Study On Gradation Measurement And Compensation Algorithm Of Manufactured Sand Based On Dynamic Image Method

It is a trend to replace the increasing shortage of natural sand with manufactured sand for the development of building materials.To meet the construction requirements,it is necessary to measure the morphology and gradation of manufactured sand that is difficult to control.To solve this problem,a new measurement method,dynamic image method,is proposed in this paper.Through the setting of camera resolution,light source selection and light source intensity,the hardware platform of the measurement system was built.The manufactured sand of dynamic falling sand,the preprocessing of particle image graying,filtering,binarization,and the extraction of particle size and shape features were studied,and the measurement system software was developed.Comparative experimental studies of manufactured sand morphology characterization parameters,repeatability experimental studies,comparative experimental studies with sieving method(SM),experimental studies of particle size correction methods,and comparative experimental studies before and after compensation were conducted.The experimental results show:(1)The optimal area characterization method,the optimal perimeter characterization method,the optimal particle size characterization method and the optimal volume characterization method are determined,which are the 45-degree outward half-pixel method,8-direction Crofton perimeter,equivalent ellipse Fetet short diameter and the the product of the half-pixel expansion method of 45 degrees and the equivalent ellipse Fetet short diameter.(2)The maximum repeatability error of A-sand gradations appear at 1.18~2.36 mm,which is 0.9%,and the maximum repeatability error at 0.3~0.6mm is only 0.29%.(3)There are some gradation errors and fineness modulus(Mx)errors between the results by image method and the results by SM,because the manufactured sand has an irregular shape.Moreover,the error between the results by image method and SM of E-sand is larger than that of A-sand.(4)The particle size of E-sand with different Mx is corrected by the dynamic correction factor K.After correction,the maximum gradation error is reduced from 5.93% to 2.77%,and the maximum error of Mx is reduced from 0.15 to 0.The correction method can make the measurement results by the image method closer to the results by SM.(5)A gradation compensation model based on the shape characterizations of manufactured sand is constructed.Before compensation,the maximum gradation error measured by the image method was 8.79% and the maximum Mx error was 0.31.After compensation,the maximum measured by the image method is 1.5%,and the maximum Mx error is ± 0.024.The measurement accuracy of the developed measurement system can meet the actual needs of the project and it can realize the quality monitoring of manufactured sand.