How are thin-walled containers and thick-walled containers distinguished? What is the theoretical basis for their strength design? What are the differences between them?

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Containers with a wall thickness-to-inner diameter ratio of δ/Di ≤ 0.1, that is, a outer diameter-to-inner diameter ratio of K = Do/Di ≤ 1.2, are considered thin-walled containers; otherwise, they are thick-walled containers. The theoretical basis for the strength design of thin-walled containers is the theory of zero moment of rotation for thin shells and the membrane stress formulas derived therefrom. The stress calculated in this way is a biaxial stress that is uniformly distributed along the wall thickness; it represents an approximate calculation result. The theoretical basis for the strength design of thick-walled vessels is the Lamé formula derived from elastic stress analysis. The stress calculated in this way is a triaxial stress, and it varies non-uniformly along the wall thickness, with the highest absolute value on the inner wall and the lowest on the outer wall. This allows for a relatively accurate representation of the actual distribution of stresses within the wall, and it is applicable to both thick-walled and thin-walled containers.