Rectangular Punch Research Articles

Effect of pressure on pull-off of flat 1-D rectangular punch adhered to membrane

ABSTRACT Pressure can sometimes be utilized to increase or decrease the strength of adhesion. This phenomenon is analyzed for pull-off of a long, flat, rectangular punch from a long rectangular membrane. A one-dimensional nonlinear analysis is conducted. The pressure is applied to the membrane, and then the adhered punch is pulled upward. Both force control and displacement control are considered, and the pressure may be positive (acting upward) or negative (acting downward) on the membrane. The membrane is assumed to be linearly elastic, and a von Kármán-type theory is used to allow moderate displacements. A JKR-type theory of adhesion is adopted. The effects of the work of adhesion, residual stress, and prestretch are investigated. With an increase in pressure, the maximum force decreases, the pull-off deflection of the punch relative to the initial flat membrane level increases, and the total punch deflection from the pressurized membrane may increase or decrease.

Effect of pressure on pull-off of punch adhered to circular or 1-D rectangular plate

Pressure can sometimes be utilized to increase or decrease the strength of adhesion. This phenomenon is analyzed for upward pull-off of (i) a flat, circular cylindrical punch from a circular plate and (ii) a long, flat, rectangular punch from a long rectangular plate. The pressure is applied, and then the punch is pulled upward. The pressure may act upward (positive) or downward (negative) on the plate. Both force control and displacement control are considered. The plate is assumed to be linearly elastic, and nonlinear von Kármán theory is used to allow moderate displacements. A transversality (debonding) condition is obtained, and the effects of the work of adhesion, the relative size of the punch, and residual stress are investigated. With an increase in pressure, the pull-off force decreases, the pull-off deflection of the punch relative to the initial flat plate level increases, and the pull-off deflection with respect to the pressurized plate may increase or decrease. Some of the results are quite different from those for a membrane (where bending stiffness is neglected).

Understanding of plasticity size-effect governed mechanical response and incomplete die filling in a microscale double-punch molding configuration

Direct replication of microscale patterns onto metal surfaces by compression molding with patterned dies is used to fabricate metal-based structures for microsystem applications. Micron scale plasticity governs both the mechanical molding response and the geometric fidelity of replicated patterns. Microscale molding replication offers a technologically relevant example in which various plasticity size effects manifest themselves and control the effectiveness of the fabrication process.Microscale compression molding of a single-crystal Al specimen was studied by combining experimentation with conventional and strain gradient plasticity finite element simulations. In the single-punch molding configuration, single rectangular punches with different widths and lengths were used. In the double-punch configuration, two identically-dimensioned rectangular punches with a spacing in between were used. Under single-punch molding at the micron scale, both the absolute punch width as well as the length-to-width ratio affected the characteristic molding pressure. Under double-punch molding, both the measured characteristic molding pressure and the material flow to fill the gap between the two rectangular punches exhibited a significant dependence on the spacing to punch-width ratio and—when this ratio was fixed—on the absolute spacing between punches. The present study elucidates the impact of plasticity size effects on the efficacy of pattern replication by molding at the micron scale.

A DLC-Punch Array to Fabricate the Micro-Textured Aluminum Sheet for Boiling Heat Transfer Control.

A diamond-like carbon (DLC) film, coated on an SKD11 (alloy tool steel) substrate, was shaped by plasma oxidation to form an assembly of DLC macro-pillars and to be used as a DLC-punch array that is micro-embossed into aluminum sheets. First, the SKD11 steel die substrate was prepared and DLC-coated to have a film thickness of 10 μm. This DLC coating worked as a punch material. The two-dimensional micro-patterns were printed onto this DLC film by maskless lithography. The unprinted DLC films were selectively removed by plasma oxidation to leave the three-dimensional DLC-punch array on the SKD11 substrate. Each DLC punch had a head of 3.5 μm × 3.5 μm and a height of 8 μm. This DLC-punch array was fixed into the cassette die set for a micro-embossing process using a table-top servo-stamper. Furthermore, through numerically controlled micro-embossing, an alignment of rectangular punches was transcribed into a micro-cavity array in the aluminum sheet. The single micro-cavity had a bottom surface of 3.2 μm × 3.2 μm and an average depth of 7.5 μm. A heat-transfer experiment in boiling water was also performed to investigate the effect of micro-cavity texture on bubbling behavior and the boiling curve.

Study of compound hydroforming of profiled tubes

Abstract This study is to propose a loading scheme combined with die crushing and axial feeding to manufacture a profiled tube with different end shapes. Carbon steel of SPFC590Y is used as the tube material. The flow stresses of SPFC590Y steel tube at room temperature are obtained by tensile tests. A finite element software DYNAFORM is adopted to simulate the plastic deformation of the profiled tube during hydroforming and crushing processes. The effects of forming schedules on the formability and thickness distributions of the products are discussed. Finally, a profiled die set and a rectangular punch head are designed and manufactured, and experiments of hydroforming and crushing processes of ERW steel tubes are conducted using a self-designed hydroforming machine. Experimental results of product shapes and thickness distributions are compared with the simulation results to verify the validity of the finite element modelling and the designed loading schedules.

Investigation of holder pressure and size effects in micro deep drawing of rectangular work pieces driven by piezoelectric actuator

Micro forming is a manufacturing process to fabricate micro parts with high quality and a cost effective manner. Deep drawing could be a favorable method for production of complicated parts in macro and micro sizes. In this paper piezoelectric actuator is used as a novel approach in the field of micro manufacturing. Also, in current work, investigations are conducted with four rectangular punches and blanks with various thicknesses. Blank holder pressure effects on thickness distributions, punch force, and springback are studied. According to the results of this work, increasing of blank holder pressure in scaled deep drawing, in contrast to thickness of drawn part, leads to decrease in the punch forces and springback. Furthermore, it is shown that in micro deep drawing, the effects of holder pressure on mentioned parameters can be ignored.

Influence of drawn radius in micro deep drawing process of rectangular work pieces via size dependent analysis using piezoelectric actuator

Micro metal forming technology is receiving attention as a means of mass production technology to fabricate micro parts with high efficiency, good product quality and low production cost. Deep drawing provides an excellent potential for the manufacturing of parts with complex shapes, even in very small sizes. Using piezoelectric actuator which is implied in this paper can be considered as a novel approach in the field of micro deep drawing. Piezoelectric actuators are kind of actuators apply even up to 70 kN forces and their movement accuracy theoretically is in atomic scale. In this paper, investigations are carried out with different rectangular punches and blanks with different thickness. Drawn radius effects are investigated on thickness distributions, punch force, and springback. Also, the appropriate piezoelectric actuators are designed for each size of scaled deep drawing, experimentally and numerically. Results show that increasing of drawn radius in scaled deep drawing, in contrast to punch force, leads to decrease the thickness of drawn part and springback. Moreover, it is concluded that in micro deep drawing process, the effects of drawn radius on thickness distributions are negligible and can be ignored.

Finite Element Simulations for CFRP Press Forming Process

The macro-scale and meso/macro-scale simulations for press forming of CFRP sheet using ABAQUS S/W were both implemented to study the influence fiber orientation on the formability of CFRP sheet. The Hashin damage criterion was used to predict the fiber failure in the forming process. The properties of plain woven fiber fabric were obtained from the tensile test and bias extension test. The forming experiments with rectangular punch were carried out to validate the numerical results.

Designing Piezoelectric Actuators for Micro Deep Drawing of Rectangular Work Pieces

Micro forming process is a promising micro manufacturing technology for producing micro parts due to its high efficiency, low production cost and good product quality. Deep drawing provides a great application potential for the manufacturing of parts with complex shapes, even in very small dimensions. Using piezoelectric actuator which is implied in this paper can be considered as a novel approach in the field of micro deep drawing. Micromachines based on piezoelectric actuators are kind of actuators assures even up to several kilo-Newton forces and movement accuracy theoretically in atomic scale. In this paper, scaled investigations are carried out with different scales of rectangular punches and the blank with different thicknesses then appropriate piezoelectric actuators are designed for each scale.

Effect of intermediate principal stress on flat-ended punch problems

The intermediate principal stress has certain effects on the yield strength of metallic materials under complex stress states. The flat-ended punch problem is a classical and fundamental problem in plasticity theory and mechanical engineering in which the metal beneath a flat-ended punch is under complex stress states. Using the finite difference codes, fast Lagrangian analysis of continua and Unified Strength Theory, the effect of the intermediate principal stress on the flat-ended punch problem is analyzed in this paper. First, the limit pressures of strip and circular punches pressed into an elastoplastic and homogeneous metallic medium are calculated by the two-dimensional finite difference method. The problems of square and rectangular punches are analyzed by the three-dimensional finite difference method. Finally, the effect of the intermediate principal stress on flat-ended punch problems with different punch geometries is analyzed.

Assessment of anisotropic tensile strength using a modified shear punch test for Cu–Cr–Zr alloy processed by severe plastic deformation

The effect of severe plastic deformation on the anisotropic strength change was investigated by equal-channel angular pressing (ECAP) experiments with various pass numbers. To overcome the size limitation for the tensile test specimen, this study proposes a shear punch test modified by using a flat-end rectangular punch to evaluate uniaxial tensile strength in multiple directions in the longitudinal and transverse sections of the ECAP-processed Cu–Cr–Zr alloy. The validity of the modified method was verified by the linear relationship between the shear punch test data and tensile test data in the longitudinal direction. Specimens were prepared at three angles (0°, 45° and 90°) with respect to the extrusion direction in the longitudinal sections and the horizontal direction in the transverse sections of the ECAP bar. The results showed that tensile strength deceased when the angle increased from 0° to 90° in both the longitudinal and transverse sections. The longitudinal sections showed a more pronounced anisotropy than the transverse sections. As the amount of plastic deformation by ECAP increased, the degree of the anisotropy decreased in the longitudinal section but increased in the transverse section. Based on the results of this study, the strength of an ECAP material must be assessed in multiple directions in both the longitudinal and transverse sections.

Influence of Intermediate Principal Stress Effect on Flat Punch Problems

Using the finite difference code FLAC3D (Fast Lagrangian Analysis of Continua in 3 Dimensions) and UST (Unified Strength Theory), the influence of the intermediate principal stress effect on the problems of flat punch are analyzed in this paper. The values of the ultimate bearing capacity resulting from numerical analyses and the analytical solution of Prandtl’s strip punch problem are compared. The three-dimensional problems of strip, rectangular, square and circular punches on a semi infinite metallic medium have been analyzed.

Realisation and application of size dependent FEM-simulation for deep drawing of rectangular work pieces

Deep drawing provides a great application potential for the manufacturing of parts with complex shapes, even in very small dimensions. The friction between blank and forming tool is one of the decisive affecting factors for this process, since it affects the punch force as well as the surface quality of drawn workpieces essentially. Using scaled deep drawing it was found in our previous works, that the friction coefficients increase significantly with decreasing process dimension. This is called tribological size effect, which must be taken into account during the development of micro deep drawing. In this work, the tribological size effect is further investigated in deep drawing of work pieces with more complicated geometry, i.e. rectangular cups. In this investigation, scaled experiments are carried out with different rectangular punches (from 1.5 × 0.75 mm 2 to 20 × 10 mm 2) and the blank material Al99.5 with different thicknesses (from 0.015 mm to 0.2 mm). Size dependent FEM-simulation for this process is performed, at which the friction functions from scaled deep drawing of circular parts in previous work are applied. The comparison of both the simulated and experimental punch force-stroke-curves shows that the friction functions from deep drawing of circular parts is also valid for the deep drawing of rectangular work pieces. The size-dependent FEM-simulation with application of friction functions can be used to determine an optimum blank shape for a flange free rectangular micro workpiece (punch 2 × 1 mm 2), which is later validated in experimental investigation.

The coupling effect of punch shape and residual stress on measuring adhesion work of membrane by pull-off test

The adhesion work of thin film, such as membrane, can be measured by pull-off test. In this kind of experiments, the residual stress in film due to pretension during sample preparation plays an important role in experimental results. Moreover, the effect of residual stress on results varies greatly depending on different punch shapes. The coupling effect of punch shape and residual stress is studied in the framework of plate theory and energy principle. The analytical expressions for the effect parameters are obtained on the basis of the energy criterion. From our study, it is found that the effect of residual stress is more significant for a circular punch than the one for a rectangular punch. For future pull-off experiments, the coupling effect should be taken into account and the rectangular punch instead of a circular punch should be prioritized in experiments to mitigate the effect of residual stress.

Delamination Mechanics of a Clamped Rectangular Membrane in the Presence of Long-Range Intersurface Forces: Transition from JKR to DMT Limits

A 1-dimensional rectangular freestanding membrane clamped at opposite ends adheres to the planar surface of a rectangular punch. A tensile load applied to the punch causes the membrane to deform and gradually delaminate from the substrate. At equilibrium, the applied load is balanced by the disjoining pressure at the membrane-punch interface with range, y, and magnitude, p. Applying the Dugdale-Barenblatt-Maugis cohesive zone approximation, the disjoining pressure is taken to be uniform and confined to a finite cohesive length at the contact edge. For a fixed adhesion energy, γ = p y, we investigate the following: (i) the Derjaguin-Muller-Toporov (DMT) limit where y → ∞ and p → 0, (ii) the Johnson-Kendall-Roberts (JKR) limit where y → 0 and p → ∞, and (iii) the general case for intermediate but finite y and p. Delamination continues until the contact area shrinks to a line prior to “pinch-off”. The results are compared with the 2-dimensional axisymmetric membrane counterpart.

The uniform motion of rectangular and parabolic punches in a viscoelastic layer

Abstract The plane contact problem of the interaction of a rigid moving punch with a viscoelastic layer is considered. It is assumed that the punch moves at a constant speed and is forced into the layer by a constant normal force. There is no friction in the contact area between the stamp and the surface of the layer. The displacement of the boundary of the layer, due to the normal load applied to it, is determined. The integral equation of the contact problem for determining the contact pressure is then derived and an approximate solution of this integral equation is constructed using the Multhopp–Kalandiya method for a rectangular punch and one of the modifications of the method of orthogonal polynomials for a parabolic punch.

Contact measurement of internal fluid flow within poly(n-isopropylacrylamide) gels

A technique is presented that is ideally suited for characterizing the mechanical and transport properties of polymer gels at small strains. A flat, circular punch and a flat, rectangular punch are used to probe the response of gels under oscillatory loading conditions. Solvent transport within the gel is driven by gradients in hydrostatic pressure, giving rise to a dissipative response quantified by the phase lag between the punch displacement and the resulting load. By comparing results for different punch sizes, it is possible to differentiate between dissipation resulting from internal solvent flow and dissipation due to the viscoelastic character of the polymer network itself. Use of the technique is illustrated with poly(n-isopropylacrylamide) gels, which undergo a reversible structural transition just above room temperature. We show that heterogeneous structure formed above the transition temperature is not conducive to internal solvent flow within these gels.

Contact Problem for a Rectangular Punch on the Porous Elastic Half-Space

The paper is concerned with a contact problem about rigid rectangular punch forced into a half-space made of a linear elastic isotropic material with voids. We use a Cowin–Nunziato model for the half-space, and reduce the problem to a double Fredholm integral equation of the first kind. Then we apply two different approaches, to solve this equation. The first one is based on a direct collocation numerical technique. The second method is asymptotic, and we use a small parameter that is the relative width of the punch. Finally, compliance of the punch is determined, and results of the two different methods are compared with each other, as well as with a Sivashinsky–Panek–Kalker solution.

Crack initiation at contact surface

By using the S-theory, the crack initiation angle from the contact surface of rectangular rigid punch and flat-surface substrate has been investigated. The coefficient of friction at the edge of contact, which characterizes the asymptotic stress field, is considered as the controlling parameter in the analysis. The predicted results are in agreement with the experimental observations. The information gained may lend insight into the different stages of damage associated with the complex process of fretting fatigue.

Adhesion of a flat punch adhered to a thin pre-stressed membrane

The mechanics of a circular membrane delaminating from a rigid punch is derived based on linear elasticity and an energy balance approach. Both the tensile prestress and the resulting concomitant stress upon external loading are considered. A "pull-off" phenomenon is predicted when the contact circle shrinks to a critical value between 0.1945 and 0.3679 of the film diameter, depending on the critical strain energy release rate and the prestress. These asymptotic limits match exactly with the prestress dominant model by Shanahan and prestress free model by Wan. Thin film delamination from a rectangular punch is also investigated. Unlike the circular punch, the rectangular contact is expected to reduce to a line contact with zero contact area at "pinch-off." The graphs and trends shown are useful in assessing thin film delamination assisted by a prestress.