Rolled Sheet Metal Research Articles

Estimation of Residual Stress in Cold Rolled Iron-Disks Using Magnetic and Ultrasonic Methods and Neutron Diffraction Technique

ABSTRACTVariation of internal stress states in cold rolled sheet metal can essentially influence the result of forming processes. Therefore it is important to control the forming process by a practicable in line testing method. For this purpose magnetic and ultrasonic nondestructive methods are available. However, it is necessary to calibrate these techniques. This paper describes a first step of such a calibration procedure making use of the neutron diffraction method. On the basis of the diffraction results an assessment of the magnetic and ultrasonic methods for the estimation of residual stress in the cold rolled iron-disks was made. Reasonable measuring concepts for practical applications to forming processes with cold rolled sheet metal are discussed.

DETERMINING THE OPTIMAL TARGET VALUE FOR A PROCESS WITH UPPER AND LOWER SPECIFICATIONS

This article develops two solutions (tabular and graphical) to determine the optimum target mean for a production process with both lower and upper quantity specifications. An example problem is presented for rolled aluminum sheet metal production...

Optimal design of biaxial tensile cruciform specimens

F or experimental investigations concerning the mechanical behaviour under biaxial stress states of rolled sheet metals, mostly cruciform flat specimens are used. By means of empirical methods, different specimen geometries have been proposed in the literature. In order to evaluate the suitability of a specimen design, a mathematically well defined criterion is developed, based on the standard deviations of the values of the stresses in the test section. Applied to the finite element method, the criterion is employed to realize the shape optimization of biaxial cruciform specimens for isotropic elastic materials. Furthermore, the performance of the obtained optimized specimen design is investigated in the case of off-axes tests on anisotropic materials. Therefore, for the first time, an original testing device, consisting of hinged fixtures with knife edges at each arm of the specimen, is applied to the biaxial test. The obtained results indicate the decisive superiority of the optimized specimens for the proper performance on isotropic materials, as well as the paramount importance of the proposed off-axes testing technique for biaxial tests on anisotropic materials.

Stress relaxation analysis in cold rolled sheet

The phenomenology, physical theory, test response, and engineering implications of stress relaxation and reviewed for the case of cold rolled metal sheet. Illustrative data and interpretations are cited for the case of a copper alloy commonly used in electrical connector applications, namely phosphor bronze. The influence of metallurgical structure and phase transformation is discussed.

高性能板材圧延機の開発と展開

高性能板材圧延機の開発と展開

Angular dependence of the ultrasonic SH wave velocity in rolled metal sheets: Sayers, C..M.; Proudfoot, G.G. United Kingdom Atomic Energy Authority, Harwell, AERE-R-12077, 29pp. (Jan. 1986)

Angular dependence of the ultrasonic SH wave velocity in rolled metal sheets: Sayers, C..M.; Proudfoot, G.G. United Kingdom Atomic Energy Authority, Harwell, AERE-R-12077, 29pp. (Jan. 1986)

Nondestructive measurement of texture and nine elastic constants of rolled metal sheets by EMAT

All the lowest-order independent coefficients W400, W420, and W440 for the crystallographic orientation distribution function were obtained nondestructively for thin rolled steel sheets by measuring ultrasonic wave speeds and making use of the known values of the single-crystal elastic constants. All the ultrasonic wave speeds were measured by EMAT so that no acoustic coupling medium was necessary, and the measurements were done quickly and with very good reproducibility. Pole figures were calculated using the obtained coefficients W400, W420, and W440 and the results were quite similar to the pole figures obtained by the x-ray diffraction method. It is well known that a rolled steel sheet can be modeled as an orthorhombic continuum having nine different elastic constants. It is also known that only six of the nine constants are independent when the sheet is a polycrystal of cubic crystallites and assuming that the macroscopic properties can be predicted by an averaging scheme. All these nine constants were calculated using the obtained W400, W420, W440, and the known single-crystal elastic constants. Young's moduli in the plane of the rolled steel sheet were also calculated and compared with the measured plastic strain ratio. Good relations were obtained between the average Young's modulus E and the average plastic strain ratio r.

Angular dependence of the ultrasonic SH wave velocity in rolled metal sheets

The ultrasonic SH wave technique is a promising method for separating out the effects of texture and stress on the ultrasonic velocity, and allows the texture and stress to be determined separately. Alen and Langman (1985) have reported measurements of the angular dependence of the SH wave velocity in several unstressed rolled metal sheets of aluminium, stainless steel, copper and brass. In this paper neutron diffraction measurements of the texture of several of these sheets are presented, and parameters entering into an expansion of the crystallite orientation distribution function are determined. These are in good agreement with the values obtained by fitting the ultrasonic results to theory. The validity of the first order expression for the effect of texture is assessed, and the contribution due to beam skewing is calculated.

Prediction of yield strength anisotropy and plastic strain ratios in textured sheet metal

AbstractA method is presented of predicting yield strengths and R values from the crystallographic texture of rolled sheet metals. The method is based on the Taylor model of plastic deformation in polycrystalline solids. A new method of representing texture, which accounts for the spread at orientation about ideal orientations, has been used in conjunction with this work. Examples of predicted yield strengths and R values are compared with experimentally determined values from sheets of face-centred cubic metals.

Directionality of Fatigue Properties in Some Textured Sheet Metals

The fatigue properties of some face-centred cubic sheet metals with cold rolling and annealing textures are reported. The observed differences between fatigue properties measured in the transverse and longitudinal directions in cold-rolled material are discussed and are related to the pole figures for the material. The study emphasizes that considerable directionality of fatigue properties can occur in rolled sheet metal.

Ultrasonic Attenuation in Thin Specimens Driven through Buffer Rods

A method is presented for measuring ultrasonic attenuation in thin solid specimens. The sample is bonded to one end of a buffer rod, and a transducer is bonded to the other end. All three elements must have plane parallel faces. The system is excited by an rf burst shorter than the round-trip travel time of the elastic wave in the buffer but longer than three times the round-trip travel time in the specimen. The specimen and its interface with the buffer act as a multiple-path elastic wave interferometer. The envelope of the returning echo in the buffer rod shows a stepwise amplitude modulation, one step per round trip in the specimen. The amplitudes of the first three steps are measured at rf frequencies at which the phase delay in the specimen is an integer multiple of π From the amplitudes, the attenuation in the specimen and the reflection coefficient at the buffer-specimen interface are computed. Measurements can be made over a broad frequency band with a single transducer, so the frequency dependence of the attenuation can be determined. The method has been applied to specimens of ferroelectric ceramic and rolled sheet metal samples of a two-phase alloy. The results are presented and interpreted.

Generalized two-dimensional model seismology with application to anisotropic Earth models

The theory of two-dimensional seismic modeling is generalized to include the effect of anisotropy. The elastic coefficient matrix for a plate with orthorhombic symmetry is derived and is used to convert three-dimensional anisotropic problems into corresponding two-dimensional model problems. This is equivalent to replacing directional body velocities by the directional plate velocities. In addition to the application to seismic modeling, this can be considered a contribution to the basic theory of long waves in anisotropic plates. As such it has application to such problems as long waves in floating ice sheets. A model consisting of an anisotropic layer over an anisotropic half-space is constructed using a formica layer and a grooved aluminum plate. It is shown that rolled metal sheets can be made appreciably anisotropic by machining grooves in the surface. The experimental Rayleigh wave phase velocities are compared with the theoretical dispersion curves computed using isotropic and anisotropic theories. Two-layer circular models of the earth, one with an isotropic and the other with an anisotropic upper mantle, are fabricated, and a comparative study of body and surface waves is made. It is found that the relative effect of anisotropy is greater on surface waves than on body waves.

Elastic wave propagation in layered anisotropic media

This is an analysis of the dispersive properties of transversely isotropic media. This kind of anisotropy is exhibited by hexagonal crystals, sediments, planar igneous bodies, ice sheets, and rolled metal sheets where the unique axis is perpendicular to the direction of surface wave propagation and the other axes are distributed randomly in the plane of the layers. Period equations are derived for waves of Rayleigh, Stoneley, and Love types, and comparisons are made, in certain cases, with ray theoretical and plane stress solutions. Anisotropy can have a pronounced effect on both the range of existence and the shape of the dispersion curves and can lead to an apparent discrepancy between Love and Rayleigh wave data. Attention is focused in this initial paper on a single solid layer in vacuo (i.e. a free plate) and a solid layer in contact with a fluid halfspace. The single layer solutions are generalized to n-layer media by the use of Haskell matrices.

Rolling of sheet and flat metal

Rolling of sheet and flat metal

X-Rays and Metallic Crystals

IN NATURE (August 14, 1913), and later in the Philosophical Magazine (October, 1913), Keene gave an account of some interesting experiments on the transmission of X-rays through rolled metal sheets. In connection with his investigation it may be of interest to record some results we have obtained in recent work on metallic crystals.

On the Transmission of X-Rays through Metals

WHEN a beam of X-rays is allowed to pass normally through thin rolled metal sheets and fall upon a photographic plate placed behind and parallel to the sheet, some curious patterns are obtained.