The high nuts withstand increased load for expansion, facilitating its even distribution along the bolt length. The process of increased height nut blanks plastic deformation characterized by uneven metal flow and changing of stressed state by the blank section. In the process of closed-die stamping of such nuts a risk of their geometry distortion arises. Results of study of the process of production a hex nut of increased height presented. The object of the research was to study the process of the metal deformation when broach a hole for thread in a hexagonal nut blank of increased height. To simulate the stress-strain state, the QForm-3D software package was chosen, which made it possible to predict with sufficient accuracy the metal flow in the blank, calculate the deformation forces and determine the stresses that occur in the tool. The models of the blank and the tool were created in the Compass 3D program without internal and external defects. When performing the work, the parameters of the stress-strain state of a hexagonal nut blank of increased height were calculated. The simulation results showed the need to change the geometry of the end part of the punch to a conical one with an angle of 150 degrees and a reduction in the size of the baffle height from 10.4 mm to 5.4 mm. The adopted changes allowed to reduce the energy and power costs of forming a through hole for the threads. Industrial testing confirmed the correctness of the calculations. Nuts with edges perpendicular to its base and the required geometrical parameters were obtained.
During manufacturing nuts of increased height, a problem of obtaining correct cylindrical form of the hole for thread and overall geometrical parameters arises. To solve the problem it is necessary to know regularity of the blank forming process. Results of the study of a technological process of high hexahedral nuts forming presented. The nuts were M18 of 22 mm height, M16 of 19 mm height and M12 of normal height 10 mm according to GOST 5915–70, accuracy class B, steel grade 10 according to GOST 10702–78. The volumetric stamping was accomplished at the five-position automatic presses of АА1822 type. It was determined, that unevenness of the metal flow in the process of plastic deformation of blanks of increased height nuts was caused by different stress conditions by their sections. To simulate the mode of deformation, the program complex QForm-3D was chosen. The complex ensured to forecast with necessary accuracy the metal flow in a blank, as well as to define the deformation force and arising stress in the working instrument. The simulation showed the presence of regularity between preliminary formed buffle and deviation of dimensions and form of a blank wall after its finishing piercing, which can be expressed by a nonlinear dependence. The limit values of the relative height of the buffle С/D = 0.56–0.588 defined, exceeding which will result in rejection of the finished product. Accounting the limit values of the relative height of the buffle will enable to correct a mode of technological operations and technological instruments at stamping of high hexahedral nuts.
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