pyLife User guide

This document aims to briefly describe the overall design of pyLife and how to use it inside your own applications, for example Jupyter Notebooks.

Overview

pyLife provides facilities to perform different kinds of tasks. They can be roughly grouped as follows

Fitting material data

This is about extracting material parameters from experimental data. As of now this is a versatile set of classes to fit Wöhler curve (aka SN-curve) parameters from experimental fatigue data. Mid term we would like to see there a module to fit tensile test data and things like that.

pylife.materialdata.woehler

Predicting material behavior

These modules use material parameters, e.g. the ones fitted by the corresponding module about data fitting, to predict material behavior. As of now these are

pylife.materiallaws.RambergOsgood
pylife.materiallaws.WoehlerCurve
Functions to calculate the true stress and true strain, see pylife.materiallaws.true_stress_strain

Analyzing load collectives and stresses

These modules perform basic operations on time signals as well as more complex things as rainflow counting.

pylife.stress.collective – facilities to handle load collectives
pylife.stress.rainflow – a versatile module for rainflow counting
pylife.stress.equistress for equivalent stress calculations from stress tensors
pylife.stress.timesignal for operations on time signals

Lifetime assessment of components

Calculate lifetime, failure probabilities, endurance limits of components based on load sequences and material data.

pylife.strength.fkm_nonlinear.assessment_nonlinear_standard – Local strain concept / FKM guideline nonlinear

See also the tutorial about FKM nonlinear.

Mesh operations

For operations on FEM meshes

pylife.mesh.meshsignal – accessor classes for general mesh operations
pylife.mesh.HotSpot for hotspot detection
pylife.mesh.Gradient to calculate gradients of scalar values along a mesh
pylife.mesh.Meshmapper to map one mesh to another of the same geometry by interpolating

VMAP interface

Import and export mesh data from/to VMAP files.

Utilities

Some mathematical helper functions, that are useful throughout the code base.

General Concepts

pyLife aims to provide toolbox of calculation tools that can be plugged together in order to perform complex operations. We try to make the use of the existing modules as well as writing custom ones as easy as possible while at the same time performing well on larger amounts of data. Moreover we try keep data that belongs together in self explaining data structures, rather than in individual variables.

In order to achieve all that we make extensive use of pandas and numpy. In this guide we suppose that you have a basic understanding of these libraries and the data structures and concepts they are using.

The page Data Model describes the way how data should be stored in pandas objects.

The page Signal API describes how mathematical operations are to be performed on those pandas objects.