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This study aims to reveal that fatigue life is improved using heat treatment in the rotational bending fatigue test, which determines the fatigue behavior closest to service conditions.

It is essential to know the mechanical behavior of the parts produced by additive manufacturing under service conditions. In general, axial stress and plane bending tests are used by many researchers because they are practical: the service conditions cannot be sufficiently stimulated. For this reason, the rotating bending fatigue test, which represents the conditions closest to the service conditions of a load-bearing machine element, was chosen for the study. In this study, the rotational bending fatigue behavior of X3NiCoMoTi18-9–5 (MS1) maraging steel specimens produced by the selective laser melting (SLM) technique was experimentally investigated under various heat treatments conditions.

As a result of the study, MS1 produced by additive manufacturing is a material suitable for heat treatment that has enabled the heat treatment to affect fatigue strength positively. Cracks generally initiate from the outer surface of the sample. Fabrication defects have been determined to cause all cracks on the sample surface or regions close to the surface.

While producing the test sample, printing was vertical to the print bed, and various heat treatments were applied. The rotating bending fatigue test was performed on four sample groups comprising as-fabricated, age-treated, solution-treated and solution + age-treated conditions.

Most literature studies have focused on the axial fatigue strength, printing orientation and heat treatment of maraging steels produced with Direct Metal Laser Sintering (DMLS); many studies have also investigated crack propagation behaviors. There are few studies in the literature covering conditions of rotating bending fatigue. However, the rotating bending loading state is the service condition closest to modern machine element operating conditions. To fill this gap in the literature, the rotating bending fatigue behavior of the alloy, which was maraging steel (X3NiCoMoTi18-9–5, 1.2709) produced by SLM, was investigated under a variety of heat treatment conditions in this study.

Military and unmanned aerial vehicles (UAV) applications like rocket motor casings, missile covers and ship hulls use components that are made of maraging steel. Maraging steel has properties that are superior to other metals, making it more suitable for the fabrication of such components. A grey relational analysis (GRA) that is based on the Taguchi method has been utilised in the current study to optimise a laser beam welding (LBW) process. Further aspects such as GRA's optimum ranges and percentage contributions were also estimated.

A Taguchi L16 orthogonal array is utilised to design and conduct the experiments. Laser power (LP), welding speed (WS) and focal position (FP) are the three parameters are chosen for the process of welding. The output responses are the upper width of the heat-affected zone (HAZup), the upper width of the fusion zone (FZup) and the depth of penetration (DOP). The effect of the above key parameters on the responses was examined using an analysis of variance (ANOVA).

The results of ANOVA reveal that the parameter that has the most influence on the overall grey relational grade (GRG) is the FP. Finally, metallographic characterisation and a microstructural analysis are conducted on the weld bead geometry to demarcate the zone of HAZ and fusion zone (FZ).

As the most important criteria for LBW of maraging steels is the provision of higher DOP, higher FZ width and lower heat-affected zone, the study intended to prove the applicability of GRA technique in solving multi-objective optimisation problems in applications like defence and unmanned systems.

The electric discharge machining (EDM) involves electrons discharged from the electrode and machining progresses due to the removal of the material from the component. This a thermal-based machining process primarily used for hard to machine components with conventional methods. This process is used to make intricate cavities and contours. The fabricated part is the replica of the tool material with high surface finish and good dimensional accuracy. This study aims to evaluate the comprehensive effect of process parameters on electric discharge machining of maraging steel.

Multiple criteria Decision making (MCDM) techniques are used to select the best parameters by comparing several responses to achieve the desired goal. There are different MCDM techniques available for optimization of machining parameters. In the current investigation, multi-objective optimization by data envelopment analysis based ranking (DEAR) approach was used for machining Maraging C300 grade steel.

The Taguchi L9 runs were planned with process parameters such as current (Amp), Tool diameter (mm) and Dielectric pressure (MPa). The effect of process parameters on the responses, namely, material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) were evaluated. High MRR is found at 15 A current, 14 mm tool diameter and dielectric pressure of 0.2 MPa. Optimum process parameters experiment showed reduced crack density.

An effort was made successfully to enhance the responses using the DEAR method and establish the decision making of selecting the optimal parameters by comparing the results obtained by machining maraging steel C300 grade.

This paper aims to identify issues with joining selective laser melting (SLM) steels with conventional cold rolled steels through remote laser beam welding.

A novel approach for substituting conventional cold rolled metal sheets with SLM metal sheets, made of 316L and 18-Ni 300, is presented. The characteristics of the interaction of wrought and SLM materials are described, and joining benchmark parameters are presented and compared to known existing joining results. Finally, the joints are assessed in line with automotive specifications. This research also addresses the importance of joining technologies for the implementation of SLM as a full-fledged manufacturing technology for the automotive industry.

New parameter ranges for laser beam welding of SLM steels are defined.

This research is limited to the examined steels and the used machines, parameters and equipment.

The presented benchmark parameters are expected to be useful for designers, product developers and machine operators.

Little knowledge is available about the behavior of SLM materials and their suitability for assembly processes. Novel information about SLM steels and their interaction with conventionally produced steel sheets is presented.

In friction welding of dissimilar joint method, few material compositions are not possible to weld effectively. For better dissimilar metal joining in friction welding, the interlayer techniques are used by the third metal to increase the diffusion for suitable metal bonding. The interlayer metals are popularly held by coating, foils, sheet and solid rod form. The coating method needs more care for surface preparation with special coating equipment with high workmanship. In case of foil as intermediate metal, more care is neededfor holding between the metal; most of the time this technique has the possibility of failure by peeling off from the contact surface during high speed rotation with pressure during friction generation.

In this investigation, a copper coin was machined to a suitable size (transition fit) to suit the recess inside the SS rod. The mating surfaces of Cu coin, SS rod and Ti alloy were machined, polished to mirror finish and handled in friction welding machine. The purpose of the transition fit between the coin and SS rod is for holding the same intact before the beginning of the process.

Successful joint was achieved with good joint strength at less time. Empirical models were established to fin out the joint strength at any given parameter within the range of investigation

The models developed can be used only within the range of investigation considered for experimentation.

The paper includes implications for the development of a method of joining any dissimilar joints

In this investigation, a copper coin was machined to a suitable size (transition fit) to suit the recess inside the SS rod. The mating surfaces of Cu coin, SS rod and Ti alloy were machined, polished to mirror finish and handled in friction welding machine. The purpose of the transition fit between the coin and SS rod is for holding the same intact before the beginning of the process.

THERE is no doubt that the outstanding difference between the structural design philosophy of the Harrier, as compared with conventional aircraft designed for similar duties, lies in the greater importance of achieving a minimum aircraft weight. This to be achieved with no loss in the ruggedness so essential to ground attack aircraft, especially when designed for use from advanced bases on semi‐prepared and natural sites. The structure represents some 35 per cent of the aircraft basic weight, and strenuous efforts have been made to keep this, together with the 65 per cent representing systems and equipment, to a minimum. It is, of course, necessary to attack weight at all times and in every aspect of design down to the smallest detail, and this policy has been pursued rigorously throughout the Harrier design.

Corrosion advisory service (1) A new service said to offer great benefits to a wide variety of companies in the engineering, nuclear and allied industries, operated by Corrosion Advisory Services Ltd., is in existence to make available expert guidance on problems related to design, service failures, production problems, use of materials and processes, specification of materials and protective treatments, and investigation of unusual problems. In addition there is an information service on all aspects of the corrosion and protection of metals and technical assistance can be provided in the field, e.g. for inspections and surveys, fault finding, etc.

IT is generally agreed there would be a significant saving in weight and consequent improvement in efficiency, if aircraft could be assembled by welding, instead of by the use of mechanical fasteners. The size of the savings is indicated and the reasons for the currently limited use of welded assemblies are listed. A short list has been chosen of those conventional and more recently developed welding procedures which might be considered suitable for assembling aircraft in future. The compatibility of these procedures and specific alloys is discussed. The relation between the welding procedures and the various components of the airframe is reviewed and some of the developments which might be possible through the use of welded construction are mentioned. There is a short discussion, also, on the joining of the composite materials which may be important in future airframe structures.

The mechanical characterization of selective laser melting (SLM) parts is an industrial challenge. This paper aims to propose a methodology to control the fatigue life of 17-4Ph stainless steel by selecting the most relevant manufacturing parameters: i.e. laser power, laser travel speed, hatch spacing and laser defocusing.

A rough and refined design of experiment (DOE) is carried out to target the best combination of process parameters. A response surface model is then constructed to predict the parameter combination that optimizes the fatigue performance.

This study results show that the fatigue limit of the specimens manufactured by SLM (471.7 MPa at 107 cycles) has reached near 90% of the value found in samples machined from a bar. This demonstrates the applicability of the method proposed to optimize the SLM process and control the fatigue life of 17-4Ph stainless steel. The study results are compared with other research works and provide an increase of 18% to the fatigue limit.

This study showcases a DOE methodology to optimize the SLM parameters to achieve fatigue performance as great as that of solid 17-4Ph stainless steel.

The primary objective of this investigation is to optimize the constricted arc tungsten inert gas (CA-TIG) welding parameters specifically welding current (WC), arc constriction current (ACC), ACC frequency (ACCF) and CA traverse speed to maximize the tensile properties of thin Inconel 718 sheets (2 mm thick) using a statistical technique of response surface methodology and desirability function for gas turbine engine applications.

The four factor – five level central composite design (4 × 5 – CCD) matrix pertaining to the minimum number of experiments was chosen in this investigation for designing the experimental matrix. The techniques of numerical and graphical optimization were used to find the optimal conditions of CA-TIG welding parameters.

The thin sheets of Inconel 718 (2 mm thick) can be welded successfully using CA-TIG welding process without any defects. The joints welded using optimized conditions of CA-TIG welding parameters showed maximum of 99.20%, 94.45% and 73.5% of base metal tensile strength, yield strength and elongation.

The joints made using optimized CA-TIG welding parameters disclosed 99.20% joint efficiency which is comparatively 20%–30% superior than conventional TIG welding process and comparable to costly electron beam welding and laser beam welding processes. The parametric mathematical equations were designed to predict the tensile properties of Inconel 718 joints accurately with a confidence level of 95% and less than 4.5% error. The mathematical relationships were also developed to predict the tensile properties of joints from the grain size (secondary dendritic arm spacing-SDAS) of fusion zone microstructure.