scholarly journals State of the art methods to post-process mechanical test data to characterize the hot deformation behavior of metals

2021 ◽  
Vol 13 (11) ◽  
pp. 168781402110610
Author(s):  
Shahin Khoddam ◽  
Soheil Solhjoo ◽  
Peter D Hodgson
Keyword(s):  
Test Data ◽  
Mechanical Test ◽  
Indirect Measurement ◽  
Data Conversion ◽  
Post Processing ◽  
Data Types ◽  
Flow Curves ◽  
Characterization Methods ◽  
Post Process ◽  
Processing Theory

Materials engineering and science rely heavily on the indirect measurement of plastic stress and strain by post-processing of mechanical test data, including tension, torsion, and compression test. There is no consensus among researchers regarding the best test or the post-processing theory nor do adequate standards exist on the characterization methods. The tests are typically performed as customized tests, discrepancies exist in the flow curves obtained by different methods and the chosen mechanical test. More critically, the curves are dominantly treated (perceived) as a set of measured data rather than calculated values. The plasticity-based calculated flow curves and their gradients are, in turn, the basis for several second-tier indirect measurements, such as stacking fault energy and recrystallization. Such measurements are quite prone to errors due to oversimplified post-processing of the tests’ data and can only be experimentally verified in a qualitative or in an average fashion. Therefore, their findings are highly restricted by the limitations of each test, data type and post-processing method, and should be used carefully. This review examines some of the most commonly used data conversion methods and some recent developments in the field followed by recommendations. It will highlight the need to develop test rigs that can provide new data types and to provide advanced post-processing techniques for the indirect measurement.

scholarly journals Thermal inactivation and growth potential of Listeria monocytogenes in smoked tench

2016 ◽  
Vol 5 (3) ◽  
Author(s):  
Raffaella Branciari ◽  
Andrea Valiani ◽  
Raffaella Franceschini ◽  
David Ranucci ◽  
Alessia Lupattelli ◽  
...  
Keyword(s):  
Experimental Study ◽  
Listeria Monocytogenes ◽  
Thermal Inactivation ◽  
Challenge Test ◽  
Listeria Innocua ◽  
Growth Potential ◽  
Post Processing ◽  
Colony Forming Unit ◽  
Post Process ◽  
Hygiene Measures

An experimental study for the evaluation of <em>Listeria monocytogenes</em> inactivation during a hot smoking process in tench was performed using <em>Listeria innocua</em> strains. Furthermore, the survival of <em>L. monocytogenes</em> in smoked tench was determined after post-processing in contaminated samples, evaluating the growth potential during storage. <em>L. innocua</em> was not detected after the smoking process. In the challenge test, the growth potential of <em>L. monocytogenes</em> was 5.68 log colony forming unit g<sup>−1</sup>. The results showed that hot smoking at an inner temperature around 72°C is able to eliminate the microorganism. Nevertheless, the product is able to support the growth of the pathogen if post-process contamination occurs, as the food is suitable for <em>Listeria</em> multiplication. Product recontamination should be prevented by means of appropriate application of hygiene measures.

scholarly journals Environmental degradation of composites for marine structures: new materials and new applications

2016 ◽  
Vol 374 (2071) ◽  
pp. 20150272 ◽  
Author(s):  
Peter Davies
Keyword(s):  
Composite Materials ◽  
Test Data ◽  
Environmental Degradation ◽  
Structural Integrity ◽  
Mechanical Test ◽  
Traditional Approach ◽  
Essential Element ◽  
Structural Testing ◽  
Marine Structures

This paper describes the influence of seawater ageing on composites used in a range of marine structures, from boats to tidal turbines. Accounting for environmental degradation is an essential element in the multi-scale modelling of composite materials but it requires reliable test data input. The traditional approach to account for ageing effects, based on testing samples after immersion for different periods, is evolving towards coupled studies involving strong interactions between water diffusion and mechanical loading. These can provide a more realistic estimation of long-term behaviour but still require some form of acceleration if useful data, for 20 year lifetimes or more, are to be obtained in a reasonable time. In order to validate extrapolations from short to long times, it is essential to understand the degradation mechanisms, so both physico-chemical and mechanical test data are required. Examples of results from some current studies on more environmentally friendly materials including bio-sourced composites will be described first. Then a case study for renewable marine energy applications will be discussed. In both cases, studies were performed first on coupons at the material level, then during structural testing and analysis of large components, in order to evaluate their long-term behaviour. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

scholarly journals On the implementation of post-processing of runoff forecast ensembles

2021 ◽  
Author(s):  
Jon Olav Skøien ◽  
Konrad Bogner ◽  
Peter Salamon ◽  
Fredrik Wetterhall
Keyword(s):  
Initial Conditions ◽  
Processing Parameters ◽  
Forecast Errors ◽  
Post Processing ◽  
Continental Scale ◽  
Post Process ◽  
Global Calibration ◽  
Calibration Methods ◽  
Verification Period ◽  
Ensemble Model Output Statistics

AbstractDifferent post-processing techniques are frequently employed to improve the outcome of ensemble forecasting models. The main reason is to compensate for biases caused by errors in model structure or initial conditions, and as a correction for under- or overdispersed ensembles. Here we use the Ensemble Model Output Statistics method to post-process the ensemble output from a continental scale hydrological model, LISFLOOD, as used in the European Flood Awareness System (EFAS). We develop a method for local calibration and interpolation of the post-processing parameters and compare it with a more traditional global calibration approach for 678 stations in Europe based on long term observations of runoff and meteorological variables. For the global calibration we also test a reduced model with only a variance inflation factor. Whereas the post-processing improved the results for the first 1-2 days lead time, the improvement was less for increasing lead times of the verification period. This was the case both for the local and global calibration methods. As the post-processing is based on assumptions about the distribution of forecast errors, we also present an analysis of the ensemble output that provides some indications of what to expect from the post-processing.

scholarly journals A Generalized Method for the Analysis of Planar Biaxial Mechanical Data Using Tethered Testing Configurations

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Will Zhang ◽  
Yuan Feng ◽  
Chung-Hao Lee ◽  
Kristen L. Billiar ◽  
Michael S. Sacks
Keyword(s):  
Stress Tensor ◽  
Test Data ◽  
Soft Tissues ◽  
Mechanical Test ◽  
Specimen Geometry ◽  
Parameter Determination ◽  
Biaxial Test ◽  
Cauchy Stress ◽  
Cauchy Stress Tensor ◽  
Thin Sections

Simulation of the mechanical behavior of soft tissues is critical for many physiological and medical device applications. Accurate mechanical test data is crucial for both obtaining the form and robust parameter determination of the constitutive model. For incompressible soft tissues that are either membranes or thin sections, planar biaxial mechanical testing configurations can provide much information about the anisotropic stress–strain behavior. However, the analysis of soft biological tissue planar biaxial mechanical test data can be complicated by in-plane shear, tissue heterogeneities, and inelastic changes in specimen geometry that commonly occur during testing. These inelastic effects, without appropriate corrections, alter the stress-traction mapping and violates equilibrium so that the stress tensor is incorrectly determined. To overcome these problems, we presented an analytical method to determine the Cauchy stress tensor from the experimentally derived tractions for tethered testing configurations. We accounted for the measured testing geometry and compensate for run-time inelastic effects by enforcing equilibrium using small rigid body rotations. To evaluate the effectiveness of our method, we simulated complete planar biaxial test configurations that incorporated actual device mechanisms, specimen geometry, and heterogeneous tissue fibrous structure using a finite element (FE) model. We determined that our method corrected the errors in the equilibrium of momentum and correctly estimated the Cauchy stress tensor. We also noted that since stress is applied primarily over a subregion bounded by the tethers, an adjustment to the effective specimen dimensions is required to correct the magnitude of the stresses. Simulations of various tether placements demonstrated that typical tether placements used in the current experimental setups will produce accurate stress tensor estimates. Overall, our method provides an improved and relatively straightforward method of calculating the resulting stresses for planar biaxial experiments for tethered configurations, which is especially useful for specimens that undergo large shear and exhibit substantial inelastic effects.

Acceptance Testing of Liquefied Natural Gas Compressors

2015 ◽  
Author(s):  
Roger Nyquist ◽  
Mike Andrews ◽  
Andrew Hunter ◽  
Oyuna Myagmar
Keyword(s):  
Mach Number ◽  
Natural Gas ◽  
Test Data ◽  
Density Ratio ◽  
Liquefied Natural Gas ◽  
Inlet Pressure ◽  
Data Conversion ◽  
Acceptance Testing ◽  
Ambient Temperatures ◽  
Similarity Laws

The majority of natural gas compressors operate on gas mixtures with molecular weights (MW) less than air. For these machines, performance acceptance tests are run on air at reduced speed. For multistage compressors, each stage is tested individually. The test speeds and inlet temperatures are selected to closely match the inlet to exit density ratios and the machine Mach numbers per the ASME PTC10 test code. The specified test inlet pressure (limited by the test variable speed motor power capacity) is always high enough to assure that the test Reynolds number is above the required PTC10 minimum; the density ratio and machine Mach number do not depend on inlet pressure. The air test data is converted to the specified natural gas conditions using similarity laws, and an in-house stage matching program is used to determine the overall machine performance. For compressors used in liquefied natural gas (LNG) transport, the MW of the natural gas mixture is lower than air. However, the inlet temperatures are so low that an air test at typical ambient temperatures needs to be run at a speed higher than design to closely match density and machine Mach number ratios. It is impractical to run air tests at higher than design speeds (especially for 60 Hz machines), thus these machines are tested on air at design speed. As before, the air test data is reduced to the specified natural gas conditions using the similarity laws. An additional “compressibility” correction is made to account for the mismatch of density ratio between test and design conditions. Running a test at lower than the required PTC10 speed means that the test density ratio will be lower than the corrected density ratio and the stage would pass more flow than the test data conversion indicates. The method used to account for the density ratio mismatch, i.e. a “compressibility” correction is discussed in detail in this paper.

A Visible Framework for Virtual Prototype of Electric Tools

2011 ◽  
Vol 120 ◽  
pp. 61-64
Author(s):  
Jiang Wei Cui ◽  
Qiang Gao ◽  
Jing Li ◽  
Xiang Chen ◽  
Xiao Lei Wang
Keyword(s):  
Real Time ◽  
Virtual Prototype ◽  
Post Processing ◽  
Linear Vibration ◽  
Post Process ◽  
Parameterized Modeling ◽  
Processing Module ◽  
Simulation Results ◽  
Analysis System ◽  
Geometry Engine

This paper developed real-time virtual prototype analysis system of electric tools that consists of pre-processing module, solver module and post processing module. Adopting the OCC (OpenCASCADE) geometry engine, the functions such as parameterized modeling, virtual assembly and visible post process of the geared rotor system of electric tools were realized, simulation results of the virtual prototype analysis of the non-linear vibration is shown effectively.

scholarly journals Model-enforced post-process correction of satellite aerosol retrievals

2021 ◽  
Vol 14 (4) ◽  
pp. 2981-2992
Author(s):  
Antti Lipponen ◽  
Ville Kolehmainen ◽  
Pekka Kolmonen ◽  
Antti Kukkurainen ◽  
Tero Mielonen ◽  
...  
Keyword(s):  
Machine Learning ◽  
Satellite Data ◽  
Data Retrieval ◽  
Post Processing ◽  
Correction Model ◽  
Post Process ◽  
Spectral Bands ◽  
Processing Step ◽  
Retrieval Algorithms ◽  
Data Products

Abstract. Satellite-based aerosol retrievals provide a timely view of atmospheric aerosol properties, having a crucial role in the subsequent estimation of air quality indicators, atmospherically corrected satellite data products, and climate applications. However, current aerosol data products based on satellite data often have relatively large biases compared to accurate ground-based measurements and distinct uncertainty levels associated with them. These biases and uncertainties are often caused by oversimplified assumptions and approximations used in the retrieval algorithms due to unknown surface reflectance or fixed aerosol models. Moreover, the retrieval algorithms do not usually take advantage of all the possible observational data collected by the satellite instruments and may, for example, leave some spectral bands unused. The improvement and the re-processing of the past and current operational satellite data retrieval algorithms would become tedious and computationally expensive. To overcome this burden, we have developed a model-enforced post-process correction approach to correct the existing operational satellite aerosol data products. Our approach combines the existing satellite aerosol retrievals and a post-processing step carried out with a machine-learning-based correction model for the approximation error in the retrieval. The developed approach allows for the utilization of auxiliary data sources, such as meteorological information, or additional observations such as spectral bands unused by the original retrieval algorithm. The post-process correction model can learn to correct for the biases and uncertainties in the original retrieval algorithms. As the correction is carried out as a post-processing step, it allows for computationally efficient re-processing of existing satellite aerosol datasets without fully re-processing the much larger original radiance data. We demonstrate with over-land aerosol optical depth (AOD) and Ångström exponent (AE) data from the Moderate Imaging Spectroradiometer (MODIS) of the Aqua satellite that our approach can significantly improve the accuracy of the satellite aerosol data products and reduce the associated uncertainties. For instance, in our evaluation, the number of AOD samples within the MODIS Dark Target expected error envelope increased from 63 % to 85 % when the post-process correction was applied. In addition to method description and accuracy results, we also give recommendations for validating machine-learning-based satellite data products.

Parametric Variation or Defects?: Statistical Post-Processing Analysis of Wafer-Sort Data

2002 ◽  
Author(s):  
W. Robert Daasch
Keyword(s):  
Spatial Patterns ◽  
Test Data ◽  
Parameter Variation ◽  
Data Driven ◽  
Normal Variation ◽  
Post Processing ◽  
Parametric Data ◽  
Original Measurement ◽  
The Subject ◽  
Measurement Variance

Abstract The subject of this paper is statistical post-processing of wafer-sort test data. Statistical post-processing (SPP) has successfully separated many of the effects of defects from normal wafer-to-wafer variation. The data-driven method is used with parametric data such as IDDQ, minVDD, and others. The neighboring die are used to form an estimate of a die’s expected value. The resulting SPP residual has smaller variance than the original measurement variance and filters most of the spatial patterns that obscure data outliers from normal variation. The method is applicable to a wide variety of process parameter variation issues of concern to both test and FA communities.

The Reliability Impact of Reballing COTS Pb-Free BGAs to Sn/Pb for Military Applications

2011 ◽  
Vol 2011 (1) ◽  
pp. 000703-000710
Author(s):  
Greg Caswell ◽  
Joelle Arnold
Keyword(s):  
Thermal Cycling ◽  
Hazardous Substances ◽  
Post Processing ◽  
Sac305 Solder ◽  
Post Process ◽  
Physical Testing ◽  
Solder Balls ◽  
Commercial Off The Shelf ◽  
Tin Silver Copper ◽  
The Cost

The electronics assembly market has experienced a material shift from lead (Pb) based solders to Pb-free solders. This is a result of the widespread adoption of Reduction of Hazardous Substances (RoHS) legislation and practices in commercial industry. As a result, it is becoming increasingly difficult to procure commercial off-the-shelf (COTS) components with tin-lead (SnPb) solder balls or finish. There are essentially three responses to the scarcity of acceptable SnPb parts: custom order, post process or adapt. Custom ordering parts with SnPb finishes negates the benefits of COTS based acquisition; however, has a reduced reliability risk because the material and processes are known. Reprocessing parts once in house saves money because the parts are COTS, but expends money and resources by performing post processing on them. Also, the additional touch labor and handling increases the risk of damaging the part. Finally, adapting to Pb-free finishes is the preferred long term approach because it preserves the cost benefits of using COTS parts and does not require post processing. It is the riskiest approach due to the lack of historical data in the DoD environment. This paper presents results regarding reballing 208 I/O Ball Grid Array (BGA) parts from tin-silver-copper (SAC305) solder to SnPb eutectic solder. It is important to understand the reliability risks associated with the reballing procedure, particularly as it relates to thermal cycling, shock and vibration environments. Three major efforts will be presented to answer these concerns. First, a survey of reballing vendors was performed to better understand the processes and variables associated with that industry. The results of that survey were used to down-select to five vendors that were used for the physical testing portion of the effort. Finally, physical testing consisting of thermal cycling, shock, and vibration was performed. The physical testing was performed on parts from the five different reballing vendors as well as native SnPb parts and native SAC305 parts. The results of these activities will be presented.

Sign in / Sign up

Export Citation Format

Share Document