Microstructural adaptation of cast iron alloys by inoculation is a well-known practice to swell their mechanical properties. In foundries, several inoculants have been used to refine grain structure, and to obtain uniform distribution of graphite flakes. Inoculation is one of the most critical steps in cast iron production. The effectiveness of inoculants depends on melt temperature, method of addition, type of inoculants, and holding time. In this paper, the effect of Ca-based, Ba-based, Ca-Ba based and Sr-based inoculants on microstructure and tensile properties of grey cast iron IS-210 and spheroidal graphite iron IS-1862 is reported. Results showed both Ca and Ba based inoculants were effective in obtaining uniform distribution of flaky and nodular graphite in IS-210, and IS-1862 cast irons, respectively. But in a case of Sr-based inoculant were highly effective for increase the nodularity of SG cast iron as well as succeed supreme yield strength for both grey and ductile cast iron. The amounts of ferrite in the as-cast matrix are excess with controlled granulometry for elimination of primary carbide in Sr-based inoculant.

Nitinol shape memory alloy is well known for its shape memory effect and super elastic effect. In the present work, the improvement of mechanical properties of nitinol alloy like yield strength, ultimate tensile strength and micro-hardness is discussed along with the study of evolution of micro-structure after every pass to extend the applications of shape memory alloys into high strength application areas. Severe plastic deformation processes are usually adopted for producing fine grain structures which improve the mechanical properties of a material. One such severe deformation process is constrained groove pressing, which is considered as one of the best severe plastic deformation techniques for sheet metals. The results of constrained groove pressing process on nitinol alloy show that the yield strength and the ultimate tensile strength have increased by about 3.6 times 2.5 times respectively, with an increment of 50% and 74% in micro-hardness after 1 st pass of constrained groove pressing and 2 nd pass of constrained groove pressing respectively. Microstructure shows increase in martensitic phase after constrained groove pressing processing. Increasing in twinning and grain boundary density can be observed in constrained groove pressing processed nitinol, which are the reasons for the tremendous increase in the strength of the alloy. Thus, the constrained groove pressing process on nitinol alloy can increase its range of application for high strength requirements.

A method to fabricate high temperature protective structural coating on top of critical gas turbine components by additive manufacturing (AM) technique using oxide dispersion strengthening (ODS) powder is presented. A novel combined mechanochemical bonding (MCB) plus ball milling (BM) process is utilized to produce ODS powders with nano-crystalline gamma prime phase. AM-assisted ODS coating by direct energy deposition (DED) method on MAR-247 substrate, with laser powers from 100W to 200W were carried out. The ODS coated samples were then subjected to cyclic thermal loadings for over 2000 cycles. Depth-profiling x-ray photoelectric spectroscopy (DP-XPS) was applied for detailed oxide formation analyses through the ODS coating layer at various thermal cycles. Corresponding mechanical properties such as Young’s modulus, yield strength and hardening component of ODS coating samples at various thermal cycles were measured at room temperature using an in-house developed non-destructive spherical micro-indentation testing method. Correlation of the measured mechanical properties with evolution of the ODS microstructures are studied. In particular, stability of gamma prime phase in the ODS coating after thermal cycles is analyzed. Test results revealed a thin steady durable alpha alumina oxide layer on ODS coating surface. After 2,200 thermal cycles, strong bonding at ODS/substrate interface is maintained for ODS coated samples with 200W laser power. Test results also showed stable substrate microstructures due to the protective ODS coating even after 2,200 thermal cycles.

The Pulsed Gas Metal Arc Welding (P-GMAW) process is used in high-technology industrial applications and it is one of the most significant arc welding processes. The quality, productivity and cost of welding will be affected by the P-GMAW welding input process parameters and are considered to the most important factors. It is necessary to determine the input and output relationship of the welding processes in order to understand and control the P-GMAW welding process parameters. P-GMAW is widely used process, especially in thin sheet metal industries. It offers an improvement in quality and productivity over regular Gas Metal Arc Welding (GMAW). The process enables stable spray transfer with low mean current and low net heat input. This paper describes the estimation and comparison of welding process parameters viz., current, gas flow rate and wire feed rate on ultimate tensile strength, yield strength, percentage of elongation and hardness. Experiments have been performed based on Taguchi’s L 27 standard orthogonal array. Estimation of welding performances have been carried out using sophisticated mathematical models viz., MRA and GMDH, and, compared. The GMDH algorithm is designed to learn the process by training the algorithm with the experimental data. Three different criterion functions, viz., regularity, unbiased and combined criterions were considered for estimation in GMDH. Different GMDH models can be obtained by varying the percentage of data in the training set and the best model can be selected from these, viz., 50%, 62.5% and 75%. Estimation and comparison of welding performances were carried out using MRA and GMDH techniques.

This paper presents the findings of destructive compression testing on Formlabs © CLEAR Resin FLGPCL02 and TOUGH Resin FLTOTL03. Compression testing ASTM D695-15 was chosen because of the extreme fragility of the Clear Resin which did not allowed proper tensile testing with our equipment. The material was subjected to a steadily increasing compressive load until complete failure occurred. Five mechanical properties were extracted from stress versus strain curves. The five experimental properties, of Formlabs © CLEAR resin, found were young’s modulus (1.52 GPa) (std = 71 MPa), yield strength (39.6 MPa) (std = 2 MPa), ultimate strength (255 MPa) (std = 35 MPa), strain at fracture (0.509 m/m) (std = 0.0159 m/m), and toughness (49.1 J/m −3 ) (std = 3.9 J/m −3 ). The five experimental properties, of Formlabs © TOUGH resin, found were secant modulus (73.9 MPa) (std = 0.87 MPa), yield strength (42.8 MPa) (std = 3.03MPa), ultimate strength (587 MPa) (std = 61 MPa), strain at fracture (0.686 m/m) (std = 0.0097 m/m), and toughness (65 J/m −3 ) (std = 6 J/m −3 ). These were then compared to Formlabs © public released values.

Ni-base superalloys are widely used for various power plants and jet engines. Since the operating temperature of thermal plants and equipment has been increasing to improve their thermal efficiency for decreasing the emission of carbon-dioxide, the initially designed microstructure was found to change gradually during their operation. Since this change of microstructure should deteriorate the strength of the materials, sudden unexpected fracture should occur during the operation of the plants and equipment. Therefore, it is very important to clarify the dominant factor of the change of the microstructure and the relationship between the microstructure and its strength for assuring the stable and reliable operation of the plants and equipment. In this study, the change of the strength of a grain and a grain boundary of Ni-base superalloys caused by the change of their microstructure was measured by using a micro tensile test system in a scanning ion microscope. A creep test was applied to bulk alloys at elevated temperatures and a small test sample was cut from the bulk alloy with different microstructure caused by creep damage by using focused ion beams. The test sample was fixed to a silicon beam and a micro probe, respectively, by tungsten deposition. Finally, the test sample was thinned to 1μm and the sample was stretched to fracture at room temperature. The change of the order of atom arrangement of the sample was evaluated by applying electron back-scatter diffraction (EBSD) analysis quantitatively. In this study, the quality of grains in Ni-base superalloys was analyzed by using image quality ( IQ ) value calculated by using Hough transform of the observed Kikuchi pattern. It was found that the order of atom arrangement was deteriorated monotonically during the creep tests and this deterioration corresponded to the change of the microstructure clearly. Both the yield strength and the ultimate tensile strength of a grain in the alloys decreased drastically with the change of the microstructure, in other words, the IQ value of the grains. There was a clear relationship between the IQ value of a grain and its strength. Therefore, this IQ value is effective for evaluating the crystallinity of the alloys and the remained strength of the damaged alloys. The change of the microstructure was dominated by the strain-induced anisotropic accelerated diffusion of component elements of the alloys and the activation energy of the diffusion was determined quantitatively as a function of temperature and the applied stress.

In this work, a new model of a recumbent bike with the tensegrity method is developed, where all elements in tension are substituted for steel cables, to improve the weight of the vehicle and to absorb some of the impacts of the tires, since the cable works as a shock absorber. The aim of this study is to determine the structural strength of each of the elements of the recumbent vehicle and to establish dimensions and construction materials. The model is divided in 6 different elements, applying the equivalent loads and constrains to simulate the interaction with other elements, the user and the road, based on the HPVC 2017 rules [1]. Results show that in the analyzed sections, the maximum Von Mises stress obtained for all elements is 116 MPa, obtaining a minimum safety factor of 2.37 against tensile yield strength. Finally, through this work it is possible to apply the finite element method for failure analysis of each of the components of a recumbent vehicle and maximize its weight and resistance.

The quality of grains and grain boundaries of polycrystalline copper thin films was analyzed by using image quality (IQ) value obtained from the observed Kikuchi pattern by applying electron back-scatter diffraction (EBSD) analysis. It is considered that the IQ value strongly correlates with the order of atomic configuration in the observed area, in other words, density of various defects, and thus, the area with high IQ value was defined as the area with high crystallinity. The yield strength of a grain was measured by using micro tensile test system in a scanning electron microscope. A bicrystal structure which had two grains with different IQ values was cut from a copper thin film by using focus ion beam (FIB) and the sample was fixed to a single-crystalline silicon beam and a micro probe, respectively, by tungsten deposition. Finally it was thinned to 1μm and stretched to fracture at room temperature. In this micro tensile test, however, the tungsten deposition on the side surface of the test samples caused serious error on the measured strength. Therefore, in this study, the experimental method was improved by the development of an effective method for elimination the excess tungsten deposition. During the tensile test, a mass of plastic deformation and necking phenomenon were obviously observed. Ductile fracture always occurred in the grain with higher Schmidt factor. It was found that the yield strength of a copper grain decreased monotonically with the increase in the IQ value when the IQ value at the grain boundary was larger than 3500.

The reputation of additive manufacturing technology has increased dramatically in recent years due to its freedom of design, customization, and waste minimization. The growing demand for complex profile components to achieve more economic and strength-to-weight efficient aero-engine components can be met by additive manufacturing technology. In this study, electron beam melting (EBM), a powder bed additive layer manufacturing process, is used to manufacture Ti-6Al-4V tensile specimens. The Ti-6AL-4V alloy has excellent corrosion and high temperature resistance with a high strength-to-weight ratio. It is widely used in the power generation, aerospace, and medical industries. An Arcam Ti-6Al-4V prealloyed powder with particle sizes ranging from 45μ–100μ is used in an Arcam A2 machine to manufacture three specimens at zero degree manufacturing orientation. The zero degree manufacturing orientation is expected to exhibit a higher strength over other orientations. The EBM manufacturing parameters were set at 15mA current and 4530 mm/sec beam speed. Tensile tests were performed at room temperature (25.5°C) under a strain rate of 0.003 mm/mm/min according to the ASTM E8 standard for strain-rate sensitive materials. Stress-strain curves are plotted and discussed. Tensile test results indicate a tensile strength of 1.2 GPa and an elongation of 8% approximately. Three Dimensional Digital Image Correlation (3D-DIC) is used to measure the full strain field and deformation evolution on the surface of the specimens. The 3D-DIC system compares digital photographs (taken at two different angles simultaneously) of the surface of a specimen and calculates the deformation and strain fields. Using the strain fields the mechanical properties are determined by the relationships in the strain tensor. The tensile test results show that for a zero degree manufacturing orientation, the yield strength (YS) and ultimate tensile strength (UTS) are higher than that typically reported for wrought products. Fractography using optical microscopy (OM) and Scanning Electron Microscopy (SEM) were conducted. Micrographs of transverse section of the specimen were obtained to identify and analyze the failure mechanism that took place during testing. The built direction, presence of voids, manufacturing defects, and unmelted particles are observed from the SEM views. Surface roughness and microstructure were observed in the OM. A comparison of the obtained results with the literature for additively manufactured Ti-6Al-4V and possible causes are discussed.

A redesign of the intake manifold on a turbo engine transformed from naturally-aspirated engine was conducted. A new intake manifold geometry was proposed to meet both the flow uniformity and structural strength requirements. Additionally, the new intake manifold design has to meet power and torque performance requirements. In order to perform this study, a systematic design methodology was proposed. One-dimensional characteristic analysis was firstly conducted using the commercial software GT-Power, by which the intake manifold length and the pressure stabilizing cavity volume were determined. The results indicate that the intake manifold length and the pressure stabilizing cavity volume have limited effect on the engine performance. Next, the commercial computational fluid dynamics (CFD) software ANSYS Fluent was utilized to simulate the flow characteristics inside the intake manifold to investigate the flow uniformity and the pressure drop. With the newly designed geometry for the intake manifold, the maximum flow uniformity coefficient is 1.83%. This is lower than the standard requirement of 3%. Due to the fact that the intake manifold for the turbo engine will experience larger pressure than the original naturally-aspirated engine, the strength and the mode frequency of the new intake manifold design were verified by using the commercial finite element analysis (FEA) software Abaqus. The maximum stresses at internal and external of intake manifold structure were 110 MPa and 93 MPa respectively, which are lower than the yield strength. Additionally, the frequencies of the first mode and second mode are 159.87 Hz and 237.10 Hz respectively, which indicates that a physical support may be needed. This comprehensive design methodology will ensure the performance of an intake manifold design for a turbo engine transformed from a naturally-aspirated engine is met.

Finite Element Analysis (FEA) has been performed on variety of a driveshaft and universal joints based on different shaft materials and shaft different operating angles. A driveshaft is particularly useful in applications such as taking of transferring torque from one piece of equipment to the other such as in vehicle of all kinds. A driveshaft transfers torque from the transmission to the rear end differential since these two pieces of equipment cannot be connected directly. The driveshaft has universal joints located on both ends of the shaft to allow for fluctuations in the angle of the transmission and rear differential. The driveshaft alone is composed of two parts, a female and male end, connected by a spline to allow changes in the length during operation. The driveshaft must be able to withstand the constant torque that is being applied throughout operation in order to increase safety for the operator and machine. Having a lower polar moment of inertia allows the driveshaft to turn with a lower torque value compared to a driveshaft with a higher moment of inertia. It is noted that driveshaft can be manufactured into a variety of lengths and diameters depending on the use and equipment it will be supporting. This paper describes a method of finite element implemented on variations of driveshaft and universal joints. Effect of material properties, geometry and operating angle of the driveshaft were considered for this numerical investigation. Five different materials such as structural steel, aluminum alloy, polyethylene, titanium, and carbon fiber with an outer diameter of 1.5 in of the driveshaft was used for this analysis. The effect of both metals and composite materials was observed. Based on the analysis it was found that a 15° operating angle allowed for the longest life cycle of the driveshaft, while the carbon fiber composite presented the highest stress resistance and safety factor, approximately 6 GPa of yield tensile strength and a safety factor of 15. It was also found that titanium had an equivalent safety factor of 15. However, the tensile yield strength of titanium was much lower than that of its composite counterpart. All of the numerical experimentation was done using the Finite Element Analysis software ANSYS. Material properties for all materials were preset in the software except the composite carbon fiber whose properties were easily found from other research papers and experiments. Based on the data collected and the general assumptions that the most effective drive shaft is the one that lasts the longest. It can be concluded that a driveshaft made of carbon fiber operating at an angle of 15° presents the optimum driveshaft design.

Laser assisted additive manufacturing (LAAM) is regarded as a complementary manufacturing method to traditional manufacturing technologies. Meantime, improving the mechanical performance of components fabricated by LAAM is an important research focus in recent years and it has drawn significant attention from both industrial and research aspects. In the present study, in order to obtain high-performance metal components by LAAM, nano-TiC particles are used to reinforce Inconel 718 and the mixed raw powder is processed by selective laser melting (SLM) technique. To investigate the effect of TiC amount on the property and performance of the composite, samples with four levels of nano-TiC addition (0, 0.4, 0.8 and 1.6 wt.%) are prepared, all other manufacturing parameters are set fixed. Furthermore, standard solid solution treatment at 980 °C for 1 hour is carried out to investigate its effect on the final properties. SEM observations are performed to analyze the microstructure of the composites. In addition, to understand the reinforcing mechanism of nano particles in LAAM-produced metal composites at both as-built and heat treated state, we consider four main strengthening mechanisms, (a) load-bearing effect, (b) enhanced dislocation density due to the residual plastic strain caused by the difference in the coefficients of thermal expansion (CTE) between the matrix and reinforcing particles, (c) Orowan strengthening effect, and (d) Hall-Petch strengthening. The effect of TiC nano particle amount on each of the four strengthening mechanisms is investigated separately and the results show that within the investigated range, the increase of reinforcement content leads to higher tensile strength. With 1.6 wt.% reinforcement, the ultimate tensile strength increases by 15%. At as-built condition, the composites have the maximum yield strength (YS) and ultimate tensile strength (UTS), while for solution treated samples, the tensile strengths are overall lower due to microstructure coarsening. Through quantitative investigation, it is found that both as-built and solution treated conditions, the load-effect strengthening effect is very small as compared with other contributors. Thermal mismatch strengthening effect is most significant at any volume fraction under as-built condition, mainly due to high SLM temperature. However, for solution-treated condition, CTE mismatch strengthening is weakened because solution treatment significantly equilibrates the thermal strain in the composite, and diminishes most strain-induced dislocations. However, Hall-Petch strengthening becomes dominating as large amount of nanoparticles effectively inhibit the grain coarsening during solution treatment.

The thermal management capability of various candidates of micro-pin fin arrays is investigated. An integrated circuit having a footprint of 4 × 3 mm with micro-pin fin array having circular, airfoil and convex cross-section is considered. The three pin fin cross-sections along with the cooling schemes are optimized to handle a uniform heat flux of 500 W/cm 2 applied to the top surface of the electronic chip. A fully three-dimensional, steady-state conjugate heat transfer analysis was performed on each cooling configuration and a constrained multi-objective optimization was carried out for each of the three micro-pin fin shapes to find pin fin designs configurations capable of cooling such high heat fluxes. The design variables were the geometric parameters defining each pin fin cross section, height of the chip and inlet speed of the coolant. The two simultaneous objectives were to minimize maximum temperature and pressure drop (pumping power), while keeping the maximum temperature below 85°C. A response surface was constructed for each objective function and was coupled with a genetic algorithm to arrive at a Pareto frontier of the best trade-off solutions. Stress-deformation analysis incorporating the hydrodynamic and thermal loads was performed on each of the three optimized configurations. The maximum displacement was found to be on the nano-level, and the Von-Mises stress for each configuration was found to be significantly below the yield strength of Silicon.

As easily recoverable hydrocarbon resources are depleting, the oil and gas industry focuses more on producing oil and gas from ultra-deep, tight and scattered pockets of reserves. However, these recoveries are not only difficult and expensive, but also require the development of new technologies and materials that can meet stringent requirements regarding operation in sub-surface environment. The emergence of expandable tubular in the late 1990s has opened a new avenue for oil and gas wells design and remediation processes. However, these tubular go through large expansion in diameter at kilometers depths in onshore and offshore wells. This alters the post expansion mechanical and microstructural properties of the tubular that may lead to premature failure during operation. The idea of understanding such variations revolve around complex mechanisms occurring at micro level including multiphase microstructure, grains sizes and morphology, and crystallographic orientations. Initial grains morphology and distribution of phases, and the subsequent changes due to the expansion process lead to significant variations in material properties at macro level. Optical micrographs showed that the expandable tubular material is composed of fine grained microstructure of ferrite phase with some traces of martensite and plate-like structures. Induced martensite results from the phase transformation of metastable austenite induced by thermomechanical processing applied during the manufacturing stage. A reasonable presence of martensite phase in the tubular material enhances its structural integrity, collapse and burst strengths, as well as provides a safeguard against possible mechanical failures such as buckling. On the other hand, the ferrite phase is a soft phase and its presence improves the formability of the tubular resulting in higher expansion ratio. It was also observed that the grains size is affected by the tubular expansion. The presence of elongated grains in the microstructure is due to the excessive deformation as well as the crystallographic reorientation of grains due to the course of tubular expansion. However, no strong texture has been found in the expanded tubular material, which may be attributed to the complex nature of loadings induced during the expansion process. In order to understand the influence of tubular expansion process on mechanical properties of tubular, samples from un-expanded and expanded sections of the tubular (expanded at 16%, 20% and 24% of the tubular original inner diameter) are investigated using standard mechanical testing procedures. Mechanical testing results revealed an increase in yield strength, ultimate tensile strength and hardness, whereas ductility and impact toughness tend to decrease. Fracture surface analysis of fractured tensile samples has also been done using scanning electron microscope (SEM). At lower expansion ratio, fracture surface micrographs revealed a predominantly ductile nature of failure with clusters of fine microscopic dimples intermingled with voids. However, at higher expansion ratio, the test specimens revealed a mixed mode of failure with both brittle and ductile features.

Polyether ether ketone (PEEK) is introduced as a material for the additive manufacturing process called fused filament fabrication (FFF), as opposed to selective laser sintering (SLS) manufacturing. FFF manufacturing has several advantages over SLS manufacturing, including lower initial machine purchases costs, ease of use (spool of filament material vs powder material), reduced risk of material contamination and/or degradation, and safety for the users of the equipment. PEEK is an excellent candidate for FFF due to its low moisture absorption as opposed to other common FFF materials, such as Acrylonitrile Butadiene Styrene (ABS). PEEK has been processed into a filament and samples have been manufactured using several build orientations and extrusion paths. The samples were used to conduct tensile, compression, flexural, and impact testing to determine mechanical strength characteristics such as yield strength, modulus of elasticity, ultimate tensile strength and maximum elongation, etc. All tests were conducted at room temperature. A microscope analysis was also conducted to show features on the failures surfaces. The mechanical property results from this study are compared to other published results using traditional thermo-plastic manufacturing techniques, such injection molding. Tensile testing was conducted at three raster orientations, 0°, 90° and alternating between 0° and 90°. Average ultimate tensile stresses were determined to be 73 MPa for 0° orientation, and 54 MPa for 90° orientation, with alternating 0°/90° orientations of 66.5 MPa. Compression testing was conducted at two raster orientations, 0° and alternating between 0° and 90°. Average ultimate strength for the single orientation direction was 80.9 MPa with the alternating orientations at 72.8 MPa. Flexural testing was conducted at three raster orientations, 0°, 90° and alternating between 0° and 90°. Ultimate flexural stress was determined to be 111.7 MPa for 0°, 79.7 MPa for 90°, and 95.3 MPa for orientations alternating between 0° and 90°. Finally, impact testing was conducted at three raster orientations, 0°, 90° and alternating between 0° and 90°. Average impact energy absorbed was determined to be 17.5 Nm in the 0° orientation, 1.4 Nm in the 90° orientation, and 0.7 Nm for the alternating 0° and 90° orientations.

Aluminum based metal matrix composites offer greater potential for light weight, wear resistant and high temperature applications. Secondary processing like extrusion results in the improvement of strength and ductility of the as-cast composites. The objective of this research is to investigate the effect of reinforcement type and extrusion process on the microstructure and mechanical properties of the hot extruded Al2014 aluminum alloy. Two different composites were made by reinforcing the alloy with 10 wt.% SiC and 10 wt.% Si 3 N 4 particles using stir casting method. The particles were electroless Ni coated to improve the wettability of reinforcement by the matrix alloy. The composite ingots were further extruded at 475 °C with an extrusion ratio of 8:1. The microstructures and the mechanical properties of the base alloy and the composites were examined systematically. The extruded composites show more homogenous microstructure with uniform distribution of particles in the matrix alloy. Both the Al/SiC and Al/Si 3 N 4 composites exhibited improved hardness compared to the base alloy in both as-cast and extruded conditions. It was also found from tension tests that the both the composites show higher yield strength, ductility and ultimate tensile strength (UTS) than the base alloy in the extruded condition. The reason for improvement in strength in the extruded conditions is explained in detail. Fracture surface analysis revealed the transition from brittle fracture mode in the as cast composites to the ductile fracture in the extruded condition.

In the rapidly growing field of additive manufacturing (AM), the focus in recent years has shifted from prototyping to manufacturing fully functional, end-use parts, particularly using metals. In order for these parts to be designed to function both safely and effectively, it is necessary to have a thorough understanding of the mechanical behavior of materials produced via the AM process. This research focuses on characterizing Inconel 718 produced via the Direct Metal Laser Sintering (DMLS) process. Specimens from three orthogonal build orientations were tested as both machined and as-fabricated specimens. Surface roughness was evaluated using non-contact profilometry. Tensile testing was performed in order to characterize material yield strength. Finally, high cycle fatigue (HCF) testing was conducted on a rotating beam apparatus. Results show that the measured elastic modulus of the as-fabricated material was 162.7 GPa for the in-plane build orientation and 72.1 GPa for the vertical build orientation. In addition, the measured fatigue strength of horizontal build orientations was greater than that of specimens built in a vertical orientation. Furthermore, it was found that the fatigue lives of the machined specimens were at least 7 times greater than those of as-fabricated specimens.

Accurate evaluation of residual stresses in structures is very important because they play a crucial role in the mechanical performance of the components. As residual stresses can be introduced into mechanical components during various thermal or mechanical processes such as heat treatment, forming, welding and additive manufacturing. As an additive manufacturing method, selective laser melting (SLM) has become a powerful tool for the direct manufacturing of three dimensional nano-composite components with complex configurations directly from powders using 3D CAD data as a digital information source and energy in the form of a high-power laser beam. Therefore, the application of the SLM technology is necessary to manufacture Inconel 718 superalloy, which has been widely employed in industrial applications due to its remarkable properties. Hence, it is critical to measure and reduce the residual stress in the Inconel 718 parts formed by SLM due to rapid cooling and reheating. In this study, the process-induced residual stress in Inconel 718 parts produced by selective laser melting (SLM) has been investigated using the model established by Carlsson et al., which is an instrumented indentation technique based on the experimental correlation between the indentation characteristic and the residual stress. The samples were sectioned from an Inconel 718 block along its build direction, and subsequently prepared with general metallographic methods for Vickers indentation and measurements by optical microscopy. The residual stress on the scanning surface (Z-plane) and side surface (X-plane) at different build heights have been evaluated in micro-scale with the contact area, indentation hardness and the equai-biaxial residual stress and strain fields. The results show that the residual stress is unevenly distributed in the SLMed parts with some areas have an maximum absolute value around 350 MPa, about 30 percent of the yield strength of Inconel 718. The average residual stresses in the Z-plane and X-plane samples are tensile and compressive, respectively. Besides, the residual stress does not change significantly along the building direction of the part. Moreover, the Vickers hardness of the parts built with the SLM process is comparable to the literature, and the X-plane surface has a higher hardness than the Z-plane surface. The microstructures and texture evolution of the SLM processed Inconel 718 alloy are also investigated. The X-plane shows the columnar structure due to the large temperature gradient while the Z-plane presents the equiaxed structures. The random texture is shown in the SLM processed specimens.

We present the design of a MEMS based single-unit actuator consisting of a single microneedle with 3D mobility. The four-sided single-unit actuator ( 4SA ) microrobot design can achieve an in-plane actuation ( x , y ) of 76 μm ( ±38 μm) at 160 V and an out-of-plane actuation ( z ) of more than 6.5 μm at 35 V. The mechanical stress developed within the operational range is between 0.08 to 0.5 percent of the yield strength of silicon i.e. 7000 MPa. We discuss both the analytical modeling and finite element analysis (FEA) simulation of the design based on the range of dimensions analyzed for the individual actuator components. Our primary goal is to integrate multiple actuators into a parallel architecture for independent actuation of multiple microneedles for targeted micro- and nano-robotic manipulation tasks, such as single-cell analyses. We have also successfully fabricated sample 4SA microrobot without the microneedle as a pre-cursor to experimenting with our future advanced design of microrobots. We demonstrate successfully the 3D actuation of the 4SA microrobot of up to 10 μm at 120 V ( in-plane ) and more than 0.5 μm at 600 V ( out-of-plane ) with minimum decoupling.

Intermetallic (IMC) layers (Cu 6 Sn 5 and Cu 3 Sn) are an essential component of a solder joint for good metallurgical bonding. However, the mechanical and physical properties of IMC layers differ significantly from the solder and substrate, and excessive IMC layers can lower the reliability of solder joints due to their brittle nature. Moreover, continuous miniaturization of packages and joints has increased the volume fraction of IMCs to a point where smaller joints could be completely composed of IMCs. Further miniaturization of joints may result in statistical grain size effects. One of the most common types of IMCs in microelectronic joints is Cu 6 Sn 5 , which is formed in a variety of bonding materials with different compositions of Sn, Cu, and Ag. Due to its large percentage of volume in solder joint; to predict the reliability of micro solder joints, it is necessary to characterize single crystal Cu 6 Sn 5 IMC completely. This study reports the information on grain growth orientation and elastic-plastic properties such as young’s modulus, hardness, yield strength and strain hardening exponent of single grain of Cu 6 Sn 5 in Sn-3.5Ag/Cu solder alloy system. IMCs materials were grown using reflow process using an experiment in which the time and temperature of reflow process was varied. Electron backscatter diffraction (EBSD) analysis was conducted after the reflow to measure the grain size and determine the preferred grain orientation. It was found that the growth orientation is in the orientation of the c-axis. Nanoindentation was carried out in 4 individual grains with different crystallographic orientation along normal to the growth axis to determine the elastic properties of Cu 6 Sn 5 single crystal. Plastic properties were predicted using the nanoindentation results and Dao reverse analysis model. The results indicate that the hardness for Cu 6 Sn 5 grains with different orientation along normal to growth axis is statistically indistinguishable. Lower elastic modulus was observed for a grain with [010] direction parallel to the loading direction. Yield strength of a grain with (001) plane parallel to the loading direction was slightly lower than other grain orientations. Overall, the experimental results obtained were found to be within the range shown in the literature.