scholarly journals Time to Fracture and Fracture Strain are Negatively Related in Sweet Cherry Fruit Skin

2016 ◽  
Vol 141 (5) ◽  
pp. 485-489 ◽  
Author(s):  
Martin Brüggenwirth ◽  
Moritz Knoche
Keyword(s):  
Tensile Test ◽  
Water Uptake ◽  
Sweet Cherry ◽  
Tensile Tests ◽  
Volume Increase ◽  
Biaxial Tensile Test ◽  
Biaxial Tensile ◽  
Rate Of Increase ◽  
Fruit Skin ◽  
Time To Fracture

Rain cracking of sweet cherry fruit (Prunus avium L.) is said to occur when the volume increase associated with water uptake, extends the fruit skin beyond its upper mechanical limits. Biaxial tensile tests recorded fracture strains (εfracture) in the range 0.17 to 0.22 mm2·mm−2 (equivalent to 17% to 22%). In these tests, an excised skin segment is pressurized from its inner surface and the resulting two-dimensional strain is quantified. In contrast, the skins of fruit incubated in water in classical immersion assays are fractured at εfracture values in the range 0.003 to 0.01 mm2·mm−2 (equivalent to 0.3% to 1%)—these values are one to two orders of magnitude lower than those recorded in the biaxial tensile tests. The markedly lower time to fracture (tfracture) in the biaxial tensile test may account for this discrepancy. The objective of our study was to quantify the effect of tfracture on the mechanical properties of excised fruit skins. The tfracture was varied by changing the rate of increase in pressure (prate) and hence, the rate of strain (εrate) in biaxial tensile tests. A longer tfracture resulted in a lower pressure at fracture (pfracture) and a lower εfracture indicating weaker skins. However, a 5-fold difference in εfracture remained between the biaxial tensile test of excised fruit skin and an immersion assay with intact fruit. Also, the percentage of epidermal cells fracturing along their anticlinal cell walls differed. It was highest in the immersion assay (94.1% ± 0.6%) followed by the long tfracture (75.3% ± 4.7%) and the short tfracture (57.3% ± 5.5%) in the biaxial tensile test. This indicates that the effect of water uptake on cracking extends beyond a mere increase in fruit skin strain resulting from a fruit volume increase. Instead, the much lower εfracture in the immersion assay indicates a much weaker skin—some other unidentified factor(s) are at work.

scholarly journals Mechanical Properties of Skins of Sweet Cherry Fruit of Differing Susceptibilities to Cracking

2016 ◽  
Vol 141 (2) ◽  
pp. 162-168 ◽  
Author(s):  
Martin Brüggenwirth ◽  
Moritz Knoche
Keyword(s):  
Mechanical Properties ◽  
Creep Strain ◽  
Water Uptake ◽  
Cell Walls ◽  
Plasma Membranes ◽  
Sweet Cherry ◽  
Tensile Tests ◽  
Cultivar Differences ◽  
Repeated Loading ◽  
Biaxial Tensile

Rain cracking of sweet cherry fruit (Prunus avium L.) may be the result of excessive water uptake and/or of mechanically weak skins. The objectives were to compare mechanical properties of the skins of two cultivars of contrasting cracking susceptibility using biaxial tensile tests. We chose ‘Regina’ as the less-susceptible and ‘Burlat’ as the more-susceptible cultivar. Cracking assays confirmed that cracking was less rapid and occurred at higher water uptake in ‘Regina’ than in ‘Burlat’. Biaxial tensile tests revealed that ‘Regina’ skin was stiffer as indexed by a higher modulus of elasticity (E) and had a higher pressure at fracture () than ‘Burlat’. There was little difference in their fracture strains. Repeated loading, holding, and unloading cycles of the fruit skin resulted in corresponding changes in strains. Plotting total strains against the pressure applied for ascending, constant, and descending pressures yielded essentially linear relationships between strain and pressure. Again, ‘Regina’ skin was stiffer than ‘Burlat’ skin. Partitioning total strain into elastic strain and creep strain demonstrated that in both cultivars most strain was accounted for by the elastic component and the remaining small portion by creep strain. Differences in E and between ‘Regina’ and ‘Burlat’ remained even after destroying their plasma membranes by a freeze/thaw cycle. This indicates that differences in skin mechanical properties must be accounted for by differences in the cell walls, not by properties related to cell turgor. Microscopy of skin cross-sections revealed no differences in cell size between ‘Regina’ and ‘Burlat’ skins. However, mass of cell walls per unit fresh weight was higher in ‘Regina’ than in ‘Burlat’. Also, the ratio of tangential/radial diameters of epidermal cells was lower in ‘Regina’ (1.86 ± 0.12) than in ‘Burlat’ (2.59 ± 0.15). The results suggest that cell wall physical (and possibly also chemical) properties account for the cultivar differences in skin mechanical properties, and hence in cracking susceptibility.

On the implementation of FEA for the design and development of a new biaxial tensile test fixture for uniaxial testing machine: a validation for cruciform test specimens

2019 ◽  
Vol 41 (9) ◽  
Author(s):  
Luis Fernando Puente Medellín ◽  
Víctor Alfonso Ramírez Elías ◽  
Antonio de Jesús Balvantín García ◽  
Perla Iris Vázquez Gómez ◽  
José Angel Diosdado De la Peña
Keyword(s):  
Tensile Test ◽  
Testing Machine ◽  
Design And Development ◽  
Test Fixture ◽  
Biaxial Tensile Test ◽  
Biaxial Tensile ◽  
Uniaxial Testing

scholarly journals Water Influx through the Wetted Surface of a Sweet Cherry Fruit: Evidence for an Associated Solute Efflux

Plants ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 440
Author(s):  
Andreas Winkler ◽  
Deborah Riedel ◽  
Daniel Alexandre Neuwald ◽  
Moritz Knoche
Keyword(s):  
Water Uptake ◽  
Sweet Cherry ◽  
Dry Mass ◽  
Bathing Solution ◽  
Full Bloom ◽  
Stage Of Development ◽  
Water Influx ◽  
Fruit Skin ◽  
Sweet Cherries ◽  
And Storage

Sweet cherries are susceptible to rain-cracking. The fruit skin is permeable to water, but also to solutes. The objectives of this study were to (1) establish whether a solute efflux occurs when a sweet cherry fruit is incubated in water; (2) identify the solutes involved; (3) identify the mechanism(s) of efflux; and (4) quantify any changes in solute efflux occurring during development and storage. Solute efflux was gravimetrically measured in wetted fruit as the increasing dry mass of the bathing solution, and anthocyanin efflux was measured spectrophotometrically. Solute and anthocyanin effluxes from a wetted fruit and water influx increased with time. All fluxes were higher for the cracked than for the non-cracked fruit. The effluxes of osmolytes and anthocyanins were positively correlated. Solute efflux depended on the stage of development and on the cultivar. In ‘Regina’, the solute efflux was lowest during stage II (25 days after full bloom (DAFB)), highest for mid-stage III (55 DAFB), and slightly lower at maturity (77 DAFB). In contrast with ‘Regina’, solute efflux in ‘Burlat’ increased continuously towards maturity, being 4.8-fold higher than in ‘Regina’. Results showed that solute efflux occurred from wetted fruit. The gravimetrically determined water uptake represents a net mass change—the result of an influx minus a solute efflux.

Numerical Biaxial Tensile Test of Aluminum Alloy Sheets Using Crystal Plasticity Model Implemented in Commercial FEM Software

2016 ◽  
Vol 725 ◽  
pp. 255-260
Author(s):  
Shohei Ochiai ◽  
Akinori Yamanaka ◽  
Toshihiko Kuwabara
Keyword(s):  
Aluminum Alloy ◽  
Tensile Test ◽  
Crystal Plasticity ◽  
Alloy Sheet ◽  
Plastic Work ◽  
Element Analysis ◽  
Material Models ◽  
Biaxial Tensile Test ◽  
Biaxial Tensile ◽  
Material Tests

To improve the accuracy of forming simulations for sheet metal, the use of material models calibrated by multiaxial material tests is essential. Adequate material models can be calibrated on the basis of the contours of equal plastic work obtained by multiaxial material tests. However, because the tests often require special experimental equipment, they are not widely used by the industry. This paper proposes a methodology for a numerical biaxial tensile test that uses ABAQUS, a popular commercial software package for finite element analysis. In numerical tests, an open-source user-defined material model (UMAT) is used to implement crystal plasticity models. In order to validate our methodology, we performed a numerical biaxial tensile test on a 6000-series aluminum alloy sheet, and the results were compared with those of biaxial tensile tests with a cruciform specimen. The results demonstrated that the proposed numerical biaxial tensile test provides a reasonable prediction of stress-strain curves and the contours of equal plastic work.

501 Development of biaxial tensile test apparatus with link mechanism

2012 ◽  
Vol 2012.18 (0) ◽  
pp. 203-204
Author(s):  
Shohei IMANO ◽  
Susumu TAKAHASHI ◽  
Toshihiko KUWABARA
Keyword(s):  
Tensile Test ◽  
Test Apparatus ◽  
Biaxial Tensile Test ◽  
Biaxial Tensile ◽  
Link Mechanism

scholarly journals Identification of Anisotropic Yield Criterion Parameters from a Single Biaxial Tensile Test

2014 ◽  
Vol 611-612 ◽  
pp. 1710-1717 ◽  
Author(s):  
Shun Ying Zhang ◽  
Lionel Leotoing ◽  
Dominique Guines ◽  
Sandrine Thuillier
Keyword(s):  
Tensile Test ◽  
Yield Criterion ◽  
Biaxial Test ◽  
Anisotropic Behavior ◽  
Yield Model ◽  
Plane Stress Condition ◽  
Cruciform Specimen ◽  
Biaxial Tensile Test ◽  
Biaxial Tensile ◽  
Strain Paths

The present work deals with the calibration strategy of yield functions used to describe the plastic anisotropic behavior of metallic sheets. In this paper, Bron and Besson yield criterion is used to model the plastic anisotropic behavior of AA5086 sheets. This yield model is flexible enough since the anisotropy is represented by 12 parameters (4 isotropic parameters and 8 anisotropic parameters in plane stress condition) in the form of two linear fourth order transformation tensors. The parameters of this anisotropic yield model have been identified from a single dedicated cross biaxial tensile test. It is shown, from finite element simulations, that the strain distribution in the center of the cruciform specimen is significantly dependent on the yield criterion. Moreover, this cross biaxial test involves a large range of strain paths in the center of the specimen. The calibration stage is performed by means of an optimization procedure minimizing the gap between experimental and numerical values of the principal strains along a specified path in the gauge area of the cruciform specimen. It is shown that the material parameters of Bron and Besson anisotropic yield model can be determined accurately by a unique biaxial tensile test.

scholarly journals Factors Affecting Mechanical Properties of the Skin of Sweet Cherry Fruit

2016 ◽  
Vol 141 (1) ◽  
pp. 45-53 ◽  
Author(s):  
Martin Brüggenwirth ◽  
Moritz Knoche
Keyword(s):  
Mechanical Properties ◽  
Water Uptake ◽  
Cell Walls ◽  
Sweet Cherry ◽  
Prunus Avium ◽  
Biaxial Strain ◽  
Factors Affecting ◽  
Fruit Skin ◽  
Cell Turgor ◽  
Cell Layers

The skins of all fruit types are subject to sustained biaxial strain during the entire period of their growth. In sweet cherry (Prunus avium L.), failure of the skin greatly affects fruit quality. Mechanical properties were determined using a biaxial bulging test. The factors considered were the following: ripening, fruit water relations (including turgor, transpiration, and water uptake), and temperature. Excised discs of fruit skin were mounted in a custom elastometer and pressurized from their anatomically inner surfaces. This caused the skin disc to bulge outwards, stretching it biaxially, and increasing its surface area. Pressure (p) and biaxial strain (ε) due to bulging were quantified and the modulus of elasticity [E (synonyms elastic modulus, Young’s modulus)] was calculated. In a typical test, ε increased linearly with p until the skin fractured at pfracture and εfracture. Stiffness of the skin decreased in ripening late stage III fruit as indicated by a decrease in E. The value of pfracture also decreased, whereas that of εfracture remained about constant. Destroying cell turgor decreased E and pfracture relative to the turgescent control. The E value also decreased with increasing transpiration, while pfracture and (especially) εfracture increased. Water uptake had little effect on E, whereas εfracture and pfracture decreased slightly. Increasing temperature decreased E and pfracture, but had no effect on εfracture. Only the instantaneous elastic strain and the creep strain increased significantly at the highest temperatures. A decrease in E indicates decreasing skin stiffness that is probably the result of enzymatic softening of the cell walls of the skin in the ripening fruit, of relaxation of the cell walls on eliminating or decreasing turgor by transpiration and, possibly, of a decreasing viscosity of the pectin middle lamellae at higher temperatures. The effects are consistent with the conclusion that the epidermal and hypodermal cell layers represent the structural “backbone” of the sweet cherry fruit skin.

Sign in / Sign up

Export Citation Format

Share Document