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.

Local scour around a bridge pier under ice-jammed flow condition – an experimental study

The appearance of an ice jam in a river crucially distorts local hydrodynamic conditions including water level, flow velocity, riverbed form and local scour processes. Laboratory experiments are used for the first time here to study ice-induced scour processes near a bridge pier. Results show that with an ice sheet cover the scour hole depth around a bridge is increased by about 10% compared to under equivalent open flow conditions. More dramatically, ice-jammed flows induce both greater scour depths and scour variability, with the maximum scour depth under an ice-jammed flow as much as 200% greater than under equivalent open flow conditions. Under an ice-jammed condition, both the maximum depth and length of scour holes around a bridge pier increase with the flow velocity while the maximum scour hole depth increases with ice-jam thickness. Also, quite naturally, the height of the resulting deposition dune downstream of a scour hole responds to flow velocity and ice jam thickness. Using the laboratory data under ice-jammed conditions, predictive relationships are derived between the flow’s Froude number and both the dimensionless maximum scour depth and the dimensionless maximum scour length.

Can chemical cues from a predator change the nest-selection of birds?

The nest-selection process of many birds can be affected by traces of potential predators. However, it remains debatable if birds are capable of recognizing and responding to chemical cues of predators when selecting their nest sites. To investigate this, I installed a pair of nest boxes at 12 sites in 2013 and 2014 and 24 sites in 2015 and 2016, each with nest conditions that differed for two variables, that is, height (high or low), hole depth (deep or shallow). Under these experimental conditions, tree swallows displayed a strong preference for high nests over low ones and deep hole nests over shallow holes. In a consecutive experiment, we applied chemical cues (i.e. urine, feces) of domestic cats to the preferred nests to determine if this would alter the nests selected; the chemical cues led to a stepwise alteration in the nests selected. The birds changed their nest selection by chemical cues of a predator when one variable (nest height or hole depth) was applied. Interestingly, however, when provided with a choice between the most preferred nest combination (high and with a deep hole) and the least preferred nest combination (low and with a shallow hole), tree swallows selected the most preferred nest even in the presence of the chemical cues.

Analytical model for the depth progress of percussion drilling with ultrashort laser pulses

A simplified analytical model is presented that predicts the depth progress during and the final hole depth obtained by laser percussion drilling in metals with ultrashort laser pulses. The model is based on the assumption that drilled microholes exhibit a conical shape and that the absorbed fluence linearly increases with the depth of the hole. The depth progress is calculated recursively based on the depth changes induced by the successive pulses. The experimental validation confirms the model and its assumptions for percussion drilling in stainless steel with picosecond pulses and different pulse energies.

Experiment and Failure Analysis of Rock-Like Material Affected by Different Excavation Depths

In order to increase the understanding of the strength and failure mechanism of rock mass during tunnel excavation, a series of uniaxial compression tests were conducted on mortar specimen with cracks and holes by using a rock mechanics servo-controlled testing system. And by monitoring the experimental process, the initiation, propagation, and coalescence process of cracks were observed and characterized. According to the experimental results, the influences of the excavation depth on the mechanical parameters and fracture characteristics of mortar specimens with single hole and the ones with single-hole crack were analyzed in detail. In the specimens with single hole, the peak strength decreases with the increase of hole depth, but the peak strain and elastic modulus have no obvious linear correlation with the hole depth. And the position and angle of initial crack change differently with the increase of the hole depth. The position of initial crack moves from the side of the hole to the top of the hole. When the hole depth exceeds 50%, the crack initiation angle is no longer inclined to the axial stress direction, but parallel to the axial stress direction. In the specimens with single prefabricated crack, the wing-shaped secondary cracks are generated at the tip of the precrack, and the antiwing-shaped secondary cracks are generated at the tip when approaching the peak stress. However, in the specimens with single-hole crack, no antiwing-shaped crack appears. And when the hole depth reaches 80%, two wing-shaped cracks appear at the precrack tip. One of the new wing-shaped cracks appears in the direction of the extension line of the precrack.

Drying performance, as well as physical and flexural properties of oil palm wood dried via the super-fast drying method

Effects of incising parameters were studied relative to the drying performance and properties of super–fast dried oil palm wood. Different incising depths (1/3, 1/2, 2/3, and 100% of the total thickness) and distance (38 mm and 50 mm) were made on the oil palm wood boards prior to the super-fast drying procedure. All the boards achieved the desired moisture content after drying. Drying defects were minimal, as only two boards indicated end checks and surface checks defects. The board density ranged from 0.44 g/m3 to 0.60 g/m3, and the thickness swelling and water absorption of the boards ranged from 8.3% to 12.5% and 45% to 67%, respectively. The specific modulus of rupture and elasticty ranged from 0.35 N m3/kg mm2 to 0.77 N m3/kg mm2 and from 77.64 N m3/kg mm2 to 118.40 N m3/kg mm2, respectively. It can be concluded that the hole distances did not exert significant effect on the properties, with exception of specific modulus of elasticity. A hole depth of 1/3 mm was preferable, since the surface looked like no incision had been made and the sample had good physical and flexural properties.