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A finite element based numerical model to simulate orthogonal machining process and associated burr formation process has been developed in the presented work. To incorporate simultaneous effects of mechanical and thermal loadings in high speed machining processes, Johnson and Cook`s thermo-visco-plastic flow stress model has been adopted in the conceived numerical model. A coupled damage-fracture energy approach has been used to observe damage evolution in workpiece and to serve as chip separation criterion. Simulation results concerning chip morphology, nodal temperatures, cutting forces and end (exit) burr have been recorded. Model has been validated by comparing chip morphology and cutting force results with experimental findings in the published literature. Effects of cutting edge geometries [Hone and Chamfer (T-land)] on burr formation have been investigated thoroughly and discussed in length. To propose optimum tool edge geometries for reduced burr formation in machining of an aerospace grade aluminum alloy AA2024, numerical analyses considering multiple combinations of cutting speed (two variations), feed (two variations) and tool edge geometries [Hone edge (two variations), Chamfer edge (four variations)] have been performed. For chamfer cutting edge, the “chamfer length” has been identified as the most influential macro geometrical parameter in enhancing the burr formation. Conversely, “chamfer angle” variation has been found least effecting the burr generation phenomenon.

The metallic glasses are known as amorphous and metastable materials. These materials have superior mechanical properties over crystalline materials with the same chemistry. Continuous efforts were made to improve the properties of metallic glass. The severe plastic deformation (SPD) method is used to improve the ductility of the glass. SPD causes the deformation at the atomic level in the disordered structure of the glass. Many methods are reported, such as cryogenic cycling, high-pressure torsion, and equal channel angular pressing, which are used for the SPD. In recent works on nanostructured metallic glasses, it has been evidenced that some properties, for example, mechanical, thermal, and magnetic, have improved compared to the bulk metallic glass. This paper has reviewed the recent progress in the SPD of the bulk and nanostructured metallic glasses. Different methods for the SPD have been addressed here. The effect of SPD on the properties of metallic glass is deliberated in this paper. Moreover, the challenging tasks of deformation occurrence in the glass and its characterization were considered, trying to develop a sound understanding of SPD in bulk and nanostructured metallic glasses.

Anaerobic digestion (AD) is an established method that has been extensively utilized for waste management, waste treatment, and biogas production. Anaerobic co-digestion (AcoD) is regarded as a practical approach to address substrate characteristics and system optimization issues. The distinction between AcoD and mono-digestion is that AcoD has a higher organic loading and significant substrate composition variation. There are many factors involved in AcoD which affect the biogas plant’s production ability and performance. Using response surface methodology (RSM) to forecast the optimal conditions for maximum biogas output, this article provides an overview of the different operational parameters in the AcoD process, modeling of the AcoD process, and overall process optimization. Standard software used for AcoD process simulation are Aspen Plus, SuperPro Designer, BioWin, CFD, and MATLAB. Review addresses design, development, and optimization frameworks for biogas production systems that take numerous aspects into account. The most significant AcoD optimization parameters include temperature, co-substrate concentration, inoculum ratio (percent), and C/N ratio.

The applications of coated mild steels are gaining significant attention in versatile industrial areas because of their better mechanical properties, anticorrosive behavior, and reproducibility. The life period of this steel reduces significantly under relative motion in the presence of friction, which is associated with the loss of billion-dollar every year in industry. Productivity is hampered, and economic growth is declined. Several pieces of research have been conducted throughout the industries to seeking the processes of frictional reduction. This study is attributed to the tribological behavior of electroplated mild steel under various operating parameters. The efficiency of commercial lubricant and self-lubrication characteristics of coated layer plays a significant role in the reduction of friction. The reciprocating and simultaneous motion in relation to pin as well as disc are considered during experimentation. The lubricating effects in conjunction with motions are responsible for compensating the friction and wear at the desired level. During frictional tests, the sliding velocity and loads are changed differently. The changes in roughness after frictional tests are observed. The coated and rubbing surfaces are characterized using SEM (Scanning Electron Microscopy) analysis. The coating characteristics are analyzed by EDS (Energy Disperse Spectroscopy), FTIR (Fourier-transform Infrared Spectroscopy), and XRD (X-ray diffraction analysis) methods. The lubrication, reciprocating motion, and low velocity result in low friction and wear. The larger the imposed loads, the smaller the frictional force, and the larger the wear rate. The machine learning (ML) concept is incorporated in this study to identify the patterns of datasets spontaneously and generate a prediction model for forecasting the data, which are out of the experimental range. It can be desired that the outcomes of this research will contribute to the improvement in versatile engineering fields, such as automotive, robotics, and complex motion-based mechanisms where multidimensional motion cannot be ignored.

In this study, the hardness and surface roughness of selective laser-melted parts have been evaluated by considering a wide variety of input parameters. The Invar-36 has been considered a workpiece material that is mainly used in the aerospace industry for making parts as well as widely used in bimetallic thermostats. It is the mechanical properties and metallurgical properties of parts that drive the final product’s quality in today’s competitive marketplace. The study aims to examine how laser power, scanning speed, and orientation influence fabricated specimens. Using ANOVA, the established models were tested and the parameters were evaluated for their significance in predicting response. In the next step, the fuzzy-based JAYA algorithm has been implemented to determine which parameter is optimal in the proposed study. In addition, the optimal parametric combination obtained by the JAYA algorithm was compared with the optimal parametric combination obtained by TLBO and genetic algorithm (GA) to establish the effectiveness of the JAYA algorithm. Based on the results, an orientation of 90°, 136 KW of laser power, and 650 mm/s scanning speed were found to be the best combination of process parameters for generating the desired hardness and roughness for the Invar-36 material.

Environmental and human-friendly welding is the need of the hour. In this context, this study explores the application of the regulated metal deposition (RMD) technique for ASTM A387-Gr.11-Cl.2 steel plates. To examine the effect of metal-cored filler wire (MCFW), MEGAFIL 237 M was employed during regulated metal deposition (RMD) welding of 6 mm thick ASTM A387-Gr.11-Cl.2 steel plates. The welding was carried out at an optimized current (A) of 100 A, voltage (V) of 13 V, and gas flow rate (GFR) of 21 L/min. Thereafter, the as-welded plates were examined for morphological changes using optical microscopy. Additionally, the micro-hardness of the as-welded plates was measured to make corroboration with the obtained surface morphologies. In addition to this, the as-welded plates were subjected to heat treatment followed by surface morphology and micro-hardness examination. A comparison was made between the as-welded and heat-treated plates for their obtained surface morphologies and microhardness values. During this, it was observed that the weld zone of as-welded plates has a dendritic surface morphology which is very common in fusion-based welding. Similarly, the weld zone of heat-treated plates has a finer and erratic arrangement of martensite. Moreover, the obtained surface morphologies in the weld zone of as-welded and heat-treated plates have been justified by their respective hardness values of 1588.6 HV and 227.3 HV.

Metal degradation due to corrosion is a major challenge in most industries, and its control and prevention has to maintain a balance between efficiency and cost-effectiveness. The rising concern over environmental damage has greatly influenced this domain, as corrosion prevention should comply with the waste regulations of different regions. In this respect, a fundamental question is which modern synthetic materials are more viable from the point of view of their effectiveness. Therefore, this paper is aims to provide an advanced and holistic review of corrosion prevention and control methods. Corrosion prevention techniques have become extensive; however, the literature indicates that polymer coatings, nano-composite coatings, and encapsulation techniques consistently provide the most efficient and feasible outcomes. Therefore, this review article examined the phenomenon of corrosion inhibition mainly from the perspective of these three techniques. Moreover, this research utilized secondary qualitative methods to obtain data and information on comparative techniques. It is found that due to the rapid development of novel materials, corrosion inhibition techniques need to be developed on scales that are more general, so that they could be applied to varying environments. The self-healing coatings are generally based on epoxy-resins incorporated with synthetic compounds such as inhibitor ions, amino-acids, or carboxylic acids. These coatings have become more widespread, especially due to bans on several traditional prevention materials such as compounds of chromium (VI). However, self-healing coatings are comparatively more costly than other techniques because of their method of synthesis and long-term durability. Therefore, although self-healing nanomaterial-based coatings are viable options for limited usage, their utilization in large and complex facilities is limited due to the costs involved. Amino acids and other biological macro-molecules provide another option to attain environmental sustainability and long durability, especially due to their origins being most of naturally occurring compounds such as lignin, cellulose, and proteins.

Biodiesel is a fuel that has numerous benefits over traditional petrodiesel. The transesterification process is the most popular method for biodiesel production from various sources, categorized as first, second and third generation biodiesel depending on the source. The transesterification process is subject to a variety of factors that can be taken into account to improve biodiesel yield. One of the factors is catalyst type and concentration, which plays a significant role in the transesterification of biodiesel sources. At present, chemical and biological catalysts are being investigated and each catalyst has its advantages and disadvantages. Recently, nanocatalysts have drawn researchers' attention to the efficient production of biodiesel. This article discusses recent work on the role of several nanocatalysts in the transesterification reaction of various sources in the development of biodiesel. A large number of literature from highly rated journals in scientific indexes is reviewed, including the most recent publications. Most of the authors reported that nanocatalysts show an important influence regarding activity and selectivity. This study highlights that in contrast to conventional catalysts, the highly variable surface area of nanostructure materials favours interaction between catalysts and substrates that efficiently boost the performance of products. Finally, this analysis provides useful information to researchers in developing and processing cost-effective biodiesel.

Additive manufacturing (AM) is among the most attractive methods to produce implants, the processes are very swift and it can be precisely controlled to meet patient’s requirement since they can be produced in exact shape, dimension, and even texture of different living tissues. Until now, lots of methods have emerged and used in this field with diverse characteristics. This review aims to comprehensively discuss 3D printing (3DP) technologies to manufacture metallic implants, especially on techniques and procedures. Various technologies based on their main properties are categorized, the effecting parameters are introduced, andthe history of AM technology is briefly analyzed. Subsequently, the utilization of these AM-manufactured components in medicine along with their effectual variables is discussed, and special attention is paid on to the production of porous scaffolds, taking pore size, density, etc., into consideration. Finally, 3DP of the popular metallic systems in medical applications such as titanium, Ti6Al4V, cobalt-chromium alloys, and shape memory alloys are studied. In general, AM manufactured implants need to comply with important requirements such as biocompatibility, suitable mechanical properties (strength and elastic modulus), surface conditions, custom-built designs, fast production, etc. This review aims to introduce the AM technologies in implant applications and find new ways to design more sophisticated methods and compatible implants that mimic the desired tissue functions.

In this paper, the effect of equal channel angular pressing (ECAP) on microstructure, mechanical, and erosion-corrosion behavior of commercial pure (CP) titanium was investigated through experimental work. Four passes of ECAP processing at 400 ℃ was performed on CP titanium. The results showed that the homogeneous structure and coarse equiaxed grains of the initial annealed sample are transformed into the combination of UFG and NS with an average size of 750 nm and 85 nm, respectively. Also, ECAP pass numbers increase the fraction of high angle grain boundaries which improves the ductility of the processed sample. The highest hardness and strength improvement rate was observed after the first pass. Furthermore, the increasing rate of hardness and strength is gradually decreased at the subsequent passes and reached the steady-state level at the 4th pass. This is due to the balance between hardening by dislocations and twinnings accumulation and softening by recovery mechanisms. As a result, a uniform hardness distribution on both the cross-sectional and longitudinal planes is achieved. It was confirmed that erosion-corrosion resistance of the processed sample is enhanced due to the grain refinement, material homogeneity, and quick formation of a strong oxide bond layer on the surface.

Severe plastic deformation is a process in which high strain is applied to the samples to improve its mechanical properties. In this research, a new severe plastic deformation method which is based on forward extrusion process is presented to improve mechanical properties of materials, by reducing pressing force and increasing strain uniformity. Also, achieving high-strength materials with bigger size which can meet the industry is another goal of this new method. Initially, the process and related die design are introduced. Then, effects of the severe forward extrusion process on the aluminum mechanical properties such as material strength, hardness, fractographic analysis, and fatigue behavior are evaluated. Next, by using finite element method, some effects of die parameters on the pressing force and strain are studied. Finally, the obtained results show that the yielding stress is increased about 108%, by applying six passes of severe forward extrusion process. Also, the hardness value after sixth pass is greatly increased about 203%. In addition, the fatigue test results show that the endurance limit is improved 123% after sixth pass.

In this paper, the effect of equal channel angular pressing (ECAP) on microstructure and mechanical properties of hypereutectic Al-20%Mg2Si and Al-15%Mg2Si, as well as hypoeutectic Al-10%Mg2Si composites has been investigated. After fabricating the composites by in-situ casting, the composites were processed using the ECAP process up to two passes at room temperature. Microstructural studies have been carried out using a field emission scanning electron microscopy equipped with an energy dispersive X-ray spectrometer. Mechanical properties were also documented using Vickers microhardness and shear punch tests. In the hypereutectic composites, a decrease in the average size of pro-eutectic Mg2Si (Mg2Sip) particles, breakages in eutectic networks, and lengthening of the Al (&alpha, ) phase in direction of shear bands were observed after the ECAP process. For instance, the average size of Mg2Sip Particles in Al-20%Mg2Si composite reduced from 40 to 17 &mu, m after 2 passes of ECAP. Furthermore, a uniform distribution of Mg2Sip particles was developed in the matrix. In hypoeutectic composite, the ECAP process caused a uniform distribution of eutectic Mg2Si (Mg2SiE) in the matrix that considered a favorable microstructure. Microhardness measurements and shear punch results showed an ascending trend after each pass of ECAP for all specimens. For example, microhardness and shear strength of Al-20%Mg2Si increased from 88 HV and 109 MPa to 119 HV and 249 MPa after two passes indicating 35% and 34% increments, respectively. Density and porosity calculations by Archimedes principle revealed that the density of the composites increased after two passes of ECAP due to the reduction of porosity.

The nature of micro- and nanoplastics and their harmful consequences has drawn significant attention in recent years in the context of environmental protection. Therefore, this paper aims to provide an overview of the existing literature related to this evolving subject, focusing on the documented human health and marine environment impacts of micro- and nanoplastics and including a discussion of the economic challenges and strategies to mitigate this waste problem. The study highlights the micro- and nanoplastics distribution across various trophic levels of the food web, and in different organs in infected animals which is possible due to their reduced size and their lightweight, multi-coloured and abundant features. Consequently, micro- and nanoplastics pose significant risks to marine organisms and human health in the form of cytotoxicity, acute reactions, and undesirable immune responses. They affect several sectors including aquaculture, agriculture, fisheries, transportation, industrial sectors, power generation, tourism, and local authorities causing considerable economic losses. This can be minimised by identifying key sources of environmental plastic contamination and educating the public, thus reducing the transfer of micro- and nanoplastics into the environment. Furthermore, the exploitation of the potential of microorganisms, particularly those from marine origins that can degrade plastics, could offer an enhanced and environmentally sound approach to mitigate micro- and nanoplastics pollution.

This work focuses on the resonance frequency determination of a horn as a main part of ultrasonic vibrated equal channel angular pressing using experimental and simulated modal analyses. A stepped shape hot-work tool steel horn was successfully designed and manufactured to promote maximum punch force reduction. The resonance frequency of the system which includes the horn with an initial length of 220 mm was obtained by simulated modal analysis. Experimental work using Audio-Technica microphone on five different horn lengths at the free condition was developed to verify the simulated modal analysis. Also, the changes in frequency with the horn length were obtained experimentally. By considering both the system resonance frequency of 18,760 Hz for the horn length of 220 mm and 90 Hz change of longitudinal frequency for 1 mm of horn length, the final horn length was obtained to be 206 mm. Moreover, it was shown that the billet length has no considerable effect on the resonance frequency of the system. Finally, 9 % reduction at the required punch load was achieved by employment of ultrasonic vibration as compared to the conventional equal channel angular pressing process.

In this paper, influence of equal channel angular pressing (ECAP) on the fracture behavior of Al-7075 alloy is experimentally investigated. The specimens are successfully processed by ECAP methodology up to four passes using different routes. Transmission electron microscope (TEM) images showed that after four passes of ECAP, the average grain size is refined from 40 μm to less than about 500 nm. The percentage increase in yield strength, ultimate strength and microhardness of the specimens after four ECAP passes was 230, 90 and 110 respectively. Standard tests on the disk-shaped compact DC(T) specimens showed that fracture toughness is decreased up to 8% at the first ECAP pass while after four passes, this parameter roused to 17% higher than that of annealed condition. Furthermore, scanning electron microscope (SEM) micrographs demonstrated that ductile fracture mechanism with large dimples occurred in the annealed samples, changed to limited ductile fracture with fine dimples after ECAP process. This research provides new insights into the effect of ECAP and grain refinement on the fracture behavior of materials.

Polyetheretherketone (PEEK) is of great interest to the biomedical industry especially for trauma, orthopedic and spinal implants. It is biocompatible and offers numerous advantages over other metallic biomedical implants. A good understanding of behavior of PEEK under different loading conditions is therefore necessary for its more efficient use. This paper investigates the notch sensitivity of PEEK in monotonic tension using the finite element modeling in ABAQUS. An unnotched specimen and three notched specimens (moderate, deep and razor) are modeled and the maximum true stress in each case is obtained. The stress distribution in front of the crack tip is also found by introducing a crack in the model for each specimen. It is observed that PEEK exhibits a ductile behavior in the absence of a stress concentration. The deformation mechanism is found to be dramatically changed from ductile to brittle in the presence of notches. Hence, the locations and severity of stress risers modeled as notches in PEEK should be taken into consideration prior to its use in biomedical implants.

To date, ECAP technique have been successfully employed to produce Ultra-fine/Nanostructure grain materials, but some materials such as hexagonal closed-packed (HCP) alloys are difficult to process by ECAP at room temperature. In this work, Transmission Electron Microscopy (TEM), Vickers hardness test and Torsion test were employed to confirm the attainment of ultrafine/nanostructured grain (UFG/NSG) commercial pure titanium (CP-Ti) Titanium fabricated by ECAP as a sever plastic deformation process. The samples were pressed by ECAP (route BC) up to four passes at elevated temperature (400° C). Finally, the Erosion-Corrosion (E-C) behavior of ultrafine/nanostructured grain (UFG/NSG) Titanium in a simulated body fluid were investigated through weight loss measurement.

Multiaxial forging (MAF) is one of the appealing methods of severe plastic deformation (SPD) techniques to fabricate ultrafine-grained (UFG) materials. In this study, the influence of process parameters such as strain rate, friction, and initial temperature has been assessed through finite element simulation of Nickel 200 alloy. The Johnson&ndash, Cook equation was applied in simulating the MAF process. The homogeneous microstructure of a material processed by MAF is an important requirement to obtain uniform mechanical and other properties. The uniformity in properties was evaluated by the investigation of the hardness measurements, effective strain (ES), and inhomogeneous factor (IF) or coefficient of standard deviation. The results showed that the inhomogeneous factor decreases with an increase in strain rate and decrease in temperature. It was found that a more homogeneous structure is observed with an increasing number of MAF cycles and the strain rate strain. Furthermore, the average grain size reduced from 850 nm to 220 nm after three cycles of MAF. Finally, experimental work was performed to validate the results.

To overcome some possible deficiencies of pure copper, dilute alloying and employment of equal channel angular pressing seem the cost-effective solutions. In this work, dilute copper alloys with the tin amount of 0.18, 0.3, and 0.5 wt.% were obtained with continuous casting and subsequently, they were subjected to ECAP process up to four passes. It was shown that integrated treatment by dilute alloying and ECAP lead to 182% improvement of the corrosion resistance as compared to the as-received condition due to the grain refinement. Meanwhile, the alloying impact on current density is decreased with the ECAP process which may result from the changes at the distribution of Sn atoms in Cu. The difference in measured corrosion current density of unprocessed and ECAPed samples for the alloys Cu-0.3%Sn and Cu-0.5%Sn are 15% and 2%, respectively. The corrosion improvement by means of current density reduction due to the alloying before the ECAP process is about 45% while this value after the ECAP diminishes to 35%. Microstructure analysis showed that four passes of ECAP process cause the average grain size of the pure copper to less than 700 nm and the Cu-0.5%Sn to about 550 nm. Also, the HAGBs fraction of the ECAPed pure Cu is 74%, while the corresponding magnitude for the Cu-0.5%Sn is 78%. © 2019 Politechnika Wrocławska

In this paper, finite element method is implemented to model stranded-wire helical springs under different loading conditions. Finite element results are coupled with multiaxial fatigue criteria such as Fatemi–Socie and Kandil–Brown–Miller together with a uniaxial fatigue criterion, Coffin–Manson, to predict fatigue life of the stranded-wire helical springs. It is shown that due to damping effects between wires, stranded-wire helical springs have longer fatigue life compared to their equivalent single-wire helical springs at a similar condition. It is also demonstrated that fatigue life is longer for loadings with higher initial displacement of spring head. As practical examples, fatigue life of stranded-wire helical springs with 9 and 15 wires are estimated and compared. It is shown that the spring with 15 wires gives longer fatigue life. It is also observed that Kandil–Brown–Miller and Fatemi–Socie criteria give the least and the highest fatigue life prediction, respectively.

Ultrafine Grained (UFG) and Nano-Structured (NS) materials have experienced a rapid development during the last decade and made profound impact on every field of materials science and engineering. The present study has been undertaken to develop ultrafine grained pure copper by severe plastic deformation method and to examine the impact property by different characterizing tools. For this aim, equal channel angular pressing die with the channel angle, outer corner angle and channel diameter of 90°, 17° and 20 mm, respectively had been designed and manufactured. Commercial pure copper billets were ECAPed up to four passes by route B C at the ambient temperature. The results indicated that there is a great improvement at the hardness measurement, yield strength and ultimate tensile strength after ECAP process. It is found that the magnitudes of HV reach 136 from 52 HV after the final pass. Also, about 285 and 125% enhancement at the YS and UTS values have been obtained after the fourth pass as compared to the as-received conditions, respectively. On the other hand, the elongation to failure and impact energy have been reduced by imposing ECAP process and pass numbers. It is needed to say that about 56% reductions in the impact energy have been attained for the samples as contrasted to annealed specimens. Furthermore, the grain size of the final pass is 800 nm for Cu sample. Finally, fracture surfaces of billets after impact test have been investigated using Scanning Electron Microscope (SEM).

Forming limit diagram of aluminum AA7075 and titanium Ti-6Al-4V alloys was examined. For this aim, various strain paths from uniaxial to equi-biaxial tensions were considered. It was established that titanium alloy stretching potential is more than of aluminum alloy due to higher average strain hardening exponent. Also, the average anisotropy factor of AA7075 is about five times lower than that of Ti-6Al-4V resulting in the reduction of resistance to thinning during sheet metal forming processes. Furthermore, employment of BBC2000 yield criterion for AA7075 and Hill’s 1993 for Ti-6Al-4V in determining numerical forming limit diagrams resulted in a closer coincidence with the experimentations. Finally, imperfection factors of 0.970 and 0.955 for AA7075, and 0.935 and 0.960 for Ti-6Al-4V are respectively attained by yield surfaces of BBC2000 and Hill’s 1993. Keywords: Bulge test, Strain paths, Imperfection factor, Strain hardening exponent, Strain hardening coefficient

A new technique to equal channel angular pressing of tubular samples has been proposed and investigated through experiments and simulations. Deformation behavior of copper tube sample was numerically analyzed during the first pass of tubular ECAP process. The investigation included the effect of various tube wall thicknesses on the effective strain magnitude and strain distribution uniformity. It is shown that tube wall thickness of 3.5 mm gives the optimum value for strain behavior. In addition, copper tube specimens with 3.5 mm wall thickness have been successfully ECAPed up to four passes with the die channel angle of 90° using flexible polyurethane rubber pad. Micro-hardness measurements on both annealed and ECAPed tubes show that 33% and 57% increases in hardness value and also, 50% and 70% reductions in the grain size were achieved after the first and fourth passes respectively. Furthermore, tube wall thickness measurements show that the process does not change the dimension of deformed specimens.

Nickel base superalloys are widely used in applications requiring strength at high temperature. During the operation of gas turbines, the blades and other elements of hot gas path suffer service induced degradation which may be natural or accelerated due to different causes. The failure analysis of the 3 MW gas turbine first stage blades made of nickel-base alloy Nimonic 80A is presented. The blade experienced base alloy degradation due to operation at high temperature. Initially the blade was sectioned for metallographic and microhardness test. The microstructure and microhardness was compared in four different blade zones i.e. root, 30%, 60%, and 90% of the total height of the hot region of the blade. On the basis of the observed microstructures and the phases present in the alloy, the main cause of failure was found to be creep damage. Finite element method (FEM) analysis is conducted considering peak loading of centrifugal force and surface (aerodynamic) loads. Based on FEM simulation results, the life of turbine blades is predicted using the Larson–Miller method. Finally to improve the blade life two heat treatment cycles were suggested and applied. The effect of heat treatments on grain size, volume friction of γ ′ primary phase, and micro hardness were investigated. A detailed analysis of the coating showed that, the loss of coatings resistant to high temperature is due to oxidation, corrosion, erosion and inters diffusion of coating-substrate, which results in diffusion of alloy elements into the coating.

Flow forming technology is widely used in the production of the axisymmetric industrial parts. The advantage of flow forming process over other manufacturing methods such as press forming is use of simple tooling, reduced forming loads due to localized deformation, and enhanced mechanical and surface quality of finished parts. In this study, the effects of thickness reduction on the mechanical properties and spinning accuracy are experimentally investigated on 7075-O aluminum tube. A prototype spinning machine has been designed and manufactured. The effects of spinning accuracy, surface roughness, percentage of elongation, yield strength, and the ultimate strength as a function of thickness reduction are experimentally examined. The experimental results show that with increment of thickness reduction, the yield strength, ultimate strength, surface hardness, and crystal refining increase, and on the other hand, it has adverse effect on diameter growth, geometrical accuracy, surface roughness, and percentage elongation of spun tube.

In view of the importance and demanding roles of steel rebar's in the reinforced concrete structures, accurate information on the properties of the steels is important at the design stage. In the steelmaking process, production variations in chemical composition are unavoidable. The aim of this work is to study the variability of the chemical composition of reinforcing steel produced throughout the Saudi Arabia and asses the quality of steel rebar's acoording to ASTM A615. 68 samples of ASTM A615 Grade 60 from different manufacturers were collected and tested using the Spectrometer test to obtain Chemical Compositions. EasyFit (5.6) software is utilized to conducted statistical analysis. Chemical compositions distributions and, control charts are generated for the compositions. Results showed that some compositions are above the upper line of the control chart. Finally, the analyses show that less than 3% of the steel failed to meet minimum ASTM standards for chemical composition.

An analytical solution for computing the radial and circumferential stresses in a FGM thick cylindrical vessel under the influence of internal pressure and temperature is presented in this paper. It has been assumed that the modulus of elasticity and thermal coefficient of expansion were varying through thickness of the FGM material according to a power law relationship. Nevertheless the value of the Poisson ratio was taken as constant throughout the material. In the analysis presented here the effect of non-homogeneity in FGM thick cylinder was implemented by choosing a dimensionless parameter, named β, which could be assigned an arbitrary value affecting the stresses in the cylinder. Using Maple 9.5, distribution of stresses in radial and circumferential directions for FGM cylinders under the influence of internal pressure and temperature gradient were obtained. Graphs of variations of stress versus radius of the cylinder were plotted for different values of β. Cases of pressure, temperature and combined loadings were considered separately. It was concluded that by changing the value of β, the properties of FGM could be so modified that the lowest stress levels were reached. The stresses which were produced in FGM and homogeneous material with the same boundary conditions were compared to obtain the optimum value of β.

Most engineering components which operate at elevated temperatures are subjected to non-steady loading during service. This paper describes the current fracture mechanics concepts that are employed to predict cracking of Nickel base supper alloy materials at high temperatures under low and high frequency cyclic loading. A model for predicting creep crack growth in terms of C* and the creep uniaxial ductility is presented at low frequency and at high frequency power law relation is used to predict the crack growth rate. When dealing with creep/fatigue interaction a simple cumulative damage concept with fractography evidence is used to predict the crack growth rate. It is shown that these models give good agreement with the experimental results.

Ultrafine grained materials have experienced a rapid development during the last two decades. Constrained groove pressing (CGP) process is one of the severe plastic deformation methods to fabricate ultrafine grain sheet materials. In this research, wear behavior of brass sheet subjected to CGP process was investigated. Generally it is shown that CGP process enhances the wear resistance of the material and this behavior is improved by increasing pass number. Also, the effect of initial pass and lower applied normal load on the wear resistance is more profound than subsequent passes and higher applied normal load, respectively. In addition, the influence of normal load is more profound than pass number at the increment of friction force. Although CGP process results in reduction at the specific wear rate, the influence of the first pass is much higher than the subsequent ones. Furthermore, lower specific wear rate is occurred at the higher applied normal load. The scanning electron microscopy analyses indicated that the wear mechanism is transferred from adhesion, delamination, abrasion and oxidation for the annealed condition to abrasion and adhesion for the third pass CGP sample. Also, it is found that there is a reverse relationship between specific wear rate and hardness. (C) 2014 Elsevier Ltd. All rights reserved.

Equal-channel angular pressing (ECAP) is a prominent technique that imposes severe plastic deformation into materials to enhance their mechanical properties. In this research, experimental and numerical approaches were utilized to investigate the mechanical properties, strain behavior, and damage prediction of ECAPed 7025 aluminum alloy in various conditions, such as die channel angle, outer corner angle, and friction coefficient. Experimental results indicate that, after the first pass, the yield strength, ultimate tensile strength, and hardness magnitude are improved by approximately 95%, 28%, and 48.5%, respectively, compared with the annealed state, mainly due to grain refinement during the deformation. Finite element analysis shows that the influence of die channel angle is more important than that of outer corner angle or friction coefficient on both the strain behavior and the damage prediction. Also, surface cracks are the main cause of damage during the ECAP process for every die channel angle except for 90°; however, the cracks initiated from the neighborhood of the central regions are the possible cause of damage in the ECAPed sample with the die channel angle of 90°. © 2014, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Recently, different industries faced the challenge of implementation of titanium alloys in order to produce components with different formability characteristics. Titanium alloy sheets are defined as hard-to-form materials regarding to their strength and formability characteristics. Consequently, in order to soundly manufacture a part made from the mentioned alloys, novel processes such as hydroforming, rubber pad forming and viscous pressure forming instead of conventional stamping or deep drawing are applied.

In this paper a combined node searching algorithm for simulation of crack discontinuities in meshless methods called combined visibility and surrounding triangles (CVT) is proposed. The element free Galerkin (EFG) method is employed for stress analysis of cracked bodies. The proposed node searching algorithm is based on the combination of surrounding triangles and visibility methods; the surrounding triangles method is used for support domains of nodes and quadrature points generated at the vicinity of crack faces and the visibility method is used for points located on the crack faces. In comparison with the conventional methods, such as the visibility, the transparency, and the diffraction method, this method is simpler with reasonable efficiency. To show the performance of this method, linear elastic fracture mechanics analyses are performed on number of standard test specimens and stress intensity factors are calculated. It is shown that the results are in good agreement with the exact solution and with those generated by the finite element method (FEM).

In this paper, a new severe plastic deformation method called equal channel forward extrusion (ECFE) process has been proposed and investigated by experimental and numerical approaches on the commercial pure copper billets. The experimental results indicated that the magnitudes of yield strength, ultimate tensile strength and Vickers micro-hardness have been markedly improved from 114 MPa, 204 MPa and 68 HV as the annealed condition to 269 MPa, 285 MPa and 126 HV after the fourth pass of ECFE process, respectively. In addition, scanning electron microscopy observation of the samples showed that the average grain size of the as-received state which is about 22 μm has been reduced to 1.4 μm after the final pass. The numerical investigation suggested that although one pass ECFE process fabricates material with the mean effective strain magnitude of about 1, the level of imposed effective plastic strain gradually diminishes from the circumference to the center of the deformed billet.