scholarly journals Formability Limits, Fractography and Fracture Toughness in Sheet Metal Forming

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1493 ◽  
Author(s):  
João P. Magrinho ◽  
Maria Beatriz Silva ◽  
Luís Reis ◽  
Paulo A. F. Martins
Keyword(s):  
Fracture Toughness ◽  
Strain Hardening ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Pure Copper ◽  
Principal Strain ◽  
Shear Tests ◽  
Double Edge ◽  
Strain Space ◽  
Determine Fracture Toughness

This paper is focused on the utilisation of double edge notched tension, staggered and shear tests to determine fracture toughness and the formability limits by fracture in principal strain space. The experiments were performed in test specimens with different geometries and ligament angles, and the influence of strain hardening was taken into consideration by selecting two materials (aluminium AA1050-H111 and pure copper), with very different strain hardening exponents. Results are plotted in principal strain space, and the discussion is focused on the link between formability limits, fracture toughness and macroscopic fractography characteristics of the specimens that fail by mode I, mode II or mixed-mode.

Experimental Study of Drawing Load Curves in Forming Conical Parts by Hydroforming and Conventional Deep Drawing Processes

2011 ◽  
Vol 291-294 ◽  
pp. 556-560 ◽  
Author(s):  
Salman Norouzi ◽  
Amir Reza Yaghoubi ◽  
Mohammad Bakhshi-Jooybari ◽  
Abdolhamid Gorji
Keyword(s):  
Experimental Study ◽  
Sheet Metal Forming ◽  
Deep Drawing ◽  
Metal Forming ◽  
Pure Copper ◽  
Experimental Program ◽  
Drawing Process ◽  
Deep Drawing Process ◽  
Load Variation ◽  
Hydroforming Process

Since conical parts have wide applications in the industry and forming these parts is one of the most complex and difficult fields in sheet metal forming processes, the study on different methods in forming these parts can be useful. Hydroforming and conventional multistage deep drawing are two deep drawing processes which have been used to form conical parts. Hydroforming deep drawing is one of the special deep drawing processes which have been introduced in order to overcome some inherent problems in the conventional deep drawing with rigid tools. In the present work, an experimental program has been carried out to compare the drawing load variation and maximum drawing load in forming pure copper conical-cylindrical cups with the thickness of 2.5 mm by hydroforming and conventional multistage deep drawing processes. The results of the study demonstrate that drawing load variation is more uniform in the forming of conical parts by hydroforming deep drawing process. The maximum drawing load for drawing copper blank occurs at a higher amount in hydroforming process.

Fracture toughness and failure limits in sheet metal forming

2016 ◽  
Vol 234 ◽  
pp. 249-258 ◽  
Author(s):  
M.B. Silva ◽  
K. Isik ◽  
A.E. Tekkaya ◽  
A.G. Atkins ◽  
P.A.F. Martins
Keyword(s):  
Fracture Toughness ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming

New methodology for the characterization of failure by fracture in bulk forming

2018 ◽  
Vol 53 (4) ◽  
pp. 242-247 ◽  
Author(s):  
Joao P Magrinho ◽  
Maria Beatriz Silva ◽  
Luis M Alves ◽  
AG Atkins ◽  
Paulo AF Martins
Keyword(s):  
Metal Forming ◽  
Stress Triaxiality ◽  
Image Correlation ◽  
Principal Strain ◽  
Bulk Metal ◽  
Bulk Metal Forming ◽  
Aisi 1045 ◽  
Steel Aisi ◽  
Strain Paths ◽  
Strain Space

This article is focused on the formability limits by fracture obtained from standard bulk metal forming tests performed with cylindrical, tapered and flanged specimens. A total of two novel features are presented: the use of digital image correlation to determine strain paths and immersion of steel specimens in liquid nitrogen after the onset of crack formation to reveal the mode of fracture. A new methodology to determine the fracture loci in principal strain space is proposed based on the combination of experimental force–displacement evolutions with in-plane strain measurements. The experimental work is performed in cold-drawn steel AISI 1045 and two new formability tests with different values of stress triaxiality are proposed for obtaining strains at fracture in regions of principal strain space that are not sufficiently well covered by standard bulk metal forming tests.

Hydrodynamic Lubrication in Hemispherical Punch Stretch Forming

1986 ◽  
Vol 53 (2) ◽  
pp. 440-449 ◽  
Author(s):  
Kuo-Kuang Chen ◽  
D. C. Sun
Keyword(s):  
Strain Hardening ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Model Problem ◽  
Hydrodynamic Lubrication ◽  
Sheet Material ◽  
Stretch Forming ◽  
Variable Friction ◽  
Hemispherical Punch

The existence and consequence of hydrodynamic lubrication in sheet metal forming is demonstrated using a model problem of hemispherical punch stretch forming. The problem is solved by incorporating a lubrication analysis into an incremental plasticity analysis. The sheet material is assumed to be elastic plastic with strain hardening, and the lubricant is assumed isoviscous. The study identifies two dimensionless parameters controlling the condition of lubrication. The resulting variable friction at the punch-sheet interface is found to affect significantly the distribution of strains in the sheet metal and its formability.

ИССЛЕДОВАНИЕ ТОЧНОСТИ ДЕТАЛЕЙ, ПОЛУЧАЕМЫХ ПРИ РАЗДЕЛИТЕЛЬНЫХ ОПЕРАЦИЯХ В ПЕРЕНАЛАЖИВАЕМЫХ ШТАМПАХ

2018 ◽  
pp. 52-63
Author(s):  
Е. А. Фролов ◽  
В. В. Агарков ◽  
С. И. Кравченко ◽  
С. Г. Ясько
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Balance Method ◽  
Experiment Planning ◽  
Practical Recommendations

To determine the accuracy of the readjustable punches for separating operations (perforation + punching out) of sheet-metal forming, the accuracy parameters were analyzed using the random balance method using the method of experiment planning. Analytical dependencies are obtained to determine the values of deviation of the outer and inner contour dimensions of perforated and punched out sheet parts. From the dependencies obtained, it is possible to estimate and predict the value of deviation in the dimensions of the resulting part at any time during the operation of the punch. Practical recommendations on the calculation of the actuating dimensions of the working elements (stamping punch, matrix) of readjustable punches are offered.

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