clase 01

Mecánica de Daño

Maestría en IngenieríaÉnfasis en Mecánica

“Rail Fracture Derails Punjab Mail; 29 Injured.” The Hindu, n.d. http://www.thehindu.com/todayspaper/tpnational/article3392017.ece.Sept. 06/2012

Fracturas en rieles

Un caso en Canada● On 30 December 1999, at approximately 1900 eastern standard time,

Canadian National (CN) train No. U-783-21-30 was travelling westward from Saint-Romuald, Quebec, on the north track of the Saint-Hyacinthe Subdivision. At Mile 50.84, near Mont-Saint-Hilaire, Quebec, cars from train No. U-783-21-30 derailed, fouling the adjacent south track. CN train No. M-306-31-30, which was travelling eastward on the south track at the time, collided with the cars of train No. U-783-21-30 as they derailed. The two crew members on train No. M-306-31-30 were fatally injured in the accident. Approximately 350 families living within a two-kilometre radius of the accident site had to be temporarily evacuated. Two locomotives and 61 cars were damaged in the accident. Approximately 2.7 million litres of hydrocarbons spilled and caught fire, damaging private property, public property and the environment.

contenu, E. name of the content author / N. en anglais de l’auteur du. (2002, August 15). English title / Titre en anglais.

Retrieved September 6, 2012, from http://www.tsb.gc.ca/eng/rapports-reports/rail/1999/r99h0010/r99h0010.asp

Un caso en Canada● On 30 December 1999, at approximately 1900 eastern standard time,

Canadian National (CN) train No. U-783-21-30 was travelling westward from Saint-Romuald, Quebec, on the north track of the Saint-Hyacinthe Subdivision. At Mile 50.84, near Mont-Saint-Hilaire, Quebec, cars from train No. U-783-21-30 derailed, fouling the adjacent south track. CN train No. M-306-31-30, which was travelling eastward on the south track at the time, collided with the cars of train No. U-783-21-30 as they derailed. The two crew members on train No. M-306-31-30 were fatally injured in the accident. Approximately 350 families living within a two-kilometre radius of the accident site had to be temporarily evacuated. Two locomotives and 61 cars were damaged in the accident. Approximately 2.7 million litres of hydrocarbons spilled and caught fire, damaging private property, public property and the environment.

contenu, E. name of the content author / N. en anglais de l’auteur du. (2002, August 15). English title / Titre en anglais.

Retrieved September 6, 2012, from http://www.tsb.gc.ca/eng/rapports-reports/rail/1999/r99h0010/r99h0010.asp

Mecánica de Daños

● ¿Qué clase de daños son predecibles?● ¿Qué clase de estudios son necesarios para

predecir los daños?● ¿Qué análisis es necesario?

La flota “Liberty”

La flota Liberty

La flota Liberty

● 2708 barcos● 1031 daños o

accidentes

La flota Liberty

● 2708 barcos● 1031 daños o

accidentes

● Brittle Failure of the U.S. Liberty Ship,Esso Manhattan, March 29, 1943, New York http://www.uh.edu/~pthompso/liberty/photos/fractures.html,

● http://siamkaewkumsai.blogspot.com/2010_06_01_archive.html

● The S.S. Schenectady (adapted from "Wikipedia Commons" http://en.wikipedia.org/wiki/SS_Schenectady, Al Rosenfield) 

La flota Liberty

● Totalmente soldados

● Esfuerzo triaxial

● Fractura frágil

● Temperatura de Transición

● Ciclo térmico por soldadura

 (6/sept/2012) Soldando los barcos Liberty. http://www.skylighters.org/troopships/welder.jpg

Crecimiento

● Concentración de esfuerzos creciente● Rata de crecimiento creciente● Resistencia residual decreciente

Cargas cíclicas y Resistencia Residual

2002.Broek, David. Elementary Engineering Fracture Mechanics. 4Th revied Ed. Kluwer. pp. 6.

Aparición de grietas

● Fallas pre-existentes● Procesos de daño acumulativo● Capacidad predictiva en el proceso del daño.

Modos de Falla

● Simple● Cizallante● Transverso

Estado de esfuerzos alrededor de una grieta.

σij=K I

√(2 π R)⋅f ij (θ)

Estado de esfuerzos alrededor de una grieta.

K I=β⋅σ⋅√(a)

β=√(π)

Elementos Finitos

● Soluciones parcialmente polinomiales● Continuas a trozos.● Dependen de una malla.

Meshing