Papers by Keyword: Frictional Heat

Abstract: Dual-phase (DP) steels are widely used in sheet metal stamping. However, they are typically characterized by low hole expansion ratios. Since hole flanging is very often applied to sheet metal parts, solutions for improving hole flangeability are needed. In this study, high-speed punch rotation is applied in hole flanging of DP 1000 to generate frictional heat and increase formability. The flanges were formed using a punch rotating at 8000 rev/min and varying axial feeds. A maximum hole expansion ratio (HER) of 3.6 is obtained in the tests compared to ~1.58 in conventional hole flanging. The high formability is explained by the high temperature recorded in the process. The effects of temperature and strain rate on the formability of DP 1000 are examined by tensile tests conducted at different conditions. The tensile tests show an increase in formability at high temperatures. Optical microscopy at the flange edge reveals a change in the microstructure of the steel from the characteristic dual phase to a martensitic structure with elongated grains.

Abstract: This paper presents the comparative investigation of temperature distributions in the pin-on-disc tribo-contact with dry friction conditions. Heat generation and distribution mechanism in contact of a pin made by phenolic resin–based brake friction composite and 35HNL steel disc counter-face material were studied. Both experimental and simulation methods were used to study the temperature changes. In order to analyse the thermal effects, the change in the coefficient of friction with time were also characterized. Experimental friction tests performed on universal “pin-on-disc"-type friction and wear test machine model MMW-1. Interface temperature measurements of the disc was conducted non-contact type infra-red laser thermometer. Heat simulations were modelled via finite element method using COMSOL Multiphysics 5.5, Heat Transfer in Solid Module. The simulations helped to determine in the increase of temperature over selected time period. Obtained experimental results compared with results of numerical analysis.

Abstract: This Paper presents the study on the weldability of two similar and two different metallic materials. The weldability of the similar metallic materials considered in the study were aluminum alloy pipes of grade AA6063. As for the weldability of two different metallic materials were aluminum alloy of grade AA6061 to low carbon steel of grade A36, dupl stainless steel of grade 2205 to low carbon steel of grade A36 and grey cast iron of grade A48 class 35 to low carbon steel BS 449 of grade 250. The differing methods of welding or joining processes are discussed herein including those of stir welding and hot pressed diffusion bonding of the similar and dissimilar metallic materials respectively as mentioned above. The weldability of between the two materials are investigated including the physical appearance of the joints and the strength integrity of those so far achieved at this stage. The paper also presented the results on the weldability of the similar and different metallic materials, recommendation for further in-depth study in pursuit for improved technologies on the subject matters and highlight the prospects of metallic materials welding or bonding or joining to fulfill the demands for different applications.

Abstract: The automobile manufacturing industry, until recent years, has been using steel for car body components and the main method for joining these components has always been Resistance Spot Welding. However, since the global trends toward CO₂ reduction and resource efficiency have significantly increased, the importance and usage of lightweight materials has enhanced as well. New lightweight materials such as aluminum and magnesium alloys, carbon-fiber-reinforced plastics, etc., have become a reality, thanks to the new fastening technologies. Flow drill screw driving (FDS) is a one–sided thermomechanical assembly process based on heat generation by frictional force and plastic deformation. A special screw, known as hole forming and self-tapping screw, is used in this process as both fastener and tool. Moreover, rotational and translation movements are applied to the screw to create special friction conditions with the workpiece. Furthermore, unlike traditional drilling and thread milling processes, there is no chip or waste of material in FDS and the machining operations are realized through plastic deformation. This paper explores flow drilling steps and the parameters which influence heating and local softening of the aluminum sheet 5182-0. An experimental study has been carried out by varying process parameters (rotational speed, drilling force), coating and geometry of the screw. As a result, an increase of rotational speed and drilling force allows significant reduction in drilling time and introduce an important variation of the torque installation. In addition, a strong dependence is observed between drilling time and torque on the one hand, and related to the screw parameters geometry and coating on the other hand. Finally, an evaluation of the heating effect on the thread forming operation is also undertaken.

Abstract: In order to research the thermomechanical behavior of multidisc friction pairs system, three dimensional model is established for numerical simulation under simulated braking process. Based on some accurate boundary conditions, the temperature fields and thermal stress fields of friction discs and separator discs are simulated using finite element method. The temperature fields and contact stress fields of friction disc and separator discs are obtained, and their regularities of distribution are studied spatially and historically. To verify the simulation results, an experimental investigation is carried out. The results offered references for analyzing failure forms and causes of the wet multidisc friction pairs system.

Abstract: Power Spilt Device (PSD) is the key power component of Hybrid Electric Vehicle (HEV). It is very important to simulate and analyze the temperature field and stress field of PSD gear train. The thermal-mechanical coupling analysis is difficult, as it involves the interaction between temperature field and stress field. This paper presents the process of the thermal-mechanical coupling simulation in ABAQUS, and tooth surface temperature and contact stress are obtained and analyzed.

Abstract: A deign study of a thermal-type contact sensor for the detection of small defects, the heights of which are less than 16 nm on the wafer surface, is described in this paper. The feasibility of the contact sensor, which would detect frictional heat generated at the contact with defects, was theoretically investigated focusing on the temperature rise of the sensor element. To investigate the temperature rise of the contact sensor due to the generated frictional heat, both the theoretical calculation with simple model of heat transfer and a simulation with a finite element model (FEM) was carried out. Relationship between the sensor size and the response of the temperature rise of the contact sensor was also investigated by using FEM simulation.

Abstract: A thermal-type contact sensor was proposed to detect small defects, the heights of which are less than 16 nm, on the wafer surface. The feasibility of the contact sensor, which detects frictional heat generated at the contact, was theoretically investigated focusing on the temperature rise of the sensor element. Simulation results with both the simple model of heat transfer and the FEM model showed that the expected temperature rise of the contact sensor is enough to be detected by the conventional electric circuit.

Abstract: A numerical simulation code was developed for estimating the surface temperature of POM wear test with different shapes. By using the developed code, the effect of sliding geometry with various contact areas on the surface temperature was numerically investigated. The simulation results show that the limiting sliding velocity depends on contact area and reaches a peak value at a certain geometry. It was also found that the simulation code leads an exact prediction of limiting velocity in the range of small contact area. This is important since the exact temperature measurement is very difficult in this range.

Abstract: The nonlinearity of material properties at different temperatures and the manner of braking force applying on a brake system are two key factors to affect the coupling of temperature and thermal stress. Considering these two factors, a finite element analysis model of automobile brake disc and pad is established. By using the model, the dynamic frictional heat and thermal stress of braking friction pair could be simulated and the coupling characters of temperature and thermal stress on friction surfaces could be studied, where the braking force is constant or controlled by an anti-skid brake system(ABS). The study results shown that the friction temperature of brake disk rises in periodic and fluctuant tendency. The fluctuant increase of temperature will influence the character of braking. The increase of friction temperature between a brake disc and pad can decrease under the control of ABS, so the effect of thermo-mechanical coupling could be reduced.