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The numerical treatment of non‐linear engineering phenomena often involves some sort of mathematical simplification. In many cases, the system under investigation is linearized about an operating point using the linear part of the Taylor’s series expansion. This allows local representation for use in incremental or iterative methods using well‐established computational tools for linear algebra. Demonstrates a different linearization technique that generally provides a higher quality fit to a certain class of functions than the standard Taylor linearization. This class of functions is general enough to represent all systems of algebraic equations. Presents a graphical demonstration of the quality of fit along with a discussion of why this alternative linearization provides a high quality fit. Also presents an engineering application of the linearization.

Additive manufacturing has paved a way for geometrical freedom and mass customization of new and innovative products. However, it has a few limitations in printing complex geometries and sizes. The purpose of this paper is three-dimensional printing of metal parts using selective laser melting (SLM) has several intricacies.

To test the capabilities of SLM, the complex geometries of varying sizes, orientations, shapes such as square and cylindrical features, thin wall structures and holes were checked for dimensional accuracy and surface roughness.

The outcome of the study represents the capabilities of SLM and provide insight for solving the technological issues and processing constraint in the manufacture of metal parts from aluminum alloy. The analysis has proven that there is significant accuracy in dimension for large features in comparison with smaller one. The dimensional reproducibility was determined with the aid of an optical measuring system and the range of errors were calculated. These results show that the dimensional accuracy of the features in the printed part was within acceptable tolerance limits. This paper also investigated the significant contributing factors influencing printing of two and three-dimensional surface roughness based on the result of surface profilometer and it was observed that the surface was smoothened with the presence of overhangs and supports.

The ability of SLM to fabricate conformer cooling channels to support mould fabrication was tested. From the experimental result, it was observed that the quality of printing of conformal cooling channels depended on the diameter of channels with larger distortions in the channel having smaller diameter. The innovative aspect of the work was the study of build orientation combined with the investigated material.

The purpose of this paper is to study the functionality of additively manufactured (AM) parts, mainly depending on their dimensional accuracy and surface finish. However, the products manufactured using AM usually suffer from defects like roughness or uneven surfaces. This paper discusses the various surface quality improvement techniques, including how to reduce surface defects, surface roughness and dimensional accuracy of AM parts.

There are many different types of popular AM methods. Unfortunately, these AM methods are susceptible to different kinds of surface defects in the product. As a result, pre- and postprocessing efforts and control of various AM process parameters are needed to improve the surface quality and reduce surface roughness.

In this paper, the various surface quality improvement methods are categorized based on the type of materials, working principles of AM and types of finishing processes. They have been divided into chemical, thermal, mechanical and hybrid-based categories.

The review has evaluated the possibility of various surface finishing methods for enhancing the surface quality of AM parts. It has also discussed the research perspective of these methods for surface finishing of AM parts at micro- to nanolevel surface roughness and better dimensional accuracy.

This paper represents a comprehensive review of surface quality improvement methods for both metals and polymer-based AM parts.

The purpose of this study aims to obtain excellent products, consistent investigation and manufacturing process control which are the preconditions that organizations have to consider. Nowadays, manufacturing industry apprise process capability index (C_pi) to evaluate the nature of their things with an expect to enhance quality and also to improve the productivity by cutting down the operating cost. In this paper, process capability analysis was applied during wire electrical discharge machining (WEDM) of titanium grade 6, to study the process performance within specific limits.

Four machine input parameters, namely, pulse ON time, pulse OFF time, wire feed and wire tension, were chosen for process capability study. Experiments were carried out according to Taguchi’s L27 orthogonal array. The value of C_pi was evaluated for two machining attributes, namely, average surface roughness and material removal rate (MRR). For these two machining qualities, single response optimization was executed to explore the input settings, which could optimize WEDM process ability.

Optimum parameter settings for average surface roughness and MRR were found to be TON: 115 µs, TOFF: 55 µs, WF: 4 m/min and WT: 6 kg⁻F and TON: 105 µs, TOFF: 60 µs, WF: 4 m/min and WT: 5 kg⁻F.

Process capability analysis constantly checks the process quality through the capability index keep in mind the end goal to guarantee that the items made are complying with the particulars, providing data for product plan and process quality enhancement for designer and engineers, giving the support to decrease the cost of item failures.

The purpose of this paper is to expose computational methods as applied to engineering systems and evolutionary processes with randomness in external actions and inherent parameters.

In total, two approaches are distinguished that rely on solvers from deterministic algorithms. Probabilistic analysis is referred to as the approximation of the response by a Taylor series expansion about the mean input. Alternatively, stochastic simulation implies random sampling of the input and statistical evaluation of the output.

Beyond the characterization of random response, methods of reliability assessment are discussed. Concepts of design improvement are presented. Optimization for robustness diminishes the sensitivity of the system to fluctuating parameters.

Deterministic algorithms available for the primary problem are utilized for stochastic analysis by statistical Monte Carlo sampling. The computational effort for the repeated solution of the primary problem depends on the variability of the system and is usually high. Alternatively, the analytic Taylor series expansion requires extension of the primary solver to the computation of derivatives of the response with respect to the random input. The method is restricted to the computation of output mean values and variances/covariances, with the effort determined by the amount of the random input. The results of the two methods are comparable within the domain of applicability.

The present account addresses the main issues related to the presence of randomness in engineering systems and processes. They comprise the analysis of stochastic systems, reliability, design improvement, optimization and robustness against randomness of the data. The analytical Taylor approach is contrasted to the statistical Monte Carlo sampling throughout. In both cases, algorithms known from the primary, deterministic problem are the starting point of stochastic treatment. The reader benefits from the comprehensive presentation of the matter in a concise manner.

In an impact phenomenon the material is subjected to very short duration high force levels resulting large plastic deformations and rise in temperature at high strain rates. A circular rod impacting against a rigid surface called as Taylor rod impact test is widely used for determining the mechanical behaviour of materials subjected to high strain rates with associated increase in temperature. A three-dimensional large deformation, thermo-elasto-plastic, dynamic, contact, finite element formulation is developed to study the effect of temperature rise due to plastic deformation and surface friction on the deformation and stress fields. It is found that the predicted equivalent plastic strain values are influenced by temperature generated due to plastic deformation and surface friction. The values of the coefficient of friction have a profound effect on the location of fracture initiation on the impacting face in a circular rod.

Field emission electric propulsion (FEEP) thruster is a type of electric propulsion based on space‐proven indium liquid metal ion sources. The lifetime of FEEP thruster limits its application in space. A better method to improve its lifetime is the reduction of emission current. This paper aims to discuss the minimum emission current of operating FEEP thrusters.

In this work, theoretical models, including fluid‐flow model and ion formation model, are analyzed. Current densities of these models are discussed and the minimum emission current is calculated.

There are few equilibrium states under low emission current conditions. However, the minimum emission current is the only stable state at which the FEEP thruster can operate.

This analysis is mainly based on the needle indium FEEP, which is compared indirectly with experiments of gallium.

This paper attempts to help designers choose appropriate electric parameters to improve the lifetime of FEEP.

By introducing and analyzing theoretical models, this paper calculates the minimum emission current for stable operation of FEEP.

The basic parameters of screen printing are discussed, and an analytical model of the screen printing process is introduced. The ink roll in front of the squeegee is treated as a pump generating, close to the squeegee edge, high hydrostatic pressure which injects ink into the screen meshes. The shearing of the ink, the mechanics of screen snap‐off and the ink transfer taking place behind the squeegee are also analysed.

Selective laser melting (SLM) is a powder metallurgical (PM) additive manufacturing process whereby a three‐dimensional part is built in a layer‐wise manner. During the process, a high intensity laser beam selectively scans a powder bed according to the computer‐aided design data of the part to be produced and the powder metal particles are completely molten. The process is capable of producing near full density (∼98‐99 per cent relative density) and functional metallic parts with a high geometrical freedom. However, insufficient surface quality of produced parts is one of the important limitations of the process. The purpose of this study is to apply laser re‐melting using a continuous wave laser during SLM production of 316L stainless steel and Ti6Al4V parts to overcome this limitation.

After each layer is fully molten, the same slice data are used to re‐expose the layer for laser re‐melting. In this manner, laser re‐melting does not only improve the surface quality on the top surfaces, but also has the potential to change the microstructure and to improve the obtained density. The influence of laser re‐melting on the surface quality, density and microstructure is studied varying the operating parameters for re‐melting such as scan speed, laser power and scan spacing.

It is concluded that laser re‐melting is a promising method to enhance the density and surface quality of SLM parts at a cost of longer production times. Laser re‐melting improves the density to almost 100 per cent whereas 90 per cent enhancement is achieved in the surface quality of SLM parts after laser re‐melting. The microhardness is improved in the laser re‐molten zone if sufficiently high‐energy densities are provided, probably due to a fine‐cell size encountered in the microstructure.

There has been extensive research in the field of laser surface modification techniques, e.g. laser polishing, laser hardening and laser surface melting, applied to bulk materials produced by conventional manufacturing processes. However, those studies only relate to laser enhancement of surface or sub‐surface properties of parts produced using bulk material. They do not aim at enhancement of core material properties, nor surface enhancement of (rough) surfaces produced in a PM way by SLM. This study is carried out to cover the gap and analyze the advantages of laser re‐melting in the field of additive manufacturing.

The purpose of this paper is to review and to provide a dipper understanding of what happens to piston rings and cylinder surfaces when manufacturing errors depicted, such as waviness and straightness. The mechanism of friction and the piston ring structural integrity, due to the surface irregularities, are analyzed either for smooth ring surface or for artificial textured, while piston ring floats into the piston groove or not.

In this work two tribological models of a piston ring- cylinder package are presented using CFD analysis. Initially, the piston ring is considered as a secured ring in the groove of piston (secured ring) while in second model, the piston ring floats into the piston groove (free ring).

Increasing the number of waves across the piston ring thickness, the structural integrity of the ring is strongly influenced. Piston ring with surface texturing reduces the mean friction force, under the consideration of cylinder straightness. The gas leaks due to existence of the ring gap, affects significantly the maximum mechanical stresses.

The novelty of this paper is the analysis of manufacturing errors, such as waviness and straightness either for smooth or for artificial textured piston ring. In particular, the piston ring structural integrity investigated while chamber gas pressure leaks through the ring gap or not. The number of the waves, their amplitude and the fluid velocity are also taken into consideration.