Forming Limits Prediction of FCC Sheet Metal Adopting Crystal Plasticity

2007 ◽  
Vol 340-341 ◽  
pp. 179-186
Author(s):  
Wing Bun Lee ◽  
Yi Ping Chen ◽  
Sandy To
Keyword(s):  
Sheet Metal ◽  
Crystal Plasticity ◽  
Initial Imperfection ◽  
Rate Sensitivity ◽  
Alloy Sheet ◽  
Forming Limits ◽  
Factors Affecting ◽  
Rate Dependent ◽  
Initial Texture ◽  
Process Factors

A rate-dependent crystal plasticity constitutive model together with Marciniak- Kuczynski(M-K) approach is employed to perform numerical simulations of forming limits diagrams(FLDs). An initial imperfection in terms of a narrow band is adopted to initialize the sheet necking. Homogeneous deformations inside and outside the band are assumed and the enforcement of compatibility and equilibrium conditions is required only on the band interface. Constitutive computations are carried out on two aggregates of FCC crystal grains, with each representing one of the two zones, respectively. Taylor homogenization assumption is employed to establish the link of stress between single crystal and polycrystal, and to derive an average response of the aggregates. The same initial texture is imparted to the two aggregates and their evolutions will be traced in the necking process. Factors affecting the FLDs prediction, such as imperfection intensity, initial texture, strain rate sensitivity and crystal elasticity will be taken into account. The above procedure will be applied to an annealed aluminium alloy sheet metal

An incremental-update formulation to simulate earing behaviour with crystal plasticity model

2011 ◽  
Vol 225 (8) ◽  
pp. 1774-1781 ◽  
Author(s):  
S Zhang ◽  
S Huang ◽  
D Li ◽  
Y Peng
Keyword(s):  
Crystal Plasticity ◽  
Deformation Behaviour ◽  
Az31 Alloy ◽  
Alloy Sheet ◽  
Plasticity Model ◽  
Explicit Finite Element ◽  
Rate Dependent ◽  
Crystal Plasticity Model ◽  
Finite Element Package ◽  
Incremental Update

To gain a better understanding about the influence of initial texture on deformation behaviour of sheet metals, an incremental-update formulation is adopted for implementing rate-dependent crystal plasticity model into the explicit finite element package, ABAQUS/Explicit. In this formulation, the configuration in the last increment serves as a reference frame, and the stress, grain orientation and hardening behaviour of crystal are updated at the end of each increment. Two user subroutines VUMAT are developed, respectively, for face-centred cubic and hexagonal close packed alloys due to different deformation mechanisms. Earing behaviours of aluminium sheet and AZ31 alloy sheet are simulated for model validation.

Calibration of Texture-Adjusted Strain-Rate Potential and its Application

2007 ◽  
Vol 340-341 ◽  
pp. 829-834
Author(s):  
Yi Ping Chen ◽  
Wing Bun Lee ◽  
Sandy To
Keyword(s):  
Sheet Metal ◽  
Crystal Plasticity ◽  
Plastic Anisotropy ◽  
Computing Time ◽  
Constitutive Models ◽  
Yield Function ◽  
Dislocation Slip ◽  
Texture Coefficients ◽  
Rate Dependent

An accurate prediction of plastic anisotropy induced by initial texture in sheet metal forming operations depends on the constitutive models adopted. Models of engineering interest include both phenomenological formulations and crystal plasticity based on dislocation slip. In addition to the above two approaches that are commonly adopted in FE analysis, now an alternative is available which describes anisotropic behavior of polycrystalline sheet metals still by an analytic yield function to keep the computing time as low as possible but at the same time which also takes explicitly into account the crystallographic texture of the material to give a more precise description of plasticity anisotropy. However, the locus of such a yielding potential determined by constitutive coefficients upon invoking the rate-independent crystal plasticity may exhibit an unrealistic concave shape, which will make it impossible to obtain a convergent solution. To circumvent the difficulty, a detailed computation procedure is presented to calculate the constitutive coefficients based on rate-dependent crystal plasticity. The combination of the coefficients obtained with experimentally measured texture coefficients of an annealed FCC polycrystalline sheet metal will provide a complete constitutive characterization of the material. As an application of the calibrated model, the process of deep drawing by hemispherical punch is simulated, in which plastic anisotropy (earring) corresponding to typical texture type is observed, thus demonstrating the applicability of the coefficients found.

Simulation of Cold Ring Rolling Based on Rate Dependent Crystal Plasticity

2007 ◽  
Vol 561-565 ◽  
pp. 1813-1817
Author(s):  
Hong Wei Li ◽  
He Yang ◽  
Zhi Chao Sun ◽  
M. Wang ◽  
Lan Yun Li
Keyword(s):  
Crystal Plasticity ◽  
Rolling Force ◽  
Rate Sensitivity ◽  
Sensitivity Coefficient ◽  
Ring Rolling ◽  
Fe Model ◽  
Forming Process ◽  
Rate Dependent ◽  
Cold Ring Rolling ◽  
Material Behaviors

Material behaviors of anisotropy and rate sensitivity affect cold ring rolling greatly. So, a self-developed incremental model of rate dependent crystal plasticity (RDCP) is utilized to forecast the deformation characteristics of this forming process based on a 3D FE model under ABAQUS/Explicit environment. The results show that the model of RDCP captures material behaviors of anisotropy and rate sensitivity better in this forming process by the comparison with the model of J2 plasticity; with the decrease of rate sensitivity coefficient, the forming process becomes more unstable with smaller rolling force and growth in ring radial direction; with the increase of feed rate of idle roll, the deformation of ring becomes more even while the rolling force becomes larger.

A Theoretical Study of the Effect of the Double Strain Path Change on the Forming Limits of Metal Sheet

2013 ◽  
Vol 554-557 ◽  
pp. 127-138 ◽  
Author(s):  
Marilena Butuc ◽  
Frédéric Barlat ◽  
José Grácio ◽  
Gabriela Vincze
Keyword(s):  
Sheet Metal ◽  
Strain Path ◽  
Theoretical Study ◽  
Alloy Sheet ◽  
Initial Shape ◽  
Forming Limits ◽  
Remarkable Effect ◽  
Strain Paths ◽  
Strain Path Change ◽  
Strain Path Changes

The present paper aims at a theoretical study of the forming limits of a sheet metal subjected to double strain path changes by using as reference material the AA6016-T4 aluminum alloy sheet. The simulation of plastic instability is carried out through the Marciniak-Kuczynski analysis. The initial shape of the yield locus is given by the Yld2000-2d plane stress yield function. The strain hardening of the material is described by the Voce type saturation law. Linear and several complex strain paths involving single and double strain path changes are taken into account. The validity of the model is assessed by comparing the predicted and experimental forming limits under linear and selected one strain path change. A good accuracy of the developed software on predicting the forming limits is found. A sensitive analysis of the influence of the type and value of the double prestain in the occurrence of the plastic flow localization is performed. A remarkable effect of the double strain path change on the sheet metal forming limits is observed.

Grain Size Effect in Sheet Metal Microforming Simulation Adopting Strain Gradient Concept

2007 ◽  
Vol 364-366 ◽  
pp. 1285-1291
Author(s):  
Wing Bun Lee ◽  
Yi Ping Chen ◽  
Suet To
Keyword(s):  
Grain Size ◽  
Size Effect ◽  
Sheet Metal ◽  
Crystal Plasticity ◽  
Strain Gradient ◽  
Grain Size Effect ◽  
Active System ◽  
Rate Dependent ◽  
Slip Resistance ◽  
Non Local

A strain gradient dependent crystal plasticity approach is adopted to model the size effect in the microforming process of sheet metal. To take into account the grain size effect in the simulation, the total slip resistance in each active system was assumed to be due to a mixed population of forest obstacles arising from both statistically stored and geometrically necessary dislocations. The non-local crystal plasticity has been established by directly incorporating the above slip resistance into the conventional rate-dependent crystal plasticity and implemented into the Abaqus/Standard FE platform by developing the user subroutine UMAT. The formulation has been recapitulated and followed by presentation of the numerical examples employing both the local and non-local formulation. The comparison of the counterpart simulation results reveals the grain size effect in the microforming process and demonstrates the availability of the code developed.

An analytic method for the prediction of ODFS with application to the shear of FCC polycrystals

1990 ◽  
Vol 430 (1880) ◽  
pp. 489-507 ◽  
Keyword(s):  
Distribution Function ◽  
Orientation Distribution Function ◽  
Rate Sensitivity ◽  
Orientation Distribution ◽  
Analytic Method ◽  
Rate Dependent ◽  
Numerical Predictions ◽  
Taylor Hypothesis ◽  
Computer Codes ◽  
Initial Texture

An analytic method is presented for calculation of the orientation distribution function (ODF). It is very rapid, since the amount of computation does not depend on the value of the applied shear. The existence of a hypothetical reference texture is also demonstrated, which plays a central role in the present approach. With the aid of this ‘texture’ and the initial texture, the current ODF is uniquely defined as a function of strain. Shear textures in face-centred cubic (FCC) polycrystals are predicted analytically in this way on the basis of the uniform strain (Taylor) hypothesis and the theory of rate dependent slip. Two special fibres are examined closely, and it is shown that they undergo periodic variations. The period is fixed for the cube-on-face fibre, but depends on rate sensitivity in the cube-on-edge case. The results obtained for the two fibres compare very well with previous completely numerical predictions, and are also consistent with the only available set of experimental results. The present predictions, which can be obtained very easily and rapidly, are useful for testing large deformation computer codes for texture simulation.

scholarly journals Enzymatic Process for Cystoseira barbata Valorization: Ethanol Production and Additional By-Products

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 741
Author(s):  
Doinita-Roxana Cioroiu Tirpan ◽  
Ancaelena Eliza Sterpu ◽  
Claudia Irina Koncsag ◽  
Alina Georgiana Ciufu ◽  
Tănase Dobre
Keyword(s):  
Ethanol Production ◽  
Alcoholic Fermentation ◽  
Ethanol Yield ◽  
Product Yield ◽  
Liquid Ratio ◽  
Experimental Conditions ◽  
Factors Affecting ◽  
Cystoseira Barbata ◽  
Main Factors ◽  
Process Factors

The aim of this study is to evaluate the potential of dried Cystoseira barbata alga for ethanol production through alcoholic fermentation. The influence of the main factors affecting the fermentation are studied in the frame of a 23 factorial experimental plan. The main factors influencing the process are the fermentation temperature (t from 25 °C to 35 °C), the solid to liquid ratio (S/L from 0.040 g/g to 0.080 g/g), and the cellulase ratio (R from 8 U/g d.m to 16 U/g d.m.). The maximum volatile compounds yield of 0.2808 g/g d.m and ethanol yield of 0.0158 g/g d.m were favored by the following experimental conditions: process temperature of 35 °C, solid to liquid ratio of 0.0415, and enzyme ratio of 16 U/g d.m. A statistical model was used to correlate the product yield with the process factors. Additionally, 19 interesting bioactive compounds were found in the enzymatic hydrolysis and alcoholic fermentation broths which seem likely to maintain natural defence mechanisms against diseases and physical disorders.

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