Comparison of mechanical properties of low carbon cast iron

1. Low carbon steel: low carbon steel is a plastic material. At the beginning, it obeys Hooke's law and rises along a straight line. After the proportional limit, the deformation accelerates, but there is no obvious yield stage. On the contrary, the figure gradually bends upward. This is because after the proportional limit, with the rapid growth of plastic deformation, the cross-sectional area of the specimen gradually increases, so it bears

Comparison of mechanical properties between low carbon steel and cast iron

Low carbon steel is a plastic material, gray cast iron is a brittle material, low carbon steel in tensile failure will have obvious yield, strengthening, and necking stage, and gray cast iron is not, it will not have the same section shrinkage as low carbon steel

Try to compare the mechanical properties of low carbon steel in tension and compression, try to compare the mechanical properties of cast iron in tension and compression

Due to the low carbon content, the ductility, toughness and plasticity of low carbon steel are higher than that of cast iron. At the beginning of stretching, the stress of low carbon steel test bar is large, and deformation occurs first. With the increase of deformation, the stress decreases gradually. When the test bar is disconnected, the stress is "0", and its stress curve is in the shape of sine wave > 0
Because of the poor toughness of cast iron, the stress is gradually increased at the beginning of drawing. When it reaches and exceeds its tensile limit, the test bar breaks, and the stress moment is "0". The stress curve is that with the extension of the stress time, a straight line develops upward, the test bar breaks, and the straight line vertically returns to "0"
The same principle: the compression resistance of low carbon steel is lower than that of cast iron. When the compression test is carried out on the low carbon steel test block, the stress gradually increases, and the test block deforms with the external force. When the deformation of the test block reaches the limit, the stress also reaches the maximum value, and the stress curve is a straight line above the syncline. Cast iron is not, and the stress situation is basically the same as that of low carbon steel at the beginning, Only when the stress of cast iron test block reaches its own failure limit, the stress gradually decreases until the test block is destroyed (cracked) under the external force, and the stress is "0", and the stress curve is the same as that of low carbon steel in tension
These are the mechanical properties of low carbon steel and cast iron in tension and compression

What is the difference between brittle materials and ductile materials? What is the difference in use?

Brittle materials can't be broken, and can't be made into thin-walled products, but the temperature resistance is generally better. Ductile materials are softer, and can be made into very thin products, such as wire drawing, film blowing, plate, pipe, etc

What is the relationship between the strength, brittleness, hardness, plasticity and toughness of metals?
For example, is the higher the strength, the greater the brittleness

Compared with plasticity, brittleness generally refers to the tendency of material fracture without plastic deformation. That is to say, when the tensile strength of material is lower than the yield strength, the material presents brittleness. The FATT of material indicates the tendency of plastic brittle transition with temperature. Plasticity refers to the ability of material to undergo permanent deformation, which is generally characterized by a-elongation and z-reduction of area
2. From the engineering point of view, the strength of a specific material generally refers to the yield strength of the material. Generally speaking, the higher the strength of the material, the stronger the resistance to plastic deformation and the higher the hardness. There is a certain linear relationship under specific conditions. The higher the strength of the material, the poorer the plasticity
3. Toughness is a comprehensive index reflecting the strength and plasticity of materials. Materials with good toughness have higher strength and better plasticity, which can be considered as having higher yield strength and ductility at the same time

In the calculation of final deformation of foundation soil, does the additional stress in soil refer to effective stress or total stress?

Refers to the effective stress

Why is the stress distribution uniform in the cross section during axial tension or compression deformation?

When the material is subjected to external force, each "fiber" of the material is consistent with the outside, resisting the "invasion" of external force, and trying to maintain the original shape. Therefore, the stress distribution is uniform. The actual situation will be different. The material is not evenly distributed on the cross section, and there are breakpoints (such as small air holes), soft points (different resistance of materials), But its influence is not great. According to the uniform distribution, it is basically consistent with the actual situation, so it is considered as uniform distribution

Explanation of deformation formula for mechanical efficiency
On the day when the teacher talked about the deformation formula, I just asked for leave. I'm going to take the exam soon. Please explain delta = GH / Fs = g / NF to you

Suppose the pulley has n ropes. If the weight of the rope is increased by 1m, the free end of the rope has to be pulled by N meters. So g * 1 / f * s = g / NF (because s = n, assume the weight of the rope is increased by 1m)

Deformation formula of mechanical efficiency of pulley block

Mechanical efficiency: n = w useful / W total = GH / Fs this is a general formula
Because s = NH
So the deformation formula of mechanical efficiency is: n = g / NF
(the former n is the mechanical efficiency, and the latter n is the effective number of strands of the rope)

Mechanical efficiency formula of pulley block
Please classify

Mechanical efficiency η = Wye / wtotal
Useful work W has = GH (g refers to the gravity of the object, H refers to the height of the object)
Additional work wtotal - Wye (total work wtotal = FS, f refers to the pulling force used, s refers to the moving length of the free end of the rope)

Comparison of mechanical properties of low carbon cast iron