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This study aims to complete the optimization design of a centrifugal impeller with both high aerodynamic efficiency and good structural machinability.

First, the design parameters were derived from the blade loading distribution and the meridional geometry in the impeller three-dimensional (3D) inverse design. The blade wrap angle at the middle span surface and the spanwise averaged blade angle at the blade leading edge obtained from inverse design were chosen as the machinability objectives. The aerodynamic efficiency obtained by computational fluid dynamics was selected as the aerodynamic performance objective. Then, using multi-objective optimization with the optimal Latin hypercube method, quadratic response surface methodology and the non-dominated sorting genetic algorithm, the trade-off optimum impellers with small blade wrap angles, large blade angles and high aerodynamic efficiency were obtained. Finally, computational fluid dynamics and computer-aided manufacturing were performed to verify the aerodynamic performance and structural machinability of the optimum impellers.

Providing the fore maximum blade loading distribution at both the hub and shroud for the 3D inverse design helped to promote the structural machinability of the designed impeller. A straighter hub coupled with a more curved shroud also facilitated improvement of the impeller’s structural machinability. The preferred impeller was designed by providing both the fore maximum blade loading distribution at a relatively straight hub and a curved shroud for 3D inverse design.

The machining difficulties of the designed high-efficiency impeller can be reduced by reducing blade wrap angle and enlarging blade angle at the beginning of impeller design. It is of practical value in engineering by avoiding the follow-up failure for the machining of the designed impeller.

The purpose of this paper is to describe a preliminary investigation into the heat treatment of Ti‐6Al‐7Nb components that had been produced via selective laser melting (SLM).

Bars of Ti‐6Al‐7Nb were produced using SLM by MCP‐HEK Tooling GmbH in Lubeck, Germany. These bars were then subjected to a range of heat treatments and the resultant microstructure evaluated with respect to its likely effect on fatigue.

It was found that the as received material consisted of an α′ martensitic structure in a metastable β matrix. Evidence of the layer‐wise thermal history was present, as were large (up to ∼500 μm) pores. Solution treatment at 955°C (below the β transus) did not completely disrupt this layered structure and is therefore not recommended. When solution treatment was performed at 1,055°C (above the β transus) a homogeneous structure was produced, with a morphology that depended on the post‐solution treatment cooling rate. It was concluded that the most promising heat treatment consisted of a moderate cooling rate after solution treatment at 1,055°C.

The study had only limited material and therefore it was not possible to perform any mechanical property testing.

The paper presents the initial findings of a project which is aimed at optimising the mechanical properties of Ti‐6Al‐7Nb components produced using SLM.

Currently, little is known about the heat treatment and subsequent mechanical properties of this Ti‐6Al‐7Nb alloy when produced using rapid manufacturing techniques. Such lack of knowledge limits the potential applications, especially in the biomedical field where the consequences of implant failure are high. The paper presents the first step in developing this understanding.

This study aims to explore the machinability of ZrB₂ using electrical discharge machining (EDM) with different tool materials.

The workpiece for this study was fabricated through powder metallurgy compaction method. The disc is machined using diamond load grinding to have parallel surfaces, then, 2 mm diameter holes are machined on the disc using EDM spark erosion machine with different tool materials (graphite, aluminium, tantalum, niobium, copper, brass, silver, tungsten and titanium). Roundness, geometry of hole, and diameter of the hole at different diametric planes, surface roughness (SR), material removal rate (MRR), tool wear rate (TWR), taper angle and recast layer (RCL) thickness are measured. The photographic analysis of tools, holes in the top view, bottom view and sectional view. SEM analysis was conducted to study the recast layer. Desirability function analysis was employed to rate the performances of tools.

A new theory is developed which relates recast layer thickness with melting point and thermal conductivity of the tool materials. Machining of ZrB₂ by EDM is feasible; graphite is identified as the best tool. Recast layer thickness of the machined surfaces are indirectly proportional to the product of melting point and thermal conductivity of tool. Ablation behaviour of ceramic workpiece lead additional material losses in the tool.

Extremely high strength and hardness of ZrB₂ due to the coexistence of strong covalent and metallic bond make mechanical machining very difficult or even impossible. No machinability studies were conducted previously on ZrB₂ using EDM; this work reveals machinability study of ZrB₂ with different tool materials.

Three-dimensional printing (3DP) is an established process to print structural parts of metals, ceramic and polymers. Further, multi-material 3DP has the potentials to be a milestone in rapid manufacturing (RM), customized design and structural applications. Being compatible as functionally graded materials in a single structural form, multi-material-based 3D printed parts can be applied in structural applications to get the benefit of modified properties.

The fused deposition modelling (FDM) is one of the established low cost 3DP techniques which can be used for printing functional/ non-functional prototypes in civil engineering applications.

The present study is focused on multi-material printing of primary recycled acrylonitrile butadiene styrene (ABS), polylactic acid (PLA) and high impact polystyrene (HIPS) in composite form. Thermal (glass transition temperature and heat capacity) and mechanical properties (break load, break strength, break elongation, percentage elongation at break and Young’s modulus) have been analysed to observe the behaviour of multi-material composites prepared by 3DP. This study also highlights the process parameters optimization of FDM supported with photomicrographs.

The present study is focused on multi-material printing of primary recycled ABS, PLA and HIPS in composite form.

The purpose of this paper is to analyze machinability of CFRP, GFRP, GLARE-type composites in drilling process taking into account their features and properties (the geometric characteristics, the volume fraction and the mechanical properties of the individual components of the composite). Drilling in non-plan surfaces and slope drilling.

The tests were carried out in two stages: perpendicular drilling of materials such as GLARE with special drill bits, and drilling of composite structures with non-planar surfaces made of unidirectional carbon fiber prepregs, using the modified special drill. Measurement of cutting forces and torque, stress distribution (photoelastic method) and a visual assessment of defects occurring during drilling allowed to determine the relationship between the type and geometry of the composite drill.

Identified great effect of kind of composite on the machinability of these materials has substantiated modification of the standard geometry of drills and matching this geometry to specific properties of the various type of composites.

Drilling of assembly holes for aerospace parts.

New type of drill geometry for different type of composite.

In features based design systems that are underpinned by solid models, buildings are designed by applying features to the design domain. A feature may be translated and/or rotated in order to position it in the desired place. Contradiction between the applied features and resulting features may occur due to the features interaction, wrong positioning, or inadequate parameters supplied by the user during the product definition. Moreover, the application of other features may cause some features to degenerate to further features. Therefore, verification of the resulting features must be performed against the applied features to establish whether the resulting features conform to the underlying geometry. Current feature‐based design systems employ a mechanism of tagging feature labels onto geometry. This approach does not guarantee the geometric correctness of the resultant feature and knowledge of the topology of the resulting feature and a geometric analysis is necessary to correctly identify the validity of the resultant feature. The research reported in this paper proposes an alternative approach which uses a product model that permits all geometrical and technological information associated with the design and construction stages to be represented. Individual features can be extracted from the product model and analysed to determine their accessibility. Methods which use the product description and other construction data to determine feature validity, accessibility and machinability are used. Each volumetric feature corresponds to a solid that can be added by one or more construction process or removed by one or more machining operations; as a consequence of applying volumetric features, surface features are generated. These surface features provide enough information to enable the accessibility, and machinability of the individual features to be determined and establish the possible routes in which the feature can be accessed if any.

The purpose of this paper is to investigate the concept of new drill bit geometry adjusted to a given composite type. This paper explores the possibility of drilling in composites without negative effects such as: delamination, rapid tool wear, matrix burns, pulling out of fibers, etc.

Appropriate modification of drill bit geometries applied to composite materials include, among other things: modifications of point angles, reduction of chisel edge width, modification of drill margins and proper preparation of drill bit corners.

Description of tool geometry for drilling of different types of composites, in particular drilling in parts included free grain surfaces but also drilling at a different angle than 90°.

Geometrical details of the tool for drilling are depended on the type of composite.

Making of montage holes in parts made of composites without negative effects during drilling.

Analysis of the current state of knowledge shows that there are insufficient solutions in terms of new drill geometry for drilling of composites. Existing solutions do not guarantee adequate stability and repeatability of the cutting process. It is necessary to create new geometry drills permit the elimination of negative phenomena during drilling.

This study aims to investigate the influence of process parameters of wire electrical discharge machining (WEDM) of Nimonic75. Nimonic75 is a Nickel-based alloy mostly used in the aerospace industry for its strength at high temperature.

One factor at a time (OFAT) approach has been used to perform the experiments. Pulse on time, pulse off time, peak current and servo voltage were chosen as input process parameters. Cutting speed, material removal rate and surface roughness (Ra) were selected as output performance characteristics.

Through experimental work, the effect of process parameters on the response characteristics has been found. Results identified the most important parameters to maximize the cutting speed and material removal rate and minimize Ra.

Very limited research work has been done on WEDM of Nickel-based alloy Nimonic75. Therefore, the aim of this paper to conduct preliminary experimentation for identifying the parameters, which influence the response characteristics such as material removal rate, cutting speed, Ra, etc. during WEDM of Nickel-based alloy (Nimonic75) using OFAT approach and found the machinability of Nimonic75 for further exhaustive experimentation work.

The purpose of this paper is to develop a mathematical model for metal removal rate and surface roughness through Taguchi method and analyse the influence of the individual input machining parameters (cutting speed, feed rate, helix angle, depth of cut and wt% on the responses in milling of aluminium-titanium diboride metal matrix composite (MMC) with solid carbide end mill cutter coated with nano-crystals.

Taguchi OA is used to optimise the material removal rate (MRR) and Surface Roughness by developing a mathematical model. End Milling is used to create slots by combining various input parameters. Five factors, three-level Taguchi method is employed to carry out the experimental investigation. Fuzzy logic is used to find the optimal cutting factors for surface roughness (Ra) and MRR. The factors considered were weight percentage of TiB₂, cutting speed, depth of cut and feed rate. The plan for the experiments and analysis was based on the Taguchi L27 orthogonal array with five factors and three levels. MINITAB 17 software is used for regression, S/N ratio and analysis of variance. MATLAB 7.10.0 is used to perform the fuzzy logics systems.

Using fuzzy logics, multi-response performance index is generated, with which the authors can identify the correct combination of input parameters to get higher MRR and lower surface roughness value with the chosen range with 95 per cent confidence intervals. Using such a model, remarkable savings in time and cost can be obtained.

Machinability characteristics in Al-TiB₂ MMC based on the Taguchi method with fuzzy logic has not been analysed previously.

The purpose of this paper is to develop a mathematical model for the surface delamination through response surface methodology (RSM) and analyse the influences of the entire individual input machining parameters (cutting speed, feed rate and depth of cut) on the responses in milling of carbon fibre reinforced polymer (CFRP) composites with solid carbide end mill cutter coated with polycrystalline diamond.

Three factors, three level face-centered central composite design in RSM was employed to carry out the experimental investigation. The “Design Expert 8.0” software was used for regression and graphical analysis of the data collected. The optimum values of the selected variables were obtained by solving the regression equation and by analyzing the response surface contour plots. Analysis of variance was used to check the validity of the model and for finding the significant parameters.

The developed second-order response surface model is used to calculate the delamination of the machined surfaces at different cutting conditions with the chosen range with 95 per cent confidence intervals. Using such model, one can obtain remarkable savings in time and cost.

The effect of machining parameters on surface delamination during milling of CFRP composites using RSM has not been previously analysed.