Have you seen the 29th episode of the "Three-Body Problem" TV series?
This episode can be called a masterpiece, almost perfectly showing the climactic plot in the first part of the original - Guzheng Action.
"The Three-Body Problem" TV series poster | Tencent Video
This is a joint action of the global military, using the nanomaterial "flying blade" developed by the character Wang Miao in the play to pull up dozens of nano thin wires at the narrowest part of the Panama Canal, like the strings on a guzheng.
When the giant ship "Judgment Day", the base camp of the Earth Rebel TO, sailed by, the extremely strong thin line cut the giant ship into more than 40 thin pieces, eliminating the ETO members on board in one fell swoop and intercepting important information of the Trisolarans.
The giant ship "Rebel Day" cut into dozens of thin slices by the "guzheng" | "The Three-Body Problem" TV series
The TV series "The Three-Body Problem" reproduces this plot, and the scene where the giant ship is quietly cut like tofu and then spread forward like a stack of playing cards is amazing.
Although "The Three-Body Problem" is a science fiction story, for such an impressive guzheng action, many readers will inevitably have a little curiosity: Is there really a filament in the real world that can cut a huge ship?
Guzheng operation, is it feasible in reality?
In our daily life, examples of thin lines cutting objects abound.
A wire can easily cut tofu, the steel wire of an egg cutter can slice eggs, and there is news that a kite thread cuts a person's body and even the body of a car...
It seems that thin linear objects are made for cutting.
The principle of the egg cutter is similar to the guzheng action
An important reason why thin wires can cut objects is that they can generate huge pressures on the surface of the object.
Pressure is the pressure of the object per unit area, in the case of the same pressure, the contact area between the thin line and the object is very small, and the huge pressure deforms or even cuts the object.
The unit of pressure is Pascal, abbreviated as Pa (Pa).
Nails can be driven into the board, but bowling pins cannot, because the pressure is different|Khan Academy
For an object cut by a thin wire, to judge whether it is easy to be cut off by a thin line, an important indicator is hardness.
According to the definition of material mechanics, hardness is the ability of a material to resist hard objects pressing into its surface under certain conditions, and the forms of pressing into the surface include deformation, scratches, cutting and so on.
Take tofu and cake as an example, it will be deformed when pinched by hand, the hardness is very low, and it is easy to cut it by finding a wire; And steel is very hard, and cutting it with thin threads is not an easy task.
There are many standards for measuring the hardness of materials, such as the familiar Mohs scale, which is defined by the scratches that minerals mark each other. However, the Mohs hardness does not reflect the absolute hardness of the material, which is not conducive to quantitative analysis.
One of the more commonly used hardness standards is Brinell scale (Brinell scale), the measurement method uses a cemented carbide ball indenter to apply force on the material to produce permanent indentation deformation, and the force applied by the experiment divided by the surface area of the indentation is the value of Brinell hardness.
Schematic diagram of Brinell hardness measurement | Wiki
The same is the force divided by the area, the unit of Brinell hardness and pressure is exactly the same, both are Pa.
The Brinell hardness of steel is generally about 200 MPa, and 1 MPa is equal to 1 million Pa. How much pressure is this? That's about the equivalent of 800 elephants standing on one of your feet at the same time. Such a large pressure can cause deformation, which shows how hard the steel is.
The Bush hardness of steel is very high, in the order of MPa Dreamstime
Although the contact area between the thin wire and the material is small, the requirements for mechanical properties are still too strict to break through the Brinell hardness of steel and achieve cutting.
In the setting of the novel, the thickness of the thin line of the cutting giant wheel is about one-tenth of the thickness of a human hair, and the diameter is about 10 microns. The length of the interception of the giant ship may be counted as 20 meters. A simple estimate shows that to achieve a pressure of 200 MPa, each thin wire is subjected to a force of up to 40,000 Newtons in the vertical direction.
The vertical force of 40,000 newtons is equivalent to stepping on an elephant on a thin line Figureworm Creative
Not only does it require a length of tens of meters, but it is also subjected to extreme pressure on the sides, and there is wear and heat generation during the cutting process, which is difficult for linear materials with a diameter of only 10 microns to bear.
For a long time to come, humans may not be able to find the right material to make such a powerful thin thread.
"Wire EDM" in mechanical engineering
Although the guzheng operation is difficult to realize in reality for the time being, in actual engineering technology, it is not uncommon to use linear tools to cut materials.
A wire saw is a tool that specializes in cutting large blocks of solid materials with metal wire or cable. The structure of a typical diamond cutting line is to use sintering, electroplating or brazing to fix the diamond abrasive grains on the high-strength steel line, and carry out high-speed grinding movement with the object to be cut, so as to achieve the purpose of cutting. From gemstones and crystals to granite and reinforced concrete, diamond cutting lines can cut almost any material less hard than diamond.
Wire saws cut granite | optimaindia.com
There is also a processing technology called "wire cutting" in the machinery manufacturing industry, the full name is wire cutting electrical discharge machining. The processing method is to use a moving metal wire as an electrode, apply a pulse voltage between the electrode and the workpiece to generate a spark discharge, and the instantaneous high temperature generated by the discharge melts or vaporizes the surface of the workpiece, and the workpiece can be cut into the intended size and shape by controlling the voltage.
EDM melting materials for wire cutting technology| sl-machining
Although on the surface the same material is cut with a thread-like object, the principle of wire saws and wire cutting is completely different from that of the filament cutting steamer planned by the guzheng.
Wire saw cutting mainly relies on high-speed friction between materials, while wire cutting is not so much "cutting" as "burning", which is to process the material with the high temperature of spark discharge, and the wire does not even have contact with the material.
In contrast, the thin line in the guzheng operation simply cuts the steamer by hard pressing, which can only be said to be the plot of the novel.
Indestructible "waterjet"
Let's ask the bottom line, if I want to directly and violently break through and cut steel by extremely high pressure, can this be achieved under the current state of the art?
Yes! The famous "waterjet" is.
Waterjet is high-pressure water jet cutting technology (Water Jet Cutting), the water flow is supercharged and ejected from a nozzle with a very small caliber, forming a "water arrow" with a rate of fire of up to 1000 meters per second (about 3 times the speed of sound), cutting the contact object with ultra-high pressure.
Waterjet cutting watch | Interesting Engineering
As mentioned above, the Brinell hardness of steel is about 200MPa, and the pressure of waterjet can exceed 400MPa, which is far beyond the limit that most materials can withstand.
Not only that, but the waterjet is mixed with abrasive particles to obtain the characteristics of the saw blade, further increasing the cutting capacity, which can cut almost any hard material.
Waterjet cut 8 inches (about 20 cm) thick stainless steel blocks | SchGo Engineered Products, Inc.
However, even the waterknife that sharpens iron like mud is still far from the cutting ability of the thin line in the guzheng operation.
The water flow of the waterjet diverges after ejecting the nozzle and is also affected by air resistance, so the energy decays rapidly with distance, and the cutting thickness can reach the order of 10-20 cm, which is completely powerless for cutting a huge object like a giant wheel.
Not to mention the huge power of the waterjet work, like the guzheng operation, quietly cutting the ship into the invisible, it is also impossible to do.
Cutting the ship is not the goal, the space elevator rushes!
I am afraid that it is really necessary to be like the sci-fi setting of "The Three-Body Problem", waiting for human beings to invent a material with super mechanical properties, that is, the "flying blade", it is possible to complete such an "evil trick" as Operation Guzheng - not only silently killing the entire ship invisible, but also ensuring to the greatest extent that the information of the Trisolarans who do not know where they exist is not destroyed.
Such a scene can only be science fiction for the time being "The Three-Body Problem" TV series
If human beings can really invent materials with such strong mechanical properties, then it will have extremely large application scenarios, not only as simple as cutting a giant ship, but also bringing leapfrog development to human civilization.
In the story line of "The Three-Body Problem", it is precisely because Wang Miao solved the mass production problem of the "flying blade" that this extremely tough nanomaterial was applied to the manufacture of space elevators in the sequel, so that 200 years later, human beings can enter space on a large scale, forming a huge space fleet composed of 2,000 interstellar warships, and confidently facing the advance probes sent by the three-body civilization.
The space elevator in "The Wandering Earth 2" also uses Wang Miao's "flying blade"... | "The Wandering Earth 2" trailer
It's a pity that such an enviable leap in space technology, the three-body civilization looks at it, but it doesn't really care ... (Can't say more, or spoiler to the second part.) ）
Fortunately, in the real world, human beings do not face a three-body crisis, and there is no need to use guzheng actions to cut giant ships, but the benefits of being able to enter space on a large scale and at low cost like a space elevator are real.
Come on real-world "Wang Miao"!
After all, our journey is a sea of stars.
bibliography
LIU Mingfang, LIU Shengxin, CHEN Yong, et al. Handbook of mechanical properties of metallic materials[M]. China Machine Press, 2011.
ZHANG Bo, LIU Wentao, HU Xiaodong, et al. Application and development of wire saw cutting technology[J]. Supermaterials Engineering, 2008(1): 45-48.
[3]https://en.wikipedia.org/wiki/Wire_saw
[4]https://www.techniwaterjet.com/cutting-steel-with-water/
[5] Chen Guangming. Characteristics and application of CNC ultra-high pressure waterjet cutting technology[J]. Machine Tool and Hydraulics, 2007, 35(8): 64-68.
[6]https://www.youtube.com/watch?v=N6CCIyRjMvo
[7]https://www.youtube.com/watch?v=FXk76rWYdEs
Author: Neutron Star
Edited by Steed
Cover image source: stills from the TV series "The Three-Body Problem"
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