Optimum Orientation Angle Research Articles

Effects of Groove Orientation on Hydrodynamic Behavior of Wet Clutch Coolant Films

A steady-state Reynolds type equation with inertia consideration is solved numerically for a coolant film entrapped between a grooved separator-friction plate pair of a multidisk wet clutch arrangement at a particular instant of the disengaged state. Straight grooves with rounded, trapezoidal, and V-section at different angular orientations are considered and the effects of their geometry and orientation on viscous torque, flow rate, and axial force are presented. Among the profiles studied, the rounded one is found to be better. Grooves inclined with the flow direction cause less viscous torque and, hence, less power loss. The choice of orientation angle, β, to give a maximum outflow or inflow may be helpful for cooling by better convection. For wider radial span and large number of grooves, the minimum operating gap ratio is suggested to be around 2.0. Inertia effects may shift the optimum orientation angle by as much as 10 deg, even at a moderate value of gap Reynolds number.

Reliability-based optimization of fibrous laminated composites

This paper is concerned with the optimum design of multiaxial fiber reinforced laminate systems under probabilistic conditions of loads and material properties. A multiaxially laminated composite is treated as a structural system with each ply contained in the composite as one element. The Tsai-Wu failure criterion is adopted as the limit state function of a unidirectional ply. It is assumed that the system failure occurs when any one of the plies in a laminate system fails. The multiple-check-point method is successfully applied to evaluate the system reliabilities of multiaxial laminates under probabilistic in-plane stresses. An optimization problem is defined to find the optimal number of fiber orientation axes, optimum orientation angles, and optimum ply ratios which yield the highest system reliability.

Piezoelectric PZT/epoxy Composites for Controlling Torsional Motion

Thin layers of the piezoceramic PZT (Lead Zir conate/Titanate) have been used to actuate and sense bending mo tion of thin, flexible structures. However, because of its transverse isotropy (mm6 symmetry), a pure PZT piezoceramic is unable to generate or sense twisting motion for applications including beams, plates or shell panels. The use of a polyvinylidene fluoride (PVF2) polymer possessing orthotropy (mm2 symmetry) allows sensing of twisting, but is not stiff enough to provide actuation because of its low modulus and typically low thickness. One possi ble method for generating a more powerful twisting actuation is to construct a piezoceramic/polymer composite element which is or thotropic in the plane and stiff enough to provide actuation. With the requirement of orthotropy in mind, composites have been fab ricated by cutting rods from a PZT plate and placing them in an epoxy matrix. The piezoelectric coupling coefficients d31 and d 32 have been measured for these composites. The ratio ( d 31/ d32) is ap proximately 2, which demonstrates the required orthotropy and thus demonstrates our ability to produce the desired twisting actua tion. A plate theory analysis provides information on the optimum orientation angle of the PZT/epoxy composite to provide twisting actuation and sensing. This theory predicts that the PZT/epoxy will demonstrate a factor of 40 improvement in actuation power over the PVF2 for a sample geometry.

Optimum Reliability Design of Multiaxially Laminated Composites using the Interior Tangent Ellipsoid Method.

In order to determine the optimum fiber orientation angles with maximum reliability under probabilistic loading conditions, a simple analytical method, which is called the interior tangent ellipsoid (ITE) method, has been proposed by one of the authors and applied to unidirectional composites, but has not been applied to laminated composites. In this paper, the ITE method is extended and applied to multiaxial laminates, based on first-ply failure. With the use of the quadratic equation of a failure criterion transformed for multiaxial laminates, an analytical solution for the relative value of reliability is formulated. The results obtained using the ITE method show good agreement with those obtained using an accurate reliability method. The calculation time for the ITE method is much less than that for the sophisticated reliability method. The ITE method enables a clear interpretation of the optimum orientation angles of laminated composites under probabilistic loading conditions. As a result, it is found that the ITE method is applicable to for multiaxial laminated composites as well as undirectional composites.

Integrated aeroelastic control optimization of laminated composite lifting surfaces

An integrated design approach for aeroelastic control of laminated composite lifting surfaces is formulated and demonstrated. The design is posed as an optimization problem to determine the optimum ply orientation angles and the control law which maximizes the aeroelastic instability speed of an actively controlled laminated composite lifting surface subject to limited control authority and structural frequency constraints. The lifting surface is simulated by a rectangular symmetric cantilevered composite plate. The formulation incorporates the Rayleigh-Ritz energy method, two-dimensional incompressible unsteady aerodynamic theory, optimum control design, and parameter optimization techniques. The particular control configuration consists of two point-force inputs applied at the leading and trailing edges of the lifting surface. In conjunction with the laminated compositeplate structural model, the control configuration effectively simulates an active flexible lifting surface. The effectiveness of the integrated approach is evaluated by comparing the optimum designs obtained by the method with designs obtained by a design procedure using aeroelastic tailoring and optimum control design as well but in a nonintegrated fashion. The illustrative studies resulted in a design that exhibited 102% higher aeroelastic instability speed with 294.4% lower control cost than designs obtained by a nonintegrated design procedure.

Optimum tilt of a solar collector

Installing solar panels or collectors with optimum orientation and tilt angles to maximise energy generation over a specific period is important to improve the economics of solar systems, and hence, their large-scale utilisation. As a general rule, for installations aiming at maximum annual solar production in the intertropical region, it is recommended to point the panel towards the Equator at a tilt angle equal to the local latitude. However, there are several situations where it is difficult or even impossible to follow these general recommendations, for example in case of the presence of an obstacle creating shading, inadequate orientation or slope of the roofs, or when roofs are inaccessible. This raises the question of the impact of non-compliance with the general recommendations on solar systems’ performance. We have used RETScreen software for the calculation of annual average irradiation on tilted panels in various locations in West and Central Africa, namely in the capital cities (latitudes between 0° N and 15° N). For each site, the maximum annual solar irradiation is simulated and taken as a reference value. The annual irradiations for various orientations and tilt angles were then recorded and compared to the reference. It appears that in West and Central Africa, a moderate deviation (up to 20°) from the optimal orientation and inclination does not significantly influence the incident solar radiation (reduction in irradiation < 5%). Construction of structures dedicated to solar installations or architectural modification to comply with general recommendations is therefore generally not justified. A set of diagrams and tables, which allow us to quickly determine the percentage of incident solar radiation on a solar panel based on its orientation and tilt angle compared to the optimal tilt and orientation for any capital city in West and Central Africa, is provided.

Vortex lattice structure of superfluid3He-A in a magnetic field

A study is made of the lattice constructed from nonsingular vortices in superfluid3He-A in a strong magnetic field. In the presence of a magnetic field the vortex texture loses axial symmetry, and the ľ vector outside the vortex core is nearly uniform and is directed perpendicular to the rotation axis. It is shown that the vortex lattice is spontaneously distorted and its energy depends on the orientation of the unit cell relative to the direction of the uniform ľ vector outside the core. It is also shown that the orientation of the lattice changes when the tilting angle of the magnetic field from the rotation axis is changed. The optimum orientation angle of the distorted vortex lattice is calculated as a function of the tilting angle.

Modification of Drill Point for Reducing Thrust

A considerable amount of thrust force during drilling is due to the cutting action at the chisel edge of drills. This is in turn due to large values of negative rake angle along with a very small cutting velocity in the zone of chisel edge. The authors have developed a grinding technique for modifying the chisel edge into a pair of auxiliary cutting edges with positive rake angle by generating two slots at the chisel point in a manner similar to Zhirov-point drills. Analytical expressions have been developed for analyzing the geometry of modified chisel edge. Experimental investigations have indicated that during drilling of cast iron such modifications result in the reduction of thrust force by about 50 percent. However, there is an optimum orientation angle and setting angle which should be chosen during grinding of drills in order to get the maximum benefit in regards to the reduction of thrust force.

The Signal Corps Synthetic Quartz Program

The role of the Signal Corps in developing the various techniques now being used to synthesize quartz crystals is reviewed from the standpoint of the quality of the material produced, growth rate, growth conditions, seed orientation, feed materials, cost, and suitability for production. Differences in the structure of synthetic quartz are indicated by variations in the optical absorption coefficients of X-irradiated quartz plates taken from different growth directions. The optical absorption measurements on the different types of synthetic quartz are compared with one another. Differences in the structure of natural and synthetic quartz are also indicated from measurements of Q made on 5-Mc high-precision resonators fabricated from samples of synthetic quartz grown under different conditions and from the occurrence of large absorption peaks at low temperatures (50°K) noted when measuring such resonators. Data is presented to show that synthetic quartz grown in the Z-direction possesses higher Q's than other quartz growth directions. None of the 5-Mc units made from synthetic quartz approach the high Q typical of natural quartz 5-Mc units between -60°C and 100°C. Comparison of the frequency temperature characteristics of overtone high frequency resonators made from synthetic quartz with those made from natural quartz show them to be about the same. The growth direction and impurity content, however, change the optimum orientation angle and inflection temperature. Resonators processed from synthetic quartz for operation in the 60-202-Mc range are shown to perform as satisfactorily as similar resonators made from natural quartz.