Beata Szałek

The assumptions of instrumental methodology for measuring dynamic loads of knitted barrier meshes were defined. A test stand was built, original in terms of both mechanical construction and electronic measuring system, connected to a computer data analysis system. Maximum values of dynamic forces in the mesh fastening strings were determined. The correctness of the strain gauges construction and measurement data transmission systems was confirmed. Tests of multidirectional resistance to dynamic loads in the mesh fastening strings were carried out. The experiment involved dropping a ball with a mass of 5 kg and a diameter of 10 cm, from a height of 1 m and 2 m onto the mesh surface. The potential impact energy equaled Ep1 = 49.05 J and Ep2 = 98.1 J. The tests showed that the highest force values were observed for meshes with square-shaped a-jour structure, and for mesh with diamond-shaped a-jour geometry the force values were lower. A symmetrical forces distribution was observed in all the strings. The highest forces were recorded in the middle strings and the lowest in the outer ones. The conducted tests confirmed the correctness of the adopted constructional solutions of test stand for identification of dynamic stress distribution in mesh fastening strings. The developed method is a useful verification tool for numerical analysis of mechanical properties of barrier meshes.

This article focuses on the analysis of mechanical properties of knitted barrier meshes and refers to general problems related to safety engineering. The conducted analysis of the effectiveness of absorbing impact energy by textile barriers, which positively affect the human body, clearly indicates the possibility of applying them in the field of road engineering as a new generation of road barriers. The characteristic features of the new generation of barriers are their openwork multiaxial structure based on various geometric shapes of the a-jour structure. Twenty models of barrier meshes with a-jour structure in the shape of tetragons (squares and diamonds), triangles, regular polygons (hexagons, octagons, and dodecagons), and circles were designed. Simulation research that aimed to optimize the structure of knitted openwork meshes to obtain minimum reduced stresses in strings, knots, and arms of the mesh was performed. The preferred solution is the four-axial eight-thread mesh with square-shaped a-jour structure with stress equal to Δб = 0.43 GPa/kg and the mesh with thickened diamond-shaped a-jour geometry with stress equal to Δб = 0.53 GPa/kg. Low stress values were also recorded for a four-axial six-thread mesh with square a-jour structure, for which Δб = 0.66 GPa/kg. The analyzed mesh models were implemented in the form of dozen designs of stitch constructions based on warp-knitting technology.