T. Wanheim's research while affiliated with Technical University of Denmark and other places
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Publications (62)
A special kind of transducer making it possible to measure normal and tangential contact stresses during rolling has been developed. As normal stresses are approximately ten times larger than the tangential, and since cross signals must occur, a proper calibration of the sensor is essential. Calibration must consist of a number of simultaneous appl...
Purpose: Progressive miniaturisation generates necessity of micro-parts production also on the field of metalforming. At present small pats are produced with a big presses which were designed for manufacturing muchbigger products. Further miniaturisation will not make possible to keep sufficient tolerances of productsmanufacturing with these standa...
To improve the quality of frictional data and to validate the simulations in rolling, a load transducer for measuring normal and frictional stresses in the deformation zone has been developed. The transducer consists of a strain-gauge-equipped insert embedded in the surface of the roll. The length of the insert exceeds the contact length. By analys...
A new procedure is proposed for measuring press stiffness, including separated horizontal and vertical loading of the press frame. The load can be eccentrically positioned for measuring rotational stiffnesses. Two loading devices and corresponding measuring equipment for registration of press deflections are designed. The press stiffness is present...
A large group of the cold forging processes is carried out in a thick-walled container with the deformation force transmitted through a punch moving axially in the container. The work-piece, being entrapped between punch and container will expand and exert a radial pressure resulting in an expansion of the bore. After unloading, the container will...
A new strain gauge sensor for measuring normal and tangential stresses in the contact arc of a rolling process has been designed and constructed. The complicated load story of the sensor results in complicated deformation patterns of it, and consequently the calibration procedure of the sensor should cover a wide range of loading cases, and would t...
Traditionally, material response to shear deformation has been studied with methods where the shear is gradually increasing from zero to the final value over a certain fixed deformation zone, e.g. in the well-known torsion test of a tube with a defined shear zone established by a machined circumferential groove. Normally shear in metal forming proc...
The paper describes the calibration and application of an integrated system for topographic characterisation of fine surfaces on large workpieces. The system, consisting of an atomic force microscope mounted on a coordinate measuring machine, was especially designed for surface mapping, i.e., measurement and tiling of adjacent areas. A calibration...
In contemporary practice, tool design and its optimisation is accomplished largely through the use of empirical knowledge and extensive experience. A considerable amount of trial and error is necessary in order to be able to set-up a tool for a reliable and reproducible process. One of the major aims of cold-forging research, therefore, is to reduc...
Production of components close to the final shape increases the demand for correct dimensions of tools. In processes where the internal pressure is low, the dimensions of the component reflect the dimensions of the die-cavity in the tool, but in processes where the internal pressure is high, die deflection in the tool causes incorrect shape of the...
In contemporary practice, tool design and its optimisation is accomplished largely through the use of empirical knowledge and extensive experience. A considerable amount of trial and error is necessary in order to be able to set-up a tool for a reliable and reproducible process. One of the major aims of cold-forging research, therefore, is to reduc...
There are three demands on a component that must undergo a die-cavity elasticity analysis. The demands to the product are specified as: (i) to be able to measure the loading profile which results in elastic die-cavity deflections; (ii) to be able to compute the elastic deflections using FE; (iii) compensating the elastic deflection must lead to clo...
A way of describing the deformation history in a process where large plastic deformation occurs is presented. For a point in the volume, the total strain tensor history is described as a curve in the 6-dimensional shear strain/normal strain space henceforth called a strain history curve (SHC). This paper focuses on the SHC concept and the uniquenes...
The main objective of the work is to study the extrusion process using physical modelling and to compare the findings of the study with finite element predictions. The possibilities and advantages of the simultaneous application of both of these methods for the analysis of metal forming processes are shown.
In this paper a new press test is introduced, where the press is described by six load/deflection curves and by two Assumed Rotation Point (ARP). The experimental measurements have been performed on a 400kN open C-press. To load and measure the deflection special equipment has been designed. The equipment can load the press in both vertical and hor...
In the present work the flow of the metal in the radial extrusion of tubular components is analysed. Different strain-hardening behaviours are used in a commercially-available finite-element code, giving remarkably different flow behaviour of the metal. The finite-element simulations are verified by metal experiments. The creation of unsound compon...
A proposed die configuration is designed to effect the in-process compensation of the errors in the form of the extrudate which arise from the elasticity of the extrusion dies. The die is in the form of a truncated, conical-shell which is either on a plane or a spherical bearing surface, to enable it to deflect elastically, thereby changing the dim...
The present paper describes the basis for a system to reduce the number of defects in a forged component. For this purpose two classifications are created as originally suggested by Dodd. The first divides the possible defects into six groups and the second classifies the probable causes of the defects. By use of these classifications, a catalogue...
Physical modelling in design of metal forming processes
(in polish)
Recent work on the radial extrusion of tubular components performed at DTH and UOS presents new results relevant to the process and to die design, This research was accomplished through physical modeling with wax and through metal experiments in aluminium, together with upper-bound and finite-element analysis. Major process parameters such as the r...
The present paper describes a systematic investigation of possible flow imperfections in forging of an H-shaped profile. The influence of geometry and volume of the slug and of friction in the tool/workpiece interface on flow are investigated by numerical as well as physical modelling. A comparison between two different FE- codes, DEFORM ans Forge2...
Die Gewinnung von Informationen über Formänderungen, Spannungen, Kräfte, Werkzeugbeanspruchungen bei realen Umformvorgängen, d. h. mit realen Werkzeugen und Werkstücken in Originalgröße aus realen Werkstoffen bei realen Prozeßbedingungen - Temperaturen, Werkzeuggeschwindigkeiten, Schmierstoffeauf realen Umformmaschinen stößt in der Regel auf große...
SummaryEarlier work by Bay has shown the introduction of brittle surface coatings by electrochemical or chemical plating to be useful when roll bonding A-A. The coating layers fracture during deformation and decover virgin surfaces which extrude through the cracks and establish contact and metallic bonding to the adjacent surface. This paper presen...
The tribological conditions in backward can extrusion at the contact between the can wall and the punch land are very severe due to heavy surface expansion. In the present paper these problems are analysed especially at low reduction (r < 50%) where they are particularly pronounced. The influence of degree of reduction, punch nose geometry, frictio...
Simulation of bulk forming processes provides a means of selecting parameter settings and predicting the outcome of the process. This may thereby be achieved without disruption of current production, without the necessity of fabricating expensive dies by trial and error and in relatively short periods of time.Numerical and experimental methods af s...
Recently, the authors have developed the special technique for the determination of the 3-D deformation pattern of workpieces in metal forming processes. This paper describes the method for the 3-D strain and strain rate analyses by use of the experimental flow fields. A new idea of the “visioplastic energy method” is also presented for the calcula...
In the last few years many of the hardware and software elements necessary to establish CIM-systems (Computer Integrated Manufacturinq)have been developed but still many problems have to be solved especially concerning integration of engineering functions/disciplines into CAD/CAM and CIM in a broader context.The present paper describes the developm...
When analysing the stress distribution in the tool/workpiece interface in plate rolling, it is conventional to assume either Amontons friction law, τ = μp, or full stiction τ = k. Neither of these two laws are, however, generally valid. This paper presents an analysis by the slab method using a general friction model developed by Wanheim and Bay. T...
Friction on the interface between tools and specimen is of the utmost importance in all metal-working processes. The magnitude of the friction stress influences, to a high degree, deformation pattern, strain pattern, temperature rises, surface pressure on tools, and the total force in metal- forming.
The mechanisms producing metallic bonds in cold welding are fracture of the contaminant surface film, extrusion of base material through the cracks and builòup of real contact and coalescing with base material of the opposite surface. Bay has earlier proposed a general model for the bond strength in cold welding based upon a continuum mechanic anal...
Simple shear zone models for orthogonal cutting describe satisfactorily the mechanics of chip formation in some cases while, in many practical cases, measured chip thicknesses are not as theoretically expected. Also, theoretical models suffer from the fact that process geometry is not directly related to the independent variables (tool rake angle a...
Based on requirements from 60 metalworking plants in Denmark, Sweden, Norway and Finland, a series of projects on simulation of metalworking processes with model materials in a Nordic “action concertée” has been carried through. The subjects dealt with are: Materials properties, simulation of friction, plane simulation of three-dimensional problems...
Frictional conditions between the tool and the specimen are important in the plastic working of materials, influencing the flow of the material and being a decisive parameter for tool/specimen interface pressure and for deformation force: the selection of the “right” lubricant for the model-material simulation is therefore a matter of importance.Th...
One serious limitation in cold forging is the folding problem that, amongst others, occurs when compressive stresses act in slender parts of the specimen. To investigate whether the model-material technique is reliable for this type of problem, a comparison has been made between folding phenomena in steel and aluminium specimens and those in model-...
A series of projects on simulation metal-working processes with model materials in a Nordic “action concertée” has been carried through. The subjects dealt with are: Materials properties, simulation of friction, plane simulation of threedimensional problems, combined model material and computer simulation, applications in cold forging, drop forging...
This investigation shows that it is possible to minimize faulty designs of new tools for sheet metal forming processes by using modelling technique. By marking the sheet model material with a circular grid, the strains can be calculated and plotted on the FLD of the sheet metal in question. This will indicate most of the problem that can arise from...
The circle grid strain analysis method has hitherto been the most commonly used method to determine strains in sheet metal parts. This method has proved very successful in a number of applications. However, the method has drawbacks, some of which can be overcome by employing a grid strain analysis — the coefficient method — based on the measuring o...
Friction, wear, and lubrication mechanisms and the resulting geometrical and mechanical properties of the surface are closely interrelated with the platic deformation of the surface and its asperities. This paper describes a line of theoretical and experimental research carried out in the laboratory, where the effects of normal pressure, tangential...
The ribbon winding process enables the manufacture of metal forming dies with higher allowable internal working pressure than is possible by conventional shrink-fit constructions. Varying the tensile stress in the ribbon in the winding process, the stress distribution in the die can be given a predetermined shape. Based on the assumption that all r...
A theory is developed which shows the influence of the normal pressure, asperity slope, friction factor and pressure-sensitive lubricant bulk modulus on the real area of contact and the friction stress between a rough specimen and a smooth tool surface. Theory as well as experiments show that the normal pressure and bulk modulus have great influenc...
The effect of load on the flattening of asperities on top of others is discussed. It is shown that the real area of contact on top of an asperity that is not interfering with others lies between 85 and 90% when only second generation asperities are involved. When third and fourth generations are taken into account, the real area of contact on the p...
The method of modeling deformation processes occurring in metal forming with the aid of plasticine models is described, and its application for the development of forming processes, tools, and process analyses is discussed.
The model-material technique makes it possible to investigate the effect of different preforms and billet sizes on the filling capacity in the final dies and to see how different preforms and billet sizes affect the flow pattern in the final product. It is possible to reveal qualitatively the effect of billet size and preform from the point of view...
This paper describes an experimental method to obtain a very good approximation to the theoretical slipline field in specimens subjected to plastic deformation under plane-strain conditions.
Special wax compositions are developed to obtain the slipline fields. The waxes have the characteristic of changing color in the areas where they are undergoin...
An experimental investigation of the plastic deformation of the surface asperities of a soft rough specimen surface in sliding contact with a hard smooth tool surface is described. The experimental equipment allows independent variation of the normal pressure and sliding length. The normal pressure was varied from 0.5 to 2.5 times the yield stress...
A theory is developed determining the real area of contact between a hard rough tool and a soft smooth specimen surface. The accordance with experiment is good. Both theory and experiment show the slope of the asperities to be of minor importance.
Based upon a slip-line analysis of the plastic deformation of surface asperities, a theory is developed determining the Ra-value (c.l.a.) and the average effective strain in the surface layer when deforming asperities in metal-working processes. The ratio between Ra and Ra0, the Ra-value after and before deformation, is a function of the nominal no...
A general theory for friction in metal working processes is developed based upon the slip-line theory as a model of analysis. The real area of contact α and the nominal friction stress τn are determined as functions of the nominal normal pressure q/2k and the friction factor m. The results show how the real area of contact increases and approaches...
A previously suggested method of estimating low friction coefficients from the bulk deformation of long rectangular laminae during plastic compression, was used for wax specimens with various lubricants to enable the choice of the best lubricant for experiments with model materials. This method was also used for aluminium specimens with liquid and...
An analysis of the process : Indentation of a cone into a semi-infinite material has until now only been made in cases of no friction between tool and specimen. By means of the axi-symmetric upper bound theory, it is shown how p/k can be determined for indentation into a prepared cavity with friction taken into consideration. Analysis has been made...
One of the most important process parameters in making compound products is the expansion of the bonding surface. Bonding is not obtained until a critical surface expansion, characteristic of the deformation process, is reached. This paper deals with an experimental investigation of the influence of a superimposed hydrostatic pressure on the critic...
Friction conditions between tool and workpiece in metal working are of the greatest importance to a number of factors such as force and mode of deformation, properties of the finished specimen and resulting surface roughness.It is shown, theoretically and experimentally, that the Amonton friction law expressed by τ = μq does not apply when normal p...
This paper describes how a model material technique has been applied in the analysis and development of a roll forming process
for heading shanks, gun nails in particular. A commercial modelling wax “Filia” is extruded to the dimension of the model
shank before the head is roll-formed by means of equipment designed for this process. The dependence...
Based on the steps used in establishing a conceptual model for a theoretical analysis of a problem in metal forming, analogous
steps are suggested when the use of a physical model is contemplated. Two lists of the types of information useful in the
design of a process are given: the aims of synthesis, and the aims of analysis. Based on this the nec...
Citations
... Hence, there are searched methods which would make easier designing of metal forming processes technology and eliminate conducting experiments on real material. These techniques allow for research on forming processes usually in room temperatures and with application of tools made from cheaper and more easily machined materials [1][2][3]. ...
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... As for hot forging, physical modeling has been a valuable alternative to numerical modeling [10] to [14]. Physical modeling based on wax is faster, easier and less expensive than a subscale production process. ...
... Asperity flattening and junction growth depend on the normal load, friction and sliding in the junctions, sub-surface straining, roughening of the surface, oxide or contaminant layers, type and amount of lubricant, and material behaviour of the workpiece itself. A review can be found in [4]. ...
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... Die Ermittlung einer geeigne ten Prozessfuhrung geht deshalb stets mit hohem Zeitund Kostenaufwand für intensive Pa rameterstudien einher. Der damit verbundene experimentelle Aufwand lässt sich zwar durch den Einsatz rechnergestützter Methoden wie der Finite-Elemente-Simulation (FE-Simulation) deutlich reduzieren [15], für die Interpretation der Simulationsergebnisse und für die Generie rung neuer, angepasster Simulationseingabedaten ist jedoch nach wie vor ein hoher personel ler Aufwand erforderlich. Dieser steigt zudem erheblich an, wenn für einen neuen Prozess, einen neuen Werkstoff oder für neue Elemente der Bauteilgeometrie gesichertes Wissen be züglich des Zusammenwirkens der Prozessparameter noch nicht verfügbar ist. ...
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... Therefore, the real contact area varies directly with the normal load. For simplicity, the contact area ratio α , which measures the effect of the real contact area on contact friction, is described as a function of only the normal load (or normal pressure), consistent with Wanheim and Bay [12], Bay [13] and Bay et al. [32]. According to the adhesion theory, the projected area of the ball is the real contact area and not the surface area. ...
... However, the precise experimental determination of the real contact area in sheet-metal forming is difficult due to the random nature of asperities. In addition, most of the efforts to create a better friction model for metal forming in the boundary regime have focused on [44]. However, there are issues with the estimation of the friction coefficient values. ...
... Physical and numerical modelling plays an important role in process planning affecting strongly on the possibilities of energy and material saving, and additionally assure flawless forging process [26,31]. Cheep model materials prepared carefully, satisfying the requirements and rules of similarity allow to investigate all processes of closed die forging, independent how complicated they are, thus physical modelling is a powerful tool for reducing the costs necessary. ...
... The mechanism behind antiviral actions of EUG is the upregulation of the expression of HSV-1glycoprotein B that checks HSV replication [95], while some studies confirmed that EUG inhibits the replication of the HSV-1 and HSV-2 DNA molecules, as well as damages the outer envelope of newly synthesized virions [96][97][98]. The benefits of using combination chemotherapy includes enhanced antiviral activity, reduced dosage of toxic substances, and lessened development of drug resistance [99]. In in vivo study involving mouse models, Eugenia caryophyllus extracts rich in EUG which were applied in combination with acyclovir (ACV) showed an anti-HSV-1 potential in the brain and skins of mice [97,100]. ...
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... A comparison of the ring test results for the real material and the model material makes it possible to determine whether in both cases identical friction conditions were maintained. The test results constitute the guidelines for the selection of the lubricating agent [30][31][32]. ...
... That is because of static behavior of bearings and thrust of electrode force. Material Properties are shown in Table 5. Contact Resistance follows model by Bay and Wanheim [22]. FEA solver has capability to calculate nugget diameter. ...
