Laboratory investigations of cutting processes applied to coal-winning machines

1968 ◽  
Vol 3 (3) ◽  
pp. 232-243 ◽  
Author(s):  
C D Pomeroy ◽  
J H Brown
Keyword(s):  
Cutting Forces ◽  
Laboratory Experiments ◽  
Cutting Process ◽  
Laboratory Findings ◽  
Cutting Mechanics ◽  
Cutting Zone ◽  
Laboratory Investigations ◽  
Cutting Processes

Laboratory experiments on cutting mechanics in coal are described, and the conclusions reached are tested in underground trials on standard coal-winning machines. In general the laboratory findings are verified but such discrepancies as are observed are attributed to the fact that in the laboratory the cutting process is studied independently of the flow of broken coal from the cutting zone, whilst in some underground applications the forces and power needed to move and cause secondary degradation of the extracted coal can swamp the true cutting forces.

Electrical Current at Metal Cutting Process: A Literature Review

2015 ◽  
Vol 808 ◽  
pp. 40-47 ◽  
Author(s):  
Raluca Daicu ◽  
Gheorghe Oancea
Keyword(s):  
Literature Review ◽  
Cutting Forces ◽  
Metal Cutting ◽  
Electrical Current ◽  
Cutting Edge ◽  
Cutting Process ◽  
Metallic Materials ◽  
Cutting Zone

Processing metallic materials by cutting using good electricity conductor cutting edges it appears an electrical current due mainly to the temperature in the cutting zone. Analyzing of the electrical current the information about the unfolding mode of the cutting process can be obtained. The cutting electrical current can be used in several applications: the estimation of the temperature in the cutting zone, the estimation of the cutting forces, the identification of the wear state of the cutting edge etc. The first researches were started in Russia and they were based on the utilization of the cutting electrical current to measure the temperature in the cutting zone. Afterwards, other applications were identified in the literature and the researches were extended in other countries like India, Japan, USA, Brazil, France, Bangladesh and Romania. This paper presents a review of the researches about the electrical current which appears at cutting process.

Soil Cutting Processes: The Cutting of Water Saturated Sand

2011 ◽  
Author(s):  
Sape A. Miedema
Keyword(s):  
Pore Water ◽  
Cutting Forces ◽  
Water Vapor Pressure ◽  
Cutting Process ◽  
Shear Stresses ◽  
Saturated Sand ◽  
Pore Water Pressures ◽  
Offshore Industry ◽  
Cutting Processes ◽  
Water Saturated

The cutting process in water saturated sand has been the subject of research in the dredging industry for decades already. The Dutch dredging industry started this research in the sixties, resulting in a number of models in the seventies and eighties (van Leussen & van Os (1987) and Miedema (1987 and later). The application of the theory in the offshore industry is rare, although Palmer (1999) used it. In the last decades trenching has been a practice where these theories can be applied and with the tendencies of working in deeper water and in arctic conditions it is useful to try to combine the knowledge from the dredging and the offshore industry regarding cutting processes. The cutting process in water saturated sand is dominated by the phenomenon of dilatancy. Due to shear stresses, the porosity of the sand increases, resulting in an absolute decrease of the pore water pressures. Since the soil stresses are a constant, and equal to the sum of the grain stresses and the pore water stresses, this implies that the grain stresses increase with decreasing pore water stresses. This results in much higher cutting forces. The decrease of the pore water stresses is limited by the water vapor pressure and so are the cutting forces. At shallow waters, the pore water may start to cavitate if the strain rates are high enough, but at very deep water this will probably not occur. In this paper the basics of the cutting theory are explained. This cutting theory however requires a lot of finite element calculations in order to determine the pore water pressures. The paper gives simplification that allows the user to apply the theory with the help of pre-calculated coefficients.

Predicting the High Speed Cutting Process of Titanium Alloy by Finite Element Method

2011 ◽  
Author(s):  
Xiangqin Zhang ◽  
Xueping Zhang ◽  
A. K. Srivastava
Keyword(s):  
Finite Element ◽  
Cutting Forces ◽  
High Speed ◽  
Cutting Temperature ◽  
Chip Morphology ◽  
Cutting Process ◽  
Fe Model ◽  
Dry Cutting ◽  
Friction Coefficients ◽  
Machining Conditions

To predict the cutting forces and cutting temperatures accurately in high speed dry cutting Ti-6Al-4V alloy, a Finite Element (FE) model is established based on ABAQUS. The tool-chip-work friction coefficients are calculated analytically using the measured cutting forces and chip morphology parameter obtained by conducting the orthogonal (2-D) machining tests. It reveals that the friction coefficients between tool-work are 3∼7 times larger than that between tool-chip, and the friction coefficients of tool-chip-work vary with feed rates. The analysis provides a better reference for the tool-work-chip friction coefficients than that given by literature empirically regardless of machining conditions. The FE model is capable of effectively simulating the high speed dry cutting process of Ti-6Al-4V alloy based on the modified Johnson-Cook model and tool-work-chip friction coefficients obtained analytically. The FE model is further validated in terms of predicted forces and the chip morphology. The predicted cutting force, thrust force and resultant force by the FE model agree well with the experimentally measured forces. The errors in terms of the predicted average value of chip pitch and the distance between chip valley and chip peak are smaller. The FE model further predicts the cutting temperature and residual stresses during high speed dry cutting of Ti-6Al-4V alloy. The maximum tool temperatures exist along the round tool edge, and the residual stress profiles along the machined surface are hook-shaped regardless of machining conditions.

Modelling of the Deburring Process

2006 ◽  
Vol 5-6 ◽  
pp. 367-374
Author(s):  
C. G. Dumitraş
Keyword(s):  
Central Composite Design ◽  
Cutting Force ◽  
Cutting Forces ◽  
Cutting Process ◽  
Central Composite ◽  
The Way

Due to robotic deburring development, the research gains a new orientation and focused on the cutting forces and the chip control. The present paper will emphasize the main difference which occurs between the normal cutting process and the deburring process, the way it develops and the parameters which characterize this process. Also the dynamics of the process are considered. Based on a central composite design one determine a relation between the geometry of the tool, workpiece hardness and cutting force.

Research of machining forces and technological features of cast PA6, POM C and UHMW-PE HD 1000

2010 ◽  
Vol 1 (1) ◽  
pp. 136-143
Author(s):  
Robert Keresztes ◽  
Gabor Kalacska
Keyword(s):  
Injection Molding ◽  
Cutting Force ◽  
Mechanical Engineering ◽  
Cutting Process ◽  
Engineering Practice ◽  
Serial Production ◽  
Machining Forces ◽  
Engineering Plastics ◽  
Machine Elements ◽  
Cutting Processes

Nowadays parts made of up-to-date engineering plastics are used more and morein mechanical engineering practice. These machine-elements are produced most frequentlyby injection molding or by one cutting process. The injection molding technology are usedgenerally for great number of pieces, in case of serial production while cutting processes arepreferred to piece (unit) or smaller number production.We used lathe and measured the main- and feeding-directional cutting force at differentengineering polymers (cast PA6, POM C and UHMW PE HD 1000). The analysis made canbe well used in practice.

scholarly journals Analysis of Forces in Vibro-Impact and Hot Vibro-Impact Turning of Advanced Alloys

2011 ◽  
Vol 70 ◽  
pp. 315-320 ◽  
Author(s):  
Riaz Muhammad ◽  
Agostino Maurotto ◽  
Anish Roy ◽  
Vadim V. Silberschmidt
Keyword(s):  
Finite Element ◽  
Cutting Forces ◽  
Three Dimensional ◽  
Element Model ◽  
Machining Process ◽  
Strain Rates ◽  
Machining Processes ◽  
Machined Surface ◽  
Cutting Zone

Analysis of the cutting process in machining of advanced alloys, which are typically difficult-to-machine materials, is a challenge that needs to be addressed. In a machining operation, cutting forces causes severe deformations in the proximity of the cutting edge, producing high stresses, strain, strain-rates and temperatures in the workpiece that ultimately affect the quality of the machined surface. In the present work, cutting forces generated in a vibro-impact and hot vibro-impact machining process of Ti-based alloy, using an in-house Ultrasonically Assisted Turning (UAT) setup, are studied. A three-dimensional, thermo-mechanically coupled, finite element model was developed to study the thermal and mechanical processes in the cutting zone for the various machining processes. Several advantages of ultrasonically assisted turning and hot ultrasonically assisted turning are demonstrated when compared to conventional turning.

scholarly journals Residual Stresses Distribution Posterior to Welding and Cutting Processes

2021 ◽  
Author(s):  
Asma Manai
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Weld Seam ◽  
Considerable Change ◽  
Cutting Process ◽  
Local Material ◽  
Weld Residual Stress ◽  
Exact Size ◽  
Cutting Processes ◽  
Welding Processes

Welding is a joining process that leads to considerable change in the local material and the formation of welding residual stresses (RS). Welding residual stresses can be compressive (beneficial for the fatigue life) or tensile (harmful for the fatigue life). In this chapter, a probabilistic analysis of residual stresses distribution posterior to welding processes is carried out. Several researchers stated that the type of the introduced stresses either compressive or tensile depends on several factors. Some of these factors are listed in this chapter. Welding of mega-structures is carried out in the workshops, then a cutting process takes place to construct the exact size of the structural components. This cutting process has a significant effect on the weld residual stresses re-distribution. A study of the re-distribution of the weld residual stress after cutting was performed. It was found that independent of the weld seam length, the residual stresses re-distributed up to 60 % of the weld seam length.

scholarly journals Clinical Characteristics and Outcomes of Diabetic COVID-19 patients in Kuwait

2020 ◽  
Author(s):  
Abdullah Alshukry ◽  
Mohammad Bu Abbas ◽  
Yaseen Ali ◽  
Barrak Alahmad ◽  
Abdullah A. Al-Shammari ◽  
...  
Keyword(s):  
Clinical Characteristics ◽  
Clinical Laboratory ◽  
Fasting Blood Glucose ◽  
List Type ◽  
Laboratory Findings ◽  
Reactive Protein ◽  
Patients With Diabetes ◽  
Laboratory Investigations ◽  
Insight Into ◽  
Variable Clinical Presentation

AbstractBackgroundCOVID-19 has a highly variable clinical presentation, ranging from asymptomatic to severe respiratory symptoms and death. Diabetes seems to be one of the main comorbidities contributing to a worse COVID-19 outcome.ObjectiveIn here we analyze the clinical characteristics and outcomes of diabetic COVID-19 patients.MethodsIn this single-center, retrospective study of 417 consecutive COVID-19 patients, we analyze and compare disease severity, outcome, associated complications, and clinical laboratory findings between diabetic and non-diabetic COVID-19 patients.ResultsCOVID-19 patients with diabetes had more severe outcomes and higher mortality than non-diabetic COVID-19 patients. Diabetic COVID-19 patients had significantly higher prevalence of comorbidities, such as hypertension. Laboratory investigations also highlighted notably higher levels of C-reactive protein in diabetic COVID019 patients and lower estimated glomerular filtration rate. They also showed a higher incidence of complications.ConclusionDiabetes could be a major contributor to worsening outcomes in COVID-19 patients. Understanding the pathophysiology underlining these findings could provide insight into better management and improved outcome of such cases.Highlights of the StudyA significantly higher proportion of Diabetic COVID-19 patients required admission to the ICU.Higher fasting blood glucose was associated with higher risk of COVID-19 associated mortality.Diabetic COVID-19 patients had significantly higher incidence of complications including sepsis, ARDS, cardiac failure and renal failure.

Effect of Large Cross-Section Oxygen-Propane Flame Cutting on Microstructure in Heat-Affected Zone

2013 ◽  
Vol 274 ◽  
pp. 249-252
Author(s):  
Zhi Xin Wang ◽  
Yong Kui Han ◽  
Yong Qiu Chen
Keyword(s):  
Cross Section ◽  
Heat Affected Zone ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Pressure Vessels ◽  
Manufacturing Industries ◽  
Cutting Process ◽  
Pure Oxygen ◽  
Cutting Processes ◽  
34Crnimo6 Steel

Many metal-manufacturing industries include oxyfuel gas cutting among their manufacturing processes because cutting was often used in metal-cutting processes, specifically in the large castings and forgings and the fabrication of pressure vessels. The oxyfuel gas cutting process uses controlled chemical reactions to remove preheated metal by rapid oxidation in a stream of pure oxygen. Previous research has demonstrated microstructure in heat-affected zone varied depending on the gas used for the combustion as well as the cutting speed (Vc) used during the process. In this research, 34CrNiMo6 steel of 900 mm in thickness and 45 carbon steel of 450 mm in thickness were cut using an oxygen-propane flame cutting process. Then, macroscopic morphology and microstructure test were done to analyze the influence of the thickness of cutting cross-section. The results showed, in general, the width of heat-affected zone increased with the thickness of cutting cross-section. Also, it was demonstrated that heat-affected zone in the bottom and top section was wider than others.

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