The B-52 Involved In Tragic Crash Was Heading out on Radar Test Sortie The mission objective was to test a new Active Electronically Scanned Array (AESA) radar system (the Raytheon APQ-188), which is a core component of the upcoming B-52J upgrade package. B-52 Crash at… Read more
Image courtesy of: https://www.rhfs.com Introduction Water hammer is one of those phenomena that every piping engineer encounters eventually—and usually remembers. It is the sudden, jarring metallic bang that makes everyone in the control room sit up straight, the distinct shudder transmitted through a facility’s pipe… Read more
As NASA’s Artemis program and international space agencies transition from short-duration sorties to a sustained human presence on the Moon, mission planners and structural engineers must confront a mechanical hazard that received little attention during the Apollo era: lunar seismicity. The Moon is not a… Read more
MEMS (Micro-Electro-Mechanical Systems) devices are miniature sensors or actuators fabricated using semiconductor manufacturing techniques, integrating microscopic mechanical structures and electronic circuitry on a single silicon chip. They use tiny moving elements such as beams, proof masses, diaphragms, or comb structures to sense or control physical… Read more
The AH-64 Apache tail rotor has four blades. The blades, however, are not oriented 90° (perpendicular) from each other as in most helicopters. This unusual arrangement is required because the two sets of blades use a “Delta-Hinge“ which allows the blades to simultaneously flap and… Read more
The Modal Truncation Problem Any mode-based dynamic analysis—whether a frequency response sweep, random vibration PSD solve, response spectrum analysis, or transient modal superposition—retains only a finite number of modes. In a finite element model with $N$ degrees of freedom (DOFs), there are technically $N$ natural… Read more
A recurring question in random vibration analysis is: How do we determine the relative displacement between two points when the structure is subjected to a Power Spectral Density (PSD) excitation? This quantity is often far more critical than the absolute response. Connector pin engagement, cable… Read more
VibrationData Blog | Structural Materials If you have ever looked at a stress-strain curve for mild (low-carbon) steel and wondered why it has that distinctive “flat shelf” between the upper and lower yield points, you are not alone. That plateau is one of the most… Read more
Estimating structural strain in a rubber vibration isolator from acceleration measurements is a challenging problem because elastomers behave very differently from metals. Their stiffness is strongly frequency dependent, highly temperature sensitive, and inherently viscoelastic. Nevertheless, useful engineering estimates can often be obtained from vibration measurements… Read more
PORON® is a commercial polyurethane foam, Rogers Corporation Introduction Microcellular Urethane (MCU) mounts are a highly capable candidate for this application and are widely utilized for military electronics isolation. Several aerospace and defense manufacturers offer products with extensive MIL-STD-810 qualification data and field history in tactical… Read more