Ratcheting Prediction at the Notch Root of Steel Samples Over Asymmetric Loading Cycles

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
A. Shekarian ◽  
A. Varvani-Farahani
Keyword(s):  
Stress Relaxation ◽  
Notch Root ◽  
Kinematic Hardening ◽  
Strain Range ◽  
Medium Carbon Steel ◽  
Computational Time ◽  
Processing Unit ◽  
Central Processing ◽  
Hardening Rules ◽  
Neuber's Rule

Abstract The present study intends to evaluate local ratcheting and stress relaxation of medium carbon steel samples under various asymmetric load levels by means of two kinematic hardening rules of Chaboche (CH) and Ahmadzadeh-Varvani (A-V). The Neuber's rule was coupled with the hardening rules to predict ratcheting and stress relaxation at the vicinity of the notch root. Stress-strain hysteresis loops generated by the CH and A-V models were employed to simultaneously control ratcheting progress over stress cycles and stress relaxation at notch root while strain range kept constant in each cycle. The higher cyclic load levels applied at the notch root accelerated shakedown over smaller number of cycles and resulted in lower relaxation rate. The larger notch diameter of 9 mm on the other hand induced lower stress concentration and smaller plastic zone at the notch root promoting ratcheting progress with less materials constraint over loading cycles compared with notch diameter d = 3 mm. Predicted ratcheting results through the A-V and CH models as coupled with the Neuber's rule were found in good agreements with the experimental data. The choice of the A-V and CH hardening rules in assessing ratcheting of materials was attributed to the number of terms/coefficients and complexity of their frameworks and computational time/central processing unit (CPU) required to run a ratcheting program.

Ratcheting Prediction of 1070 and 16MnR Steel Alloys Under Uniaxial Asymmetric Stress Cycles By Means of Ohno–Wang and Ahmadzadeh–Varvani Kinematic Hardening Rules

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
G. R. Ahmadzadeh ◽  
S. M. Hamidinejad ◽  
A. Varvani-Farahani
Keyword(s):  
Kinematic Hardening ◽  
Uniaxial Stress ◽  
Cyclic Stress ◽  
Processing Unit ◽  
Central Processing ◽  
Hardening Rule ◽  
Ratcheting Strain ◽  
Stress Cycles ◽  
Time Required ◽  
Hardening Rules

The present study predicts ratcheting response of 1070 and 16MnR steel samples using nonlinear kinematic hardening rules of Ohno–Wang (O–W) and Ahmadzadeh–Varvani (A–V) under uniaxial stress cycles. The ratcheting values predicted based on the O–W model were noticeably influenced by the magnitude of exponents and the number of backstress components. Taking into account both material and cyclic stress level dependent coefficients, the A–V hardening rule offered a simple framework to predict ratcheting strain over loading cycles. A comparative study of these hardening rules to assess ratcheting of 1070 and 16MnR steel samples undergoing uniaxial loading conditions resulted in a close agreement of the A–V and O–W models. The choice of hardening rules in the assessment of materials ratcheting was further discussed based on the complexity of the hardening rule, number of constants/coefficients required to characterize ratcheting response, and central processing unit (CPU) time required to run the models.

A design procedure for improving the effectiveness of fractal layouts formation

2014 ◽  
Vol 28 (1) ◽  
pp. 1-26 ◽  
Author(s):  
Yung Chin Shih ◽  
Eduardo Vila Gonçalves Filho
Keyword(s):  
Design Procedure ◽  
Current Approach ◽  
Computational Time ◽  
Shop Floor ◽  
Processing Unit ◽  
Performance Parameters ◽  
Trade Off ◽  
Central Processing ◽  
Search Heuristics ◽  
Functional Layout

AbstractRecently, new types of layouts have been proposed in the literature in order to handle a large number of products. Among these are the fractal layout, aiming at minimization of routing distances. There are already researchers focusing on the design; however, we have noticed that the current approach usually executes several times the allocations of fractal cells on the shop floor up to find the best allocations, which may present a significant disadvantage when applied to a large number of fractal cells owing to combinatorial features. This paper aims to propose a criterion, based on similarity among fractal cells, developed and implemented in a Tabu search heuristics, in order to allocate it on the shop floor in a feasible computational time. Once our proposed procedure is modeled, operations of each workpiece are separated in n subsets and submitted to simulation. The results (traveling distance and makespan) are compared to distributed layout and to functional layout. The results show, in general, a trade-off behavior, that is, when the total routing distance decreases, the makespan increases. Based on our proposed method, depending on the value of segregated fractal cell similarity, it is possible to reduce both performance parameters. Finally, we conclude the proposed procedure shows to be quite promising because allocations of fractal cells demand reduced central processing unit time.

Modeling of Dynamic Cuttings Transportation during Drilling of Oil and Gas Wells by Combining 2D CFD and 1D Discretization Approach

SPE Journal ◽  
2020 ◽  
Vol 25 (03) ◽  
pp. 1220-1240 ◽  
Author(s):  
Feifei Zhang ◽  
Yidi Wang ◽  
Yuezhi Wang ◽  
Stefan Miska ◽  
Mengjiao Yu
Keyword(s):  
Oil And Gas ◽  
Continuous Model ◽  
Computational Time ◽  
Superposition Method ◽  
Processing Unit ◽  
Flow Profile ◽  
Gas Wells ◽  
Central Processing ◽  
Bed Height ◽  
Oil And Gas Wells

Summary This paper presents an approach that combines a two-dimensional (2D) computational fluid dynamics (CFD) and one-dimensional (1D) continuous model for cuttings transport simulation during drilling of oil and gas wells. The 2D CFD simulates the flow profile and the suspended cuttings concentration profile in the cross section of the wellbore and the 1D continuous model simulates the cuttings transportation in the axial direction of the wellbore. Different cuttings sizes are considered in the model by using a new proposed superposition method. Experimental tests conducted on a 203 × 114 × 25 mm3 flow loop are used to validate the model from three different perspectives: the single-phase flow pressure drop, the steady-state cuttings bed height, and the transient pressure changes. Compared to layer models, the new approach is able to catch accurate flow details in the narrow flow region and overcome the shortcoming of traditional models that underpredict bed height under high flow rate conditions. The computational time increases by the order of 104∼105 from the level of millisecond to seconds but is still within the acceptable range for engineering applications, and the model provides close to three-dimensional (3D) accuracy at a much shorter central processing unit (CPU) time compared to 3D CFD models.

scholarly journals Numerical comparison of reduced order models for non-linear vibrations of damped plates

2012 ◽  
Author(s):  
F. Boumediene ◽  
L. Duigou ◽  
A. Miloudi ◽  
J.M. Cadou
Keyword(s):  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Computational Time ◽  
Numerical Comparison ◽  
Processing Unit ◽  
Reduced Order Models ◽  
Reduced Order ◽  
Central Processing ◽  
Non Linear ◽  
Linear Vibrations

This work deals with the computation of the non-linear solutions of the vibration of damped plates by coupling a harmonic balance method and the asymptotic numerical method. These computations can lead to lengthy central processing unit (CPU) times if the solution sought contains an important number of harmonics. In this study, we propose two reduced order models which can be applied to solve this type of problem. Both reduced methods are based on a first computation carried out with a small number of harmonics (here two). Numerical examples of plate vibration show that these algorithms help save a great deal of computational time and can be applied to problems involving numerous harmonics.

scholarly journals A Review of Parallel Heterogeneous Computing Algorithms in Power Systems

Algorithms ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 275
Author(s):  
Diego Rodriguez ◽  
Diego Gomez ◽  
David Alvarez ◽  
Sergio Rivera
Keyword(s):  
Power Systems ◽  
Power System ◽  
Graphics Processing Units ◽  
Heterogeneous Computing ◽  
System Simulation ◽  
Computational Time ◽  
Processing Unit ◽  
Power System Simulation ◽  
Central Processing ◽  
Computing Platforms

The power system expansion and the integration of technologies, such as renewable generation, distributed generation, high voltage direct current, and energy storage, have made power system simulation challenging in multiple applications. The current computing platforms employed for planning, operation, studies, visualization, and the analysis of power systems are reaching their operational limit since the complexity and size of modern power systems results in long simulation times and high computational demand. Time reductions in simulation and analysis lead to the better and further optimized performance of power systems. Heterogeneous computing—where different processing units interact—has shown that power system applications can take advantage of the unique strengths of each type of processing unit, such as central processing units, graphics processing units, and field-programmable gate arrays interacting in on-premise or cloud environments. Parallel Heterogeneous Computing appears as an alternative to reduce simulation times by optimizing multitask execution in parallel computing architectures with different processing units working together. This paper presents a review of Parallel Heterogeneous Computing techniques, how these techniques have been applied in a wide variety of power system applications, how they help reduce the computational time of modern power system simulation and analysis, and the current tendency regarding each application. We present a wide variety of approaches classified by technique and application.

scholarly journals An Ensemble-based Supervised Machine Learning Framework for Android Ransomware Detection

2021 ◽  
Vol 18 (3A) ◽  
Author(s):  
Shweta Sharma ◽  
Rama Krishna ◽  
Rakesh Kumar
Keyword(s):  
Machine Learning ◽  
Graphics Processing Unit ◽  
Principal Component ◽  
Supervised Machine Learning ◽  
Computational Time ◽  
Processing Unit ◽  
Central Processing ◽  
Analysis Technique ◽  
Malicious Apps ◽  
Time Required

With latest development in technology, the usage of smartphones to fulfill day-to-day requirements has been increased. The Android-based smartphones occupy the largest market share among other mobile operating systems. The hackers are continuously keeping an eye on Android-based smartphones by creating malicious apps housed with ransomware functionality for monetary purposes. Hackers lock the screen and/or encrypt the documents of the victim’s Android based smartphones after performing ransomware attacks. Thus, in this paper, a framework has been proposed in which we (1) utilize novel features of Android ransomware, (2) reduce the dimensionality of the features, (3) employ an ensemble learning model to detect Android ransomware, and (4) perform a comparative analysis to calculate the computational time required by machine learning models to detect Android ransomware. Our proposed framework can efficiently detect both locker and crypto ransomware. The experimental results reveal that the proposed framework detects Android ransomware by achieving an accuracy of 99.67% with Random Forest ensemble model. After reducing the dimensionality of the features with principal component analysis technique; the Logistic Regression model took least time to execute on the Graphics Processing Unit (GPU) and Central Processing Unit (CPU) in 41 milliseconds and 50 milliseconds respectively

A Unified Viscoplastic Model for Creep and Fatigue-Creep Response Simulation of Haynes 230

2015 ◽  
Author(s):  
Paul Ryan Barrett ◽  
Tasnim Hassan
Keyword(s):  
Constitutive Model ◽  
Kinematic Hardening ◽  
Strain Range ◽  
Parameter Determination ◽  
Secondary Creep ◽  
Damage Modeling ◽  
Haynes 230 ◽  
Static Recovery ◽  
Hardening Rules ◽  
Creep Regime

A Chaboche-based unified viscoplastic constitutive model, including features of strain range dependence, strain rate-dependence, static recovery, and mean stress evolution is developed and evaluated for simulating fatigue-creep and creep responses of Haynes 230. In other words, this constitutive model attempt to simulate not only strain-controlled fatigue and fatigue-creep responses of Haynes 230, but also stress-controlled creep responses. After investigating various flow rules and kinematic hardening rules, a unified viscoplastic constitutive model is developed for simulating both the fatigue-creep and creep responses. The parameter determination for this constitutive model, however, requires a robust optimization algorithm. The proposed unified constitutive model can adequately simulate fatigue-creep responses, and creep responses up to the secondary creep regimes. However, with the introduction of damage modeling features the constitutive model can simulate the tertiary creep regime responses, but with some limitations in simulating fatigue-creep responses. Nonetheless, the unified viscoplastic constitutive model with or without damage modeling features has shown to be able to capture the stress-controlled creep responses while still maintaining high fidelity in capturing the strain-controlled fatigue and fatigue-creep responses.

A Line Heat Input Model for Additive Manufacturing

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Jeff Irwin ◽  
P. Michaleris
Keyword(s):  
Additive Manufacturing ◽  
Heat Source ◽  
Heat Input ◽  
Computational Time ◽  
Processing Unit ◽  
Powder Bed ◽  
Central Processing ◽  
Time Increment ◽  
Input Model ◽  
Time Required

A line input (LI) model has been developed, which makes the accurate modeling of powder bed processes more computationally efficient. Goldak's ellipsoidal model has been used extensively to model heat sources in additive manufacturing (AM), including lasers and electron beams. To accurately model the motion of the heat source, the simulation time increments must be small enough such that the source moves a distance smaller than its radius over the course of each increment. When the source radius is small and its velocity is large, a strict condition is imposed on the size of time increments regardless of any stability criteria. In powder bed systems, where radii of 0.1 mm and velocities of 500 mm/s are typical, a significant computational burden can result. The line heat input model relieves this burden by averaging the heat source over its path. This model allows the simulation of an entire heat source scan in just one time increment. However, such large time increments can lead to inaccurate results. Instead, the scan is broken up into several linear segments, each of which is applied in one increment. In this work, time increments are found that yield accurate results (less than 10% displacement error) and require less than 1/10 of the central processing unit (CPU) time required by Goldak's moving source model. A dimensionless correlation is given that can be used to determine the necessary time increment size that will greatly decrease the computational time required for any powder bed simulation while maintaining accuracy.

scholarly journals A Novel Parallel Algorithm with Map Segmentation for Multiple Geographical Feature Label Placement Problem

2021 ◽  
Vol 10 (12) ◽  
pp. 826
Author(s):  
Mohammad Naser Lessani ◽  
Jiqiu Deng ◽  
Zhiyong Guo
Keyword(s):  
Parallel Algorithm ◽  
Large Scale ◽  
Computational Time ◽  
Processing Unit ◽  
Placement Problem ◽  
Central Processing ◽  
Label Placement ◽  
Map Segmentation ◽  
Real World Datasets ◽  
Geographical Feature

Multiple geographical feature label placement (MGFLP) is an NP-hard problem that can negatively influence label position accuracy and the computational time of the algorithm. The complexity of such a problem is compounded as the number of features for labeling increases, causing the execution time of the algorithms to grow exponentially. Additionally, in large-scale solutions, the algorithm possibly gets trapped in local minima, which imposes significant challenges in automatic label placement. To address the mentioned challenges, this paper proposes a novel parallel algorithm with the concept of map segmentation which decomposes the problem of multiple geographical feature label placement (MGFLP) to achieve a more intuitive solution. Parallel computing is then utilized to handle each decomposed problem simultaneously on a separate central processing unit (CPU) to speed up the process of label placement. The optimization component of the proposed algorithm is designed based on the hybrid of discrete differential evolution and genetic algorithms. Our results based on real-world datasets confirm the usability and scalability of the algorithm and illustrate its excellent performance. Moreover, the algorithm gained superlinear speedup compared to the previous studies that applied this hybrid algorithm.

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