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Eventos casi periódicos en la plasticidad cristalina y el oscilador de avalancha autoorganizado
Stefanos Papanikolaou1, Dennis M Dimiduk, Woosong Choi
1Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520-8286, USA. stefanos.papanikolaou@yale.edu
Nature
|October 27, 2012
Resumen
Las avalanchas en sistemas estresados pueden ser influenciadas por procesos de relajación lenta. Este estudio revela un nuevo estado crítico del "oscilador de avalancha autoorganizado", que afecta la dinámica de las avalanchas en los materiales y los eventos geológicos.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- Física de la materia condensada Física de la materia condensada
- La geofísica es la geofísica.
Sus antecedentes:
- Las tensiones externas en los sistemas a menudo se alivian por eventos repentinos e impulsivos llamados avalanchas.
- Sin embargo, pueden ocurrir procesos lentos de relajación entre estos eventos, lo que influye en el comportamiento de la avalancha.
- Los ejemplos incluyen el flujo de agua entre los terremotos y el flujo de dislocación en cristales.
Objetivo del estudio:
- Investigar experimentalmente el impacto de la relajación lenta en la dinámica de avalanchas en sistemas estresados.
- Explorar el surgimiento de nuevos estados críticos y sus propiedades.
- Desarrollar y validar un modelo teórico que incorpore la relajación lenta.
Principales métodos:
- Compresión experimental de microcristales de níquel a través de tres órdenes de magnitud en la velocidad de deformación.
- Modelado analítico y computacional de avalanchas de dislocación, ampliado para incluir la relajación de la dislocación.
- Observación y análisis de ráfagas de avalanchas cuasi periódicas y exponentes críticos.
Principales resultados:
- Se observaron explosiones de avalanchas no convencionales casi periódicas en microcristales de níquel.
- Notó exponentes críticos más altos a medida que disminuía la tasa de deformación, lo que indica un comportamiento crítico alterado.
- Los hallazgos experimentales validados con un modelo refinado de avalancha de dislocación.
Conclusiones:
- Descubrió un nuevo estado crítico: el oscilador de avalancha auto-organizado.
- Este estado exhibe aproximaciones oscilatorias a un punto crítico en desarrollo.
- Los hallazgos sugieren que la invarianza de escala cuasi-periódica surge cuando las avalanchas compiten con la relajación lenta, aplicable a diversos sistemas como la microplasticidad y los terremotos.
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