<p>The introduction of carbon-fibre reinforced plastics in loadbearing automotive structures provides a great potential toreduce vehicle weight and fuel consumption. To enable themanufacture and assembly of composite structural parts,reliable and cost-effective joining technologies must bedeveloped. This thesis addresses several aspects of joining andload introduction in carbon-fibre reinforced plastics based onnon-crimp fabric reinforcement.</p><p>The bearing strength of carbon fibre/epoxy laminates wasinvestigated considering the effects of bolt-hole clearance.The laminate failure modes and ultimate bearing strength werefound to be significantly dependent upon the laminate stackingsequence, geometry and lateral clamping load. Significantreduction in bearing strength at 4% hole deformation was foundfor both pin-loaded and clamped laminates. The ultimatestrength of the joints was found to be independent of theinitial bolt-hole clearance.</p><p>The behaviour of hybrid (bolted/bonded) joints wasinvestigated both numerically and experimentally. Athree-dimensional non-linear finite element model was developedto predict the load transfer distribution in the joints. Theeffect of the joint geometry and adhesive material propertieson the load transfer was determined through a parameter study.An experimental investigation was undertaken to determine thestrength, failure mechanisms and fatigue life of hybrid joints.The joints were shown to have greater strength, stiffness andfatigue life in comparison to adhesive bonded joints. However,the benefits were only observed in joint designs which allowedfor load sharing between the adhesive and the bolt.</p><p>The effect of the environment on the durability of bondedand hybrid joints was investigated. The strength and fatiguelife of the joints was found to decrease significantly withincreased ageing time. Hybrid joints demonstrated increasedfatigue life in comparison to adhesive bonded joints afterageing in a cyclic freeze/thaw environment.</p><p>The strength and failure mechanisms of composite laminatessubject to localised transverse loading were investigatedconsidering the effect of the specimen size, stacking sequenceand material system. Damage was found to initiate in thelaminates at low load levels, typically 20-30% of the ultimatefailure load. The dominant initial failure mode wasintralaminar shear failure, which occurred in sub-surfaceplies. Two different macromechanical failure modes wereidentified, fastener pull-through failure and global collapseof the laminate. The damage patterns and ultimate failure modewere found to depend upon the laminate stacking sequence andresin system. Finite element analysis was used to analyse thestress distribution within the laminates and predict first-plyfailure.</p><p><b>Keywords:</b>Composite, laminate, bearing strength,joining, load introduction, hybrid joint, finite elementanalysis, mechanical testing.</p>

Several problems must be solved in the construction, design, and operation of a nuclear fusion reactor. One of the chief problems in the manufacture of high-powered copper/polymer composite magnets is the difficulty to precisely control the fiber volume fraction. In this thesis, the effect of variations in fiber volume fraction on thermal stresses in copper/cyanate ester composite cylinders is investigated. The cylinder is a composite that uses copper wires that run longitudinally in a cyanate ester resin specifically developed by Composite Technology Development, Inc. This composite cylinder design is commonly used in magnets for nuclear fusion reactors. The application of this research is for magnets that use cylindrical coil geometry such as the Mega Amp Spherical Tokamak (MAST) in the UK. However, most stellarator magnet designs use complex geometries including the National Compact Stellarator Experiment (NCSX), and the Quasi-Poloidal Stellarator (QPS). Even though the actual stresses calculated for the cylindrical geometry may not be directly applicable to these projects, the relationship between fiber volume fraction and stresses will be useful for any geometry. The effect of fiber volume fraction on stresses produced by mechanical, thermal and magnetic loads on cylindrical magnet coils is studied using micromechanics with laminate plate theory (LPT) and finite element analysis (FEA).Based on the findings of this research, variations in volume fraction do significantly affect the stress experienced by the composite cylinder. Over a range of volume fractions from 0.3 to 0.5, the LPT results demonstrate that thermally induced stresses vary approximately 30% while stresses due to pressure vary negligibly. The FEA shows that magnetic stresses vary much less at around only 5%. FEA results seem to confirm the LPT model. It was also concluded that the stress in the insulation layers due to all types of loadings is significant and must be considered when using this system in fusion applications.

Nowadays, almost all existing wheelchairs have the problem that they only satisfy the disabled people to use for normal moving and transportation. A new wheelchair with a gear system guide rail which installed in the car is presented in this paper. The gear guide rail system will transport the whole wheelchair and person on it into the car. This wheelchair system will help people with disability whatever passengers or drivers to get into cars automatically. In this paper, the operation and the strength will be analysed through 3D model and theoretical calculations. Surveying to Swedish market, Volvo XC60 and V60 is chosen to design the size of the wheelchair. Besides, this new wheelchair system also can be suitable for the cars which are larger than those two car models.

Laboratory test of reinforced and prestressed concrete structures have been used widely to explore the behavior of reinforced and prestressed concrete components and structures; Such tests are often time-consuming and costly. However, numerical models have been shown to compare favorably with experiments. Thus, computations are viewed nowadays as efficient alternatives to tests, time-wise and cost-wise. In the research reported in this thesis, finite-element model were used in a study of pretressed structural components in order to correlate levels of pretension with deflection and strain measurements. The two main objectives were to develop a suitable finite element model of prestressed concrete beams and to forecast beam prestension on the basis of deformations resulting from specified simple load, e.g., a uniformly distributed transverse load. A commercial finite-element analysis package (ANSYS 12) was used to set up, use and evaluate the computational model. Furthermore, a finite-difference model was employed in order to ascertain the validity of ANSYS results by comparison with engineering beam theory taking into account the applied pretension. This study demonstrates the potential usefulness of deflection and strain measurements as indicators of the pretension applied or remaining in prestressed concrete beams. / text

Suction caissons with a smaller aspect (length to diameter) ratio are increasingly used for supporting offshore structures, such as wind turbines and oil and gas production facilities. The design of these stubbier foundations is usually governed by lateral loads from wind, waves, or currents. It is desired to have more physical understanding of the behavior of less slender suction caissons under cyclic lateral loading condition and to have robust design tools for analyzing these laterally loaded caissons. In this study, one-g model tests with 1:25 and 1:50 suction can foundation scale models with an aspect ratio of one are conducted in five different soil profiles: normally consolidated clay, overconsolidated clay, loose siliceous sand, cemented siliceous sand, and cemented calcareous sand. This test program involves monitoring settlements, lateral displacements (walking), tilt, lateral load and pore water pressures in the suction can during two-way cyclic lateral loading at one, three and five degrees of rotation. The model foundations are monitored during installation, axial load tests, and pullout tests. In one and two-degree (±0.5 and ±1 degree) rotation tests, the suction can does not have significant walking or settlement in all the five soil profiles after 1000 load cycles. However, more significant walking or settlement may occur at extreme conditions such as the 5-degree (±2.5 degrees) rotation tests. Gaps between the foundation wall and the soil may also form in these extreme conditions in overconsolidated clay, cemented siliceous sand, and cemented calcareous sand. Plastic limit analysis, finite element analysis, and finite difference analysis are used to evaluate the laterally loaded suction can in clay. The plastic limit analysis originally developed for more slender suction caissons appears to predict a lateral capacity close to the measured short-term static capacity of the caisson with an aspect ratio of one when undisturbed undrained shear strength of soil is used. However, this plastic limit model underestimates the long-term cyclic lateral load capacity of the caisson when the remolded undrained shear strength was used. The finite element model developed in this study can simulate the development and effect of a gap between the foundation and surrounding soil as observed in the experiments in overconsolidated clay. The lateral load-displacement response predicted by this finite element model matches well with the experimental data. Finally, finite difference analysis for a rigid caisson with lateral and rotational springs was developed by fitting the lateral load-displacement response of the suction can in clay. The calibrated p-y curves for rigid caisson are significantly stiffer and have higher ultimate resistance than the p-y curves recommended by API which is consistent with other studies. This finite difference model provides an efficient approach to analyze a laterally loaded caisson with a small aspect ratio in clay. / text

Titanium alloys are widely utilized in the aerospace, biomedical,marine, petro-chemical and other demanding industries due to theirdurability, high fatigue resistance and ability to sustain elevateoperating temperature. As titanium alloys are difficult to machine, dueto which machining of these alloys ends up with higher environmentalburden. The industry is now embracing the sustainable philosophy inorder to reduce their carbon footprint. This means that the bestsustainable practices have to be used in machining of titanium alloys aswell as in an effort to reduce the carbon footprint and greenhouse gas(GHG) emissions.In this thesis, a better understanding towards the feasibility of shiftingfrom conventional (dry and flood) cooling techniques to the vegetableoil based minimum quantity cooling lubrication (MQCL) wasestablished. Machining performance of MQCL cooling strategies wasencouraging as in most cases the tool life was found close to floodstrategy or sometimes even better. The study revealed that theinfluence of the MQCL (Internal) application method on overallmachining performance was more evident at higher cutting speeds. Inaddition to the experimental machinability investigations, FiniteElement Modeling (FEM) and Computational Fluid Dynamic (CFD)Modeling was also employed to prediction of energy consumed inmachining and cutting temperature distribution on the cutting tool. Allnumerical results were found in close agreement to the experimentaldata. The contribution of the thesis should be of interest to those whowork in the areas of sustainable machining. / <p>QC 20150915</p>

Material property heterogeneity is present ubiquitously in various natural and man-made materials, such as bones, seashells, rocks, concrete, composites, and functionally graded materials. A fundamental understanding of the structure-property relationships in these material systems is crucial for the development of advanced materials with extreme properties. Well-developed homogenization schemes exist to establish such relationships in elasticity, electrostatics, magnetism, and other time- or history-independent material properties. Nevertheless, one’s understanding of the effective fracture properties of heterogeneous media is remarkably limited. The challenge here is that heterogeneous fracture, as a history-dependent process, involves complex interaction and negotiation of a discontinuity front with local heterogeneities. The determination of effective fracture properties necessitates a critical interrogation of this evolutionary process in detail. In this work, a combined experimental and modeling effort is made to examine and control fracture mechanisms in heterogeneous elastic solids. A two-phase laminated composite, which mimics the key microstructural features of many tough biological materials, is selected as a model material. In the computational part of this work, finite element analysis with cohesive zone modeling is used to model crack propagation and arrest in the laminated direction. A crack-tip-opening controlled algorithm is implemented to overcome the instability problems associated with inherently unstable crack growth. Computational results indicate that the mismatch of elastic modulus is an important factor in determining the fracture behaviors of the heterogeneous model material. Significant enhancement in the material’s effective fracture toughness can be achieved with appropriate modulus mismatch. Systematic parametric studies are also performed to investigate the effects of various material and geometrical parameters, including modulus mismatch ratio, phase volume fractions, T-stress, and cohesive zone size. Concurrently, a novel stereolithography-based additive manufacturing system is developed and used for fabricating heterogeneous test specimens with well-controlled structural and material properties. Fracture testing of each specimen is performed using the tapered double-cantilever beam (TDCB) test method. With optimized material and geometrical parameters, heterogeneous TDCB specimens are found to exhibit higher fracture toughness than their homogenous counterparts, which is in good agreement with the computational predictions. The integrative computational and experimental study presented here provides a fundamental mechanistic understanding of the fracture mechanisms in brittle heterogeneous materials and sheds light on the rational design of ultra-tough materials through patterned heterogeneities.

The IKEA sliding door system is widely employed on IKEA’s wardrobes. In view of the massive usage of it, any optimization for reducing production costs is crucial. This work attempts to develop a special static test rig for a component of IKEA’s sliding door system. It will be used to check the quality of the component in production. The simulation-driven design method will be used in the entire process. Therefore, before proceeding with the details of the test rig, the priority should be given to the simulation. In particular, the nonlinear finite element method (FEM) will be used to identify the break load of the studied component. Finite element models were created in ABAQUS/Standard. Four kinds of POM were used to define the model’s material properties. Meanwhile the compression experiment were also conducted. Finite element models were used to predict the load capacity and compare it with the experimental results. The closest prediction in relation to the test results was 2124N, merely 6N smaller than the experimental results, giving the proof of a good finite element analysis. Based on the results of simulations and compression tests, a proper test rig consisting of a pneumatic system and load cell was selected from four concepts. The air cylinder can provide 3175N when the supplied air is 0.7MPa, which is fully met the design requirements with reasonable price.

The majority of a bridge designer’s time is spent ensuring strength and serviceability limit states are satisfied for the completed structure under various dead and live loads. Anecdotally, the profession has done an admirable job designing safe bridges, but engineering the construction process by which bridges get built plays a lesser role in the design offices. The result of this oversight is the complete collapse of a few large bridges as well as numerous other serviceability failures during construction. According to the available literature there have been only a few attempts to monitor a full-scale bridge in the field during the entire construction process. Another challenge for engineers is the lack of analysis tools available which predict the behavior of the bridge during the intermediate construction phases. During construction, partial bracing is present and the boundary conditions can vary significantly from the final bridge configuration. The challenge is magnified for complex bridge geometries such as curved bridges or bridges with skewed supports. To address some of the concerns facing engineers a three span curved steel I-girder bridge was monitored throughout the entire construction process. Field studies collected data on the girder lifting behavior, partially constructed behavior, and concrete deck placement behavior. Additional analytical studies followed using the field measurements to verify the finite element models. Finally, conclusions drawn from the physical and analytical testing were utilized to derive equations that predicted behavior, and analysis tools were developed to provide engineers with solutions to a wide range of construction related problems. This dissertation describes the development of two design tools, UT Lift and UT Bridge. UT Lift is a macro-enabled Excel spreadsheet that predicts the behavior of curved I-girders during lifting. The derivation of the equations necessary to accomplish these calculations and the implementation are described in this dissertation. UT Bridge is a PC-based, user-friendly, 3-D finite element program for I-girder bridges. The basic design philosophy of UT Bridge aims to allow an engineer to take the information readily available in a set of bridge drawings and easily input the necessary information into the program. A straight or curved I-girder bridge with any number of girders or spans can then be analyzed with a robust finite element analysis for either the erection sequence or the concrete deck placement. The development of UT Bridge as well as the necessary element formulations is provided in this dissertation. / text

Computer generated three-dimensional (3-D) models are being used at increasing rates in the fields of entertainment, education, research, and engineering. One of the aspects of interest includes the behavior and function of the musculoskeletal system. One such tool used by engineers is the finite element method (FEM) to simulate the physics behind muscle mechanics. There are several ways to represent 3-D muscle geometry, namely a bulk, a central line of action and a spline model. The purpose of this study is to exmine how these three representations affect the overall outcome of muscle movement. This is examined in a series of phases with Phase I using primitive geometry as a simplistic representation of muscle. Phases II and III add anatomical representations of the shoulder joint with increasing complexity. Two methods of contraction focused on an applied maximal force (Fmax) and prescribed displacement. Further analyses tested the variability of material properties as well as simulated injury scenarios. The results were compared based on displacement, von Mises stress and solve time. As expected, more complex models took longer to solve. It was also supported that applied force is a preferred method of contraction as it allows for antagonistic and synergistic interaction between muscles. The most important result found in these studies was the consistency in the levels of displacement and stress distribution across the three different 3-D representations of muscle. This stability allows for the interchangeability between the three different representations of muscles and will permit researchers to choose to use either a bulk, central line of action or a spline model. The determination of which 3-D representation to use lies in what physical phenomenon (motion, injury etc.) is being simulated.