Авіаційно-космічна техніка та технологія (Apr 2021)
Experimental determination of the state of textile materials of the D-5 series 2 landing parachute system after long-term storage. Message 1. Actual state of strength of textile materials of the main parachute
Abstract
The subject matter of the article is a comparative analysis of indicators of strength and elasticity of textile materials of the main parachute canopy before and after long-term storage. A simplified approach proposed by N. A. Lobanov and P.O. Fomichov was used, the coefficients of degradation of the strength characteristics of the textile materials of the main parachute of the D-5 landing parachute system of series 2 after its long-term storage were experimentally determined. These coefficients are defined as the ratio of the strength characteristics of individual elements of the parachute system in the design sections after the operation or long-term storage to their initial value adopted in the design of the parachute. The goal is to obtain an array of data to assess the state of the physical and mechanical characteristics of the main parachute materials. It is known that in the process of long-term storage there is a deterioration (degradation) of the strength characteristics of the strongest elements of the frame of the parachute canopy, lines, canopy fabrics, reinforcing tapes, etc. Further operation beyond the established period while maintaining sufficient safety factors is possible only with the availability of modern data. Tasks: to develop and test a method of sampling materials, experimentally determine the characteristics of materials, choose an effective algorithm for calculating safety factors. The following methods and equipment were used. The actual value of the indicators was established by destructive strength measurements. The methodology for preparing test samples of D-5 series 2 landing parachute systems, taking point and elementary samples of textile materials of individual elements of the parachute system in design sections for laboratory research to determine mechanical characteristics (strength, elongation, and air permeability) has been improved. The tearing machine is equipped with specialized clamping devices. The batch size was 25 parachute systems. The breaking load and the relative elongation were measured for slings and braids, for fabric - along the warp and weft, a total of 1250 elementary samples. Degradation coefficients were calculated. The array of empirical data was processed by mathematical and statistical methods of the Descriptive Statistics software package from the add-in of the MS EXCEL Analysis Package. The following results were obtained. In terms of breaking load, the fabric of the main parachute canopy slightly (up to 3 percent) exceeds the standard value. The elastic characteristics of the fabric fully meet the requirements - exceeding 1 ÷ 4 percent. During storage, the slings of the main parachute lost up to 21% in strength, but at the same time retained their elastic properties - exceeding up to 3 times. The tapes have satisfactory strength characteristics (exceeding from 3 to 12 percent), in terms of elongation at break, they have lost from 15 to 25 percent. Conclusions. The novelty of the results obtained is as follows: for the first time, the strength characteristics were measured and evaluated in the design sections of the fabric, reinforcing tapes of the power frame of the canopy and lines of the main parachute of the D-5 landing parachute system of series 2 on a large sample of 25 parachutes; it is shown that the obtained data will be correct for all parachute systems produced in 1973-1974.
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