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Bending in sheet metal forming is defined as uniformly straining process around a linear axis. A V-bending process is normally used in sheet metal working due to the tool and process simplicity. The main problem in bending process is a springback occurrence which causes an error in part dimension. In a micro level, the springback angle is difficult to be assessed because of the influence of size effects in all aspects of the system. The springback behavior has been investigated in many previous kinds of research. However, the springback correction is still needed to be studied extensively so that it can be implemented reliably in micro-bending. The purpose of this research is to investigate the influence of punch velocity and holding time to the springback angle. The process is performed to the 0.1 mm thickness of copper foil. The punch velocities are 0.1 mm/s, 1 mm/s, and 10 mm/s. While the variation of holding time, which is set during the bottoming stage, are 7 s, 9 s, and 11 s. The result shows that the punch velocity clearly influences the springback angle. In addition, the holding time during the bottoming stage is a potential factor in springback angle correction.

Superplastic forming (SPF) is a material forming technique that uses superplastic exceptional elongations and deformation characteristics to form superplastic materials into certain shapes. The combination of superplastic forming with diffusion bonding (SPF/DB) gives rise to an almost unlimited extension of superplastic forming since more integral lightweight cellular structural components can be manufactured. This paper discusses numerical modelling of the mechanism of superplasticity in metallic materials. The SPF computational method based on the finite element technique augmented with the controlling rate of deformations is developed to examine a range of design or operating conditions leading to more economical forming processes. The non-Newtonian 'viscous flow' material is used to model the constitutive of superplastic material during the forming period. The contact mechanics between the sheet material and the mold surface and the intersheet material contact mechanics are imposed using the penalty control method, in which the sticking contact boundary conditions are employed. The space discretization is carried out using the membrane element under plane strain and axisymmetric flow stress conditions, while the implicit time integration technique is utilized to follow the shape changes of the formed sheet material. The validation of the SPF finite element formulation was performed by comparing it with the available analytical solution of Hydraulic Free Bulging of Thin strips. The SPF of a hemispherical dome made of 7475 aluminum sheet alloy was performed to demonstrate the forming process as well as to validate the results obtained between the SPF finite element numerical simulation and the experimental results. The SPF/DB of the multicell component section is considered in the final part. [ABSTRACT FROM AUTHOR]

A Pulsed Laser Deposition (PLD) technique is a type of physical vapor deposition (PVD) technology. This research is one of a series of PVD studies aimed at determining the best PLD coating that can minimize the damage of steel pins made of SKD61 with a hardness of 48±1 HRc. The study began with the dummy blocks from SKD61 as research samples, followed by PVD-PLD with three coating materials as alternatives: Al/Cr (70:30), Al/Ti1 (50:50), and Al/Ti2 (63:37), all without active gases (N and C). The procedures used to test the research findings were FESEM, SEM, XRF, EDS, Vickers, and Rockwell Microhardness. The experiments were conducted at the BRIN Fotonic Research Center and the PT AHM Laboratory. The PLD process lasted for 10 minutes and employed an Nd: YAG laser with a wavelength of 1064 nm, a Q-switch with a time delay of 180 s, a pulse energy of 70 mJ, and a vacuum pressure of 1.161.35 Torr. Based on the results of the coating study, an AlTi1 coating was found to be the most effective material coating. The coating consisted of amorphous particles with a size range of 10 nm to 20 nm The coating had a thickness of 23 µm, and the surface hardness was measured to be 474-523 mHv for the single-layer coating and 477-501 mHv for the multilayer coating. The materials in both single-layer and multilayer coating samples have the same hardness in ascending order: AlCr, AlTi2, AlTi1, with a Ti concentration rise from 0.7% to 3.7%. The impact of the Ti element is also crucial in increasing hardness, wear resistance, and roughness. [ABSTRACT FROM AUTHOR]

Sheet metal bending is defined as a straining process of flat strip material around a linear axis. The micro V-bending process was conducted to investigate its punch force behavior with 0.1 mm thick copper foil. The V-shaped configuration of the punch and die provides a simplicity of tools and an ability to produce different bending angles with a single tool. During the straining of material, a unique force profile, which is related to punch trajectory, occurs. The process was performed with the punch speeds 0.5 mm/s, 1.0 mm/s, 5.0 mm/s and 10.0 mm/s. The results showed that the punch force profile consists of the free-bending stage and the coin-bending stage. In the free-bending stage, the force magnitude was not influenced by the punch speed for the same geometrical and mechanical properties of the sheet material. Furthermore, during the coin-bending stage, the force magnitude increased significantly since the material needed to be bottomed. [ABSTRACT FROM AUTHOR]

The present study investigated the mechanical properties and microstructure of ultrafine grained (UFG) brass processed by four passes of equal channel angular pressing (ECAP) and annealed at elevated temperatures. The mechanical properties of all samples were assessed using tensile and micro-hardness tests. Microstructure analysis was performed using optical microscopy (OM) and scanning electron microscopy (SEM). Ultimate tensile strengths (UTS) and yield strengths (YS) of 878 and 804 MPa, respectively, ductility of 15%, and hardness of 248 HV were obtained for samples processed by four passes of ECAP with equivalent true strain of 4.20. Annealing at 300°C caused UTS and YS to decrease significantly, to 510 and 408 MPa, respectively, ductility to increase to 28%, and hardness to decrease to 165 HV. Fractography analysis of un-annealed samples after four ECAP passes showed small brittle fractures with shallow dimpling. Ductile failures were found on annealed samples. After four ECAP passes, the microstructure of un-annealed samples was UFG and dominated by lamellar grain with shear band. In contrast, after annealing, the microstructure changed due to recrystallization, showing nucleation and grain growth. [ABSTRACT FROM AUTHOR]

The performance of ball bearings is strongly influenced by the lubrication system. In this research, the development of a lubrication system was performed by the formation of an interlocking system through a composite coating, i.e. Zn3(PO4)2 / MoS2 / MWCNT / nanographite / Na2SiO3 prepared by chemical immersion. The coating was applied through the one-mixing-layer and multi-layer techniques. The results showed that the one-mixing-layer technique has the ability to form an homogeneous thin layer with a surface roughness index that varies between 1.00 µm and 1.35 µm, whereas the thickness of the composite layers was found to be in the range from 5 µm to 6 µm. The multi-walled carbon nanotube (MWCNT) technique increased the interlocking capabilities of the coating and the solid lubricant. The one-mixinglayer technique indicated better results than that of multi-layer coated balls in terms of distribution and uniformity of elements on the coating surface, good interlocking between the composite compounds, and the thickness of the layer formed. The performance of nanocomposite coatings on the friction of the steel balls also showed that the ball bearings with a one-mixing-layer composite coating have a higher wear resistance than that of both the uncoated and the multi-layer coated ball bearings. [ABSTRACT FROM AUTHOR]

Amylopectin (Ap) was grafted with three different methacrylate by atom transfer radical polymerization (ATRP) to create controllable hydrophobic chain on amylopectin. The macro initiator Amylopectin-Ethyl α-bromoisobutyrate (Ap-EBiB) was prepared by esterification of hydroxyl groups on amylopectin with Ethyl α-Bromoisobutyrate (EBiB). In this research, amylopectin was grafted with methyl methacrylate (MMA), butyl methacrylate (BMA) and hexyl methacrylate (HMA) and the grafting conditions were optimized. Influence of grafting conditions on % monomer conversion, and % grafting efficiency were studied. Grafted samples were analyzed for their thermal behavior using thermo gravimetric analysis (TGA) and differential scanning calorimeter (DSC) and grafting was confirmed using nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). It was found that increasing length of alkyl chains increased grafting efficiency but improved the thermal behavior with better properties. The result of this study indicated that the Amylopectin-g-PHMA have % grafting higher than others. [ABSTRACT FROM AUTHOR]