Generalized Yield Model Research Articles

Fracture in concrete-filled square hollow section to H-section joints under low-cycle loading

This article presents a simple engineering procedure to assess the fracture failure in the welded connection between a concrete-filled square hollow section and an open flange H-section, so as to enhance the ductility of the composite connection. This procedure predicates on an elliptical fracture envelope and a generalized yield model proposed and verified in previous studies. The experimental program compares the performance of a BASE specimen without openings in the flange of the connected H-section and two specimens (denoted as B1 and B2) with openings introduced near the connection. The numerically computed fracture index and yielding index for all specimens agree with the physical failure mechanisms observed in the test. This study demonstrates that openings in the flange of an H-section improve effectively the ductility of the highly stiffened connection between a concrete-filled tube and an open flange steel beam.

Tensile tests and analyses of notched specimens fabricated from high strength steels using a generalized yield model

ABSTRACTThis article summarises the uniaxial tension tests for 20 notched bars fabricated from high strength steel Q345 specified in Chinese National Standards. The effects of the notch radius, r, and that of the notch depth ratio, d/D, on the ductility and fracture resistance of this high strength steel are examined. The experimental data are further analyzed using a generalized yield model together with an elliptical fracture stress envelope originally proposed by the first author. The experimental results demonstrate that cracks initiate at the notched section, with the fracture surface filled with many dimples and shearing marks. Specimens with a sharper notch radius (a smaller r) and a larger notch depth (a smaller d/D ratio) show poor ductility, but high fracture strength. The stress field computed from the numerical procedure including the generalized yield model indicates that the crack initiation occurs at the centre of the notched section which experiences the highest stress triaxiality ratio (σm/σseq). As the stresses at the notched section reach the limiting values determined from the elliptical fracture criterion, macroscopic fracture failure in the notched bar occurs.

A General Yield Model From Design to Product Engineering

This paper proposes a yield model for integrated circuits that includes the impact of design measures for robust design as well as traditional defect density parameters. This model is a powerful extension to common practice at silicon foundries and integrated device manufacturers. It is suitable for big digital designs, medium communication chips with analog parts, and just as well small circuits with nonvolatile memories. A new formula for parametric yield combining worst-case distance (WCD) and process capability indices enhances the conventional approach. A special yield part is introduced to account for the increasing relevance of lithography yield loss. The different parts are based on a common mathematical relation combining macroscopic and microscopic view. Simple learning functions are used for yield prognosis. The model has been implemented successfully for CMOS and embedded nonvolatile memory processes. Examples with measured yields demonstrate application and forecast quality.

Fracture Test and Numerical Analysis of Structural Steel Notched Plates Based on Generalized Strength Model

To study rupture mechanism of structural steel, fracture experiments were tested on 12 notched plates with different thickness. The results of experiments indicated that the first crack initiated at the notched edge and expanded rapidly along the width of the plates after running through the thickness. Finally, the specimens fractured at the critical section, the fracture ductility decreased with the thickness. By numerically simulating the fracture stress field of the notched plates at initial cracking based on generalized yield model, the applicability and accuracy of the suggested fracture criterion were comparatively verified.

A fuzzy set approach for yield learning modeling in wafer manufacturing

The yield of semiconductor manufacturing can be improved through a learning process. A learning model is usually used to describe the learning process and to predict future yields. However, in traditional learning models such as Gruber's general yield model, the uncertainty and variation inherent in the learning process are not easy to consider. Also there are many strict assumptions about parameter distributions that need to be made. These result in the unreliability and imprecision of yield prediction. To improve the reliability and precision of yield prediction, expert opinions are consulted to evaluate and modify the learning model in this study. The fuzzy set theory is applied to facilitate this consulting process. At first, fuzzy forecasts are generated to predict future yields. The necessity of specifying strict parameter distributions is thus relaxed. Fuzzy yield forecasts can be defuzzified, or their /spl alpha/-cuts can be considered in capacity planning. The interpretation of such a treatment is also intuitive. Then, experts are requested to evaluate the learning model and express their opinions about the parameters in suitable fuzzy numbers or linguistic terms defined in advance. Two correction functions are designed to incorporate expert opinions in the learning model. Some examples are used for demonstration. The advantages of the proposed method are then discussed.

A Flexible Yield Model for Regional Timber Forecasting

Abstract Projecting the development of a regional timber resource in response to specific harvest patterns is an important activity for wood procurement planners and forest sectors modelers. Central to this is the development of suitable timber production functions. However, general yield models covering all possible growing sites, regimes, and tree species are simply not available. This paper introduces a general yield model for age-class based timber resource projection. The model is driven by mean annual increment (MAI) and can be used where reasonable estimates of MAI, based on historical evidence are available. South. J. Appl. For. 17(2):112-115.

Remote sensing estimators of potential and actual crop yield

Spectral-reflectance patterns, vegetative indices of infrared/red, were utilized to signal the beginning and ending times for a stress-degree-day summation. The maximum vegetative index ( mss 7 5 ) corresponded to the beginning of head-emergence in grain sorghum and the boot-stage in wheat. When the vegetative index declined to 0.5 of the maximum, 90% of the reproductive dry matter had been accumulated, delineating the reproductive portion of the growth cycle. In both grain sorghum and wheat, a linear relationship was found between yield and stress-degree-days over the reproductive period defined by the vegetative index. However, in all years, the grain sorghum data did not fit the same linear relationship because of differences in cultural practices. It was found that the maximum vegetative index could be used to define the potential harvestable yield that was encountered during the reproductive stage. A linear relationship was then found between the yield harvested relative to this potential harvestable yield and the summation of the stress-degree-days. In these experiments, there was a wide range in ground covers and yield providing a rigorous test of the relationship. This technique provides a method for defining the interval of the stress-degree-day accumulation and has applicability as a generalized yield model.