Articles
BENDING OF ONE-YEAR-OLD APRICOT TREE STEMS: CONFORMATION OF A MECHANICAL MODEL TO EXPERIMENTAL DATA
Article number
584_6
Pages
63 – 70
Language
English
Abstract
A biomechanical model previously developed for forestry, was adapted to simulate the bending of a fruit tree stem under axillary load, accounting for both vegetative axillary shoots and fruit load.
Datasets were collected on apricot (Prunus armeniaca L.) in order to assess the model.
Fifteen one-year-old stems were observed from early in the growing season to harvest.
Radial stem growth was quite negligible until fruit pit hardening while the loading of the stem increased considerably.
Variations in stem geometry were recorded every two weeks, using a digitizing method.
Elastic properties of the wood were measured by in-situ bending tests.
In addition, creep tests were performed during winter to observe the effect of delayed elasticity.
The model allowed the simulation of the final form of the stems, based on initial form and diameters, final loads and the modulus of elasticity.
These final forms were compared to observations, using three different sets of assumptions for simulations: (i) assuming small displacements resulted in an underestimation of the mean slope variation of 48%; (ii) accounting for large displacements reduced the underestimation to 29% and (iii) accounting for the viscoelasticity reduced it to 14%. The possible source of the residual errors was analyzed in relation to the assumptions made in the model.
This study shows that, in the case of young fruit-trees stems, the effects of large displacements and of viscoelasticity must be taken into account to achieve satisfactory simulations of shoot bending.
Datasets were collected on apricot (Prunus armeniaca L.) in order to assess the model.
Fifteen one-year-old stems were observed from early in the growing season to harvest.
Radial stem growth was quite negligible until fruit pit hardening while the loading of the stem increased considerably.
Variations in stem geometry were recorded every two weeks, using a digitizing method.
Elastic properties of the wood were measured by in-situ bending tests.
In addition, creep tests were performed during winter to observe the effect of delayed elasticity.
The model allowed the simulation of the final form of the stems, based on initial form and diameters, final loads and the modulus of elasticity.
These final forms were compared to observations, using three different sets of assumptions for simulations: (i) assuming small displacements resulted in an underestimation of the mean slope variation of 48%; (ii) accounting for large displacements reduced the underestimation to 29% and (iii) accounting for the viscoelasticity reduced it to 14%. The possible source of the residual errors was analyzed in relation to the assumptions made in the model.
This study shows that, in the case of young fruit-trees stems, the effects of large displacements and of viscoelasticity must be taken into account to achieve satisfactory simulations of shoot bending.
Publication
Authors
T. Alméras, E. Costes, J. Gril
Keywords
Prunus armeniaca, biomechanics, model evaluation, viscoelasticity, large deflexions
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