Yahia M. Al-Smadi

Planar Four-Bar Motion Generation With Static Structural Conditions

A planar four-bar motion generation model that also includes static structural conditions is formulated and demonstrated in this work. Using this model, planar four-bar motion generators are also synthesized with respect to static torque, deflection constraints, and buckling constraints for a given rigid-body load.

Geared five-bar path generation with structural constraints

The specific contribution made by this work in the area of geared five-bar path generation is the formulation of a non-linear optimization problem that includes elastic deflection, static torque and buckling constraints. Using this model, geared five-bar path generators are also synthesized with respect to static torque, deflection constraints and buckling constraints for a given rigid-body load.

Four-bar motion generation with elasticity constraints and optimization

Abstract In conventional planar four-bar motion generation, all mechanism links are assumed rigid or non-deforming. Although the assumption of link rigidity in kinematic synthesis may be generally appropriate and often practiced, a statically loaded planar four-bar mechanism will undergo a degree of elastic deflection, particularly the crank and follower links. In this work, a non-linear optimization problem is formulated for planar four-bar motion generation that considers an applied coupler force and corresponding crank static torque, crank transverse deflection, and follower buckling. The output from the non-linear optimization problem – mechanism fixed and moving pivot loci – are input for a search algorithm that down selects a mechanism solution that satisfies transmission angle conditions, Grashof conditions, and a mechanism compactness condition. The final output of the presented method is planar four-bar motion generator that approximates prescribed coupler poses with satisfactory crank deflection and without follower buckling and also satisfies conditions for link rotatability, transmission angle and compactness.

Numerical Simulation of Blast Wave Mitigations on RC Buildings via Improved Structural Configuration and Column Cross-Section Properties

Blast mitigation became of a global interest for architects and civil engineers with the increase of terror threats that targets key structures worldwide. The current work, which is largely exploratory in nature, involves blast wave traveling within a matrix of columns. The fluid structure interactions reach a maximum peak of vibration at a particular set of input parameters. Therefore, possible damage which affects structural integrity and reliability may occur. The presented numerical blast tests will accompany the study of different column cross-sections and orientation taking into account the charge weight and the stand-off distance variations. The effects of these variables have been quantified and compared to find a safety criterion for reinforced concrete buildings that might be subjected to blasting. Reliable and robust analysis (ANSYS and LS-DYNA) software will be used to complete a threedimensional finite element model and conduct numerical testing. Analyst of this study will be able to find blast wave mitigation strategies to minimize the structural damage and/or progressive collapse and recommendation for safe design against blast loading. With the help of the guidelines mentioned in this study, the designer will be able to apply one or more of the mitigation techniques to build up a safer and more reliable model which if subjected to blast will have the minimum degree of collapse. This academic work also inspires researchers to develop more blast wave mitigation strategies using economical and practical solutions similar to those discussed in this study.

Numerical Simulations on the Performance of Passive Mitigation Under Blast Wave Loading

The current work, which is largely exploratory in nature, involves blast wave travelling within a matrix of piles or columns. The fluid structure interactions reach a maximum peak of vibration at a particular set of input parameters. Therefore, possible damage, which affects vibration structural integrity and reliability, may occur. The presented numerical blast tests will accompany the introduction of new structural design concepts associated with mitigation details. Reliable and robust analysis (ANSYS and LS-DYNA) software will be used to complete 3D finite element model and conduct numerical testing.

Design of Experiments Study to Obtain a Robust 3D Computational Bridge Model

Ambient traffic vibration tests for the three continuous span bridge were conducted to investigate the dynamic response of the bridge in order to identify the natural frequencies and the mode shapes. Understanding the dynamic response of the bridge in its existing, unretrofitted condition is the starting point for developing confidence in the computer model because the same model will evolve from the existing bridge to the retrofitted bridge. A robust 3D computational model is developed using design of experiments (DOE) techniques. Extensive full factorial experiments are carried out to determine simultaneously the individual and interactive effects of many factors such as concrete density, concrete modulus of elasticity and steel modulus of elasticity that could affect the natural frequencies of the bridge. Data is processed to derive natural frequencies and modes shapes, which are remarkably consistent over the range of experiment conditions. ANSYS is used to complete the finite element model and analysis. In the DOE each factor is given two values. The set of allowable model factors which causes the model to match the tested natural frequencies and mode shapes are presented in this paper.

Nonlinear FEA Simulation of Thorax Considering Transient CPR Forces and Sternotomy

The median sternotomy has become the desired incision in the modern era of cardiac surgery. The objective of this study is to investigate the sternum loading due to daily forces after sternotomy and during healing. Two models of thorax were built. The first is to simulate the healthy thorax and the second is to simulate the thorax after sternotomy and got closure using stainless steel stitches. In this paper, ANSYS was used to build the throax model. The results that have been collected after solving the model were analyzed. The analysis was promising and proved that the model was working properly and its ability to simulation what happens in the real life.Copyright

Dynamic Response of RC Structures Subjected to Blast Wave Shock Loading

The collapse of significant structures caused by terrorist attacks in the past decades has motivated engineers to study the stability of current structural systems and their susceptibility to collapse. This collapse usually occurs due to blast waves generated by the high explosive bursts in the air that hit the structural components of the buildings leading to catastrophic damages which unfortunately happen before the evacuation. In an effort to find a safety criterion for buildings subjected to blasting; this study uses the nonlinear FEA explicit software LS-DYNA to highlight the effect of blast wave propagation on reinforced concrete column taking into account the standoff distance and charge weight variations. The effects of these two variables have been quantified through the comparison of resulted pressures, displacement and impulses.Copyright

Spatial Four-Bar Motion Generation With Static Control Condition

In conventional motion generation, the objective is to calculate the mechanism parameters required to achieve or approximate a set of prescribed rigid-body poses. This mechanism design objective is particularly useful when the rigid-body must achieve a specific displacement sequence for effective operation. A spatial four-bar motion generation model that also includes static structural conditions is formulated and demonstrated in this work. Using RRSS mechanism, spatial four-bar motion generators are synthesized with respect to static torque.Copyright

Nonlinear FEA Simulation of Thorax Considering Transient CPR and Lateral Forces

Boxing or martial arts are games where players chests are subject to lateral impact, the impact loads travel through skin, ribs, mediastinum (i.e. a thoracic compartment) and then through the skeleton to the rest of the body. When thorax is subject to lateral force exceeding the elastic limit of thoracic compartment, players often go in shock demanding prompt resuscitation. This paper investigates the thorax response of boxer being subject to lateral impact followed by Cardiopulmonary resuscitation (CPR). Due to complexity of thorax structure and materials, three dimensional finite element model in ANSYS was created to perform the computational biomechanical analysis of two-stage loading (i.e. lateral impact load and CPR forces). Model input parameters such as material, loading and boundary conditions have been defined. Post processing values such as deformations and stresses have been presented.Copyright