Modelling of strains experienced by aluminium shells during machining

Abstract

The study analyzes whether it is feasible to use high-strength aluminum alloys for making high-pressure cylinders. It is shown that replacing highstrength complex alloyed steel with the V95-like aluminum alloys is feasible. Aluminum alloys were not investigated for stresses and displacements occurred when workpieces are fixed in three-law grippers. The study is relevant because all the physical and mechanical properties of aluminum alloys (yield strength, ultimate strength) are about a third of the respective steel properties. Using the available references, we estimated the cutting force components and the clamping force at each jaw required to hold the workpiece in the gripper. Wide and long jaws are usually used to hold thin-wall shell workpieces in three-jaw lathe grippers. The total workpiece circumference coverage by the jaws is close to a full circle. The estimated force was applied to each jaw. A 3D model was created with SolidWorks and simulated. The simulation showed that the higher stress occurs mostly in the tooling parts amounting to 1.269...1.384 MPa. The stress in the gripper body segments contacting the jaws is 0.69...0.923 MPa. The most of the body is under a low stress: 0.015...0.023 MPa. The max stress in the workpiece is found at the lower edges of its bottom. The stress at the jaw-to-segment interface reaches 1.24 MPa. At these points, the wide jaws compress the workpiece; the segment at the center of the wide jaws is stiffer since there is a jaw and a stiffener behind its wall. There are three equally distributed stress points. Still, the stress in the rest of the segment is 0.015...0.023 MPa. The deformed workpiece has a faceted shape. The out-of-roundness is 0.0014 to 0.00165 mm. It is well below the out-of-roundness tolerance.