On the hydrodynamic deep-drawing process

The feasibility of deep-drawing aided by hydrodynamic flow beneath the blank is demonstrated. The analytical background for directing the design of the process is based on the limit analysis in plasticity theory coupled with flow analysis of viscous, non-inertial fluid. It is done for isotropic non-hardening material with inclusion of constant friction coefficient as an additional parameter acting on plastic/rigid interfaces.The main attention is focused on approximating the Limit Drawing Ratio (LDR) via upper and lower bound and comparing the conventional process to the suggested hydrodynamic-aided process. The unique features of the process along with its limitations (geometrical and material-wise) are exhibited. The prominent role of the die curvature with regard to LDR is emphasized. A non-dimensional number combining fluid viscosity, punch speed, material strength and a characteristic length of the process (identified as Sommerfeld Number) appears as a useful measure for the clearance height through which the fluid flows. The study is corroborated with experiments.     

Rupture instability in hydroforming deep-drawing process

The critical fluid-pressure locus above which rupture by tensile instability may occur in the hydroforming deep-drawing process, is formulated and tested. The formulation is based on the classical theory of plasticity (with simple power-law hardening and Mises-Hill normal anisotropic yielding) assuming plane strain tensile failure. Further simplifications, such as assuming constant blank thickness and a constant Coulomb friction coefficient, enable one to account for the coupling effect between the self-adjusted blank curvature and the governing material parameters on rupture. Experiments with copper blanks are aimed to demonstrate that under certain conditions, failure by rupture may be prevented if the path of the working fluid pressure nowhere exceeds the predicted critical-pressure locus path. On the other hand, it is shown that the working fluid pressure should nowhere be lower than a predetermined minimum pressure locus to prevent wrinkles at the rim. Thus a distinct operating zone, lying between the upper and the lower pressure loci, is identified and recommended for practical use.     

Numerical study of the flange earring of deep-drawing sheets with stronger anisotropy

A Barlat–Lian anisotropy yield function is introduced into a quasi-flow corner theory of elastic–plastic finite deformation and the elastic–plastic large deformation finite element formulation based on the principle of virtual velocity and the discrete Kirchhoff triangle plate shell element model. The focus of the present researches is on the numerical simulation of the flange earring of deep-drawing process of circular sheets with stronger anisotropy, based on which, the schemes for controlling the flange earring are proposed.     

旋转体拉深件切边专机的改进

切边毛刺和废料卡阻现象是旋转体拉深件大批量切边生产中长期困扰生产现场的问题 ,在深入现场调研的基础上找出产生上述问题的原因 ,提出工艺改进方案并设计制造新型切边专机 ,经过使用证明 ,实际效果良好。     

Curvature area prediction for the deep drawing-ironing process of a cylindrical cup using finite element method and regression analysis

Journal of Mechanical Science and Technology - Products with long, cylindrical or rectangular can-shaped sidewalls are manufactured using a deep drawing-ironing (DDI) process. The volume of a...     

A hydrodynamic lubrication model for the deep-drawing process

A steady hydrodynamic lubrication model that includes the pressure viscosity factor has been developed for the deep-drawing process. Equations for lubricant film thickness, radial and drawing stresses are presented. Analysis reveals that the pressure viscosity factor has a significant influence on estimating lubricant film thickness and radial and drawing stresses.     

The buckling of annular plates in relation to the deep-drawing process

Based on a two-dimensional buckling model of an elastic-plastic annular plate and the well-known energy method, the critical conditions for the elastic buckling and the plastic buckling of the flange of a circular blank during the deep-drawing process are obtained to improve upon previously given results[1, 4]. The influence of a blankholder upon buckling and on the number of waves generated can also be quantitatively predicted.     

Calculation of wear (f.i. wear modulus) in the plastic cup of a hip joint prosthesis

The wear equation is applied to the wear process in a hip joint prosthesis and a wear modulus is defined. The sliding distance, wear modulus, wear volume, wear area, contact angle and the maximum normal stress were calculated and the theoretical calculations applied to test results.During the wear process the increase of the wear modulus is about 100 Nmm^?2 per mm sliding distance in the Charnley and the Charnley-Muller hip joint prosthesis. From the wear volume point of view the Charnley prosthesis is probably superior to the Charnley-Muller prosthesis if run-in before implantation.     

Effect of hob wear on the sounds emitted in the gear hobbing process

Increasing demand for precision and economy in gear manufacture necessitates control of the essential parameters in the hobbing process. Recognizing this necessity, research was undertaken to develop a hob wear detector. Using an empirical procedure, the acoustic signal emitted in hobbing was assessed with respect to its capacity to provide information about the extent of hobbing cutter wear. It was shown that signals from measurement of acoustic pressure in full bandwidths are unsuitable for the purpose. Frequency analysis of the acoustic signal enabled a third-octave frequency range with a centre frequency of 160 Hz to be singled out, wherein the acoustic signal level showed a close correlation with hob wear. The suitability of the signal is independent of most of the basic machine and process parameters and, for the purposes of hob wear detection, is reduced with higher values of module pitch of the hobbed gear     

Study on process parameters and its analytic application for nonaxisymmetric rectangular cup of multistage deep drawing process using low carbon thin steel sheet

Multistage deep drawing process is widely used to obtain various nonaxisymmetric rectangular cups. This deep drawing scheme including drawing and ironing processes consists of several tool sets to carry out a continuous production within one progressive press. To achieve the successive production, design and fabrication of the necessary tools such as punch, die, and other auxiliary devices are critical, therefore, a series of process parameters play an important role in performing the process design. This study focuses on the tool design and modification for developing the rectangular cup with an aspect ratio of 5.7, using cold-rolled low carbon thin steel sheet with the initial thickness of 0.4 mm. Based on the design results for the process and the tools, finite element analysis for the multistage deep drawing process is performed with thickness control of the side wall in intermediate blanks as the first approach. From the results of the first approach, it is shown that the intermediate blanks could experience failures such as tearing, wrinkling, and earing by excessive thinning and thickening. To solve these failures, the modifications for the deep drawing punches are carried out, and the modified punches are applied to the same process. The simulation results for the multistage rectangular deep drawing process are compared with the thickness distributions before and after the punch shape modifications, and with the deformed shape in each intermediate blank, respectively. The results of finite element reanalysis using the modified punches show significant improvement compared with those by using the original designed punch shapes.     

A finite element analysis of rigid-plastic deformation of the flange in a deep-drawing process based on a fourth-degree yield function

A general formulation for finite element analyses of very large rigid-plastic deformation is given by introducing a local system of convected co-ordinates into each element and taking the rotation of the principal axes of orthotropy of the material into consideration with respect to the two cases: (1) the case where the equivalent strain-rate is given by a function of strain-rate components and (2) the case where is defined by the formula , where σ_ij are stress components and gs is the equivalent stress. example, large deformation of the flange region in a deep-drawing process of a circular orthotropic metal sheet is analyzed on the basis of the conventional quadratic yield function and a fourth-degree one. The result shows that the effect of the axis rotation suppresses the ear-development to a certain extent, that any explicit expression of in terms of is not necessarily required for calculation and the definition suffices for the purpose, that the fourth-degree yield function gives us the shape of the deformed flange in good agreement with the experiment in contrast with the quadratic one which gives a too excessive ear-development, and so forth.     

Multi-laboratory simulator studies on effects of serum proteins on PTFE cup wear

A multi-laboratory, simulator study investigated the wear of polytetrafluorethylene (PTFE) cups run in bovine serum. Each laboratory used its own test protocol with a variety of simulator types. Our wear model incorporated 32 mm dia CoCr heads matched to PTFE cups run with serum protein-concentrations in the range 17–69 mg/ml. The multi-lab data demonstrated that protein-concentration had the most significant effect on wear performance. Both inverted and anatomical cups followed the same trend with first a rapid increase in wear-rates apparent for the initially low-protein levels and then a wear-rate reduction effect becoming apparent beyond 17 mg/ml of proteins. The results showed that as the protein concentration increased from 17 to 69 mg/ml, the magnitude of the wear-rates increased 200% but the protein wear-rate gradient decreased 24–60% with “inverted” and “anatomical” cups, respectively. This effect was more pronounced with ‘anatomical” than “inverted” cups. Thus, the wear-trends with “inverted” cups were generally the more consistent, particularly at the low-protein levels. Increasing the serum volume by two-fold in one study increased the PTFE wear-magnitudes approximately 40% and the protein-wear gradient by 30%. These PTFE wear phenomena were consistent with the concept that low-concentrations of proteins promoted polymer wear but high-protein concentrations resulted in a protein-degradation phenomenon which progressively masked the actual polymer wear. In the selected protein range 17–69 mg/l, the multi-laboratory simulator data consistently overestimated the average clinical wear-rate by at least 50–100% depending on protein range. It would, therefore, appear clinically relevant to study PTFE wear with an inverted-cup model using a large volume of serum but only in low-protein concentrations. The protein-related wear phenomena observed with PTFE cups in this multi-laboratory project may also have relevance for wear-simulation of UHMWPE cups.     

Characterization of interfacial friction in coated sheet steels: influence of stamping process parameters and wear mechanisms

By means of a tensile strip testing system, the nature of interfacial friction in stamping operations were investigated for three different coated sheet steels. Friction coefficient measurements were taken at seventeen distinct operating conditions by varying the sheet strip coating material (lead and zinc), applied lubricant (oil-base lubricants and greases) and pin radii (10 and 20 mm). In addition to determining the friction coefficient, the surface roughnesses of the sheet strips were measured before and after the completion of each test. From the experimental results, several relationships were ascertained for the role of the microscopic wear in determining the character of interfacial friction during stamping processes.     

Microscopic observations of the wear sheet formation by delamination

A series of experimental results showing the process of wear sheet formation has been obtained by observing the wear tracks and the deformed subsurface of ductile metals using a scanning electron microscope. These results substantiate the delamination theory of wear. The experimentally observed delamination process initiates when the extensive sub-surface plastic deformation causes the nucleation of voids. With further deformation these voids elongate and link up to form long cracks in a direction nearly parallel to the wear surface. At a “critical” length, these cracks shear to the surface, yielding a wear particle in the form of a long thin sheet. The top surface of the wear sheet is generally smooth, while the fractured surface is rough, often showing dimples and ruptured needle points of typical ductile fracture. When the delamination process is slow, the wear track has a very cratered appearance. The process of delamination and the morphology of the wear surface and sheets are markedly influenced by the structure and microstructure of the material.     

Peculiarities of hardmetals wear in blanking of sheet metals

The objective of this paper was to analyze some features of the surface damage process of hardmetal tools in blanking of sheet metals. Comparative wear trials of hardmetals in abrasive-erosion and adhesive surface failure conditions were conducted and the worn areas by SEM and XRD examined. The dependence of wear on tool material microstructure is shown. It was found that hardmetal resistance to the surface damage during blanking of sheet steels is controlled by its resistance to adhesive wear and origin–propagation of fatigue cracks.