Moscow State University of Technology “STANKIN”, Moscow, Russia:
E. N. Sosenushkin, Professor, e-mail: sen@stankin.ru
E. A. Yanovskaya, Associate Professor
T. V. Gureeva, Postgraduate Student at the Department of Plastic Deformation Systems

Moscow State University of Humanities and Economics, Moscow, Russia:

V. A. Kadymov, Professor

Cylinder-shaped forgings with external longitudinal ribs are considered complex-shape forgings. During forging the flow of metal is constrained due to new surfaces and a constantly growing material/tool contact area. In this case the boundary value problem of the plasticity theory should have a 3D formulation, which does not have an exact analytical solution. Using the wellknown methods of continuum mechanics, a three-dimensional problem of plastic layer extrusion can be deduced to a two-dimensional problem on the basis of Ilyushin’s special kinematical hypotheses related to contact friction under full metal slide and maximum shear stresses conditions. The paper substantiates the statement and describes a solution of the boundary value problem in relation to three unknown functions averaged to the deformed layer thickness – i.e. contact pressure and two flow velocity components. Analytical dependences were obtained which can be used to evaluate the contact pressure, deformation forces, flow velocity components and strains when a hollow cylinder-shaped forging is being formed and some metal is flowing in the thin longitudinal ribs. The authors established how the extrusion force, the flow velocity and the deformation rate tend to change and how they are related to the dimensions of the forging. The authors found a general solution, so it can be applied to forgings with any number of ribs. A series of experiments proved the possibility of making ribbed forgings from the АК7 aluminium alloy withzero structural flaws.

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