admin Here is a C++ program which generates random numbers for a user-selected distribution. monte_carlo_random.cpp monte_carlo_random.exe The distribution options are: 1. Uniform 2. Normal 3. Rayleigh 4. Weibull 5. Gumbel 6. Binomial The random numbers can then be used in a Monte Carlo analysis. * *… Read more
There is a need to derive a PSD envelope for nonstationary acceleration time histories, including launch vehicle data, which may be similar to that shown in the above figure. A PSD can be derived using rainflow fatigue cycle counting along with a Miners-type relative fatigue… Read more
Question: What is meant exactly by “fatigue exponent”. I generally input a value between 3 (for notched parts) and 6 (for (unnotched ones). Is it right?…I’ve found confusing and contrasting definitions about b and m exponent (among MIL-STD-810 G and various other documents) Answer:… Read more
The Newmark-beta method can be used to solve structural dynamics problems in the time domain, of the form: M (d^2x/dt^2) + C dx/dt + K x = F This method performs direct integration on the mass, damping and stiffness matrices which may be fully-coupled. Here… Read more
The Newmark-beta method can be used to solve structural dynamics problems in the time domain, of the form: M (d^2x/dt^2) + C dx/dt + K x = F This method performs direct integration on the mass, damping and stiffness matrices which may be fully-coupled. Here… Read more
One of my responsibilities to NASA is to provide training sessions and materials as an outreach to the engineering community. Occasionally, I provide onsite training, but these classes are becoming increasingly difficult to organize for a variety of reasons. As an alternative, I am considering… Read more
A number of methods have been derived for performing rainflow cycle counting for a response PSD. Note that they tend to be conservative. The Dirlik method is an example of a semi-empirical method for cycle identification. A Matlab script for performing this method is given… Read more
Here is a method for converting modal damping to a damping coefficient matrix for all modes. It is based on a pseudo inversion of the modal damping matrix. The resulting coefficient matrix will be fully populated. The damping terms will not necessary corresponding to physical dashpots,… Read more
The Newmark-beta method can be used to solve structural dynamics problems in the time domain, of the form: M (d^2x/dt^2) + C dx/dt + K x = F This method performs direct integration on the mass, damping and stiffness matrices which may be fully-coupled. Here… Read more
A transfer function is a type of frequency response function (FRF) that gives the steady-state response to a force input as a function of frequency. Transfer functions for structural dynamics problems can be calculated from the natural frequencies, modal damping ratios and normal modes. This… Read more