Design of Testing Period for Reliability Assessment of Numerical Control Machine Tools Considering Working Conditions

Table 2

The curves fitted to the upper limit or the lower limit of MTBF interval estimation under different covariates.

Covariates		The curves fitted to the upper limit of MTBF interval estimation		The curves fitted to the lower limit of MTBF interval estimation
Fc(KN)	Nh(n/h)
0.35	2		0.9567		0.9791
0.43	17		0.9711		0.9869
0.54	4		0.9785		0.9813
0.78	10		0.9804		0.9835
0.81	4		0.9895		0.9815
0.84	6		0.9879		0.9830
1.03	14		0.9766		0.9667
The method in [1]			0.9796		0.9846