Plastic Analysis of Metal Sheet Forming with SD Effects

2013 ◽  
Vol 299 ◽  
pp. 216-220
Author(s):  
Zhen Yu Chen ◽  
Chun Du Wu ◽  
Zhong Xian Wang
Keyword(s):  
Shear Stress ◽  
Yield Criterion ◽  
High Strength ◽  
Sheet Forming ◽  
Metal Sheet ◽  
Film Stress ◽  
Strength Differential ◽  
Thin Film Stress ◽  
Plastic Analysis ◽  
Tension And Compression

Generally, many high-strength alloy materials used in aerospace, power and chemical industries have strength differential effect in tension and compression (SD effects). Usually, in mechanical calculations of sheet metal forming, Treasca yield criterion and Mises yield criterion are applied. Because the yield criterions don’t take SD effects into consideration, the calculation result may have errors for certain materials. However, generalized twin shear stress yield criterion, which takes into account the influence of the intermediate principal stress, is more suitable for most metal materials than Mohr-Coulomb strength theory. Therefore, this article has made plastic analysis on thin film stress issues of metal sheet forming with generalized twin shear stress yield criterion. We have obtained a unified plastic solution to the internal and external stretching issue of thin material with rounded holes and different tension and compression ratio. Providing a new result with wider applicability is very significant.

Unified Stresses Solution for Sheet Forming

2012 ◽  
Vol 463-464 ◽  
pp. 629-633
Author(s):  
Xiao Wei Li ◽  
Jun Hai Zhao ◽  
Qi Yao Wang
Keyword(s):  
Shear Stress ◽  
Compression Ratio ◽  
Yield Criterion ◽  
Mechanical Analysis ◽  
Sheet Forming ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
Tension And Compression ◽  
Special Case

Based on unified strength theory, the unified stresses solution for sheet forming is presented according to mechanical analysis developed, and accurate enough for much material due to the contributions of both intermediate principal shear stress and varying tension-compression-ratio included. Notably, by denoting a notation of h, the expressions presented to estimate stresses of billet for sheet forming can be apply to both drawing and extrusion. In addition, when material has identical strength in tension and compression, i.e., the tension-compression-ratio of the material is equal to unit, the stresses solution based on unified strength theory become that based on unified yield criterion. Accordingly, it can be proved that the stresses solution based on Mises criterion is just a special case of that based on unified yield criterion.

Maximum Reduction in Thickness in a Single Sheet Forming Pass Based on Unified Strength Theory

2012 ◽  
Vol 159 ◽  
pp. 151-155 ◽  
Author(s):  
Xiao Wei Li ◽  
Jun Hai Zhao ◽  
Qi Yao Wang
Keyword(s):  
Compression Ratio ◽  
Yield Criterion ◽  
Sheet Forming ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
Maximum Reduction ◽  
Special Cases ◽  
Wide Range ◽  
Tension And Compression ◽  
Single Sheet

Based on unified strength theory, the equation for estimating the maximum reduction in thickness in a single sheet forming pass is obtained. Included the contribution of both intermediate principal shear stress and varying tension-compression-ratio to material mechanical property, the equation developed by this paper can reasonably apply to a wide range of material. It can be proved that the equation for estimating the maximum reduction based on unified strength theory becomes that based on unified yield criterion, when material has equal strength in tension and compression, i.e., the tension-compression-ratio of material is equal to units; and, that the values of the maximum reduction obtained previously based on Mises, or Tresca criterion, are all just special cases of those based on unified yield criterion. In addition, the maximum reduction in thickness for sheet drawing and extrusion is equal to one another.

Advanced High Strength Steel Sheet Forming and Springback Simulation

2010 ◽  
Vol 97-101 ◽  
pp. 200-203 ◽  
Author(s):  
Ke Chen ◽  
Jian Ping Lin ◽  
Mao Kang Lv ◽  
Li Ying Wang
Keyword(s):  
High Strength Steel ◽  
Yield Criterion ◽  
Kinematic Hardening ◽  
Sheet Material ◽  
High Strength ◽  
Material Model ◽  
Sheet Forming ◽  
Isotropic Hardening ◽  
Advanced High Strength Steel ◽  
Springback Prediction

With the increasing use of finite element analysis method in sheet forming simulations, springback predictions of advanced high strength steel (AHSS) sheet are still far from satisfactory precision. The main purpose of this paper was to provide a method for accurate springback prediction of AHSS sheet. Material model with Hill’48 anisotropic yield criterion and nonlinear isotropic/kinematic hardening rule were applied to take account the anisotropic yield behavior and the Bauschinger effect during forming processes. U-channel forming and springback simulation was performed using ABAQUS software. High strength DP600 sheet was investigated in this work. The simulation results obtained with the proposed material model agree well with the experimental results, which show a remarkable improvement of springback prediction compared with the commonly used isotropic hardening model.

Measurement of Thin-Film Stress, Stiffness, and Strength Using an Enhanced Membrane Pressure-Bulge Technique

2003 ◽  
Vol 795 ◽  
Author(s):  
Aaron J. Chalekian ◽  
Roxann L. Engelstad ◽  
Edward G. Lovell
Keyword(s):  
Thin Films ◽  
Microelectromechanical Systems ◽  
Applied Pressure ◽  
High Strength ◽  
Film Stress ◽  
Intrinsic Stress ◽  
Positive Pressure ◽  
Bulge Test ◽  
Thin Film Stress ◽  
The One

ABSTRACTAccurate mechanical properties of thin films are essential for viable design and fabrication of semiconductor devices and microelectromechanical systems. Relevant properties of thin films such as intrinsic stress, biaxial modulus, and fracture strength can be significantly different than their corresponding bulk values, and much more difficult to measure. However, such data can be obtained from the pressure-deflection response of clamped freestanding membranes, i.e., the so-called pressure-bulge test. Experimental challenges include membrane leakage prevention, ensuring proper structural boundary conditions, and accurately measuring applied pressure and transverse displacements simultaneously. In addition to these issues, most previously-developed pressure-bulge instruments rely on vacuum pump loadings. Such tools are limited by the one-atmosphere differential pressure over the membrane, which is inadequate for burst testing of high-strength films. Consequently, an enhanced pressure-bulge tool has been developed and will be described in this paper. It incorporates positive pressure to overcome the one-atmosphere load limitation, improved edge constraints, and the ability to test an array of membrane windows across a single substrate.

Stresses Unified Solution for Wire Forming Based on Unified Strength Theory

2012 ◽  
Vol 472-475 ◽  
pp. 835-838
Author(s):  
Xiao Wei Li ◽  
Jun Hai Zhao ◽  
Wei Chen
Keyword(s):  
Compressive Strength ◽  
Shear Stress ◽  
Compression Ratio ◽  
Yield Criterion ◽  
Wire Drawing ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
Tension And Compression ◽  
The Wire ◽  
Special Case

For known well the contributions of both tension-compression-ratio of material and intermediate principal shear stress to wire forming, the wire forming problem is developed based on unified strength theory. By denoting a notation of D, the unified stresses solution for wire forming is gained, which is suitable to both wire drawing and extrusion. In addition, when material has identical strength in tension and compression, the stresses solution based on unified strength theory become that based on unified yield criterion. Notably, it is proved that the stresses of wire forming are independent of the intermediate principal shear stress. Whether any yield criterion (e.g., Mises, Tresca or unified yield criterion) is adopted, for it is assumed that the tensile and compressive strength is equal to one another, the stresses solution is as same as that based on unified yield criterion, and is merely a special case of the unified stresses solution developed by this paper.

Tension and Compression Behavior of Pre-Stressed Steel Strands at High Strain Rate

2011 ◽  
Vol 82 ◽  
pp. 154-159 ◽  
Author(s):  
Anatoly M. Bragov ◽  
Ezio Cadoni ◽  
Alexandr Yu. Konstantinov ◽  
Andrey K. Lomunov
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
High Strength ◽  
Gauge Length ◽  
Hopkinson Pressure Bar ◽  
Dog Bone ◽  
Tension And Compression ◽  
Set Up

In this paper is described the mechanical characterization at high strain rate of the high strength steel usually adopted for strands. The experimental set-up used for high strain rates testing: in tension and compression was the Split Hopkinson Pressure Bar installed in the Laboratory of Dynamic Investigation of Materials in Nizhny Novgorod. The high strain rate data in tension was obtained with dog-bone shaped specimens of 3mm in diameter and 5mm of gauge length. The specimens were screwed between incident and transmitter bars. The specimens used in compression was a cylinder of 3mm in diameter and 5mm in length. The enhancement of the mechanical properties is quite limited compared the usual reinforcing steels.

Localized Necking in a Round Tensile Bar with HCP Material Considering Tension-Compression Asymmetry in Plastic Flow

2013 ◽  
Vol 535-536 ◽  
pp. 164-167
Author(s):  
Jonghun Yoon ◽  
Oana Cazacu ◽  
Jung Hwan Lee
Keyword(s):  
Yield Criterion ◽  
Matrix Material ◽  
Ductile Failure ◽  
Material Behavior ◽  
Strength Differential ◽  
The Matrix ◽  
Void Evolution ◽  
Hcp Materials ◽  
Spherical Voids ◽  
Tension Compression Asymmetry

In spite of this progress in predicting ductile failure, the development of macroscopic yield criteria for describing damage evolution in HCP (hexagonal close-packed) materials remains a challenge. HCP materials display strength differential effects (i.e., different behavior in tension versus compression) in the plastic response due to twinning. Cazacu and Stewart [1] developed an analytic yield criterion for a porous material containing randomly distributed spherical voids in an isotropic, incompressible matrix that displays tension-compression asymmetry. The matrix material was taken to obey the isotropic form of the Cazacu et al. [2] yield criterion, which captures the tension-compression asymmetry of the matrix material. In this paper, finite element calculations of a round tensile bar are conducted with the material behavior described by the Cazacu and Stewart [1] yield criterion. The goal of these calculations is to investigate the effect of the tension-compression asymmetry on the necking induced by void evolution and propagation.

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