Comparative Analysis of Chatter Vibration Frequency in CNC Turning of AISI 4340 Alloy Steel with Different Boundary Conditions

In this study, an experimental investigation of chatter vibration frequency in CNC turning of AISI 4340 Alloy Steel material was carried out, with uncoated carbide tool insert (TPG 322) on Fanuc 0i TC CNC lathe machine, with two boundary conditions. The experimental design adopted for this study is the Taguchi parameter design with L9 orthogonal array. Turning tests were carried out on nine samples of the test-piece material for the clamped-free (C-F) condition, and the tests replicated on another set of nine test-pieces for Clamped-Pinned, so-called C-SS workpiece boundary condition.  Chatter vibration frequencies were measured using MXC-1600 digital frequency counter and the frequency plots continuously analysed through DTO 32105 sound signal and frequency analyzer. The main objective is to investigate the process parameters’ performances on the work-piece material of AISI 4340 alloy steel, and to carry out comparisons between the two different boundary conditions vis-à-vis the effects of process parameters which are cutting speed, feed rate and depth of cut on the chatter vibration frequency for the orthogonal turning operation. Chatter vibration frequency values for the C-SS scenario were found to be up to 30% lesser when compared to the C-F machining scenario. Introduction of the tailstock used in pinning the free-end of the slender work-pieces reduced the chances that workpiece would bend; whereas absence of the pinned end means that workpiece may be skewed at an angle in the chuck with increased dynamic deflections at the free end leading to more aggressive workpiece and cutting tool perturbations which are known to favour cutting instability

INVESTIGATION OF CREEP RESPONSES OF SELECTED ENGINEERING MATERIALS

Mechanical Testing, a concept totally ignored previously, is now a major area of concern. Before now, the concept of testing was merely an afterthought of the procurement process. With the advent of science and technology especially of the type seen in our today’s world, the concept of testing is now an integral part of research and development, product design and manufacturing. This work investigated the creep responses of selected engineering materials (Lead, Polypropylene, and Aluminum alloy samples). Procedure for creep testing and analysis of creep properties of engineering materials from test data are reviewed. The experimental results reveal that the creep resistance of PP was the least with a creep rate of 1.66x10-3 min-1 at 33 OC and 14.22 MPa. Typical values of Creep Strain Rates obtained are 23.5x10-3 min-1 for Pb (BS 1178) at 33 OC and 10.34 MPa; and 4.8X10-6 hr-1 for Wrought Al alloy at 200 oC and 54.58 MPa

EVALUATION OF CHATTER VIBRATION FREQUENCY IN CNC TURNING OF 4340 ALLOY STEEL MATERIAL

In this study, an experimental investigation of chatter in CNC turning for 4340 Alloy Steel material was carried out. Empirical study of chatter and critical cutting condition in CNC turning has been conducted through a well- designed three-factor three-level experiment, and regression models developed for chatter frequency prediction with up to 99.5% accuracy for the material. The arising model and the mean-effect plots of the cutting speed, feed rate, and depth of cut against Signal-to-Noise (S/N) ratio indicates that increasing feed rates and depth of cuts would bring about increase in chatter vibration frequency while high cutting speeds would have attenuating effects on chatter vibration frequency, thereby suppressing it. The percentage contribution of the cutting parameters to chatter vibration frequency established, and optimal machining condition for the machine chatter optimization obtained at a cutting speed of 320 m/min, feed rate of 0.05mm/rev and depth of cut of 0.5mm. The optimal chatter vibration frequency for the turning tests was found to be 130.00 Hz. With the obtained optimum input parameters for chatter vibration frequency, production operations will be enhanced

Experimental and Mathematical Modeling for Prediction of Tool Wear on the Machining of Aluminium 6061 Alloy by High Speed Steel Tools

In recent machining operation, tool life is one of the most demanding tasks in production process, especially in the automotive industry. The aim of this paper is to study tool wear on HSS in end milling of aluminium 6061 alloy. The experiments were carried out to investigate tool wear with the machined parameters and todevelopedmathematicalmodelusingresponsesurface methodology.Thevariousmachiningparametersselected fortheexperimentarespindlespeed(N),feedrate(f),axialdepthofcut(a)andradialdepthofcut(r).Theexperimentwasdesignedusingcentralcompositedesign(CCD) inwhich31sampleswererunonSIEG3/10/0010CNCend milling machine. After each experiment the cutting tool wasmeasuredusingscanningelectronmicroscope(SEM). Theobtainedoptimummachiningparametercombination arespindlespeedof2500rpm,feedrateof200mm/min, axialdepthofcutof20mm,andradialdepthofcut1.0mm wasfoundouttoachievedtheminimumtoolwearas0.213 mm. The mathematical model developed predicted the toolwearwith99.7%whichiswithintheacceptableaccuracyrangefortoolwearpredictio

Effects of Process Parameters on Vibration Frequency in Turning Operations of Perspex Material

Effects of process parameters on vibration frequency of Perspex round plastic bars was investigated experimentally under clamped - free (C - F) boundary condition during turning operation. Mathematical models were developed using Taguchi L9 orthogonal array design. Spindle speed (V), feed rate (f), and depth of cut (d) were selected as input variables in order to predict the effects of vibration frequency on the work-piece. Nine samples were run in a CNC lathe machine, and each of the experimental result was measured using DTO 32105 frequency analyser and a MXC-1600 digital frequency counter. A minimum vibration frequency of 104.8 Hz was obtained at a cutting speed of 320 m/min, feed rate 0.05 min/rev and at a depth of cut of 0.5 mm. The mathematical model developed shows the accuracy of predicting the vibration frequency to be 99.5% and the various combinations of parameters that results in the minimum vibration frequency were determined. Obtained optimum input parameters for vibration frequency indicated that production operations of Perspex round plastic bars could be enhanc

Experimental and Mathematical Modeling for Prediction of Tool Wear on the Machining of Aluminium 6061 Alloy by High Speed Steel Tools

In recent machining operation, tool life is one of the most demanding tasks in production process, especially in the automotive industry. The aim of this paper is to study tool wear on HSS in end milling of aluminium 6061 alloy. The experiments were carried out to investigate tool wear with the machined parameters and to developed mathematical model using response surface methodology. The various machining parameters selected for the experiment are spindle speed (N), feed rate (f), axial depth of cut (a) and radial depth of cut (r). The experiment was designed using central composite design (CCD) in which 31 samples were run on SIEG 3/10/0010 CNC end milling machine. After each experiment the cutting tool was measured using scanning electron microscope (SEM). The obtained optimum machining parameter combination are spindle speed of 2500 rpm, feed rate of 200 mm/min, axial depth of cut of 20 mm, and radial depth of cut 1.0mm was found out to achieved the minimum tool wear as 0.213 mm. The mathematical model developed predicted the tool wear with 99.7% which is within the acceptable accuracy range for tool wear prediction

Effect of Thermal Processing on the Nutritional Status of Soy Milks and Yoghurts Produced by Enhanced Spontaneous Fermentation

This research was carried out to determine the effects of thermal process of boiling of soy bean seeds on the nutritional status of soy milk and soy yoghurt produced by fermentation. The soybean seeds were de-hulled, boiled and thermally processed to soymilk. Food sweetener (Glucose -D), cassava stabilizer and starter cultures were added to the samples to enhance the spontaneous fermentation. Staphylococcus aureus, Bacillus spp, Escherichia coli, Streptococcus Lactobacillus spp, Aspergillus spp and Saccharomyces spp were isolated from the fermenting samples. The proximate composition showed that the soy yoghurt had more protein content than soymilk while the soymilk had more crude fiber, moisture content, fat content, ash content and carbohydrate. The soy yoghurt was more acidic pH 3.7 than the soy milk pH 6.4. The acidic nature of the soy yoghurt together with other metabolites of Lactic acid bacteria prevented the continued growth of food borne pathogens and spoilers thus ensuring the safety of soy yoghurt. Soy yoghurt can be used as a close substitute for cow milk which is relatively expensive to the rural dwellers

Review: The impact of changing human environment and climate change on emerging and re-emerging parasitic diseases

Emerging infectious and parasitic diseases are the newly identified and previously unknown infections of public health importance while re-emerging diseases, on the other hand, are those that had been brought under control but reappear and increase in alarming rate. The current population explosion, with the consequent urban expansion, or growth of urban slums, and squatter settlements have led to rapid deterioration of human environment. The infrastructural facilities of these settlements already limited in their capacities fail to provide adequate housing, sanitation, health-care and other public utilities. These together with ignorance and human behaviour result in serious changes to our environment to the advantage of these diseases. Some well-intended socioe-conomic development projects, as a result of inadequate ecological assessment and evaluation, have after completion caused untold public health problems. The resulting changes either aggravate the prevalence of some parasitic diseases [re-emergence] or introduce the diseases into new areas by providing new and permanent habitats for the parasites and their vectors as well as disease transmission. The changes in worldís ecosystem are now being joined by human-induced changes to trigger out-breaks of emerging and re-emerging diseases. These changes are linked with human population explosion, rapid international travels, changes in food handling and processing as well as deteriorating public health infrastructure, and drug resistance. The impact of human-induced climate change through industrialization with the consequent depletion of the ozone layer of the environment is now observed to compromise the sustainability of human development as it threatens the ecological support system on which life depends in addition to encouraging the emergence and re-emergence of vector-borne parasitic diseases. The public health and epidemiological implications of these are discussed. Keywords: previously unknown infections, ecosystem, human-induced climate change, re-emergence of parasitic diseases, vector-borne diseases. Nigerian Journal of Parasitology Vol. 28 (2) 2007: pp. 135-14

External and internal morphology of seed germination and seedling establishment in the white Guinea Yam, Dioscorea rotundata poir

No Abstract. Bio-Research Vol. 5 (2) 2007: pp. 269-27

Prevalence of lymphatic complications due to onchocerciasis infection in Imo State, Nigeria

The study was conducted to determine the prevalence of lymphatic complications due to onchocerciasis infection in 38 endemic rural communities in the Imo River Basin, Nigeria. Using standard parasitological and clinical methods of diagnosis, 7,144 consenting individuals aged 5 years and above were examined for Onchocerca volvulus microfilaria and clinical lymphatic symptoms of onchocerciasis. Of the 7,144 individuals, examined, 1,646 (23.0%) were positive for O. volvulus microfilariae, while 1,045 (14.6%) had various degrees of lymphatic complications. The prevalence of lymphatic complications were lymphadenopathy (7.9%), hanging groin (3.2%) and inguinal hernia (3.5%). Subjects 30 years and above had the highest microfilarial densities which coincided with higher prevalences of these lesions suggesting their chronicity. Sex-prevalence showed an insignificant borderline difference, 17.3% in males and 14.3% in females (p > 0.05). Lymphadenopathy and hanging groin were strongly associated with microfilarial density (r = 0.54;