Model System Studies of Wear Mechanisms of Hard Metal Tools when Cutting CFRP

AbstractWithin the publicly-funded ZAFH research project SPANTEC light, the Competence Center for Tribology in Mannheim, Germany, examines the wear mechanisms of hard metal tools when cutting carbon-fiber-reinforced plastic in drilling and milling processes. The research project includes a test series with a tribological model test.The development of a new tribological simulation model system, a modified pin-on-disc system respectively called as edge-on-disc system, for cutting CFRP with hard metal composites is systematically analyzed and presented in this work. With this model system, a new method for tool wear analysis of the tool materials against CFRP is described.As result, there are further findings on the wear mechanism of the hard metal tungsten carbide in cobalt matrix (WC-Co) compared with carbon-fiber-reinforced plastic (CFRP). Research parameters for the tribological system in this paper are the WC-Co materials, with their WC-grain size and cobalt content, and the carbon fiber orientation.This study introduces a first approach to determine WC-Co wear compared with a CFRP-specimen, unlike most hard metal wear tests. Furthermore it is shown, that properties of the drilling and milling processes can be adapted by altering the model systems rotating speed and normal force. The results originality is also provided by using a variety of WC grain size classes (sub-μm to approximately 7-9μm grain size) and cobalt contents far above usual CFRP-machining properties to show the wear process between carbon fibers and WC-Co in detail

Functional dyspepsia

Functional dyspepsia is one of the most prevalent functional gastrointestinal disorders. Functional dyspepsia comprises three subtypes with presumed different pathophysiology and aetiology: postprandial distress syndrome (PDS), epigastric pain syndrome (EPS) and a subtype with overlapping PDS and EPS features. Functional dyspepsia symptoms can be caused by disturbed gastric motility (for example, inadequate fundic accommodation or delayed gastric emptying), gastric sensation (for example, sensations associated with hypersensitivity to gas and bloating) or gastric and duodenal inflammation. A genetic predisposition is probable but less evident than in other functional gastrointestinal disorders, such as irritable bowel syndrome (IBS). Psychiatric comorbidity and psychopathological state and trait characteristics could also play a part, although they are not specific to functional dyspepsia and are less pronounced than in IBS. Possible differential diagnoses include Helicobacter pylori infection and peptic ulceration. Pharmacological therapy is mostly based on the subtype of functional dyspepsia, such as prokinetic and fundus-relaxing drugs for PDS and acid-suppressive drugs for EPS, whereas centrally active neuromodulators and herbal drugs play a minor part. Psychotherapy is effective only in a small subset of patients, whereas quality of life can be severely affected in nearly all patients. Future therapies might include novel compounds that attempt to treat the underlying gastric and duodenal inflammation.status: publishe

Postprandial changes in human MIC-1/GDF15 serum levels.

<p>Changes in serum MIC-1/GDF15 levels over time were measured in 17 subjects that received 5 different isocaloric meals on 5 separate occasions. (A) Changes in MIC-1/GDF15 serum levels do not differ for the 5 subjects fed the 5 different meals (<i>n</i> = 17, <i>p</i> = 0.26 <i>repeated measure ANOVA</i>). (B) When average data from all meals was pooled and normalised to baseline concentrations, there was significant time dependent alteration in circulating MIC-1/GDF15 levels (<i>n</i> = 5 meal; 17 subject/meal, <i>p</i> < 0.001 <i>one-way ANOVA</i>). (C) The postprandial profile of MIC-1/GDF15 serum levels (red) described in panel B were not significantly from its 24 h oscillatory pattern (<i>p</i> = 0.28, <i>repeated measure ANOVA</i>). Data represented as mean ± s.e.m.</p

Effect of satiety factor infusions on serum levels of human MIC-1/GDF15.

<p>(A) Subjects receiving CCK-8 infusion alone had significant time dependent increase in serum levels of MIC-1/GDF15 with significant increases at 120, 150 and 180 minutes of infusion. Infusion of GLP-1 or CCK plus GLP-1 had no significant effect on serum MIC-1/GDF15 level (<i>n</i> = 9, <i>vehicle vs GLP-1</i>, <i>p</i> = 0.2; <i>vehicle vs CCK-8 + GLP-1</i>, <i>p</i> = 0.06). (B) PYY1-36 or PYY3-36 or saline was infused in subjects that were fasted overnight and had a 310-Kcal meal. Neither PYY1-36 nor PYY3-36 infusions had a significant effect on serum MIC-1/GDF15 levels (<i>n</i> = 8, <i>vehicle vs PYY1-36</i>, <i>p</i> = 0.18; <i>vehicle vs PYY3-36</i>, <i>p</i> = 0.34). Data were analysed by ANOVA <i>with Bonferroni correction</i> and are presented as mean ± s.e.m. * represents <i>p</i> < 0.05.</p

Correlation of monozygotic within-pair differences in MIC-1/GDF15 serum levels and within-pair differences in BMI.

<p>Correlation between within twin-pair difference in serum MIC-1/GDF15 levels and within twin-pair difference in BMI (<i>n</i> = 72 twins), performed by Spearman regression, identifies a highly significant correlation. In general the twin of the twin pair with a higher serum MIC-1/GDF15 level generally had a lower BMI than their identical twin pair. The reverse was also true.</p

Fasting diurnal variation of human MIC-1/GDF15 serum levels.

<p>Serum MIC-1/GDF15 levels were measured on blood sample taken from participants every 30min during a 24h period. The oscillatory pattern of serum MIC-1/GDF15 levels for each individual subject was fitted to a cosine curve function.</p

Time of day for maximum and minimum MIC-1/GDF15 serum levels.

<p>Time of day for maximum and minimum MIC-1/GDF15 serum levels.</p