Conventional methods of aspheric surface production utilize sub-diameter rigid tooling. The spherical tool has a slight misfit with respect to the aspheric optic being produced. This misfit leads to long working times due to minimal surface contact. It also leads to high frequency zones due to the mechanics of grinding and polishing. To remedy both of these problems, a non-rigid tool is employed. A thin membrane (∼1 mm) of aluminum or plastic is machined or pressed to the correct radius and grinding/polishing pads are glued to the lap. These semi-flexible laps make better contact with the work surface, thus reducing production time. They also make much smoother surfaces than does conventional tooling. This thesis details the theoretical analysis and simulations as well as experimental results and conclusions. The experimental results include: static deflection testing, removal rate testing as a function of spatial frequency, and production data from two fabrication projects.

Modern sport helmets have been effective in reducing catastrophic head injuries such as skull fracture and subdural hematoma; yet, the high prevalence of minor traumatic brain injuries (mTBI) is an unresolved public health concern. Consequently, there is a need for greater scrutiny in a helmet's ability to mitigate collision forces that may correspond to mTBI risk. Current safety standards primarily assess a helmet's ability to minimize the whole head's peak acceleration during blunt impacts. Absent are dynamic measures local to the impact site itself due to the technical challenge to spatial map high impact force magnitudes with high temporal resolution. Inclusion of the latter measures may enhance the functional assessment of helmets. Thus, the aim of this research was to develop a localized impact mapping system (LIMS) for placement between the helmet and head interface and then to utilize the LIMS to evaluate the mechanical behaviour of various padding foams and helmets during controlled headform drop and projectile collision tests. Interposed between the helmet shell/padding and head surface, this LIMS consists of an array of discrete, thin force sensors connected to a compact signal conditioner and high speed data acquisition digital recorder. A first study demonstrated the feasibility of the LIMS to accurately capture impact events in terms of both force magnitude and temporal response. The results of this initial study demonstrated that the system could capture impact forces with acceptable error (~5%) and high correlation (0.97) between measures of global force and the sensor array. Furthermore, the LIMS demonstrated the ability to capture impact "footprints" that functionally differentiated material properties of density and temperature. A second study incorporated the LIMS as part of a standard controlled surrogate headform drop test for blunt impacts. The LIMS performed equally well on the curved cranial surface geometry of the headform and was able to differentiate unique impact contact distribution patterns based on the ice hockey helmet model's shell and padding configurations, including identification of high focal force concentrations (>16 MPa) during side impact. Of note, global head impact acceleration measures did not correspond to the magnitude of localized contact forces (R-square=0.22), but did correspond to net global contact force (R-square=0.98). A third study used the LIMS between a Hybrid III surrogate headform and an ice hockey helmet during controlled puck projectile collisions. The LIMS was effective at capturing local force distributions dynamics for short impact events lasting 2-4 ms, and again was able to distinguish between varied helmet model's padding materials and installed configurations. Five helmet models were subject to highly localized puck impact at two different velocities (V1=24.2 m/s, V2=33.3 m/s). At V2, peak contact pressures, averaged across all helmet models, were nearly double (393 N/cm^2) those recorded at the same location during vertical drop testing (201 N/cm^2). Again, linear acceleration data did not discern these differences in localized pressures. In summary, this novel testing approach provides an instrument for the assessment of helmet design and material properties on local impact dynamics, and demonstrates merit as an industrial and research tool to enhance head protection. / Les casques de sport modernes ont été efficaces pour réduire les traumatismes crâniens sévères tels que les fractures du crâne et les hématomes sous-duraux. Malgré tout, la prévalence élevée des lésions cérébrales traumatiques mineures reste un problème de santé publique non résolu. Par conséquence, il existe un besoin important pour un examen plus approfondi de la capacité des casques à atténuer les forces de collision qui pourraient correspondre à un risque de traumatisme cérébral mineur. Les normes actuelles évaluent principalement l'efficacité des casques à minimiser les accélérations maximales de la tête lors d'impacts contondants. L'absence de mesures dynamiques locales, plus précisément au site d'impact, est surtout dû au défi technique qui est d'insérer des matrices sensorielles avec une haute résolution temporelle. Le développement de cette dernière technique de mesure pourrait améliorer l'évaluation fonctionnelle des casques en général. Ainsi, l'objectif principal de cette recherche était de développer un système de cartographie d'impact local (CIL) tout en permettant l'insertion de ce système entre le casque et la tête, et ainsi, utiliser le CIL afin d'évaluer les caractéristiques mécaniques de differentes mousses de rembourrage et différents casques au cours de chute et de collision contrôlée sur une fausse tête. Interposé entre la calotte/rembourrage et la surface de la tête, ce CIL est constitué d'un réseau de capteurs de force discrets, minces, connectés à une grande vitesse d'acquisition de données numériques. Une première étude a démontré la faisabilité d'utiliser le CIL pour capturer avec précision des événements d'impact en termes d'amplitude et de force ainsi que la réponse temporelle. Par ailleurs, le CIL a démontré la capacité de capturer les «empreintes» d'impact et de différencier fonctionnellement divers matériaux en mousse et des densités. Une deuxième étude a intégré le CIL dans le cadre d'une norme d'essai contrôlé de fausse tête de substitution lors de chute sur objets contondants. Le CIL s'est révélé tout aussi précis sur la géométrie de la surface crânienne courbe et a été en mesure de différencier les modèles uniques d'impact de contact de distribution basé sur le modèle de coque des casques de hockey et de configurations de remplissage, y compris l'identification de concentrations élevées de force de contact (>16 MPa). Fait à noter, l'impact global des mesures d'accélération de la tête ne correspond pas nécessairement à l'ampleur des forces d'intervention (R-square=0.22). Une troisième étude a utilisé le CIL entre une fausse tête de substitution Hybrid III et un casque de hockey sur glace lors de collisions de projectiles. Le CIL est efficace pour capturer des distributions locales de forces dynamiques lors d'événements de moins de 4 ms, et encore une fois a été en mesure de faire la distinction entre les matériaux de rembourrage des modèles de casques variés. En résumé, cette approche de test innovatrice s'est avérée être un instrument précis pour l'évaluation de la conception du casque et des propriétés des matériaux sur la dynamique d'impact local, et démontre le mérite d'un outil industriel et de recherche visant à améliorer la protection de la tête.

This investigation deals with the possibility of local failure in 4" aluminum I beams due to insufficient bearing area at end reactions and includes an investigation of the column theory of such failure. A comparison is made between the failure of two types of aluminum alloy, 17-ST and 65-ST. The application and determination of design formulae to determine the width of bearing necessary is explained and demonstrated for the 4” I beam.

The severity of the Canadian winters has, in the past, and does now, affect the construction business. Not only does it lower the efficiency of the working men, it affects the quality of the finished product. This is particularly noticeable in concrete construction where: 1.The formwork is erected more carelessly. 2. Batching weights are less accurate due to human failure and frost affecting the moving parts of the scales. 3. Placing and vibrating are poorly done due to the men being cold.

Controlled-stress, consolidated-undrained triaxial tests with pore pressure measurements were performed on partly saturated bentonite specimens prepared by two different methods of compaction, static and kneading, to give different structural arrangement of the sail particles. The results indicate that the static method employing higher compaction pressure tends to align particles in a more horizontal array as a result of the larger shear strains induced. Samples prepared by the same method of kneading compaction but using different compactive effort of twenty and ten blows with a 20-pound tamper on each of the five layers designated 20-20-5 and 10-20-5 samples respectively show that the less dense 10-20-5 samples have a higher pore pressure response than the 20-20-5 samples as predicted.

The shear strengths of silt samples of a given porosity were compared for three different types of triaxial test, under varying conditions of lateral pressure, drainage and saturation. The three types of triaxial test conducted were: I) Unconsolidated drained test on dry silt. II) Unconsolidated undrained test on partially saturated silt. III) Unconsolidated drained test on a partially saturated silt. The maximum strength was exhibited by the dry silt and was considered to be primarily a function of the effective stress on the contact area.

The results of model footing tests on a remoulded clay are described. For the clay used in these tests, the observed deformations and bearing capacities were not in agreement with those expected from the conventional bearing theories. The observed bearing capacity was about 25 percent less than that given by the latter theories, due to a punching or local shear failure. An approximate theory developed by Bishop et al (1945), to determine the load required to force a punch into a semi-infinite cohesive mass, was examined. The bearing capacity determined from this theory was in reasonable agreement with the results of the model tests, and also a limited amount of other data which could be examined. On the basis of these limited results, a relation is suggested for the bearing capacity of surface footings on saturated clay which includes, and predicts from the stress-strain properties of the clay, the case where a local shear failure occurs.

Tests on four concrete beams with transverse-longitudinal steel ratio varying from zero to 1.86 are reported. The strength of the rectangular reinforced concrete beams, all of which fail due to direct shear and torsion, agree favourably with the tensile strength of concrete determined from indirect tension tests. Initial cracks occurred in all the beams at a load corresponding to a combined shear stress of 346 psi in an unreinforced section under combined bending, shear and torsion. Results indicate that the shear reinforcement ceases to be fully effective as the Pt/p+p' ratio approaches and exceeds unity. Moreover the concept of a transition from elastic to plastic states of stress is proved by the results. Expressions have been derived for the stresses and unit angle of rotation for the central section of the beam remaining plane. The results of the limited number of tests appear to agree well with the modified theory.

Composite concrete-steel beams are widely used for highway bridge structures and to a lesser extent for building floors. These structures are made from steel beams which support a concrete slab. The concrete slab serves a dual purpose: It provides a deck or working surface and it acts as the top flange of the supporting beam. The compressive forces are resisted by the concrete slab; the tensile forces are resisted by the steel beam; and the horizontal shear between these two elements is resisted by shear connectors which are welded to the steel beam and embedded in the concrete slab. The resulting structure has greater stiffness, shallower construction, greater live load factor of safety and often greater economy than a non-composite structure designed for the same loads.

Measurements on the swelling pressure of oriented samples of Na-montmorillonite at dialysate concentrations of 10^-4 and 10^-2 M NaCl were made at temperatures ranging from 0°C to 25°0 in a specially designed temperature - swelling apparatus. The results indicate that at a dialysate concentration of 10^-4 M NaCl, the swelling pressure predicted from the combined Poisson-Boltzmann equation agreed closely with the measured pressures at the temperatures considered – swelling pressure decreased with decreasing temperature as predicted from the equation. Measured pressures were in all cases slightly smaller than the predicted pressures.