scholarly journals A New Compression Test for Determining Free Surface Roughness Evolution in Thin Sheet Metals

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 451 ◽  
Author(s):  
Tsuyoshi Furushima ◽  
Kohei Aoto ◽  
Sergei Alexandrov
Keyword(s):  
Surface Roughness ◽  
Free Surface ◽  
Compression Test ◽  
Thin Sheet ◽  
Principal Strain ◽  
Strain Rates ◽  
Thin Sheets ◽  
Strain Paths ◽  
Effect Of The Support ◽  
Metallic Sheet

In sheet microforming processes, in-surface principal strain rates may be compressive such that the thickness of the sheet increases in the process of deformation. In general, the evolution of free surface roughness depends on the sense of the principal strain normal to the free surface. Therefore, in order to predict the evolution of free surface roughness in processes in which this normal principal strain is positive by means of empirical equations, it is necessary to carry out experiments in which the thickness of the sheet increases. Conventional experiments, such as the Marciniak test, do not provide such strain paths. In general, it is rather difficult to induce a sufficiently uniform state of strain in thin sheets of increasing thickness throughout the process of deformation because instability occurs at the very beginning of the process. The present paper proposes a compression test for thin sheets. Teflon sheets are placed between support jigs and the metallic sheet tested to prevent the occurrence of instability and significantly reduce the effect of the support jigs on the evolution of surface roughness. The test is used to determine the evolution of surface roughness in thin sheets made of C1220-O under three strain paths.

Identification of an Empirical Equation for Predicting Free Surface Roughness Evolution in Thin Sheets of Aluminum Alloy and Pure Copper

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Tsuyoshi Furushima ◽  
Hideki Sato ◽  
Ken-ichi Manabe ◽  
Sergei Alexandrov
Keyword(s):  
Numerical Simulation ◽  
Surface Roughness ◽  
Aluminum Alloy ◽  
Free Surface ◽  
Empirical Equation ◽  
Pure Copper ◽  
Numerical Results ◽  
Experimental Program ◽  
Thin Sheets ◽  
Surface Roughness Evolution

This paper deals with the identification of an empirical equation for predicting free surface roughness evolution. The equation has been proposed elsewhere, and, in contrast to widely used equations, assumes that the evolution of free surface roughness is controlled by two kinematic variables, the equivalent strain, and the logarithmic strain normal to the free surface. Therefore, an experimental program is designed to account for the effect of the mode of deformation on free surface roughness evolution. Thin sheets of aluminum alloy A5052-O and pure copper C1220P-O alloys are used to conduct the experimental program. In addition, numerical simulation is performed to calculate the evolution of free surface roughness under the same conditions. Comparison of experimental and numerical results shows that the accuracy of the numerical results is good enough. Then, numerical simulation is extended to the domain in which no experimental results are available. Discrete functions so found are fitted to polynomials. As a result, continuous functions that represent the empirical equation for predicting free surface roughness evolution for A5052-O and C1220P-O alloys are determined. These equations can be used in conjunction with solutions to boundary value problems in plasticity for predicting the evolution of free surface roughness in metal forming processes.

Characterization of Tensile and Compressive Behavior of Microscale Sheet Metals Using a Transparent Micro-Wedge Device

2011 ◽  
Author(s):  
James Magargee ◽  
Jian Cao ◽  
Rui Zhou ◽  
Morgan McHugh ◽  
Damon Brink ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Thin Sheet ◽  
Thin Sheets ◽  
Stainless Steel Sheet ◽  
Sheet Metals ◽  
Compressive Behavior ◽  
Buckling Modes ◽  
Full Field ◽  
Compressive Loads

The cyclic and compressive mechanical behavior of ultra-thin sheet metals was experimentally investigated. A novel transparent wedge device was designed and fabricated to prevent the buckling of thin sheets under compressive loads, while also allowing full field strain measurements of the specimen using digital imaging methods. Thin brass and stainless steel sheet metal specimens were tested using the micro-wedge device. Experimental results show that the device can be used to delay the onset of early buckling modes of a thin sheet under compression, which is critical in examining the compressive and cyclic mechanical behavior of sheet metals.

scholarly journals Wrapping Liquids, Solids, and Gases in Thin Sheets

2019 ◽  
Vol 10 (1) ◽  
pp. 431-450 ◽  
Author(s):  
Joseph D. Paulsen
Keyword(s):  
Recent Progress ◽  
Geometric Model ◽  
Thin Sheet ◽  
Nonlinear Problems ◽  
Small Scale ◽  
Thin Sheets ◽  
Interfacial Film ◽  
Metal Foils ◽  
High Flexibility ◽  
Significant Attention

Many objects in nature and industry are wrapped in a thin sheet to enhance their chemical, mechanical, or optical properties. Similarly, there are a variety of methods for wrapping, from pressing a film onto a hard substrate to inflating a closed membrane, to spontaneously wrapping droplets using capillary forces. Each of these settings raises challenging nonlinear problems involving the geometry and mechanics of a thin sheet, often in the context of resolving a geometric incompatibility between two surfaces. Here, we review recent progress in this area, focusing on highly bendable films that are nonetheless hard to stretch, a class of materials that includes polymer films, metal foils, textiles, and graphene, as well as some biological materials. Significant attention is paid to two recent advances: a novel isometry that arises in the doubly-asymptotic limit of high flexibility and weak tensile forcing, and a simple geometric model for predicting the overall shape of an interfacial film while ignoring small-scale wrinkles, crumples, and folds.

scholarly journals Rhombus and Rhomboid Parallelogram Patterns on Glaciers: Natural Indicators of Strain

1979 ◽  
Vol 22 (87) ◽  
pp. 247-261 ◽  
Author(s):  
Charles J. Waag ◽  
Keith Echelmeyer
Keyword(s):  
Strain Rate ◽  
Flow Direction ◽  
Acute Angle ◽  
Principal Strain ◽  
Obtuse Angle ◽  
Strain Rates ◽  
Ice Flow ◽  
Glacier System ◽  
Glacier Ice

AbstractSubtle rhombus and rhomboid parallelogram patterns occur on Vaughan Lewis Glacier and the Gilkey Glacier System, Juneau Icefield, Alaska. The patterns are within the firn at the firn-ice interface, are formed by differential recrystallization within narrow preferred zones, and are apparently manifestations of stresses transferred upward from the glacier ice. On the glaciers of the Gilkey System the patterns occur where intense lateral shortening is indicated by abrupt convergence of medial moraines and an abundance of extension crevasses. The short axes of the rhombi and the obtuse angle bisectors of the rhomboids are subparallel to the strike of extension crevasses, therefore to the axis of shortening. The long axes of the rhombi and the acute angle bisectors of the rhomboids are parallel to the foliation, and ice-flow direction. The angles of the parallelograms are variable locally, but average 105° and 75°; the variation seems to reflect intensity and duration of stress. Similar parallelograms occur within the troughs of wave bulges below the Vaughan Lewis Icefall. In the wave bulges, the foliation arcs parallel the wave. The long axes of the rhombi and acute angle bisectors of the rhomboids parallel the foliation around the foliation arc. The short axes of the rhombi and the obtuse angle bisectors of the rhomboids parallel the strikes of radial crevasses, are perpendicular to the direction of extension, and form a fan divergent down-stream. The precise mechanisms and conditions of formation of the parallelograms are not yet understood. Preliminary strain-rate measurements suggest, however, that correlations exist between the orientations of the principal strain-rates and the axes of the patterns, and between the magnitude of the strain-rates and the axial lengths of the patterns.

The Influence of Shielding Gas on Strength of the Laser Welded Thin Sheet Lap Welds

2018 ◽  
Vol 786 ◽  
pp. 98-103 ◽  
Author(s):  
Markku Keskitalo ◽  
Aappo Mustakangas ◽  
Mikko Hietala ◽  
Kari Mäntyjärvi
Keyword(s):  
Energy Input ◽  
Thin Sheet ◽  
Thin Plates ◽  
Thin Sheets ◽  
Laser Weld ◽  
Shielding Gas ◽  
Corrosion Properties ◽  
Weld Joints ◽  
Gas Nozzle ◽  
Better Than

The laser welding is usable method for joining thin plates with low energy input and precise penetration control. When joining of very thin sheets such as 0.5 mm the shape of the weld must be complete in order to achieve a good strength of the joint. The part of the test welds were welded without shielding gas and other part of the test welds by using 65 mm shielding gas nozzle behind the key hole. The strength of the laser weld of 0.5 mm Austenitic stainless steel (ASS) plate was measured in welds without shielding gas and Ar shielded weld. The strength of the shielded weld joints was significantly better than the joint weld without shielding gas due to convex shielded welds. In addition the shielded welds were bright which improves the corrosion properties of the joint.

A Model for Analyzing Multi-Asperity Contact of Thin Sheets With Real Surfaces on Both Sides

2005 ◽  
Author(s):  
John J. Jagodnik ◽  
Sinan Mu¨ftu¨
Keyword(s):  
Thin Sheet ◽  
Beam Theory ◽  
Contact Problems ◽  
Elastic Half Space ◽  
Asperity Contact ◽  
Thin Sheets ◽  
Bending Rigidity ◽  
Bernoulli Beam ◽  
Substrate Rigidity ◽  
Euler Bernoulli Beam

A model for two-sided contact of a thin sheet of material, with real surfaces on both sides is presented. The model combines cylindrical-contact equations, with Euler-Bernoulli beam theory to examine the importance of substrate rigidity in two-sided contact problems. A finite difference program for solving this model is developed. Results for two-sided contact of numerically generated surfaces on thin tapes are presented. The effects of tape thickness and tension are explored. It is shown that substrate’s bending rigidity contributes significantly to the overall equilibrium, for typical tape thicknesses and tension values used by the industry. However, large thickness values exists for which substrate bending is negligible and elastic half-space solutions applied to both sides of the tape are adequate.

Deburring of Sheet Metal by Barrel Finishing

2007 ◽  
Vol 344 ◽  
pp. 193-200 ◽  
Author(s):  
Alberto Boschetto ◽  
Armando Ruggiero ◽  
Francesco Veniali
Keyword(s):  
Surface Roughness ◽  
Experimental Investigation ◽  
Sheet Metal ◽  
Process Parameters ◽  
Working Time ◽  
Thin Sheets ◽  
Secondary Operation ◽  
Barrel Finishing ◽  
Technological Model ◽  
Local Deformations

In sheet metal processes the burrs cannot be completely eliminated during the process but can be minimized by optimization of the process parameters. Hence the deburring often becomes an essential secondary operation. Most of the deburring operations are hand-made and therefore several manufacturers tend to eliminate these tedious and labor-intensive operations due to time and cost issues. Moreover, clamping problems can arise which, together with the deburring forces, can induce dimension alterations and local deformations, particularly for thin sheets. Barrel finishing is an old technique commonly used to improve the surface roughness of complicated parts, but can find interesting applications also in the deburring. Aim of this work is to present an experimental investigation on the deburring of sheet metal performed by barreling. A technological model has been developed in order to assess the height of the burr as a function of the initial burr and of the working time.

Shearing Edging Investigation in High-Speed Blanking Process Applying Precision Progressive Die

2013 ◽  
Vol 668 ◽  
pp. 460-464
Author(s):  
Zhen Yuan Huang ◽  
Feng Ruan
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
Orthogonal Experiment ◽  
Thin Sheet ◽  
Progressive Die ◽  
Small Complex ◽  
Thin Sheet Metal ◽  
The One ◽  
Blanking Process

The high-speed blanking process applying precision progressive die represents the one of the highest level of today’s stamping technology, mainly is used for the production of the ultra-thin, small, complex electronic components. An orthogonal experiment scheme with three factors (including blanking clearance, surface roughness of the die, stamping speed) was established in this paper based on the actual production. The high-speed blanking process experiment applying precision progressive die was carried out base on this scheme. The quality of the shearing edging of blanking parts was used to evaluate the different influence degree of three factors. The result showed that the surface roughness of the die affected the quality of the shearing edging more than that of the other two. The higher the die surface accuracy, the better the quality of the shearing edging. The result also showed that the high speed can reduce the quantity of the burr of the blanking of the ultra-thin sheet metal.

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