Evaluation of Tribological aspects of Al-Si 12 alloy and their Metal Matrix hybrid Composites produced by Liquid-metal Forging Method

Particulate Aluminium Metal Matrix Composites (Al-MMC) have emerged as advanced engineering materials in view of their improved properties. Ceramic reinforced Al-MMC were more suitable because of being economical and exhibiting isotropic properties. Al-MMCs manufacturing methods are expensive, demand skilled and complex operations and vortex liquid metallurgy results into higher porosity. The liquid-metal forging/squeezed casting of stirred molten slurry can eliminate porosity as molten metal is pressurized during solidification forming near net shapes. During many instances, influence of process parameter (PP)s on mechanical part properties is being studied. In the present study, composites were produced using Al-Si12 alloy as base material, aluminium oxide and silicon carbide particles as reinforcements by varying the PPs. Tribological tests were conducted under dry sliding condition at room temperature showed hard reinforcements in Al alloy reduced the wear rate (WR) and increased the coefficient of friction (f) for all PPs. For PPs, increasing the squeeze pressure and decreasing the pouring and die preheating temperature resulted in a reduction of WR and f with an increase in normal load and sliding velocity. Initially f falls and then raised with an increase in normal load, but only raised with growing sliding velocity compared to Aluminium base material.

Evaluation of Tribological aspects of Al-Si 12 alloy and their Metal Matrix hybrid Composites produced by Liquid-metal Forging Method

Particulate Aluminium Metal Matrix Composites (Al-MMC) have emerged as advanced engineering materials in view of their improved properties. Ceramic reinforced Al-MMC were more suitable because of being economical and exhibiting isotropic properties. Al-MMCs manufacturing methods are expensive, demand skilled and complex operations and vortex liquid metallurgy results into higher porosity. The liquid-metal forging/squeezed casting of stirred molten slurry can eliminate porosity as molten metal is pressurized during solidification forming near net shapes. During many instances, influence of process parameter (PP)s on mechanical part properties is being studied. In the present study, composites were produced using Al-Si12 alloy as base material, aluminium oxide and silicon carbide particles as reinforcements by varying the PPs. Tribological tests were conducted under dry sliding condition at room temperature showed hard reinforcements in Al alloy reduced the wear rate (WR) and increased the coefficient of friction (f) for all PPs. For PPs, increasing the squeeze pressure and decreasing the pouring and die preheating temperature resulted in a reduction of WR and f with an increase in normal load and sliding velocity. Initially f falls and then raised with an increase in normal load, but only raised with growing sliding velocity compared to Aluminium base material.

Modeling and Simulating the Static Structural Response and Lift Off of a Preloaded Bolted Joint on a Flange

The present paper describes the structural analysis performed on a preloaded bolted joint. The first joint modeled was comprised of a conventional cylindrical flange that was sliced to simplify the analysis for two bolts in lieu of four. This involved an L-shaped flat segment flange. Parametric studies were performed using elastic, large-deformation, non-linear finite element analysis to determine the influence of several factors on the bolted-joint response. The factors considered included bolt preload, contact surfaces, edge boundary conditions, and joint segment length in this first approach. The second model applied the previous preloaded torque on a complex flange to study the flange lift off. Joint response is reported in terms of displacements, gap opening, and surface strains. Most of the factors studied were determined to have minimal effect on the bolted joint response

Design of Shape-Morphing Structures Consisting of Bistable Compliant Mechanisms

This dissertation presents a design concept for shape-morphing structures that have two stable configurations. The design concept defines the methodology of transforming a planar structural shape into spatial structural shape using bistable compliant mechanisms. Bistable complaint mechanisms are used to achieve structural stable configurations. The dissertation incorporating geometrical relationships for the mechanisms that form the primary structure described in step-by-step process. This dissertation implements the design layouts for designer to creating shape-morphing structures including origami. The novel contribution of the work is classified in three models. The first model presents a methodology to induce bistability behavior into an origami reverse fold and partially spherical compliant mechanism. The second model presents the design and development of a bistable triangle-shaped compliant mechanism with motion limits and dwell behavior at the two stable configurations. This mechanism can be arrayed to create shape-morphing structures. The third model presents a design and development for a collapsible bistable compliant mechanism used for a shape morphing lamina-emergent frustum. Finally, physical prototypes of all models are presented as proof of concept

Bistable collapsible compliant mechanisms and shape-changing structures that comprise them

A bistable collapsible compliant mechanism including a first sub-mechanism comprising opposed first and second quaternary links and multiple binary links, each link being connected to at least two other links in the sub-mechanism, and a second sub-mechanism connected to the first sub-mechanism, the second sub-mechanism also comprising opposed first and second quaternary links and multiple binary links, each link being connected to at least two other links in the sub-mechanism, wherein the bistable collapsible compliant mechanism can be alternatively be placed in a stable extended orientation in which the bistable collapsible compliant mechanism has a trapezoidal shape and in a stable contracted orientation in which the bistable collapsible compliant mechanism has a polygonal spiral shape

A Lamina-Emergent Frustum Using a Bistable Collapsible Compliant Mechanism

This paper presents a new bistable collapsible compliant mechanism (BCCM) that is utilized in a lamina-emergent frustum. The mechanism is based on transforming a polygon spiral into spatial frustum shape using a mechanism composed of compliant links and joints that exhibits a bistable behavior. A number of mechanism types (graphs) were considered to implement the shape-morphing spiral, including 4-bar, 6-bar, and 8-bar chains. Our design requirements permitted the selection of a particular 8-bar chain as the basis for the BCCM. The bistable behavior was added to the mechanism by introducing a snap-through bistability as the mechanism morphs. A parametric CAD was used to perform the dimensional synthesis. The design was successfully prototyped. We anticipate that the mechanism may be useful in commercial small animal enclosures or as a frame for a solar still

Effect of a Rapid Tooling Technique in a 3D Printed Part for Developing an EDM Electrode

The role of rapid tooling (RT) in additive manufacturing (AM) seems essential in improving and spreading out the vista of manufacturing proficiency. In this article, attempts were made to discover the feasibility and the accomplishments of the RT electrode in the field of electro-discharge machining (EDM). Fused deposition modeling (FDM) is one of the AM processes adopted to fabricate the EDM electrode prototype by coating with copper. The copper is deposited on FDM-built ABS plastic component for about 1 mm through thick electroplating. The copper-coated FDM (CCF) and solid copper (SC) electrodes are used to conduct experiments on a die-sinking EDM machine using tool alloy steel as a workpiece. The CCF polymer electrode can be efficiently used in EDM operations as the build time of any complex shape was substantially reduced. However, the material removal rate (MRR) is far less than that of the SC electrode. It is recommended that the CCF electrode is used for semifinishing and finishing operations in which MRR happens to be less. However, CCF can get spoiled as high temperatures are generated on the machining tool, and the plastic core hardly sustains such high temperatures

Effect of part build orientations and sliding wear factors on tribological characteristics of FDM processed parts

Fused Deposition Modeling (FDM) components are commonly used for either prototypes or end products, mostly made of polymers. Polymers offer low frictional resistance to wear, so most of the engineering polymers find their increased usage in day-to-day industrial as well as domestic needs. The influence of many process controlling elements on the mechanical part properties is already being studied extensively, which demands the study of tribological characteristics like friction and wear rate under varying normal load (NL), sliding velocities (V) and part building orientations (PBO). The results showed a significant impact of the PBO and NL at various V on the tribological properties under various significant suitable sliding circumstances. Cracks were formed in the cylindrical tribometer specimens of Acrylonitrile butadiene styrene (ABS) fabricated at low PBO when operated at high NL, and V. Vertical PBO to the FDM building platform in the layers form where a number of inter-layers can bear maximum NL at higher values of V resulted in uniform wear and low frictions. Friction was noticed very low at minimum NL when PBO was 0° (horizontal) and 90° (vertical), but increased at high NL between PBO of 15° to 60°. The FDM parts improved compared to those from conventional manufacturing processes

High-Temperature Corrosion of APS- and HVOF-Coated Nickel-Based Super Alloy under Air Oxidation and Melted Salt Domains

Various thermal spraying approaches, such as air/atmospheric plasma spraying (APS) and high-velocity oxy-fuel (HVOF) spraying, are widely employed by plants owing to their flexibility, low costs and the high surface quality of the manufactured product. This study focuses on the corrosion behavior of a Ni superalloy coated with powder Cr3C2-25NiCr through APS and HVOF at 950 °C under air oxidation and Na2SO4 + 0.6V2O5 molten salt environments (MSE). The results show that HVOF-deposited Ni superalloys have higher hardness and bond strength than the respective APS coating. The thermo-gravimetric probe reveals that the Ni superalloys exposed to an oxidizing air environment has a minor mass gain compared to those under the MSE domain for both non-coated and coated samples, in line with the parabola curvature rate oxidizing law. The Ni superalloys show good corrosion resistance but poor oxidation resistance in APS-deposited Ni superalloys under the MSE. HVOF-coated Ni superalloys in both environments exhibit better corrosion resistance and lower mass gain than APS-coated superalloys. The excellent coating characteristics of HVOF-coated Ni superalloys lead to their better high-temperature corrosion performance than APS

Assessment of the Corrosion Behavior of Friction-Stir-Welded Dissimilar Aluminum Alloys

The fuel consumption of high-density automobiles has increased in recent years. Aluminum (Al) alloy is a suitable material for weight reduction in vehicles with high ductility and low weight. To address environmental problems in aircraft and maritime applications, in particular rust development and corrosion, the current study assesses the corrosion behavior during friction stir welding (FSW) of two dissimilar Al alloys (AA6061 and AA8011) in various corrosive conditions using salt spraying and submersion tests. Two acidic solutions and one alkaline solution are used in these tests, which are performed at room temperature. The two specimens (AA6061 and AA8011) and the weld region are suspended in a salt spraying chamber and a 5 wt.% NaCl solution is continually sprayed using the circulation pump for 60 h, with the specimens being weighed every 15 h to determine the corrosion rates. According to the salt spraying data, the weld zone has a higher corrosion resistance than the core components. For twenty-eight days, individual specimens are submerged in 3.5 wt.% HCl + H2O and H2SO4 + H2O solutions and seawater. The weld area specimens exhibit stronger corrosion resistance than the base material specimens, and weight loss in the saltwater medium is lower when compared to the other test solutions, according to the corrosion analysis. The scanning electron microscope (SEM) analysis demonstrates that the base metal AA8011 is considerably corroded on its surface