Groove Corner Research Articles

Effects of process parameters on cutting forces, material removal rate, and specific energy in trochoidal milling

Trochoidal milling has been developed to enhance tool life during slot machining. It is characterized by reduced cutting forces, cutting temperature, and tool wear as compared to conventional milling processes. It is effective in machining difficult-to-cut materials, high-speed machining, and groove corners. However, this process has not been deeply investigated enough to discover its advantages and optimize its parameters. A full factorial design of 144 experiments has been applied in this paper to investigate extensively the effects of axial depth of cut, feed rate, and trochoidal step on material removal rate, cutting forces, and specific energy in trochoidal milling. Trochoidal step and axial depth of cut almost have the same contributions on cutting forces by 32% and 31% respectively, followed by feed rate by 25%. Feed rate, trochoidal step, and axial depth of cut influence the material removal rate by 37%, 30%, and by 19% respectively. The contributions of feed rate, trochoidal step, and axial depth of cut on relative specific energy are 57%, 24%, and 8% respectively. The increase of axial depth of cut increases the maximum resultant force till a threshold value, then it stabilizes. This behavior occurred due to the increase of the maximum engagement angle to a certain limit, then it does not increase any more. Both feed rate and trochoidal step linear affect maximum resultant force and material removal rate, while the relationships are non-linear for specific energy. It is recommended to machine slots in full depth with the highest possible trochoidal step and feed rate, considering the increase of tool wear and surface roughness. It is preferred to use a cutting tool of a large helix angle and small diameter to reduce the threshold axial depth of cut. Overall, this study is significant in characterizing, designing, and optimizing of trochoidal milling through experimental work.

STUDYING THE EFFECT OF RIFLING PARAMETERS ON THE STRESS STATE IN A GUN BARREL WALL WHEN FIRING

The problem of determining the stress state of the rifled-bore barrel when firing was presented in this article. Where the effects of rifling parameters such as the quantity of grooves n, groove width a, depth of groove t, radius of groove corner ρ were investigated. A rifled-bore barrel has been modeled and investigated by using Ansys software on the basis of finite element method. The problem has only been treated under pressure load in static case. The article can be used for reference to improve the accuracy in calculating design and manufacturing gun barrel.

Artificial Neural Network Predictive Modelling of Laser Micro-Grooving for Commercial Pure Titanium (CP Ti) Grade 2

Grooving is the process of making a narrow channel on a surface of flat or cylindrical workpiece. Groove is precisely made to parts used in automotive, biomedical, and electronics industries. In automotive industries, groove plays an important role especially on mechanical parts to precisely locate seal (o-ring) to prevent gas/oil leakage between dynamic mating parts. On the other hand, artificial neural network (ANN) has been widely used in developing predictive models of various manufacturing processes to save huge amount of production time and money for industries. Unfortunately, very limited research has been investigated on micro groove quality employing ANN predictive models. Therefore, this research work presents on how the Artificial Neural Network (ANN) predictive model has been established, optimised and utilised to predict the laser micro-grooving quality of commercial pure titanium grade 2 material. A 3KW CO2 laser cutting machine was employed considering laser power, gas pressure, cutting speed, depth of cut and focal distance as the design parameters for modelling. On the other hand, three significant responses namely groove depth, groove width and groove corner radius were investigated. Experimental results were fed to establish the ANN predictive model, which then its parameters were optimized to gain high level prediction accuracy. The predicted results of ANN model presented the mean absolute percentage error for groove depth, groove width and groove corner radius at about 7.29%, 10.93% and 11.96% respectively. The obtained predictive results were found quite promising with the average of mean absolute percentage error (MAPE) for quality predictions which falls between 10 to 15%, concluding the validity of the developed ANN predictive model.

Using Textured-DLC Coating to Improve the Wear Resistance of Stainless Steel Plate Under Dust-Containing Lubricant Condition

Sliding mechanical parts working under heavy loads and at high speeds in harsh environments are often subjected to sand and dust, leading to abnormal wear and seizing. Although sliding surfaces can be hardened and textured, there is a need for even higher wear and seizure resistance. We therefore did this study to confirm the trapping effect of surface texturing on dust by finding a way to visualize the dust. As a result, we confirmed that the dust became trapped in the grooves of the texture during the sliding. In addition, to produce a sliding surface having both seizure and wear resistance, we produced a surface combining a diamond-like carbon (DLC) film and surface texturing, and we evaluated its tribological characteristics. In dusty conditions, the specific wear rate was about 1/20 on surfaces where DLC film and the surface texturing were used in conjunction, and its wear resistance was higher than that of a non-treated stainless steel substrate. On the other hand, a rise in the coefficient of friction due to a rise in contact stress on the corners of the texturing grooves was confirmed. Therefore, when the tribological characteristics were evaluated by changing the radii of the groove corners and the parameters of the groove depth, the coefficient of friction was the lowest, decreasing about 50% for the test sample with a corner radius of 7.1 μm.

Influence of Structural Parameters on the Behavior of an Asymmetric Linearly Graded Workfunction Trapezoidal Gate SOI MOSFET

This paper presents a dual metal trapezoidal recessed channel metal oxide semiconductor field effect transistor (MOSFET) embedded with asymmetric stack gate with linearly graded metal work-function technique to improve the carrier transport efficiency and device switching performance. The analytical model for the proposed asymmetric-linearly graded trapezoidal gate (ASY–LGTG) silicon on insulator (SOI) MOSFET has been developed considering parabolic approximation of 2-D Poisson’s equation. The threshold voltage of the device is extracted using minimum surface potential. The simulation work has been carried out using a Silvaco TCAD tool to validate the results of the analytical model. This grooved structure exhibits the corner effect, which plays a dynamic role in the improvement of the device performance. However, the impact of the corner effect can be controlled by the groove corner angle and doping concentration. We have also investigated the impact of different structural parameters such as negative junction depth (NJD), corner angle, substrate doping and stack gate features (upper oxide permittivity and oxide thickness ratio) on the performance of minimum surface potential, sub-threshold slope (SS), drain induced barrier lowering (DIBL), threshold voltage and device switching characteristics.

Experimental and analytical investigations into wire electrochemical micro turning

Electrochemical turning (ECT) has been studied by researchers for making axially symmetric parts of different materials by using shaped tools fed radially into the rotating workpiece. Despite having various advantages over other advanced machining processes, ECT has failed to gain much attention by the manufacturing industries and researchers because of the complexity involved in designing a shaped tool to give a desired shape and tolerances to the workpiece. In the present work, a systematic study is presented to understand the applicability of a microwire as a replacement for a shaped tool in this process. Simulations are carried out to understand the distribution of electric field lines and current density in case of wire electrochemical turning (ECT). The effects of insulting wire up to different angles on the evolved groove profile are investigated by performing simulation study. Minimum groove width is observed at the lowest value of ‘tool exposed angle’ (30°), while maximum groove depth is observed at the highest value of tool exposed angle (270°). In the later part of the work, an experimental study is performed to characterize a groove profile using a bare copper wire of diameter 200 µm. The effects of input parameters, such as workpiece rpm, tool radial insertion, applied potential and electrolyte concentration on responses like groove width, corner radius and taper angle are investigated. Finally, the understanding of behaviour of different process parameters is applied to perform operations like multi-step turning, microgroove turning and taper turning on copper and micro-threading on stainless steel 304.

Finite Element-Smeared Crack Combined Algorithm based Bridge Corbel Analysis

A practical combined algorithm for the corbel of common reinforced concrete bridge is put forward. Based on material nonlinearity, combining the professional finite element software Midas Civil and MIDAS FEA with Smeared crack model, the Thorenfeldt and Constant curves are used as concrete compression and tension constitutive model to numerical analyze the corbel’s stress and crack. Example results show that the normal stress of the corbel and crack are greater than design value of C35 concrete tensile strength, and part areas are in the plastic state. The groove corner region of the corbel has abrupt stress. The crack of the corbel is firstly generated at the groove and the top plate, and gradually expands with the increase of the load coefficient. It develops sufficiently in the groove region, but there is not any full-length crack. The corbel has a group-strip-like crack farther from groove corner region. The calculation results are consistent with the bridge disease condition, which shows that Finite Element-Smeared Crack Combined Algorithm proposed in this paper is effective for the analysis of corbel.

Numerical simulation of heat and mass transfer in a 3D model of a loop heat pipe evaporator

The article presents results of 3D numerical simulation of flow and conjugate heat and mass transfer in a model of the TacSat-4 satellite loop heat pipe evaporator. The mathematical model includes the Reynolds-averaged Navier–Stokes equations describing the flow in the liquid and vapor regions, Darcy's law for filtration modeling in the wicks and the energy equation with accurate coupling of connected sub-domains including effects of evaporation on interfaces between the porous and vapor regions. According to the simulation results, the evaporation localizes mainly at the vapor groove corners near the evaporator body. The vapor grooves operate under essentially different conditions, as a result, the flow rates differ by several times. Significant thickening of the evaporator body yields only weak reduction in a level of the grooves’ flow rate non-uniformity.

Fabrication of three-dimensional parylene HT diaphragms using D-RIE with a Si substrate

This work demonstrates the fabrication of parylene diaphragms with three-dimensional configurations using deep-reactive ion etching (D-RIE, or ion-coupled plasma etching using the Bosch process) and assessed the characteristics of the resulting products. Parylene HT, which has superior temperature resistance up to 350°C, was used due to the significant heat generated in the D-RIE process. Parylene was first deposited on a silicon substrate and a diaphragm configuration was etched on the backside of this substrate. In contrast to wet etching, D-RIE was able to fabricate any outline of diaphragms with fine projections, such that could be employed in a microelectromechanical system (MEMS). Planar diaphragms were produced to ascertain the heat resistance of the parylene, and diaphragms (5mm in diameter, 10μm thick) with corrugated rectangular grooves (30–50μm deep) were also fabricated. Scanning electron microscopy (SEM) identified some defects in the corners of grooves when employing a depth of 50μm. Such grooves were eventually fabricated without defects by converting the rectangular corners to rounded shapes and by depositing aluminum on the parylene layer. It was found to be necessary to carefully assess the thermal stress in the vicinities of corners, and that this stress was primarily affected by the groove depth. Surface roughness and mechanical properties of the parylene layers, including Young’s modulus and yield stress, were assessed after the D-RIE process.

Around the corner: Colloidal assembly and wiring in groovy nematic cells.

We study colloids suspended in nematic liquid crystal in grooves with homeotropic anchoring. We observe "eyelashes", topological dipole chains that follow the local, curved director field. These beget wires that connect the groove corners to topographical features on the cell lid to yield oriented, curvilinear colloidal wires spanning the cell, formed in a nonsingular director field. As the groove aspect ratio changes, we find different ground states and corroborate our observation with numerics. Our results rely upon on the scale of topographical features, the sharpness of edges, and the colloid-sourced distortions; all these elements can be exploited to guide the formation of reconfigurable structures in nematics.

Ion-Sensitive Field-Effect Transistors With Periodic-Groove Channels Fabricated Using Nanoimprint Lithography

This letter addresses the characteristic of ion-selective field-effect transistors (ISFETs) with periodic-groove channels. The channels with the groove width/space about 1:1, 200/200 nm, were fabricated by ultraviolet nanoimprint lithography. The proposed ISFETs exhibited higher sensitivity, lower hysteresis, and lower drift characteristics than single channel. The nanoscale corners of periodic grooves can improve the surface potential response to the ion concentration. With this approach, high-performance ISFETs can be fabricated for future biosensor applications.

Two-step design protocol for patterned groove micromixers

Micromixers are essential components of microreactor technology. In this paper, a simple two-step design protocol for patterned groove micromixers based on numerical simulations is presented. In the first step, one groove of the staggered herringbone micromixer (SHM) is designed based on the average magnitude of transversal velocity vAVGyz at the end of the groove. In the second step, different configurations of six grooves are investigated. A slightly better mixing is achieved compared to the established SHM and significantly fewer grooves are needed. Due to fewer grooves and rounded groove corners, the new design is easier to be produced by microengineering technologies (MET). Additionally, good mixing was also achieved with a modified slanted groove micromixer (SGM) configuration with the largest rounding radius at the edges. A SGM prototype was machined by micro EDM milling. The simulation results were experimentally verified with flow visualization and a good agreement was observed. The presented protocol vastly reduces the number of optimal patterned groove geometry configuration candidates to be evaluated; it is simple and effective for practical applications.

Wedge-Splitting Test – Determination of Minimal Starting Notch Length for Various Cement Based Composites Part II: Crack and Notch Fracture Mechanics Approaches

The paper focuses on the geometrical proportions of cube-shaped quasi-brittle specimens subjected to a wedge-splitting test (WST). The minimal/optimal initial crack/notch length for successful performance of WST on these specimens is studied numerically (ANSYS). This second part of the paper treats the problem asymptotically, i.e. from the point of view of a very fine grained silicate composite material with negligible characteristic length which describes the level of the material brittleness (i.e. brittle). The problem of competition of the crack initiation point between the notch tip and the groove corner in the load-imposing area of the specimen is solved using theories of both linear elastic fracture mechanics and fracture mechanics of generalized singular stress concentrators. The numerically obtained crack/notch length is compared to results of numerical simulations using cohesive crack model reported in the first part of the paper. The minimal notch length is recommended.

Wedge-Splitting Test – Determination of Minimal Starting Notch Length for Various Cement Based Composites Part I: Cohesive Crack Modelling

The geometric proportions of cube-shaped specimens subjected to wedge-splitting tests are numerically studied in the paper. The minimal notch length for specimens made of cement based composites varying in characteristic length of the material (a measure of material brittle-ness/heterogeneity) is verified using finite element method code with an implemented cohesive crack model (ATENA). The problem of assigning the crack initiation point (the notch tip vs. the groove corner in the load-imposing area of the specimen) is solved numerically also using both the theory of linear elastic fracture mechanics and the theory of the fracture mechanics of generalized singular stress concentrators in the second part of the two-part paper. Results ob-tained by the different approaches are compared. The minimal notch length is recommended.

Action of a gas flux on the surface layer of the bore

The heating parameters and temperature of the surface layer in the bore are determined in the case of a single shot, for sections of the bore subject to the action of a gas flux at the corners of grooves that are unfilled by the bullet’s casing.

Rigid-plastic and elastic-plastic finite element analysis on the clinching joint process of thin metal sheets

This article describes the joining of thin metal sheets by a single stroke clinching process. Elastic-plastic and rigid-plastic finite element analysis were applied by employing Coulomb friction and constant shear friction in order to investigate the behavior of the clinch joint formation process. Four process variables, such as die diameter, die depth, groove width, and groove corner radius were selected to investigate the parametric effect on the clinch joint. The strength of clinch joints were evaluated by examining the separation strengths, such as peel strength and tensile shear strength, respectively. A failure diagram was constructed that summarizes the analysis results. The simulation results showed that die diameter and depth were the most decisive parameters for controlling the quality of the clinch joint, while the bottom’s thickness was the most important evaluation parameter to determine the separation strengths.

Diamond cutting of a large off-axis Fresnel lens Mold

The oxygen-free copper (OFC) is often used for the substrate material of the molds for the hot hydraulic press, the injection, and the light guide plate. The diamond cutting is usually used for the high precision finish process of the nonferrous metals. In this article, an OFC mold, which is used for testing the hot hydraulic press process of the large segmental double-side polymethyl methacrylate (PMMA) Fresnel lens, was designed. The rotary radius of this mold is about 1000mm and the mold must be fabricated to the high form accuracy and the low surface roughness. According to the conventional machining method, a rotary table with the radius larger than 1000mm is necessary for fabricating this mold. However, this mold is justly used for the first test of the hot hydraulic press of the large segmental double-side PMMA Fresnel lens. Thus, the fabrication of this mold should be carried out at the lower cost using the holding machine tool. In order to cut this mold on an ultraprecision air hydrostatic bearing rotary table of 500mm in diameter, a special method was proposed by the authors of this article. In this experiment, the diamond cutting process of the mold was investigated. The single crystal diamond cutting tool with the tip radius of 1μm was used at the depth of cut 1μm for the finish process in order to get the mold with the very small groove corner. After the finish cutting process, the surface has a very low roughness.

Influence of microgroove dimension on cell behavior of human gingival fibroblasts cultured on titanium substrata

The purpose of this study was to determine the dimension of surface microgrooves on titanium (Ti) substrata that shows the greatest positive influence on characterizing specific cell behavior of cultured human gingival fibroblasts. Commercially pure Ti disks with surface microgrooves of monotonous 3.5 mm in depth and respective 15, 30, and 60 microm in width were fabricated using photolithography and used as the culture substrata in the three experimental groups in this study (TiD15, TiD30, and TiD60 groups), whereas the smooth Ti disk was used as the control substrata (smooth Ti group). Human gingival fibroblasts were cultured on the four groups of Ti substrata on successive timelines. Cell behaviors, such as adhesion, morphology,viability and proliferation, and gene expression were analyzed and compared between all groups using crystal violet stain, scanning electron microscopy (SEM), XTT assay, and reverse transcriptase-polymerase chain reaction, respectively. SEM demonstrated that cells were able to readily descend into the microgrooves of TiD30 at the early phase of culture. Cells on the ridge edges or in groove corners were spindle shaped with abundant filopodia formation toward the acid-etched surface inside the microgrooves, thus mimicked the cell shape in three-dimensional (3D) nanoenvironment. TiD15 significantly increased the cell viability and proliferation compared with the smooth Ti substrata after 72 h of culture. Up-regulation of fibronectin(FN) and alpha5 integrin genes was noted in cells cultured on TiD15 and TiD30. Gene expression pattern specific to the cells in 3D-matrix culture, such as down-regulation of alpha-smooth muscle actin gene along with up-regulation of FN and p21 genes, was pronounced in cells cultured on TiD30. This study indicates that surface microgrooves of both 15 and 30 microm in widt hand a monotonous 3.5 microm in depth on Ti substrata increase various cell behaviors of cultured human gingival fibroblasts.

Propagation loss of terahertz surface plasmon polaritons on a periodically structured Ag surface

We analyze the propagation of terahertz surface plasmon polaritons on a periodically structured Ag surface by using a full-vectorial finite-difference time-domain method. The impact of some structural parameters on the dispersion relation and the propagation loss is analyzed. As the groove width increases, the dispersion curves asymptotically reach lower frequency values at the Brillouin zone edge, while the relation between the propagation loss and the groove width is somewhat complicated. For a fixed air filling factor, the period of the structure has little influence on the asymptotic frequency but has a relatively large influence on the propagation loss. The effects of the groove depth and the shape of the groove corners are also studied. It is found that the propagation loss is mainly determined by the total area of the sidewalls of the grooves in a unit length. For a typical structure with a groove width of 2 μm, a groove depth of 10 μm, and a period of 10 μm, the propagation loss is less than 0.2 dB/10 μm below 5.67 THz, while it increases dramatically beyond this frequency.

크린칭 접합의 성형특성에 관한 연구

This paper is concerned with joining of thin metal sheets by single stroke clinching process. This method has been used in sheet metal work as it is a simple process and offers the possibility of joining similar-dissimilar thin sheet metals. Clinching generates a joint by overlapping metal sheets deforming plastically by punching and squeezing sequence. AA 5754 aluminum alloy of 0.5 mm thick sheets have been selected as a modal material and the process has been simulated under different process conditions and the results have been analyzed in terms of the quality of clinch joints which are influenced mainly by tool geometries. The rigid-plastic finite element method is applied to analyses in this paper. Analysis is focused mainly on investigation of deformation and material flow patterns influenced by major geometrical parameters such as die diameter, die depth, groove width, and groove corner radius, respectively. To evaluate the quality of clinch joints, four controlling or evaluation parameters have been chosen and they are bottom, neck thickness of bottom and top sheets, and undercut thickness, respectively. It has been concluded from the simulation results that the die geometries such as die depth and diameters are the most decisive process parameters influencing on the quality of clinch joints, and the bottom thickness is the most important evaluation parameter to determine if the quality of clinch joints satisfies the demand for industrial application.