Effect of indirect cryogenic cooling on the machining accuracy and tool vibration in the turning of polysulfone

2021 ◽  
pp. 1-25
Author(s):  
Yongqing Wang ◽  
Siqi Wang ◽  
Kuo Liu ◽  
Yongquan Gan ◽  
Lingsheng Han ◽  
...  
Keyword(s):  
Cryogenic Cooling ◽  
Machining Accuracy ◽  
Cryogenic Machining ◽  
Tool Vibration ◽  
Internally Cooled ◽  
Cutting Deformation ◽  
The Mean ◽  
Common Problems ◽  
Microscopic Morphology ◽  
Machined Surfaces

Abstract Cutting deformation and cracks are common problems during the machining of precise polymer parts. This paper aims to explore the effect of different conditions on the contour profile of machined surfaces and tool vibration. Turning experiments of polysulfone (PSU) were performed under three conditions: dry, conventional flood cooling, and indirect cryogenic cooling. Then the formation mechanism of machined surfaces contour profile under different cutting conditions was clarified by the Eyring equation from the perspective of molecular chains relaxation time. Furthermore, extension models of crazing and cracks were proposed through the microscopic morphology of machined surfaces and the discriminant formula of crazing generation to explain the differences in tool vibration. The results indicated that the indirect cryogenic cooling condition with the internally cooled cutting tool could significantly improve the machinability of polysulfone, and have an excellent performance on the contour profile of machined surfaces with and the inhibition of crazing. Compared with dry and conventional flood cooling, indirect cryogenic cooling could reduce the mean of the Contour profile (Ra) by 40.3% and 30.1% and the machining accuracy error by 41% and 83%. The indirect cryogenic cooling method proposed in this work provides a reference for the cryogenic machining for polymers.

scholarly journals Research on Stagger Coupling Mode of Pulse Duration and Tool Vibration in Electrochemical Machining

2018 ◽  
Vol 8 (8) ◽  
pp. 1296 ◽  
Author(s):  
Xiaochen Jiang ◽  
Jia Liu ◽  
Di Zhu ◽  
Mingming Wang ◽  
Ningsong Qu
Keyword(s):  
Pulse Duration ◽  
Feed Rate ◽  
Electrochemical Machining ◽  
Machining Accuracy ◽  
Electrode Gap ◽  
Tool Vibration ◽  
Coupling Mode ◽  
Machining Localization ◽  
Electrolysis Products ◽  
Gas Void Fraction

Tuning the coupling of pulse duration and tool vibration in electrochemical machining (PVECM) is an effective method to improve machining accuracy and surface quality. In general, the pulse is set at the same frequency as the tool vibration, and a symmetrical distribution is attained at the minimum inter-electrode gap. To analyse the characteristics of the electrolyte fluid flow and of the electrolysis products in the oscillating inter-electrode gap, a dynamic simulation of the PVECM process was carried out. The simulation results indicated that the electrolyte pressure and gas void fraction when the pulse arrived as the inter-electrode gap was narrowing clearly differed from those when the inter-electrode gap was expanding. Therefore, in addition to the traditional symmetry coupling mode, two other coupling modes called the pre-position and the post-position coupling modes are proposed which use a pulse either just before or just after the minimum inter-electrode gap. Comparative experiments involving the feed rate and machining localization were carried out to evaluate the influence of the three coupling modes. In addition, current waveforms were recorded to analyse the differences between the three coupling modes. The results revealed that the highest feed rate and the best machining localization were achieved by using the pre-position coupling mode.

Cryogenic Machining of Titanium Ti-5553 Alloy

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Yusuf Kaynak ◽  
Armin Gharibi
Keyword(s):  
Titanium Alloy ◽  
Tool Wear ◽  
Cutting Temperature ◽  
Cryogenic Cooling ◽  
Machining Process ◽  
Dry Machining ◽  
Cryogenic Machining ◽  
Machining Performance ◽  
Wide Range ◽  
New Generation

Titanium alloy Ti-5Al-5V-3Cr-0.5Fe (Ti-5553) is a new generation of near-beta titanium alloy that is commonly used in the aerospace industry. Machining is one of the manufacturing methods to produce parts that are made of this near-beta alloy. This study presents the machining performance of new generation near-beta alloys, namely, Ti-5553, by focusing on a high-speed cutting process under cryogenic cooling conditions and dry machining. The machining experiments were conducted under a wide range of cutting speeds, including high speeds that used liquid nitrogen (LN2) and carbon dioxide (CO2) as cryogenic coolants. The experimental data on the cutting temperature, tool wear, force components, chip breakability, dimensional accuracy, and surface integrity characteristics are presented and were analyzed to evaluate the machining process of this alloy and resulting surface characteristics. This study shows that cryogenic machining improved the machining performance of the Ti-5553 alloy by substantially reducing the tool wear, cutting temperature, and dimensional deviation of the machined parts. The cryogenic machining also produced shorter chips as compared to dry machining.

scholarly journals Precision Machining of Nimonic C 263 Super AlloyUsing WEDM

Coatings ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 590
Author(s):  
Katerina Mouralova ◽  
Libor Benes ◽  
Josef Bednar ◽  
Radim Zahradnicek ◽  
Tomas Prokes ◽  
...  
Keyword(s):  
Electrical Discharge ◽  
Cutting Speed ◽  
Machining Process ◽  
Precision Machining ◽  
Machining Accuracy ◽  
Pulse On Time ◽  
Pulse Off Time ◽  
Super Alloy ◽  
Machined Surfaces

Wire electrical discharge machining (WEDM) is an unconventional and very efficient technology for precision machining of the Nimonic C 263 super alloy, which is very widespread, especially in the energy, aerospace and automotive industries. Due to electrical discharge, defects in the form of cracks or burned cavities often occur on the machined surfaces, which negatively affect the correct functionality and service life of the manufactured components. To increase the efficiency of the machining of Nimonic C 263 using WEDM, in this study, extensive design of experiments was carried out, monitoring input factors in the form of machine parameters like Pulse off time, Gap voltage, Discharge current, Pulse on time and Wire feed, the output of which was comprehensive information about the behaviour of such machined surfaces, which allowed the optimization of the entire machining process. Thus, the optimization of the Cutting speed was performed in relation to the quality of the machined surface and the machining accuracy, as well as an analysis of the chemical composition of the machined surfaces and a detailed analysis of the lamella using a transmission electron microscope. A detailed study of the occurrence of surface or subsurface defects was also included. It was found that with the help of complex optimization tools, it is possible to significantly increase the efficiency of the machining of the Nimonic C 263 super alloy and achieve both financial savings in the form of shortened machine time and increasing the quality of machined surfaces.

scholarly journals Quality of life in adolescents with primary headaches

2013 ◽  
Vol 53 (6) ◽  
pp. 350
Author(s):  
Naomi Riahta ◽  
Muhammad Ali ◽  
Bistok Saing ◽  
Yazid Dimyati ◽  
Johannes Saing
Keyword(s):  
Quality Of Life ◽  
Cross Sectional Study ◽  
Primary Headaches ◽  
Sectional Study ◽  
Quality Oflife ◽  
Cross Sectional ◽  
The Mean ◽  
Common Problems

Background Headaches are common problems in adults,adolescents, and children. Headaches impact a child's life, theirfamily life, and even society. An assessment of quality of life inadolescents with primary headaches may help to determine actionsnecessary to improve the quality of life of these patients.Objective To assess the quality oflife of adolescents with primaryheadach es compared to healthy adolescents.Methods We conducted a cross-sectional study in December2009 on adolescents aged 13 to 18 years. The headache groupconsisted of children with primary headaches according to theInternational Classification of Headache Disarders and the controlgroup consisted of healthy adolescents. Subjects were selected byconsecutive sampling, with 75 subjects in each group. Subjectsfilled the Pediatric Quality of Life Inventary version 4.0 (PedsQL4.0) questionnaire.Results The mean PedsQL total score was significantly lowerin the headache group than in the contra 1 group [ l 7 5. 7 vs.392.2, respectively, (95%CI of differences -28.l to -219.3, P =0.001)]. However, out of23 items in the questionnaire, 9 werenot significantly different between the headache and controlgroups.Conclusions Primary headaches in adolescents is associatedwith lower quality of life. Most quality of life domains scoresare significantly lower in adolescents with primary headachescompared to those without primary headaches.

Surface Integrity and Fatigue Strength of Hard Milled Surfaces

2011 ◽  
Author(s):  
W. Li ◽  
Y. B. Guo ◽  
M. E. Barkey ◽  
C. Guo ◽  
Z. Q. Liu
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Surface Integrity ◽  
Endurance Limit ◽  
Flank Wear ◽  
Machining Accuracy ◽  
Tool Flank Wear ◽  
Radial Depth ◽  
Aisi H13 Tool Steel ◽  
Machined Surfaces

Tool flank wear during hard milling adversely affects surface integrity and, therefore, fatigue strength of machined components. Surface integrity and machining accuracy deteriorate when tool wear progresses. In this paper, surface integrity and its impact on endurance limit of AISI H13 tool steel (50 ± 1 HRC) by milling using PVD coated tools are studied. The evolutions of surface integrity including surface roughness, microhardness and microstructure were characterized at three levels of tool flank wear (VB = 0, 0.1mm, 0.2mm). At each level of tool flank wear, the effects of cutting speed, feed, and radial depth-of-cut on surface integrity were investigated respectively. Fatigue endurance limits of the machined surfaces at different reliability levels were calculated and correlated with the experimentally determined fatigue life. The good surface finish and significant strain-hardening on the machined surfaces enhance endurance limit, which enables machined components have a fatigue life over 106 cycles.

scholarly journals Determining Model for Maximum Blood Request (MSBOS) for Surgery: An Elective Surgery in Imam Ali Hospital, Zahedan, Iran

2019 ◽  
Author(s):  
Seyed Mehdi Hashemi ◽  
Seyed Hossein Soleimanzadeh Mousavi ◽  
Zeinab Tavakolikia
Keyword(s):  
Surgical Procedures ◽  
Blood Donation ◽  
Elective Surgery ◽  
Cross Sectional Study ◽  
Blood Transfusions ◽  
Hernia Surgery ◽  
Cross Sectional ◽  
Elective Surgical Procedures ◽  
The Mean ◽  
Common Problems

Background: Nowadays, excessive blood intake is one of the most common problems in educational hospitals, causing issues such as the lack of proper distribution of blood products among centres, increases in costs and blood bank workloads. So, programs such as a Maximum Surgical Blood Ordering Schedule (MSBOS) were introduced to design a blood ordering schedule, which is a guide to normal transfusion needs for common surgical procedures.  Materials and Methods: This study was a descriptive cross-sectional study. The sampling method was designed and distributed among all sectors of the hospital. Each sector according to the demand for blood and cross-matched transfused units entered the rate of wasted and unused blood bags on the related forms. This study was performed on 1568 patients, of whom 562 (35/84%) were given blood transfusions. Results: The aim of this study was to determine the pattern for the maximum surgical blood order schedule (MSBOS) for elective surgical procedures/in elective surgery cases in Imam Ali Hospital, Zahedan. This study was performed on 1568 patients, of whom 562 (35/84%) were given blood transfusions. The mean C/T ratio was 1.61 ± 0.99, the mean TI was 0.61 ± 0.38, and the mean T index was 36.4 ± 30.16%. Conclusion: In general, only 55% of the blood units were used. Hernia surgery, thyroidectomy, and patients with renal problems had the greatest number of wasted units. Therefore, according to the results, indications of blood donation should be made correctly by health care personnel in all patients requiring a blood transfusion, and if there is an increased number of indications, packed cells are requested.  

scholarly journals Microscopic morphology and testis morphometry of captivity-bred Adult bullfrogs (Lithobates catesbeianus Shaw, 1802)

2009 ◽  
Vol 52 (6) ◽  
pp. 1461-1472 ◽  
Author(s):  
Jaqueline Carlos ◽  
Sérgio Luis Pinto da Matta
Keyword(s):  
Young Adult ◽  
Adult Male ◽  
Leydig Cell ◽  
Sertoli Cells ◽  
Rainy Season ◽  
Leydig Cells ◽  
Lithobates Catesbeianus ◽  
Nuclear Diameter ◽  
The Mean ◽  
Microscopic Morphology

The aim of this work was to study the testicular morphometry of captivity-bred adult bullfrogs. Fifteen young adult male were studied, in the rainy season and a lengthy photoperiod. The GSI was established at 0.15%. The nuclear diameter of germinative and Leydig cells, the nucleolus diameter of Sertoli cells and the area of cysts and tubules were determined and the mean number of ISPC, IISPC and SPT per cyst and the mean number of cysts per tubule was estimated. The nucleoplasmatic proportion of the nucleus of the Leydig cell was 76.22%, indicating less cytoplasmic activity. Eight generations of spermatogonia were found. The spermatogenesis efficiency in meiosis and in mitosis was 63 and 49%, respectively. The spermatogenesis of bullfrog fited in the pattern of other captivity Anurans, with differences as the morphology of Sertoli and Leydig cells nuclei.

An ex-vivo experimental study on optimization of bipolar radiofrequency liver ablation using perfusion-cooled electrodes

2005 ◽  
Vol 46 (5) ◽  
pp. 443-451 ◽  
Author(s):  
J. M. Lee ◽  
J. K. Han ◽  
S. H. Kim ◽  
J. Y. Lee ◽  
K. S. Shin ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Bovine Liver ◽  
Coagulation Necrosis ◽  
Electrode Spacing ◽  
Tissue Impedance ◽  
Electrode Distance ◽  
Bipolar Radiofrequency ◽  
Internally Cooled ◽  
The Mean ◽  
The Ideal

Purpose: To determine optimal parameters for bipolar radiofrequency ablation (RFA) using perfusion-cooled electrodes to create a large ablation volume in ex vivo bovine liver. Material and Methods: Three sets of RF experiments were performed using a 200-Watt generator and two 15-gauge perfusion-cooled or internally cooled electrodes in ex vivo bovine livers. In the first set of experiments, to find the ideal inter-electrode distance for creating large coagulation necrosis, 30 ablation lesions were created by bipolar RFAs at inter-electrode spacings of 3 cm, 4 cm, and 5 cm. In the second set of experiments, to explore the ideal duration of RF application, bipolar RFAs were performed for 10 min and 20 min. In the first and second experiments, 10 lesions were made for each condition with infusion of 6% hypertonic saline (HS) at 2 ml/min. In the third set of experiments, 10 ablation lesions were created by bipolar RFAs using internally cooled electrodes without HS infusion. The mean volume of those ablation lesions was then compared to that of the lesions created by bipolar RFA using perfusion-cooled electrodes in the second experiments. Tissue impedance, dimension, and shape of the ablated areas were compared in each condition. Results: In the first set of experiments, bipolar RFA created a homogeneous oval or spherical-shaped ablation area between the electrodes at 3–5 cm spacing, but showed a more spherical-shaped lesion at 3 cm inter-electrode spacing than at 4 cm and 5 cm spacing. In the second set of experiments, RF energy delivered for 20 min created a larger dimension of coagulation necrosis than energy delivered for 10 min: 107.6±34 cm3 versus 59.5±27 cm3 ( P<0.05). In addition, the mean volume of ablation regions obtained with bipolar RFA using the internally cooled electrode was 47.5±17 cm3, which was significantly less than that with bipolar RFA using perfusion-cooled electrodes ( P<0.05). Conclusion: Bipolar RFA using perfusion-cooled electrodes achieves homogeneous areas of coagulation necrosis between two electrodes, preferably at 3 or 4 cm inter-electrode distance for 20 min, and is better in creating large coagulation necrosis than bipolar RFA using internally cooled electrodes.

Foam bubble size is significantly influenced by sclerosant concentration for polidocanol but not sodium tetradecyl sulphate

2021 ◽  
pp. 026835552199501
Author(s):  
Kaichung Wong ◽  
David Ewan Connor ◽  
Osvaldo Cooley Andrade ◽  
Kurosh Parsi
Keyword(s):  
Light Microscopy ◽  
Bubble Size ◽  
Bubble Diameter ◽  
Gas Content ◽  
Low Concentrations ◽  
Primary Determinant ◽  
Spherical Bubbles ◽  
The Mean ◽  
Sodium Tetradecyl Sulphate ◽  
Microscopic Morphology

Objectives To determine the effect of liquid gas fraction (LGF), sclerosant type and concentration, and filter use on foam bubble size and count. Methods Sclerosant foam microstructure was investigated using light microscopy for a range of LGFs (1 + 2, 1 + 4 and 1 + 8), for both sodium tetradecyl sulphate (STS) and polidocanol (POL), at a range of concentrations (0.5–3%), with and without the addition of micro-filters. Foam was generated using a modified Tessari method and placed into wells for analysis by light microscopy. Foam microscopic morphology was photographically documented, and bubble diameters and counts were quantified. Results Spherical bubbles were observed at lower LGF and a trend towards polyhedral morphology was observed at the higher LGF of (1 + 8). The higher gas content in LGF led to larger but fewer bubbles. POL bubble diameters appeared to be more influenced by concentration than STS with smaller bubbles observed at higher concentrations of POL. The mean bubble diameters were slightly larger for STS than POL at the highest concentration of 3% but smaller at lower concentrations of 1% and 1.5%. Conclusions LGF is the primary determinant of bubble diameter and count. In contrast to STS, POL concentration influences the foam bubble size with smaller bubbles generated at higher concentrations of POL and larger bubbles appearing at low concentrations of this agent.

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