Investigation of the performance of carbide cutting tools with hard coatings in hard milling based on the response surface methodology

Machining of hard materials has become a great challenge for several decades. One of the problems in this machining process is early tool wear, and this affects the machinability of hard materials. In order to increase machinability, cutting tools are widely coated with nanostructured physical vapor deposition hard coatings. The main characteristics of such advanced hard coatings are high microhardness and toughness as well as good adhesion to the substrate. In this paper, the influence of hard coatings (nanolayer AlTiN/TiN, multilayer nanocomposite TiAlSiN/TiSiN/TiAlN, and commercially available TiN/TiAlN) and cutting parameters (cutting speed, feed rate, and depth of cut) on cutting forces and surface roughness were investigated during face milling of AISI O2 cold work tool steel (～61 HRC). The experiments were conducted based on 3¹³ factorial design by response surface methodology, and response surface equations of cutting forces and surface roughness were obtained. In addition, the cutting forces obtained with the coated and uncoated tools were compared. The results showed that the interaction of coating type and depth of cut affects surface roughness. The hard coating type has no significant effect on cutting forces, while the cutting force F _z is approximately two times higher in the case of uncoated tool.     

Atomic Force Microscope Cantilever Flexural Stiffness Calibration: Toward a Standard Traceable Method

The evolution of the atomic force microscope into a useful tool for measuring mechanical properties of surfaces at the nanoscale has spurred the need for more precise and accurate methods for calibrating the spring constants of test cantilevers. Groups within international standards organizations such as the International Organization for Standardization and the Versailles Project on Advanced Materials and Standards (VAMAS) are conducting studies to determine which methods are best suited for these calibrations and to try to improve the reproducibility and accuracy of these measurements among different laboratories. This paper expands on a recent mini round robin within VAMAS Technical Working Area 29 to measure the spring constant of a single batch of triangular silicon nitride cantilevers sent to three international collaborators. Calibration techniques included reference cantilever, added mass, and two forms of thermal methods. Results are compared to measurements traceable to the International System of Units provided by an electrostatic force balance. A series of guidelines are also discussed for procedures that can improve the running of round robins in atomic force microscopy.     

Investigation of machining performance in high-pressure jet assisted turning of Inconel 718: An experimental study

This paper investigates the application of the high-pressure jet assistance (HPJA) in rough turning of Inconel 718 with coated carbide tools. The region of operability, which sets the boundaries of the process parameters, has been experimentally determined using the tool–material pair (TMP) methodology. The assessment of HPJA machining performance is based on response surface methodology (RSM), which integrates a design of experiment (DOE) and a regression modelling technique for fitting a model to experimental. This leads to a new insight into the influence of the cutting process on chip breakability, cutting forces, contact length, surface finish and tool temperature, which are the key machining performance measures.     

Capability of high pressure cooling in the turning of surface hardened piston rods

An experimental study was performed to investigate the capabilities of dry, conventional and high pressure cooling (HPC) in the turning of surface hardened piston rods used in fluid power applications. Machining experiments were performed using coated carbide tools at cutting speeds up to 160 m/min. The cooling capabilities are compared by monitoring of chip breakability, process regions of operability, cooling efficiency, tool wear, tool life and cutting forces. Test results showed that dry cutting could not be performed due to long and ductile chips that were formed for all investigated cutting conditions. In comparison to conventional cooling the significant increase of cutting speed and feed rate region of operability was recorded when machining with HPC. Tool life analysis proved a five times increase in tool life when machining with HPC. Furthermore HPC also improved chip breakability and reduced coolant consumption.     

Prognostic factors in metastatic melanoma

BACKGROUND: Each year, 6000 people die in the United States from metastatic melanoma. Further study of factors affecting the prognosis of patients with this disease is needed. METHODS: The authors analyzed response and survival data from 635 patients who had entered three Eastern Cooperative Oncology Group trials for metastatic melanoma. RESULTS: Factors associated with poorer survival after study entry included poor performance status and the presence of symptoms, such as reduced appetite, fever, or nausea/vomiting. Male patients had poor survival, as did patients entering the study less than 1 year after a documented recurrence to study entry. As expected, characteristics of the initial primary disease (treatment and symptoms) had little association with survival after entering the advanced disease protocol. Two summary measures of the extent of metastatic involvement had a strong influence on survival. These were the number of nonbone metastases and the clinician's assessment as to the most significant metastatic site. Patients with the liver as their clinically most significant metastatic site had a poorer prognosis than those otherwise classified, including those with central nervous system metastases. The prognosis also worsened with an increasing number of sites of nonbone metastases, including skin and soft tissue. Tumor response occurred in only 11% of the patients. Patients with poor performance status and those with lung involvement had a significantly lower response rate than did others. Although the frequency of response was low, patients with objective responses survived significantly longer than did the nonresponders (based on an analysis appropriately adjusted for the time of response using a time-dependent proportional-hazards model). CONCLUSIONS: These results provide useful guidelines for the design and analysis of clinical trials in metastatic melanoma.     

Prognostic factors for survival in patients with brain metastases from renal cell carcinoma

BACKGROUND: Patients presenting with brain metastases from renal cell carcinoma portend a poor prognosis, with a reported median survival of 4-6 months. Given their short life expectancy, these patients generally have been excluded from clinical trials that assess the efficacy of medical treatments. However, clinical impression suggests that some patients may achieve long term palliation. METHODS: The clinical features of 68 patients who were treated at the Institut Gustave Roussy for brain metastases from renal cell carcinoma were collected retrospectively. Using univariate and multivariate analyses, a prognostic model based on independent prognostic factors was established. An external data set of 57 patients was used to validate the model. RESULTS: The median survival was 7 months. On univariate analysis survival was related significantly to the following adverse prognostic factors: no initial nephrectomy, left side and temporal location of brain metastases, presence of fever or weight loss, erythrocyte sedimentation rate > 50 mm/h, and time from initial diagnosis to brain metastases < or = 18 months. Multivariate analyses identified the previous variable as well as the presence of other visceral metastases as independent prognostic factors. Forty-four patients (65%) with no or 1 adverse prognostic factor (average risk group) had a median survival of 8 months and a 26% 1-year survival rate. Twenty-four patients (35%) with 2 adverse prognostic factors (poor risk group) had a median survival of 3 months and a 1-year survival rate of 9%. This model proved to be discriminant in an external data set; the median survival of patients assigned to the average risk group was 11 months (46% 1-year survival rate) compared with 4 months (9% 1-year survival rate) for patients assigned to the poor risk group. CONCLUSIONS: Patients presenting with brain metastases from renal cell carcinoma and poor risk prognostic factors are highly unlikely to benefit from medical treatments except symptomatic procedures. Conversely, the enrollment of patients with average risk prognostic factors into clinical trials dealing with chemotherapy or immunotherapy may be considered.     

Accumulation and depuration of tetramethyllead by rainbow trout

Tetramethyllead was found very toxic especially to juvenile rainbow trout (Salmo gairdneri). It was accumulated rapidly from the water by the fish and the highest concentration was found in the lipid layer of the intestine. Depuration of Me₄Pb from the fish organs was initially quite rapid, followed by a slower decrease and eventually reaching residual levels. Environmental concentrations of Me₄Pb detected in the fishery products thus represent a balance between uptake and depuration of this compound in fish.In conjunction with this study, a dosing system for exposing rainbow trout to Me₄Pb was developed.