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CD Naiju

Bio: CD Naiju is an academic researcher from VIT University. The author has contributed to research in topics: Direct metal laser sintering & Fatigue limit. The author has an hindex of 3, co-authored 8 publications receiving 30 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, the reliability of components manufactured by direct metal laser sintering (DMLS) for fatigue strength has been evaluated using an orthogonal array of L4 experiments.
Abstract: This work presents the results of a study to determine the reliability of components manufactured by direct metal laser sintering (DMLS) for fatigue strength. A standard procedure and specimen according to IS 5075-1986 had been used in the experiment. Using Taguchi's experimental design techniques, an orthogonal array of L4 experiments had been developed. Fatigue testing was carried out and analysis of variance (ANOVA) technique was employed to investigate the process parameters in order to identify the main process parameter that affects the performance of the fatigue component. It has been found that scan spacing had more influence on fatigue strength as compared to sintering speed and hatch type. The two-parameter Weibull distribution was adopted to find the reliability of the manufactured components. The Weibull shape parameter and scale parameter was estimated and found approximately by a normal distribution. Micro structural analysis shows that there is a better bonding between the materials when the sintering speed is reduced.

15 citations

Journal Article
TL;DR: In this article, the optimum process parameters influencing the fatigue cycles to failure of DMLS components were determined for the purpose of determining the optimal process parameters to determine the optimum fatigue cycle.
Abstract: Direct Metal Laser Sintering (DMLS) is one of the methods in layered manufacturing technologies by which metal powder can be directly used to produce both prototype and production tools. Fatigue strength is one of the important mechanical properties for the functional application of DMLS parts. This study was carried out to determine the optimum process parameters influencing the fatigue cycles to failure of DMLS components. Sintering speed, scan spacing, post-contouring speed, infiltration and hatch type are the process parameters taken up for the study. Statistical design of experiments using Taguchi’s orthogonal array was employed for this study. Experimental data obtained were analysed using analysis of variance (ANOVA). From the results, it is found that one of the process parameters, sintering speed affects the fatigue properties of parts produced by this technology to a significant extent

3 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the ability of shot and laser peening to enhance the fatigue lifetime and strength of AM parts is evaluated, including for the case of geometric stress risers as expected for fielded AM components.
Abstract: Additive manufacturing (AM) is rapidly moving from research to commercial applications due to its ability to produce geometric features difficult or impossible to generate by conventional machining. Fielded components need to endure fatigue loadings over long operational lifetimes. This work evaluates the ability of shot and laser peening to enhance the fatigue lifetime and strength of AM parts. As previously shown, peening processes induce beneficial microstructure and residual stress enhancement; this work takes a step to demonstrate the fatigue enhancement of peening including for the case of geometric stress risers as expected for fielded AM components. We present AM sample fatigue results with and without a stress riser using untreated baseline samples and shot and laser peening surface treatments. Laser peening is clearly shown to provide superior fatigue life and strength. We also investigated the ability of analysis to select laser peening parameters and coverage that can shape and/or correctively reshape AM components to a high degree of precision. We demonstrated this potential by shaping and shape correction using our finite element based predictive modeling and highly controlled laser peening.

124 citations

Journal ArticleDOI
29 Jun 2018
TL;DR: In this paper, the impact of heat treatment, machining, and micro-shot-peening on the fatigue strength of DMLS-produced Maraging Steel MS1, when it is used in the “as fabricated” state, was investigated experimentally.
Abstract: The main motivations for this study arise from the need for an assessment of the fatigue performance of DMLS-produced Maraging Steel MS1, when it is used in the “as fabricated” state. The literature indicates a lack of knowledge from this point of view; moreover, the great potentials of the additive process may be more and more incremented, if an easier and cheaper procedure could be used after the building stage. The topic has been tackled experimentally, investigating the impact of heat treatment, machining, and micro-shot-peening on the fatigue strength with respect to the “as built state”. The results indicate that heat treatment may improve the fatigue response, as an effect of the relaxation of the process-induced tensile residual stresses. Machining can also be effective, but it must be followed (not preceded) by shot-peening, to benefit from the compressive residual stress state generated by the latter. Moreover, heat treatment and machining are related by a strong positive interaction, meaning their effects are synergistically magnified when they are applied together. The experimental study has been completed by fractographic as well as micrographic analyses, investigating the impact of the heat treatment on the actual microstructure induced by the stacking process.

115 citations

Journal ArticleDOI
18 Apr 2021
TL;DR: This work aims to document post-processing technologies and their applications concerning different AM processes and their integrations with AM process.
Abstract: Additive manufacturing (AM) technology has rapidly evolved with research advances related to AM processes, materials, and designs. The advantages of AM over conventional techniques include an augmented capability to produce parts with complex geometries, operational flexibility, and reduced production time. However, AM processes also face critical issues, such as poor surface quality and inadequate mechanical properties. Therefore, several post-processing technologies are applied to improve the surface quality of the additively manufactured parts. This work aims to document post-processing technologies and their applications concerning different AM processes. Various types of post-process treatments are reviewed and their integrations with AM process are discussed.

62 citations

Journal ArticleDOI
TL;DR: In this article, grey relational analysis and fuzzy technique of order preference by a similarity to ideal solution (fuzzy TOPSIS) methods are proposed for selection of rapid prototyping systems considering both benefit and non-benefit criteria.
Abstract: In this paper, grey relational analysis and fuzzy technique of order preference by a similarity to ideal solution (fuzzy TOPSIS) methods are proposed for selection of rapid prototyping systems considering both benefit and non-benefit criteria. The criteria may be qualitative or quantitative in nature. The results of grey relational analysis are compared with well-known fuzzy TOPSIS method. The advantage of grey theory over fuzzy theory is that grey theory considers the condition of the fuzziness, i.e., grey theory can deal flexibly with the fuzziness situation. Six RP systems are chosen and compared addressing to various criteria such as dimensional accuracy and surface quality, part cost, build time and material properties. Finally, it has been concluded that selective laser sintering (SLS 2500) is the most appropriate RP system for better dimensional accuracy and surface quality whereas 3-D printing (Z 402) is an appropriate RP system for better build time.

34 citations

Journal ArticleDOI
TL;DR: In this article , a bibliometric knowledge mapping approach is used to provide a bird's eye view of the current research status in the physical Internet (PI) and digital twin (DT) area.

30 citations