Effects of Constrained Groove Pressing (CGP) on the plane stress fracture toughness of pure copper

Mohammadi, Bijan,Tavoli, Marzieh,Djavanroodi, Faramarz Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.5

Among severe plastic deformation methods, groove pressing is one of the prominent techniques for producing ultra-fine grained sheet materials. This process consists of imposing repetitive severe plastic deformation on the plate or sheet metals through alternate pressing. In the current study, a 2 mm pure Cu sheet has been subjected to repetitive shear deformation up to two passes. Hardness and tensile yield and ultimate stress were obtained after groove pressing. Fracture toughness tests have been performed and compared for three conditions of sheet material namely as received (initial annealed state), after one and two passes of groove pressing. Results of experiments indicate that a decrease in the values of fracture toughness attains as the number of constrained groove pressing (CGP) passes increase.

Simulation of tissue differentiation around acetabular cups: the effects of implant-bone relative displacement and polar gap

Mukherjee, Kaushik,Gupta, Sanjay Techno-Press 2014 Advances in biomechanics & applications Vol.1 No.2

Peri-acetabular bone ingrowth plays a crucial role in long-term stability of press-fit acetabular cups. A poor bone ingrowth often results in increased cup migration, leading to aseptic loosening of the implant. The rate of peri-prosthetic bone formation is also affected by the polar gap that may be introduced during implantation. Applying a mechano-regulatory tissue differentiation algorithm on a two-dimensional plane strain microscale model, representing implant-bone interface, the objectives of the study are to gain an insight into the process of peri-prosthetic tissue differentiation and to investigate its relationship with implant-bone relative displacement and size of the polar gap. Implant-bone relative displacement was found to have a considerable influence on bone healing and peri-acetabular bone ingrowth. An increase in implant-bone relative displacement from $20{\mu}m$ to $100{\mu}m$ resulted in an increase in fibrous tissue formation from 22% to 60% and reduction in bone formation from 70% to 38% within the polar gap. The increase in fibrous tissue formation and subsequent decrease in bone formation leads to weakening of the implant-bone interface strength. In comparison, the effect of polar gap on bone healing and peri-acetabular bone ingrowth was less pronounced. Polar gap up to 5 mm was found to be progressively filled with bone under favourable implant-bone relative displacements of $20{\mu}m$ along tangential and $20{\mu}m$ along normal directions. However, the average Young's modulus of the newly formed tissue layer reduced from 2200 MPa to 1200 MPa with an increase in polar gap from 0.5 mm to 5 mm, suggesting the formation of a low strength tissue for increased polar gap. Based on this study, it may be concluded that a polar gap less than 0.5 mm seems favourable for an increase in strength of the implant-bone interface.

Measurement and prediction of geometric imperfections in structural stainless steel members

Cruise, R.B.,Gardner, L. Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.24 No.1

Geometric imperfections have an important influence on the buckling response of structural components. This paper describes an experimental technique for determining imperfections in long (5.7 m) structural members using a series of overlapping measurements. Measurements were performed on 31 austenitic stainless steel sections formed from three different production routes: hot-rolling, cold-rolling and press-braking. Spectral analysis was carried out on the imperfections to obtain information on the periodic nature of the profiles. Two series were used to model the profile firstly the orthogonal cosine and sine functions in a classic Fourier transform and secondly a half sine series. Results were compared to the relevant tolerance standards. Simple predictive tools for both local and global imperfections have been developed to enable representative geometric imperfections to be incorporated into numerical models and design methods.

The effect of microstructural inhomogeneity on the growth paths of surface-cracks in copper processed by equal channel angular pressing

Goto, M.,Ando, Y.,Han, S.Z.,Kim, S.S.,Kawagoishi, N.,Euh, K. Pergamon Press ; Elsevier Science Ltd 2010 Engineering fracture mechanics Vol.77 No.11

The growth behavior of cracks is monitored on specimens of ultrafine grained copper produced by equal channel angular pressing. Temporary retardation of crack growth under low stress amplitudes occurs when the crack length reaches about 0.1mm, but there is no similar retardation at high stress amplitudes. Dependent on stress amplitude, different crack growth path morphologies develop. Analysis of the fracture surfaces is conducted by scanning electron microscopy, showing planer, granular and striated surfaces. The physical background of growth path and fracture surface formation is discussed by considering crack growth mechanism and microstructural inhomogeneity.

Synthesis of a high-performance citric acid-based polyester elastomer by a hot-pressing technique

Chon, Y.J.,Koo, J.M.,Park, Y.J.,Hwang, S.Y.,Jung, Y.M.,Im, S.S. IPC Science and Technology Press 2017 Polymer Vol.125 No.-

The high-performance bio-based elastomer, poly (1, 4-cyclohexanedimethanol succinate-co-citrate) (PCSC), was successfully synthesized through the combination of melt polymerization and hot pressing. Owing to the structural characteristics of citric acid (CA), an effective process of thermal- and pressure-integrated crosslinking was possible, revealing CA to be a progressive tetra-functional monomer. In the composition of PCSC, there can be four types of ester bonds amongst monomers, of which CA was used in three. Specifically, the stepwise hot-pressing method allowed β-carboxylic acid and hydroxyl group of CA to remain within the synthesized elastomer to enhance its crosslinking density via esterification. As a result, the synthesized PCSC possessed a wide range of mechanical properties along with good thermal resistance. The resulting characteristics were demonstrated by fourier-transform infrared spectroscopy (FT-IR), two-dimensional correlation spectroscopy (2D-COS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile and swelling tests. PCSC is a sustainable and versatile material that can be utilized in the field of engineering.

Ultra-robust bonding between MXene nanosheets and stretchable, self-healable microfibers

Shin, Yoo Bin,Kim, Youngmin,Kang, Chang Goo,Oh, Jung-Min,Kim, Jong-Woong Techno-Press 2021 Advances in nano research Vol.11 No.5

To develop a reliable fibrous device, a strong bond between conducting materials and fibers must be ensured. While the external surface of the film is relatively flat, making it easy to deposit the electrode materials uniformly, the walls of the polymer fibers inside the porous film pose a greater challenge for ensuring a uniform coating and robust bonding with electrode material. Herein, a microfibril-based porous film was prepared by electrospinning polybutadiene-based urethane (PBU), a newly synthesized self-healing polymer, and Ti₃C₂-based MXene nanosheets were coated thereon to fabricate a pressure sensor whose resistance decreases with pressure. The PBU microfibrils were crosslinked under mild conditions via Diels-Alder (DA) reaction by exploiting low activation energy of the PBU. An exceptionally robust bonding between the PBU and MXene was enabled by subjecting the PBU to a retro-DA and subsequent DA reactions. The temporary increase in surface fluidity of the PBU leaded to a conformal contact between the MXene and fibers without collapse of fibrous structure, resulting in an ultra-robust bond between them. A stretchable and self-healable pressure sensor was implemented by removing unnecessary MXenes by applying ultrasonic energy to the thus-fabricated sample. The fabricated sensor showed a pressure sensitivity of around 27.9 /kPa for a wide range of pressure which is the highest level among the reported stretchable self-healing pressure sensors, while maintaining its performance even after 1000 cycles of stretching and pressing. Further, sensors attached around the carotid artery could be used to precisely detect P-, T-, and D-waves arising from blood pressure.

An efficient decal transfer method using a roll-press to fabricate membrane electrode assemblies for direct methanol fuel cells

Mehmood, A.,Ha, H.Y. Pergamon Press ; Elsevier Science Ltd 2012 International journal of hydrogen energy Vol.37 No.23

This study has focused on the development of a roll-press based decal transfer method to fabricate membrane electrode assemblies (MEAs) for direct methanol fuel cells (DMFCs). This method exhibits an outstanding transfer rate of catalyst layers from substrates to the membrane, despite hot-pressing at a considerably lower pressure and for a much shorter duration than the flat-press based conventional decal method. The MEA produced by a roll-press (R-MEA) delivers an excellent single-cell performance with power densities more than 30% higher than that fabricated using a flat-press (F-MEA). The new method considerably improves catalyst active sites in both electrodes and renders a high cathode porosity. The superior pore structure of the cathode makes the R-MEA more efficient in terms of performance and operation stability under lower air stoichiometries. Moreover, MEAs can be prepared in a continuous mode using this new method due to the unique design of the roll-press. All these advantages demonstrate the superiority of this method over the conventional flat-press decal method and make it suitable for use in the commercial manufacturing of MEAs for direct methanol fuel cells.

Testing and evaluation of the corrosion behavior of Aluminum/Alumina bulk composites fabricated via combined stir casting and APB process

Abdalkareem Jasim,Ghassan Fadhil Smaisim,Abduladheem Turki Jalil,Surendar Aravindhan,Abdullah Hasan Jabbar,Shaymaa Abed Hussein,Muneam Hussein Ali,Muataz S. Alhassan,Yasser Fakri Mustafa Techno-Press 2023 Advances in materials research Vol.12 No.4

In this study, AA1060/Alumina composites were fabricated by combined stir casting and accumulative press bonding (APB). The APB process was repeated up to six press bonding steps at 300Ċ. As the novelty, potential dynamic polarization in 3.5Wt% NaCl solution was used to study the corrosion properties of these composites. The corrosion behavior of these samples was compared and studied with that of the annealed aluminum alloy 1060 and versus the number of APB steps. So, as a result of enhancing influence on the number of APB process, this experimental investigation showed a significant enhancement in the main electrochemical parameters and the inert character of the Alumina particles. Together with Reducing the active zones of the material surfaces could delay the corrosion process. Also, at higher number of steps, the corrosion resistance of composites improved. The sample produced after six number of steps had a low corrosion density in comparison with high corrosion density of annealed specimens. Also, the scanning electron microscopy (SEM), was used to study the corrosion surface of samples.

Properties of solid wood and laminated wood lumber manufactured by cold pressing and heat treatment

Kwon, J.H.,Shin, R.H.,Ayrilmis, N.,Han, T.H. Scientific and Technical Press ; Elsevier Science 2014 Materials & design Vol.62 No.-

Physical, mechanical, and morphological properties of solid wood lumbers which were cold pressed in a press and then heat treated in a kiln. Two different kinds of domestic thinning small-diameter softwood (Ginko biloba L.) and hardwood (Tilia amurensis Rupr.) were used in this study. First 50mm thick lumbers were cold pressed until 35mm (30% of control lumber) using a stopper for 5min. Then the cold pressed lumbers were heat treated in an electric kiln at 180<SUP>o</SUP>C for 6, 12, 24, or 48h. To increase the utilizability of woods, the LVLs were produced from 4mm thick veneers prepared from the heat treated lumbers using a veneer saw. Each LVL sample consisted of 5 layers which were subsequently 48h-, 24h-, 12h-, and 6h-treated veneers and untreated veneer (from top layer to bottom layer). The shrinkage rates of softwood and hardwood were considerably decreased with increasing temperature. The mechanical properties of heat treated samples were better than those of unpressed control samples. The bending strength and modulus of elasticity of the LVLs manufactured from cold pressed and then heat treated lumbers were slightly lower than those of untreated woods. The colour values obtained from the heat treated wood samples showed a clear effect of the temperature on the colour changes.

The TFG-TEC fusion gene created by the t(3;9) translocation in human extraskeletal myxoid chondrosarcomas encodes a more potent transcriptional activator than TEC.

Lim, Bobae,Jun, Hee Jung,Kim, Ah-young,Kim, Sol,Choi, JeeHyun,Kim, Jungho IRL Press] ; Oxford University Press 2012 Carcinogenesis Vol.33 No.8

<P>The t(3;9)(q11-q12;q22) translocation associated with human extraskeletal myxoid chondrosarcomas results in a chimeric molecule in which the N-terminal domain (NTD) of the TFG (TRK-fused gene) is fused to the TEC (Translocated in Extraskeletal Chondrosarcoma) gene. Little is known about the biological function of TFG-TEC. Because the NTDs of TFG-TEC and TEC are structurally different, and the TFG itself is a cytoplasmic protein, the functional consequences of this fusion in extraskeletal myxoid chondrosarcomas were examined. The results showed that the chimeric gene encoded a nuclear protein that bound DNA with the same sequence specificity as the parental TEC protein. Comparison of the transactivation properties of TFG-TEC and TEC indicated that the former has higher transactivation activity for a known target reporter containing TEC-binding sites. Additional reporter assays for TFG (NTD) showed that the TGF (NTD) of TFG-TEC induced a 12-fold increase in the activation of luciferase from a reporter plasmid containing GAL4 binding sites when fused to the DNA-binding domain of GAL4, indicating that the TFG (NTD) of the TFG-TEC protein has intrinsic transcriptional activation properties. Finally, deletion analysis of the functional domains of TFG (NTD) indicated that the PB1 (Phox and Bem1p) and SPYGQ-rich region of TFG (NTD) were capable of activating transcription and that full integrity of TFG (NTD) was necessary for full transactivation. These results suggest that the oncogenic effect of the t(3;9) translocation may be due to the TFG-TEC chimeric protein and that fusion of the TFG (NTD) to the TEC protein produces a gain-of-function chimeric product.</P>