Rounded Edges Research Articles

Influence of machining parameters on fretting fatigue life of Inconel 718

This work focuses on the analysis of the influence of different machining factors on the fretting fatigue behaviour of Inconel 718. Fretting fatigue tests using a flat-to-flat with rounded edges contact were carried out using specimens with different manufacturing process parameters. The results pointed out the high impact that machining parameters possess in the Inconel 718 fatigue lifetime. Tool wear has shown to be the most significant parameter. Residual stresses measured along the direction of fatigue load have proved to be a relevant indicator of the fretting fatigue behaviour. Lastly, surface roughness has been shown to possess a weaker influence.

Design of a simple shear test for large strains with sequential re-machining of the specimen edges

The simple shear test is a standard experiment used for the calibration of plasticity models. For thin sheets, the specimen can be as simple as a rectangular strip, or feature optimized geometries of the free edges. These enhancements are mainly motivated by the undesirable initiation of fracture from the free edges, which limit the usable strain range of the test. Previous studies have shown that fracture from the edges occurs due to a local stress state close to uniaxial tension in these areas. In an attempt to increase the maximum strain, a sequential simple shear test is proposed. The specimen is a sheet metal strip with two opposing cut-outs with rounded concave edges. The specimen is mounted in a shear testing device, composed of two jaws with a prismatic joint connection. The shear test protocol includes multiple two-steps sequences. First, an interrupted shear test is performed up to a given value of displacement. Second, the shear testing device, along with the clamped specimen, is positioned in a milling machine and the rounded free edges of the specimen are re-machined. The application of the proposed testing protocol is presented for three engineering materials. It is found that the valid range of this experiment (i.e. the maximum strains attained before specimen failure) can be substantially extended through repeated re-machining of the specimen boundaries.

Ultrasonographic diagnosis of hepatic coccidiosis in rabbits

Eimeria (E.) stiedae is a protozoan parasite causing hepatic coccidiosis in rabbits. It mostly infects younger animals and causes nonspecific signs like stunted growth, weakness, dehydration, diarrhea and anorexia. Macroscopically, the liver has a typical appearance. It is enlarged, showing firm yellow-white lesions on the surface. These lesions are enlarged bile ducts filled with bile and necrotic debris. Although all diagnostic tools for hepatic coccidiosis in live animals are currently impracticable or inconclusive, ultrasound might be useful for the diagnosis of hepatic coccidiosis. However, the appearance of liver changes associated with E. stiedae on ultrasonography has poorly been described in the literature. In this study, ex-vivo ultrasound of 24 livers was performed, i.e. the livers of two healthy rabbits and 22 livers of rabbits with suspected liver coccidiosis. Hyperechoic lesions of variable size and shape were found in all affected livers. In some of these livers, other signs of hepatic disease were detected: heterogenous liver parenchyma, appearance of hepatomegaly with round edges, gallbladder sludge and thickening of the gallbladder wall.

Effect of Die Edge Roundness on Crack Initiation near Punch Edge in Blanking

In this study, the effect of die edge radius on crack initiation was discussed in finish blanking. Experiments were carried out using die with rounded cutting edge. As a result, it was confirmed that crack initiation near the punch edge occurred earlier than that near the die edge. It was also confirmed that the burnished surface increased with an increase in the die edge radius. Finite element method was carried out from the initial stage of shearing and until the punch penetration depth was achieved just before the occurrence of the cracks to investigate the distribution of the mean stress. As a result, it was confirmed that the punch stroke, where the mean stress began to increase rapidly to a positive value, increased with an increase in the die edge radius, and the punch stroke at which the mean stress increased rapidly also increased.

Wear mechanism and quantification of polycrystalline diamond milling cutter in high speed trimming of carbon fiber reinforced epoxy

The use of polycrystalline diamond cutters (PCD) in machining of composite material is increasing. Understanding their wear mechanism and clarity on wear measurement methodology will lead to their productive usage and cost justification. This study focuses on understanding wear in PCD milling cutters at the micro, macro level, and its physical characterization when employed for fibrous composite machining. This leads to the development of a proposal for a clear methodology on consistent wear measurement, which includes a suitable selection of techniques and identification of wear parameters. Continuous diamond skeleton structure made during binder infiltration is captured in worn out PCD edge with the help of scanning electron microscopy. Overall wear process appears to be a complex mixture of losing binder, smaller grains, and pieces of continuous diamond skeleton. This results in cavities of various shapes and forms on the cutting edge making substantial variations in edge recession and edge width. After analyzing, different tool parameters, it was found out that the distance from apex to edge roundness of clearance or rake face is a reliable and repeatable wear parameter. These are shown to be comparable between different wear locations, flutes, and tools suggesting higher wear predictive capabilities. Among different techniques, three-dimensional high-resolution profile scanning of the cutter has been identified as the most efficient tool for tracking wear at regular intervals in tool life prediction studies.

Flat and rounded contacts: Modelling the effect of a moment with application to fretting fatigue tests

The problem of elastic indentation by a punch having the form of a flat front face but with edge rounding, and subject to both a normal load and moment, indenting an elastically similar half-plane is considered. Contact pressure in the neighbourhood of the edges shows a local peak, and the object of the paper is to show how different combinations of normal load and moment can give rise to the same near edge behaviour and peak pressure. The result found is very simple, and of direct practical application in fretting fatigue studies, both analytical and experimental.

Effects of tool coating and tool wear on the surface quality and flexural strength of slotted CFRP

Machining of carbon fibre reinforced polymer (CFRP) is abrasive and causes significant tool wear. The effect of tool wear on static flexural strength is investigated, using edge trimming with uncoated carbide and chemical vapour deposition (CVD) diamond coated burr style tools. Edge rounding (ER) criteria along with flank wear are used to observe tool degradation with ER shown to preferentially wear allowing the tool to become cyclically sharper and duller, corresponding to fluctuating dynamometer readings, a novelty for CFRP machining. Areal surface metrics degraded for an uncoated tool due to changes in cutting mechanism, whilst for up to 16.2 m of linear traverse, the coated tool showed limited changes. Tool wear, caused by edge trimming 7.2 m of CFRP, using an uncoated carbide tool, provided a flexural strength reduction of up to 10.5 %, directly linking tool wear to reduced mechanical strength.

Highly sensitive chlorite ion sensor developed on the basis of etching of incurvate gold nanohexahedrons

Incurvate gold nanohexahedrons (AuNHs) are feasible colorimetric probes for the monitoring of chlorite (ClO2−) ions. In this study, incurvate AuNHs were found to respond to ClO2− ions selectively, and the addition of ClO2− ions to water samples induced selectively the etching of incurvate AuNHs, eroding the sharp apexes to rounded edges, which brought in hypsochromic shift absorption attended by a color alternation from cobalt blue to violet pink. The process of etching of incurvate AuNH vertices was characterized using X-ray photoelectron spectroscopy and atom probe tomography. ClO2− ions were successfully detected using the incurvate AuNH-based probe at pH 2.0 and 25 °C with 20 mM NaCl. The A563 nm/A631 nm were linear in proportion to the ClO2− concentrations with two different slopes in the ranges 0.00–0.06 μM and 0.075–0.15 μM, and detection limits of 3.03 and 3.27 nM in tap water and waste water, respectively. The hypersensitive and selective optical assay reported herein has been excellently implemented to determine ClO2− concentrations in spiked tap water, waste water, Clorox cleaning solution, and disinfecting wipes.

Effect of cutting edge radius on end milling Ti–6Al–4V under minimum quantity cooling lubrication – Chip morphology and surface integrity study

The effect of cutting edge radius (30–55 μm) during milling Ti–6Al–4V under minimum quantity cooling lubrication (MQCL) conditions is studied. A trial study is conducted to compare the performance of dry, wet, and MQCL using unprepared tools with edge radius of 30 μm alone. Subsequently, inserts having initial radius of 30 μm are prepared to 40–55 μm radius using drag finishing and milling of Ti–6Al–4V under MQCL is studied for different edge radii. Rounded edge tools are found to produce thinner and more curvilinear chips resulting in easier chip removal from the machining zone. The chip thickness and curl radius were up to 54% and 47% lower for the larger edge radius tools as compared to the 30 μm edge radius tool. This improves the penetration of the MQCL aerosol jet into the cutting zone thus producing better tribological results. The better penetration of MQCL aerosol into the cutting zone for larger edge radius tools results in lowering the resultant process forces (up to 16%), tool-chip interface temperature (15%), tool wear (40%) and surface roughness (30%) for the 48 μm radius tool as compared to the unprepared (30 μm) tool. There is deterioration in process forces, tool wear and surface integrity for the 55 μm tool possibly suggesting the existence of an optimum edge radius closer to 48 μm.

Synthesis of zeolite A with high whiteness from coal gangue by two‐step pretreatment method

AbstractThe comprehensive utilization of coal gangue (CG) is restricted by color elements in CG including C and FexOy. The magnetic separation and hydrothermal acid leaching are combined to pretreat the solid waste CG to synthesize zeolite A with high whiteness. Firstly, Fe2O3 component in CG is in situ reduced by C to magnetite in the process of high‐temperature calcination for decarburization followed by physical magnetic separation. Secondly, the residual Fe impurity in CG is further removed by hydrothermal acid leaching. The effects of calcination temperature, calcination time, acid leaching temperature, acid concentration, and liquid to solid ratio on Fe removal rate (RFe2O3) and the whiteness of the synthesized zeolite A are investigated. The influence of Fe impurities on the Ca2+ ion exchange capacity (E) of the zeolite A synthesized from CG is clarified. RFe2O3 could reach the value of 88.53%. The synthesized zeolite A exhibits a typical cubic morphology with rounded edges, the high whiteness of 95.46%, and the satisfactory E with the value of 296.02 mgCaCO3·g−1, both of which meet the requirements of national standard. This work suggests that this pretreatment method for CG would have broad prospects in the efficient resource utilization of CG.

A New Method for the Calculation of Characteristics of Disc Springs with Trapezoidal Cross-Sections and Rounded Edges.

In the European standards specifying disc spring manufacturing, geometry, shape and characteristic, an edge rounding is prescribed. Common methods for the calculation of disc spring characteristics, even in these standards, are based on a rectangular cross-section. This discrepancy can lead to a considerable divergence of the computed characteristic from the characteristic determined by testing. In literature, this divergence has not yet been examined with regard to rounded edges. In this paper, a new method addressing this problem is introduced. For this purpose, the geometry of idealized disc springs is parameterized. Based on four edge radii and two angles of the inner and outer faces, equations to compute the initial cone angle and the lever arm are introduced. These equations are used to formulate an algorithm to adapt other computation methods to non-rectangular cross-sections and rounded edges. The method is applied to the formulas by Almen–Laszlo, Curti–Orlando, Zheng and those by Kobelev. FE simulations of disc springs with rounded edges and a non-rectangular cross-section were used to verify the new formulas. The results show that the introduced method can be applied to known characteristic computation methods and result in a model expansion taking cross-section variations into account. The adjusted characteristics show more accurate alignment to the FE simulation for the cross-section variations investigated. These findings not only close the geometric gap between the manufacturing guidelines and the computation on an analytical basis, they also define a new parameter space for designs of disc springs and a corresponding force computation method to optimize spring characteristics.

Highly Transparent and Polarization-Maintained Terahertz Plasmonic Metamaterials Based on Metal-Wire-Woven Hole Arrays: Fundamentals and Characterization of Transmission Spectral Peaks.

Metal-hole-supported terahertz (THz) waves through the structure of a metal-wire-woven hole array (MWW-HA) present high-frequency-passed transmittance spectra of one plasmonic metamaterial with artificial plasmonic frequencies, which are inversely proportional to metal-hole widths. For the transmitted THz waves of MWW-HA, transverse-electric (TE) and transverse-magnetic (TM) waveguide modes mix within a symmetric metal-hole boundary. THz resonance waves transversely crossing the holes of MWW-HA are experimentally characterized with spectral peaks in the frequency range of 0.1–2 THz that are correlated with aperture sizes, unit-cell-hole widths, metal-wire thicknesses, and wire-bending angles. The metal-hole-transported resonance waves of MWW-HA are dominated by TE waveguide modes instead of TM ones because a hole width of MWW-HA is approximate to the half wavelength of a resonance wave. The round metal edges of the woven metal wires can minimize the effective optical length of a thick metal hole to transmit THz resonance waves, thereby resulting the smallest rotation angle of linear polarization and high transmittance up to 0.94. An MWW-HA structure is therefore reliable for supporting metal-hole resonance waves with low resistance, whereas a metal-slab-perforated hole array cannot achieve the same result.

A new discrete element modelling approach to simulate the behaviour of dense assemblies of true polyhedra

A new molecular dynamics-like modelling approach aimed at simulating the mechanical behaviour of true polyhedra dense assemblies is presented. Thanks to an improved version of the Gilbert-Johnson-Keerthi contact detection algorithm called GJK − TD, this approach involves no edge or corner rounding and accounts for multipoint face − face or edge − face contacts between any set of two particles. Furthermore, torques equations are simply and efficiently solved using an improved leap-frog Verlet non-iterative method suggested by Omelyan [I.P. Omelyan, Molecular Simulation, 22 : 3, 213–236 (1999)], in which no periodic renormalization of the quaternions is necessary. The potential of this new discrete element approach is then highlighted by simulating the gravity packing of frictionless polyhedra and the gavity flow of frictional polyhedra down an incline, and comparing the results with those reported in the literature. Of particular interest in the stationary flow regime, a linear decrease of the bulk solid fraction and a power law decrease of the bulk coordination number with increasing inertial number are observed, thus generalizing to polyhedra these observations initially made with disks in plane shear flow by da Cruz and co-workers [F.da Cruz, S. Emam, M. Prochnow, J.N. Roux and F. Chevoir, Phys. Rev. E 72, 021309, (2005)]. Beyond this regime, in the collisional regime, the granular temperature was found to achieve its maximum a few particle diameter above the rough bottom, suggesting the localization of significant particle agitation close to the flowing bed.

Prediction of Local Strain and Hardness in Sheet Forming

Abstract A simulation procedure to predict local deformation and properties in deep drawing and other sheet forming processes has been developed, and model experiments were performed to verify the predicted local strain after various ways and degrees of deformation. A strip of aluminium alloy sheet was pulled through a gap between a die and a punch, and bent around a rounded edge and bent back again. Local strains in a cross section of the sheet were estimated from hardness values measured before and after bending by using the hardness – strain relationship obtained for the alloy from tests carried out in tension and compression and with alternating deformation. The finite element (FE) model using ABAQUS was adjusted to the experimental set-up as closely as possible. The agreement between predictions and experiments is in the range of experimental scatter and the general trends are excellently reproduced. However, the precision of hardness measurements is not high enough to check the reliability of the numerical predictions in detail.

Development of equipment and technology for precision air-plasma cutting of plate steel

The authors have investigated the structure of cutting seams obtained after cutting steel 09G2S with a new narrow-jet plasma torch of PMVR-5.3 type which has a number of design features in gas dynamic stabilization system (GDS) of plasma arc. To increase the efficiency of GDS in PMVR-5.3 plasma torch, a symmetrical input of plasma-forming gas (PFG) into the flow division system and a gas-dynamic flow stabilizer using two (forming and stabilizing) swirlers with a variable number of swirl channels were used. It is shown that the achieved advantage in GDS efficiency makes it possible to obtain high cutting quality of steel 09G2S with thickness of 40 mm with high productivity and lower energy costs. Analytical methods have proved a high degree of cutting precision of the new torch– a small cut width, no melting and rounding of the upper edge, as well as a grate in the cut lower part and splashes in the cut upper part, almost zero angular deviation, minimum values of the surface microrelief and width of the thermal impact zone. Metallographic analysis and determination of hardness showed the presence of three subzones in the thermal impact zone with significant structural changes in two of them. A number of factors were noted influencing the revealed changes in the structure formation, as well as changes in the elemental composition of the cutting seam surface layer revealed during the X-ray spectral analysis. Attention is drawn to the surface microrelief after plasma cutting, which in all quality indicators is commensurate with machining of the surface after milling and corresponds to the second class of quality in terms of surface cleanliness. It was proved that the use of the new narrow-jet plasma torch allows high-quality cutting of plate steel in thickness range up to 40 mm or more. However, welding of blanks without pre-machining can be carried out with a cutting thickness of no more than 20 mm.

Thermal loading of steel in molten aluminium

Abstract A test stand for thermal loading of steels was developed for the simulation of die casting of Al products. Special specimens were made which were subjected to automatic immersion into molten Al and a cooling emulsion (water + graphite). At the inside, the specimens were water-cooled. In the course of repeated cycles, the temperature inside the specimens was measured at two different points. A computer program permitted the calculation of temperature, stress and deformation distributions in the specimens. A comparison of the measured and calculated temperatures is shown for two points in the specimen. After 6000 cycles, the surface and the interior of the specimens were examined. The number, length and depth of cracks were determined. It was found that major damages occurred at the specimen edges. The damages included edge rounding, cracks, and material hardening just beneath the surface.

Material piling up and spreading effects in the cutting processes with small feed rates

Previous studies only reported that the material piling up effect will occur in the cutting processes with relatively small feed rates, and even in this case, there is no further theoretical report to touch its generation mechanism. In this work, it is the first time to experimentally report that obvious material spreading phenomenon together with the material piling up effect appears in the cutting process, whose uncut chip thickness is less than the minimum uncut chip thickness (MUCT). It is found that one part of the material to be cut will be piled up in front of the cutter’s rake face. Meanwhile, the remained part flows into the cutter’s clearance face, followed by further compression. As a result, the cutting tooth actually does not remove the material, but rolls the material by its rounded edge. Just because of this rolling effect, the flowed material is deformed and spread along the width direction of the workpiece surface, and this spreading behaviour leads to that the width of the machined workpiece is larger than its initial value. The spread width of the workpiece is quantitatively characterized by using Tselikov’s theory, which is widely used to capture the rolling behaviour. The volume of the material piled up in front of the cutter’s rake surface is calculated by subtracting the volume of the spread material, which is calculated based on the spread width, from the volume of the initial material to be cut according to the volume invariance principle. Subsequently, the height of the piled up material is calculated by geometrically modelling the piling up area as a triangle region. Based on the above analyses, the material spreading and piling up mechanisms in cutting are theoretically explored. The validity of the theoretically calculated spread width and piling up height is verified by the numerical results obtained from finite element simulations. Finally, a cutting force model that can characterize the influences of spreading and piling up effects is established. Several cutting experiments, including both the micro and conventional milling tests, confirm that the proposed methods can give better prediction accuracy of the cutting forces, especially when the ratio of feed rate to the radius of the rounded cutting edge is small.

Pathological characterization and cause of a novel liver disease in largemouth bass (Micropterus salmoides)

With the rapid development of intensive aquaculture in recent years, liver disease of largemouth bass has been increasingly prominent both in China and even around the world. The main gross pathology found the liver is swollen, pale or white in color, with round and blunt edges, and brittle texture. The morbidity and mortality varied. In some cases, the cumulative mortality could reach more than 20%. To investigate the etiology of largemouth bass, histopathological and ultrastructural pathology were performed. The results showed that diseased fish expressed fat accumulation around the pyloric caeca, and the liver showed hepatomegaly with extensive yellowish or whitish color. Hepatocytes had degenerated vacuoles that were different from fatty liver disease. Large number of irregular vesicles that accumulated in hepatic cells which contained a mass of glycogen-like granules and myeloid bodies. This novel liver disease was a common phenomenon in the culture of largemouth bass. The animal feeding experiment was to investigate the causes of the disease, and the results confirmed that a high carbohydrate diet was one of the causes of novel liver disease of largemouth bass. Additionally, blood biochemical indexes suggested that the disease can cause systemic metabolic disorder. Overall, the results demonstrated that the death of a large number of largemouth bass was caused by novel liver disease, due to a high carbohydrate diet.

Analytical model for predicting tool wear in orthogonal machining of unidirectional carbon fibre reinforced polymer (CFRP)

Progressive tool wear due to abrasive carbon fibres is one of the main issues in machining of CFRP and responsible for the short tool life. Because of occurring wear during machining, the tool’s micro-geometry changes continuously resulting in higher process forces and an increasing risk for workpiece damages. In this paper, a novel analytical model is presented in order to predict the wear-related change of the micro-geometry in orthogonal machining of CFRP depending on the fibre orientation and the initial tool geometry. For this purpose, a concept called the wear rate distribution is introduced which represents a measure to quantify the wear rate along the active micro-geometry. Based on experimental investigation, it is shown that the shape of an arbitrary wear rate distribution between two closely spaced wear states can be approximated and parameterised with a “line - curve - line” approach. Using the authors’ previously published analytical force model, the wear rate distribution can be calculated as function of five wear parameters that are used to parameterise the active micro-geometry of an arbitrary wear state. Based on an iterative solver, this is used to simulate the tool wear progression during machining. For model validation, the simulation is compared to experimental data in terms of the cutting edge profiles, the amount of worn tool material and the process forces. Accordingly, the wear model is capable to reproduce the most important wear characteristics, e.g. the cutting edge rounding, the decreasing clearance angle and the increasing contact length at the flank face.

Analysis of the grinding wheel wear and machining result during cutting edge preparation with elastic bonded grinding wheels

Cutting edge preparation can be considered as one of the most effective methods for optimizing the cutting tool life and the machining result. In this article, a preparation technique using elastic bonded superabrasive grinding wheels is applied. This method proved to be highly flexible in terms of the achievable cutting edge geometry. However, very little knowledge exists about the grinding wheel wear behavior and therefore the process reliability during cutting edge preparation. In this article, the impact of the process kinematics and parameters on the grinding wheel wear and preparation result is investigated and discussed. For this purpose, the impact of the depth of cut (20, 40 and 60 μm) was investigated, because it serves as the major setting parameter for the size of the cutting edge rounding. However, it also impacts the contact conditions and thermo-mechanical loads in the grinding wheel. The experimental results show that this preparation method achieves a high preparation accuracy and repeatability at small and medium depths of cut (20 and 40 μm). For a depth of cut of 60 μm, the preparation result became more inappropriate (increased deviation of the cutting edge shape from an ideal radius) with an increasing number of prepared cutting edges. Here, the soft grinding wheel exhibited a higher process stability in terms of repeatable machining results. The machining results correspond to the experimental findings from the grinding wheel radial wear Δrs. At a depth of cut of 20 and 40 μm, the grinding wheel radial wear for the hard bond was lower than for the soft bond. At a depth of cut of 60 μm, the grinding wheel radial wear for the hard bond exceeds the value for the soft bond by 10%. However, the grinding (G) ratios for the hard bond were higher for all investigated depths of cut. The highest difference was observed at a depth of cut of 20 μm. Here, the G ratio for the soft grinding wheel was 7.92 and for the hard one 18.53. Furthermore, an application scenario was introduced using suitable dressing cycles, so that up to 138,000 cutting edges (equals 34,500 indexable inserts) could be prepared with one grinding wheel using this preparation technique in industrial tool manufacturing applications.