Materials Science Forum Vols. 773-774

Abstract: In order to accomplish the circular cup drawing of the sheet material whose ductility is extremely poor under the cold forming condition, the Maslennikov's technique was applied. A deformable rubber ring was used instead of the hard punch. Test material was magnesium alloy AZ31-O sheet. Small die profile radius was applied, which was twice or 4 times of the sheet thickness. A semisolid lubricant was used for the lubrication of the blank - die interface, on the other hand, the rubber - blank interface was degreased to increase friction. The limiting drawing ratio of 1.31 was attained. A peculiar fracture mode arises, where the material suddenly fractured with crack evolution emanating from the flange periphery. The fracture strain is found approximately equal to the work hardening exponent n-value in plastic property. Another kind of crack arose in the circumferential direction of the cup during unbending process with smaller die profile radius. To decrease the scratched lines of the cup surface caused by very high sliding contact pressure to the die, high-speed drawing was tested using a drop-weight. The surface was improved, because the material - tool contact was successfully prevented by the hydrodynamic lubrication film.

Abstract: Inconel 718 is a material exhibiting characteristic that are able to maintain strength and integrity at elevated temperatures, but it is well known as a material with poor machinability. This paper presents a study of the performance in high speed machining of TiAlN/AlCrN nanomultilayer PVD coated Inconel 718 with minimum lubrication. Investigations have been made into the effects of cutting speed, feed rate and depth of cut (DOC) on the tool life. A toolmakers microscope and a scanning electron microscope (SEM) were used to examine the tool wear and chemical attrition, respectively, on the cutting tool during machining. In the machining of aged Inconel 718, the cutting tool experienced attrition, abrasion and notch wear throughout the experiment. Notch wear was found to be the dominant failure mode during milling; this wear appeared severe when localized flank wear reached the critical zone. The influence of radial depth despite the cutting speed, well known as having the most significant effect on tool life, is also discussed.

Abstract: Generation of a micro feature on mono-crystalline silicon surface using an industrial laser is presented. The main objective is to investigate the capability of the industrial laser, Nd:YAG, in generating a micro-feature on silicon surface. The unpolished silicon surface was irradiated with the Nd:YAG laser beam of controlled pulse width and power. In phase 1, the irradiations were done without incorporating an assist gas into the process. In phase 2, the compressed air maintaining its pressure at 4 bars, was supplied as an assist gas during laser irradiation. Design of experiment was adopted to systematically determine the number of experimental runs in each phase as well as to fine tune the important parameters through the statistical analysis. Laser-generated structures were observed under scanning electron microscope. Micrographs reveal that most of the features appear to be cone-like with an almost true circle at the base. The diameter of the cone is found to be as small as 200 m. The quality of such micro-features and analysis of the effect of the process parameters on the feature quality show that in general, laser pulse width has more appreciable effect than the laser power on the micro-feature geometry as well as quality. Laser irradiation without the assist gas produces better results in terms of a feature size .

Abstract: This paper investigates the adsorption behavior of triblock copolymer Poly (propylene oxide)-poly (ethylene oxide)-poly (propylene oxide), PPO-PEO-PPO on silicon and iron surfaces by using the contact angle goniometer, spectroscopic ellipsometer and atomic force microscopy (AFM). After adsorption, the decrease of water contact angle was observed on each surface; and a larger reduction of water contact angle occurred on the surface covered by the copolymer film with longer and higher weight percent of hydrophilic PEO block. This means that the PEO block may be on the top of the adsorbed copolymer film. The film thickness measurement shows that the copolymer with longer and higher weight percent of PPO block forms a thicker film on the hydrophobic surface, which suggests that the hydrophobic PPO block of the copolymer in the aqueous solution plays the main role during the adsorption of PPO-PEO-PPO onto the hydrophobic surface. It has been found from the AFM results that the roughness of the surface decreased after adsorption and the smoother topography was observed on the surface adsorbed by a thicker adsorbed film.

Abstract: Tribology performances (friction and anti-wear) of aqueous symmetrical tri-block normal and reverse copolymer solutions have been investigated. The ball-on-disk experiment was carried out to measure the coefficient of friction of solutions used at ~25°C and ~50°C. The interaction of alkyl phosphate ester, an anionic surfactant, and the aqueous copolymer solutions was also investigated. When solution was supplied at ~50°C, high friction and severe wear were found indicated that the solutions were not able to protect the surface. The friction and the anti-wear was found to improve when solution used at ~25°C. However, adding alkyl phosphate ester as extreme pressure additive into aqueous solutions produced a stronger adsorbed lubricant film protecting the surface. Low COFs were obtained from solutions below and above the cloud point. For the wear volume, the presence of phosphate ester produced comparable wear with the solution without added alkyl phosphate ester. The stainless steel was found less reactive to the alkyl phosphate ester hence the wear not much reduced. The possible lubrication mechanism is discussed by analysing the worn tracks using Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM) and the water contact angle measurements.

Abstract: Vibration-assisted micro-forging was proposed for metal foil surface finishing. The mechanism was investigated by analysis of strain, surface roughness, microhardness, real / nominal contact area ratio and forming work at different vibration time and frequencies. Results show that vibration time and frequency influence the surface deformation by means of real contact area and forming work accordingly.

Abstract: In recent years, plastic lenses have been widely adopted for optical components in consumer products because of the significant improvement in microelectronics technology. Currently, plastic lenses are mass produced for applications in 3G/4G smart mobile phones, digital still/motion cameras, and micro-projectors. During mass production, one of the key factors in costs reduction is to enhance lifetime of the molding tools. Electroless nickel phosphorus plating (Ni-P) is the most popular mold and die surface treatment process because of its excellent machinability in single-point diamond turning process. However, Ni-P plated molds cannot sustain satisfactory tool life under the adhesion forces between the mold surface and the molten plastic. In this study, a novel material made of a nickel-phosphorus-polytetrafluoroethylene (Ni-P-PTFE) compound was plated electrolessly on experimental dies to study relevant properties. Since Ni-P-PTFE exhibits strong anti-adhesion properties, it is noted to improve the lifetime of the dies. After machining of the dies, the surface roughness was measured by confocal microscopy together with the particle size being measured by scanning electron microscopy (SEM). In conclusion, the adhesion phenomenon is interpreted via hydrophobic contact angles showing that hydrophobic contact angle of Ni-P-PTFE surfaces is smaller when compared to Ni-P surfaces which infers the anti-adhesion properties of Ni-P-PTFE materials.

Abstract: This paper investigates the mechanical properties of potassium dihydrogen phosphate (KDP) crystals with the aid of nanoindentation using a conical diamond indenter. It was found that when unloading is after the first pop-in, the common method of obtaining elastic modulus from the unloading curve of nanoindentation is no longer applicable, because the unloading is inelastic. The study revealed that the pop-in could be due to dislocation nucleation and propagation, and that the first pop-in occurs under a stress below that of the major dislocation burst. Hence, the macroscopic yielding point, which is usually regarded as the onset of plasticity of a material, is nanoscopically not a critical point of the first dislocation in KDP. The study found that the elastic modulus of KDP indenting on its (001) plane is 52.8±3.8GPa. The hardness of the material is 1.89±0.05GPa.

Abstract: In recent years, micro lens arrays have played a crucial role in optical illumination systems. The function of micro lens arrays (MLAs) is to create a uniform light intensity or shape the light profile. Polymers that are commonly used as MLAs have several advantages, such as cost effectiveness, light weight, and easy formation. In general, the ultra-precision diamond-turning technique and plastic injection molding technique have been combined to fabricate MLAs with polymer materials. However, residual stress and non-balance injection pressure are produced on MLAs during injecting processing. Therefore, this paper presents the fabrication of MLAs using a direct molding method (DMM). The STAVAX with electroless nickel coating and PMMA were used as the mold and polymer preform, respectively. First, a mold of MLA with 100% filling factor was fabricated using the ultra-precision diamond-turning technique. A high filling factor can decrease the non-effective area of the MLA in an optical system. Subsequently, an MLA was formed on the PMMA surface using DMM processing. This paper shows the DMM process parameters, including molding temperature, molding force, and cooling rate. Moreover, the profile of the MLA was measured using a laser confocal microscope. Finally, a high filling factor MLA with a diameter of 11.5 mm, and lenses with a height of 8.5 μm and a radius of 470 μm were formed on PMMA.

Abstract: This paper presents some newest and potential developments on artificial intelligent technologies for welding manufacturing process in Shanghai Jiao Tong University (SJTU), which contains multi-information acquirement and fusion processing of arc welding dynamical process; Intelligent computing for welding process; Intelligent control methods for welding process and quality control; artificial intelligent technologies for welding robot systems and robotic welding process; and some application in welding engineering. The ideas of intelligentized welding manufacturing technology (IWMT) and intelligentized welding manufacturing engineering (IWME) are presented in this paper for systematization of intending researches and applications on intelligentized technologies for modern welding manufacturing.