deformation and failure of a biaxially stretched sheet by M. Azrin

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Biaxial straining has been done by first producing a uniformly thinned, elongated patch at the center of a much larger metal sheet. The patch was gridded with lines per in, separated from the loading tool with an annular spacer of polyethylene, and then deformed incrementally by stretching the sheet over a large-radius hemispherical punch.

By regulating patch eccentricity, the imposed Cited by:   The deformation and failure of a biaxially stretched sheet Azrin, Morris; Backofen, Walter A. Abstract. Biaxial straining has been done by first producing a uniformly thinned, elongated patch at the center of a much larger metal sheet.

The patch was gridded with lines per in, separated from the loading tool with an annular spacer of Cited by: Study to Predict Failure in Biaxially Stretched Sheets of Aluminum Alloy T3', Materials and Manufacturing Processes,- To link to this article: DOI: /   A theoretical and numerical analysis of the formation of a localized neck in a biaxially stretched sheet is presented.

A time-independent constitutive law is assumed to be incrementally non-linear as suggested by micromechanical studies of the elastoplastic deformation of Cited by:   The uniaxial tensile properties (i.e.

E and σ Y) of the biaxially stretched sheet was determined in accordance with ISO Type 1BA using an Instron Universal Material Testing machine (Instron, UK).

The samples tested (n = 3) were dumb-bell in shape; samples were punched from biaxially stretched sheet in the MD and the by: 2. The study of deformation and failure of biaxially stretched sheets is of considerable practical interest in the area of sheet metal press forming.

During biaxial stretching of sheet metal, the uniform plastic straining regime is often followed by a localised plastic straining regime which finally leads to. This study is particularly relevant to the injection stretch blow moulding (ISBM) process where PET material is typically biaxially stretched to form bottles for the water and carbonated soft drinks industry.

The aim of this paper is to investigate the effect of biaxial stretching on the mechanical properties of Polyethylene Terephthalate (PET) using a custom built biaxial testing machine.

The structure evolution and deformation behavior of tenter-frame biaxially oriented polyethylene (TF-BOPE) films were investigated in this study.

For sequential biaxial stretching, the original spherulites were broken into small pieces, and the fibrillar structure simultaneously formed during the machine direction (MD) stretching. Subsequently, the single fibrils were pulled away, and some.

Ghosh, Plastic Flow Properties in Relation to Local ized Necking in Sheets, in:“Mechanics of Sheet Metal Forming-Material Behavior and Deformation and failure of a biaxially stretched sheet book Analysis”, D.

Koistinen, and N-M. Wang, eds., pp. –, Plenum Press (). Google Scholar. Abstract. First introduced informing limit diagrams (FLDs) have been empirically constructed to describe the strain states, or combinations of major (e 1) and minor (e 2) principal strains, at which a highly localized zone of thinning or necking becomes visible in the surface of sheet tory rigid-punch and pressshop experiments have shown that a single, gage-corrected FLD.

Criteria for diffuse and local necking in sheet metals stretched over a hemispherical punch have been developed. During stretching, a peak develops in the distribution of strain across the dome. This peak is a ring of thinned material around the pole which moves outward radially with continued deformation.

The present approach essentially focuses on the loading rate of the region bounded by. In fact, during the deformation localization process, the nucleation and growth of microvoids plays an important role [4, 5].

Needleman and co-workers [6, 7] adopted the M-K model and Gurson's constitutive equations [8] to investigate the influence of porosity on localized necking in a biaxially stretched sheet.

The forming limit curve (FLC) of the biaxially stretched AAT4 sheet metal under the superimposed double-sided pressure had improved and the fracture locus shifts to the left. Plastic deformation in sheet metal consists of four distinct phases, namely, uniform deformation, diffuse necking, localized necking, and final rupture.

The last three phases are commonly known as nonuniform deformation. A proper forming limit diagram (FLD) should include all three phases of the nonuniform deformation. The effects of void nucleation occurring during the deformation history on forming limit curves are considered for both in-plane and punch stretching employing a constitutive model of a porous plastic solid.

Both plastic strain controlled and stress controlled nucleation processes are simulated by a two parameter void nucleation criterion.

In the present study, the Gurson-Tvergaard-Needleman (GTN) damage model combined with finite element method is used to investigate the influence of double-sided pressure on the deformation behavior of biaxially stretched AAT4 sheet metal, including nucleation and growth of microvoids, evaluation of stress triaxiality, and so forth.

Request PDF | Two-Dimensional (2D) Damage Percolation/Finite Element Modeling of Sheet Metal Forming | Experimental evidence and numerical simulation have established that ductile damage.

1 INTRODUCTION. Polypropylene (PP) is widely used for the biaxially oriented film using the sequentially biaxial‐oriented process and the supply capacity in reached over 10 million tons/year. 1 This film is mainly used in the field of food packaging and industrial usage because of the high transparency, high physical properties, heat resistance, and chemical resistance, etc.

It is found that the superimposed double-sided pressure improves the forming limit curve (FLC) of the biaxially stretched sheet metal. Furthermore, the formability increase value (FIV) is. Melt compounded polypropylene/clay composites in sheet form were biaxially stretched at a variety of processing conditions to examine the effect of high temperature, high strain and high strain.

This content is not included in your SAE MOBILUS subscription, or you are not logged in. (2) Biaxially stretched acrylic material: Stretching acrylic material aligns the polymer chains to give a laminar structure parallel to the axis of stretch, which enhances resistance to crazing, reduces crack propagation rates, and improves tensile properties.

Stretching acrylic material reduces the. Analyses of the notched tension tests of carbon steel show that ductile failure is initiated when the sum of flow stress and mean stress reaches the limit for the material, regardless of stress triaxiality.

Therefore, this explicit critical stress condition could be a candidate criterion for local failure. Industrial revolution toward weight reduction and fuel efficiency of the automotive and aerospace vehicles is the major concern to replace heavy metals with light weight metals without affecting much strength.

For this, aluminum alloys are the major contributors to those industries. Moreover, aluminum alloys are majorly categorized as 1xxx, 2xxx, 3xxx, 4xxx, 5xxx, 6xxx, 7xxx, and 8xxx based.

failure properties of the material cannot be obtained by using such geometries. Therefore the shape of the cruciform has to be altered in such a way that failure occurs in the biaxially loaded zone. Literature survey Mu¨ller et al.[2] proposed two new methods to determine the yield locus of the biaxially loaded zone of a sheet metal.

A Predictive Tool for Delaying Wrinkling and Tearing Failures in Sheet Metal Forming J. Cao, J. Cao Effect of Kinematic Hardening on Localized Necking in Biaxially Stretched Sheets,” Effect of Precipitates on Plastic Deformation Behavior of High Entropy Alloy Al CoCrFeNi Under High Strain Rate Loading.

Eng. Mater. arrangement is that the elastomer sheet can be pre-stretched biaxially prior to the placement of the wire electrodes and subsequent embedding of the elastomer. The polymer blocks on either side of the elastomer sheet were made from a two component polyurethane mixture (Smooth CastSmooth-On) that, once cross-linking had initiated, was cast.

HPDE was biaxially stretched at °C at a strain rate of 4s −1, under equal biaxial deformation (EB). The results showed a level of biaxial orientation was induced which was accompanied by an increase in the modulus from MPa in the non-stretched sample to MPa in the stretched.

drawing of a sheet and disassembled for the removal of a drawn sheet, is shown in figures 2 and 3, respectively. Uniformity of Forming and Equation for Elongation To determine whether the amount of stretching is uniform over the face of the biaxially stretched pieces, the following experiments were made: A in.

disk of Lucite HC, which. Chapter Biaxially stretched polyamide film. Abstract: Introduction. Processing of biaxially oriented polyamide (BOPA) BOPA film properties. Part II: Applications of biaxial films.

Chapter Fresh-cut produce packaging and the use of biaxial stretched films. Abstract: Introduction. Quality factors determining shelf.

uniformity, and spherulite deformation during the biaxial stretching process, even though the biaxial stretched film is widely used all over the world. For these reasons, the in situ stretching evaluation method is required to observe the structure development during the biaxial stretching which can obtain stretchability, thickness uniformity.

Theoretical Analysis of Film Deformation Behavior in Casting. Analysis of Draw Resonance Instability in the Film Casting Process. Multilayer Films. Biaxially Oriented Films. Influence of Processing Conditions on Structure and Physical Properties of Biaxially Stretched Engineering Thermoplastics.

Theoretical Analysis of Tentering Process. biaxially stretched sheets containing imperfections in the At room temperature, there is a small degree of strain-rate form of patches with varying aspect ratios,[7]a single planar hardening such thatm5dlns/dln«‚ groove,[8]and a series of axisymmetric indentations with As shown in Figure 1, we used a double-edge notched.

In this study, compression deformation was used to impart a high degree of orientation to linear polyethylenes. Compressive deformation was developed by the Dow Chemical Co. (, 23) and was part of a proposed scrapless forming process where the. Square specimens 85 X 85 [2] were cut from the compression-molded sheets, marked with a grid pattern, and were simultaneously equi-biaxially stretched at temperatures of, and [degrees]C at an engineering strain rate of.

applied across them. This absence of deformation is not the case for soft elastomers and indeed their change in thickness with an applied voltage has been exploited to create electric field-induced actuators Very large actuation strains can be achieved using soft elastomer dielectrics but they must first be biaxially stretched.

INTRODUCTION In film manufacturing processes, surface smoothness and thickness uniformity are two important parameters [1, 2]. It has been found in open publications that there are only a few articles on correlation of mechanical deformation with the surface roughness and thickness uniformity of uni- and biaxially stretched homopolymers and alloys and blends [].

Introduction. Titanium alloy sheets have gained extensive applications in the aviation and aerospace fields due to its superior mechanical and physical properties, such as high specific strength, superior thermal stability and good corrosion resistance [1,2,3,4,5].The forming limit is an important performance index in the sheet metal forming process, which can reflect the maximum degree of.

At higher temperatures instead of yielding the deformation was a quasi-rubber-like. This behaviour was also reported when the films were stretched at high strain rates (over mm/s). They also observed that the non-homogeneity of the deformation reduced with increasing strain rate.

The present study investigates whether the deformation and failure behavior of the single phase nematic PMDA-ODA polyimide at a very low strain rate (%/minute) at room temperature is similar to that previously observed for isotactic polypropylene at its low strain rate failure envelope limit (%/minute or below at room temperature).

• Sheet metal is marked with small circles, stretched over a punch, and deformation is observed in failure areas • FLD shows boundary between safe and failure zones (a) Strains in deformed circular grid patterns. (b) Forming-limit diagrams (FLD) for various sheet metals.

Although the major strain is always positive (stretching), the minor.Title: An analysis of localized necking in biaxially stretched sheets Advisor: Needleman, Alan; Freudmann, Varda (Sc.M.: Engineering, )Title: Crack tip deformation fields of a deeply machine notched bend specimen with a vertex on the yield surface Advisor: Needleman, Alan; George, Ernest David (Sc.M.: Engineering, ).Necking of biaxially stretched thin sheets modelled by a nonlocal plasticity theory (L.P.

Mikkelsen). Nucleation, Consolidation and Phase Transformation. Deformation by moving interfaces: from single crystal experiments to the modelling of industrial SMA (P. Sittner et al.).

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