scholarly journals Springback Analysis of AA5754 under Warm Stamping Conditions

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Jun Liu
Keyword(s):  
Empirical Model ◽  
Elevated Temperatures ◽  
Stress Gradient ◽  
Bending Moment ◽  
Analytical Models ◽  
Cold Forming ◽  
Bending Tests ◽  
Model Predictions ◽  
Gradient Models ◽  
Good Agreement

Prediction of springback has been thoroughly investigated for cold forming processes; however with the rising prominence of lightweight materials and new forming technologies, predicting springback at elevated temperatures has become essential. In this paper, three analytical models and one empirical model were proposed to predict springback of an aluminium alloy AA5754 at warm forming conditions. The analytical models developed were based on the effect of the linear bending moment, uniform bending moment and through-thickness stress gradient respectively on springback, while the empirical model was developed using the results of L-shape bending tests. The model predictions were compared with the experiment results for various forming conditions. At room temperature, all four models had very good agreement. At elevated temperatures, the linear bending moment model was preferred for a die radius of 8mm, whereas empirical and stress gradient models were more suitable for a die radius of 4mm; in both cases, very close agreement was achieved where errors were within 5%.

Springback Behavior of an Invar Sheet and Its Perforated Form

2006 ◽  
Vol 505-507 ◽  
pp. 781-786
Author(s):  
Yi Che Lee ◽  
Fuh Kuo Chen
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Test Results ◽  
Bending Tests ◽  
Predicted Values ◽  
Springback Behavior ◽  
Good Agreement

The springback behavior of an invar sheet and its perforated form were examined in the present study. The mechanical properties for invar sheet and perforated invar-sheet at elevated temperatures were first obtained from tensile tests. The test results suggest that both invar sheet and perforated invar-sheet have favorable formability at temperature higher than 200oC. An analytical model was also established to predict the springback of the invar sheet and its perforated form under bending conditions at various elevated temperatures. In order to verify the predicted results, the V-bending tests were conducted for the invar sheet at various temperatures ranging from room temperature to 300. The experimental data indicate that the springback decreases with the rise in temperature for both invar sheet and perforated invar-sheet. The good agreement between the experimental data and the predicted values confirms the validity of the proposed theoretical model as well.

Electrical Resistivity Characterization and Modeling of Carbon Nanofiber-Polymer Suspension

2006 ◽  
Author(s):  
Kuang-Ting Hsiao ◽  
Peter Gadalla ◽  
Francis M. Donovan
Keyword(s):  
Electrical Resistivity ◽  
Empirical Model ◽  
Carbon Nanofiber ◽  
Weight Fraction ◽  
Experimental Results ◽  
Model Predictions ◽  
Electrical Resistivities ◽  
Thermal And Electrical Properties ◽  
Dc Sensor ◽  
Good Agreement

Carbon nanofibers (CNFs) and carbon nanotubes (CNTs) are considered as potential fillers for improving the mechanical, thermal, and electrical properties of polymer and polymer composites. One of the applications is to enhance the electrical conductivity of polymer by using CNFs as fillers. This kind of treatment will be useful in the situations where electrostatic dissipation capability of the polymer part is important. This paper presents an investigation of the electrical resistivities of CNF/polymer suspensions of different CNF concentrations, i.e., 2.0wt%, 3.0wt%, 4.5wt%, and 6.0wt%. For determining the electrical resistivities of the CNF/polymer suspensions, a DC-sensor was constructed and used in the experiments. The experimental results indicate that the electrical resistivity of the CNF-polyester suspension decreases as CNF weight fraction increases. In addition, the results show a dramatic decrease of the resistivity when the measurement time prolongs. An empirical model to predict the electrical resistivity evolution of the CNF/polyester suspension was proposed in this paper. Good agreement between the empirical model predictions and the experimental results was found.

Influence of Strain Gradient on Springback of Thin Pure Titanium Foils in Microbending Assisted by Resistance Heating

2016 ◽  
Vol 716 ◽  
pp. 215-224
Author(s):  
Qiu Zheng ◽  
Tetsuhide Shimizu ◽  
Ming Yang
Keyword(s):  
Grain Size ◽  
Strain Gradient ◽  
Elevated Temperatures ◽  
Pure Titanium ◽  
Bending Moment ◽  
Resistance Heating ◽  
Different Temperatures ◽  
Increasing Temperature ◽  
Titanium Foils ◽  
Good Agreement

Strain gradient is known as an important factor that influences springback of bent components in microscale. Compared with thicker foils, thinner foils usually indicate more strain gradient due to non-uniform material deformation. A resistance heating (RH) method is an effective approach to obtain homogenous material flow by heating foils within only several minutes. To predict springback of foils bent at elevated temperatures, an investigation of the influence of strain gradient on springback is indispensable. To achieve this, microbending tests assisted by RH were conducted at different temperatures ranging from 298 to 723 K in the present study. 0.05 mm-thick pure Ti foils with varying grain sizes of 2.7, 14.7, and 24.5 μm were used. As results, normalized bending moment decreased with increasing temperature and with increasing grain size. The less strain gradient of the foils with larger grain size and at elevated temperatures was confirmed to be the reason according to a theoretical analysis of springback using the constitutive model considering statically stored dislocations (SSDs) and geometrically necessary dislocations (GNDs). The predicted normalized bending moment by theoretical calculation showed good agreement with experimental results at the temperature of 573 K or higher but not at the temperature lower than 573 K. It was found that the springback of the foils was influenced by the strain gradient at low temperatures. Furthermore, the size effects caused by strain gradient reduced as the bending temperature increases.

scholarly journals Creep and Yield Loci of Zircaloy Cladding at Elevated Temperatures

1987 ◽  
Vol 7 (3) ◽  
pp. 211-226 ◽  
Author(s):  
K. Linga Murty ◽  
Ratnaji R. Kola ◽  
Sheikh T. Mahmood
Keyword(s):  
Elevated Temperatures ◽  
Cold Work ◽  
Orientation Distribution ◽  
Distribution Functions ◽  
Prism Slip ◽  
Pole Figures ◽  
Model Predictions ◽  
Yield Loci ◽  
Cold Worked ◽  
Good Agreement

Crystal plastic models are applied to textured Zircaloy in order to explain the recent experimental results on yield and creep loci by Suzuki et al. Crystallite orientation distribution functions were developed using texture pole figures obtained on cold-worked stress-relieved and recrystallized Zircaloy-4 tubings. The model predictions are in good agreement with experimental loci, and clearly point out the predominance of prism slip contribution for recrystallized material while the contribution of the basal slip increased as the amount of cold work increased.

A Hybrid Membrane/Shell Method for Rapid Estimation of Springback in Anisotropic Sheet Metals

1998 ◽  
Vol 65 (3) ◽  
pp. 671-684 ◽  
Author(s):  
F. Pourboghrat ◽  
K. Chung ◽  
O. Richmond
Keyword(s):  
Plane Strain ◽  
Yield Criterion ◽  
Bending Moment ◽  
Isotropic Hardening ◽  
Normal Anisotropy ◽  
Bending Tests ◽  
Reverse Loading ◽  
Draw Bending ◽  
Springback Prediction ◽  
Good Agreement

A semi-analytical method to predict springback in sheet metal forming processes has been developed for the case of plane strain. In the proposed hybrid method, for each deformation increment, bending, and unbending stretches are analytically superposed on membrane stretches which are numerically obtained in advance from a membrane finite element code. Springback is then obtained by the unloading of a force and a bending moment at the boundary of each element treated as a shell. Hill’s 1948 yield criterion with normal anisotropy is used in this theory along with kinematic and isotropic hardening laws during reverse loading. The method has been applied for the springback prediction of a 2008-T4 aluminum alloy in plane-strain draw-bending tests. The results indicate the necessity of including anisotropic hardening (especially Bauschinger effects) and elastoplastic unloading in order to achieve good agreement with experimental results.

Tube Bending Under Axial Force and Internal Pressure

2005 ◽  
Vol 128 (2) ◽  
pp. 598-605 ◽  
Author(s):  
Jyhwen Wang ◽  
Rohit Agarwal
Keyword(s):  
Internal Pressure ◽  
Axial Force ◽  
Shape Control ◽  
Analytical Models ◽  
Thickness Variation ◽  
Tube Bending ◽  
Cross Sectional ◽  
Thickness Change ◽  
Model Predictions ◽  
Good Agreement

Tube bending is a widely used manufacturing process in the aerospace, automotive, and various other industries. During tube bending, considerable in-plane distortion and thickness variation occurs. Additional loadings such as axial force and internal pressure can be used to achieve better shape control. Based on plasticity theories, analytical models are developed to predict cross-sectional distortion and thickness change of tubes under various loading conditions. The model predictions are in good agreement with finite element simulations and published experimental results. The models can be used to evaluate tooling and process design in tube bending.

Assessment of the load carrying performance of composite cross joints

2019 ◽  
Vol 54 (11) ◽  
pp. 1431-1439
Author(s):  
Liyang Liu ◽  
Mengfei Cai ◽  
Xiaoliang Geng ◽  
Peiyan Wang ◽  
Zhufeng Yue
Keyword(s):  
Damage Model ◽  
Bending Moment ◽  
Comparative Assessment ◽  
Progressive Damage ◽  
Bending Tests ◽  
Air Inlet ◽  
Four Point Bending ◽  
Load Carrying ◽  
Progressive Damage Model ◽  
Good Agreement

Composite cross joints are common structures in an airframe. When this type of joint is used on an air inlet stiffened structure, it will undertake large bending moment, especially under overpressure of the engine. In this paper, two types of cross joints are tested experimentally and simulated to investigate the load bearing characteristics and make comparative remarks. Four-point bending tests are conducted and the load deflection curves are obtained; besides, the damage pattern of the joints is reported. Based on composite progressive damage model, the numerical simulations have a good agreement with experimental results, revealing the joint failure mechanism and fastener force feature of various joints. The comparative assessment of two types of joints is summarized.

Rigid-Plastic Impact of Single Angular Particles

2021 ◽  
Author(s):  
Sandeep Dhar
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Orientation Dependence ◽  
Particle Orientation ◽  
Rigid Plastic ◽  
Plastic Model ◽  
Model Predictions ◽  
Good Agreement ◽  
Angular Particles

The trajectory of an angular particle as it cuts a ductile target is, in general, complicated because of its dependence not only on particle shape, but also on particle orientation at the initial instant of impact. This orientation dependence has also made experimental measurement of impact parameters of single angular particles very difficult, resulting in a relatively small amount of available experimental data in the literature. The current work is focused on obtaining measurements of particle kinematics for comparison to rigid plastic model developed by Papini and Spelt. Fundamental mechanisms of material removal are identified, and measurements of rebound parameters and corresponding crater dimensions of single hardened steel particles launched against flat aluminium alloy targets are presented. Also a 2-D finite element model is developed and a dynamic analysis is performed to predict the erosion mechanism. Overall, a good agreement was found among the experimental results, rigid-plastic model predictions and finite element model predictions.

Viscosity Models Based on Network Theory for Polymer Melts

2010 ◽  
Vol 129-131 ◽  
pp. 1244-1247
Author(s):  
Hai Hang Xu ◽  
Lei Zhong
Keyword(s):  
Experimental Data ◽  
Kinetic Equation ◽  
Constitutive Equation ◽  
Polymer Composites ◽  
Network Theory ◽  
Polymer Melts ◽  
Structure Parameter ◽  
Viscosity Models ◽  
Model Predictions ◽  
Good Agreement

New shear and extensional viscosity models based on Fredrickson kinetic equation coupled with Dewitt constitutive equation were established to predict viscosities of polymer melts. The experimental data of 125°C LDPE and LDPE filled with 35% glass beads reported from references were compared with the model predictions. The predictions showed good agreement with the measurements. The models are simple and easy to use. Because they contain no structure parameter, they are capable to describe the viscosities of pure polymer and polymer composites.

Experimental Investigation on the Effect of Arm Length on Accuracy of Torque Wrench

2016 ◽  
Vol 853 ◽  
pp. 216-220 ◽  
Author(s):  
You Gang Peng ◽  
Yong Wang
Keyword(s):  
Experimental Investigation ◽  
Structural Design ◽  
Bending Moment ◽  
Theoretical Solution ◽  
Calibration Laboratory ◽  
Moment Measurement ◽  
Torque Wrench ◽  
Actual Use ◽  
Good Agreement

Experiments were carried out to investigate the effect of arm length on the accuracy of two typical conventional torque wrenches, namely, setting type torque wrench (STW) and indicating type torque wrench (ITW). The experiment results demonstrate that the measurement values of STW rises rapidly with decreasing arm length while measured torque of ITW shows irrelevant to arm length. Theoretical solution with respect to STW shows quite good agreement with experiment results. Irrelevance of arm length regard to ITW may be attributable to compensation of bending moment measurement due to proper arrangement of circuit and structural design. In order to conduct a proper assessment at a calibration laboratory or ensure its reliability with reference to actual use conditions, a torque wrench should be used by a customer at the loading point as recommended.

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