Improving part qualifying performance using compliance crack monitoring under rotating bending tests

Abstract: Part qualifying testing is a critical part of product development especially for mission critical components. This is more pronounced in cases where new manufacturing techniques such as high speed machining, additive manufacturing and wire electrical discharge machining are applied. Such techniques invariably modify the surface integrity of the components by introducing amongst others residual stresses and altering surface roughness. If left unattended, this may affect the performance of the product in service. Therefore, there is a need to qualify products before full commercial production and to link the manufacturing strategy to anticipate in service part performance. Endurance qualifying tests for certain products and components may include full scale endurance testing and/or a machining strategy endurance evaluation by fatigue testing either axially or in bending. Crack growth monitoring can be used to indicate the durability and performance of the product. However, crack growth monitoring during axial or rotating bending conditions is challenging and expensive. The aim of this paper is, therefore, to report on the development of a compliance based crack monitoring technique that can reduce the cost and improve the effectiveness of product qualifying tests. Tests are conducted on grade 5 titanium alloy (Ti6Al4V) specimens produced using high speed turning. These are then subjected to a rotating four point bending configuration test. Defect (crack) formation and growth (size) may then be estimated by compliance (strain) monitoring. This technique was found to be a viable low cost option for monitoring components during rotating bending conditions and to link the manufacturing technique to part performance with specific reference to dynamic loading

Minimum quantity lubrication (MQL) assisted machining of grade-4 titanium

Abstract: This paper presents the results of an experimental investigation for turning of Grade-4 titanium with carbide cutting tool inserts with minimum quantity lubrication (MQL). Experiments were designed based on Taguchi’s L9 orthogonal array. The MQL parameters of flow rate (50-70-90 mL/hr); nozzle distance (20-30-40 mm) and air pressure (4-5-6 bar) were varied for three different levels each. Cutting speed, feed and depth of cut were fixed at 125 m/min; 0.2 mm/rev and 1 mm respectively. The grey relational method in conjunction with the Taguchi technique was used for optimizing the MQL parameters. The nozzle distance was recognized as the most significant parameter. The data further indicated that the optimum MQL parameters were a flow rate of 70 mL/hr, nozzle distance of 30 mm and air pressure of 6 bar. When compared to dry and wet cutting conditions MQL was shown to have significant advantages

A parametric design and optimization approach to enhance the fatigue life of a male pyramid socket adapter

Abstract: This research paper presents a parametric design approach to optimize a male pyramid socket adapter as used on a transtibial prosthetic limb for enhanced fatigue life. These adapters are prone to premature failure when used by individuals partaking in athletic sports. A parametric design and optimization approach is presented and applied. A current design was assessed for structural integrity by finite element analysis in combination with the load criteria as recommended by the ISO 10328:2016 code of practice. Highly-stressed regions where identified and improved using a parametric design approach to reduce the maximum 1st Principal stress while adhering to the industry code of practice as applicable to pyramid socket adapter design. The optimization was validated by experimentally comparing the current design and the optimised design for an appropriate load case by low cycle fatigue testing. The socket adapters were manufactured from Ti6Al4V and subjected to a simulated resultant knee bending moment. The fatigue validation indicated a significant improvement in fatigue life for the optimized socket geometry commensurate with a reduction in stress and comparison to an appropriate SN curve for Ti6Al4V. The parametric optimization process as utilized was found to be effective and should be applicable to many different applications in a more general sense

Towards energy management during the machining of titanium alloys

The manufacturing industry needs to address challenges as regards to the machining process in the multifaceted context of sustainability. The current cost of energy and the reduction in material reserves highlights the need for machining systems to be more energy-efficient. This paper aims to provide a systematic overview of advanced approaches to manage energy and resource efficiency in cutting operations. The research experimentation focuses on the machining of a selected titanium alloy, Ti6Al4V, using carbide cutting tools. Tool wear, chip formation, cutting force and energy use were measured and analysed for selected cutting parameters. The experimental results illustrate the importance of selecting optimum cutting parameters and machining strategy. The results further help to define the boundary conditions for the various input parameters. Future research is also discussed

Effects of acute pre-treatment with ethanolamine on isoprenalineinduced myocardial infarction in adult Wistar rats

Ethanolamine (Etn), a biogenic amine, protects isolated hearts against MI, but its effects in vivo are unknown. In this study, we investigated the effects of Etn pretreatment on isoprenaline (ISO)-induced MI in vivo. Wistar rats were treated with either Etn (10mg.kg-1, i.p.) or saline, prior to either ISO (67mg.kg-1, s.c.) or saline. Haemodynamic- and electrocardiographic parameters were recorded under anaesthesia, 24 hours post-treatment with ISO. Infarct sizes were determined by triphenyltetrazolium chloride staining. Oxidative stress plasma parameters, conjugated dienes (CD) and thio-barbituric acid reactive substances (TBARS), were measured by spectrophotometric analysis. Etn decreased ISO-induced pathological Q-waves, but had no effect on ISO-induced low-voltage electrocardiogram. In addition, Etn decreased overall mortality induced by ISO treatment. However, Etn did not prevent ISO-induced infarction or the systolic- and diastolic hypotensive effects. Etn also enhanced the ISO-induced increase in heart-to-body weight ratio, and reversed the decrease in lungs-to-body weight ratio. Neither ISO nor Etn altered CD or TBARS. These results suggest that, despite a tendency to modulate cardiac electrical activity, Etn did not prevent ISO-induced MI or myocardial dysfunction in vivo

Recent developments in sustainable manufacturing of gears: a review

Abstract: Environment awareness is of the utmost importance to all socially responsible manufacturers. To be competitive on a global scale manufacturing needs to be aligned with various strict environmental regulations. The manufacturing industry at large is striving to improve productivity and product quality while maintaining a clean and sustainable environment. This can only be achieved by adopting sustainable techniques of manufacturing which include minimizing the number of manufacturing steps by employing advanced and alternative methods, environment-friendly lubricants and lubrication techniques while machining, reducing wastage, active waste management and minimizing energy consumption etc. Gear manufacturing industries, the major service providers to all other industrial and manufacturing segments are also focusing on to implement the techniques targeting overall sustainability. Some of the recent developments to achieve sustainability in gear manufacturing can be summarized as reducing the use of mineral-based cutting fluids by employing alternative lubrication techniques i.e. minimum quantity lubrication (MQL) and dry machining, material saving, waste reduction, minimizing energy consumption and maintaining economic efficiency by reducing the number of gear manufacturing stages (eliminating the necessity of finishing processes) by utilizing advanced methods such as gear rolling and wire electric-discharge machining (WEDM), and finally increasing productivity by minimizing tool wear at high gear cutting speeds through the use of alternative tool materials and coatings. This paper reviews and amasses the current state of technology for sustainable manufacturing of gears and also recommends ways to improve the productivity and quality while simultaneously ensuring environmental sustainability

Residual stress depth profiling of commercially pure titanium subjected to high-speed machining using energy dispersive diffraction

Residual stress is well-known to influence the mechanical properties of machined components. The magnitude and distribution of these stresses are critical to determine the component’s life, specifically under fatigue loading. There exists a growing need to better understand the effects of cutting parameters on residual stress and to identify more innovative methods to evaluate residual stress. Titanium has been widely used, but many of the same qualities that enhance titanium’s appeal for most applications also contribute to it being one of the most difficult to machine materials. High-speed cutting experiments were conducted on commercially pure (CP) titanium and the residual stress depth profile was analysed using energy dispersive diffraction (EDDI). The residual stress depth profile of CP Grade 4 titanium was then evaluated. Experimental results show that cutting speed and depth of cut have a significant effect on the residual stress profile. At a low cutting speed, the surface residual stresses are largely compressive, becoming less compressive with an increase in cutting speed. An increase in depth of cut also introduces more compressive residual stresses into the material

Strength of Materials 4A

Exam paper (Supplementary) for second semeste

Science of Materials 2B

Exam paper (Supplementary) for second semeste

Separation of alkanes and alcohols with supercritical fluids. Part II. Influence of process parameters and size of operating range

This paper is the continuation of a previous study on the investigation of the separation of detergent range alkanes and alcohols with supercritical fluids. Specifically this paper presents results on the optimisation of the process parameters for the separation of n-tetradecane and 1-dodecanol with supercritical carbon dioxide and ethane. The optimum operating conditions were determined from the results of a study of the influence of the process parameters, as well as an investigation into the size of the operating range. The results showed that the optimum temperature is a balance between good separation at lower temperatures and better control at higher temperatures. The solvent-to-feed ratio should be kept low (within the range of vapour-continuous operation) as lower solvent-to-feed ratios result in improved separation, as well as lower energy requirements. The use of reflux is necessary for good separation when using carbon dioxide as solvent, but is not required with ethane as solvent. An analysis of the operating range showed that a process using ethane is easier to control. Ethane as solvent is technically superior to carbon dioxide yet, depending on the exact process and location, costs, safety and logistics may favour the use of carbon dioxide. © 2011 Elsevier B.V. All rights reserved.Articl