The Testing Blog

by Vesta I. Bateman, Chair, IEST Working Group DTE032

The IEST Recommended Practice on pyroshock testing has been revised and updated to reflect advances in the art of pyroshock testing and to address common problems related to data accuracy in the pyroshock community. The key changes to IEST-RP-DTE032: Pyroshock Testing Techniques are described here.

New definitions for near-field pyroshock, mid-field pyroshock, and far-field pyroshock adopted by IEST-RP-DTE032.2 are consistent with the definitions given in MIL-STD-810G, Method 517, as shown in the table and the spectra definitions below. The definitions and table values are quantified in terms of shock response spectra (SRS). The SRS, with an appropriate damping value, is the most widely used tool to analyze pyroshock data and is calculated using acceleration measurements near components and subsystems that must be qualified separately. The Jet Propulsion Laboratory will be revising NASA-STD-7003 during the coming year, and the current NASA values for near-field, mid-field, and far-field pyroshock are also shown in the table.

A near-field pyroshock test requires frequency control up to and above 10 kHz for amplitudes greater than 10,000 g. A pyrotechnically excited simulation technique is usually appropriate, although in some cases a mechanically excited simulation technique may be used.

A mid-field pyroshock test requires frequency control from 3 kHz to 10 kHz for amplitudes less than 10,000 g. A mechanically excited simulation technique other than shaker shock is usually required.

A far-field pyroshock test requires frequency control no higher than 3 kHz for amplitudes less than 1,000 g. A shaker shock or a mechanically excited simulation technique is appropriate.

via: Pyroshock Testing, Institute of Environmental Sciences and Technology

National Technical Systems Inc. (NASDAQ: NTSC) (NTS), is pleased to announce the addition of tunable resonant beam apparatus for metal-to-metal simulated Pyroshock testing at its Tinton Falls, NJ engineering and test facility.

Pyroshock testing is designed to simulate the high-frequency, high-magnitude shock pulse that a product may experience as the result of an explosive event, such as an explosive impact on a military tank structure or the separation of booster rockets from the space shuttle during flight. This type of explosive impact can cause failures in electronic components and thus endanger the survival of the system as a whole.

The Pyroshock test differs from other mechanical shock tests in that there is very little rigid body motion of the product. In this test method, an aluminum bar with rectangular cross-section is clamped to a massive base. Clamps are intended to impose nearly fixed-end conditions on the beam. When the beam is struck with a cylindrical mass fired from the air gun beneath the beam, the beam will resonate at the first bending frequency of the beam, which is a function of the distance between the clamps. The tunable resonant beam method provides a good, general purpose Pyroshock simulator, since the knee frequency is continuously adjustable over a wide frequency range, 500 Hz to 3,000 Hz for example.

NTS’ new 17,000 pound system is designed to simulate the far-field Pyroshock spectrum. The original system design was developed by Neil Davie, Principal Member of the Technical Staff, Mechanical Environments, Sandia National Laboratories. The design was then adopted as a “recommended practice” by the Institute for Environmental Science and Technology and published in the “Pyroshock Testing Techniques” IEST-RP-DTE032.1 document.

“The addition of this new test capability demonstrates both the technical expertise of the NTS engineering team in its construction, and our commitment to continue to add capabilities and capacity to meet the ongoing needs of our customers in the defense and aerospace markets” commented NTS General Manager Richard Gaynor, “We look forward to demonstrating this unique new capability.”

For more information – click here.