The University of Michigan * Engineering Research Institute 2621-4-P AN INVESTIGATION OF METAL SPINNING Progress Report June 30, 1958 Summary Report on Mechanically Spun Cones B Avitzur S, Floreen W. D. Carleton Eo Eo Hucke Do Vo Ragone Spincraft Inco Milwaukee, Wisconsin REF' Contract DA-ll-022-ORD-2542 Army Ballistic Missile Agency

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The University of Michigan ~ Engineering Research Institute INTRODUCTION Spinning is a metal shaping process that is widely used to fabricate pieces having rotational symmetry, In common spinning practice a pattern having the final shape of the desired piece is mounted on a lathe. A flat sheet of metal is then clamped to the pattern, and while the pattern and sheet are revolving, the sheet is forced back over the pattern by pressing aginst the sheet with some type of spinning tool. Reduction in thickness of the sheet may or may not take place. Generally the spinning tool is a roller or a heavy wooden stick. The process can be done by hand, where the spinning is done by a skilled craftsman who knows by experience how to lay the sheet against the pattern; or it can be done mechanically, in which case the forces are applied by some mechanical system. Many shapes and sizes can be spun, with pieces up to 10 feet in diameteI being common. Because of the nature of the process very large reduction in thickness, up to 75% per pass in some cases, can be achieved. With suitable equipment it is also possible to hot spin. There does not seem to be any restrictions as to deformable materials which can be spun. Aluminum, brass, stainless steel, titanium, and super-alloys for example, have all been success fully spun. Because of the simplicity of the operation, spinning offers some distinct economical advantages. Lengbridge (1) has shown that for producing a small number of pieces that spinning is more economical than deep drawing because of the low set-up time and costs. The pattern used for spinning, for example, can often be made of wood, which saves a great deal of tooling expense. In spite of the relatively wide useage of spinning as a forming process there is very little information concerning the mechanical properties of spun pieces. Several investigations (2,3,4)5,96) have noted a considerable increase in hardness after spinning; and a- general increase in the tensile strength and fatigue resistance (4,5,6). The effects produced by spinning appear to be quite similar to those produced by cold rolling, with the microstructures of spun pieces show grains elongated in the direction of spinning (5). To date, however, there has been no systematic attempt to determine how the mechanical properties in spun pieces vary with the shape of the piece, amount of reduction, and so forth. Y~~~~~

The University of Michigan ~ Engineering Research Institute In the same manner there is. little- analysis of a quantitative nature of the deformation process during spinning. Siebel and Droge (7) have shown that the reduction in thickness of a spun piece is proportional to the head-in pressure, that is, the pressure applied in a direction perpendicular to the pattern. The axial pressure, the pressure parallel to the pattern, increases only slightly with increasing reductions. Siebel and Droge also note that the head-in pressure is proportional to the feed rate, and that spinning tool should have a small radius of curvature in order to minimize the resistance to flow in the axial direction. In the present investigation an attempt was made to determine the mechanical properties of spun materials, and also to study the plastic deformations produced by the spinning operation. A series of pieces were mechanically spun on a machine equipped with suitable guages and controls so that the various forces, feed rates, and other variables employed could be measured. After spinning, sections were cut from the pieces and the mechanical properties measured. Also, the dimensions of the pieces were measured before and after spinning in order to determine the nature of the deformations. APPARATUS AND PROCEDURE Materials Two materials were used in this investigation, cartridge brass (70%Cu30%Zn) and 1100 (2S) aluminum. The materials were purchased in the form of annealed sheet. The brass sheet was.081" thick. Two thicknesses of aluminum sheet were used,.081" and.125", so that the effect of sheet thickness could be determined. Tests on As-Reoeived Sheet A series of hardness and tensile tests were performed on the asreceived sheets to determine the variations in properties between sheets of the same material, and also to determine the extent of anisotropy in the sheets. A further series of tensile tests were performed to determine the effect of the size of the tensile specimen on the tensile properties. The standard ASTM tensile specimens for sheet materials is one inch wide and eight inches long. It was felt that a specimen of this size would be too large for testing many of the spun pieces. Therefore -tensile tests were conducted to determine the variation in tensile properties when smaller specimens were used

The University of Michigan ~ Engineering Research Institute Spinning Procedure The spinning of the test pieces was done by Spincraft Inc. of Milwaukee, Wisconsin. The pieces were spun in the form of truncated cones. A photograph of a typical cone is given in Figure 1. The different reductions were obtained by varying the apex angles of the cones. The angles selected as shown schematically in Figure 2, were 630, 850~ and 1080. In all cases the final diameters of the cones was approximatel constant, and equal to the original diameter of the unspun blank. This deformation process has also been called stretch-forming, roll-forming, hydroforming, and flow turning by various authors. For the brass cones this diameter was approximately 12 inches. For the aluminum cones of both thicknesses, the diameters were about 16 inches. To aid in the study of the deformation process a number of cones were spun to 50% or 95% of completeness. These cones are shown schematically in Figure 3. To further the study of the deformation process, grids were layed out on the blanks of all the cones that were fully spun. The grids, as shown schematically in Figure 4,consisted of two sets of points laid out at 900 to each other. Originally these grids were placed on the spun surface of the cones, that is to say the surface on which the spinning tool was applied. It was found however, that the tool tended to erase the grids during the spinning operation. The grids then were placed on the under surface of the cones, the surface that laid against the pattern,and these grids were preserved. By measuring the grids in a cone after spinning, the amount of the deformation of the piece could be ascertained. A series of small holes forming a grid pattern gave unsatisfactory results due to tearing during the spinning. All of the cones were spun on the same machine and by the same operator. The machine was equipped with pressure guages, and a recording of the pressures,feed rates, spinning tool, was kept fbr each of the cones. A complete listing of all the cones that were spun and the spinning variables that were used is presented in Table Io The spinning variables listed in this table may be described as follows: No load RPM - The speed of rotation of the lathe before the spinning tool was applied in revolutions per minute. Full Load REM -The speed of rotation of ithe lathe during the spinning operation (revolutions per minute).

The University of Michigan ~ Engineering Research Institute Head-in Psi - The radial pressure (pressure in the cylinder forcing the tool in: a direction perpendicular to the pattern) applied by the spinning tool against the piece. (pounds per square inch.) Table forward iPM - The rate at which the tool traveled forward axially (inches per minute) Roller radius - (See figure 5) Roller land - (See figure 5) Comments - Observations made by the operator during the spinning operati-on, The following are kept constant for all the cones. Table forward pressure = 700 psi = axial pressure, the pressure parallel to the pattern. Clamp pressure = 600 psi - Pressure holding the sheet to the patterno Roller material and pattern material were of steel, The lubricant used was the same Spincraft blend, Testing of Spun Cones 1. Measurements of Mechanical Properties. Tensile specimens were cut from all of the fully spun cones, In all cases a 4" specimen was used, as is shown schematically in Figure 6. The specimen had dimensions that are one-half of those of the standard ASTM 8" specimen. Four specimens were taken from each cone, two in an axial direction and two in a tangential direction (Figure 7). The specimens were taken with th ir axis either parallel or perpendicular to the original rolling direction of the sheets so that the effect of any anisotropy in the sheets could be determined. Some curvature was noted in many of the specimens because of the curvature of the material from which they were cut. These specimens were straightened by hand, which might have caused some deviations in the recorded tensile properties. These deviations appear to be unavoidable, but are probably very small since the sheets were already in a heavily cold-worked condition. Hardness readings were taken on the surface of a number of the coneso In some cases however, the variations in thickness of the specimens made accurate measurements difficult o Micro-hardness measurements were made on the

The University of Michigan; Engineering- Research Institute cross sections of several cones in order to measure the variation in hardness from the spun surface to the surface lying against the pattern. Several additional spot tests were also made on some of the coneso These tests will be described later in the report. 2. Measurements of Deformations. Two types of deformation measurements were made, measurements of the thickness, and measurements on the grids, distorting the fully-spun coneso Thickness measurements were made on all the cones and consisted merely of cutting pieces from the cones and measuring the thickness with a micrometer. The grid measurements were made before the cones were sectioned and consisted of locating the points in the grid with a divider and measuring the distance between the divider points on a scale. The grid measurements were rather complex because the different types of deformation that were found. A full description of how these various deformations were measured will be given under'"Results". RESULTS 1 - Tests on Standard Sheetso On the basis of the tensile and hardness tests of the as-received sheets it was concluded that the anisotropy in the sheets was negligible. The tests also showed that there was no significant difference in properties between sheets of the same material, except for a slight difference between the.125" and.081" aluminum. In this case it was found that the.125" aluminum had slightly lower tensile and hardness values that the.081" sheet. The average, as-received properties of the three types of sheet are summarized in Table II. Tests using 4" and 8"1 sized tensile specimens are also listed in Table II. The results show that the 4" specimen had comparable tensile properties to the standard 8" specimen. In view of this similarity it seems likely that the 4" specimens that were used in the testing of cones, gave properties that would approximate very closely those that would be obtained using the standard 8" specimens.

The University of Michigan ~ Engineering Research Institute 2 - Mechanical Properties in Spun Cones. The results of the tensile tests on the spun cones are summarized in Table II. The results show that the tensile and yield strengths increase as the cone angle decreases, or, in other words, the tensile properties increase with the increasing reductions in thickness, as would be expected. The elongations values decrease with increasing reductions which again is what would be expected. In general it was found that the orientation of the specimens in the cone had no effect on the tensile properties, In some cones the specimens in the axial direction had slightly higher tensile strengths than those taken in a longitudinal direction, or vice versa, but these variations were not systematic. These local variations probably represent characteristics of an indivi dual cone only and not the overall process. In the same manner it was found that the original rolling direction of the sheet had no effect on the tensile properties. This result is not surprising since the anisotropy in the as-received sheets are negligible. Some difficulty was encountered in performing the tensile tests because of the variations in thickness in the specimen. The magnitude of these thick= ness variations will be brought out in the next section. It should be pointed out however, that the specimens failed at the region of smallest cross-section Therefore the reported tensile values are not representative of an average reduction of the cone but of some localized spot in the cone where the thickness was a minimum. Finally the tensile data show that there is no significant difference in the properties of the.081" and.125" aluminum cones. Hence it would appea: that the original thickness of the sheet, at least in the range studied, has no significant effect on the resultant mechanical properties. The surface hardness of the spun cones are tabulated in Table IVo A great deal of scatter was observed'in the hardness readings, and for this reason the average hardnesses only are tabulated in Table IV. The hardness values in general increase with increasing reduction in the expected manner. Knoop microhardness readings were taken on the cross sections of a number of cones, but once again the scatter in the data tended to mask the hardness variations. The data for one of these cones is given in Table V, and plotted in Figure 8, Because of the scatter in the data the hardness values are probably best plotted as a band, as shown in Figure 8.

The University of Michigan ~ Engineering Research Institute To determine just how much scatter might be found in microhardness readings of this order of magnitude, several pieces of the as-received sheet were cold-rolled to similar reductions in area, Microhardness measurements were then made on these pieces and the average variation was determined by statistical analysis. It was found that the variations in the cold-rolled pieces were of the same order of magnitude as those found in the cones. Hence the variations found in the cones appear to be due primarilly to the inherent scatter in the method of measuring the hardness, and not to variations in the cones themselves. In general the hardnesses tabulated in Table V are typical of the cones examined, and the decrease in hardness with distance from the spun surface (Figure 8?) is representative of most of the cones. Metallographic examination of the cones also show the variation in hardening under the spun surface. Some photomicrographs of cross-sections of the brass cones are given in Figure 9, The photomicrographs show that the spun surface of the cone is highly deformed, and that the deformation decreases as the distance below the spun surface increases. As mentioned above, most of the cones showed a progressive decrease in hardness with increading depth below the spun surface. Several cones however, showed a slight increase in hardness, just below the spun surface. (Figure 10) In order to confirm this observation several additional tests were made on one of these cones. The first test consisted of cutting a small section from the spun portion of one of these cones and measuring the Rockwell B hardness of the spun surface in the conventional manner, A layer of material was then removed from the spun surface by immersing the piece in concentrated nitric acid. The hardness of the newly exposed surface, which lay several thousanths under the original spun surface, was then measured, Another layer was then removed and the hardness measured again. Repeating this procedure several times gave the results shown in Figure 11, The figure shows that there appears to be a distinct increase in hardness in the region under the spun surface. A second test consisted of immersing the piece in acid before and then measuring the X-ray line breadth after each surface removal. The results are shown in Figure 12. The increase in line breadth shows that the region under the spun surface shows greater distortion than the surface. As a final test, several pieces of the cone were annealed at various lengths of time at 626~F and then examined metallographically, Courser grains were found under the surface which shows that recrystallization began in this region. This would be rue only f the regon had a larger amount of energy stored up through a larger distortion.

The University of Michigan ~ Engineering Research Institute In view of these results it appears that the region under the surface o this cone is really harder than the spun surface. The reason for this behavio] is uncertain, but is probably due to the partial recovery of the spun surface of the cone. Considerable heat is generated during spinning, and this heat could cause partial recovery of the highly deformed region at the spun surface The region under the surface however, would not be subjected to temperatures as high as the surface temperature and therefore would not recover. Thus, after the spinning was completed the region under the surface would be the more distorted because no recovery had taken place. There does not seem to be any reason in terms of the pressures, feed rate, and other spinning variables, why some cones should show partial recover while others did not. A Possible explanation may be that insufficient lubrical t was used during spinning of these pieces. This would increase the friction between the spinning tool and the sheet, and therefore produce a higher temperature in the sheet. Unfortunately there is no data to indicate whether or not this was the case. In general the mechanical properties of spun pieces are similar to thos produced by rolling. A comparison of the properties produced by these two methods are shown in Figure 13 and 14. The agreement seems quite good, particularly for the aluminum. Hardness values are not included in the aluminum data because of the uncertain values found. Thus for these materials the tensile properties of a spun piece can be estimated by knowing the properties produced by cold rolling to the same reduction. It must be recognized that the properties are not completely analogous, in view of the variations in work hardening from one surface to the opposite surface,in a spun piece. This variation may be very important when one uses a spun piece in some service applicationo Spinning produces a much more nonhomogeneous deformation than rolling, and it is only the average value taken through the whole cross-section of the piece which gives comparable properties with a cold rolled piece. Furthermore, as will be brought out in the next section, there may be large variations in thickness in a spun piece. The tens le properties of a spun piece are dependent upon its minimum thickness and not on the average thickness. Thus care must be taken to locate the region of minimu~ thickness and use the tensile value for the reduction in this region and not those for the overall reduction when making any estimateso With these limitations in mind however, it would seem fairly reliable estimates of the mechanical properties can be made from rolling data.

The University of Michigan ~ Engineering Research Institute 3 - Deformations in Spun Coneso The thicknesses founld in the spun cones are summarized in Figure 15. In these plots the thickness of etach cone is plotted against thie distance from the bend., that is, the radial di.stance from the spot where spinning'began. As would be expected, the thickness of the cones depends upon, the cone angle, wit the smaller angle cones having smaller thicknesses. In general the results show this, but they also show that there may be considerable variations in thickness in a single cone, and also between cones of the same:included angle. In general it appears that the variations nIn. t;hickness are g~reIater in the brass cones than in the aluminum ones. Comparison of the results of the 50%, 95%, and fully spun cones for the same cone angle show that the thickness does not appear to be influenced by how much of the cone has been spun.. In other words, it does not appear that furthe spinning on the piece alters the thickness of the portion that has already been spun. Thus the thickness at any region in the cone is dependent only' upon the forces that act on that particular region, and is not affected by deformations taking place in other regions of the cone; — that is, the plastic:e deformation.takes place under the roller. Comparison of the thickness measurements of the 0.081"1 and 0.125"' aluminum cones shows that'the variations in'thickness along the cone are of the same magnitude. Hence, the original thickness to have little effect on this aspect of the deformationo This result is in agreement with the mechanical tests, which showed that the tensile properties we:re the same o The grid d.stort ions found.i. the fully spun cones are shown schemati.call. y in Figure 16. As shown in the f.igure, two types of distortion were found.. The first is a radI.al elongation of the grids because of the'ncrease in lengt;h of the sheet in'the spun region. The second is an tangential. movement of the grids because o sheang the sg acton of te spining tolo The magni'tud.e of this shear was determained by extend.ing an or'2gilnal l.ine of thbe grid from the unspun region of the cone and measuring the d.istance of this new extended line to the grid points. No change in the width of the grids was noticed. The radial elongatliorns vs the d.istarnce from t;he bend fo'r the various cones are shown in Figure 1.7o In these figures the distance f-rom the bend was taken at half the d.istance between the two g:r:d. po'nts that give the correspond ing elongation value o The overall elongation. that is the elongation between. the first and last poi.nt are also plotted. The results show that there are considerable variations in the elongations:Ln the coneso It should. be pointed. out again however, that'the grids were on the undersid-e of the cones and thus only approximate the deformat;ion of the wh.ole.e piece Once again the results on the al9umi.nzum sheets al.so suggest that the elosga't;:-ion's _not,,affected. by the original. thi. ckne1 ss o

The University of Michigan ~ Engineering Research Institute Conservation of volume requires that there should be a direct relationship between the elongation and the thickness in a deformed pieces Comparison of the radial elongations and thicknesses in the fully spun cones are presente in Figure 18, The figures show that there is a sample linear relationship between the two. The tangential movements of the grids are plotted in Figure 19 as a function of the distance from the bendo This distortion should be due to the shearing force, and if the shear force were constant these curves would be straight lines. In the present case it appears that the shearing force was usually lower at the start, and then increased slightly.o The overall results show groups of cones which seem inconsistent insofar as their deformation is concerned, The first set includes 4A1B and 4AlCo In these cones the thicknesses are greater than would be expected on the basis of the thickness values for the other 125" aluminum coneso The operators comments (Table I) note that not much spinning was done on cone 4A1Co The same could probably be said for 4A1B. It is interesting to compare the thicknesses of these two cones with that of the third cone, 4A1A, that was spun to this shape. The thicknesses of the first two cones are on the order o o.096"t, while the thickness of 4A1A is about.:066". Thus a difference in thickness of approximately 30o can be found in pieces of the same geometry. The spinning forces were not the same for these three cones, however. The other data which appears out of line involves the tangential displacements in cones 3A3P and 3A3F, and 4A2M and 4A3Eo It seems reasonable to assume that the amount of tangential displacement would increase with increasing reductions in thickness. In these two sets of cones however9 the order of displacement is reversed, That is, a cone with greater reductions show less displacement and vice versa. The reason for this effect will be discussed in the following section DISCUSSION In order to correlate the deformations in the cones with the spinning variables used (Table I) it is necessary to establish certain basic assumptions. The first assumption is that spinning may be treated as a plastie flow problem, and that the general laws of plasticity are obeyed. The second assumption is that it would be desirable to spin a piece in which the thickness is Constant. This assumption is certainly not the only one that could be made. and. the problem could be treated equally well using other approaches. On -the'basis of strength, response to heat treatment, and other metallurgical variables, however 10

The University of Michigan ~ Engineering Research Institute this second assumption is a very practical one. For example the agehardening characteristics and the corrosion resistance could be markedly different in various regions of a spun plece if the deformation was not uniform, The final assumption is that the diameter of the piece after spinnin is equal to the diameter of the unspun blank. On the basis of these assumptions the thickness of the cone should be a function of the cone angle, and can be expressed by the relation: S i S sin a/2 where S = thickness of the spun section So = thickness of the blank =a cone angleo From the above equation the required thicknesses of the spun sections of the cones can be calculated. These calculated thicknesses are listed in Table VI, A comparison of the calculated thicknesses with those actually found in the cones shows that in most cases there is a distinct departure from the ideal case of constant thicknesso Since the thickness of a cone is controlled by the spinning variables that were used, the problem is to show how changes in the spinning variables cause departures from constant thickness. Unforn tunately the data are not sufficiently complete to make a fully rigorous solution possible. To do this would require information concerning the magi nitudes and extent of the regions of elastic and plastic strains in the cone. It is possible however, to show in general how the thickness is influenced by the spinning variables. On the basis of the thicknesses found in cones of the same geometry but spun to 50%b, 95% and fully complete, it would appear that the thickness at any spot in the cone is determined solely by the action of the spinning tool as it went by that spot. In other words, the thickness at any spot -is due onl1 to the instantaneous spinning forces acting at the spot. Once the spot has been deformed its thickness is unaffected'by the deformations in. other regions of the cone. Thus variations in thickness must be due to variations in the applied forces, or to the variation in the resultant force. 1.1

The University of Michigan ~ Engineering Research Institute In the present investigation two forces were measured, the force perpendicular to the surface of the cone (head-in pressure) and the force paralle to the cones surface (axial pressure)- This second force (pressure) was kept constant for all of the cones that were spun in this investigation. The thick ness of the cone would probably not be changed a great extent by changes in the axial force however, since its main use is only to bend the material down in front of the tool. (Figure 20) This conclusion is in agreement with Siebel and Droge (7), who show that the axial force changes only slightly with large thickness changes. The force which primarilly controls the thickness is the head-in force (Figure 20). Siebel and Droge show that the change in thickness is almost directly proportional to the head-in pressure. Thus one should find that when. this force is large the thickness is small, and vice versa. Comparison of the thickness data with the head-in pressures in Table I support this conclusion quite well. The magnitude of this force is of course dependent upon the mater al being spun. Thus one finds pressures on the order of 20-25 psi for the alumin cones and 300=500 psi for the brass canes. The magnitude of the head-in pressure will also depend upon the cone angle. Smaller cone angles will require a greater reduction in thickness and consequently a greater hand-in pressure, The relative change in pressure with thickness will of course be dependent upon the plastic properties of -the material. In the present investigation, the applied pressures (radial and axial) were kept constant during the spinning of each single con.e. Thus some question might be raised as to why the thickness of the cone varles as a function of the distance from the bend, if the pressure were constant. The answer to this question. hinges upon the resistance of the sheet to deformation. The resultant thickness depends upon the net:force applied to the material., which is the sum of the applied forces (pressures) minus the sum of the resisting forces in the material.. These resisting forces are a func'tion of the distance from the bend. Thus the net force and consequently the thickness will be a function of the distance from the bendo Let us consider the case where the splnnlng tool is still near the bend. (Figure 21) Ahead of the tool there is a ring of metal which is as-yet unspun. Now this ring of metal will be elastically stressed because of the deformation that has already taken place in front of this ring. These elastic stresses will then act to either aid or hinder the deformation stresses of the spinning tool. 12

The University of Michigan *. Engineering Research Institute Suppose that the head-in pressure is too small, and that the thickness of the spun region near the bend is therefore larger than the ideal thickness. The outer ring'is then being pulled' inward and consequently there is a tensile stress built up in the metal at the point where the spinning tool is being applied. This tensile stress favors the reduction in thickness and therefo:re the thickness should be less at this region. Continued spinning therefore should decrease the thickness of the piece. Further out from the bend however some point must be reached where the elastic stresses in the ring become too small because the size of the ring has been progressively decreasl.ng. The helping stress will then become progressively smaller until it becomes zero at the final outer edge of the cone. The thickness will therefore become greater toward the outer edge of the cone, By the same style of reasoning it can be shown that when the head-in pressure is too large that the thickness should be less than the Ideal thickness at the region near the bendo In this case however, the unspun ring will exert a compressive stress which will tend to act against the head-in pressure. Thus the thickness will increase with increasing distance from'the bend, When the unspun ring becomes small the compressive stresses will be lessened, and.thus the thickness will decrease at the outer edge of the cone, On the basis of this type of reasoning the cone thicknesses should vary as shown schematically in Figure 22. Comparison of the p:redicted'thickness variations with the actual variations found in the cones shows fairly good agree mento For example, cones 4A1A, 4AlC, 5AiF, and 5A1G have thicknesses that are greater than the predicted value,9 and in these cones the thickness's greater at the bend, decreases slightly, and then increases, in accordance with the general theory o For cones where thickness is less than the calculated value, the theory does not seem to hold as well. These cones have low thickness valueS at the bend and increase in thickness with increasing distances from the bend, in the expected mannIer, A decrease in thickness does not generally occur at some further distance from the bend, as would be predicted. Examples of this type are cones 5A2J, 5A2R, and 6A2So It may,'be that some other variable is coming into play in these cases, such as the feed. rate, which is tending to further affect the deformation. The results also show that some of the cones are approaching the ideal condition where the thickness is the calculated thickness. These cones are 3A3DD, 3A2N, 3AlD, 3A3EE, 3A1E, 3A3FF, 3AlH, and 5A15o Thus it seems possible to produce cones of constant thickness by a proper select.ion of spinning variables, As mentioned previously, the results are not suitable for making a rigorous analysis, but they do show in which di.rection the variables should be altered in order to produce the calculated thickness, 13

The University of Michigan ~ Engineering Research Institute In addition to the cone angle and the head-in pressure, other variables which will affect the deformati.on are the feed rate and the roller:radius. it is quite easy to see that an increase in the feed rate would tend to increase the thickness of the cone, Perhaps the best way to illustrate this is by analogy to the common. tensile test. It is well known that the tensile strength increases when the strain rate is increasedo In spinning, an increase in the feed rate is equivalent to increasing the strain rateo Thus tihe tensile strength- of the material would be greater and consequentlyy the reduct.on in thickness would be lesso The net result would be that the final thickness woul be greater with increasing feed rate. In most materials however, small changes n the strain rate do not significantly alter the ten.sile propertieso Thus the thnickness should not vary a great deal. as long as the feed rate is not changed over several orders of magnitude~ Other factors, such as the surface smoothnesS of the piece, also enter in when the feed rate is changedo It may'be desirable., in some cases to change the feed rate in order to produce a good surface, regar d less of the effect on the thickness. The roller radius w.ll also InfLuence the thickness of the piece to some extent. The effect is comparable to the effect of the roll radius in cold rolling. When a smaller radius is u.sed in cold rolling the contact area between the roll and the piece is decreased, if the applied force remains'the same, of course. Because the contact area is dec:reased the applied pressure.s greater and is also better directed, and therefore the deformation is greater. Spinnin may be likened to cold rolling with only one roll at least to a rough approximation, and thus the effect of decreasing roll radilus should be to decrease to thickness of the spun piece with a given set of forceso It is difficult to fin. a concrete example of this effect in the data, but the general results tend to support this point of viewo In addition Siebel and Droge al.so note that the roaLl radius should be kept small to minimize flow in the axial direction. While all of the discussion thus far has been based on the th-ickness of the piece, the other deformations noted in the cones may also be related to| the spinning variables in the same mannero The radial elongation was shown. to be proportional to the thickness, for example, and thus the elongations in the cones can be explained in the same manner as the thicknesses. The tangential displacements are also influenced by the spinning variables, but in this case the relationship is more uncertaino The tangential displacements are due to the tangen:tial. force produced in the cones. No direct measurement of this tangential force was made. The tangential. force is actuall'Y a resultant force obtained from the head-in and. axia:l forces, and. thus is dependent upon the magnitudes of these forces. It is also dependent upon the cone angle. Furthermore the tangental force should al.so be dependent upon the friction between the roller and the cone, and although the same lubricant was used throughout, there is no guarantee'that the fr:iction force was constanto

The University of Michigan ~ Engineering Research Institute In general one would expect to find that the tangential. d.isplacement increases with increasing applied pressures, and this seems to be true in most caseso The exceptions to this were noted in the results section, in which the displacements of several of the al.uminum cones do not vary rin th.s expected manner. A number of the spinning variables were altered between these cones and therefore it is not easy to assign the cause of the exceptions to a single varianleo From an overall comparison of the va:riables in Table I, though, it would appear that the difference in the roller diameter is the most likely cause. The cones which show too much deflection were formed with the 3/8' ( radius roller, while those showing too little deflection were formed with the 1/8" radius roller. In view of the comments already made concerning the effect of the roller radius it would seem likely that a larger radius roller would tend to produce a greater tangential force, and vice versa. A difference in the friction could also account for the differences in deflection however, 9 and therefore a definite conclusion cannot be made. In any case this concern over the tangential displacement may be of little importance since it would not be of m'jo0ri concern Jin determining, the properties of the piece. The foregoni.g discussion has been:intended to describe how the deformations produced by spinning are controlled by the various spinning variables~ It should not be implied however, that the variables that were discussed are the only ones which will affect the deformationo Examples of the variables that have not been systematically varied are; rotational speed of the spinning lathe, spinning tool shape, lubrication, and the initial blank temperature~ It is expected that the effects of these variables will, be considered in future worko CONCLUS IONS On the basis of this investigation the followi,_ng conclusions can be made concerning the properties of spun pieceso 1 Mechanical Properties, a) The tensile and yield strength and hardness of spun pieces increases with increasing reductions. b) The tensile elongations decrease with increasing reductions~ c) The tensile properties and hardness produced. by spinning are in general quite similar to those produced by cold:rolling to the same reduction. Thus, to a first approximation, the mech.an.ical 15

The University of Michigan ~ Engineering Research Institute properties of spun pieces may be estimated from the cold-rolled properties. Some care must be taken to locate the region of minimum thickness in the spun piece because this is where tens.l.e failure will occur. d) There is a difference in the degree of cold working from the spun surface to the opposite surface. In some cases the maximum residual distortion may occur beneath the spun surface2 presumably because of the recovery of the spun surfaceo e) For the thicknesses studied, the resultant mechanical properties do not depend on the original thickness of the sheet. 2 Deformations. a) There may be large variations in thickness of spun pieces, and also large variations in thicknesses between pieces spun to the same reduction. b) In the same manner there may be large variatilons i.n the elongati.on.s and the tangential displacements in the pieces. c) Spinning to 50%, 95% or 100% completion does not appear to alter the deformations in the pieceso d) It seems that a qualitative picture of the deformation process can be used to describe the deformation process, and how the thickness should vary in terms of the spinning variables~ In general the spin.nding variables should act as follows1o The reduction in thickness is controlled primarily by head-in pressure, and large head-in pressure shoul.d cause large reductions. 2. Smaller feed rates should cause greater reductions~ 3o Small. roller radius should increase the reduction, Lnd probably tend to decrease the tangential displacements. K The axial pressure, and the rotational speed of t'he _athe do not appear to be impo:rtant variables and small ihanges in, these quantities should not affect the reduct~i.oln 16

The University of Michigan ~ Engineering Research Institute REFERENCES 1. J. Lengbridge. Tool Eng. 30 (1953) 89 2. J. R. Young - Machinery - London 86 (1955) 187. 3. F. L. Banta - Product Eng. 25 (1954) 189. 4. K. Stalker and K. Moore - Am - Machinist 99 (1955) 126. 5. Anon. - Product Eng. 27 (1956) 135. 6. K. W. Stalker - ASME preprint no. 57-A-271 - 1958. 7. E. Siebel and K. Droge - Werkstatto and Mach. 45 - 1955.

Table I - Listing of Spun Cones Sample No. %Spun No Load Full Load Head=in Table Forward Roller Roller Comments RPM RPM psi 1 p.m. Rado Land 5AlG 50 400 400 400 20 1/8" 1/4"t Metal not completely. on block. Not enough head, in pressure, 5A1F 95 400 40 300 20 1/8"1 1/4" Metal block completely~ Not - enough headin pressure. 0 5A1J 100 400 400 500 20 1/8" 1/49" Large amount of.ead'-n pressure required to metal on block 3A!D 50 350 350 25 28 1/8" /4" Unspunportion of blank m distorted due to excess. table forward, 3 3A1E 95 350 350 25 25 1/8 st 1/41" Cut. down table forward speed to eliminate wrinkle.Pm on er.nd. 3A'LH 100 350 350 25 25 1/8" 1/4" O.K. 4A.iC 50 350 350 50 28 1/8" i/4"' Speed of spindle unchanrg::n during spinning Nots mluc h spinning was done. o 4A1B 95 350 320 50 28 1/8" 1/4 99 nease table speed t-o elminate spirals.

Sample No, %Spun No Load Full Load Head-in Table Forward Roller Roller Comments RPM RPM psi 1 p.m. Rad. Land -I 4AlA 100 350 300 50 20 l/8?t 1/4" Table forward speed too C slow spirals occurin spinning. Spindle speed - drop occurs at maximum stroke. 6A2S 50 44o 44o 500 20 1/8" 1/4" O.K. 5A2R 95 440 440 550 20 1/8" 1/4t" O.K. 5A2T 100 4oo 400 425 20 1/8" 1/4t? O.K. 3A2N 50 400 400 25 48 1/8" 1/4?? O.K. 3A20 95 400 400 25 48 1/8" 1/4?? O.K. 3A2P 100 400 400 20 48 1/8?? 1/4t? O.K. 4A2K 50 350 350 50 25 1./80V 1/4"1 Table forward was too slow, Spirals occured on large end. 4A2L 95 350 350 50 28 1/822 1/4H Table forward too slow = spindle speed too slow. Spirals occured. 4A2m 100 400 400 50 48 l/8T? 1/41 Increased speed of spndie~ and table forward to elmc nate spirals. Piece good.

Sample %Spun No Load Full Load Head-in Table Forward Roller Roller Comments RPM RPM psi 1 p.m. Rad. Land 6A3GG'- 50 500 480 375 20 1/8"1 1/4" Head-in pressure too greati Metal flared back against roller. V1 6A3HH 95 500 480 300 20 1/8" 1/4" Head-'in pressure stll too < great. Metal falring back. O 5A3JJ 100 500 48o 275 20 1/8" 1/4" OoK. 0 3A3DD 50 46o 46o 10 42 3/8" 3/16" 0.K. 3A3EE 95 46o 460 10 42 3/8" 3/16" it K. 3A3FF 100 460 460 10 42 3/8t? 3/16" 0tK. m 4A3AA 50 400 400 25 28 1/8" 1/4"1 Roller too sharp and headc 3 in pressure too great. Material tends to back over radius of roller. 4A3BB 95 46o 460 15 28 3/8" 3/16" 0 K. 4A3cc 100 46o 460 15 28 3/8" 3/16" 0.K.

For all Specimens Table forward psi = 700 Clamp psi = 600 Lubricant = Socony Spincraft Blend #1. Legend In the sample numbers, the first number refers to the material, No. 5 and 6 = Brass No. 3 =.081" aluminum VN No. 1. =.125" aluminum9 -3 0)'A

The University of Michigan * Engineering Research Institute TABLE II Tensile Tests Data on As-Received Sheets Total Width Avg. Tensile Avg. Yield Material Length Test Section Strength psi Strength psi Elongo Brass.081" thick 9".562" 47,650 16,400 57 8".500" 47,500 16,800 65 7" o.423" 48,500 17,000 65 6" ~500" 47,700 17,500 67 6" ~.378" 48,200 19,500 63 5".338" 48,100 17,800 70 4".500" 47,800 17,800 70 4".250" 47,100 17,200 65 4".125" 52,100 20,300 60+ Aluminum.081" thick 8" o 500" 13, 600 5,400 41 6" ~375" 13,600 5,700 40 4".250" 13,600 6,200 37 Aluminum.125" thick 8".500" 11,100 4,100 40 4".250" 11,600 4,600 38

TABLE III - Tensile Properties of Spun Cones Each value is average of two specimens, one parallel and one perpendicular to the original rolling direction. radial direction = direction from center of cone to outer edge. - tangential direction = direction parallel to outer edge of cone or perpendicular to radial direction. Cone Average Tensile Strength Yield Strength Elongation Cone Angle Thickness" (psi) psi.2% offset % 1" Brass 5-A-lJ —radial diro 63~.042 79,900 75,100 7 tang. diro 630.042 86,oo000 68,ooo000 9 Brass 5-A-2J —radial dir. 850.051 77,800 62,500 10 tang. dir. 850.051 80,000 63,200 * Brass 5-A-3J —radial dir. 1080 o063 69,500 66,200 9 tango dir. 1080 o063 71,100 57,800 12.081" Al 3AlH-radial dir. 630.044 18,500 17,190 9 tang. dir. 630 o044 18,600 17,250 9'.081" Al 3A2P-radial dir. 85~ oO051 17,700 16,150 10 tang. dir, 85.051 17,900 16,900 9.5.081" Al 3A F -radial dir. 1080.062 15,950 15,050 12 tang. dir. 1080.062 15,800 15,070 11.125" Al 4AlA-radial dir. 630.177 19,200 18,400 85 tang. dir. 630.177 19,200 17,950 10.125" Al 4A2M-radial dir. 85~.194 18,250 17,300 9.5 tang. dir, 850.194 18,950 17,600 10,5.125" Al 4A3CC-radial dir. 1080.235 16,150 15,050 13.5 tango dir. 1080.235 16,100 14,900 15 * Both specimens broke at gage marks.

The University of Michigan ~ Engineering Research Institute MECHANICALLY SPUN Table IV Hardness of Spun Surface of Mechanically Spun Cones Cone Average Hardness Rockwell B Scale 630 Brass 87 850 Brass 85 1080 Brass 8d Average Brinnel Hardness No. 500 Kg load 10 mm ball 630 081" Al 30 850 081" Al 28 1080 081" Al 27 630 125" Al 29 850 125" Al 27 1080 125" Al 27

The University of Michigan ~ Engineering Research Institute Table V - Microhardness Readings on Cross-sections of cone 6A3GG. Knoop indenter, 1000 gram load. Positions 1 and 2 are in the unspun section of the cone. The remaining positions are all at a various region in the spun section Position on Specimen Total thickness Distance from Knoop Hardness (relative units) Spun surface Number (relative units) 1 202 25- 79o9 65 83.4 105' 76.2 145 77.7 185 78,8 2 200 20 7502 60o 830o 100 80,7 140 81Ll 180 79 5 30 180 20 164.6 50 15701 80 166o9 110 15902 135 143.4 160 133.1 4 174 20 17604 48- 165.7 76 170.4 104 168.0 132 139o0 154 133.9 5 170 17 182.8 55 180,2 83 171.5 101 163.5 129 149 0 153 123.8 6 160 15 171.5 42 17809 69 16507 96 168.0 123 153o0 145 152.0

The University of Michigan * Engineering Research Institute Position on Specimen Total thickness Distance from Knoop Hardness (relative units) Spun Surface Number ( relat ive units ) 7 158 15 18208 42 188.2 69 182.8 96 178.9 123 157.1 145 149 o 8 152 18 185.4 48 180o2 78 186.8 108 165 7 134 1.49. o0 9 147 18 193.7 48 186.8 78 175.2 108 169.2 129 155.0 10 146 18 198.1 48 18002 78 17809 108 160o2 130 1540 o 11 149 18 188.2 48 184.1 78 177o7 108 158,1 130 145.2

Fig. 1. Photograph of spun cone.

THIS REGION NOT SPUN / APEX ANGLE Aa —-. -. 630 SPUN REGION n o 85~ -; % 108 SCHEMATIC VIEW SHOWING CONE ANGLES FIG. 2

SPUN REGION NOT SPUN 50% SPUN SPUN REGION NOT SPUN 95% SPUN SCHEMATIC VIEW SHOWING 50% AND 95% SPUN CONES FIG. 3

1/2" T LAYOUT OF GRIDS ON BLANKS BEFORE SPINNING FIG. 4

SCHEMATIC VIEW OF ROLLER SHOWING RADIUS AND, LAND FIG. 5

1-3/J16" 1/4" 3J8" |, 1-1/8" min 3/8" e~L 4" FOUR INCH TENSILE SPECIMEN FIG. 6

RADIAL SPECIMENS TANGENTIAL SPECIMENS LOCATIONS WHERE TENSILE SPECIMENS WERE CUT FROM CONES FIG. 7

CONE 6A3GG 200 Spun region u 180 I 160 Z I < 120 0 too Unspun region 0 z 80 20 40 60 80 100 120 140 160 DISTANCE FROM SURFACE - RELATIVE UNITS VARIATION IN MICROHARDNESS WITH DEPTH BELOW SPUN SURFACE FIG. 8

Pictures tilted to show complete cross sect~io 1$ (a) Unspun center portion of cone. (b) Region at bend of cone. Note beginning of cold worked microstructure. Pictures tilted to show complete cross section.

Nl-'~~~~~ z-'MI' r ~ ~ i.:~r~r.~g~qrw~ ~C~B~F; -g* (c) Spun region of cone. Note difference in microstructure at top (spun surface) and bottom. Fig. 9. Continued

CONE 6A2S 200 Spun Region ceo' 140 z [ 120 I | 0 100 Unspun region 0 z I / 60 20 40 60 80 D00 120 140 160 DISTANCE FROM SURFACE - RELATIVE UNITS VARIATION IN MICROHARDNESS WITH DEPTH BELOW SPUN SURFACE FIG. 10

(CONE 6-A-2-S) EACH POINT IS AVG. OF 4 OR MORE READINGS 88 uJ z 3 86 O/ uJ I 84 0 82 80 1 l l l l I.000.002.004.006.008.010.012 DEPTH FROM SPUN SURFACE, IN. VARIATION OF HARDNESS WITH DEPTH FROM SPUN SURFACE FIG. 11

20 > 19,, 18 I XL 16 15 X.002.004.006.008.010.012 DISTANCE FROM SPUN SURFACE (IN.) X-RAY LINE BREADTH vs DISTANCE FROM SPUN SURFACE CONE 6A2S FIG. 12

90 HARDNESS D SPUN LTENSILE STRENGTH 80 40 eZ DATA FOR COLD-ROLLED _.., / -,to SPUN BRASS FROM - FRENCH, u / TR-AIME 1944, VOL. 156 coROLE P195 0. 70 IL LU ~ Z Z k. PL ru 60 r/ * 12 0 Iu - I \SPUN 50 _2 10 40 0 10 20 30 40 50 60 70 80 90 PERCENT REDUCTION COMPARISON OF MECHANICAL PROPERTIES OF BRASS PRODUCED BY SPINNING AND ROLLING FIG. 13

o.081-IN. ALUMINUM CONES.125-IN. ALUMINUM CONES ROLLING DATA FROM METALS HANDBOOK 25 20 SPINNING TENSILE STRENGTH 15 g40 u,~n~~~~ ~ ~~ROLLING -:3 0 - z Z,u O I BY SPINNING 20 FIG. 1400 ELONGATION Z ROLLING 51 I I I I 1 i 0 0 10 20 30 40 50 60 PERCENT REDUCTION IN THICKNESS COMPARISON OF MECHANICAL PROPERTIES OF ALUMINUM PRODUCED BY SPINNING AND ROLLING FIG. 14

.066.064'P.o —c 5A3J ~~~~t ~~'''~.......p....._...d..062' 0 O X O.060 X ( 6A3HH.058 6A3GG.056 z L — - - -_ 054 5A2J LU I,.052 O6A2 -.050 5A2R.048 15A1F.046.044. —*0- "'5A1J.042 0 DISTANCE FROM BEND, IN. THICKNESS vs. DISTANCE FROM BEND - BRASS CONES FIG. 15a

.066.064 --- O *f3.062 o —:3A3DD No,2 3A3FF.060 3A3EE.058.056 n.054 3A20,.052 3 2.050 b..........o-.. 0.048 8'.' 3A2N.046.044 [A -A A 3A1E.042 0*Q..Qa1 s - mm - Ohmme.wo..040._ A 0 2 3 4 5 6 7 DISTANCE FROM BEND, IN. THICKNESS vs. DISTANCE FROM BEND -.081-lN. ALUMINUM CONES FIG. 15b

.120 p 4A3AA (50%).115.1 10 I 4A1C (50%) 4A2K (50%),10, / 4A2L (95%).090 -.085' 4A1B (95%).080 o 4A2M.075.065 0 2 3 4 5 6 7 DISTANCE FROM BEND, IN. THICKNESS vs. DISTANCE FROM BEND - 0.125-IN. ALUMINUM FIG. 15c

UNSPUN CENTER REGION BEND SPUN REGION | J |THIS LINE SCRIBED | ON CONE AFTER SPINNING /-/7 I RADIAL E LONGATION / i' JTANGENTIAL /~ /,:,,DISPLACEMENT OUTER EDGE OF CONE / GRID DISTORTIONS IN FULLY SPUN CONES FIG. 16

OVERALL 100 --- -- OVERALL 80 840 0 5-A-2-J (850) 20 0 2 3 4 5 DISTANCE FROM BEND, IN. RADIAL GRID ELONGATION-BRASS CONES FIG. 17a

100 OVERALL 90 __ - - 3-A-1-H (63~) 80 70 0 60 OVERALL o - --- --— i 3-A-2-P (8 5~) 0u 50 40 30 o OVERALL * —'"-'-ON=".~ qm~ ammmm 3-A-3-FF (108~) 20 10oL I..I..I II I I I I I I 0 2 4 6 8 10 DISTANCE FROM BEND, IN. RADIAL GRID ELONGATION -.081-IN. ALUMINUM CONES FIG. 17b

90 OVERALL 80 70 4-A-1-A (63~) 60 OVERALL 0 O o 4-A-2-M (850) 40 30 _ 0 4-A-3-CC (108LL OV.ERALL 20 / I 0 0 2 4 6 8 10 12 DISTANCE FROM BEND, IN. RADIAL GRID ELONGATION-.125-IN. ALUMINUM CONES FIG. 17c

0 100 90 80 70 a 0 <3 60 0 z 0 A10 40 30 20 I0.040.050.060.070 THICKNESS, IN. ELONGATION vs. THICKNESS-BRASS CONES FIG. 18a

100 0 90 80 _o 60 0 40 30 20 10 0.040.050.060.070 THICKNESS, IN. ELONGATION vs. THICKNESS-.081-IN. ALUMINUM CONES FIG. 18b

100 90 0 90~~~~ 80 0 70 70 I \o O 60~~~~~~ o 0 ~.60 0 - 50 0 Z 0 0 -J40 30 20 10 0 1.060.070.080.090.100.110 THICKNESS, IN. ELONGATION vs. THICKNESS-.125-IN. ALUMINUM CONES FIG. 18c

5-A-1-J (630).8.7.6 Z -.5 O L. 0 Z 5-A-2-J (85~) I,.4 U LUI 5-A-3-JJ (108~).3.2.. 0 I 2 3 4 5 DISTANCE FROM BEND, IN. TANGENTIAL GRID MOVEMENT-BRASS CONES FIG. 19a

3-A-1-H (630),5.1 / z4/ A4 / 3-A-3-F (1080) O L3 L" L,2 I A. -- 3-A-2-P (850) 1 3 4 5 6 7 8 9 10 0 I 2 3 4 5 6 7 8 9 10 DISTANCE FROM BEND, IN. TANGENTIAL GRID MOVEMENT-.081-IN. ALUMINUM CONES FIG. 19b

4-A-1-A (6308').5 I,cl.. |L: 4-A-3-CC (1080) 0 z 03.i l X 4-A-2-M (850) 0 1 2 3 4 5 6o 8 9 10 DISTANCE FROM BEND, IN. TANGENTIAL GRID MOVEMENT-125-IN. ALUMINUM CONES FIG. 19c

CONE TABLE FORWARD FORCE = AXIAL FORCE HEAD-IN FORCE IATTERN///// VIEM OF FEED RATE SCHEMATIC VIEW OF SPINNING FORCES FIG. 20

TOOL ELASTICALLY STRAINED REGION ELASTIC STRESSES DURING SPINNING FIG. 21

Head-in pressure too small Ideal case S=So sin C/2 LJ I Head-in pressure too large DISTANCE FROM BEND PREDICTED VARIATION IN THICKNESS vs DISTANCE FROM BEND FIG. 22

UNIVERSITY OF MICHIGAN 3 901 5 02227 08731111111 3 9015 02227 0873