Wenwu Wu

Investigating effects of non-uniform preload on the thermal characteristics of angular contact ball bearings through simulations

Methods utilising rigid preloading and constant preloading in ball bearing systems may not be adequate to address the optimisation of problems in which preloading occurs. This is because of non-uniform loading on the bearings that is induced by manufacturing error, assembly error and external loads. A non-uniform preload is presented for the analysis of non-uniform bearing loading. A simulation method is developed to determine the effects on non-uniform loading on bearing thermal performance under different preloads. A three-degree-of-freedom model is built to simulate the heat generation rate of angular contact ball bearings under non-uniform preloads. In this model, the non-uniform preload is divided equally into two parts: a uniform preload and an equivalent moment. The bearing heat generation rate can then be employed in finite element analysis software to simulate the temperature field associated with the entire ball bearing. The simulation data shows that non-uniform preloading conditions on ball bearings can decrease heat generation. The results also show that non-uniform preloads can alleviate heating concentrations and reduce peak temperature values under working conditions.

Investigation of non-uniform preload effect on stiffness behavior of angular contact ball bearings:

Preloading is an effective way to maintain good performance of angular contact ball bearings. Traditionally, the rigid and constant preload are applied by uniform approaches on the bearing system. However, non-uniform loads occur while the surfaces of spacer are obliquitous at rigid preload or the stiffnesses of springs are inconsistent at constant preload. In this article, a new approach is proposed to incorporate the non-uniformity effect. Using this approach, the bearing performance under practical operating conditions could be improved. At first, the critical relationship between the stiffness behavior and the non-uniform preload of the ball bearing system is studied. Then, based on Jones’ model, the stiffness function of angular contact ball bearings with non-uniform preload is established analytically. Based on the functions, boundary conditions are determined and used to calculate the local contact deformation and predict the bearing stiffness when the preload is non-uniform. Finally, the stiffness of both ceramic and steel ball bearings under non-uniform preload and various operating conditions is simulated. Comparing with traditional methods, the new method has better performance in stiffness prediction under non-uniform preload. It will give a designer a deep insight on the dynamic analysis and optimization of the rotor-bearing system.

Dry and minimum quantity lubrication high-throughput drilling of compacted graphite iron

ABSTRACT This research studies the sustainable and high-throughput drilling of compacted graphite iron (CGI), a high strength, lightweight material for automotive powertrain applications. CGI drilling experiments were conducted using a 4 mm diameter coated carbide drill at 26.5 mm/s feed rate. In two repeated tests under three lubrication conditions: dry, dry with through-the-drill compressed air, and through-the-drill minimum quantity lubrication (MQL), the drills were able to produce a maximum of 1,740, 3,150 and 2,948 holes, respectively, before the breakage of the drill. The Joule–Thomson effect due to the expansion of high pressure air from through-the-drill holes at the drill tip, chip shape, chip size and chip speed are investigated. Flank wear of the drill cutting edge is measured and results are correlated to drill life. Results indicate that dry machining of CGI is technically feasible. Chip evacuation and advanced tool cooling are important factors that affect drill life for high-throughput sustainable dry drilling of CGI.

Influence of Bearing Configuration on Spindle Modal Characteristics

Since bearing configuration has significant influence on the spindle modal characteristics which can reflect the dynamic performance of spindle system in machine tools, so it would be of extraordinary importance and necessity to analyze the spindle modal characteristics through simulation and experiment when it comes to designing spindle system. In this paper, the number and span of bearings, the spacer of bearing set and the overhang of spindle are considered as the main designing parameters of the spindle system. Firstly, a coupled spindle-bearing model is established considering the radial deformation of the bearing inner ring caused by interference fits of spindle assembly, as well as the centrifugal and thermal deformations. Based on the model, the modal characteristics of different bearing configurations are analyzed. Secondly, a spindle test bench is designed and constructed. Finally, modal characteristics of the spindle system are tested with different bearing configurations. From the simulation and experimental results, it’s indicated that there is a correlation between the natural frequency and the number of bearings. The using of short spacer inside the bearing set can increase spindle natural frequency slightly. Besides, the first natural frequency of the spindle system rises with the bearing span, whereas the second one tends to decrease. And shortening the overhang of spindle can also increase its natural frequencies, which can be taken into account in spindle design.Copyright

An improved model of motorized spindle for transient thermo-structural analysis

The prediction of the temperature distribution and thermal deformation for motorized spindle dependent on time is critical in its design process .The thermo-structural model of a grinding motorized spindle is developed with accurate thermal boundary conditions of the spindle-bearing system based on experimental data and numerical calculation. The following thermal boundary conditions are improved: the heat transfer coefficient of natural convection between spindle surface and ambient air through heat flux measurement, the heat transfer coefficient of forced convection of cooling water by the simulation analysis. In addition, a method of heat distribution applied to the bearing model is proposed. The thermo-structural model with structural deformation constraints is validated experimentally based on the transient temperature of typical regions, the axial thermal deformation of the shaft and the thermal equilibrium time.

High Precision Reverse Engineering Design for Complex Structural Component Based on Meta Feature

A high precision reverse engineering design method for complex structural component which based on the meta feature is presented. The defining method for minimal discretization meta feature is studied through the case study of an axial compressor’s impeller. Then the evaluation model of matching quality between RE planning and meta features on the basis of feature analysis and fuzzy synthesis evaluation method is put forward to select the optimal RE planning for different kinds of meta features. Combined with the split silicone mould replication method in engineering, the 3D geometry data acquisition is accurately accomplished and the reconstruction of the impeller’s model is realized from the geometric constraint angle of view and the point cloud registration of multiple views technology based on characteristic constraint. The results indicate that this method is effective for improving the measuring efficiency and quality.

The Non-Uniform Preloading Effect on Stiffness Behaviour of Angular Contact Ball Bearings

With the increasing demand of higher operating speed for bearing system, more challenges have been exposed on the maintaining of the bearing performance. Preloading is an effective method to handle these challenges. Traditionally, the preloading of bearing system has been applied by uniform approaches such as rigid preload and constant preload. However, this treatment may hardly deal with the optimization of preloading problem due to the non-uniformity of the bearing stiffness becomes more apparent under high-speed operating conditions. A novel and practical approach is therefore presented in this paper to incorporate the non-uniformity effect to improve the structural performance of bearing under actual operating conditions. Firstly, the critical relationship between the stiffness behaviour and the non-uniform preload is evaluated for bearing system. The stiffness problem of angular contact ball bearing system is then formulated analytically by Jones’ model. With this approach, boundary conditions are achieved to solve the local contact deformation and predict the bearing life under non-uniform preload. Finally, both the uniform preload and the non-uniform preload cases for bearing system are simulated under various operating conditions. Comparing with traditional methods, the proposed method can provide a better solution in both stiffness and life that will enable a designer to obtain a deep insight on the optimization of bearing system.Copyright