scholarly journals Prediction of Hole Expansion Ratio of Titanium Alloys Using R Programming

2020 ◽  
Vol 12 (2) ◽  
pp. 125-137
Author(s):  
J. S. Kwame ◽  
E. Yakushina ◽  
P. Blackwell
Keyword(s):  
Regression Model ◽  
Titanium Alloys ◽  
Model Equation ◽  
Model Fitting ◽  
Expansion Ratio ◽  
Uniaxial Tensile ◽  
Index Number ◽  
Hole Expansion ◽  
Hole Expansion Ratio ◽  
R Programming

The hole expansion ratio (HER) is an important material property which defines the extent of edge formability of sheet metals. The stress states observed at the hole edge after the hole expansion test are similar to those seen during traditional uniaxial tensile deformation. This observation has provoked research, directed at ascertaining a correlation between the HER and tensile properties. In order to account for the forming behaviour of complex materials like titanium, a highly robust model that takes into account the material formability in all sheet-processing directions must be considered. The R programming language was used in this research to build a model fitting expression capable of predicting the HER as well as generating a regression model equation for titanium alloys, based on their thickness and Erichsen index number. The proposed regression model equation for predicting HER of titanium alloys exhibited an excellent statistical significance (p= 0.00076), indicating the robustness of the model fitting expression to predict HER values of titanium alloys. An accompanying adjusted R squared value of 0.9987 for the generated regression model equation also shows how well the regression line fits the data for accurate prediction of the HER of titanium alloys. A numerical validation analysis of the strength of the relationship derived between the predicted and the experimental HERs gave a correlation coefficient of 0.9884. This result shows a strong linear relationship between the experimental and predicted HER values of the titanium alloys with an average absolute error of 8.8%.

Fundamental aspect of stretch-flangeability of sheet metals

2018 ◽  
Vol 233 (10) ◽  
pp. 2115-2119 ◽  
Author(s):  
Surajit Kumar Paul
Keyword(s):  
Tensile Test ◽  
Sheet Metal ◽  
Expansion Ratio ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Hole Expansion ◽  
Expansion Test ◽  
Localized Necking ◽  
Hole Expansion Test ◽  
Hole Expansion Ratio

Stretch-flangeability of sheet metal is normally represented by hole expansion ratio. Hole expansion ratio cannot be determined from uniaxial tensile test though uniaxial tensile deformation occurs at the hole’s edge, because of fundamental difference in deformation and damage processes present between hole expansion test and uniaxial tensile test. It is proposed that only localized necking is observed in hole expansion test; however, diffuse necking followed by localized necking is observed in uniaxial tensile test of sheet metal. It is noticed that the hole expansion ratio is marginally higher than maximum diffuse neck strain determined from uniaxial tensile test with local strain measurement by digital image correlation technique. The absence of diffuse neck in hole expansion test with defect-free central hole (i.e. electrical discharge machined hole) results far higher hole expansion ratio than uniform elongation of the material.

Effect of punch geometry on hole expansion ratio

2019 ◽  
Vol 234 (3) ◽  
pp. 671-676 ◽  
Author(s):  
Surajit Kumar Paul
Keyword(s):  
Tensile Deformation ◽  
Expansion Ratio ◽  
Central Hole ◽  
Uniaxial Tensile ◽  
Flat Bottom ◽  
Hole Expansion ◽  
Hole Edge ◽  
Hole Expansion Ratio ◽  
Punch Geometry ◽  
Identical Test

Stretch-flangeability of sheet metal is normally quantified by hole expansion ratio. Researchers have determined hole expansion ratio with various punch geometries such as conical, flat-bottom and hemispherical, and reported different hole expansion ratio values for identical test condition. Finite element investigation confirms that alteration of deformation path with punch geometries consequence different hole expansion ratio values. Necking and failure take place slightly away from the central hole edge for flat-bottom and hemispherical punches, while at the central hole edge for conical punch. Approximately plane strain tensile deformation prevails at the failure location for flat-bottom and hemispherical punches, while pure uniaxial tensile deformation prevails for conical punch.

Prediction of hole expansion ratio for various steel sheets based on uniaxial tensile properties

2018 ◽  
Vol 24 (1) ◽  
pp. 187-194 ◽  
Author(s):  
Jae Hyung Kim ◽  
Young Jin Kwon ◽  
Taekyung Lee ◽  
Kee-Ahn Lee ◽  
Hyoung Seop Kim ◽  
...  
Keyword(s):  
Tensile Properties ◽  
Expansion Ratio ◽  
Uniaxial Tensile ◽  
Hole Expansion ◽  
Steel Sheets ◽  
Hole Expansion Ratio

Prediction of hole expansion ratio for automotive grade steels

2014 ◽  
Vol 89 ◽  
pp. 189-197 ◽  
Author(s):  
Surajit Kumar Paul ◽  
Monideepa Mukherjee ◽  
Saurabh Kundu ◽  
Sanjay Chandra
Keyword(s):  
Expansion Ratio ◽  
Hole Expansion ◽  
Hole Expansion Ratio

The Study in Improvement of Hole Expansibility for High-Strength Steel of 980MPa Grade

2018 ◽  
Vol 941 ◽  
pp. 492-497
Author(s):  
Kuo Cheng Yang ◽  
J.F. Tu ◽  
L.J. Chiang ◽  
W.J. Cheng ◽  
C.Y. Huang
Keyword(s):  
Yield Strength ◽  
High Strength Steel ◽  
Dual Phase Steel ◽  
Single Phase ◽  
High Strength ◽  
Expansion Ratio ◽  
High Yield ◽  
Dual Phase ◽  
Hole Expansion ◽  
Hole Expansion Ratio

Recently, due to the requirements of lightweight and safety, the grade of 980MPa high-strength steel has the demand of high hole expansibility and high yield strength. Due to the large difference of hardness between the soft ferrite and hard martensite, the traditional DP980Y dual phase steel has poor hole expansibility. In order to improve the hole expansibility of DP980Y dual phase steel, the best way is to modify the microstructure into a single-phase to eliminate the large difference of hardness. In this paper, the steel of nearly full bainite microstructure with small amount of ferrite and M/A constituents was studied. Compared to the DP980Y dual phase steel, it was found that this modified steel with a single-phase microstructure has the same grade of 980MPa of tensile strength, but can achieve the demand of higher yield strength and hole-expansion ratio. This study shows reducing the amount of ferrite can increase the homogeneity of matrix with the single phase to improve the hole expansibility. In addition, the use of lower bainite transformation temperature and lower carbon content has the higher hole-expansion ratio due to the less amount of M/A constituents.

Improving Hole Expansion Ratio by Parameter Adjustment in Abrasive Water Jet Operations for DP800

2018 ◽  
Vol 11 (3) ◽  
pp. 241-252
Author(s):  
Bernd-Arno Behrens ◽  
David Diaz-Infante ◽  
Taylan Altan ◽  
Deniz Yilkiran ◽  
Kai Wölki ◽  
...  
Keyword(s):  
Expansion Ratio ◽  
Water Jet ◽  
Abrasive Water Jet ◽  
Parameter Adjustment ◽  
Hole Expansion ◽  
Hole Expansion Ratio
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