Modeling of Ordnance-Induced Pyrotechnic Shock Testing
Design of an ordnance-induced pyrotechnic shock test to meet a specific acceleration based Shock Response Spectrum (SRS) test requirement for a given test article has traditionally been an empirical process. Based on experience, the test engineer will determine a potential test configuration and then, through a trial-and-error process, modify the test parameters and configuration until acceptable SRS levels have been achieved. As a complement to this approach, National Technical Systems (NTS) has developed an explicit finite element based modeling approach to simulate an ordnance-induced pyrotechnic shock test. This tool may be used to assist with test configuration design for particularly challenging test requirements or to streamline the process of arriving at acceptable test levels during the calibration phase of a test program.
Improved recursive formula for calculating shock response spectra
NOMENCLATURE x(t) = base input displacement of a single-degree-of-freedom system y(t) = response displacement of a single-degree-of-freedom system) t (x & & = base input acceleration) t (y & & = response acceleration z(t) = relative displacement y(t) – x(t) ζ = fraction of critical damping n ω = natural frequency of a single-degree-of-freedom system, rad/sec s = complex variable H = transfer function L[ ] = Laplace transform L-1 [ ] = Inverse Laplace transform Z = z transform Z-1 = Inverse z transform d ω = damped natural frequency, 2 1 n ζ − ω T = sample interval) t (δ = delta function;) t (δ = 1 for t = 0 ,) t (δ = 0 elsewhere d m = digital delta function; d m = 1 for m = 0 , d m = 0 all other m SDOF = single degree of freedom u(t) = units step function; u(t) = 1 for t > 0 , u(t) = 0 for t < 0 t = time
New approach to vision-based BGA package inspection
Ball grid array (BGA) techniques have developed very fast due to the advantages of more I/O ports, small size, and so on. In this paper, a vision-based algorithm for BGA package inspection is proposed to accurately estimate center and diameters of solder-balls of BGA packages, so that defects of BGA packages, such as missing or extra balls, oversize or undersize balls, over-height or under-height balls, and pitch can be detected for ensuring the quality of BGA packages.