Experimental and Numerical Analysis of Residual Stress Change Caused by Thermal Loads During Grinding

During the process of grind-hardening, the dissipated heat from the process is utilized for a surface layer hardening of machined components made of steel. A martensitic phase transformation occurs within the affected subsurface regions and compressive residual stresses are induced. However, the layout of a grind-hardening process for given hardness results (material modification) is very difficult. Thus, a series of extensive experimental tests is required. To reduce this experimental effort, the newly developed concept of Process Signatures is used to describe the material modifications based on the thermal load appearing during the grind-hardening process. Based on an analytical calculation of the temperature fields during the grind-hardening process (surface-and external-cylindrical-grind-hardening), the internal thermal load was characterized by the maximum contact zone temperature and the maximum temperature gradient at the surface and was correlated with the process quantities (heat flux to the workpiece and the contact time).Metallographic investigations were used to analyze the surface hardening depth and the hardness change at the surface, which were correlated with the quantities describing the internal material loads. The results show that the surface hardening depth was mainly governed by the maximum contact zone temperature and the maximum temperature gradient at the surface, whereas the hardness change at the surface was influenced additionally by the quenching time.

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“…For the processes of induction heating and conventional grinding such correlations were already found [16,20].…”

Section: Experimental Setup and Methodsmentioning

confidence: 62%

Correlations between Thermal Loads during Grind-Hardening and Material Modifications Using the Concept of Process Signatures

Kolkwitz

Kohls

Heinzel

et al. 2018

JMMP

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“…surface burn and quenching cracks might have adverse effects on the service life of rails and the running safety of trains. [28][29][30] In this study, different speeds of grinding train (8,12,16,18, 20 km/h) were explored. When the rail was ground by the whole grinding train, the rail surface experienced different temperatures.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, the temperature rise and mechanical action by grinding will lead to the generation of residual stresses, which should also be explored systematically for the better operation of rail grinding. [17][18][19] At present, there were few simulation studies based on the field rail grinding pattern. Moreover, researches about rail grinding temperature field were not deeply explored, especially the whole temperature field of rail ground by the grinding train under a grinding pattern.…”

Section: Grinding Heat Generation and Its Influencementioning

confidence: 99%

Simulation research on temperature field and stress field during rail grinding

Huang

Ding

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part F:

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The rail grinding process generates a large amount of heat, which could lead to heat damage on the ground rails. But, the whole temperature field of rail ground by the grinding train has not been explored in detail. In the present study, finite element models of a rail and grinding wheel were established to simulate the rail grinding process. The temperature field and the thermo-mechanical coupling stress during rail grinding, and the residual stress after grinding were studied. Furthermore, through simplifying grinding wheels into heat sources, the temperature field of rail ground by a whole grinding train was investigated as well. The results indicated that the grinding temperature and the residual stress increased with the grinding depth and rotational speed, but decreased with the feed speed and radius of rail head. The thermo-mechanical coupling stress increased with the radius of rail head and grinding depth, and decreased with the rotational speed and feed speed. When ground by the whole grinding train, the increase in the number of grinding wheels at the same grinding angle and adjacent angles could lead to a rise in temperature on the rail surface. The speeds of grinding train and the rail head radius also have an influence on the temperature. The optimal feed speed of the grinding train should be below 12 km/h for R300, 16 km/h for R80, and 18 km/h for R13. The results could be used to optimize the grinding parameters and grinding pattern in the field.

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“…Since no coolant is applied in the experiments, it can be assumed that the thermal impact of the process is much higher than others like the mechanical, which is a common assumption in the analysis of grinding processes [14,15]. Therefore, the simulation setup is derived from Kuschel et al [19], using a moving heat source on the workpiece surface. To represent the experimental setup more realistic, the simulative setup is transferred to a 3D elasto-plastic modelling approach.…”

Section: Fem Approach and Simulative Setupmentioning

confidence: 99%

Investigations on Material Loads during Grinding by Speckle Photography

Tausendfreund

Borchers

Kohls

et al. 2018

JMMP

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The knowledge of the loads occurring during a manufacturing process (e.g., grinding) and of the modifications remaining in the material is used in the concept of process signatures to optimize the manufacturing process and compare it with others (e.g., laser processing). The prerequisite for creating a process signature is that the loads can be characterized during the running process. Due to the rough process conditions, until now there is no in-process technique to measure the loads in the form of displacements and strains in the machined boundary zone. For this reason, the suitability of speckle photography is demonstrated for in-process measurements of material loads in a grinding process without cooling lubricant and the measurement results are compared with finite element method (FEM) simulations. As working hypothesis for the simulation it is assumed, that dry grinding is a purely thermally driven process. Despite the approximation by a purely thermal model with a constant heat source, the measured displacements differ only by a maximum of approximately 20% from the simulations. In particular, the strain measurements in feed speed direction are in good agreement with the simulation and support the thesis, that the dry grinding conditions used here lead to a primarily thermally affecting process.

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Experimental and Numerical Analysis of Residual Stress Change Caused by Thermal Loads During Grinding

Cited by 23 publications

References 8 publications

Correlations between Thermal Loads during Grind-Hardening and Material Modifications Using the Concept of Process Signatures

Correlations between Thermal Loads during Grind-Hardening and Material Modifications Using the Concept of Process Signatures

Simulation research on temperature field and stress field during rail grinding

Investigations on Material Loads during Grinding by Speckle Photography

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