Punch Diameter Research Articles

Production of aluminium-copper alloy by transient liquid phase sintering : M.Ozawa et al. (Muroran Inst. of Technology, Japan.) J. Jpn Inst. Light Metals,vol 46, no 4, 1996, 171–176. (In Japanese.)

In this paper, a study on the quasi-static penetration resistance behaviour of unidirectional carbon fiber fabric/High Density Polyethylene (HDPE) composite with two different thicknesses which are laminated 4L and 12L (4 layers & 12 layers), i.e., HC = 3.1 mm and 9.3 mm, is presented using the quasi-static punch shear test (QS-PST) methodology for the experiments. The penetration resistance is usually shown by a load–displacement graph, integral of which is the energy dissipated by the composite during penetration. The penetration energy varies with the diameter of the support span which can be equal or higher than the punch diameter. During tests, a flat punch of diameter 7.6 mm with a range of support spans 8.89 mm–50.8 mm has been used and QS-PST experiments are carried out for varying support span to punch diameter ratios (i.e., SPR = 1.16, 1.33, 1.67, 2.00, 2.33, 2.67, etc.). Their damage mechanisms for different SPRs and thickness are documented. Stiffness, peak force, deflection, damage area, and energy dissipation results are presented in detailed form.

Dynamic behavior of lung parenchyma in shear.

Dynamic shear properties of excised rabbit lungs were studied by measuring creep deformation after application of a step indentation force to the pleural surfaces by a rigid cylindrical punch. The punch diameter was 9.5 mm, and punch forces were 2,4, and 6 g. Measurements were made at lung volumes of 40, 60, and 90% of the total lung capacity before and after lavage with 3-dimethyl siloxane, which provided a constant surface tension of 16 dyn/cm at the alveolar surfaces. A power-law model was fitted to creep data and then transformed into the frequency (f) domain by using Laplace transforms. The optimum model parameters were used to calculate shear elastance (E mu), shear resistance (R mu), and shear hysteresivity (2 pi fR mu/E mu) between 0.01 and 2.0 Hz. It was found that E mu slightly increased and R mu decreased nearly hyperbolically with increasing f, both decreased with increasing indentation force, and both increased with increasing mean lung volume. Shear hysteresivity decreased sharply from 0.01 to 0.25 Hz and then assumed a nearly steady value that was an order of magnitude lower than the value reported previously for uniformly oscillated lungs. Changes in E mu and R mu after lavage were correlated with changes in transpulmonary pressure and not with changes in surface film properties. These results suggest that in the breathing range of frequencies 1) the energy loss of lung parenchyma is a much smaller fraction of the stored elastic energy in shear than in uniformly oscillated lungs and 2) transpulmonary pressure, not dynamic properties of surface film, is the primary determinant of lung dynamic properties in shear.

Deformation processes during disc bend loading

A miniaturised disc bend test technique has been used to measure yield and ultimate load values for high purity aluminium, oxygen free high conductivity copper, and normalised and tempered 2·25Cr–1Mo steel. For each material details of load displacement behaviour were recorded with the test variables disc thickness, punch diameter, and die clearance. Data analysis permitted relationships to be established correlating disc behaviour with results from standard tensile tests. These correlations are discussed in terms of testing variables and the strength and ductility of the materials.MST/3347

Deformation processes during disc bend loading

A miniaturised disc bend test technique has been used to measure yield and ultimate load values for high purity aluminium, oxygen free high conductivity copper, and normalised and tempered 2·25Cr–1Mo steel. For each material details of load displacement behaviour were recorded with the test variables disc thickness, punch diameter, and die clearance. Data analysis permitted relationships to be established correlating disc behaviour with results from standard tensile tests. These correlations are discussed in terms of testing variables and the strength and ductility of the materials.MST/3347

Redrawing Process during One Stroke for Increasing Cup Height.

With a view to regarding deep drawing as a new process for fabricating bottomless tubular elements, a deep drawing test was conducted with thick aluminum material. Two diameters of punches were used for a tapered die during one stroke. The diameter of the first punch was larger than the inner diameter of the straight part of the die and the diameter of the second punch was smaller than the inner diameter. Since the first punch was used only for the die tapered region before punch exchange, the limiting drawing ratio and cup height was increased efficiently.

Deep Drawing of Commercially Pure Titanium Sheets.

The technology of deep drawing of commercially pure Ti cold-rolled sheet for obtaining drawn cup without defects was developed. Oil hydraulic press of 490 kN punch force and 98 kN blank holding force (BHF) and 300 mm/min drawing speed were used. Ti sheets (TP28C) of 0.8 mm sheet thickness (t) were used. The punch diameter is φ40 mm, and various radii were used. First, blanks lubricated with machine oil were deep drawn. BHF values were calculated by Dr. Fukui's formula. The limiting drawing ratio (LDR) was about 1.8, inferior to steel sheets. Next, two 30 μm polyethylene (PE) films were used on each side of Ti sheet and BHF values were calculated by Dr. Fukui's formula. When LDR increased to e.g. 2.5, large and numerous wrinkles were found. By BHF increasing to 98 kN, only traces of wrinkles were found.Last, punch lubrication was eliminated. The LDR increased to 2.6, but severe earing was formed. By the consideration of characteristics of test piece of each direction, the breaking mechanism was qualitively explained. By adequate blank shape, this earing was nearly eliminated.

Forming behaviour of some sheet steel materials when drawn through a conical die

An experimental study of the deep-drawing of three different steels (namely, stainless-steel 304 grade, dual-phase steel and aluminium-killed drawing-quality steel, which together cover a wide range of mechanical properties) through a conical die using flat-bottomed and hemispherical-ended punches is discussed in this paper. It is well-established that the use of a conical die can enhance the limiting draw ratio (LDR) compared with that obtainable in a conventional drawing operation. The most commonly observed failure mode in this process is the fracture of the material in the vicinity of the punch profile radius or wrinkling in the flange region when a thin sheet blank is drawn in. The present investigation shows that the limiting draw ratio obtained for thin sheet materials can be related to a non-dimensional parameter index involving the punch diameter, the sheet material thickness, the average plastic strain ration and the average strain- or work-hardening exponent value. Finally, an attempt is also made to study the wrinkling behaviour of the above sheet materials under different conditions of lubrication.

Deep penetration of polycarbonate by a cylindrical punch

An experimental and theoretical investigation has been conducted to determine the deep penetration response of polycarbonate (PC). A series of low speed deep penetration tests was performed with steel punches to establish the load versus indentation response, and to enable detailed observation of the penetration processes. The effects of nose shape, lubrication and punch diameter were determined. We found that the average pressure on the indenting end of the penetrator is equal to 4–5 times the tensile yield stress and is independent of nose shape and penetrator diameter. A hackle zone of microcracked material extends to a diameter of 1.4 times that of the penetrator, and this is surrounded by a plastic zone which extends to a diameter of 3.5 times that of the penetrator. A model of deep penetration is developed, based on the assumption that the average pressure on the nose of the penetrator equals the pressure required to expand an infinitely small circular cylindrical void to the diameter of the penetrator. The model assumes the existence of an outer elastic zone, a plastic zone and a hackle zone surrounding the penetrator. The predicted penetration pressure and the diameters of the hackle and plastic zones are reasonably accurate.

Punching Mechanism of Aluminum-Stainless Steel Two-Layer-Clad Material.

Effects have been investigated of punch diameter, clearance and thickness ratio of components in two-layer-clad materials on punching. Two kinds of clad material produced slightly different tendencies in punching load-time curve and specific shearing stress due to mechanical properties and thickness ratio of components. Specific shearing stress measured was compared with those calculated by law of mixture and double punching method of monolithic materials. The stress calculated by the latter is smaller, however not always closer to the measured value than the former.

Direct determination of atmospheric lead by Zeeman solid sampling graphite furnace atomic absorption spectrometry (GFAAS)

Atmospheric lead was collected by membrane filters using two low volume air samplers at Julich, Stolberg, and Wetzlar, Federal Republic of Germany. Sampling times varied from 2 to 8 h. After sampling, each filter was subsampled in two cross-sections using a clean stainless steel punch (diameter 5 mm). The lead content of each subsample disc was determined directly by Zeeman GFAAS, calibrated with aqueous standard solutions and supported by solid reference materials. The distribution of lead between the subsamples was generally homogeneous, with standard deviations ranging from 11 to 37%, but typically <15% for samples with 8 h sampling time. The analysis of each filter usually took about 30 min. The differences in air quality between the three sampling locations, as measured by the lead concentrations, are discussed. In general, Stolberg appears to have the highest lead concentrations. The mass particle-size distribution of lead in the aerosol samples collected by membrane filters using a cascade impactor at Stolberg was also investigated with the same analytical technique. Using graphite platform boats as direct samplers, it is possible for the dry deposition flux of lead to be estimated. This provides a quick means of assessing the levels of lead pollution in the atmospheric environment. With lead concentrations measured in parallel, the dry deposition velocities of lead can be estimated under various meteorological conditions. Application of similar sampling and analytical techniques to other atmospheric trace metals may be possible.

The effect of work-hardening on deep-drawing through a conical die

An experimental study of the deep-drawing of ten sheet metals through a conical die is described. This is an important process in its own right and also as thefirst stage of a drawing and multiple ironing process. It is shown that the optimum die angle depends on whether the drawing process fails by fracture or by flange wrinkling. If the mode of failure is fracture then a high R-value is beneficial; if the mode of failure is flange wrinkling then the most important variable is the n-value. In the latter case a semi-empirical approach is adopted to demonstrate the relationships between blank diameter, punch diameter, punch profile-radius, sheet thickness and n-value.

Deep drawing of double cylindrical shells

Using the complex-potential method, an analytical technique in hydrodynamics, a plane-strain velocity field in the flange region of a double cylindrical shell is calculated theoretically: two sinks of equal strength are set at the center of each circular die cavity. Blank shapes are determined theoretically from the velocity field to obtain double cylindrical shells with flanges of constant width. Experimentation is carried out on cold-rolled steel sheet (SPCE) for three different punch intervals. It is found that: (i) the theoretical streamlines in the flange region are in good agreement with experimental ones; (ii) there exists an optimal punch interval — of about 1.8 times the punch diameter — which gives the deepest shell, the height of which is about half of the punch diameter (iii) the optimal blank-width for obtaining the deepest shell is 2.1–2.2 times the punch diameter; (iv) the above conclusions (i)–(iii) will also hold for other types of double-bowl shells in which twin non-circular shells are joined together.

Effects of Prestrain With Strain Gradient Present on Sheet Metal Formability

In this investigation, two double-stage forming processes are used to study the effects of prestrain on sheet metal formability. The processes chosen are the bulge test and the plunger test using a die throat to punch diameter ratio of 2.42. It is seen that during the second stage of forming, deformation and shape of the deformed shell are influenced by the level of prestrain and strain gradients on the prestrained workpiece. An improved formability is observed when the workpiece for the plunger test is prestrained by hydroforming, but the formability is reduced when the prestraining process becomes the plunger test. The present results also imply that care should be taken in utilizing the forming limit diagram even if it is constructed from double-stage forming, in which strain gradient on the prestrained workpiece is generally absent.

Stresses in the punch in the impact pressing of metal powders

The most heavily stressed element of the pressing tool, operating under the most severe conditions, is the upper punch. A dominant influence on the operating life of the punch is exerted by the stress set up in it during impact. In the most heavily stressed, upper part of the punch the compressive stress is a minimum when the striker and punch diameters are equal. The stress diminishes with increasing punch length. Use of a striker with a spherical end face produces a substantial stress concentration in the contact zone, which may lead to the fracture of the punch. Decreasing the radius of the sphere significantly reduces this stress. With increasing impact velocity, the stress in the punch grows. In each specific case the maximum permissible impact velocity is limited by the maximum stress that the punch can withstand.

Investigation of Tool Wear in Bulk Metal Forming by Model Experiments

Tool wear in bulk metal forming as a function of parameters such as lubricant, tool material, workpiece material, temperature and stress was investigated by two model experiments: “Backward extrusion of cans” and “upsetting between plane parallel dies”. During upsetting a characteristic profile of die wear was determined depending on the mechanical stresses and thermal conditions. The depth of this profile was used as a measure of linear amount of wear as function of the number of produced parts. During backward extrusion of cans wear of the front face of the extrusion punch and of its edge radius could be neglected. However, strong wear was observed at the diameter of extrusion punch (“punch land”) resulting into a decrease of the inner diameter of produced cups. This wear was measured as a decrease of the inner diameter of cup. A comparison of both model experiments showed that wear as a function of various parameters such as lubricant, tool material, workpiece material and number of produced parts exhibits the same tendency for both experiments. The results obtained are also helpful for a systematic choice of tool material for a given application with respect to reduction of wear.

Pencil slip in beta-tin single crystals

Pencil slip was observed when a punch was pressed over the (0 0 1) surface of a β-tin single crystal. A bulge of similar size and shape as the punch appeared at the opposite surface directly across the thickness of the crystal. Slip line observations inside the sample showed slip activity confined to a cylindrical shell whose inner diameter was the same as the punch and whose axis was parallel to the [0 0 1] direction. The thickness of the slip shell increased with the punching stress and with the ratio between punch diameter and sample thickness. The effects of punching stress on the entering velocity of the punch and on the exiting velocity of the bulge were studied and the results compared with those of impression creep reported previously. The situation in which the bulge was not allowed to form was also studied.

Evaluation of force—displacement measurements during one-sided powder compaction in a die — the influence of friction with the die wall and of the diameter of punches and die on upper and lower punch pressure

On an instrumented single-punch press, working at an overall rate of 30 strokes per minute, the influence of diameter of punches and die on upper and lower punch pressure, measured during the densification of a powder with an initial height of 8.0 mm, has been investigated. The upper punch pressure necessary to effect a certain state of density, proved to decrease with increasing diameter, whereas the lower punch pressure proved to be independent of the diameter. The upper punch pressure differences, found for diameters ranging from 11 to 17 mm, could not be accounted for by differences in the actual speed of compaction between the individual force displacement measurements and it could be concluded that these pressure differences were exclusively due to an influence of the diameter on the process of compaction. By using a number of hyportheses concerning friction with the die wall, it was possible to derive a mathematical model for the pressure distribution on the upper punch which qualitatively agreed with the experimental results.

Impression creep of LiF single crystals

Abstract Impression creep tests of LiF single crystals at 600–750[ddot]C and under punching stresses of 4-30 MN/m2 are reported. Both temperature and stress dependences are comparable with those of conventional compression creep tests under similar conditions. These dependences give a power law stress exponent of 4–5 and an activation enthalpy of 52 kcal/mole. A finite element numerical analysis shows consistency between the measured impressing velocity and the conventional power law constitutive equation assumed for the plastic deformation of each element. The dislocation structure developed under the punch as revealed by etch pits indicates that the depth of the plastic zone is comparable to the punch diameter.

Effect of cup geometry on ear height and thickening in cylindrical flatbottomed steel cups

AbstractAn investigation of the effect of cup geometry on ear height and wall thickening in cylindrical flat-bottom cups made from various mild steels has been carried out, and empirical relationships relating these factors have been established. The work has shown that, with reasonable accuracy, the ear height E is given by:E=MP (B2–P2/P)(B–P/P)1·5where B is the blank diameter, P is the punch diameter, and MP is a dimensionless earing parameter of the steel which may vary substantially between different steels. The mean increase in thickness at the top of the cup is given by:(Tm–To)=KPTo (B–P/P)where Tm is the mean final thickness at the top of the cup, To is the starting sheet thickness, and KP is a parameter which varies from steel to steel. The variation in thickness at the top of a cup due to earing ∆Te is given by:∆Te=2·66 MPTo (B2–P2/P2)(B–P/P)1·5Equations similar in form were found to hold when P was replaced by the die diameter D and these were about as accurate as those involving P. The empirica...

A Contact Problem In Poroelasticity

The paper examines the axisymmetric problem of the indentation of poroelastic layer which rests in contact with a rough rigid and impermeable base. The indenting punch has a circular planform and the smooth contact is assumed to be either permeable or impermeable. The paper develops the integral equations governing the problem for the generalized case where the the pore-fluid is considered to be compressible. Numerical results are presented to illustrated the influence of layer thickness, drainage conditions, and the compressibility characteristics of the pore fluid on the degree of consolidation settlement of the indenting punch. INTRODUCTION The classical theory of poroelasticity which is applicable to the study of the mechanics of deformable fluid saturated porous medium was first developed by Biot [5]. This theory has been widely applied to the study of various loading and contact problems associated with halfspace and infinite space regions. A majority of these discussions have focussed on the evaluation of the response of the poroelastic medium which is saturated with an incompressible pore fluid. In this paper, attention is focussed on the problem of the indentation of a poroelastic layer by a smooth rigid circular punch. The term thin is intended to signify a layer thickness which is smaller than the diameter of the indenting circular punch. The punch is in smooth contact with the poroelastic layer which exhibits either permeable or impermeable pore pressure boundary conditions over the entire surface. The layer is underlain by an impermeable rigid base 1 Currently at The Infrastructure Laboratory, Institute for Research in Construction, National Research Council of Canada, Ottawa, Ontario, Canada K1A OR6 Transactions on Engineering Sciences vol 1, © 1993 WIT Press, www.witpress.com, ISSN 1743-3533 286 Contact Mechanics and the displacement contact conditions are considered to be adhesive (Figure 1). The paper summarizes the integral equations governing the mixed boundary value problems associated with boundary variables in the Laplace transform domain. The paper illustrates the influences of the relative thickness of the consolidating layer and the Poisson's ratios of the pore fluid on the degree of the consolidation of the poroelastic layer. A permeable or impermeable surface A rigid circular smooth indentor t A poroelastic layer saturated with a compressible pore fluid xA rough rigid and impermeable base Figure 1. An axisymmetric contact problem in poroelasticity GOVERNING EQUATIONS In the ensuing we shall present a brief account of the governing equations referred to a Cartesian tensor notation. The constitutive equations governing the quasi-static response of a poroelastic medium, which consists of an isotropic poroelastic soil skeleton saturated with a compressible pore fluid takes the forms (1) 3(1 2r/,) where cr^ is the total stress tensor, p is the pore fluid pressure, Cij are the soil skeleton strains defined by £.. = !(„..+„,.) (2) where Ui are the corresponding displacement components. In the absence of body forces, the quasi-static equations of equilibrium take the forms °ij,i = 0 (3) The equations governing quasi-static fluid flow are defined by Darcy's law which take the form %, = -/W (4) Transactions on Engineering Sciences vol 1, © 1993 WIT Press, www.witpress.com, ISSN 1743-3533 Contact Mechanics 287 and the continuity equation associated with quasi-static fluid flow is The above governing equations are characterized by the five basic material parameters which are represented by the drained and undrained Poisson's ratios v and z/% respectively, the shear modulus //, Skempton's [7] pore pressure coefficient B, and the K (=fc/7 , where k is the coefficient of permeability and 7%, is the unit weight of pore fluid). From the consideration of the positive definiteness of a strain energy potential, it can be shown that the material parameters should satisfy the following thermodynamic constraints: /j > 0, 0 0 (see. e.g., Rice and Cleary [6]). Avoiding details, it can be shown (Yue [3]) that the following sets of solution representations exist for the field variables in a linear, isotropic, poroelastic medium of layer extent saturated with a compressible pore fluid. In either the temporal domain or the Laplace transform domain and in the cylindrical coordinate systems (r, #, z) and (p, y, z), we have % roc r2ir } u(r, 0,z,t) = — I I -TlawK 27T Jo JQ p I roc /-27T ,(r, 0, z, f ) = — / / n, rA 2?r Vo Vo