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The stresses occurring in the cloth of an opening parachute and at steady state are calculated. The method is based on assumed instantaneous and steady state shapes and related pressure distributions. It is general and may be applied to any type and size of canopy built out of solid cloth. The presented analysis is limited to canopies constructed of triangular gores, but can be extended to other gore patterns. A numerical calculation is made for the Solid Flat, Circular Parachute during the opening and at steady state.
The stresses occurring in the cloth of a parachute during the period of inflation and at a steady state are calculated for a number of instantaneous shapes that are characteristic of the opening process and the steady state. The method is general and may be applied to any type of parachute built out of solid cloth, concentric rings, or ribbons. The presented analysis is related to canopies consisting of triangular gores but can be extended to other gore patterns. A numerical calculation is made for a solid flat circular parachute during the period of opening and at steady state.
The stresses occurring in the cloth of a parachute during the period of inflation and under steady state are calculated for a number of instantaneous shapes which are characteristic of the opening process and the steady state. The method is general and may be applied to any type of parachute built out of solid cloth, concentric rings or ribbons. The presented analysis is related to canopies consisting of triangular gores but can be extended to other gore patterns. A numerical calculation is made for a solid flat circular parachute during the period of opening and at steady state.
The stresses occurring in the cloth of a parachute during the period of inflation and under steady state are calculated for a number of instantaneous shapes which are characteristic of the opening process and the steady state. The method is general and may be applied to any type of parachute built out of solid cloth, concentric rings or ribbons. The presented analysis is related to canopies consisting of triangular gores but can be extended to other gore patterns. A numerical calculation is made for a solid flat circular parachute during the period of opening and at steady state. (Author).
During the period from 1965 to 1969, two new methods for stress calculations have been proposed and general remarks primarily concerning the elasticity characteristics of a parachute cloth and pressure distribution have been made. The conservative way of performing a parachute stress snalysis consists of first establishing the geometry of the parachute canopy and then applying a certain pressure distribution. Subsequently, the pressure distribution has been linked to the instantaneous parachute force which can be obtained from an opening shock calculation. In this manner one can possibly obtain closed solutions with a minimum of empirical factors. An example of this approach is presented in detail in the following chapters.
At the 4th Aerodynamic Deceleration Systems Conference, 1973, the development of the Omega Stress Sensor and initial canopy circumferential stress measurements were reported. Following the first success, the Omega sensor was tested under conditions of rapid loading. No dynamic effects were recorded at strain rates up to 100% per second. In the further pursuit of experimental stress analysis, initial measurements of radial canopy stress were made, and it was found that at certain locations the radial stress is as high or higher than the circumferential stress. Finally, exploratory tests were made in which circumferential stresses were measured on a 5 ft model parachute during the periods of inflation and at the following steady state. All tests were made under infinite mass conditions. The stresses were measured versus time, and their instantaneous values vary with respect to time and location on the parachute canopy.
This paper describes the results of an experimental study of canopy stresses in bias constructed solid flat parachutes. Stresses were measured in the warp and fill directions during inflation and at steady state for different values of dynamic pressure. Omega sensors were used to measure stress. These sensors were mounted along the gore center lines so that the warp and fill stress distributions could be determined as a function of distance from the vent. It was found that stresses in the fill direction were substantially larger than stresses in the warp direction.
This paper describes the results of an experimental study of canopy stresses in a model ribbon parachute. The distribution of circumferential stress was measured during inflation and at steady state for different values of dynamic pressure. Testing was performed in the wind tunnel at the infinite mass condition. Omega sensors were used to measure stresses and were mounted in different ribbons along the gore centerline. It was found that the steady state stress had two maxima of about equal value. One maxima was near the skirt, the other half-way between the vent and skirt. The distribution of maximum stress during inflation was similar to the steady state distribution and the ratio of maximum stress during inflation to steady state stress ranged from 1.25 to 1.75 and was essentially independent of dynamic pressure. The spectral density of the steady state stress measured at several points on the canopy.
AD-702041 documented a new method of determining the steady-state inflated shape and included volume of several types of parachutes in 12-gore and 16-gore configurations. This report uses the methods and technique of AD-702 041 to extend the data to 24-gore and 30-gore configurations of the flat circular, 10 percent extended skirt, 16 percent porous ring slot and 24 percent porous ribbon parachutes. The inflated elliptical shapes of the various canopies were obtained from photographic records of the wind-tunnel tests at various velocities from 17 mph to 200 mph using parachute models of approximately 40-inch flat diameter. The steady-state canopy volume includes the volume of the billowed gore panel and an air volume ahead of the canopy skirt hem. The results of this investigation are particularly applicable to studies of canopy stress analysis and determination of the volume of air which must be collected during canopy inflation process for use in the calculation of opening-shock force. (Author).