P. Ghiasi; A. Masoumi; A. Hemmat; Gh. Najafi
Abstract
Harvesting is one of the most important field operations in sunflower production. Seed damage and low separation efficiency are the top concerns of harvesting sunflower. In this study, a threshing cylinder with rubber teeth and a concave for harvesting sunflower were designed and evaluated. The variable ...
Read More
Harvesting is one of the most important field operations in sunflower production. Seed damage and low separation efficiency are the top concerns of harvesting sunflower. In this study, a threshing cylinder with rubber teeth and a concave for harvesting sunflower were designed and evaluated. The variable parameters were threshing cylinder speed (TCS), threshing space (TS) and moisture content (MC) of sunflower head. Azargol variety was used to evaluate the threshing unit. The tests were performed at three cylinder speed levels (280, 380 and 480 rpm), two threshing spaces (8 and 10 cm) and two moisture content of sunflower head based on the crop condition (20% and 45% wet basis). An ANN model was developed to predict the amount of materials in each part of the concave. Results showed that the sunflower seeds had no damage during the threshing process and the presented model could predict the amount of materials in each part of the concave with a regression coefficient R2=0.95. Based on the ANN model, with a decrease in MC and TS, and an increase in TCS, the separation efficiency was increased. Furthermore, optimal parameters for the threshing unit which were suggested by Design Expert software to maximize the separation efficiency were 18% w.b, 450 rpm and 10.5 cm for MC, TSC, and TS, respectively and in this condition separation efficiency was determined to be 94.92%.
H. Kargarpour; T. Tavakoli Hashjin; A. Hemmat; B. Ghobadian
Abstract
Introduction The olive fruit (Olea europaea L.) is so sensitive to impact like many other crops that would lead to mechanical damage and bruising which reduce the quality of it. The olive fruit damage includes a brownish bruise at the bruised location. Most mechanical impact damage occurs during harvesting, ...
Read More
Introduction The olive fruit (Olea europaea L.) is so sensitive to impact like many other crops that would lead to mechanical damage and bruising which reduce the quality of it. The olive fruit damage includes a brownish bruise at the bruised location. Most mechanical impact damage occurs during harvesting, handling and transportation. Bruise sensitivity of two common olive cultivars in Iran (cv. Roghani and cv. Conservolea) was studied by free fall method because of development of the area under olive cultivation in Iran, and necessity to mechanical harvest in near future. Materials and Methods Two cultivar of olive fruit named Conservolea and Roghani were collected from Research Orchard of Horticultural Department of Isfahan University of Technology. A free-fall device was designed and built to accomplish an impact experiment which included a load cell monitoring system to measure impact force. The effect of cultivar, height and mass were studied in a factorial experiment. The factors consisted of two cultivar, height at five levels, and mass at three levels with 10 replications. The experiments were performed according to completely randomized design. The effect of impact force and absorbed energy was also studied for the two cultivars. The dimensions of bruising was measured 24 hours after the tests by a caliper with an accuracy of 0.01 mm. The bruising area and volume was calculated assuming the elliptical model for the bruised region. Experimental data were subjected to analysis of variance (ANOVA). Mean comparison was performed based on least significant difference (LSD) test with. Results and Discussion For both cultivars the bruising occurred under the skin and near to the stone. This could show the effect of stone at bruising. The shape of bruised region was elliptical in cv. Roghani and spherical in cv. Conservolea. The bigger stone index and the lower flesh width of cv. Roghani might be one of the reasons of more volume of bruising in this cultivar. This variety could be due to less sphericity in cv. Roghani than cv. Conservolea. The distribution of bruising was more in Roghani cultivar since it had more oil and less water content that might led to more bruising distributed under impact condition so the volume of bruising was more than Conservolea cultivar. The effects of cultivar, height and mass were significant on area and volume of bruising. Increasing height and mass significantly resulted to increase the area and volume of bruising for both cultivars. The bruise area and volume were significantly higher in cv. Roghani. This could be due to differences in physical properties of the cultivars. Roghani cultivar had a higher pit/flesh ratio in comparison with Conservolea cultivars that could contribute to more area of bruising in this cultivar. Increasing the force and energy led to increase in bruise volume for both cultivars. In cv. Roghani, despite the lower levels of force and energy, the bruise volume was more than cv. Conservolea. The reason of lower energy and force in cv. Roghani might be as a result of lower mass than cv. Conservolea. Conclusion The results showed that the effects of independent variables were significant on the volume and area of bruising so that, increasing height and mass increased the volume and area of bruising. The Roghani cv. was significantly more sensitive to bruising compared to Conservolea cv. The energy and force levels were higher in cv. Conservolea since it was heavier than cv. Roghani while the volume of the bruise was more in cv. Roghani. This might be due to the lower sphericity and flesh/pit ratio in cv. Roghani. The shape of mechanical damage which was appeared with a brownish bruising on olive tissue was related to the geometric shape of the fruit i.e. for cv. Roghani and cv. Conservolea the bruising was elliptical in and spherical just like the geometric shape of the cultivars.
Z. Nemati; A. Hemmat; M. R. Mosaddeghi
Abstract
Introduction The compaction of soil by agricultural equipment has become a matter of increasing concern because compaction of arable lands may reduce crop growth and yield, and it also has environmental impacts. In nature, soils could be compacted due to its own weights, external loads and internal forces ...
Read More
Introduction The compaction of soil by agricultural equipment has become a matter of increasing concern because compaction of arable lands may reduce crop growth and yield, and it also has environmental impacts. In nature, soils could be compacted due to its own weights, external loads and internal forces as a result of wetting and drying processes. Soil compaction in sugarcane fields usually occurs due to mechanized harvesting operations by using heavy machinery in wet soils. Adding plant residues to the soil can improve soil structure. To improve soil physical quality of sugarcane fields, it might be suggested to add the bagasse and filter cake, which are the by-products of the sugar industry, to the soils. When a soil has been compacted by field traffic or has settled owing to natural forces, a threshold stress is believed to exist such that loadings inducing lower than the threshold cause little additional compaction, whilst loadings inducing greater stresses than the threshold cause much additional compaction. This threshold is called pre-compaction stress (σpc). The σpc is considered as an index of soil compactibility, the maximum pressure a soil has experienced in the past (i.e. soil management history), and the maximum major principal stress a soil can resist without major plastic deformation and compaction. Therefore, the main objective of this study was to investigate the effects of wetting and drying cycles, soil water content, residues type and percent on stress at compaction threshold (σpc). Materials and Methods In this research, the effect of adding sugarcane residues (i.e., bagasse and filter cake) with two different rates (1 and 2%) on pre-compaction stress (σpc) in a silty clay loam soil which was prepared at two relative water contents of 0.9PL (PL= plastic limit, moist) and 1.1PL (wet) with or without wetting and drying cycles. This study was conducted using a factorial experiment in a completely randomized design with three replications. A composite disturbed sample of topsoil (0–200 mm deep) of a silty clay loam soil was collected from Isfahan province (32 31.530 N; 51 49.40E) in center of Iran. The mean annual precipitation and temperature of the region are about 160 mm and 16 C, respectively. Sugarcane residues (bagasse and filter cake) were obtained from the sugarcane fields in Ahvaz, Khuzestan province (Iran). The samples were air-dried and passed through a 2-mm sieve. Soil treated by bagasse and filter cake in different rates was poured and knocked lightly into cylinders with diameter and height of 25 and 8 cm, respectively. Large air-dry disturbed soil samples were prepared and some of them were exposed to five wetting and drying cycles. Finally, the soil surface was covered by a plastic sheet and was left overnight in the laboratory (for 24 hours) to enable the moisture to equilibrate. The loading tests were performed the next day. The pre-compaction stress was determined by plate sinkage test (PST). The loading test for PST was performed using CBR apparatus. The compression for PST was continuous at the same constant displacement rate of the CBR (i.e. 1 mm min-1). Determination of the σpc was done using Casagrande’s graphical estimation procedure (Casagrande, 1936) in a program written in MatLab software. Results and Discussion The results showed that σpc was significantly decreased by adding residues to the soil at both water contents, and with/without wetting and drying process. For untreated treatments (control), the σpc decreased with increasing water content. Although σpc decreased with adding the residues to the soil, however, the effect of residue types and percentages and soil water content on σpc was not significant for the soil samples treated with residues. Conclusion In order to prevent re-compaction of the soil and improve its structure, it is suggested that traffic control system with permanent routes for the movement of machinery to be used in sugar cane plantations and the residues (after desalination) to be added into strips that are placed under cultivation.
S. M. Mir-ahmadi; S. A. Mireei; M. Sadeghi; A. Hemmat
Abstract
Introduction: Iran is one of the main producers of kiwifruit in the world. Unfortunately, the sorting and grading of the kiwifruits are manual, which is a time consuming and labor intensive task. Due to the lack of appropriate devices for sorting and grading of kiwifruit based on the quality parameters, ...
Read More
Introduction: Iran is one of the main producers of kiwifruit in the world. Unfortunately, the sorting and grading of the kiwifruits are manual, which is a time consuming and labor intensive task. Due to the lack of appropriate devices for sorting and grading of kiwifruit based on the quality parameters, only 10% of total production is exported (Mohammadian & Esehaghi Teymouri, 1999).
One of the main quality attribute for evaluating the kiwifruits is weight. Based on the standards, the minimum weight for an excellent kiwifruit is 90 g, while these values for the first and second classes should be 70 and 65 g, respectively (Abedini, 2003). Therefore, developing a device for fast weighing of fruits in the sorting lines can be useful in packaging, storage, exporting and distributing kiwifruit to the consumer markets.
In the past, the mechanical-based systems were commonly used for online weighing of the agricultural materials, but they did not lead to the promising accuracy and speed in sorting lines. Today, electrical instruments equipped with the precise load cells are substituted for fast weighing in the sorting lines. The dropping impact method, in which a free falling fruit drops on a load cell, is one of the suitable techniques for this purpose.
Different studies have addressed the application of dropping impact for fast weighing of agricultural materials (Rohrbach et al., 1982; Calpe et al., 2002; Gilman & Bailey, 2005; Stropek & Gołacki, 2007; Elbeltagi, 2011). The aim of this study reported here was to develop an on-line system for fast weighing of kiwifruit and compare the accuracy of different methods for extracting the weight predictive models.
Materials and Methods:
Sample selection: A total of 232 samples with the weight range of 40 to 120 g were selected. Before conducting the main experiments, the weight and dimensions of the sample were measured using a digital balance and caliper, with the precisions of 0.001 g and 0.01 mm, respectively.
Impact measuring system: The impact signals of kiwifruits in an online situation were acquired using a system, including conveying and ejecting unit, a load cell and data acquisition unit (Fig.1). The load cell was a single point load cell with 5 kg capacity. The load cell was connected to the data acquisition unit (Fig.2) in order to record the impact signal of the device in time domain of 0-5 s.
Before performing the main experiments, the load cell was calibrated using 100, 200, 500 and 1000 g standard masses. All the tests were carried out on three different forward speeds of conveyor, including 1, 1.5 and 2 m s-1 in order to obtain the optimum forward speed.
Data Analysis: In this study, two different methods were applied to build the weight predictive models. In the first method, the main components of the impact signal, including the force value at the first peak Fp, time required to peak force Dp, and the impulse or area under the first peak Ip were calculated and used as independent variables to develop the weight predictive models. In the second method, the impact components were calculated for the 40 successive peaks. Multiple linear regression (MLR) analyses were used to correlate the independent (impact components) and dependent (weight) variables.
Results and Discussion: The weight statistical characteristics of the samples, including the maximum, minimum, average, standard deviation and coefficient of variability in total data, calibration and test sets are shown in Table 1. As depicted, almost the same range and variability were observed for calibration and test data sets, indicating the proper distribution of the samples.
Table 2 summarizes the results of simple and multiple linear regressions for predicting the weight from the signal components (Fp, Dp, Ip) of the first peak at different speeds of 1, 1.5 and 2 m s-1. As shown, at the forward speeds of 1 and 2 m s-1, the multiple regression models based on all three signal components, and at forward speed of 1.5 m s-1, the model based on the combination of Fp and Ip, resulted to the best prediction powers. Among different forward speeds, the forward speed of 1 m s-1 gave the best model with SDR value of 2.180. Fig.4 depicted the predicted versus true values of weight obtained from the best linear regression models using components of Fp, Dp, Ip, Fp-Ip, and multiple of the first peak of impact signal.
The results of simple and multiple linear regression for predicting the weight from the signal components (Fp, Dp, Ip) of the first forty peaks at different speeds of 1, 1.5 and 2 m s-1 are summarized in Table 3. The best models were obtained by multiple combination of all three impact signals at the forward speed of 1 and 2 m s-1, and combination of Fpi-Ipi (i=1,...,40) at 1.5 m s-1 speed. Compared with the first peak results, the accuracy of prediction reached to 84%, 60% and 52% at forward speeds of 1, 1.5 and 2 m s-1, respectively. The best results were obtained at a forward speed of 2 m s-1, in which the SDR reached to a satisfactory value of 2.857 by applying the Ipi (i=1,...,40) values. The predicted versus true values of weight obtained from the best linear regression models using components of Fp, Dp, Ip, Fp-Ip, and multiple of the first forty peaks of impact signal are illustrated in Fig.5.
Conclusions: The results of this study revealed that among different impact component, Ip was the best predictor of the kiwifruits weight. Moreover, the developed models based on impact components of the first forty successive peaks gave the best accuracy with respect to the first peak components.
Modeling
B. Ghasemi; A. Hemmat; A. Ghasemi; A. Habibi Rad
Abstract
Introduction: Apple is one of the most important horticultural crops of Iran. Its production in the country stands in the second place after citrus. Iran holds the fourth place in the world production of apples and gains a major share in the export of this product. Therefore, it is necessary to enhance ...
Read More
Introduction: Apple is one of the most important horticultural crops of Iran. Its production in the country stands in the second place after citrus. Iran holds the fourth place in the world production of apples and gains a major share in the export of this product. Therefore, it is necessary to enhance the quantity and quality of the fruit in order to maintain and promote its position among the countries importing this product from Iran. Most of the mechanical damages to fruits and vegetables occur due to contact stresses under static, quasi-static and impact loading. To obtain stress distribution inside the fruit we can use finite element analysis. The aim of this study was to simulate the behavior of the apple as a viscoelastic body subjected to quasi-static loading and also to determine the failure criteria (maximum normal stress or shear stress) of apple flesh to estimate its susceptibility to mechanical bruising.Materials and methods: In this study, Golab kohanz apple was used. Two samples were removed from each apple using a core sampler, one was used for uniaxial compression and the other was used for confined compression test using Instron universal tension and compression machine. Spherical indenter and parallel plate tests were performed in order to study apple susceptibility to bruising at four deformation levels (1, 2, 3 and 4 mm) and the bruise volume was then measured after 24 hours. Stress-strain curves were plotted and then, the elastic and viscoelastic properties were obtained. Then, by using the data obtained from apple properties, the apple was modeled in Abaqus software as spherical and cylindrical shapes with viscoelastic behavior subjected to quasi-static loadings.Results and Discussion: The normal stress distribution of the modeled apple in the shape of a cylindrical sample is shown in Fig. 4. The value of maximum normal stress was obtained (0.51 MPa) at the contact point of the loading plate with the sample. Experimental and modeled stress-strain curves are shown in Fig. 5. Up to the bio-yield point, the two curves are nearly matched; and beyond that point, there are some overestimations in the predicted stress values. The location and pattern of failure have often been used to explain the cause of failure in fruits. When specimens of fruit are subjected to a uniaxial compression, the failure often occurs the maximum shear stress plane. Failure patterns in the tested samples indicate that the failure occurs due to shear stresses. Another explanation that has been used by researchers for shear failure is the bruising position inside the fruit after loading. The position of bruising in most of the tested apples was a distance away from the apple surface (Fig. 7).According to the experiments results at the three deformation levels of 2, 3, and 4 mm, the maximum generated normal stress inside the apple was above the point of failure of the cylindrical samples. Based on the empirical results, the bruising was almost zero for the apples subjected to one or two mm deformation (Fig. 9a). The experimental value of the shear strength of the Golab kahanz apple was obtained to be 0.23 MPa. The maximum shear stress inside the modeled apple due to the two mm deformation was 0.195 MPa, which was lower than the shear strength of the apple. On the other hand, by applying three and four mm of deformation, the maximum shear stresses were obtained to be 0.24 and 0.26 MPa, respectively, indicating that the induced stress exceeded the shear strength of apple flesh; therefore, the bruising was observed in the flesh of these apples. The location of the maximum shear stress corresponds to the location of bruising in the tested samples as shown in Fig. 9b.According to the obtained results from the modeling in the finite element software, we can use this software in order to recognize and investigate the damages in agricultural products during different loading conditions (Harvesting, transportation, packaging and storage).Conclusions: In this work, Golab apple was considered as a viscoelastic material and its behavior under quasistatic loading was modeled using finite element method. Elastic, viscoelastic properties and shear strength of apple flesh were obtained and used in the simulation. Comparison of modeling and experimental results shows that the model simulates the behavior of apples during quasistatic loading well. The location of bruise occurrence in the flesh of tested apple and the location of maximum shear stress in the simulated apple was the same. Therefore, the maximum shear stress criterion can be used to estimate the susceptibility of apple varieties to internal bruising under quasistatic loading. Modeling of apple as a viscoelastic sphere in Abaqus software assuming constant bulk modulus could properly simulate apple behavior under quasistatic loading.
M. Rajabi Vandechali; A. Hemmat; A. Ghanbari Malidarreh
Abstract
About 60% of the mechanical energy consumed in mechanized agriculture is used for tillage operations and seedbed preparation. On the other hand, unsuitable tillage system resulted in soil degradation, affecting soil physical properties and destroying soil structure. The objective of this research was ...
Read More
About 60% of the mechanical energy consumed in mechanized agriculture is used for tillage operations and seedbed preparation. On the other hand, unsuitable tillage system resulted in soil degradation, affecting soil physical properties and destroying soil structure. The objective of this research was to compare the effects of three types of secondary tillage machines on soil physical properties and their field performances. An experiment was conducted in a wheat farm in Jouybar area of Mazandaran as split plots based on randomized complete block design with three replications. The main independent variable (plot) was soil moisture with three levels (23.6-25, 22.2-23.6 and 20.8-22.2 percent based on dry weight) and the subplot was three types of machine (two-disk perpendicular passing harrow, Power harrow and Rotary tiller). The measured parameters included: clod mean weight diameter, soil bulk density, specific fuel consumption, machine efficiency and machine capacity. The effects of treatments and their interactions on the specific fuel consumption, machine efficiency and machine capacity and also the effects of treatments on bulk density were significant (P
A. Ghasemi; A. Ghodarzi; A. Hemmat
Abstract
The changes in viscoelastic properties of potatoes (Tubuls Agria) stored at 4 ˚C for 4 months were modeled and evaluated by using the creep-recovery test. Cylindrical specimens with 15 mm in diameter and 35 mm long were used. The samples were allowed to deform gradually under the constant stress (110 ...
Read More
The changes in viscoelastic properties of potatoes (Tubuls Agria) stored at 4 ˚C for 4 months were modeled and evaluated by using the creep-recovery test. Cylindrical specimens with 15 mm in diameter and 35 mm long were used. The samples were allowed to deform gradually under the constant stress (110 kPa) for about 30 min. After removing the load, the sample recovery was registered. Deformation of the specimens with time were measured and recorded. Strain-time curve was plotted for loading and recovery process. Four-element (Burgers) mechanical model adequately described the creep response of the potato tissue. The coefficients of instantaneous elasticity, elastic and viscous coefficients of the retarded elastic part, Newtonian viscous flow and retardation time were determined, as they can be used to study the effect of storage conditions on the quality of the stored potatoes. These values were decreased significantly (P
Design and Construction
E. Movahedi; M. Rezvani; A. Hemmat
Abstract
For planting fine seeds in cellular trays, an automatic pneumatic seeder was designed, constructed and evaluated. CATIA software was used to design and analysis the system parts of the seeder. Different parts of the seeder, including vibrating seed hopper, vacuum boom, seed picking nozzles, seed tube, ...
Read More
For planting fine seeds in cellular trays, an automatic pneumatic seeder was designed, constructed and evaluated. CATIA software was used to design and analysis the system parts of the seeder. Different parts of the seeder, including vibrating seed hopper, vacuum boom, seed picking nozzles, seed tube, pneumatic system and electronic control unit for automation of the seeder, were designed and constructed. The area of nozzle orifice was used to calculate the required pressure of nozzle tip. The seeder was evaluated using two sizes of trays. Experiments were performed with five replications and the error of planting the seeds in the 105 and 390-cellular trays were 1.9 and 0.46 percent, respectively. The time of planting for 105 and 390 cellular trays reduced from 20 min (for manual seeding) to 35 s and from 90 min to 160 s, respectively.
