Analysis on Stop-hole Parameters for Fatigue Cracks at Arc Notch in Steel Bridge Deck

Two types of fatigue cracks at arc notch in steel bridge deck were repaired by drilling stop-holes. The effect of stop-holes with different diameters and positions was considered. Based on finite element models, the variation laws of stress distribution and the effects of stress concentration were compared for different stop-hole diameters and positions. Analysis results indicated that stop-hole can effectively improve the stress concentration at crack tip and the fatigue life of components can be considerably increased. The crack-stopping performance enhances with the increase of stop-hole diameter, but large stop-hole cannot effectively retard crack growth. The stop-hole performs well with the location at -0.5D∼0.5D. The maximum stress point still appears at crack tip when the stop-hole is outside or inside the crack. The stop-hole diameter has no effect on the stop-hole location.

Experimental study on the hole quality during abrasive waterjet drilling of CFRP

Abrasive Waterjet (AWJ) machining is considered an excellent alternative to conventional machining processes due to its superb machining characteristics. More specifically, Abrasive Waterjet drilling is nowadays a promising non-conventional process for obtaining high quality holes. In the present study, drilling experiments based on Taguchi L9 orthogonal design method were conducted via AWJ on carbon fiber reinforced polymer (CFRP) plate at various waterjet parameters, namely, different pressure, abrasive mass flow rate and standoff distance values. The purpose of the experiments was to investigate the impact of these process parameters on the quality of holes. The hole quality was determined by measuring the hole diameter error as well as the hole taper. The optical evaluation was implemented with the use of optical microscope and special measuring software. The ANOVA analysis of the results showed a significant influence of standoff distance regarding the hole diameter error and a combined influence of waterjet pressure and standoff distance regarding the hole taper. Furthermore, the optimal process parameter values for the optimization of the hole diameter error and hole taper were determined. The hole quality in terms of defects appearance was also quantitatively inspected, through optical imaging.

PENGARUH ARANG KAYU ULIN SEBAGAI CATALYTIC CONVERTER TERHADAP EMISI GAS BUANG DAN KONSUMSI BAHAN BAKAR PADA MESIN TOYOTA KIJANG 5K

Catalytic Converter adalah pengubah (modifier) yang menggunakan media yang memiliki katalis, dimana media tersebut diharapkan dapat membantu atau mempercepat proses perubahan zat (reaksi kimia) sehingga gas seperti CO dapat dioksidasi menjadi CO2, media katalis kimia pada suhu tertentu, tanpa perubahan atau penggunaan oleh reaksi itu sendiri. Catalytic converter berbahan arang kayu ulin untuk emisi gas buang dan konsumsi bahan bakar. Jenis penelitian ini adalah penelitian eksperimen. Pengujian yang dilakukan pada penelitian ini ada 2 yaitu knalpot tanpa catalytic converter dan knalpot dengan catalytic converter berbahan arang kayu ulin dengan variasi rpm 1500, 2500, 3500. Pengujian emisi gas buang menggunakan alat yang disebut gas analyzer. Berdasarkan hasil penelitian dapat disimpulkan bahwa catalytic converter berbahan arang kayu ulin dengan diameter lubang 20 mm mampu mereduksi emisi CO dengan reduksi sebesar 52,23%, dan emisi HC lubang berdiameter 20 mm dengan jumlah 85,63. Catalytic Converter is a converter (modifier)that uses media that has a catalyst, where the media is expected to help or accelerate the process of changing substances (chemical reactions) so that gases such as CO can be oxidized to CO2, chemical catalyst media at a certain temperature, without change or use by the reaction itself. Catalytic converters made from ironwood charcoal to exhaust emissions and fuel consumption. This type of research is experimental research. There are 2 tests of this research, namely exhaust without catalytic converter and exhaust with catalytic converter made from ironwood charcoal with variations in rpm 1500, 2500, 3500. Examination of exhaust emissions using a device called a gas analyzer. Based on the results of the study it can be concluded that catalytic converters made from ironwood charcoal with a hole diameter of 20 mm were able to reduce CO emissions with a reduction of 52.23%, and HC emissions of a hole diameter of 20 mm with an amount of 85.63,

Application of TOPSIS Method for Prediction of Optimum Design Parameters of Micro Hole Textured Cutting Inserts in Turning of Al-MMC

Metal Matrix Composite (MMC) has better mechanical properties and it is possible to produce near net shape. Aluminum-based MMC (Al-MMC) has challenges in terms of machinability studies and estimation of its optimum process parameters. Alternative cutting fluid research is a challenging area in machining. To avoid, existing hydrocarbon oil-based cutting fluid, textured inserts embedded with a solid lubricant are one of the alternative solutions. Micro hole textured inserts make a hole on the rake face of the cutting tool inserts. Texture includes various important design parameters namely hole diameter, hole depth and pitch between the holes. These optimum parameters influence the machining process. In this work, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method is used to find the optimum design parameters (hole diameter, hole depth and pitch between holes) during turning of Al- MMC. The objective parameters considered are minimization of surface roughness, power consumption and tool flank wear. The optimum combination of these design parameters is obtained by the higher relative closeness value of the TOPSIS method. The result of the investigation revealed that these design parameters are important to obtain improved machining performance. Also, it is understood that the TOPSIS method has an appropriate procedure to solve multiple objective optimization problems in manufacturing industries.

A Newly Developed Empirical Predictive Model for the Dispersed Phase (DP) Holdup in Rotating Disc Contactors

Newly novel developed correlations were derived to predict the dispersed phase (DP) holdup in a rotating disc contactor (RDC) extraction column. DP holdup is one of the significant parameters in the design of liquid–liquid contactors and for calculating their production capacity. Despite the availability of quite a large number of holdup prediction correlations for the RDC, most of these correlations are either general in nature or valid for a limited range of operating conditions. This study conducted an experimental and theoretical investigation of the RDC holdup under the influence of varying geometries, including variations in the dispersed phase distributor, speed of the disc, flow rate, and physical characteristics of the system. The analysis revealed that the holdup decreased with an increasing distributor hole diameter and increased with an increasing disc speed and total flow rate. The effect of the physical properties on the holdup was larger than the effect of the disc speed. Using the measurements of over 150 runs, two RDC column holdup predictive models were proposed and evaluated. The first correlation was derived in terms of the distributor hole diameter, operating parameters, system physical properties, and column geometry. The second correlation excluded the column geometry. These correlations, which consider the distributor hole inlet diameter in predicting the DP holdup for an RDC column, were presented for the first time in this study. The predictive capability of these correlations was evaluated via their standard deviation (SD) and mean average percentage error (MAPE). The respective SD and MAPE of the two correlations were 1.7 and 5.2% for the first correlation and 1.6 and 11.4% for the second.

Influence of Hole Arrangement on the Section of Cavity Formed by Cutting Blast

In order to optimize the arrangement of cutting holes in tunnel blast in Dahongshan Copper Mine, theoretical analysis and numerical simulation were combined to preliminarily determine the diameter of the hollow hole and the distance between the charge hole and the hollow hole during cut blast, which was verified through the field blast test. The research results show that with the increase of the hole diameter, the peak compressive stress of rock surrounding the empty hole gradually decreases, and the peak tensile stress gradually increases, which is consistent with the calculation results; when the hole diameter is 10 cm, the two first blast holes are arranged horizontally and 30 cm from the empty hole, two second blast holes are arranged vertically and 40 cm away from the empty hole, and the four third blast holes are arranged at a horizontal distance of 45 cm and a vertical distance of 45 cm from the empty hole; the contour area in numerical simulation is the maximum. The difference in contour area, contour width, and contour and contour height between the measured value and the simulation result is 5.3%, 3.3%, and 3.4%, respectively, indicating that the combination of theoretical calculation and numerical simulation is suitable for prediction of cavity section after blast in tunnel excavation.

SURVEYING THE EFFECT OF GAS-VENT HOLE DIAMETER AND CLEARANCE BETWEEN PISTON AND CYLINDER ON AUTOMATIC FIRING SYSTEM OF 23mm ЗY23-2

On the basis of analyzing the real model 23mm ЗY23-2, the paper chooses an alternative physics model, building a mathematical modeling dynamics, set up a system of equations and solve to find the cycle of operation on automatic firing system, change some parameters of cylinder and study on its effect to do automatic firing system; besides surveying the effect of gas-vent hole diameter and clearance between piston and cylinder on automatic firing system of 23mm ЗY23-2. The research method is based on the calculation theory to ensure compliance with the manufacturer's gun design and use documents.

Differentiated Approach to Strategies of Surgical Treatment of Idiopathic Macular Holes

Background. 25G or 27G three-port vitrectomy, followed by staining and removal of the internal limiting membrane with vitreous cavity air or gas tamponade, is one of the main modern vitreoretinal surgery principles for primary macular holes. However, not all patients manage to obtain a functional outcome when the anatomical outcome is achieved. Purpose. To present clinical cases of surgical treatment of idiopathic macular holes (IMH) exhibiting a differentiated approach.Matherials and methods. This article analyzes clinical cases of four patients with primary idiopathic macular holes, differing in terms of development, hole diameter and the presence of comorbidities. Results. The results of surgical treatment were evaluated 14 days and 1 month after surgery. In all clinical cases, surgical treatment resulted in a positive anatomical outcome by blocking a retinal defect. Best corrected visual acuity increased, on average, from 0.08 ± 0.05 to 0.4 ± 0.05.Conclusion. The analysis of the presented clinical cases clearly demonstrates the need for a timely and differentiated approach to the treatment of patients with IMH, that considers etiology of the pathological process, period of its existence as well as concomitant and general somatic pathologies.