Plastic Instability of Thin Shells Deformed by Rigid Punches and by Hydraulic Pressure

1973 ◽  
Vol 95 (1) ◽  
pp. 36-40 ◽  
Author(s):  
Bilgin Kaftanog˘lu
Keyword(s):  
Large Deformations ◽  
Initial Conditions ◽  
Plastic Anisotropy ◽  
Plastic Instability ◽  
Strain History ◽  
Thin Shells ◽  
Hydraulic Pressure ◽  
Varying Thickness ◽  
New Criterion ◽  
Hydraulic Bulging

A theory has been developed to provide a solution for axisymmetrical shells in the plastic range for large deformations up to fracture. It includes the effects of strain history, nonlinear strain-hardening characteristics of materials, plastic anisotropy in the thickness direction, prestrain, through-thickness stress, and boundary tractions. It is also possible to use nonuniform initial conditions such as varying thickness and varying prestrain. A numerical solution has been developed especially suitable for stretch forming by a rigid punch and for hydraulic bulging of shells or diaphragms. It can easily be modified for the deep-drawing problem. Different instability criteria have been studied. It was found that the conventional criteria would not yield satisfactory results. A new criterion called the “strain propagation” criterion gave satisfactory results in the prediction of the onset of fracture. It could expalin the fracture taking place at increasing or decreasing pressures in the hydraulic bulging problem.

scholarly journals Design of Hydraulic Bulging Die for Automobile Torsion Beam and Optimization of Forming Process Parameters

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Kefan Yang ◽  
Youmin Wang ◽  
Kexun Fu
Keyword(s):  
Friction Coefficient ◽  
Process Parameters ◽  
Orthogonal Experiment ◽  
Die Design ◽  
Molding Pressure ◽  
Hydraulic Pressure ◽  
Forming Process ◽  
Torsion Beam ◽  
Supporting Pressure ◽  
Hydraulic Bulging

The hydraulic bulging technology of tubes can provide hollow parts with special-shaped cross sections. Its manufacturing process can effectively improve material utilization and product accuracy and reduce the number and cost of molds. However, the hydraulic bulging process of parts is very complicated. The size of the tube blank, the design of the loading route, and the forming process parameters will have an effect on the molding quality. Closed tubular torsion automobile beam is considered as the research object to study hydraulic bulging die design and optimize forming process parameters. CATIA software is used to design torsion beam product structure and hydraulic bulging die. AMESim software is employed to design hydraulic synchronous control system for cylinders on both sides of the hydraulic bulging die. Mathematical control model is established and verified in Simulink software. DYNAFORM software is applied to conduct numerical simulation of hydraulic expansion. The supporting pressure, molding pressure, friction coefficient, and feeding quantity are taken as orthogonal experiment level factors. Maximum thinning and maximum thickening rates are taken as hydraulic pressure expansion evaluation indexes to complete the orthogonal experiments. Main molding process parameters are analyzed via orthogonal experiment results and optimized by employing the Taguchi method. Optimal hydraulic bulging parameters are obtained as follows: supporting pressure of 20 MPa, molding pressure of 150 MPa, feeding quantity of 25 mm, and friction coefficient of 0.075. Simulation analysis results indicate that the maximum thinning rate is equal to 9.013%, while the maximum thickening rate is equal to 16.523%. Finally, the design of hydraulic bulging die for torsion beam was completed, and its forming process parameters were optimized.

Two Methods to Broaden the Bandwidth of a Nonlinear Piezoelectric Bimorph Power Harvester

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Hongping Hu ◽  
Longxiang Dai ◽  
Hao Chen ◽  
Shan Jiang ◽  
Hairen Wang ◽  
...  
Keyword(s):  
Large Deformations ◽  
Initial Conditions ◽  
Flexural Vibration ◽  
Nonlinear Effects ◽  
Voltage Source ◽  
Energy Scavenging ◽  
Piezoelectric Bimorph ◽  
Near Resonance ◽  
Jump Phenomena ◽  
Power Harvester

We propose two methods to broaden the operation bandwidth of a nonlinear pinned–pinned piezoelectric bimorph power harvester. The energy-scavenging structure consists of a properly poled and electroded flexible bimorph with a metallic layer in the middle, and is subjected to flexural vibration. Nonlinear effects at large deformations near resonance are considered by taking the in-plane extension of the bimorph into account. The resulting output powers are multivalued and exhibit jump phenomena. Two methods to broaden the operation bandwidth are proposed: The first method is to extend the operation frequency to the left single-valued region through optimal design. The second method is to excite optimal initial conditions with a voltage source. Larger output powers in the multivalued region of the nonlinear harvester are obtained. Hence, the operation bandwidth is broadened from the left single-valued region to the whole multivalued region.

Recrystallization Texture of Ferrite Steels: Beyond the γ-Fibre

2011 ◽  
Vol 702-703 ◽  
pp. 790-793 ◽  
Author(s):  
Patricia Gobernado ◽  
Roumen H. Petrov ◽  
Jaap Moerman ◽  
Carla Barbatti ◽  
Leo Kestens
Keyword(s):  
High Resolution ◽  
Deep Drawing ◽  
Recrystallization Texture ◽  
Essential Role ◽  
Plastic Anisotropy ◽  
Plastic Instability ◽  
Scanning Microscopy ◽  
Nucleation Process ◽  
Localized Deformation ◽  
Cross Rolling

The recrystallization texture of highly cold deformed IF steels is addressed. The latter is characterized by the //ND fibre and a certain spread towards the {311} orientation. The //ND fibre is the optimum texture for enhanced deep-drawing properties whereas the presence of any other component, such as {311}, will deteriorate the plastic anisotropy of the material. Previous works concluded that the recrystallized {311} orientation results from an oriented nucleation process related to the plastic instability of {001} deformed grains. In the present work, the microstructural nature of such plastic instability is investigated by high resolution orientation scanning microscopy on an annealed IF sample after cross-rolling. Present data indicate that localized deformation in near {001} grains plays an essential role in the nucleation of {311} orientations.

COF Measurement of Tubes by Hydraulic Bulging with Radial Crushing

2011 ◽  
Vol 189-193 ◽  
pp. 2597-2600
Author(s):  
Lian Fa Yang ◽  
Cong Qiang Wu ◽  
Feng Jun Chen
Keyword(s):  
Internal Pressure ◽  
Fe Simulation ◽  
Tube Hydroforming ◽  
Measuring Method ◽  
Relative Displacement ◽  
Hydraulic Pressure ◽  
Radial Compression ◽  
Forming Process ◽  
The Coefficient Of Friction ◽  
Hydraulic Bulging

A new method of determining the coefficient of friction (COF) in expansion zone of tube hydroforming (THF) is proposed. The measuring method features that a round tube is hydro-formed into a square one by a radial compression accompanying a constant internal hydraulic pressure p, and the difference ΔL of the two diagonal lengths of the square section of deformed tube is taken as measuring index for COF. The relationships between the ΔL and the p, COF, relative displacement S/S0 of moving punches are established by the finite element (FE) simulation of the forming process. The COF can be determined by matching the indexes ΔL from experiments and simulation. The FE simulation results show that the measuring index ΔL is in exponent proportion to COF and the internal pressure p, it is extremely sensitive to the friction force or COF and conveniently measured and especially under a higher internal pressure.

Plastic Deformation of Anisotropic Tubes in Hydraulic Bulging

1978 ◽  
Vol 100 (4) ◽  
pp. 421-425 ◽  
Author(s):  
D. M. Woo ◽  
A. C. Lua
Keyword(s):  
Strain Distribution ◽  
Circumferential Strain ◽  
Plastic Anisotropy ◽  
Strain Ratio ◽  
Stress Strain ◽  
Thickness Strain ◽  
Process Comparison ◽  
Tension Tests ◽  
Anisotropy Effect ◽  
Hydraulic Bulging

The anisotropy of tubular material is assessed from the values of the width/thickness strain ratio determined in the tension tests. Applying Hill’s theory of plastic anisotropy, these values are incorporated in the expressions for determining the stress/strain characteristics for anisotropic material in the tension and bulge tests, and also in the theoretical analysis of the hydraulic bulging of anisotropic tubes. Experiments have been carried out on copper tubes. Taking into account the anisotropy effect, the stress/strain curves determined in the tension and bulge tests agree closely except at the low strain region. In the analysis of the bulging process, comparison is made between the theoretical and the experimental circumferential strain distribution. The results appear satisfactory.

Experimental Analysis of Forming Limits and Thickness Strains of DP600-800 Steels

2016 ◽  
Vol 835 ◽  
pp. 230-235 ◽  
Author(s):  
Marcelo Costa Cardoso ◽  
Alexandre de Melo Pereira ◽  
Fabiane Roberta Freitas da Silva ◽  
Luciano Pessanha Moreira
Keyword(s):  
Shear Failure ◽  
Plastic Anisotropy ◽  
Rolling Direction ◽  
Tensile Tests ◽  
Plastic Instability ◽  
Tensile Fracture ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Plastic Behavior ◽  
Fractured Surface

In this work, the plastic behavior of cold-rolled zinc coated dual-phase steel sheets DP600 and DP800 grades is firstly investigated by means of uniaxial tensile and Forming Limit Curve (FLC) testing. The uniaxial tensile tests were carried out at 0o, 45o and 90o angular orientations with respect to the rolling direction to evaluate the mechanical properties and the plastic anisotropy Lankford r-values. The forming limit strains are defined according to Nakajima’s procedure. Thickness measurements of tested Nakajima’s samples cut perpendicular to the fracture allowed to identify a rapid decrease of the strain, which governs the plastic instability that preceded the fracture in the drawing region of the FLC. Optical metallographic and scanning electron microscopy techniques helped to characterize and distinguish the orientation of rotated grains and flat fractured surface (ductile shear failure in blank specimens close to plane-strain tension) from no grain rotations and rough fractured surface (ductile tensile fracture in blank geometries in the biaxial stretching domain).

scholarly journals Rotation, inversion and perversion in anisotropic elastic cylindrical tubes and membranes

2013 ◽  
Vol 469 (2153) ◽  
pp. 20130011 ◽  
Author(s):  
Alain Goriely ◽  
Michael Tabor
Keyword(s):  
Internal Pressure ◽  
Large Deformations ◽  
Axial Strain ◽  
Cylindrical Shells ◽  
Thin Shells ◽  
Structural Elements ◽  
Response Behaviour ◽  
Wide Range ◽  
Cylindrical Tubes ◽  
Anisotropic Elastic

Cylindrical tubes and membranes are universal structural elements found in biology and engineering over a wide range of scales. Working in the framework of nonlinear elasticity, we consider the possible deformations of elastic cylindrical shells reinforced by one or two families of fibres. We consider both small and large deformations and the reduction from thick cylindrical shells (tubes) to thin shells (cylindrical membranes). In particular, a number of universal parameter regimes can be identified where the response behaviour of the cylinder is qualitatively different. This include the possibility of inversion of twist or axial strain when the cylinder is subject to internal pressure.

EFFECT OF HYDRAULIC PRESSURE ON WARM HYDRO MECHANICAL DEEP DRAWING OF MAGNESIUM ALLOY SHEET

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1975-1980 ◽  
Author(s):  
WEI LIU ◽  
LINZHI WU ◽  
SHIJIAN YUAN
Keyword(s):  
Magnesium Alloy ◽  
Deep Drawing ◽  
Experimental Studies ◽  
Alloy Sheet ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Hydraulic Pressure ◽  
Different Temperatures ◽  
Hydraulic Bulging

The uniaxial tensile test and hydraulic bulging test of AZ31 magnesium alloy sheets were applied to study the influence of temperature on the material properties and obtain the forming limit curves at different temperatures. Numerical simulations of warm hydro mechanical deep drawing were carried out to investigate the effect of hydraulic pressure on the formability of a cylindrical cup, and the simplified hydraulic pressure profiles were used to simulate the loading procedure of hydraulic pressure. The optimal hydraulic pressure at different temperatures were given and verified by experimental studies at temperature 100°C and 170V.

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