Experimental and Numerical Studies of Welded Tubes Formability

2009 ◽  
Vol 614 ◽  
pp. 129-134 ◽  
Author(s):  
A. Ayadi ◽  
Abel Cherouat ◽  
Mohammed Ali Rezgui ◽  
Najeh Mezghani
Keyword(s):  
Experimental Study ◽  
Heat Affected Zone ◽  
Constitutive Equations ◽  
Tube Hydroforming ◽  
Global Measure ◽  
Anisotropic Hardening ◽  
Material Parameters ◽  
Numerical Studies ◽  
Displacement Thickness ◽  
Welded Tube

This paper presents a numerical methodology which aims to improve 3D welded tube hydroforming formability. This methodology is based on elastoplastic constitutive equations accounting for non-linear anisotropic hardening. The experimental study is dedicated to the identification of material parameters (the parent and the heat-affected zones) using the global measure response of tube displacement, thickness evolution and internal pressure expansion. Applications are made to study numerically the effect of the anisotropic parameters, the hardening flow and the heat-affected zone shape on the hydro-formability of welded tubes.

Reliability Based Design Optimisation of Hydroformed Welded Tubes

2011 ◽  
Vol 423 ◽  
pp. 31-52
Author(s):  
Ayadi Mahfoudh ◽  
Abel Cherouat ◽  
A. El Hami ◽  
Bouchaib Radi
Keyword(s):  
Heat Affected Zone ◽  
Raw Materials ◽  
Thickness Distribution ◽  
Basic Material ◽  
Nanoindentation Test ◽  
Reliability Based Design ◽  
Displacement Thickness ◽  
Welded Tube ◽  
Hydroforming Process ◽  
Assembly Operations

This paper presents an experimental/numerical methodology which aims to improve 3D welded tube considering their anisotropic effect, geometrical singularities found in the welded joint, and heat affected zone behaviour by hydroforming process. This process contributes to reduce the number of welding and assembly operations needed to generate complex structures, while improving the weight saving and quality of finished parts. In spite of the advances in the performance of this manufacturing technology, some problems are linked to particularities of certain raw materials and additional studies must be developed, like in the case of welded tubes. The experimental study is dedicated to the identification of stress-strain flow of the base metal and the heat-affected zone from the global measure of tube displacement, thickness evolution and internal pressure expansion. Nanoindentation test is adapted to investigate the heat affected zone mechanical behaviour. Workpiece behaviour's models used to simulate the expansion tests, made it possible to highlight the combined effects of the inhomogeneous behaviour of basic material and heat affected zone, as well as the geometrical singularities found in the welded tubes. From the simulations carried out, it is clear the influence of the plastic flow behaviour of the welded tube in the final results (thickness distribution, stress instability, tube circularity, critical thinning and rupture).

scholarly journals Material Characteristics Evaluation for DC04-Welded Tube Hydroforming

2021 ◽  
Author(s):  
Liqun Niu ◽  
Qi Zhang ◽  
Bin Han
Keyword(s):  
Work Hardening ◽  
Tube Hydroforming ◽  
Strain Curve ◽  
Prediction Equation ◽  
Approximate Determination ◽  
Test Machine ◽  
Sheet Blank ◽  
Material Characteristics ◽  
Welded Tube ◽  
Strain Stress

Abstract Tube hydroforming (THF) technology is widely applied, especially in the automotive and aircraft industries. Material characteristics of tubular workpieces should be evaluated in terms of bending and THF processes. A mathematical model, which combines the assumption of elliptical contour of a bulged wall and the prediction equation of wall thickness, is provided to analyze the THF process and to obtain the strain-stress relationship of tubes. Material characteristics of a DC04-welded tube is obtained by using a self-designed THF test machine. Considering the effects of pre-work hardening, we discuss the material strain-stress relationships of the tube and original sheet blank. An approximate determination method is proposed to obtain the stress-strain curve of the tube by using the curve of the original sheet blank and the hardness of the tube and sheet blank. A suitable constitutive equation with pre-work hardening is applied to the DC04-welded tubes through simulation and experimental methods.

Damage Evolution and Life Prediction of a P91 Longitudinal Welded Tube Under Internal Pressure Creep

2008 ◽  
Author(s):  
Takashi Ogata ◽  
Takayuki Sakai ◽  
Masatsugu Yaguchi
Keyword(s):  
Internal Pressure ◽  
Heat Affected Zone ◽  
Void Growth ◽  
Damage Evolution ◽  
Life Prediction ◽  
Prediction Method ◽  
Creep Damage ◽  
Creep Tests ◽  
Creep Analysis ◽  
Welded Tube

Clarification of creep damage mechanism and establishment of remaining life prediction methods of longitudinal welded piping of P91 steel are important subjects to maintain reliable operation of boilers in thermal power plants. Internal pressure creep tests were conducted on P91 steel longitudinal welded tubes to characterize the evolution of creep damage with time and to evaluate a life prediction method. Interrupted creep tests were utilized for damage observation in addition to rupture tests. Three dimensional FE creep analysis of the creep tested specimens were conducted to identify stress and creep strain distribution within the specimen during creep. Failure occurred at a heat affected zone without significant macroscopic deformation. It was found that initiation of creep voids had concentrated at mid-thickness region rather than surface. The creep analysis results indicated that triaxial tensile stress yielded at the mid-thickness region of the heat affected zone due to difference of creep deformation property between the base metal, heat affected zone and weld metal. It was suggested that the triaxial stress state caused acceleration of the creep damage evolution in the heat affected zone resulting in internal failure of the tube specimens. A rupture time prediction method of the welded tube is proposed based on the maximum principal stress and the triaxial stress factor. Void growth behavior in the heat affected zone was well predicted by the previously proposed void growth simulation method by introducing void initiation function to the method.

Experimental Study on Aging Performance of Building Membrane Materials

2020 ◽  
Vol 852 ◽  
pp. 189-198
Author(s):  
Bin Wang ◽  
Jian Zheng ◽  
Fei Cai Wu ◽  
Shunsuk Otaka
Keyword(s):  
Experimental Study ◽  
Constitutive Equations ◽  
Performance Degradation ◽  
Current Status ◽  
Background Current ◽  
Membrane Materials ◽  
Membrane Performance ◽  
And Performance ◽  
Relaxation Characteristics ◽  
Aging Performance

The paper introduces the research background, current status and performance of architectural membrane materials, analyzes the superiority of PVC and PTFE performance, discusses the aging and standards of architectural membrane materials, and conducts new rheological destruction of architectural membrane materials. The aging and relaxation characteristics described by the constitutive equations, and the viscos-elastoplastic rheological failure of architectural membranes for constitutive experiments. At the end of the thesis, the aging performance degradation of architectural membrane materials is discussed, and the aging of architectural membrane materials and the significance of membrane performance degradation are explored in depth.

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