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N.k. Gupta - One of the best experts on this subject based on the ideXlab platform.
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3d numerical simulations of sharp nosed projectile impact on ductile targets
International Journal of Impact Engineering, 2010Co-Authors: M A Iqbal, Anupam Chakrabarti, Surendra Beniwal, N.k. GuptaAbstract:Abstract Three-dimensional FE model is presented for perforation under normal and oblique impact of sharp nosed projectiles on single and layered ductile targets. Numerical simulations have been carried out to study the behavior of Weldox 460 E steel and 1100-H12 aluminum targets impacted by conical and ogive nosed steel projectiles respectively. Weldox 460 E steel targets of 12 mm thickness in single and double layered combination (2 × 6 mm) and 1100-H12 aluminum targets of 1 mm thickness in single and double layered combination (2 × 0.5 mm) impacted at 0°, 15° and 30° obliquity were considered for simulations. The results of monolithic and layered targets were compared for each angle of impact. Monolithic targets were found to have higher ballistic resistance than that of the layered in-contact targets of equivalent thickness. Failure of both the targets occurred through ductile Hole Enlargement. However, ogive nosed projectile failed 1 mm thick aluminum target through petal formation and conical nosed projectile failed 12 mm thick steel target through a circular or elliptical Hole enclosed by a bulge at rear surface. The explicit algorithm of ABAQUS finite element code was used to carry out the numerical simulations. Various parameters which play critical role in numerical simulation such as element size and its aspect ratio have been studied.
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3d numerical simulations of ductile targets subjected to oblique impact by sharp nosed projectiles
International Journal of Solids and Structures, 2010Co-Authors: M A Iqbal, Gagan Gupta, N.k. GuptaAbstract:Abstract Three-dimensional numerical simulations have been performed to study the behaviour of ductile targets subjected to normal and oblique impact by sharp nosed cylindrical projectiles. Twelve-mm-thick Weldox 460 E steel targets were impacted by 20 mm diameter projectiles with conical nose and 1-mm-thick 1100-H12 aluminum targets were impacted by 19 mm diameter ogive nosed projectiles. In both the cases, the targets were impacted at 0°, 15°, 30°, 45° and 60° obliquity or until the ricochet of the projectile occurred. The ballistic limit of 12 mm steel targets was found to be almost same up to 30° obliquity and thereafter it increased sharply. However, in the case of 1 mm aluminum targets a consistent increase in the ballistic limit was observed with increase in obliquity. The critical angle of projectile ricochet was found to increase with increase in impact velocity. Both the targets failed through ductile Hole Enlargement. Petal formation occurred in the aluminum targets and four petals were generally formed in each plate, however, the size of the upper two petals decreased and that of the lower two petals increased with increase in target obliquity. In the case of the steel targets the perforation occurred through the formation of a Hole enclosed by a bulge. Both the bulge and the Hole were circular in normal impact and elliptical in oblique impact. Petal formation in steel targets was observed at 60° obliquity. The ABAQUS/explicit finite element code was used to carry out numerical simulations.
M A Iqbal - One of the best experts on this subject based on the ideXlab platform.
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effect of eccentricity and obliquity on the ballistic performance and energy dissipation of hemispherical shell subjected to ogive nosed
Thin-walled Structures, 2021Co-Authors: Nikhil Khaire, Gaurav Tiwari, M A IqbalAbstract:Abstract A numerical study was undertaken to investigate the effect of projectile eccentricity and obliquity impact on the ballistic performance of the Aluminium 1100-H12 1 mm thick hemispherical shell against ogive nose projectile. The projectile eccentric distance was taken with respect to the radius of the shell such as 0th, R/4th, 2R/4th and 3R/4th whereas, the incidence angle of the projectile as 0°, 15°, 30°, 45°, and 60° for each shell (68, 100, 150 and 200 mm diameter). The projectile was impacted at different velocities for each incidence angle and eccentric distance and ballistic limit obtained. Three-dimensional finite element simulations were carried out by using the Abaqus/explicit solver. Johnson cook material model was used to simulate the behaviour of a hemispherical shell. The results of the numerical study were elucidated through the experimental result conducted for normal impact. Moreover, user-defined coding written in python was used to obtain the energy dissipation in different stretching mode. The result showed that the ballistic performance of the target was influenced by both the eccentricity and obliquity. Also, the target was failed in ductile Hole Enlargement with petals formation however, the number of petals form was depended upon the eccentricity and obliquity.
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3d numerical simulations of sharp nosed projectile impact on ductile targets
International Journal of Impact Engineering, 2010Co-Authors: M A Iqbal, Anupam Chakrabarti, Surendra Beniwal, N.k. GuptaAbstract:Abstract Three-dimensional FE model is presented for perforation under normal and oblique impact of sharp nosed projectiles on single and layered ductile targets. Numerical simulations have been carried out to study the behavior of Weldox 460 E steel and 1100-H12 aluminum targets impacted by conical and ogive nosed steel projectiles respectively. Weldox 460 E steel targets of 12 mm thickness in single and double layered combination (2 × 6 mm) and 1100-H12 aluminum targets of 1 mm thickness in single and double layered combination (2 × 0.5 mm) impacted at 0°, 15° and 30° obliquity were considered for simulations. The results of monolithic and layered targets were compared for each angle of impact. Monolithic targets were found to have higher ballistic resistance than that of the layered in-contact targets of equivalent thickness. Failure of both the targets occurred through ductile Hole Enlargement. However, ogive nosed projectile failed 1 mm thick aluminum target through petal formation and conical nosed projectile failed 12 mm thick steel target through a circular or elliptical Hole enclosed by a bulge at rear surface. The explicit algorithm of ABAQUS finite element code was used to carry out the numerical simulations. Various parameters which play critical role in numerical simulation such as element size and its aspect ratio have been studied.
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3d numerical simulations of ductile targets subjected to oblique impact by sharp nosed projectiles
International Journal of Solids and Structures, 2010Co-Authors: M A Iqbal, Gagan Gupta, N.k. GuptaAbstract:Abstract Three-dimensional numerical simulations have been performed to study the behaviour of ductile targets subjected to normal and oblique impact by sharp nosed cylindrical projectiles. Twelve-mm-thick Weldox 460 E steel targets were impacted by 20 mm diameter projectiles with conical nose and 1-mm-thick 1100-H12 aluminum targets were impacted by 19 mm diameter ogive nosed projectiles. In both the cases, the targets were impacted at 0°, 15°, 30°, 45° and 60° obliquity or until the ricochet of the projectile occurred. The ballistic limit of 12 mm steel targets was found to be almost same up to 30° obliquity and thereafter it increased sharply. However, in the case of 1 mm aluminum targets a consistent increase in the ballistic limit was observed with increase in obliquity. The critical angle of projectile ricochet was found to increase with increase in impact velocity. Both the targets failed through ductile Hole Enlargement. Petal formation occurred in the aluminum targets and four petals were generally formed in each plate, however, the size of the upper two petals decreased and that of the lower two petals increased with increase in target obliquity. In the case of the steel targets the perforation occurred through the formation of a Hole enclosed by a bulge. Both the bulge and the Hole were circular in normal impact and elliptical in oblique impact. Petal formation in steel targets was observed at 60° obliquity. The ABAQUS/explicit finite element code was used to carry out numerical simulations.
Batista F.a.f. - One of the best experts on this subject based on the ideXlab platform.
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Behavior Of Ultrasonic Waves In Wood With Presence Of Holes [comportamento De Ondas De Ultrassom Na Presença De Ocos Na Madeira]
2015Co-Authors: Secco C.b., Goncalves R., Cerri D.g.p., Vasques E.c., Batista F.a.f.Abstract:This work aimed to analyze the pattern of variation in wave lengths in presence of wood Holes and to develop a model capable of describing the process. To attain that end, wood pieces were used from species pequiá (Aspidosperma desmanthum), on which circular and linear artificial Holes were made and gradually enlarged. Ultrasonic tests were performed using USLab equipment and 45 kHz transducers. Measurements were taken first on the intact piece and then after each stage of artificial Hole Enlargement. Results demonstrated that propagation velocities of ultrasonic waves are affected by presence of Holes and also that reduction in velocity is caused by changes in wave path, since waves tend to deviate from empty space and travel through matter. The circular Hole type had a slightly stronger influence on velocity reduction than the linear Hole type. Variation in velocity as a function of increasing percentage of hollow space relative to the intact piece can be represented by a linear model
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Behavior Of Ultrasonic Waves In Wood With Presence Of Holes [comportamento De Ondas De Ultrassom Na Presença De Ocos Na Madeira]
'FapUNIFESP (SciELO)', 2015Co-Authors: Secco C.b., Goncalves R., Cerri D.g.p., Vasques E.c., Batista F.a.f.Abstract:This work aimed to analyze the pattern of variation in wave lengths in presence of wood Holes and to develop a model capable of describing the process. To attain that end, wood pieces were used from species pequiá (Aspidosperma desmanthum), on which circular and linear artificial Holes were made and gradually enlarged. Ultrasonic tests were performed using USLab equipment and 45 kHz transducers. Measurements were taken first on the intact piece and then after each stage of artificial Hole Enlargement. Results demonstrated that propagation velocities of ultrasonic waves are affected by presence of Holes and also that reduction in velocity is caused by changes in wave path, since waves tend to deviate from empty space and travel through matter. The circular Hole type had a slightly stronger influence on velocity reduction than the linear Hole type. Variation in velocity as a function of increasing percentage of hollow space relative to the intact piece can be represented by a linear model.183507514Apolinário, F.E., Martius, C., Ecological role of térmites (Insecta, Isoptera) in tree truncks in central Amazonian rain forests (2004) Forest Ecology and Management, 194, pp. 23-28. , Amsterdam(1997) NBR 7190: Projeto De Estruturas De Madeira, p. 107. , ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS, Rio de JaneiroBucur, V., (2006) Acoustics of Wood, p. 303. , Berlin: Springer-VerlagDeflorio, G., Fink, S., Schwarze, F.W.M.R., Detection of incipient decay in tree stems with sonic tomography after wounding and fungal inoculation (2007) Wood Science and Technology, 42, pp. 117-132. , New YorkLin, C.J., (2008) Application of An Ultrasonic Tomographic Technique For Detecting Defects In Standing Trees, 62, pp. 432-441. , International Biodeterioration & Biodegradation, BirminghamNajafi, S.K., Shalbafan, A., Ebrahimi, G., Internal decay assessment in standing beech trees using ultrasonic velocity measurement (2009) European Journal of Forest Research, 48 (1), pp. 1-6. , OxfordWang, X., Divos, F., Pilon, C., Brashaw, B.K., Ross, R.J., Pellerin, R.F., (2004) Assessment of Decay In Standing Timber Using Stress Wave Timing Nondestructive Evaluation Tools: A Guide For Use and Interpretation, p. 12. , Washington: USDA, General Technical Report FPL-GTR-14
Batista, Fernando Augusto Franco - One of the best experts on this subject based on the ideXlab platform.
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Comportamento de ondas de ultrassom na presença de ocos na madeira
'FapUNIFESP (SciELO)', 2015Co-Authors: Secco, Chiara Barros, Gonçalves Raquel, Cerri, Domingos Guilherme Pelegrino, Vasques, Érica Caroline, Batista, Fernando Augusto FrancoAbstract:This work aimed to analyze the pattern of variation in wave lengths in presence of wood Holes and to develop a model capable of describing the process. To attain that end, wood pieces were used from species pequiá (Aspidosperma desmanthum), on which circular and linear artificial Holes were made and gradually enlarged. Ultrasonic tests were performed using USLab equipment and 45 kHz transducers. Measurements were taken first on the intact piece and then after each stage of artificial Hole Enlargement. Results demonstrated that propagation velocities of ultrasonic waves are affected by presence of Holes and also that reduction in velocity is caused by changes in wave path, since waves tend to deviate from empty space and travel through matter. The circular Hole type had a slightly stronger influence on velocity reduction than the linear Hole type. Variation in velocity as a function of increasing percentage of hollow space relative to the intact piece can be represented by a linear model.Neste trabalho, objetivou-se estudar o comportamento da variação do percurso da onda em presença de oco na madeira bem como elaborar um modelo que o descrevesse. Para atingir esse objetivo, foram utilizadas peças de madeira da espécie pequiá (Aspidosperma desmanthum) nos quais foram confeccionados orifícios artificiais (circular e linear). Esses orifícios foram sendo aumentados gradualmente. Os ensaios de ultrassom foram realizados utilizando equipamento da marca USLab e transdutores de 45 kHz. As medições foram realizadas na peça íntegra e após cada fase de confecção do oco artificial. Os resultados permitiram confirmar que as velocidades de propagação de ondas de ultrassom são afetadas pela presença de ocos e que a redução da velocidade é provocada pela mudança de percurso da onda, que tende a se desviar do vazio e percorrer o material. O oco do tipo circular teve influência levemente superior na redução da velocidade do que o oco do tipo linear. A variação da velocidade com o aumento da porcentagem de oco em relação à peça integra pode ser representada por um modelo linear.507514Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq
Huan Huang - One of the best experts on this subject based on the ideXlab platform.
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preparation of open cage fullerenes and incorporation of small molecules through their orifices
Advanced Materials, 2010Co-Authors: Dazhi Yang, Qianyan Zhang, Huan HuangAbstract:: Open-cage fullerenes can act as hosts for small molecules such as water, nitrogen, or hydrogen, forming endohedral fullerenes. Following a brief summary of carbon, nitrogen, and oxygen insertion in the fullerene framework to form homofullerenes, methods of creating a Hole in the fullerene surface are surveyed. Techniques of Hole Enlargement and the insertion of atoms or molecules through the orifice to form endohedral fullerenes are described. Finally, the possibility of subsequent closure of the Hole is considered.