Categorypublications

ANALYSIS OF THE IMPACT OF SURFACE ROUGHNESS ON THE CAPACITY OF ADHESIVE JOINTS FROM ALUMINUM ALLOY 2024

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The purpose of the article was to deepen the state of knowledge regarding the impact of surface roughness on the capacity of single-lap adhesive joints from aluminum alloy 2024. The surfaces with a triangular outline and various height and longitudinal parameters have been deliberately shaped. The surface roughness of the samples was shaped by milling with four different table feed of 30, 50, 70 and 90 [mm/min]. Surface roughness was tested in a 2D system using a contact profilometer. The samples were connected using Loctite EA 3430 epoxy adhesive and then subjected to a static tensile test. As a result of the performed statistical analysis, it was shown that in the adopted variability area, along with the increase of the feed value, the value of roughness parameters and the capacity of joints increased. The highest capacity was obtained for the parameters Ra = 20,83 μm, Rz = 101,33 μm, Rv = 41,97 μm, Rku = 2,62 μm, RSm = 0,746 mm.

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SELECTION OF JOINTS FOR TESTING A FATIGUE LIFE OF AVIATION RIVETS

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During the operation of aircraft, rivets sometimes loosen, what requires their replacement. The use of original rivets in repairs is troublesome and sometimes impossible due to the lack of access to the interior of the airframe structure. In this case, blind rivets should be used, provided that they have greater or equivalent strength to the original rivets. The aim of the study was to compare the statistical strength and fatigue life of the rivets that are usually used in the construction of the Mi-24 airframe and blind rivets that can be their substitutes. The object of the study included one-sided rivets: titanium core threaded MBF2110AB-05-15 with round head (4.2 mm diameter) and one-side Huck rivet with an extruded core (diameter 4.8 mm). The properties of these rivets were compared with those of ordinary 3558A-4-10 mushroom rivets manufactured from the W65 alloy used in the construction and repair of Mi24 helicopters. Comparative tests of rivet shear strength, head and end pull-off strength and fatigue life were carried out. An important problem turned out to be the selection of such a sample for fatigue tests, so that rivets and not the plates connected with them were destroyed by fatigue. These requirements were met by single strap samples in which C profile was strap.

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HIERARCHICAL METHOD OF RESCHEDULING FOR ASSEMBLY LINES WITH INTERMEDIATE BUFFERS

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A method of scheduling assembly in flexible assembly lines without parallel machines is presented. The method applies to lines fitted with intermediate buffers with limited capacities. The developed method is distinguished by the possibility of rescheduling. This is very significant in the case of a need to provide for new, urgent orders, as well as machine failures. The first level of the method concerns balancing the load of the assembly machines. Starting times of individual operations are determined at the second level of the method. Integer programming was used to solve the tasks allocated to both levels of the method. The results of computational experiments regarding the method are described.

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