Shock and vibration environments produce dynamic stresses which can cause material failure in structures. The potential failure modes include fatigue, yielding, and ultimate stress limit. F.V. Hunt wrote a seminal paper on this subject, titled “Stress and Stress Limits on the Attainable Velocity in Mechanical… Read more
Wayne Tustin is a pioneer in the field of shock and vibration training. I have had the opportunity to learn from him at several IEST meetings and other conferences. He taught me the meaning of SRS (G) and PSD (G^2/Hz) units, when I was… Read more
I recently flew as a passenger in a CRJ900 jet similar to the one shown in Figure 1. This aircraft has two GE CF34-8C5 engines, as shown in Figure 2. This engine has two high pressure axial flow stages that drive the N2 compressor, and… Read more
Introduction Spacecraft must withstand vibration from pre-launch transportation and from powered flight. The spacecraft is not powered during these events. In addition, a spacecraft must withstand “microvibration” or “jitter” from its own moving parts once it reaches orbit and becomes operational. This vibration is… Read more
We are not human beings having a spiritual experience; we are spiritual beings having a human experience. – Pierre Teilhard de Chardin (1881-1955) * * * Also quoted by: President Thomas S. Monson, BYU Devotional Be a Light to the World, November 1, 2011 *… Read more
PowerPoint File: webinar_19_digital_filtering.ppt Audio/Visual File: NESC Academy Digital Filtering – Recommend viewing in Firefox with Sliverlight plugin * * * Python version: webinar_19_digital_filtering_python.ppt Python script: Python Signal Analysis Package GUI * * * Data: sm.txt – unscaled relative displacement vs. time (sec) * * * Reference… Read more
Method 1 Secondary & Component loads can be specified in the form of a Mass-Acceleration curve as described in: NASA-STD-5002, Paragraphs 4.2.1.2, 5.3.2, 5.4. The Mass-Acceleration curve can be derived from measured flight or test data, or analytical loads. Care must be taken to avoid… Read more
PowerPoint File: webinar_18_force_VRS.pptx Audio/Visual File: NESC Academy Force_VRS * * * Python version: webinar_18_force_VRS_python.pptx – Recommend viewing in Firefox with Sliverlight plugin Python script: Python Signal Analysis Package GUI * * * Reference Papers: The Steady-state Response of Single-degree-of-freedom System to a Harmonic Excitation Force: sforce.pdf… Read more
NASA-STD-5002, Load Analyses of Spacecraft and Payloads, 1996 5.3.2 Transient load analysis (excerpt) Statistical variation of parameters governing the forcing functions is accommodated by generating multiple cases of forcing functions for a single flight event. After all cases are analyzed, the maximum transient load is… Read more
Deuteronomy 5 [13] Six days thou shalt labour, and do all thy work: [14] But the seventh day is the sabbath of the LORD thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, nor thy manservant, nor… Read more