Practical work (TP) : Tensile test analysis¶

In this session you are asked to analyze data coming from the tensile test.

This analysis aims at extracting mechanical properties of the material, such as the Young modulus, mechanical strength and yield strength from the load/displacement curve.

At the end of this session you should have a class that is able to deal with the data coming from a tensile test.

This class must be able to :¶

Level 0¶

read the data in a csv file
compute the nominal stress and nominal strain
compute the true stress and true strain
plot the relevant curves

Level 1¶

read automatically the header metadata of csv file
determine the Young modulus $E$
determine the Yield stress and the Yield stress a 0.02% of strain
determine the mechanical strength

Level 2¶

compute the plastique strain ($:raw-latex:varepsilon_p = :raw-latex:`\varepsilon `- :raw-latex:`dfrac{sigma}{E}` $)
fit the stress / plastic strain curve with a power plastic law ($:raw-latex:sigma `= :raw-latex:sigma`_0 + K {:raw-latex:`\varepsilon`_p}^n $)

Level 3¶

Run the procedure over all the batch.

#Setup
%load_ext autoreload
%matplotlib nbagg
%autoreload 2
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import matplotlib as mpl

Steps to structure your work¶

1- Find the way to extract the relevant data from one dataset (E, Re, Rm, …)

2- Structure your work using the class structure of python

3- Perform analysis on several loads/displacement curves

The dataset are in the following files :¶

*unit are s/N/mm*

Test_1.csv
Test_2.csv
Test_3.csv
Test_4.csv

Useful function¶

line = "z = 143.2"
a,b = line.split("=")
print(a, b)s

z   143.2

Here is a simple template of the class that you should build¶

class TensileTest():
    """
    this class is able to ....
    """
    def __init__(self, csv_file='xxx'):
        self.csv_file = csv_file
        # ...

    def __repr__(self):
        return "<tensileTest: (file: {0}, E = {1:.2} MPa)>".format(self.csv_file, self.get_YoungModulus())

    def get_YoungModulus(self):
        """
        TODO
        """
        return 1.

test1 = TensileTest() # call the __init__ function

test1 # call the __repr__ function

<tensileTest: (file: xxx, E = 1.0 MPa)>