This review briefly describes some of the techniques available for analysing surfaces and illustrates their usefulness with a few examples such as a metal and alloy. In particular, Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and laser Raman spectroscopy are all described as advanced surface analytical techniques. In analysing a surface, AES and XPS would normally be considered first, with AES being applied where high spatial resolution is required and XPS where chemical state information is needed. Laser Raman spectroscopy is useful for determining molecular bonding. A combination of XPS, AES and Laser Raman spectroscopy can give quantitative analysis from the top few atomic layers with a lateral spatial resolution of
It is the aim of all clinicians to accomplish biological tooth movement, which implies the use of low, continuous force. Constant unrelented search for a better wire, which can deliver optimal orthodontic force, has led to the invention of a lot of orthodontic wires such as Stainless steel, Beta Titanium, Nickel Titanium and multi stranded wires. In this study, the loading and unloading properties of 0.016 inch, 0.016x0.022 inch and 0.017x0.025 inch dimensions of stainless steel, conventional NiTi, Super elastic NiTi, and TMA arch wires were determined by means of a modified three point bending test for two inter bracket widths of 5 mm and 6.5 mm for deflection of 1 to 3 mm. The applied forces dependence on cross-sectional size differs from the linear-elastic prediction in super elastic NiTi wires. The stainless steel wires had the highest force values on all the three dimensions and cross section. On loading and unloading, TMA wires had force values in-between stainless steel, conventional NiTi and super elastic NiTi. The conventional NiTi had much lower force values compared to stainless steel and TMA and were linearly progressing compared to Super elastic NiTi. On loading and unloading the super elastic NiTi had force values in the range of conventional NiTi and had constant forces on higher deflection. The studies showed that the force value was comparatively higher in 5 mm inter bracket width than the 6.5 mm inter bracket width for all the cross section and dimension of wires.
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.
Introduction: Most patients with malocclusion are given orthodontic leveling therapy with the aim of reducing the vertical discrepancy between teeth. This computational study aims to evaluate the degree of deformation of su- perelastic NiTi arch wire upon bending at different deflections in a bracket system. Methods: A three-dimensional finite-element model of a wire-bracket system was developed to simulate the bending behavior of superelastic NiTi arch wire in three-brackets configuration. A superelastic subroutine was integrated in the model to anticipate the superelastic behavior of the arch wire. The mid span of the arch wire was loaded to different extent of deflections, ranging from 1.0 to 4.0 mm. The mechanical deformation of the arch wires was accessed from three parameters, in specific the unloading force, the bending stress and the martensite fraction. Results: The superelastic wire deflected at 4.0 mm yielded smaller unloading force than the wire bent at 1.0 mm. The bending stress was highly localized at the wire curvature, with the stress magnitude increased from 465 MPa at 1.0 mm to 951 MPa at 4.0 mm deflection. The martensite volume consistently increased throughout the bending, with a fully transformed martensite was ob- served as early as 2.0 mm of deflection. The magnitude of bending stress and the volume of fully transformed mar- tensite increased gradually in relation to the wire deflection. Conclusion: The wire-bracket system induced localize wire deformation, hindering complete utilization of superelasticity during orthodontic treatment.
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.
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.
Resistance spot welding (RSW) of dual phase (DP) steels is a challenging task due to formation of brittle martensitic structure in the fusion zone (FZ), resulting in a low energy capacity of the joint during high-rate loading. In the present study, in situ postweld heat treatment (PWHT) was carried out by employing a double pulse welding scheme with the aim of improving the mechanical performance of DP590 steel resistance spot weld joint. Taguchi method was used to optimize in situ PWHT parameters to obtain maximum peak load and failure energy. Experiments were designed based on orthogonal array (OA) L16. Mechanical performance was evaluated in terms of peak load and failure energy after performing low dynamic tensile shear (TS) test. Microstructural characterization was carried out using a scanning electron microscope (SEM). The results show that improvements of 17 and 86% in peak load and failure energy, respectively, were achieved in double-pulse welding (DPW) at optimum conditions compared to traditional single-pulse welding (SPW). The improvement in mechanical performance resulted from (i) enlargement of the FZ and (ii) improved weld toughness due to tempering of martensite in the FZ and subcritical heat affected zone (SCHAZ). These factors are influenced by heat input, which in turn depends upon in situ PWHT parameters.
The evolution of internal compressive stress from the intermetallic compound (IMC) Cu6Sn5 growth is commonly acknowledged as the key inducement initiating the nucleation and growth of tin (Sn) whisker. This study investigates the effect of Sn-0.7Cu-0.05Ni on the nucleation and growth of Sn whisker under continuous mechanical stress induced. The Sn-0.7Cu-0.05Ni solder joint has a noticeable effect of suppression by diminishing the susceptibility of nucleation and growth of Sn whisker. By using a synchrotron micro X-ray fluorescence (µ-XRF) spectroscopy, it was found that a small amount of Ni alters the microstructure of Cu6Sn5 to form a (Cu,Ni)6Sn5 intermetallic layer. The morphology structure of the (Cu,Ni)6Sn5 interfacial intermetallic layer and Sn whisker growth were investigated by scanning electron microscope (SEM) in secondary and backscattered electron imaging mode, which showed that there is a strong correlation between the formation of Sn whisker and the composition of solder alloy. The thickness of the (Cu,Ni)6Sn5 IMC interfacial layer was relatively thinner and more refined, with a continuous fine scallop-shaped IMC interfacial layer, and consequently enhanced a greater incubation period for the nucleation and growth of the Sn whisker. These verification outcomes proposes a scientifically foundation to mitigate Sn whisker growth in lead-free solder joint.
Welding parameters obviously determine the joint quality during the resistance spot welding process. This study aimed to investigate the effect of welding current and electrode force on the heat input and the physical and mechanical properties of a SS316L and Ti6Al4V joint with an aluminum interlayer. The weld current values used in this study were 11, 12, and 13 kA, while the electrode force values were 3, 4, and 5 kN. Welding time and holding time remained constant at 30 cycles. The study revealed that, as the welding current and electrode force increased, the generated heat input increased significantly. The highest tensile-shear load was recorded at 8.71 kN using 11 kA of weld current and 3 kN of electrode force. The physical properties examined the formation of a brittle fracture and several weld defects on the high current welded joint. The increase in weld current also increased the weld diameter. The microstructure analysis revealed no phase transformation on the SS316L interface; instead, the significant grain growth occurred. The phase transformation has occurred on the Ti6Al4V interface. The intermetallic compound layer was also investigated in detail using the EDX (Energy Dispersive X-Ray) and XRD (X-Ray Diffraction) analyses. It was also found that both stainless steel and titanium alloy have their own fusion zone, which is indicated by the highest microhardness value.
This paper reviews the phase structures and oxidation kinetics of complex Ti-Al alloys at oxidation temperatures in the range of 600-1000 °C. The mass gain and parabolic rate constants of the alloys under isothermal exposure at 100 h (or equivalent to cyclic exposure for 300 cycles) is compared. Of the alloying elements investigated, Si appeared to be the most effective in improving the oxidation resistance of Ti-Al alloys at high temperatures. The effect of alloying elements on the mechanical properties of Ti-Al alloys is also discussed. Significant improvement of the mechanical properties of Ti-Al alloys by element additions has been observed through the formation of new phases, grain refinement, and solid solution strengthening.
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.
Micro-turning is a micro-mechanical cutting method used to produce small diameter cylindrical parts. Since the diameter of the part is usually small, it may be a little difficult to improve the surface quality by a second operation, such as grinding. Therefore, it is important to obtain the good surface finish in micro turning process using the ideal cutting parameters. Here, the multi-objective optimization of micro-turning process parameters such as cutting speed, feed rate and depth of cut were performed by response surface method (RSM). Two important machining indices, such as surface roughness and material removal rate, were simultaneously optimized in the micro-turning of a Ti6Al4V alloy. Further, the scanning electron microscope (SEM) analysis was done on the cutting tools. The overall results depict that the feed rate is the prominent factor that significantly affects the responses in micro-turning operation. Moreover, the SEM results confirmed that abrasion and crater wear mechanism were observed during the micro-turning of a Ti6Al4V alloy.
Resistance spot welding (RSW) is one of the most effective welding methods for titanium alloys, in particular Ti-6Al-4V. Ti-6Al-4V is one of the most used materials with its good ductility, high strength, weldability, corrosion resistance, and heat resistance. RSW and Ti-6Al-4V materials are often widely used in industrial manufacturing, particularly in automotive and aerospace industries. To understand the phenomenon of resistance spot weld quality, the physical and mechanical properties of Ti-6Al-4V spot weld are essential to be analyzed. In this study, an experiment was conducted using the Taguchi L9 method to find out the optimum level of the weld joint strength. The given optimum level sample was analyzed to study the most significant affecting RSW parameter, the failure mode, the weld nugget microstructure, and hardness values. The high heat input significantly affect the weld nugget temperature to reach and beyond the β-transus temperature. It led to an increase in the weld nugget diameter and the indentation depth. The expulsion appeared in the high heat input and decreased the weld nugget strength. It was caused by the molten material ejection in the fusion zone. The combination of high heat input and rapid air cooling at room temperature generated a martensite microstructure in the fusion zone. It increased the hardness, strength, and brittleness but decreased the ductility.
In the present investigation, the non-recrystallization temperature (TNR) of niobium-microalloyed steel is determined to plan rolling schedules for obtaining the desired properties of steel. The value of TNR is based on both alloying elements and deformation parameters. In the literature, TNR equations have been developed and utilized. However, each equation has certain limitations which constrain its applicability. This study was completed using laboratory-grade low-carbon Nb-microalloyed steels designed to meet the API X-70 specification. Nb- microalloyed steel is processed by the melting and casting process, and the composition is found by optical emission spectroscopy (OES). Multiple-hit deformation tests were carried out on a Gleeble® 3500 system in the standard pocket-jaw configuration to determine TNR. Cuboidal specimens (10 (L) × 20 (W) × 20 (T) mm3) were taken for compression test (multiple-hit deformation tests) in gleeble. Microstructure evolutions were carried out by using OM (optical microscopy) and SEM (scanning electron microscopy). The value of TNR determined for 0.1 wt.% niobium bearing microalloyed steel is ~ 951 °C. Nb- microalloyed steel rolled at TNR produce partially recrystallized grain with ferrite nucleation. Hence, to verify the TNR value, a rolling process is applied with the finishing rolling temperature near TNR (~951 °C). The microstructure is also revealed in the pancake shape, which confirms TNR.
In this work, nanocrystalline Ge1-xSnx alloy formation from a rapid thermal annealed Ge/Sn/Ge multilayer has been presented. The multilayer was magnetron sputtered onto the Silicon substrate. This was followed by annealing the layers by rapid thermal annealing, at temperatures of 300 °C, 350 °C, 400 °C, and 450 °C, for 10 s. Then, the effect of thermal annealing on the morphological, structural, and optical characteristics of the synthesized Ge1-xSnx alloys were investigated. The nanocrystalline Ge1-xSnx formation was revealed by high-resolution X-ray diffraction (HR-XRD) measurements, which showed the orientation of (111). Raman results showed that phonon intensities of the Ge-Ge vibrations were improved with an increase in the annealing temperature. The results evidently showed that raising the annealing temperature led to improvements in the crystalline quality of the layers. It was demonstrated that Ge-Sn solid-phase mixing had occurred at a low temperature of 400 °C, which led to the creation of a Ge1-xSnx alloy. In addition, spectral photo-responsivity of a fabricated Ge1-xSnx metal-semiconductor-metal (MSM) photodetector exhibited its extending wavelength into the near-infrared region (820 nm).
Duplex stainless steels (DSSs) are complex materials and they have been widely used in the marine environment and gas industries, primarily offering a better resistance of pitting corrosion and good mechanical properties. In the present work, the effects of heat treatment on duplex stainless steel (DSS) weld overlay samples that were heat treated at three different temperatures, namely 350 °C, 650 °C, and 1050 °C, and followed by air cooling and water quenching were studied. Stress relief temperature at 650 °C had induced sigma phase precipitation in between delta ferrite and austenite (δ/γ) grain boundaries, resulting in the loss of corrosion resistance in the weld metal. Interestingly, post weld heat treatment (PWHT) test samples that were reheated to solution annealing temperature had shown no weight loss. The ferrite count determination in the region of weld metal overlay increased at hydrogen relief and decreased at stress relief temperatures due to slow cooling, which is more favorable to austenite formation. The amount of ferrite in the weld metals was significantly reduced with the increment of solution anneal temperature to 1050 °C because of sufficient time for the formation of austenite and giving optimum equilibrium fraction in the welds.
Automobile, aerospace, and shipbuilding industries are looking for lightweight materials for cost effective manufacturing which demands the welding of dissimilar alloy materials. In this study, the effect of tool rotational speed, welding speed, tilt angle, and pin depth on the weld joint were investigated. Aluminum 5052 and 304 stainless-steel alloys were joined by friction stir welding in a lap configuration. The design of the experiments was based on Taguchi's orthogonal array for conducting the experiments with four factors and three levels for each factor. The microstructural analysis showed tunnel defects, micro voids, and cracks which formed with 0° and 1.5° tilt angles. The defects were eliminated when the tilt angle increased to 2.5° and a mixed stir zone was formed with intermetallic compounds. The presence of the intermetallic compounds increased with the increase in tilt angle and pin depth which further resulted in obtaining a defect-free weld. Hooks were formed on either side of the weld zone creating a mechanical link for the joint. A Vickers hardness value of HV 635.46 was achieved in the mixed stir zone with 1000 rpm, 20 mm/min, and 4.2 mm pin depth with a tilt angle of 2.5°, which increased by three times compared to the hardness of SS 304 steel. The maximum shear strength achieved with 800 rpm, 40 mm/min, and a 4.3 mm pin depth with a tilt angle of 2.5° was 3.18 kN.
It is well known that three-dimensional (3D) printing is an emerging technology used to produce customized implants and surface characteristics of implants, strongly deciding their osseointegration ability. In this study, Ti alloy microspheres were printed under selected rational printing parameters in order to tailor the surface micro-characteristics of the printed implants during additive manufacturing by an in situ, controlled way. The laser path and hatching space were responsible for the appearance of the stripy structure (S), while the bulbous structure (B) and bulbous⁻stripy composite surface (BS) were determined by contour scanning. A nano-sized structure could be superposed by hydrothermal treatment. The cytocompatibility was evaluated by culturing Mouse calvaria-derived preosteoblastic cells (MC3T3-E1). The results showed that three typical microstructured surfaces, S, B, and BS, could be achieved by varying the 3D printing parameters. Moreover, the osteogenic differentiation potential of the S, B, and BS surfaces could be significantly enhanced, and the addition of nano-sized structures could be further improved. The BS surface with nano-sized structure demonstrated the optimum osteogenic differentiation potential. The present research demonstrated an in situ, controlled way to tailor and optimize the surface structures in micro-size during the 3D printing process for an implant with higher osseointegration ability.
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.
Implants are widely used in the human body for the replacement of affected bones. Fatigue failure is one of the serious concerns for implants. Therefore, understanding of the underlying mechanism leading to fatigue failure is important for the longevity of biomaterial implants. In this paper, the fracture toughness and fatigue crack growth of titanium alloy biomaterial Ti-27Nb has been experimentally investigated. The Ti-27Nb material is tested for fatigue crack growth in different environmental conditions representing the ambient and in vitro environments for 504 hours and 816 hours, respectively. Fractography of the tested specimen is conducted using Scanning Electron Microscope (SEM). The results of the fatigue crack growth propagation of the ambient and in vitro samples are similar in the Paris crack growth region. However, in the threshold region, the crack growth rate is higher for the Simulated Body Fluid (SBF) treated specimen. The fracture surface morphology of in vitro samples shows brittle fracture as compared to ambient specimens with significant plasticity and striations marks. It is proposed that a similar investigation may be conducted with specimens treated in SBF for prolonged periods to further ascertain the findings of this study.