In this work, the Sandvik uncoated carbide insert, CNGG 120408-SGF-H13A was used as a cutting tool in high-speed turning of titanium alloy Ti-6A1-4V EH (extra-low interstitial) with hardness of 32 HRC. Wear is one of the problems that cannot be avoided in machining process. Therefore, the objective of this paper was to investigate tool-wear behavior of various cutting-speed values (high-speed range) on the tool life of the cutting tools, especially in finishing titanium alloy. The experiments were performed under flooded coolant condition using water-based mineral-oil. The cutting speeds employed were 120, 170 and 220 mlmin. The feed rate was constant at 02 mm/rev and the depth of cut was 0.4 mm. Based on the results, the highest cutting speed of 220 m/min caused the highest wear rate. By linking the machine operations and the tool life curves obtained using flank wear data, the wear behavior of uncoated carbide was described.
The anti-corrosion performances of single(TEOS) and hybrid (APTES-TEOS) sol-gel coatings on Al alloy samples exposed to 3.5 wt% NaCl were evaluated employing electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The data acquired using the three corrosion analysis techniques were in accordance with each other where hybrid sol-gel coating offered the lowest corrosion rate and current density in comparison to the single precursor silanol coating. Tafel curves suggested that the hybrid silane coatings mitigate both the anodic and cathodic reactions simultaneously (mixed type inhibitor). These techniques justified that incorporation of hybrid sol-gel improved the Al corrosion protection performance considerably.
Newly prepared titanium alloy (Ti-13Zr-13Nb (TZN)) using powder metallurgy is considered in this investigation. Titanium alloys (TZN) are used in hip and knee replacement for orthopedic implants. Conventional machining, TZN alloys produce higher tool wear rate and poor surface quality, but this can be reduced by Electrical Discharge Machining (EDM) method. Moreover, EDM produce good biological and corrosion resistant surface. In this research, experiments were conducted by considering the influential process factors such as pulse on time, pulse off time, voltage, and current. The experiments were designed based on Response Surface Methodology (RSM) of face centered central composite design. Analysis of Variance (ANOVA) was conducted to identify the significance process factors and their relation to output responses such as Electrode Wear Rate (EWR), Surface Roughness (SR) and Material Removal Rate (MRR). Further, an empirical model was developed by RSM in order to predict the output responses.
The mechanical properties of Dual Phase Steel (DPS)-duplex structure-produced by quenching in pre-heated bitumen have been investigated. Medium carbon steels intercritically heated at different temperatures and holding times were quenched in hot bitumen. Optical and scanning electron microscopy characterisation of the duplex structure showed extensive network of fibrous martensite in a ferritic matrix with occasional presence of polygonal martensite. The duplex phase structure exhibited continuous yielding dynamics, improving the tensile and hardness values by about 42 and 35%, respectively, relative to the normalised structure. But, the elongation and impact values decreased by about 42 and 50%, respectively, when compared to the normalised structure. These values are similar to those obtained in duplex structure produced using conventional oil quenching. The tensile fractured surface showed transition between a predominantly cleavage mode in the lower annealing temperature to a mixed mode in the upper bound of the annealing temperature. These findings suggest that pre-heated bitumen can be exploited for the production of DPSs.
A single paragraph of about 200 words maximum. For research articles, abstracts should give a pertinent overview of the work. We strongly encourage authors to use the following style of structured abstracts, but without headings: (1) Background: Place the question addressed in a broad context and highlight the purpose of the study; (2) Methods: Describe briefly the main methods or treatments applied; (3) Results: Summarize the article's main findings; and (4) Conclusions: Indicate the main conclusions or interpretations. The abstract should be an objective representation of the article, it must not contain results which are not presented and substantiated in the main text and should not exaggerate the main conclusions. Please add in this section. The aim of the study was to investigate the fracture behaviour of four different groups of zirconia abutments with internal and external connections: (A) Astra Tech ZirDesign™ abutment on Astra Tech Implants, (B) Procera® Esthetic abutment on Nobel Biocare MK III Groovy Implants, (C) IPS e.max® on Straumann Implants, and (D) ZiReal® Posts on Biomet 3I implants. The load was applied on the assemblies using a Zwick universal testing machine: the initial and final failure loads and amplitude were recorded using acoustic emission technique. Mean initial and final failure force was found to be significantly different in each group (P < 0.001). IPS e.max® Straumann abutments exhibited the highest resistance to final fracture force compared to other abutment types. Acoustic emission can be used as one of the methods to detect fracture behaviour of implant abutments. There were no significant differences in fracture loads between the internal and externally connected zirconia abutments studied. However, externally connected abutments demonstrated screw loosening and some deformations.
The significant increase in metal costs has forced the electronics industry to provide new materials and methods to reduce costs, while maintaining customers' high-quality expectations. This paper considers the problem of most electronic industries in reducing costly materials, by introducing a solder paste with alloy composition tin 98.3%, silver 0.3%, and copper 0.7%, used for the construction of the surface mount fine-pitch component on a Printing Wiring Board (PWB). The reliability of the solder joint between electronic components and PWB is evaluated through the dynamic characteristic test, thermal shock test, and Taguchi method after the printing process. After experimenting with the dynamic characteristic test and thermal shock test with 20 boards, the solder paste was still able to provide a high-quality solder joint. In particular, the Taguchi method is used to determine the optimal control parameters and noise factors of the Solder Printer (SP) machine, that affects solder volume and solder height. The control parameters include table separation distance, squeegee speed, squeegee pressure, and table speed of the SP machine. The result shows that the most significant parameter for the solder volume is squeegee pressure (2.0 mm), and the solder height is the table speed of the SP machine (2.5 mm/s).
Driven by the trends towards miniaturization in lead free electronic products, researchers are putting immense efforts to improve the properties and reliabilities of Sn based solders. Recently, much interest has been shown on low silver (Ag) content solder SAC105 (Sn-1.0Ag-0.5Cu) because of economic reasons and improvement of impact resistance as compared to SAC305 (Sn-3.0Ag-0.5Cu. The present work investigates the effect of minor aluminum (Al) addition (0.1-0.5 wt.%) to SAC105 on the interfacial structure between solder and copper substrate during reflow. The addition of minor Al promoted formation of small, equiaxed Cu-Al particle, which are identified as Cu₃Al₂. Cu₃Al₂ resided at the near surface/edges of the solder and exhibited higher hardness and modulus. Results show that the minor addition of Al does not alter the morphology of the interfacial intermetallic compounds, but they substantially suppress the growth of the interfacial Cu₆Sn₅ intermetallic compound (IMC) after reflow. During isothermal aging, minor alloying Al has reduced the thickness of interfacial Cu₆Sn₅ IMC but has no significant effect on the thickness of Cu₃Sn. It is suggested that of atoms of Al exert their influence by hindering the flow of reacting species at the interface.
Laser shock processing (LSP) is an innovative surface treatment technique with high peak power, short pulse, and cold hardening for strengthening metal materials. LSP is based on the application of a high intensity pulsed laser beam (I > 1 GW/cm(2); t < 50 ns) at the interface between the metallic target and the surrounding medium (a transparent confining material, normally water) forcing a sudden vaporization of the metallic surface into a high temperature and density plasma that immediately develops inducing a shock wave propagating into the material. The shock wave induces plastic deformation and a residual stress distribution in the target material. In this paper we study the increase of microhardness and surface roughness with the increase of laser pulse energy in 2024-T3 Al alloy. The influence of the thickness of the confining layer (water) on microhardness and surface roughness is also studied. In addition, the effect of LSP treatment with best conditions on wear behaviors of the alloy was investigated.
There has been, and is still, concern about the high elastic modulus of Ti alloys compared to bone. Any reduction in the Young's modulus value of the implant is expected to enhance stress redistribution to the adjacent bone tissues, minimize stress shielding and eventually prolong device lifetime. Dynamic Monte Carlo simulation is used to predict the gradual reduction in Young's modulus values between the bulk of Ti alloys and the modified surface layers due to Ca ion implantation. The simulation can be used as a screening step when applying new alloys and/or coatings.
This article reports the in vitro degradation and cytotoxicity assessment of Zn-3Mg alloy developed for biodegradable bone implants. The alloy was prepared using casting, and its microstructure was composed of Mg2Zn11 intermetallic phase distributed within a Zn-rich matrix. The degradation assessment was done using potentiodynamic polarization and electrochemical impedance spectrometry. The cell viability and the function of normal human osteoblast cells were assessed using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and alkaline phosphatase extracellular enzyme activity assays. The results showed that the degradation rate of the alloy was slower than those of pure Zn and pure Mg due to the formation of a high polarization resistance oxide film. The alloy was cytocompatible with the normal human osteoblast cells at low concentrations (<0.5 mg/mL), and its alkaline phosphatase activity was superior to pure Mg. This assessment suggests that Zn-3Mg alloy has the potential to be developed as a material for biodegradable bone implants, but the toxicity limit must be carefully observed.
Stainless steel wrought wires used as clasp arms for removable partial dentures in Thailand were compared with those used in some other countries (in the as-received condition) in terms of flexibility, Vickers microhardness and composition. The results showed that there were significant differences (P< or =0.05) among the wires. A Japanese stainless steel wire (SK) was obviously different from the others. It had the lowest proportional limit and microhardness, but its flexibility was almost the same. The chemical composition of each wire was not greatly different. The wires were about 18-20 wt% chromium and 8-9 wt% nickel, except for the SK wire, which had about 12 wt% nickel.
The purpose of this in vitro study was to determine if packable resin composite with/without flowable resin composite has the ability to prevent coronal leakage in restored endodontic access openings following aging.
Matched MeSH terms: Dental Alloys/chemistry; Metal Ceramic Alloys/chemistry*
This paper deals with a review of the inhibition activity of a Schiff bases on the deterioration of mild steel in hydrochloric acid media. Two Schiff base ligands namely N,N’- Bis(salicylidene) ethylenediamine (Sadimine) and N,N’-Bis(bromosalicylidene)- ethylenediamine (Brosadimine) were synthesized from the condensation reactions of salicylaldehyde or 5-bromosalicylaldehyde with ethylenediamine respectively and evaluated as corrosion inhibitor for mild steel in 1 M HCl solution using weight loss method. The use of inhibitors is one of the most practical methods for protection of mild steel against corrosion in acidic media. Schiff bases are widely being employed in such applications. This paper highlights the influence of structure–inhibition activity relationship of Schiff base compounds
on their performance as corrosion inhibitors of mild steel in acid media. Sadimine and
Brosadimine show appreciable corrosion inhibition efficiency against the corrosion of mild
steel in 1 M HCl solution at room temperature. It has been found that Brosadimine shows
greater corrosion inhibition efficiency than Sadimine due to extra halogen group presence in
the structure. As the concentration of studied inhibitors increases, the corrosion inhibition
efficiency of the prepared compounds also increases. This study demonstrated that corrosion
inhibitors for metals and alloys can preserve the quality and life of metals from corrosion.
Stainless steels are increasingly used in construction today, especially in harsh environments, in which steel corrosion commonly occurs. Cold-formed stainless steel structures are currently increasing in popularity because of its efficiency in load-bearing capacity and its appealing architectural appearance. Cold-rolling and press-braking are the cold-working processes used in the forming of stainless steel sections. Press braking can produce large cross-sections from thin to thick-walled sections compared to cold-rolling. Cold-forming in press-braked sections significantly affect member behaviour and joints; therefore, they have attained great attention from many researchers to initiate investigations on those effects. This paper examines the behaviour of residual stress distribution of stainless steel press-braked sections by implementing three-dimensional finite element (3D-FE) technique. The study proposed a full finite element procedure to predict the residual stresses starting from coiling-uncoiling to press-braking. This work considered material anisotropy to examine its effect on the residual stress distribution. The technique adopted was compared with different finite element techniques in the literature. This study also provided a parametric study for three corner radius-to-thickness ratios looking at the through-thickness residual stress distribution of four stainless steels (i.e., ferritic, austenitic, duplex, lean duplex) in which have their own chemical composition. In conclusion, the comparison showed that the adopted technique provides a detailed prediction of residual stress distribution. The influence of geometrical aspects is more pronounced than the material properties. Neglecting the material anisotropy shows higher shifting in the neutral axis. The parametric study showed that all stainless steel types have the same stress through-thickness distribution. Moreover, R/t ratios' effect is insignificant in all transverse residual stress distributions, but a slight change to R/t ratios can affect the longitudinal residual stress distribution.
The enhancement of microwave absorbing properties in nickel zinc ferrite (Ni0.5Zn0.5Fe2O4) via multiwall carbon nanotubes (MWCNT) growth is studied in this research work. Ni0.5Zn0.5Fe2O4 was initially synthesized by mechanical alloying followed by sintering at 1200 °C and the microstructural, electromagnetic and microwave characteristics have been scrutinized thoroughly. The sintered powder was then used as a catalyst to grow MWCNT derived from chemical vapor deposition (CVD) method. The sample was mixed with epoxy resin and a hardener for preparation of composites. The composite of multi-walled carbon nanotubes/Ni0.5Zn0.5Fe2O4 shown a maximum reflection loss (RL) of -19.34 dB at the frequency and bandwidth of 8.46 GHz and 1.24 GHz for an absorber thickness of 3 mm for losses less than -10 dB. This acquired result indicates that multi-walled carbon nanotubes/Ni0.5Zn0.5Fe2O4 could be used as a microwave absorber application in X-band.
Effects of processing parameters on preheated (heat-assisted) clinching process to join aluminum alloy 5052-H32 (AA5052) and thermoplastic carbon-fiber-reinforced-plastic (TP-CFRP) sheets for cross-tension (CT) specimens were first studied. Preheating was critical since brittle TP-CFRP could be softened to avoid fracturing or cracking during clinching process. Four processing parameters, including punching force, die depth, heating mode, and heating temperature, were considered. Quasi-static tests and microscope observations were taken to evaluate AA5052/TP-CFRP clinch joints in CT specimens and determine appropriate processing parameters for fatigue tests. Finally, fatigue data and failure mode of clinch joints in CT specimens were obtained and discussed.
Introduction: Post-implantation rod deformation is anticipated in scoliosis surgery but the difference in rod deformation between titanium and cobalt chrome rod has not been elucidated. This study aims to compare the difference in rod deformation between two groups. Materials and Methods: Twenty-one adolescent idiopathic scoliosis (AIS) patients were recruited from a single center. The over-contoured concave rods were traced prior to insertion. Post-operative sagittal rod shape was determined from lateral radiographs. Rod deformation was determined using maximal rod deflection and angle of the tangents to rod end points. The differences between pre- and post-operative rod contour were analysed statistically. Rod deformation and thoracic kyphosis between two types of implants were analysed. Results: Both rods exhibited significant change of rod angle and deflection post-operatively. Curvature of the titanium rod and cobalt chrome rod decreased from 60.5° to 37°, and 51° to 28° respectively. Deflection of titanium rod and cobalt chrome rod reduced from 28mm to 23.5mm and 30mm to 17mm respectively. There was no significant difference between titanium and cobalt chrome groups with regard to rod angle (p=0.173) and deflection (p=0.654). Thoracic kyphosis was increased from 20° to 26° in titanium group but a reduction from 25° to 23° was noticed in cobalt chrome group, but these findings were not statistically significant. Conclusion: There was no statistical difference in rod deformation between the two groups. Thus, the use of titanium rod in correction of sagittal profile is not inferior in outcome compared with cobalt chrome but with lower cost.
Introduction: Coated archwires improve aesthetics during orthodontic treatment. However, little is known regarding
their clinical benefit. This randomised controlled trial (RCT) compared the tooth alignment (TA), coating loss (CL),
colour change (∆E*), and patient perception of coated archwires with their controls. Details of ∆E* and perception were reported in the second part of the articles. Methods: This RCT was done at three centres. Participants
were randomised to receive one of four treatment interventions using 0.014” superelastic coated nickel-titanium
archwires from Orthocare, RMO, G&H, and conventional uncoated 3M Unitek® archwires. These archwires were
ligated during bonding and collected after eighth week and questionnaires were distributed to participants in the
experimental groups only. After removal, TA and CL were measured using Little’s Irregularity Index and Autodesk®
AutoCAD® software, respectively. At the time of this preliminary reporting, 84 participants had completed the trial. Two archwires fractured and were excluded. Therefore, 166 archwires (n = 166) were analysed. Results: Only
non-extraction cases showed statistically significant differences in TA change between all groups (p = 0.005) and
RMO showed significantly lowest mean of TA (1.5 mm). RMO and Orthocare showed significant TA change in the
upper and lower arches (p = 0.037, 0.048). CL was found to be insignificant for both extraction and non-extraction
cases (p >0.05). Comparison between upper and lower arches revealed no significant difference in TA and CL in all
groups (p >0.05). Conclusion: From this preliminary analysis, Orthocare provides better TA in non-extraction cases
despite highest percentage of coating loss.
This paper presents a multitasking electrical impedance tomography (EIT) system designed to improve the flexibility and durability of an existing EIT system. The ability of the present EIT system to detect, locate, and reshape objects was evaluated by four different experiments. The results of the study show that the system can detect and locate an object with a diameter as small as 1.5 mm in a testing tank with a diameter of 134 mm. Moreover, the results demonstrate the ability of the current system to reconstruct an image of several dielectric object shapes. Based on the results of the experiments, the programmable EIT system can adapt the EIT system for different applications without the need to implement a new EIT system, which may help to save time and cost. The setup for all the experiments consisted of a testing tank with an attached 16-electrode array made of titanium alloy grade 2. The titanium alloy electrode was used to enhance EIT system's durability and lifespan.
The search for a high temperature lead-free solder replacement for high temperature leaded solder eutectic alloy has been an evolving process as the threat of a regional lead ban became a reality in July 2006. The advantages and disadvantages of lead-free solder in terms of manufacturing, performance and reliability have been increasingly revealed through companies’ Research and Development (R&D), industrial consortia and university researchers. Materials and component design are the primary criteria to focus on the development for the current generation of high temperature lead-free solder alloys. According to the current status of high temperature lead free soldering, there are many unsolved technical problems such as explanation on the lift-off phenomenon, establishment of high temperature lead-free plating technology, construction of a database of physical properties (solder, parts, PCBs), standardization of high temperature solder materials evaluation technology, and most importantly, the best candidate material for high temperature solder. Clearly, high temperature soldering is one of the unsolved problems of the century in lead-free soldering. Moreover, most of the questions still remain unanswered by researchers. This paper reviews research conducted on the Bi-Ag solder alloy, which is one of the candidate alloys that has been proposed as an alternative for high temperature lead-free solder.