Amtec (United States)

The present study is part of a series aimed at enhancing the reliability of JIS B 1759, ”Estimation of tooth bending strength of cylindrical plastic gears.” This study examined the stress correction factor converting the nominal tooth bending stress into the local one. The current version has a problem with underestimating the load capacity of internal gears, but considering the contact ratio under load has alleviated the problem. Nevertheless, some issues remain, which led the present paper to determine an alternative stress correction factor through finite element analyses of internal virtual spur gears. Before discussing the alternative factor, examining the fillet profile of injection-molded internal spur gears led to proposing a single circular arc as the standard fillet. Based on that, FEAs of internal virtual spur gears with a single circular fillet determined the modified stress correction factor, which can relieve JIS B 1759 of the underestimations. The modified factor enables the standard to estimate load capacity regardless of external or internal gears, which improves the reliability of the standard.

Abstract Previously, in Europe, in gasket tests mainly Nitrogen was used as the test medium. This medium was easy to handle, safe and cheap to buy. With increased sealing requirements on the sealing elements, however, a test medium had to be used, with which smaller leakage quantities can be reliably measured. In laboratory testing, Helium prevailed, with which in the vacuum method using a mass spectrometer these tightness requirements could be easily achieved. Other media, such as hydrogen or Methane, were not used in standard tests because of their hazard potential and detection limitation. Particularly in performance tests, a practice-oriented medium has always been favored in sealing tests in the USA. Methane is the first choice as the smallest hydrocarbon molecule. In ASME B16.20, a new performance test has been introduced, in which the tightness requirement of spiral wound gaskets in a leakage test with Methane should be checked. And also in the valve test in ISO 15848-1, Methane is defined as an alternative test medium for Helium. In this paper, the difference in the leakage test between Nitrogen, Helium and Methane in terms of handling, use in the test laboratory, the measurement of leakage rates and the detection limits between Nitrogen, Helium and Methane will be shown.

The present paper describes edge contact analyses for power transmission gears using tooth-flank-film elements, which have been proposed for finite element analyses of tooth stresses. For edge contact analyses, the tooth-flank-film elements are placed not only on usable flanks but also over tooth edges. Finer elements on edge neighboring areas and on the parts of usable tooth flanks where tend to contact with mating edges enable the edge contact to be analyzed. Comparisons of calculated distributions of tooth contact stress with observed tooth flanks after a running test showed the validity of the proposed method for edge contact analyses.

Power distribution by the plastic gear is decreased for the lighten machine and the compact machine. Also, the reduction of a few energy losses, too, is wanted for the global environmental problem. Gears with a different profile from the involute curve could be effective for the reduction of energy loss in gearing systems, and could enable them to be small and light. The present paper describes plastic gears with a sine curve profile, and analytically discusses their possibility of reducing the energy loss. As a result, it is confirmed that gears with a sine curve profile have smaller sliding between tooth flanks than ones with the involute curve, and would enable the energy loss to be reduced.

We present a series of algorithms and preliminary work towards developing a fully autonomous and real-time lightning severity prediction capability enabling one hour ahead forecasting based on local lightning strike characteristics. Our approach characterizes total, cloud to cloud, and cloud to ground strikes as input variables to derive the number of strikes

We present a novel mathematical framework for Data Mining blogger text entries and converting latent conceptual information into analytical predictive equations. These differential equations are conceptual models of the blogger's topic and state-of-mind transition dynamics. The mathematical framework is explored for its value in characterization of topic content and topic tracking as well as identification and prediction of topic dynamic changes.

The effect of the rise in tooth temperature on tooth bending strength is not considered in the calculation of load capacity of plastic gears. The tooth temperature of a plastic gear greatly rise with the rise of heat due to tooth flank friction and hysteresis. However, calculation of tooth bending strength of a plastic gear does not include the effect. In the present paper, the temperature-rise factor is discussed. It will be incorporated in calculation of tooth bending strength of a plastic gear to include the effect. Three-dimensional analyses of heat generation and conduction in plastic gear pair were performed using a developed computer program, and the calculated tooth flank temperatures were compared with measured ones obtained from experiments with POM gears with various facewidths.The temperature-rise factor was proposed in basis of these calculated and measured tooth temperature and thermal behavior of the allowable bending strength of the material.

Simulating a supersonic wake flow field behind a conical body is a computing intensive task. It requires a large number of computational cells to capture the dominant flow physics and a robust numerical algorithm to obtain a reliable solution. High performance parallel computers with unique distributed processing and data storage capability can provide this need. They have larger computational memory and faster computing time than conventional vector computers. We apply the PINCA Navier-Stokes code to simulate a wind-tunnel supersonic wake experiment on Intel Gamma, Intel Paragon, and IBM SP2 parallel computers. These simulations are performed to study the mean flow in the near wake region of a sharp, 7-degree half-angle, adiabatic cone at Mach number 4.3 and freestream Reynolds number of 40,600. Overall the numerical solutions capture the general features of the hypersonic laminar wake flow and compare favorably with the wind tunnel data. With a refined and clustering grid distribution in the recirculation zone, the calculated location of the rear stagnation point is consistent with the 2D axisymmetric and 3D experiments. In this study, we also demonstrate the importance of having a large local memory capacity within a computer node and the effective utilization of the number of computermore » nodes to achieve good parallel performance when simulating a complex, large-scale wake flow problem.« less

A coupled zonal method has been developed for modeling flows about aircraft with highly integrated advanced nozzle installations in which the exhaust plume interacts with the aircraft flow field to enhance performance. A cost effective flow analysis is achieved by dividing the flow domain into zones and coupling the zonal solutions. PAN AIR is used to model the flow in the inviscid zone which surrounds the aircraft. The plume zone flow field is solved with a PNS code. The flow in the optional internal nozzle zone is modeled using a full Navier-Stokes code. An automated iterative procedure couples the inviscid and plume zones by passing updated boundary conditions between the zones. The coupled analysis provides converged solutions for the overall flow field. The method is demonstrated for a highly integrated nonaxisymmetric vectored nozzle installed on a swept-wing aircraft.