Influence of the geometry of metal-wire gauze nets on their porosity

Abstract

Porous wire-gauze materials are produced by either hot forge rolling or by diffusion welding of briquets of metal nets and can be regarded as a special type of porous metals [1 ].The coefficients of hydraulic resistance and penetration, heat capacity, mechanical, and other characteristics of a material depend on its porosity [2]. To determine the porosity of materials, it is necessary to know the data on the porosity of the nets used for their manufacturing. Quite often, these are nets with square cells of linen (Fig. 1 a) or serge (Fig. lb) braiding. The formulas for the evaluation of the porosity of these nets were suggested and improved in [1,3].However, the actual thickness of the nets h is greater than its calculated values due to the difference between the angles of inflection of wires in two mutually perpendicular directions (warps and wefts) [2]. This can be explained by different tensile forces applied to the wires in the process of braiding. For this reason, the conventional model of a net with h = 2d, where d is the diameter of wire, does not agree with its actual structure and the porosity P computed according to this model must also differ from its actual value.The difference between the actual and calculated values of the thickness of the net is taken into account by an empirical coefficient k. For nets with square cells, we haveTo determine the porosity of nets taking into account the indicated differences, its is necessary to use models capable of a more correct description the structure of nets. In this case, the classification of wires into warps and wefts is, in fact, artificial.In addition to the indicated geometric quantities, the nets are also characterized by the size of cells a, mm (GOST 6613-73), the step of the net t = a + d, mm, and a dimensionless parameter t n ~ -.dIts structure can be reproduced by parallel translations in both directions of the elements separated in Fig. 1 by dashed lines. Therefore, the porosity of the nets P (the ratio of the volume of holes V l to the volume of the net V) is equal to the porosity of these elements, i.e.,where V 2 is the volume occupied by the solid material (in the case under consideration, this is the volume of wires).For an element of the net with linen braiding (Fig. 1 a), we can write V = 2t*2t*h = 2nd*2nd*2kd = 8kned 3,"L'vivs'ka Politekhnika" State University, L'viv.