Blind Holes Research Articles

Electric discharge drilling of blind holes in titanium alloy Ti6Al4V

PurposeThis experimental study aims to deal with the improvement of process performance of electric discharge drilling (EDD) for fabricating true blind holes in titanium alloy Ti6Al4V. Micro EDD was performed on Ti6Al4V and blind holes were drilled into the workpiece.Design/methodology/approachThe effects of input parameters (i.e. voltage, capacitance and spindle speed) on responses (i.e. material removal rate, tool wear rate and surface roughness [SR]) were evaluated through response surface methodology. The data was analyzed using analysis of variance and multi-optimization was performed for the optimized set of parameters. The optimized process parameters were then used to drill deeper blind holes.FindingsBlind holes have few characteristics such as SR, taper angle and corner radius. The value of corner radius reflects the quality of the hole produced as well as the amount of tool roundness. The optimized process parameters suggested by the current experimental study lower down the response values (i.e. SR, taper angle and corner radius). The process is found very effective in producing finished blind holes.Originality/valueThis experimental study establishes EDD as a feasible process for the fabrication of truly blind holes in Ti6Al4V.

Combustion Synthesis of Metal-Intermetallic-Ceramic Laminate AlMg6-NiAl-TiC Composite

In this study, SHS was used to produce metal-intermetallic-ceramic laminate AlMg6-NiAl-TiC composite. The experiment conducted without a cylindrical powder pellet holder produced no joint between the NiAl and AlMg6 sheet. On the other hand, the experiment conducted inside a cylindrical powder pellet holder (CPPH) with a blind hole produced a joint. It was found that the AlMg6 sheet had a temperature of 400–550 °C across its entire thickness during SHS. The study of the microstructure and energy-dispersive analysis (EDS) of AlMg6-NiAl-TiC composite showed that it had five layers: (1) ceramic layer of 7-mm-thick TiC; (2) the upper diffusion layer that formed at the interface between NiAl and TiC consisted of TiC + NiAl; (3) an intermetallic layer, which consisted of 13-mm-thick NiAl; (4) the lower diffusion layer, which formed at the interface between NiAl and AlMg6; and (5) a layer of 4-mm-thick aluminum alloy AlMg6. The EDS showed that during the synthesis of NiAl and its interaction with the surface of the AlMg6 sheet, mixing of the components of the initial materials (NiAl, AlMg6) in the joint interface occurs. At the interface of NiAl and AlMg6, the microhardness was 790–870 HV, which indicates the presence of quenching structures in the melted zones.

The development of triangular kinematic module to calculate the deformation pressure in the extrusion processes

Аliieva L. І., Levchenko V. M., Aliiev I. S., Kartamyshev D. O. The development of triangular kinematic module to calculate the deformation pressure in the extrusion processes
 The article presents the universal kinematic module developed on the basis of the energy upper bound method, designed for use in mathematical simulations of combined processes of cold forging. In particular, this module can be used for force regime simulating and tool loads analyzing at radial-forward extrusion of hollow products with blind hole of continuous workpieces to describe deformation zones during metal flow to the center and turn zones from radial flow to backward one. The kinematically possible velocity field for convex curvilinear (parabolic) triangular module and the equations of its parabolic inclined boundary are given. Analytical dependencies for power of deformation forces, friction and shear at the boundaries of the module, as well as for the reduced pressure in a parametric form are obtained. The developed curvilinear kinematic module, the use of which makes it possible to increase the efficiency of the upper bound method for studying the processes of combined extrusion, has been tested and described. It is shown that value of reduced pressure for the curvilinear turn module is most affected by the relative thickness of the flange, its radius, the thickness of the wall of the tubular workpiece, as well as friction conditions. The possibility of correct using of curvilinear triangular module for the analysis of complex schemes of processes with several zones is demonstrated. The simulation for calculation schemes of radial-forward workpiece extrusion with variable flange height was carried out. It has been determined that the developed curvilinear triangular module due to the reducing the value of the velocity jump at its boundaries, makes it possible to reduce the upper estimate of the tool loads in comparison with the variants of simulations that were previously based on rectangular modules.

ROTARY BROACHING - TECHNOLOGY, APPLICATION AND CAPABILITY

The present paper presents a relatively new technology called rotary broaching for processing external and internal profile surfaces –. The technology can be implemented on lathes (turning centers, multi-task machines) and milling machines with CNC, using a special holder with a tool having the geometry of the processed profile surface installed on it. The tool holder has a specific geometry, providing an angular location of the tool axis relative to the machined surface of 1֠, offering the possibility of machining. One of the main advantages of this technology is that it allows the processing of profile surfaces in blind holes and closed external surfaces, for example, on the steps of rotating parts. It requires preliminary preparation of the treated surface, where for internal profile surfaces, it is necessary to process a starting hole with a certain diameter and length, depending on the size of the profile surface. Furthermore, processing by this technology implies obtaining high productivity, as it works with feed for a speed of 0.01 ÷ 0.12 mm/rev and spindle speed (workpiece) 1000 ÷ 3000 min-1 depending on the processed material. According to the manufacturers of tools used for a rotary broach, various types of material with tensile strength Rm up to 1400 N / mm2 can be processed, such as stainless steel, cast iron, aluminum and copper alloys, titanium, brass, and others.

Experimental characterization and mechanism of hydraulic pulsation waves driving microscopic residual oil

To clarify microscopic mechanisms of residual oil displacement by hydraulic pulsation wave, microscopic visualization experiments of hydraulic pulsation wave driving residual oil were carried out by using the microscopic visualization device of pulsating water drive. For the four types of residual oil left in the reservoir after water flooding, i.e. membrane, column, cluster, and blind end residual oils, hydraulic pulsation waves broke the micro-equilibrium of the interface by disturbing the oil-water interface, so that the injected water invaded into and contacted with the remaining oil in small pores and blind holes, and the remaining oil was pushed or stripped to the mainstream channel by deformation superposition effect and then carried out by the injected water. In the displacement, the pulsation frequency mainly affected the cluster and blind end remaining oil, and the hydraulic pulsation wave with a frequency of about 1 Hz had the best effect in improving the recovery. The pulsation amplitude value mainly affected the membrane and column residual oil, and the larger the amplitude value, the more remaining oil the hydraulic pulsation wave would displace. The presence of low intensity continuous flow pressure and holding pressure end pressure promoted the concentration of pulsating energy and greatly improve the recovery of cluster residual oil. The rise in temperature made the hydraulic pulsation wave work better in displacing remaining oil, improving the efficiency of oil flooding.

Investigation on the microstructure and mechanical properties analysis of 304L stainless steel multi-pass filler welding joint for pipeline

The multi-pass welding of 45 mm thick 304 L stainless steel is carried out by flux-cored wire arc welding. The mechanical property of the welded joint is characterized. Residual stress measurement on the surface of welded joints is carried out by blind hole method. The finite element model of multi-pass welding joint is established based on actual weld morphology. The temperature and stress field have been investigated by the double ellipsoid heat source model during the welding process. The microstructure analysis results show that the upper surface is consist of austenite and ferrite phase, which is larger than the lower weld zone. And the microhardness distribution is shown as welded metal < heat affected zone < base metal. After welding, the maximum longitudinal residual stress is 398 MPa, and the maximum transverse residual stress is 441 MPa.

Machinability and parametric optimization of aluminum silicon carbide metal matrix composite (Al-SiC MMC) machined through µ-EDM

Aluminum silicon carbide metal matrix composite (Al-SiC MMC) is widely used because of its exceptional mechanical and thermal properties. Some engineering applications include aerospace, automobile, electronics, and medical devices. In the present investigation, aluminum 7075 alloy (Al-7075) as a matrix material with reinforcement particles of 10% silicon carbide (SiC) is fabricated using stir casting. The developed Al-SiC MMC is machined using an in-house developed micro-electro discharge machine (µ-EDM) setup. Experiments are carried out with input parameters—voltage (V), capacitance (µF), and pulse-on time (µs)—to analyze the responses such as hole depth (HD), material removal rate (MRR), tool wear rate (TWR), surface roughness (SR), and circularity error (CE). Taguchi L16 orthogonal array is adopted to conduct 16 experiments with varying process parameters for 5 minutes’ duration with a copper tool electrode of Ø720 µm on the Al-SiC MMC workpiece of size 20 mm × 20 mm × 2.5 mm. The dielectric medium used for all experimentation is EDM oil. The resultant blind holes are characterized using scanning electron microscopy (SEM) images and a 3D profilometer. Later, the signal-to-noise ( S/N) ratio technique is used to optimize the process parameters to enhance individual output responses. The obtained results are discussed in the article. Further, analysis of variance (ANOVA) is performed to find out the contribution of each parameter to the output responses. Grey relational analysis (GRA) is also used for multiobjective optimization to get quality blind holes. The best parametric combination obtained through GRA are at 28 V, 100 µF, and 100 µs, resulting in 823 µm of HD, 0.38 mg/min of MRR, 0.10 mg/min of TWR, 8.98 µm of SR, and 48.37 µm of CE.

The effect of quaternary ammonium salts with different chain lengths on copper filling behavior in blind holes of printed circuit board

The rapid and defect free blind hole copper super filling is the key technology to ensure the quality and development of printed circuit boards (PCBs). The linear quaternary ammonium compounds with a low molecular weight are expected to act as a potential suppressor for blind hole copper filling. Here, three quaternary ammonium salts with different molecular chain lengths (the dodecyl trimethyl ammonium chloride, the cetyl trimethyl ammonium chloride and the stearyl trimethyl ammonium chloride) were selected to study the effects of the molecular chain length of quaternary ammonium salt on the copper filling behavior of the PCB blind holes. The electrochemical results show that the three quaternary ammonium salts show greater inhibition ability on copper deposition compared with the traditional additives (polyethylene glycol (PEG) and Cl−) and furthermore, the suppressor effect becomes stronger with the increase of molecular weight. The blind hole copper filling experiment of PCB is also carried out to study the copper filling capacity of three quaternary ammonium salts. The filling experiment reveals that compared with the traditional suppressors (PEG and Cl−), the filling quality of blind hole copper is significantly improved when the three quaternary ammonium salts are used as suppressors. Moreover, under the coordination of accelerator (bis (3-sulfopropyl) disulfide (SPS)), the three quaternary ammonium salts can realize more rapid copper super filling without chloride ion in the electrolyte. Cross-section and surface morphological analysis further illuminates that the quaternary ammonium salt as an suppressor can also more effectively inhibit the deposition of copper on the PCB surface and reduce the roughness of the copper layer. The present results imply that quaternary ammonium salts have greater advantages for copper filling and are expected to replace traditional suppressors as new suppressors.

Dual-Mode Dielectric Waveguide Monoblock Filter Design

This paper presents a design of dielectric waveguide filter using dual-mode dielectric waveguide resonators (DWRs). The filter is formed by a ceramic monoblock, thus it is compact and ease of fabrication. The employed degenerate modes of DWR are TE101 and TE011 mode, which can be coupled by a slot on the dielectric block. The coupling between a dual-mode DWR and a single-mode DWR is realized by aperture and slot. The external coupling is realized by a silver-coated blind hole that aligns to the mode for excitation. Transmission zero (TZ) can be flexibly generated above or below passband, by changing the relative position of coupling slot. A sixth order bandpass filter working at 4.9 GHz is designed using dual- and single-mode DWRs. The filter is fabricated and measured, agreeing well with simulation. This filter has compact size, low insertion loss, good selectivity and wide spurious-free response, which is applicable to 5G base stations.

Investigating the effects of different particulate deposition techniques on the fabrication of AA 2014/TiC surface composites using friction stir processing

Aluminium matrix surface composites play a significant role as in many of the engineering application surface properties rather than bulk properties determines the life of the components. Friction stir processing (FSP) which is a thermo-mechanical process is emerging as an excellent choice for fabricating metal matrix surface composites. The present work aims to study the effects of different particulate deposition techniques for the processing of AA2014/TiC surface composite using FSP. Three different reinforcement techniques were considered in this research work and microhardness of each processed specimen was measured. The observed microhardness value for all three specimens was greater than the microhardness value of the base material (BM). But the reinforcement technique with groove capped by the means of a pin less FSP tool shows a substantial enhancement in microhardness value of 25.37%. Performing FSP without capping the groove results in the agglomeration of the reinforcing particles. This also resulted in increased tool wear because of the direct interaction of reinforcing particles with the FSP tool. A defect-like cavity was formed during FSP when the reinforcing particles were filled in the blind holes. The experimental results demonstrated that for fabricating surface composites using FSP, a straight capped groove shows a significant enhancement in microhardness compared to the other two techniques.

Effect of simulated axial residual stress and transverse residual stress in welded P92 pipe and plates including plasticity error

The paper deals with the measurement of the residual stresses in P92 welded pipe using the blind hole drilling technique.The post weld heat treatment (PWHT) of P92 welded pipe was also conducted to study their effect on residual stresses .The P92 pipe weld joints were prepared using gas tungsten arc welding process. The residual stress measurement was carried out using the strain gauge rosette that was associated with the plastic deformation of material and stress concentration effect of multi-point cutting tool. The corrective formulation was developed for calculating the corrected value of residual stresses from the experimentally obtained strain value. The Strain gauge response was estimated experimentally using the tensile testing for the uniaxial loading while finite element analysis was performed for biaxial loading. Gas tungsten arc welds joint was prepared for conventional V-groove and narrow groove design.

5-Amino-1,3,4-thiadiazole-2-thiol as a new leveler for blind holes copper electroplating: Theoretical calculation and electrochemical studies

High density interconnection printed circuit board PCB puts forward high requirements for defect free blind holes copper filling. Here, 5-amino-1,3,4-thiadiazole-2-mercaptan, a small molecular compound containing sulfur and nitrogen heterocycles, is proposed as a new leveling agent to try to meet the top-down blind holes filling of high-density interconnected printed circuit board (PCB). The cross-sectional images of blind holes captured by optical microscopy show that the selected heterocyclic compounds with small molecules containing nitrogen and sulfur have good leveling ability and can realize the top-down super filling of blind holes. The electrochemical measurements were used to analyze the inhibition behavior of the leveling agent on copper ion deposition and its interaction with other additives. An atomic force microscope (AFM) and X-ray diffractometer (XRD) were used to study the effect of inhibitors on the surface morphology and crystal structure of copper crystals. In addition, quantum chemistry calculations and molecular dynamics simulations also were used to analysis the structure-performance correlation (active sites) and adsorption energy of the leveler at the molecular level to further understand the function of the levelers in the electrolyte system. This work will be inspiring for discovering new and effective levelers in the future.

Influence of hybrid pin profile on enhancing microstructure and mechanical properties of AA5052/SiC surface composites fabricated via friction stir processing

ABSTRACT In friction stir processing (FSP), conventional pin tools like square and threaded cylindrical pins require multipass to produce defect-free and homogenous reinforcement particle dispersion. Thus, the effectiveness of the hybrid pin profile in a single pass was investigated in the current work to produce surface composites. The hybrid pin profile combines the features of square and threaded pins. The drilled blind holes were filled with SiC particles in the AA5052-H32 alloy. A pinless rotating tool was moved over the blind holes to avoid the spattering of inserted SiC particles during FSP. Thereafter, the FSP was performed using threaded, square, and hybrid pin tools. The mechanical and microstructural characteristics of the developed surface composites were studied. The results revealed that the hybrid pin tool uniformly distributed SiC particles due to lateral downward material movement and pulsating action. The hybrid pin tool produced smaller grain size of 9.32 µm than the conventional pin tool (i.e. 12.28 and 17.52 µm). The hybrid pin tool obtained the highest microhardness of 117 HV and tensile strength of 216.34 MPa. Using a hybrid tool saves processing time by half while attaining high mechanical properties that favour FSP commercialization.

Prediction Model for Liquid-Assisted Femtosecond Laser Micro Milling of Quartz without Taper.

The strong nonlinear absorption effect and “cold” processing characteristics of femtosecond lasers make them uniquely advantageous and promising for the micro- and nanoprocessing of hard and brittle materials, such as quartz. Traditional methods for studying the effects of femtosecond laser parameters on the quality of the processed structure mainly use univariate analysis methods, which require large mounts of experiments to predict and achieve the desired experimental results. The method of design of experiments (DOE) provides a way to predict desirable experimental results through smaller experimental scales, shorter experimental periods and lower experimental costs. In this study, a DOE program was designed to investigate the effects of a serious of parameters (laser repetition frequency, pulse energy, scan speed, scan distance, scan mode, scan times and laser focus position) on the depth and roughness (Ra) of the fabricated structure through the liquid-assisted femtosecond laser processing of quartz. A prediction model between the response variables and the main parameters was defined and validated. Finally, several blind holes with a size of 50 × and a depth of 200 were fabricated by the prediction model, which demonstrated the good consistency of the prediction model.

A magnetoelectric-ultrasonic multimodal system for synchronous NDE of surface and internal defects in metal

In the field of non-destructive evaluation (NDE) of solid metal materials, it has been a challenge to detect surface and internal defects simultaneously by using a single physical mechanism technique. Conventionally, different testing techniques, in which each one is particularly sensitive to a certain type of defect, are employed to gain full defect information. However, a separated testing method is always a time-consuming and laborious work. Here, we report a magnetoelectric-ultrasonic hybrid transducer and multimodal system for quantitative NDE of metal, which integrates a magnetoelectric composite wrapped with a coil for generating alternating current field and simultaneously measuring magnetic abnormal of surface defects (referred to as ME-ACFM) and a dual-piezoceramic ultrasonic transducer (DP-UT) for generating acoustic pulses and detecting the echo signal of internal defects, respectively. A bipulse signal with different pulse widths is used for excitation of the hybrid transducer, in which one is corresponded to the resonant frequencies of 5 MHz for DP-UT, and another to 122 kHz for ME-ACFM. The huge difference between two resonant frequencies is helpful for restraining signal interference each other. Experimental investigations show that when scanning the tested specimens (standard steel No.45 and aluminum plates), the surface and internal defects information can be obtained simultaneously almost without a dead zone. The surface defect resolutions of 0.1 mm width and 0.1 mm depth, and the inside defect resolution of 2 mm blind hole are obtained; the experimental errors for surface defect (crack) depth up to 5 mm are around 5 %; while experimental errors for ultrasonic depth measurement (with a blind zone of 1.25 mm) is less than 0.63 mm. The proposed hybrid transducer and multimodal system open up a new way for designing multi-physical mechanism based NDEs.

Novel compact bandpass filter using sextuple‐mode ceramic cavity resonator

This letter proposes a novel compact ceramic cavity bandpass filter with surface silver coating and air coupling apertures. It is constituted of a sextuple-mode ceramic cavity as the main resonator, two single-mode cavities to connect the sextuple modes transversely with source and load, and two single cavities to suppress higher harmonics. This proposed filter has the advantages of compact size, wide band, low insertion loss, high selectivity, wide spurious-free window, as well as coplanar source and load interfaces. There are no blind holes in the filter, which is beneficial for improving the machining accuracy. One prototype filter operating at 3.5 GHz is fabricated and measured. The minimum insertion loss in the passband is 0.65 dB. The inherent spurious mode of the sextuple-mode resonator at around 1.2fC (fC center frequency) is suppressed under −30 dB. The measured and simulated results are in good agreement.

A Triple-Quasi-TEM-Resonance Dielectric Cavity for Bandpass Filter Design

This letter presents a triple-quasi-TEM-resonance dielectric cavity for compact bandpass filter design. The proposed dielectric cavity is silver coated and has three blind holes which form three distinct quasi-TEM mode resonators. The external coupling structure for the resonator is realized by tapping hole. The inter-resonator couplings are realized and controlled by slots on the outer surfaces of the dielectric block. A three-pole filter with two controllable transmission zeros is designed and implemented. The measured results agree well with the simulated results, verifying the proposed triple-resonance dielectric cavity structure and coupling mechanisms.

The synergistic effects of additives on the micro vias copper filling

• N-(3-(5-Mercapto-1H-tetrazol-1-yl) phenyl) acetamide was investigated as leveler to develop the microvia with or without cracked plating. • An optimal plating solution was found and applied to carry out superfilling of microvias. • the cracked plating occur on the side and bottom of the microvia when without accelerator. A nitrogen-containing heterocyclic compound N-(3-(5-Mercapto-1H-tetrazol-1-yl) phenyl) acetamide (named L) was investigated as a new leveler to develop the microvias Cu filling with or without cracked plating in blind via. The synergistic effects of L with other plating additives were investigated by galvanostatic measurements (GMs) and cyclic voltammetry (CV) measurements. The GMs show that the Δη values (Potential difference at different speeds of Cu rotating disk electrode) are approximately 24 mV which usually suggests better Cu filling performance for the corresponding electrolyte additives. In addition, the optical microscope (OM) measurements indicated that microvias cracked plating was more likely to occur when there is no accelerator in the copper plating solution. The results of OM experiments also show that the microvia super-filling would not appear although the copper plating rate at the bottom of the blind hole is higher than that of the outer copper layer of the blind hole if there is no air agitation in the copper plating solution. The finest copper electroplating formula made up of the virgin acid solution (VAS) only added the PEP, L, SPS, Cl − was found and applied to carry out superfilling of microvias.

Template-free microwave-assisted growth of 3D hexagonal ZnO rods

Here, a rapid synthesis method for growing template-free three-dimensional hexagonal zinc oxide (ZnO) micro-rods (HZMR) using a pulsed-microwave (p-MW) irradiation technique is reported. The effects of microwave exposure time and power are shown to tune the morphology of hexagonal rods from solid to blind hole to hollow rods. X-ray diffraction (XRD) confirmed the growth of pure ZnO phase. Morphological investigations by Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM), optical properties by micro-Raman, Diffuse Reflectance Spectroscopy (DRS), Attenuated Total Reflectance (ATR) and Photoluminescence (PL) spectroscopy techniques were carried out. The PL studies reveal a dominant red emission along with characteristic blue and green emissions. The resulting structures have the scope of being applied as miniature sensors or in lasing applications. The blind-holed structures can be used as miniature crucibles/pots in reactions. This template-free growth of hexagonal rods is a very simple and economical technique that can result in solid, hollow or one-end blind hexagonal rods. The paper discusses the growth mechanism of these unique hierarchical HZMR.

Experimental and finite element analysis of temperature distribution in 409 M ferritic stainless steel by TIG, MIG and SMAW welding processes

ABSTRACTIn this study, three different arc welding processes, namely tungsten inert gas (TIG), metal inert gas (MIG) and shielded metal arc welding (SMAW) processes, are used to weld 409 M ferritic stainless steel. K-type thermocouples are located in the area of heat-affected zone by drilling blind holes in a plate at a distance of 3 mm and 7 mm from the weld line, revealing the contours of the temperature distribution of the weld. The experimental results are compared with the results of simulations using ANSYS by Goldak heat source model. The temperature is experimentally measured in the heat-affected region with the help of a thermocouple. The temperature distribution profile by the finite element method using ANSYS is compared with the experimental temperature distribution profile with the heat source. The experimental and simulation results for TIG, MIG and SMAW welding processes have been found to be excellent.