Shock and vibration test specifications for avionics and military equipment have almost always been specified in terms of acceleration. The main reason is that acceleration can easily be measured by accelerometers. Velocity sensors are also available but are less common. Gaberson, Chamblers et al, claim… Read more
Introduction Neither shock nor vibration response should be used to cover rigid-body acceleration because material limits depend on the strain rate and on the duration of the load. Furthermore, static deflection shapes differ from dynamic mode shapes. Material Stress Limits The following is an excerpt… Read more
The flight accelerometer data was measured on a launch vehicle which shall remain anonymous. This was due to an oscillating thrust vector control (TVC) system during the burn-out of a solid rocket motor. This created a “tail wags dog” effect. The resulting vibration occurred throughout… Read more
Response Spectrum Response spectrum is a plot of the maximum responses (acceleration, velocity, or displacement) of idealized single-degree-of-freedom oscillators as a function of the natural frequencies of the oscillators for a given damping value. The response spectrum is calculated for a specified vibratory motion input… Read more
Launch vehicle avionics components must be designed and tested to withstand random vibration environments. These environments are often derived from flight accelerometer data of previous vehicles. This data tends to be nonstationary as shown in the figure above. The typical method for post-processing is to… Read more
The Bible teaches: Cast thy bread upon the waters: for thou shalt find it after many days. (Ecclesiastes 11:1) This means that we should serve others without expecting any immediate reward. Eventually, we will receive blessings. As Melvin J. Ballard said “A person cannot give… Read more
The children of Israel traveled through the Sinai wilderness. The following story is given in Numbers 21. [4] And they journeyed from mount Hor by the way of the Red sea, to compass the land of Edom: and the soul of the people was much… Read more
Naaman was a captain of the king of Syria’s army. Naaman had leprosy, a terrible disease, according to 2 Kings 5. The maid of Naaman’s wife said unto her mistress, “Would God my lord were with the prophet (Elisha) that is in Samaria! for he… Read more
* * * The Greek philosopher Socrates said: “The unexamined life is not worth living.” There are far too many people in the world who are careless and who do not accept responsibility for their actions. And there are many who say “Eat, drink and… Read more
Please help me send Bibles to poor people throughout the world: Support Link * * * The New Testament contains a short book called Philemon. Here is a summary: The Apostle Paul introduces himself as a prisoner of Jesus Christ. Paul was under house arrest… Read more