Drawing Of Sheets Research Articles

Some experimental results on yield condition in plane stress state

In the present paper, the determination of yield locus curves for deep drawing sheet metal is described. The experiments are based on the combination of biaxial tension tests on plane cross-shaped specimens with uniaxial tension and compression tests performed on conventional specimens. The influence of preloading (prestrain) on the hardening behaviour is discussed. The material coefficients are computed through the equalization of the test results by means of a quadratic formulation of the yield condition. Finally, the material coefficients are given as functions of the prestrain of specimens in the rolling direction.

Anatomical Drawings From the Royal Library, Windsor Castle

Leonardo on the Human Body, by Leonardo da Vinci, 506 pp, with illus, paper, $10.95, New York, Dover Publications Inc, 1983. These two books differently emphasize Leonardo's genius as artist and anatomist. One is the elegant catalogue of the exhibit of 50 sheets of Leonardo's drawings presented at the Metropolitan Museum of Art in early 1984. The exhibition comprised perhaps 25% of the Leonardo holdings of the Royal Library in Windsor Castle. The illustrations are illuminated by the explanatory notes of Kenneth Keele and Jane Roberts. Keele has an established reputation as an authority on Leonardo as an anatomist. Keele also contributes five pages of general comment, and there are brief comments by others. The book is intended to delight the eye, rather than nourish the brain, and it succeeds. The other book comprises 215 sheets of drawings with four scholarly essays on general matters plus comments on the plates,

Drawing and extrusion of composite sheets, wires and tubes

Some basic steady forming processes, in particular drawing and extrusion, of composite (multilayered) metal sheets, wires and tubes are analyzed within the framework of continuum plasticity. Material behaviour is modelled as rigid/perfectly-plastic and a radial flow pattern is assumed within the working zone. Simplified versions of the respective Nadai-Hill and Shield radial flow solutions are used for the description of the stress field and velocity profile in each phase (layer). The matching requirements along the interfaces between the different layers, together with the friction conditions at the walls and the entry/exit load specification, lead to a system of algebraic equations that admit a simple solution. The main outcome are elegant formulae for the drawing tension, and extrusion pressure, valid for any number of layers. The applicability of the results is restricted to dies of sufficiently small angles, taper and wall friction. Comparison with experimental results for the drawing stress of bimetallic composites shows a nice agreement, within that range of validity.

Ultrasonographic Mapping of Vitreoretinal Abnormalities

We conducted a prospective study of 50 consecutive eyes to determine the accuracy of ultrasonographic mapping of vitreoretinal abnormalities. The 50 eyes, all of which had opaque media, underwent A- and B-scan ultrasonography before undergoing vitrectomy. The location and differentiation of any abnormalities were mapped on a fundus drawing sheet. At the time of vitrectomy, the surgeon independently examined the fundus and recorded his findings on a second drawing sheet. When we compared the two sets of drawings, we found that ultrasonography correctly predicted the position of the retina in 45 of 50 eyes and the presence or absence of macular detachment in 48 of 50 eyes. These two findings are particularly important to the surgeon. Ultrasonography also correctly predicted the presence or absence of posterior vitreous detachment in all 50 eyes, correctly described the exact extents of the retinal detachments in 44 of 50 eyes, and located points of vitreoretinal adhesion in 39 of 50 eyes.

The effect of change of the size of the drawing sheet on the H-T-P IQ scores.

Administered the achromatic H-T-P test using four different sizes of drawing forms, to 24 college students, aged 18-21. In addition to the standard form sheet (8 1/2 X 7 inches), a much smaller (4 1/2 X 5 1/2 inches) was used by the same Ss. The third form was the usual typing sheet (8 1/2 X 11 inches), and the fourth form was even larger (8 1/2 X 14 inches). The drawings were scored and H-T-P IQs obtained. Out of 20 comparisons, only 2 were significant at the .05 level. The results were interpreted as failing to support the hypothesis that the use of the drawing sheet has a significant influence upon the quantitative aspects of the drawing. However, a caveat was expressed with regard to the form size and the qualitative evaluation of the drawings.

A viscous shell formulation for the analysis of thin sheet metal forming

A finite element method to analyse large plastic deformations of thin sheets of metal is presented. The formulation is based on an extension of the general viscoplastic flow theory for continuum problems to deal with thin shells. Axisymmetric situations are considered first and here the simple two noded reduced integration element is used. Numerical results for the stretch forming and deep drawing of circular sheets are presented and comparison with experimental results is made. The second part of the paper deals with the deformation of sheets of arbitrary shape. The general viscous shell element is derived from the standard reduced integration, “thick shell element. Numerical results for simple 3-D sheet forming problems are given.

Differential Cue Utilization by Males and Females in Pattern Copying

Previous research on pattern copying indicates that male performance improves when reference cues are added to the task, but that female performance remains unaffected by the additional information. Results of experiment 1 reveal that it is the presence of cues in the modeled pattern, rather than on the drawing sheet, that is primarily responsible for the improved copying accuracy. The data also replicate the differential cue utilization by male and female 10-year-olds. Experiment 2 found no such differential performance with a 7-year-old sample. The findings are considered relative to other visual-spatial research.

Corrosion resistance of deep drawing sheet steel

1. With increasing numbers of nonmetallic inclusions, the corrosion resistance of steels 08Yu, 20YuT, and 08GSYuT decreases. 2. The corrosion resistance of the steels tested is highest for steel 08Yu after hot rolling. This treatment can be recommended to improve the corrosion resistance of sheet steels. 3. As the plastic deformation increases in the course of cold stamping, the corrosion resistance of cold-rolled steel 08Yu decreases.

A placement algorithm for logic schematics

This paper presents an automatic placement algorithm for placing logic symbols on a schematic, in a computer aided drafting system. This package is a subsystem of a Design Automation System for Printed Circuit Boards, currently being developed at the SDS Group of T.I.F.R. This heuristic algorithm, attempts to place the logic symbols automatically on the drawing sheet. The information for placement is extracted from the user-supplied wiring list and a central data-base for ICs. The Main aim of the algorithm is to maintain the logical signal flow and minimize the need for human interaction. The algorithm has been successfully implemented in PASCAL on a DEC System-10.

An Investigation into Plasto-Hydrodynamic Lubrication with a Cold Sheet Drawing Test

For the experimental and theoretical elucidation of the mechanism of the plasto-hydrodynamic lubrication in cold metal forming processes, sheet drawing tests through a wedge-shaped die are carried out as a model process which facilitates accurate determination of the frictional coefficient and interfacial temperature. Aluminium strips of 2 cm width, 2 mm thickness and 1 m length are drawn at speeds up to 10 m/sec with some lubricants in a testing machine specially designed and constructed for the present purpose. By modifying the existing plasto-hydrodynamic lubrication theory, the frictional coefficients are calcualted and are compared with the observed. The condition for the occurrence of the hydrodynamic lubrication is discussed with the aid of the results of the above comparison, the predicted and measured temperatures and the observed surface roughnesses of the drawn specimens.

The air gap phenomenon in children's landscape drawings

The “air gap” phenomenon was found to be very common in the free landscape drawings of middle and later childhood. Three experiments are reported in which the contextual cues for such drawings were systematically manipulated. When subjects were supplied with drawing sheets constructed to imply the absence of the air gap, the phenomenon was eliminated in most of their drawings. When supplied with sheets constructed to imply its presence, most subjects produced air gap drawings using contextually provided reference lines. There were no consistent transfer effects across different cuing orders. The susceptibility of the air gap phenomenon to modification by task manipulation suggests that it results from problems of production rather than from defects in the child's internal representation of the world.

The Welding Mechanism in Drawing of Aluminum Sheet

As a continuation of the previous report which dealt with a mild steel sheet, this study covers the welding phenomena at a tool-work interface in deformation processing of aluminum sheet which has been investigated experimentally by using a two dimensional drawing-type friction testing machine. Variation mode of the frictional coefficient during the drawing process can be classified into four types, namely,- constant, increasing, decreasing and waving type. In both the increasing and decreasing types, the welding occurs at a die exit portion, similar to the case of mild steel reported previously. In the waving type, a process of growth and the peeling away of the welding layer is repeated at a central portion of the die, and corresponding frictional coefficient waves develop. The frictional shear stress on the welding region is constant (about 68.6 MPa), approximately equaling the yield shear stress of the aluminum. The ability to repair the welding has been examined by measurement of the frictional coefficient at the designated drawing travel for mineral oils with various viscosities and compositions.

A slip-line field for mid-plane cracking or splitting in sheet drawing

Many of the two-centred fan slip-line field solutions for sheet drawing have been shown to be statically inadmissible due to overstressing at the die exit when the mid-plane hydrostatic pressure approximately equals -κ. An attempt is made to overcome this problem by the proposal of an alternative slip-line field which allows exit splitting at the mid-plane. The limitations on the use of this slip-line field are described and in the light of these limitations a further possible field is suggested for wall ironing.

Comment

WHEN I went to visit a friend who was spending a few days as a patient in Northwick Park Hospital, it seemed natural, as I was in ‘foreign’ territory, to investigate the local library facilities. To anyone who passed their SRN finals in a non‐teaching hospital in the mid‐60's, and then discontinued nursing practice, the likelihood of finding a special library service for nurses would seem as remote as disposable syringes and the removal of rubber draw sheets from hospital beds.

Determination of output parameters in the synthesis of ACSTP of making and drawing sheet glass

Determination of output parameters in the synthesis of ACSTP of making and drawing sheet glass

Plane-strain radial flow of plastic materials

A closed-form solution is given for plane-strain radial flow of a rigid/linear-hardening material. The flow-rule used is that of von Mises and advantage is taken of the Eulerian formulation of the problem in steady-state flow. The applicability of the solution to sheet drawing or extrusion is discussed. It is suggested that these processes can be simulated by the present solution, with integral boundary-conditions, provided that the die angle is small compared with the reduction. A useful approximate formula for the drawing tension and extrusion pressure is derived and shown to be in good agreement with existing experimental results for drawing. Finally, some simple but accurate results are derived for uniform flow of an elastic/plastic material with arbitrary hardening.

Rolling of low-carbon steel sheets in the temperature range 300–700°C

Low-carbon steel sheets for motor-car bodies are usually produced by cold rolling and annealing. Recently, however, warm rolling has been proposed for the production of these sheets. In the presently reported work, sheets produced by schemes including warm rolling are compared with cold-rolled sheets. Warm-rolled sheets show higher strength than cold-rolled ones, especially when the rolling temperatures is in the range 300–500°C. After anealing, however, the ductility of warm-rolled sheets becomes superior to that of cold-rolled sheets. In order to explain this effect, the Petch equation parameters σ 0 and K, the microstructure, the mechanical properties and the textures of the warm-rolled and cold-rolled sheets are compared. The study of Petch equation parameters has shown that the higher drawability of sheets rolled by schemes including warm rolling is due to the obtaining of a more pure ferrite matrix after warm rolling and annealing, as a result of dynamic strain ageing. When the Mn content of the steel is not higher than 0.25%, warm rolling with subsequent rapid annealing can be used for the production of deep-drawing sheets. In order to prevent the precipitation of AlN during warm rolling of Al-killed steel sheets, the rolling temperature should not be higher than 300°C, although higher temperatures can be used if the warm strain is small.

The effect of temperature and deformation rate on transformation-dependent ductility of a metastable austenitic stainless steel

Recently-published investigations into the warm deep-drawing of metastable austenitic stainless steels have suggested that increased drawing ratios may be achieved by allowing controlled transformation to martensite at a strain close to that at which instability of the austenite would otherwise occur. A so-called maximum elongation temperature (M.E.T.), the temperature at which the major principal strain is maximum, determined from tests in uniaxial tension, is usually quoted. The authors confirm that it is formation of sufficient martensite in the region of incipient instability close to the instability strain which is responsible for increased tensile ductility, but there is no unique M.E.T. for a given steel. It depends, critically, on the rate of loading. Further, the M.E.T. in the uniaxial tensile test differs from that determined from the notched tensile-, bulge-, and cupping tests, so that it is not independent of the stress system, and the M.E.T. in the uniaxial tension usually quoted in the literature, may have little relevance to sheet drawing in which the stress system is essentially biaxial. The M.E.T. determined from the biaxial tests coincided with the temperature at which the limiting drawing ratio in the Swift flat-bottomed cup test was greatest.

The nature of yielding and plastic deformation in rubber-modified polystyrene

Obliquely grooved sheet samples of high-impact polystyrene were used to establish conditions that lead to the early stage of plastic deformation under combined-stress loading conditions. By applying the plasticity theory and the method proposed by Hill to the thermoplastic, it was demonstrated that the basis for relating incremental strain rate with the corresponding deviatoric stress could be established. Yielding under the combined-stress loading condition was also shown to be strongly dependent on the sign of stress. Some insight into the asymmetric yielding behaviour was gained by determining the density and orientation dependence of crazes around the rubber-modified particles. It was shown that the process of craze initiation depended on the prevailing stress state and did not follow the stress or strain criterion. Based on the testing method used, a simple procedure of predicting sheet drawability is outlined.

The strain-dependence of plastic strain ratio (rm value) of deep drawing sheet steels determined by simple tension test

The strain-dependence of plastic strain ratio (rm value) of deep drawing sheet steels determined by simple tension test