Model of Ploughing Cortical Bone with Single-Point Diamond Tool

Generating topological microstructures on the surface of cortical bone to establish a suitable microenvironment can guide bone cells to achieve bone repair. Single-point diamond tools (SPDTs) have advantages in efficiency and flexibility to fabricate surface microstructures. However, the cutting force during ploughing cannot be predicted and controlled due to the special properties of cortical bone. In this paper, a novel cutting model for ploughing cortical bone using an SPDT was established, and we comprehensively considered the shear stress anisotropy of the bone material and the proportional relationship between the normal force and the tangential force. Then, the orthogonal cutting experiment was used to verify the model. The results show that the error of calculated value and the experimental data is less than 5%. The proposed model can be used to assist the fabrication of microstructures on cortical bone surface using an SPDT.

Effects of Submerged Convective Cooling In The Turning of AZ31 Magnesium Alloy For Tool Temperature And Wear Improvement

Low melting point and material adhesion attributed by the magnesium alloy led to extreme built-up edge (BUE) and built-up layer (BUL) formations. Dry machining is favourable for machining magnesium alloy; however, this strategy inflicts excessive adhesive wear on the cutting tool. Therefore, this current work focuses on innovative cooling technique known as submerged convective cooling (SCC) for the turning of the AZ31 magnesium alloy. Prior to cutting experiment, a computational fluid dynamics (CFD) simulation was conducted to evaluate internal structure of cooling module. Based on the CFD simulation, small inlet/outlet diameter significantly contribute to reduction of tool temperature because of effective heat transfer coefficient of cooling fluid in the SCC. Experimental results revealed that SCC has effectively reduced the tool temperature by 50% and contributed to 37% improvement in surface roughness when compared to dry cutting. Finally, both BUE and BUL were observed in dry and SCC conditions, but the severity of these wear mechanisms improved or decreased remarkably under SCC conditions.

Effect of Cutting Parameters on Chips and Burrs Formation With Traditional Micromilling and Ultrasonic Vibration Assisted Micromilling

In the traditional micromilling(TMM) of Inconel718 alloy, due to the influence of material plasticity and size effect, relatively large burr will be produced. In order to solve the burr problem in micromilling, ultrasonic vibration in feed direction is applied to the workpiece to complete vibration cutting. Combined with trajectory simulation and cutting experiment, the burr formation mechanism of TMM and ultrasonic vibration assisted micromilling(UVAMM) was studied. The results show that when the ratio of amplitude(A) to feed per tooth(ƒz) is greater than 0.5, continuous cutting changes to intermittent cutting. Compared with TMM, UVAMM improves chip breaking ability, facilitates the propagation of burr crack and effectively inhibits the formation of burr. However, due to the influence of cutting edge radius, A/ƒz should be set larger. When the chip breaking condition is reached, the burr shape is usually tearing or flocculent. Under the conditions of low speed(n), large ƒz and large A, the burr suppression is more obvious.

Design and Application of Simulating Cutting Experiment System for Drum Shearer

When the shearer cuts coal or rock with different hardness, it will produce corresponding cutting state information. This paper develops a simulation cutting experiment system for the drum shearer based on similarity theory. It took the spiral cutting drum of a shearer as the research target and derived the principal similarity coefficients through the dimensional analysis method. Meanwhile, this paper designed the structure of the cutting power system and hydraulic system. Then, it chose a certain amount of coal powder as an aggregate, cement 325# as cementing material, sand, and water as auxiliary materials to prepare simulated coal samples. The paper adopted the orthogonal experiment method and used a proportion of cement, sand, and water as the influencing factors in designing a simulated coal sample preparation plan. In addition, it utilized the range analysis method to research the influence of various factors on the density and compressive strength of simulated coal samples. Finally, it conducted simulated coal sample cutting tests. The results show that the density of the simulated coal samples is between 1192.59 Kg/m3–1483.51 Kg/m3, and the compressive strength range reaches 0.16 MPa–3.94 MPa. The density of the simulated coal sample is related to the mass proportion of cement and sand. When the ratio gradually increases, the influence of sand increases. Furthermore, the compressive strength is linearly proportional to the proportion of cement. The self-designed simulation cutting experiment system could effectively carry out the relevant experiments and obtain the corresponding cutting condition signals through the sensors. There are differences in vibration signals generated by cutting different strength materials. Extracting the kurtosis value as the characteristic value can distinguish various cutting modes, which can provide a reliable experimental solution for the research of coal-rock identification.

Kinematic, Workspace and Force Analysis of a five-DOF Hybrid Manipulator R(2RPR)R/SP+RR

In the present study, the over-constrained hybrid manipulator R(2RPR)R/SP + RR is considered as the research objective. In this paper, kinematics of the hybrid manipulator, including the forward and inverse position, are analyzed. Then, the workspace is checked based on the inverse position solution to evaluate whether the workspace of the hybrid manipulator meets the requirements, and the actual workspace of the hybrid robot is analyzed. After that, the force analysis of the over-constrained parallel mechanism is carried out, and an ADAMS-ANSYS rigid-flexible hybrid body model is established to verify the simulation. Based on the obtained results from the force analysis, the manipulator structure is design. Then, the structure optimization is carried out to improve the robot stiffness. Finally, calibration and workspace verification experiments are performed on the prototype, cutting experiment of an S-shaped aluminum alloy workpiece is completed, and the experiment verifies the processing ability of the prototype and proves that the prototype has good application prospects.

Full coverage cutting path planning of robotized roadheader to improve cutting stability of the coal lane cross-section containing gangue

The purpose of this work is to improve the cutting stability of robotized roadheader through the full coverage cutting path planning of the coal lane cross-section containing gangue. Cutting gangue will bring serious pick wear and severe vibration, which will reduce the service life of robotized roadheader. Therefore, the strategy that avoiding the gangue and cutting the remaining coal-rock was recommended. Firstly, the environment grid map of the cross-section containing gangue was established and the grid attribute was assigned. To describe the arbitrary position of gangue, a random generation method was developed. On this basis, the combination of biologically inspired neural network (BINN) and floating template method was proposed to overcome the shortcomings of traditional BINN and the full coverage cutting path planning simulation was carried out. The simulation shows a better result that the average repetition rate is approximately 10% under the condition that the cutting coverage rate is more than 95%. Finally, the cutting experiment of the coal-rock sample containing gangue on the robotized roadheader cutting platform was performed. Based on the infrared thermography and cutting signal obtained by the previous round cutting, the cutting path of the second round was planned and the cutting experiment was conducted. The experiment results show that the cutting temperature rise and the cutting vibration of the second round cutting can be effectively reduced by approximately 60% and 90%, which demonstrated that the cutting stability of the cross-section containing gangue can be effectively improved by the cutting path planning strategy of avoiding gangue.

Investigation on the size effect in micro end milling considering the cutting edge radius and the workpiece material

Previous research has found that the peripheral and end cutting edges of the cutter had different cutting mechanisms in the micro end cutting process considering the size effect. This investigation is a further study on this point considering the cutting edge radius of the cutter and the material of the workpiece based on the methods of finite element simulation and the micro end cutting experiment. This study adopts a combination of simulation and experiment research methods and the cutting edge radius and the workpiece material as two variables. Considering the cutting mechanisms of the peripheral cutting edge and the end cutting edge are different, the peripheral cutting edge and the end cutting edge are studied respectively. Meanwhile, the minimum undeformed chip thickness (MUCT) value is determined in three ways, chip morphology, cutting force, and surface roughness, so the final result obtained by comparing three kinds of results has a very important reference value. Not only are the chip morphology obtained by finite element simulation and the surface roughness obtained by the micro end cutting experiment used to identify the MUCT value, but also the cutting force. The simulation and experimental results show that the cutting force can be used to identify the MUCT value for the peripheral cutting edge, but it cannot be used for the end cutting edge. The MUCT value increases with the increase of the cutting edge radius, no matter which process it is. The material property has some effects on the MUCT value; even the cutting parameters and the cutting edge radius remain unchanged for the peripheral cutting edge. However, the material property has no effect on the MUCT value for the end cutting edge. In this study, the influence of important variables on MUCT is studied as much as possible to reflect a real application situation.

MAIZE STRAW CUTTING PROCESS MODELLING AND PARAMETER CALIBRATION BASED ON DISCRETE ELEMENT METHOD (DEM)

In order to simulate straw cutting process, this paper established a maize straw cutting model with discrete element method (DEM) based on straw cutting experiment. Firstly, maize straw model consisting of several small particles was established by DEM. Then, a straw cutting experiment was conducted and the maximum straw cutting resistance was 199 N for straw with 15 mm diameter. Then, single-factor experiment was conducted to analyze the effect of DEM parameters on straw cutting effect and the max straw cutting resistance Fmax. The normal stiffness between particles and blade (ball-facet-kn) and shear stiffness between particles and blade (ball-facet-ks) were found to be the significant factors affecting Fmax, and the value of the parameters that has no significance was determined. The optimum combination of the significant parameters was 17662 N·m-1 of ball-facet-kn and 52499 N·m-1 of ball-facet-ks. The verification test results showed that the maize straw model was cut off, thus it could simulate the real straw cutting effect, and the relative error of max straw cutting resistance Fmax between the simulation and the experiment was below 9.1%. Thus, it could be concluded that the established maize straw cutting model was accurate and reliable.

MAIZE STRAW CUTTING PROCESS MODELLING AND PARAMETER CALIBRATION BASED ON DISCRETE ELEMENT METHOD (DEM)

In order to simulate straw cutting process, this paper established a maize straw cutting model with discrete element method (DEM) based on straw cutting experiment. Firstly, maize straw model consisting of several small particles was established by DEM. Then, a straw cutting experiment was conducted and the maximum straw cutting resistance was 199 N for straw with 15 mm diameter. Then, single-factor experiment was conducted to analyze the effect of DEM parameters on straw cutting effect and the max straw cutting resistance Fmax. The normal stiffness between particles and blade (ball-facet-kn) and shear stiffness between particles and blade (ball-facet-ks) were found to be the significant factors affecting Fmax, and the value of the parameters that has no significance was determined. The optimum combination of the significant parameters was 17662 N·m-1 of ball-facet-kn and 52499 N·m-1 of ball-facet-ks. The verification test results showed that the maize straw model was cut off, thus it could simulate the real straw cutting effect, and the relative error of max straw cutting resistance Fmax between the simulation and the experiment was below 9.1%. Thus, it could be concluded that the established maize straw cutting model was accurate and reliable.