Development of a MIAB welding module and experimental analysis of rotational behavior of arc—simulation of electromagnetic force distribution during MIAB welding of steel pipes using finite element analysis

Magnetically impelled arc butt (MIAB) welding is a unique forge welding process in which an arc is drawn in the gap between the two tubes to be welded in order to raise them to a high temperature to allow forging to form a solid-state weld. In this case, the arc is rotated with a high speed around the weld line by an electromagnetic force resulting from the interaction of the magnetic field and the arc current. This paper presents the details of the results and the conclusions of the experimental trials conducted on the MIAB module designed and developed based on the principle. Further, nonlinear electromagnetic analysis has been performed to determine the magnetic field and electromagnetic force distribution in MIAB process using finite element package ANSYS. Typical results of this analysis pertaining to magnetic field are compared with the experimental data for steel tubes (outer diameter 47 mm and thickness of 2 mm). It is observed that the results from finite element analysis and the experimental trials are in excellent agreement. The proposed three-dimensional finite element method model for electromagnetic force distribution facilitates comprehensive understanding of the arc rotation process in MIAB welding.     

Wheel/rail adhesion — the overriding influence of water

Water from the atmosphere affects all rails, depositing in quantities far greater than the minute amounts of oily contamination normally present. Laboratory experiments are described which show how water reduces friction between rail and tyre steel surfaces. Depending on the amount of oily contamination the friction coefficient is reduced to a value between 0.3 (no oil present) and the friction which is characteristic of an excess of the oil. Lower friction on oil-free surfaces is observed using laboratory machines which involve continuous rolling; water mixes with wear debris or surface rust to form a lubricating paste and friction coefficients as low as 0.05 result. The lowest friction occurs when the ratio of water to debris is small and a viscous (non-Newtonian) paste is formed which is observed on the laboratory rigs for a few seconds whenever wetted surfaces are on the point of drying completely. Trains similarly encounter low adhesion in slightly wet conditions, most noticeably on little used lines where a substantial coverage of debris particles is present on the wear band.     

A comparison of tribological properties of evenly distributed and agglomerated diamond nanoparticles in lubricated high-load steel–steel contact

The tribological properties of evenly distributed and agglomerated nanodiamonds on steel contact surfaces were compared in ethylene glycol lubricated tests using a pin-on-disc tribometer with a steel counter ball. The nanodiamond distributions were studied on silicon and steel surfaces using scanning electron microscopy. Friction and wear decreasing effects were observed with both sprayed and agglomerated nanodiamonds. The average friction coefficient with pure ethylene glycol lubricated contacts decreased from 0.16 to 0.12 with agglomerated nanodiamonds when 100 N load was applied. A minimum for both disc wear rate (0.40×10⁻⁶ mm³/Nm) and ball wear rate (0.29×10⁻⁶ mm³/Nm) was observed with agglomerated nanodiamonds. One of the mechanisms of nanodiamond lubrication was observed to be the incorporation of nanodiamond particles in to the tribolayer.     

Influence of tilt angle of plate on friction and transfer layer—A study of aluminium pin sliding against steel plate

In the present investigation, unidirectional grinding marks were attained on the steel plates. Then aluminium (Al) pins were slid at 0.2°, 0.6°, 1.0°, 1.4°, 1.8°, 2.2° and 2.6° tilt angles of the plate with the grinding marks perpendicular and parallel to the sliding direction under both dry and lubricated conditions using a pin-on-plate inclined sliding tester to understand the influence of tilt angle and grinding marks direction of the plate on coefficient of friction and transfer layer formation. It was observed that the transfer layer formation and the coefficient of friction depend primarily on the grinding marks direction of the harder mating surface. Stick-slip phenomenon was observed only under lubricated conditions. For the case of pins slid perpendicular to the unidirectional grinding marks stick-slip phenomenon was observed for tilt angles exceeding 0.6°, the amplitude of which increases with increasing tilt angles. However, for the case of the pins slid parallel to the unidirectional grinding marks the stick-slip phenomena was observed for angles exceeding 2.2°, the amplitude of which also increases with increasing tilt angle. The presence of stick-slip phenomena under lubricated conditions could be attributed to the molecular deformation of the lubricant component confined between asperities.     

A sensitivity analysis of centrifugal compressors’ empirical models

The mean-line method using empirical models is the most practical method of predicting off-design performance. To gain insight into the empirical models, the influence of empirical models on the performance prediction results is investigated. We found that, in the two-zone model, the secondary flow mass fraction has a considerable effect at high mass flow-rates on the performance prediction curves. In the TEIS model, the first element changes the slope of the performance curves as well as the stable operating range. The second element makes the performance curves move up and down as it increases or decreases. It is also discovered that the slip factor affects pressure ratio, but it has little effect on efficiency. Finally, this study reveals that the skin friction coefficient has significant effect on both the pressure ratio curve and the efficiency curve. These results show the limitations of the present empirical models, and more resonable empirical models are reeded.     

Correlation between surface-hardness degradation and erosion resistance of carbon steel—Effects of slurry chemistry

The paper studied the effects of slurry chemistry on erosion of carbon steel. According to experimental measurements, the erosion rate in corroding slurries was a linear function of logarithm of anodic current density. In near-neutral or alkaline slurries, the erosion rates are independent of solution chemistry while the erosion rates in the acidic slurries were sensitive to slurry chemistry. To investigate the underlying mechanism, the in-situ surface hardness in corroding environments was measured with the nano-indentation technique under galvanostatic control. The results indicated that the surface hardness would decrease as anodic current was applied. The surface hardness degradation in near-neutral or alkaline electrolytes were almost unaffected by solution chemistry but that in acidic electrolyte depended heavily on solution chemistry. A linear correlation between the accelerated erosion and surface hardness degradation indicated that corrosion-induced surface-hardness degradation would be the dominant mechanism of corrosion-enhanced erosion.     

Experimental analysis of coating layer behavior of Al–Si-coated boron steel in a hot bending process for IT applications

The utilization of high-strength steel for automotive structural parts has increased since the oil crisis in the 1970s owing to its high strength and potential for weight reduction. Because of the limited formability of high-strength steels, automotive components are increasingly produced through hot press forming. In some instances, high-strength steel sheets are coated with an Al–Si layer in order to prevent scaling of components during hot press forming, and this can increase their reliability with a view to the dimensional accuracy and stress distribution when they are in service. In this contribution, the coating degradation mechanisms of Al–Si-coated boron steel after the hot bending process are reported. The issues related to coating degradation during hot press forming are critically reviewed at different positions on a part that was subject to hot bending. In addition, the hardness and friction coefficient were tested by a nano-indenter at various positions. The relationship between the experimental parameters and coating layer properties is also reported. It is concluded that the bending deformation affected the coating layer behavior the most.     

Chemical and mechanical analysis of tribofilms from fully formulated oils Part 1 – Films on 52100 steel

Abstract

The authors report, for the first time, a comprehensive chemical and mechanical characterisation of antiwear films prepared from a fully formulated oil that is commercially available. Wear increases substantially when using the fully formulated oil compared to using ZDDP alone. X-ray absorption near edge structure (XANES) spectroscopy at the P K- and L-edges, S K-edge, Mo L-edge, B K-edge, Ca L-edge, O K-edge and Fe and Zn L-edges permits chemical characterisation of the major elements in the thin films. Ca phosphates, ZnS and MoS₂ are the main P and S species formed, contrary to previous studies involving only ZDDPs, whereby Zn phosphates are the dominant species. These findings can be accounted for by using the hard and soft acid and bases (HSAB) principle. Small amounts of CaCO₃ are present, but no B was detected, implying it does not become incorporated into the film. Atomic force microscopy (AFM) reveals continuous pads with a relatively uniform indentation moduli (125 ± 10 GPa), separated by trenches that are essentially comprised of uncovered steel substrate.     

Geometrical analysis of thread milling—part 1: evaluation of tool angles

Reel-to-reel processes like rotary hot embossing allow micro-patterning of flexible foil based polymer substrates. Such technologies have the potential to be the basis for extremely cheap micro-products. This is due to the low price for polymer foils as well as to the high throughput of reel-to-reel processes. An application field which could benefit of this technology is micro-fluidics. In this paper, a new type of reel-to-reel hot embossing machine will be presented. In contrast to commercially available reel-to-reel embossing machines, the machine described here is capable of doing continuous and discontinuous hot embossing. It is thus suited for fabrication of low, medium and high quantities of micro-patterned polymer components. It has been investigated how parameters like foil temperature, feed rate, embossing force, hardness of the counter roller and temperature of the embossing roller will influence the quality of the embossed structures. The results of this investigation will be presented and discussed.     

A study of the structure of forged pieces of 75X3MΦ steel using the ultrasonic method for quality control

The microstructures of 75X3M?? steel specimens that were sampled from forged pieces of support shafts of rolling mills was investigated. A correlation between the presence of a carbide network and increased attenuation of ultrasonic waves was established. Ultrasonic testing was performed using a Krautkremer ultrasonic flaw detector. The microstructure was studied using conventional metallographic-analysis methods. The nanoindentation method was used to measure the Young modulus of the phase components of 75X3M?? steel specimens, carbides, and the matrix. A comparative evaluation of their acoustic characteristics was performed.     

Dynamical analysis of transmission line cables. Part 2—damping estimation

In this work the authors try to establish a procedure to identify damping of transmission line cables in order to estimate in a simple (proportional) way the system damping matrix. The procedure is based on experimental and simulated data. The experimental data are collected through five accelerometers and the simulated data are obtained using the finite element method. To validate the mathematical model, the reduction of the system is used considering measured degrees-of-freedom. After that, the system damping matrix is estimated through different procedures.     

Experimental Study on Molecular Arrangement of Nanoscale Lubricant Films——A Review

In order to understand lubrication mechanism at the nanoscale, researchers have used many physical experimental approaches, such as surface force apparatus, atomic force microscopy and ball-on-disk tribometer. The results show that the variation rules of the friction force, film thicknessand viscosity of the lubricant at the nanoscale are different from elastohydrodynamic lubrication(EHL). It is speculated that these differences are attributed to the special arrangement of the molecules at the nanoscale. However, it is difficult to obtain the molecular orientation and distribution directly from the lubricant molecules in these experiments. In recent years, more and more attention has been paid to use new techniques to overcome the shortcomings of traditional experiments, including various spectral methods. The most representative achievements in the experimental research of molecular arrangement are reviewed in this paper: The change of film structure of a liquid crystal under confinement has been obtained using X-ray method. The molecular orientation change of lubricant films has been observed using absorption spectroscopy. Infrared spectroscopy has been used to measure the anisotropy of molecular orientation in the contact region when the lubricant film thickness is reduced to a few tens of nanometers. In situ Raman spectroscopy has been performed to measure the molecular orientation of the lubricant film semi-quantitatively. These results prove that confinement and shear in the contact region can change the arrangement of lubricant molecules. As a result, the lubrication characteristics are affected. The shortages of these works are also discussed based on practicable results. Further work is needed to separate the information of the solid-liquid interface from the bulk liquid film.     

A software tool for automatic analysis of selected area diffraction patterns within Digital Micrograph™

A software package “SADP Tools” is developed as a complementary diffraction pattern analysis tool. The core program, called AutoSADP, is designed to facilitate automated measurements of d-spacing and interplaner angles from TEM selected area diffraction patterns (SADPs) of single crystals. The software uses iterative cross correlations to locate the forward scattered beam position and to find the coordinates of the diffraction spots. The newly developed algorithm is suitable for fully automated analysis and it works well with asymmetric diffraction patterns, off-zone axis patterns, patterns with streaks, and noisy patterns such as Fast Fourier transforms of high-resolution images. The AutoSADP tool runs as a macro for the Digital Micrograph program and can determine d-spacing values and interplanar angles based on the pixel ratio with an accuracy of better than about 2%.     

Can sterilization methods influence surface properties of resin composites? A purpose for previewing bias in laboratory bacterial adhesion tests

This study aimed to evaluate the influence of sterilization methods on conventional and bulk-fill resin composites' (BFRCs) surface properties in an attempt to preview bias in laboratory bacterial adhesion tests. Two regular viscosity conventional resin composites [Filtek Z350 XT™ (Z350) and IPS Empress Direct™ (ED)] and two regular viscosity BFRCs [Filtek Bulk Fill™ (FILT) and Tetric N-Ceram Bulk Fill IVA™ (TBF)] were used. The materials were characterized by Scanning Electron Microscopy (SEM), surface roughness (SR), and wettability (W) after sterilization with hydrogen peroxide gas plasma (HPGP) and steam sterilization (SS). Nonsterilized samples served as a control group (n = 5). Statistical analysis was performed using two-way analysis of variance (ANOVA) and Tukey post hoc test (p < 0.05). For SR, there were no statistically significant differences among the groups (p > .05). SS method decreased the contact angle for FILT and Z350 (p < .01). The SS promoted more exposition of filler particles, while the HPGP method did not alter the tested materials' morphology. Therefore, sterilization methods affected the resin composites tested selectively. HPGP seems to be the most recommended method to sterilize the tested resin composites before laboratory bacterial adhesion tests.     

Continuous-time operational modal analysis in the presence of harmonic disturbances—The multivariate case

Recently [R. Pintelon, B. Peeters, P. Guillaume, Continuous-time operational modal analysis in the presence of harmonic disturbances, Mechanical Systems and Signal Processing 22 (5) (2008) 1017–1035] a single-output algorithm for continuous-time operational modal analysis in the presence of harmonic disturbances with time-varying frequency has been developed. This paper extends the results of Pintelon, et al. [Continuous-time operational modal analysis in the presence of harmonic disturbances, Mechanical Systems and Signal Processing 22 (5) (2008) 1017–1035] to multi-output signals. The statistical performance of the proposed maximum likelihood estimator is illustrated on simulations and real helicopter data.     

Engineered surfaces Part 1.— A philosophy of manufacture

In recent years considerable progress has been made in the characterisation of surface finish in three dimensions, and in the development of protocols which can be used for international standardisation. Although the subject as it has currently developed has much further to go if the process of surface characterisation is to impact on manufacture, control and specification of the manufacturing process itself. Researchers in this important area are beginning to realise that if the subject is to have great impact on manufacturing industries, surface characterisation must be broadened to include measures of surface integrity of the component and in addition be related to the functional demands imposed on the surface. The functional demands being a requirement of the engineering situation in which the components are employed. If these three factors are considered simultaneously, surface characterisation, surface integrity and component function, then a new and important subject is born, the subject of the Engineered Surface. Part 1 of this paper attempts to draw together the elements which go together to create the subject, ‘The Engineered Surface’. The paper presents a method by which this important subject can be developed to the benefit of manufacturing industries. The paper also discusses the importance of a co-ordinated approach to the subject and the way that information can be documented to eventually provide a useful atlas of controlling parameters which are essential for a range of material processing industries as they strive to meet the ever more stringent and cost effective requirements of the manufacture.     

An investigation of cell adhesion and growth on micro/nano-scale structured surface—Self-assembled micro particles as a scaffold

A controlled cellular behavior (adhesion, migration and growth) on a scaffold is a technical issue on development of cultured cell applications such as biosensor and tissue engineering. The present paper describes fundamental experiments about effects of some micro/nano-scale structures on cell adhesion and growth. Micro/nano-scale structures of scaffold are fabricated by both top-down and bottom-up processes using some unique materials. For fine spherical particles, they are self-assembled on a substrate. The micro/nano-structured particles provide non-angular and regularly-arranged surface asperity with two-dimensional opal structure, which is also permeable to a culture solution because of fine gaps among assembled particles. Some polymers are formed into an array of micro-ridges with rectangular cross-section by nano-imprint process. Most cells are selectively adhered on micro-structured silica particles, while a flat surface has low affinity for the cells. The present study intends to explain a preferential surface for cell adhesion and growth in terms of geometry and biochemical property of micro-structure.