Image reference: https://www.sciencedirect.com/science/article/abs/pii/S0020740323003296 Introduction Classical fatigue analysis is built on stress. The stress-life (S-N) approach correlates nominal stress amplitude to cycles to failure; the strain-life ($\varepsilon$-N) approach handles the plasticity at notch roots through the Coffin-Manson equation; linear elastic fracture mechanics (LEFM) characterizes crack growth… Read more
Introduction Liquid hydrogen (LH₂) and liquid oxygen (LOX) are the highest-performing chemical propellant combination available to launch vehicle designers, delivering specific impulse values in the 450–460 second range in vacuum. The BE-3U engine powering Blue Origin’s New Glenn GS-2 upper stage, the RL-10 family powering… Read more
A good question came up recently regarding the practical design of a satellite bus panel for low random vibration response. The concern was not simply whether the panel is strong enough, but whether the panel can be designed so that mounted components see a lower… Read more
Rolling-element bearings are a masterpiece of mechanical engineering. They are also a notorious headache for Finite Element Analysis (FEA) engineers. Because they rely on Hertzian contact, bearings are inherently non-linear systems. The rolling elements, raceways, contact angles, internal clearances, and thermal conditions all shift dynamically… Read more
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