A simplified mathematical model for total temperature rise calculation in non-oriented silicon steel cold rolling deformation zone

In tandem cold rolling, the control of the temperature of high-grade non-oriented silicon steel is a difficult problem for its large deformation resistance and the preheating procedure before rolling. And it is complicated to calculate the total temperature rise of rolling deformation zone due to the comprehensive influence of the plastic deformation heat, the friction heat and the contact heat loss. So, to precisely calculate the total temperature rise, firstly, based on the four classical cold rolling force formulas, the initial total temperature rise calculation models are established correspondingly by theoretically analyzing the temperature rise of deformation heat, the temperature rise of friction heat and the temperature drop of contact heat loss; then, the model based on the improved Lian rolling force formula is adopted, which leads to calculated best matching the measured temperature; finally, considering the complex formula calculation of the initial model, based on the influences of different rolling parameters on the total temperature rise, a simplified model for convenient calculation is proposed by the nonlinear regression analysis of the initial model calculation results and main rolling parameters, which is convenient for the actual application by the field technicians.

Influence of Natural Serpentine on the Tribological Performance of Phosphate Bonded Solid Coatings

Natural serpentine powders were incorporated into phosphate bonded solid coatings to promote the anti-wear performance of the phosphate coatings. Optimal mass percent of natural serpentine in phosphate coatings was firstly explored. Thereafter, in order to stimulate layer slip of natural serpentine and strengthen interfacial interaction between natural serpentine and counterface during the friction process, tribological performance of the composite coatings under different friction condition was properly investigated. The experimental result indicated that the optimal incorporation of natural serpentine in phosphate coatings was 10 wt.%, through which anti-wear performance of phosphate coatings was significantly elevated. Additionally, accompanied by the increase of applied load and sliding speed, natural serpentine was activated by friction force and local friction heat, and simultaneously interfacial interactions between naturals serpentine and counterface were intensified. As a result, a continuous protective tribo-film was in-situ formed on the counterface, through which anti-wear performance of phosphate coatings were significantly promoted. At the same time, serious furrows generated on the counterface were also effectively self-repaired during the friction process, and further abrasion on the counterface was greatly restrained.

Thermal detonation wave in liquid lead – water mixture

It was developed the model of thermal detonation in a mixture of continuous liquid lead and dispersed steam/water particles. Stationary equations of mass, impulse and energy conservations laws for multiphase continuum are applied to describe internal structure of thermal detonation wave. They are supplemented by closing relations describing interfacial friction, heat transfer, and fragmentation. Conditions at leading shock wave and at Chapman-Jouguet plane are used as boundary conditions.

Temperature Distribution And Mechanical Properties of FSW Medium Thickness 2219 Aluminum Alloy

Friction stir welding (FSW) is a solid-state jointing technology, which has the advantages of high joint strength, low residual stress aXnd small deformation after welding. During the process of FSW, the welding temperature has an important effect on the quality of the weldment. Therefore, the heat generation model of FSW of medium thickness 2219 aluminum alloy is established based on the friction heat generation at the interface between the tool and the workpiece and the plastic deformation heat generation of the weldment material near the tool. The heat transfer model is set under the premise of considering heat conduction, thermal convection, and thermal radiation. Using JMatPro technology, the temperature-related material parameters of 2219 aluminum alloy are calculated based on the material composition, and the heat generation model is imported into the ABAQUS simulation software based on the DFLUX subroutine, and the establishment of the FSW thermodynamic model is realized. The effectiveness of the model is verified by FSW experiments. The thermodynamic model takes into account both heat generation (friction heat generation and plastic deformation heat generation) and heat transfer (heat conduction, thermal convection and thermal radiation), so it has a high prediction accuracy. Based on the FSW thermodynamic model, the influence of welding parameters on temperature distribution is explored, subsequently the influence of welding temperature on mechanical properties of welded joint are also studied. The research can provide guidance for predicting and characterizing the temperature distribution and the improvement of mechanical performance of FSW.

Study on the Unbalanced Curl Seal Failure of the Magnetorheological Fluid Sealing Device of the Hydraulic Turbine Main Shaft under Different Speed Abrupt Conditions

The fluid flow in the runner of a hydraulic turbine has serious uncertainties. The sealing failure of the magnetorheological (MR) fluid sealing device of the main shaft of the hydroturbine, caused by a sudden change in speed, has always been a difficult topic to research. This study first derives the MR fluid seal pressure and unbalanced curl equations of the hydroturbine main shaft, and then analyzes the seal pressure and friction heat under different rotational speed mutation conditions through experiments. After verification, the temperature field and magnetic field distribution of the MR fluid sealing device of the main shaft of the hydraulic turbine are obtained via numerical calculation. The results show that the external magnetic field affects the magnetic moment of the magnetic particles in the MR fluid, resulting in a significant change in frictional heat, thereby reducing the saturation of magnetic induction intensity of the MR fluid. This results in a decrease in the sealing ability of the device. The size and abrupt amplitude of the main shaft of the hydraulic turbine, and friction heat is positively correlated reducing the sealing ability of the device and causing sealing failure. Based on our results, we recommend adding the necessary cooling to the device to reduce the frictional heat, thereby increasing the seal life of the device.

Comparison of Suction/Injection Effect on Flow, Heat and Mass Transfer in Porous Media Using a Combined Similarity-Numerical Solution

This investigation deals with a comparison of suction/injection effect on flow, heat and mass transfer in porous media using a combined similarity-numerical solution. With this method of transformation, the governing transport PDEs are transformed into ODE and then solved numerically. The study reveals that suction/injection effect is more pronounce on the velocity distribution of a creeping flow (Darcy flow). The Darcy-Forchheimer flow has the steepest velocity curves due to non-linearity and has higher skin friction, heat and mass transfer rate when compared to the other porous media investigated.

Abrasive wear response of Al-Si–SiCp composite: Effect of friction heat and friction coefficient

The effects of friction heat and friction coefficient on the abrasive wear response of Al-7.5Si–SiCp composite against low-cost hypereutectic (Al-17.5Si) alloy were investigated as functions of the abrasive size and applied load in both as-cast and after heat-treatment conditions. Experiments were performed on pin-on-disc apparatus at 38 –80 μm abrasive size, 5 – 20 N applied load, 100 –400 m abrading (sliding) distances and 1 m s–1 constant sliding speed. The frictional heating of as-cast and heat-treated composite was superior compared to the matrix alloy and hypereutectic alloy, whereas the trend reversed for the friction coefficient. The frictional heating and friction coefficient of the materials increased with the abrasive size and applied load in both as-cast and after heat-treatment. The worn surface and wear debris particles were examined by using field emission scanning electron microscopy to understand the wear mechanism.

Numerical and experimental modeling of the thermal flow in a modern rotary transfer machine

The aim of this study is to estimate the relative displacement between the spindle nose and the clamping vice in a rotary transfer machine due to temperature variations. The study was focused on the relative displacements caused by temperature variations produced by two heat sources: the environment around the machine and the 3-axis computer numerical control station during the duty cycle. Regarding the last point, an analytical model was developed, in order to account for different thermal sources inside the 3-axis module (e.g. ball screws, rolling bearings and guideways friction heat, as well as heat generation in the motor). The complete numerical model was calibrated and successfully validated. Comparison was run between numerical results and experimental data in the framework of trials involving a newly developed transfer machine. Finally, the complete model, considering the combination of both the heat sources, has made it possible to estimate spindle nose-clamp relative displacement during a typical working day, highlighting that the radial displacement risks affecting seriously the accuracy of a workpiece.

IRREVERSIBILITY OF FRICTION AND WEAR PROCESSES

Ways of energy dissipation by friction are analysed from a thermodynamic perspective. The non-equilibrium and irreversibility of processes in tribological systems are found to be sufficient conditions for energy dissipation. M. Planck’s currently prevailing opinion that mechanical work can be converted into heat without limitations, e.g., by means of heat, is demonstrated not to apply to the friction of solids subject to wear. Ranges of work conversion into friction heat are determined. The generation of tribological wear particles is dependent on work of mechanical dissipation and its components – surface and volume work. A friction pair or its fragments, where energy is directly dissipated, are treated as open thermodynamic systems. The processes in place are described with the first law of thermodynamics equation. The effect of friction heat and the work of mechanical dissipation on variations of internal energy, enthalpy, and energy transferred to the environment as heat are defined. These dependences should be addressed when planning and interpreting tribological tests.