Journal articles on the topic 'Laser induced projectile impact testing'
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Sousa, Bryer C., Kristin L. Sundberg, Matthew A. Gleason, and Danielle L. Cote. "Understanding the Antipathogenic Performance of Nanostructured and Conventional Copper Cold Spray Material Consolidations and Coated Surfaces." Crystals 10, no. 6 (June 12, 2020): 504. http://dx.doi.org/10.3390/cryst10060504.
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The role of high strain rate and severe plastic deformation, microstructure, electrochemical behavior, surface chemistry and surface roughness were characterized for two copper cold spray material consolidations, which were produced from conventionally gas-atomized copper powder as well as spray-dried copper feedstock, during the course of this work. The motivation underpinning this work centers upon the development of a more robust understanding of the microstructural features and properties of the conventional copper and nanostructured copper coatings as they relate to antipathogenic contact killing and inactivation applications. Prior work has demonstrated greater antipathogenic efficacy with respect to the nanostructured coating versus the conventional coating. Thus, microstructural analysis was performed in order to establish differences between the two coatings that their respective pathogen kill rates could be attributed to. Results from advanced laser-induced projectile impact testing, X-ray diffraction, scanning electron microscopy, electron backscatter diffraction, scanning transmission microscopy, nanoindentation, energy-dispersive X-ray spectroscopy, nanoindentation, confocal microscopy, atomic force microscopy, linear polarization, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and copper ion release assaying were performed during the course of this research.
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Odaci, Kutlay, Cenk Kılıçaslan, Alper Taşdemirci, Athanasios G. Mamalis, and Mustafa Güden. "Projectile Impact Testing Aluminum Corrugated Core Composite Sandwiches Using Aluminum Corrugated Projectiles: Experimental and Numerical Investigation." Materials Science Forum 910 (January 2018): 102–8. http://dx.doi.org/10.4028/www.scientific.net/msf.910.102.
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E-glass/polyester composite plates and 1050 H14 aluminum trapezoidal corrugated core composite sandwich plates were projectile impact tested using 1050 H14 aluminum trapezoidal fin corrugated projectiles with and without face sheets. The projectile impact tests were simulated in LS-DYNA. The MAT_162 material model parameters of the composite were determined and then optimized by the quasi-static and high strain rate tests. Non-centered projectile impact test models were validated by the experimental and numerical back face displacements of the impacted plates. Then, the centered projectile impact test models were developed and the resultant plate displacements were compared with those of the TNT mass equal Conwep simulations. The projectiles with face sheets induced similar displacement with the Conwep blast simulation, while the projectiles without face sheets underestimated the Conwep displacements, which was attributed to more uniform pressure distribution with the use of the face sheets on the test plates.
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Badziak, J., E. Krousky, J. Marczak, P. Parys, T. Pisarczyk, M. Rosiński, A. Sarzynski, et al. "Efficient acceleration of a dense plasma projectile to hyper velocities in the laser-induced cavity pressure acceleration scheme." Laser and Particle Beams 36, no. 1 (January 25, 2018): 49–54. http://dx.doi.org/10.1017/s0263034617000945.
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AbstractThe experimental study of the plasma projectile acceleration in the laser-induced cavity pressure acceleration (LICPA) scheme is reported. In the experiment performed at the kilojoule PALS laser facility, the parameters of the projectile were measured using interferometry, a streak camera and ion diagnostics, and the measurements were supported by two-dimensional hydrodynamic simulations. It is shown that in the LICPA accelerator with a 200-J laser driver, a 4-μg gold plasma projectile is accelerated to the velocity of 140 km/s with the energetic acceleration efficiency of 15–19% which is significantly higher than those achieved with the commonly used ablative acceleration and the highest among the ones measured so far for any projectiles accelerated to the velocities ≥100 km/s. This achievement opens the possibility of creation and investigation of high-energy-density matter states with the use of moderate-energy lasers and may also have an impact on the development of the impact ignition approach to inertial confinement fusion.
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Chen, Shawn H., Amanda J. Souna, Christopher L. Soles, Stephan J. Stranick, and Edwin P. Chan. "Using microprojectiles to study the ballistic limit of polymer thin films." Soft Matter 16, no. 16 (2020): 3886–90. http://dx.doi.org/10.1039/d0sm00295j.
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In this work, a microballistic impact test called laser induced projectile impact test (LIPIT) was used to study the perforation behavior of polycarbonate thin films to demonstrate the importance of film thickness on the film's ballistic limit.
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Xing, Jie, and Yin Xian Duo. "Vibration Influence of Artillery Autoloader Analysis and Testing." Advanced Materials Research 711 (June 2013): 540–44. http://dx.doi.org/10.4028/www.scientific.net/amr.711.540.
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The inconsistency of the projectile's seizing-bore stroke of the large caliber gun during feeding process will lead to differences of the volume of propellant chamber and starting pressure of projectiles.It will also affect guns' muzzle velocity and firing accuracy.In order to improve the positioning accuracy of projectiles in an arm-type autoloader,first of all,high speed photography was used and only to find that there will be vibrations of projectiles in the direction of gravity.The vibrations will consume kinetic energy of the projectile and contribute to inconsistency of the retaining force.By means of analyzing the working mechanism of the rammer,the motion relationship among the parts during ramming process came to clear eventually.Then the position of the exciting source which causes vibrations of the projectile can be determined by analyzing the force situation of the rammer in the stationary state and the state of motion,and next,testing the amplitude and frequency of the position using laser displacement sensor.Finally,the improved scheme was raised to eliminate the impact of the vibration on stability of ramming.
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Figliola, Nino, David Schmidt, and Jae-Hwang Lee. "Pressure- and Size-Dependent Aerodynamic Drag Effects on Mach 0.3–2.2 Microspheres for High-Precision Micro-Ballistic Characterization." Applied Sciences 12, no. 13 (June 30, 2022): 6622. http://dx.doi.org/10.3390/app12136622.
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The acceleration of microparticles to supersonic velocities is required for microscopic ballistic testing, a method for understanding material characteristics under extreme dynamic conditions, and for projectile gene and drug delivery, a needle-free administration technique. However, precise aerodynamic effects upon supersonic microsphere motion at sub-300 Reynolds numbers have not been quantified. We derive drag coefficients for microspheres traveling in air at subsonic, transonic, and supersonic velocities from the measured trajectories of microspheres launched by laser-induced projectile acceleration. Moreover, the observed drag effects on microspheres in atmospheric (760 Torr) and reduced pressure (76 Torr) are compared with existing empirical data and drag coefficient models. We find that the existing models adequately predict the drag coefficient for subsonic microspheres, while rarefaction effects cause a discrepancy between the model and empirical data in the supersonic regime. These results will improve microsphere flight modeling for high-precision microscopic ballistic testing and projectile gene and drug delivery.
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KOMINE, Ryoma, Takumi FURUTANI, Yugo SAKAI, and Akio YONEZU. "Development of Laser-induced Projectile Impact method and plastic deformation behavior at high strain rate." Proceedings of the Materials and Mechanics Conference 2021 (2021): OS0505. http://dx.doi.org/10.1299/jsmemm.2021.os0505.
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Peng, Yifei, Guohu Luo, Yongxiang Hu, and Ding-Bang Xiong. "Extreme strain rate deformation of nacre-inspired graphene/copper nanocomposites under laser-induced hypersonic micro-projectile impact." Composites Part B: Engineering 235 (April 2022): 109763. http://dx.doi.org/10.1016/j.compositesb.2022.109763.
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Badziak, J., M. Kucharik, and R. Liska. "Production of sub-gigabar pressures by a hyper-velocity impact in the collider using laser-induced cavity pressure acceleration." Laser and Particle Beams 35, no. 4 (September 21, 2017): 619–30. http://dx.doi.org/10.1017/s0263034617000660.
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AbstractProduction of high dynamic pressure using a strong shock wave is a topic of high relevance for high-energy-density physics, inertial confinement fusion, and materials science. Although the pressures in the multi-Mbar range can be produced by the shocks generated with a large variety of methods, the higher pressures, in the sub-Gbar or Gbar range, are achievable only with nuclear explosions or laser-driven shocks. However, the laser-to-shock energy conversion efficiency in the laser-based methods currently applied is low and, as a result, multi-kJ multi-beam lasers have to be used to produce such extremely high pressures. In this paper, the generation of high-pressure shocks in the newly proposed collider in which the projectile impacting a solid target is driven by the laser-induced cavity pressure acceleration (LICPA) mechanism is investigated using two-dimensional hydrodynamic simulations. A special attention is paid to the dependence of shock parameters and the laser-to-shock energy conversion efficiency on the impacted target material and the laser driver energy. It has been found that both in case of low-density and high-density solid targets, the shock pressures in the sub-Gbar range can be produced in the LICPA-based collider with the laser energy of only a few hundreds of joules, and the laser-to-shock energy conversion efficiency can reach values of 10–20%, by an order of magnitude higher than the conversion efficiencies achieved with other laser-based methods used so far.
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Khandaker, Morshed, Abdellah Ait Moussa, Desmond Nuyebga Sama, Fereshteh Safavinia, Susmita Hazra, Onur Can Kalay, Fatih Karpat, Erik Clary, and Amgad Haleem. "Laser-Induced Microgrooves Improve the Mechanical Responses of Cemented Implant Systems." Micromachines 11, no. 5 (April 29, 2020): 466. http://dx.doi.org/10.3390/mi11050466.
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The impact of a laser-induced microgroove (LIM) architecture on mechanical responses of two cemented implant systems was evaluated. One system consisted of two aluminum alloy rods bonded end-to-end by polymethylmethacrylate cement. The second system consisted of a custom-made, aluminum tibial tray (TT) cemented in an artificial canine tibia. Control specimens for each system were polished smooth at the cement interface. For LIM samples in the rod system, microgrooves were engraved (100 µm depth, 200 µm width, 500 µm spacing) on the apposing surface of one of the two rods. For TT system testing, LIM engraving (100 µm spacing) was confined to the underside and keel of the tray. Morphological analysis of processed implant surfaces revealed success in laser microgrooving procedures. For cemented rods tested under static tension, load to failure was greater for LIM samples (279.0 ± 14.9 N vs. 126.5 ± 4.5 N). Neither non-grooved nor grooved TT samples failed under cyclic compression testing (100,000 cycles at 1 Hz). Compared with control specimens, LIM TT constructs exhibited higher load to failure under static compression and higher strain at the bone interface under cyclic compression. Laser-induced microgrooving has the potential to improve the performance of cemented orthopedic implants.
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Rus, Janez, Alex Gustschin, Hubert Mooshofer, Jan-Carl Grager, Klaas Bente, Mate Gaal, Franz Pfeiffer, and Christian U. Grosse. "Qualitative comparison of non-destructive methods for inspection of carbon fiber-reinforced polymer laminates." Journal of Composite Materials 54, no. 27 (June 15, 2020): 4325–37. http://dx.doi.org/10.1177/0021998320931162.
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In the rapidly expanding composite industry, novel inspection methods have been developed in recent years. Particularly promising for air-coupled testing are cellular polypropylene transducers which offer better impedance matching to air than piezoelectric transducers. Furthermore, broadband transmitters (laser-induced ultrasound and thermoacoustic emitters) and receivers (optical microphones) have opened a completely new chapter for advanced contact-free ultrasound inspection. X-ray dark-field radiography offers a different approach to detect porosity and microcracks, employing small angle X-ray scattering. These innovative ultrasonic and radiographic alternatives were evaluated in comparison with well-established inspection techniques. We applied thirteen different non-destructive methods to inspect the same specimen (a carbon fiber-reinforced polymer laminate with induced impact damage): air-coupled ultrasound testing (using piezoelectric transducers, broadband optical microphones, cellular polypropylene transducers, and a thermoacoustic emitter), laser-induced ultrasound testing, ultrasonic immersion testing, phased array ultrasonic testing, optically excited lock-in thermography, and X-ray radiography (projectional absorption and dark-field, tomosynthesis, and micro-computed tomography). The inspection methods were qualitatively characterized by comparing the scan results. The conclusions are advantageous for a decision on the optimal method for certain testing constraints.
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Alil, Luminita Cristina, Michel Arrigoni, Lorena Deleanu, and Marcel Istrate. "Assessment of Delamination in Tensylon� UHMWPE Composites by Laser-induced Shock." Materiale Plastice 55, no. 3 (September 30, 2018): 364–71. http://dx.doi.org/10.37358/mp.18.3.5031.
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Ultra-High Molecular Weight Polyethylene (UHMWPE) composites are the result of recent developments in material research for ballistic protection due to their ability to absorb the kinetic energy of the bullet by various mechanisms of dissipation, among which an important one is delamination. In order to study this mechanism independently, the laser induced shock wave testing procedure has been used on thin Tensylon� laminate samples. Laser-induced shock represents a modern approach that can be used for assessing the interlaminar bond strength between two plies of a composite material, in dynamic conditions, at high strain rates representative for a ballistic impact. Through this technique, a delamination failure stress threshold can be determined. In the present work, the laser induced shock technique was applied on the commercial UHMWPE material called Tensylon�. The delamination threshold of this material was determined by using the Novikov approach, and, compared to the literature, the results match the values determined by other means of measurement.
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Bourguille, Judith, Luca Bergamasco, Gilles Tahan, Daniel Fuster, and Michel Arrigoni. "Shock Propagation Effects in Multilayer Assembly Including a Liquid Phase." Key Engineering Materials 755 (September 2017): 181–89. http://dx.doi.org/10.4028/www.scientific.net/kem.755.181.
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During a ballistic impact, the protective material that plays the role of armour has to dissipate the kinetic energy in order to limit the projectile penetration in the target. Our aim is to emphasis on the role played by a liquid-filled system on the impact energy mitigation due to cavitation inception and later bubble expansion. To observe this, small scale experiments have been carried out on a three layers sample (Aluminium-Water-PMMA) submitted to shock waves induced by laser impact applied on the Al face. Rapid camera visualizations allow reproducing, at small scale, the effects of projectiles on armours for various monitored impact energies. We observe the formation of bubbles for sufficiently intense impacts due to traction effects in the water caused by the multiple reflections of waves within the sample. The cavitation threshold of water under dynamic loading is then experimentally investigated for two samples: one with 600 μm thick Al / 400 μm of water and 3 mm of PMMA, the other with 1000 μm thick Al / 1600 μm of water and 3 mm of PMMA. Using dimensional analysis, we show that the energy taken during the process of inception and bubble expansion becomes more important as the energy of the impact increases.
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AZIZ, Sara, Dalia EL-FIKY, Gad M. GAD, and Ayman MAHROUS. "Optimization laser parameters to simulate solar cell degradation induced by space radiation." INCAS BULLETIN 13, no. 2 (June 4, 2021): 205–18. http://dx.doi.org/10.13111/2066-8201.2021.13.2.18.
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Space radiation has a catastrophic impact on solar cells performance, appears as a degradation in their electrical and physical properties, this may cause a satellite failure; to overcome this issue, ground testing is required. In this paper, the pulsed laser was used as an alternative irradiation tool to induce degradation in solar cell performance in order to simulate the space radiation effect on solar cells. Firstly, the solar cells were irradiated with a wavelength of 532 nm at different locations, with the same power to optimize the most effective area to irradiation. Secondly, the solar cells were irradiated to the optimized location with different laser fluences; the results showed a degradation in electrical and physical performance. The amount of degradation is proportional to the laser fluence. Dark current voltage (DIV) curves have been measured before and after laser irradiation. Solar cell degradation rates have been calculated based on the Degradation coefficients (KL, RC) and electrical damage models.
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Munro, Cameron, Allison E. Nolting, Xin Jin Cao, and Priti Wanjara. "Hybrid Laser-Arc Welding of HSLA-65 Steel Plate: Microstructural and Mechanical Property Evaluation of Butt Welds." Materials Science Forum 706-709 (January 2012): 2992–97. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.2992.
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High strength low alloy (HSLA) steel, namely HSLA-65, has shown promise as a replacement for more common high strength shipbuilding steels. However, conventional high heat input welding processes can cause significant distortion, often requiring expensive post-weld reworking. Butt welds in HSLA-65 steel were fabricated using a hybrid fibre laser-gas metal arc welding (GMAW) procedure to investigate the efficacy of distortion mitigation via low heat input joining. Heat input from the laser and arc sources were roughly equal at ~5.2 kW each, and plates were welded in either the laser-leading or arc-leading configuration. In either case, butt welds in ~9 mm thick plates could be made in a single pass at a total heat input of ~0.4 kJ/mm. Welding induced distortion was minimal. Analysis of the microstructure and microhardness of the welds is provided, along with some preliminary results of mechanical and impact testing.
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Boukhicha, Rym, Erik Johnson, D. Daineka, Antoine Michel, J. F. Lerat, Thierry Emeraud, and Pere Roca i Cabarrocas. "Impact on Thin Film Silicon Properties and Solar Cell Parameters of Texture Generated by LaserAnnealing and Chemical Etching of ZnO:Al." MRS Proceedings 1536 (2013): 45–50. http://dx.doi.org/10.1557/opl.2013.914.
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ABSTRACTThe use of a laser annealing and chemical texturing process (dubbed the LaText process) on room-temperature sputtered ZnO:Al has been shown to generate unusually high haze properties, favorable for thin film silicon solar cells.This is due to the melting of the ZnO:Al layer by the XeCl laser, and the formation of crystalline domains onthe surface, for which the grains and grain boundaries are subsequently etched at different rates. The unusual surface morphology produced through this process can strongly impact the nature of the amorphous or microcrystalline silicon material deposited thereupon. In this paper, we report on results for amorphous silicon devices, for which the surface texture is seen to slightly impact thelight absorption in the material, but more interestingly, also the light-induced degradation of the cells.For co-deposited cells, devices deposited on surfaces with the characteristic "LaText" morphologyundergo a much lesser degradation. Furthermore, the decreased degree of degradation coincides with a notable shift in the Raman scattering peak. This provides a rapid diagnostic for testing multiple textures and deposition parameters.
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Shaloo, Masoud, Martin Schnall, Thomas Klein, Norbert Huber, and Bernhard Reitinger. "A Review of Non-Destructive Testing (NDT) Techniques for Defect Detection: Application to Fusion Welding and Future Wire Arc Additive Manufacturing Processes." Materials 15, no. 10 (May 21, 2022): 3697. http://dx.doi.org/10.3390/ma15103697.
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In Wire and Arc Additive Manufacturing (WAAM) and fusion welding, various defects such as porosity, cracks, deformation and lack of fusion can occur during the fabrication process. These have a strong impact on the mechanical properties and can also lead to failure of the manufactured parts during service. These defects can be recognized using non-destructive testing (NDT) methods so that the examined workpiece is not harmed. This paper provides a comprehensive overview of various NDT techniques for WAAM and fusion welding, including laser-ultrasonic, acoustic emission with an airborne optical microphone, optical emission spectroscopy, laser-induced breakdown spectroscopy, laser opto-ultrasonic dual detection, thermography and also in-process defect detection via weld current monitoring with an oscilloscope. In addition, the novel research conducted, its operating principle and the equipment required to perform these techniques are presented. The minimum defect size that can be identified via NDT methods has been obtained from previous academic research or from tests carried out by companies. The use of these techniques in WAAM and fusion welding applications makes it possible to detect defects and to take a step towards the production of high-quality final components.
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Heckner, Tobias, Michael Seitz, Sven Robert Raisch, Gerrit Huelder, and Peter Middendorf. "Selective Laser Sintering of PA6: Effect of Powder Recoating on Fibre Orientation." Journal of Composites Science 4, no. 3 (August 6, 2020): 108. http://dx.doi.org/10.3390/jcs4030108.
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In Selective Laser Sintering, fibres are strongly orientated during the powder recoating process. This effect leads to an additional increase of anisotropy in the final printed parts. This study investigates the influence of process parameter variation on the mechanical properties and the fibre orientation. A full factorial design of experiment was created to evaluate the processing parameters of recoating speed, layer thickness and laser power on the part’s modulus of elasticity. Based on the mechanical testing, computed tomography was applied to selected samples to investigate the process-induced fibre microstructure, and calculate the fibre orientation tensors. The results show increasing part stiffness in the deposition direction, with decreasing layer thickness and increasing laser power, while the recoating speed only shows little effect on the mechanical performance. This complies with computed tomography imaging results, which show an increase in fibre orientation with smaller layer thickness. With thinner layers, and hence smaller shear gaps, shear stresses induced by the roller during recoating increase significantly, leading to excessive fibre reorientation and alignment. The high level of fibre alignment implies an increase of strength and stiffness in the recoating direction. In addition, thinner layer thickness under constant laser energy density results in improved melting behaviour, and thus improved fibre consolidation, consequently further increasing the mechanical properties. Meanwhile, the parameters of recoating speed and laser power do not have a significant impact on fibre orientation within their applicable process windows.
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Sheikholeslami, Ghazal, Jonathan Griffiths, Stuart P. Edwardson, Ken Watkins, and Geoff Dearden. "Laser Forming of ERW Steel Square Tubes within Metallurgical Constraints." Key Engineering Materials 549 (April 2013): 68–75. http://dx.doi.org/10.4028/www.scientific.net/kem.549.68.
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Laser forming (LF) is a non-contact method to shape metallic sheets and tubes by induced thermal stress without melting using a de-focused laser beam. Laser forming offers the industrial promise of controlled shaping of metallic and non-metallic components for prototyping, correction of design shape or distortion and precision adjustment applications. In order to fulfil this promise in a manufacturing environment the process must have a high degree of control, be repeatable and have a minimal impact on the material and mechanical properties of the part to be formed. In order to demonstrate the capability of the LF process a study is presented in this paper on the 3D Laser Forming of ERW steel square tubes SHS EN10305-5 E220 +CR2 (1.5x25x25mm and 1.5x50x50mm 300mm long tube) using a 1.5kW CO2laser and industrial 5 axis gantry. Strategies have been developed for out of plane bending with specific emphasis on process throughput balanced with minimising adverse localised changes to material properties that could lead to stress concentration features in a component in service. Presented in this paper is empirical 3D LF shape data verified by a scanning laser profiler, a metallurgical study, hardness testing and a FEM model developed in Comsol Multi-Physics. The results of these studies were employed to develop optimised scan strategies for the controlled laser forming of the ERW steel square tubes within strict metallurgical constraints.
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Iorio, Lorenzo. "On Testing Frame-Dragging with LAGEOS and a Recently Announced Geodetic Satellite." Universe 4, no. 11 (October 29, 2018): 113. http://dx.doi.org/10.3390/universe4110113.
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Recently, Ciufolini and coworkers announced the forthcoming launch of a new cannonball geodetic satellite in 2019. It should be injected in an essentially circular path with the same semimajor axis a of LAGEOS (Laser Geodynamics Satellite), in orbit since 1976, and an inclination I of its orbital plane supplementary with respect to that of its existing cousin. According to their proponents, the sum of the satellites’ precessions of the longitudes of the ascending nodes Ω should allow one to test the general relativistic Lense–Thirring effect to a ≃0.2% accuracy level, with a contribution of the mismodeling in the even zonal harmonics Jl, l = 2, 4, 6, . . . of the geopotential to the total error budget as little as 0.1%. Actually, such an ambitious goal seems to be hardly attainable because of the direct and indirect impact of, at least, the first even zonal J2. On the one hand, the lingering scatter of the estimated values of such a key geophysical parameter from different recent GRACE/GOCE-based (Gravity Recovery and Climate Experiment/Gravity field and steady-state Ocean Circulation Explorer) global gravity field solutions is representative of an uncertainty which may directly impact the summed Lense–Thirring node precessions at a ≃70–80% in the worst scenarios, and to a ≃3–10% level in other, more favorable cases. On the other hand, the phenomenologically measured secular decay à of the semimajor axis of LAGEOS (and, presumably, of the other satellite as well), currently known at a σà≃0.03 m yr–1 level after more than 30 yr, will couple with the sum of the J2-induced node precessions yielding an overall bias as large as '20–40% after 5–10 yr. A further systematic error of the order of ≃2–14% may arise from an analogous interplay of the secular decay of the inclination I˙ with the oblateness-driven node precessions.
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Dychtoń, Kamil, Andrzej Gradzik, Łukasz Kolek, and Krzysztof Raga. "Evaluation of Thermal Damage Impact on Microstructure and Properties of Carburized AISI 9310 Gear Steel Grade by Destructive and Non-Destructive Testing Methods." Materials 14, no. 18 (September 14, 2021): 5276. http://dx.doi.org/10.3390/ma14185276.
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Advanced aircraft gearboxes operate under high mechanical loads. Currently, aircraft gears are manufactured from chromium–nickel–molybdenum steel grades such as AISI 9310 or Pyrowear 53. The major causes of gear failure are wear and fatigue cracking. As the crack initiation occurs predominantly on the component surface, the gears are routinely subjected to surface hardening processes such as low-pressure carburizing and case hardening. The gears are manufactured in a multiple operation process, in which teeth grinding is a crucial step. Selection of improper grinding conditions can lead to local heat concentration and creation of grinding burns, which are small areas where microstructure and properties changes are induced by high temperature generated during grinding. Their presence can lead to significant reduction of gear durability. Therefore destructive and non-destructive (NDT) quality-control methods such as chemical etching or magnetic Barkhausen noise (MBN) measurements are applied to detect the grinding burns. In the area of a grinding burn, effects related to the over-tempering or re-hardening of the carburized case may occur. In this paper, the results of the studies on the characterization of microstructure changes caused by local heating performed to simulate grinding burns are presented. The areas with the over-tempering and re-hardening effects typical for grinding burns were formed by laser surface heating of carburized AISI 9310 steel. Analyses of the microstructure, residual stresses, retained austenite content, and non-destructive testing by the MBN method were performed. The correlation between the MBN value and the properties of the modified surface layer was identified. It was also found that the re-hardened areas had similar characteristics of changes in the Barkhausen noise intensity, despite the significant differences in the width of the overheated zone, which depended on the laser-heating process conditions.
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Muck, Martina, Benedikt Wolfsjäger, Karoline Seibert, Christian Maier, Shaukat Ali Lone, Achim Walter Hassel, Werner Baumgartner, and Johannes Heitz. "Femtosecond Laser-Processing of Pre-Anodized Ti-Based Bone Implants for Cell-Repellent Functionalization." Nanomaterials 11, no. 5 (May 20, 2021): 1342. http://dx.doi.org/10.3390/nano11051342.
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Microstructures and nanostructures can be used to reduce the adhesion of the cells on the auxiliary material. Therefore, the aim of our work was to fabricate laser-induced hierarchical microstructures and nanostructures by femtosecond laser-treatment (wavelength 1040 nm, pulse length 350 fs, repetition rates in the kHz range) to reduce the cell adhesion. Additionally, surface chemistry modification by optimized electrochemical anodization was used to further reduce the cell adhesion. For testing, flat plates and bone screws made of Ti-6Al-4V were used. Bone-forming cells (human osteoblasts from the cell line SAOS-2) were grown on the bone implants and additional test samples for two to three weeks. After the growth period, the cells were characterized by scanning electron microscopy (SEM). While earlier experiments with fibroblasts had shown that femtosecond laser-processing followed by electrochemical anodization had a significant impact on cell adhesion reduction, for osteoblasts the same conditions resulted in an activation of the cells with increased production of extracellular matrix material. Significant reduction of cell adhesion for osteoblasts was only obtained at pre-anodized surfaces. It could be demonstrated that this functionalization by means of femtosecond laser-processing can result in bone screws that hinder the adhesion of osteoblasts.
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Eckner, Ralf, Lutz Krüger, Mykhaylo Motylenko, Andrey S. Savinykh, Sergey V. Razorenov, and Gennady V. Garkushin. "Deformation mechanisms and microplasticity of austenitic TRIP/TWIP steel under flyer plate impact." EPJ Web of Conferences 183 (2018): 03007. http://dx.doi.org/10.1051/epjconf/201818303007.
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Abstract. The focus of this study is on the deformation mechanisms of high-alloy cast austenitic TRIP/TWIP steel with the nominal composition Fe-16Cr-6Mn-6Ni. Due to its chemical composition, the material exhibits a low stacking-fault energy of 17.5 mJ/m2 which facilitates the formation of the deformation-induced γ (fcc) → ε (hep) → α’ (bcc) transformation. Consequently, the steel exhibits a tensile strength of 800 MPa with fracture elongation of 55 % under quasi-static loading. The experiments presented demonstrate the response of this steel to flyer-plate impact (FPI) at room temperature using two different test setups. In the first setup, laser interferometry measurements of the sample free surface were used for determination of the dynamic mechanical properties (Hugoniot elastic limit / HEL. spall strength) after impact with aluminium plates accelerated up to 650 m/s. In the second setup, an experimental shock testing device developed at the Freiberg High-Pressure Research Centre was used for impacting large cylindrical samples without the occurrence of spallation. Subsequently, microstructural investigations were carried out by scanning electron microscopy (SEM) and transmission election microscopy (TEM) in combination with diffraction techniques and magnetic martensite measurements. Their results facilitate the representation of a complete image of deformation mechanisms during shock wave loading.
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Brika, Salah Eddine, and Vladimir Brailovski. "Influence of Powder Particle Morphology on the Static and Fatigue Properties of Laser Powder Bed-Fused Ti-6Al-4V Components." Journal of Manufacturing and Materials Processing 4, no. 4 (November 9, 2020): 107. http://dx.doi.org/10.3390/jmmp4040107.
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In this work, two Ti-6Al-4V powder lots were produced using two different techniques: plasma atomization and gas atomization, with the first producing more spherical particles than the second. Testing specimens were then manufactured with these powder lots using an identical set of printing parameters and the same laser powder bed fusion system. Next, the porosity levels and distributions as well as the static and fatigue properties of the specimens from both powder lots were compared. Regarding the static mechanical properties, a noticeable difference was observed between the plasma-atomized powder specimens and their gas-atomized equivalents (7% greater ultimate and 4% greater yield strengths, but 3% lower elongation to failure, respectively). However, with regard to the fatigue resistance, the advantages of the plasma-atomized powder specimens in terms of their mechanical resistance were somewhat counterbalanced by the presence of pores aligned in the direction perpendicular to that of applied load. Conversely, specimens printed with the gas-atomized powder manifested a similar level of porosity, but a uniform pore distribution, which reduced the impact of the processing-induced porosity on fatigue cracks initiation and propagation.
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Colella, Giuseppe, Ciro Emiliano Boschetti, Rita Vitagliano, Chiara Colella, Lebei Jiao, Natalie King-Smith, Chong Li, et al. "Interventions for the Prevention of Oral Mucositis in Patients Receiving Cancer Treatment: Evidence from Randomised Controlled Trials." Current Oncology 30, no. 1 (January 10, 2023): 967–80. http://dx.doi.org/10.3390/curroncol30010074.
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Oral mucositis is a common and most debilitating complication associated with cancer therapy. Despite the significant clinical and economic impact of this condition, there is little to offer to patients with oral mucositis, and the medications used in its management are generally only palliative. Given that mucositis is ultimately a predictable and, therefore, potentially preventable condition, in this study we appraised the scientific literature to evaluate effective methods of prevention that have been tested in randomised controlled trials (RCTs). Published high-level evidence shows that multiple preventative methods are potentially effective in the prevention of oral mucositis induced by radiotherapy, chemotherapy, or both. Anti-inflammatory medications (including benzydamine), growth factors and cytokines (including palifermin), cryotherapy, laser-and-light therapy, herbal medicines and supplements, and mucoprotective agents (including oral pilocarpine) showed some degree of efficacy in preventing/reducing the severity of mucositis with most anticancer treatments. Allopurinol was potentially effective in the prevention of radiotherapy-induced oral mucositis; antimicrobial mouthwash and erythropoietin mouthwash were associated with a lower risk of development of severe oral mucositis induced by chemotherapy. The results of our review may assist in highlighting the efficacy and testing the effectiveness of low-cost, safe preventative measures for oral mucositis in cancer patients.
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Liu, Yaolu, Shijie Zhou, Huiming Ning, Cheng Yan, and Ning Hu. "An Inverse Approach of Damage Identification Using Lamb Wave Tomography." Sensors 19, no. 9 (May 10, 2019): 2180. http://dx.doi.org/10.3390/s19092180.
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A pulse laser combined LWT technique with a two-stage reconstruction algorithm was proposed to realize rapid damage location, or even the evaluation of damage size for plate-like structures. Since the amplitude of Lamb waves in propagation is highly sensitive to damage, including inside damage, the change of the attenuation coefficient of Lamb waves in the inspection region was used as a damage index to reconstruct damage images. In stage one, the rough area of the damage was identified by a comparison of the amplitude of the testing signal data and reference data (undamaged state). In stage two, the damage image was reconstructed using an inverse approach based on the least-square method. In order to verify the effectiveness of the proposed rapid approach, experiments on an aluminum plate with a non-penetrating notch and a carbon fiber-reinforced plastic laminated plate with internal delamination induced by a low-velocity impact were carried out. The results show that the notch can be detected with accurate location, and the delamination image can be reconstructed successfully.
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Hanna, Reem, Snehal Dalvi, Stefano Benedicenti, Andrea Amaroli, Tudor Sălăgean, Ioana Delia Pop, Doina Todea, and Ioana Roxana Bordea. "Photobiomodulation Therapy in Oral Mucositis and Potentially Malignant Oral Lesions: A Therapy Towards the Future." Cancers 12, no. 7 (July 18, 2020): 1949. http://dx.doi.org/10.3390/cancers12071949.
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Photobiomodulation therapy (PBMT) is an effective treatment modality, which has the significant advantage of enhancing a patient’s quality of life (QoL) by minimising the side effects of oral cancer treatments, as well as assisting in the management of potentially cancerous lesions. It is important to note that the major evidence-based documentation neither considers, nor tackles, the issues related to the impact of PBMT on tumour progression and on the downregulation of cellular proliferation improvement, by identifying the dose- and time-dependency. Moreover, little is known about the risk of this therapy and its safety when it is applied to the tumour, or the impact on the factor of QoL. The review aimed to address the benefits and limitations of PBMT in premalignant oral lesions, as well as the conflicting evidence concerning the relationship between tumour cell proliferation and the applied dose of photonic energy (fluence) in treating oral mucositis induced by head and neck cancer (H&N) treatments. The objective was to appraise the current concept of PBMT safety in the long-term, along with its latent impact on tumour reaction. This review highlighted the gap in the literature and broaden the knowledge of the current clinical evidence-based practice, and effectiveness, of PBMT in H&N oncology patients. As a result, the authors concluded that PBMT is a promising treatment modality. However, due to the heterogeneity of our data, it needs to undergo further testing in well-designed, long-term and randomised controlled trial studies, to evaluate it with diligent and impartial outcomes, and ensure laser irradiation’s safety at the tumour site.
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Xu, Zongwei, Zhongdu He, Ying Song, Xiu Fu, Mathias Rommel, Xichun Luo, Alexander Hartmaier, Junjie Zhang, and Fengzhou Fang. "Topic Review: Application of Raman Spectroscopy Characterization in Micro/Nano-Machining." Micromachines 9, no. 7 (July 21, 2018): 361. http://dx.doi.org/10.3390/mi9070361.
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The defects and subsurface damages induced by crystal growth and micro/nano-machining have a significant impact on the functional performance of machined products. Raman spectroscopy is an efficient, powerful, and non-destructive testing method to characterize these defects and subsurface damages. This paper aims to review the fundamentals and applications of Raman spectroscopy on the characterization of defects and subsurface damages in micro/nano-machining. Firstly, the principle and several critical parameters (such as penetration depth, laser spot size, and so on) involved in the Raman characterization are introduced. Then, the mechanism of Raman spectroscopy for detection of defects and subsurface damages is discussed. The Raman spectroscopy characterization of semiconductor materials’ stacking faults, phase transformation, and residual stress in micro/nano-machining is discussed in detail. Identification and characterization of phase transformation and stacking faults for Si and SiC is feasible using the information of new Raman bands. Based on the Raman band position shift and Raman intensity ratio, Raman spectroscopy can be used to quantitatively calculate the residual stress and the thickness of the subsurface damage layer of semiconductor materials. The Tip-Enhanced Raman Spectroscopy (TERS) technique is helpful to dramatically enhance the Raman scattering signal at weak damages and it is considered as a promising research field.
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Wang, Yan, Liguang Zhu, Qingjun Zhang, Caijun Zhang, and Shuoming Wang. "Effect of Mg Treatment on Refining the Microstructure and Improving the Toughness of the Heat-Affected Zone in Shipbuilding Steel." Metals 8, no. 8 (August 6, 2018): 616. http://dx.doi.org/10.3390/met8080616.
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The effect of Mg treatment on the microstructure and toughness of the heat-affected zone (HAZ) of shipbuilding steel after high-heat-input welding was investigated via laboratory and industrial testing. The welding process and Charpy impact tests were also carried out to evaluate the HAZ toughness of steel plates. First, typical inclusion characteristics were characterised with an ASPEX PSEM Explorer. Then, confocal laser scanning microscopy (CLSM) was used to observe the diameters of austenite grains under different holding times. The results showed that when the addition of microalloy elements were in the order of Al–Mg–Ti, this had an effect on dispersing inclusions, the largest proportion of which were micro-inclusions that had a particle size range of 1.0–1.5 μm. This accounted for 25.4% of the total inclusions, which was the highest amount. The micro inclusion particle size that was mainly distributed in the range of 0.5–3.5 μm accounted for 82.8% of all the micro-inclusions. The inclusion structure induced intragranular acicular ferrite (IAF) in austenite as follows: MgO and Al2O3 formed the core and Ti2O3 adhered to the Al–Mg complex inclusions to produce smaller particle sizes and dispersions of Al, Mg, and Ti complex inclusions. The 40-mm-thick plate obtained in the industrial test after welding had an average impact absorbed energy 2 mm from the weld joint in the heat-affected zone of 198.9 J at −20 °C, while the welding heat input was 150 kJ/cm, compared with the parent material’s low-temperature performance, which exceeded 88%.
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Xu, Xiao, Miao-Miao Wang, Zhi-ling Sun, Dan-ping Zhou, Ling Wang, Fu-qiang Wang, Zhi-yang Xu, and Qian Ma. "Discovery of Serum Proteomic Biomarkers for Prediction of Response to Moxibustion Treatment in Rats with Collagen-Induced Arthritis: An Exploratory Analysis." Acupuncture in Medicine 34, no. 3 (June 2016): 184–93. http://dx.doi.org/10.1136/acupmed-2015-010909.
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Objective To examine the possible impact of moxibustion on the serum proteome of the collagen-induced arthritis (CIA) rat model. Materials and Methods Thirty-six male Sprague-Dawley rats were included in this experiment. The CIA animal model was prepared by injection of type II bovine collagen in Freund's adjuvant on the first and seventh day. The 36 rats were randomly divided into two groups: the untreated CIA group (control), and the CIA plus treatment with moxibustion (CIA+moxi) group. Moxibustion was administered daily at ST36 and BL23 for 7, 14 or 21 days (n=12 rats each). Arthritis score was used to assess the severity of arthritis. At the end of each 7 day treatment, blood samples from the control group and the CIA+moxi group were collected. After removal of high abundance proteins from serum samples, two-dimensional gel combined with matrix-assisted laser desorption ionisation time-of-flight MS/MS (MALDI-TOF-MS/MS) techniques were performed to examine serum protein expression patterns of the CIA rat model with and without moxibustion treatment. In addition, the relevant proteins were further analysed with the use of bioinformatics analysis. Results Moxibustion significantly decreased arthritis severity in the rats in the CIA+moxi group, when compared with the rats in the CIA group 35 days after the first immunisation (p=0.001). Seventeen protein spots which changed >1.33 or <0.77 at p<0.05 using Bonferonni correction for multiple testing were found to be common to all three comparisons, and these proteins were used for classification of functions using the Gene Ontology method. Consequently, with the use of the Ingenuity Pathway Analysis, the top canonical pathways and a predicted proteomic network related to the moxibustion effect of CIA were established. Conclusions Using the proteomics technique, we have identified novel candidate proteins that may be involved in the mechanisms of action underlying the beneficial effects of moxibustion in rats with CIA. Our findings suggest that immune responses and metabolic processes may be involved in mediating the effects of moxibustion. Moreover, periodxiredoxin I (PRDX1) and inositol 1,4,5-triphosphate receptor (IP3R) may be potential targets.
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Gu, Z. P., Y. J. Cheng, K. L. Xiao, K. Li, X. Q. Wu, Q. M. Li, and C. G. Huang. "Geometrical scaling law for laser-induced micro-projectile impact testing." International Journal of Mechanical Sciences, April 2022, 107289. http://dx.doi.org/10.1016/j.ijmecsci.2022.107289.
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Kumar, Vishnu Vijay, Suresh Rajendran, G. Balaganesan, S. Surendran, Arul Selvan, and Seeram Ramakrishna. "High velocity impact behavior of Hybrid composite under hydrostatic preload." Journal of Composite Materials, August 21, 2022, 002199832211229. http://dx.doi.org/10.1177/00219983221122923.
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The Hybridization concept creates a niche within the composite segment to customize materials for specific applications with reduced cost without sacrificing strength and durability. The composite structures develop strain during continuous operation, and any sudden impact on these preloaded parts might result in catastrophic accidents. Studying impact response during such conditions is essential in designing and developing structures. This study experimentally investigates the high velocity impact response of Hybrid (Carbon-Glass) composite under normal and hydrostatic preload conditions. Mechanical tests involving Tensile, Izod, and Charpy are conducted. High velocity impact testing is carried out with a vertical single-stage gas gun with additional provision for hydrostatic preloading. An oscilloscope with a laser source measures the initial velocity, and Photogrammetry using a high-speed camera measure the residual velocity of a projectile. The mechanical test results suggest that Hybridization resulted in a significant property enhancement. The high velocity impact resistance and energy absorption are higher for Hybrid under both normal and preloaded impact.
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McPhee, Samuel, Alexander Groetsch, Jonathan D. Shephard, and Uwe Wolfram. "Heat impact during laser ablation extraction of mineralised tissue micropillars." Scientific Reports 11, no. 1 (May 26, 2021). http://dx.doi.org/10.1038/s41598-021-89181-9.
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AbstractThe underlying constraint of ultrashort pulsed laser ablation in both the clinical and micromachining setting is the uncertainty regarding the impact on the composition of material surrounding the ablated region. A heat model representing the laser-tissue interaction was implemented into a finite element suite to assess the cumulative temperature response of bone during ultrashort pulsed laser ablation. As an example, we focus on the extraction of mineralised collagen fibre micropillars. Laser induced heating can cause denaturation of the collagen, resulting in ultrastructural loss which could affect mechanical testing results. Laser parameters were taken from a used micropillar extraction protocol. The laser scanning pattern consisted of 4085 pulses, with a final radial pass being 22 $$\upmu {\text {m}}$$ μ m away from the micropillar. The micropillar temperature was elevated to 70.58 $$^{\circ }{\text {C}}$$ ∘ C , remaining 79.42 $$^{\circ }{\text {C}}$$ ∘ C lower than that of which we interpret as an onset for denaturation. We verified the results by means of Raman microscopy and Energy Dispersive X-ray Microanalysis and found the laser-material interaction had no effect on the collagen molecules or mineral nanocrystals that constitute the micropillars. We, thus, show that ultrashort pulsed laser ablation is a safe and viable tool to fabricate bone specimens for mechanical testing at the micro- and nanoscale and we provide a computational model to efficiently assess this.
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Tomac, Mehmet N., Kevin Yugulis, James W. Gregory, James Loftus, and Tony Ferrito. "Investigation of Vibration Phenomena Induced by Air Flow Over Side View Mirror." Journal of Fluids Engineering 133, no. 12 (December 1, 2011). http://dx.doi.org/10.1115/1.4005425.
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This work develops an understanding of the flow mechanisms that induce vibrations on automotive side view mirrors. The unsteady nature of the flow over side view mirrors causes unsteady aerodynamic load distributions and flow-induced vibrations on the mirror assembly. These vibrations generate blurred rear-view images and higher noise levels, affecting the mirror functionality and passenger comfort. Certain geometrical design features of side view mirrors can exacerbate the flow-induced vibration levels of the mirror assembly significantly. This work quantifies the impact of these design features on the vibration amplitude, develops a methodology for testing mirror vibrations in a small, low-speed wind tunnel using only the mirror of interest, and delves into the interactions between the bluff body mirror geometry and its wake. Two similar side view mirror designs were investigated in this work by using laser-based vibrometry, flow visualization, particle image velocimetry, hot film anemometry, and surface stress sensitive film techniques. The magnitude of the vibrations was found to depend on the level of excursion in the dynamic location of flow separation, particularly when characteristic flow frequencies couple with the mirror housing natural frequency.
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Wang, Xuchen, and Mostafa Hassani. "Ultra-High Strain Rate Constitutive Modeling of Pure Titanium Using Particle Impact Test." Journal of Applied Mechanics 87, no. 9 (June 9, 2020). http://dx.doi.org/10.1115/1.4047290.
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Abstract With the advent of advanced testing techniques such as laser-induced particle impact test, it is possible to study materials mechanics under extremely high deformation rates, i.e., above 106 s−1, a relatively less explored regime of strain rates. Inspired by the classical Taylor impact test, in this study, we accelerate microparticles of commercially pure titanium to a range of impact velocities, from 144 to 428 m/s, toward a rigid substrate and record their deformation upon impact in real-time. We also conduct finite element modeling of the experimentally recorded impacts using two constitutive equations, namely, Johnson–Cook and Zerilli–Armstrong. We show that the titanium microparticles experience strain rates in the range of 106–1010 s−1 upon impact. We evaluate the capability of the Johnson–Cook and Zerilli–Armstrong equations in predicting the deformation response of pure Ti at ultra-high strain rates. With an optimization-based constitutive modeling approach, we also propose updated strain rate-related parameters for both equations and improve the extent to which the two models can describe the deformation of pure titanium at ultra-high strain rates.
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Mrzljak, Selim, Lars Gerdes, Jan Keuntje, Verena Wippo, Peter Jaeschke, and Frank Walther. "Assessment of laser cutting parameters and heat-affected zone on microstructure and fatigue behaviour of carbon fibre-reinforced epoxy." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering, November 25, 2022, 095440892211396. http://dx.doi.org/10.1177/09544089221139656.
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In this study, the effects of laser cutting on the fatigue properties of carbon fibre-reinforced polymers are investigated. For this purpose, unidirectional carbon fibre-reinforced epoxy laminate is cut by laser. The material to be cut evaporates directly in the laser beam and the laser beam can produce thermally induced damage, which is referred to as heat-affected zones. Specimens are cut with two different parameters (varying cutting velocity and break time between passes) to widths up to 15 mm for investigation of the heat-affected zones effects on fatigue behaviour. Prior to fatigue tests microstructure is evaluated using light and scanning electron microscopy with regard to cutting geometry and heat-affected zones. Fatigue tests are performed using multiple amplitude tests with a stress ratio of 0.1, instrumented with a video extensometer system and thermocouples for strain and temperature measurements to determine the influence on mechanical properties and evaluate the sensitivity of the used testing method and measurement instrumentation for this use case. Lower cutting velocities and break time passes lead to a larger edge angle and thus in different specimen widths on front (laser inlet) and bottom (laser outlet) of the carbon fibre-reinforced epoxy laminate. Therefore, the resulting true geometry was considered using statistical approaches to eliminate possible cross-sectional errors regarding mechanical stress application. The results show that the specimen widths and process parameters impact the fatigue properties, highlighting the importance of knowledge about heat induction and the detection of inflicted laminate damage.
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Koch, Lothar, Andrea Deiwick, Jordi Soriano, and Boris Chichkov. "Laser bioprinting of human iPSC-derived neural stem cells and neurons: Effect on cell survival, multipotency, differentiation, and neuronal activity." International Journal of Bioprinting 9, no. 2 (January 18, 2023). http://dx.doi.org/10.18063/ijb.v9i2.672.
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Generation of human neuronal networks by three-dimensional (3D) bioprinting is promising for drug testing and hopefully will allow for the understanding of cellular mechanisms in brain tissue. The application of neural cells derived from human induced-pluripotent stem cells (hiPSCs) is an obvious choice, since hiPSCs provide access to cells unlimited in number and cell types that could be generated by differentiation. The questions in this regard include which neuronal differentiation stage is optimal for printing of such networks, and to what extent the addition of other cell types, especially astrocytes, supports network formation. These aspects are the focus of the present study, in which we applied a laser-based bioprinting technique and compared hiPSC-derived neural stem cells (NSCs) with neuronal differentiated NSCs, with and without the inclusion of co-printed astrocytes. In this study, we investigated in detail the effects of cell types, printed droplet size, and duration of differentiation before and after printing on viability, as well as proliferation, stemness, differentiation potential, formation of dendritic extensions and synapses, and functionality of the generated neuronal networks. We found a significant dependence of cell viability after dissociation on differentiation stage, but no impact of the printing process. Moreover, we observed a dependence of the abundance of neuronal dendrites on droplet size, a marked difference between printed cells and normal cell culture in terms of further differentiation of the cells, especially differentiation into astrocytes, as well as neuronal network formation and activity. Notably, there was a clear effect of admixed astrocytes on NSCs but not on neurons.
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Chen, Zhong, Yanpeng Xiong, Yuanyuan Tang, Yuxi Zhao, Junwen Chen, Jinxin Zheng, Yang Wu, Qiwen Deng, Di Qu, and Zhijian Yu. "In vitro activities of thiazolidione derivatives combined with daptomycin against clinical Enterococcus faecium strains." BMC Microbiology 22, no. 1 (January 7, 2022). http://dx.doi.org/10.1186/s12866-021-02423-8.
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Abstract Background Previous reports have demonstrated two thiazolidione derivatives (H2-60 and H2-81) can robustly inhibit the planktonic growth and biofilm formation of S. epidermidis and S. aureus by targeting the histidine kinase YycG. Whereas the antibacterial and anti-biofilm activity of these two thiazolidione derivatives (H2-60 and H2-81) against Enterococcus faecium remains elusive. Here, the pET28a-YycG recombinant plasmid were in vitro expressed in E. coli competent cell BL21 (DE3) and induced to express YycG’ protein (conding HisKA and HATPase_c domain) by 0.5 mM IPTG and was purified by Ni – NTA agarose and then for the autophosphorylation test. Antimicrobial testing and time-killing assay were also be determined. Anti-biofilm activity of two derivatives with sub-MIC concentration towards positive biofilm producers of clinical E. faecium were detected using polystyrene microtiter plate and CLSM. Results The MICs of H2-60 and H2-81 in the clinical isolates of E. faecium were in the range from 3.125 mg/L to 25 mg/L. Moreover, either H2-60 or H2-81 showed the excellent bactericidal activity against E. faecium with monotherapy or its combination with daptomycin by time-killing assay. E. faecium planktonic cells can be decreased by H2-60 or H2-81 for more than 3 × log10 CFU/mL after 24 h treatment when combined with daptomycin. Furthermore, over 90% of E. faecium biofilm formation could markedly be inhibited by H2-60 and H2-81 at 1/4 × MIC value. In addition, the frequency of the eradicated viable cells embedded in mature biofilm were evaluated by the confocal laser microscopy, suggesting that of H2-60 combined with ampicillin or daptomycin was significantly high when compared with single treatment (78.17 and 74.48% vs. 41.59%, respectively, P < 0.01). Conclusion These two thiazolidione derivatives (H2-60 and H2-81) could directly impact the kinase phosphoration activity of YycG of E. faecium. H2-60 combined with daptomycin exhibit the excellent antibacterial and anti-biofilm activity against E. faecium by targeting YycG.