Yasir M. Shariff

Finite-Element Analysis of Forces in Drilling of Ti-Alloys at Elevated Temperature

Demand for high-strength alloys in aerospace, marine and off-shore industries has grown significantly over last decades, primarily thanks to their high strength, light weight as well as good fatigue and corrosion-resistance properties. However, these materials are extremely difficult to machine with conventional machining methods. Hot machining is an alternative technique used by many researchers for cutting of hard-to-cut materials in turning and milling operations. In this assisted machining technique, an external heat source is used to reduce shear strength of the machined workpiece, enhancing material removal of such alloys. Drilling is one of the most important and basic operations for producing cylindrical holes in machined components. In this work, a three-dimensional finite-element (FE) model of drilling process is developed in a commercial FE software DEFORM 3D. A nonlinear temperature-dependent material behaviour is incorporated in numerical simulations. The effect of an external heat source on thrust forces and torque on a drill-bit was investigated with the developed FE model. Advantages of hot drilling in reducing thrust force and torque reduction are demonstrated.

Effect of Cutting Conditions on Temperature Generated in Drilling Process: a FEA Approach

Heat generated during a drilling process has a major influence on the tool life and the workpiece material behaviour that are significantly affected by cutting conditions (cutting speed, feed rate). In this paper, the effect of cutting conditions on temperature generated in drilling process is investigated by means of finite element (FE) simulations using commercially available code MSC MARC MENTAT. A Johnson Cook material model is used to describe elasto-plastic deformation behaviour. The updated Lagrangian procedure is used to implement the transient analysis for the elasto-plastic material in the model. A modified shear friction model is employed to model friction at the tool tip-workpiece interface. The effect of friction on chip shape is investigated with FE simulations. Experiments were carried out to verify the FE results.

Computational Analysis of a High-Lift and Low Reynolds Number Airfoil at Turbulent Atmospheric Conditions

Selection of airfoil is crucial for better aerodynamic performance and design of aerodynamic applications such as wind turbine and aircrafts. In this paper, a high-lift and low-Reynolds number airfoil has been selected and investigated through computational analysis for applying it for small-sized wind turbines as blades. The S1223 airfoil, designed by the University of Illinois at Urbana-Champaign, was chosen for its high-lift characteristics at low Reynolds number typically encountered by the small wind turbines. CFD work is performed with S1223 airfoil profile over a wide range of conditions of interest to analyze the performance of the airfoil using the Spalart-Allmaras turbulence model. The results obtained from the simulation works have been compared with experimental data for validation purpose. It has been found that the Spalart-Allmaras model conforms well with the experimental results, though the values of lift coefficients (Cl) are slightly less than the experimental results. In the present analysis, velocity distributions are analyzed at different angle of attacks for different turbulence intensities. It has been observed that there is vortex shedding around the trailing edge of the airfoil for both turbulence levels. It has been observed in the present study that due to increase in turbulence intensity, both the maximum lift coefficient and the stall angle increases significantly. It has been found after investigating the effect of turbulence intensity over lift-to-drag coefficient ratio that it drastically decreases due to increase in turbulence intensity up to certain value (about 3.5%), then it starts decreasing in gradual manner.Copyright

Response of first active teaching / learning course at Taibah University

The past decade has seen an explosion of interest among college faculty in the teaching methods variously grouped under the terms ’active learning’ and ’cooperative learning’. However, even with this interest, there remains much misunderstanding of and mistrust of the pedagogical “movement” behind the words. The majority of all college faculty still teach their classes in the traditional lecture mode. Some of the criticism and hesitation seems to originate in the idea that techniques of active and cooperative learning are genuine alternatives to, rather than enhancements of, professors’ lectures. In this paper, We are providing a response of active learning techniques which were obtained from students.

Superfluous Curriculum Burdens on Mechanical Engineering Students, Causes and Remedies

Conventional mechanical engineering curriculum practiced world wide, offers courses on manufacturing engineering, thermodynamics, heat transfer, industrial engineering, mechanisms, vibration and control, and mechanical design in single or multiple fashion. This scheme contains extra or repeated (superfluous) subjects and lack some fundamental courses. These superfluous courses need to be addressed for removal. The current engineering field expects the professional to excel beyond the boundaries of conventional curriculum. If the expected mechanical engineer is trained according to the expectations of the companies without making him to know all conventional trades, the curriculum burden can be reduced to a large extent. Different streams of specialties are to be created in the curriculum to satisfy the job market. A decision needs to be made whether some portion of the curriculum can be shifted to the companies to train the engineering bachelors according to their taste or such a burden be put on the student in the college. Strong intellectual, innovative and technical foundations need to be made of the engineering bachelors by addressing, curriculum, faculty, laboratories and computational facilities like issues in an optimised form.

Enhancement of Single-Phase Refrigerant Mixture (R-407C) Flow in Meso-Scale Heat Exchangers Using Micro-Coils

Experimental results from single-phase refrigerant mixture flow in smooth and micro-coil enhanced meso-channels are presented. R-407C — a mixture of R-32 (23%)/R-125 (25%)/R-134a (52%) — is used as the working fluid and different micro-coils are used in conjunction with two meso-channels (2.78mm and 3.97 mm) to obtain distinct roughness parameters. The flow was varied over a range of Reynolds numbers and experiments were conducted over a heat flux range of 2 to 11 kW/m2 . The heat transfer coefficient was found to be dependent on both the heat flux as well as mass flux levels. Results show that heat transfer characteristics are comparable to R-113, and that micro-coil inserts enhanced the heat transfer performance compared to the performance in smooth meso-channels.Copyright

Boiling Characteristics of Refrigerant Mixture Flow in Micro Scale Heat Exchangers Enhanced With Micro-Coils

Flow in three horizontal channels for subcooled and saturated boiling characteristics are reported in this study. An experimental setup composed of heating elements provided heat flux variations on the channels. The heat transfer coefficient was found to be dependent on both the heat flux as well as mass flux levels. Results show that micro-coil inserts enhanced the heat transfer performance over that in smooth channels by 25% as compared to correlations for wire-coil inserts and 30% as compared to correlation for convective boiling process.Copyright