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Post yield evaluation of induced residual stress- a conceptMcGrath, PJ, Hattingh, DG, James, MN 01 January 2004 (has links)
Summary
Residual stress dssess ment by means of the hole
drilling techniqae is still regarded by many analysts
as a phenomenon whose use is restricted to isotropic
and homogeneous materials. The work caFried
out in this paper tends to address this 'lack of
certainty' through introdacing a verilication approach
of experimentally assess ed residual stress
values, The components investigated were produced
under pure bending conditions and anulysed for
their residual stress behaviour using a customized
strain gaage rosette. This rosette was employed in
order to detect the average and peak maximam
strain relaxstion os a result of producing a hole by
the high speed drilling technique. It is envisaged
that the concept of the verffication method could
lead to a better understanding with regard to residual
stress analysis.
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Estudo do efeito springback em aços avançados de alta resistência aplicados a indústria automobilística /Silva, Erika Aparecida da. January 2012 (has links)
Orientador: Marcelo dos Santos Pereira / Banca: Marcelino Pereira Nascimento / Banca: Rosinei Batista Ribeiro / Resumo: Este projeto é um estudo do efeito springback em quatro tipos de aços de alta resistência, sendo estes bifásico, baixo carbono, endurecível após pintura e com interstícios livres, aplicados atualmente como matéria-prima na produção de veículos. Neste contexto está inserido o desenvolvimento de novos aços avançados de alta resistência em consonância com o projeto ULSAB-AVC, que visa à produção de veículos seguros e econômicos para o século 21. A caracterização mecânica do efeito springback foi realizada por intermédio de ensaio de conformação mecânica, denominado dobramento de três pontos ao ar, como uma adaptação ao ensaio de flexão cilíndrica livre. Foram avaliadas também as propriedades mecânicas do material definidas pelo ensaio de tração, objetivando a determinação da resistência à tração, do limite de escoamento e do alongamento. Além disso, foi avaliada a caracterização microestrutural dos aços avançados, identificando e quantificando-se as fases presentes em coexistência por meio do processamento digital de imagens. Os resultados mostram que o efeito springback no aço bifásico, devido à sua alta resistência mecânica, apresenta as maiores taxas de springback e causa uma diminuição na "razão de aspecto" dos grãos que sofreram conformação mecânica e tentaram retornar às suas formas originais. Aços de baixo carbono e endurecíveis após a pintura, não sofrem efeito springback suficiente para causar alteração na forma dos grãos, sendo que a variação da "razão de aspecto" depende da combinação do alongamento e resistência mecânica destes aços. Já o aço com interstícios livres, devido a sua menor resistência mecânica, o efeito springback apresenta as menores taxas e a variação da razão de aspecto depende somente da capacidade de alongamento desse aço / Abstract: This is a study of the springback effect on four kinds of high strength steel, wich are dual-phase, low carbon, bake hardening and interstitial free, currently used as feedstock in the production of vehicles. In this context is inserted the development of new advanced high steel resistance in accordance with the project ULSAB-AVC, which aims to produce safe and economical vehicle for the 21st century. The mechanical characterization of the springback effect was performed by means of a test of mechanical conformation, called three-point air bending, done by adapting to unconstrained cylindrical bending test. Were also evaluated the mechanical properties of material defined by the tensile test, in order to determine the tensile strength, yield strength and the elongation. Furthermore, was performed the microstructural characterization of advanced steels by identificating and quantificating of present phases in coexistence by means digital image processing. The results indicates that the springback effect in dual-phase steel, due to its high mechanical strength, has the highest springback rates and causes a decrease in the "aspect ratio" of the grains that suffered mechanical conformation attempting to return to its original forms. Low carbon and bake hardening steels, have not enough springback effect to cause change in the shape of the grains and the change of the "ratio aspect" depends on the combination of both elongation and mechanical strength of these steels. Yet on the interstitial free steel, due to its lower mechanical strength, the springback effect has the lowest rates and the change in "aspect ratio" depends only on elongation capacity of the steel / Mestre
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Estudo do efeito springback em aços avançados de alta resistência aplicados a indústria automobilísticaSilva, Érika Aparecida da [UNESP] 05 March 2012 (has links) (PDF)
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silva_ea_me_guara.pdf: 1498613 bytes, checksum: 06fa171181e5ced1500ca8c7e2468fc9 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este projeto é um estudo do efeito springback em quatro tipos de aços de alta resistência, sendo estes bifásico, baixo carbono, endurecível após pintura e com interstícios livres, aplicados atualmente como matéria-prima na produção de veículos. Neste contexto está inserido o desenvolvimento de novos aços avançados de alta resistência em consonância com o projeto ULSAB-AVC, que visa à produção de veículos seguros e econômicos para o século 21. A caracterização mecânica do efeito springback foi realizada por intermédio de ensaio de conformação mecânica, denominado dobramento de três pontos ao ar, como uma adaptação ao ensaio de flexão cilíndrica livre. Foram avaliadas também as propriedades mecânicas do material definidas pelo ensaio de tração, objetivando a determinação da resistência à tração, do limite de escoamento e do alongamento. Além disso, foi avaliada a caracterização microestrutural dos aços avançados, identificando e quantificando-se as fases presentes em coexistência por meio do processamento digital de imagens. Os resultados mostram que o efeito springback no aço bifásico, devido à sua alta resistência mecânica, apresenta as maiores taxas de springback e causa uma diminuição na “razão de aspecto” dos grãos que sofreram conformação mecânica e tentaram retornar às suas formas originais. Aços de baixo carbono e endurecíveis após a pintura, não sofrem efeito springback suficiente para causar alteração na forma dos grãos, sendo que a variação da “razão de aspecto” depende da combinação do alongamento e resistência mecânica destes aços. Já o aço com interstícios livres, devido a sua menor resistência mecânica, o efeito springback apresenta as menores taxas e a variação da razão de aspecto depende somente da capacidade de alongamento desse aço / This is a study of the springback effect on four kinds of high strength steel, wich are dual-phase, low carbon, bake hardening and interstitial free, currently used as feedstock in the production of vehicles. In this context is inserted the development of new advanced high steel resistance in accordance with the project ULSAB-AVC, which aims to produce safe and economical vehicle for the 21st century. The mechanical characterization of the springback effect was performed by means of a test of mechanical conformation, called three-point air bending, done by adapting to unconstrained cylindrical bending test. Were also evaluated the mechanical properties of material defined by the tensile test, in order to determine the tensile strength, yield strength and the elongation. Furthermore, was performed the microstructural characterization of advanced steels by identificating and quantificating of present phases in coexistence by means digital image processing. The results indicates that the springback effect in dual-phase steel, due to its high mechanical strength, has the highest springback rates and causes a decrease in the “aspect ratio” of the grains that suffered mechanical conformation attempting to return to its original forms. Low carbon and bake hardening steels, have not enough springback effect to cause change in the shape of the grains and the change of the “ratio aspect” depends on the combination of both elongation and mechanical strength of these steels. Yet on the interstitial free steel, due to its lower mechanical strength, the springback effect has the lowest rates and the change in “aspect ratio” depends only on elongation capacity of the steel
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Geometric estimation of strains in car body panelsHeap, Graham Stewart January 1988 (has links)
The thesis focuses on the manufacture of car body panels at Austin Rover and in particular the phenomenon of spring-back. After pressing of a shallow drawn panel its shape is often flatter than required. This loss of shape control corresponds to areas of small strains. The aim of the thesis is to describe the generation of a database of small strain information at discrete points on a drawn panel, which could be used in the numerical modelling of the drawing process.
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EXPERIMENTAL, ANALYTICAL, AND FINITE ELEMENT STUDY OF THE BENDING AND SPRINGBACK BEHAVIOR OF DP780 AND DP90 STEEL SHEETSLim, Timothy 06 1900 (has links)
The bending and spring back behaviors of DP780 and DP980 were
investigated using experiments, analytical models, and PEA. An PEA study using
3D shells was first performed of the work by Queener and DeAngelis (1968) and
demonstrated that the 3D shell element behavior in bending and springback, is
similar to that from simple bending theory.
Experimental and FE studies were then performed using DP780 and
DP980 steels under simple and general bending conditions. Simple bending
conditions were studied in V -die bending. General bending was studied for
DP780 using a commercial bending machine. The PEA examined the effect of
element formulation and material hardening assumptions on springback, bending
stresses, and the residual stress distributions after springback. Corresponding
simple and general bending analytical models were also compared. The simple
bending model was from Queener and DeAngelis ( 1968), and the general bending
model was from Tan et al. ( 1995), modified for Ludwig hardening.
Overall, the PEA predicted the springback magnitude in the order; 2D
continuum >3D continuum> 3D shells, and kinematic hardening> mixed
hardening> isotropic hardening.
In the V -die bending study the 3D shell PEA, using a calibrated mixed
hardening assumption, produced the most accurate results. The PEA using pure
isotropic hardening demonstrated that bending and springback behaviors for both steels were consistent with that described by simple bending theory. The
behaviors demonstrated by the FEA using mixed or pure kinematic hardening
were not.
In the general bending study, the 3D continuum element FEA using pure
kinematic hardening was the most accurate. The 3D continuum element FEA
captured the bending stress interaction with the hardening assumption as well as
thinning deformation, in agreement with the analytical model and thinning
measured experimentally. 3D Shell elements could not capture these behaviors
and significantly under-predicted springback under the pure isotropic hardening
assumption. / Thesis / Master of Applied Science (MASc)
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Prediction of Springback in AA6016-T4 Sheets Using Isotropic Finite Element and EPSC Modeling ApproachesSargeant, Dane Roger 19 April 2022 (has links)
Strain path changes are common in complex automotive stampings, where sheet materials undergo a combination of drawing, stretching, and bending to achieve a desired part shape. Aluminum sheet alloys are increasingly used in vehicle structure light-weighting efforts, but limited formability and high levels of springback present challenges to the manufacturing and assembly processes. The current work explores springback levels in AA6016-T4 sheet after various pure bending operations, where sheets were first pre-strained in uniaxial, plane-strain, and biaxial tension. Finite element modeling of the pre-straining and subsequent bending operations will be performed using both isotropic and elasto-plastic self-consistent (EPSC) crystal plasticity approaches. Because the EPSC model incorporates backstresses informed by GND content, as measured via high-resolution EBSD, the predictions are more accurate than those of the isotropic model. The benefits and limitations of the current EPSC model, regarding accuracy of the predictions for the proposed strain path changes, are discussed.
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Investigation of fracture and springback in hot and cold formingKishore, Siddharth January 2014 (has links)
No description available.
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Modeling evolution of anisotropy and hardening for sheet metalsChoi, Yangwook 06 November 2003 (has links)
No description available.
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Springback investigationsJiang, Sen January 1997 (has links)
No description available.
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Complex Unloading Model for Springback PredictionSun, Li 17 March 2011 (has links)
No description available.
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