13 research outputs found
Understanding the Mechanisms Leading to FSW Property Variations to Aid in Defect Formation Identification via Post-Weld Data Processing
The study of defect formation and identification is important to the further application of friction stir welding in industry. To better understand the topic, a systematic study was undertaken to describe material flow effects on the formation of defects, to list the various types of defects encountered across a parameter window, and to identify features in the weld force data that can then be used to recognize defects within the weld without destructive testing. Tracer studies were used to determine the impact of the material flow on defect formation with a determination that proper shoulder contact is necessary to obtain sufficient material flow to fully consolidate the weld. A series of welds across a range of rotational speeds was used to identify mechanisms that led to variations in the mechanical properties of the welded panels. A balance between the x- and yorces on the tool is needed to produce robust welds that were defect free. UMF was shown to identify regions of changing material flow conditions; however, the identification of intermittent defects was not as successful
A Study of an Alternative Carbon Source to Improve Environmental Sustainability in Steel Production
No abstract availabl
Recommended from our members
Layer-Wise Profile Monitoring of Laser-Based Additive Manufacturing
Additive manufacturing (AM) is a novel fabrication technique capable of producing highly
complex parts. Nevertheless, a major challenge is improving the quality of fabricated parts. While
there are a number of ways of approaching this problem, developing data-driven methods that use
AM process signatures to identify these part anomalies can be rapidly applied to improve overall
part quality during build. The objective of this study is to build a new layer-wise process signature
model to create the thermal-microstructure relationship. In this study, we derive novel key process
signatures for each layer (from melt pool thermal images), which are reduced using multilinear
principal component analysis (MPCA) and are directly correlated with layer-wise quality of the
part. Using these key process signatures, a Gaussian SVM classifier model is trained to detect the
existence of anomalies inside a layer. The proposed models are validated through a case study of
real-world direct laser deposition experiment where the layer-wise quality of the part is predicted
on the fly. The accuracy of the predictions is calculated using three measures (recall, precision,
and f-score), showing reasonable success of the proposed methodology in predicting layer-wise
quality. The ability to predict layer-wise quality enables process correction to eliminate anomalies
and to ultimately improve the quality of the fabricated part.Mechanical Engineerin
Recommended from our members
Investigating the Relationship Between In-Process Quality Metrics and Mechanical Response in the L-PBF Process
Laser powder bed fusion (L-PBF) additive manufacturing is a process that utilizes a high-
powered laser to build near net-shaped parts in a layer-by-layer fashion using metal powder as the
feedstock material. Traditionally, the analysis of L-PBF produced parts has relied solely on post-
build characterization to understand the relationship between the printing process and the final
mechanical properties. Recent developments of in-process quality assurance systems, such as
Sigma Additive Solutions’ PrintRite3D, can measure in-process thermal signatures and melt pool
disturbances in real-time. This research aims to examine the relationship between process
parameters (e.g., scan strategy, scanning speed, and layer thickness) and in-process quality metrics
(IPQMs) captured by the PrintRite3D system on a Renishaw AM400. The mechanical response of
multiple part geometries (NIST residual stress bridges, single-arched bridges) and build materials
(Ti6Al4V) includes residual stress deflection and hardness; the results are compared with the
IPQMs.Mechanical Engineerin
Recommended from our members
Prediction of Fatigue Lives in Additively Manufactured Alloys Based on the Crack-Growth Concept
This paper aims to predict the fatigue behavior of additively manufactured alloys using crack-growth data. Among different sources of damage under cyclic loadings, fatigue due to cracks
originated from voids is the most life-limiting failure mechanism in powder-based metal additive
manufacturing (AM) parts. Hence, the ability to predict the fatigue behavior of AM materials based
on the void features is the first step toward improving AM part reliability. Test results from the
literature on AM alloys are analyzed herein to model fatigue behavior based on the semi-circular
surface flaws. The fatigue-life variations in the specimens are captured using the distribution of
defect size. The results indicate that knowing the statistical distribution of the defect size can
provide the opportunity of predicting the scatter in the fatigue-life of the AM materials, using an
appropriate fatigue analysis code.Mechanical Engineerin
Recommended from our members
Effect of Powder Reuse on Microstructural and Fatigue Properties of Ti-6Al-4V Fabricated via Directed Energy Deposition
In metal additive manufacturing (AM) processes, due to the high cost of metal powder, it
is common to reuse the collected powder from the build envelope for future builds. Powder reuse
may adversely affect the powder characteristics, including the flowability, size distribution,
chemical composition, resultant microstructural, and consequently, mechanical properties of the
fabricated parts. This study aims to investigate the effect of powder reuse on the microstructural
features and fatigue performance of Ti-6Al-4V specimens fabricated using a directed energy
deposition (DED) process. Characteristics of reused powder particles, such as the size distribution
and chemical composition, were evaluated and compared with that of virgin powder.
Microstructural features and characteristics of the process-induced defects were examined using
scanning electron microscopy and x-ray computed tomography, respectively. Fatigue performance
of the specimens fabricated using reused powder was evaluated and compared to their control
counterparts, fabricated using virgin powder.Mechanical Engineerin
Recommended from our members
Effects of Process Interruption During Laser Powder Bed Fusion on Microstructural and Mechanical Properties of Fabricated Parts
Despite appropriate planning, various incidents can stop the additive manufacturing (AM)
process of metals and cause build interruption, such as power outage, lack of powder feedstock,
and/or shielding gas to mention a few. Due to the layer-by-layer nature of fabrication, an
interruption to the AM process can be resumed from the location where the stoppage occurred.
However, build interruption may adversely affect the structural integrity of the fabricated parts, by
causing localized failure near the interruption location. This study aims to investigate the influence
of build interruption during the laser powder bed fusion (LPBF) process on the microstructural
and mechanical properties of Ti-6Al-4V and Al-Si-10Mg specimens. For the Ti-6Al-4V
specimens, results indicate that tensile failures near the interruption location are most likely to
happen for non-heat-treated specimens in the as-built surface condition. Whereas for the Al-Si-
10Mg specimens, the failure location is more influenced by the prolonged stoppage and air
exposure.Mechanical Engineerin
Recommended from our members
Effects of Process Interruption During Laser Powder Bed Fusion on Microstructural and Mechanical Properties of Fabricated Parts
Despite appropriate planning, various incidents can stop the additive manufacturing (AM)
process of metals and cause build interruption, such as power outage, lack of powder feedstock,
and/or shielding gas to mention a few. Due to the layer-by-layer nature of fabrication, an
interruption to the AM process can be resumed from the location where the stoppage occurred.
However, build interruption may adversely affect the structural integrity of the fabricated parts, by
causing localized failure near the interruption location. This study aims to investigate the influence
of build interruption during the laser powder bed fusion (LPBF) process on the microstructural
and mechanical properties of Ti-6Al-4V and Al-Si-10Mg specimens. For the Ti-6Al-4V
specimens, results indicate that tensile failures near the interruption location are most likely to
happen for non-heat-treated specimens in the as-built surface condition. Whereas for the Al-Si-
10Mg specimens, the failure location is more influenced by the prolonged stoppage and air
exposure.Mechanical Engineerin