Lightweight Structures and Impact Engineering MSc

Compulsory

• Advanced Transient Simulation Methods

  Designing advanced lightweight structures to perform an intended function over its lifecycle, when subject to static and dynamic loading conditions encountered during normal operation and extreme loading conditions, requires expertise in a range of areas. This expertise primarily relates to the application of advanced numerical simulation to understanding non-linear material and structural response over different operating conditions, which may include large or rapid deformation, failure (static and transient), and high strain rate loading (inertial effects, wave propagation and shockwaves). As new simulation and material technologies emerge, there is a continuing need for engineers with a strong, applied understanding in structural analysis and testing, together with competent technical skills in non-linear numerical simulation (mesh and meshfree methods) that can be directly applied to industrial problems. This module will review the available numerical methods, including their strengths and weaknesses, covering both theoretical background and numerical implementation. To reinforce the underlying theory, practical computational lab sessions are used to simulate a range of non-linear, transient problems.

  Indicative Content:

  • Nature and treatment of geometric and material non-linearities;
  • Space discretisation (semi-discretisation) methods, Lagrangian, Eulerian and hybrid approaches;
  • Solution procedures for static analyses and time integration procedures dynamic analyses, formulation and implementation;
  • Review different element technologies: beam, shell and solid elements;
  • Strain, strain rate and temperature dependent strength models and equations of state;
  • Contact algorithms, including coupling of different discretisation methods;
  • Smoothed particle hydrodynamics and meshless methods approach to large deformation, transient problems;
  • Supporting case studies, including dynamic structural collapse and high velocity impact;
  • Practical computational lab sessions using non-linear transient analysis codes.
• Applied Continuum Mechanics 1: Fundamentals

  The basic principles and mathematics of continuum mechanics is fundamental to modern engineering structural and solid mechanics analysis. This module introduces these principles and mathematics along with their numerical implementation within the material models used in non-linear analysis computer code. Topics include an introduction to tensor calculus, motion and deformation of continuum bodies, the concept of stress and the fundamental equations governing the motion of a continuum. The second part discusses the use of this fundamental knowledge within engineering analysis computer codes and the numerical implementation of constitutive laws.

  Indicative Content:

  • The fundamental rules and standard results of the tensor algebra used in continuum mechanics;
  • Gradients and related operators for vector and tensor functions;
  • Motion of continuum bodies, measures of deformation and strain;
  • Concept of stress in the current configuration; Stress in reference and intermediate configurations;
  • Conservation of mass, momentum balance, energy balance;
  • Computational continuum elasticity and plasticity;
  • Numerical implementation of constitutive relations within structural and solid mechanics computer codes.
• Applied Continuum Mechanics 2: FEA

  Finite Element Analysis is a widely used and industry standard technique to simulate complex, real-world engineering problems. With an appropriate mathematical model representative of the engineering physics, FEA provides structural insight into the load path, identification of design faults, reducing the need for physical prototypes, as well as the potential for design optimisation, or investigate “what if” design changes virtually. However, for those new to FEA, the learning curve is steep, not only in developing the model, but also in post-processing results. This module provides an understanding of the inner workings of the finite element method through introducing key numerical and mathematical aspects. Knowledge and training to solve day-to-day structural mechanics problems will be demonstrated through progressive examples using commercial analysis codes. The lessons learned relate to good finite element practice and are code independent to help avoid common numerical and modelling user errors, many of which stem from a “blackbox” approach to this technique.

  Indicative Content:

  • Background, history, applicability to different physics problems;
  • Illustration of direct stiffness method based on 2 dimensional beam elements;
  • Principle of Minimum Potential Energy;
  • Development of stiffness and mass matrices for a 2-dimensional membrane element;
  • Isoparametric 1,2 and 3D elements;
  • Numerical integration;
  • Problems and errors associated with applying FEM to the solution of actual problems;
  • Practical aspects of FE modelling: 1-2-3 dimensional meshing;
  • Geometric modelling of simple components;
  • Importing of geometric models from other software;
  • Simulation of different types of loads and boundary conditions for different types of analyses;
  • Mesh generation (quality) and selection techniques;
  • Application of commercial codes for linear / nonlinear structural analysis;
  • Advanced post-processing and interpretation of results.
• Composite Materials and Structures

  Composite materials are routinely used in the development of lightweight engineering structures as they can be developed with tailored mechanical properties to meet specific performance targets. Consequently, the module provides a synthesis of the principles of composite and high-performance materials design and selection under linear and non-linear dynamic loading, including the evaluation of those materials in impact and energy absorbing structures. The module also includes an introduction to damage mechanics, fatigue and fracture/failure modelling in advanced CAE tools, together with practical issues related to numerical modelling.

  Indicative content:

  • Introduction to composite materials: key characteristics / properties, fabrication methods and manufacturing;
  • Elasticity of long and short-fibre composites, equivalent elastic properties and stress-strain relationships;
  • Lamination theory for prediction of stiffness, strength and failure;
  • Interlaminar / thermal residual stresses as a consequence of complex material structure;
  • Introduction to strength/stiffness optimisation;
  • Design case studies: optimum lay up for buckling, bonded joints, crash energy absorption;
  • Introduction to damage mechanics and damage modelling, principles of fatigue and failure;
  • Static and dynamic material characterisation methods: strain gauges and non-destructive testing methods for composites;
  • Finite Element Modelling, including static and dynamic examples using commercial FE codes;
  • Simulation of composite damage and failure at different loading rates: low to high and hyper velocity impact.
• Fracture Mechanics and Fatigue Analysis
• ME5707 Impact and Crashworthiness

  Understanding the response of lightweight engineering structures and materials to impact loading, requires an understanding of the physics involved, which are characterised by large or rapid deformation, failure (static and transient), and high strain rate loading (inertial effects, wave propagation). Part one covers a conceptual understanding of how solids and structures respond to different rates of loading, ranging from low through to hypervelocity impacts. The specialist experimental methods needed for dynamic testing at different strain-rates of interest will be reviewed, together with different impact protection systems from low, high and hypervelocity regimes for land, air and space applications. The second part provides the principles involved in the analysis and design of crashworthy structures, by reviewing relevant crash regulations and understanding the implications of local and global collapse of thin and thick-walled sections. The module will cover methods of analysing structural collapse using hand calculations and hybrid (numerical) approaches in order to design a structural assembly able to provide appropriate stiffness and strength properties for impact loading.

  Indicative Content:

  • Overview of crash and impact protection: Threats and design context; Occupant protection & injury criteria;
  • Large deformation and strain-rate dependent material behaviour of structural materials;
  • Stress wave propagation, equation of state of solids;
  • Energy management approach to design; modes of energy absorption; absorption mechanism control; dynamic effects;
  • Review of aerospace and automotive crashworthiness and impact regulation;
  • Material vs structural response to impact: design of structural impact protection systems;
  • Local collapse of structural components: Collapse of thick-walled sections; collapse of thin walled sections;
  • Global collapse of structures: Identification of collapse mechanism, geometric effects;
  • Impact testing of structures and materials: material test methods, structural crash and impact testing;
  • Analysis methods: analytical methods (energy balance), hybrid numerical models, capability of detailed numerical models.
• Metallurgy and Materials
• Dissertation

Optional

• Automotive Integral Vehicle Structures

  Thin-walled structures are commonly used in the design of lightweight structures, allowing an engineer to minimise material cost, whilst at the same time, ensuring sufficient strength / stiffness to meet performance targets. To support the conceptual vehicle design process, the Simplified Structural Surfaces (SSS) approach can greatly simplify modern automotive integral structural design. Based on the principles of Statics, this approach allows an engineer to identify load paths in a vehicle body-in-white (BIW) for integral cars, light truck and vans for different load cases. Using a first principle approach, you will learn how to identify and propose design solutions for load path faults and carry out preliminary component sizing through detail stressing. The training provided will enable you to take key structural design decisions before investment in further detailed design.

  Indicative Content:

  • Background and development of SSS method;
  • Vehicle load cases and load factors;
  • Overview of principle vehicle structural types;
  • Vehicle body load paths for major load cases using the Simple Structural Surfaces (SSS) approach;
  • Consideration of different vehicle types: Bus, hatchback, estate and pick-up truck;
  • Stress analysis of thin walled structures under shear and torsion loads;
  • Warping and warping restraint effects;
  • Shear lag.
• Thin-Walled Structures

  Thin-walled structures are commonly used in the design of lightweight structures, allowing an engineer to minimise material cost, whilst at the same time, ensuring sufficient strength / stiffness in order for a component or structure to meet performance targets in automotive, aerospace, offshore and transportation sectors. However, the buckling stability of such structures is often one of the key parameters driving the design. This module provides fundamental knowledge and understanding of thin walled structures, subject to shear and torsional loads, covering:

  • A first principles approach to calculate stress, shear flows around open / closed sections, together with warping and warping restraint effects.
  • Buckling and post buckling collapse of thin walled structures.

  Indicative Content:

  • Stress analysis of open / closed thin walled structures under shear and torsion loads;
  • Warping and warping restraint effects
  • Shear Lag
  • Buckling of thin-walled structures: Columns, plates and shells
  • Stable and unstable equilibrium – principle of minimum potential energy;
  • The Rayleigh-Ritz method and alternative methods for buckling analysis for columns / plates
  • Elastic buckling, shear buckling of plates, torsional buckling, combined buckling
  • Post-buckling behaviour of plates
  • Buckling of stiffened plates
  • Use of ESDU sheets for buckling analysis