Pseudo-velocity is a product of relative displacement and natural frequency. If you have a demand pseudo-velocity, you can use this free Excel calculator to calculate the correlated acceleration SRS.
Approximating Relative Velocity
In industries such as aerospace and seismic testing, labs often perform complex shock testing using the shock response spectrum (SRS) as the response demand.
The SRS uses a theoretical set of single-degree-of-freedom (SDOF) mass-damper-spring oscillators to model a test article’s response to a shock event. It displays the absolute maximum acceleration of the SDOF oscillators at various natural frequencies in response to the excitation. Although theoretical, the SRS provides valuable information about an article’s maximum dynamic load as a function of frequency.
Depending on the application, an engineer may also calculate the relative velocity or relative displacement during SRS testing. Velocity correlates with fatigue severity. Displacement is beneficial for testing environments with low-frequency components, particularly in seismology and earthquake engineering.
As the SRS provides maximum response at various frequencies, engineers can calculate relative velocity or relative displacement from the SDOF response. However, it is common to approximate relative velocity as a pseudo-velocity because pseudo-velocity helps indicate structural damage potential. Engineers can derive pseudo-velocity or pseudo-displacement from the SRS response.
Why Pseudo-velocity?
Acceleration SRS quantifies shock environments, helping identify how a system reacts to excitation. Pseudo-velocity relates to maximum strain energy, indicating potential damage. Since many mechanical failures are related to stress and strain, pseudo-velocity can indicate damage potential better than peak acceleration alone.
Pseudo-velocity is a common requirement in naval applications and can be graphed as a pseudo-velocity SRS or a pseudo-velocity shock spectrum on four-coordinate paper.