Surface quality finish in laser cutting using Taguchi design

Cilj je ovoga rada dobivanje parametrijske kombinacije kako bi se postigla najbolja završna obrada i procijenili učinci odabranih parametara obrade na kvalitetu laserskog rezanja kod uporabe lasera. To pomaže kod proučavanja promjena u parametru reakcije (vrijednost Ra) za različite razine odabranih parametara procesa. U ovom radu korišten je uzorak mekog čelika i kritički je analiziran učinak ključnih parametara kao što su frekvencija laserskog impulsa (brzina ponavljanja impulsa), širina impulsa i brzina rezanja na završnu obradu. Za plan pokusa i analizu parametara rabljen je robusni dizajn tj. frakcijski faktorski plan pokusa s prikladnim ortogonalnim nizom nastavljenim analizom varijance i odnosa zvuka i šuma.The present work aims at obtaining parametric combination to achieve the best surface finish and assess effects of selected process parameters on a laser cut quality for laser cutting. This helps to study the variation in response parameter (Ra value) for various levels of selected process parameters. In the present work mild steel specimen is used and the effect of the key parameters such as laser pulse frequency (pulse repetition rate), laser pulse width and cutting speed on surface finish are critically analysed. For experimental design and parametric analysis robust design is used i.e. a fractional factorial experimental design with an appropriate orthogonal array followed by variance and sound to noise ratio analysis

Critical Damage Analysis of WC-Co Tip of Conical Pick due to Coal Excavation in Mines

WC-Co based tools are widely used in the field of coal and rock excavation because of their unique combination of strength, hardness, and resistance to abrasive wear. Conical pick is one of the coal cutting tools. The tip of the pick is made of WC-Co material. As coal and rock are heterogeneous elements, they pose various constraints during excavation. As a result the tools wear out during the process. Other parameters like cutting techniques, tool orientation, and environmental conditions also affect the tool significantly. The wearing phenomenon greatly reduces the service life of the tools and thereby cuts down the production rate. To prevent such wearing process, it is important to investigate the different wear mechanisms in WC-Co. Simultaneously, there has to be an ongoing endeavour for the development of better quality WC-Co. This paper focuses on different wear mechanisms in a conical pick which has been used in a continuous miner machine for coal cutting. The worn out surface has been observed by using FE-SEM (field emission scanning electron microscopy) and EDS (energy dispersive X-ray spectroscopy). The mechanisms, namely, coal/rock intermixing, cracking and crushing of WC grains, and adhesion of rock particles, have been predominantly investigated in this study. A little indication of corrosive decay in the WC grain has also been reported. The EDS has detected material concentration in a selected area or point of the worn-out surface. The spectrograph confirms the presence of coal/rock materials. Elements such as W, C, Ca, K, O, and Co have been mainly found in different concentrations at different positions

Critical analysis of moving heat source shape for ARC welding process of high deposition rate

Analiza oblika izvora topline važna je za razumijevanje EPP proces zavarivanja. Ovdje se u analitičkom rješenju toplinskog polja pokušalo istražiti odnos procesa utemeljenog na visokoj brzini taloženja poput EPP. Pretpostavljeno je da pokretni izvor topline slijedi Gaussovu raspodjelu. Realne pretpostavke parametara oblika napravljene su radi teorijskog opisa procesa. Iznijeto je mišljenje da je za EPP proces najprikladniji oblik izvora topline približno ovalni.Analysis of heat source shape is important for comprehending Submerged Arc Welding Process. Here an attempt is made to investigate into the analytical solution of the thermal field related to a high deposition rate based process like SAW. It is assumed that a moving heat source follows Gaussian distribution. The realistic assumptions of the shape parameters are made to describe the process theoretically. It is opined that for SAW process the most appropriate heat source shape is approximately oval

Meta-analysis and forest plots for sustainability of heavy load carrier equipment used in the industrial mining environment

It is a common recommendation not to attempt a reliability analysis with a small sample size. However, this is feasible after considering certain statistical methods. One such method is meta-analysis, which can be considered to assess the effectiveness of a small sample size by combining data from different studies. The method explores the presence of heterogeneity and the robustness of the fresh large sample size using sensitivity analysis. The present study describes the approach in the reliability estimation of diesel engines and the components of industrial heavy load carrier equipment used in mines for transporting ore. A meta-analysis is carried out on field-based small-sample data for the reliability of different subsystems of the engine. The level of heterogeneity is calculated for each subsystem, which is further verified by constructing a forest plot. The level of heterogeneity was 0 for four subsystems and 2.23% for the air supply subsystem, which is very low. The result of the forest plot shows that all the plotted points mostly lie either on the center line (line of no effect) or very close to it, for all five subsystems. Hence, it was found that the grouping of an extremely small number of failure data is possible. By using this grouped TBF data, reliability analysis could be very easily carried out.The authors are grateful to FCT—Fundação para a Ciência e Tecnologia—who financially supported this work through the RD Units Project Scope: UIDP/04077/2020 and UIDB/04077/202

Dissimilar friction stir welding of Al to non-Al metallic materials : an overview

The paper presents a comprehensive review on dissimilar friction stir welding (FSW) of Al to non-Al metallic materials, wherein the combination of Al–Mg, Al–Cu, Al-steel and Al–Ti are covered. The summary revealed that FSW is observed as one of the most feasible solutions in the family of welding in case of dissimilar materials combinations of Al to non-Al metallic materials. The challenges such as the formation of intermetallic compounds, defects, and degradation of mechanical properties at the joint area are extensively managed in the case of dissimilar FSW compared to dissimilar conventional welding

Strengthening Effect after Disintegration of Stainless Steel Using Pulsating Water Jet

The article deals with the measurement of micro-hardness of the track by the action of ultrasonic excitation of pulsating water jet. The cumulative effect of liquid matter in the form of droplets concentrated in waveform measurements was provided in horizontal and vertical direction to material core (AISI 304). The material was subjected to pressures of p = 40, 50 and 60 MPa with the actuator working at a frequency of 20,14 kHz and traverse speed v = 1,1 mm/s, v = 0,80 mm/s and v = 0,30 mm/s respectively. The micro hardness measurement was carried out after machining it by pulsating water jet. The values were recorded in the zone located transversally under the trace to the depth of 1,5 mm with 0,1 mm distance between successive points. It was found that the deformation of material was ascertained from the boundary to the outer environment created by pulsating water jet to the inner core of the material. The results indicate that the pressure was the most influential parameter, which was responsible for the deformation strengthening of the material

Heat input effect of friction stir welding on aluminum alloy aa 6061-t6 welded joint

The paper deals with the heat input and maximum temperature developed during friction stir welding with different parameters. Aluminum alloy (AA 6061-T6) has been used for experimental and numerical analysis. Experimental analysis is based on temperature measurements by using infrared camera, whereas numerical analysis was based on empirical expressions and finite element method. Different types of defects have been observed in respect to different levels of heat input

Technical risk assessment for the safe design of a man-rider chair lift system

Underground mining is a difficult area for miners to work. Miners must go to the working faces by walking, which is not only time consuming but also physically demanding. In mines, a man-rider chair lift system (MRCL) has been developed to alleviate the strain stresses caused by walking lengthy and uneven distances up to the working faces. All parameters, including horizontal and vertical distances, variation and inclination of underground mines, slope forces considering the weight of persons and chair, forces acting towards return and drive unit, curves angles, power to operate, and rope safety factor, are calculated mathematically while modelling a man-rider chair lift system for both the installation and extension phases. We analyzed the analytical approach in conjunction with practical installation of the man-rider chair lift system to establish if the installation and extension of MRCL is genuinely feasible in the current scenario. We also created a simulation model of steel wire rope in Creo 8.0 for analyzing the various stresses on it with the Ansys R 16.2 software. In both phase I and phase II, the factor of safety is above that recommended, and the system is a hundred percent reliable, risk-free, and safe for operation.The authors are grateful to FCT—Fundação para a Ciência e Tecnologia (Portugal)—who partially financially supported this work through the RD Units Project Scope: UIDP/04077/2020 and UIDB/04077/2020

A comparative numerical analysis on the effect of welding consumables on the ballistic resistance of SMAW joints of armor steel

In the present investigation, a comparative study of ballistic impact behavior of Armox 500T (base metal) and its weldments prepared by low hydrogen ferrite (weldment-1) and austenitic stainless steel (weldment-2) consumables against 7.62 AP bullet has been performed with the help of finite element analysis code Abaqus 2017. Further, the result is validated with the experimental results. The experiment has been performed on the base metal, weldment-1, and weldment-2 against 7.62 AP bullet. Further, a two-dimensional explicit model has been developed for given purpose to simulate the bullet penetration at such high strain rate (103 s−1). Both bullet and plate are considered as deformable. Experimental results revealed that the depth of penetration in the base metal, weldment-1, and weldment-2 is 10.93, 13.65, and 15.20 mm respectively. Further computational results revealed that the depth of penetration of base metal, weldment-1, and weldment-2 is 10.11, 12.87, and 14.60 mm, respectively. Furthermore, weldment-1 shows more resistance against 7.62 AP bullet than weldment-2 in experimentation as well as FEA results. The percentage difference between experimental and FEA results are less than 10% which shows the prediction capability of FEA models. A feasibility analysis has been presented for using the welding consumables to weld the Armox 500T plate. Finally, in terms of ballistic resistance, the low hydrogen ferrite consumables are more appropriate than austenitic stainless-steel electrodes

Characterization of Friction Surfaced Coatings of AISI 316 Tool over High-Speed-Steel Substrate

Nowadays friction surfacing (FS) has become a popular solid state surface coating technology suitable for a range of substrates. The technology has the ability to produce coatings with marginal dilution and good metallurgical bonding. The present study has aimed at producing a single-track and a three-track overlapping coatings on high-speed steel substrates using an AISI 316 consumable rod. Microhardness of coatings was examined by a Vickers micro hardness tester. Coatings of all the friction surfaced samples in as-deposited condition showed significant hardness. The infrared thermography showed that the peak temperature achieved by the AISI 316 coating was about 1020 ͦ C. The coatings, thus attained, were further analysed for their microstructural features and interfacial characteristics by using FE-SEM. The EDX analysis showed the presence of nickel, chromium and oxygen, which indicates the formation of oxide compounds. The formation of AISI 316 deposits on the HSS substrate and the effect of coating overlapping are discussed in this article