Influence of Grinding Conditions on Residual Stress Profiles after Induction Surface Hardening

2005 ◽  
Vol 490-491 ◽  
pp. 346-351
Author(s):  
Janez Grum
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Surface Hardening ◽  
Physical And Mechanical Properties ◽  
Grinding Wheel ◽  
Workpiece Material ◽  
Heat Effects ◽  
Grinding Conditions ◽  
Induction Surface Hardening ◽  
Hardened Surface

Induction surface hardening creates very desirable residual stresses in the hardened surface layer. Residual stresses are always of a compressive nature and are usually present to the depth of the induction-hardened layer. By the appropriate selection of grinding wheel and grinding conditions and taking into account the physical and mechanical properties of the workpiece material very favourable compressive residual stresses in the hardened surface layer can be retained. How is it possible to assure a desirable surface and surface layer quality after induction hardening and fine grinding? Finding an answer to this question requires a very good knowledge of the process of grinding on the micro-level as well as knowledge of mechanical and heat effects acting on the layer of the workpiece including the type and condition of the grinding wheel. An allinclusive consideration of the numerous influences of the kind and condition of the tool on the changes on the surface and in the surface layer of the workpiece in the given machining conditions is described by the term “surface integrity”.

Analysis of residual stresses in main crankshaft bearings after induction surface hardening and finish grinding

2003 ◽  
Vol 217 (3) ◽  
pp. 173-182 ◽  
Author(s):  
J Grum
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Subsurface Layer ◽  
Physical And Mechanical Properties ◽  
Fatigue Cracking ◽  
Correct Selection ◽  
Grinding Wheel ◽  
Process Conditions ◽  
Workpiece Material ◽  
Compressive Residual Stresses

The exact pattern of residual stresses will depend on the heat treatment temperatures employed, the depth of hardening and the type of quenchant. Process conditions that give rise to compressive residual stresses on the surface of heat-treated components are favourable. This type of residual stress delays the initiation of fatigue cracking in service, which typically occurs on the surface of the part under the action of cyclic tensile stresses. The last phase in the manufacturing of crankshafts is finish grinding in order to achieve the desirable condition of the surface and the subsurface layer, i.e. suitable dimensions, suitable surface roughness and the corresponding distribution of relative grinding residual stress in the subsurface have to be ensured. By correct selection of the grinding wheel and grinding conditions, taking into account the physical and mechanical properties of the workpiece material, the very favourable compressive residual stresses in the hardened surface layer will be retained after grinding.

Analysis of Surface and Subsurface Layers after Shot Peening of Various Aluminium Alloys

2010 ◽  
Vol 89-91 ◽  
pp. 53-58
Author(s):  
Sebastjan Žagar ◽  
Janez Grum
Keyword(s):  
Surface Layer ◽  
Crack Initiation ◽  
Residual Stresses ◽  
Surface Integrity ◽  
Shot Peening ◽  
Aluminium Alloys ◽  
Surface Hardening ◽  
Hardened Layer ◽  
Operating Pressure ◽  
Subsurface Layers

In the paper two aluminium alloys, i.e. 6082 and 7075, which were cold hardened by shot peening under different conditions, are treated. Surface hardening was carried out with S170 steel shot of the same diameter, particle hardness being 56 HRC. Other conditions were the operating pressure, mass flow, which provide different Almen intensities. The hardened layer was described by surface integrity. Macroscopic and microscopic analyses consisted in analyses of hardened profiles of hardness, and residual stresses in the thin surface layer. Research results indicated that there were significant differences among the characteristics chosen to describe surface integrity and that they had an important influence on the final condition of the surface layer. With too severe settings of the peening parameters, the surface properties got worse because of damages, which resulted in crack initiation and growth of the existing cracks.

The influence of technological factors on the nature of the distribution of residual stresses on the surface of the workpiece during cutting

2021 ◽  
pp. 34-43
Author(s):  
A. A. Chudina
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Experimental Studies ◽  
Cutting Speed ◽  
Chemical Properties ◽  
Operating Conditions ◽  
Workpiece Material ◽  
Technological Factors ◽  
Compressive Stresses ◽  
Compressive Residual Stresses

This article describes the basic information about the residual stresses that occur as a result of mechanical processing. The influence of such technological factors as geometric parameters of the cutting part of the tool, physical and chemical properties and structural and phase state of the workpiece material to be processed, cutting modes (feed, cutting speed, cutting depth) and lubricating and cooling technological means on the nature of the distribution of residual stresses in the surface layer of the workpiece is studied. The literature sources that present experimental studies of the influence of the above factors are analyzed. As a result, it was found that the negative front angle contributes to the appearance of compressive residual stresses on the surface. It was established that an increase in the area of the wear surface leads to a decrease in compressive stresses and the appearance of tension stresses. An increase in the cutting speed leads to a decrease in the amount of tension stresses. However, an increase in the speed when turning steel 45 does not lead to compressive residual stresses, as the heat factor will prevail during processing, and when turning steel 309, a high cutting speed will contribute to the hardening of the surface layer and, as a result, the appearance of residual compressive stresses. Depending on the ductility of the material, an increase in the feed can lead to both compressive residual stresses and tension stresses. This is due to the fact that when using other materials, heating can lead to quenching or tempering of the surface layer and, accordingly, to other results that will depend on the phase structural transformations occurring in the material. However, the effect of cutting coolant is ambiguous and will depend on how much heat is released in the cutting area. Thus, knowing the operating conditions of the product, it is possible to adjust the nature of the distribution of residual stresses on the surface by changing certain technological factors.

Investigations for Safe Grinding of Ti-6Al-4V Parts Produced by Direct Metal Laser Sintering (DMLS) Technology

2014 ◽  
Author(s):  
Radu Pavel ◽  
Anil K. Srivastava
Keyword(s):  
Titanium Alloy ◽  
Additive Manufacturing ◽  
Residual Stresses ◽  
Diffraction Method ◽  
Laser Sintering ◽  
Grinding Wheel ◽  
Material Structure ◽  
Direct Metal Laser Sintering ◽  
Machining Processes ◽  
Grinding Conditions

Direct Metal Laser Sintering (DMLS) is an additive manufacturing technology that can construct medium to small size parts very efficiently in comparison to traditional machining processes. The ability of this technology to grow complex parts made of high strength titanium- and nickel-based alloys led to increasing interest from aerospace, defense, and medical industries. Although the technology allows growing parts close to their final shape, the active surfaces still need a finishing operation such as grinding to meet the tight tolerances and surface finish requirements. Due to the novelty of the DMLS technology, and the relatively recent developments of titanium alloy powders, there is a need for testing and validating the capabilities of the components manufactured through a combination of DMLS and grinding processes. This paper presents the findings of an experimental study focused on the effect of various grinding conditions on the surface integrity of titanium alloy (Ti-6Al-4V) specimens produced using DMLS technology. The goal is to identify dressing and grinding conditions that would result in ground surfaces free of defects such as micro-cracks, discoloration of surfaces and/or burn marks due to high heat generated during grinding. The residual stresses were used to quantify the effect of the grinding conditions on the ground surfaces. These investigations were conducted on an instrumented CNC surface grinding machine, using a silicon-carbide grinding wheel and a water-based fluid. The X-ray diffraction method was used to measure the residual stresses. Two batches of specimens were manufactured for these tests. The growing strategy of the specimens and the presence of apparent defects in material structure are considered some of the main causes for the differences observed in the outcomes of the grinding trials. The results of these investigations support the need for continuing research in the additive manufacturing field to develop methods and technologies that will ensure a high level of consistency of the grown parts.

Experimental Investigation into Surface Integrity Finished by Abrasive Jet with Grinding Wheel as Restraint

2007 ◽  
Vol 359-360 ◽  
pp. 244-248 ◽  
Author(s):  
Chang He Li ◽  
Shi Chao Xiu ◽  
Guang Qi Cai
Keyword(s):  
Residual Stresses ◽  
Surface Integrity ◽  
High Surface ◽  
Surface Hardness ◽  
Ground Surface ◽  
Grinding Wheel ◽  
Workpiece Material ◽  
Machined Surface ◽  
X Ray ◽  
Finished Surface

The surface integrity finished by abrasive jet with grinding wheel as restraint was experimentally investigated. Experiments were performed with plane grinder M7120 equiped with abrasive jet finishing device and harded workpiece material 45 steel which was ground with the surface roughness values of Ra=0.6μm.The machined surface morphology was studied using Scanning Electron Microscope (SEM) and microscope and microcosmic geometry parameters were measured with TALYSURF5 instrument. The surface hardness for ground and finished surface was measured with HVS-1000 instrument and the phase structure was analyzed by X-ray energy dispersive spectram and residual stresses were measured by PW3208 X-ray diffraction. The Results show that longitudinal geometry parameter values were diminished and ripple was obviously improved comparing with ground surface. Furthermore, the finished surface has condensible residual stresses and high surface hardness comparability compared to grinding machining surface. As a result, life and precision consistency of finished workpiece were improved.

Modeling and Simulation of Phase Transformation during Grinding

2011 ◽  
Vol 223 ◽  
pp. 743-753 ◽  
Author(s):  
Michael Duscha ◽  
Atilim Eser ◽  
Fritz Klocke ◽  
Christoph Broeckmann ◽  
Hagen Wegner ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Surface Layer ◽  
Residual Stresses ◽  
Temperature History ◽  
Grinding Process ◽  
Thermal Loads ◽  
Transformation Kinetics ◽  
Workpiece Material ◽  
Holistic Model ◽  
Phase Transformation Kinetics

The grinding process is one of the most important finishing processes in production industry. During the grinding process the workpiece is subjected to mechanical and thermal loads. They can induce thermal damages in terms of phase transformation due to critical temperature history. A holistic model helps to describe and predict the influence of these loads on the residual stresses in the surface layer. In this paper, a very promising approach using the Finite Element Method (FEM) to simulate the surface grinding process in terms of thermal and mechanical loads during grinding of hardened and tempered steels with vitrified bonded CBN grinding wheels is introduced. The investigations were conducted for deep, pendulum and speed stroke grinding. The change of workpiece material properties was modelled as a function of temperature and phase history. The results lead to the necessary time depending temperature distribution within the surface layer. Hence, the phase transformation can be calculated. The FEM software "Sysweld" was used to analyze the phase transformation kinetics. Hence, the size of the rehardened zone after grinding can be predicted. The evaluation of the FEM model with micrographs of ground workpiece specimens showed a strong correlation for different grinding parameters. Based on the understanding of mechanical and thermal loads as well as phase transformation kinetics in the surface layers the resulting residual stresses can be determined.

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