A Magic Cube Approach for Crashworthiness and Blast Protection Designs of Structural and Material Systems.

Crashworthiness design is one of the most challenging tasks in automotive product development, and blast protection design is crucial for military operations. The goal is to design an optimal crashworthy or blast-protective structure in terms of topology, shape, and size, for both structural and material layouts. Due to the difficulties in the crash analyses and the complexity of the design problems, previous studies were limited to component-level examinations, or considered only a simple design aspect. In this research, an advanced approach entitled the Magic Cube (MQ) approach is proposed, which for the first time, provides a systematic way to examine general crashworthiness and blast protection designs in terms of both structural and material aspects. The MQ developed in this research consists of three major dimensions: decomposition, design methodology, and general consideration. The decomposition dimension includes the major decomposition approaches developed for the crashworthiness design problems, and it can be applied to the blast protection design. It has three layers: time (process) decomposition, space decomposition, and scale decomposition. The design methodology dimension is related to the methodologies employed in the design process; three layers in this dimension are: target cascading, failure mode management, and the optimization technique. The general consideration dimension has three layers, which are multidisciplinary objectives, loadings, and uncertainties. All these layers are coupled with each other to form a 27-element magic cube. A complicated crashworthiness or blast protection design problem can be solved by employing the appropriate approaches in the MQ, which can be represented by the corresponding elements of the MQ. Examples are given to demonstrate the feasibility and effectiveness of the proposed approach and its successful application in real vehicle crashworthiness, blast protection, and other related design problems. The MQ approach developed in this research can be readily applied to other similar design problems, such as those related to active safety and vehicle rollover.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/58392/1/cqi_1.pd

Measurements of reflected overpressure in the extreme near field

Blast protection design requires a detailed knowledge of the loading imparted on a structure by a particular blast threat. This includes an understanding of the mechanisms involved in the rapid energy release that leads to fireball expansion and air shock development. In the far field (Z > 2 m/kg1/3) reliable semi-empirical methods exist for both the positive and negative phases of the blast wave. In the far field the explosion is sufficiently far away that only the propagating air shock interacts with the structure, while in the near field the fireball is still driving the air shock and can itself interact with the structure. There is currently a lack of reliable experimental data in this near field region, as the incredibly high pressures and temperatures pose particular experimental challenges. This is particularly the case in the extreme near field (Z < 0.5 m/kg1/3), where semi-empirical and physics-based predictions can vary by an order of magnitude. This paper presents the design of an experimental facility capable of recording spatially resolved reflected pressures in the extreme near field. The Mechanisms and Characterisation of Explosions (MaCE) facility is an evolution of the Characterisation of Blast Loading (CoBL) facility used for buried blasts, but with key near fieldspecific adaptations. An array of Hopkinson pressure bars embedded in a stiff target plate is used to make pressure measurements over a 100 mm radius instrumented area. Maraging steel pressure bars and specially designed strain gauges are used to increase the measurement capacity from 600 MPa to 1800 MPa, and 33 pressure bars in a radial grid are used to improve the spatial resolution from 25 mm to 12.5 mm. In addition, the pressure bar diameter is reduced from 10 mm to 4 mm, which greatly reduces stress wave dispersion, increasing the effective bandwidth. This enables the observation of high-frequency features in the pressure measurements, which is vital for validating the near-field transient effects predicted by numerical modelling and developing effective blast mitigation methods

Calculation of Blast Loads for Application to Structural Components. Administrative Arrangement No JRC 32253-2011 with DG-HOME Activity A5 - Blast Simulation Technology Development

This technical report describes a procedure that can be followed for the calculation of the loads to be applied to a structure as a consequence of a blast. The report considers explosions taking place outside a building, which are not addressed directly at the relevant European Standards (Eurocode EN1991-1-7) dealing with accidental loading scenarios. The aim is the production of a simple, self-contained guide enabling the structural engineer to conduct a preliminary design of buildings for possible terrorist attacks. Aspects of the theory of blast waves have been included at an introductory level. The approach of the empirical methods for the prediction of blast loads has been chosen, which is more straightforward and has resulted from extensive experimental testing. For the determination of the main blast parameters, several graphs and diagrams have been included, which have been collected and properly adapted from several authoritative sources. This should make the load calculation procedure easier to grasp and less demanding in terms of mathematical complexity and computational capacity. Selected case studies are also presented in order to demonstrate through simplified examples the steps that must be followed for the calculation of blast pressures on the surfaces of a structure.JRC.G.4-European laboratory for structural assessmen

Topology Optimization for Multi-Functional Components in Multibody Dynamics Systems.

This research extends topology optimization techniques to consider multibody dynamics systems with a much more open design space, which can include passive, active, and reactive components, with a special application focus on a gunner restraint system (GRS) design problem. General representative models for the multi-functional components are established in a multibody dynamics system. The topology optimization process has been advanced for the optimization of geometrically nonlinear, time-dependent, and timing-dependent multibody dynamics systems undergoing large nonlinear displacements with nonlinear dynamics responses as design objectives. Three efficient sensitivity analysis methods have been proposed, which include the constant dynamic loading method, the time integration incorporated method based on the Generalized-Alpha algorithm and the iterative method. These new methods have made it possible to calculate the sensitivities in complicated multibody dynamic systems and provide users with choices to significantly reduce the computational costs, especially, in the topology optimization process, and to obtain desired accuracy in the sensitivity analysis. In addition to the sensitivity analysis methods, an efficient and reliable Kriging variable screening method based on the REML criterion has been developed to identify significant variables in the systems to determine the worst cases for various system uncertainty studies. A specific application of the multi-functional components system optimization technology is the GRS design problem, in which both the vehicle and the gunner can undergo large relative and absolute motions under various driving or threat conditions. In meanwhile, the restraint components may need to allow amplitude-dependent, time-dependent, timing-dependent nonlinear response behaviors, such as those seeing in restraint belts, airbags, and retractors. The restraint system layout design needs to keep a wide open design space, thus to find the truly optimal design. The developed methodologies have been employed in the GRS design problems to demonstrate usage of the new methodologies.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91444/1/dongg_1.pd

Temporally and spatially resolved reflected overpressure measurements in the extreme near field

The design of blast-resistant structures and protective systems requires a firm understanding of the loadings imparted to structures by blast waves. While empirical methods can reliably predict these loadings in the far field, there is currently a lack of understanding on the pressures experienced in the very near field, where physics-based numerical modelling and semi-empirical fast-running engineering model predictions can vary by an order of magnitude. In this paper, we present the design of an experimental facility capable of providing definitive spatially and temporally resolved reflected pressure data in the extreme near field (Z<0.5 m/kg1/3 ). The Mechanisms and Characterisation of Explosions (MaCE) facility is a specific near-field evolution of the existing Characterisation of Blast Loading (CoBL) facility, which uses an array of Hopkinson pressure bars embedded in a stiff target plate. Maraging steel pressure bars and specially designed strain gauges are used to increase the measurement capacity from 600 MPa to 1800 MPa, and 33 pressure bars in a radial grid are used to improve the spatial resolution from 25 mm to 12.5 mm over the 100 mm radius measurement area. In addition, the pressure bar diameter is reduced from 10 mm to 4 mm, which greatly reduces stress wave dispersion, increasing the effective bandwidth. This enables the observation of high-frequency features in the pressure measurements, which is vital for validating the near-field transient effects predicted by numerical modelling and developing effective blast mitigation methods

Review on Glass Curtain Walls under Different Dynamic Mechanical Loads: Regulations, Experimental Methods and Numerical Tools

This chapter explores the behaviour and performance of glass curtain wall systems under various dynamic mechanical loads, including seismic, wind and impulsive loads. The classification of glass facade systems, comprising framed and frameless types, is first shortly discussed, along with their core components such as glass panels and frames. The challenges posed by glass material, including its vulnerability to impact, stress peaks and extreme loads, are acknowledged. The study further delves into various design standards and regulations for glass facade systems under dynamic loads, addressing seismic events and wind and impulsive loads and hence outlining parameters for assessment, performance criteria, and design considerations in use of glass curtain walls. Additionally, numerical methods are explored as effective tools for simulating and analysing the mechanical response of glass curtain walls under dynamic loads. The utility of these methods is showcased through a case study involving the Finite Element (FE) modelling of a glass curtain wall system exposed to a lateral in-plane load. The results of FE analysis are then compared with literature experimental results, which indicates its capacity to anticipate structural responses and even complex mechanisms under dynamic loads

Guideline - Building Perimeter Protection: Design Recommendations for Enhanced Security against Terrorist Attacks

The purpose of the current document is to provide guidance to security and law enforcement officials, building/site owners, venue organizers, state organizations, engineers and other stakeholders that are in charge of securing facilities and critical infrastructures against the growing international terrorist threat. The focus of the report narrows down into recommendations for a robust and usable approach for the physical protection of infrastructures against this borderless phenomenon. It addresses shortcomings encountered in the design of such security solutions and aims at producing a simple, self-contained practical guide to enable the selections and installation of elements that are able to stop and/or deter potential terrorist attacks. A detailed analytical procedure is illustrated for identifying the weaknesses of potential terrorist targets and assess the relevant risk for different terrorist tactics. Advice is provided for the introduction of protection measures against both external and internal explosions and design methodologies are presented for minimizing the likelihood for the development of a progressive collapse mechanism. Moreover, specialized perimeter physical protection measures are proposed that may successfully restrict unauthorized vehicle and intruder access, supplemented by the employment of modern digital technologies, such as video surveillance, smart sensors and video analytics. The novel and emerging threat landscape is also addressed, such as the malicious use of Unmanned Aircraft Systems, requiring new response strategies that call for the adoption of state-of-the-art counter technologies.JRC.E.4-Safety and Security of Building

Modeling the dynamic response of low-density, reticulated, elastomeric foam impregnated with Newtonian and non-Newtonian fluids

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references.Engineering cellular solids, such as honeycombs and foams, are widely used in applications ranging from thermal insulation to energy absorption. Natural cellular materials, such as wood, have been used in structures for millennia. However, despite their extensive use, a comprehensive understanding of the dynamic interaction between the interstitial fluid in the cells of the foam and the foam itself has yet to be developed. In this thesis, we explore the dynamic, compressive response of low-density, reticulated, elastomeric foam impregnated with Newtonian and non-Newtonian fluids. To develop tractable analytical models for this complex, non-linear phenomenon, a study is first undertaken on the permeability of foam under deformation. Using these results, a model is developed for the dynamic, uniaxial compressive response of low-density, reticulated, elastomeric foam filled with a viscous Newtonian fluid. This comprehensive model is found to be well approximated by a simpler model, based on the lubrication approximation. Furthermore, in the lubrication limit, a model for the dynamic, uniaxial compressive response of foam filled with a non-Newtonian fluid is also developed. All of the models presented in this thesis are supported by extensive experimental studies. The experiments also suggest that these models are applicable over a wide-range of parameters, such as strain, strain rate, and pore size. Finally, these models are used in two case studies to assess the feasibility of composite structures containing a layer of liquid-filled foam in dynamic loading applications. The first case study focuses on applications in energy absorption with the experimental design of a motorcycle helmet. The second case study focuses on applications in mitigating the effects of blast waves with a parametric study of the design of a blast wall.(cont.) These studies provide insight into the usefulness of the models and demonstrate that composite structures with a layer of liquid-filled foam have enormous potential in a wide range of dynamic loading applications.by Matthew A. Dawson.Ph.D