Case

Case

It is a sheet-like structure surrounded by two inner and outer curved surfaces with a thickness t much smaller than the smaller radius of curvature R of the middle surface and the plane size. It is a general term for thin shells and medium thick shells. According to Hebei foundry manufacturers, there are mainly the following types on the market at present, such as plastic shells, aluminum shells, sheet metal shells, and stainless steel shells. Thin shell refers to a shell with t/R less than 0.05.

The shell mainly resists the external load by the middle surface stress uniformly distributed along the thickness, rather than the bending stress along the thickness change. This internal force characteristic of the shell makes it more fully utilize the strength of the material than a flat plate, and thus has a greater load-bearing capacity. In water conservancy projects, shells are widely used, such as double-curved flat-shell gates, arch dams, etc.

Shell theory belongs to the category of applied elastic mechanics, and new assumptions need to be cited in addition to the basic assumptions of elastic mechanics. It includes thin shell theory and medium thick shell theory.

The thin shell theory is a classic theory in shells. It is based on the assumption of straight normals. These assumptions are: the normal strain perpendicular to the direction of the midplane is extremely small and can be ignored; the normal of the midplane remains a straight line, and the right angle between the normal of the midplane and its vertical segment remains unchanged, that is, the shear in the two directions The strain is zero; the normal stress on the section parallel to the midplane, that is, the extrusion stress, is much smaller than the normal stress on the vertical plane, so its influence on the deformation can be ignored.

Under certain conditions, the internal bending force of a thin shell mainly produces edge effects near the edge, and most of the middle area of the thin shell is dominated by the internal force of the film. Therefore, the method of superimposing the upper edge effect solution can be solved by the moment-free theory to simplify the thin shell. calculate.