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Abstract

In this paper were conducted virtual tests to assess the impact of geometry changes on the response of metallic hexagonal honeycomb structures to applied loadings. The lateral compressive stress state was taken into consideration. The material properties used to build numerical models were assessed in laboratory tests of aluminium alloy 7075. The modelling at meso-scale level allow to comprehensive study of honeycomb internal structure. The changes of honeycomb geometry elements such as: fillets radius of the cell edges in the vicinity of hexagonal vertexes, wall thickness were considered. The computations were conducted by using finite element method with application of the ABAQUS finite element method environment. Elaborated numerical models allowed to demonstrate sensitivity of honeycomb structures damage process response to geometry element changes. They are a proper tools to perform optimization of the honeycomb structures. They will be also helpful in designing process of modern constructions build up of the considered composite constituents in various branches of industry. Moreover, the obtained results can be used as a guide for engineers. Conducted virtual tests lead to conclusion that simplification of the models of internal honeycomb structure which have become commonplace among both engineers and scientist can lead to inaccurate results.
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Abstract

Aluminum profiles play an important role in civil engineering (facades, walls with windows) as well as in mechanical engineering (production lines, constructions of 3D printers and plotters). To ensure quick assembly, disassembly or changed the dimensions of constructions it is not possible to use such methods as welding, adhesive or riveting joints. The solution may be to use the so-called “popular lock”. It is a mechanism, the closure of which is caused by tightening of the conical screw, joining the “T” profile in the node. In order to properly design using the presented type of connection, it is necessary to know its strength and stiffness both in simple and complex loads states, also including imperfections. In the literature there is no information about the operation of the construction node with the so-called “popular lock”. The paper presents the results of experimental tests for connections subjected to uniaxial tensile test, paying special attention to the defects that may appear during the assembly. In the next step, a 3D solid connection model was created. Numerical simulations were performed in the Abaqus / Explicite program for both uniaxial tensile test and bending tests in two planes. Limit values of loads above which there is a plastic deformation of the material were determined. Determination of stiffness and strength of a single node allowed to make a simplified connector model. Using the numerical model, the analysis was performed taking into account the influence of imperfections on the work of the entire connection.
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Abstract

Snap-fit connections have been used for many years in various fields of technology and everyday objects. They often have complex shapes, which is allowed by the processing technology of the polymers from which they are made, but they are not designed to carry loads. Changing the material to a metal or fiber composite allows these types of joints to be used as replacements for rivets or screws, but there are problems with the closing technique – an increase in closing force due to the large Young’s modulus of these materials relative to polymers without reinforcement. One of the methods to solve this problem may be the use of a thermo-bimetallic effect consisting in heating both or one of the connection parts to the appropriate temperature. This kind of treatment results in deflection of the beam of the clip (Fig. 1), followed by assembly with zero force or less in relation to the case without heating. The paper presents the results of numerical simulations for the connection in which the beam of the clip consisted of two materials: (1) a fiber composite designed to carry loads, (2) thin metal layer tied with the composite and designed to create a thermo-bimetallic effect. In the case of this solution, the main parameter is the difference in coefficients of linear thermal expansion of both materials. The paper presents results for two cases of connection work: closing and opening. The calculations were carried out in the Abaqus/Standard solver using thermal-displacement steps.
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