Design Rules and Failure Modes of DMFC Stack Development

2019 ◽  
Vol 26 (1) ◽  
pp. 287-294 ◽  
Author(s):  
Youngseung Na ◽  
Seong Kee Yoon ◽  
Jungkurn Park ◽  
Jun Won Suh ◽  
Inseob Song ◽  
...  
Keyword(s):  
Failure Modes ◽  
Design Rules

Applicability of Design Rules for Openings in Shells, ASME B&PV Code, Section VIII, Division 2 - A Case Study

2021 ◽  
Author(s):  
Gurumurthy Kagita ◽  
Krishnakant V. Pudipeddi ◽  
Subramanyam V. R. Sripada
Keyword(s):  
Stress Analysis ◽  
Failure Modes ◽  
Element Analysis ◽  
Design Rules ◽  
Area Method ◽  
Replacement Method ◽  
Local Stresses ◽  
Pressure Area ◽  
Section Viii ◽  
Division 2

Abstract The Pressure-Area method is recently introduced in the ASME Boiler and Pressure Vessel (B&PV) Code, Section VIII, Division 2 to reduce the excessive conservatism of the traditional area-replacement method. The Pressure-Area method is based on ensuring that the resistive internal force provided by the material is greater than or equal to the reactive load from the applied internal pressure. A comparative study is undertaken to study the applicability of design rules for certain nozzles in shells using finite element analysis (FEA). From the results of linear elastic FEA, it is found that in some cases the local stresses at the nozzle to shell junctions exceed the allowable stress limits even though the code requirements of Pressure-Area method are met. It is also found that there is reduction in local stresses when the requirement of nozzle to shell thickness ratio is maintained as per EN 13445 Part 3. The study also suggests that the reinforcement of nozzles satisfy the requirements of elastic-plastic stress analysis procedures even though it fails to satisfy the requirements of elastic stress analysis procedures. However, the reinforcement should be chosen judiciously to reduce the local stresses at the nozzle to shell junction and to satisfy other governing failure modes such as fatigue.

Translating Yield Learning Into Manufacturable Designs

2006 ◽  
Author(s):  
Vijay Chowdhury ◽  
Irfan Rahim ◽  
Ada Yu ◽  
Girish Venkitachalam
Keyword(s):  
Failure Modes ◽  
Analog Circuit ◽  
Yield Loss ◽  
Process Variations ◽  
Design Sensitivity ◽  
Design For Manufacturability ◽  
Design Rules ◽  
Circuit Layout ◽  
Manufacturing Defects ◽  
Yield Learning

Abstract Improving semiconductor yield is a multi-dimensional process that must include design, fabrication, and test aspects. Incorporating design-for-manufacturability (DFM) concepts needs to include prior and ongoing learning and experience on what worked and what did not. As feature sizes shrink beyond 130nm, it is possible to identify another class of failures that is more systematic and related not to manufacturing defects but to DFM marginalities related to layout. In this article, it is shown that DFM can also help reduce design sensitivity to process variations. Examples of these failure modes and the lessons learnt are listed: relaxed design rules for repeated patterns, relaxing design rules to reduce yield loss, and special considerations for analog circuit layout.

Comparison of Ellipsoidal and Equivalent Torispherical Heads Under Internal Pressure: Buckling, Plastic Collapse and Design Rules

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Jinyang Zheng ◽  
Yehong Yu ◽  
Yehong Chen ◽  
Keming Li ◽  
Zekun Zhang ◽  
...  
Keyword(s):  
Failure Modes ◽  
Good Prediction ◽  
Plastic Collapse ◽  
Design Equation ◽  
Fe Method ◽  
Shape Deviation ◽  
Design Rules ◽  
Collapse Pressure ◽  
Current Design ◽  
The Difference

Abstract Ellipsoidal and torispherical heads, whose geometric shapes are close, are usually used as end closures of internally pressurized vessels. In pressure vessel codes, for example, ASME BPVC Section VIII and EN13445-3, ellipsoidal heads are designed as torispherical heads using geometric equivalency approaches. However, the difference between ellipsoidal and equivalent torispherical heads has not been studied in detail. In this paper, we first investigate shape deviation between the two types of heads. Then we compare elastic–plastic behaviors between ellipsoidal and equivalent torispherical heads as well as their failure modes, i.e., buckling and plastic collapse (bursting). It is found that ellipsoidal heads have more buckling resistance than equivalent torispherical heads, indicating that the current design rules for buckling of ellipsoidal heads based on the geometric equivalency approaches result in uneconomical design. In addition, experimental and numerical results show that such heads experience geometric strengthening. The finite element (FE) method considering the effect of geometric strengthening provides a good prediction of plastic collapse pressure. However, the current design equation for bursting does not consider the effect of geometric strengthening, also leading to uneconomical design. Therefore, in order to avoid uneconomical design, we recommend that (1) with respect to buckling of ellipsoidal heads, a new design equation be proposed rather than implementing the geometric equivalency approaches, and (2) the current design equation for bursting be deleted, and a new design equation, considering the effect of geometric strengthening, be proposed for bursting of ellipsoidal and torispherical heads.

scholarly journals Make No Mistake

2009 ◽  
Vol 131 (06) ◽  
pp. 48-51
Author(s):  
Jean Thilmany
Keyword(s):  
Human Error ◽  
Engineering Students ◽  
Failure Modes ◽  
End User ◽  
Color Code ◽  
Human Reliability Analysis ◽  
Design Rules ◽  
Fault Trees ◽  
Standard Design ◽  
Event Trees

This paper explains the concept of goof-proofing and its usefulness in engineering design. No standard design rules exist for engineers to follow in anticipation of human error. Human reliability analysis tools such as event trees and fault trees to model a human's contribution to events such as decreasing one's speed on an exit ramp. To minimize human error, engineering students color code wires and use specific prong configurations in the design of an automobile. It is observed that engineers follow failure modes and effects analysis procedures. The failure modes procedure isolates potential failures within a system or product. Effects analysis is the study of the consequences of those failures. The attitude on the part of designers is that they have the requisite knowledge, either from past projects or due to their expertise. The paper concludes that regardless of how engineers go about goof-proofing their designs, they must keep the end user in mind.

Cold-formed steel battened built-up columns: Experimental behaviour and verification of different design rules developed

2021 ◽  
pp. 136943322110480
Author(s):  
A.R. Dar ◽  
S. Vijayanand ◽  
M. Anbarasu ◽  
M. Adil Dar
Keyword(s):  
Failure Modes ◽  
Numerical Models ◽  
Experimental Studies ◽  
Design Standards ◽  
Uniform Compression ◽  
Design Rules ◽  
The North ◽  
Current Design ◽  
Cold Formed Steel ◽  
In The Beginning

Some of the past studies on cold-formed steel (CFS) battened built-up columns have resulted in the development of new design rules for predicting their axial strengths. However, the main drawbacks of such studies are that they are purely numerical and the numerical models developed for such parametric studies were validated using the test results on similar built-up column configurations, but not the exact ones. Therefore, experimental studies on CFS battened columns comprising of lipped channels are needed for verifying the accuracy of the proposed design rules for CFS battened columns. This paper reports an experimental study performed on CFS built-up battened columns under axial compression. Adequately spaced identical lipped channels in the back-to-back arrangement were used as chords and were connected by batten plates laterally with self-driving screws to form the built-up members. The dimensions of chords were fixed as per the geometric limits given out in the North American Specifications (NAS) for the design of CFS structural members. The sectional compactness of the chords and the overall slenderness of the built-up columns were varied by altering the thickness of the channels and height of the built-up columns, respectively. A total of 20 built-up sections were tested under uniform compression to investigate the behavioural changes in the built-up columns due to these variations. The behaviour assessment was made in terms of peak strengths, load–displacement response and failure modes of the test specimens. The current design standards on CFS structures were used to determine the design strengths and were compared against the test strengths for assessing their adequacy. Furthermore, as discussed in the beginning, the test strengths were used to verify the accuracy of the different relevant proposed design rules in the literature.

Comparison of Ellipsoidal and Equivalent Torispherical Heads Under Internal Pressure: Buckling, Plastic Collapse and Design Rules

2019 ◽  
Author(s):  
Jinyang Zheng ◽  
Keming Li ◽  
Yehong Yu ◽  
Zekun Zhang ◽  
Wenzhu Peng ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Failure Modes ◽  
Bursting Pressure ◽  
Good Prediction ◽  
Plastic Collapse ◽  
Design Equation ◽  
Fe Method ◽  
Shape Deviation ◽  
Design Rules ◽  
Current Design

Abstract Ellipsoidal and torispherical heads, whose geometric shapes are close, are usually used as end closures of internally pressurized vessels. In pressure vessel codes, for example, ASME BPVC Section VIII, ellipsoidal heads are designed as torispherical heads using geometric equivalency approaches. However, the difference between ellipsoidal and equivalent torispherical heads has not been studied in detail. In this paper, we first investigate the shape deviation between the two types of heads. Then we compare the elastic-plastic behaviors between ellipsoidal and equivalent torispherical heads as well as their failure modes, i.e., buckling and plastic collapse. It is found that ellipsoidal heads have more buckling resistance than equivalent torispherical heads, indicating that the current design rules for buckling failure based on the geometric equivalency approaches result in uneconomical design. Nevertheless, the shape deviation has little effect on plastic collapse pressures of ellipsoidal and equivalent torispherical heads, showing that the geometric equivalency approaches are applicable for such heads that fail by plastic collapse (bursting). In addition, the experimental and numerical results show that such heads experience geometric strengthening. The FE method considering the effect of geometric strengthening provides a good prediction about plastic collapse (bursting) pressure. However, the current design equation for bursting does not consider the effect of geometric strengthening, also leading to uneconomical design. Therefore, in order to avoid uneconomical design, we recommend that (1) with respect to the buckling of ellipsoidal heads, a new design equation be proposed rather than implementing the geometric equivalency approaches, and (2) the current design equation for bursting be deleted, and a new design equation, considering the effect of geometric strengthening, be proposed for the bursting of ellipsoidal and torispherical heads subjected to internal pressure.

Torispherical Shells under Internal Pressure—Failure due to Asymmetric Plastic Buckling or Axisymmetric Yielding

1985 ◽  
Vol 199 (3) ◽  
pp. 225-238 ◽  
Author(s):  
G D Galletly ◽  
J Błachut
Keyword(s):  
Internal Pressure ◽  
Pressure Vessel ◽  
Shell Theory ◽  
Failure Modes ◽  
Finite Deflection ◽  
Plastic Buckling ◽  
Design Rules ◽  
Failure Pressure ◽  
Pressure Failure ◽  
Approximate Equations

In the diameter-to-thickness range 250 < D/t < 1000, internally pressurized torispherical shells can fail either by plastic buckling or by axisymmetric yielding. However, the present Code rules cater only for the axisymmetric yielding mode and they also restrict the D/t ratios to being less than 500. The rules are based on limit analysis results and these can be conservative for this problem. With regard to internal pressure buckling, there are as yet no design rules in either the American or the British pressure vessel Codes to prevent its occurrence. To provide guidance for a more accurate formulation of design rules for both of these failure modes over the range 300 < D/t < 1500, the authors have made a series of calculations to determine the values of Pcr (the internal buckling pressure) and pc (the axisymmetric yielding pressure) for perfect torispherical shells. The availability of these results, obtained with a finite-deflection shell theory, enables curves to be drawn showing when buckling is the controlling failure mode and when axisymmetric yield controls. A comparison is also made, for D/t < 600, between the controlling failure pressures mentioned above and the Drucker-Shield limit pressures. The ratio between the former and the latter varied between 1.2 and 1.8, depending on the geometry of the shell and the magnitude of the yield point, σyp. Considerable economies in the designs of many torispherical shells could, therefore, be achieved if the relevant sections of the Codes were to be modified to take advantage of the foregoing results. The controlling failure pressure curves also indicate how Code rules to prevent plastic buckling for D/t > 500 might be formulated. For the benefit of designers, the numerical values of pcr and pc were transformed, using curve-fitting techniques, into simple approximate equations. Although these equations are for perfect torispherical shells, they should be very beneficial when analysing the related problems of fabricated torispheres in practice.

Scanning Electron Microscopy in Hybrid Microelectronics

1976 ◽  
Vol 34 ◽  
pp. 456-457
Author(s):  
S. Khadpe ◽  
R. Faryniak
Keyword(s):  
Integrated Circuits ◽  
Thick Film ◽  
Integrated Circuit ◽  
Failure Modes ◽  
Three Dimensional ◽  
Circuit Components ◽  
Hybrid Microcircuit ◽  
Electrical Connections ◽  
Scanning Electron

The Scanning Electron Microscope (SEM) is an important tool in Thick Film Hybrid Microcircuits Manufacturing because of its large depth of focus and three dimensional capability. This paper discusses some of the important areas in which the SEM is used to monitor process control and component failure modes during the various stages of manufacture of a typical hybrid microcircuit.Figure 1 shows a thick film hybrid microcircuit used in a Motorola Paging Receiver. The circuit consists of thick film resistors and conductors screened and fired on a ceramic (aluminum oxide) substrate. Two integrated circuit dice are bonded to the conductors by means of conductive epoxy and electrical connections from each integrated circuit to the substrate are made by ultrasonically bonding 1 mil aluminum wires from the die pads to appropriate conductor pads on the substrate. In addition to the integrated circuits and the resistors, the circuit includes seven chip capacitors soldered onto the substrate. Some of the important considerations involved in the selection and reliability aspects of the hybrid circuit components are: (a) the quality of the substrate; (b) the surface structure of the thick film conductors; (c) the metallization characteristics of the integrated circuit; and (d) the quality of the wire bond interconnections.

Contrasting underlying mechanisms of different barrier coating types

TAPPI Journal ◽  
2018 ◽  
Vol 17 (01) ◽  
pp. 31-37
Author(s):  
Bryan McCulloch ◽  
John Roper ◽  
Kaitlin Rosen
Keyword(s):  
Food Packaging ◽  
Underlying Mechanism ◽  
Consumer Products ◽  
Mechanical Degradation ◽  
Design Rules ◽  
Barrier Coatings ◽  
Barrier Materials ◽  
Barrier Coating ◽  
Coating Type ◽  
Underlying Mechanisms

Barrier coatings are used in applications including food packaging, dry goods, and consumer products to prevent transport of different compounds either through or into paper and paperboard substrates. These coatings are useful in packaging to contain active ingredients, such as fragrances, or to protect contents from detrimental substances, such as oxygen, water, grease, or other chemicals of concern. They also are used to prevent visual changes or mechanical degradation that might occur if the paper becomes saturated. The performance and underlying mechanism depends on the barrier coating type and, in particular, on whether the barrier coating is designed to prevent diffusive or capillary transport. Estimates on the basis of fundamental transport phenomena and data from a broad screening of different barrier materials can be used to understand the limits of various approaches to construct barrier coatings. These estimates also can be used to create basic design rules for general classes of barrier coatings.

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