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The aim of this paper is to study the effect of pressure angle and helix angle on bending stress at the root of helical gear tooth under dynamic state. Gear design is a highly complex process. The consistent demand to build low-cost, quieter and efficient machinery has resulted in a gradual change in gear design. Gear parameters such as pressure angle, helix angle, etc. affect the load-carrying capacity of gear teeth. Adequate load-carrying capacity of a gear is a prime requirement. The failure at the critical section because of bending stress is an unavoidable phenomenon. Besides this fact, the extent of these failures can be reduced by a proper gear design. The stresses produced under dynamic loading conditions in machine member differ considerably from those produced under static loading.

The present work is intended to study the effect of pressure angle and helix angle on the bending stress at the root of helical gear tooth under dynamic state. The photostress method has been used as experimental methods. Theoretical analysis was carried out by velocity factor method and Spott’s equation. LS DYNA has been used for finite element (FE) analysis.

The results show that experimental method gives a bending stress value that is closer to the true value, and bending stress varies with pressure angle and helix angle. The photostress technique gives clear knowledge of stress pattern at root of tooth.

The outcomes of this work help the designer use optimum weight-to-torque ratio of gear; this is ultimately going to reduce the total bulk of the gear box.

The purpose of this paper is to originate a statistical model for delamination factor, surface roughness, machining force and also to determine and compare the effects of machining parameters (spindle speed, fiber orientation angle, helix angle and feed rate) on the output responses during end-milling of glass fiber reinforced polymers (GFRP) by using desirability functional analysis (DFA) and grey relational analysis (GRA).

Based on Taguchi’s L27 orthogonal array, milling experiments were carried on GFRP composite plates employing solid carbide end mills with different helix angles. The machining parameters were optimized by an approach based on DFA and GRA, which were useful tools for optimizing multi-response considerations, namely, machining force, surface roughness and delamination factor. A composite desirability index was obtained for multi-responses using individual desirability values from DFA. Based on this index and grey relational grade the optimum levels of parameters were identified and significant contribution of parameters was ascertained by analysis of variance.

Fiber orientation angle (66.75 percent) was the significant parameter preceded by feed rate (15.05 percent), helix angle (7.76 percent) and spindle speed (0.30 percent) for GFRP composite plates.

Multi-objective optimization in end-milling of GFRP composites using DFA and GRA has not been performed yet.

The purpose of this paper is to determine the optimum level of geometrical parameters such as helix angle, nose radius, rake angle and machining parameters such as cutting speed, feed rate and depth of cut to arrive minimum surface roughness and tool wear during end milling of Al 356/SiC metal matrix composites (MMCs) using high speed steel end mill cutter.

L27 Taguchi orthogonal design with six factors and three levels is employed for conducting experiments. Analysis of variance (ANOVA) is carried out using Minitab16 software to find the influence of each input parameter on output performance measure. Grey-fuzzy logic multi optimisation algorithm is used to find the optimum level of the input parameters for minimum surface roughness and tool wear simultaneously.

It is found that optimal combination of helix angle 40°, nose radius 0.8 mm, rake angle 12°, cutting speed 90 m/min, feed rate 0.04 mm/rev and depth of cut 1.5 mm have generated minimum surface roughness of 0.4063 µm and tool wear of 0.0375 mm. From ANOVA analysis, it is found that cutting speed influence is more on output performance followed by helix angle and rake angle compared with other machining and geometrical parameters.

The influence of tool geometry during end milling of MMC using Grey-fuzzy logic algorithm has not been explored previously.

The purpose of this paper is to optimise the process parameters, namely, fibre orientation angle, helix angle, spindle speed, and feed rate in milling of glass fibre-reinforced plastic (GFRP) composites using grey relational analysis (GRA) and desirability function analysis (DFA).

In this work, experiments were carried out as per the Taguchi experimental design and an L27 orthogonal array was used to study the influence of various combinations of process parameters on surface roughness and delamination factor. As a dynamic approach, the multiple response optimisation was carried out using GRA and DFA for simultaneous evaluation. These two methods are best suited for multiple criteria evaluation and are also not much complicated.

The process parameters were found optimum at a fibre orientation angle of 15°, helix angle of 25°, spindle speed of 6,000 rpm, and a feed rate of 0.04 mm/rev. Analysis of variance was employed to classify the significant parameters affecting the responses. The results indicate that the fibre orientation angle is the most significant parameter preceded by helix angle, feed rate, and spindle speed for GFRP composites.

An attempt to optimise surface roughness and delamination factor together by combined approach of GRA and DFA has not been previously done.

In milling process the surface roughness and delamination are the most important performance characteristics, which are influenced by many factors like fibre orientation angle, helix angle, feed rate and spindle speed. The selection of these parameters at optimum level plays a vital role in getting minimum surface roughness and delamination factor. The purpose of this paper is to present multi-objective optimisation of Computer Numerical Control milling parameters using Grey-Taguchi method to get minimum surface roughness and delamination factor in machining of glass fibre reinforced plastics (GFRP) composites used in automotive, aircraft and manufacture of space ships.

The experiments are designed and conducted based on Taguchi's L₂₇ orthogonal array by taking fibre orientation angle, helix angle, feed rate and spindle speed at three levels and responses are surface roughness and delamination factor. Taguchi's signal-to-noise (S/N) ratio are determined based on their performance characteristics. A Grey relation grade is obtained by using S/N ratio. Based on Grey relational grade value, optimum levels of parameters have been identified by using response table and response graph.

Optimum levels of parameters for GFRP composites have been identified by using response table and response graph and the significant contributions of controlling parameters are estimated using analysis of variance.

The combined effect of fibre orientation angle and helix angle during milling of GFRP composites using Grey relational analysis has not been previously attempted for analysis.

The purpose of this paper is to present key points relating to the development of micro drill bits with high aspect ratios and to provide a solution for high aspect ratio hole drilling.

Based on the analysis of challenges in high aspect ratio hole drilling, key points for the development of micro drills bit with high aspect ratio are discussed. A design example of a micro drill bit with 0.3 mm diameter and a 7.2 mm flute length is presented. Experiments are conducted to verify the performance of the developed micro drill bit.

Helix angle, web thickness and flute land ratio are three key parameters that significantly influence the behaviour of micro drill bits with high aspect ratios. Large helix angle, web thickness and flute land ratio are beneficial in terms of improving the performance of high aspect ratio micro drill bits. Step drilling is essential to prevent drill breakage and to ensure smooth debris evacuation. Meanwhile, proper steps and drilling parameters are of great importance to complete high aspect ratio hole drilling.

The paper highlights key points relating to the development of micro drill bits with high aspect ratios that can provide a satisfactory solution for high aspect ratio micro drill bit design.

This paper aims to present an analytical approach for the determination of helical gear tooth geometry and introduces the necessary parameters. Tooth geometry including tooth chamfer, involute curve, root fillet, helix as well as tooth microgeometry can be obtained using the presented approach.

The presented analytical approach involves deriving the equivalent equations at the transverse plane rather than the normal plane. Moreover, numerical evaluation of microgeometry modifications is presented for tooth profile, tooth lead and flank twist.

An analytical approach is presented and equations are derived and explained in detail for helical gear tooth geometry calculation, including tooth microgeometry. Method 1, which was presented by Lopez and Wheway (1986) for obtaining the root fillet, is examined and it is proven that it does not work accurately for helical gears, but rather it works perfectly in the case of spur gears. Changing the normal plane parameters in Method 1 to the transverse plane ones does not give correct results. Two alternative methods, namely, Methods 2 and 3, are developed in the current research for the calculation of the tooth root fillet of helical gears. The presented methods and also the numerical evaluation presented for microgeometry modification are examined against the geometry obtained from Windows LDP software. The results show very good agreement, and it is feasible to apply the approach using the presented equations.

In the gear design process, it is important to model the correct gear tooth geometry and deliver all related dimensions and calculations accurately. However, the determination of helical gear tooth geometry has not been presented adequately by equations to facilitate gear modelling. The detailed helical gear tooth root has been enveloped using software tools that can simulate the cutter motion. Deriving those equations, presented in this article, provides gear design engineers and researchers with the possibility to model helical gears and perform design calculations in a structured, applicable and accurate method.

Glass fibre reinforced plastics (GFRP) contain two phases of materials with drastically distinguished mechanical and thermal properties, which brings in complicated interactions between the matrix and the reinforcement during machining. Surface quality and dimensional precision will greatly affect parts during their useful life especially in cases where the components will be in contact with other elements or materials during their useful life. The purpose of this paper is to discuss the application of the Taguchi method with fuzzy logic to optimise the machining parameters for machining of GFRP composites with multiple characteristics.

The machining tests were performed on a CNC milling machine using solid carbide (K10) End mill cutting tool with three different helix angles. Experiments were planned using Taguchi’s orthogonal array with the cutting conditions prefixed.

The machining parameters, namely, helix angle of the end mill cutter, spindle speed, feed rate, depth of cut, and work piece fibre orientation (specially applied to the GFRP composites) were optimised with considerations of multiple response characteristics, including machining force, material removal rate, and delamination. The results from confirmation runs indicated that the determined optimal combination of machining parameters improved the performance of the machining process.

Multi-response optimisation of machinability behaviour of GFRP composites using fuzzy logic has not been attempted previously.

The paper aims to present key points regarding the development of an ultra‐small micro drill bit for packaging substrate hole processing.

Key points for the development of ultra‐small drill bits are presented. These are based on a study of the influential mechanisms of micro drill bit material properties, key parameters and coating techniques on the behaviours of micro drill bit. Experiments were conducted to verify the drilling capability of the developed ultra‐small micro drill bits.

The material properties of micro drill bits are of great importance in ensuring the performance. Helix angle, primary face angle and point angle are three key parameters that significantly influence drill bit behaviour. Computer‐aided engineering analysis, temperature monitoring and video monitoring techniques in high‐speed drilling are useful tools for achieving the optimal design of ultra‐small drill bits. Using coating technology on ultra‐small drill bits can improve their hit limits by nearly four times.

The paper highlights key points to consider when developing ultra‐small micro drill bits. The presented points can provide an overall understanding of the challenges and solutions during ultra‐small micro drill bit design. Additionally, this paper presents a solution for packaging substrate ultra‐small hole processing by mechanical drilling.

Presents a mathematical treatment of the large‐scale bending behaviour of multi‐ply yarn. Based on the assumptions that: each individual fibre in the yarn has the form of a doubly‐wound helix; each fibre is an inextensible slender rod; and interaction between fibres is ignored. The yarn‐bending rigidity is calculated as an average rigidity of an assembly of coaxial helices. There is good agreement between the predicted and measured values of yarn bending rigidity for a wool worsted knitting yarn. Also predicts the position, curvature and twist components as well as the strain energy of the deformed fibre.