Experiments and finite element simulations on micro-milling of Ti–6Al–4V alloy with uncoated and cBN coated micro-tools

This paper presents experimental investigations and finite element simulations on micro-milling of Ti–6Al–4V alloy with fine grain uncoated and cBN coated micro-end mills. Micro-milling of Ti–6Al–4V using uncoated and cBN coated tungsten carbide micro-end mills are conducted; surface roughness, burr formation and tool wear are measured. Effects of machining parameters on surface roughness, burr formation, and tool wear for uncoated and cBN coated micro-tools are investigated. Finite element modelling is utilized to predict forces, temperatures, and wear rate for uncoated and cBN coated micro-tools. Predicted temperature and tool wear contours for uncoated and cBN coated micro-tool edges reveal advantages of cBN coatings. Optimization studies on the experimental results are also conducted to identify the optimum process parameters which minimize both surface roughness and burr formation concurrently.     

Polymeric Linoleic Acid–Polyolefin Conjugates: Cell Adhesion and Biocompatibility

To diversify edible-oil polymer composite, polymeric linoleic acid (PLina) peroxide was obtained by the auto-oxidation of linoleic acid in a simple way for use as a macroinitiator in free radical polymerization of vinyl monomers. Peroxidation, epoxidation, and/or perepoxidation reactions of linoleic acid under air at room temperature resulted in PLina, having soluble fraction more than 91 weight percent (wt%), with molecular weight ranging from 1,644 to 2,763 Da, and containing up to 1.0 wt% of peroxide. PLina initiated the free radical polymerization of ether styrene (S), methyl methacrylate (MMA), or n-butyl methacrylate (nBMA) to give PLina-g-polystyrene (PS), PLina-g-poly-MMA (PMMA), and PLina-g-poly- nBMA (PnBMA) graft copolymers. The polymers obtained were characterized by proton nuclear magnetic resonance (¹H NMR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC) techniques. Microstructure of the graft copolymers was observed by using scanning electron microscope (SEM). Graft copolymers obtained contained polymeric linoleic acid in a range between 8.5 and 19.3 mol percent (mol%). PLina-g-PS, PLina-g-PMMA and PLina-g-PnBMA graft copolymer samples were also used in cell culture studies. Fibroblast and macrophage cells were strongly adhered and spread on the copolymer film surfaces. These newly synthesized copolymers were tested for their effects on human blood protein adsorption compared with PMMA graft copolymers containing polymeric soybean oil and polymeric linseed oil; interestingly we observed a dramatic decrease in the protein adsorption on the linoleic acid graft copolymer, which is important in tissue engineering.     

Mechanics of high speed cutting with curvilinear edge tools

High speed cutting is advantageous due to the reduced forces and power, increased energy savings, and overall improved productivity for discrete-part metal manufacturing. However, tool edge geometry and combined cutting conditions highly affects the performance of high speed cutting. In this study, mechanics of cutting with curvilinear (round and oval-like) edge preparation tools in the presence of dead metal zone has been presented to investigate the effects of edge geometry and cutting conditions on the friction and resultant tool temperatures. An analytical slip-line field model is utilized to study the cutting mechanics and friction at the tool-chip and tool–workpiece interfaces in the presence of the dead metal zone in machining with negative rake curvilinear PCBN tools. Inserts with six different edge designs, including a chamfered edge, are tested with a set of orthogonal cutting experiments on AISI 4340 steel. Friction conditions in each different edge design are identified by utilizing the forces and chip geometries measured. Finite-element simulations are conducted using the friction conditions identified and process predictions are compared with experiments. Analyses of temperature, strain, and stress fields are utilized in understanding the mechanics of machining with curvilinear tools.     

On‐chip label‐free impedance‐based detection of antibiotic permeation

Biosensors are analytical tools used for the analysis of biomaterial samples and provide an understanding about the biocomposition, structure, and function of biomolecules and/or biomechanisms by converting the biological response into an electrical and/or optical signal. In particular, with the rise in antibiotic resistance amongst pathogenic bacteria, the study of antibiotic activity and transport across cell membranes in the field of biosensors has been gaining widespread importance. Herein, for the rapid and label‐free detection of antibiotic permeation across a membrane, a microelectrode integrated microfluidic device is presented. The integrated chip consists of polydimethylsiloxane based microfluidic channels bonded onto microelectrodes on‐glass and enables us to recognize the antibiotic permeation across a membrane into the model membranes based on electrical impedance measurement, while also allowing optical monitoring. Impedance testing is label free and therefore allows the detection of both fluorescent and non‐fluorescent antibiotics. As a model membrane, Giant Unilamellar Vesicles (GUVs) are used and impedance measurements were performed by a precision inductance, capacitance, and resistance metre. The measured signal recorded from the device was used to determine the change in concentration inside and outside of the GUVs. We have found that permeation of antibiotic molecules can be easily monitored over time using the proposed integrated device. The results also show a clear difference between bilayer permeation that occurs through the lipidic bilayer and porin‐mediated permeation through the porin channels inserted in the lipid bilayer.     

A new penternary semiconductor Cu2CoSn(SSe)4 nanocrystal: a study on structural,dielectric and optical properties

Journal of Materials Science: Materials in Electronics - In recent years, the penternary nanocrystals synthesized as an alternative to Pt in dye-sensitized solar cells have attracted the attention...     

The effect of ultraviolet‐curable water‐borne polyurethane acrylate binder concentration on the printing performance of synthetic leather

In this paper, synthetic leather samples were screen printed with pigmented pastes including two types of photoinitiators and three different concentrations of ultraviolet (UV)‐curable water‐borne polyurethane acrylate binder. The curing process was conducted under different combinations of lamps (gallium, mercury, gallium/mercury and gallium/gallium/mercury) at three power levels. Abrasion resistance, crock fastness, hardness and colour strength were investigated. Chemical changes in the clear and pigmented film structures because of UV curing were analysed by Fourier Transform‐infrared spectroscopy measurements. In hardness measurements, the highest hardness values were obtained with clear and pigmented formulations which have the highest solid content (57%). In colour measurements, higher K/S values were obtained in samples printed with the formulation having a binder concentration of 46%. Wet crock fastness values improved as the energy level increased during curing, and the highest values were obtained with a formulation which had a binder concentration of 57%. Greater amounts of binder in the formulations and increased amounts of energy applied to the surface during curing increased the hardness value of the prints, thus better abrasion resistance was obtained. Overall results suggested that the highest hardness, crock fastness and abrasion resistance values were obtained with the formulation with a binder concentration of 57%. However, for ease of application, printing efficiency and colour strength, the formulation with a binder concentration of 46% is recommended for printing, and curing under consecutive passes with gallium and mercury lamps at 120 W/cm is proposed in terms of energy efficiency and printing performance.     

Effects of unbalance on the adhesively bonded composites-aluminium joints

This article presents the experimental and numerical results of adhesively bonded hybrid single-lap joint (SLJ) geometry with different configurations of lower and upper adherends subject to a four-point bending test. AA2024-T3 aluminium alloy and carbon/epoxy composites with different lamina numbers and four different stacking angles as adherend and two-part liquid, structural adhesive DP 125 as paste adhesive were used. In the experimental studies, three different types of SLJs were produced using lower material that had a constant thickness of AA2024-T3 aluminium alloy and upper material of composite material that had different numbers of layers and four different stacking sequences ([0], [0/90], [45/?45], [0/45/?45/90]). In the numerical analysis, stress analyses of the SLJs were performed with a three-dimensional non-linear finite element method and the composite adherends were assumed to behave as linearly elastic materials, while the adhesive and aluminium adherend were assumed to be non-linear. Consequently, the change of stacking sequence and thickness of the composite in adhesively bonded SLJs altered the location of the neutral axis in the joint. This situation substantially influences the load-carrying capacity of the joint.     

Plasma-induced adhesion improvement of cotton/polypropylene-laminated fabrics

In this study, improvement in the adhesion strength of plasma-pretreated and laminated cotton/polypropylene (PP) fabrics using acrylic-based adhesive was investigated. Low-temperature, low-pressure oxygen plasma was utilized for surface modification of cotton/PP-laminated fabrics. Water absorption time was measured on plasma-treated cotton fabrics at different plasma power and treatment time conditions. The plasma conditions providing the fastest liquid absorption on the surface were selected and applied during plasma pretreatments. Surface wettability increased with increasing plasma power and plasma exposure time. Plasma-induced surface morphology changes were observed via Scanning Electron Microscope (SEM) images. X-ray Photoelectron Spectroscopy (XPS) analysis showed that oxygen content on the surface increased with plasma treatment, which contributed to the surface polarity and hydrophilicity. Peel bond strength results of untreated and plasma-treated samples were analyzed to determine the effect of plasma pretreatment process. Adhesion strength values of laminated samples, before washing and after 40 wash cycles, were determined by peel bond strength tests. Before washing, adhesion strength of plasma pre-treated, laminated samples was 28–60% higher than that of untreated laminated fabrics. After 40 wash cycles, adhesion strength of plasma pre-treated and laminated samples was about 40–69% higher than the untreated laminated fabrics. Peel bond strength values decreased with the increased number of wash cycles. Plasma pretreatment enhanced both the adhesion strength and washing resistance of laminated samples.     

Effect of Curing Pressure on the Strength of Adhesively Bonded Joints

It is important to be able to predict the mechanical response of adhesively bonded joints. To succeed in this, the accurate simulation of the behavior of adhesively bonded joints is an essential requirement because of the strain rate, temperature, and hydrostatic sensitivity of adhesive properties, which should be taken into consideration when developing a material model [1-11 Dean , G. D. and Crocker , L. E. , Comparison of the Measured and Predicted Deformation of an Adhesively Bonded Lap-Joint Specimen, NPL CMMT(A) 293 ( National Physical Laboratory , Teddington , UK , 2000 ). Read , B. E. , Dean , G. D. , and Ferriss , D. H. , An Elastic–Plastic Model for the Non-linear Mechanical Behaviour of Rubber-Toughened Adhesives, NPL CMMT(A) 289 ( National Physical Laboratory , Teddington , UK , 2000 ). Broughton , W. R. , Crocker , L. E. , and Urquhart , J. M. , Strength of Adhesive Joints: A Parametric Study , NPL MATC(A) 27 ( National Physical Laboratory , Teddington , UK , 2000 ). Dean , G. D. , Crocker , L. E. , Read , B. , and Wright , L. , Int. J. Adhes. Adhes. 24 , 295 – 306 ( 2004 ). Adams , R. D. , Coppendale , J. , Mallick , V. , and Al-Hamdan , H. , Int. J. Adhes. Adhes. 12 ( 3 ), 185 – 190 ( 1992 ). Wang , C. H. and Chalkley , P. , Int. J. Adhes. Adhes. 20 ( 2 ), 155 – 164 ( 2000 ). Adams , R. D. , The Mechanics of Bonded Joints Structural Adhesives in Engineering ( ImechE Conference Publications , Suffolk , UK 1986 ). Harris , J. A. and Adams , R. D. , Int. J. Adhes. Adhes. 4 ( 2 ), 65 – 78 ( 1984 ). Crocombe , A. D. , Int. J. Adhes. Adhes. 15 ( 1 ), 21 – 27 ( 1995 ). Zgoul , M. and Crocombe , A. D. , Int. J. Adhes. Adhes. 24 ( 4 ), 355 – 366 ( 2004 ). Adams , R. D. and Harris , J. A. , Int. J. Adhes. Adhes. 7 ( 2 ), 69 – 80 ( 1987 ). ]. On the other hand, the load capabilities of adhesively bonded joints are affected by both applied pressure and temperature during cure. For this reason, in this study, the tensile load capabilities of single lap joints (SLJs) bonded with a flexible adhesive that possesses pressure-sensitive properties were experimentally investigated with respect to the applied pressure during the curing operation, and the experimental results were compared with finite element analysis (FEA) results. Finally, in addition to other parameters, such as the dependence on strain rate and the lack of yield criteria of adhesives, it was seen that the residual thermal stresses that occurred as a result of the applied pressure during the curing process at elevated temperature need to be taken into consideration to accurately simulate the mechanical behavior of adhesively bonded joints.