Mechanical Engineering & Applied Mechanics Masters Theses

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Effects of processing parameters and thickness on compression-molded PET/GF composites
(North Dakota State University, 2024) Reinholz, Jacob
Polymer-matrix composites (PMCs) have become an integral material in many industries due to excellent strength-to-weight ratio and low cost. When semi-crystalline polymer thermoplastics, such as polyethylene terephthalate (PET), are heated past their melt temperature then cooled during compression molding, the long polymer chains in the amorphous regions unravel and align to form crystalline regions with improved strength and stiffness. This research aimed to understand the effect of compression molding processing parameters such as temperature, pressure, dwell, and cooling rate as well as the overall panel thickness on crystallinity and mechanical properties of unidirectional glass fiber-reinforced PET. It was found that a slower cooling rate and a slightly increased dwell time had the most significant effect on PMC properties. Additionally, uniform crystallinity and scattered mechanical property data taken from specimens throughout thick-section samples suggests there was no symmetric property gradient through the cross-section that affected material performance.
Additive manufacture of advanced composites using reactive resins and continuous carbon fiber
(North Dakota State University, 2024) Aryal, Bibek
To overcome the significant limitations such as slow processing times, substantial energy needs of conventional additive manufacturing technology, reactive extrusion additive manufacturing (REAM) process was developed. As printed objects with neat reactive resin exhibited insufficient mechanical performance for advanced application, continuous fiber reinforcement is an effective route to improve mechanical performances. Continuous carbon fiber reinforced 3D printing was performed using a commercially available reactive resin system and an experimentally synthesized one at NDSU. The mechanical properties of the printed carbon fiber reinforced samples were compared with the neat resin samples. The tensile strength of printed sample using Pentaerythritol-xylendiamine resin system increased by 217% with 2.88% carbon fiber content. Similarly tensile strength of Epon-Epikure sample increased by 151% with the fiber-volume fraction of 4.4%. Therefore, reinforcement with continuous carbon fiber has potential to overcome the barrier of low mechanical strength exhibited by neat reactive resin system.
Stress-function variational method for stress and progressive cracking analysis of polymer composite laminates
(North Dakota State University, 2024) Islam, Md Shariful
Polymer matrix composites (PMCs) are widely used in various industries, including aerospace, vehicles, sports utilities, and civil infrastructures. Understanding the failure process and mechanisms of PMCs subjected to external loads is crucial for their reliability. This study aims to develop a semi-analytic stress-function variational method for accurate prediction of interfacial stresses and progressive cracking in PMC laminates. The method uses a three-layered cross-ply laminate model with periodic transverse ply cracks, introducing two unknown interfacial shear and normal stress functions at each laminate interface. The stress field is expressed in terms of these stress functions, using Euler-Bernoulli beam theory and elasticity. The method also considers transverse deflections of the plies, resulting in accurate predictions of interface stresses. The method can be used for scaling analysis of interfacial stresses and progressive cracking in PMC laminates as validated by finite element analysis (FEA).
Experimental Characterization of a Novel Integrated Flow Control Method
(North Dakota State University, 2010) Baqui, Muhammad Niamul
Flow control methods can be used in many areas of aerodynamics such as separation control, wind turbines, landing gears and micro satellites. Flow separation in the boundary layer is one of the fundamental problems of aerodynamics. Separated flow in the airfoil boundary layer causes the aircraft to stall. Blowing and Dielectric Barrier Discharge (DBD) Plasma Actuator based techniques have proven successful in limited applications of separation control. However, Blowing techniques require high pressure source and Plasma Actuators are only successful in low speed application. The current research incorporated experimental techniques in characterizing a novel integrated flow control method by combining blowing flow control with Dielectric Barrier Discharge (DBD) Plasma Actuator based flow control. Integrated control would be applicable in wider flow domain than individual plasma or blowing. Initially, characterization experiments were performed as a proof of concept for the integrated control and then, the integrated control was applied in airfoil separation control. Characterization experiments were performed with a vertically fired cylindrical jet having plasma actuator around the jet periphery. The cylindrical jet was used to simulate blowing. The results obtained from characterization experiments indicated 63% reduction in blowing ratio due to plasma addition. The integrated control was placed on NACA 0025 airfoil with blow opening at 25% x/C and plasma actuator at 25.5% x/C location. Windtunnel tests were performed at freestream velocities of 3 mis and 4.5 mis with airfoil angle set at 10 degree. Results indicate 110% increase in airfoil near wall velocity for 3mls when integrated control was applied. Separation was experienced in the region when other flow control methods were used.
Computational Simulation of Droplets Wetting on Micro and Nano Filaments
(North Dakota State University, 2010) Bedarkar, Amol Anil
In this thesis, wetting properties of liquid droplets on micro and nano filaments were explored. First, droplet-on-filament systems were considered, made of liquid droplets and wetting between parallel filaments of identical geometries and surface wetting properties. Criteria for morphology transition between barrel-shaped droplet and droplet-bridge morphology was determined in terms of critical droplet volume at varying filament spacing, droplet volume, and contact angle. A family of wetting characteristic curves was obtained as a universal law of morphology transition in such systems. Additionally, wetting lengths of the above droplet-on-filament systems were demonstrated at varying geometries and surface properties. Secondly, a surface finite element method was employed to simulate the capillary torque generated in a droplet bridge formed between two misaligned filaments at varying filament spacing, contact angle, droplet volume, and filament orientation angle. Consequently, a novel, hydroelastic model was developed to examine the capillary effect in the mechanical response of ultrathin, soft filaments wetted with droplets and subjected to axial stretching. The filament was modeled as a hyperelastic, MooneyRivlin solid, and an explicit stress-stretch relationship was determined. The results obtained in this research broaden the theoretical understanding of droplet wetting and spreading on filaments and are applicable for design and analysis of filament-based microfluidic devices, biological cell manipulators, drug delivers, fiber wetting property differentiators, etc.
Impact. of Environmental Conditions on Fiberglass-reinforced Polyurethane Foam Composites
(North Dakota State University, 2010) Fisk, Aron Mark
Incorporating reinforcement within a polymer (i.e. composite) can obtain substantial performance increases. However, composites may he susceptible to conditions that could have a significant impact on their performance. The objective of this study was to characterize SpaceAge Synthetics (SAS) fiberglass-reinforced rigid, closed-cell polyurethane foam (PU) after subjected to various environmental conditions. SAS composites were characterized as a function of material composition after conditioned to extreme temperatures, moisture, ultraviolet irradiation (UV), or a combination thereof. The experimental process involved accelerated conditioning to further induce property changes and assure long-term integrity. Empirical expressions for SAS composites were generated to represent performance changes for different environmental conditions. Increasing temperature 93 °C from ambient showed an 18% decrease in strength and 24% decrease in stiffness for a 450 kg/m3 foam density reinforced with 7.6% fiber volume fraction. This performance loss resulted from the ductility of the polymer increasing with temperature. Decreasing temperature 68 °C from ambient showed a 56% increase in strength and 26% increase in stiffness. When SAS composites were subjected to moisture at room temperature, no statistical difference was observed after being exposed to l 00% RH for 72 h duration. These mechanical performance analyses included varying material parameters such as: foam density, fiber content, void content, and thickness. The addition of heat to the l 00% RH moisture drastically reduced mechanical performance up to 33% in strength and 22% in stiffness. Ultraviolet irradiation caused chemical changes within the SAS composites, which was first noted by the pronounced color shift within the yellowness index (YI). Additional reinforcement near the surface created a 269% lower shift in YI. It was observed that initially cross-linking occurred while at the same time chain scission was occurring at a larger rate. Fourier Transform Infrared Spectroscopy proved that UV penetrated 0.25 mm within the surface, showing the effects occur mainly on the surface. Finally, SAS composites exhibited a 31 % increase in strength and a 12% increase in stiffness with a post cure process. Post curing for 4 h at 100 °C raised the glass transition temperature from 119 °C to 128 °C. The performance increase was attributed from the post cure process inducing additional cross-linking within polymer chains.
Implementation Of Particle Model Control Approach To A Fixed Axle UGV
(North Dakota State University, 2010) Gupta, Nikhil
Robotic vehicles are normally modeled as rigid bodies under general motion, combining translation and rotation motions. While such modeling results in motion controllers that are easy to implement, these controllers are also limited in the number of degrees of freedom (DOF) that can be controlled. The robotic vehicle with limited DOF operates well in structured terrain conditions with sufficient stability and friction. When the vehicle is operated in unstructured terrains, such as those that are sandy, snowy, or steep terrains, which might be slippery, such an approach fails to operate well. Since additional applications of robotic vehicles are in unstructured terrains, it is important to find alternative control models that will increase the number of controllable DOF and add more robustness and flexibility to the vehicle's performance. This thesis proposes the modeling of a vehicle as a system of particles centered at the wheels, with each particle controlled independent of one another in order to achieve the desired vehicle motion. In this work, the Particle Model Control approach was tested on the robotic platform BIBOT-1. The work illustrated the major vehicle kinematics under different steering modes and how the controls for the robotic motion can be formulated on the basis of Particle Modeling. A control system, based on Particle Modeling using decentralized control architecture, was designed and tested on BIBOT-1. The preliminary test results obtained from the trial runs were then analyzed on the basis of root mean square (R.M.S.) error performance factors. Some future work was also suggested in order to gather more results and validate the modeling approach.
Performance Prediction Model for a Hybrid PVT System
(North Dakota State University, 2010) Hasan, Md. Arif
Photovoltaic cells convert, depending on the cell type, 6-18% of the incoming solar radiation into electricity with a higher percentage converted into heat. The heat in turn affects the cell temperature which has direct impact on its efficiency. In literature, both water and air have been used for PV cooling through a thermal unit attached to the back of the module yielding a photovoltaic-thermal (PVT) system. But the use of water requires more extensive modifications to prevent leakage and corrosion. Hence, an air channel operating on forced convection that would substantially improve the heat transfer aspects was chosen. This study investigates the performance of a low-cost heat-extraction improvement in the channel of a PVT air system that achieves higher thermal output and PV cooling while keeping the electrical efficiency at acceptable level. This study presents the use of a "helical insert" along the air channel as heat transfer augmentation that improves the PVT system's overall performance. Based on energy balance of each component of PVT system, an analytical expression for the temperature of the PV module, back wall and the outlet air has been derived. The developed model was first validated with the experimental data obtained by researchers. By confirming a good agreement with the experimental data, simulations were carried out to optimize various operating parameters, like the channel hydraulics, air mass flow rate, twist angle of helical insert and number of inserts. Then the steady-state thermal efficiency of the modified system equipped with helical insert is compared with those of typical PVT air systems. The modification results in a substantial increase m the overall thermal and electrical efficiencies to about 66.5% and 13.5%, respectively. Hence, these techniques would positively impact the applications of PV systems, more specifically Building Integrated Photovoltaics (BIPV).
Foaming Kinetics of Closed Cell Rigid Polyurethane Foam
(North Dakota State University, 2010) Meyer, Kimberly Nicol
Rigid polyurethane foams have shown promise in several applications as a means to reduce weight without compromising structural properties. Information about the chemical formula of the liquid components, the reaction to produce foaming, and the curing kinetics of rigid polyurethane foam are discussed. The chemical formulas of the liquid components are described, and the reaction required to produce foaming and cure of the polyurethane is stated. The foaming kinetics of the polyurethane were determined based on experimental work as well as theoretical modeling. It was determined that there was a relationship between the initial load the frame was placed under and the amount of pressure measured during the foaming process. The theoretical modeling was conducted for an equilibrium scheme as well as viscosity and diffusion controlled stages. Each of the models predicted the bubble growth to be much quicker than was seen in experimental work, but captured dimensional properties in the foam. The curing kinetics of the liquids and thermal profile of the foaming reaction were measured and a plan for incorporation into future modeling is discussed.
Experimental Study of Effects of Leading-Edge Structures on the Dynamic Stall of a Vertical Axis Wind Turbine Airfoil
(North Dakota State University, 2020) Zhao, Jiaming
Vertical axis wind turbine, developed as one of the main methods to utilize the wind energy, has a promising future; however, the major issue to limit its performance is the uneven loading on the blade during operation. Flow control mechanisms have been employed in the aerodynamic field to improve the performance of airfoils. In this study, two types of leading-edge structures, including flexible leading-edge and leading-edge roughness, are experimentally investigated to analyze their effects on altering the aerodynamic characteristics of NACA 0018 airfoil under steady flow condition and dynamic pitching condition. Current experimental results indicate that 1) during the steady flow condition, both of leading-edge structures contribute to the delay of the static stall; 2) for the dynamic pitching process, the leading-edge structures either delayed the dynamic stall angle or increased the area of the coefficient of pressure loop as a function of angle of attack.
Development and Characterization of Reactive Extrusion Additive Manufacturing System and Polymer
(North Dakota State University, 2021) Patton, Dallas
Additive manufacturing with polymers can rapidly produce complex geometry and prototypes but does not usually utilize thermoset polymers aside from photocurable polymers. In this study two-part reactive thermoset resin systems were used to additively manufacture parts utilizing a commercial resin and a custom resin system. Two displacement syringe drivers were used to feed each part of the reactive resin into a mix chamber that utilized a helical static mix rod and was extruded through a 3D printed nozzle. After print parameters were fine-tuned, the resulting reactive resin specimens featured high strength, quick curing, and fast deposition rate. Optimization of the resin system is required to allow for support structures to be created as well as for overhangs and other additive manufacturing advantages to be realized. Continued study on reactive extrusion methods can lead to the utilization of continuous fiber to allow for the creation of complex geometry high performance composites.
A Molecular Dynamics Study of Mechanical Properties of Carbon Nanotube Polymer Composites and Graphene Nanoplatelet Polymer Composites
(North Dakota State University, 2010) Yerramaddu, Suchitra Reddy
Carbon nanotubes have been the main focus in science and engineering fields lately for their extraordinary properties. But carbon nanotube fabrication process is very expensive, particularly for reinforcements and structural composite applications. Instead of working towards developing lower cost nanotubes, an alternate solution to resolve the problem is to formulate a cost effective reinforcement referred to as graphene nanoplatelets. These nanoplatelets have excellent mechanical as well as electronic properties opening up for several applications in various fields. Their structure with carboncarbon bonds make them stronger and stiffer. Single nanotubes can be used as reinforcements in one direction, while the graphite nanoplatelets are effective in two directions yielding a higher degree of stiffness and strength in a matrix In this thesis, a molecular dynamic computer simulation technique was used to explore the atomic scale and dynamics of graphene nanoplatelets and carbon nanotubes embedded in polyethylene matrix. The mechanical properties of the carbon nanotubes and nanoplatelets polymer composite models were studied individually along with a comparison between composite models. The overall system was modeled using material studio software with the implementation of periodic boundary conditions to determine the properties. The stress strain curves revealed that the length and the volume fraction of the nanotube/nanoplatelets had a significant effect on the mechanical properties of the composite. The stiffness of the composite with long reinforcement length increased relative to the polymer in the longitudinal direction and shows an anisotropic behavior. Significant enhancement was observed in the Young's modulus with the increase in the volume fraction of the nanotubes/nanoplatelets because of the well known effect of the increase in the load transfer between the polymer and the reinforcements. Also increasing the volume fraction of the short nanotubes/nanoplatelets provided very little improvement in stiffness compared to the longer length nanotubes/nanoplatelets. Results also showed that the graphene nanoplatelet reinforced composite properties were very comparable to the nanotubes reinforced composites even under weak vander Waal interactions.
Numerical Simulation of a Direct Expansion Geothermal Heat Pump Using Carbon Dioxide in a Transcritical Cycle
(North Dakota State University, 2011) Austin, Brian Thomas
Many of the synthetic refrigerants used in heat pump and air conditioning systems are potent greenhouse gases. In light of the increasing concern regarding climate change, there has been an increased interest in natural refrigerants such as carbon dioxide which have a comparatively negligible impact on climate change. Direct expansion geothermal heat pumps require a very large volume of refrigerant, making the use of a natural refrigerant particularly beneficial from an environmental perspective. In this study a numerical model has been developed to analyze the steady state performance of a direct expansion geothermal heat pump water heater using carbon dioxide in a transcritical cycle. The system incorporates a compressor, a counter-flow gas cooler, an expansion device and a ground heat exchanger which is the system evaporator. The model was developed by means of thermodynamic, heat transfer and fluid flow analysis of each component of the system. A comparison between predicted component performance and experimental results available in the literature indicated that the simulation can provide a reasonably accurate representation of an actual system. Given this verification, the simulation was used to gain an understanding of the direct expansion CO2 geothermal heat pump's performance under varying design and operating parameters. The salient parameters which were studied include: compressor speed, ground coil length, number of ground circuits and gas cooler length. The effect of monthly soil temperature variation was also investigated. The parametric study revealed several factors which are important for system optimization. First, at any given soil temperature an optimum mean evaporation temperature exists; even a small deviation from this optimum can have a significant impact on coefficient of performance. Another important factor is the number of evaporator circuits. Finally, the gas cooler and evaporator capacities were shown to have a large impact on performance; heat exchanger capacities should be matched for optimum performance. Utilizing the findings of the study, an optimized system was simulated and compared to the baseline. The optimized system achieved a coefficient of performance of 2.58, representing an 18% improvement over the baseline system. Heating capacity increased 17% to 12.3 kW. The study suggests that with further research and optimization, carbon dioxide can perform well in a direct expansion geothermal heat pump and is a suitable replacement for more environmentally degrading refrigerants.
Performance Analysis of an Advanced Emission Reduction Technology Engine During Diesel-Hydrogen Dual Fuel Operation
(North Dakota State University, 2011) Bottelberghe, Bottelberghe
The primary objective of this study was to determine the capability of a CAT engine controlled by an advanced combustion emission reduction technology (ACERT) electronic control module to operate in a dual fuel mode. A CAT 6.6-liter ACERT test engine was outfitted to operate on a hydrogen-diesel fuel mixture. A continuous stream of hydrogen was infused into the intake air charge after the turbocharger. At 50% of rated load, the addition of hydrogen, at three different speeds (1300, 1800, and 2100 RPM), was examined. The hydrogen addition varied from 0-60% of input energy. The maximum amount of hydrogen added before knock occurred, for 1300, 1800, and 2100 RPM, was 54%, 46%, and 55%, respectively. At 1300 RPM, the addition of hydrogen resulted in a decrease in specific energy consumption (SEC) for all levels of hydrogen. For 1800 and 2100 RPM, the SEC improved only when hydrogen was added beyond 46% and 55%, respectively. Emissions testing, while using hydrogen, showed a consistent decrease in carbon dioxide (CO2) emissions and an increase in nitrogen oxides (NOx) emissions for all test speeds. The carbon monoxide (CO) emissions showed improvement at levels of hydrogen exceeding 40% for all test speeds. The hydrocarbon (HC) emission did not vary during the addition of hydrogen.
An Experimental Study of Fluid-Structure Interaction in Collapsible Vessels
(North Dakota State University, 2022) Schmeling, Jennifer
The fluid-structure interaction in collapsible thin-walled vessels is an important topic of research to better understand the physical mechanisms behind many physiological processes and diseases. In this work, we established an experimental setup to study the collapsible tube deformation and fluid-structure interaction within a thin-walled collapsible vessel. The effects of transmural pressure and flow rate were characterized experimentally using high-frequency pressure transducers and optical measurements. Various transmural pressures were also simulated through finite element analysis. Results suggest that the deformation of thin-wall vessel follows the pattern described by Shapiro’s tube law. The collapsed pattern and cross-sectional area changes with different transmural pressure and flow pressure gradients. Below a certain negative transmural pressure threshold, we observed self-induced oscillations whose frequency and magnitude are functions of flow rates. The critical non-dimensional parameter thresholds for self-induced oscillation and the related fluid flow behaviors were examined using Particle Image Velocimetry.
Regolith Based Polymer Matrix Composites for In-Situ Additive Manufacturing for Long Term Extraterrestrial Missions
(North Dakota State University, 2022) Matetich, Christopher
The completed study investigated Martian regolith simulant composites’ material properties when there was variation in the type of used Martian regolith simulant. Four types of Martian regolith simulant were mixed at varying weight percent loadings with polypropylene using twin screw extrusion. Test parts were made via injection molding with all the polymeric composites, and additive manufacturing with select polymeric composites. ASTM standard based tests and ANOVA tests were completed to investigate material characteristics. Depending on the creation process, the results suggested that Martian regolith simulant type impacted several material characteristics. During material processing, a foaming behavior was observed with all the materials, especially material that used MGS-1S. Additive manufactured parts were found to be impacted by the foaming behavior. A literature based thermal breakdown study suggested that thermal releases from the Martian regolith simulants were the likely candidates for the foaming behavior.
Stress-Function Variational Method and Its Applications in the Strength Analysis of Bonded Joints and Hard Coatings
(North Dakota State University, 2011) Jenson, Robert Allen
High concentrations of interfacial stress near the adherend ends are primarily responsible for the debonding failure of bonded joints, such as those structured extensively in civil and structural engineering; aeronautical, ground, and marine vehicles; and flexible electronics and microelectronic packaging. Accurate determination of these interfacial stresses is crucial to improved structural design and optimization as well as health monitoring of the structures in which such joints are found. A variety of joint models have been available in the literature for joint strength analysis and structural design. Yet, a few deficiencies still exist in most of these models in accurate prediction of joint stresses, including the violation of the generalized Hooke's law of the adhesive layers and failure to satisfy the physical traction conditions at the free edges of joint adherends. In this thesis, a generalized stress-function variational method is developed for the determination of the interfacial shear and normal stresses in general bonded bimaterial joints subjected to mechanical and thermomechanical loads. Specifically, three types of joints are considered in this study, including single-sided bonded joints, single-sided strap joints, and single-lap joints. During the formulation, two unknown interfacial stress functions are directly introduced to satisfy the traction boundary conditions of the joints; the Euler-Bernoulli elementary beam theory and 2D elasticity are used to determine the stress components of the adherends in terms of the interfacial stress functions. By utilizing the theorem of minimum complementary strain energy, the governing equations of the bimaterial joint are obtained as a system of two coupled 4th-order ordinary differential equations (ODEs) of the introduced stress functions. These ODEs are formatted into a generalized eigenvalue problem, and are further solved numerically by designing robust and efficient computational codes using MATLAB™. The results of the analysis are validated by comparison with elementary mechanics of materials as well as detailed finite element analysis (FEA) using ANSYS™; the current models can accurately satisfy the shear stress-free boundary conditions at the adherend edges. In addition, the proposed method is further applied to the analysis of progressive cracking in hard coatings. In this analysis, a cracked hard coating layer bonded onto a substrate is modeled as a single-sided bonded joint, and the expressions of strain energy derived in this study are incorporated into energy-based cracking criteria of the system. Using the above variational method, the critical loads (i.e., applied axial stress, shear force, bending moment, or temperature change) for initial cracking can be determined. Thus, the present method is also capable of modeling progressive cracking in hard coating systems.
Potential for Industrial Vehicle Electrical Applications
(North Dakota State University, 2011) Hill, Aaron Glen;
Synthetic metals are a branch of material science that deals with conducting organic molecules. The quantum mechanics of these materials show that doping can fundamentally change the conduction method and significantly increase their conductivity. Addition of conductive fillers to these synthetic metals can create a composite with even higher conductivities, with the most promising being carbon nanotubes. Ultimately, most of the research into synthetic metals is utilized for the creation of new technologies, but replacing metal in existing systems has many benefits, such as lighter weight and improved corrosion resistance. Industrial vehicle electrical systems are one such system that could benefit from synthetic metals via simplified manufacturing, assembly, and increased robustness. This paper explores the conduction methods in synthetic metals and carbon nanotubes, looks at past research on synthetic metals and conductive composites, and postulates what future research would be required to, make synthetic metals commercially viable in existing industrial vehicle applications.
A Numerical Study and Optimization of a Morphing and Pitching Boeing Vertol VR-12 Rotorcraft Airfoil
(North Dakota State University, 2022) Sprengeler, Thomas
The helicopter blade has not undergone any major change in design in recent history, only minor adjustments like swept blade tips, variable twist blade, and application of small gurney flap style trailing edge devices. With the advancement of technology in both hardware and software this research aims to show the development of a modern shape morphing airfoil, specifically for helicopter application by utilizing high power computing and advanced turbulence modeling to find optimal shape morphing regimes. The experimental development and testing of the new airfoils were performed at North Dakota State University. The result of this research show that a system was developed in order to optimize the flow over a rotorcraft airfoil using advanced CFD methods. Three initial shapes to include leading and trailing edge deflections were chosen for their increase in aerodynamic performance over a wide range of angles of attack.
An Investigation on Residual Stress Build-Up in Cold Sprayed Metallic Samples: Effect of Stress Relaxation Heat Treatment
(North Dakota State University, 2022) Shrestha, Deepika
Residual stress formation during cold spraying process may result in deteriorative effects on the performance of coating materials. The objective of this investigation is to characterize residual stress built-up in some of well-known metallic alloys deposited by cold spraying. Two different nickel based super alloys (Inconel 625 and Inconel 718) and the most commercially used titanium alloy (Ti-6Al-4V) were considered for investigation in this study. The average residual stress was higher in Inconel samples compared to the titanium one. Stress relaxation heat treatment helped in the reduction of porosities. However, the recovery of residual stress was highest in Ti-6Al-4V compared to nickel-based samples. Mechanical properties such as hardness, porosities and crack formation were investigated in all samples and tribological behavior of Ti-6AL-4V was particularly studied. The relation between the crack formation and residual stress before and after heat treatment was established for Inconel samples. It was tried to define same relationship for wear resistance and residual stress in Ti-6Al-4V sample.

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