The objective of this paper is to design a quadruped robot with compliant legs. Compliant legs are developed using flexible joints, which allow the robot to attenuate the effect of support-leg exchange. A model of the legs is generated in SimMechanics and optimized to minimize the maximum torque required by the actuators. The control of the robot is divided into two stages: (i) a gait central pattern generator, and (ii) a control system with feedback linearization. The gait pattern generator is developed based on optimal inverse kinematics with the use of Bezier polynomials. The resulting gait is used as a set-point in a closed-loop feedback control, which achieves a stable gait locomotion over rough, uncertain terrain. The uncertainty on the terrain causes unknown impacts in the robot. These impacts are absorbed by the compliance of the leg mechanisms. The proposed leg mechanisms are tested in a 3D-printed quadruped robot with fifteen degrees of freedom. Since, the robot is designed with eight actuators, the robot has seven degrees of under-actuation. The lack of actuators in this robot is overcame through the proposed gait pattern generator.

This paper presents the development of a service robot platform for various assistive tasks in human-centered environment. The main design objective is to enable the robot to safely navigate indoor areas and to provide cross-platform accessibility to human-users. To accomplish the goal, two technical design requirements which include the rough-terrain locomotive mechanism and the web-server based operating system are addressed and explored in this study. First, the overall control system architecture of the robot which consists of three different layers (human-interaction, environment-interaction and movement) is presented. Then, the mechanical and electronic specification of the robot’s dual drive system and the power management system are described with their design process. The robot’s software platform (which consists of the server, client and real time controller) is also provided for the selected service task. Last, the built platform is tested and evaluated through experimentations in the real world settings.

Natural Convection heat transfer from horizontal rectangular fin array with various knurling patterns is studied experimentally to find the effect of varying surface roughness on the heat transfer rate. The experimental parametric study is performed to investigate the effect of knurl produced surface roughness of fin on heat transfer rate. The parameters like knurling height from base, knurling depth and fin spacing might affect the flow characteristics and hence it is investigated to find the effect on heat transfer coefficient. The knurling is usually accomplished using one or more very hard rollers that contain the reverse of the pattern to be imposed. The result of this study shows that there are some important geometric factors related to knurling affecting the design of fin arrays and also heat transfer augmentation of natural convection heat transfer is observed.

Solar thermal panels’ heat enhancement through cooling techniques is important for the effective use of the panels. This study is performed on a simulated internal cooling channel of a solar thermal cell with an artificial technique using angled dimpled rough end-wall and exploring the combination of the different geometrical surface to enhance the heat transfer from the wall. Circular and oval shape dimples combination arranged in staggered form are tested. However, the oval geometrics are varied typical to flow direction. The following combinations of circular and oval dimpled are therefore examined (1) 90° circular by 90° oval dimples to the mainstream (2) 90° circular by 60° oval dimples to the mainstream (3), 90° oval by 90° circular dimples to the mainstream and (4) 60° oval by 90° circular to the mainstream. All of which are having pitch/depth ratio, P/δ of 6, dimple centre to centre, P, of 30 mm, and print diameter, D, of 20 mm (for both circular and oval shape), oval small diameter of 10 mm. These combinations are tested for three aspect ratios of 0.049, 0.035 and 0.0249. This study is conducted for a Reynolds number range of 1,000–11,000, and local and averaged heat transfer coefficient values are presented for all the geometries. Pressure drops are measured along the mainstream of the smooth and dimpled channel end-wall and friction factors are calculated. The combination of the 60° oval and 90° circular dimple surface exhibits the best performance of all the cases considered, a moderate pressure drop was also observed compared with others like a combination of pin fins, ribs-protrusions, grooves etc. These values were higher or comparable to the best-performing dimple geometries commonly used for the internal cooling process.

A comprehensive study is conducted to evaluate the heat transfer characteristics of laminar nanofluid flow in an annular tube. Thermo-physical properties of the nanofluid is considered to be variable and for the inner and outer walls, there exists serrated surface roughness. The study focuses on the velocity distribution, friction factor and Nusselt number. All results are compared with those for the smooth channel and constant property nanofluid as well. The results show that the tube with serrated wall experiences greater maximum velocity. Moreover, decrease in velocity gradient and some other thermal characteristics result in decrease in average Poiseuille and Nusselt numbers for the rough tube with variable-property fluid.

Experimental data of thermal contact conductance (TCC) between two metallic rough surfaces versus the applied load (pressure) distinctly exhibit non-linear behavior that can be split into two regimes with two distinct slopes. When the load is small, the rate of change of TCC with load is linear with a small slope. At intermediate loads, this slope increases. A third slope has been exhibited in some cases at extremely high loads — one in which the slope decreases again. In this study, two types of analysis are conducted on a simplified model system comprised of a single asperity compressed by two flat surfaces. The first analysis assumes one-dimensional heat conduction across the asperity, resulting in a fin-equation type model. In the second analysis, two-dimensional heat conduction through the asperity is considered, and the governing steady state heat conduction equation is solved numerically. Results show that the first two slopes at low and intermediate loads can be captured by both models. However, when the asperity is significantly depressed (high load regime) and deformed, the experimental behavior of the third reduced slope can only be captured by the two-dimensional numerical model. This implies that when the asperity deforms significantly, multi-dimensional heat transport becomes a critical limiting factor for the TCC.

Biopolymers are emerging materials with numerous capabilities of minimizing the environmental hazards caused by synthetic materials. The competitive mechanical properties of bio-based poly(lactic acid) (PLA) reinforced with cellulose nanocrystals (CNCs) have attracted a huge interest in improving the mechanical properties of the corresponding nanocomposites. To obtain optimal properties of PLA-CNC nanocomposites, the compatibility between PLA and CNCs needs to be improved through uniform dispersion of CNCs into PLA. The application of chemical surface functionalization technique is an essential step to improve the interaction between hydrophobic PLA and hydrophilic CNCs. In this study, a combination of a time-efficient esterification technique and masterbatch approach was used to improve the CNCs dispersibility in PLA. Nanocomposites reinforced by 1, 3, and 5 wt% functionalized CNCs were prepared using twin screw extrusion followed by injection molding process. The mechanical and dynamic mechanical properties of pure PLA and nanocomposites were studied through tensile, impact and dynamic mechanical analysis. The impact fractured surfaces were characterized using scanning electron microscopy. The mechanical test results exhibited that tensile strength and modulus of elasticity of nanocomposites improved by 70% and 11% upon addition of functionalized CNCs into pure PLA. The elongation at break and impact strength of nanocomposites exhibited 43% and 35% increase as compared to pure PLA. The rough and irregular fracture surface in nanocomposites confirmed the higher ductility in PLA nanocomposites as compared to pure PLA. The incorporation of functionalized CNCs into PLA resulted in an increase in storage modulus and a decrease in tan δ intensity which was more profound in nanocomposites reinforced with 3 wt% functionalized CNCs.

In this study, the tribological behavior of the Trihexyl tetradecylphosphonium-bis(2,4,4-trimethylpentyl)phosphinate [THTDP][Phos] ionic liquid with and without single-wall carbon nanotubes (SWCNT) dispersion as a thin boundary layer was intended for investigation. However, the surface heat treatment process was not sufficient to form a thin film on the sample surfaces. Thus, in each test condition, the lubricating agents were used as external (liquid) lubricants. Specifically, [THTDP][Phos] and ([THTDP][Phos]+0.1 wt.% SWCNT) boundary film layers were applied on 6061-T6 aluminum alloy disk samples and tested under sliding contact with 1.5 mm diameter 420C stainless steel balls using a ball-on-flat linearly reciprocating tribometer. A commercially available Mobil Super 10W-40 engine oil (MS10W40) was also tested and used as this investigation’s datum. The tribological behavior of [THTDP][Phos] and ([THTDP][Phos]+SWCNT) boundary film layers was analyzed via wear volume calculations from optical microscopy measurements, as well as by observation of the transient coefficient of friction (COF) obtained through strain gauge measurements made directly from the reciprocating member of the tribometer. Results indicate the potential for reduction of wear volume and coefficient of friction in the IL lubricated steel-on-aluminum sliding contact through (SWCNT) dispersion in the ionic liquid. Wear results are based on measurements obtained using optical microscopy (OM). Results discussed display improved tribological performance for both [THTDP][Phos] and ([THTDP][Phos]+SWCNT) over baseline MS10W40 oil lubricant for both roughness values tested for the steel-on-aluminum contact. No measurable improvements were observed between [THTDP][Phos] and ([THTDP][Phos]+SWCNT) tests.

This paper presents an energy-regenerative suspension device that is able to harvest some of the wasted energy that is generated in a suspension system. For a traditional road vehicle suspension system, shock absorbers are mainly dissipating energy to reduce vibration. The dissipated energy may be collected to improve the fuel economy of road vehicles. In this research, CarSim and Simulink are used to simulate and determine the harvestable energy in a conventional shock absorber under different operating conditions. A conceptual energy-regenerative absorber is designed and tested using a fabricated prototype. A variable speed motor is implemented to adapt the change of stroke length of a mechanism due to the various road roughness. Instruments, e.g., laser tachometer, pressure gauge, ammeter, voltmeter, and stopwatch, are used to collect data. The simulation and prototype testing results indicate that the proposed energy-regenerative suspension device could harvest dissipated energy to improve vehicle fuel economy.

With recent advancements in the field of additive manufacturing, the design domain for development of complicated cooling configurations has significantly expanded. The motivation of the present study is to develop high-performance impingement cooling designs catered towards application’s requiring high rates of heat removal, e.g. gas turbine blade leading edge and double-wall cooling, air-cooled electronic devices etc. Jet impingement is a popular cooling technique which results in high convective heat rates. In the present study, jet impingement is combined with strategic roughening of the target surface, such that a combined effect of impingement-based and curved-surface area based enhancement in heat transfer coefficient could be achieved. Traditionally, for surface roughening, cylindrical and cubic elements are used. We have demonstrated, through our steady-state experiments, a novel “concentric” shaped roughness element design which has resulted in about 20–60% higher effectiveness compared to smooth target jet impingement, for jet-to-target spacing of one jet diameter. The cubic shaped roughened target yielded about 20% to 40% enhancement in effectiveness, and the cylindrical shaped roughened target yielded 10% to 30% enhancement. Through the plenum pressure measurements, it was found that the addition of the micro-roughness elements does not result in a discernable increment in pressure losses, compared to the standard impingement on the smooth target surface. Hence, the demonstrated configuration with the highest heat transfer coefficient also resulted in the highest thermal hydraulic performance.

Wettability gradient in radial direction and evaporation rate gradient can cause droplet motion on a solid surface. Here a theoretical model is proposed. Besides, an equation of droplet velocity is derived on a solid surface. We consider the wettability and evaporation rate gradients are mainly caused by the chemical composition and surface roughness, only along the radial direction. Surface tension at the liquid-vapor interface is constant as it is assumed that the temperature does not change during the whole process. Thus, Marangoni effect induced by the liquid-vapor surface tension gradient is neglected. Besides, as droplet size is set as less than the capillary length ( l = γ / ρ g ), the gravity effect is ignored as well. The velocity at the droplet center on a gradient surface along the radial direction is half of that along the x-direction. With the simulation of water droplet, the center velocity decreases with time and the droplet radius increases at the beginning part and then decreases.

This present work is to investigate the effects of chrome plating in reciprocating air compressors that result in reduction of power consumption. Reciprocating air compressors are the most commonly used compressors for domestic and industrial purposes to give required air output in terms of free air delivery, delivery temperature and maximum working pressure. This study also develops a better understanding on the effect of honing in the cylinder which reduces the surface roughness in the cylinder liner and results in greater air output. Cylinders are made of graded cast iron. The cylinder liner was honed to a thickness of about 0.26 mm and hard chrome plated to the same thickness. The honing improves the volumetric efficiency and hard chrome plating reduces the power consumption. The adequacy of this model can be verified using thermal image analysis, which includes the various temperature distribution plots around the compressor components. Further delivery temperature, actual displacement and free air delivery pressure are the parameters that conclude the deviation in actual and experimental values. Power consumption and efficiency owe for the major expenditures and maintenance for Reciprocating air compressors. This paper suggests the need of hard chrome plating to a compressor cylinder that resulted in annual power savings of about 25%. The increase in volumetric efficiency was about 20–30% from the actual conditions.

The necessity of understanding the influence of cutting variables in orthogonal cutting of Carbon Fiber Reinforced Polymer (CFRP) is vital because of their significant influences to the quality of manufactured parts. In this present research work the influences of different cutting depths to the cutting and thrust forces have been analyzed and a comparison between an equivalent homogeneous material (EHM) macro-model and experimental results have been made. The reasons of the beginning high cutting and thrust forces have been studied and explained. The post analysis of the experimental machined surfaces has been done to analyze the generated surface roughness and fiber-matrix interface crack generation. Five different cutting depths and four individual fiber orientations have been tested both numerically and experimentally. Significant influence of cutting depths to the cutting force has been found and the surface quality of newly generated machined part is discovered as a function of cutting depth and fiber orientation.

Ni3Al based superalloy is a kind of intermetallics, it is a relatively new superalloy, its superior high temperature characteristic makes it the fifth generation aero-engine turbine blade material. The machinability of Ni3Al based superalloy is poor, and its process parameters have significant influence on grinding force and surface integrity. The creep feed grinding experiments of Ni3Al based superalloy IC10 were carried out with different process parameters. The experimental results show that the workpiece speed has the greatest effect on grinding force, surface roughness and 3D surface topography, followed by grinding depth, the wheel speed has the smallest influence. Grinding force is positively correlated with grinding depth and workpiece speed, and negatively correlated with grinding wheel speed. Similarly, surface roughness is positively correlated with grinding depth and workpiece speed, and negatively correlated with grinding wheel speed. The higher the workpiece speed, the deeper the grooves and the higher the peaks of the surface topography. In order to maintain high surface quality, small workpiece speed and grinding depth should be chosen during grinding process.

Additive manufacturing (AM) can enable complex and novel designs that are otherwise infeasible with traditional metal manufacturing techniques. In low-volume production scenarios, particularly for specialized applications which can benefit from customized designs, traditional metal manufacturing techniques may be limited by costs associated with tooling. The ability to produce novel designs is particularly interesting in heat exchanger (HX) design where performance is often largely based on the achievable geometry. However, consequences of the AM process such as surface roughness, deviation from specified dimensions, and defects such as cracks and voids could also affect HX performance. These effects may vary between identically designed AM parts based on AM machine settings. The goal of this work is to gain a better understanding of the performance variations across several different implementations of the same heat exchanger design. More specifically, the objective of this work is to experimentally compare the thermal and hydraulic performances of a traditionally manufactured, stamped-aluminum aircraft oil cooler and three geometrically equivalent, additively manufactured counterparts. Compared to the traditionally manufactured heat exchanger, the AM HXs exhibited significantly higher air-side pressure loss and higher heat transfer despite having nominally similar geometries. Between AM HXs, there were slight differences in surface roughness characteristics based on optimal profilometry measurements. In addition, the thickness of the air-side fins varied as much as 15 percent between the AM HXs. The net effect, without the contribution of each cause clear, was higher air-side pressure loss and slightly higher heat transfer for the AM HX with thicker fins. This study indicates that functional heat exchangers built using AM vary in performance even when the same digital model is used to print them, and that AM HXs as a group perform considerably differently than their traditional counterparts. Thus, there is a need to account for anticipated surface roughness, geometric deviations, and potential defects when designing HXs. Proper consideration could result in improved thermal performance for future heat exchangers.

In situ TiB 2 /7050 Al metal matrix composites are processed by mixed-salt reaction method to improve the interfacial reactions and enhance the material properties. However, the lack of research on its machinability limits its wide application in the industry. In the present study, the effects of rake angle and feed rate on the surface quality while turning in situ TiB 2 /7050 Al metal matrix composites have been investigated. Three types of polycrystalline diamond (PCD) tools with 0° ∼ 5° ∼ 10° rake angles were utilized in this work. The surface roughness, surface topography and residual stress profile developed in TiB 2 /7050 Al composites by cylindrical turning were evaluated. The experimental results reveal that feed rate has more significant impact for surface roughness than rake angle. The smooth surface topography without void and defects indicates that the chips are formed in ductile mode. Unlike other metallic alloys, the surface residual stress of TiB 2 /7050 Al composites are always in compressive state. In addition, the increase of feed rate contributes to deeper residual stress penetration layer. Through the discussion in this study, the role of TiB 2 reinforcement particles on the machinability of TiB 2 /7050 Al composites can be better understood.

Additive manufacturing (AM) can produce highly complex engineering components that are either extremely challenging for the conventional subtractive manufacturing route or not possible otherwise. High surface roughness can make an AM component highly vulnerable to premature failure during fatigue loading. Post-processing aiming to reduce surface roughness is essential to make as produced AM parts functional. We have explored electropolishing route to achieve optimum surface roughness and surface chemistry. We have performed electropolishing treatment on the steel AM parts around 70 °C in an electrolyte comprising the phosphoric acid and sulfuric acid. Profilometry and scanning electron microscopy were performed to study the electropolished and unpolished areas. Optical profilometry study showed that one needs to remove nearly ∼200 μm material from the surface to achieve very smooth surface. Electropolishing was effective in reducing the surface Ra roughness from ∼2 μm rms to ∼0.07 μm rms. Such low rms roughness makes an AM component suitable for almost every engineering application for which a smooth surface is required. Scanning electron microscopy revealed that electropolished area on AM component possessed distinctively different microstructure as compared to the untreated surface of an AM component. We also conducted the compositional analysis of the electropolished area to investigate the possibility of residual contamination from the electropolishing process. Our study revealed that electropolishing is a highly promising route for improving the surface finishing of AM components.

Reducing surface roughness is critical for improving the mechanical properties of metal 3D printed components. As produced laser sintered metal 3D printed components suffer from high surface roughness. This problem is enormously big for the 3D printed components with intricate geometries involving a large internal surface area. To address this issue, we performed chemical polishing of the 3D printed 316 steel components. After 30 minutes of chemical polishing the color of 3D printed steel components’ surface became dull grey to bright lustrous. According to optical profilometer study, the surface morphology improved dramatically. The Rq roughness parameter changed from ∼8 um to ∼0.6 um. We also applied chemical polishing on cubical metal 3D printed components with internal surfaces. This surface finishing method was equally effective for the internal and external surfaces.

Organic Rankine cycle (ORC) has gained an increasing worldwide attention due to its high efficiency in converting low-grade thermal energy into electricity. The expander is the most critical component in the ORC system. Among the influential factors that define the performance of the expander, the velocity coefficient of the nozzle is crucial. This work numerically investigates the effects of the nozzle height, length, surface roughness, outlet geometric angle, and expansion ratio, on the velocity coefficient of the nozzle in the ORC turbine with hexamethyldisiloxane (MM) as working fluid. In the 3-D viscous numerical analysis, the shear stress transports k-ω turbulence model is employed and the numerical method is verified by the experimental data of the nozzle with pressured air based on hotwire technology. The numerical results show that the velocity coefficient is almost independent of expansion ratio compared to other factors due to the relatively small flow boundary layer and high Reynolds number. Since the existing correlations for the gas nozzle cannot well predict the velocity coefficient of the organic nozzle, an empirical equation is proposed according to the numerical results with the maximum deviation of 3.0%.

For long-term operation, blades start to show some defects with increasing operating hours, such as fouling, erosion, corrosion, damage and tip clearance. As the basic unit components of gas turbines, the health conditions of blades directly affect the energy conversation efficiency and service life of the whole equipment. The process from first installation to scrap is blades’ whole operation life cycle. It is an effective way to establish the whole operation life cycle model of blades for real-time monitoring, troubleshooting and prevention, so as to improve the management of equipment. The current research on the whole operation life cycle model is mostly limited to a single subject, such as thermal effects or stress effects. It lacks a profound analysis of this issue from the multi-disciplinary perspective. Meanwhile, the deterioration of blades influence on geometry variation of the blade surface is not taken into consideration in detail. Therefore, the current blade life model is not accurate enough to represent the actual situation. In this paper, the typical gas path deterioration is characterized by blade profile parameters, including the increment of the blade leading edge thickness, the increment of the blade trailing edge, and the change of the blade surface roughness in the whole operation life cycle model of blades. The influencing factors of aerodynamics and strain are synthetically characterized through the study of their multi-disciplinary influence mechanism. And the relationship between the corresponding influencing factors and the variation of blade profile parameters is established. Thus, the numerical simulation model under multi-physics is built to reveal its distribution and trends of the flow field and stress in the gas path. The result shows that it can protect the blades, ensure safe and stable operation, and reduce the deterioration rate.