4.校核齿根弯曲疲劳强度NO
1)齿形系数:
当量齿数Z v1=Z1/cos3β=27/cos312036'12''=29
Z v2=Z2/cos3β=81/cos312036'12''=87
图12.21page229
Y Fa1=2.55
Y Fa2=2.22 应力修正系数:图12.22page230 Y Sa1=1.62
Y Sa2=1.78 重合度系数Yε:εα=[1.88-3.2(1/Z1+1/Z2)]cosβ
=[1.88-3.2(1/29+1/87)]cos12036'12''
εα=1.69
Yε=0.25+0.75/εα=0.25+0.74/1.69
Yε=0.69
螺旋角系数Yβ:Yβ=max(1-εββ0/1200,1-0.25εβ,0.75)
=max(1-1×12.60/1200,1-0.25×1,0.7
5)
Yβ=0.9 2)载荷系数
a.齿间载荷分配系数:表12.10page217
K Fα=εα/cos2βb=1.69/cos212.60
K Fα=1.75
b.齿向载荷分布系数:图12.14page219
b/h=83/(2.25×2.5)=12.3
K Fβ=1.36 c.载荷系数:K=K A K v K FαK Fβ=1.5×1.2×1.75×1.36
K=4.28
3)许用应力: (同直齿轮例题)[σF]=σFlim Y N Y X/s Fmin
a.极限应力:图12.23page231 σFlim1=600Mpa
σFlim2=450M
pa
b.当量应力循环次数:
设3×106 12.15page226m=49.1 N L1=60γnt h∑[(t hi/t h)(T i/T max)m] =60×1×1000×4800[0.2×149.1+0.5 ×0.549.1+0.3×0.249.1] =5.76×107(与假设一致) N L1=5.76× 107 N L2=N L1/μ=5.76×107/3 N L2=1.92×107 c.弯曲寿命系数:图12.24page232 Y N1=0.95 Y N2=0.97 d.尺寸系数:图12.25page232 Y X=1.0