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AbstractMost published works related to gas metal arc welding processes focus on quality criteria, while energy consumed has not been considered. In this study, key parameters of the gas metal arc welding (GMAW) operation of the AISI 1045 steel, including the current (I), voltage (V), flow rate (F), and nozzle stand-off distance (D) are optimized to minimize energy consumed (EC) and enhance the ultimate tensile strength (TS) as well as elongation (EL). The radial basis function network (RBFN) is employed to propose GMAW responses. The Entropy method, modified grey wolf optimizer (MGWO), and Multi-Attributive Border Approximation Area Comparison (MABAC) were utilized to compute the weights, generate feasible solutions, and determine the best optimality. As a result, the optimal I, V, F, and D were 137 A, 23 V, 12 L/min, and 12 mm, respectively. The EC was reduced by 5.8%, while the TS and EL were improved by 3.3% and 20.7%, respectively, at the optimality. The EC and EL models were primarily affected by the I, V, F, and D, respectively. The TS model was mainly influenced by the I, D, F, and V, respectively. The RBFN-MGWO could be employed to present non-linear data and achieve better optimal results, as compared to the traditional approach. The obtained outcomes could be used to produce high-quality welds with minimizing environmental impacts. [ABSTRACT FROM AUTHOR]

Equal Channel Angular Pressing (ECAP) is one of the severe plastic deformation methods that is applied to metals, alloys and composite materials in order to convert the normal grain structure into ultra-fine grain structure, so as to increase the strength of the metal and its ductility. The uniqueness of ECAP is that the severe plastic deformation apply large strains on the material without affecting the original dimensions of material. ECAP process was chosen among the other severe plastic deformation methods, because of its cost-effectiveness and simplicity. Die angle, corner angle, ECAP routes, number of passes and heat treatments have great impact on the micro-structure and mechanical properties of various materials. The grain refinement enhances the yield strength, tensile strength, hardness, ductility and corrosion resistance on ECAPed materials, which are commonly used for engineering and bio-medical applications. Many researchers have contributed greatly to this method. This article mainly focuses on the effect of ECAP die orientations and on novel ECAP methods that exclusively combines ECAP with heat treatment or hot working on aluminium, magnesium, titanium and other materials. [ABSTRACT FROM AUTHOR]

AbstractTo correlate µTBS of different resin cements with their film thickness (FT), Vickers hardness (HV), and ultimate tensile strength (UTS). Human molars (N = 30) were divided into six-groups according to 1: Resin cement: Bifix QM, (BF), GrandioSo Heavy Flow (GHF) and VisCalor Bulk (VB), and 2: Adhesive mode (Optibond Universal): Etch-and-rinse (E&R) or self-etching (SE). CAD/CAM blocks (7 × 7 × 4 mm3) were air-abraded using 50 μm Al2O3 and silane was applied (60 s), and air dried (10 s). For E&R, dentin was etched (15 s), rinsed (30 s), and blot-dried. For both modes, adhesive was applied (20 s), air-dried (5 s), and photo-polymerized (10 s). Sticks (1 × 1 mm2) were stored for 24-h or 6-months. Sticks were pulled in tension (1 mm/min). Debonded sticks were evaluated for failure mode analysis. For FT, nine-bonded slabs from each cement was prepared and evaluated. For UTS, eight-hourglass specimens from each cement were prepared and tested in tension. For HV, five-discs from each cement was prepared and evaluated using a HV tester. Data were analyzed using ANOVA/Pearson’s correlation tests (α = 0.05). No correlation between µTBS/HV was revealed (p > 0.05). A positive correlation between µTBS/FT and µTBS/UTS (p < 0.05) was observed. Three-way ANOVA revealed all experimental factors had a significant effect on µTBS (p < 0.05). The VB showed significantly lower µTBS (20.8 ± 9.3 MPa). The E&R mode showed higher µTBS (26.0 ± 10.9 MPa), and 24-h revealed a higher µTBS (27.4 ± 10.0 MPa). Mixed failure was the predominant type (42.51%). The VB showed the highest FT (122.2 ± 11.9 µm), with GHF revealed higher UTS and HV (112.5 ± 19.7 MPa and 91.6 ± 0.4 Kgf, respectively). Photo-polymerized flowable composite can substitute dual-polymerized cement for CAD/CAM composite bonding. [ABSTRACT FROM AUTHOR]

Aluminium-Silicon (Al-Si) based alloys are gaining more prominence among researchers for automotive applications. In this paper, the impact of copper alloying element and artificial ageing treatment on the mechanical response and microstructural evolution of Al-Si based alloys synthesised from aluminium scrap are examined, as there is need to gear up the urge for the usage of metallic scraps for production of alloys for automotive applications. The as-cast Al-Si alloy and its form with copper as alloying element (1.5% and 3% Cu) were produced using liquid metallurgy route. Solution heat treatment was carried out at 500℃ and artificial ageing was carried out at 190℃ for 0.5, 1, 1.5, 2 and 2.5 h. Mechanical properties and microstructural characterisations of the as-cast and artificially aged forms of Al-Si based alloys were performed. The hardness tests were performed according to ASTM A29/A29M–15. Impact strength was determined according to ASTM D256. Tensile tests were performed based on ASTM E8. Microstructures of the synthesised Al-Si alloys were examined using optical microscopy and scanning electron microscopy techniques. In as-cast condition of the Al-5Si-Cu alloy, impact strength increases with increase in copper content. Al5Si-Cu alloy with 3% copper content and artificially aged at 190°C for 2.5 h exhibited the highest impact strength. Hardness number increases with the increase in copper content up to 1.5% and the ageing time. Additional increase in the ageing time yielded decrease in the hardness number. Results revealed that artificial ageing enhances mechanical and microstructural characteristics of the Al-Si alloys. Ageing treated Al-Si alloys exhibited peak hardness, impact strength and ultimate tensile strength (UTS) values of 77.47 kgf/mm2, 17 J/mm2 and 137.80 MPa, respectively. The obtained results are indicative of mechanical properties enhancement when compared with as-cast Al-Si alloys with maximum hardness, impact strength and UTS of 43.71 kgf/mm2, 12.92 J/mm2 and 123.18 MPa, respectively. Significant improvement in mechanical properties was achieved in Al-Si-Cu alloy with copper content and artificial ageing when compared to that without copper inclusion. This may be attributed to the evolution of equiaxed precipitates and the fact that copper-rich Al-Si-Cu alloys promotes formation of precipitation strengthening phases of α-AlFeMnSi. This study shows that the mechanical properties of Al-5Si-Cu alloys produced using aluminium scrap-based materials were enhanced using artificial ageing treatment and the benefit can be utilised for automotive applications. [ABSTRACT FROM AUTHOR]

This paper gives the investigation of the mechanical properties of Jutton-Glass hybrid polymer nanocomposite with multi walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) as reinforcements. For preparing the composites, the vacuum bagging technique was used with the composition of hybrid nano-material taken as 0, 0.25, and 0.5 wt. % of Graphene nanoplatelets and MWCNTs and the samples were tested for mechanical properties as per ASTM standards. The samples prepared have been subjected to various testing, and the results are reported. Prior to the preparations of composites, the polymer was mixed with surface-modified nanomaterials and stability tests were conducted to assess uniform dispersion with the aid of UV-Vis spectroscopy, the outcomes showed that the samples were exceptionally uniform over a period. The hardness and tensile properties were evaluated, and it was found that surface-modified nanomaterials could improve the properties better compared to the use of pristine nanomaterials as reinforcements. It was found that 0.25% MWCNT and graphene nanoplatelets (GNPs) show more improved properties than 0.5% MWCNT and Graphene nanoplatelets. However, the composite samples with Graphene nanoplatelets also showcased encouraging mechanical properties like hardness and tensile strength. [ABSTRACT FROM AUTHOR]

Metallic nanowires are now extensively used in several nanoscale devices and applications. To further enhance their efficient usage, the estimation and prediction of thermal and mechanical properties of these nanowires is very important. Performing experimental studies on the objects of such a small dimension is quite challenging. Molecular dynamics simulation technique can easily simulate and perform virtual experimentation on the objects of nanoscale dimensions. In the present work, silver nanowires of known dimension simulated and a uniaxial stress has been implemented using the Molecular dynamics approach. The stress-strain data generated by MD simulation, has been utilized to train, test and validate different machine learning models. These machine-learning models offer a reasonably good amount of predictability of the tensile characteristics of the silver nanowire at any temperature. [ABSTRACT FROM AUTHOR]

This study investigates the relationship between four welding input parameters (voltage, current, heat input, and welding speed) and the ultimate tensile strength (UTS) and yield strength (YS) of a welded joint. The work joined two super-duplex stainless-steel pipes of outside diameter 0.630 inches (16.002 mm) and a thickness of 0.065 (1.651 mm), using Gas Tungsten Arc Welding. Factorial design was used to ascertain the main and interaction effects of the welding input parameters on the UTS and YS of the welded joint. Results revealed a significant interaction between voltage, current, welding speed and heat input for UTS, and a significant interaction between the welding speed and heat input for YS. Results further revealed that as voltage increases from 9.3 V to 11.6 V, the UTS decreases by 2.69 MPa, while YS increases significantly by 24.25 MPa. When the current increases from 30 A to 38 A, the UTS increases by 10.81 MPa, while the YS increases by 4.25 MPa. In the case of the welding speed, an increase from 0.46 to 0.71 mm/s results in a decrease of the UTS by 7.94 MPa and a significant increase of the YS by 33.25 MPa. When the heat input increases from 0.54 to 0.70 kJ/mm, the UTS decreases by 15.06 MPa, whereas the YS decreases significantly by 35.25 MPa. Also, the optimum voltage, current, welding speed and heat input for UTS are 11.60 V, 30.0 A, 0.71 mm/s, and 0.70 kJ/mm, respectively, and those of YS are 9.30 V, 30.0 A, 0.46 mm/s, and 0.70 kJ/mm, respectively. [ABSTRACT FROM AUTHOR]

Hemicellulose and lignin were progressively removed from hemp fiber by hydrolysis. SEM, FTIR, XRD analysis and tensile properties evaluation on technical fibers were carried out to understand the structural and mechanical properties of hemp fibers. Significant influence of hemicellulose and lignin content on tensile properties was verified by ANOVA. The fiber tensile strength and initial modulus were decreased with the extensive removal of hemicellulose, along with a constant increasing of elongation at rupture. Torsion and expansion were observed in hemp fibers. It was suggested that the internal structure destruction and reorganization in the ultimate fiber cells was the main reason for the variation of mechanical properties when hemicellulose was gradually dissolved. On the other hand, fiber individualization was achieved by lignin removal and contributed to the elevation of fiber tensile properties. The elongation at break of the hemp fibers decreased slightly with the removal of lignin. NaClO2 solution treatment affected the fiber cells slightly, but effectively changed the properties of the middle lamella jointing between the ultimate fiber cells. The mechanical properties of the hemp fiber were mainly decided by the shearing between single fibers caused by the plastic-like deformation of the middle lamella. [ABSTRACT FROM AUTHOR]

The stir casting technique has proved to be a well-known method for processing Metal Matrix Composites (MMCs) owing to the fact that it is an easy and cost-effective process. The current work explores themicrostructure characteristic and mechanical property of Zirconium dioxide (ZrO2) particle reinforced with Aluminium 6061 (Al6061) matrix fabricated through the stir casting method. Casting is carried out with ZrO2 as reinforcement phase for 2, 4, 6, 8 and 10 wt%. Specimens for different testing were prepared through machining in confirmation with ASTM standards for composites. In this study, SEM morphology is used to analyse the reinforcement distribution in a metal matrix, and it demonstrates that there is a uniform distribution of hardened particles in the metal matrix, with no cluster formation, resulting in increased strength. Tensile and hardness studies reveal that Brinell Hardness Number (BHN) and Ultimate Tensile Strength (UTS) increase with an increase in the percentage of reinforcement and maximum UTS is observed to be 223 MPa for 6% of reinforcement. Further increase in wt% of percentage of reinforcement tends to decrease the UTS and hardness property of MMCs. Overall, with the addition of reinforcement MMCs have shown 49% increase in tensile strength and 15–20% increase in hardness. [ABSTRACT FROM AUTHOR]

The mechanical properties of fused filament-fabricated specimens are the primary considerations of researchers. Process parameters have a significant impact on the mechanical strength of 3D-printed parts. In this work, the effect of process variables such as infill volume, pattern, layer height, nozzle temperature, and print speed on tensile and compressive strength of polylactic acid samples are investigated. The maximum tensile strength of 27.87 MPa was obtained at 90% infill density for gyroid pattern of a layer thickness of 0.1 mm at a nozzle temperature of 220°C and print speed of 30 mm/s. The maximum compressive strength of 38.21 MPa was achieved at 90% infill density for the triangle pattern of a layer thickness of 0.1 mm at a nozzle temperature of 220°C and print speed of 30 mm/s. Thermal annealing as a post processing method to enhance the mechanical properties is also explored. The effect of annealing temperatures 65°C, 95°C and 125°C and time 30, 60 and 120 minutes on mechanical strength were studied. Ultimate tensile strength showed an improvement of 25.26% to achieve 34.91 MPa whereas compressive strength increased by 21.87% to give 46.57 MPa strength. [ABSTRACT FROM AUTHOR]

Austenitic Stainless-Steel grade 316 L is one of the huge ASS grades used in different industry sectors, nuclear power plants and pharmaceutical applications. Because of these various applications at high temperature, it is a must to know its properties at different conditions. The present work focued on to improve the mechanical properties, like ultimate tensile strength (UTS), yield strength (YS), strain hardening exponent (n) and % elongation. These are assessed depending on the test information obtained from the uniaxial isothermal tensile tests. A total of 27 tests based on fullfactorial designed to performe temperature at 750°C, 825°C and 900°C, three orientations (0, 45, 90) degrees to the rolling direction and strain rates (0.1, 0.01 and 0.001 s−1) were chosen. From the experimental results, it is clear that temperature and strainrate has a significant effect on material properties. With the rise in temperature, % elongation increases and a considerable decline in strength was observed. The scanning electron microscope and microstructural analysis was carried out at elevated temperatures to type of fracture. From ANOVA analysis, it was observed that temperature for UTS, combine temperature * strain rate for YS and strain rate*strain rate for % elongation with 85.889%, 38.93 and 65.73% contribution respectively. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of pre-heating a dual-polymerized adhesive and a dual-polymerized core build-up resin composite on their dentin micro-shear bond strength (µSBS), degree of conversion (DC%) and ultimate tensile strength (UTS). For µSBS, 45 human molars were divided into 9 groups (n = 5) according to two factors: (1) Adhesive temperature (25 °C/32 °C/40 °C) and 2- Resin composite temperature (25 °C/32 °C/40 °C). Dual-polymerized adhesive (Futurabond U/FBU) was applied over occlusal dentin at each temperature following the manufacturer's instructions. Four dual-polymerized composites (Rebilda DC/RDC, VOCO) micro-cylinders (1.2 mm diameter × 1 mm height) were built-up over each dentin disc, after being pre-heated at each temperature. After storage (48 h/37 °C), µSBS testing was run at a crosshead speed of 1 mm/min. DC% of FBU/RDC was evaluated at each temperature after 48 h using FTIR. Hourglass-shaped specimens were fabricated from both materials at each respective temperature and pulled apart to evaluate UTS after 48 h storage. Data were analyzed by ANOVA/Tukey's test/Pearson's correlation (p = 0.05). Neither adhesive/composite temperature nor their interaction had a significant effect on µSBS. No significant difference in µSBS between groups, except within 40 °C FBU. Predominant failure mode was a mixed type. No significant difference in DC% of FBU groups. RDC at 40 °C had significantly higher DC% than 25 °C. No significant difference in UTS of FBU and RDC groups. Application of both dual-polymerized adhesive and resin composite at 40 °C seemed to reduce µSBS. Raising the temperature to 40 °C improved DC% of resin composite, with no effect on adhesive. Pre-heating did not influence the UTS of both materials. [ABSTRACT FROM AUTHOR]

In this paper, nanoscale mechanical properties and failure behavior of graphene with Stone-Wales defect concentration were investigated using molecular dynamics simulations with the latest ReaxFFC-2013 potential that can accurately capture bond breakages of graphitic compounds. The choice of interatomic potential plays an essential role in capturing the deformation mechanism accurately. Stable configuration of two-dimensional graphene experiences out-of-plane deformation leading to ripples and wrinkles in graphene. It is observed that the mechanical properties such as Young's modulus, ultimate tensile strength, and the fracture strain are dependent on the out-of-plane deformation, temperature, defect concentration, defect orientation, defect layout and loading configuration. It is observed that the post transient phase non-homogenous ripples and wrinkles influence the mechanical properties at low and high defect concentrations, respectively. [ABSTRACT FROM AUTHOR]

In this research work the machining waste white cast iron powder (WCI) is introduced in the age hardenable Al7075 alloy matrix with the objective of enhancing the tensile properties by well-known age hardening treatment. This material holds good in light duty dies where in the strength-related characteristics improvement is the order of the day. In view of this the effect of aging kinetics on the hardness pattern and tensile strength of stir cast Al7075-white cast iron (WCI) particulate reinforced composites in as cast and peak aging conditions is investigated. The composite is cast by two step liquid stir casting route. During precipitation hardening heat treatment, reinforcement weight percentage (internal variable) and aging temperature (external variable) are considered to be the major strengthening variables. To understand the nature of failure in tensile study, fracture surface analysis is carried out using SEM. The experimental values revealed that there is a substantial enhancement in the desired properties during the precipitation hardening treatment, if the strengthening variables are properly controlled. Hardness and tensile strength of the composite have increased with increase in weight percentage of reinforcement and reduction in aging temperature. Maximum hardness and tensile strength are observed when Al7075 alloy is reinforced with 6 weight% of WCI, aged at 100ᴼC. SEM images of tensile fracture surface exhibits abundant cup-like depressions or dimples as well as river patterns indicating mixed mode of failure. The equally aligned facets (dendrites) present in the peak-aged fracture surfaces is the evidence for the attainment of optimum (peak) aging condition. The aim of the present research work is to improve the hardness-related properties by the combined effect of precipitation of secondary phases (intermetallics) through aging treatment and dispersion strengthening by the introduction of hard reinforcement WCI. [ABSTRACT FROM AUTHOR]

Austenitic Stainless-Steel grade 316L is one among the significant ASS grades which is most used in various industry sectors. It has excellent corrosion resistance in ordinary atmospheric and in more arduous environments such as saltwater. Whilst performing well when exposed to relatively high temperatures, this grade of ASS also maintains its strength and toughness at sub-zero temperatures, making this an excellent choice for various applications in industrial sectors such as Marine, general construction and water treatment. Therefore, present study focused on evaluating the mechanical properties, ultimate tensile strength (UTS), yield strength (YS) and strain hardening exponent (n) are evaluated based on the experimental data obtained from the uniaxial isothermal tensile tests performed at an interval of −25°C from 0°C to −50°C and at three orientations 0, 45, 90 degrees to the rolling direction and cross-head velocity 3, 5, 7 mm/min were chosen. Total of 27 experiments have been planned based on design-of-experiments. A mathematical model for the prediction of UTS, YS and n was developed using process parameters such as temperature, orientation and cross-head velocities. Results have shown that mechanical properties can be predicted with a reasonable accuracy within the range of process parameters considered in this study. [ABSTRACT FROM AUTHOR]

7075 alloys were prepared using metals of 99.99% high purity in the vacuum atmosphere. These alloys were directionally solidified upwards under various growth velocities (8.3–166.0 μm/s) using a Bridgman-type directional solidification furnace. Dendritic spacings (λ1, λ2) and microhardness (HV) were measured from both longitudinal and transverse sections of the samples. Ultimate tensile strength (σU) and yield strength (σy) of the solidified samples at room temperature were examined. The HV increased from 75.2 to 112.8 MPa, the σU increased from 155.8 to 210.1 MPa, and the σy increased from 198.4 to 319.8 MPa with increasing growth velocity from 8.3 to 166.0 μm/s. Exponent values of the V for the λ1, λ2, HV, σU and σy were calculated as 0.27, 0.41, 0.05, 0.11 and 0.15, respectively. The results show that the hot tearing in the 7075 alloy is caused by the fracture of dendrites structures. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical properties of thermoelectric Mg2Si are investigated using molecular dynamics (MD) method, with Mg2Si in the forms of bulk, nanofilm, and nanowire, respectively. The effects of the Mg vacancy on the mechanical properties of Mg2Si in these three forms are studied in details. First of all, the equilibrium state of Mg2Si is simulated after choosing the proper potential function, boundary conditions, and the speed algorithm. Nondimensionalization is also implemented during the simulations. This part of simulation aims to verify the correctness of the crystal model established via the use of the molecular dynamics analysis. Next, the models of Mg2Si in the forms of bulk, nanofilm, and nanowire are established with different Mg vacancy proportions, and then the mechanical properties of each model are studied via the uniaxial tensile test. Finally, the stress–strain curve and subsequently the ultimate tensile strength are obtained for each model. Simulation results indicate that the ultimate tensile strength of Mg2Si in each model is decreased with the increase of the Mg vacancy proportion. Moreover, through the comparison of the ultimate tensile strengths of Mg2Si bulk, nanofilm, and nanowire, it is found that low-dimensionalization significantly reduces the ultimate tensile strength of thermoelectric Mg2Si. Results obtained in this paper can provide valuable guidance to the future applications of thermoelectric devices. [ABSTRACT FROM AUTHOR]

This article focuses on the optimisation of electrical and mechanical properties of hybrid blends of polyoxymethylene (POM) as primary thermoplastic matrix, polypyrrole (PPY) as secondary conducting polymer and graphene (G) as reinforcement. An initial Taguchi analysis was performed with a focus on improving electrical conductivity (σ) and tensile strength. A mixture analysis using ‘simplex’ statistical design was applied to develop an experimental subset that identified an optimal combination in weight-percentage. Both electrical and mechanical properties were improved by the addition of PPY and graphene particles due to hybridisation mechanism as well as double percolation threshold. The maximum electrical conductivity of 0.95 S cm−1 was achieved with POM reinforced with 3 wt.% of G and 2.5 wt.% of PPY loading. The mechanical properties were found to be increased with increase in addition of both G and PPY. [ABSTRACT FROM AUTHOR]

This article focuses on the hybridization of thermoplastic polymer matrices with conducting polymers and graphene derivatives. Polypropylene (PP), polymethylmethacrylate (PMMA) and polyoxymethylene (POM) were used as primary polymer matrices and polypyrrole (PPY) and polyaniline (PANI) as secondary conducting polymers. Highly conductive-reduced graphene oxide (rGO) and graphene (G) have been used as reinforcements. A Taguchi analysis has been performed for the blends to find the optimal combination of the blends with respect to electrical conductivity (σ) and mechanical properties. Both electrical and mechanical properties were improved by the hybridization process. The maximum electrical conductivity of 0.85 S.cm−1has been acquired with POM/PPY/G blend with 3 wt.% and 5 wt.% of PPY and graphene loading, respectively. The mechanical properties have been found to improve with all the blends but, PP/PPY/G blend with 3 wt.% and 6 wt.% of PPY and graphene loading displays overall better properties in comparison with other blends. [ABSTRACT FROM AUTHOR]

This work focuses on the effect of graphite particle addition on the properties of AA6082 metal matrix composites fabricated by conventional stir casting method. The percentage of reinforcement was varied from 0% to 12% in a step of 3%. The results revealed that with the addition of graphite particles, the micro- and macro-hardness decreased by 11.11% and 10.44%, respectively. The ultimate tensile strength also decreased by 5.88% with a reduction in percentage elongation from 8.7 to 6.8. The density decreased by 4.1% with an increase in porosity from 0.37% to 2.27% as the weight percentage of graphite particles increased from 0% to 12%. [ABSTRACT FROM PUBLISHER]

High-tensile strength 950 MPa steel, HT950, which is steel used in penstocks, was developed to provide two vital properties: fracture arrest to stop brittle fracture and high weldability. This steel has been already used for penstocks in some hydropower plants in Japan. To widely apply high-tensile strength steels in penstocks in the future, fewer restrictions against their welding conditions such as pre-heat and post-heat temperature controls are required. One proposed solution is to undermatch the strength of the filler metal to that of the base material. This allows less pre-heating, or no pre-heating at all, and the use of conventional rod and process management is easier. Previous studies have shown that there are softening conditions under which the strength of the joint can be considered as that of the base material. However, the shape and distribution of the soft region are assumed to be ideal. In this study, the method for calculating the change of the strength in heat-affected zone (HAZ) during the welding process is discussed. Then, the influence of the strength distribution of HAZ and welded zone to the strength of the joint is investigated by a wide plate test in both experiment and elastic–plastic analysis. Applicability of undermatched joints to penstock fabrication is considered by these discussions. As a result, it is concluded that the Vickers hardness distribution in the HAZ can be estimated by the method which is proposed in this study and the strength of the under-matched joints is high enough in both experiment and analysis in which the Vickers hardness distribution is considered. From these conclusions, the applicability of undermatched joints, of which the weld metal is the HT570 class, to penstock fabrication is conformed. [ABSTRACT FROM AUTHOR]

The present article evaluates the influence of independent control factors such as microstructural degradation, impact velocity, impingement angle, and erodent size on solid particle erosion behavior of 2.25Cr-1Mo steel using a statistical approach. Microstructural degradation in this steel has been introduced as a result of thermal aging corresponding to Larson-Miller parameter (LMP) values of 33,012, 35,402, 37,846, and 38,374. Solid particle erosion tests were carried out using a sand blast–type test rig following a well-planned experimental schedule based on Taguchi's orthogonal arrays. The erosion rate of this steel decreases with increase in the severity of thermal aging. This observed phenomenon could possibly be attributed to spheroidization of lenticular-shaped carbides to globular-shaped carbides as a result of increase in the severity of thermal aging. With the help of signal-to-noise ratios and analysis of variance (ANOVA), an optimal combination of control factors to minimize the solid particle erosion behavior of 2.25Cr-1Mo steel was determined. Among all four control factors, the LMP representing the extent of thermal aging is the most significant control factor influencing the solid particle erosion behavior of this steel, followed by impingement angle, impact velocity, and size of erodent. Results indicated that the LMP has a greater static influence of 46.33%, impingement angle has an influence of 42.51%, impact velocity has an influence of 7.47%, and size of erodent has an influence of 1.13% on solid particle erosion of this steel. Material loss during solid particle erosion of 2.25Cr-1Mo steel is found to be ductile in nature and primarily controlled by cutting and ploughing action. [ABSTRACT FROM AUTHOR]

Hole expansion ratio has been designed in recent past to characterize formability/stretch flangeability of hot-rolled high-strength steel. Various factors influencing the determination of hole-expansion ratio has been discussed. Parameters such as yield strength, ultimate tensile strength, elongation, carbon equivalent have been correlated with the hole-expansion ratio of various grades of hot-rolled steel. It is found that the ultimate tensile strength of steel is the most important criterion that correlates with hole expansion ratio provided the strengthening mechanism in the steel is the same. [ABSTRACT FROM AUTHOR]

Dissimilar metal welds (DMW's) between ferritic and austenitic materials at elevated temperatures have concerned boiler manufacturers and operators for decades because of the proven potential for premature failure. The industry has desired an improved filler metal that would minimize or eliminate DMW failures and, with the current trend toward higher boiler steam pressures and temperatures, have suitable creep strength for joining higher strength materials such as Grade 91 steels After years of research, the Electric Power Research Institute (EPRI) concluded the development and commercialization of a nickel-based filler metal, EPRI P87, for application in shielded metal arc welding (SMAW). This work describes the subsequent development of an EPRI P87 solid wire welding product for application in gas tungsten arc and gas metal arc welding (GTAW and GMAW) processes, and the initial research into the performance of DMWs produced with the new solid wire P87 product. A 135 kg heat of solid wire was produced and tested using various welding processes and evaluation methods to ensure that the material would meet required weldability and design specifications. Welding methods included GMAW-P, GTAW and hot-wire GTAW in welds up to 50 mm in thickness. The weld joint tested was a dissimilar metal weld of grade 91 to 347H, which was assessed using microstructure evaluation, creep testing, hot tensile testing, circular patch, and edge build-up investigations to examine hot-cracking susceptibility. This paper summarizes the research completed to date on the EPRI 87 filler wire which supports the acceptability of this material for its intended use in high-temperature power generation applications. [ABSTRACT FROM AUTHOR]

The joining of dissimilar materials poses a challenge in mechanical structures. The objective of this research was to investigate the effect of joining parameters such as bolt spacing, geometry configuration, and overlap length on ultimate failure strength and stiffness of composite-metal hybrid joints. Woven fiberglass/epoxy and unidirectional carbon-fiber/epoxy composites have been manufactured and tested under tensile loads to obtain their mechanical properties. Composite test coupons were joined to metal coupons of higher Young's modulus, varying the aforementioned parameters in each joint and tested to failure. It was found that the variation of the joining parameters affected unidirectional carbon-fiber/epoxy-steel joints more noticeably than the woven fiberglass-aluminum joints. [ABSTRACT FROM AUTHOR]

Shaped metal deposition is a novel technique to build near net-shape components layer by layer by tungsten inert gas welding. Especially for complex shapes and small quantities, this technique can significantly lower the production cost of components by reducing the buy-to-fly ratio and lead time for production, diminishing final machining and preventing scrap. Tensile testing of Ti-6Al-4V components fabricated by shaped metal deposition shows that the mechanical properties are competitive to material fabricated by conventional techniques. The ultimate tensile strength is between 936 and 1014MPa, depending on the orientation and location. Tensile testing vertical to the deposition layers reveals ductility between 14 and 21%, whereas testing parallel to the layers gives a ductility between 6 and 11%. Ultimate tensile strength and ductility are inversely related. Heat treatment within the α β + β phase field does not change the mechanical properties, but heat treatment within the β phase field increases the ultimate tensile strength and decreases the ductility. The differences in ultimate tensile strength and ductility can be related to the α lath size and orientation of the elongated, prior β grains. The micro-hardness and Young's modulus are similar to conventional Ti-6Al-4V with low oxygen content. [ABSTRACT FROM AUTHOR]

It has been reported that the mechanical properties and corrosion resistance of metallic alloys depend strongly on the solidification microstructural arrangement. The correlation of corrosion behavior and mechanical properties with microstructure parameters can be very useful for planning solidification conditions in order to achieve desired final properties. The aim of the present work is to investigate the influence of dendritic microstructural parameters of an Al-9 wt.% Si alloy on mechanical properties and corrosion resistance. The experimental results establish correlations between secondary dendrite arm spacings (λ2) and ultimate tensile strength (σu), yield strength (σy), corrosion potential (ECorr), and corrosion rate (iCorr). [ABSTRACT FROM AUTHOR]

The effect of additives on the degree of dispersion of a TiO2 pigment in an automotive coating layer and the consequential effects on its mechanical and surface topographical properties were investigated. The pigment was incorporated into a polyester–melamine polymer solution in a water/n-methylpyrrolidone vehicle with the aid of four different dispersants over a range of pigment loading levels up to a pigment volume concentration (pvc) of 50%. The quality of the dispersion was evaluated using scanning electron microscopy for the coatings formulated with the different dispersants. Two of the dispersants were found to produce high degrees of dispersion, while the remaining two yielded large aggregates. Surface smoothness and gloss of the cured coatings were found to correlate directly with the quality of the dispersion. The mechanical properties of the cured coatings were investigated using tensile tests which revealed that, for pigment loadings above 30% pvc, strength correlated directly with the quality of the dispersion. Crack propagation was found to occur through the matrix polymer in all cases. The structure of the crack path in well-dispersed systems was different from the path profile observed with the poorly dispersed systems. [ABSTRACT FROM AUTHOR]

The effect of additives on the degree of dispersion of a TiO2 pigment in an automotive coating layer and the consequential effects on its mechanical and surface topographical properties were investigated. The pigment was incorporated into a polyester–melamine polymer solution in a water/n-methylpyrrolidone vehicle with the aid of four different dispersants over a range of pigment loading levels up to a pigment volume concentration (pvc) of 50%. The quality of the dispersion was evaluated using scanning electron microscopy for the coatings formulated with the different dispersants. Two of the dispersants were found to produce high degrees of dispersion, while the remaining two yielded large aggregates. Surface smoothness and gloss of the cured coatings were found to correlate directly with the quality of the dispersion. The mechanical properties of the cured coatings were investigated using tensile tests which revealed that, for pigment loadings above 30% pvc, strength correlated directly with the quality of the dispersion. Crack propagation was found to occur through the matrix polymer in all cases. The structure of the crack path in well-dispersed systems was different from the path profile observed with the poorly dispersed systems. [ABSTRACT FROM AUTHOR]