Multi-objective Optimization of Turning Tool Geometric Parameters Based on Kriging Model

Cutting performance parameters of turning tool in different geometric parameters are obtained using finite element model, and the Kriging models of cutting stress and temperature are constructed, taking the cutting performance parameters as training samples. The multi-objective optimization model of turning tool geometric parameters is established based on the constructed cutting performance Kriging models, in which the design variables are rake angle, relief angle and cutting-edge radius, the objective parameters are cutting stress and temperature. The multi-island genetic algorithm is used to obtain the optimum turning tool geometric parameters: rake angle γo is 10.59°, relief angle λs is 6.15°and cutting-edge radius γE is 0.73mm. The simulation results after optimization demonstrate that the corresponding cutting temperature reduces 263.1°C, cutting stress drops by 550.8MPa.

Research on the Strength Characteristics and Crack Propagation Law of Noncoplanar Nonthrough Jointed Rock Mass by PFC2D

In this study, five groups of numerical models with different conditions were established by using PFC2D (particle flow code) to simulate the direct shear tests of noncoplanar nonthrough jointed rock mass. It is proved that normal stress and shear rate, as well as the connectivity rate, relief angle, and inclination angle of joints, have significant influence on the strength characteristics, number of cracks, and the stress of the rock mass according to measurement taken at five different measurement circles in the rock mass. Moreover, it is determined that in the process of shearing, no matter which group of tests are conducted, the number of cracks in the rock mass caused by tension is far more than that caused by the shear action. In other words, the failure of rock mass with different planes and discontinuous joints is mainly caused by the tension in the process of the direct shear test.

Mathematical equations for pressure relief angle of protective seam inclination in outburst coalmine

Protective seam mining is one kind of most effective measure to reduce coal and gas outburst risk. The pressure relief angles along inclination (δm) are key parameters for evaluating the effect of protective seam mining. However, the numerical relation between δm and coal seam dip (a) is defined by discrete data and is difficult to determine δm accurately. In this study, the variations of δm with respect to seam dips are analyzed to derive analytical equations that can be used to accurately calculate δm. The relationship between δm and seam dip (a) can be expressed as parabolic or inverted parabolic curves. Mathematical equations for δm are derived by curve fitting technique. Furthermore, polynomial equations are determined as the most appropriate for δm calculation when the polynomial order is selected as 7, 6, 4 and 5 respectively. These derived equations are computationally solved and verified using actual and field test data of δm. with satisfactory consistency and accuracy. The equations are suggested as supplement and improvement for Detailed Rules on Prevention of Coal and Gas Outburst.

Improving the Performance of EDM through Relief-Angled Tool Designs

Among the family of carbides, tungsten carbide (WC) and its variants have extensive use in numerous applications including cutting tools, dies, and many wear resistant parts. Such applications need machining of WC, which is famously considered as challenging due to high tool wear mainly in traditional machining. Sinking electric discharge machining (EDM) can be considered as a suitable alternate but the low machining rate of EDM, with conventional tool design, poses limitations. In this research, the conventional tool design is modified by providing relief angles to the tool electrodes. The relief-angled tool electrodes are first time introduced in this research to machine through holes. The role of the relief angle during EDM has been investigated in terms of six response characteristics, i.e., machining time, hole taper angle, radial overcut at the hole entrance, radial undercut at the hole exit, longitudinal tool wear, and roughness of inside hole surfaces. The performance of the relief-angled electrodes is found to be significantly better than the performance of conventional cylindrical tool. In addition to improvements in other responses, a 49% reduction in the machining time has been realized by the use of relief-angled electrode indicating a worthwhile contribution in the field of electric discharge machining.

A Mathematical Model for Grinding a Stick Blade Profile to Cut Hypoid Gears

Cutter head with multiple stick blades is widely used in the mass production of hypoid and spiral bevel gears because they allow more blades per revolution of the head cutter. However, the stick blade geometry for a head cutter that is used in face-milling and face-hobbing methods to produce hypoid and spiral bevel gears is complicated and difficult to describe. The geometry of a stick blade is defined in terms of cutting parameters such as the rake angle, the hook angle, and the side relief angle that are required to perform cutting and the theoretical cutter profile in the offset plane or the neutral cutter profile in the normal plane of an imaginary generating crown gear. This study uses a 5-axis profile grinder to grind the stick blade. The machine settings for the profile grinder and the corresponding grinding wheel geometry are derived for the grinding of each face of the stick blade. A sensitivity analysis for the machine settings is conducted to determine the accuracy of the profile grinder. The numerical example shows that the proposed mathematical model is sufficiently accurate for industrial applications.

Simulation on cutting forces and cutting temperature in broaching of 300M steel

In this paper, using the method of single factor experiment, set the test parameters of 300M steel through AdvantEdge software broaching process simulation test, simulation results for the finishing, analyzed the influence of broach rake angle and relief angle, tooth lift and cutting speed on cutting force and cutting temperature in the process of broaching, observed the cutting temperature in the broaching process of regional changes, through the analysis, provides theory basis for reasonable design of the broach. The results show that the tooth lift has the greatest influence on the cutting speed, and the tooth lift and cutting speed have the greatest influence on the cutting temperature.

Application of brazing process design in optimization structure design of scraper

To effectively enhance the service life, the research of milling machine scraper structure design and welding process are optimized. Through the structural optimization analysis, the improved structure is obtained, and the working resistance force is reduced. The full factor test is used to optimize the brazing process, and the best parameters are obtained, which improves the shear strength. The accuracy of the model is verified by experiments. The results show that compared with the working resistance force, the improved scraper tends to be slow and the peak value is smaller. The cutting rake and relief angle of the scraper are optimized. When the cutting rake angle is 6° and the cutting relief angle is 9°, both working resistance force and impact force are minimum. It proves the accuracy of the simulation results. Using CT861 solder, brazing temperature is 75°C, and the brazing time is 10s. While the cooling method uses furnace cold, the minimum value of shear strength is 200MPa. The average working life of the scraper is raised from 800 hours to 1600 hours after the optimization design. Research results have guiding significance for the structure design and the welding process optimization of the scraper.

Design and Testing of a Kiwifruit Harvester End-Effector

Mechanisms to aid fruit harvesting are undergoing constant development with increasing available technologies. However, fruits grown on vines, such as kiwifruit, have complex tree architectures and present difficulties in confirming design parameters. The objective of this research was to develop an end-effector for a kiwifruit harvester based on integrating the physical characteristics of the fruit, such as stem length, the space between mature fruits, and the growing environment provided by a trellised system into the design. These properties contribute to developing a mechanism that is lightweight, battery operated, and requires only one translational joint for positioning. Scissor cutting actuated by a linear solenoid is used to provide the required torque of 1.38 Nm to completely sever Hayward variety kiwifruit at the stem using a curved blade with a 20° relief angle. The cutting of the stem is actuated by a force sensor located on the device that enables cutting at less than 10 N, preventing premature detachment of the fruit and damage to the vine. The cutting time was measured to be 0.1 s ±0.03 s per cut. This end-effector design adds to the body of research aimed at developing a fully mechanized kiwifruit harvester. Keywords: Detachment force, End-effector, Fruit harvester, Kiwifruit, Linear solenoid.