Cockcroft-Latham Ductile Fracture Criteria for Non Ferrous Materials

2014 ◽  
Vol 782 ◽  
pp. 373-378 ◽  
Author(s):  
Tibor Kvačkaj ◽  
Juraj Tiža ◽  
Július Bacsó ◽  
Andrea Kováčová ◽  
Robert Kočiško ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Ductile Fracture ◽  
Compression Test ◽  
Copper Alloys ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Compression Tests ◽  
Fracture Criteria ◽  
Ductile Fracture Criteria

The determination of ductile fracture criteria as well as friction coefficient, stress-strain curves, constants for Hollomon's equation and a material workability based on analytical methods as a forming limit diagram, a normalized Cockcroft-Latham criteria (nCL)) ring and compression tests for two materials based on aluminum and copper alloys were carried out. A calculation of nCL criteria on the basis of a compression test and numerical simulations was made. The critical values nCL criteria resulting from compression test were determined. Prediction of nCL criteria by numerical simulations were confirmed by laboratory compression tests. The values obtained from numerical simulations and compression tests for both materials show a good coincidence in results.

scholarly journals Determination of ductile fracture criteria for bulk and PM materials

2016 ◽  
Vol 52 (05) ◽  
pp. 249-254 ◽  
Author(s):  
T. KVACKAJ ◽  
J. TIŽA ◽  
A. KOVÁČOVÁ ◽  
R. KOČIŠKO ◽  
J. BACSÓ
Keyword(s):  
Ductile Fracture ◽  
Fracture Criteria ◽  
Ductile Fracture Criteria

Determination of FLD for Ti-6Al-4V Titanium Alloy Sheet

2016 ◽  
Vol 687 ◽  
pp. 171-178
Author(s):  
Piotr Lacki
Keyword(s):  
Titanium Alloy ◽  
Numerical Simulations ◽  
Real Time ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Forming Limit Diagram ◽  
Alloy Sheet ◽  
Forming Limit

Ti-6Al-4V is the most widely applied titanium alloy in technology and medicine due its good mechanical properties combined with low density and good corrosion resistance. However, poor technological and tribological properties make it very difficult to process, including the problems with sheet-metal forming. The best way to evaluate sheet drawability is to use Forming Limit Diagram (FLD), which represents a line at which failure occurs. FLD allows for determination of critical forming areas.The FLDs can be determined both theoretically and experimentally. Recently, special optical strain measurement systems have been used to determine FLDs.In this study, material deformation was measured with the Aramis system that allows for real-time observation of displacements of the stochastic points applied to the surface using a colour spray. The FLD was determined for Ti-6Al-4V titanium alloy sheet with thickness of 0.8 mm. In order to obtain a complete FLD, a set of 6 samples with different geometries underwent plastic deformation in stretch forming i.e. in the Erichsen cupping test until the appearance of fracture.The real-time results obtained from the ARAMIS software for multiple measurement positions from the test specimen surface were compared with numerical simulations of the cupping tests. The numerical simulations were performed using the PamStamp 2G v2012 software dedicated for analysis of sheet-metal forming processes. PamStamp 2G is based on the Finite Element method (FEM). The major and minor strains were analysed. The effect of friction conditions on strain distribution was also taken into consideration

scholarly journals Evaluation of Varying Ductile Fracture Criteria for 42CrMo Steel by Compressions at Different Temperatures and Strain Rates

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Guo-zheng Quan ◽  
Gui-chang Luo ◽  
An Mao ◽  
Jian-ting Liang ◽  
Dong-sen Wu
Keyword(s):  
Strain Rate ◽  
Ductile Fracture ◽  
Ductile Damage ◽  
Compression Tests ◽  
Fracture Criteria ◽  
Ductile Fracture Criteria ◽  
Bulk Forming ◽  
42Crmo Steel ◽  
Different Temperatures ◽  
Tension Testing

Fracturing by ductile damage occurs quite naturally in metal forming processes, and ductile fracture of strain-softening alloy, here 42CrMo steel, cannot be evaluated through simple procedures such as tension testing. Under these circumstances, it is very significant and economical to find a way to evaluate the ductile fracture criteria (DFC) and identify the relationships between damage evolution and deformation conditions. Under the guidance of the Cockcroft-Latham fracture criteria, an innovative approach involving hot compression tests, numerical simulations, and mathematic computations provides mutual support to evaluate ductile damage cumulating process and DFC diagram along with deformation conditions, which has not been expounded by Cockcroft and Latham. The results show that the maximum damage value appears in the region of upsetting drum, while the minimal value appears in the middle region. Furthermore, DFC of 42CrMo steel at temperature range of 1123~1348 K and strain rate of 0.01~10 s-1are not constant but change in a range of 0.160~0.226; thus, they have been defined as varying ductile fracture criteria (VDFC) and characterized by a function of temperature and strain rate. In bulk forming operations, VDFC help technicians to choose suitable process parameters and avoid the occurrence of fracture.

Ductile Fracture Criteria Based on Mesoscopic Void-Damage of Metals under Plastic Forming

2014 ◽  
Vol 633-634 ◽  
pp. 620-623
Author(s):  
Dao Fu Tang ◽  
Lian Fa Yang
Keyword(s):  
Tensile Stress ◽  
Ductile Fracture ◽  
Maximum Tensile Stress ◽  
Triaxial Stress ◽  
Forming Limit ◽  
Fracture Criteria ◽  
Ductile Fracture Criteria ◽  
Plastic Forming ◽  
Void Damage ◽  
Main Factor

In the process of plastic forming of metals, ductile fracture is an important factor influencing the improvement of forming limit of metals, while ductile fracture criteria can predict when and where ductile fracture occurs. Some conventional ductile fracture criteria based on mesoscopic void-damage and their application in different plastic forming of metals are introduced in this paper. And the ductile fracture criteria will be summarized into two categories: based on triaxial stress degree and based on maximum tensile stress. Because the triaxial stress degree and maximum tensile stress are a main factor deciding the occurrence of the ductile fracture.

Finite Element Analysis of the Hydro-Mechanical Punching Process

2006 ◽  
Vol 505-507 ◽  
pp. 871-876
Author(s):  
Jong Hun Yoon ◽  
Hoon Huh ◽  
Yong Sin Lee ◽  
Seung Soo Kim ◽  
E.J. Kim ◽  
...  
Keyword(s):  
Hydrostatic Pressure ◽  
Ductile Fracture ◽  
Sheet Material ◽  
Middle Surface ◽  
Initial Crack ◽  
Fracture Criteria ◽  
Element Analysis ◽  
Final Fracture ◽  
Ductile Fracture Criteria ◽  
Punching Process

This paper investigates the characteristics of a hydro-mechanical punching process. The hydro-mechanical punching process is divided into two stages: the first stage is the mechanical half piercing in which an upper punch goes down before the initial crack is occurred; the second stage is the hydro punching in which a lower punch goes up until the final fracture is occurred. Ductile fracture criteria such as the Cockcroft et al., Brozzo et al. and Oyane et al. are adopted to predict the fracture of a sheet material. The index value of ductile fracture criteria is calculated with a user material subroutine, VUMAT in the ABAQUS Explicit. The hydrostatic pressure retards the initiation of a crack in the upper region of the blank and induces another crack in the lower region of the blank during the punching process. The final fracture zone is placed at the middle surface of the blank to the thickness direction. The result demonstrates that the hydro-mechanical punching process makes a finer shearing surface than the conventional one as hydrostatic pressure increases.

Damage evaluation in tube spinnability test with ductile fracture criteria

2015 ◽  
Vol 100 ◽  
pp. 99-111 ◽  
Author(s):  
Hao Ma ◽  
Wenchen Xu ◽  
Bo Cheng Jin ◽  
Debin Shan ◽  
Steven R. Nutt
Keyword(s):  
Ductile Fracture ◽  
Damage Evaluation ◽  
Fracture Criteria ◽  
Ductile Fracture Criteria
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