MATHEMATICAL MODELING OF EAR GRAIN SEPARATION PROCESS DEPENDING ON THE LENGTH OF THE AXIAL FLOW THRESHING APPARATUS

Modeling the threshing and separation process involves the application of a method of description, analysis and analytical determination of system performance: threshing apparatus - working process. The modeling of the process of separating the seeds passing through an axial flow threshing device was performed taking into account that the separation function ss(x) is given depending on the length of the threshing apparatus. Then, models were made to describe the variation of the percentage (cumulative) of separated seeds ss (x=L), corresponding to the modification of the threshing apparatus functional parameters (depending on the peripheral speed of the rotor, the flow of straw parts and the moisture of straw parts).

The Influence of Crystal Orientation on Subsurface Damage of Mono-Crystalline Silicon by Bound-Abrasive Grinding

Subsurface damage (SSD) produced in a grinding process will affect the performance and operational duration of single-crystal silicon. In order to reduce the subsurface damage depth generated during the grinding process by adjusting the process parameters (added), experiments were designed to investigate the influence of machining factors on SSD. This included crystal orientation, diamond grit size in the grinding wheel, peripheral speed of the grinding wheel, and feeding with the intention to optimize the parameters affecting SSD. Compared with isotropic materials such as glass, we considered the impact of grinding along different crystal directions <100> and <110> on subsurface damage depth (added). The Magnetorheological Finishing (MRF) spot technique was used to detect the depth of SSD. The results showed that the depth of SSD in silicon increased with the size of diamond grit. SSD can be reduced by either increasing the peripheral speed of the grinding wheel or decreasing the feeding rate of the grinding wheel in the <100> crystal orientation, if the same size of diamond grit was employed. In addition, we proposed a modified model around surface roughness and subsurface crack depth, which considered plastic and brittle deformation mechanisms and material properties of different crystal orientations. When the surface roughness (RZ) exceeded the brittle-plastic transition’s critical value RZC (RZC<100> > 1.5 μm, RZC<110> > 0.8 μm), cracks appeared on the subsurface. The experimental results were consistent with the predicted model, which could be used to predict the subsurface cracks by measuring the surface roughness. However, the model only gives the approximate range of subsurface defects, such as dislocations. The morphology and precise depth of plastic deformation subsurface defects, such as dislocations generated in the fine grinding stage, needed to be inspected by transmission electron microscopy (TEM), which were further studied.

Improvement of the Form Accuracy of a Slender Workpiece in Cylindrical Traverse Grinding

During the cylindrical traverse grinding of a slender workpiece, the ground workpiece is easily bent by the normal grinding force owing to its low stiffness. Therefore, it is difficult to finish the slender workpiece with high accuracy. To prevent the elastic deformation of a workpiece during the grinding process, a steady rest is generally used. However, considerable skill of the worker is required to use a steady rest. Therefore, we developed a new traverse grinding method without any steady rest. In this method, the elastic deformation of a workpiece was kept constant by controlling the traverse speed of the workpiece. At the middle of the ground workpiece, where the elastic deformation increased easily, the traverse speed was slowed down. However, this method had a longer grinding cycle time because the average traverse speed decreased compared to that of the conventional method. To shorten the cycle time, the peripheral speed of the grinding wheel was increased to decrease the normal grinding force. Basic grinding experiments were carried out under several grinding conditions by changing the peripheral speed of the wheel. From these grinding experiments, it was confirmed that the normal grinding force and the form error of the ground workpiece decreased as the peripheral wheel speed increased. By using results obtained from basic experiments, grinding experiments involving changes in the traverse speed were carried out at two peripheral wheel speeds. The grinding cycle time was reduced successfully by increasing the peripheral wheel speed without an increment in the form error of the ground workpiece. Furthermore, a form error was observed at the end of the workpiece where the grinding wheel traveled away from the workpiece. The form error occurred because the normal grinding force decreased rapidly when the contact length between the workpiece and the wheel was decreased at the end of the workpiece. To prevent rapid changes in the normal grinding force, the traverse speed of the workpiece was increased at the end of the workpiece. By using this method, a ground workpiece with high form accuracy was obtained.

Crimping analysis of textured polyester multifilament yarn

The properties of textured POY PES multifilament yarns are conditioned by texturing temperature, texturing speed, stretching degree and by the ratio of disc peripheral speed and yarn speed. In the paper attention is focused on crimping of yarns. New method for defining crimping limits is proposed. The method is based on the flow analysis of the force-elongation function. POY multifilament polyester yarns, having the fineness of 167f36x1 dtex were analyzed. The texturing of PES multifilament yarns was performed using different first heater temperatures (350 oC, 400 oC, 450 oC) and maintaining the constant temperature of the second heater (180 oC), then with different texturing speeds (500 m/min, 600 m/min, 700 m/min, 900 m/min, 1000 m/min, 1100 m/min), using different ratio of the disc circumferential speed to yarn speed (2.15, 2.20, 2.25) and at the extension degree of 1.665.

Structuring of Bioceramics by Micro-Grinding for Dental Implant Applications

Metallic implants were the only option for both medical and dental applications for decades. However, it has been reported that patients with metal implants can show allergic reactions. Consequently, technical ceramics have become an accessible material alternative due to their combination of biocompatibility and mechanical properties. Despite the recent developments in ductile mode machining, the micro-grinding of bioceramics can cause insufficient surface and subsurface integrity due to the inherent hardness and brittleness of these materials. This work aims to determine the influence on the surface and subsurface damage (SSD) of zirconia-based ceramics ground with diamond wheels of 10 mm diameter with a diamond grain size (dg) of 75 μm within eight grinding operations using a variation of the machining parameters, i.e., peripheral speed (vc), feed speed (vf), and depth of cut (ae). In this regard, dental thread structures were machined on fully sintered zirconia (ZrO2), alumina toughened zirconia (ATZ), and zirconia toughened alumina (ZTA) bioceramics. The ground workpieces were analysed through a scanning electron microscope (SEM), X-ray diffraction (XRD), and white light interferometry (WLI) to evaluate the microstructure, residual stresses, and surface roughness, respectively. Moreover, the grinding processes were monitored through forces measurement. Based on the machining parameters tested, the results showed that low peripheral speed (vc) and low depth of cut (ae) were the main conditions investigated to achieve the optimum surface integrity and the desired low grinding forces. Finally, the methodology proposed to investigate the surface integrity of the ground workpieces was helpful to understand the zirconia-based ceramics response under micro-grinding processes, as well as to set further machining parameters for dental implant threads.

Optimization of operational parameters for mechanized harvesting of mung-bean (Vignaradiata (L.) Wilczek) with combine harvester

The present study was aimed at optimizing operational and crop parameters influencing the mechanized harvesting and threshing of mung-bean crop with combine harvester. Two varieties of summer mung-bean SML-668 and SML-832 and one variety of kharif mung-bean ML-818 were selected for the study. Concave clearance was kept as 25 mm at front side and 10 mm from rear side. The height of cut the crop ranged from 8-9.5 cm. Threshing efficiency was more than 98% at cylinder peripheral speeds C3 and C4 in all varieties except SML-832. The percent grain damage was higher for higher cylinder peripheral speed and lower for higher forward speed. The grain damage ranged from 1.54 – 3.22 percent for C1, C2 and C3 cylinder peripheral speed in all crop varieties. Peripheral speed of 18.91 m/s and forward speed of 1.5 km/h was found to be optimum for harvesting mung-bean with combine harvester for all crop varieties.

Optimization of operational parameters for mechanised harvesting of pigeon-pea (Cajanus cajan) with combine harvester

Pigeon-pea is very thick and woody stem crop, therefore the harvesting and threshing of this crop is a drudgery and time consuming. At present in India pigeon-pea is harvested manually with sickle and after that the crop is left in the field in the form of heaps for 7-10 days for sun drying. After sun drying the crop is threshed with suitable thresher or beating with stick etc. Lack of mechanization of harvesting and threshing operation is one of the limitations to the increase production and productivity of pigeon-pea. Therefore, the present study was aimed at optimizing operational and crop parameters influencing the mechanized harvesting and threshing of pigeon-pea crop with combine harvester. PAU-881, AL-1856, AL-1817 and AL-1811 of extra-short duration pigeon-pea were selected for the study. The moisture content of crop and grain varied from 38 to 48% and 22 to 25% on wet basis respectively for crop varieties AL-1817 and AL-1811 and it was 48 to 53% and 24 to 27% on wet basis respectively for crop varieties PAU-881 and AL-1856. Concave clearance was kept as 16 mm at front side and 7 mm from rear side. Threshing efficiency was more than 98% at cylinder peripheral speed of 26.61 m/s and 34.85 m/s in all varieties except PAU-881. The percent grain breakage was higher for higher cylinder peripheral speed and lower for higher forward speed. The grain damage was below 1% for 23.85m/s, 26.61 m/s and 34.85 m/s cylinder peripheral speed in all crop varieties except AL-1811. The optimum values of peripheral velocity and forward speed of combine harvester harvesting pigeon-pea were 26.61 m/s and 2.0 km/h for all selected varieties.

EVALUATION OF SOME TECHNICAL INDICATORS OF THE LOCALLY MODIFIED SHELLER FOR CORN GRAIN

This study was carried out during 2017, at the factory of shelling corn grains at Al-musayyib /Babylon governorate. The objective of this study was to evaluate some technical indicators of the locally modified sheller for corn grain by using sheller machine locally modified with different peripheral speed of shelling cylinder 900, 1100 and 1300 m/min, different clearance between shelling cylinder and concave 23 and 28 mm on some the properties, such as sheller productivity, quality productivity, power consumption and unshelled grains. This research was done by applying the split plot design experiment within RCBD using four replicates. The results showed the following: clearance between shelling cylinder and concave 28 mm indicated significant superiority up on the clearance between shelling cylinder and concave 23 mm with highest sheller productivity (2.474 ton/h) and quality (193.735 kg.h.kw-1), while the clearance between shelling cylinder and concave 23 mm had lower power consumption 11.62 kw and lower percentage of unshelled grains 2.53%. The increasing in the peripheral speed of shelling cylinder from 900 to 1100 and 1300 m/min increased the sheller productivity, quality and power consumption. The peripheral speed of shelling cylinder (1300 m/min) indicated significant superiority up on the peripheral speed of shelling cylinder 900 and 1100 m/min in achieving higher sheller productivity 3.039 ton/h and higher quality productivity 205.061 kg.h/kw. while the peripheral speed of shelling cylinder 900 m/min achieving lower power consumption 11.78 kw and lower percentage of unshelled grains 2.37 %.

Developments of a Flow Visualization Borescope and a Two-Phase Flow Probe for Aeroengine Transmission Gears

In order to reduce oil dynamic power loss in aeroengine gearboxes, visualizations and measurements of the oil-flow are effective. In the research presented in this paper, we developed a flow visualization borescope which can qualitatively visualize oil flow and a two-phase flow probe which can quantitatively measure oil/air ratio and the flow velocity. The flow visualization borescope consists of a 16mm diameter pipe in which an air purge passage for removing oil mist and a borescope are integrated with an illumination laser light and optical lenses, enabling clear high-speed photography. The two-phase probe consists of a 5mm diameter pipe with a 1mm diameter measurement hole and has a pressure adjustment pipe inside the pipe. For a demonstration, a shrouded spur gear with 100 m/s peripheral speed and 20 liters/min oil supply was used. Flow visualization at 30000 frame/sec imaging shows that oil outflow from the shroud opening spreads turbulently over the whole width of the opening. Oil/air ratio and flow velocity measurement by the two-phase flow probe show that there was thin oil-rich layer on the shroud wall and the flow speed was slow compared with the gear peripheral speed. The measurement equipment we developed was easily installed to the gearbox and therefore it is expected to apply to real aeroengine gearboxes.