The Experts below are selected from a list of 1263 Experts worldwide ranked by ideXlab platform

Hugo M Ortner - One of the best experts on this subject based on the ideXlab platform.

  • analytical investigations concerning the wear behaviour of cutting tools used for the machining of Compacted Graphite Iron and grey cast Iron
    International Journal of Refractory Metals & Hard Materials, 2008
    Co-Authors: Martin Heck, U Reuter, Hugo M Ortner, Stefan Flege, Wolfgang Ensinger
    Abstract:

    Compacted Graphite Iron (CGI) is the material for the upcoming new generation of high-power diesel engines. Due to its increased strength compared to grey cast Iron (CI) it allows an increase in the cylinder-pressures and therefore a better fuel economy and a higher power output are possible. First examples of such engines are the 3.3 L Audi V8 TDI and the 4.0 L BMW V8. The reason why CGI is not used to a larger extent in large scale production up to now is its much more difficult machinability as compared to conventional CI, especially at high cutting speeds. In modern transfer lines high cutting speeds are used in the cylinder-boring operation. And especially in these continuous cutting operations the tool life decreased due to the change from CI to CGI by about a factor of 20. As was found out previously by us, the difference in tool lifetime can be explained by the formation of a MnS-layer on the tool surface in the case of CI. This layer cannot form when machining CGI because the formation of MnS-inclusions is not possible in this material due to the higher magnesium content which in turn is responsible for the formation of the Graphite vermicles. The MnS-layer acts as a lubricant and prevents the adhesion of workpiece particles. This is the reason for the greatly reduced wear of CI in high speed machining operations. This MnS-layer is inspected closer by X-ray diffraction, X-ray induced photoelectron spectrometry, atomic force microscopy and secondary ion mass spectrometry in this work. Furthermore, available information on the performance of MnS as lubricant in PM-steels is comparatively discussed. This knowledge led to an economic solution of high productivity machining of CGI. The key was to reduce the cutting speed, replacing single insert tools with multiple insert tools. This allowed to increase the feed rate. By increasing the feed rate in the same amount as decreasing the cutting speed, the same productivity can be realized. This concept is leading to a number of multiple insert tools thus realizing a high productivity machining of CGI cylinder-bores with multi-layer-coated carbide tools.

  • investigation of the wear mechanism of cubic boron nitride tools used for the machining of Compacted Graphite Iron and grey cast Iron
    International Journal of Refractory Metals & Hard Materials, 2000
    Co-Authors: Michael Gastel, Christoph Konetschny, U Reuter, Claudia Fasel, Herbert Schulz, Ralf Riedel, Hugo M Ortner
    Abstract:

    Various experiments were performed to investigate the wear mechanism of cubic boron nitride (cBN) tools used for the machining of Compacted Graphite Iron (CGI). Comparative studies for tools used to machine grey cast Iron (CI) were also performed in order to find out why in this case the tool lifetime is significantly higher. Two main effects were found that are responsible for tool wear, namely: (1) oxidation of the tool, and (2) interdiffusion of constituting elements between tool and CGI. These wear mechanisms are more or less the same for the machining of CGI and grey CI. The difference in tool lifetime can be explained by the formation of a MnS layer on the tool surface in the case of grey CI. This layer is missing in the case of CGI. The MnS layer acts as a lubricant and as a diffusion barrier and is the reason for the reduced wear in the case of grey CI.

  • sims analysis of the wear of boron nitride tools for the machining of Compacted Graphite Iron and grey cast Iron
    Fresenius Journal of Analytical Chemistry, 1999
    Co-Authors: Michael Gastel, U Reuter, Herbert Schulz, Hugo M Ortner
    Abstract:

    Cubic boron nitride (cBN) is a common material for tools for the machining of cast Irons at high cutting speed. During the machining of Compacted Graphite Iron (CGI) in continuous cutting the wear of the cBN tools was found to be significantly higher compared to the machining of grey cast Iron. This is possibly a result of a heating of the tool surface during the cutting of CGI. One possible reason for the wear is diffusion of some elements from the cutting tool into the CGI or from the CGI into the cutting tool. SIMS measurements were carried out which prove the existence of such diffusion processes. A static model experiment has been performed by heating cBN tools to 700 °C while in contact with CGI or cast Iron (CI). SIMS depth profiles of the cBN tools and of CGI/CI show that there is a diffusion of several elements in both directions (B, W and Ti from the cBN tools into the CGI or CI, Fe and Si from the CGI or CI samples into the cBN) up to a depth of 20 μm.

Z F Zhang - One of the best experts on this subject based on the ideXlab platform.

  • mechanical damage behavior of metal matrix composites with the arbitrary morphology of particles
    Journal of materials research and technology, 2020
    Co-Authors: Rilin Shen, Jianchao Pang, Yanyan Zhang, Lin Zhang, Z F Zhang
    Abstract:

    Abstract Metal matrix composites have significant applications in the engineering field. During service, the fracture is one of the most typical failure modes. In this study, the digital image-based technique (DIT) combined with a micro-scale damage cohesive finite element model (CFEM) was employed to reconstruct the microstructures of metal matrix composites with the arbitrary morphology of particles. The cohesive finite element in this model can predict the process of crack initiation and propagation spontaneously, and the effectiveness of the model was verified by the in-situ tensile tests of the Compacted Graphite Iron (CGI) sample. We found that the morphology and distribution of the Graphite particles play important roles in crack initiation and propagation under tensile and compressive loadings. The relationship between the Graphite particle size and yield strength was established, and an optimal Graphite particle size was found for the maximum yield strength, which is different from the previous results. The relationship between microstructures and tensile properties of CGI could contribute to the design and development of metal matrix composites with optimal mechanical properties.

  • the low cycle fatigue property damage mechanism and life prediction of Compacted Graphite Iron influence of strain rate
    International Journal of Fatigue, 2020
    Co-Authors: J C Pang, L J Chen, Chunlong Zou, Z F Zhang
    Abstract:

    Abstract The low cycle fatigue (LCF) damage mechanism and fatigue life of Compacted Graphite Iron (CGI) at two strain rates were compared and analyzed at different temperatures. The results show that the strain rate has only little effect on the fatigue life of CGI at 25 °C, but the fatigue life reduces significantly with the decrease of strain rate at high temperatures (400 °C, 500 °C). The variation trend of fatigue life at 400 °C may be attributed to the initial cyclic hardening caused by the dynamic strain aging (DSA) effect combined with the serious damage localization of CGI. At 500 °C, the cyclic hardening is inhibited by serious oxidation. The fatigue life decreases with the decrease of strain rate can be ascribed to more oxidative damage and much serious grain boundary cracking. A prediction model for the fatigue life based on quadratic function relation was established through hysteresis energy and the variety of parameters (W0, β ) was explained by the corresponding damage mechanism. The quadratic relationships between the parameters and temperature can effectively predict the variation tendency of fatigue life versus temperature (0–650 °C).

  • the high cycle fatigue deformation and fracture of Compacted Graphite Iron influence of temperature
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018
    Co-Authors: J C Pang, C L Zou, Mengxiao Zhang, Y Qiu, L J Chen, Zhinan Yang, Z F Zhang
    Abstract:

    Abstract The microstructure, tensile strength, high-cycle fatigue property and corresponding damage mechanisms of Compacted Graphite Iron at room temperature (25 °C), 400 °C and 500 °C, were investigated. It is found that the fatigue strength increases at first and then decreases with the increase of the testing temperature. At 25 °C, the fatigue crack mainly initiates from Graphite debonding and propagates along the Graphite clusters. At 400 °C, the fatigue crack initiation is influenced by oxidation; the fatigue strength may be improved by dynamic strain aging. At 500 °C, the oxidation becomes more serious and the oxide layer accelerates the crack to propagate along the matrix. At the same time, the phenomenon of grain boundary softening, one of the reasons resulting in the reduction of fatigue strength, appears. Then, the model of damage mechanism was proposed according to the propagation behavior of fatigue crack at high temperatures, and the quantitative relationship between the fatigue strength and the ratio of the interphase corrosion depth to the critical crack length was established. This investigation may enrich the fundamental understanding on the damage mechanism of Compacted Graphite Iron.

  • investigation on tensile deformation behavior of Compacted Graphite Iron based on cohesive damage model
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018
    Co-Authors: Yu Qiu, Yan Zhang, Jianchao Pang, Rilin Shen, Z F Zhang
    Abstract:

    Abstract Compacted Graphite Iron (CGI) is a typical engineering material with double phases, of which Graphite morphology largely determines its mechanical performances. Although microstructural effects have been widely investigated, quantitative relations between mechanical properties and microstructures are still limited. In this study, a micro-scale damage cohesive finite element model (CFEM) was reconstructed and identified based on the tensile properties and damage characteristics of CGI, and then the effects of Graphite including distribution, size, volume fraction and morphology on tensile behaviors were investigated. The agreement of yield strength and fracture mechanism between experimental and simulation results shows that the developed methods, combining the digital image-based technique (DIT) and CFEM, can be used to simulate CGI effectively. Furthermore, the quantitative relations between yield strength and microstructures were established. It is found that Graphite distribution and volume fraction affect the yield strength much more compared with Graphite size and morphology. Specifically, interesting results were found that yield strength does not monotonically change with volume fraction and aspect ratio of Graphite, but reaches a maximum value under an optimal Graphite size, which is in contrast to the traditional results. The established quantitative relations between microstructures and tensile properties of cast alloys can be utilized to design and manufacture the metallic composite with optimal mechanical properties.

  • influence of thermal exposure on microstructure evolution and tensile fracture behaviors of Compacted Graphite Iron
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016
    Co-Authors: Yu Qiu, J C Pang, E N Yang, M X Liang, Z F Zhang
    Abstract:

    Abstract The mechanical properties of Compacted Graphite Iron (CGI) may undergo degradation when it exposes at high temperature envIronment for a long period of time. In this study, the influences of thermal exposure conditions on microstructure evolution, tensile properties, especially in-situ tensile fracture behaviors of CGI were investigated. The experimental results show that the cementite surrounding the vermicular Graphite (VG) gradually decomposes into ferrite and Graphite with increasing the thermal exposure time. The increase of ferrite content with lower strength but higher ductility around VG particles, and the size and content of VG particles can lead to the easier initiation of crack, decrease of strain hardening rate, and the retard of the crack propagation rate in the matrix. All these factors often cause the decrease of strength but increase of elongation to fracture for CGI. Finally the relationship among yield strengths of CGI and matrix, and Graphite content was discussed.

U Reuter - One of the best experts on this subject based on the ideXlab platform.

  • analytical investigations concerning the wear behaviour of cutting tools used for the machining of Compacted Graphite Iron and grey cast Iron
    International Journal of Refractory Metals & Hard Materials, 2008
    Co-Authors: Martin Heck, U Reuter, Hugo M Ortner, Stefan Flege, Wolfgang Ensinger
    Abstract:

    Compacted Graphite Iron (CGI) is the material for the upcoming new generation of high-power diesel engines. Due to its increased strength compared to grey cast Iron (CI) it allows an increase in the cylinder-pressures and therefore a better fuel economy and a higher power output are possible. First examples of such engines are the 3.3 L Audi V8 TDI and the 4.0 L BMW V8. The reason why CGI is not used to a larger extent in large scale production up to now is its much more difficult machinability as compared to conventional CI, especially at high cutting speeds. In modern transfer lines high cutting speeds are used in the cylinder-boring operation. And especially in these continuous cutting operations the tool life decreased due to the change from CI to CGI by about a factor of 20. As was found out previously by us, the difference in tool lifetime can be explained by the formation of a MnS-layer on the tool surface in the case of CI. This layer cannot form when machining CGI because the formation of MnS-inclusions is not possible in this material due to the higher magnesium content which in turn is responsible for the formation of the Graphite vermicles. The MnS-layer acts as a lubricant and prevents the adhesion of workpiece particles. This is the reason for the greatly reduced wear of CI in high speed machining operations. This MnS-layer is inspected closer by X-ray diffraction, X-ray induced photoelectron spectrometry, atomic force microscopy and secondary ion mass spectrometry in this work. Furthermore, available information on the performance of MnS as lubricant in PM-steels is comparatively discussed. This knowledge led to an economic solution of high productivity machining of CGI. The key was to reduce the cutting speed, replacing single insert tools with multiple insert tools. This allowed to increase the feed rate. By increasing the feed rate in the same amount as decreasing the cutting speed, the same productivity can be realized. This concept is leading to a number of multiple insert tools thus realizing a high productivity machining of CGI cylinder-bores with multi-layer-coated carbide tools.

  • investigation of the wear mechanism of cubic boron nitride tools used for the machining of Compacted Graphite Iron and grey cast Iron
    International Journal of Refractory Metals & Hard Materials, 2000
    Co-Authors: Michael Gastel, Christoph Konetschny, U Reuter, Claudia Fasel, Herbert Schulz, Ralf Riedel, Hugo M Ortner
    Abstract:

    Various experiments were performed to investigate the wear mechanism of cubic boron nitride (cBN) tools used for the machining of Compacted Graphite Iron (CGI). Comparative studies for tools used to machine grey cast Iron (CI) were also performed in order to find out why in this case the tool lifetime is significantly higher. Two main effects were found that are responsible for tool wear, namely: (1) oxidation of the tool, and (2) interdiffusion of constituting elements between tool and CGI. These wear mechanisms are more or less the same for the machining of CGI and grey CI. The difference in tool lifetime can be explained by the formation of a MnS layer on the tool surface in the case of grey CI. This layer is missing in the case of CGI. The MnS layer acts as a lubricant and as a diffusion barrier and is the reason for the reduced wear in the case of grey CI.

  • sims analysis of the wear of boron nitride tools for the machining of Compacted Graphite Iron and grey cast Iron
    Fresenius Journal of Analytical Chemistry, 1999
    Co-Authors: Michael Gastel, U Reuter, Herbert Schulz, Hugo M Ortner
    Abstract:

    Cubic boron nitride (cBN) is a common material for tools for the machining of cast Irons at high cutting speed. During the machining of Compacted Graphite Iron (CGI) in continuous cutting the wear of the cBN tools was found to be significantly higher compared to the machining of grey cast Iron. This is possibly a result of a heating of the tool surface during the cutting of CGI. One possible reason for the wear is diffusion of some elements from the cutting tool into the CGI or from the CGI into the cutting tool. SIMS measurements were carried out which prove the existence of such diffusion processes. A static model experiment has been performed by heating cBN tools to 700 °C while in contact with CGI or cast Iron (CI). SIMS depth profiles of the cBN tools and of CGI/CI show that there is a diffusion of several elements in both directions (B, W and Ti from the cBN tools into the CGI or CI, Fe and Si from the CGI or CI samples into the cBN) up to a depth of 20 μm.

Michael Gastel - One of the best experts on this subject based on the ideXlab platform.

  • investigation of the wear mechanism of cubic boron nitride tools used for the machining of Compacted Graphite Iron and grey cast Iron
    International Journal of Refractory Metals & Hard Materials, 2000
    Co-Authors: Michael Gastel, Christoph Konetschny, U Reuter, Claudia Fasel, Herbert Schulz, Ralf Riedel, Hugo M Ortner
    Abstract:

    Various experiments were performed to investigate the wear mechanism of cubic boron nitride (cBN) tools used for the machining of Compacted Graphite Iron (CGI). Comparative studies for tools used to machine grey cast Iron (CI) were also performed in order to find out why in this case the tool lifetime is significantly higher. Two main effects were found that are responsible for tool wear, namely: (1) oxidation of the tool, and (2) interdiffusion of constituting elements between tool and CGI. These wear mechanisms are more or less the same for the machining of CGI and grey CI. The difference in tool lifetime can be explained by the formation of a MnS layer on the tool surface in the case of grey CI. This layer is missing in the case of CGI. The MnS layer acts as a lubricant and as a diffusion barrier and is the reason for the reduced wear in the case of grey CI.

  • sims analysis of the wear of boron nitride tools for the machining of Compacted Graphite Iron and grey cast Iron
    Fresenius Journal of Analytical Chemistry, 1999
    Co-Authors: Michael Gastel, U Reuter, Herbert Schulz, Hugo M Ortner
    Abstract:

    Cubic boron nitride (cBN) is a common material for tools for the machining of cast Irons at high cutting speed. During the machining of Compacted Graphite Iron (CGI) in continuous cutting the wear of the cBN tools was found to be significantly higher compared to the machining of grey cast Iron. This is possibly a result of a heating of the tool surface during the cutting of CGI. One possible reason for the wear is diffusion of some elements from the cutting tool into the CGI or from the CGI into the cutting tool. SIMS measurements were carried out which prove the existence of such diffusion processes. A static model experiment has been performed by heating cBN tools to 700 °C while in contact with CGI or cast Iron (CI). SIMS depth profiles of the cBN tools and of CGI/CI show that there is a diffusion of several elements in both directions (B, W and Ti from the cBN tools into the CGI or CI, Fe and Si from the CGI or CI samples into the cBN) up to a depth of 20 μm.

Thomas Pardoen - One of the best experts on this subject based on the ideXlab platform.

  • Proposal of Characterization Procedure of Metal–Graphite Interface Strength in Compacted Graphite Iron
    Materials, 2018
    Co-Authors: Edwin A. Lopez-covaleda, Sepideh Ghodrat, Charles-henry Sacre, Leo Kestens, Thomas Pardoen
    Abstract:

    Compacted Graphite Iron is the material of choice for engine cylinder heads of heavy-duty trucks. Compacted Graphite Iron provides the best possible compromise between optimum mechanical properties, compared to flake Graphite Iron, and optimum thermal conductivity, compared to spheroidal Graphite Iron. The vermicular-shaped Graphite particles, however, act as stress concentrators, and, as a result of delamination from the metal matrix, they are responsible for crack initiation during the thermomechanical fatigue cycles occurring through engine startup and shutdown cycles. Scratch tests driven over the matrix and into the Graphite particles were performed in order to characterize the strength of the metal–Graphite interface. Samples extracted from a cylinder head in as-cast condition were compared to samples subjected to a heat-treatment at 700 °C for 60 h. The former samples were composed of a primarily pearlitic matrix and Graphite particles (~11.5 vol %), whereas, after annealing, a certain pearlite fraction decomposed into Fe and C, producing a microstructure with Graphite–ferrite interfaces, exhibiting a partially spiky morphology. The scratch test revealed that the ferrite–Graphite interfaces with spiky nature exhibited a stronger resistance to delamination compared to the ferrite–Graphite interfaces with smooth morphology. One reason for the high interface strength is the mechanical interlocking between Graphite spikes and ferrite, increasing the contact area between the two phases.

  • Proposal of Characterization Procedure of Metal–Graphite Interface Strength in Compacted Graphite Iron
    'MDPI AG', 2018
    Co-Authors: Edwin A. Lopez-covaleda, Sepideh Ghodrat, Charles-henry Sacre, Leo Kestens, Thomas Pardoen
    Abstract:

    Compacted Graphite Iron is the material of choice for engine cylinder heads of heavy-duty trucks. Compacted Graphite Iron provides the best possible compromise between optimum mechanical properties, compared to flake Graphite Iron, and optimum thermal conductivity, compared to spheroidal Graphite Iron. The vermicular-shaped Graphite particles, however, act as stress concentrators, and, as a result of delamination from the metal matrix, they are responsible for crack initiation during the thermomechanical fatigue cycles occurring through engine startup and shutdown cycles. Scratch tests driven over the matrix and into the Graphite particles were performed in order to characterize the strength of the metal–Graphite interface. Samples extracted from a cylinder head in as-cast condition were compared to samples subjected to a heat-treatment at 700 °C for 60 h. The former samples were composed of a primarily pearlitic matrix and Graphite particles (~11.5 vol %), whereas, after annealing, a certain pearlite fraction decomposed into Fe and C, producing a microstructure with Graphite–ferrite interfaces, exhibiting a partially spiky morphology. The scratch test revealed that the ferrite–Graphite interfaces with spiky nature exhibited a stronger resistance to delamination compared to the ferrite–Graphite interfaces with smooth morphology. One reason for the high interface strength is the mechanical interlocking between Graphite spikes and ferrite, increasing the contact area between the two phases