scholarly journals Diffraction-Based Residual Stress Characterization in Laser Additive Manufacturing of Metals

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1830
Author(s):  
Jakob Schröder ◽  
Alexander Evans ◽  
Tatiana Mishurova ◽  
Alexander Ulbricht ◽  
Maximilian Sprengel ◽  
...  
Keyword(s):  
Residual Stress ◽  
Additive Manufacturing ◽  
Interaction Model ◽  
Research Field ◽  
Laser Additive Manufacturing ◽  
Metal Structures ◽  
Grain Interaction ◽  
Future Demands ◽  
Non Destructive

Laser-based additive manufacturing methods allow the production of complex metal structures within a single manufacturing step. However, the localized heat input and the layer-wise manufacturing manner give rise to large thermal gradients. Therefore, large internal stress (IS) during the process (and consequently residual stress (RS) at the end of production) is generated within the parts. This IS or RS can either lead to distortion or cracking during fabrication or in-service part failure, respectively. With this in view, the knowledge on the magnitude and spatial distribution of RS is important to develop strategies for its mitigation. Specifically, diffraction-based methods allow the spatial resolved determination of RS in a non-destructive fashion. In this review, common diffraction-based methods to determine RS in laser-based additive manufactured parts are presented. In fact, the unique microstructures and textures associated to laser-based additive manufacturing processes pose metrological challenges. Based on the literature review, it is recommended to (a) use mechanically relaxed samples measured in several orientations as appropriate strain-free lattice spacing, instead of powder, (b) consider that an appropriate grain-interaction model to calculate diffraction-elastic constants is both material- and texture-dependent and may differ from the conventionally manufactured variant. Further metrological challenges are critically reviewed and future demands in this research field are discussed.

X-Ray Diffraction Determination of Metallurgical Damage in Turbo Blower Rotor Shafts

1988 ◽  
Vol 142 ◽  
Author(s):  
John F. Porter ◽  
Dan O. Morehouse ◽  
Mike Brauss ◽  
Robert R. Hosbons ◽  
John H. Root ◽  
...  
Keyword(s):  
Residual Stress ◽  
Hole Drilling ◽  
X Ray Diffraction ◽  
X Ray ◽  
Turbo Blower ◽  
Diffraction Determination ◽  
Defence Research ◽  
Stress Profiles ◽  
Non Destructive

AbstractStudies have been ongoing at Defence Research Establishment Atlantic on the evaluation of non-destructive techniques for residual stress determination in structures. These techniques have included neutron diffraction, x-ray diffraction and blind-hole drilling. In conjunction with these studies, the applicability of these procedures to aid in metallurgical and failure analysis investigations has been explored. The x-ray diffraction technique was applied to investigate the failure mechanism in several bent turbo blower rotor shafts. All examinations had to be non-destructive in nature as the shafts were considered repairable. It was determined that residual stress profiles existed in the distorted shafts which strongly indicated the presence of martensitic microstuctures. These microstructures are considered unacceptable for these shafts due to the potential for cracking or in-service residual stress relaxation which could lead to future shaft distortion.

Determination of Residual Stress Fields with High Local Resolution

2006 ◽  
Vol 524-525 ◽  
pp. 279-284
Author(s):  
Bernd Hasse ◽  
Mustafa Koçak ◽  
Walter Reimers
Keyword(s):  
Material Processing ◽  
Residual Stress ◽  
Stress Distribution ◽  
High Spatial Resolution ◽  
Residual Stress Distribution ◽  
Stress Fields ◽  
Selective Determination ◽  
Position Sensitive ◽  
Non Destructive

The non-destructive and phase selective determination of residual stresses caused by material processing (such as welding) in polycrystalline samples is usually performed by diffraction methods. In order to obtain information about stress fields at high spatial resolution with conventional methods, for example with micro beam techniques, the sample needs to be scanned in a very time consuming manner. A much faster method is the simultaneous investigation of a larger area using position sensitive diffractometry. This method was used for the analysis of the residual stress distribution in laser beam welded thin (2 mm and 3 mm) magnesium sheets.

Determination of depth gradients of grain interaction and stress in Cu thin films

2008 ◽  
Vol 41 (6) ◽  
pp. 1067-1075 ◽  
Author(s):  
M. Wohlschlögel ◽  
W. Baumann ◽  
U. Welzel ◽  
E. J. Mittemeijer
Keyword(s):  
Residual Stress ◽  
Incidence Angle ◽  
Incident Beam ◽  
Angle Measurement ◽  
Grain Interaction ◽  
Low Incidence ◽  
Depth Gradients ◽  
Sputter Deposited ◽  
Cu Thin Film

Grain-interaction and residual stress depth gradients in a sputter-deposited Cu thin film (thickness 4 µm) were determined by employing X-ray diffraction stress measurements at constant information depths in the range between 200 and about 1500 nm. A novel procedure, which allows the determination of an effective grain-interaction parameter on the basis of thef(ψ,hkl) method and the Voigt and Reuss models of elastic grain interaction, was used. The range of accessible penetration depths was maximized by employing different photon energies using a laboratory diffractometer with Cu Kα radiation and a diffractometer at a synchrotron beamline. The variation of grain interaction with depth could be successfully related to the microstructure of the specimen. The tensile residual stress in the film parallel to its surface decreases with decreasing depth. By measuring the lattice spacing for several reflections at one penetration depth with two different photon energies (i.e.using small and large incident beam angles) it was found that the surface roughness of the specimen counteracts the effect of beam refraction to some degree. As a consequence, irrespective of whether a refraction correction is applied or neglected for the low-incidence angle measurement, erroneous results are obtained for lattice spacings derived from reflections at small incidence angles; reliable grain-interaction and stress analysis requires measurements at high incidence angle.

Characterization of LAM-Fabricated Porous Superalloys for Turbine Components

2016 ◽  
Author(s):  
Brandon Ealy ◽  
Luisana Calderon ◽  
Wenping Wang ◽  
Jay Kapat ◽  
Ilya Mingareev ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Porous Structure ◽  
Turbine Blade ◽  
Leading Edge ◽  
Laser Additive Manufacturing ◽  
Internal Impingement ◽  
Edge Segment ◽  
Cycle Efficiency ◽  
Non Destructive

The limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Inconel alloys remain the material of choice for most hot gas path components in gas turbines, however recent increases in turbine inlet temperature (TIT) are associated with the development of advanced convective cooling methods and ceramic thermal barrier coatings (TBC). Increasing cycle efficiency and cycle specific work are the primary drivers for increasing TIT. Lately, incremental performance gains responsible for increasing the allowable TIT have been made mainly through innovations in cooling technology, specifically convective cooling schemes. An emerging manufacturing technology may further facilitate the increase of allowable maximum TIT, thereby impacting cycle efficiency capabilities. Laser Additive Manufacturing (LAM) is a promising manufacturing technology that uses lasers to selectively melt powders of metal in a layer-by-layer process to directly manufacture components, paving the way to manufacture designs that are not possible with conventional casting methods. This study investigates manufacturing qualities seen in LAM methods and its ability to successfully produce complex features found in turbine blades. A leading edge segment of a turbine blade, containing both internal and external cooling features, along with an engineered-porous structure is fabricated by laser additive manufacturing of superalloy powders. Various cooling features were incorporated in the design, consisting of internal impingement cooling, internal lattice structures, and external showerhead or transpiration cooling. The internal structure was designed as a lattice of intersecting cylinders in order to mimic that of a porous material. Variance distribution between the design and manufactured leading edge segment are carried out for both internal impingement and external transpiration hole diameters. Through a non-destructive approach, the presented geometry is further analyzed against the departure of the design by utilizing x-ray computed tomography (CT). Employing this non-destructive evaluation (NDE) method, a more thorough analysis of the quality of manufacture is established by revealing the internal structures of the porous region and internal impingement array. Flow testing was performed in order to characterize the uniformity of porous regions and flow characteristics across the entire article for various pressure ratios (PR). Discharge coefficient of internal impingement arrays and porous structure are quantified. The analysis yields quantitative data on the build quality of the LAM process, providing insight as to whether or not it is a viable option for manufacture of micro-features in current turbine blade production.

scholarly journals The Examination of Restrained Joints Created in the Process of Multi-material FFF Additive Manufacturing Technology

2020 ◽  
Author(s):  
Janusz Kluczynski ◽  
Lucjan Sniezek ◽  
Alexander Kravcov ◽  
Krzysztof Grzelak ◽  
Pavel Svoboda ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Acrylonitrile Butadiene Styrene ◽  
Tensile Tests ◽  
Lower Amount ◽  
Internal Quality ◽  
Experimental Production ◽  
Destructive Testing ◽  
Non Destructive

The paper is focused on the examination of the internal quality of joints created in a multi-material - additive manufacturing process. The main part of the work focuses on experimental production and non-destructive testing of restrained joints of modified PLA (polylactic acid) and ABS (Acrylonitrile butadiene styrene) 3Dprinted on RepRap 3D device that works on the "open source" principle. The article presents the outcomes of non-destructive materials test in the form of the data from the Laser Amplified Ultrasonography, microscopic observations of the joints area and tensile tests of the specially designed samples. The samples with designed joints were additively manufactured of two materials: specially blended PLA (Market name – PLA Tough) and conventionally made ABS. The tests are mainly focused on the determination of the quality of material connection in the joints area. Based on the results obtained, the samples made of two materials were compared in the end to establish which produced material joint is stronger and have a lower amount of defects.

Experimental Study on Residual Stress in Titanium Alloy Laser Additive Manufacturing

2013 ◽  
Vol 431 ◽  
pp. 20-26 ◽  
Author(s):  
You Bin Lai ◽  
Wei Jun Liu ◽  
Ji Bin Zhao ◽  
Yu Hui Zhao ◽  
Fu Yu Wang ◽  
...  
Keyword(s):  
Residual Stress ◽  
Titanium Alloy ◽  
Additive Manufacturing ◽  
Stress Measurement ◽  
Scanning Speed ◽  
Obtuse Angle ◽  
Alloy Sample ◽  
Laser Additive Manufacturing ◽  
Scanning Angle ◽  
Pressure Stress

The residual stress in laser additive manufacturing titanium alloy sample was measured using indentation stress measurement method. The residual stress variation formulas was fitted with the major process parameters such as laser power, scanning speed, the powder feed rate etc.. It was studied that the influence of processing layers and scanning corner on the specimen residual stress. The results show that the specimen residual stress increases first and then decreases with the increase of processing layers, and the maximum appears in the fiftieth layer, in addition, the residual stress in the side of corner sample is mainly pressure stress, the maximum appearing in the 150°scanning angle, the minimum appearing in the 120°scanning angle. Therefore, it can reduce the overall sample residual stress effectively by an obtuse angle scanning trajectory.

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