Search

• A good prediction model of the average liquid film thickness on the simulant was established, and the relative error is within 10 %. • The PDF curves corresponding to the instantaneous liquid film thickness distribution on the simulants exhibit multimodality. • The liquid film thickness distributions on the simulants have multi-frequency characteristics. • The ash slag simulants with a size larger than the distribution slit will cause the liquid film to be biased or unevenly distributed, which should be avoided in actual operation. To explore the influence of ash slag adhering to the scrubbing-cooling tube on the turbulent falling film flow, three hemispheres with different radii (R = 2 mm, 4 mm, and 6 mm) were used to simulate the slag. Ultrasonic Doppler Velocimetry was used to investigate the liquid film's thickness distribution and fluctuation characteristics under Reynolds number of liquid film Re f ≈8.75 × 103 ––2.63 × 104. The liquid film thickness distribution at low Reynolds numbers exhibits an isosceles triangle when subjected to R = 4 mm and 6 mm hemispheres. At high Reynolds numbers, the average thickness of the liquid film is smaller downstream of the three simulants. The simulants can enhance the liquid film's perturbations. A mathematical model has been established to predict the mean liquid film thickness on hemispherical simulants, and the relative difference is within 10 %. The probability density distribution curves of the instantaneous liquid film thickness on the simulant exhibit multimodality. [ABSTRACT FROM AUTHOR]

It has been a challenge to efficiently make titanium alloy thin-walled components by sheet metal forming. Incremental sheet forming (ISF) method provides a promising way to increase the formability of low-ductility metallic sheets, but making titanium alloy sheet panels still needs heating by electricity or laser. The present work investigates the deformation mechanism in fabricating truncated cones of titanium alloy with tooth features realized by flexible free incremental sheet forming (FFISF) at room temperature. Experimental investigations on auxiliary sheets and tool path selections, analytical modeling, finite element simulation, and microstructure characterization have been conducted to evaluate the deformation mechanism in terms of the geometric deviation, thickness distribution and microstructure evolution of TA2 and TC4. Results indicate that the I-O loading path coupled with an optimized auxiliary sheets selection can ensure the successful fabrication of designed panel without defects. An analytical model is proposed to predict the free edge dependent law of thickness distribution in FFISF, indicating the material thinning is positively correlated with the distance from the free edge, while the thinning rate is inversely proportional to the yield strength. A more uniform thickness of TC4 panel is obtained compared with TA2. Finally, the improved formability of titanium alloys by FFISF can be attributed to grain subdivision, decreasing of intragranular deformation, and optimization of dislocation movement. [Display omitted] • Obtained truncated cone with tooth features of titanium alloy by FFISF at room temperature. • Determined optimal process set with feasible auxiliary sheet set and I-O loading path. • Found out free edge dependent thickness distribution against Cosine law. • Revealed homogenous deformation with less intragranular deformation for improved formability. [ABSTRACT FROM AUTHOR]

This paper presents the implementation and verification of a dual-probe measurement system with a novel method and easily integrated chromatic confocal probes, for synchronous evaluation of not only the inner and outer cylindricity but also the thickness distribution of a ring-type cylinder. A pair of measuring probes mounted on a four-axis scanning stage, which is composed of XYZ -slides and a spindle, is utilized to target the two sides of the ring-type cylinder. In the developed system, to reduce the influence of the positioning errors and tilt misalignments of the confocal probes and the cylinder, alignment methods are developed. The outputs of the measuring probes are employed to accurately evaluate the geometric errors of the ring-type cylinder through performing spiral scanning while separating the Z -slide and spindle motion errors of the scanning stage based on a reversal error separation method. To verify the performance of the proposed system and method, the geometric errors of a thin-walled cylinder which has a nominal outer diameter of 50 mm, an inner diameter of 40 mm, and a length of 100 mm are evaluated in experiments. The experimental results are further compared with those by a coordinate measuring machine (CMM), and the high correspondence of the comparison results well confirm the feasibility of the implemented measurement system. Finally, measurement uncertainty analysis is conducted to demonstrate the reliability of the proposed method for the evaluation of the geometric errors of ring-type cylinders. The measurement accuracy is comparable to that of a CMM. • A dual-probe measurement system was developed for geometrical evaluation of ring-type cylinders. • The inner, outer roundness and thickness distribution of a ring-type cylinder was simultaneously measured. • The measurement uncertainty was analyzed to confirm the reliability of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, formability of dissimilar friction stir welded AA 6061 and AA 5083 blanks during single point incremental forming (SPIF) is investigated numerically and experimentally. Sheets from AA6061, AA5083 and FSWed AA6061 to AA5083 are formed by SPIF with different cone angles, and the limiting wall angles are determined. Additionally, the effects of SPIF and FSW processes on the microstructure, mechanical properties and fracture mode are investigated. The empirical results demonstrate that the formability of dissimilar FSWed sheets are not so much different from that of the base metal sheets. Dissimilar FSWed specimen is fractured from the AA 6061 base metal and far from the FSWed region. Although investigation of the fracture surfaces of the tensile tests shows a ductile fracture for AA 5083, AA 6061 and dissimilar FSWed sheets, it is a combination of ductile and brittle fracture after the SPIF. Furthermore, the SPIF of FSWed sheets is simulated numerically using the ABAQUS/Explicit. The results show that the thickness and the major strain have uniform distributions for both FSWed and base metal sheets. On the other hand, minor strain has a non-uniform distribution in the wall of the formed conical part of the FSWed sheet, despite the base metal sheets. [ABSTRACT FROM AUTHOR]

Abstract Attributes of gypsum vein arrays in the Triassic massive mudstones of SW England were analyzed to infer the process of vein network evolution. Field data demonstrate that there is no clear correlation between vein orientation and thickness; however, sub-horizontal veins have a higher average thickness than the inclined veins. Vein thickness distribution is best characterized by a log-normal distribution. The fractal dimensions ' D ' of vein networks analyzed range from 1.44 to 1.71. Vein networks, which contain abundant bridging veins between neighbouring sub-horizontal veins to form an anastomosing pattern, exhibit a higher D value. The fraction of vein volume derived from image analysis ranges from 6.75 to 17.94%. A positive correlation is revealed by plotting the fractal dimensions of the vein networks versus the number of vein-intersection points, suggesting that an anti-clustering distribution of veins could contribute to more interactions and also intersections of the gypsum veins. The vein attribute data presented indicate that mineralization in the massive mudstones is mainly localized to some of the largest veins as a result of mechanical interaction of neighbouring veins during vein propagation, hindering the nucleation of new veins as a consequence. Accommodation of the bulk rock strain could be facilitated mainly by expansion of the large, backbone veins, which follow a positive feedback mechanism of growth. This study reveals a strong link between the geometric parameters of opening-mode fractures with the history of their formation, propagation and intersection. Highlights • We analyzed multiple attributes of gypsum veins in mudstones to infer vein network evolution. • Vein thickness follows a log-normal distribution. • The anti-clustering vein distribution leads to more vein intersections. • Mineral precipitation is localized to the largest veins due to mechanical interaction. [ABSTRACT FROM AUTHOR]

Thin-walled bent tubes are a significant component utilized in the aerospace, shipbuilding, and chemical industries, as well as considering that they are employed as fluid and gas transporters, the quality of their manufacturing and production is critical. In recent years, new technologies for the manufacture of these structures have been developed, the most promising of which is the flexible bending process. Nevertheless, during tube bending, defects like an increase in contact stress and friction force in the bending area, thinning of the bent tube in the extrados zone, ovalization, and spring-back are some of the issues that arise. So, based on the softening and surface effects induced by ultrasonic energy in metal forming, this paper is suggested a novel method to fabricate the bent components by adding ultrasonic vibrations into the static motion of the tube. Therefore, experimental tests and finite element (FE) simulations are employed to assess the impact of ultrasonic vibrations on the forming quality of the bent tubes. Initially, an experimental setup was designed and built to guarantee the transmission of ultrasonic vibrations with a frequency of 20 kHz to the bending area. Afterward, based on the experimental test and its geometrical parameters, a 3D finite element model of the ultrasonic-assisted flexible bending (UAFB) process was developed and validated. According to the findings, forming forces were significantly reduced when the ultrasonic energy was superimposed, and thickness distribution in the extrados zone was significantly enhanced as a result of the acoustoplastic effect. In the meantime, the UV field's application effectively diminishes the contact stress between the bending die and tube, as well as greatly reduces the material flow stress. In the end, it was found that applying UV at the appropriate vibration amplitude can effectively improve ovalization and spring-back. The current study will assist researchers in better understanding the role of ultrasonic vibrations in performing the flexible bending process and achieving improved tube formability. • The influence of ultrasound on the flexible bending process of the thin-walled circular tubes made from aluminium is investigated. • The decrease of the plastic deformation force concomitant with increase the formability is achieved, and the corresponding data was used to verify the established finite element model (FEM). • All three phenomena of acoustic softening, surface effect, and stress superposition were included in the modeling. • Uniaxial tensile test was performed to check material flow stress and calculate strain rate parameter under ultrasonic conditions. • Ultrasonic compression test was developed to calculate the friction coefficient in different vibration amplitude. Therefore, by establishing a relationship between the surface roughness and the amplitude of ultrasonic vibrations, the phenomenon of surface effect was included in the simulations. • Effects of ultrasound on the forming force and thickness distribution is investigated. Based on the simulations, extrados wall thinning and intrados wall thickening can be eliminated and a uniform distribution of bent tube can be created. • UV application under micro-hammer condition significantly reduces the forming force. Also, in the amplitude of 13.5 μ m, the defect of the spring back for the bent tube is effectively reduced. On the other hand, due to the facilitation of material flow into the die cavity, the ovalization after the bending process is also reduced. [ABSTRACT FROM AUTHOR]

In this work, the influence of titanium interlayer thickness distribution on mechanical properties of Ti/TiN multilayer coatings is reported. Coating samples are deposited by arc ion plating on 304 stainless steel and (100) silicon substrates. XRD and SEM measurements are carried out to characterize the crystallographic structure and morphology of the sample coatings, respectively. Mechanical properties, such as hardness, indentation toughness, adhesion and residual stress, are evaluated. The effect of titanium interlayer thickness distribution on titanium grain size, hardness and indentation toughness is observed. Adhesion and residual stress show little dependence on titanium interlayer thickness distribution. The effect of titanium interlayer thickness distribution on coating mechanical properties is investigated and the mechanism is discussed with the support of finite element method. [ABSTRACT FROM AUTHOR]

• A high-resolution and non-contact method for measuring the thickness of the insulating ceramic coating. • Analysis of the chromatic confocal sensor's geometric light path. • Simulation of the eddy-current sensor with COMSOL software. • Real-time displaying of insulating coating thickness and 3D surface reconstruction. A high-resolution and non-contact method for measuring the thickness of the insulating ceramic coating is proposed. The measurement system consists of a chromatic confocal sensor, eddy-current sensor, prism, mirror, and high-precision rotatable and liftable platform. The chromatic confocal sensor can obtain the distance from the outer surface of the insulating coating, and the eddy-current sensor can get the distance from the inner surface of the insulating coating. The coating thickness can be obtained from the two sensors' data combination and calculation. The geometrical optical path is analyzed to study the effect of the prism and mirror on the confocal sensor. The eddy-current sensor is simulated by COMSOL software with electromagnetic theories to explore the relationship between its output response and the measured surface's curvature. The sensing parameters of the two sensors are calibrated and optimized through simulation and experimental validation. Measurement software is developed by Labview to display the coating thickness in real time and reveal its distribution by 3D surface reconstruction. The measuring system's performance is tested by an insulating bearing with a 60 mm outer radius. The results show that the axial resolution of the measuring system is 0.1 μm, the repeatable linearity is less than 3 μm, the dynamic measuring linearity relative to the mean value of the coating's thickness is less than 8 μm, the detection speed is about 50 points/min. It has the advantages of high precision, non-contact, quick speed, stability, and visual display. [ABSTRACT FROM AUTHOR]

Pulsed laser deposition exploiting a KrF excimer laser was used to fabricate amorphous As-S thin films from bulk As 2 S 3 glass target. Thickness profile of the film was extracted from variable angle spectroscopic ellipsometry data. The dependence of thickness distribution of prepared thin layer on laser beam plume deflection angle was evaluated and corresponding equations were suggested. [ABSTRACT FROM AUTHOR]

Kinetic model of development of lamellar thickness distribution and average lamellar thickness during melt crystallization is proposed. The model bases on the Avrami–Evans and Hoffman–Lauritzen approaches to the crystallization and crystal growth kinetics and involves a thermal thickening model proposed in this paper which accounts for two processes – lamellar doubling transformation and logarithmic thickening of the doubled crystals. In the thickening model, continuity equation for the lamellar thickness distribution is proposed which includes a term responsible for fast creation of doubled crystals during a doubling time introduced as phenomenological parameter and a term which accounts for slow, logarithmic with time thickening subsequent to the doubling transformation. The model concerns melt crystallization in systems where the undercooling in the crystallization and melting processes refers to the same thermodynamic point – the thermodynamic equilibrium melting temperature. Analytical formulae for time-dependent lamellar thickness distribution vs. crystallization time are obtained by solving the continuity equation for the case of isothermal crystallization, as well as for the development of the average lamellar thickness of the doubled and un-doubled crystals during the crystallization time. The model predictions are illustrated by example computations for isothermal crystallization of PE grades characterized by high differences in the crystallization half-time resulting in high differences in the development of lamellar thickness distribution. Relative contributions of doubled and un-doubled crystals are predicted during the conversion and influence of the doubling time and logarithmic thickening parameters is discussed. [ABSTRACT FROM AUTHOR]

This paper presents a newly developed flexible sheet forming approach with better sheet thickness distribution and reduced processing time comparing to the conventional incremental sheet forming. In the approach, a two-step forming process has been proposed: multi-point forming as preforming is employed to achieve an initial shape and designed thickness distribution; After the preforming, incremental sheet forming process is then applied to finalize part geometry with desired thickness distribution. In the work, a numerical model for predicting the thickness distribution of the final part is developed by integrating finite element simulation and analytical prediction of ISF process. To achieve the uniformity of final thickness distribution, the preformed shape is optimized based on the developed thickness prediction model. Additionally, a real industrial case problem of forming an aerospace cowling is used to validate the proposed hybrid flexible sheet forming approach. Satisfactory results are obtained, which demonstrates the feasibility and effectiveness of the developed forming process. [ABSTRACT FROM AUTHOR]

Abstract: Laser indirect shock micro-embossing is a novel micro-high velocity forming technique, which uses laser-driven flyer to load the workpiece. In this paper, laser indirect shock micro-embossing of commercially pure copper and titanium sheet are investigated using both experimental and numerical methods. A fully 3-D finite element mode is proposed to simulate the transient deformation behaviors. The effects of material and laser energy on the deformations are investigated experimentally. Thickness distribution at the cross-section of the micro-channel is analyzed experimentally. Strain states during micro-embossing are used to interpret the variation in thickness distribution. Fracture along the inner edges of the micro-mould occurs for 8μm copper when the pulse energy is 1200mJ, 1380mJ and 1550mJ. Moreover, the 13μm titanium is completely sheared off along the inner edge of the micromould when the pulse energy is 1550mJ. With further development, the laser-driven flyer technique can realize the blanking forming. And experimental data obtained are then used to validate the corresponding simulation model. The results show that the finite element analysis can predict the final shape of the work piece properly. [Copyright &y& Elsevier]

Highlights: [•] Two open-loop analytical models for multi-pass deformation design have been developed and tested given the predicted thickness strain of the final part as a main parameter using the assumption of shear deformation. [•] A comprehensive methodology for closed-loop multi-stage deformation pass design incorporating two developed models is proposed. [•] FEA and experimental tests have been performed to validate the comprehensive closed-loop design methodology with two analytical models. [•] The proposed closed-loop pass design methodology with M2 is proved to be an effective approach to designing multi-stage deformation passes in order to quantitatively control the material flow. [ABSTRACT FROM AUTHOR]

Abstract: Square-sectional parts are most commonly used on automobiles. The thickness uniformity is one of the key factors that affect the performance of hydroformed parts. In the present paper, the thickness distribution along the cross-section of a square-sectional hydroformed part is studied mathematically. The effects of the friction coefficient, the strain-hardening exponent and the anisotropic coefficient on the thickness distribution, and the variation regularity of the wall thickness are numerically explored. The analytical and simulation results show good agreement with those of the experiments. This study helps to further understand the mechanics of the tube hydroforming process and to provide more knowledge for die design and material selection. [Copyright &y& Elsevier]

Abstract: Hydro-mechanical deep drawing combines the features of conventional deep drawing and hydroforming. In this process, the punch deforms the blank to its final shape by moving against a controlled pressurized fluid. Hydro-mechanical deep drawing offers several advantages over conventional deep drawing like higher drawability, uniform strain distribution, better surface finish and improved dimensional accuracy. The process parameters such as initial pressure in the chamber (pre-bulging pressure), the peak chamber pressure (cutoff pressure) and oil gap have strong influence on the process. In view of this, the effect of the pre-bulging pressure and the cutoff pressure on thickness distribution and surface finish in hydro-mechanical deep drawing were studied in this paper. Experiments have been carried out on extra-low carbon steel sheets by varying these parameters. It was found out that thickness distribution along cup wall is more uniform for intermediate pre-bulging pressures. At too low pre-bulging pressure necking takes place at punch corner (similar to the conventional deep drawing) and at very high pre-bulging pressure, necking shifts towards wall region. So a region of safe pressure (combination of pre-bulging and cutoff pressure) was found out in which cups of better quality in terms of uniform thickness distribution and better quality surface can be drawn successfully. [Copyright &y& Elsevier]

Abstract: A two-stage forming process of tailor blanks having local thickening for controlling the distribution of wall thickness of stamped parts was developed. In the 1st stage, the target portion of the sheet for the local thickening is drawn into the die cavity, and then the bulging ring is compressed with the flat die under the clamping of the flange portion in the 2nd stage. The effects of the punch stroke, the clearance between the punch projection and die, and the projection width on the amount of the location thickening were examined. A 12% increase in thickness of the blank was obtained in an experiment. The tailor-formed blank having local thickening was applied to increase the wall thickness at the inner corner of a wheel disk. An 11% increase in wall thickness at the inner corner was successfully obtained in the experiment. The tailor blanks having local thickening obtained by the two-stage forming process are effective in controlling the distribution of wall thickness of the stamped parts. [Copyright &y& Elsevier]

Abstract: In this work the thickness distribution of NTC thermistor thin films produced by low deposition rate (0.8nms−1) electron-beam evaporation is investigated. The target preparation, deposition conditions and geometrical set-up of the evaporation mechanism are described in detail. The evaporation geometry is shown to be critical for the thickness distribution of evaporated films. The film thickness distribution of evaporated layers was measured across a macroscopic film surface using Alpha Step stylus profileometer. The thickness distribution was fitted using a geometrical model derived from evaporation theory, based on the Hertz–Knudsen equation and a modified version of the cosine law of emission. From this model, the sticking coefficient of the vapour on the substrates could be estimated to be 80±1.5%. [Copyright &y& Elsevier]

Abstract: In this study, to enhance the accuracy of products in metal forming, the product accuracy in two-stage cylindrical cup deep drawings was investigated. To consider the local and global forming factors simultaneously, we focused on milli-scale order, which is classified as the intermediate region between micro- and macro-scales. For evaluation of the drawn cups, the cup wall geometry, thickness distribution and surface roughness were precisely investigated using both experimental and finite element (FE) analyses. Milli-scale deep drawing experiments were performed with mirror-polished and unpolished tool sets to investigate the effect of tool roughness. The validity of the modeling of surface roughness as well as the effect of tool roughness on drawn cup surface accuracy was investigated via FE simulation. Some evaluated characteristics in the experiment were in good agreement with FE simulation results. It was also shown that tool roughness is strongly related to frictional behavior, but does not affect the cup surface accuracy under the condition of less than 0.1μm tool roughness. [Copyright &y& Elsevier]

Abstract: Single Point Incremental Forming (SPIF) is an emerging sheet-metal-forming technology, capable of manufacturing complex parts at low cost for small to medium-batch production. The present paper is focused on presenting an innovative and viable method to test the thinning limits of sheet metals in Negative Incremental Forming along with verification of the Cosine''s law of thickness distribution. The Cosine''s law was verified by comparing the experimentally measured thicknesses of incrementally formed parts with those predicted by the law. To test the thinning limit of a sheet metal, the idea is based on the forming of an axi-symmetric part varying its slope with depth corresponding to varying thinning. An arc of a circle was selected as generatrix to model such an axi-symmetric part. Based on the Cosine''s law, mathematical expressions were derived to predict the thickness distribution along the depth of the part and the thinning limit of the sheet-metal. The Aluminum sheet metal was used as an experimental material. In order to test its thinning limit, the axi-symmetric part, modeled with a generatrix arc, was formed incrementally until it cracked. Thickness of the fractured part was measured at various points along its depth and compared with that predicted by the Cosine''s law. The maximum thinning at a point, at which thickness followed the Cosine''s law, was called the thinning limit of the sheet metal. In order to obtain accurate results, four such parts having the same generatrix design were formed. Based on these results, several axi-symmetric and asymmetric parts were formed at fixed slopes. It was found that the thinning limits obtained from the parts formed at fixed slopes were a little lower than those obtained from the parts modeled with the same generatrix design. As conclusion, a strategy to test the lowest possible thinning limits of sheet metals has been proposed. The proposed method is capable to test the thinning limits of sheet metals at reduced processing time and cost. [Copyright &y& Elsevier]

Abstract: Growth characteristics and surface morphology of boron carbide films fabricated by ablating a B4C target in high vacuum with a traditional KrF excimer laser and a high brightness hybrid dye/excimer laser system emitting at the same wavelength while delivering 700fs pulses are compared. The ultrashort pulse processing is highly effective. Energy densities between 0.25 and 2Jcm−2 result in apparent growth rates ranging from 0.017 to 0.085nm/pulse. Ablation with nanosecond pulses of one order of magnitude higher energy densities yields smaller growth rates, the figures increase from 0.002 to 0.016nm/pulse within the 2–14.3Jcm−2 fluence window. 2D thickness maps derived from variable angle spectroscopic ellipsometry reveal that, when ablating with sub-ps pulses, the spot size rather than the energy density determines both the deposition rate and the angular distribution of film material. Pulse shortening leads to significant improvement in surface morphology, as well. While droplets with number densities ranging from 1×104 to 7×104 mm−2 deteriorate the surface of the films deposited by the KrF excimer laser, sub-ps pulses produce practically droplet-free films. The absence of droplets has also a beneficial effect on the stoichiometry and homogeneity of the films fabricated by ultrashort pulses. [Copyright &y& Elsevier]

Abstract: Superplasticity in materials is characterized by large neck-free elongation under low flow stress when they are formed at temperature exceeding about one half of the melting point. The bulge forming technique is considered the most common practice employed in forming superplastic materials. A common technical problem in superplastic forming is non-uniform wall thickness distribution of formed parts. In this proposed work, eutectic Pb–Sn superplastic sheet materials were considered. Cast sheet blanks were thermo-mechanically treated to obtain superplastic properties. A sophisticated PC-controlled loading system was prepared for the bulge-forming process. An optimum pressure–time profile based on variable pressure was proposed. In addition, the optimum preforming required for improving the uniform thickness distribution and dome height was also analyzed. The thickness distribution after preforming effect was compared with optimum pressure–time performance. This combined method based on variable pressure and preforming gives good results than the variable strain rate method. This work reduces the system complications on the variable strain rate method. The cavitations in the various process samples were also analyzed. The combined method based on optimum variable pressure paths and the preforming gives more reduction in cavitations in formed parts. [Copyright &y& Elsevier]

During the physical vapour deposition (PVD) of coatings, the orientation of cemented carbides insert surfaces to the plasma flux direction affects the film thickness distribution on the rake and flank, which, in turn, might influence the wear propagation in cutting processes. The cutting performance in milling of PVD TiAlN-coated cemented carbide inserts with various thicknesses on the rake and flank is introduced and, with the aid of FEM-supported calculations, explained. The investigation results revealed that a thicker film on the tool rake in comparison to the one on the flank, and, moreover, a thick and uniformly deposited film in the cutting wedge region significantly enhances the cutting performance in milling. [Copyright &y& Elsevier]

In superplastic forming, the controlling of the thickness distribution is a very important problem. Since 1982, the authors have been developing the technology for controlling the thickness distribution in superplastic forming. Up to now, some new methods, such as superplastic forming accompanied by compression in the axial direction, direct and reverse superplastic forming and superplastic moving die have been applied successfully to the fabrication of some parts with complex shapes. With the aid of finite element software, accurate control of the thickness distribution in superplastic forming has been achieved. [Copyright &y& Elsevier]

Tube hydroforming is a near-net shape metal forming process in which a straight or a pre-bent tubular blank is placed in a closed die cavity and its cross-sectional shape is changed using internal hydraulic pressure that forces the tube to conform to the shape of the die cavity. This paper reports on the results of two-dimensional plane-strain finite element models of the tube hydroforming process, which were conducted using the commercial finite element code ABAQUS/Standard. The objective of the study is to examine the interaction of material properties and die geometry on the selection of hydroforming process parameters. The paper discusses the effects of the strain-hardening exponent, initial tube wall thickness, and die corner radii on corner filling and thickness distribution of the hydroformed tube. [Copyright &y& Elsevier]

Capsule coatings have a wide range of applications as they afford protection to active pharmaceutical ingredients. However, few studies have focused on capsule coating owing to the sensitivity of hard gelatin shells to solvents and high temperature. In the present study, we aimed to coat capsules using two thermoforming coating techniques: vacuum forming coating (VFC) and centrifugal forming coating (CFC). Rheological and mechanical properties were investigated to comprehensively elucidate the processes and mechanisms underlying the two coating techniques. The corresponding coating integrity and drug release behavior were characterized and compared. Herein, we observed that a lower temperature was more suitable for the VFC process than the CFC process. The drug release rate decreased with the film thickness increased. Both optimal VFC and CFC capsules revealed a 24 h sustained-release property following Fick's diffusion law. The coating thickness distribution was more homogeneous for the VFC capsule than the CFC capsule. With the advantage solvent-free of functional capsule coatings, thermoforming coating techniques are convenient and efficient solutions for small-scale personalized coating of oral solid preparations. [Display omitted] [ABSTRACT FROM AUTHOR]

Following the development of various complex optical elements, especially those involving aluminum alloys with several free-form surfaces, it is critical to understand the material coating methods. This report provides guidance for coating aluminum alloy optical elements containing four free-form surfaces with reflective silver films. To determine a proper film deposition thickness with high reflectivity applied by magnetron sputtering, a model is proposed to explain how the reflectivity is affected by the thickness of the silver film on the aluminum alloy substrates. Additionally, to optimize the uniformity of film thickness deposited from a magnetron source, a more accurate distribution model was developed by introducing gas pressure parameters. This modified model provides excellent agreement between simulated and experimental results. Finally, the film thickness distribution on the optical element integrated with four free-form surfaces is simulated using the modified model, and the influence of the relative position of sources and substrates on the film thickness uniformity is explored. • A model is proposed to explain the effecet of film thickness on reflectivity. • A more accurate distribution model is developed by introducing air pressure. • The film thickness distribution of complex optical element is simulated. [ABSTRACT FROM AUTHOR]

• Tube hydroforming tests for characterization and validation of tubular material behavior. • Proposal of identification strategy to calibrate CB 2001 yield criterion based on reduced number of experimental tests. • Accurate validation of the proposed identification strategy by comparing experimental and finite element analysis results. The present work focuses upon the use of tube hydroforming into square cross sectional-die as validation test for new constitutive parameter identification strategy. It presents how a developed identification startegy using a reduced set of experimental data in conjuction with some generated artificiel input data are proficient to identifiy the anisotropy parameters of an advanced Cazacu & Barlat yield criterion CB2001, which requires a large number of experimental data for its calibration. Two tubular materials are investigated, namely: mild steel S235 and AA6063 aluminum alloy, which manifest miscellaneous plastic behaviors. The concordance between numerical and experimental thickness distribution along a profile of the hydroformed part into cross sectional-die are the main facing challenges for the validation of the proposed calibration strategy. The analysis of the present findings reveals good agreement between numerical simulation and experimental results. Eventually, the proposed approach is a user friendly-identification strategy and effective method, which can be applied for the calibration of recent developed yield functions for better modeling anisotropic plastic behavior of sheet and tube metals and then could likely widespreadly used in research laboratories as well as in automative industry. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The new forming technology – tube hydro-forging (THFG) was completely different from traditional tube hydroforming, the die closing force instead of internal pressure is the deformation force to compress the cross-section and increase the thickness, also result in a special contact stress state. In this paper, a mathematical model is developed to determine the strain and stress along the tube wall, also predict the die closing force, thickness distribution and contact stress; furthermore, the effects of various factors on the die closing force, thickness distribution and contact stress were discussed. At last, finite element analyses and experiments of THFG are conducted. The experimental and simulation results of die closing force, thickness distribution and contact stress are compared with the theoretical results to verify the correctness of this mathematical model. This model can provide a guideline for determining the technique parameters and designing rational die, also helps in understanding the mechanism of THFG. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical behavior of aluminum foam sandwich plate (AFSP) subjected to repeated impact loadings is investigated. Firstly, the method to achieve repeated impacts of AFSP in the numerical simulation is proposed. Then dynamic responses obtained from repeated impact tests are compared with those of numerical simulations, and the results show good agreements. Besides, the mechanism of energy absorption of the AFSP under repeated impacts are examined. Results show that the elastic deformation energy of AFSP increases with the impact number, but the increment declines. On the contrary, the plastic deformation energy decreases with the impact number. In addition, the effects of thickness distribution of face sheets on impact resistance of AFSP under repeated impacts are investigated. It can be found that as the thickness of front face sheet increases, the peak impact force and the energy absorbed by front face sheet increase, while the deflections of front and back face sheets, the energy absorbed by back face and aluminum foam decrease. [ABSTRACT FROM AUTHOR]