scholarly journals The Solution of Two-Dimensional Heat Conduction Problems for Predicting Operating Temperature and Power Handling Capabilities of Hybrid Circuits

1980 ◽  
Vol 7 (1-3) ◽  
pp. 97-105 ◽  
Author(s):  
G. P. Ferraris ◽  
M. Tudanca
Keyword(s):  
Heat Conduction ◽  
Theoretical Calculations ◽  
Two Dimensions ◽  
Design Stage ◽  
Early Design ◽  
Early Design Stage ◽  
Power Handling ◽  
Accurate Design ◽  
The Stability ◽  
Numerical Approaches

The problems of heat conduction in hybrid thin and thick film circuits have been investigated using both analytical and numerical approaches.The calculations were restricted to two dimensions by assuming zero temperature gradient across the thickness of the substrate (slightly more than half millimeter).All normally recognized parameters were taken into consideration, such as film temperature, power dissipated, substrate area, etc.Allowances have also been made for lead conduction and connection technology, for horizontal or vertical circuit assembly, and for flush or stand-off mounting on the mechanical support.The measured results for practical cases show close agreement with the theoretical calculations.This approach provides a simple tool for the calculation, at an early design stage of power handling capacities of hybrid circuits using composite resistive configurations.Very little difference was found between temperatures predicted from the theoretical approach and those measured in practical cases of circuits under load.The availability of such accurate design information means that the stability, life, and reliability of hybrid circuits can be predicted with considerable accuracy at an early design stage.

Dynamics of Labyrinth Gas Seals With Air Injection

2001 ◽  
Author(s):  
K. Kwanka
Keyword(s):  
Stability Limit ◽  
Air Injection ◽  
Design Stage ◽  
Early Design ◽  
Early Design Stage ◽  
Dynamic Coefficients ◽  
Exciting Forces ◽  
Gas Seals ◽  
The Stability ◽  
The Impact

Exciting forces generated in gas seals and blading of turbo-machinery can lead to vibrations of the rotor with unacceptably high amplitudes (Thomas [1958], Alford [1965]). It is important to predict in an early design stage the stability limit of the rotor so as to avoid the occurrence of self-excited vibrations. In the field, there are only few possibilities to stabilize the rotor. One way minimizing the cross-forces is by injecting air into the seal and counteracting the exciting mechanisms. The paper will present experimental dynamic coefficients of a gas seal of the teeth on stator type with eight cavities. The coefficients will be compared to the values obtained with a tangential injection of air into the first cavity in co-rotating and in counter-rotating direction. It seems that the impact of air injection is not as effective as swirl brakes or honeycomb stators.

Identification of Human Errors During Early Design Stage Functional Failure Analysis

2018 ◽  
Author(s):  
Lukman Irshad ◽  
Salman Ahmed ◽  
Onan Demirel ◽  
Irem Y. Tumer
Keyword(s):  
Failure Analysis ◽  
Human Error ◽  
System Level ◽  
Design Stage ◽  
Human Factors Engineering ◽  
Human Errors ◽  
Functional Failure ◽  
Early Design ◽  
Early Design Stage ◽  
Early Design Stages

Detection of potential failures and human error and their propagation over time at an early design stage will help prevent system failures and adverse accidents. Hence, there is a need for a failure analysis technique that will assess potential functional/component failures, human errors, and how they propagate to affect the system overall. Prior work has introduced FFIP (Functional Failure Identification and Propagation), which considers both human error and mechanical failures and their propagation at a system level at early design stages. However, it fails to consider the specific human actions (expected or unexpected) that contributed towards the human error. In this paper, we propose a method to expand FFIP to include human action/error propagation during failure analysis so a designer can address the human errors using human factors engineering principals at early design stages. To explore the capabilities of the proposed method, it is applied to a hold-up tank example and the results are coupled with Digital Human Modeling to demonstrate how designers can use these tools to make better design decisions before any design commitments are made.

scholarly journals A Comprehensive Method of Apportioning Reliability Goals for New Product of Hydraulic Excavator

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Wenting Liu ◽  
Qingliang Zeng ◽  
Lirong Wan ◽  
Chenglong Wang
Keyword(s):  
Real Life ◽  
Chemical System ◽  
Design Stage ◽  
Hydraulic Excavator ◽  
Effect Analysis ◽  
Reliability Allocation ◽  
Early Design ◽  
Construction Machinery ◽  
Early Design Stage ◽  
Fmea Method

It is important to allocate a reliability goal for the hydraulic excavator in the early design stage of the new system. There are some effective methods for setting reliability target and allocating its constituent subsystems in the field of aerospace, electric, vehicles, railways, or chemical system, but until now there is no effective method for the hydraulic excavator or engineering machinery. In this paper, an approach is proposed which combines with the conventional reliability allocation methods for setting reliability goals and allocating the subsystem and parts useful in the early design stage of the hydraulic excavator newly developed. It includes Weibull analysis method, modified Aeronautical Radio Inc. (ARINC) method, and modified systematic failure mode and effect analysis (FMEA) method. After completing reliability allocation, it is necessary to organize the designers and experts to evaluate the rationality of the reliability target through FEMA analysis considering feasibility of the improvement technically for the part which was new developed or had fault in its predecessor. The proposed approach provides an easy methodology for allocate a practical reliability goal for the hydraulic excavator capturing the real life behavior of the product. It proposes a simple and unique way to capture the improvement of the subsystems or components of the hydraulic excavator. The proposed approach could be extended to consider other construction machinery equipment and have practicality value to research excellent mechanical product.

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