Which Material has the Most Tensile Strength?
The ability of a material to resist damage under external forces is called its strength. When a material is subjected to an external force, stress is generated in the material, and the external force is increased, and the stress is increased accordingly, until the bonding force between the internal particles of the material is insufficient to resist the applied external force, the material is damaged. The limit value of the stress reached during material failure is called the ultimate strength of the material, which is often expressed by f. The unit of material strength is megapascals (MPa). [1]
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- Material strength studies the internal force distribution of a structure, including the structure of the structure and how the structure deforms and fails under load. Understanding these forces and their distribution allows engineers to economically and safely design and measure load beams, shafts, and column structures. It mainly involves material stress, strain, elastic modulus, tensile test, moment of inertia and fatigue of metal.
- Strength grade is the classification of materials according to strength. Building materials are often divided into several grades or brands according to their strength values. Brittle materials are classified by compressive strength, and steels are classified by yield strength. For example, sintered ordinary bricks are divided into 5 strength grades such as MU10 according to compressive strength; Portland cement is divided into 6 strength grades such as 42.5 and compressive strength; ordinary concrete is divided into 14 strengths such as C15 according to compressive strength. Grade; carbon structural steel is divided into 4 grades such as Q235 according to the yield strength.
- The classification of grades or grades of building materials according to strength is of great significance to both producers and users. It enables producers to rely on evidence to control product quality in production, thereby ensuring product quality. For users, it is beneficial to grasp the performance indicators of materials, facilitate the rational selection of materials, the correct design and control of engineering construction quality.
- The difference and connection between strength and strength grade: Strength refers to the limit value of the material and is the only measured value; strength grade is the artificially specified range of strength; the determination of the strength grade must be based on its limit strength value, each strength grade Includes a range of intensity values. [1]
- It is known from the test that the failure stress measured by different samples of the same material is not a fixed value, but changes within a certain range. Its value is random. The statistical parameters of random variables include average, standard deviation (or coefficient of variation), maximum, minimum, and range. The design specification for building structures takes the failure stress with a 95% guarantee rate as the standard value of material strength, which is represented by fk, which is equal to the average value of material strength minus 1.645 times the standard deviation. The 95% guarantee rate means random sampling inspection of a batch of materials. The probability that the measured strength is not lower than f k is 95%, and the risk assumed by the user is only 5% (that is, the probability that the material strength cannot reach f k is 5%). [2]
- The material strength design value f is divided by the material strength standard value f k by the material partial coefficient M. In the design of building structure, the material partial coefficient M is 1.4 for concrete, 1.1 for HRB400 and below ordinary steel bars, 1.1 for HRB500 steel bars, 1.15 for masonry, 1.087 for carbon structural steel, and 1.087 for high strength low alloy structural steel Take 1.111. In the design of the bridge structure, the reliability of the design is higher than that of the building structure, so the value of the material partial coefficient is larger, 1.45 for concrete and 1.2 for ordinary steel bars. The strength design values of various materials can be consulted online. [2]