An Experimental and Numerical Study on Forming Force, Fracture Behavior, and Strain States in Two Point Incremental Forming Process

2016 ◽  
Vol 725 ◽  
pp. 586-591
Author(s):  
Chen Hao Wang ◽  
William J.T. Daniel ◽  
Hai Bo Lu ◽  
Sheng Liu ◽  
Paul Anthony Meehan
Keyword(s):  
Plastic Strain ◽  
Fracture Behavior ◽  
Numerical Study ◽  
Equivalent Plastic Strain ◽  
Fem Simulation ◽  
Forming Force ◽  
Forming Process ◽  
Approaches To Study ◽  
Tool Diameter ◽  
Numerical Approaches

Two-point incremental sheet forming process (TPIF) is an emerging and promising manufacturing process for the production of complex geometries or customized functional sheet components. In this study, the single-pass TPIF process is investigated using experimental and numerical approaches to study the forming force evolution, fracture behavior and strain states with a varied wall angle hemisphere shape. It can be concluded that both the peak force and fracture depth increases with tool diameter and incremental depth in TPIF process. It seems the deformation mechanism or the failure mechanism is strongly dependent on particular forming conditions based on a failure parts morphology observation. FEM simulation results indicated that the major plastic strain is positive while the minor plastic strain is negative in the TPIF process on a hemiphere shape. it can be concluded that the strain increment and total equivalent plastic strain is affected by both tool diameter and incremental depth.

scholarly journals Strain Rate-Dependent Constitutive and Low Stress Triaxiality Fracture Behavior Investigation of 6005 Al Alloy

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Yong Peng ◽  
Xuanzhen Chen ◽  
Shan Peng ◽  
Chao Chen ◽  
Jiahao Li ◽  
...  
Keyword(s):  
Flow Stress ◽  
Plastic Strain ◽  
Strain Rate ◽  
Fracture Behavior ◽  
Equivalent Plastic Strain ◽  
Stress Triaxiality ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Stress States

In order to study the dynamic and fracture behavior of 6005 aluminum alloy at different strain rates and stress states, various tests (tensile tests at different strain rates and tensile shearing tests at five stress states) are conducted by Mechanical Testing and Simulation (MTS) and split-Hopkinson tension bar (SHTB). Numerical simulations based on the finite element method (FEM) are performed with ABAQUS/Standard to obtain the actual stress triaxialities and equivalent plastic strain to fracture. The results of tensile tests for 6005 Al show obvious rate dependence on strain rates. The results obtained from simulations indicate the feature of nonmonotonicity between the strain to fracture and stress triaxiality. The equivalent plastic strain reduces to a minimum value and then increases in the stress triaxiality range from 0.04 to 0.30. A simplified Johnson-Cook (JC) constitutive model is proposed to depict the relationship between the flow stress and strain rate. What is more, the strain-rate factor is modified using a quadratic polynomial regression model, in which it is considered to vary with the strain and strain rates. A fracture criterion is also proposed in a low stress triaxiality range from 0.04 to 0.369. Error analysis for the modified JC model indicates that the model exhibits higher accuracy than the original one in predicting the flow stress at different strain rates. The fractography analysis indicates that the material has a typical ductile fracture mechanism including the shear fracture under pure shear and the dimple fracture under uniaxial tensile.

Evaluation of Ductile Cracking Criterion for Grade X100 Linepipe and Relationship to Large Scale Fracture Behavior

2003 ◽  
Author(s):  
Nobuyuki Ishikawa ◽  
Shigeru Endo ◽  
Alan Glover ◽  
David Horsley ◽  
Masao Toyoda
Keyword(s):  
Plastic Strain ◽  
Ductile Fracture ◽  
Fracture Behavior ◽  
Large Scale ◽  
Notch Root ◽  
Equivalent Plastic Strain ◽  
High Strength ◽  
Fracture Initiation ◽  
Linepipe Steels ◽  
Ductile Fracture Initiation

Recent developments in the manufacturing process of steel plate for high strength linepipe have enabled superior toughness to prevent brittle fracture of the pipe body. Techniques for non-destructive inspection have also improved, and large flaws that could lead to brittle fracture are highly unlikely in recent high strength pipelines. However, large amounts of plastic deformation can be expected in seismic or permafrost regions. Prevention of ductile fracture of the pipe body or weldment therefore becomes a key issue in defining the tensile strain limit. Ductile fracture is considered to occur by growth and coalescence of voids, and is affected by stress triaxiality and plastic straining at the cracked region. Although many studies have been carried out to evaluate ductile cracking criteria, its transferability to large-scale fracture behavior has not been thoroughly investigated. In this study, ductile cracking of high strength linepipe steels, Grade X80 and X100, was investigated. Notched round bar specimens with different notch root radii were tested to determine the precise conditions for initiation of ductile fracture. Stress and strain conditions at the notch regions were evaluated by FE analysis, and the “critical equivalent plastic strain” was defined at conditions corresponding to ductile fracture initiation in the experimental small specimen tests. Ductile crack initiation behavior was also determined for wide plate test specimens by making close observations of the notch root area. 3-D FE analysis of the wide plate tensile test showed that the equivalent plastic strain at the point of ductile fracture initiation was in close agreement with that in the notched round bas specimen. Thus, the “critical equivalent plastic strain,” determined by small notched round bar specimens, can be considered as a transferable criterion to predict large-scale fracture behavior in wide plate tests. Concepts of strain based design in terms of preventing ductile failure from a surface flaw by applying critical strain to cracking were also discussed in this paper. Results were compared to conventional grade linepipe steels and structural steels, showing that recent high strength linepipe steels have higher resistance to ductile cracking than conventional structural steels. In addition, 3-D FE analyses were used in a parametric study to determine the effects of Y/T and uniform strain on the onset of ductile cracking behaviour. The results of these analyses show the relative importance of materials properties on the resistance to ductile cracking.

Numerical Study on Forming Process by Continuous Resistance Heating

2010 ◽  
Vol 154-155 ◽  
pp. 867-872
Author(s):  
Zheng Xing Men ◽  
Jie Zhou ◽  
Meng Han Wang ◽  
Chang Wei Shao
Keyword(s):  
Temperature Distribution ◽  
Contact Resistance ◽  
Numerical Study ◽  
Mechanical Analysis ◽  
Transient Temperature ◽  
Resistance Heating ◽  
Forming Force ◽  
Forming Process ◽  
Billet Temperature ◽  
Die Geometry

In the present study, an axis-symmetric electro-thermo-mechanical model has been developed to analyze a deformation process by continuous resistance heating. To obtain the transient temperature field prior to forming, a novel temperature-dependent model of the contact resistance was developed in the thermal-electrical analysis. The influences of the contact resistance, the current intensity and the die geometry on the temperature distribution were investigated. In the subsequent electro-thermo-mechanical analysis of the forming process by continuous resistance heating, the variations of the billet temperature distribution, forming force were obtained. The simulation results correspond well with experimental measured values. Furthermore, the influence of a current increasing during forming on the billet temperature and forming force was predicted in order to optimize the forming technology by continuous resistance heating.

scholarly journals A Numerical Study on the Effect of Variable Wear Coefficient on Fretting Wear Characteristics

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1840
Author(s):  
Shengjie Wang ◽  
Magd Abdel Wahab
Keyword(s):  
Plastic Strain ◽  
Numerical Study ◽  
Equivalent Plastic Strain ◽  
Fretting Wear ◽  
Partial Slip ◽  
The Finite Element Method ◽  
Wear Coefficient ◽  
Wear Characteristics ◽  
Slip Regime ◽  
The Difference

Fretting wear is a common phenomenon that happens between contact parts when there is an oscillatory relative movement. To investigate wear characteristics history in the fretting process, the finite element method (FEM) is commonly applied to simulate the fretting by considering the wear in the model. In most literature publications, the wear coefficient is considered as a constant, which is not a real case based on the experimental results. To consider the variation of wear coefficient, a double-linear model is applied in this paper, and the tribologically transformed structure (TTS) phase is considered in the study of the wear coefficient variation model. By using these models for variable wear coefficient for both flat and cylinder, the difference of wear characteristics, plastic strain, and stress between variable wear coefficient model (VWCM) and constant wear coefficient model (CWCM) are analyzed. The results show that the variable wear coefficient has no significant effect on the wear characteristic at the end of the process in the gross sliding regime. However, in the partial slip regime, the effect of variable wear coefficient on wear characteristics is significant. Due to the difference in contact geometry in the fretting process between VWCM and CWCM, the tangential and shear stress and equivalent plastic strain also show differences during the fretting process.

Numerical and Experimental Studies on Hydro-Forming of a Thin Metallic Disc

2022 ◽  
Vol 1048 ◽  
pp. 270-278
Author(s):  
Kanakadandi Gopinath ◽  
Vijayabaskar Narayanamurthy ◽  
Yendluri Venkata Daseswara Rao
Keyword(s):  
Plastic Strain ◽  
Fluid Pressure ◽  
Experimental Studies ◽  
Equivalent Plastic Strain ◽  
Sheet Thickness ◽  
Isotropic Hardening ◽  
Hydraulic Pressure ◽  
Forming Process ◽  
Element Analysis ◽  
Explicit Finite Element

This paper deals with the hydro-forming of a flat thin metallic disc to achieve a forward domed disc which will be subsequently adopted to manufacture a rupture disc. The plastic deformation induced by the hydraulic energy is numerically simulated through an isotropic hardening plasticity model using a non-linear explicit finite element analysis (FEA). The variation in disc’s central deformation, thickness, equivalent plastic stress and equivalent plastic strain with respect to the applied hydraulic pressure are determined from FEA simulations. The hydro-forming setup is then designed and manufactured, and the metallic disc is experimented under hydro-forming process. The reduction in thickness due to stretching of the thin disc is evaluated from experiment and simulation and a close agreement is found. This research attempt helped in finalizing the hydro-forming fluid pressure, the feasibility and the accuracy of practically achieving the desired geometry of the metallic disc. The near-fixidity effects on abrupt variation in sheet thickness and plastic strain are well captured through simulations which are very difficult to be studied through hydro-forming experiments.

FEM Simulation of Main Deformation during Cage Roll-Forming Process

2013 ◽  
Vol 395-396 ◽  
pp. 1239-1242
Author(s):  
Sheng De Hu ◽  
Jing Zhang ◽  
Li Xin Li ◽  
Yong Liu
Keyword(s):  
Plastic Strain ◽  
High Frequency ◽  
Fem Simulation ◽  
Element Model ◽  
Roll Forming ◽  
Effective Plastic Strain ◽  
Linear Section ◽  
Forming Process ◽  
Roll Forming Process ◽  
Main Deformation

Cage roll-forming is an advanced roll-forming technique widely used in high frequency welding (HFW) pipes production. However, to the authors' knowledge, the real cage roll-forming production is mainly on experience rather than science. Few publications can be found on cage roll-forming for its complexity. In order to improve the understanding of the technique, a large deformation elastic-plastic finite element model for the HFW660 cage roll-forming mill was established and simulated through adopting the dynamic explicit algorithm. The distribution of effective plastic strain and the deformed geometry of the strip at the pre-forming and linear section were obtained. The simulation results were validated with the measurements. The results show that the biggest effective plastic strain (EPS) occurs at the center of strip. The distribution of EPS is far from uniform on the cross-section of the strip. This may owe to the uneven distribution of down-hill amount.

Influences of Process Parameters on Forming Performance of Sheet Metal Incremental Forming Based on Numerical Simulation

2012 ◽  
Vol 562-564 ◽  
pp. 294-297
Author(s):  
Jun Chao Li ◽  
Pei Geng ◽  
Jun Jie Pan
Keyword(s):  
Process Parameters ◽  
Influence Factor ◽  
Thickness Distribution ◽  
Equivalent Plastic Strain ◽  
Forming Force ◽  
Wall Angle ◽  
Sheet Metal Incremental Forming ◽  
Experimental Approaches ◽  
Tool Diameter ◽  
Depth Increment

In order to investigate the process of ISF through numerical and experimental approaches, finite element method (FEM) models for two truncated pyramids were developed to simulate the process and the simulated thickness distributions were compared with experimental results. The influences of process parameters on equivalent plastic strain, the maximum equivalent plastic stress and forming force were also discussed. The results show that ISF process is basically to be a plane strain deformation. Wall angle is a more significant influence factor of forming performance than tool diameter and depth increment. With increasing tool diameter, decreasing wall angle and step increment, uniform thickness distribution will be achieved. However, more wall angel, less tool diameter and depth increment contributes to decrease forming force. Additionally, process parameters have no connection with work hardening for a certain material during ISF.

Analyzing Fracture Behavior of Beam-Column Joints Using Micromechanical Fracture Models

2015 ◽  
Vol 744-746 ◽  
pp. 3-7
Author(s):  
Chen Zhang ◽  
Yu Ping Sun ◽  
Ju Tao Zhang ◽  
Yu Gu
Keyword(s):  
Finite Element ◽  
Plastic Strain ◽  
Fracture Behavior ◽  
Equivalent Plastic Strain ◽  
Stress Triaxiality ◽  
Bolted Connection ◽  
Finite Element Software ◽  
Maximum Value ◽  
Fracture Models ◽  
Welded Connection

The micromechanical fracture models were used to study the fracture behavior of the welded connection and welded-bolted connection joints. The Void Growth Model was implemented in commercial finite element software ABAQUS through the user-defined subroutines. The results predicted that cracks initiated at the edge of the welds and extended along the length and thickness of the welds. Comparing the effects of equivalent plastic strain and stress triaxiality for the fracture of the first failure element of both beam-to-column joints, we found that the equivalent plastic strain grew linearly as the loads increased and the weld of the lower flange generated cracks when the stress triaxiality increased at maximum value.

Finite Element Analysis for the Roll Forming Process of Rib

2018 ◽  
Vol 878 ◽  
pp. 302-307
Author(s):  
Dong Won Jung
Keyword(s):  
Finite Element ◽  
Plastic Strain ◽  
Equivalent Plastic Strain ◽  
Von Mises Stress ◽  
Roll Forming ◽  
Thickness Variation ◽  
Forming Process ◽  
Element Analysis ◽  
High Production Rate ◽  
Roll Forming Process

Roll forming is a continuous profile production process to form sheet metal progressively into the desired shape with closer tolerances. The process offers several advantages such as complex geometrical shapes, high strength, dimensional accuracy, closer tolerances, better quality and consistency, high production rate, improved conformity, and good surface finish. Several parts of automobile body are produced with this process. Nowadays roll forming technology draws more attentions than before in the automotive industry. In this paper, A Finite Element Method applied to study von mises stress, equivalent plastic strain, thickness, plastic strain, longitudinal strain and spring back of the metal sheet with ribs formed by roll forming process. The thickness variation was almost -6.144%.

Schwingungsüberlagertes Axialformen/Superimposed Oscillated Axial Forming

2020 ◽  
Vol 110 (11-12) ◽  
pp. 838-843
Author(s):  
Philipp Müller ◽  
Bernd-Arno Behrens ◽  
Sven Hübner ◽  
Hendrik Vogt ◽  
Daniel Rosenbusch ◽  
...  
Keyword(s):  
Surface Quality ◽  
Economic Importance ◽  
Combined Effect ◽  
Wird Eine ◽  
Forming Force ◽  
Forming Process ◽  
Forming Technology ◽  
Great Economic Importance ◽  
Gear Geometry

Techniken zur Steigerung der Formgebungsgrenzen in der Umformtechnik sind von hoher wirtschaftlicher Bedeutung. In dieser Arbeit wird eine Schwingungsüberlagerung im Krafthauptfluss eines Axialformprozesses zur Ausprägung einer Verzahnungsgeometrie untersucht. Die Auswirkungen der Schwingung auf die erzielbare Ausfüllung der Zahnkavitäten werden analysiert sowie die Parameter Schmierung und Oberflächengüte der Halbzeuge in ihrer kombinierten Wirkung untersucht. Es konnte eine Reduzierung der mittleren Umformkraft sowie eine Erhöhung der Formfüllung festgestellt werden. Techniques for extending the production limits in forming technology are of great economic importance. In this research, a superimposed oscillation in the main force flow of an axial forming process to form an axial gear geometry is investigated. The effects of the superimposed oscillation on the achievable form-filling of the tooth cavities are analyzed and the parameters lubrication and surface quality of the semi-finished products are investigated in their combined effect. A reduction of the averaged forming force as well as an increase of the form-filling could be achieved.

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