No 4 (2014)

The process of chip formation and possible ways of its control during plastic material processing is considered. The dependence of the chips type on the cutting conditions is determined. Processing of some plastic materials such as fiberglass is accompanied by several problems: the tendency to form burns and peeling of the material; heterogeneity of the structure; strong abrasive effect on the tool; reduced thermal conductivity; difficulty in applying lubricating substances. Chip formation process in this case is very important to ensure the quality of the manufactured products, the smooth operation of the equipment and, as a result, increase in efficiency, security of workers. These studies have determined the type of chips from the cutting conditions. Nomograms, reflecting areas that preclude the emergence of the flow chips and ingress of discontinuous and dusty chip into the air are obtained. It is showed that when creating a model of the process of chip formation it is necessary to consider the above-mentioned features of plastic materials processing and solve the problem of designing systems with complex geometric configuration and irregular physical structure.

The article shows the way to ensure the geometric accuracy of large segmented-ring structures, for example sections of Geohod. The method of installation, consisting in location of the sector by the shell surface on a fixed support therewith the shells of individual sectors approximate shell section as a whole, is offered. Mathematical expressions of deviation profile of the sector with the real sector size and distances, which define a position of the supports, are received. The factors affecting geometric accuracy of the shell section and the impact of these factors on the accuracy are examined. Problem of determination of the maximum deviation of the profile of the sector, depending on the tolerance of the sector size and distance, establishing the position of the supports, is set. The dependences of the maximum values of the deviation of the sector profile on the of the tolerance levels are gotten. It is shown that the proposed scheme can be installed to provide higher accuracy of the shell section, than that which has a separate sector.

The results of research of WC-Co hard alloy VK10KS after hardening from 1150 °С in waterpolymeric liquid Termovit M with concentration of 4 % under the temperature of 40 °С are considered. The changes in the structure of the alloy which are connected with the partial solution of WC during heating before hardening and, therefore, reducing its sizes from 5...8 in the initial state up to 2…4 after heat treatment are discovered. The solution of WC leads to the additional alloying of Co phase by C and W. In the initial samples in sintered state the average amount of dissolved tungsten is 10.89 %, but after hardening its concentration is increased up to 20.18 %. All above mentioned changes in the structure of the hard alloy after hardening lead to the increase of its modulus of rupture in bending up to 10 %, and decrease the area of friction up to 35 % in comparison with the sintered state when tribologic testing was conducted.

One of the criteria for evaluating the reliability of the aviation gas turbine engine housing is their ability to retain broken elements of the rotors and, primarily, the fan blades. The paper presents the results of numerical simulation of deformation and fracture of the aviation gas turbine engine housing after a high-speed collision with a fan blade at its emergency breakage. Parameters of Johnson-Cook model, describing the behavior of alloys VT6, OT4 and OT4-0, is verified. Comparison with experimental data showed a good agreement for the flying residual velocity of the broken blade and forms of punched holes. It is shown that depending on the housing material, its thickness and blade breakage velocity, there is a possibility of penetration of the housing by a broken blade and its departure beyond or localization of the broken blade inside the housing.

Samples cut from AK4-1T alloy plates with thickness h = 45 mm are experimentally investigated at T = 195 ºС under tension and compression conditions. The alloy is strain-hardening and has different resistance to tension and compression under creep. Constants for power-law dependences describing creep strain rates are defined according to the experimental data. The model based on the “transformed” space of stresses, taking into account properties of hardening and different resistance of material to tension and compression at creep is developed. The model is tested for the problem of AK4-1T alloy plates’; pure torsion in assuming of planes stress-strain state. Experimental data on flexible plates’; torsion and finite elements’; calculation in geometrically nonlinear statement using constants only on tension or compression are presented. Experimental values are located between the relevant calculated lines, that confirms the complex properties of alloy. These properties should be taken into account in the calculations.

The problem of inverse elastic-plastic calculation of predictive snap on the base of residual contour of the detail is solved with taking into account the elastic recovery after load removal for technology of shaping of large-sized finned panels. The form of the detail corresponds to a complex surface of double curvature with zones of convexity and concavity. Panel reinforcement ribs are under tension, compression and torsion during shaping. Preliminary test calculations of elastic-plastic bending at a temperature of 195 ºС of the t-shaped cross-section samples of alloy AK4-1T cut from the plate with the thickness h = 42mm showed satisfactory compliance to the experimental data. Such samples bending is simulation of the deformation of the stiffener with attached aircraft skin. An iterative method of calculation using finite element package ANSYS allowed to get close enough to practice form of detail surface, which can be considered as an initial approximation for developing the technology of shaping process in real conditions.