Moiré assisted fruit packing.

Transcription

1 Moiré assisted fruit packing. Inacio Maria Dal Fabbro *, Silvestre Rodrigues **, Daniel Albiero ***. * inacio@agr.unicamp.br - Professor,Faculty of Agricultural Engineering, UNICAMP, Campinas, SP, Brazil **PhD candidate,,faculty of Agricultural Engineering, UNICAMP, Campinas, SP, Brazil ***Master candidate,,faculty of Agricultural Engineering, UNICAMP, Campinas, SP, Brazil Abstract: This research work reports an experimental determination of packed fruits spatial arrangement by means of a shadow moiré technique. Bruise is considered a major problem associated to fruit packing and storing as well as transporting system design and planning. Agricultural operation is recognized to generate mechanical damage and consequently losses. The experimental setup included a continuous sinusoidal grid and a higher resolution CCD camera. The physical model consisted of a set of white plastic spheres held in cubic as well as in rhomboid arrangement. The results included a digital map of the real spatial fruit distribution. The paper concluded that the use of polychromatic light is considered the initial step for future laser light application. The proposed technique is of simple application, yielding reliable results. Keywords: fruit packing, moiré. I Introduction. Mechanical injuries on vegetable are generally associated to mechanical handling as harvesting, transportation, packing, reaching significant levels as reported by the pertinent literature. Bruise is considered a major problem associated to fruit selection, packing and storing being important to transport system design and planning. Agricultural operation is recognized to generate mechanical damage and consequently losses. The study of mechanical behavior of packed fruits is of particular interest to transportation and storage processes. As an example, orange is frequently stored in large containers in which bottom layers may yield, depending on the height of the pile. Shahabasi (1979) and Dal Fabbro et al. (1997) modeled a pack of nearly spherical fruits as a bidimensional truss in which the members were represented by the segments joining the centers of the spheres, having the deformation at the contact point calculated by Hertz Theory, determining the deformation at the bottom layers. Packed fruits spatial arrangement can be assumed rhomboid or cubical as shown on Figure 01, (Dal Fabbro et al, 1997), for primarily studies. Such geometrical configurations is important for further strain and stress distribution, void spaces determination, heat transfer and respiration study, aiming pack design optimization. Real fruits exhibit nearly spherical shape with varying dimensions which greatly modify its spatial geometry as well as the contact points distribution. Dias et al. (2004) presented a preliminary experimental study on 332

2 fruit pack by employing a moiré technique. The experimental setup included a continuous sinusoidal grid and a higher resolution CCD camera. The physical model consisted of a set of white plastic spheres held in cubic as well as in rhomboid arrangement. Based on what it has been exposed before, the objective of this research work can be summarized as to generate a digital map of the real spatial fruit distribution from an experimental shadow moiré technique. 1(A) (B) Figure 01. Rhombic arrangement of spheres (A) and cubic arrangement of spheres (B). II Methodology. The present work was carried out in the Laboratory of Mechanical Properties of Biological Materials at Unicamp, Campinas, SP, Brazil. The experimental setup included a multimedia projector, a PC, a digital camera and styrofoam spheres. Spheres were packed in rhombic as well as cubic geometrical arrangement. A set of four sinusoidal grids as shown on Figure 02 was generated with the software CorelDraw 11 and transformed in a slide sequence being π/2 radians out of phase by means of the MS PowerPoint software. These grids were then projected onto the packed spheres and photographed. Corel Photo Paint and Idrisi software were employed for image analysis. Figure 03 exhibits the experimental setup. 333

3 Figure 02: Sinusoidal grid employed in the tests. Figure 03. Experimental setup. III Results. Figure 04 and exhibits the final result of three dimensional view of the cubic arrangement of spheres, displaying, respectively, phase I, phase II, phase III and phase IV, which are out of phase by π/2 radians. Results are obtained by reducing noise effect to a minimum level. PHASE I. 334

4 PHASE II. PHASE III. 335

5 PHASE IV. Figure 04. Phase map displaying the three-dimensional view of spheres in cubic arrangement, out of phase by π/2 radians. Scale given in degrees. IV Conclusions. Based on what it has been exposed before it can be concluded that the proposed technique yields reliable results. The three dimensional mapping of fruits arrangements can support computational model input. 336

6 Figure 03. Experimental setup. V References. [1]CLOUD, G Optical methods of engineering analysis. Cambridge cambridge University Press. [2]Genta, G Vibration of Structures and Machines, Springer Verlag, New York. [5]Livnat, A., Post, D The governing Equations for Moiré Interferometry and Their Identity to Equations of Geometrical Moiré, Experimental Mechanics, vol 25, n4, pp [6]Schiammarella, C. A The moiré method A review. Experimental Mechanics. v.44, n.8, p , nov. [7]Shabana, A.A Theory of Vibration; vol. II: Discrete and Continuous Systems, Springer Verlag, New York. [8]Oster, Gerald; Nishijima, Yasunori Moiré patterns. Scientific American Resource Library: Readings in the Physics Sciences and Technology. Washington. v.3. Offprints p [9] Souza, F.D.; Dal Fabbro, I.M.; Shitakubo, F.; Albiero, D. A Moiré Supported Mechanical Behavior Study of Packed Nearly Spherical Fruits. AgEng 2004, Leuven, Belgium. 337