# Direct Fatigue Damage Spectrum Calculation for a Shock Response Spectrum

Here is an empirical method for directing calculating a fatigue damage spectrum from a shock response spectrum: srs_fds.pdf * * * See also: Using Random Vibration Testing to Cover Shock Requirements – Tom Irvine

# Fatigue Damage Spectrum, Frequency Domain

There is an occasional need to compare the effects of two different power spectral density (PSD) base input functions for a particular component. This would be the case if the component has already been tested to one PSD but now … Continue reading

# Fatigue Damage Spectrum, Time Domain

Consider a single-degree-of-freedom system subjected to base excitation where the input is an arbitrary time history. The response of the system can be calculated via a digital recursive filtering relationship, which is the numerical engine embedded in the SRS calculation. … Continue reading

# Fatigue Analysis Webinars

This is a work-in-progress… I am creating a series of webinars with Matlab exercises for fatigue analysis Matlab script: Vibrationdata Signal Analysis Package Here are the slides: Unit 1  Fatigue Introduction Unit 2  Fracture Unit 3  Sine Vibration Unit 4 … Continue reading

# Webinar 40 Shock Fatigue

Shock Fatigue 1. Determine whether a given PSD can cover an SRS Specification 2. Derive an Optimized PSD which will cover an SRS * * * Aerospace Pyrotechnic-type SRS tests are almost always more difficult to configure and control in … Continue reading

# Miner’s Cumulative Fatigue via Rainflow Cycle Counting

This blog entry is a work-in-progress. Fatigue analysis can be performed in the time domain using rainflow cycle counting.   This is an elegant, brute-force approach.  One advantage of the time domain approach is that it tends to highlight the occurrences … Continue reading

# Rainflow Fatigue Cycle Counting

Endo & Matsuishi (1968) developed the Rainflow Counting method by relating stress reversal cycles to streams of rainwater flowing down a Pagoda.  This method is very useful for fatigue analysis. The rainflow method allows the application of Miner’s rule in … Continue reading

# Tom’s Conference Papers & Slide Index

I am trying to collect all my presentations. This is a work-in-progress… Thank you, Tom Irvine * * * * * * NAFEMS World Congress 2017 Introduction to Vibration Spectral Functions Random Vibration Vibration Fatigue Shock 1 & 2 Videos … Continue reading

# Nonstationary Vibration Enveloping Method Comparison

There is a need to derive a power spectral density (PSD) envelope for nonstationary acceleration time histories, including launch vehicle data, so that components can be designed and tested accordingly. Three methods are considered in the following paper using an … Continue reading

# Optimized PSD Envelope for Multiple Accelerometer Time Histories

Prerequisite Reference Papers David O. Smallwood, An Improved Recursive Formula for Calculating Shock Response Spectra, Shock and Vibration Bulletin, No. 51, May 1981.  DS_SRS1.pdf Rainflow Counting Tutorial Fatigue Damage Spectrum, Time Domain Fatigue Damage Spectrum Dirlik Method for PSDs Optimized … Continue reading