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The machinability of Ti-6Al-4V alloy has been a constant challenge in the industry, although the material is widely used in the aerospace and medical industries due to its mechanical properties, particularly its strength-to-weight ratio. The current research presents a hybrid laser- and ultrasonic-assisted machining (LUAM) technique to improve the machinability of Ti-6Al-4V alloy in a turning process. This is compared with ultrasonic-assisted machining (UAM), laser-assisted machining (LAM), and convectional turning (CT). The results reveal that UAM and LAM can reduce the cutting forces and surface roughness (Ra) compared to the CT. However, these are achieved mainly at the lowest range of cutting speeds. The hybrid LUAM process demonstrates process improvement with wider range of cutting speeds and depths of cut, which is achieved due to the combined force reduction and thermal softening effect by the hybrid process. [ABSTRACT FROM AUTHOR]

Machining chatter has detrimental effects on surface quality, tool life, and machining efficiency. Therefore, it is of vital significance to predict and avoid this undesirable phenomenon. This paper presents an Adams-Moulton-based method for the stability prediction of milling operations. Generally, delay differential equations with time-periodic coefficients are applied to model the milling dynamics that include the regenerative effect. To begin with, the tooth-passing period is divided into free vibration time period and forced vibration time period. Subsequently, the Adams-Moulton method is utilized to construct the transition matrix over one period through dividing the forced vibration time period equally into small time intervals. Finally, the milling stability can be obtained by examining the eigenvalues of the transition matrix based on Floquet theory. A comparison with the first-order semi-discretization method and the Simpson-based method is conducted to evaluate the convergence rate and the computation efficiency of the proposed algorithm. The results verify that the proposed method is highly accurate and efficient; thus, it is practical for workshop technicians to select chatter-free machining parameters. [ABSTRACT FROM AUTHOR]

The development of sustainability assessment for machining process is considered as one of the crucial strategies to realize sustainable design and manufacturing, while existing methods focusing on environmental assessment have limits due to neglect economic and social impacts. This paper proposes an assessment approach for evaluating sustainability performance of machining process with respect to a consistent set of environmental, economic, and social criteria in order to select a machining strategy from sustainable manufacturing viewpoint. Sustainability assessment criteria are identified to compare different machining parameter alternatives; cutting noise, especially, is defined as an important criterion of social impact, and energy, lubricant oil, and cutting fluids consumption are identified as criteria of environmental impact. Additionally, the weights of criteria are determined using entropy weight approach with the advantage of objective evaluation by exploiting the useful information of data to a maximum extent. Furthermore, sustainability performance of machining process is calculated based on extension theory through utilizing correlation function between evaluated matter-element and classical field matter-element. Face milling test conducted on CNC vertical machining center not only illustrates validity of the proposed method for assisting the engineers or designers to define sustainability performance of machining process, but also proves the relationship between cutting parameters and cutting noise. [ABSTRACT FROM AUTHOR]

During laser cleaving of brittle materials, with the controlled fracture technique, thermal stresses are generated which induce the crack and extend it along the cutting path, subsequently causing material separation. One of the problems in laser cutting of glass with this technique is the cut path deviation at the leading and the trailing edges of the glass sheet. Previous work with a continuous beam diode laser has shown the deviation to be partly due the high magnitudes of thermal stresses generated near the edges of the sheet. This paper reports on the effects of using a pulsed diode laser to cut soda lime glass. The effect of pulse parameters and cutting speed on the quality output variables such as cut deviation angle and surface finish are studied. Finite element modelling is also used to simulate the effects of the moving beam on stress generations to facilitate the understanding of the process mechanisms, and the results are compared with the experimental data. This work shows how to minimise the cut path deviation at the edges by reducing thermal stresses using optimum pulsed diode laser parameters and providing additional flexibility to the process. [ABSTRACT FROM AUTHOR]

The present study investigates the effects of four controllable variables on the metallurgy and drilling velocity of laser percussion drilled acute (30° to surface) blind holes in 2 mm thick flat pieces of nickel superalloy—CMSX-4 material. Design of experiment and statistical modelling were used in the experimental study to understand parameter interactions. Pulse energy, pulse width, pulse frequency and gas pressure were chosen as the independent process variables. The response surface method was used to develop the models for each of the responses: physical characteristics of wall and bottom recast layer and drilling velocity (function of material removal rate). A central composite design was chosen as it offered the most economical number of experiments for the required information. The significant process factors in each model were identified based on the analysis of variance and the models were checked by complete residual analysis. It was found that high pulse energy and short pulse width gave the maximum drilling velocity and lowest recast layer thickness at the hole bottom, whereas low pulse energy and short pulse width minimised the wall recast layer thickness. [ABSTRACT FROM AUTHOR]