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The ability to predict the critical depth for ductile-mode grinding of brittle materials is important to grinding process optimization and quality control. The traditional models for predicting the critical depth are mainly concerned with the material properties without considering the operation parameters. This article presents a new critical energy model for brittle–ductile transition by considering the strain rate effect brought by the grinding wheel speed and chip thickness. The experiments will be conducted through a high-speed diamond grinder on reaction-sintered silicon carbide materials under different grinding speed and chip thickness. Through detailed analysis of the strain rate effect on the dynamic fracture toughness, a new fracture toughness model will be established based on the Johnson–Holmquist material model (JH-2) and calibrated through experiments based on the indentation fracture mechanics. Then, the new critical model for brittle–ductile transition will be established by introducing the dynamic facture toughness model considering the wheel speed and chip thickness. According to scanning electron microscope observations, the results show that ductile-mode grinding can be obtained through a combination of higher grinding speed and smaller chip thickness. Moreover, the critical value for ductile grinding of brittle materials can be improved through the elevation of the grinding speed or reduction in the chip thickness.

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ObjectiveTo investigate the clinical and genetic characteristics of hereditary spherocythemia (HS) in Chinese children, and to analyze the potential genotypic/phenotypic associations.MethodsThe clinical data and gene test results of children with HS were collected. All patients were diagnosed by gene test results, and the laboratory results were obtained before splenectomy. The data of red blood cell (RBC), hemoglobin (HB), mean red blood cell volume (MCV), mean red blood cell hemoglobin (MCH), mean red blood cell hemoglobin concentration (MCHC), and hematocrit (HCT) were statistically analyzed according to different mutation genes. Statistical methods for comparison between groups Mann–Whitney test analysis, two-terminal p < 0.05 was considered significant difference.ResultsA total of 15 children were enrolled in our hospital, and 14 variants were found (nine variants have not been reported before), including 10 ANK1 mutations (seven ANK1 truncated mutations) and five SPTB mutations. Patients with ANK1 mutations had more severe anemia than those with SPTB mutations (significantly lower RBC, HB, MCHC, and HCT).ConclusionThis is one of the few studies on the genetic and clinical characteristics of children with HS in China. This study identified the unique genetic and clinical characteristics of Chinese children with HS and analyzed the pathogenic genotype–phenotypic association. The results confirmed that the anemia degree of HS patients caused by ANK1 was more serious than that of patients with SPTB deficiency. However, further study of the correlation between genotype and phenotype requires a larger sample size.

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Grinding of brittle materials is characterized by a complex removal mechanism of both ductile and brittle removal. Therefore, the traditional force models, which are mainly targeted to metallic materials, cannot be fully applied to the force prediction of brittle materials. This paper will propose a new grinding force model for brittle materials considering co-existing of ductile removal force and brittle removal force. The ductile removal force is mainly composed of rubbing force, ploughing force, and chipping force. However, the brittle removal force is more related to rubbing force and fracture chipping force. The proportional coefficient of ductile removal and crack size will be modeled through a series of experiments under different wheel speed and undeformed chip thickness. The working status for a single grit was separated based on the Hertz Theory and chip thickness modeling of Rayleigh probability density function. Grinding experiments have been undertaken by using a high speed diamond grinder on Silicon Carbide, and the results was compared to the force model predictions for validation. The predictive force model shows a reasonable agreement quantitatively with the experimental force data.