DISEÑO DE ELEMENTOS MECANICOS.
Enviado por co1994 • 9 de Febrero de 2017 • Apuntes • 825 Palabras (4 Páginas) • 313 Visitas
CARGA VARIABLE
Se. Limite de duración
Se | Acero | Hierro fundido | Metales y aleaciones no ferrosas |
Limite de duracion | 0.5Su | 0.4Su | 0.3Su |
Factores que modifican el limite de fatiga
- Factores de correcion para carga diferente a la flexion con inversión
A=0.7 pruebas de carga axial invertida
A=0.6 no pruebas de carga axial invertida
A=0.577 carga torsional invertida
- Factores de corrección por tamaño
B=o.869d-0.097 si 0.3˂d˂10
B=1 si d˂0.3
C= factor de corrección por acabado superficial
Su | Pulido | Rectificado | Maquinado C | Laminado en caliente | forjado |
60 | 1 | 0.9 | 0.84 | 0.70 | 0.54 |
80 | 1 | 0.9 | 0.77 | 0.60 | 0.46 |
100 | 1 | 0.9 | 0.73 | 0.55 | 0.40 |
120 | 1 | 0.9 | 0.71 | 0.50 | 0.36 |
140 | 1 | 0.9 | 0.69 | 0.45 | 0.33 |
160 | 1 | 0.9 | 0.67 | 0.45 | 0.30 |
180 | 1 | 0.9 | 0.65 | 0.38 | 0.27 |
200 | 1 | 0.9 | 0.64 | 0.36 | 0.25 |
220 | 1 | 0.9 | 0.63 | 0.34 | 0.22 |
240 | 1 | 0.9 | 0.62 | 0.30 | 0.20 |
Kc =Factor de confiabilidad
[pic 1]
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[pic 6][pic 7]
[pic 8]
[pic 9]
[pic 10][pic 11][pic 12]
[pic 13][pic 14][pic 15][pic 16]
[pic 17][pic 18][pic 19][pic 20][pic 21]
[pic 22]
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[pic 24]
[pic 25][pic 26][pic 27][pic 28]
[pic 29]
[pic 30]
[pic 31][pic 32][pic 33][pic 34][pic 35][pic 36]
[pic 37]
Su=137KSI
Sy=125KSI
Sc=0.5Su
N=1.5
[pic 38]
Se real= ABCKcKdSe
Sereal= (0.71)(0.869D-0.097)(0.69)(0.753)(1)(68500)=21959 D-0.097
A=0.71
B=0.869D-0.097
C=0.69
Kc=0.753
Kd=1
Se=0.5Su=0.5(137000)=68500PSI
[pic 39]
[pic 40]
[pic 41]
[pic 42]
Kf=1
[pic 43]
D=1.32
P[pic 44][pic 45][pic 46][pic 47][pic 48][pic 49][pic 50][pic 51][pic 52][pic 53][pic 54][pic 55][pic 56][pic 57][pic 58][pic 59][pic 60][pic 61][pic 62][pic 63][pic 64][pic 65]
b[pic 66][pic 67][pic 68]
D d
Datos
b = 0.25 pulg Su = 120 KSI
D = 2 pulg Sy = 70 KSI
d = 1 pulg P = 2500 lb
r = 0.5 pulg
[pic 69]
[pic 70][pic 71]
[pic 72]
[pic 73]
Obteniendo el valor de tablas para Kt = 1.63 sensibilidad en la entalla[pic 74]
Su a[pic 75][pic 76][pic 77]
100 20 0.0070[pic 78]
25 120 x y 0.0020 ; [pic 79][pic 80]
125 0.005
[pic 81]
[pic 82]
[pic 83]
[pic 84]
A = 0.71; B = ; C = 0.71; Kc = 0.814 para 99 %;[pic 85]
Kd = 1 T ˂ 450°C ; Se = 0.5Su = 0.5(120,000) = 60 KSI
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