Void Growth and Local Necking in Biaxially Stretched Sheets

1978 ◽  
Vol 100 (2) ◽  
pp. 164-169 ◽  
Author(s):  
A. Needleman ◽  
N. Triantafyllidis
Keyword(s):  
Void Growth ◽  
Plastic Material ◽  
Material Model ◽  
Forming Limit ◽  
Equivalent Thickness ◽  
Forming Limit Diagrams ◽  
Local Necking ◽  
Classical Plasticity ◽  
Porous Plastic

The role of void growth in triggering local necking in biaxially stretched sheets is investigated. A recently proposed constitutive equation for porous plastic materials is employed in conjunction with the model of localized necking introduced by Marciniak and Kuczynski. An increased initial volume concentration of voids within the incipient neck plays the role of the imperfection. The predictions of this analysis are compared with corresponding predictions based on classical plasticity theory with various types of initial inhomogeneities. It is found that the porous plastic material model predicts forming limit diagrams qualitatively in accord with experimental results. However, the results also show that any microstructural inhomogeneity that gives rise to a continually decreasing rate of hardening in the neck would be expected to predict qualitatively similar forming limit diagrams. It is also found that the hypothesis of an equivalent thickness imperfection is not necessarily appropriate for high hardening materials.

A Continued Evaluation of the Role of Material Hardening Behavior for the NeT TG1 and TG4 Specimens

2014 ◽  
Author(s):  
David J. Dewees ◽  
Phillip E. Prueter ◽  
Seetha Ramudu Kummari
Keyword(s):  
Structural Integrity ◽  
Plastic Material ◽  
Critical Factor ◽  
Material Model ◽  
Standard Test ◽  
Material Behavior ◽  
Weld Residual Stress ◽  
Hardening Models ◽  
Elastic Plastic Material

Modeling of cyclic elastic-plastic material behavior (hardening) has been widely identified as a critical factor in the finite element (FE) simulation of weld residual stresses. The European Network on Neutron Techniques Standardization for Structural Integrity (NeT) Project has provided in recent years both standard test cases for simulation and measurement, as well as comprehensive material characterization. This has allowed the role of hardening in simulation predictions to be isolated and critically evaluated as never before possible. The material testing information is reviewed, and isotropic, nonlinear kinematic and combined hardening models are formulated and tested. Particular emphasis is placed on material model selection for general fitness-for-service assessments, as it relates to the guidance for weld residual stress (WRS) in flaw assessments of in-service equipment in Annex E of the FFS standard, API 579-1/ASME FFS-1.

scholarly journals Insight into the Influence of Punch Velocity and Thickness on Forming Limit Diagrams of AA 6061 Sheets—Numerical and Experimental Analyses

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2010
Author(s):  
Sasan Sattarpanah Karganroudi ◽  
Shahab Shojaei ◽  
Ramin Hashemi ◽  
Davood Rahmatabadi ◽  
Sahar Jamalian ◽  
...  
Keyword(s):  
Finite Element ◽  
Fe Simulation ◽  
Forming Limit Diagram ◽  
Material Model ◽  
Forming Limit ◽  
Forming Limit Diagrams ◽  
Punch Velocity ◽  
Experimental Analyses ◽  
Insight Into ◽  
Good Agreement

In this article, the forming limit diagram (FLD) for aluminum 6061 sheets of thicknesses of 1 mm and 3 mm was determined numerically and experimentally, considering different punch velocities. The punch velocity was adjusted in the range of 20 mm/min to 200 mm/min during the Nakazima test. A finite element (FE) simulation was carried out by applying the Johnson–Cook material model into the ABAQUSTM FE software. In addition, a comparison between the simulation and the experimental results was made. It was observed that by increasing the punch velocity, the FLD also increased for both thicknesses, but the degree of the improvement was different. Based on these results, we found a good agreement between numerical and experimental analyses (about 10% error). Moreover, by increasing the punch velocity from 20 mm/min to 100 mm/min in 1 mm-thick specimens, the corresponding FLD increased by 3.8%, while for 3 mm-thick specimens, this increase was 5.2%; by increasing the punch velocity from 20 mm/min to 200 mm/min in the 3 mm-thick sheets, the corresponding FLD increased by 9.3%.

scholarly journals Role of Twinning in Texture Development and in Plastic Deformation of Hexagonal Materials

1988 ◽  
Vol 7 (4) ◽  
pp. 265-301 ◽  
Author(s):  
M. J. Philippe ◽  
C. Esling ◽  
B. Hocheid
Keyword(s):  
Plastic Deformation ◽  
Uniaxial Tension ◽  
Mechanical Twinning ◽  
Extensive Study ◽  
Texture Development ◽  
Forming Limit ◽  
Forming Limit Diagrams ◽  
Hexagonal Materials ◽  
Zr Alloys

This paper presents an extensive study of the conditions of appearance of mechanical twinning and its role in the texture development during uniaxial tension, biaxial expansion and rolling of Ti and Zr alloys.With the help of literature, the analyses are extended to alloys of Mg, Zn and Be.Finally, the influence of twinning on the shape of the forming limit diagrams and on formability is discussed for hexagonal metals.

scholarly journals A numerical approach for the modelling of forming limits in hot incremental forming of AZ31 magnesium alloy

2021 ◽  
Author(s):  
Davide Campanella ◽  
Gianluca Buffa ◽  
Ernesto Lo Valvo ◽  
Livan Fratini
Keyword(s):  
Room Temperature ◽  
Incremental Forming ◽  
Material Model ◽  
Numerical Approach ◽  
Forming Limit ◽  
Material Strength ◽  
Wall Angle ◽  
Analytical Expression ◽  
The Poor ◽  
Specific Material

AbstractMagnesium alloys, because of their good specific material strength, can be considered attractive by different industry fields, as the aerospace and the automotive one. However, their use is limited by the poor formability at room temperature. In this research, a numerical approach is proposed in order to determine an analytical expression of material formability in hot incremental forming processes. The numerical model was developed using the commercial software ABAQUS/Explicit. The Johnson-Cook material model was used, and the model was validated through experimental measurements carried out using the ARAMIS system. Different geometries were considered with temperature varying in a range of 25–400 °C and wall angle in a range of 35–60°. An analytical expression of the fracture forming limit, as a function of temperature, was established and finally tested with a different geometry in order to assess the validity.

Stresses in Ultrasonically Assisted Turning

2006 ◽  
Vol 5-6 ◽  
pp. 351-358 ◽  
Author(s):  
N. Ahmed ◽  
A.V. Mitrofanov ◽  
Vladimir I. Babitsky ◽  
Vadim V. Silberschmidt
Keyword(s):  
Ultrasonic Vibration ◽  
Vibration Frequency ◽  
Cutting Forces ◽  
Plastic Material ◽  
Process Zone ◽  
Three Dimensional ◽  
Rate Sensitivity ◽  
High Strength ◽  
Material Model ◽  
Shear Stresses

Ultrasonically assisted turning (UAT) is a novel material-processing technology, where high frequency vibration (frequency f ≈ 20kHz, amplitude a ≈15μm) is superimposed on the movement of the cutting tool. Advantages of UAT have been demonstrated for a broad spectrum of applications. Compared to conventional turning (CT), this technique allows significant improvements in processing intractable materials, such as high-strength aerospace alloys, composites and ceramics. Superimposed ultrasonic vibration yields a noticeable decrease in cutting forces, as well as a superior surface finish. A vibro-impact interaction between the tool and workpiece in UAT in the process of continuous chip formation leads to a dynamically changing stress distribution in the process zone as compared to the quasistatic one in CT. The paper presents a three-dimensional, fully thermomechanically coupled computational model of UAT incorporating a non-linear elasto-plastic material model with strain-rate sensitivity and contact interaction with friction at the chip–tool interface. 3D stress distributions in the cutting region are analysed for a representative cycle of ultrasonic vibration. The dependence of various process parameters, such as shear stresses and cutting forces on vibration frequency and amplitude is also studied.

Elasto-Plastic Analysis of Thermal Stress Development During VAR of Ingots

1999 ◽  
Author(s):  
M. K. Alam ◽  
K. K. Wong ◽  
S. L. Semiatin
Keyword(s):  
Thermal Stresses ◽  
Plastic Material ◽  
Material Model ◽  
Thermomechanical Properties ◽  
Vacuum Arc ◽  
Aerospace Materials ◽  
Temperature Dependent ◽  
Vacuum Arc Remelting ◽  
High Cooling Rates ◽  
Dc Arc

Abstract The vacuum arc remelting (VAR) process has been developed to melt and cast high quality aerospace materials such as titanium alloys. VAR comprises the continuous remelting of a consumable electrode by means of a dc arc under vacuum or a low partial pressure of argon. The molten metal solidifies in a water-cooled copper crucible leading to high cooling rates that often results in large thermal stresses. The development of temperature gradients and the resulting thermal stresses during the VAR processes was investigated using an elasto-plastic material model with temperature dependent thermomechanical properties. Detailed solutions were obtained by using the commercial finite element code ABAQUS.

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