在地球内核的压力下,铁的塑性变形
1Department of Geology and Geophysics, University of California, Berkeley 94720, USA. wenk@seismo.berkeley.edu
Nature
|July 13, 2000
概括
实验表明,由于变形,铁晶体在地球内核中排列. 这提供了在极端压力条件下地震异构机制的直接证据.
科学领域:
- 地质物理学 地质物理学
- 材料科学 材料科学 材料科学
- 矿物物理 矿物物理
背景情况:
- 地球内核的地震异构性表明了水晶的对齐.
- 以前的研究提出了各种机制,但在核心压力下缺乏实验验证.
研究的目的:
- 在地球核心压力条件下实验确定铁的弹性和塑性变形机制.
- 为了调查内部核心的地震异性质的原因.
主要方法:
- 在钻石子细胞中,在轴应力下测量铁的同步射线X射线衍射测量.
- 模拟相当于地球核心的极端压力条件.
主要成果:
- -铁 (六角密封) 晶体表现出强烈的偏好方向,c轴与压缩方向平行.
- 在多晶可塑性理论中,观察到的晶体对齐与基底滑动作为初级或二级滑动系统是一致的.
结论:
- 这项研究提供了地球内核中发生的变形机制的直接实验证据.
- 引入了一种新的实验室方法,用于在极端压力下研究材料类风学.
相关概念视频
Plastic Deformations
588
Plastic deformation represents a fundamental concept in materials science, which explains the irreversible change in the shape of a material when it experiences stress beyond its elastic capability. This phenomenon is important in structural engineering, especially in designing and analyzing cantilever beams—structures that are securely fixed at one end and bear loads at the opposite end. When these beams are subjected to loads within their elastic range, they will return to their...
588
Plastic Deformations
639
It is essential to understand how structural members behave under plastic deformation when the bending stress exceeds the material's yield strength. This state of deformation permanently alters the shape of the member, in contrast to the linear elastic behavior observed before yielding. The strain at any point in the member is expressed in terms of maximum strain. Notably, the neutral axis, which coincides with the centroid during elastic bending, shifts away from the centroid under plastic...
639
Plastic Deformation in Circular Shafts
562
When materials are subjected to forces that surpass their yield strength, they undergo a process known as plastic deformation. This results in a permanent alteration or strain in their structure. This concept can be specifically applied to circular shafts, where the deformation leads to a change in its shape. The precise evaluation of this plastic deformation requires understanding the stress distribution within the circular shaft, which is achieved by calculating the maximum shearing stress in...
562
Temperature Dependent Deformation
615
In a nonhomogeneous rod made up of steel and brass, restrained at both ends and subjected to a temperature change, several steps are involved in calculating the stress and compressive load. Due to the problem's static indeterminacy, one end support is disconnected, allowing the rod to experience the temperature change freely. Next, an unknown force is applied at the free end, triggering deformations in the rod's steel and brass portions. These deformations are then calculated and added...
615
Plasticity
3.3K
Plasticity is the property where an object loses its elasticity and undergoes irreversible deformation, even after the deformation forces are eliminated. If a material deforms irreversibly without increasing stress or load, then this is called ideal plasticity. For example, when a force is applied to an aluminum rod, it changes its shape, but it does not return to its original shape once the force is removed. Plastic deformation or ductility is thus a permanent deformation or change in the...
3.3K
Plastic Behavior
742
A material's elastic behavior is characterized by the disappearance of stress once the load is removed, allowing the material to return to its original state. However, when stress surpasses the yield point, yielding commences, marking the onset of plastic deformation or permanent set. This change from elastic to plastic behavior is influenced by the peak stress value and the duration before the load is removed. An intriguing observation occurs when a specimen is loaded, unloaded, and...
742


