What Is Thermal Cycling?

Thermal cycle means that in a thermodynamic process, the system starts from the initial state and goes back to the initial state after a series of processes, that is, the final state of the system coincides with the initial state.

There are two directions for a system to follow a certain closed curve: one is in a clockwise direction, called a positive cycle; the other is in a counterclockwise direction, called a reverse cycle. Due to the different directions of the process, the mechanism of energy conversion performed by the system is also different.

Literature ^[1]

The design service life of highway pavement is generally 15 years, but most of China's highway pavements are semi-rigid base pavements. The actual service life of highway pavements is 5-8 years, or even less. The main reason is that heavy vehicles are overloaded in highway operations. There are many phenomena, and another important reason is that the technical characteristics of semi-rigid base roads are prone to cause road damage early. For this reason, people have tried to solve the above-mentioned engineering problems by seeking new materials and using flexible base materials instead of semi-rigid base materials that are prone to disease.

Literature ^[3]

In order to verify the correctness of the numerical simulation of the welding temperature field of thin plates, the literature ^[4]

Standard ^[5]

The support structure of the mirror directly affects the shape and position accuracy of the lens, and then affects the performance of the entire optical system. Therefore, it has always been one of the focuses and difficulties of the optical-mechanical structure design. When the temperature of the working environment of the mirror changes, due to the different thermal characteristics of the material of the lens and the support structure, the size of the lens and the support will not match after the temperature change, which will cause the stress between the lens and the support to increase sharply and the lens to deform. The shape accuracy is reduced, which further seriously affects the optical performance of the lens.

Invention patent ^[6] discloses a flexible support structure for a small-sized mirror suitable for thermal cycling, including a lens frame for mounting a lens in a frame body, and further includes a connector and a flexible support plate. The coefficient of linear expansion is similar to that of the lens. One side of the connector and the lens are connected by optical glue. The other side of the connector is connected to the flexible support plate. The flexibility The support plate is fixedly mounted on the inner wall of the mirror frame. The invention patent adopts a structure with flexible support on the periphery, which has a simple structure and is suitable for supporting small-sized reflectors; a connection structure that uses an adhesive method and a screw connection, has a compact structure, uniform stress distribution, and good temperature adaptability; Deformation under the conditions of thermal cycling, and the design of a three-sided flexible support structure is conducive to the stress release of the lens and the connector, and improves the shape and position accuracy of the lens.