12 Dynamic Measurements on Miniature Springs for Flaw and Damage Detection 129 Table 12.1 Healthy spring natural frequencies ( indicates mode not found in data) Mode 1 Mode 2 Mode 3 Mode 4 Mode 5 Mode 6 Mode 7 Mode 8 Mode 9 Mode 10 Mode 11 Mode 12 Mode 13 Spring 1 test 1 1511 1978 2592 2669 3467 4122 5334 6150 6713 7716 8006 9197 9613 Spring 1 test 2 1497 1981 2595 2680 3456 4125 5355 6141 6719 7722 8034 – 9633 Spring 1 test 3 1344 1938 2580 – 3277 4048 5330 5989 6644 7670 7983 9195 9595 Spring 1 test 4 1278 1909 2573 – 3195 4006 5288 5941 6595 7633 8316 – 9569 Spring 2 test 1 1403 – – – 3902 – – 6088 6556 – – 9203 9577 Spring 2 test 2 1403 2055 2600 2667 3364 4247 5323 6095 6838 7733 8003 9292 9695 Spring 2 test 3 1566 2159 2617 2695 3694 4425 5380 6419 6997 7823 8122 9548 9756 Spring 2 test 4 1369 2014 2588 2641 3344 4192 5272 6075 6797 7695 7931 9272 9680 Spring 3 test 1 1547 1981 2589 – 3528 4138 5331 6188 6752 7698 8000 9328 9697 Spring 3 test 2 1572 1881 2588 – 3558 4023 – 6211 6653 7608 – 9336 9650 Spring 3 test 3 1408 1988 2592 2680 3331 4142 5345 6044 6748 7700 8008 9223 9684 Spring 3 test 4 1442 2053 2608 2691 3408 4264 5378 6103 6873 7766 8088 9261 9739 Spring 4 test 1 1645 2070 2614 2683 3747 4305 5353 6372 6920 7788 8066 9431 9791 Spring 4 test 2 1588 2000 2602 2684 3586 4197 5352 6234 6813 7742 8025 9316 9750 Spring 4 test 3 1823 2109 2622 2684 3909 4363 5358 6538 6969 7814 8072 9548 9811 Spring 4 test 4 1672 2097 2617 2686 3761 4342 5359 6423 6956 7805 8072 9459 9811 Spring 5 test 1 1328 1941 2594 2663 3252 4067 5295 5950 6673 7678 7923 9153 9656 Spring 5 test 2 1419 1991 2613 – 3355 4145 5350 6058 6745 7733 8013 9245 9692 Spring 5 test 3 1403 1981 2606 – 3333 4134 5345 6017 6741 7714 – 9213 9700 Spring 5 test 4 1680 2113 2636 2698 3806 4388 5372 6484 7022 7850 8080 9559 9841 Spring 6 test 1 1356 1958 2583 2663 3300 4098 5330 6005 6705 7708 – 9197 9655 Spring 6 test 2 1588 2008 2598 2672 3628 4192 5342 6289 6803 7755 8019 9391 9706 Spring 6 test 3 1530 1945 2583 2663 3484 4077 5325 6150 6673 – – 9303 9638 Spring 6 test 4 1547 1997 2594 2680 3513 4169 5358 6163 6767 7744 8022 9314 9683 Spring 7 test 1 1667 2059 2614 2708 3683 4261 5400 6356 6847 7814 8108 9494 9686 Spring 7 test 2 1556 2014 2603 2705 3523 4184 5395 6203 6788 7767 8089 9363 9697 Spring 7 test 3 1609 2041 2609 2700 3625 4238 5386 6297 6845 7795 8100 9420 9714 Spring 7 test 4 1625 2067 2613 2706 3675 4283 5398 6339 6881 7816 8122 9450 9723 Mean value 1513 2012 2601 2682 3525 4192 5348 6190 6787 7742 8052 9335 9694 Standard deviation 130 66 15 17 198 111 32 165 119 61 79 122 69 Fig. 12.9 Flawed spring with a focused ion beam cut
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