Fracture fatigue entropy determination

Patent metadata

Field	Value
Publication number	US-9243985-B2
Application number	US-89810010-A
Country	US
Kind code	B2
Filing date	Oct 5, 2010
Priority date	Oct 5, 2009
Publication date	Jan 26, 2016
Grant date	Jan 26, 2016

Abstract

A method and apparatus are disclosed for approximating in real time the fracture fatigue entropy (FFE) of a metallic object subjected to cyclic loading. Such objects experience fatigue, which can lead to failure after a number of loading cycles. The disclosed invention allows for real time monitoring of the entropy increase in a metallic object under cyclic loading, and allows for removing the object from service before fatigue fracture occurs. Through use of the present invention, users may keep metallic objects in service for longer periods, because such objects may be safely taken closer to the fatigue fracture point. The invention therefore can effectively extend the useful life of many critical components and reduce downtime resulting from repair or premature replacement.

First claim

We claim:

1. A method for preventing the mechanical failure of a metallic object; wherein the metallic object is subject to cyclic loading; and wherein said method comprises the following steps:
(a) measuring the temperature of the surface of the metallic object, in the vicinity of the location of incipient mechanical failure, using a temperature sensor;
(b) approximating the accumulated volumetric entropy production γ in the vicinity of the location of incipient mechanical failure of the metallic object, using a relationship that is equivalent to:
γ=∫ 0 t′ ( W p /T ) dt

wherein t denotes the time, t′ denotes the particular time for which γ is being determined, T denotes the temperature of the surface of the metallic object in the vicinity of the location of incipient mechanical failure, and Wp denotes the cyclic plastic energy for the metallic object;

(c) predicting the time of mechanical failure of the metallic object when γ is approaching the value of γ f , or is approaching a user-specified fraction of the value of γ f , wherein γ f denotes the mean volumetric fracture fatigue entropy for the metallic object; and
(d) stopping the cyclic loading of the metallic object, using a controller, when γ approaches the value of γ f , or when γ approaches a user-specified fraction of the value of γ f .

Assignees

• Khonsari Michael M
• Abadi Mehdi Naderi
• Darehbidi Mehdi Amiri
• Univ Louisiana State

Inventors

• Khonsari Michael M
• Abadi Mehdi Naderi
• Darehbidi Mehdi Amiri

Classifications

• G01N3/32 Primary

  by applying repeated or pulsating forces · CPC title

• G01N2203/0069

  Fatigue, creep, strain-stress relations or elastic constants · CPC title

• G01N2203/0005

  Repeated or cyclic · CPC title

• G01N2203/0073

  Fatigue · CPC title

• C22C38/00

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title