Spatially resolved acoustic spectroscopy for selective laser melting

Smith, Richard J.; Hirsch, M.; Patel, Rikesh; Li, Wenqi; Clare, Adam T.; Sharples, S. D.

doi:10.1016/j.jmatprotec.2016.05.005

Cited by 109 publications

(39 citation statements)

References 19 publications

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“…A distinction commonly done in the literature is between spherical pores and non-spherical pores (Sharratt, 2015). The voids observed between the layers are referred to as "acicular pores" by some authors (Smith et al, 2016) and they are characterized by an elongated shape. Fig.…”

Section: Categories Of Defects 221 Porositymentioning

confidence: 99%

“…Once the area of interest has been located, the OCT can apply a higher resolution scan and provide a higher-detail evaluation of the sub-surface. Smith et al (2016) studied the spatially resolved acoustic spectroscopy technique for part inspection in SLM applications. The technique can be used to investigate the process parameter effect on the part quality and for the internal and sub-surface porosity characterization.…”

Section: Off-axial Sensingmentioning

confidence: 99%

“…The technique can be used to investigate the process parameter effect on the part quality and for the internal and sub-surface porosity characterization. Smith et al (2016) discussed the possibility of an in-situ implementation suggesting a possible co-axial integration of the instrument in SLM systems.…”

Section: Off-axial Sensingmentioning

confidence: 99%

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Process defects andin situmonitoring methods in metal powder bed fusion: a review

Grasso

Colosimo

2017

Meas. Sci. Technol.

558

246

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Despite continuous technological enhancements of metal Additive Manufacturing (AM) systems, the lack of process repeatability and stability still represents a barrier for the industrial breakthrough. The most relevant metal AM applications currently involve industrial sectors (e.g., aerospace and bio-medical) where defects avoidance is fundamental. Because of this, there is the need to develop novel in-situ monitoring tools able to keep under control the stability of the process on a layer-by-layer basis, and to detect the onset of defects as soon as possible. On the one hand, AM systems must be equipped with in-situ sensing devices able to measure relevant quantities during the process, a.k.a. process signatures. On the other hand, in-process data analytics and statistical monitoring techniques are required to detect and localize the defects in an automated way. This paper reviews the literature and the commercial tools for insitu monitoring of Powder Bed Fusion (PBF) processes. It explores the different categories of defects and their main causes, the most relevant process signatures and the in-situ sensing approaches proposed so far. Particular attention is devoted to the development of automated defect detection rules and the study of process control strategies, which represent two critical fields for the development of future smart PBF systems.

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Section: Categories Of Defects 221 Porositymentioning

confidence: 99%

Section: Off-axial Sensingmentioning

confidence: 99%

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Process defects andin situmonitoring methods in metal powder bed fusion: a review

Grasso

Colosimo

2017

Meas. Sci. Technol.

558

246

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“…Such length scales are not compatible with current analysis techniques, such as EBSD. However, there are exciting new techniques, including spatially resolved acoustic spectroscopy (SRAS) (Smith et al, 2014(Smith et al, , 2016bSharples et al, 2006;Li et al, 2012) which may provide a way to conduct large scale analysis of variations in the orientation of grains, providing a way to correlate processing with properties and performance (Haden et al, 2015). There are some non-destructive methods to assess anisotropy, including X-ray-based tomographic approaches, but they are sensitive to sample thickness and can be hindered by a spatially varying crystallographic texture.…”

Section: Inclusionsmentioning

confidence: 99%

Powder-based additive manufacturing - a review of types of defects, generation mechanisms, detection, property evaluation and metrology

Taheri

Shoaib

Koester³

et al. 2017

IJASMM

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Powder-based additive manufacturing (AM) technologies have been evaluated for use in different fields of application (aerospace, medical, etc.). Ideally, AM parts should be at least equivalent, or preferably better quality than conventionally produced parts. Manufacturing defects and their effects on the quality and performance of AM parts are a currently a major concern. It is essential to understand the defect types, their generation mechanisms, and the detection methodologies for mechanical properties evaluation and quality control. We consider the various types of microstructural features or defects, their generation mechanisms, their effect on bulk properties and the capability of existing characterisation methodologies for powder based AM parts in this work. Methods of in-situ non-destructive evaluation and the influence of defects on mechanical properties and design considerations are also reviewed. Together, these provide a framework to understand the relevant machine and material parameters, optimise the process and production, and select appropriate characterisation methods.Abstract: Powder-based additive manufacturing (AM) technologies have been evaluated for use in different fields of application (aerospace, medical, etc.). Ideally, AM parts should be at least equivalent, or preferably better quality than conventionally produced parts. Manufacturing defects and their effects on the quality and performance of AM parts are a currently a major concern. It is essential to understand the defect types, their generation mechanisms, and the detection methodologies for mechanical properties evaluation and quality control. We consider the various types of microstructural features or defects, their generation mechanisms, their effect on bulk properties and the capability of existing characterisation methodologies for powder based AM parts in this work. Methods of in-situ non-destructive evaluation and the influence of defects on mechanical properties and design considerations are also reviewed. Together, these provide a framework to understand the relevant machine and material parameters, optimise the process and production, and select appropriate characterisation methods.Reference to this paper should be made as follows: Taheri, H., Shoaib, M.R.M., Koester, L., Bigelow, T.A., Collins, P.C. and Bond, L.J. (2017) 'Powder-based additive manufacturing -a review of types of defects, generation mechanisms, detection, property evaluation and metrology', Int. Institute of Aviation Technology conducting research on UAVs and designing and printing 3D parts for UAVs. His research interest areas include engineering mechanics, additive manufacturing and non-destructive testing.Lucas W. Koester received his PhD from the University of Nebraska at Lincoln studying wave propagation and scattering in polycrystalline media. His current and past research interests include wave propagation in polycrystalline media, defect scattering, and modelling with emphasis on additive manufacturing processes and materials.Powder-based additive...

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“…The technique is non-contact, all optical and non-destructive. In previous work, we showed that it was possible to use SRAS to image the surface texture [9], and identify both surface and subsurface defects [10] on prepared samples made using SLM. In these cases, prepared samples were polished so that the surface roughness was R a < 100 nm.…”

Section: Introductionmentioning

confidence: 99%

Imaging Material Texture of As-Deposited Selective Laser Melted Parts Using Spatially Resolved Acoustic Spectroscopy

et al. 2018

Self Cite

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Additive manufacturing (AM) is a production technology where material is accumulated to create a structure, often through added shaped layers. The major advantage of additive manufacturing is in creating unique and complex parts for use in areas where conventional manufacturing reaches its limitations. However, the current class of AM systems produce parts that contain structural defects (e.g., cracks and pores) which is not compatible with certification in high value industries. The probable complexity of an AM design increases the difficulty of using many non-destructive evaluation (NDE) techniques to inspect AM parts—however, a unique opportunity exists to interrogate a part during production using a rapid surface based technique. Spatially resolved acoustic spectroscopy (SRAS) is a laser ultrasound inspection technique used to image material microstructure of metals and alloys. SRAS generates and detects `controlled’ surface acoustic waves (SAWs) using lasers, which makes it a non-contact and non-destructive technique. The technique is also sensitive to surface and subsurface voids. Work until now has been on imaging the texture information of selective laser melted (SLM) parts once prepared (i.e., polished with R a < 0 . 1 μ m)—the challenge for performing laser ultrasonics in-process is measuring waves on the rough surfaces present on as-deposited parts. This paper presents the results of a prototype SRAS system, developed using the rough surface ultrasound detector known as speckle knife edge detector (SKED)—texture images using this setup of an as-deposited Ti64 SLM sample, with a surface roughness of S a ≈ 6 μ m, were obtained.

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Spatially resolved acoustic spectroscopy for selective laser melting

Cited by 109 publications

References 19 publications

Process defects andin situmonitoring methods in metal powder bed fusion: a review

Process defects andin situmonitoring methods in metal powder bed fusion: a review

Powder-based additive manufacturing - a review of types of defects, generation mechanisms, detection, property evaluation and metrology

Imaging Material Texture of As-Deposited Selective Laser Melted Parts Using Spatially Resolved Acoustic Spectroscopy

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