Table 1. Experimental Values of DR and ER from RSM.

	variable levels
run	x1	x2	x3	x4	DR, y1 (kN)	RR, y2 (%)
1	12	100	6	120	221.4	5.10
2	16	100	6	120	89.9	10.17
3	12	140	6	120	283.6	4.98
4	16	140	6	120	187.5	6.66
5	12	100	10	120	217.2	4.49
6	16	100	10	120	136.9	8.86
7	12	140	10	120	228.1	4.03
8	16	140	10	120	168.9	6.48
9	12	100	6	160	231.7	5.89
10	16	100	6	160	127.8	8.99
11	12	140	6	160	284.9	5.48
12	16	140	6	160	213.2	4.35
13	12	100	10	160	253.9	6.17
14	16	100	10	160	215.4	8.97
15	12	140	10	160	264.1	5.66
16	16	140	10	160	218.9	6.37
17	10	120	8	140	302.5	4.84
18	18	120	8	140	166.3	8.52
19	14	80	8	140	103.2	6.03
20	14	160	8	140	198.7	4.50
21	14	120	4	140	291.6	8.10
22	14	120	12	140	289.0	6.66
23	14	120	8	100	160.3	2.82
24	14	120	8	180	220.3	6.76
25	14	120	8	140	297.5	3.16
26	14	120	8	140	288.0	2.67
27	14	120	8	140	296.6	2.21
28	14	120	8	140	289.0	3.51
29	14	120	8	140	283.6	4.26
30	14	120	8	140	290.3	3.70
31	14	120	8	140	290.8	3.25