In situ micro-scale high-speed imaging for evaluation of fracture propagation and fracture toughness of thermoplastic laminates subjected to impact

2019 ◽  
Vol 210 ◽  
pp. 747-754 ◽  
Author(s):  
H. Wafai ◽  
A. Yudhanto ◽  
G. Lubineau ◽  
M. Mulle ◽  
T. Alghamdi ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
High Speed ◽  
Fracture Propagation ◽  
High Speed Imaging ◽  
Micro Scale

Some Observations on How Mechanochemical Effect Determines Deformation Mode and Chip Morphology in Cutting of Metals

2019 ◽  
Author(s):  
Tatsuya Sugihara ◽  
Mojib Saei ◽  
Koushik Viswanathan ◽  
Anirudh Udupa
Keyword(s):  
High Speed ◽  
Chip Morphology ◽  
Deformation Mode ◽  
Flow Mode ◽  
High Speed Imaging ◽  
Mechanochemical Effect ◽  
Workpiece Surface ◽  
Buckling Instability ◽  
Smooth Flow

Abstract We analyze unsteady plastic flow modes in cutting of metals using high-speed imaging of the deformation zone, in situ. For metals which exhibit high levels of strain hardening, the commonly assumed steady (smooth) flow is inherently unstable. Instead, the cutting is characterized by unsteady sinuous flow, with large-amplitude folding, that is triggered by a plastic buckling instability linked to the material microstructure. A mechanochemical effect caused by Al-Alcohol chemical reaction on workpiece surface, which is coupled to the unsteady flow mode, is highlighted. Experimental results reinforce the hypothesis pertaining to flow stability governing the deformation mode and chip type.

scholarly journals In situ analysis of flow dynamics and deformation fields in cutting and sliding of metals

2015 ◽  
Vol 471 (2178) ◽  
pp. 20150194 ◽  
Author(s):  
Yang Guo ◽  
W. Dale Compton ◽  
Srinivasan Chandrasekar
Keyword(s):  
Material Removal ◽  
High Speed ◽  
Ductile Failure ◽  
Rake Angle ◽  
Flow Dynamics ◽  
High Speed Imaging ◽  
Image Velocimetry ◽  
Material Forming ◽  
Continuous Chip

The flow dynamics, deformation fields and chip-particle formation in cutting and sliding of metals are analysed, in situ , using high-speed imaging and particle image velocimetry. The model system is a brass workpiece loaded against a wedge indenter at low speeds. At large negative rake angles, the flow is steady with a prow of material forming ahead of the indenter. There is no material removal and a uniformly strained layer develops on the workpiece surface—the pure sliding regime. When the rake angle is less negative, the flow becomes unsteady, triggered by formation of a crack on the prow free surface and material removal ensuing—the cutting regime. The strain on the prow surface at crack initiation is found to be constant. Chip morphologies, such as discrete particle, segmented chip and continuous chip with mesoscale roughness, are shown to arise from a universal mechanism involving propagation of the prow crack, but to different distances towards the indenter tip. The simple shear deformation in continuous chip formation shows small-angle oscillations also linked to the prow crack. Implications for material removal processes and ductile failure are discussed.

scholarly journals In-situ characterization of laser-powder interaction and cooling rates through high-speed imaging of powder bed fusion additive manufacturing

2017 ◽  
Vol 135 ◽  
pp. 385-396 ◽  
Author(s):  
Umberto Scipioni Bertoli ◽  
Gabe Guss ◽  
Sheldon Wu ◽  
Manyalibo J. Matthews ◽  
Julie M. Schoenung
Keyword(s):  
Additive Manufacturing ◽  
High Speed ◽  
Powder Bed Fusion ◽  
In Situ Characterization ◽  
High Speed Imaging ◽  
Cooling Rates ◽  
Powder Bed

In Situ Analysis of Deformation Mechanics of Constrained Cutting Towards Enhanced Material Removal

2019 ◽  
Author(s):  
Yang Guo ◽  
Jisheng Chen ◽  
Amr Saleh
Keyword(s):  
Free Surface ◽  
Surface Finish ◽  
Simple Shear ◽  
Chip Formation ◽  
Material Removal ◽  
High Speed ◽  
Image Correlation ◽  
High Speed Imaging ◽  
Deformation Mechanics

Abstract Chip formation in conventional cutting occurs by deformation that is only partially bounded by the cutting tool. The unconstrained free surface is a complication in determining the deformation of chip formation. The constrained cutting employs a constraining tool in the cutting process to confine the otherwise free surface and enable direct control of the chip formation deformation. A study has been made on the deformation mechanics of plane-strain constrained cutting using high speed imaging and digital image correlation (DIC) methods. For different constrained levels (including unconstrained free cutting), material flow of chip formation is directly observed; strain rate and strain in the chip as well as the subsurface region are quantified; cutting forces are measured; and surface finish are examed. The study shows that chip formation in constrained cutting can occur in two different deformation modes, i.e., simple shear and complex extrusion, depending on the constrained level. Constrained cutting in simple shear regime can reduce strain, reduce cutting force and energy, and improve surface finish compared to free cutting, therefore it is more efficient for material removal than free cutting. Constrained cutting in the complex extrusion regime imposes a significant amount of surface / subsurface deformation and consumes a very high cutting energy, and therefore is not suitable for material removal. Furthermore, the mechanics of chip formation in both free cutting and constrained cutting, especially the roles played by the free surface and the constraining tool, are discussed.

High Speed Imaging Study of the Dynamics of Ultrasonic Bubbles at a Liquid-Solid Interface

2013 ◽  
Vol 765 ◽  
pp. 230-234 ◽  
Author(s):  
Dong Yue Tan ◽  
Jia Wei Mi
Keyword(s):  
High Speed ◽  
Primary Dendrite ◽  
Imaging Study ◽  
High Speed Imaging ◽  
X Ray ◽  
Dendrite Fragmentation ◽  
X Ray Imaging ◽  
Wave Induced ◽  
Photon Source

High speed imaging, including the ultrafast synchrotron X-ray imaging facility at the beamline 32-ID-B of the Advanced Photon Source (APS), was used to study in-situ (1) the dynamics of ultrasonic bubbles inside a water suspension with an acoustic field of varied pressure; and (2) the interaction of a pulsing bubble at a primary dendrite arm tip inside a succinonitrile-1wt% camphor organic transparent alloy. A simple finite element based model was developed to simulate the stress distribution inside the dendrite due to the pulsing of the ultrasonic bubble, providing more evidence for understanding quantitatively the ultrasonic wave induced dendrite fragmentation phenomenon.

scholarly journals In situ motions of individual inner-hair-cell stereocilia from stapes stimulation in adult mice

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yanli Wang ◽  
Charles R. Steele ◽  
Sunil Puria ◽  
Anthony J. Ricci
Keyword(s):  
Hair Cell ◽  
High Speed ◽  
Ex Vivo ◽  
Ionic Currents ◽  
Hair Bundle ◽  
Sensory Cells ◽  
Apical Surface ◽  
Inner Hair Cell ◽  
High Speed Imaging

AbstractIn vertebrate hearing organs, mechanical vibrations are converted to ionic currents through mechanoelectrical-transduction (MET) channels. Concerted stereocilia motion produces an ensemble MET current driving the hair-cell receptor potential. Mammalian cochleae are unique in that the tuning of sensory cells is determined by their mechanical environment and the mode of hair-bundle stimulation that their environment creates. However, little is known about the in situ intra-hair-bundle motions of stereocilia relative to one another, or to their environment. In this study, high-speed imaging allowed the stereocilium and cell-body motions of inner hair cells to be monitored in an ex vivo organ of Corti (OoC) mouse preparation. We have found that the OoC rotates about the base of the inner pillar cell, the hair bundle rotates about its base and lags behind the motion of the apical surface of the cell, and the individual stereocilia move semi-independently within a given hair bundle.

The Microstructural Origin of Sinuous Flow in Metal Cutting

2018 ◽  
Author(s):  
Vandana A. Salilkumar ◽  
Narayan K. Sundaram
Keyword(s):  
Plastic Deformation ◽  
Surface Finish ◽  
High Speed ◽  
Metal Cutting ◽  
Ofhc Copper ◽  
Polycrystalline Aggregate ◽  
High Speed Imaging ◽  
Material Microstructure ◽  
Cutting Simulations

In situ, high-speed imaging experiments have revealed the existence of sinuous flow, a recently discovered mode of chip formation in machining. The origin and consequences of sinuous flow are still being investigated, but it is now known that sinuous flow involves extensive redundant plastic deformation, poor surface finish and paradoxically high cutting forces. Here, we use full-scale simulations to show that microstructure related inhomogeneity is a major cause of sinuous flow. The simulations are conducted in a Lagrangian FE framework, and use a simple pseudograin model to represent the metal workpiece as a polycrystalline aggregate. The model successfully captures all essential features of sinuous flow in metals like OFHC copper and CP aluminum, and points to the importance of including material microstructure in cutting simulations.

scholarly journals In situ high speed imaging study and modelling of the fatigue fragmentation of dendritic structures in ultrasonic fields

2019 ◽  
Vol 165 ◽  
pp. 388-397 ◽  
Author(s):  
S. Wang ◽  
J. Kang ◽  
Z. Guo ◽  
T.L. Lee ◽  
X. Zhang ◽  
...  
Keyword(s):  
High Speed ◽  
Imaging Study ◽  
High Speed Imaging ◽  
Ultrasonic Fields ◽  
Dendritic Structures
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