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[en] FATIGUE LIFE IMPROVEMENT OF THE R4 STUCTURAL STEEL / [pt] OTIMIZAÇÃO DA VIDA-FADIGA DO AÇO ESTRUTURAL R4LUIZ DINIZ CORREA 26 April 2006 (has links)
[pt] Esta pesquisa teve como objetivo avaliar o efeito do
jateamento de partículas
(shot-peening) sobre a vida-fadiga do aço estrutural R4,
largamente adotado na
fabricação de componentes estruturais para sistemas de
ancoragem de unidades
flutuantes. Inicialmente, amostras cilíndricas do material
foram retiradas das seções
retas de elos tipo Kenter. Em seqüência, algumas amostras
foram temperadas e
revenidas em diferentes tempos de tratamento, com o
objetivo de se promover uma
homogeneidade microestrutural, bem como propriedades
mecânicas similares àquelas
dos elos tratados industrialmente. As amostras foram
submetidas a ensaios de dureza e
tração e, com base nos resultados, providenciou-se o
tratamento térmico de todas as
amostras. Dando continuidade a etapa experimental, corpos
de prova para ensaios de
fadiga foram usinados das amostras tratadas e submetidos a
jateamento com
microesferas de aço temperado sob pressões de 20 psi, 30
psi e 40 psi. Finalmente,
corpos de prova nas condições sem jateamento e após
jateamento foram submetidos a
ensaios de fadiga por flexão rotativa, com o objetivo de
se levantar a curva tensão
versus número de ciclos para a falha (curva S-N) do aço
estrutural R4 nas diferentes
condições de superfície. A extensão da vida em fadiga do
aço estrutural R4 foi
relacionada com o jateamento de microesferas. De acordo
com os resultados, houve
uma influência benéfica do tratamento de superfície sobre
a vida-fadiga do material.
Tal influência foi caracterizada por um maior número de
ciclos para a falha e aumento
do limite de resistência à fadiga. Os resultados mostraram
que a extensão da vida útil
esteve diretamente relacionada com a intensidade do
jateamento, significando que uma
maior intensidade de jateamento provocou uma maior
extensão da vida-fadiga do
material. / [en] The objective of the present work was to evaluate the
effect of shot
peening on the fatigue life of a grade R4 structural
steel, largely adopted for
fabricating offshore mooring chains. Initially,
cylindrical samples of the material
were cut of from the straight sections of Kenter links. In
the sequence, a number
of specimens were austenitized ed and tempered making use
of different treatment
times, in order to promote a microstructural homogeneity
as well as mechanical
properties similar to those associated with industrial
heat treatments. The
specimens were subjected to hardness and tensile tests and
on the basis of the
results, all samples were heat treated. After that,
fatigue specimens were machined
from the treated samples and shot peened with quenched
steel shots under
pressures of 20 psi, 30 psi and 40 psi. Finally, rotating
bend fatigue tests were
performed with unpeened and shot peened specimens aiming
to establish the
stress-life curves of the grade R4 structural steel. The
fatigue life extension of the
grade R4 structural steel was related to the shot peening.
Regarding the results, the
surface treatments affected the fatigue life of the
material beneficially. This
influence was characterized by a longer fatigue cycles and
a fatigue life
improvement. The results showed that the fatigue life
extension was directly
related to the shot peening intensity, i.e., the fatigue
life extension has increased
when increasing the shot peening intensity.
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The Effect of Shot-peening on the Fatigue Limits of Four Connecting Rod SteelsMirzazadeh, Mohammad-Mahdi January 2010 (has links)
This work was carried out to study the effect of shot-peening on the fatigue behaviour of carbon steels. Differently heat treated medium and high carbon steel specimens were selected. Medium carbon steels, AISI 1141 and AISI 1151, were respectively air cooled and quenched-tempered. A high carbon steel, C70S6 (AISI 1070), was air cooled. The other material was a powder metal (0.5% C) steel. Each group of steels was divided into two. One was shot-peened. The other half remained in their original conditions. All were fatigue tested under fully reversed (R=-1) tension-compression loading conditions. Microhardness tests were carried out on both the grip and gage sections of selected non shot-peened and shot-peened specimens to determine the hardness profile and effect of cycling. Shot-peening was found to be deeper on one side of each specimen. Compressive residual stress profiles and surface roughness measurements were provided. Shot-peening increased the surface roughness from 0.26±0.03µm to 3.60±0.44µm. Compressive residual stresses induced by shot-peening reached a maximum of -463.9MPa at a depth of 0.1mm.The fatigue limit (N≈106 cycles) and microhardness profiles of the non shot-peened and shot-peened specimens were compared to determine the material behaviour changes after shot-peening and cycling. Also their fatigue properties were related to the manufacturing process including heat and surface treatments. Comparing the grip and gage microhardness profiles of each steel showed that neither cyclic softening nor hardening occurred in the non shot-peened condition. Cyclic softening was apparent in the shot-peened regions of all steels except powder metal (PM) steel. The amount of softening in the shot-peened region was 55.0% on the left side and 73.0% on the right in the AISI 1141 steel , 46.0% on the left side and 55.0% on the right in the C70S6AC steel and 31.0% on the right side in AISI 1151QT steel. Softening was accompanied by a decrease in the depth of surface hardness. It is suggested that although the beneficial effects of shot peening, compressive residual stresses and work hardening, were offset by surface roughness, crack initiation was more likely to occur below the surface. Surface roughness was not a significant factor in controlling the fatigue lives of AISI 1141AC and C70S6 steels, since they were essentially the same for the non shot-peened and shot-peened conditions. Shot-peening had very little effect on the push-pull fatigue limit of C70S6 steel (-2.1%), and its effect on AISI 1141AC steel was relatively small (6.0%). However, the influence of shot-peening on the AISI 1151QT and PM steels was more apparent. The fatigue limit of the PM steel increased 14.0% whereas the fatigue limit of the AISI 1151QT steel decreased 11.0% on shot peening.
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Experimental Investigation Of Residual Stresses Introduced Via Shot Peening And Their Effect On Fatigue Life Of Ball BearingsKucukyilmaz, Ali 01 February 2010 (has links) (PDF)
In this study, residual stresses introduced via application of shot peening on the raceways of bearing rings and their effect on the fatigue life was investigated experimentally. For improvement of residual compressive stress state, shot peening operation with different parameters was utilized. Residual stress measurements were conducted via X-ray diffraction technique. Optimization of residual stress state during the production of ball bearings is the main target of this study. Process parameters for shot peening and super-finishing were studied for determination of the parameters that induce the most favorable residual stress state. The fatigue life of ball bearings were determined by life cycle tests and tabulated to show the results of the study. The results of the thesis are believed to help for optimization of residual stress distribution and improvement of service life of ball bearings.
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Monitoring Variation Of Surface Residual Stresses In The Shot Peened Steel Components By Magnetic Barkhausen Noise MethodSavas, Serdar 01 July 2010 (has links) (PDF)
Shot peening is a cold-working process by which residual compressive stresses are being induced in the surface region to increase the fatigue strength and the resistance to stress-corrosion cracking. This study covers non-destructive measurement of surface residual stresses in the shot-peened steel components by a micro-magnetic technique, named as Magnetic Barkhausen Noise (MBN) method. For this purpose, various low alloy steel specimens were prepared by a controlled shot peening process with different intensity, impact angle and coverage values. The measurements showed that a clear relationship exists between residual stresses and the MBN signals. Residual stress values determined by MBN technique were also verified by X-ray diffraction measurements.
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The Effect of Shot-peening on the Fatigue Limits of Four Connecting Rod SteelsMirzazadeh, Mohammad-Mahdi January 2010 (has links)
This work was carried out to study the effect of shot-peening on the fatigue behaviour of carbon steels. Differently heat treated medium and high carbon steel specimens were selected. Medium carbon steels, AISI 1141 and AISI 1151, were respectively air cooled and quenched-tempered. A high carbon steel, C70S6 (AISI 1070), was air cooled. The other material was a powder metal (0.5% C) steel. Each group of steels was divided into two. One was shot-peened. The other half remained in their original conditions. All were fatigue tested under fully reversed (R=-1) tension-compression loading conditions. Microhardness tests were carried out on both the grip and gage sections of selected non shot-peened and shot-peened specimens to determine the hardness profile and effect of cycling. Shot-peening was found to be deeper on one side of each specimen. Compressive residual stress profiles and surface roughness measurements were provided. Shot-peening increased the surface roughness from 0.26±0.03µm to 3.60±0.44µm. Compressive residual stresses induced by shot-peening reached a maximum of -463.9MPa at a depth of 0.1mm.The fatigue limit (N≈106 cycles) and microhardness profiles of the non shot-peened and shot-peened specimens were compared to determine the material behaviour changes after shot-peening and cycling. Also their fatigue properties were related to the manufacturing process including heat and surface treatments. Comparing the grip and gage microhardness profiles of each steel showed that neither cyclic softening nor hardening occurred in the non shot-peened condition. Cyclic softening was apparent in the shot-peened regions of all steels except powder metal (PM) steel. The amount of softening in the shot-peened region was 55.0% on the left side and 73.0% on the right in the AISI 1141 steel , 46.0% on the left side and 55.0% on the right in the C70S6AC steel and 31.0% on the right side in AISI 1151QT steel. Softening was accompanied by a decrease in the depth of surface hardness. It is suggested that although the beneficial effects of shot peening, compressive residual stresses and work hardening, were offset by surface roughness, crack initiation was more likely to occur below the surface. Surface roughness was not a significant factor in controlling the fatigue lives of AISI 1141AC and C70S6 steels, since they were essentially the same for the non shot-peened and shot-peened conditions. Shot-peening had very little effect on the push-pull fatigue limit of C70S6 steel (-2.1%), and its effect on AISI 1141AC steel was relatively small (6.0%). However, the influence of shot-peening on the AISI 1151QT and PM steels was more apparent. The fatigue limit of the PM steel increased 14.0% whereas the fatigue limit of the AISI 1151QT steel decreased 11.0% on shot peening.
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Impact Velocity, Almen Strip Curvature and Residual Stress Modelling in Vibratory FinishingCiampini, David 30 July 2008 (has links)
The surface-normal impact velocity distributions, impact frequencies and impact power per unit area were measured using a force sensor in a vibratory finisher for two types of spherical media. These parameters control the degree, rate and character of plastic deformation of a workpiece surface in vibratory finishing. The force sensor was also used to quantify the effect of media type, finisher amplitude, and location within the finisher on the probability distribution of the particle impact velocity normal to the workpiece. It was found that reducing the total media mass in the finisher and moving closer to the wall resulted in a more aggressive process. It was also found that contacts occured periodically within time periods that corresponded to the finisher’s driving frequency.
The Almen system was adapted to a vibratory finishing process to characterize the effect of varying process parameters for the purposes of process development and control. Saturation curves for two types of aluminum Almen strips were obtained by finishing at two distinct conditions. Comparison with the normal contact forces and effective impact velocities, measured for both these conditions, provided insight into the mechanics of the vibratory finishing process. An electromagnetic apparatus was constructed to simulate the normal impacts in the vibratory finisher. It was found that surface-normal impacts at velocities comparable to the higher range in the vibratory finisher produced Almen saturation curves similar to those created in the vibratory finisher. This provided support for the modeling approximation of treating all contact events in a vibratory finisher as effective surface-normal impacts, and the accuracy of the effective impact velocity measurement.
A model of the process by which Almen strips were plastically deformed by media impacts in vibratory finishing was presented. The motivation was to extend the use of Almen strip measurements as a means of characterizing vibratory finishing through an improved understanding of the process parameters that controlled time-dependent curvature development. Two thicknesses of Almen strip were tested for two finishing conditions. The quantitative agreement between the model saturation curves and the experimental curves was fair, although the overall trends were predicted very well.
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Impact Velocity, Almen Strip Curvature and Residual Stress Modelling in Vibratory FinishingCiampini, David 30 July 2008 (has links)
The surface-normal impact velocity distributions, impact frequencies and impact power per unit area were measured using a force sensor in a vibratory finisher for two types of spherical media. These parameters control the degree, rate and character of plastic deformation of a workpiece surface in vibratory finishing. The force sensor was also used to quantify the effect of media type, finisher amplitude, and location within the finisher on the probability distribution of the particle impact velocity normal to the workpiece. It was found that reducing the total media mass in the finisher and moving closer to the wall resulted in a more aggressive process. It was also found that contacts occured periodically within time periods that corresponded to the finisher’s driving frequency.
The Almen system was adapted to a vibratory finishing process to characterize the effect of varying process parameters for the purposes of process development and control. Saturation curves for two types of aluminum Almen strips were obtained by finishing at two distinct conditions. Comparison with the normal contact forces and effective impact velocities, measured for both these conditions, provided insight into the mechanics of the vibratory finishing process. An electromagnetic apparatus was constructed to simulate the normal impacts in the vibratory finisher. It was found that surface-normal impacts at velocities comparable to the higher range in the vibratory finisher produced Almen saturation curves similar to those created in the vibratory finisher. This provided support for the modeling approximation of treating all contact events in a vibratory finisher as effective surface-normal impacts, and the accuracy of the effective impact velocity measurement.
A model of the process by which Almen strips were plastically deformed by media impacts in vibratory finishing was presented. The motivation was to extend the use of Almen strip measurements as a means of characterizing vibratory finishing through an improved understanding of the process parameters that controlled time-dependent curvature development. Two thicknesses of Almen strip were tested for two finishing conditions. The quantitative agreement between the model saturation curves and the experimental curves was fair, although the overall trends were predicted very well.
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Thermo-mechanical Behaviour of Turbine Disc Assembly in the Presence of Residual StressesMaricic, Luke A. 05 December 2013 (has links)
A comprehensive three dimensional coupled thermo-mechanical finite element study is performed on turbine blade attachments in gas turbine engines. The effects of the self-generated centrifugal forces of the disc and the associated blades, thermal loads, and shot peening residual are all considered in this thesis. Three aspects of the work were accordingly examined. The first was concerned with the coupled thermo-mechanical stress analysis and load sharing between the teeth of the fir-tree root. The second was devoted to the development of a complete model incorporating the effect of shot peening residual stresses upon the developed stress state. The effectiveness of shot peening treatment in response to cyclic thermo-mechanical loadings at the contact interface has also been studied. The third was concerned with the validation of some aspects of the developed models analytically using closed form solutions and experimentally using photoelasticity.
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Thermo-mechanical Behaviour of Turbine Disc Assembly in the Presence of Residual StressesMaricic, Luke A. 05 December 2013 (has links)
A comprehensive three dimensional coupled thermo-mechanical finite element study is performed on turbine blade attachments in gas turbine engines. The effects of the self-generated centrifugal forces of the disc and the associated blades, thermal loads, and shot peening residual are all considered in this thesis. Three aspects of the work were accordingly examined. The first was concerned with the coupled thermo-mechanical stress analysis and load sharing between the teeth of the fir-tree root. The second was devoted to the development of a complete model incorporating the effect of shot peening residual stresses upon the developed stress state. The effectiveness of shot peening treatment in response to cyclic thermo-mechanical loadings at the contact interface has also been studied. The third was concerned with the validation of some aspects of the developed models analytically using closed form solutions and experimentally using photoelasticity.
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ショットピーニングしたセラミックスの表面下の残留応力分布田中, 啓介, TANAKA, Keisuke, 秋庭, 義明, AKINIWA, Yoshiaki, 森下, 裕介, MORISHITA, Yusuke 12 1900 (has links)
No description available.
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