For design and application of particulate reinforced metal matrix composites(PRMMCs),it is essential to predict the material strengths and understand how do they relate to constituents and microstructural features.To ...For design and application of particulate reinforced metal matrix composites(PRMMCs),it is essential to predict the material strengths and understand how do they relate to constituents and microstructural features.To this end,a computational approach consists of the direct methods,homogenization,and statistical analyses is introduced in our previous studies.Since failure of PRMMC materials are often caused by time-varied combinations of tensile and shear stresses,the established approach is extended in the present work to take into account of these situations.In this paper,ultimate strengths and endurance limits of an exemplary PRMMC material,WC-Co,are predicted under three independently varied tensile and shear stresses.In order to cover the entire load space with least amount of weight factors,a new method for generating optimally distributed weight factors in an n dimensional space is formulated.Employing weight factors determined by this algorithm,direct method calculations were performed on many statistically equivalent representative volume elements(SERVE)samples.Through analyzing statistical characteristics associated with results the study suggests a simplified approach to estimate the material strength under superposed stresses without solving the difficult high dimensional shakedown problem.展开更多
The cutting performance of particle reinforced meta ll ic matrix composites (PRMMCs) SiC p/Al in ultrasonic vibration cutting and comm on cutting with carbide tools and PCD tools was experimentally researched in the p...The cutting performance of particle reinforced meta ll ic matrix composites (PRMMCs) SiC p/Al in ultrasonic vibration cutting and comm on cutting with carbide tools and PCD tools was experimentally researched in the paper. The changing rules of chip shape, deformation coefficient, shear angle a nd surface residual stress were presented by ultrasonic vibration cutting. Resul ts show: when adopting common cutting, spiral chip with smaller curl radius will be obtained. The chip with zigzag contour is short and thick. There are lots of sheet cracking both on the face of the chip and on the machined surface. That i s to say, the cutting process of metallic matrix composites(MMCs) is not all lik e the cutting process of plastic material. It is akin to the breaking process of brittle material. By comparison, when adopting ultrasonic cutting, because tool contacts with workpiece intermittently in high frequency, deformation of chip i s small, loose spiral chip with larger curl radius is long and thin. The phenome non is just similar to vibration cutting of plastic material. But the chip still belongs to plastic or semi-plastic segmental chip due to the structure charact eristics of the material itself. Furthermore, the tangential residual compressio n stress of vibration cutting is larger than that of common cutting, axial resid ual stress has a relation to the feed rate and residual stress does not changes obviously with cutting depth and they are in the same order of magnitude on the whole. According to the test result analyzing, the following conclusions are put forward: 1) The extruding deformation is serious in common cutting PRMMCs, defo rmation of it’s chip is larger, and the chip with lesser curl radius is short. Whereas, the deformation of chip in vibration cutting PRMMCs is lesser, the curl radius is bigger, and the loose chips are obtained at every turn. 2) The cuttin g deformation coefficient of chip in vibration cutting is lesser than that in co mmon cutting, however the shear angle is bigger. 3) The tangential residual compression stress of vibration cutting is larger than that of common cutting, a nd residual stress does not change obviously with cutting depth, they are in the same order of magnitude on the whole.展开更多
通过调整WC颗粒尺寸(50μm和100μm)和质量分数(25%、35%和45%),采用新型的复合电冶熔铸工艺制备了4种WC颗粒增强钢基复合材料,以及作为对比的5Cr Ni Mo钢,对经过不同热处理的复合材料进行干滑动摩擦磨损试验,研究了各试样的摩擦因数和...通过调整WC颗粒尺寸(50μm和100μm)和质量分数(25%、35%和45%),采用新型的复合电冶熔铸工艺制备了4种WC颗粒增强钢基复合材料,以及作为对比的5Cr Ni Mo钢,对经过不同热处理的复合材料进行干滑动摩擦磨损试验,研究了各试样的摩擦因数和磨损量,并对磨损形貌进行分析。结果表明:随着WC含量或颗粒度在一定范围内增大,摩擦因数呈提高的趋势。在1000℃淬火+180℃回火,粗颗粒的WC含量为45%时,复合材料表现出最佳的耐磨性,是5Cr Ni Mo钢的21.96倍,是粗颗粒含量25%和35%时的10.65倍和8.91倍,是细颗粒含量45%时的5.35倍。PRMMC在干滑动摩擦磨损条件下的磨损机制为磨粒磨损和氧化磨损。展开更多
基金Supported by the National Natural Science Foundation of China(Grant No.52075033)Fundamental Research Funds for the Central Universities of China(Grant No.2020RC202).
文摘For design and application of particulate reinforced metal matrix composites(PRMMCs),it is essential to predict the material strengths and understand how do they relate to constituents and microstructural features.To this end,a computational approach consists of the direct methods,homogenization,and statistical analyses is introduced in our previous studies.Since failure of PRMMC materials are often caused by time-varied combinations of tensile and shear stresses,the established approach is extended in the present work to take into account of these situations.In this paper,ultimate strengths and endurance limits of an exemplary PRMMC material,WC-Co,are predicted under three independently varied tensile and shear stresses.In order to cover the entire load space with least amount of weight factors,a new method for generating optimally distributed weight factors in an n dimensional space is formulated.Employing weight factors determined by this algorithm,direct method calculations were performed on many statistically equivalent representative volume elements(SERVE)samples.Through analyzing statistical characteristics associated with results the study suggests a simplified approach to estimate the material strength under superposed stresses without solving the difficult high dimensional shakedown problem.
文摘The cutting performance of particle reinforced meta ll ic matrix composites (PRMMCs) SiC p/Al in ultrasonic vibration cutting and comm on cutting with carbide tools and PCD tools was experimentally researched in the paper. The changing rules of chip shape, deformation coefficient, shear angle a nd surface residual stress were presented by ultrasonic vibration cutting. Resul ts show: when adopting common cutting, spiral chip with smaller curl radius will be obtained. The chip with zigzag contour is short and thick. There are lots of sheet cracking both on the face of the chip and on the machined surface. That i s to say, the cutting process of metallic matrix composites(MMCs) is not all lik e the cutting process of plastic material. It is akin to the breaking process of brittle material. By comparison, when adopting ultrasonic cutting, because tool contacts with workpiece intermittently in high frequency, deformation of chip i s small, loose spiral chip with larger curl radius is long and thin. The phenome non is just similar to vibration cutting of plastic material. But the chip still belongs to plastic or semi-plastic segmental chip due to the structure charact eristics of the material itself. Furthermore, the tangential residual compressio n stress of vibration cutting is larger than that of common cutting, axial resid ual stress has a relation to the feed rate and residual stress does not changes obviously with cutting depth and they are in the same order of magnitude on the whole. According to the test result analyzing, the following conclusions are put forward: 1) The extruding deformation is serious in common cutting PRMMCs, defo rmation of it’s chip is larger, and the chip with lesser curl radius is short. Whereas, the deformation of chip in vibration cutting PRMMCs is lesser, the curl radius is bigger, and the loose chips are obtained at every turn. 2) The cuttin g deformation coefficient of chip in vibration cutting is lesser than that in co mmon cutting, however the shear angle is bigger. 3) The tangential residual compression stress of vibration cutting is larger than that of common cutting, a nd residual stress does not change obviously with cutting depth, they are in the same order of magnitude on the whole.
文摘通过调整WC颗粒尺寸(50μm和100μm)和质量分数(25%、35%和45%),采用新型的复合电冶熔铸工艺制备了4种WC颗粒增强钢基复合材料,以及作为对比的5Cr Ni Mo钢,对经过不同热处理的复合材料进行干滑动摩擦磨损试验,研究了各试样的摩擦因数和磨损量,并对磨损形貌进行分析。结果表明:随着WC含量或颗粒度在一定范围内增大,摩擦因数呈提高的趋势。在1000℃淬火+180℃回火,粗颗粒的WC含量为45%时,复合材料表现出最佳的耐磨性,是5Cr Ni Mo钢的21.96倍,是粗颗粒含量25%和35%时的10.65倍和8.91倍,是细颗粒含量45%时的5.35倍。PRMMC在干滑动摩擦磨损条件下的磨损机制为磨粒磨损和氧化磨损。
