CRACK DETECTOR

摘要

PURPOSE:To detect the presence or absence of a crack by using the output difference of acoustic emission sensors when a press device is driven under no load and under load. CONSTITUTION:The acoustic emission (AE) sensors 1A-1D are mounted to the optional positions of an upper metallic mold 2 where the crack is liable to arise based on the experience and rule of thumb. The output signals from the AE sensors 1A-1D are subjected to A/D conversion in a signal processing circuit 3 via preamplifiers 2A-2D and are stored into a memory 5. A start signal is applied to the circuit 3 and A/D conversion is started when the load of a load relay 4 attains a set value or above. The press device 20 is driven under no load and under load and the output signals from the circuit 3 are stored respectively into the 1st and 2nd regions 51, 52. An arithmetic part 6 reads out the storage contents in both regions of the memory 5 and calculates the difference between the signal under load in the region 52 and the signal under no load in the region 51. The calculated values are subjected to D/A conversion and square-law processing in an output part 7 and are displayed on a monitor 8. The values are compared with the prescribed threshold value and an alarm 9 is triggered if the values are larger then the threshold value.