Effects Of Main Test Conditions On Detecting Accuracy Of Log Hole Defect Based On Stress Wave

In the process of timber production, it's very important to evaluate its quality and capability in advance. So it is necessary to detect the lacuna (especially the hole) in the log in order to improve its value. With easy manipulation and safe use, lossless measure technology based on the stress wave is well developed, especially has important applicable value to improve the utilizing effect of log, and can provide quality insurance for its utilization.On the basis of principle of stress wave transmission and hole lacuna imaging, this thesis carried the research on whether there was a hole in log firstly. Under the same disturbing, the difference of transmission time of stress wave between a log that has a hole and a log that has not a hole was researched, on the basis of which we can estimate whether there was a hole in the log. An intact log was selected as a sample in the experiment. The impulse single was produced by the knocking of swinging hammer. The transmission time of stress wave was measured under the same knocking on the sample that is intact and the sample that there is a hole on the side end. The experiment result showed that the transmission time of stress wave in the sample of hole was longer.Secondly, this thesis researched on the effects of containing water ratio, knocking speed of swing hammer and quantity of sensor on testing. As an evaluation index of testing, quality coefficient of identifying area was defined to reflect the difference between the testing dimension and real dimension of hole in the sample.Containing water ratio was measured by the way of weighting in the sample. Effect of containing water ratio on quality coefficient of identifying area under the same quantity of sensors and knocking speed, effect of knocking speed on quality coefficient of identifying area under the same quantity of sensors and containing water ratio, and effect of quantity of sensors on quality coefficient of identifying area under the same knocking speed and containing water ratio were analyzed. Six sensors to sixteen sensors were selected in the experiment and different size holes were produced on one side end of sample. Knocking every sensor under the condition of controlling the containing water ratio and the angle of the swing hammer, quality coefficient of area identifying was calculated. The experiment result showed that quality coefficient of area identifying was higher under the conditions of lower containing water ratio, higher knocking speed and more sensors quantity. The research showed that quality coefficient of area identifying became low when enhancing the containing water ratio and decelerating the knocking speed. Increasing the sensors quantity properly can improve the testing quality obviously.