Hole Piercing Research Articles

AN IN-DEPTH INVESTIGATION ON KERF ANGLE IN PIERCED HOLE ON INCONEL-625 SUPERALLOY USING ABRASIVE WATERJET CUTTING PROCESS

This work investigates the piercing of microholes in turbine shroud rings (Inconel-625) using the Abrasive Waterjet Cutting process. The concern with the hole piercing is the kerf angle caused by the attenuation of the jet energy and stand-off distance, which seriously impacts the processing precision of abrasive water jet piercing. The effects of piercing parameters like machining time (40, 60 and 80[Formula: see text]s), abrasive mesh size (80 mesh and 120 mesh), stand-off distance (1, 2, 3 and 4[Formula: see text]mm), abrasive jet pressure (100, 125, 150 and 175[Formula: see text]MPa) are studied to reduce the kerf angle. The kerf angle increased linearly with a stand-off distance increase at different machining times. By piercing for 60[Formula: see text]s and 80[Formula: see text]s, the lowest values of kerf angle are obtained (0.03∘ and 0.02∘). The optimum conditions for making a pierced hole with a minimum kerf angle of 0.02∘ were achieved with a machining time- of 60[Formula: see text]s, abrasive mesh size- of 20 mesh, and abrasive jet pressure- of Scanning electron microscope (SEM) images and visual measuring system (VMS) images are used to identify the surface characteristics in kerf zone. The features, including ploughing, particle embedment, lip impression and wear path due to the ductile mode of erosion caused by high energy impact, is also discussed.

Modernization of Electrode Composite Material Based on Copper Powder for Electrical Discharge Machining of High-Strength Alloys

As a result of implemented modernization of known electrode composite material based on Cu-3% wt BN copper powder successfully used for electrical discharge machining of high-strength alloys, composite material (Cu - 3% wt BN) – 0.5 % wt Al – 0.25 % wt in the form of high-density long thin-wall plates for operations of electrical discharge cutting and piercing of hard-to-machine materials was obtained. The new material was obtained with the use of the method of reactionary mechanical alloying of initial powder components in the attritor. Tool electrodes made of the new material during electrical discharge piercing of rectangular holes in titanium alloy sheets ensure a 1.6 times higher machining rate comparing to tool electrodes made of the Cu-3% wt BN prototype material. After replacement of rolled copper in tool electrodes with the new composite material the machining rate will increase 4.1 times. The tool electrodes made of this material have significantly lower electrical discharge wear comparing to the wear of tool electrodes made of the prototype material and rolled copper.

Mechanisms and predictive models for the erosion process of super hard and brittle materials by a vibration-assisted slurry jet

The mechanisms under which vibration assistance improves the material removal process in slurry jet machining of super hard and brittle materials are seminally studied based on the erosive theories, viscous flow principles and particle dynamics under the effect of vibration. It is shown that brittle erosion by the impact of jet particles is dominant in the material removal, followed by a secondary erosive process driven by the vortices induced on a viscous crossflow. The vibration applied to the work surface perturbates the crossflow and promotes the forces to accelerate the particles on both the impact zone and within the crossflow layer, which allows particles to overcome the viscous restriction and move more freely in the suspending liquid. The number of the particles accumulated in the impact zone therefore is reduced or, if at the optimal condition, is eliminated, making a more efficient transfer of the impact energy to the target material. From this new understanding, process models are developed which can be used to guide the selection of process parameters for micro-machining such as hole piercing. The models are then assessed on the SiC polymorphs, 4H-SiC, with relatively softer SiC abrasives and shown to be able to predict the time required for creating a desired cavity geometry and the optimal vibration amplitude for an increased impact energy transfer efficiency.

Mechanism of EDM Intensification at Ultrasound Application

This paper considers some theoretical provisions on the impact ultrasonic mechanical vibrations have on the throughput of an electroerosive piercing of small-diameter holes. The approximate estimates confirm the hypothesis that the cumulative jets mechanism makes the greatest contribution to the intensification of a multiphase medium flow in the interelectrode gap. A model is proposed for a periodic localization of the cavitation region in the bottom part of the annular side gap. It allows explaining the occurrence of a multiphase medium flow during hole processing.

CALCULATION OF THROTTLEMENT PARAMETERS IN PARALLEL CHANNELS OF DRILLING PIPERS FOR DEEP HOLE

The article presents a method for calculating the characteristics of the throttling elements of the lubricating-cooling technical medium (COTS) Yu used in deforming piercing. A feature of the proposed technique is the method of supplying cutting fluids under pressure through the grooves made on the outer surface of the mandrel teeth, when the pressure of the working medium and its flow rate are divided into parallel flows, one of which provides pressure on the piercing when the hole is mandrelled with a normalized speed in its axial movement the second provides the calculated parameters of throttling between the surface of the grooves on the mandrel teeth and the machined surface, where they create "damping cushions", improving the mandrel process and reducing wear of the piercing [3]. The presented calculation of the characteristics (coolant pressure, flow rate, etc.) with the location of the conditional chambers formed by the grooves of the punching teeth and the processed surface confirms the possibility of using throttles to implement the conditions for using throttling elements during cutting-deforming piercing of deep holes in long tube blanks and increasing by this basis of its effectiveness.

Long-length tubular Electrode-Tools from Composite Material for Electrical Discharge Machining of Hard Alloys

The article deals with long-length tubular electrode-tools made of the engineered composite [(WC+3wt%Co)+3wt%BN)]+14wt%Cu, which, during electrical discharge piercing of holes in a hard alloy WC+6wt%Co (ISO 513:2012) in the optimal mode, have a productivity that is almost 8 times higher than the productivity of the process, when it is performed using copper electrode-tools. Therewith, electrical discharge wear of the electrode-tools made of the new material is 4.1 ... 4.5 times less than the wear of the copper electrode-tools. To obtain hollow electrodetools from the specified material, the powder composition was radially molded by the pressure of a impulsed magnet field, and the resulting porous blank was impregnated with copper during its further sintering.

Combined multi-electrode piercing of holes in hard-to-process materials

The possibilities of combined piercing through and “blind” holes in hard-to-process materials are considered. The possibilities of intensifying the processing process by using multi-electrode tools are presented. A fundamentally new element of the new technology is the creation and use of a new working environment based on a rheological fluid with variable viscosity. This determines the conditions for mass removal of processing products from the hole forming site and creates conditions for process stabilization. The method is protected by a Russian patent and has been used in many factories countries. The article considers the technology of processing parts in the proposed working environment, which implements the proposed method in the form of a technological process in the manufacture of parts with holes of different cross-sections. At the same time, the use of combined multi-electrode cross-linking allowed up to 3 times to speed up the production of channels for cooling parts of the hot zone of thermal machines, and to achieve stability of cross-section sizes within ±5%. This technology expands the use of electrical processing methods in General and special engineering in the manufacture of parts from hard-to-process alloys.

Linking constituent phase properties to ductility and edge stretchability of two DP 980 steels

Two DP 980 steels were characterized with multiple methods to determine its microstructure characteristics, tensile properties and edge stretchability. The first (DP980-B) is a commercial grade DP980 steel produced by AK Steel, while the second (DP980-T) is a modification of the first one by a tempering process. Both contain two individual phases: ferrite and martensite with body centered cubic (BCC) and tetragonal (BCT) crystal structure respectively. ASTM standard tensile tests were performed for both materials, revealing that DP980-B has higher work hardening and larger total elongation than DP980-T. Standard hole piercing and subsequent hole expansion and extrusion tests were also performed. The critical hole expansion ratio (HER) of hole pierced sheet at different nominal clearances, on the other hand, show an opposite trend: the HER of DP980-T almost doubles that of DP980-B. This indicates the tensile ductility and edge stretchability are determined by different mechanisms due to different deformation modes. The ductility of sheet metal during uniaxial tension is determined by deformation instability, i.e. necking, due to less constraint at the region of deformation and fracture will occur quickly after necking. The contribution of post-necking deformation to the total elongation is insignificant for the high strength grades such as DP980 steels. The ductility during hole-expansion, however, is mainly determined by material fracture behavior that is dependent on phase property disparity and material intrinsic fracture parameters. With the individual phase properties for both DP steels determined by in situ tensile tests under high energy X-ray diffraction, the results show that DP980-T steel has lower property disparities between the two phases than DP980-B steel, due to the tempering process. This explains why the DP980-T steel has higher HER than DP980-B steel: lower phase disparity will lead to less local deformation during loading. The higher work hardening rate for DP980-B steel contributes to its higher uniform elongation compared with DP980-T steel based on the maximum load condition of deformation instability. An integrated finite element simulation framework for studying hole expansion is also presented here, based on the calculated individual phase properties from the combined high energy x-ray diffraction (HEXRD) and elastic plastic self-consistent modeling. The simulation results correlate well with the experimental results on the HER difference between the two materials.

The effects of shear affected zone on edge crack sensitivity in dual-phase steels

Dual phase steels offer good combination of mechanical properties which is attractive for automotive industry. However, some challenges still remain and suppress using them widely. One of these challenges is the formation of premature cracks at shear-cut edges during the subsequent forming processes, which cannot be predicted by the conventional finite element methods. Therefore, the present study aims to propose a numerical tool to predict edge cracks in DP steel components. In this regard, the hole expansion method was applied as an edge crack detection technique on DP1000 steel sheets. To elaborate the study, parallel finite element simulations were performed as well. The simulation method considered the whole hole piercing process and the following hole expansion test as a one-stroke two-step strategy. The hole piercing process was applied in the first step on the sheet and a hole was cut. The results reveal that this process forms some surface irregularities and applies a special amount of damage at the cut edge, which both could have effects on the edge crack sensitivity. To study these effects, the subsequent hole expansion test was simulated on the manufactured hole. Thus, the effects of both surface irregularities and residual damage from hole piercing process were investigated in different case studies with all possible combinations of these effects. This strategy provides possibilities to numerically separate effects of surface quality and residual damage. The contribution shows on the one hand the experimental investigations and on the other hand deals with the numerical influence analyses.

Intelligent design and group assembly of male and female dies for hole piercing of automotive stamping dies

The design and assembly of piercing components of automotive stamping dies, such as male and female dies, is a complex and time-consuming process, which significantly affects the development period and quality of automotive panels. Therefore, a new automation and intelligent design system of piercing male and female dies was proposed based on a full parameterization modeling and group assembly, which is seamlessly integrated into the NX software. First, the system automatically identifies and designs holes in the panels based on characteristics of the hole boundaries. Second, two different designs and assembly methods are proposed to solve the design problems of male and female dies for standard and non-standard holes. For the standard holes, a network component library was built through the family parts, and the components of the holes are automatically matched and instantiated based on the group assembly technology. However, for non-standard holes, based on fully parameterized templates, piercing components can be achieved by replacing hole elements in the new design. Finally, the system accurately adjusts the positions of components after assembly to ensure that the cutting depth and installation coordinates meet the requirements. In addition, a large amount of design knowledge and specifications are integrated into the system. More importantly, the design and assembly quality are inspected throughout the entire process. Examples demonstrate that the system exhibits excellent performances for the piercing process, automation, and intelligent design of piercing components for holes, which can significantly improve the design efficiency and quality.

Consideration of hydraulic limitations in setting the mode parameters of combined piercing the holes

The paper considers the hydrodynamic limitations in the combined machining, caused by the non-rigidity of the tubular cathode-tool. It is shown that increasing the inertia moment of the cathode-tool cross section is possible only in decreasing the diameter of the hole for pumping the electrolyte. It should be noted that reducing the diameter of the hole increases the hydrodynamic losses of the electrolyte flow in the hydraulic path and, as a result, leads to a significant reduction in the range of the mode regimes. Thus, to implement the combined piercing of deep holes of small diameter, it is necessary to quantify the hydrodynamic limitations in using the tubular cathode-tool of significant length to establish the mode parameters.

АНАЛИЗ МЕТОДОВ ПОЛУЧЕНИЯ МИКРООТВЕРСТИЙ. ЧАСТЬ 2

Electric discharge machining is shown to be the best method developed and used for drilling precision micro-holes. High-performance piercing of micro holes with non-rigid requirements to hole surface accuracy and quality requires to use laser and electron-beam methods. The methods of casting and assembly are used to obtain super deep micro holes with the depth of 100 or more diameters. A comparative scientific and technical analysis of the world industrial technologies of obtaining micro holes in the historical development forms the methodological basis of the research. The article gives a physico-technical characteristic of ten methods of micro hole drilling, describes the equipment used and process capabilities the methods under discussion. The quantitative and qualitative assessment of technological processes is given as well. The rational application fields of ten methods of micro hole drilling are determined. The promising directions of improving the precision micro hole technology are developed.

Finite Element Simulation of Punch Shear during Hole Piercing in Auto Chain Components

The capabilities of presses are sometimes limited due to larger cutting force requirement for some sheet metal operations. Reducing the tonnage requirements for such operations will sometimes make the presses capable of doing such operations. FEM simulation can be a reliable tool in predicting the amount of tonnage required for the metal stamping operation. An attempt is taken in this study to analyse the behaviour of the hole piercing operation in an automobile chain part using DEFORM 3D software. The main focus is on the prediction of tonnage requirement with different shear methods on the piercing. Simulations were conducted with flat, single sheared, double sheared, reverse double sheared, convex sheared and concave sheared punches and analyzed for variations in the press load. The phenomena of piercing are also observed through the simulation based on AISI 1060 steel component used for automobile chain as inner plate. Simulation results showed that the shear angles provided on piercing punches will reduce the punch load significantly.

プレスシェービングによる超高強度鋼板の平滑穴抜き加工

プレスシェービングによる超高強度鋼板の平滑穴抜き加工

An integrated finite element-based simulation framework: From hole piercing to hole expansion

An integrated finite element-based modeling framework is developed to predict the hole expansion ratio (HER) of AA6111-T4 sheet by considering the piercing-induced damages around the hole edge. Using damage models and parameters calibrated from previously reported tensile stretchability studies, the predicted HER correlates well with experimentally measured HER values for different hole piercing clearances. The hole piercing model shows burrs are not generated on the sheared surface for clearances less than 20%, which corresponds well with the experimental data on pierced holes cross-sections. Finite-element-calculated HER also is not especially sensitive to piercing clearances less than this value. However, as clearances increase to 30% and further to 40%, the HER values are predicted to be considerably smaller, also consistent with experimental measurements. Upon validation, the integrated modeling framework is used to examine the effects of different hole piercing and hole expansion conditions on the critical HERs for AA6111-T4.

Abstract 5500: Sensitivity of metastatic breast cancer (4T1) cells to apoptotic effect by Lactobacillus kefiri P-IF via a mechanism that involves hole piercing in cancer cells

Abstract Objective: Metastasis, the spread of cancer from its origin, is primarily responsible for the majority of deaths from human solid-organ cancer. Lactobacillus kefiri P-IF, a freeze-dried form of heat-killed L. kefiri, is a specific strain of lactic acid bacteria that has a unique DNA sequence and PET scans showing a 99.6% homology with regular kefiris. In the current study, we evaluate the apoptotic effect of L. kefiri P-IF on metastatic breast cancer (MBC) cells. Materials and Methods: 4T1, murine MBC, were cultured with different concentrations of L.kefiri P-IF (0, 1.25, 2.5 and 5 mg/ml) and the apoptotic response was assessed by propidium iodide assay and trypan blue exclusion test. Changes in mitochondrial membrane potential (MMP) were monitored by flow cytometry. Changes in percentages of cancer cells bearing holes were examined by Giemsa-stained cytospin preparation under a light microscope. Results: L.kefiri P-IF induced apoptosis in 4T1 cells. Incubation with L. Kefiri P-IF at 5 mg/ml induced apoptosis in 91% of 4T1 cells compared to 7% apoptosis for control untreated cells. A significant apoptotic effect by L.kefiri P-IF was detected as early as 90 min post exposure with cancer cells, showing 25 fold increase in apoptotic non-adherent cells as compared to control untreated cells. The apoptotic effect was further increased 30 to 75 fold at 24 and 48 hours, respectively. The induction of apoptosis by L.kefiri P-IF was associated with significant decrease in the polarization of MMP and an increase in the percentages of adherent cells bearing multiple holes, suggesting that the mechanism by which L.kefiri P-IF induces its apoptotic effect involves piercing holes in cancer cells. Thes holes are shown to vary in circumference and depth. Control untreated adherent cells showed 40% cells with no holes and 43% cells bearing more than 5 holes. In contrast, L.kefiri P-IF treated adherent cells showed only 7% cells with no holes, while cells bearing more than 5 holes reached 87 %, this represents a 2 fold increase in cells with multiple holes over control cells. Conclusion: These results suggest that L.kefiri P-IF exerts an apoptotic effect on MBC cells by a mechanism that involves the hole piercing in cancer cells, and may represent a new class of adjuvants for the treatment of metastatic breast cancer. L.kefiri P-IF was provided by Paitos Co., Ltd. Yokohama, Kanagawa, Japan. Citation Format: Mamdooh H. Ghoneum. Sensitivity of metastatic breast cancer (4T1) cells to apoptotic effect by Lactobacillus kefiri P-IF via a mechanism that involves hole piercing in cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5500. doi:10.1158/1538-7445.AM2014-5500

Micro Hole Piercing for Ultra Fine Grained Steel

Ultra fine grained steels have been developed by many researchers. However, the study of influence on processes and product functions from different grain size are limited because the size of bulk material was small for these products. Authors have developed the production process of thin ultra fine grained stainless steel coil, and the effects are able to be clarified. This paper will firstly report the influence on micro hole piercing by comparing different grain size materials. Secondly, orifices are produced from these materials, and the liquid flow volume is measured as the functional effect of different grain size. The effects of grain size differences were discussed with observing the hole conditions and measuring flow volume. The effects of reduction of the grain size were summarized as follows: (1) Accurate small hole is produced when ultra fine grained stainless steel is employed. (2) Product functional improvement is possible, and the phenomena are useful for liquid control devices.

Micro Hole Piercing for Ultra Fine Grained Steel

Ultra fine grained steels have been developed by many researchers. However, studies on the effects of different grain size on processes and product functions have been limited because the size of the bulk material has been small for these products. The authors have developed a production process for thin ultra fine grained stainless steel coil, and the effects have been clarified. This paper first reports the effects onmicro hole piercing by comparing materials with different grain sizes. Secondly, orifices are produced from these materials, and the liquid flow volume is measured as the functional effect of different grain sizes.

Finite element analysis of deep drawing and hole flanging processing of an oil filter cover

Trial and error is a tedious way of working which has been implemented for long time in the sheet metal forming processing. Finite Element Analysis (FEA) is one of the most advanced solutions that can eliminate time and money consumption. The present investigated part is an oil filter cover and contains outer flange processed by deep drawing and inner flange processed by hole flanging. Inner flange ripping usually happens on the rim. Both flanging techniques have been analyzed by FEA. Failure modelling according to three damage theories was applied to detect reasons of inner flange ripping. Metal simply cannot withstand elongation required for hole flanging. FEA proposed deep drawing technique of the inner flange followed by hole piercing and finally deep drawing is used for outer flange.

Study on piercing mechanism of small holes

FEM analysis and experiments were conducted on small hole piercing to clarify the piercing mechanism. In this paper, small hole piercing is defined as a piercing performed using a punch with a diameter smaller than the material thickness. To discuss the mechanism, new concepts on the incremental ratio are introduced in addition to an aspect ratio already known. The results of this study clarified the following: the piercing mechanism distinctly changes with increasing aspect ratio. When the ratio is larger than one, the initial stage resembles simple indenting and the latter stage resembles traditional blanking. High aspect piercing up to 12.5 was successfully achieved with the aid of good lubricants.