicit model provides improved ability to predict fatigue life for both the creep-fatigue and pure-fatigue conditions for engineering design.

Resolution and measurement in the scanning electron microscope

1987 ◽  
Vol 45 ◽  
pp. 534-537 ◽  
Author(s):  
Michael T. Postek
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Engineering Design ◽  
Resolving Power ◽  
Practical Applications ◽  
Instrument Resolution ◽  
Accurate Definition ◽  
Definition Of ◽  
Scanning Electron ◽  
Better Than

The term ultimate resolution or resolving power is the very best performance that can be obtained from a scanning electron microscope (SEM) given the optimum instrumental conditions and sample. However, as it relates to SEM users, the conventional definitions of this figure are ambiguous. The numbers quoted for the resolution of an instrument are not only theoretically derived, but are also verified through the direct measurement of images on micrographs. However, the samples commonly used for this purpose are specifically optimized for the measurement of instrument resolution and are most often not typical of the sample used in practical applications.SEM RESOLUTION. Some instruments resolve better than others either due to engineering design or other reasons. There is no definitively accurate definition of how to quantify instrument resolution and its measurement in the SEM.

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