Failure Prediction of Tubular Hydroforming Process Following Pre-Bending

2003 ◽  
Author(s):  
Z. C. Xia
Keyword(s):  
Forming Limit Diagram ◽  
Forming Limit ◽  
Straight Tube ◽  
Production Environment ◽  
Damage Growth ◽  
Complex Process ◽  
Metal Stamping ◽  
Bending Process ◽  
Hydroforming Process ◽  
Automotive Parts

Tubular hydroforming process for a majority of automotive parts is a complex process where the initially straight tube undergoes a series of pre-bending, pre-forming, die closure and then the final pressurization. The pre-bending process is usually carried out by a rotary bending machine and utilizes an inside mandrel to prevent the tube from collapsing during bending. Because of the high pressure exerted by the mandrel in the normal direction of the tube sheet, the failure mechanism for the tube in the subsequent hydroforming process will differ significantly from that experienced in sheet metal stamping process, which can be well characterized by the Forming Limit Diagram (FLD). The presentation begins with experimental evidence of material failure during hydroforming following pre-bending, and continues with two predictive models for analysis. One is a Gurson-type void growth model, and the other a damage based model which takes into account the effect of hydrostatic pressure in damage growth. Numerical examples are given to illustrate the effectiveness of both models and are compared to experimental data. Their applicability in an industrial production environment is discussed.

Optimization of Tube Hydroforming Process Using Probabilistic Constraints on Failure Modes

2011 ◽  
Vol 62 ◽  
pp. 21-35 ◽  
Author(s):  
Anis Ben Abdessalem ◽  
A. El Hami
Keyword(s):  
Failure Modes ◽  
High Reliability ◽  
Thickness Distribution ◽  
Tube Hydroforming ◽  
Forming Limit Diagram ◽  
Plastic Instability ◽  
Probabilistic Constraints ◽  
Forming Limit ◽  
Reliability Based Design ◽  
Hydroforming Process

In metal forming processes, different parameters (Material constants, geometric dimensions, loads …) exhibits unavoidable scatter that lead the process unreliable and unstable. In this paper, we interest particularly in tube hydroforming process (THP). This process consists to apply an inner pressure combined to an axial displacement to manufacture the part. During the manufacturing phase, inappropriate choice of the loading paths can lead to failure. Deterministic approaches are unable to optimize the process with taking into account to the uncertainty. In this work, we introduce the Reliability-Based Design Optimization (RBDO) to optimize the process under probabilistic considerations to ensure a high reliability level and stability during the manufacturing phase and avoid the occurrence of such plastic instability. Taking account of the uncertainty offer to the process a high stability associated with a low probability of failure. The definition of the objective function and the probabilistic constraints takes advantages from the Forming Limit Diagram (FLD) and the Forming Limit Stress Diagram (FLSD) used as a failure criterion to detect the occurrence of wrinkling, severe thinning, and necking. A THP is then introduced as an example to illustrate the proposed approach. The results show the robustness and efficiency of RBDO to improve thickness distribution and minimize the risk of potential failure modes.

Reliability Analysis of the Tube Hydroforming Process Based on Forming Limit Diagram

2005 ◽  
Vol 128 (3) ◽  
pp. 402-407 ◽  
Author(s):  
Bing Li ◽  
Don R. Metzger ◽  
Tim J. Nye
Keyword(s):  
Automotive Industry ◽  
Metal Forming ◽  
Tube Hydroforming ◽  
Forming Limit Diagram ◽  
Probability Of Failure ◽  
Alternative Methods ◽  
Forming Limit ◽  
Forming Process ◽  
Hydroforming Process ◽  
Free Bulging

Tube hydroforming is an attractive manufacturing process in the automotive industry because it has several advantages over alternative methods. In order to determine the reliability of the process, a new method to assess the probability of failure is proposed in this paper. The method is based on the reliability theory and the forming limit diagram, which has been extensively used in metal forming as the criteria of formability. From the forming limit band in the forming limit diagram, the reliability of the forming process can be evaluated. A tube hydroforming process of free bulging is then introduced as an example to illustrate the approach. The results show this technique to be an innovative approach to avoid failure during tube hydroforming.

M–K Analysis of Forming Limit Diagram Under Stretch-Bending

2012 ◽  
Author(s):  
Ji He ◽  
Z. Cedric Xia ◽  
Shuhui Li ◽  
Danielle Zeng
Keyword(s):  
Sheet Metal ◽  
Deformation Theory ◽  
Plane Deformation ◽  
Forming Limit Diagram ◽  
Flow Theory ◽  
Forming Limit ◽  
Bending Effect ◽  
Stretch Bending ◽  
Right Hand ◽  
Bending Process

Since the Forming limit diagram (FLD) was introduced and developed by Keeler etc. about four decades ago, it has been intensively studied by researchers and engineers. Most work has been focused on the in-plane deformation which is considered as the dominant mode of the most forming processes. However the effect of out-of-plane deformation modes especially bending effect becomes important in accurate prediction of formability when thick sheet metal and smaller forming radii are encountered. Recent work on experiment research of stretch-bending induced FLD (BFLD) shows that it gives higher formability than conventional forming limit. In this paper, bending effect through the sheet metal thickness on right-hand side of FLD is studied. The Marciniak-Kuczynski (M-K) analysis is extended to include bending and models based on both flow theory and deformation theory are proposed. The radial return method is adopted as the frame to calculate the stress states from given strain and deformation history. The effect of bending and unbending process on the Right-Hand-Side FLD is investigated and compared. The obtained results show that the bending process slightly decreases the sheet metal formability on right-hand side in flow theory based model which is a discrepancy with the prediction of deformation theory based BFLD model. The insight gained from new proposed FLD prediction model in this paper provides an understanding of how the bending process effects on the FLD. This is important for the further research to reconsider the problems of how the bending effect evolves in forming process to enhance the conventional FLD and how to get a perfectly true theoretical explanation for this phenomenon.

Improving Formability in Sheet Metal Stamping With Active Drawbead Technology

2000 ◽  
Vol 123 (4) ◽  
pp. 504-510 ◽  
Author(s):  
M. L. Bohn ◽  
S. G. Xu ◽  
K. J. Weinmann ◽  
C. C. Chen ◽  
A. Chandra
Keyword(s):  
Strain Distribution ◽  
Forming Limit Diagram ◽  
Temporal Variations ◽  
Forming Limit ◽  
Sheet Metal Stamping ◽  
Metal Stamping ◽  
Comparison Of The Results ◽  
Restraining Force ◽  
Diagram Analysis ◽  
Good Agreement

Aluminum is expected to gain popularity as material for the bodies of the next generation of lighter and more fuel-efficient vehicles. However, its lower formability compared with that of steel tends to create considerable problems. A controllable restraining force caused by adjusting the penetration of drawbeads can improve the formability. This paper describes the effects of temporal variations in drawbead penetration on the strain distribution in a symmetric stamped part. Comparison of the results of numerical simulations with the corresponding experimental results shows that the predictions of strain distribution on the panel are in very good agreement. Furthermore, forming limit diagram analysis indicates that the active drawbead concept is beneficial to the formability of AA 6111-T4.

Reliability Analysis of the Tube Hydroforming Process Based on Forming Limit Diagram

2003 ◽  
Author(s):  
Bing Li ◽  
Don R. Metzger ◽  
T. J. Nye
Keyword(s):  
Tube Hydroforming ◽  
Forming Limit Diagram ◽  
Alternative Methods ◽  
Forming Limit ◽  
Process Conditions ◽  
Forming Process ◽  
Element Simulation ◽  
Hydroforming Process ◽  
Free Bulging ◽  
The Relationship

Tube hydroforming has become an increasingly attractive manufacturing process in automotive industry due to it having several advantages over alternative methods. The forming limit diagram has been extensively used in metal forming as the criteria of formability. A method to assess the probability of failure of the process based on reliability theory and the forming limit diagram is proposed in this paper. The tube hydroforming process is affected by many parameters such as geometry, material properties, and process conditions. Finite element simulation was used to predict the relationship between the strain and these parameters, and a numerical method was applied to get the statistical distribution of the strain. Based on the forming limit band in the forming limit diagram, the reliability of the forming process can be evaluated. A tube hydroforming process of free bulging is then introduced as an example to illustrate the approach. The results show this reliability evaluation technique to be an innovative approach for product designers and process engineers to avoid failure during tube hydroforming.

Improving Formability in Sheet Metal Stamping With Active Drawbead Technology

2000 ◽  
Author(s):  
M. L. Bohn ◽  
S. G. Xu ◽  
K. J. Weinmann ◽  
C. C. Chen ◽  
A. Chandra
Keyword(s):  
Strain Distribution ◽  
Forming Limit Diagram ◽  
Temporal Variations ◽  
Forming Limit ◽  
Sheet Metal Stamping ◽  
Metal Stamping ◽  
Comparison Of The Results ◽  
Restraining Force ◽  
Diagram Analysis ◽  
Good Agreement

Abstract Aluminum is expected to gain popularity as material for the bodies of the next generation of lighter and more fuel-efficient vehicles. However, its lower formability compared with that of steel tends to create considerable problems. A controllable restraining force caused by adjusting the penetration of drawbeads can improve the formability. This paper describes the effects of temporal variations in drawbead penetration on the strain distribution in a symmetric stamped part. Comparison of the results of numerical simulations with the corresponding experimental results shows that the predictions of strain distribution on the panel are in very good agreement. Furthermore, forming limit diagram analysis indicates that the active drawbead concept is beneficial to the formability of AA 6111-T4.

Hydroforming analysis of exhaust pipe connectors

2020 ◽  
Vol 62 (9) ◽  
pp. 901-908
Author(s):  
S. Ozmen Eruslu ◽  
R. Marangoz ◽  
I. S. Dalmış
Keyword(s):  
Residual Stress ◽  
Fem Analysis ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Exhaust Pipe ◽  
Minimum Thickness ◽  
Element Analysis ◽  
Deformation And Failure ◽  
Process Pressure ◽  
Hydroforming Process

Abstract In this work, a hydroforming analysis of an exhaust pipe clamp adaptor made of galvalume steel was performed. Deformation and failure of galvalume exhaust pipe connectors and its coatings via the hydroforming process were studied. An explicit type (LsDyna) numerical analysis approach was adapted for the development of the hydroforming process. Pressure rate, unconstraint length, residual stress, strain hardening, and spring-back effects were considered in the analysis. The failure of tubular parts was evaluated via a forming limit diagram (FLD) according to Hill- Swift criteria. The hydroforming process was developed according to three models, which are found in the safety forming region of FLD studies. Minimum thickness values obtained from the experiments were compared with finite element analysis (FEM). The maximum percentage thinning ratio in the tubular section was more than 18 - % at 65 MPa internal pressure. The relationship between thickness reduction at plastically work hardening regions and residual stress was discussed. The deformation characteristics of the produced connector headers were also analyzed by scanning electron microscopy (SEM) and micro Vickers hardening measurements. The FEM analysis and FLD examination indicated that the failure did not occur in hydroformed specimens, whereas damage was observed at coated’ plastic work regions through microscopical investigation.

M–K Analysis of Forming Limit Diagram Under Stretch-Bending

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Ji He ◽  
Z. Cedric Xia ◽  
Shuhui Li ◽  
Danielle Zeng
Keyword(s):  
Deformation Theory ◽  
Plane Deformation ◽  
Forming Limit Diagram ◽  
Flow Theory ◽  
Dominant Mode ◽  
Forming Limit ◽  
Thick Sheet ◽  
Bending Effect ◽  
Stretch Bending ◽  
Bending Process

Since the forming limit diagram (FLD) was introduced by Keeler, etc., five decades ago, it has been intensively studied by researchers and engineers. Most work has focused on the in-plane deformation which is considered as the dominant mode of the majority forming processes. However the effect of out-of-plane deformation becomes important in the accurate prediction of formability when thick sheet metals and/or smaller forming radii are encountered. Recent research on the stretch-bending induced FLD (BFLD) has been inconclusive. Some studies indicated that the bending effect will enhance a sheet metal's formability while others suggested otherwise. In this paper, we present an in-depth study of the through-thickness bending effect on the forming limits. The Marciniak–Kuczynski (M–K) analysis is extended to include bending, and models based on both flow theory and deformation theory of plasticity are proposed. The study is limited to the right-hand-side of FLD where the bending is along the major stretch direction. The radial return method is adopted as the framework to integrate constitutive equations. The results show that the bending process decreases the sheet metal formability with the flow-theory based model, while the opposite is true if the deformation theory based analysis is adopted. A detailed examination of the deformation histories from those two models reveals that the loading–unloading-reverse loading process during stretch-bending holds the key to the understanding of the conflicting results. The insight gained from the proposed FLD prediction model in this paper provides a new understanding of how the bending process affects the FLD, which can be used to predict and explain the localized necking phenomenon under the stretch-bending condition.

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