Search results

The purpose of this paper is to investigate the buckling strength of simply supported plates with mechanical extension-twisting coupling. Bounds of the compression buckling strength are presented for a special sub-class of extension-twisting coupled laminate that is free from the thermal distortions that generally arise in this class of coupled laminate as a result of the high temperature curing process. These special laminates are generally referred to as hygro-thermally curvature-stable (HTCS).

This paper gives an overview of the methodology for developing laminates with extension-twisting coupling properties, which are derived from a parent laminate with HTCS properties. A closed form buckling solution is applicable for this special class of coupled laminate, which facilitates an assessment of compression buckling strength performance for the entire laminate design space.

Extension-twisting coupled laminates have potential applications in the design of aero-elastic compliant rotor blades, where the speed of the rotating blade, and the resulting centrifugal force, can be used to control blade twist. Extension-twisting coupling reduces the compression buckling performance of the blade, which represents an important static design constraint. However, the performance has been shown to be higher than competing designs with extension-shearing coupling in many cases.

Bounds of the buckling curves have been presented for the entire HTCS laminate design space, possessing extension-twisting and shearing-bending coupling, in which the laminates contain standard ply angle orientations and up to 21 plies. These laminates can be manufactured without the undesirable thermal warping distortions that generally affect this class of coupled laminate, and in particular, those containing angle plies only; previously thought to be the only form of laminate design from which this particular type of mechanical coupling can be derived.

The purpose of this paper is to demonstrate new design concepts for 24 classes of laminate, which have been derived as part of an ongoing study on the development of a unified approach to the characterization of coupled laminates. The paper presents a description of each class of coupled laminate.

The paper gives an overview of the desired performance and requirements of a smart leading edge device, its aerodynamic design for the wind tunnel tests and the structural pre‐design and sizing of the full‐scale leading edge section which will be tested in the wind tunnel.

Coupled laminates have potential applications in the design of aero‐elastic compliant rotor blades or aircraft wing structures, by introducing tailored extension‐twist and/or shear‐extension coupling at the laminate level; or in the design of thermally activated morphing structures, by exploiting more complex coupling behaviour.

These laminates contain standard cross‐ply and/or angle‐ply combinations, although double angle‐ply laminates are also considered, and correspond to any standard fibre/matrix system with a constant ply thickness throughout.

The vast majority of the laminate described possess coupling behaviour not previously identified in the literature.

Presents the results of investigation of fabrics’ and fused systems shrinkage force and its influence on the shape instability of fused textile systems after various treatments such as wetting and drying. Also the method for determination and prediction of the twisting phenomenon of fused composites is presented. From the analysis of the data the twisting phenomenon was characterised by several parameters. They are system’s twisting sign, the shape of twisted system, the twisting coefficient and fused system’s twisting direction.

This paper aims to design a novel jaw gripper with human-sized anthropomorphic features to be suitable for precise in-hand posture transitions, such as twisting and re-positioning. The growing demand from traditional high-mix low-volume and new massive customized manufacturing industry requires the robot with configurability and flexibility. In the electronic manufacturing industry particularly, the design of the robotic hand with sufficient dexterity and configuration is important for the robot to accomplish the assembly task reliably and robustly. It is important for the robot to be able to grasp and manipulate a large number of assembly parts or tools.

In this research, a novel jaw-like gripper with human-sized anthropomorphic features is designed for online in-hand precise positioning and twisting. It retains the simplicity feature of traditional industrial grippers and dexterity features of dexterous robotic hands.

The gripper is able to apply suitable gripping force on assembly parts and performs reliable twisting movement within limited time to meet the industrial requirements. Manipulating several cylindrical assembly parts by robot, as an experimental case in this paper, is studied to evaluate its performance. The effectiveness of proposed gripper design and mechanical analysis is proved by the simulation and experimental results.

The main originality of this research is that a novel jaw gripper with human-sized anthropomorphic features is designed to be suitable for precise in-hand posture transitions, such as twisting and re-positioning. With this gripper, the robotic system will be sufficiently flexible to deal with various assembly tasks.

The paper aims to develop a cownose ray-inspired robotic fish which can be propelled by oscillating and chordwise twisting pectoral fins.

The bionic pectoral fin which can simultaneously realize the combination of oscillating motion and chordwise twisting motion is designed based on analyzing the movement of cownose ray’s pectoral fins. The structural design and control system construction of the robotic fish are presented. Finally, a series of swimming experiments are carried out to verify the effectiveness of the design for the bionic pectoral fin.

The experimental results show that the deformation of the bionic pectoral fin can be well close to that of the cownose ray’s. The bionic pectoral fin can produce effective angle of attack, and the thrust generated can propel robotic fish effectively. Furthermore, the tests of swimming performance in the water tank show that the robotic fish can achieve a maximum forward speed of 0.43 m/s (0.94 times of body length per second) and an excellent turning maneuverability with a small radius.

The oscillating and pitching motion can be obtained simultaneously by the active control of chordwise twisting motion of the bionic pectoral fin, which can better imitate the movement of cownose ray’s pectoral fin. The designed bionic pectoral fin can provide an experimental platform for further study of the effect of the spanwise and chordwise flexibility on propulsion performance.

The purpose of this paper is to evaluate the effect of main parameters and their interactions on the workers' Lifting Index in a steel rolling mill.

NIOSH (National Institute for Occupational Safety and Health) lifting equation has been used to evaluate the risk of lifting tasks with respect to low back injury under varying load (10, 15, 20 kg), frequency (2, 3, 4 lifts/min), and twisting angle (0, 30, 45 degree).

The level of importance of the parameters on lifting index at origin and destination has been determined using analysis of variance (ANOVA).The analysis draws on lifting parameters and uses both main effects and interactions to describe the variation in Lifting Index and to identify the social influence associated with back injury. The interactions between object weight and twisting angle and object weight and lifting frequency turn out to be significant (p<0.05), whereas the interaction between twisting angle and lifting frequency is less significant (p=0.061).

The study includes a specific location (steel rolling mills located in Jammu region of India) only.

The findings suggest that focus should be made on all lifting parameters, rather than sole emphasis on the load to be lifted.

The paper supports the view that load, twisting angle and lifting frequency greatly influence the physical stressfulness of the task. It is suggested that the workplace should be designed for negligible twisting and moderate lifting frequency, so as to have minimum Lifting Index.

Finite elements based on Mindlin plate theory are used to study the distribution of shear forces and twisting moments on the boundaries of plates with various support conditons and thickness‐to‐span ratios. Differences between results obtained using Mindlin and Kirchhoff plate theories are highlighted. Potential difficulties in the interpretation of results obtained from finite element analysis are discussed and appropriate shear force sampling procedures are reviewed. The present work is a pilot study for a larger project with the basic aim of providing engineers with an unambiguous method for obtaining stress resultants in Mindlin plate analysis. Some examples are presented which illustrate the excellent results which may be obtained with judicious mesh division even in regions with steep gradients of the stress resultants near plate corners. These examples also demonstrate some of the difficulties facing engineers who have to try to interpret finite element results for plates.

An exact analysis is presented for the creep deformation of solder interconnects subjected to the actions of bending moment, twisting moment and axial force. Dimensionless interaction curves and charts which relate the variables, interconnect geometry, solder material properties, axial force, bending moment, twisting moment, bending stress, shearing stress, curvature rate and twist rate are also provided for engineering practice convenience. The constitutive relationship of the 96.5Sn3.5Ag solder interconnects is described by the Garofalo‐Arrhenius steady‐state creep equation.

An exact analysis is presented of the creep deformation of cylindrical solder interconnects subjected to the actions of bending moments, twisting moments, and axial forces. Dimensionless interaction curves and charts are also provided for engineering practice convenience. These charts show the interactions of the relevant variables, i.e. interconnect geometry; solder material properties; axial force; bending moment; twisting moment; bending stress; shearing stress; curvature rate; and twist rate. In the results presented the Garofalo‐Arrhenius steady‐state creep equation is used to provide the constitutive relationship for SnPb36Ag2 solder interconnects.

The tourist sector in Mauritius is aiming at welcoming 2 million tourists by the year 2015 and coming up with creative ideas and products branded with ‘Made in Mauritius’ to boost the country’s craft sector. This project looks into the manufacture of paper-yarn. Different types of paper were cut into ribbons of varying widths and converted into yarn by two methods: twisting and folding. The folds were made along the axis of a ribbon while twisting required prior moistening and was carried out on a modified yarn-twist measuring device. The relationship between the number of folds/twists and the strength of the resulting paper yarn was investigated. Yarn of high quality can be obtained by twisting ribbons of relatively smaller widths or folding relatively wider ribbons. The yarn can be used for manufacturing craft products.