Shafique M.A. Khan

Analysis of mixed mode crack initiation angles under various loading conditions

Abstract A detailed analysis of mixed mode I–II crack initiation angles under different loading conditions is presented using different criteria. In addition, the maximum tangential stress criterion (MTS), which was proposed originally for brittle materials, is modified such that it can be used for ductile materials. A variable radius for the plastic core region based on von Mises elastic plastic boundary is introduced and incorporated in the formulation of the MTS-criterion. The limited available experimental data exhibits large scatter, and does not support a certain criterion for different loading conditions. This presents the need for a close examination of the limitations and capabilities of each criterion, which is the main purpose of this study.

Towards sensor array materials: can failure be delayed?

Abstract Further to prior development in enhancing structural health using smart materials, an innovative class of materials characterized by the ability to feel senses like humans, i.e. ‘nervous materials’, is discussed. Designed at all scales, these materials will enhance personnel and public safety, and secure greater reliability of products. Materials may fail suddenly, but any system wishes that failure is known in good time and delayed until safe conditions are reached. Nervous materials are expected to be the solution to this statement. This new class of materials is based on the novel concept of materials capable of feeling multiple structural and external stimuli, e.g. stress, force, pressure and temperature, while feeding information back to a controller for appropriate real-time action. The strain–stress state is developed in real time with the identified and characterized source of stimulus, with optimized time response to retrieve initial specified conditions, e.g. shape and strength. Sensors are volumetrically embedded and distributed, emulating the human nervous system. Immediate applications are in aircraft, cars, nuclear energy and robotics. Such materials will reduce maintenance costs, detect initial failures and delay them with self-healing. This article reviews the common aspects and challenges surrounding this new class of materials with types of sensors to be embedded seamlessly or inherently, including appropriate embedding manufacturing techniques with modeling and simulation methods.

Initial Investigation Into Optimizing Design of a Pressure Vessel Saddle

The ASME Boiler and Pressure Vessel Code does not provide details of the pressure vessel saddle supports. The existing design guidelines are based on classical stress analysis with several assumptions to simplify the problem. With the advances in the computational technology and numerical methods, it is now possible to obtain more detailed information about stress distribution and hence provide optimal saddle design guidelines. This study will present an initial investigation into a 3D computational modeling and analysis of the saddle design. Results are presented for maximum von Mises stress occurring in various parts of the saddle with the increase in load.Copyright