The past three decades have witnessed the explosion of nanoscience and technology, where notable research eftbrts have been made in synthesizing nanomaterials and controlling nanostructures of bulk materials. The unco...The past three decades have witnessed the explosion of nanoscience and technology, where notable research eftbrts have been made in synthesizing nanomaterials and controlling nanostructures of bulk materials. The uncovered mechanical behaviors of structures and materials with reduced sizes and dimensions pose open questions to the community of mechanicians, which expand the framework of continuum mechanics by advancing the theory, as well as modeling and experimental tools. Researchers in China have been actively involved into this exciting area, making remarkable contributions to the understanding of nanoscale mechanical processes, the development of multi-scale, multi-field modeling and experimental techniques to resolve the processing-microstructures-properties relationship of materials, and the interdisciplinary studies that broaden the subjects of mechanics. This article reviews selected progress made by this community, with the aim to clarify the key concepts, methods and applications of micro- and nano-mechanics, and to outline the perspectives in this fast-evolving field.展开更多
When pointed V-notches weaken structural components, local stresses are singular and their intensities are expressed in terms of the notch stress intensity factors （NSIFs）. These parameters have been widely used for...When pointed V-notches weaken structural components, local stresses are singular and their intensities are expressed in terms of the notch stress intensity factors （NSIFs）. These parameters have been widely used for fatigue assessments of welded struc- tures under high cycle fatigue and sharp notches in plates made of brittle materials subjected to static loading. Fine meshes are required to capture the asymptotic stress distributions ahead of the notch tip and evaluate the relevant NSIFs. On the other hand, when the aim is to determine the local Strain Energy Density （SED） averaged in a control volume embracing the point of stress singularity, refined meshes are, not at all, necessary. The SED can be evaluated from nodal displacements and regular coarse meshes provide accurate values for the averaged local SED. In the present contribution, the link between the SED and the NSIFs is discussed by considering some typical welded joints and sharp V-notches. The procedure based on the SED has been also proofed to be useful for determining theoretical stress concentration factors of blunt notches and holes. In the second part of this work an application of the strain energy density to the fatigue assessment of A17075 notched plates is presented. The experimental data are taken from the recent literature and refer to notched specimens subjected to different shot peening treatments aimed to increase the notch fatigue strength with respect to the parent material.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 11472150)
文摘The past three decades have witnessed the explosion of nanoscience and technology, where notable research eftbrts have been made in synthesizing nanomaterials and controlling nanostructures of bulk materials. The uncovered mechanical behaviors of structures and materials with reduced sizes and dimensions pose open questions to the community of mechanicians, which expand the framework of continuum mechanics by advancing the theory, as well as modeling and experimental tools. Researchers in China have been actively involved into this exciting area, making remarkable contributions to the understanding of nanoscale mechanical processes, the development of multi-scale, multi-field modeling and experimental techniques to resolve the processing-microstructures-properties relationship of materials, and the interdisciplinary studies that broaden the subjects of mechanics. This article reviews selected progress made by this community, with the aim to clarify the key concepts, methods and applications of micro- and nano-mechanics, and to outline the perspectives in this fast-evolving field.
基金supported by the Italian Research Program(Grant No.CPDA100715)entitled"Static and fatigue behaviour of structural notched components subjected to tension and torsion under small or large scale yielding"the Italian PRIN project(Grant No.2009Z55NWC_001)
文摘When pointed V-notches weaken structural components, local stresses are singular and their intensities are expressed in terms of the notch stress intensity factors （NSIFs）. These parameters have been widely used for fatigue assessments of welded struc- tures under high cycle fatigue and sharp notches in plates made of brittle materials subjected to static loading. Fine meshes are required to capture the asymptotic stress distributions ahead of the notch tip and evaluate the relevant NSIFs. On the other hand, when the aim is to determine the local Strain Energy Density （SED） averaged in a control volume embracing the point of stress singularity, refined meshes are, not at all, necessary. The SED can be evaluated from nodal displacements and regular coarse meshes provide accurate values for the averaged local SED. In the present contribution, the link between the SED and the NSIFs is discussed by considering some typical welded joints and sharp V-notches. The procedure based on the SED has been also proofed to be useful for determining theoretical stress concentration factors of blunt notches and holes. In the second part of this work an application of the strain energy density to the fatigue assessment of A17075 notched plates is presented. The experimental data are taken from the recent literature and refer to notched specimens subjected to different shot peening treatments aimed to increase the notch fatigue strength with respect to the parent material.
