» 延展性和脆性

延展性和脆性

1850
在材料科学实验室对金属样品进行拉伸测试,以评估延展性和脆性。

Ductility is a measure of a material’s ability to undergo significant plastic deformation before rupture, often quantified by percent elongation or percent reduction in area. Ductile materials, like steel, show a long plastic region on their stress-strain curve. Brittleness is the opposite; brittle materials, like ceramics or cast iron, fracture with little to no plastic deformation.

The distinction between ductile and brittle behavior is clearly visible on the stress-strain curve. A ductile material exhibits a significant strain after the yield point and before the fracture point. This large area under the curve after yielding indicates that the material can absorb a great deal of energy before it breaks. This property is crucial for safety in many engineering applications, as a ductile failure provides a visible warning (e.g., bending or stretching) before a complete collapse. Key measures of ductility are percent elongation, [latex](\frac{L_f – L_0}{L_0}) \times 100[/latex], and percent reduction in area, [latex](\frac{A_0 – A_f}{A_0}) \times 100[/latex], where the ‘f’ subscript denotes the final dimension at fracture.

Conversely, a brittle material shows very little strain after its elastic limit. The fracture stress is often close to the ultimate tensile strength, and failure occurs suddenly and without warning. Ceramics, glasses, and some polymers are classic examples. The behavior of a material can also depend on external conditions. For instance, many steels that are ductile at room temperature undergo a ductile-to-brittle transition at low temperatures, a phenomenon that has led to catastrophic failures, such as in the Liberty ships during World War II.

UNESCO Nomenclature: 3322
- 材料科学

类型

Material Property

中断

基础

使用方法

广泛使用

前体

  • 退火和回火冶金实践以控制材料性能
  • 早期工程结构中材料失效模式的观察
  • 拉伸试验作为标准表征方法的发展

应用

  • 根据成型应用选择材料(例如车身)
  • 结构设计确保失效是渐进的(延性的)而不是灾难性的(脆性的)
  • 拉丝和金属挤压工艺
  • 评估材料在低温下的性能,许多材料在低温下会变脆

专利:

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Related to: ductility, brittleness, plastic deformation, fracture, elongation, reduction in area, ductile failure, brittle fracture, material behavior, stress-strain curve.

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