Frustum Of Pyramid Research Articles

Friction Stir Incremental Forming of AA7075-O Sheets: Experimental Investigations on Performance Evaluation of Formed Parts

A comprehensive performance of formed parts by AA7075-O sheets was studied in friction stir incremental forming (FSIF). Various tool rotation speeds were set to form two typical parts (truncated funnel and pyramid frustum). The formability, surface quality, tensile strength, micro-hardness and thickness distribution of the formed parts were investigated. Results show that the formability generally increases as tool rotation speeds increase. On the contact surface, variation trends of the surface roughness are different in horizontal direction (parallel to tool path) and vertical direction (perpendicular to tool path). However, the surface roughness on the non-contact surface is almost not affected by tool rotation speed. Furthermore, mechanical properties including tensile strength and surface micro-hardness in formed parts are obviously enhanced compared to those of the initial sheet, of which the hardness values begin to fall down gradually after rotation speed reaches 3000 r/min. As for thickness measurement, more uniform thickness distribution of formed parts can be obtained at relative high tool rotation speeds. In general, parts formed at high rotation speed have a better comprehensive performance except the mechanical property.

Impedimetric determination of Staphylococcal enterotoxin B using electrochemical switching with DNA triangular pyramid frustum nanostructure.

An electrochemical switching strategy is presented for the sensitive determination of Staphylococcus enterotoxin B (SEB). It is based on the use of DNA triangular pyramid frustum nanostructure (TPFDNA) consisting of (a) three thiolated probes, (b) one auxiliary probe, and (c) an aptamer against SEB. The TPFDNA was assembled on the gold electrode, with the SEB aptamer designed on top of the TPFDNA. The electron transfer to hexacyanoferrate acting as an electrochemical probe is strongly inhibited in the TPFDNA-modified electrode. This is assumed to be due to the formation of a 3D TPFDNA structure that limits access of hexacyanoferrate to the electrode. Therefore, the Faradaic impedance is large. However, in the presence of SEB, it will bind to the aptamer and dehybridize the hybrid formed between aptamer and its complementary sequence. As a result, the TPFDNA nanostructure changes to an equilateral triangle DNA nanostructure. This results in a more efficient electron transfer and a smaller Faradaic impedance. The method has a detection limit of 0.17ngmL-1 of SEB (at an S/N of 3) and a dynamic range that covers the 0.2-1000ngmL-1 concentration range. The applicability and reliability of the method was demonstrated by anayzing (spiked) milk samples, and the results were compared to those obtained with an ELISA kit. The relative standard deviations between the two methods range between -6.59 and 9.33%. Graphical abstract An electrochemical switching strategy is presented for the sensitive detection of Staphylococcus enterotoxin B based on 3D DNA structure conversion of nanostructure from triangular pyramid frustum to equilateral triangle.

Formability Assessment in Single Point Incremental Sheet Forming through Finite Element Analysis

Incremental sheet forming (ISF) is a very important process for forming different sheet metal component by the use of Computer Numerically Control (CNC) movement of spindle tool. It is effective for small batch size component as compared to conventional sheet metal forming. ISF is also known as dieless manufacturing. This paper emphasizes on the formability of single point Incremental Sheet Forming (ISF) to attain this aim FE analysis of ISF is done. This paper presents an experimental study to understand the formability of non-axis symmetric components with the analysis of stress produces at various tool locations and thickness variation occurred during incremental sheet forming. Geometry of a frustum of pyramid, dome and the frustum of cone has been considered for the study and fabricated experimentally on the vertical CNC milling machine. Deformation produced on sheet metal has been simulated on the LS – DYNA software package for plotting Forming Limit Diagram (FLD).

Design and manufacturing of a fixing device for incremental sheet forming process

In incremental sheet forming processes, the expensive dedicated tool are avoided and replaced with a cheap and simple fixing device which support the sheet metal blanks. The current paper presents how a fixing device used for single point incremental forming device is designed, FEM simulated and manufactured. The fixing device can be used for parts with a cone frustum and pyramidal frustum made of DC05 deep drawing steel. The forces developed in the process and the device displacements were estimated using FEM simulation. The device components were manufactured using a CNC machines and the physical assembly is also presented in the paper.

The influence of thermal oxidation and tool-sheet contact conditions on the formability and the surface quality of incrementally formed grade 1 titanium thin sheets

The incremental sheet metal forming process combines a series of characteristics, such as the capacity to produce large deformations, flexibility and low-cost tooling, making it preferable to conventional forming processes. One of the key factors in this process are the contact conditions between the forming tool and the sheet to be formed. The incremental forming process of titanium and its alloys is widely studied; on the other hand, the influence of some heat treatments that can induce superficial modifications is not fully known and understood yet. In this study, the influence of thermal oxidation and tool-sheet contact conditions on the formability and the surface quality of grade 1 titanium thin sheets manufactured by incremental forming was investigated by using both a sphere and a hemispherical head tool. The results of the experimental campaign, based on the production of conical and pyramid frusta, highlight the beneficial effects of the heat treatment on the process repeatability, reducing the occurrence of galling for all the contact conditions, and provide information on the quality of the worked surfaces.

Friction stir incremental forming of AA7075-O sheets: investigation on process feasibility

Abstract Friction Stir Incremental Forming (FSIF), as a simple and effective hot incremental forming technology, has attracted increasing attentions from researchers in recent years. In FSIF, frictional heat generated by tool rotation on the interface between tool and workpiece is utilized to soften localized deformation zone, thus enhancing material formability. In order to facilitate the development of FSIF, a comprehensive analysis of process feasibility is needed for the performance evaluation of formed parts. In this work, FSIF has been employed to process 7075-O aluminum alloy sheets (a kind of hard-to-form light alloy materials) for assessing the formability, surface quality, tensile strength and micro-hardness of two typical parts (truncated funnel and pyramid frustum). Experimental results show that the formability generally enhances with the help of local frictional heating as tool rotation speeds increase. On the tool-sheet contact surface, surface roughness shows a different trend of variation in horizontal (parallel to tool path) and vertical directions (perpendicular to tool path). Furthermore, mechanical properties including tensile strength and surface micro-hardness in formed parts are obviously enhanced compared to the initial sheet, of which the micro-hardness values begin to fall down gradually when the tool rotation speed is greater than 3000 rpm.

Single Point versus Two Point Incremental Forming of thermoplastic materials

In order to be able to produce highly customised products at a reasonable manufacturing cost, several innovative forming processes have been developed. Incremental Sheet Forming (ISF) has gained importance in the last years, becoming the focus of interest of many researches. The present paper focuses on determining the influence of the main process parameters in order to produce a truncated pyramid frustum with a circular generatrix using polyvinylchloride (PVC) and polycarbonate (PC). The results of two variants of the technology, Single Point and Two Point Incremental Forming, (SPIF) and (TIPF), are compared. As it was expected with TPIF, it is possible to enhance the geometrical accuracy of the final parts and reduce the effect of the springback. Furthermore, the results show a significant effect of the spindle speed in the ISF process of polymeric materials, not only on the maximum forming force but also on its formability, by means of the maximum depth reached. This is a consequence of the triggered increment of temperature obtained due to the friction between the tool and the sheet blank, as far as temperature variation is supposed to be the main factor causing the variation in the mechanical properties of thermoplastic polymers.

Polymer incremental sheet forming process: Temperature analysis using response surface methodology

ABSTRACTTo reduce costs associated with the manufacturing of customized products, several innovative forming processes have been developed. Incremental sheet forming (ISF) is one of these new technologies, becoming, in the past decade, more interesting for the academic and industrial community. The influence of main process parameters, namely, tool diameter, spindle speed, feed rate, and step down, is studied in depth in this paper. The maximum temperature achieved during the forming process of a truncated pyramid frustum with a circular generatrix using three nonbiocompatible and two biocompatible polymer materials is measured. Box–Behnken design of experiments and the response surface methodology have been utilized to statistically analyze the results and to provide models able to predict the maximum temperatures.

An experimental study on dimensional accuracy, surface quality, and hardness of Ti-6Al-4 V titanium alloy sheet in hot incremental forming

In this study, an electrical heater device that employs alternative electrical current was designed and used to perform the sheet incremental forming process at elevated temperatures. The main advantage of the new device over the existing designs is the use of alternate current electricity which makes the process safer for the operator, requires less expensive equipment, and is more available than the direct current electricity. In this device, the electrical current passes through the tool and generates the maximum heat at the sheet-tool interface. The device was mounted on an incremental forming setup, and the temperature was measured during the forming process. The temperature measurements showed that the device was able to effectively raise the sheet temperature. Furthermore, Ti-6Al-4 V sheets were incrementally formed into a few basic important shapes: conical frustum, variable wall angle conical frustum, and pyramidal frustum. The effect of different process parameters on the dimensional accuracy, surface quality, and workhardening of the fabricated workpieces was studied. The results showed that the highest deviation from ideal geometry occurs at the workpiece tip, and it considerably decreases a few millimeters away from the tip. In addition, the roughness of the inner surface where the tool contacts the workpiece is greater than the outer surface. Micro-hardness test results also showed that the hardness increased from flange to vertex of the workpiece where larger plastic deformation and hence more workhardening is expected to occur.

728 金型を用いたアルミニウム合金板の摩擦撹拌インクリメンタルフォーミング法

Friction stir incremental forming is a new sheet forming process that combined incremental forming and friction stir welding together. It can manufacture the hard-to-work material product of complex shape under the traditional CNC machine and only use a hemispherical tool. In most reports using friction stir incremental forming process, sheets were formed into concave shape. On the other hand, sheets were formed into convex shape with simple back support dies by the conventional incremental forming. In this study, sheet metals were formed into convex shape by friction stir incremental forming process with a back support die. A5052-H34 aluminum alloy sheets were used for specimen. The dimension of the sheet was 100 mm x 100 mm x 0.5 mm. A hemispherical stick tool with a diameter of 6 mm was used for forming. The shape of back support die is a frustum of pyramid. The sheet was fixed to the upper face of the back support die by a bolt and formed along the die shape by pushing with the forming tool. Tool rotation rate and fool feed rate were changed and formability was evaluated by the minimum formable wall angle. From the experimental results, formability was maximum and the wall angle was 25 ° when the tool feed rate was 1000 mm/min and the tool rotation rate was 10000 rpm. The formed shapes with and without the back support die were compared. The formed shape with the back support die was closer to the objective shape, especially at the flange part.

Enhancement of performance in porous bead-based microchip sensors: Effects of chip geometry on bio-agent capture.

Measuring low concentrations of clinically-important biomarkers using porous bead-based lab-on-a-chip (LOC) platforms is critical for the successful implementation of point-of-care (POC) devices. One way to meet this objective is to optimize the geometry of the bead holder, referred to here as a micro-container. In this work, two geometric micro-containers were explored, the inverted pyramid frustum (PF) and the inverted clipped pyramid frustum (CPF). Finite element models of this bead array assay system were developed to optimize the micro-container and bead geometries for increased pressure, to increase analyte capture in porous bead-based fluorescence immunoassays. Custom micro-milled micro-container structures containing an inverted CPF geometry resulted in a 28% reduction in flow-through regions from traditional anisotropically-etched pyramidal geometry derived from Si-111 termination layers. This novel "reduced flow-through" design resulted in a 33% increase in analyte penetration into the bead and twofold increase in fluorescence signal intensity as demonstrated with C-Reactive Protein (CRP) antigen, an important biomarker of inflammation. A consequent twofold decrease in the limit of detection (LOD) and the limit of quantification (LOQ) of a proof-of-concept assay for the free isoform of Prostate-Specific Antigen (free PSA), an important biomarker for prostate cancer detection, is also presented. Furthermore, a 53% decrease in the bead diameter is shown to result in a 160% increase in pressure and 2.5-fold increase in signal, as estimated by COMSOL models and confirmed experimentally by epi-fluorescence microscopy. Such optimizations of the bead micro-container and bead geometries have the potential to significantly reduce the LODs and reagent costs for spatially programmed bead-based assay systems of this type.

Forming forces in incremental forming of a geometry with corner feature: investigation into the effect of forming parameters using response surface approach

Single-point incremental forming (SPIF) is an emerging sheet forming process. The force-parameter correlation is yet not well clear in this process, specifically for geometries with corners. In the present study, a new level of understanding on the parameter-force relationship is presented. A simple shape with corners (i.e., frustum of pyramid containing corners and oblique wall) is opted as the test geometry. Following the response surface method, a design of experiments (DoE) comprising of 47 runs obtained by varying five forming parameters namely sheet thickness, tool diameter, wall angle, step size, and flow stress is performed. The analysis of the results reveals that the parameter-force relation in SPIF is complex and interactive, explaining that the effect of variation in a parameter on the force magnitude is closely associated with the value and the type of the other parameters employed for forming. From the analysis of the forces involved in forming the pyramid, it is found that the corner requires more force than does the wall. Further, the normal force (i.e., force along normal to sheet plane) is greater than the in-plane force. The use of very small tools, especially low d/to where d is the tool diameter and to is the sheet thickness, is observed to cause fabrication defects leading to substantial rise in the magnitude of forming force thus endangering the machine tool. Finally, a set of force models is proposed using which one can predict a set of forming parameters simultaneously minimizing the force and preventing the fabrication problems.

Performance analysis for the CALIFA Barrel calorimeter of the R3B experiment

The CALIFA calorimeter is an advanced detector for gamma rays and light charged particles, accordingly optimized for the demanding requirements of the physics programme proposed for the R3B facility at FAIR. The multipurpose character of CALIFA is required to fulfil challenging demands in energy resolution (5–6% at 1MeV for gamma rays) and efficiency. Charged particles, e.g. protons of energies up to 320MeV in the Barrel section, should also be identified with an energy resolution better to 1%.CALIFA is divided into two well-separated sections: a “Forward EndCap” and a cylindrical “Barrel” covering an angular range from 43.2° to 140.3°. The Barrel section, based on long CsI(Tl) pyramidal frustum crystals coupled to large area avalanche photodiodes (LAAPDs), attains the requested high efficiency for calorimetric purposes. The construction of the CALIFA Demonstrator, comprising 20% of the total detector, has already been initiated, and commissioning experiments are expected for 2014.The assessment of the capabilities and expected performance of the detector elements is a crucial step in their design, along with the prototypes evaluation. For this purpose, the Barrel geometry has been carefully implemented in the simulation package R3BRoot, including easily variable thicknesses of crystal wrapping and carbon fibre supports. A complete characterization of the calorimeter response (including efficiency, resolution, evaluation of energy and reconstruction losses) under different working conditions, with several physics cases selected to probe the detector performance over a wide range of applications, has been undertaken. Prototypes of different sections of the CALIFA Barrel have been modeled and their responses have been evaluated and compared with the experimental results. The present paper summarizes the outcome of the simulation campaign for the entire Barrel section and for the corresponding prototypes tested at different European installations.

Remarks on the Surface Area and Equality Conditions in Regular Forms Part IV: Pyramidal Forms

Following the same methodology and rules that were applied in the previous Parts I–III of this work, Part IV presents the mathematical remarks on the right regular pyramidal forms, either complete or truncated (a frustum of pyramid). The first remark examines the effects of θ and β on S. The second remark calculates the minimum total surface area (SMin) in two cases, case of constant θ (variable β) and case of variable θ (constant β). The third remark calculates walls ratio RW and the critical walls ratio RWo. The last remark calculates the numerical equality between S and V. In conclusion, the importance of the findings of the entire work (Parts I–IV) in advanced building analysis is highlighted and discussed.

Influence of Geometrical Parameters, Wall Angle and Part Shape on Thickness Reduction of Single Point Incremental Forming

The aim of this paper is to study the thickness reduction during the whole single point incremental forming process. The experimental setup is realized in such a way that the blank sheet is in the vertical position and forming is done using an anthropomorphic robot with six degrees of freedom. The vertical positioning of the blank sheet allows the on-line visualization using an optical measuring system of the major and minor strains and of the thickness reduction. The wall angle varied between values of 450, 550 and 650 respectively. The logarithmic major strain and minor strains and logarithmic thickness reduction were analyzed in order to allow a comparison with values obtained based on the sine law. The results show that indeed, the maximal values of the thickness reduction observe the sine law for the parts but only after a “critical value” of the part's height is reached, the variation of the thickness reduction on the lateral faces of the pyramidal frustum are large, the thickness reduction is significant in some areas as compared to the maximal values.

Quantum interference effects induced by multiple magnetic impurities on a triangular lattice f-wave superconductor

The effects of multi-impurity quantum interference on triangular lattice f-wave superconductors are studied by self-consistently solving Bogoliubov-de Gennes equations within the t−t′−J−V model. An overall phase diagram is presented, which shows that f-wave superconductivity dominates near 0.3 doping. Rich phenomena are induced by quantum interference effects, such as periodic modulations in charge orders, pyramid frustum structures, and a magnetic moment reverse transition, which are qualitatively different from the single-impurity case. We also examine the local density of states to show how localized quasiparticle states are created at or near the impurity sites, which can be directly measured by scanning tunneling microscopy experiments.

Ultrasensitive electrochemical cocaine biosensor based on reversible DNA nanostructure

We proposed an ultrasensitive electrochemical cocaine biosensor based on the three-dimensional (3D) DNA structure conversion of nanostructure from Triangular Pyramid Frustum (TPFDNA) to Equilateral Triangle (ETDNA). The presence of cocaine triggered the aptamer-composed DNA nanostructure change from “Close” to “Open”, leading to obvious faradaic impedance changes. The unique properties with excellent stability and specific rigid structure of the 3D DNA nanostructure made the biosensing functions stable, sensitive, and regenerable. The Faradaic impedance responses were linearly related to cocaine concentration between 1.0nM and 2.0μM with a correlation coefficient of 0.993. The limit of detection was calculated to be 0.21nM following IUPAC recommendations (3Sb/b). It is expected that the distinctive features of DNA nanostructure would make it potentially advantageous for a broad range of biosensing, bionanoelectronics, and therapeutic applications.

Improving the Accuracy of Parts Manufactured by Single Point Incremental Forming

The aim of this paper is to enrich the knowledge related to the single point incremental forming (SPIF) process by evaluating the efficiency of two optimization methods - the response surface method and the neural network method - to improve the accuracy of manufactured parts by prescribing a proper combination of the process parameters. The analysis is performed for a double frustum of pyramid made by stainless steel. It was found a good ability of prediction of both methods, demonstrating their suitability for physical implementation in solving problems associated to the SPIF process.

The Effect of Residual Stresses on the Accuracy of Parts Processed by SPIF

The aim of the present work was to investigate the residual stresses distribution within parts processed by single point incremental forming (SPIF) as a function of the working parameters and to determine its influence on the parts accuracy. The study was performed for a double frustum of pyramid made by 304 stainless steel. An experimental analysis was first conducted by using the strain-rosette method. Since the method allowed determining the residual stresses only locally, a numerical model was then elaborated to inspect the distribution of residual stresses throughout the whole part. It was found that a favorable state of residual stresses and implicitly a good accuracy of parts can be obtained when small values of tool diameter and tool vertical steps, respectively high values of feed rate and spindle speed, are used.

Reversible switches of DNA nanostructures between “Closed” and “Open” states and their biosensing applications

A novel and versatile biosensing platform based on the structural conversion of 3D DNA nanostructures from ETDNA (Equilateral Triangle) to TPFDNA (Triangular Pyramid Frustum) was proposed for the first time. The inputs of aptamers and their relative targets made the DNA structure change from the "Open" to the "Closed" state, leading to the faradaic impedance changes as the output signals. The specific properties of excellent stability and specific rigid structure of 3D DNA nanostructures made the biosensor function as a regenerable, reusable and intelligent platform. The sensor exhibited excellent selectivity for IFN-γ detection with a wide linear range of 1.0 × 10(-9) to 2.0 × 10(-6) M and a low detection limit of 5.2 × 10(-10) M. The distinctive features of DNA nanostructures make them potentially advantageous for a broad range of biosensing, bionanoelectronics, and therapeutic applications.