fracmechpy 0.0.3

A Python package for fracture growth modeling.

fracmechpy: Fracture Mechanics

Overview

fracmechpy is a Python package that calculates the fatigue crack growth rate (da/dN) and the stress intensity factor range (ΔK) for Compact Tension (CT) specimens with the Secant method based on ASTM E647.

Features

• Computes fatigue crack growth rate (da/dN)
• Computes stress intensity factor range (ΔK)
• Implements ASTM E647 standard
• Includes error handling for ASTM E647 validity limits
• Newly added: Incremental Polynomial Regression (IncPoly) method for crack growth rate calculation.

Installation

Installing from PyPI (Future Deployment)

If fracmechpy is available on PyPI, you can install it using:

pip install fracmechpy

Installing from Source

To install the package manually:

1. Clone the repository:

   git clone https://github.com/dhaselib/fracmechpy.git
   

2. Navigate to the directory:

   cd fracmechpy
   

3. Install using pip:

   pip install .
   

Ensure you have NumPy installed using:

pip install numpy

Functions

Secant(N, af, ab, W, p_max, p_min, B)

This function calculates the fatigue crack growth rate (da/dN) and the stress intensity factor range (ΔK) for a CT specimen.

Parameters:

• N (numpy array): Number of cycles
• af (numpy array): Crack length at the front face of the specimen
• ab (numpy array): Crack length at the back face of the specimen
• W (float): Width of the specimen
• p_max (float): Maximum applied load
• p_min (float): Minimum applied load
• B (float): Thickness of the specimen

Returns:

• dadN (numpy array): Fatigue crack growth rate (da/dN)
• dK (numpy array): Stress intensity factor range (ΔK)

IncPoly(N, af, ab, W, p_max, p_min, B, n)

This function calculates the crack growth rate (da/dN) using the Incremental Polynomial Regression method for a CT specimen.

Parameters:

• N (numpy array): Number of cycles
• af (numpy array): Crack length at the front face of the specimen
• ab (numpy array): Crack length at the back face of the specimen
• W (float): Width of the specimen
• p_max (float): Maximum applied load
• p_min (float): Minimum applied load
• B (float): Thickness of the specimen
• n (int): Number of neighboring points for regression

Returns:

• dadN (numpy array): Incremental crack growth rate (da/dN)
• dK (numpy array): Stress intensity factor range (ΔK)

Limitations on Choosing the Value of n

• Dataset Size: Ensure that n is smaller than the length of the dataset. If n exceeds the available data points, the method may fail to run, leading to errors or empty results.

• Accuracy vs. Data Availability: A larger n improves regression accuracy but may result in fewer available data points, especially in smaller datasets. Conversely, smaller n might yield less stable results but can handle more data points.

• Edge Effects: For data points near the beginning or end of the dataset, the number of available neighbors may be limited. If n is too large, it may not be possible to compute regression near the edges.

• Performance Considerations: Large values of n can increase memory usage and slow down performance, especially for larger datasets. Start with smaller values of n and increase it as needed.

Example Usage

import numpy as np
from fracmechpy import Secant, IncPoly

# Sample input data
N = np.array([70000, 90000, 100000, 110000,120000,130000])
af = np.array([1.90, 3.09, 3.78, 4.45, 6.19, 6.84])
ab = np.array([0.89, 2.07, 2.81, 3.53, 5.09, 6.21])
W = 50  # Width in (mm)
p_max = 4000  # Maximum load in (N)
p_min = 400  # Minimum load in (N)
B = 5  # Thickness in (mm)
n = 1  # Number of neighboring points for regression

# Compute crack growth rate and stress intensity factor range using Secant method
dadN_secant, dK_secant = Secant(N, af, ab, W, p_max, p_min, B)
print("Secant Method - da/dN:", dadN_secant)
print("Secant Method - dK:", dK_secant)

# Compute crack growth rate and stress intensity factor range using IncPoly method
dadN_incpoly, dK_incpoly = IncPoly(N, af, ab, W, p_max, p_min, B, n)
print("IncPoly Method - da/dN:", dadN_incpoly)
print("IncPoly Method - dK:", dK_incpoly)

Error Handling

The function enforces ASTM E647 validity limits for crack growth increments (da). If the increment exceeds the standard-defined limits based on α = aᵥₑ/W , the function prints an error message and returns None.

License

This package is distributed under the MIT License.

Contact

For questions or contributions, please reach out to the author at [e-mail].

### Key Updates:
1. **New Section for `IncPoly`**: Added a description of the `IncPoly` method in the functions section.
2. **Updated Example Usage**: Added an example that demonstrates the usage of both `Secant` and `IncPoly` functions.
3. **Feature Addition**: Mentioned the addition of the `IncPoly` method in the Features section.
4. **Limitations of `n`**: Provided detailed information about the limitations on choosing the value of `n`, including dataset size, accuracy vs. data availability, edge effects, and performance considerations.

This should now fully reflect the functionality of the `IncPoly` method and the limitations for the `n` parameter.