To address the problems of the difficult processing and internal microstructure disorder of porous bearing cages, Polyetheretherketone (PEEK) porous self-lubricating bearing cage material was ...prepared based on a fused deposition molding (FDM) process, and the porous samples were heat-treated on this basis, the research was carried out around the synergistic design of the material preparation, microstructure, and tribological properties. The results show that the pore size of the PEEK porous material prepared by the FDM process meets the requirements of the porous bearing cage; the samples with higher porosity also have higher oil content, and all the samples show high oil retention. Under dry friction conditions, the higher the porosity of the porous material, the larger the friction coefficient, and the friction coefficients of each sample after heat treatment show the same pattern; under starved lubrication conditions, the friction coefficient of the porous PEEK material decreased significantly compared to the compact PEEK material, showing a better self-lubrication effect, and the porous samples reached the best self-lubrication effect after heat treatment. The optimal process parameters were 60% mass fraction of NaCl, 40% mass fraction of PEEK, and the applied heat treatment process.
In the process of dynamic unbalance detection for precision cylindrical rollers, challenges such as difficulty in achieving effective driving and susceptibility to surface damage during driving ...significantly impact the accuracy of unbalance detection. This hinders the industry’s ability to achieve the non-destructive detection of cylindrical rollers. Therefore, this paper proposes a novel driving method to enable non-destructive driving of precision cylindrical rollers. The structural principles of the driving mechanism are presented, and a mechanical model for the cylindrical roller is established to analyze the force distribution. Subsequently, a mathematical model for the air film bearing the cylindrical roller is developed to study the variation characteristics of the air film’s load-bearing capacity. The optimal air film thickness is determined, and the rationality of the mathematical model is validated through simulation analysis. Finally, an experimental platform for non-destructive driving is constructed to further verify the effectiveness of the proposed method. This research provides a prerequisite for the non-destructive detection of dynamic unbalance in precision cylindrical rollers.
•A method for sphericity error evaluation using Geometry Optimization Searching Algorithm (GOSA) is a new sphericity evaluation method.•The algorithm is no requirement to the distribution of the ...measure points, and can realize error evaluation to the spherical surface and the spherical cap.•The algorithm is simple, intuitive and easy to program, and it has the commonality, better astringency and stability.
According to geometrical characteristics of the sphericity error, a new evaluation algorithm for sphericity error based on geometry optimization searching method has been presented. First, the reference point is established and the initial error is calculated by using the measured points, Second, a regular hexahedron of side length f is collocated by taking the reference point as datum point, and the maximum difference of the radius of all measured points are calculated by regarding each vertex of the hexahedron as the centre of the measured spherical surface. Third, the reference point or side length of the hexahedron is changed by comparing the initial error and the maximum difference of the radius. Step by step, the sphericity error value of corresponding evaluation method (including Minimum Zone Sphere method (MZS), Minimum Circumscribed Sphere method (MCS) and Maximum Inscribed Sphere method (MIS)) are obtained. The principle and the steps of using the algorithm to solve the sphericity error are described in detail and the mathematical formula and program flowchart are given. The experimental results show that the sphericity error can be evaluated effectively and exactly with this algorithm.
► A method for cylindricity error evaluation using Geometry Optimization Searching Algorithm (GOSA) has been presented. ► It is not necessary to require evenly distributed sampling interval and ...assume small error and deviation in this algorithm. ► The cylindricity error of MZC, MIC and MCC can be gained at one time by using the GOSA. ► The algorithm is simple, intuitive and easy to program, and it has the commonality and better practicability.
According to the geometrical characteristics of cylindricity error, a method for cylindricity error evaluation using Geometry Optimization Searching Algorithm (GOSA) has been presented. The optimization method and linearization method and uniform sampling could not adopt in the algorithm. The principle of the algorithm is that a hexagon are collocated based on the reference points in the starting and the end measured section respectively, the radius value of all the measured points are calculated by the line between the vertexes of the hexagon in the starting and the end measured section as the ideal axes, the cylindricity error value of corresponding evaluation method (include minimum zone cylinder method (MZC), minimum circumscribed cylinder method (MCC) and maximum inscribed cylinder method (MIC)) are obtained according to compare, judgment and arranged hexagon repeatedly. The principle and step of using the algorithm to solve the cylindricity error is detailed described and the mathematical formula and program flowchart are given. The experimental results show that the cylindricity error can be evaluated effectively and exactly using this algorithm.
In order to meet the condition of high precision,efficiency and speed of modern NC machine tools and to improve the static,dynamic performance as well as lightweight design of their basic ...components,the design of bed saddle which is the key components of ADGM numerical control machine tool was optimized based on topology optimization method. Firstly,according to variable density method,which makes bed saddle quality be objective function and allows stiffness as well as natural frequency to be constraint condition was established,then the best structure layout of bed saddle was acquired as a result of topology optimization.Finally,the integral design of the bed saddle was accomplished,with the basis of best structure layout of bed saddle and the requirements of the reasonable design. Compared with the original design,new design reduces 13% of bed saddle’s weight,and the maximal displacement decreases 6%. Also,the first order natural frequency increases 8%,while the second order natural frequency increases 7%,a
Abstract
Aiming at the mechanization and automation of cleaning the hardening on the wall of the cement silo, a silo cleaning robot is designed. The kinematics and dynamics mathematical models of the ...cleaning robot are established respectively. With the 12000mm diameter silo as the cleaning object, the dynamics model is constructed with virtual prototype. There is an analysis of the relationship between the angular velocity and angular acceleration of the mechanical arm, and the relationship between the thrust of the cylinder over time were analyzed. The results show that the calculation results of the mathematical model and the simulation model are close, the change trend is consistent, and the movement is stable and meets the design requirements, which verifies the correctness of the mathematical model. The research results provide a theoretical basis for the next step of control system design and strength analysis. This silo cleaning robot solution can be extended to the cleaning construction of other silos such as coal bunkers, granaries and ore silo.
To address the problems of the difficult processing and internal microstructure disorder of porous bearing cages, Polyetheretherketone (PEEK) porous self-lubricating bearing cage material was ...prepared based on a fused deposition molding (FDM) process, and the porous samples were heat-treated on this basis, the research was carried out around the synergistic design of the material preparation, microstructure, and tribological properties. The results show that the pore size of the PEEK porous material prepared by the FDM process meets the requirements of the porous bearing cage; the samples with higher porosity also have higher oil content, and all the samples show high oil retention. Under dry friction conditions, the higher the porosity of the porous material, the larger the friction coefficient, and the friction coefficients of each sample after heat treatment show the same pattern; under starved lubrication conditions, the friction coefficient of the porous PEEK material decreased significantly compared to the compact PEEK material, showing a better self-lubrication effect, and the porous samples reached the best self-lubrication effect after heat treatment. The optimal process parameters were 60% mass fraction of NaCl, 40% mass fraction of PEEK, and the applied heat treatment process.
In order to solve the design and regulation problems of graded porous scaffolds, the triply periodic minimal surface (TPMS) that based on implicit function was taken as the pore unit for constructing ...the porous scaffolds. And the TPMS structure was controlled by selecting different types of TPMS and defining the distance function. The transition of different structures of TPMS was performed by the weight fusion method. And the dual contouring (DC) algorithm and octree algorithm were used to divide the solid model of the defect bone into hexahedral elements to determine the target assembly spatial. Through the coordinate transformation of the isoparametric element method, the pore units were mapped into the hexahedral elements to construct porous structure. Finally, a Boolean operation was used to obtain a bone scaffold model with porous structure. The examples showed that the gradient model of various irregular pores could be constructed, and the pore size, porosity, and specific surface area of porous scaffolds could be controlled by adjusting the deformation, distribution, volume of the hexahedral elements, and the structure of the TPMS pore units, which provides a feasible method for the design and regulation of heterogeneous porous scaffolds.
To meet the self-lubricating performance requirements of aerospace bearing cages, poly-ether-ether-ketone (PEEK)-based self-lubricating bearing cage materials were prepared based on the Fused ...Deposition Molding (FDM) process. The mechanical and tribological properties under high temperature condition (200°C) of the porous self-lubricating materials were researched. The results of microstructure analysis of porous sample showed that under laboratory conditions, NaCl can exhibit excellent pore-forming effect and could be effectively removed. The mechanical test results showed that the mechanical properties of the samples showed a significant decrease with the increase in porosity, and were affected by the synergistic effect of pore creation. However, the mechanical properties of heat-treated samples can meet the performance requirements of the bearing cage. The results of the tribological performance tests under high temperature conditions showed that the wear process of the dense samples was more smoother. Further comparing with the tribological properties at room temperature, it was found that the wear resistance of PEEK samples decreased under high temperature conditions. The normalized results of the mechanical and tribological properties data show that the samples with 50 wt% of porogenic agent can express the most balanced and excellent overall performance.
In order to seek a lattice structure with better mechanical properties, a reverse Kagome lattice unit cell model is proposed based on the point group theory, and it is contrastively analyzed with the ...kagome unit cell model in the mechanical properties. The stress and strain theory is used to determine the key parameter of the reverse Kagome unit cell, which is the range of the inclination angle ω on the constraint condition of realizing the compression performance, shearing property and reaching the relative density and bearing capacity of the reverse Kagome. Combined with the finite element analyze results, it can determine the value of ω of this model under the best mechanical performance. An experiment of the reverse Kagome lattice model is performed to verify the correctness of the theoretical analysis. The research shows that when the tilt angle ω is 52°, the reverse Kagome lattice structure has the best compression resistance, and when the tilt angle ω is 38°, the shear performance of this structure is
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