avaliaÇÃo comportamental de juntas soldadas de um … · dissertação de mestrado apresentada ao...
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UNIVERSIDADE FEDERAL DE OURO PRETOESCOLA DE MINAS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA CIVIL
Dissertação de Mestrado
AVALIAÇÃO COMPORTAMENTAL DE JUNTAS SOLDADAS DEUM AÇO ESTRUTURAL DO TIPO SAC 50 SOB FADIGA
Autor: José Geraldo Araújo Silva
Orientador: Luiz Cláudio Cândido
Setembro de 2001
ii
José Geraldo Araújo Silva
AVALIAÇÃO COMPORTAMENTAL DE JUNTAS SOLDADAS DE UM AÇOESTRUTURAL DO TIPO SAC 50 SOB FADIGA
Dissertação de Mestrado apresentada ao Curso de Pós-Graduação em Estrutura Metálica
do Departamento de Engenharia Civil, da Escola de Minas, da Universidade Federal de
Ouro Preto
Área de concentração: Estruturas Metálicas
Orientador: Prof. Luiz Cláudio Cândido
Ouro Preto
2001
iv
AGRADECIMENTOS
A Deus, por todas as pessoas que Ele colocou no meu caminho.
v
RESUMO
Este trabalho apresenta o estudo do comportamento de juntas soldadas de um aço
estrutural, do tipo SAC 50, sob fadiga. O material foi soldado através do emprego do
processo ao arco elétrico com eletrodo revestido. Além dos ensaios mecânicos
tradicionais, aplicou-se metodologias da Mecânica de Fratura, através de ensaios de
tenacidade à fratura (COD e Integral J), e ensaios de propagação de trincas por fadiga.
Avaliou-se as características comportamentais das três regiões do material: zona
fundida, zona termicamente afetada e metal base. Verificou-se, em termos de tenacidade,
que as três regiões do material, pelo efeito da soldagem, apresentaram comportamento
semelhante. Correlacionou-se os valores obtidos nos ensaios de tenacidade com ensaios
de impacto Charpy. A zona fundida apresentou valor de COD, δm, maior que a zona
termicamente afetada e o metal base, o que significa maior resistência à propagação de
trincas. O efeito do fator R não influenciou significativamente o posicionamento das
curvas de propagação de trinca por fadiga na região II. No entanto, para R = 0,7, o valor
limiar (threshold), ∆Kth, sofreu uma alteração significativa, diminuindo para o caso do
metal base. Pôde-se verificar, também, que para o ensaio de propagação de trinca por
fadiga, o valor limiar, para o metal base foi inferior às outras regiões do CP,
caracterizando um pior desempenho. A partir do ensaio de Integral J pôde-se estimar um
valor de JQ para o metal base. E ainda, fez-se análises microfractográficas dos CPs
ensaiados. Verificou-se o aspecto dúctil das fraturas do material, através de “dimples”.
No entanto, para ensaios de impacto Charpy, em ‘baixas” temperaturas, o material
apresentou o aspecto frágil das fraturas através da presença de facetas de clivagem.
vi
ABSTRACT
This work studied the behavior of welded joints of structural steel type “SAC 50” under
fatigue. The material was welded using the process of electric arc with coated electrodes.
Besides using the traditional mechanical tests, methods of fractures mechanics were
applied through tests of fracture resistance (COD and J integral) and of the fatigue crack
propagation. The behavioral features of three areas of interest (cast zone, heat affected
zone and base metal) were determined. In terms of strength, the conclusions were that
the three areas presented similar behavior considering the welding effect. The values
obtained from resistance tests were later related to those from Charpy impact tests. The
cast zone presented a higher COD value than the base metal i.e. higher fracture
toughness. The effect of the R factor did not present a strong influence in the position of
the fatigue crack propagation curves caused by fatigue. However, for R = 0.7, the
threshold value (∆Kth), was slightly altered, being reduced in the case of the base metal.
For the fatigue crack propagation test, the threshold value for the base metal was lower
than that in the another areas of the specimens, indicating a worse performance.
Considering the J integral test, it is possible to estimate a JQ value for the base metal.
Also, microfractography analyses of specimen were made. The ductile aspect of the
material fractures was revealed by the existence of dimples, although, for the Charpy
impact test performed under low temperature, the brittle aspect was revealed by
cleavage.
vii
SUMÁRIO
1. INTRODUÇÃO .........................................................................................................1
2. OBJETIVOS ..............................................................................................................3
3. RELEVÂNCIA DO TRABALHO ...........................................................................4
4. REVISÃO BILIOGRÁFICA ....................................................................................5
4.1 – Introdução à Soldagem ...................................................................................5
4.1.1 – Definição/Caracterização .......................................................................5
4.1.2 – Histórico ...................................................................................................6
4.2 – Principais Processos Convencionais de Soldagem .......................................9
4.2.1 – Soldagem com eletrodo revestido ..........................................................9
4.2.2 – Soldagem com proteção gasosa ............................................................12
4.2.3 – Soldagem por arco submerso ...............................................................15
4.3 – Aço Estrutural ...............................................................................................16
4.3.1 – Histórico .................................................................................................20
4.3.2 – Aços patináveis ......................................................................................21
4.4 – Fundamentos da Fadiga ...............................................................................25
4.4.1 – Histórico .................................................................................................26
4.4.2 – Aspectos básicos da fadiga ....................................................................27
4.4.3 – O processo de fadiga .............................................................................32
4.4.3.1 – Início do processo de fadiga .....................................................33
4.4.3.2 – Propagação da trinca de fadiga..................................................35
4.5 – Fundamentos da Mecânica de Fratura .......................................................36
4.5.1 – Histórico .................................................................................................36
4.5.2 – Generalidades ........................................................................................40
4.5.3 – Fator de intensidade de tensão ............................................................42
4.5.4 – Tenacidade à fratura (KIC.) .................................................................46
4.5.5 – Estado plano de deformação versus estado plano de
tensão.................................................................................................. 48
4.5.6 – Integral J ................................................................................................49
4.5.7 – Abertura de trinca (CTOD) .................................................................51
4.5.8 - Aplicação da Mecânica de Fratura em fadiga .....................................52
viii
5. MATERIAIS E MÉTODOS ................................................................................. 56
5.1 – Materiais ....................................................................................................... 56
5.2 – Métodos ..........................................................................................................61
5.2.1 – Soldagem do material ...........................................................................62
5.2.2 – Obtenção da pré-trinca de fadiga ........................................................63
5.2.3 – Ensaios de propagação de trinca por fadiga
(da/dN) x ∆∆∆∆K...........................................................................................63
5.2.4 – Ensaios de impacto Charpy ..................................................................63
5.2.5 – Ensaios de Kc e δδδδm .................................................................................64
5.2.6 – Ensaios de integral J .............................................................................65
5.2.7 – Análise de falhas ...................................................................................65
6. RESULTADOS E DISCUSSÃO ............................................................................66
6.1 – Ensaios de tração ..........................................................................................66
6.2 – Ensaios de impacto Charpy ..........................................................................66
6.3 – Ensaios de microdureza ................................................................................69
6.4 - Ensaios de tenacidade à fratura .................................................................. 70
6.5 – Ensaios de integral J .....................................................................................73
6.6 – Ensaios de propagação de trincas (fadiga) .................................................76
6.7 – Análise de fraturas ........................................................................................78
6.7.1 – Microfractografias de CPS ensaiados em impacto Charpy ..............79
6.7.2 – Microfractografias de CPs ensaiados em tenacidade à fratura ....... 81
6.7.3 - Microfractografias de CPs ensaiados à fadiga ................................... 85
7. CONCLUSÕES .......................................................................................................86
8. SUGESTÕES PARA FUTUROS TRABALHOS ................................................ 87
9. REFERÊNCIAS BIBLIOGRÁFICAS ................................................................ 88
ix
LISTA DE FIGURAS
Figura 4.1 – Evolução dos processos de soldagem ao longo do tempo ............................9
Figura 4.2 – Soldagem por eletrodo revestido ................................................................10
Figura 4.3 – Processo de soldagem TIG ..........................................................................13
Figura 4.4 – Processo de soldagem MIG/MAG ..............................................................14
Figura 4.5 – Processo de soldagem por arco submerso ...................................................15
Figura 4.6 – Curvas tensão x deformação para diferentes classes de aços ......................17
Figura 4.7 – Perda de espessura em ambiente industrial agressivo .................................22
Figura 4.8 – Prefeitura de Salvador/BA; aço do tipo SAC 41, sem pintura ...................24
Figura 4.9 – Escola de Minas – Campus UFOP/ Ouro Preto .........................................25
Figura 4.10 – Representação esquemática de uma superfície de fratura por fadiga;
1- fratura instável final; 2 - marcas de praia; 3 - região de início .........28
Figura 4.11 – Tipos de tensões cíclicas ...........................................................................29
Figura 4.12 – Curva de Wöhler .......................................................................................30
Figura 4.13 – Esquema de ensaio de uma viga em escala real ........................................33
Figura 4.14 – Montagem de um corpo-de-prova do tipo tração-compacto .....................34
Figura 4.15 – Resultado típico do ensaio fadiga S-N mostrando o limite de fadiga .......35
Figura 4.16 – Propagação para uma trinca de fadiga ......................................................36
Figura 4.17 – Navio Liberty rompido por fratura frágil ..................................................41
Figura 4.18 – Placa infinita com uma trinca de largura 2a .............................................42
Figura 4.19 – Sistema de coordenadas ............................................................................42
Figura 4.20 – Estado de tensão na vizinhança de uma trinca ..........................................43
Figura 4.21 – Modos de deformação ...............................................................................44
Figura 4.22 – Linhas de força de uma barra entalhada ensaiada à tração .......................46
Figura 4.23 – Variação do fator de intensidade de tensão versus espessura ...................47
Figura 4.24 – Origens dos efeitos de constrição .............................................................48
Figura 4.25 – Figura 4.25 – Ilustração do embotamento na ponta da trinca ...................52
Figura 4.26 – Tipo de corpo-de-prova (a); dados de ensaio (b); curva da/dN x ∆K (c)..53
Figura 4.27 – Comportamento do crescimento de trincas em metais .............................54
Figura 5.1 – Fotomicrografias das três zonas estabelecidas na soldagem (ataque com
nital 3%, aumento de 100X) ......................................................................58
x
Figura 5.2 – Fotomicrografias do material estudado: zona fundida (a), zona termicamnte
afetada (b) e metal base (c). Ataque com nital 3%; aumento de 500X.......59
Figura 5.3 – Representação esquemática de como os CPs foram retirados para ensaio .60
Figura 5.4 – Corpo-de-prova utilizado (tipo tração-compacto, ASTM E 399/90) ..........60
Figura 5.5 – Máquina de eletro-erosão para confecção dos entalhes nos CPs para ensaios
de fadiga .....................................................................................................61
Figura 5.6 – Vista geral da máquina servohidráulica, MTS 10t, para ensaios de
tenacidade à fratura e fadiga ....................................................................62
Figura 5.7 – Posicionamento dos entalhes em corpo-de-prova para enaios Charpy; (a)
entalhe ao longo da espessura (orientação T-S); (b) entalhe ao longo do
cordão de solda (orientação T-L). As setas indicam a direção da espessura;
dimensões do CP (em mm): 10 x 10 x 55 ..................................................64
Figura 5.8 – Posicionamento de clipe gage para medição de CTOD .............................64
Figura 6.1 – Curva de energia absorvida em ensaio de impacto na região da ZTA;
entalhe ao longo da espessura (MARTINS et alli, 2001).........................67
Figura 6.2 – Curva de energia absorvida em ensaio de impacto na região da ZTA com
entalhe ao longo do cordão de solda. (MARTINS et alli, 2001)................67
Figura 6.3 – Figura 6.3 – Perfil de microdureza do material ensaiado (MARTINS et alli,
2001) ..........................................................................................................69
Figura 6.4 – Localização dos pontos para ensaio de microdureza (MARTINS et alli,
2001) ............................................................................................................70
Figura 6.5 – Ensaio de tenacidade à fratura, corpo-de-prova com orientação T-L,
entalhe no metal de base ..........................................................................71
Figura 6.6 – Ensaio de tenacidade à fratura, CP com orientação T-L, entalhe na zona fun-
dida (metal de solda) ...................................................................................71
Figura 6.7 – Ensaio de tenacidade à fratura, CP com orientação T-L, entalhe na zona
termicamente afetada .................................................................................72
Figura 6.8 – Curva de carga versus COD para o metal base ...........................................74
Figura 6.9 – Curva de integral J para o metal base .........................................................75
Figura 6.10 – Curva da/dN versus ∆K para metal de base, zona termicamente
afetada e zona fundida; R = 0,3; f = 30 Hz ..............................................76
Figura 6.11 – Curva da/dN versus ∆K para metal de base, zona termicamente afetada
e zona fundida; R = 0,7; f = 30 Hz ..........................................................77
xi
Figura 6.12 – Curva da/dN versus ∆K para metal de base, zona termicamente afetada e
zona fundida; R = 0,7 e 0,3; f = 30 Hz ......................................................77
Figura 6.13 – Microfractografia do material na região da ZTA; entalhe ao longo do
cordão de solda; -197oC; facetas de clivagem; aumento de 750X
(MEV).......................................................................................................79
Figura 6.14 – Idem à Figura 6.13; aumento de 1500X (MEV) ......................................79
Figura 6.15 – Microfractografia do material na região da ZTA; entalhe ao longo do
cordão de solda; 0oC; fratura semi-frágil; aumento de 750X (MEV).........79
Figura 6.16 – Idem à Figura 6.15; 1 - dimples; 2 - facetas de clivagem; aumento de
2000X (MEV) ..........................................................................................79
Figura 6.17 – Microfractografia do material na região da ZTA; entalhe ao longo da
espessura; -85oC; fratura semi-frágil; aumento de 750X (MEV) ............79
Figura 6.18 – Idem à Figura 6.17; aumento de 1500X (MEV) .......................................80
Figura 6.19 – Microfractografia do material na região da ZTA; entalhe ao longo da
espessura; -5oC; fratura semi-frágil; aumento de 750X (MEV) ..............80
Figura 6.20 – Idem à Figura 6.17; aumento de 1500X (MEV) .......................................80
Figura 6.21 – Microfractografia de CP empregado no ensaio de tenacidade; entalhe na
ZF; região da pré-trinca de fadiga; aumento de 1000X (MEV) ..............81
Figura 6.22 – Microfractografia de CP empregado no ensaio de tenacidade; entalhe na
ZF; fratura dúctil; aumento de 1000X ( MEV) ........................................81
Figura 6.23 – Detalhe da Figura 6.22, presença de partícula, caracterizando um dimple;
aumento de 5000X (MEV) ......................................................................81
Figura 6.24 – Microfractografia de CP ensaiado em tenacidade à fratura; entalhe na
ZTA; região da pré-trinca de fadiga; aumento de 1000X (MEV) ..........82
Figura 6.25 – Microfractografia de CP ensaiado em tenacidade à fratura; entalhe na
ZTA; região de transição entre a pré-trinca de fadiga e a fratura; aumento
de 200X (MEV) .......................................................................................82
Figura 6.26 – Microfractografia de CP ensaiado em tenacidade à fratura; entalhe na
ZTA; região de fratura; aumento de 100X (MEV) ..................................82
Figura 6.27 – Microfractografia de CP ensaiado em tenacidade à fratura; entalhe na
ZTA; fratura dúctil; aumento de 1000X (MEV) ......................................83
Figura 6.28 - Detalhe da Figura 6.27; presença de partícula; aumento de 1500X
(MEV).......................................................................................................83
xii
Figura 6.29 - Microfractografia de CP ensaiado em tenacidade à fratura; entalhe no MB;
região da pré-trinca de fadiga; aumento de 1000X (MEV)........................83
Figura 6.30 – Microfractografia de CP ensaiado em tenacidade à fratura; entalhe no
MB; região de transição entre a pré-trinca de fadiga e a fratura; aumento
de 200X ....................................................................................................83
Figura 6.31 – Microfractografia de CP ensaiado em tenacidade à fratura; entalhe no MB;
região da fratura; aumento de 100X (MEV) ............................................84
Figura 6.32 – Microfractografia de CP ensaiado em tenacidade à fratura; entalhe no MB;
fratura dúctil; aumento de 1000X (MEV) ................................................84
Figura 6.33 – Detalhe da Figura 6.30; presença de partícula; aumento de 1500X
(MEV).......................................................................................................84
Figura 6.34 – Microfractografia de CP ensaiado à fadiga; entalhe no MB; região de
fratura do CP; aumento de 500X (MEV) .................................................85
Figura 6.35 – Microfractografia de CP ensaiado à fadiga; entalhe na ZTA; região de
fratura do CP; aumento de 500X (MEV) .................................................85
Figura 6.36 – Microfractografia de CP ensaiados à fadiga; entalhe na ZF; região de
fratura do CP; aumento de 500X (MEV) ................................................85
xiii
LISTA DE TABELAS
Tabela 4.1 – Resultados típicos para um aço estrutural submetido a ensaio de fadiga com
inversão de carregamento, R = - 1 .............................................................34
Tabela 5.1 – Propriedades mecânicas do aço tipo SAC-50 .............................................56
Tabela 5.2 – Composição química do aço tipo SAC-50 (% do peso) - USIMINAS
(1999) .......................................................................................................56
Tabela 5.3 – Composição química nominal do eletrodo E7018 (% do peso) .................57
Tabela 5.4 – Composição química da zona fundida (% do peso) ...................................57
Tabela 5.5 – Propriedades mecânicas do aço tipo SAC-50 .............................................57
Tabela 5.6 – Parâmetros utilizados na abertura da pré-trinca e ensaio de propagação de
trinca ...........................................................................................................63
Tabela 6.1 – Energia absorvida em ensaios de impacto, Charpy, a 25oC .......................68
Tabela 6.2 – Valores aproximados de tenacidade à fratura KC (orientação T-L) ............70
Tabela 6.3 – Tenacidade à fratura δm (orientação T-L) ...................................................73
xiv
NOMENCLATURA E ABREVIATURAS
A: Área
a: Comprimento de trinca
ao: Comprimento inicial de trinca
AASHTO: American Association of State Highway of Transportation Officials
AISC: American Institute of Steel Construction
ASME: American Society of Mechanical Engineers
ASTM: American Society Testing Materials
AWS: American Welding Society
B: Espessura do corpo-de-prova
CDTN: Centro de Desenvolvimento da Tecnologia Nuclear
CNEN: Comissão Nacional de Energia Nuclear
COD: Crack open displacement
CP: Corpo-de-prova
CTOD: Crack tip opening displacement
CVN: Energia absorvida em CP entalhado
da/dN: Taxa de crescimento de trinca por fadiga
E: Módulo de elasticidade (Young)
EPD: Estado plano de deformação
EPT: Estado plano de tensão
I: Corrente de soldagem
J: Integral J
Ji: Integral J para início de crescimento estável da trinca
JIC: Valor crítico da integral J para modo I
Je: Integral J avaliada na região elástica
Jp: Integral J avaliada na região plástica
K: Fator de intensidade de tensão
KIC: Fator de intensidade de tensão crítico para modo I, no EPD
KJC: Fator de intensidade de tensão crítico para modo I, calculado a partir de JIC
KI: Fator de intensidade de tensão para o modo I
xv
Kmin: Valor limiar para tenacidade à fratura
L: Comprimento do corpo-de-prova
MAG: Metal active gas
MB: Metal base
MEV: Microscópio eletrônico de varredura
MIG: Metal inert gas
MLEF: Mecânica linear elástica de fratura
MPa: Mega Pascal, unidade de tensão
MTS: Metal testing system
R: Relação entre tensões σmín e σmáx
SAC: Soldável anticorrosivo
TIG: Tungsten inert gas
ZF: Zona fundida
W: Largura do corpo-de-prova
ZTA: Zona termicamente afetada
ν: Coeficiente de Poisson
σys: Limite de escoamento
σmáx: Tensão máxima
σmín: Tensão mínima
σav: Tensão média
σsr: Amplitude de tensões
δ: Valor do COD
δi: Valor do COD no início de crescimento estável da trinca
ε: Deformação (%)
∆Kth: Valor limiar de ∆K
σx: Tensão normal na direção do eixo x
σy: Tensão normal na direção do eixo y
σz: Tensão normal na direção do eixo z
τxy: Tensão cisalhante paralela ao plano xy
!
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2. OBJETIVOS
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3. RELEVÂNCIA DO TRABALHO
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4. REVISÃO BIBLIOGRÁFICA
E$ #(9,*)$ #()@$ 4(*'&$ ,%&$ )(B*#0/$ C*C1*/9)@4*2&$ )(4()(-'($ &/#$ '(%&#$ (-B/1B*./#$ -(#'(
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4.1 -$Introdução à Soldagem
H/%$&$(B/1,50/$'K2-*2&$($&$4&C)*2&50/$.($&5/#$.($%(18/)$+,&1*.&.($(%$(#2&1&$*-.,#')*&17
4/*$-(2(##@)*/$+,($/#$#*#'(%&#$.($#/1.&9(%$'&%CK%$&2/%3&-8&##(%$(#'&$(B/1,50/>
E',&1%(-'(7$ &$ #/1.&9(%$ K$ &%31&%(-'($ (%3)(9&.&$ -/#$ %&*#$ .*B()#/#$ 2&%3/#$ .&#
&'*B*.&.(#$8,%&-$#(-./$3&)&$(#'(#$+,&#($*%3/##AB(1$3(-#&)$-/$%,-./$%/.()-/$#(%$&
,'*1*I&50/$.&$#/1.&9(%7$3/*#$(1&$(#'@$3)(#(-'($.(#.($,%$#*%31(#$(+,*3&%(-'/$2*)h)9*2/
&'K$%(#%/$-&#$B*&9(-#$(#3&2*&*#>
4.1.1 - Definição/Caracterização
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4.1.2 - Histórico
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4.2 -$Principais Processos Convencionais de Soldagem
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4.2.1 - Soldagem com eletrodo revestido
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#*%31*2*.&.(7$ ($ C&*M/$ 2,#'/>$ E$ B&)*(.&.($ .($ &31*2&56(#$ K$ %,*'/$ 9)&-.(7$ *-./$ .($ ,%
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4.2.2 - Soldagem com proteção gasosa
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3/.(%$#()$2/-#,%AB(*#$/,$-0/$2/-#,%AB(*#>
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Z-')($ /#$ 3)/2(##/#$ 2/-8(2*./#$ '(%/#$ /$ ^Qu$ PTungsten Inert GasU7$XQu$ PMetal Inert
GasU$($/$XEu$PMetal Active GasU>$E$#(9,*)$.*#2/))()G#(G@$#,2*-'&%(-'($#/C)($2&.&$,%
.(1(#>
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4.2.3 - Soldagem por arco submerso
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./#$(4(*'/#$.&$&'%/#4()&$P"vWXWdE$($^E?QuWHqQ7$!STaU>$E$g*9,)&$\>Y$(#+,(%&'*I&
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E#$3)*-2*3&*#$B&-'&9(-#$.(#'($3)/2(##/$#0/$P"vWXWdE$($^E?QuWHqQ7$!STaU[
G 3/##*C*1*'&$,%&$#/1.&9(%$.($C/&$+,&1*.&.(7$.(B*./$:$3)/'(50/$3(1/$41,M/`
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4.3 -$Aço Estrutural
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B().&.(7$&1K%$.($4())/$($2&)C/-/7$8@$&$3)(#(-5&$.($(1(%(-'/#$/)*,-./#$./#$3)/2(##/#$.(
4&C)*2&50/$($/,')/#$&.*2*/-&./#$3&)&$2/-4()*)$.('()%*-&.&#$2&)&2'()A#'*2&#$(#3(2A4*2&#$&/
%(#%/>$R(9,-./$HqQEpZdQ?Q$P!ST_U7$,%&$.(4*-*50/$3&)&$&5/$#()*&[
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56
!"#"$%&'()%)*"'"$+&,-,*
Serão descritos neste item os materiais e a metodologia utilizados para a realização dos
ensaios.
!./"#"$01234045
A partir das chapas de aço estrutural anticorrosivo do tipo SAC-50, com 12 mm de
espessura, soldou-se ao arco elétrico com eletrodo revestido (E-7018) para avaliar as
características do material através do ensaio de fadiga. Realizou-se a caracterização
química e mecânica onde os valores encontram-se nas Tabelas 5.1-5.4 e 5.5
respectivamente.
A Tabela 5.1 apresenta a composição química do material utilizado, obtida no
laboratório da empresa VDL (Valadares Diesel Ltda) de Itabirito/MG.
Tabela 5.1 - Composição química do aço tipo SAC-50 (% peso)
Elemento C Mn Si P S Ni Cr
Composição 0,14 1,15 0,37 0,04 0,02 0,18 0,39
A Tabela 5.2 mostra a composição química nominal do material, segundo o catálogo da
USIMINAS (1999).
Tabela 5.2 - Composição química do aço tipo SAC-50 (% do peso) - USIMINAS (1999)
Elemento C Mn Si P S Ti Cr Cu Nb
Composição 0,18 1,50 0,15-0,55 0,03 0,025 0,15 0,40-0,65 0,25-0,50 0,050
O eletrodo para soldagem utilizado foi o tipo E7018, cuja composição química nominal,
segundo a ESAB (2001), é apresentada na Tabela 5.3.
57
Tabela 5.3 - Composição química nominal do eletrodo E7018 (% peso)
Elemento C Mn Si P S Ni Cu
Composição 0,07 1,00 0,30 ---- ---- 0,18 0,45
Analisou-se quimicamente a zona fundida nos laboratórios da VDL e os resultados são
apresentados na Tabela 5.4.
Tabela 5.4 - Composição química da zona fundida (% peso)
Elemento C Mn Si P S Ni Cr
Composição 0,12 1,20 0,42 0,06 0,02 0,89 0,11
Tabela 5.5 - Propriedades mecânicas do aço tipo SAC-50
Limite de
Escoamento (MPa)
Limite de
Resistência (MPa)
Deformação
(%)
385 495 24
Segundo a Usiminas (1999), fabricante deste tipo de aço, os valores para a resistência
são:
- Limite de escoamento: 360 MPa
- Limite de resistência: 485 Mpa
Caracterizou-se o material, onde fez-se o perfil de microdureza da junta soldada,
analizando-se as diversas regiões, mapeando as amostras a partir do metal base,
passando pela zona termicamente afetada e finalizando na zona fundida.
Para análise metalográfica, uma amostra da chapa contendo a zona fundida (ZF), zona
termicamente afetada (ZTA), e metal base (MB) foi analisada no Laboratório de
Metalografia do Departamento de Engenharia Metalúrgica e de Materiais (DEMET) da
58
Escola de Minas/UFOP, onde a mesma foi lixada até a lixa de granulometria número
600 e polida em alumina. As Figuras 5.1 e 5.2 mostram as microestruturas das três zonas
(ZF, ZTA, MB), podendo-se ver as diferenças nos tamanhos dos grãos das três regiões.
6&%"""""""""""""""""""""""""""""""""""""""""""$7""""""""""""""""""68""""""""""""""""""""""""""""""""""""""""""""""6&%
Figura 5.1 - Fotomicrografias das três zonas estabelecidas na soldagem (ataque com nital
3%; aumento de 100X)
Os CPs para ensaios de fadiga foram retirados das chapas no sentido L-T, conforme
Figura 5.3. Estão indicados ainda nesta figura o local da soldagem e a posição de
retirada dos CPs para ensaio de tração.
As amostras foram retificadas, pois a região da ZF ficou irregular em relação às zonas
não fundidas. Com isso, de certa forma, diminuiu-se a espessura original das chapas.
Confeccionou-se os CPs com entalhes direcionados segundo as áreas de interesse (ZTA,
ZF e MB). Lixou-se as amostras até a lixa número 600, onde posteriormente foram
polidas; em seguida, atacou-se com nital a 3% para diferenciação das zonas de interesse
e então pôde-se cortar os CPs para posicionamento dos entalhes dentro das medidas
normativas. A Figura 5.4 mostra o CP do tipo tração-compacto, para ensaio de fadiga,
empregado neste trabalho. As dimensões foram estabelecidas de acordo com a norma
ASTM E399/90.
59
(a)
(b)
(c)
Figura 5.2 - Fotomicrografias do material estudado: zona fundida (a), zona termicamente
afetada (b) e metal base (c) – estrutura ferrita (branco) e perlita (escuro).
Ataque com nital 3%; aumento de 500X
60
""""
Figura 5.3 - Representação esquemática de como os CPs foram retirados para os ensaios
Figura 5.4 - Corpo-de-prova utilizado (tipo tração-compacto, ASTM E 399/90)
TRAÇÃO NA SOLDA
60°
790 131
238
143 480
152
165
59
200
203
356
446
921
960
480143
238
200
200
59
152
165
61
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Para confecção dos entalhes nos CPs, utilizou-se uma máquina de eletro-erosão de
eletrodo fixo (Figura 5.5), com tensão de 90V e corrente de 30A.
Para os ensaios de tenacidade à fratura e fadiga utilizou-se uma máquina
servohidráulica, MTS (Metal Testing System), de 10t, acoplada a um computador com
um software específico, onde foram registrados os dados, conforme está mostrado na
Figura 5.6.
Figura 5.5 - Máquina de eletroerosão para confecção dos entalhes nos CPs para ensaios
de fadiga
62
Figura 5.6 - Vista geral da máquina servohidráulica, MTS 10t, para ensaios de
tenacidade à fratura e fadiga
!.9./"#"*;=<0>2?"<;"?012340=
A soldagem foi realizada no Centro de Desenvolvimento da Tecnologia Nuclear
(CDTN) - Comissão Nacional de Energia Nuclear (CNEN, Belo Horizonte), sendo
adotada a seguinte especificação do procedimento de soldagem:
- Corrente: 130 Ampéres
- Tensão: 22 Volts
- Número de passes: 6
- Velocidade de soldagem: 300mm/minuto
- Pré-aquecimento: 50oC
- Pós-aquecimento: não houve
- Descrição do eletrodo: E7018, diâmetro 5mm
- Chanfros: em 1/2V
63
!.9.9"#",@12ABC;"<0"D3:#134AE0"<2"F0<4>0
Fez-se pré-trincas nos CPs para ensaios de tenacidade à fratura, KIC, e ensaios de
propagação de trinca (fadiga) adotando-se os preceitos da norma ASTM E 813/89.
Utilizando a máquina servohidráulica e adotando-se os parâmetros apresentados na
Tabela 5.6, obteve-se as pré-trincas.
Tabela 5.6 - Parâmetros utilizados na abertura da pré-trinca e ensaio de propagação de
trinca
Parâmetros/variáveis R = 0,3 R = 0,7
Freqüência (Hz) 30 30
Carga (N) 350 a 1160 1770 a 2530
Comprimento (mm) 13 13
Kmáx ( mMPa ) 20 20
!.9.G"#"'A504;5"<2"D3;D0>0BC;"<2"134AE0"D;3"F0<4>0"H<aI<JK"L"MN
Após a"obtenção de pré-trincas, os CPs foram ensaiados para avaliação de propagação
de trincas. Os parâmetros utilizados durante estes ensaios são apresentados na
Tabela 5.6.
!.9.O"#"'A504;5"<2"4?D0E1;"PQ03DR
A partir de CPs de ensaios de impacto, do tipo Charpy, com entalhe em V, foram
realizados ensaios onde registrou-se a energia absorvida versus temperatura na região da
ZTA, nas direções da espessura e longitudinalmente, sendo que esta metodologia está de
acordo com o proposto por YOUNG (1989). A Figura 5.7 apresenta a posição do entalhe
nos CPs.
64
Figura 5.7 - Posicionamento dos entalhes em corpos-de-prova para ensaios Charpy; (a)
entalhe ao longo da espessura; (b) entalhe ao longo do cordão de solda. As
setas indicam a direção da espessura; dimensões do CP (em mm): 10x10x55
!.9.!"#"'A504;5"<2"NE"2"δδδδ?
Realizou-se ensaios de tenacidade à fratura na máquina servohidráulica e pelos valores
obtidos através do clip gage, posicionado nos CPs conforme mostra a Figura 5.8, pôde-
se medir o deslocamento de abertura na ponta da trinca (CTOD).
Figura 5.8 - Posicionamento do clip gage para medição de CTOD
65
!.9.S"#"'A504;5"<2")A12>30="T
Mesmo considerando que este tópico não era objeto deste trabalho, fez-se um ensaio de
Integral J, para avaliar o comportamento do metal base. Utilizou-se a técnica de um
único CP, que usa a determinação da compliance (inverso da rigidez). Registrou-se,
inicialmente, a curva carga aplicada versus o deslocamento (flecha) da linha de carga. O
comprimento de trinca é calculado em intervalos regulares durante o ensaio, através de
descarregamentos parciais e de medição da compliance. Obteve-se, também, a curva
variação de J com a extensão de trinca, onde estimou-se um valor de tenacidade, JQ.
!.9.U"#"%AV=452"<2"F0=Q05
Fez-se análises microfractográficas das amostras ensaiadas, empregando-se o
microscópio eletrônico de varredura (MEV), do CDTN/CNEN. Analisou-se também
macrofractograficamente os CPs, utilizando-se um estereoscópio acoplado a um
microscópio ótico quantitativo.
__
6. RESULTADOS E DISCUSSÃO
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6.1 - Ensaios de tração
"CD('*B&-./$2&)&2'()*I&)$/$%(2&-*2&%(-'($/$%&'()*&17$)(&1*I/,G#($/#$(-#&*/#$.($')&50/>
"#$)(#,1'&./#$(-2/-')&./#7$NTY$XJ&$3&)&$&$'(-#0/$.($(#2/&%(-'/$($\SYXJ&$3&)&$1*%*'(
.($ (#2/&%(-'/$ (#'0/$ 3)<M*%/#$ &/#$ B&1/)(#$ 4/)-(2*./#$ 3(1/$ 4&C)*2&-'(>$ E$ ),3',)&$ ./#
HJ#$/2/))(,$-/$XV7$%/#')&-./$2/%$*##/$&$+,&1*.&.($.&$#/1.&$+,($4/*$(M(2,'&.&>
6.2 - Ensaios de impacto Charpy
E#$ g*9,)&#$ _>!$ ($ _>a$ &3)(#(-'&%7$ )(#3(2'*B&%(-'(7$ /#$ )(#,1'&./#$ ./#$ (-#&*/#$ 2/%
(-'&18(#$2/-4(22*/-&./#$&/$1/-9/$.&$(#3(##,)&$($&/$1/-9/$./$2/).0/$.($#/1.&$./#$HJ#>
Z#'(#$(-#&*/#$4/)&%$)(&1*I&./#$-&#$.(3(-.=-2*&#$./$HL^?lH?Z?$PXEd^Q?R$et alli7
aOO!U>$?/'&G#($ &$ ')&-#*50/$.h2'*1G4)@9*1$ ./$%&'()*&1$ -&#$.,&#$ #*',&56(#$ (-#&*&.$ 3/*#
3&)&$%&*/)(#$ '(%3()&',)&#$&$2&3&2*.&.($.($&C#/)50/$.($(-()9*&$ 4/*$ )(1&'*B&%(-'($ &1'&7
2&)&2'()*I&-./$ ,%$ 2/%3/)'&%(-'/$ .h2'*1>$ ?/$ (-'&-'/7$ 3&)&$ '(%3()&',)&#$ *-4()*/)(#7
(#3(2*&1%(-'($ &C&*M/$ .($ GYO/H7$ /$ %&'()*&1$ 2/%3/)'/,G#($ 4)&9*1%(-'(>$ Q##/$ 4/*
2/-4*)%&./$&')&BK#$.&#$&-@1*#(#$.($4)&',)&>
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2/%/$#(-./$&$(-()9*&$&C#/)B*.&$%K.*&7$'(%G#($3&)&$&#$g*9,)&#$_>!$($_>a7$&#$'(%3()&',)&#
.($')&-#*50/$.h2'*1l4)@9*1$(%$'/)-/$.($O/H$($GaY/H7$)(#3(2'*B&%(-'(>$R(-./$&##*%7$-/'&G
#($&$#*',&50/$(%$+,($/$(-'&18($(-2/-')&B&G#($&/$ 1/-9/$./$2/).0/$.($ #/1.&$&3)(#(-'/,
%(18/)$ 3()4/)%&-2(7$ 3/*#$ &$ '(%3()&',)&$ .($ ')&-#*50/$ .h2'*1l4)@9*1$ K$ %(-/)
P&3)/M*%&.&%(-'($GaY/HU>
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-250$ -200$ -150$ -100$ -50$ 0$ 50$ 100$ 150$ 200$
0$
20$
40$
60$
80$
100$
120$
140$ $
Equação da curva:$y=57,717+59,939*tanh[(x+2,166)/60]$Coeficiente de Correlação (R)=0,97398$
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Temperatura (ºC)$g*9,)&$ _>!$ G$ H,)B&$ .($ (-()9*&$ &C#/)B*.&$ (%$ (-#&*/$ .($ *%3&2'/$ -&$ )(9*0/$ .&$ w^E`
(-'&18($&/$1/-9/$.&$(#3(##,)&$PXEd^Q?R$et alli7$aOO!U
-250$ -200$ -150$ -100$ -50$ 0$ 50$ 100$ 150$ 200
0$
20$
40$
60$
80$
$
Equação da curva:$y=34,094+33,801*tanh[(x+34,094)/45]$Coeficiente de correlação(R)=0,9882$
Ene
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da(J
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Temperatura (ºC)$
g*9,)&$_>a$G$H,)B&$.($(-()9*&$&C#/)B*.&$(%$(-#&*/$.($*%3&2'/$-&$)(9*0/$.&$w^E$2/%
(-'&18($&/$1/-9/$./$2/).0/$.($#/1.&$PXEd^Q?R$et alli7$aOO!U
E$ ^&C(1&$ _>!$ &3)(#(-'&$ /#$ B&1/)(#$ &3)/M*%&./#$ .($ (-()9*&$ &C#/)B*.&$ -&$ '(%3()&',)&
&%C*(-'($PaY/HU$3&)&$&#$.,&#$#*',&56(#$&-&1*#&.&#>
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J(1/#$)(#,1'&./#$&-'()*/)(#7$/C#()B&G#($+,($/#$HJ#$2/%$(-'&18($-&$.*)(50/$.&$(#3(##,)&
&3)(#(-'&%$,%&$ 2&3&2*.&.($ .($ &C#/)50/$ .($ (-()9*&$ #,3()*/)$ &/#$HJ#$ 2/%$(-'&18($ -&
.*)(50/$ ./$ 2/).0/$ .($ #/1.&7$ /$ +,($ *%31*2&$ .*I()$ +,($ ,%&$ ')*-2&$ #($ 3)/3&9&$ %&*#
4&2*1%(-'($-&$.*)(50/$1/-9*',.*-&1$./$+,($-&$.*)(50/$')&-#B()#&1$.&$D,-'&$#/1.&.&>
J&)&$ ,%$ &5/$ #(%(18&-'($ &/$ .(#'($ ')&C&18/7$ 3/)K%$ 2/%$ (#3(##,)&$ .($ aY$ %%$ ($ HJ
)('*)&./$ -&$ wg7$ dE^?EJWmQ$ et alli$ P!SSTU$ (-2/-')&)&%$ 3&)&$ (-#&*/#$ .($ *%3&2'/
H8&)3r$&$O/H7$,%&$(-()9*&$&C#/)B*.&$.($SOz>
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&/$ 1/-9/$.&$(#3(##,)&7$($(-#&*&./$&$,%&$ '(%3()&',)&$.($O/H>$J&)&$/$HJ$(-'&18&./$&/
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2/-.*56(#7$28(9/,G#($&/$B&1/)$(%$'/)-/$.($Y_$z>$Z#'(#$B&1/)(#$(#'0/$.*4()(-'(#$./$B&1/)
(-2/-')&./$ 3/)$ dE^?EJWmQ$ et alli$ P!SSTU7$ #(-./$ +,($ &#$ 3)/B@B(*#$ 2&,#&#$ #0/$ &#
.*4()(-5&#$.($(#3(##,)&$./$%&'()*&1$(-#&*&./$($.&#$(#3(2*4*2&56(#$.($3)/2(.*%(-'/$.(
#/1.&9(%$&./'&.$&1K%$.&#$I/-&#$&-&1*#&.&#$#()(%$.*4()(-'(#>$R(9,-./$dZZLGqQmm
P!STaU7$ &$ (#3(##,)&$ ./$ %&'()*&1$ (M()2($ *-41,=-2*&$ -/$ (#'&./$ .($ '(-#6(#>$ Z%
2/-#(+k=-2*&$.*#'/7$&$.,2'*1*.&.(7$'&%&-8/$.&$I/-&$31@#'*2&7$2/%3/)'&%(-'/$:$4)&',)&$(
'(-&2*.&.($3/.(%$#/4)()$&1'()&56(#$2/%$&$B&)*&50/$.&$(#3(##,)&$./$HJ$P^"vQXE^RW
et alli7$!SSYU>$R(9,-./$dE^?EJWmQ$et alli$P!SSTU7$3&)&$/$XV7$-&$%(#%&$'(%3()&',)&
PO/HU7$ /$ B&1/)$%K.*/$ .($ (-()9*&$ &C#/)B*.&7$ H8&)3r7$ /$ 4/*$ .($ !\_$ z>$?/'&G#($ +,($ (#'(
B&1/)$ K$ .*4()(-'($ ./$ (-2/-')&./$ 3&)&$ &$ w^E7$ #(9,-./$ /#$ .&./#$ $ &3)(#(-'&./#$ -&#
g*9,)&#$_>!$($_>a>
E19,%&#$2/))(1&56(#$(-')($(-()9*&$.($*%3&2'/$H8&)3r$($&$'(-&2*.&.($:$4)&',)&$vQH$#0/
&3)(#(-'&.&#$3/)$VEdR"X$($d"mgZ$P!STfU7$3&)&$.*B()#/#$'*3/#$.($&5/>$J&)&$/$2&#/$./
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&5/$./$'*3/$REHGYO7$2/%$(#3(##,)&$.($!a$%%$($1*%*'($.($(#2/&%(-'/$.($NTY$XJ&7$,%&
2/))(1&50/$+,($3/.($#()$&./'&.&$K$&$.('()%*-&.&$3(1&$(+,&50/$�_>!�[
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ ( )O7Yp��H H!\7_� = $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$�_>!�
/-.([
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Hp?$G$(-()9*&$&C#/)B*.&$H8&)3r$(%$z
H/%$ /#$ )(#,1'&./#$ ./#$ (-#&*/#$ .($ *%3&2'/$ H8&)3r$ /C'*./#$ &-'()*/)%(-'(7$ '(%G#(
vQH %XJ&!Na≅ $3&)&$/$HJ$2/%$(-'&18($-&$.*)(50/$.&$(#3(##,)&$($vQH %XJ&!!Y≅
3&)&$/$HJ$2/%$(-'&18($-&$.*)(50/$./$2/).0/$.($ #/1.&>$Z#'(#$ )(#,1'&./#$ (%C/)&$ #(D&%
(%3A)*2/#7$.0/$,%&$ *.K*&$./#$B&1/)(#$.($ '(-&2*.&.($ :$ 4)&',)&>$?/$(-'&-'/7$ 3&)&$ #()(%
28(2&./#$ K$ -(2(##@)*/$ )(&1*I&)$ (-#&*/#$ +,&-'*'&'*B/#$ &31*2&-./G#($ %('/./1/9*&#$ .&
%(2;-*2&$.($4)&',)&7$3/*#$&$4/)%,1&50/$-0/$4/)-(2($&$B&)*&50/$.($'(%3()&',)&$&2(*'@B(1
3&)&$#,&$,'*1*I&50/>
6.3 - Ensaios de microdureza
"#$ (-#&*/#$ .($ %*2)/.,)(I&$ 4/)&%$ )(&1*I&./#$ -&#$ .(3(-.=-2*&#$ ./
HL^?lH?Z?PXEd^Q?R$ et alli, aOO!U>$ E$ g*9,)&$ _>N$ &3)(#(-'&$ /$ 3()4*1$ .(
%*2)/.,)(I&$/C'*./$&')&BK#$./#$(-#&*/#$.($%*2)/.,)(I&$p*2s()#7$ ($&$g*9,)&$_>\
&3)(#(-'&$,%$(#+,(%&$./$3/#*2*/-&%(-'/$./#$3/-'/#$/-.($4/)&%$)(&1*I&./#$/#
(-#&*/#>
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$6.4 - Ensaios de tenacidade à fratura
"#$ )(#,1'&./#$ ./#$ (-#&*/#$ .($ '(-&2*.&.($ :$ 4)&',)&$ (%$ %&'()*&*#$ +,($ &3)(#(-'&%
2/%3/)'&%(-'/$ 1*-(&)$ (1@#'*2/$ #0/$ &3)(#(-'&./#$ (%$ '()%/#$ ./$ (-#&*/$ .($ vQH>$ ?(#'(
')&C&18/7$ ,'*1*I/,G#($ /$ (-'&18($ &/$ 1/-9/$ ./$ 2/).0/$ .($ #/1.&>$ H/%/$ &$ (#3(##,)&$ ./
%&'()*&1$ (-#&*&./$ 4/*$ .($ !a%%7$ #(-./$ 3/)'&-'/$%(-/)$ +,($ /$%A-*%/$ -(2(##@)*/$ 3&)&
9&)&-'*)$ /$ZJL$ P(#'&./$ 31&-/$ .($ .(4/)%&50/U7$a
QHvY7aV
≥
ysσ7$ /$ (-#&*/$ -0/$ 3F.($ #()
'/%&./$(M&'&%(-'($2/%/$(-#&*/$.($vQH>$?/$(-'&-'/7$/#$B&1/)(#$/C'*./#$#()B*)&%$3&)&
2/%3&)&50/$ .&#$ '(-&2*.&.(#$ .&#$ ')=#$ )(9*6(#$ &-&1*#&.&#>$ E$ ^&C(1&$ _>a$ &3)(#(-'&$ /#
B&1/)(#$/C'*./#$3&)&$/#$(-#&*/#>
^&C(1&$_>a$G$p&1/)(#$&3)/M*%&./#$.($'(-&2*.&.($:$4)&',)&$ve$P/)*(-'&50/$^GmU7$&$aY/H
d(9*0/$./$(-'&18( ve$P %XJ& U
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w/-&$'()%*2&%(-'($&4('&.& fa
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P2rack open displacementU7$(#'0/$&3)(#(-'&.&#$3(1&#$g*9,)&#$_>YG_>f>
0 1 2 3 4
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500
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METAL DE BASE
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COD (mm)
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0$ 1$ 2$ 3$ 4$
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COD (mm)$
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COD (mm)$
g*9,)&$_>f$ G$ Z-#&*/$ .($ '(-&2*.&.($ :$ 4)&',)&7$HJ$ 2/%$/)*(-'&50/$^Gm7$ (-'&18($ -&$ I/-&
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#($(#3()&)$.&A$,%$2/%3/)'&%(-'/$#(%(18&-'($.&#$')=#$)(9*6(#$&/$1/-9/$.&$D,-'&$#/1.&.&>
"#$ )(#,1'&./#$ /C'*./#$ 3(1/#$ (-#&*/#$ #0/$ *-4()*/)(#$ &/#$ /C'*./#$ 3(1&$ 4<)%,1&$ (%3A)*2&
�_>!�>$ Q#'/$B(%$%/#')&)$+,($&$ 4/)%,1&50/$3)/3/#'&$.(3(-.($.($/,')&#$B&)*@B(*#7$ ($+,(
3&)&$ ,'*1*I@G1&$ .(B(G#($ /C#()B&)$ &19,-#$ 2)*'K)*/#7$ ($ &*-.&7$ (#3(##,)&$ ./#$ HJ#$ -0/$ K
#,4*2*(-'($3&)&$9&)&-'*)$/$ZJL`$3/)'&-'/7$'(%G#($B&1/)(#$.($ve$($-0/$.($vQH>
"CD('*B&-./$(#',.&)$/$2/%3/)'&%(-'/$:$4)&',)&$.&$D,-'&$#/1.&.&7$,'*1*I/,G#($/#$9)@4*2/#
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B&1/)$.($H"L$#,3()*/)$:#$/,')&#$ )(9*6(#7$/$+,($(+,*B&1($.*I()$+,($(#'&$ )(9*0/$ '(-.($&
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6.5 - Ensaios de Integral J
E$ g*9,)&$ _>T$ &3)(#(-'&$ &$ 2,)B&$ .($ 2&)9&$ versus$ H"L7$ &')&BK#$ .&$ +,&1$ /$ software
2&12,1/,$/$B&1/)$.&$Q-'(9)&1$z$3&)&$/$%('&1$C&#(7$#(-./$+,($&$2,)B&$2/))(#3/-.(-'($&/
(-#&*/$.($Q-'(9)&1$z$versus$∆a$(#'@$&3)(#(-'&.&$-&$g*9,)&$_>S>$?/'&G#($+,($(#'&#$4*9,)&#
4/)&%$/C'*.&#$.*)('&%(-'($./$software.$Z#'($4/)%&'/$.($2,)B&$4/*$/$%(#%/$(-2/-')&./
3/)$ RJQ?ZmmQ et alli P!SSfU$ &/$ &B&1*&)$ &$ '(-&2*.&.($ .($ D,-'&#$ #/1.&.&#$ .($ &1'&
)(#*#'=-2*&$3(1/$%K'/./$.&$Q-'(9)&1$z>
W%&$)(1&50/$(-')($z$($H^"L$4/*$3)/3/#'&$3/)$R8*8$P!ST!U7$($1(B&$(%$2/-#*.()&50/$/#
.(#1/2&%(-'/$($&#$3)/3)*(.&.(#$.($(#2/&%(-'/$./$%&'()*&1>$Z#'&$(M3)(##0/$K$&$#(9,*-'([
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$δ$$�$$r#
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g*9,)&$_>T$G$H,)B&$2&)9&$versus$H"L$3&)&$/$%('&1$C&#(
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g*9,)&$_>S$G$H,)B&$.($Q-'(9)&1$z$3&)&$/$%('&1$C&#(
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.&$ )('&$ $ .&.&$ 3(1&$ (+,&50/$ z$ �$ a$ σ/$ ∆a PoffsetU7$ 2/%$ &$ 2,)B&$ z$ M$ ∆a7$ #(-./$ +,(
a/utsys σσ
σ+
= 7$ /-.($ σys$ ($ σuts$ #0/$ /$ 1*%*'($ .($ (#2/&%(-'/$ ($ 1*%*'($ .($ )(#*#'=-2*&7
)(#3(2'*B&%(-'(>$ L($ &2/)./$ 2/%$ /#$ .&./#$ 4/)-(2*./#$ 3(1/$ software7$ '(%G#($ +,(
ze$ ≅ $SS7Y$?%%l%%a>
L($&2/)./$2/%$&$-/)%&$ER^X$ZT!NGTS7$&-&1*#&-./$&3(-&#$/$+,(#*'/$(#3(##,)&7$/$B&1/)
.($ze$(-2/-')&./$3/.($#()$'/%&./$2/%/$zQH7$3/*#$&$(#3(##,)&$(%3)(9&.&$-/$HJ$P!a%%U
K$#,3()*/)$&/$%A-*%/$(M*9*./$Pf7!%%U>
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6.6 - Ensaios de propagação de trincas (fadiga)
E#$2,)B&#$/)*9*-&.&#$&')&BK#$./#$(-#&*/#$.($4&.*9&$2/%$&#$)(#3(2'*B&#$)(1&56(#$.($2&)9&
3&)&$&#$ ')=#$ )(9*6(#$(-#&*&.&#$ PXV7$w^E$($wgU7$ #0/$%/#')&.&#$-&#$g*9,)&#$_>!OG_>!a7
#(-./$+,($&$g*9,)&$_>!a$)(3)(#(-'&$ '/.&#$&#$2,)B&#$(%$2/-D,-'/$3&)&$+,($#($3/##&$ '()
,%&$ B*#,&1*I&50/$ %(18/)$ ./$ 2/%3/)'&%(-'/$ ./#$ %&'()*&*#$ ($ '&%CK%$ &#$ .*4()(-'(#
2,)B&#$.($&2/)./$2/%$&#$)(1&56(#$.($2&)9&#$&31*2&.&#$P4&'/)$dU>
1 10 1001E-7
1E-6
1E-5
1E-4
1E-3
0,01
R = 0,3∆P = 760 kgf
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&4('&.&$($I/-&$4,-.*.&`$d$�$O7N`$4$�$NO$qI
ff
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1E-5$
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R = 0,7$∆$P = 760 kgf$
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METAL DE BASE$ZTA$METAL DE SOLDA$
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3&)&$/$XV$2/%$4&'/)$.($2&)9&$*9,&1$&$O7f$#/4)(,$,%&$3(+,(-&$&1'()&50/7$.*%*-,*-./$/
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6.7 - Análise de fraturas
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6.7.1 - Microfractografias de CPs ensaiados em impacto Charpy
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%/#')&.&#$ &')&BK#$ .&#$ g*9,)&#$ _>!NG_>aO>$ ?/'&G#($ /$ (4(*'/$ .&$ %&*/)$ 4)&9*1*I&50/$ ./
%&'()*&1$:$%(.*.&$+,($&$ '(%3()&',)&$K$.*%*-,A.&7$&')&BK#$.($ 4&2('&#$.($ 21*B&9(%>$?/
(-'&-'/7$ 2/%$ /$ &,%(-'/$ .&$ '(%3()&',)&7$ 3/)$ (M(%31/7$ &2*%&$ .($ O/H7$ -/'&G#($ /
#,)9*%(-'/$ '&%CK%$ .($ dimples7$ 2&)&2'()*I&-./$ /$ (2'/$ .h2'*1$ .&$ 4)&',)&$ (%
'(%3()&',)&#$)(1&'*B&%(-'($&1'&#>
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6.7.2 - Microfractografias de CPs ensaiados em tenacidade à fratura
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%&'()*&1$ #/1.&./$ /$ %&'()*&1$ &3)(#(-'/,$ 4)&',)&$ .h2'*17$ 2&)&2'()*I&.&$ 3(1&$ 3)(#(-5&$ .(
dimples>$Q#'/$3/.($#()$/C#()B&./$-/$')&C&18/$.($XEd^Q?R$et alli$PaOO!U>
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6.7.3 - Microfractografias de CPs ensaiados à fadiga
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4)&',)&$ .h2'*17$ 2/-4*)%&-./$ .(#'&$ 4/)%&$ /$ '*3/$ .($ 4)&',)&$ (#3()&.&7$ ,%&$ B(I$ +,($ /#
(-#&*/#$.($4&.*9&$4/)&%$)(&1*I&./#$:$'(%3()&',)&$&%C*(-'($PaY/HU>
$$$ $$$$$$$$$$$
g*9,)&$ _>N\$ G$ X*2)/4)&2'/9)&4*&$ .($ HJ
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7. CONCLUSÕES
G E$3&)'*)$ .($ (-#&*/#$.($ *%3&2'/$H8&)3r$B()*4*2/,G#($+,($/#$HJ#$ (%$+,($/$ (-'&18(
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.h2'*1l4)@9*1$%(-/)7$3/)'&-'/$%(18/)$.(#(%3(-8/`
G "#$ B&1/)(#$ .($ '(-&2*.&.($ /C'*./#$ -/#$ (-#&*/#$ 4/)&%$ *-4()*/)(#$ &/#$ (-2/-')&./#
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&C#/)B*.&$-/#$(-#&*/#$.($*%3&2'/$H8&)3r`
G E')&BK#$./#$(-#&*/#$.($'(-&2*.&.($:$4)&',)&$/C'(B(G#($B&1/)(#$.($ve7$/-.($B()*4*2/,G
#($+,($&#$')=#$)(9*6(#$PXV7$w^E$($wgU$&3)(#(-'&)&%$B&1/)(#$3)<M*%/#`
G "$(-#&*/$.($')&50/$%/#')/,$+,($&$4)&',)&$/2/))(,$-/$%('&1$C&#(`$*#'/$#*9-*4*2&$+,($/
3)/2(##/$.($,-*0/$3/)$#/1.&9(%$-(#'($%&'()*&1$4/*$&.(+,&./`
G "#$(-#&*/#$.($4&.*9&$%/#')&)&%$+,($&$%(-/)$)(#*#'=-2*&$&/$*-A2*/$.($3)/3&9&50/$.(
')*-2&$4/*$-/$%('&1$C&#(7$4&'/)$d$�$O7f7$2/%$�v'8$ %XJ&\≅ `$-/$(-'&-'/7$&$%&*/)
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(%$2()'/#$#(9%(-'/#$.&$)(9*0/$QQ$&#$2,)B&#$#($#,3()36(%`
G "$(-#&*/$.($Q-'(9)&1$z$#()B*,$2/%/$'K2-*2&$#,31(%(-'&)$3&)&$&B&1*&50/$.&$'(-&2*.&.(
:$ 4)&',)&$ ./$ %&'()*&17$ /-.($ (-2/-')/,G#($ /$ B&1/)$ .($ zQH$ 3&)&$ /$ %('&1$ C&#($ .(
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G E#$&-@1*#(#$.($4)&',)&#$./#$HJ#$(-#&*&./#$%/#')&)&%$+,($3&)&$(-#&*/#$.($ *%3&2'/
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4&2('&#$ .($ 21*B&9(%>$ ?/#$ (-#&*/#$ .($ 4&.*9&7$ /C#()B/,G#($ /#$ (2'/#$ 'A3*2/#$ .(
#,3()4A2*(#$.($4)&',)&$3/)$4&.*9&$($.($),3',)&$3/)$')&50/7$/-.($3F.(G#($/C#()B&)$/#
idimplesj7$2&)&2'()A#'*2/#$.($4)&',)&$.h2'*1>
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8. SUGESTÕES PARA TRABALHOS FUTUROS
G Z%3)(9&)$ /,')/$ '*3/$ .($ 'K2-*2&$ .($ #/1.&9(%7$ 3/)$ (M(%31/7$XQu7$ 3&)&$ &B&1*&)$ &#
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G Z%3)(9&)$/$HJ$./$'*3/$2&))(9&%(-'/$(%$')=#$3/-'/#`
G d(&1*I&)$ (-#&*/$ .($ Q-'(9)&1$ z$ &31*2&-./G#($ B@)*/#$ HJ#7$ '*)&-./G#($ ,%&$%K.*&$ ./#
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G Z#',.&)$/$2/%3/)'&%(-'/$.($(#'),',)&#$%('@1*2&#$(%$'&%&-8/$)(&17$#,D(*'&#$:$2&)9&#
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9. REFERÊNCIAS BIBLIOGRÁFICAS
!> EXZdQHE?$ ERR"HQE^Q"?$ "g$ R^E^Z$ qQuqcE�$ E?L$ ^dE?RJ"d^E^Q"?"ggQHQEmR>$ Standard specifications for highway bridges. !a>$ (.>$ c*-9'/-7!Sff>
a> EXZdQHE?$ Q?R^Q^W^Z$ "g$ R^ZZm$ H"?R^dWH^Q"?>$ Specification for thedesign, fabrication and erection of structural buildings.$S>$(.>$H8*2&9/7$!STS>
N> EXZdQHE?$R"HQZ^�$g"d$^ZR^Q?u$E?L$XE^ZdQEmR>$Standard test methodfor plane-strain toughness of metallic materials7$Z$NSSG!SSO
\> EXZdQHE?$R"HQZ^�$g"d$^ZR^Q?u$E?L$XE^ZdQEmR>$Standard test methodfor JIC, a measure of fracture toughness7$Z$T!NG!STS
Y> EXZdQHE?$R"HQZ^�$g"d$XZ^EmR>$ASM Handbook.$$S>$$(.>$$!SSa>$B>$!!>
_> EXZdQHE?$R"HQZ^�$g"d$XZ^EmR>$Metals handbook>$"8*/[$X('&1#$J&)s7$$!Sf!>B>$_>
f> E?LZdR"?7$^>$m. Fracture mechanics – Fundamentals e applications>$V/2&$$$$$$d&'/-$[$HdH$J)(##7$!SS!>
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!O> VZmmZQ7$Q>$q>$Edifícios industriais em aço>$$R0/$J&,1/[$J*-*7$!SS\>
!!> VdE?H"7$ H>$ $ E>$ u>$X>$ ('$ &11*>$Fadiga de estruturas soldadas>$ m*#C/&[$ g,-.&50/H&1/,#'($u,1C(-s*&-7$!ST_>
!a> Vd"Zv7$L>$Elementary engineering fracture mechanics>$>H/))(2'[$X&)'*-,#$?*D8/447$!ST_>
!N> Vd"Zv7$ L>$ The Pratical use of fracture mechanics>$ \>$ (.>$ L/).)(28'7$ q/11&-.[v1,t()$E2&.(%*2$J,C1*#8()#7$!SS\>
!\> H�?LQL"7$m>$H$($u"LZgd"QL7$m>$V>$Notas de aulas da disciplina Tecnologia demateriais metálicos. ",)/$J)('/[$dZLZXE^$PWg"JlHZ^ZHlWZXuU7$aOOO>$$Y!3>
!Y> HZ^mQ?7$J>$d>$et al. Análise de fraturas>$R0/$J&,1/[EVX7$!ST_>
!_> HqQEpZdQ?Q7$p>$Tecnologia mecânica>$a>$(.>$d*/$.($z&-(*)/[$X&2u)&t$q*117$$!SS_>
TS
!f> LZEeWQ?"7$ H>$ ^>$ Z>$ ($ E?LdELZ7$ E>$ q>$ J>$ E$ *-'(9)&1$ z$ |$ ,%&$ &C/).&9(%(M3()*%(-'&1>$ >$ Q->$ RZXQ?{dQ"$ LZ$ XZH�?QHE$ LE$ gdE^WdE7$ !>7$ !SS_7$ ",)/J)('/>$Anais... ",)/$J)('/[$Wg"J7$!SS_>$ 3>$a\!GaY_>
!T> LQER7$m>$E>$X>$Estruturas de aço: 2/-2(*'/#7$'K2-*2&#$($1*-9,&9(%>$a>$(.>$R0/$J&,1/[w*9,)&'(7$!SST>
!S> Z#&C>$Caracterísiticas dos eletrodos Esab[$2&'@1/9/>$H/-'&9(%7$aOO!>
aO> ZcEmLR7$ q>$ m>`$ cE?qQmm7$ d>z>q>$ Fracture mechanics>$ ?(t$ �/)s[$ d/,'1(.9(7H8&3%&-$&-.$q&117$$!SS!>
a!> u"LZgd"QL7$ m>$ V> Fundamentos de mecânica de fratura>$ a>$ (.>$ ",)/$ J)('/$ [Wg"J7$!SSY>
aa> u"LZgd"QL7$m>$V>$Aplicação da mecânica de fratura no projeto estrutural ",)/J)('/$[$Wg"J7$!SS_>
aN> qELLdQmm7$L>$X>$Welding fume extraction, a guide to equipment selection>$X('&1H/-#'),2'*/-7$B>$!\7$->$\7$!STa>
a\> vmZR?Qm>$X>`$mWvER7$J>$Fatigue of metallic materials>$J)&9&[$Z1#(B*()7$$!SSa>
aY> vWwXE?"pQH7$ V>$ ($cQmmZXR7$?>$Steel design for structural engineers>$ a>$ (.>?(t$z()#(r[$J)*-'*2($q&117$!STN>
a_> mE?HER^Zd7$z>g>$Metallurgy of welding>$Y>$(.>$m(-.()#$[$H8&3%&-$�$q&117$!SS\>
af> XE?WEm$C)&#*1(*)/$3&)&$2@12,1/$.($(#'),',)&#$%('@1*2&#>$V)&#A1*&7$!STS>$B>$!>
aT> XEdeWZR7$J>$p>$Tecnologia de soldagem>$V(1/$q/)*I/-'($[$ZREV7$!SS!>
aS> XEd^Q?R7$u>$ J>$ et al.$ Q-41,=-2*&$ .($ .(4(*'/#$ 31&-&)(#$ .($ #/1.&9(%$ -&$ '(-&2*.&.($ :4)&',)&$.($&5/$(#'),',)&1$&31*2&./$:$2/-#'),50/$2*B*1>$Projeto Fapemig TEC 2503/967EC)*1GaOO!>
NO> $?W?ZR7$Z>$H>`$?E^Em7$�>$L>$Palestra sobre soldagem>$",)/$J)('/$[$Wg"J7$!STY>
N!> "vWXWdE7$ ^>`$ ^E?QuWHqQ7$ H>$ Engenharia de soldagem e aplicações>$ d*/$ .(z&-(*)/$[$m^H$m*B)/#$^K2-*2/#$($H*(-'A4*2/#7$!STa>
Na> JE^^"?7$c>$z>$Ciência e técnica de la Soldadura>$V*1C&/7$Z#3&-8&[$W)%/$Z.*2*/-(#7!SfY>
NN> JZmmQ?Q>$Apud. u"LZgd"QL7$m>$V>$Aplicação da mecânica de fratura no projetoestrutural ",)/$J)('/[$Wg"J7$!SS_>
SO
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NY> dEL"?7$z>$H>$Fatigue crack growth in the threshold region>$R'/2s8/1%7$!STa>
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