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.

A techno-economic analysis of partial repowering of a 210 MW coal fired power plant

Samanta, Samiran,Ghosh, Sudip Techno-Press 2015 Advances in energy research Vol.3 No.3

This paper presents a techno-economic analysis of a partial repowering scheme for an existing 210 MW coal fired power plant by integrating a gas turbine and by employing waste heat recovery. In this repowering scheme, one of the four operating coal mills is taken out and a new natural gas fired gas turbine (GT) block is considered to be integrated, whose exhaust is fed to the furnace of the existing boiler. Feedwater heating is proposed through the utilization of waste heat of the boiler exhaust gas. From the thermodynamic analysis it is seen that the proposed repowering scheme helps to increase the plant capacity by about 28% and the overall efficiency by 27%. It also results in 21% reduction in the plant heat rate and 29% reduction in the specific $CO_2$ emissions. The economic analysis reveals that the partial repowering scheme is cost effective resulting in a reduction of the unit cost of electricity (UCOE) by 8.4%. The economic analysis further shows that the UCOE of the repowered plant is lower than that of a new green-field power plant of similar capacity.

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.

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.

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.

Techno-economic design of a grid-tied Photovoltaic system for a residential building

Asad A. Naqvi,Talha Bin Nadeem,Ahsan Ahmed,Muhammad Uzair,S. Asad Ali Zaidi Techno-Press 2022 Advances in energy research Vol.8 No.1

Increasing cost of electricity due to rising price of fuel is one of the local community's main issues. In this research, switching of grid dependent system to the grid-tied Photovoltaic (PV) system with net metering for a residential building is proposed. The system is designed by considering the maximum energy demand of the building. The designed system is analyzed using RETScreen on technical, economic and environmental grounds. It is found that the system is able to produce 12,000 kWh/year. The system is capable to fulfill the electricity demand of the building during day time and is also capable to sell the energy to the local grid causing the electric meter to run in reverse direction. During night time, electricity will be purchased from grid, and electric meter will run in the forward direction. The system is economically justified with a payback period of only 3 years with net present value of PKR. 4,758,132. Also, the system is able to reduce 7.2 tons of CO₂ not produced in the entire life of the project.

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.

Correlation of strength development of RCA in quaternary blended cementitious system

Sastri, M.V.S.S.,Rao, K. Jagannadha,Bhikshma, V. Techno-Press 2021 Advances in materials research Vol.10 No.3

Recycled concrete aggregate (RCA) obtained from demolished structures can be used for concrete making, and is established as a promising material in the field of construction. In the present study, the effect of RCA on the mechanical properties of different strength concretes admixed with Micro silica, fly ash and nano-silica as a part replacement to cement was considered. The quantity of cement varied from 350-690 kg/m³ with the additions of Fly ash at 0, 20 and 30%, micro silica at 0, 5, 10 and 15%, and Nano silica at 0, 1, 2, 3 and 4%. The samples were cured for 7, 28, 56 and 90 days and tested for Compressive strength. Split tensile and flexural strength evaluation was carried out on samples which have been cured for 28 days. The workability of fresh concrete was determined. With the help of the tested database, equations for prediction of compressive strength using modified Bolomey's equation were generated. Equations for the flexural strength and split tensile strengths based on compressive strength were developed and compared with equations available in the literature.

Improving aeroelastic characteristics of helicopter rotor blades in hovering

Badran, Hossam T.,Tawfik, Mohammad,Negm, Hani M. Techno-Press 2021 Advances in aircraft and spacecraft science Vol.8 No.3

Flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. This includes aircraft, helicopter blades, engine rotors, buildings and bridges. Flutter occurs as a result of interactions between aerodynamic, stiffness, and inertia forces on a structure. The conventional method for designing a rotor blade to be free from flutter instability throughout the helicopter's flight regime is to design the blade so that the aerodynamic center (AC), elastic axis (EA) and center of gravity (CG) are coincident and located at the quarter-chord. While this assures freedom from flutter, it adds constraints on rotor blade design which are not usually followed in fixed wing design. Periodic Structures have been in the focus of research for their useful characteristics and ability to attenuate vibration in frequency bands called "stop-bands". A periodic structure consists of cells which differ in material or geometry. As vibration waves travel along the structure and face the cell boundaries, some waves pass and some are reflected back, which may cause destructive interference with the succeeding waves. In this work, we analyze the flutter characteristics of helicopter blades with a periodic change in their sandwich material using a finite element structural model. Results shows great improvements in the flutter rotation speed of the rotating blade obtained by using periodic design and increasing the number of periodic cells.

Methods to determine the volume of infrapatellar fat pad as an indicator of anterior cruciate ligament tear

Cheruvu, B.,Tsatalis, J.,Laughlin, R.,Goswami, T. Techno-Press 2016 Biomaterials and biomedical engineering Vol.3 No.1

Anterior knee pain is a major problem among adolescents and young adults especially those who participates in sports. The most common pathogenesis of anterior knee pain can arise from compression and shear forces in the patellofemoral joint. It is also caused by impingement of infrapatellar fat pad. Fat pad impingement can occur when the fat pad becomes swollen and inflamed due to a direct blow or chronic irritation. As a result, the bottom tip (or inferior pole) of the patella can pinch the fat pad. One of the many causes of swollen fat pad can be secondary to anterior cruciate ligament (ACL) injury. The aim of this study was to compare the infrapatellar fat pad volume in patients with acute ACL injury and a group of age-, gender-, and activity- matched controls with intact ligament. Axial magnetic resonance (MR) images have been performed on 32 patients with torn ACL and 40 control patients. The volume of the fat pad was measured digitally from MR image by using a 3d Reconstruction software, ellipsoidal approximation, and a MATLAB code. The results were compared between patients with torn ACL and control group. Patients with a torn ACL had a significantly larger fat pad than the controls (P=0.01). There was no significant difference between the methods used to measure the infrapatellar fat pad volume (P=0.83-0.87). Thus, lesions of the infrapatellar fat pad is often associated with ACL injury.