Multi-scale roughness transfer in cold metal rolling

We report on a comparative Atomic Force Microscope (AFM) multi-scale roughness analysis of cold rolled Al alloy and steel roll, in order to characterize the roughness transfer from the steel roll to the workpiece in cold strip rolling processes. More than three orders of length-scale magnitudes were investigated from 100 microns to 50 nanometers on both types of surfaces. The analysis reveals that both types of surfaces are anisotropic self-affine surfaces. Transverse and longitudinal height profiles exhibit a different roughness exponent (Hurst exponent) ζ=0.93±0.03 and ζ=0.5±0.05 Different length-scale cut-offs are obtained in each direction l^sup=50μm, l^sup>100μm. Height and slope distributions are also computed to complement this study. The above mentionned self-affine characteresitics are found to be very similar for the roll and the strip surfaces, which suggest that roughness transfer takes place from the macroscopic (100 μm) to the very small scale (50 nm).     

Molecular dynamics simulation of polyethylene under cyclic loading: Effect of loading condition and chain length

Two nano-blocks of polyethylene (PE) are made and subjected to cyclic deformation with various loading conditions, i.e., strain vs. stress control, zero lateral strain vs. zero lateral stress, and different load amplitude by using the coarse grained molecular dynamics simulation. The one block is filled with 1000 random coil chains of [-CH₂-]³⁰⁰ (long chain), while the other 10 000 chains of [-CH₂-]³⁰ (short chain). The random coil chains are freely grown and relaxed in a simulation box of , then compressed to and relaxed to obtain a stress-free equilibrium. Under the zero lateral stress condition, σ^′=0, the long-chain block shows a leaf-like hysteresis curve both in the stress- and strain-controlled cyclic loading. The area of the hysteresis loop increases as the maximum load is changed to , and , respectively. The “Mullin's effect” is also observed, i.e., the stress-strain curve depicts lower path in the 2nd or later loading, although the target is never a rubber with filler. Under the zero lateral strain condition, ε^′=0, the long-chain block shows little hysteresis with the stress amplitude of 100 MPa, while it shows rapid or unstable elongation around at ε=0.35 in the simulation of ε_max=0.5 and . The short-chain block also shows unstable elongation under the ε^′=0 condition even with the stress amplitude of 100 MPa, noting that it has an upper yield point of at ε=0.35 and lower one around at ε=1.6. On the other hand, the short-chain block is stretched without remarkable stress increase up to the strain around 1.0, under the lateral condition of σ^′=0. Then the block shows “strain hardening” and comes up to the external stress of 100 MPa. It is worth noting that the block shows a leaf-like hysteresis in the 2nd or later cycle; the stress goes back to zero around ε=1.0 in the unloading process and rises up immediately when the load is reversed, as same as the long-chain block.     

Effects of oil inlet pressure and inlet position of axially grooved infinitely long journal bearings. Part II: Nonlinear instability analysis

This paper extends the analysis of Part I to investigate the influence of oil inlet pressure and its position on the dynamic characteristics of axially grooved journal bearings. Using the dynamic fluid force derived in Part I, the equations of motion are solved for the locus of the journal center. A trial-and-error method is used to identify the instability threshold speed for a given Sommerfeld number S. The effects of oil inlet pressure (in the range of ) and inlet position (in the range of 0Θ_i90°) on the instability threshold speed of a rotor-bearing system are investigated and discussed. It is shown that the instability threshold speed with oil inlet position Θ_i=0 decreases on increasing the oil inlet pressure from 0 to 1.0 while the influence of oil inlet position on the instability threshold speed depends on the steady state eccentricity ratio ε.     

Microstructural tomography of a superalloy using focused ion beam microscopy

A focused ion beam (FIB) microscope has been used to simultaneously depth profile and image the γ–γ^′ microstructure of a nickel base superalloy using normal incidence milling in order to characterize the precipitate microstructure in three dimensions (3D). The normal incidence milling rates of the γ and γ^′ phases in this alloy are closely matched when the orientation of the depth-profiled surface is near , which allows for uniform material removal to depths up to a couple of microns. Depth-profiling experiments consisted of automated ion milling and collection of ion-generated secondary-electron images at specified intervals, and was demonstrated for a voxel resolution of roughly . Image-processing software was used for automated processing of the 2D image sequence to render the γ precipitate structure in 3D.     

Characterization of nanoscale recording mark on Ge2Sb2Te5 film

We have fabricated nanoscale recording marks on Ge₂Sb₂Te₅ (GST) films with conductive atomic force microscope (AFM). GST films were deposited on glass or polyimide film with thickness of 150–200 nm by the rf–sputtering method. Through current–voltage (I–V) spectroscopy, good cantilevers for fabrication and characterization of nanoscale marks on GST were selected. A fresh and highly conductive tip showed voltage-switching characteristic in the I–V curve, where the threshold voltage was 1.6 V. Nanoscale dot and wire arrays of crystalline phases were successfully obtained by varying sample bias voltage from −10 to 10 V. With highly conductive tips, nanowires having full-width at half-maximum of 20 nm could be fabricated, whereas nanowires could not be fabricated with bias voltage below −2 V. The width of the nanoscale mark was increased by repetition of AFM lithography even with same applied voltage and lithography speed. For a thicker nanowire, the width measured in current-image (C-image) was observed to be 2 times of that measured in topography-image (T-image). This result supports that current sensing provides an image of phase-changed GST area with higher resolution than topography sensing.     

Transverse and longitudinal vibrations of a frame structure due to a moving trolley and the hoisted object using moving finite element

This paper aims at presenting a technique to replace the moving load by an equivalent moving finite element so that both the transverse and the longitudinal inertial effects due to the moving mass may easily be taken into account simultaneously. Where the mass, damping and stiffness matrices of the moving finite element are determined by the transverse () inertia force, Coriolis force and centrifugal force of the moving mass, respectively. From the numerical examples illustrated, it has been found that, in addition to the conventional transverse () responses, the inertial effects of the moving load also affect the longitudinal () responses of the portal-frame structure significantly.     

Potential genomic biomarkers of obesity and its comorbidities for phthalates and bisphenol A mixture: <i>In silico</i> toxicogenomic approach

This in silico toxicogenomic study aims to explore the relationship between phthalates and bisphenol A (BPA) co-exposure and obesity, as well as its comorbid conditions, in order to construct a possible set of genomic biomarkers. The Comparative Toxicogenomics Database (CTD; http://ctd.mdibl.org) was used as the main data mining tool, along with GeneMania (https://genemania.org), ToppGene Suite (https://toppgene.cchmc.org) and DisGeNET (http://www.disgenet.org). Among the phthalates, bis(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) were chosen as the most frequently curated phthalates in CTD, which also share similar mechanisms of toxicity. DEHP, DBP and BPA interacted with 84, 90 and 194 obesity-related genes/proteins, involved in 67, 65 and 116 pathways, respectively. Among these, 53 genes/proteins and 42 pathways were common to all three substances. 31 genes/proteins had matching interactions for all three investigated substances, while more than half of these genes/proteins (56.49%) were in co-expression. 7 of the common genes/proteins (6 relevant to humans: CCL2, IL6, LPL, PPARG, SERPINE1, and TNF) were identified in all the investigated obesity comorbidities, while PPARG and LPL were most closely linked to obesity. These genes/proteins could serve as a target for further in vitro and in vivo studies of molecular mechanisms of DEHP, DBP and BPA mixture obesogenic properties. Analysis reported here should be applicable to any mixture of environmental chemicals and any disease present in CTD.     

Elastic–plastic solid disk with nonuniform heat source subjected to external pressure

The elastic–plastic stress distribution of a solid disk due to nonuniform heat source under external pressure is investigated in this work. The nonuniform heat generation rate is taken to be a function of the radial position in the form , where a denotes radius of the solid disk; q₀, n and s are constants. The exact solution presented is based on the usual assumptions of plane stress, Tresca's yield condition, its associated flow rule and linear strain hardening material behaviour. According to this analysis, the plastic core in the general case consists of three parts with different forms of the yield condition. The present solution is illustrated by numerical results and is compared with uniform heat generation case. This work provides the basis for a comprehensive investigation of the influence of nonuniform heat generation.     

Radial fretting behaviours of dental ceramics

Radial fretting tests on a Si₃N₄ ceramics ball opposite to the two dental ceramics flats (Vita VMK95 and Cerec Vita Mark II) have been carried out. The test apparatus was developed from a tension-compression hydraulic machine. Maximum normal load (F_max) was varied from 100 to 800 N with a speed of 6 mm/min, and the number of cycles from 1 to 10⁵. The fretting scars were examined by optical microscope and laser confocal scanning microscope (LCSM). The results of kinetics behaviours showed that all loading and unloading curves of load (F)–displacement (D) curves were almost superposed in the whole fretting process for two dental ceramics under a lower normal load (), and all F–D curves opened, correspondingly some micro-cracks initiated and developed in contact area, when the normal load increased to a higher level (). Under lower normal load, the fretting scars displayed the worn zones in shape of annulus. The cracks in shape of homocentric circularity can be observed for Vita VMK95 at and for Cerec Vita Mark II at . Therefore, there is better radial fretting damage resistance for Cerec Vita Mark II. In the microslip zone, the microscopic analysis showed that the particles detached by the mechanism of delamination. It the meantime, the competing mechanisms of fatigue cracks and wear also were discussed in this paper.     

Image cytometric method for quantifying the relative amount of DNA in bacterial nucleoids using Escherichia coli

An image cytometric method for quantifying integrated fluorescence was developed to measure the relative DNA contents of bacterial nucleoids. Image analysis was performed with newly developed macros in combination with the program Object-Image, all downloadable from http://simon.bio.uva.nl/object-image.html. Four aspects of the method were investigated. (i) Good linearity was found over a ten-fold range of fluorescence intensity in a test with a calibration kit of fluorescent latex spheres. (ii) The accuracy of the method was tested with a narrowly distributed Escherichia coli population, which was obtained by growing cells into stationary phase. The width of the image cytometric distribution was approximately 6%, in good agreement with results obtained by flow cytometry. (iii) The error contribution of manual focusing could be kept below 2%, although a strong dependency between integrated fluorescence and focus position was observed. (iv) The results were verified with a flow cytometer, which gave similar distributions for the DNA contents per cell expressed in chromosome equivalents (4.8 fg of DNA). We used the presented method to evaluate whether the DNA conformation had any effect on the total fluorescence of bacterial nucleoids. Experiments using nucleoids with the same amount of DNA in either a dispersed or a compact conformation showed no significant difference in integrated fluorescence, indicating that it is possible to determine the DNA content per nucleoid independently of the actual organization of the DNA.