Construction of Aluminum Alloy Constitutive Model Based on BP Neural Network and the Study of Non-isothermal Hydroforming

With the continuous development of high-end technology in aerospace and automotive, in order to meet the needs of high performance, high precision and lightweight of parts, the materials used are lightweight and strong, but very difficult to deform, so it is difficult to obtain high-quality, high-precision parts. In order to improve the forming quality and precision of parts, taking 6061-T6 aluminum alloy cylindrical cup with spherical bottom as the research object, the non-isothermal hydroforming process is studied by combining numerical simulation with experiment. The key of numerical simulation technology lies in the accuracy of simulation, which depends on the establishment of a suitable rheological stress relationship. So, a constitutive model that can truly reflect the thermoforming characteristics of 6061-T6 aluminum alloy materials is established through a uniaxial tensile test and BP neural network. Applying the constitutive model to the study of numerical simulation of non-isothermal hydroforming, the cylindrical cup with spherical bottom with high quality is obtained through the optimization of non-isothermal process parameters. After experimental verification, the results of numerical simulation are highly compatible with the actual forming results of parts, and have high reliability.

Mathematical Simulating of the Process of Friction Stir Welding for the Manufacture of Tank Bottoms in Aerospace Construction

In modern aerospace technology, one of the perspective ways of assembly parts of thin metal plates is friction stir welding. The advantage of this method is the higher strength of the welds of aluminum alloy joints, compared with the traditional MIG welding for the assembly of rockets and space constructions. However, the lack of friction stir welding is a necessity of formation of the system “machine –tool - part” significantly more effort, which is caused by the need to stir the material in the weld zone in a plastic state. Friction stir welding is used to connect the individual elements of tanks and bodies, in particular, panels, elements of the bottoms with each other. In this paper, is consider the typical design for rocket and space technology bottoms of large tanks. For industrial robot equipped with a special head for friction welding with mixing, a mathematical model of obtaining a spherical bottom from individual segments is proposed. The paper presents a mathematical model describing the geometry of a spherical bottom with a flap articulation and a working zone of an industrial robot, which allows defining constraints on process operation continuous seam welding for standard designs of bottoms and hulls of rocket and space technology. The dependences allowing determining the initial position of the robot relative to the bottom for performing friction stir welding of the continuous seam are proposed.

Development of technological extrusion process of oversized cup type part with spherical bottom and flange

The stamping technology of hollow large-sized cylindrical parts with spherical bottom and fl ange made of AK6 aluminium alloy, the results of calculations for upsetting operation for preparing of the initial shape the workpiece, reverse extrusion of the workpiece by spherical end punch and its direct extrusion to thinning the forging wall are presented

Evaluation of Constraint Effect due to Crack Location and Bottom Head Shape

The aim of this paper is to evaluate the constraint effect due to the crack location and bottom head shape. To do so, two types of bottom head shape such as a semi-spherical bottom head and semi-elliptical bottom head were considered. In addition, five types of axial crack and two types of circumferential crack, classified by location, were adopted to conduct FE analyses. As a result, the bottom head shape does not affect the stress intensity factor of the circumferential flaw. Moreover, the crack location is not a sensitive parameter of the stress intensity factor for an axial crack located at the semi-spherical bottom head. In contrast, the crack location should be considered when the stress intensity factor of an axial crack located at the semi-elliptical bottom head is calculated. In addition, a heatup curve and cooldown curve were derived from the FE analysis results. As a result, the constraint effect owing to a crack location, except for the transition area, is not shown in the case of a semi-spherical bottom head. In the case of a semi-elliptical bottom head, the difference between each crack location is shown. These results will be helpful to enhance the understanding of the constraint effect and P-T limit curve.