Mechanical efficiency formula all deformation formulas Talk about the deformation process

Mechanical efficiency formula all deformation formulas Talk about the deformation process

η = w with / W total * 100% pulley η = g / G + G material η = f v

According to the results of tensile, compression and torsion tests, the mechanical properties of low carbon steel and cast iron were analyzed
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It can be concluded that the toughness of low carbon steel is stronger than that of cast iron, and the brittleness of cast iron is higher than that of low carbon steel. The yield strength of low carbon steel is higher than that of cast iron. (cast iron is very brittle, and there is almost no yield strength), but the tensile strength of cast iron is higher than that of low carbon steel, because the carbon content of cast iron is higher than that of low carbon steel

Compare the mechanical properties of low carbon steel and cast iron under axial tension and compression
If the title, as long as the embodiment of mechanical properties, and similarities and differences, for God, thank you

Same: first elastic deformation, then plastic deformation, and then
Difference: low carbon steel has larger deformation, can be drawn longer or pressed coarser, and has larger elongation
Cast iron deformation is small, tensile deformation is small has broken, elongation is small
Compression may be directly crushed, deformation is small

What is the yield stage of low carbon steel in tension?
In my book, in the tensile test of low carbon steel, the tensile force F increases all the time
1. In the elastic stage, before the elastic limit, the deformation can completely disappear except the tensile force. However, after entering the yield stage and removing the tensile force, some deformation cannot disappear. According to the figure in the book, the stress at the yield limit is higher than that at the elastic limit. That is to say, the yield limit and the elastic limit are not coincident, There is also a section of value between them. Why should yield limit be taken as the reference standard to determine the allowable stress of plastic materials? Why not take elastic limit as the standard to ensure no deformation?
2. In the yield stage, the strain increases obviously, but the stress does not change. Stress = f / A. the cross-sectional area a must be decreasing, but according to the experimental conditions, does not f increase all the time? How can the stress basically remain unchanged? At this time, a becomes smaller, and f only becomes smaller, so the stress can remain unchanged? Does f become smaller, or not, or other situations?

1. The allowable stress is obtained according to the strength theory of plastic materials. The strength theory is a theory to judge whether a material is damaged under complex stress state. There are two different failure forms of materials under the action of external force: one is the sudden fracture without significant plastic deformation, which is called brittle failure; the other is the failure that cannot continue to bear load due to significant plastic deformation, It is called plastic failure, that is yield failure. For low carbon steel, it is plastic material, and the failure mode is yield. Therefore, the yield limit should be used as the standard and a certain safety factor should be given to determine the allowable stress. Although the yield limit is similar to the elastic limit, it is not the same
2. In the test, the stress reading is obtained indirectly by the load reading of the testing machine, that is, the load f is larger than the upper cross-sectional area A0. In the yield stage, the length of the specimen increases, and the cross-sectional area has no significant change (the original area A0 is still considered if the deformation is ignored), while the load f shakes up and down in a small range (F is not a fixed value, but a small fluctuation)

What are proportional limit, yield limit and strength limit

Proportional limit
Proportional limit symbol: the OE section in the σ P (subscript) tensile curve, the maximum stress that the material can bear without deviating from the proportional relationship between stress and strain (Hooke's law). Steel in the elastic stage is divided into two parts: linear elastic and non-linear elastic. The relationship between stress and deformation of steel in the linear elastic stage is completely linear, and the highest point of stress is the proportional limit
Yield limit
This phenomenon is called "yield". The stress of yielding phenomenon is called yield point, or yield limit, which is expressed by σ s. The yield point of some materials is not obvious. It is often stipulated in engineering that the stress value when the residual deformation reaches 0.2%, As "conditional yield limit", it is expressed as σ 0.2
Strength limit
Symbol: σ B (subscript); unit: MPa (or N / mm2) appears in the stage of tensile curve sb, and the member is further deformed under the action of external force. It is the maximum stress that the member can bear under the condition of maintaining the mechanical strength of the member, According to the different types of stress, it can be divided into tensile strength (σ T), compressive strength (σ C), shear strength (σ s), etc

What is the phenomenon of low carbon steel yielding

The appearance of low carbon steel does not show obvious change when yielding, and the measured length becomes larger

Do not know the yield limit, but know the tensile strength, bending strength and compressive strength, how to calculate the allowable stress?

Generally, the yield strength is 60% of the tensile strength

What are the strength limit (tensile strength) and yield limit?

The strength limit and yield limit are determined by experiments. In the process of tensile test, although the stress reaches a certain value, it does not increase or even slightly decrease, the strain of the specimen continues to increase and produce obvious plastic deformation, as if the material has temporarily lost the ability to resist deformation. This phenomenon is called material yield

It is known that the stress at a certain point in the soil is in the limit equilibrium state, the minimum principal stress is σ & # 8323; = 150kPa, and the shear strength index of the soil is C = 50kPa, φ = 30 °,
(1) Find the maximum principal pressure σ & # 8321; and the maximum shear stress ζ max
(2) The normal stress and shear stress on the shear failure surface of the point are calculated
(3) It shows that the maximum shear stress surface is not the shear failure surface

&(1) find the maximum principal pressure σ &; and the maximum shear stress ζ Max & nbsp; σ 1 = σ 3tan & ᙧ 178; (45 + 0.5 φ) + 2ctan (45 + 0.5 φ) & nbsp; σ 1 = 150tan & ᙧ 178; (45 + 0.5 * 30) + 2 * 50tan (45 + 0.5 * 30) & nbsp; σ 1 = 150 * 3 + 100 * 1.732 & nbsp; σ 1 = 450 + 173.2 & nbsp

What is the strength limit of Ti-15-3? What is the difference between strength limit and ultimate tensile stress?

Tensile strength, also known as strength limit, refers to the maximum stress value of a material before breaking. Yield stress is the stress at the yield point on the stress-strain curve. Yield strength is the yield limit, which is the critical stress value of material yield. For plastic material, when it reaches yield and significant plastic deformation occurs, it loses normal work