Effect of mechanical damage on the quality characteristics of banana fruits during short-term storage

Fresh fruits like bananas are very susceptible to mechanical damage during postharvest handling which can result in a substantial decline in quality. The study aims to evaluate the effect of bruise damage and storage temperatures on the quality of banana fruits after 48 h storage. Each ‘Grand Naine’ banana fruit was impacted once by using a drop impact test using three different heights (10, 30, and 50 cm) and storage temperatures (13 and 22 °C) after 48 h of storage. Different quality analyses were measured like bruise measurements (impact energy, bruise area, bruise volume, and bruise susceptibility), weight loss, total soluble solids (TSS), color (L*, a*, b*, hue°, chroma, yellowness index, yellowness value) headspace gases (respiration and ethylene production rate). The results showed that bruise measurements (bruise area, bruise volume, and bruise susceptibility) were highly affected by drop height. The quality parameters like weight, color, total soluble solids and headspace gases were affected by drop height and storage condition. Weight loss, total soluble solids, respiration rate, and ethylene production rate increased as drop height and storage temperature rise. Storage at ambient conditions (22 °C) accelerated bruising occurrence in banana fruits. Fewer changes were observed after 48 h of storage. The least value of yellowness index was observed on the non-bruised banana fruits (84.03) under 13 °C storage conditions. The findings of the study can provide baseline data to understand the mechanical damage mechanism on fruit quality, hoping to create awareness and educate farming communities and consumers. Storage temperature management is another approach that needs to be followed to reduce the occurrence of mechanical damage in fresh produce.

Impact Behavior of Composite Reinforced Concrete Beams with Pultruded I-GFRP Beam

The present study experimentally and numerically investigated the impact behavior of composite reinforced concrete (RC) beams with the pultruded I-GFRP and I-steel beams. Eight specimens of two groups were cast in different configurations. The first group consisted of four specimens and was tested under static load to provide reference results for the second group. The four specimens in the second group were tested first under impact loading and then static loading to determine the residual static strengths of the impacted specimens. The test variables considered the type of encased I-section (steel and GFRP), presence of shear connectors, and drop height during impact tests. A mass of 42.5 kg was dropped on the top surface at the mid-span of the tested beams from five different heights: 250, 500, 1000, 1500, and 1900 mm. Moreover, nonlinear Finite Element (FE) models were developed and validated using the experimental data. Static loading was defined as a displacement-controlled loading and the impact loading was modeled as dynamic explicit analysis with different drop velocities. The validated models were used to conduct a parametric study to investigate the effect of the concrete compressive strength on the performance of the composite beams under static and impact loadings. For the composite specimen with steel I-sction, the maximum impact force was 190% greater than the reference specimen NR-I at a drop height of 1900 mm, whereas the maximum impact forces for the specimens composite specimens with GFRP I-sction without and with shear connectors were 19% and 77%, respectively, more significant than the reference beam at the same drop height. The high stiffness for the steel I-beams relative to the GFRP I-beam was the reason for this difference in behavior. The concrete compressive strength was more effective in improving the impact behavior of the composite specimens relative to those without GFRP I-beams.

EXPERIMENTAL TEST AND FINITE ELEMENT ANALYSIS OF POTATO IMPACT ACCELERATION

To analyze the maximum acceleration (amax) of a potato colliding with different objects, both experimental test and finite element analysis (FEA) methods were used. Results showed that when potatoes were collided with the single rod, the steel plate and the double rods, the average discrepancies of FEA and experimental test values were 5.3%, 3.95% and 5.04%. The maximum acceleration increased with the increase of potato drop height, and decreased with the increase of potato mass. Under the same conditions, the maximum acceleration decreased in turn when the potatoes were collided with the steel plate, the single rod and the double rods. The FEA results showed that the maximum acceleration in collision with the steel plate was 60.78% to 96.29% higher than that with the double rods. The maximum acceleration in collision with the steel plate was 53.89% to 83.27% higher than that with the double rods. The maximum acceleration in collision with the single rod covered with soil was 37.65% and 31.54% lower than that without soil. The research methods and conclusions of this article provided a basis for the analysis of impact mechanics and damage mechanism of potatoes, and contributed to further researches related to solid-like agricultural and food products.

Simple Method for Apples’ Bruise Area Prediction

From the producers’ point of view, there is no universal and quick method to predict bruise area when dropping an apple from a certain height onto a certain type of substrate. In this study the authors presented a very simple method to estimate bruise volume based on drop height and substrate material. Three varieties of apples were selected for the study: Idared, Golden Delicious, and Jonagold. Their weight, turgor, moisture, and sugar content were measured to determine morphological differences. In the next step, fruit bruise volumes were determined after a free fall test from a height of 10 to 150 mm in 10 mm increments. Based on the results of the research, linear regression models were performed to predict bruise volume on the basis of the drop height and type of substrate on which the fruit was dropped. Wood and concrete represented the stiffest substrates and it was expected that wood would respond more subtly during the free fall test. Meanwhile, wood appeared to react almost identically to concrete. Corrugated cardboard minimized bruising at the lowest discharge heights, but as the drop height increased, the cardboard degraded and the apple bruising level reached the results as for wood and concrete. Contrary to cardboard, the foam protected apples from bruising up to a drop height of 50 mm and absorbed kinetic energy up to the highest drop heights. Idared proved to be the most resistant to damage, while Golden Delicious was medium and Jonagold was least resistant to damage. Numerical models are a practical tool to quickly estimate bruise volume with an accuracy of about 75% for collective models (including all cultivars dropped on each of the given substrate) and 93% for separate models (including single cultivar dropped on each of the given substrate).

Exploring the transverse wicking behavior of mechanically robust warp super-elastic woven fabric for tight-fitting garments

The ability of a fabric to wick moisture away from the human body directly determines the moisture management ability of any given textile, and thereby has a great influence on the comfort offered by garments made from that textile. In this paper, the effects of tensile extension and liquid drop height on the transverse wicking behavior of a warp stretch woven fabric were systematically investigated. By virtue of the unique structure of the nylon/spandex air-covered warp yarn, the woven fabric has a denser and tighter surface, which facilitates its warp elastic stretchability beyond 60%. Furthermore, an acceptable cyclic tensile behavior at an extension of 30% was obtained, indicating the superior mechanical robustness of the fabric to a certain extent. The experimental results demonstrated that the transverse wicking performances of the fabric, including the wetting time and liquid spreading area, were dependent on the tensile extensions and the heights between the water droplet and the fabric surface. Specifically, the wetting time increased with an increase of tensile extension or a decrease of liquid drop height. The spreading area of the water droplet increases as a function of the wicking time, and it fits a power relation appropriately. In addition, the water vapor transmission behavior of our fabric during stretch was clarified. Such work is essential to get an in-depth evaluation of the wicking behavior of complex stretchable fabric structures.

Variable Heights Influence Lower Extremity Biomechanics and Reactive Strength Index during Drop Jump: An Experimental Study of Male High Jumpers

Introduction. This study finds the lower limbs’ reactive strength index and biomechanical parameters on variable heights. Objective. This research aims to reveal the effects of drop height on lower limbs’ reactive strength index and biomechanical parameters. Methods. Two AMTI force platforms and Vicon motion capture system were used to collect kinematic and dynamic signals of the lower limbs. Results. The drop height had significant effects on peak vertical ground reaction force and peak vertical ground reaction force in the extension phase, lower limbs’ support moment, eccentric power of the hip joint, eccentric power of the knee joint, eccentric power of the ankle joint, and concentric power of the hip joint. The drop height had no significant effects on the reactive strength index. Reactive strength index (RSI) had no significant correlations with the personal best of high jumpers. The optimal loading height for the maximum reactive strength index was 0.45 m. Conclusion. The optimal loading height for the reactive strength index can be used for explosive power training and lower extremity injury prevention.

Modelling of Non-Newtonian Starved Thermal-elastohydrodynamic Lubrication of Heterogeneous Materials in Impact Motion

This study presents a numerical model for the thermal-elastohydrodynamic lubrication of heterogeneous materials in impact motion, in which a rigid ball bounces on a starved non-Newtonian oil-covered plane surface of an elastic semi-infinite heterogeneous solid with inhomogeneous inclusions. The impact–rebound process and the microscopic response of the subsurface inhomogeneous inclusions are investigated. The inclusions are homogenized according to Eshelby’s equivalent inclusion method. The Elrod algorithm is adopted to determine the lubrication starvation based on the solutions of pressure and film thickness, while the lubricant velocity and shear rate of the non-Newtonian lubricant are derived by using the separation flow method. The dynamic response of the cases subjected to constant impact mass, momentum, and energy is discussed to reveal the influence of the initial drop height on the impact–rebound process. The results imply that the inclusion disturbs the subsurface stress field and affects the dynamic response of the contact system when the surface pressure is high. The impact energy is the decisive factor for the stress peak, maximum hydrodynamic force, and restitution coefficient, while the dynamic response during the early approaching process is controlled by the drop height.

Exploratory Finite Element Analysis of Monolithic Toughened Glass Panes Subjected to Hard-Body Impact

The paper reports the results of an extensive experimental campaign, in which simply supported toughened glass samples with dimensions of 500 × 360 mm2 and three thicknesses (6, 8 and 10 mm) were subjected to hard-body impact. A steel ball (4.11 kg) was released from different drop heights, starting from 10 cm above the sample and increasing by 10 cm in each step until glass breakage occurred. In this way, for all samples a critical drop height (causing fracture of glass) was determined. Experiments were carried out for 35 samples for each thickness; thus 105 samples were tested in total. A 3D numerical model of the experimental setup was developed using the commercial finite element analysis (FEA) software ABAQUS and Implicit Dynamic solver. The numerical study was aimed at numerical reproduction of the experiments and determination of the maximum principal stress in the glass that occurs during the impact. To reduce the number of FEs and increase the computational efficiency of the simulations, only a quarter of the nominal geometry with appropriate boundary conditions were modelled. The simulations were performed for a given weight of the steel impactor, glass thickness and the corresponding critical/breaking drop height found in the experimental campaign. In this way, an impact strength of the toughened glass was retrospectively evaluated. The simulations were used to investigate the impact history in terms of stress in glass, acceleration and velocity. Moreover, the resulting history of impact force was determined.

A novel retractable landing gear of a light amphibious airplane design, synthesis, analysis, and implementation

Purpose The purpose of this paper is to present a novel retractable main landing gear for a light amphibious airplane, while the design, synthesis and analysis are given in details for constructing the main landing gear. Design/methodology/approach The constraint three-position synthesis has given the correct path of all linkages that suitably fit the landing gear into the compartment. The additional lock-link is introduced into the design to ensure the securement of the mechanism while landing. Having the telescopic gas-oil shock strut as a core element to absorb the impact load, it enhances the ability and efficiency to withstand higher impact than others type of light amphibious airplane. Findings By kinematics bifurcation analysis, the optimized value of the unlock spring stiffness at 90 N/m can be found to tremendously reduce the extended-retracted linear actuator force from 500 N to 150 N at the beginning of the retraction sequence. This could limit the size and weight of the landing gear actuator of the light amphibious airplane. Practical implications The drop test of the landing gear to comply with the ASTM f-2245 (Standard Specification for Design and Performance of a Light Sport Airplane) reveals that the novel landing gear can withstand the impact load at the drop height determined by the standard. The maximum impact loading 4.8 G occurs at the drop height of 300 mm, and there is no sign of any detrimental or failure of the landing gear or the structure of the light amphibious airplane. The impact settling time response reaches the 2% of steady-state value in approximately 1.2 s that ensure the safety and stability of the amphibious airplane if it subjects to an accidentally hard landing. Originality/value This paper presents unique applications of a retractable main landing gear of a light amphibious airplane. The proposed landing gear functions properly and complies with the drop test standard, ensuring the safety and reliability of the airplane and exploiting the airworthiness certification process.