Enabling Thin-Edged Part Machining of Nomex Honeycomb Composites via Optimizing Variable Angle of Disc Cutters

Machining Nomex honeycomb composites (NHCs), which are widely-used materials in the aerospace industry, is an imperative process to obtain desired profiles. However, when machining NHCs to obtain a thin-edged surface, some problems can arise due to large cutting forces. To avoid these defects, a method of ultrasonic vibration machining with variable angles of the down milling disc cutter was proposed in this study. The processing principles and motion characteristics of this method were elaborated. A theoretical model of its cutting process was established. The principle of cutting force reduction was qualitatively analyzed based on the model, and an experimental validation was conducted. The results demonstrated that, due to a smaller swing angle in each pass, the proposed method could reduce the fractal dimension of the machined surface by 6.01% compared to 1° with 10° of angle in each pass. And severe machining defects were decreased. Additionally, comparing the process of the fixed 10° angle of ultrasonic vibration machining with the process of a 1° angle in a pass, cutting force can be significantly reduced by 33.5%, demonstrating the effectiveness of the proposed method which improved surface quality by reducing cutting forces

Robustness of Surface Roughness against Low Number of Picture Elements and Its Benefit for Scaling Analysis

Surface roughness is widely used in the research of topography, and the scaling characteristics of roughness have been noticed in many fields. To rapidly obtain the relationship between root-mean-squared roughness (Rq) and measurement scale (L) could be helpful to achieve more understandings of the surface property, particularly the Rq-L curve could be fitted to calculate the fractal dimension (D). In this study, the robustness of Rq against low number of picture elements was investigated. Artificial surfaces and the surfaces of two actual samples (a silver thin film and a milled workpiece) were selected. When the number of picture elements was lowered, Rq was found to be stable within a large portion of the concerned scope. Such a robustness property could validate the feasibility of Rq-L curve obtained by segmenting a single morphological picture with roughness scaling extraction (RSE) method, which was proposed in our previous study. Since the traditional roughness (TR) method to obtain Rq-L curves was based on multiple pictures, which used a fixed number of picture elements at various L, RSE method could be significantly more rapid than TR method. Moreover, a direct comparison was carried out between RSE method and TR method in calculating the Rq-L curve and D, and the credibility and accuracy of RSE method with flatten order 1 and 2 was verified

Tool Wear Characteristics and Strengthening Method of the Disc Cutter for Nomex Honeycomb Composites Machining with Ultrasonic Assistance

Nomex honeycomb composites are used extensively in aerospace, automotive, and other industries due to their superior material properties. However, the tool wear during their machining can compromise the processing accuracy and the stability of the whole machining process, thus studies on the tool wear and strengthening method are urgently needed. This study presents a radial difference calculation method (RDC) to evaluate the tool wear of the disc cutter quantitatively in both conventional cutting and ultrasonic assisted cutting. The morphology of the tool wear process and its characteristics were analyzed. Two different heat treatments (salt bath quenching and vacuum quenching) were carried out to strengthen the tool performance. The research results demonstrated that ultrasonic vibration could significantly reduce the tool wear of the disc cutter, by up to 36%, after the same machining time. Salt bath quenching and vacuum quenching can both strengthen the tool performance. Particularly, after vacuum quenching treatment, the disc cutter’s metallographic grains were refined, and the tool wear could be reduced by 64%, compared to the as-received disc cutter. The findings in this study could be instructive to obtain further understanding of the machining mechanism and to improve methods in ultrasonic assisted cutting of Nomex honeycomb composites

Tool Wear Characteristics and Strengthening Method of the Disc Cutter for Nomex Honeycomb Composites Machining with Ultrasonic Assistance

Nomex honeycomb composites are used extensively in aerospace, automotive, and other industries due to their superior material properties. However, the tool wear during their machining can compromise the processing accuracy and the stability of the whole machining process, thus studies on the tool wear and strengthening method are urgently needed. This study presents a radial difference calculation method (RDC) to evaluate the tool wear of the disc cutter quantitatively in both conventional cutting and ultrasonic assisted cutting. The morphology of the tool wear process and its characteristics were analyzed. Two different heat treatments (salt bath quenching and vacuum quenching) were carried out to strengthen the tool performance. The research results demonstrated that ultrasonic vibration could significantly reduce the tool wear of the disc cutter, by up to 36%, after the same machining time. Salt bath quenching and vacuum quenching can both strengthen the tool performance. Particularly, after vacuum quenching treatment, the disc cutter’s metallographic grains were refined, and the tool wear could be reduced by 64%, compared to the as-received disc cutter. The findings in this study could be instructive to obtain further understanding of the machining mechanism and to improve methods in ultrasonic assisted cutting of Nomex honeycomb composites

Occurrence and Bioaccumulation of Psychotropic Pharmaceuticals and Their Metabolites in Water and Fish in a Shallow Lake in China: Implications for Ecological and Human Health Risks

Psychotropic pharmaceuticalsand their metabolites are a growing concern for aquatic environments and may accumulate in aquatic organisms. In this study, 21 parent psychotropic pharmaceuticals and 8 metabolites from three categories of psychotropic drugs (anxiolytics, antiepileptics, and antidepressants) were evaluated in Gao–Bao–Shaobo lake (GBSL), a shallow lake in China. Among them, 18 psychotropic pharmaceuticals and 8 metabolites were detected in water samples from GBSL (0.2 up to ∼24.5 ng/L), and 13 psychotropic pharmaceuticals and 5 metabolites were identified in fish (1 up to ∼126.2 ng/g dw). In the wet season, concentrations of psychotropic pharmaceuticals and their metabolites showed an increase from the inflow to the discharge subarea. Carbamazepine and sertraline were the dominant pharmaceuticals detected in fish with bioaccumulation factors, exceeding 5000 L/kg. Physicochemical parameters (log Kow and MW) were negatively correlated with the pharmaceutical levels in fish. Carbamazepine posed a moderate risk to aquatic organisms in all subareas. Hazard quotient results showed that the consumption of fish from GBSL is unlikely to exhibit a direct adverse effect on humans. Our results indicated that a comprehensive understanding of psychotropic pharmaceutical contaminations in surface waters should consider not only the parent pharmaceuticals but also the subsequent accumulation of their metabolites in fish

Relationships between blood bone metabolic biomarkers and anemia in patients with chronic kidney disease

AbstractIntroduction Blood bone metabolic biomarkers are noninvasive indices for evaluating metabolic bone diseases. We investigated the relationships between blood bone metabolic biomarkers and anemia in chronic kidney disease (CKD) patients and analyzed the effects of parathyroidectomy (PTX) on the above indices.Methods In this cross-sectional study, 100 healthy controls and 239 CKD patients, including 46 secondary hyperparathyroidism (SHPT) patients with PTX, were enrolled. Moreover, a prospective study was conducted in which 28 PTX patients were followed up. The degree of anemia was classified as mild, moderate, or severe based on the tertiles of hemoglobin (Hb) levels of the anemic CKD patients, with cutoff values of 83 g/L and 102 g/L. Bone metabolic biomarkers, including calcium (Ca), phosphorus (P), intact parathyroid hormone (iPTH), fibroblast growth factor 23 (FGF23), and α-klotho, were tested.Results The mean estimated glomerular filtration rate (eGFR) in CKD patients was 25.7 ± 36.0 ml/min/1.73 m2, and 84.10% of CKD patients had anemia. The baseline Hb levels in the mild, moderate, and severe anemia subgroups were 110.86 ± 5.99 g/L, 92.71 ± 5.96 g/L, and 67.38 ± 10.56 g/L, respectively. CKD patients had higher adjusted Ca, P, alkaline phosphatase (ALP), iPTH, and FGF23 levels and lower α-klotho levels than controls. Baseline adjusted Ca, P, iPTH, and α-klotho levels were associated with Hb levels in CKD patients. Blood adjusted Ca, P, and iPTH levels were correlated with anemia severity. After PTX (median interval: 6.88 months), anemia and high blood adjusted Ca, P, iPTH, and FGF23 levels were ameliorated, while α-klotho levels were increased.Conclusions Blood adjusted Ca, P, iPTH, and α-klotho levels were correlated with Hb levels in CKD patients. Correction of bone metabolic disorders may be a therapeutic strategy for anemia treatment