 ## 字幕表 動画を再生する

• Hi,guys,

• In this episode, let's talk about the relationship between the force and objects ,

• first this blue is an object,

• it has contains both are convex and concave,

• and also relatively wider and narrower parts,

• when after the concept of the objects enters, we will to produce the proportional scale,

• the unit is what that not the focus,

• this an object is subjected to variety of different roles by the forces and moment couple now,

• so it produced a certain the deformation,

• and the dashed line is the object line after it's deformed,

• maybe it still will start to moves or rotations after thrust surface,

• the force will causes objects the moves dip direction,

• the moment couple will causes objects to have rotates dip direction,

• the soil mechanics did not use to the moment couple,

• so it will not appear again after this episode appears.

• that, we consider of the objects are also not rotation occurs ,

• because the soil will not rotation,

• ok, next let's take a look at the force.

• first, we can see it withstand the concentrated force of F1

• and the force of F2

• there are also f1 and f2

• the uniform force and distributed force,

• that, let's explain the nouns now,

• focusing on role by the object on 1 point is called the concentrated force,

• the concentrated force can act on or outside the objects,

• can be understood as the force at a distance, (but actually is vector movement), that's no problem,

• the force of unit we use is Newton N,

• the concentrated force actually is abstract concept,

• assume the force acts on a certain particle,

• this particle doesn't exist in the real world,

• the force of real world must be demonstrated in the distributed force manner,

• even if you poke the potato with one needle,

• the tip also has certain area,

• next, let's look at the distributed force,

• the distributed force can be called uniformity force in certain case,

• that is, it the same with role of "density"form on a certain acreage,

• that used here was is similar to the concept of density,

• the distributed force unit actually is how many Newtons is acts on per square meter,

• actually also is mean the how many Newtons is acts on each unit area,

• in fact, the distribution force can be equivalent to the concentrated force,

• the equivalent manner is as follows:

• first to consider this the uniform force ,

• the density of the uniform force is f2

• the interaction length is l2,

• what is the equivalent concentrated force of such a force?

• write the concentrated force as the red arrow,

• it's value = f2 * l2

• then multiply the unit area is 1

• this 1 can be as length of paper surface prominence,

• we use angle of the three dimension to see is so

• so it acts on an area,

• the magnitude by the concentrated force is the volume of the rectangular parallelopiped,

• i.e f2*l2*1

• where is such a the concentrated force acting?

• acting on above the centroid of the rectangle,

• the centroid is in the middle...so we draw the concentrated force right here,

• point of application in about 1/2l2 the place,

• another one distributed force is the triangle,

• in fact, the distributed force can have any shape,

• the triangle...that accordance with the rectangle,

• the magnitude is the bottom multiplied by the height divided by two

• point of application in 1/3l1 the place,

• when in the exam, we used to take the uniform force

• to calculates after change to the concentrated force,

• because for the objects ,them are equivalent ,

• the so-called the equivalent is the same with the effect of generated,

• that let's consider a question now.

• what happens after an object is cuts ?

• we know the object is for the maintain its shape before the thrust surface,

• when subjected to external forces, internal forces are also will generated within the object,

• so soil mechanics is defined...

• the force that can be observed before cutting is the external force

• the force that emerges after being cut is called the internal force.

• the internal force is actually very complicated,

• and with the angle or way you cut,

• the internal forces generated both are also different,

• the internal forces must have appeard with form of distributed forces,

• it main can be divided into two types,

• one is the normal stress and one is the tangential stress,

• the so-called the normal stress is the direction of stress vertical to the section,

• the so-called the tangential stress is the direction of stress parallel to the section,

• such as red arrows

• the external force and internal force are gives to objects...

• effects produced are not the same,

• what's the effects produced of the external force?

• has movement, rotation, reaction force, work and so on ...

• for the internal force, it will make the...

• the stress in the object changes,

• deformation, transformation energy...and so on.

• for in soil mechanics...

• when the external force continue to increase in the case, the internal force will rise accordingly,

• the normal stress in the soils will causes soil consolidation,

• that is the density increases (strength rises),

• the increase of the tangential stress will make the the general shear failure of soils,

• the main form of soil damage is the general shear failure,

• finally, let's supplement the concept of "the rigid body",

• the rigid body is considered as the ideal objects for the internal effects are not exist.

• can imagine the rigid body don't exist in the real world,

• within the subjects of engineering mechanics is

• the objects are all assumed be the rigid bodies,,

• that is, only the effects of external and external effects are considered,

• the material mechanics will considered of internal force the part,

• then the soil mechanics is builted on top of these two subjects,

• so the scope of consideration is will again broader,

• ok, the above is all the content today. Bye ~

Hi,guys,

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# 土壌力学 (Soil mechanics)

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WC に公開 2021 年 01 月 14 日