Water sensitive papers simulation to assess deposits on targets

Aim of the study is to assess the possibility to use water sensitive papers to estimate, beside the superficial coverage, also the amount of deposit on the target at varying the spray features. To point out the main quantities influencing the deposit, the behaviour of the water sensitive papers was simulated by assuming some simplifying hypotheses: log-normal distribution of the diameter population of the drops and circular spots. Several images (630) of water sensitive papers, sprayed with drops of different mean diameter (from 100 up to 500 μm), constant coefficient of variation (0.50), and theoretical percentage of covered surface ranging from 10 up to 100%, were produced by means of simulation. These images were considered as effective water sensitive paper images and then analysed by means of an image processing software. The correlations between measured and effective values were studied and they allowed for an estimate of deposit and spray features from the image data. This implies that the analysis of the water sensitive paper images allows the determination of more complex parameters such as the unitary deposit and the impact density, all data strictly related to the efficacy of a phytosanitary treatment

FEM Analysis of Effects of Mechanical Impact Parameters on Fruit Characteristics

Mechanical impact on fresh agriculture commodities may be a criterial issue during mechanical processes such as grading, sorting, conveying, packing or transport. The applications of electronic measuring devices in form of artificial fruits like ‘Instrumented Spheres’ (IS) are an aid to quantify influences of mechanical impact on the value of fruit, vegetable and potato. Additionally, modelling and simulation of impact on fruits helps to identify those influencing parameters. In this study, modelling and simulation runs were performed based on the Finite Element Method (FEM). For dropping tests an ‘Acceleration Measuring Unit’ (AMU) was used which can be implemented into real or artificial fruits to measure the accelerations upon impact. The test stand was equipped with a force sensor. The relevant parameters Young moduli, density, mass, fruit dimensions, and dropping test heights were varied for the tests. FEM simulation results were compared with measured acceleration values of the AMU and force values of the test stand. On dropping potato tubers with mass of 100‑120 g from 25 cm height onto steel plates, the impact force ranged from 190 to 220 N. Simulations showed that the impact force in similar conditions (mass of 102‑113 g and Young moduli of 2.5‑3.5 MPa) ranged from 198 to 242 N, which is in good agreement with the experimental results. When the tuber mass was 190‑210 g, the measured impact force varied from 310 to 325 N. Simulations for masses of 199–221 g resulted in impact forces of 306‑325 N, again in good agreement with the experimental results. However, AMU acceleration values ranged from 922‑932 m s-2, for masses of 100‑200 g, to 765‑824 m s-2 for masses of 190‑210 g. Simulations, in similar conditions, provided acceleration values of 1934‑2314 m s-2 for masses of 102‑221 g (Young moduli 2.5‑3.5 MPa) and ranging from 1497 to 1843 m s-2 for masses of 199‑221 g, which are about twice as high than measured, probably due to effects from imperfect fit when implanted the AMU into the test fruit

parameters influencing deposit estimation when using water sensitive papers

The aim of the study was to assess the possibility of using water sensitive papers (WSP) to estimate the amount of deposit on the target when varying the spray characteristics. To identify the main quantities influencing the deposit, some simplifying hypotheses were applied to simulate WSP behaviour: log-normal distribution of the diameters of the drops and circular stains randomly placed on the images. A very large number (4704) of images of WSPs were produced by means of simulation. The images were obtained by simulating drops of different arithmetic mean diameter (40-300 μm), different coefficient of variation (0.1-1.5), and different percentage of covered surface (2-100%, not considering overlaps). These images were considered to be effective WSP images and then analysed using image processing software in order to measure the percentage of covered surface, the number of particles, and the area of each particle; the deposit was then calculated. These data were correlated with those used to produce the images, varying the spray characteristics. As far as the drop populations are concerned, a classification based on the volume median diameter only should be avoided, especially in case of high variability. This, in fact, results in classifying sprays with very low arithmetic mean diameter as extremely or ultra coarse. The WSP image analysis shows that the relation between simulated and computed percentage of covered surface is independent of the type of spray, whereas impact density and unitary deposit can be estimated from the computed percentage of covered surface only if the spray characteristics (arithmetic mean and coefficient of variation of the drop diameters) are known. These data can be estimated by analysing the particles on the WSP images. The results of a validation test show good agreement between simulated and computed deposits, testified by a high (0.93) coefficient of determination

First results on the assessment of impact damage of vegetables by means of the FEM approach

Mechanical harvest and post-harvest handling induce numerous mechanical impacts on vegetables. These impacts may cause damage such as black-spot bruise, resulting in severe economic losses. Impact forces and accelerations arising from collisions, are among the main indices taken into account when studying the damage of fruit and vegetables during post-harvest activities. A miniaturised Acceleration Measuring Unit (AMU) has been recently developed at the Institut für Agrartechnik, Potsdam-Bornim (ATB): when implanted into a real product like a potato tuber, it is able to measure the accelerations at the centre of the fruit deriving from a impact. This PhD Thesis represents a first contribution on the study of mechanical impacts of vegetables (potato tubers), arising from mechanical harvest and post-harvest handling, by means of simulations based on the Finite Element Method (FEM) approach. Simulations were developed by using the Linux distribution CAELinux2011, that contains several technical-engineering software, among which stand out Salome-Meca and Code-Aster. Salome-Meca was used for modelling, meshing and post-processing activities, while Code-Aster was used for processing models. The work has been developed in collaboration with the Institut für Agrartechnik, Potsdam-Bornim (ATB), Germany, where they were conducted laboratory tests (drop tests to measure impact forces and texture analyses to measure modulus of Young) with two spherical artificial fruits. After the development of several preliminary simple models to gain familiarity with the computational software Salome-Meca and Code-Aster and to acquire an acceptable agreement between simulated and experimental tests, it was carried out an extensive set of drop test simulations with a spherical artificial fruit aimed at evaluating the effects of drop height, size of the fruit, density and modulus of Young of the material, on the impact indices (maximum impact force and maximum acceleration at the centre of the fruit). Simulated material parameters were chosen to approach potato tubers properties. All the factors examined (drop height, sphere diameter, modulus of Young and density of the material, mass of the fruit) affected the maximum impact force and the maximum acceleration at the centre of the sphere. Their increase always caused an increase in the maximum impact force, whereas the maximum acceleration at the centre of the sphere decreased vs sphere diameter, material density and mass, and increased vs drop height and modulus of Young. The decreasing trends are due to the cushioning effect produced by the sphere material itself. Moreover, the maximum impact forces reported in the experimental results by Geyer et al. (2009), referring to drop tests of potato tubers onto steel plates, are in good agreement with the values of impact forces provided by the simulations. Instead, simulations provided acceleration values about twice as many those measured in the experimental results with the AMU device. This difference could be due to the implantation system of the AMU inside the tuber. In fact, comparing the measured impact force and the force computed by means the second law of Newton (F = m · a), Geyer et al. in the cited work report that the computed force was approximately half the measured one, meaning an under-estimation of the acceleration provided by the AMU. Ultimately, the concordance between measured and simulated impact forces confirmed the validity of FEM approach, although the limitations owing to the simplicity of the model developed in this work

Parameters influencing deposit estimation when using water sensitive papers

The aim of the study was to assess the possibility of using water sensitive papers (WSP) to estimate the amount of deposit on the target when varying the spray characteristics. To identify the main quantities influencing the deposit, some simplifying hypotheses were applied to simulate WSP behaviour: log-normal distribution of the diameters of the drops and circular stains randomly placed on the images. A very large number (4704) of images of WSPs were produced by means of simulation. The images were obtained by simulating drops of different arithmetic mean diameter (40-300 μm), different coefficient of variation (0.1-1.5), and different percentage of covered surface (2-100%, not considering overlaps). These images were considered to be effective WSP images and then analysed using image processing software in order to measure the percentage of covered surface, the number of particles, and the area of each particle; the deposit was then calculated. These data were correlated with those used to produce the images, varying the spray characteristics. As far as the drop populations are concerned, a classification based on the volume median diameter only should be avoided, especially in case of high variability. This, in fact, results in classifying sprays with very low arithmetic mean diameter as extremely or ultra coarse. The WSP image analysis shows that the relation between simulated and computed percentage of covered surface is independent of the type of spray, whereas impact density and unitary deposit can be estimated from the computed percentage of covered surface only if the spray characteristics (arithmetic mean and coefficient of variation of the drop diameters) are known. These data can be estimated by analysing the particles on the WSP images. The results of a validation test show good agreement between simulated and computed deposits, testified by a high (0.93) coefficient of determination