Voyager design studies. volume iv- orbiter- bus design, part 1

Voyager project - design of unmanned spacecraft to perform scientific orbiter-lander missions to Mars and Venus - orbiter-bus desig

The effects of different degrees of confinement on the deformation of square plates subjected to blast loading

Includes abstract.Includes bibliographical references.This work relates to the effcts of the degree of confiement for air blasts only. The response of a structure subjected to a blast load is dependent on several factors; for instance stand off distance, geometry and mass of explosive, geometry of the structure, medium (air, water, soil) and degree of confinement. Depending on the location of the explosion relative to the surrounding structures different degrees of confinement are obtained. In addition, depending on the degree of confinement the accumulation of high temperature gas products will exert additional loads on the structure. This thesis reports the results of experimental and numerical investigations into the effct of the different degrees of confinement and target plate thickness on the response of square mild steel target plate

Diffusing wave spectroscopy applied to material analysis and process control

Diffusing Wave Spectroscopy (DWS) was studied as a method of laboratory analysis of submicron particles, and developed as a prospective in-line, industrial, process control sensor, capable of near real-time feedback. No sample pre-treatment was required and measurement was via a noninvasive, flexible, dip in probe. DWS relies on the concept of the diffusive migration of light, as opposed to the ballistic scatter model used in conventional dynamic light scattering. The specific requirements of the optoelectronic hardware, data analysis methods and light scattering model were studied experimentally and, where practical, theoretically resulting in a novel technique of analysis of particle suspensions and emulsions of volume fractions between 0.01 and 0.4. Operation at high concentrations made the technique oblivious to dust and contamination. A pure homodyne (autodyne) experimental arrangement described was resilient to environmental disturbances, unlike many other systems which utilise optical fibres or heterodyne operation. Pilot and subsequent prototype development led to a highly accurate method of size ranking, suitable for analysis of a wide range of suspensions and emulsions. The technique was shown to operate on real industrial samples with statistical variance as low as 0.3% with minimal software processing. Whilst the application studied was the analysis of TiO2 suspensions, a diverse range of materials including polystyrene beads, cell pastes and industrial cutting fluid emulsions were tested. Results suggest that, whilst all sizing should be comparative to suitable standards, concentration effects may be minimised and even completely modelled-out in many applications. Adhesion to the optical probe was initially a significant problem but was minimised after the evaluation and use of suitable non stick coating materials. Unexpected behaviour in the correlation in the region of short decay times led to consideration of the effects of rotational diffusion coefficient. The inherent instability of high density suspensions instigated high speed analysis techniques capable of monitoring suspensions that were undergoing rapid change as well as suggesting novel methods for the evaluation of the state of sample dispersion

A selective list of acronyms and abbreviations

A glossary of acronyms, abbreviations, initials, code words, and phrases used at the John F. Kennedy Space Center is presented. The revision contains more than 12,100 entries

The effects of 3D printed material properties on shaped charge liner performance

© Cranfield University, 2019Shaped charges operate by explosively loading a (typically metallic) liner to produce a jet travelling at extremely high velocity (9-12 km/s). Such explosive loading involves highly non-linear transient phenomena. As such, a very wide range of physical processes must be considered to enable accurate characterisation of such events – with material behaviour within these (pressure / strain-rate) regimes providing insight into problems ranging from shaped charge performance itself through to formation of new material phases at high pressures. Unlike other high strain impact events, the shaped charge phenomenon results in hydrodynamic material flow of the liner which is an integral aspect of the shaped charge design. As such, the study of shaped charge liners has been the subject of numerous scientific research studies for over 50 years since its discovery. When explosively loaded, the liner is stretched extensively during their elongation to form a jet. The jet length depends on the ductility of the liner material, and this is strongly linked to the microscopic crystal structure, which depends on the original material properties and the processes used to produce the liners. There are several processes currently used for liner production. This thesis outlines the different liner production techniques, their advantages/disadvantages and explores the potential of employing additive manufacturing (3D printing) technique for shaped charge liner production. As 3D printed parts are being considered as a possible replacement for conventionally processed parts, this PhD work fits into this long-term vision; with built parts compared in density and mechanical strength to their bulk material equivalents. More so, 3D printing is shown to present some potential benefits for the production of efficient liners including high precision, cost-effectiveness and the potential to realise customized geometries. The use of fine powders may also allow alternative microstructures to be produced with potentially interesting results. This element of the study forms the first part of this thesis, aimed at investigating the mechanism elucidating the performance of 3D printed liners processed through direct metal laser sintering process (selective laser sintering) and filament deposition modelling processes (Polylactic Acid). The next part of this work provided additional insights on the additive manufactured processed employed through investigation of the dynamic behaviour of polylactic acid, employed in the filament deposition modelling process and static (optical and scanning micrographs) observation of the laser sintered liners in their as - manufactured and deformed state, in comparison with traditional machined liners. Autodyn 2D numerical hydrocode was employed to understand how temperature influences the deformation pattern (grain refinement); providing new insights on liner deformation. Finally, a novel computational technique to determine the Virtual Origin of shaped charges was developed to provide a ready route to predict more accurate SC performance

Crashworthiness Characterisation of the Car Front Bumper System Based on FEA Analysis

This thesis investigated different designs and material selections of vehicle front bumper system to improve the vehicle crashworthiness during the low impact speed (impact velocity=15km/h, 9.32mph) via FEA simulations. The primary purpose is to identify the most important parameters directly related to the improvement of crashworthiness using numerical parametric study. It is found the cross-section profile, curvature shape, material of the bumper beam, together with the connection to the crash box have been all identified that directly influence the crashworthiness performance of the front bumper system. The bumper system, including the sub-components such as bumper beam, crash box, and the connection methods were carried all the parameters, including a number of folds, curvature shapes and spot welds were in-built while creating them into the CAD models using Solidworks. The final assembled complete bumper system is then imported into the ANSYS for further geometry checks and adjustment. Solver Autodyn is used to perform the FEA simulation, and numbers of results files were generated. Results files such as force reaction, plastic work, and equivalent stress, normal stress was all exported it into the Excel for parametric analysis and discussions. Cross-section Profile-Out of proposed Single fold (fold 1) and Triple fold(fold 3) bumper beam profiles, Double fold (fold 2) bumper beam profile presented the best results of force reaction on both smoothness and force value, while the plastic work remained almost identical to profile fold 1 and 3 gained. Fold 2 profile is considered as a good performer since this profile regulated the deformation behaviour of the beam resulted in a smooth increasing force reaction curve. Where the force reaction curve on both fold 1 and fold 3 were fluctuated dramatically due to catastrophic structural failure. Material-In between structural steel and aluminium alloy used in the bumper beam, while the structural steel made bumper beam achieved good force reaction and plastic work. Switched to aluminium can achieve similar force reaction trend and rate with Cross-section neglectable amount of plastic work reduced. Particularly the weight of the bumper beam is dropped down to 5.357 kg while maintaining similar crashworthiness performance to the structural steel. Crash box Crash box connection- The bonded connection is considered as an ideal scenario and was xvii Sensitivity: Internal favoured in much other literature due to it simplifies the connection setting in the FEA environment since it automatically considers it as perfect contact. Three alternative connection methods were therefore proposed to simulate the more realistic scenario. It defined as welding connection that is constituted by a number of spot welds at left, right, top and bottom of the crash box. Since the bonded method contains no spot welds, a method of weld L+R was indicated by totally 4 spot welds appeared at both left and right side of the crash box. On top of this, 4 additional spot welds were added to the top and bottom of the crash box. Totally 4 spot welds were added only to both the top and bottom of the crash box to extend the comparison. While both bonded and weld L+R methods suffered from buckling effect to the crash box, particularly concentrated at the left and right side with high equivalent and normal stresses. It is discovered weld full method provided promising results by reducing the buckling effect to both left and right faces of the crash box, and also managed to lower the equivalent stress down to 336.48MPa and normal stress on the connection surface down to 66MPa. Weld T+B also observed similar performance when compared with both bonded and weld L+R methods. While registered with very small amount of equivalent and normal stresses, the buckling effect is significantly reduced. This thesis contributed the knowledge to the improvement of vehicle front bumper system. Particularly to the failure mode of both bumper beam and crash box, and offered the related optimisation.N/