Next Article in Journal
Elastoplastic Fracture Analysis of the P91 Steel Welded Joint under Repair Welding Thermal Shock Based on XFEM
Next Article in Special Issue
High Strain Rate Superplasticity of WE54 Mg Alloy after Severe Friction Stir Processing
Previous Article in Journal
Initial Corrosion Behavior of 12Cr1MoV Steel in Thiosulfate-Containing Sodium Aluminate Solution
Previous Article in Special Issue
Hot Deformation Behavior and Processing Map of High-Strength Nickel Brass
Article

New Developments in Understanding Harper–Dorn, Five-Power Law Creep and Power-Law Breakdown

Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089, USA
Metals 2020, 10(10), 1284; https://doi.org/10.3390/met10101284
Received: 1 September 2020 / Revised: 21 September 2020 / Accepted: 23 September 2020 / Published: 25 September 2020
(This article belongs to the Special Issue High-Temperature Behavior of Metals)
This paper discusses recent developments in creep, over a wide range of temperature, that may change our understanding of creep. The five-power law creep exponent (3.5–7) has never been explained in fundamental terms. The best the scientific community has done is to develop a natural three power-law creep equation that falls short of rationalizing the higher stress exponents that are typically five. This inability has persisted for many decades. Computational work examining the stress-dependence of the climb rate of edge dislocations may rationalize the phenomenological creep equations. Harper–Dorn creep, “discovered” over 60 years ago, has been immersed in controversy. Some investigators have insisted that a stress exponent of one is reasonable. Others believe that the observation of a stress exponent of one is a consequence of dislocation network frustration. Others believe the stress exponent is artificial due to the inclusion of restoration mechanisms, such as dynamic recrystallization or grain growth that is not of any consequence in the five power-law regime. Also, the experiments in the Harper–Dorn regime, which accumulate strain very slowly (sometimes over a year), may not have attained a true steady state. New theories suggest that the absence or presence of Harper–Dorn may be a consequence of the initial dislocation density. Novel experimental work suggests that power-law breakdown may be a consequence of a supersaturation of vacancies which increase self-diffusion. View Full-Text
Keywords: creep; Harper-Dorn; power-law-breakdown creep; Harper-Dorn; power-law-breakdown
Show Figures

Figure 1

MDPI and ACS Style

Kassner, M.E. New Developments in Understanding Harper–Dorn, Five-Power Law Creep and Power-Law Breakdown. Metals 2020, 10, 1284. https://doi.org/10.3390/met10101284

AMA Style

Kassner ME. New Developments in Understanding Harper–Dorn, Five-Power Law Creep and Power-Law Breakdown. Metals. 2020; 10(10):1284. https://doi.org/10.3390/met10101284

Chicago/Turabian Style

Kassner, Michael E. 2020. "New Developments in Understanding Harper–Dorn, Five-Power Law Creep and Power-Law Breakdown" Metals 10, no. 10: 1284. https://doi.org/10.3390/met10101284

Find Other Styles
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Search more from Scilit
 
Search
Back to TopTop