The golden crispy skin is wrapped in a light sense of air, and the "click" sound is pleasant, making people enjoy the delicious taste and feel happy. When you pull open the bucket again, do you have a moment of curiosity: why do the chips have the shape they do?

The problem of the shape of potato chips seems to have become an Internet celebrity problem, and there is a lot of discussion on the Internet, and the arguments are basically similar: the shape of the saddle surface has more stable performance and can be more unbroken during manufacturing and transportation. A few years ago, Bi Dao found another way, and did not discuss the stability of the saddle surface, but put forward a more nonsensical "tangent and edible theory", which is really eye-catching.

So in the field of potato chips, does the saddle surface shape really take advantage of its stability, so as to facilitate manufacturing and transportation?

Are potato chips all the same shape?

Potato chips can be divided into bags and barrels according to the packaging style. Potato chips in bags are real original chips that have been cut out, while potato chips in buckets are made by pressing mashed potatoes through molds. Therefore, the shape of the tub chips is uniform, which is convenient for sequential packaging. The shape of bagged potato chips is more random and can only be packed into air bags.

The shape of the bucket chips depends on the mold that is formed, and can theoretically be made into any shape. However, there are actually three common shapes of barreled potato chips on the market: single curved surface, hyperboloid surface (saddle surface), and wavy surface. The common bagged potato chips (the top one in the picture below) also take on the shape of a saddle surface. Is this a coincidence, or is it inevitable?

In fact, in a bag of potato chips, there is more or less a bit of a "saddle surface" shape. Potato chips puff up after frying, but their expansion is uneven and warping occurs. In addition, due to factors such as the fiber that grows in the sliced potatoes, there are two directions of warping, and the saddle surface is finally formed.

Therefore, saddle noodles are actually curved surfaces that are naturally formed after the original cut potato chips are fried.

Sturdy saddle surface

No matter how the saddle surface is placed, the two points on both sides touch the ground; When the opening of the single surface is upward, the contact surface with the ground is a "line", and when the opening is downward, it is the same as the saddle surface. According to the formula in the figure below, it can be seen that under the same conditions, the bending moment (M1) of the single-surface hazard cross-section with the opening up is greater than that of the saddle surface and the single-surface opening downward (M2). From this point of view, after the potato chips are compressed, the saddle surface relieves the bending moment (M2) at the internal danger position due to the frictional moment (fh) at the contact position, thereby increasing the strength.

However, for potato chips, the contrast of strength in this condition is not very useful. Tub chips are packed very strongly, and there is little chance of chips crushing and chipping. Here, the difference in the shape of the chips is not so important. It can be seen that the shape of the saddle surface is not simply designed for high strength.

However, tubs of potato chips do shatter. The potato chips located at both ends of the package will oscillate back and forth during transportation and will collide with the end of the box. Warped potato chips, under the action of this collision force, are more prone to crumble due to the bottom being vacated. Conversely, if it is made in a flat shape, the possibility of shock fragmentation caused by this transport process is much less.

Why are potato chips made into saddle noodles?

In this case, why do some brands still have to make saddle noodles? In fact, this is largely the pursuit of product differentiation, which is mainly reflected in the appearance and taste.

In terms of appearance, it is clear that the saddle surface is more artistic. In terms of taste, the saddle surface has a stronger cracking sensation after being stressed. After the potato chips enter the mouth, the force is applied to the upper and lower directions of the potato chips when biting, and under the action of this force, the single-curved potato chips are more likely to break into two pieces at the groove, while the saddle potato chips are equivalent to having two grooves, at least breaking into four pieces.

It is worth mentioning that it is not the saddle surface that is stressed more evenly that the potato chips are more broken. In fact, under oral occlusion conditions, the force on the inside of the potato chips is uneven.

Saddle roofing

The mechanics of saddle roofing are completely different from the chipping principle of potato chips. The force on the potato chips is relatively random, while the force on the saddle roof is fixed, that is, the roof load is vertically downward. It is also under the action of this vertical uniform load that the saddle roof can reflect its superiority.

We cut the saddle and there will be an "arched" structure. As we all know, the bearing capacity of the arch structure is large, thanks to which the structure can convert the self-weight and load of the structure into the extrusion force inside the structure, eliminating the weakness of the pulling force.

The internal force on the saddle surface is similar to that of the arch structure, but with some differences. After the saddle surface is cut along the concave line, the upper concave section (the blue section in the figure) is the compression profile, and the middle concave section is similar to the symmetrical surface of the arch structure, and the two sides are pressed against each other, and the concrete is used as a compression material. The concave profile (green in the figure) is a tensile profile, which resembles a catenary connecting surfaces and stretches against each other, and in this direction reinforcement must be arranged to enhance the tensile properties.

The pull and pressure of the saddle surface just give full play to the performance of the reinforced concrete steel and concrete structure. This structure has many applications, such as: Guangdong Xinghai Concert Hall, South China University of Technology Gymnasium, Puerto Rico Pontis Stadium, Berlin World Expo Conference Hall, etc. However, the span of the concrete thin-shell structure of the entire saddle surface is limited after all, and if it is used in the gymnasium, it needs to be divided into 4 saddle surfaces like the gymnasium of South China University of Technology, which are supported separately.

The entire saddle roof structure of the large gymnasium is not made of this steel-concrete thin shell structure, which is more different from the saddle surface of potato chips. In order to reduce the dead weight, a flexible rope structure is adopted, such as the roof of the Ice Ribbon National Speed Skating Hall in China. In the flex rope structure, there is no pressure, only tension. The entire roof structure is naturally concave under the action of gravity of its own weight and other ancillary facilities. The designer pushed the boat down the river and achieved such a saddle-shaped roof structure, turning mechanics into art.