Efficient Fatigue and Ratcheting Computation in Case of Multi-Parameter Loading

2020 ◽  
Author(s):  
Bastian Vollrath ◽  
Hartwig Hübel
Keyword(s):  
Cyclic Load ◽  
Computational Effort ◽  
Load Parameter ◽  
Cyclic Shear ◽  
Linear Elastic ◽  
Elastic Loading ◽  
Incremental Step ◽  
Lifecycle Design ◽  
Walled Cylinder

Abstract Cyclic and over-elastic loading can lead to an accumulation of plastic strains. If there is a cyclic load, which is driven by a single parameter, the lifecycle design can be very costly in terms of computational effort. If more than one cyclic load parameter is to be taken into account, which is then a multi-parameter loading, this task can become even more complex and costly. To solve this problem efficiently, different techniques are proposed. One of these techniques is based on step-by-step calculations of the strain ranges for a reduced set of loadings. Once these strain ranges are known, the accumulated state for each individual load case can be estimated using the Simplified Theory of Plastic Zones (STPZ), which requires just a few linear elastic analyses. It is shown that cyclic loads, which occur in intervals, can be replaced by interval-free calculations, which reduce the computational effort enormously. All these techniques lead to a procedure, which delivers good estimations in terms of post-shakedown quantities with very low computational effort compared to incremental step-by-step calculations. The results of the STPZ are presented by an example. A thick-walled cylinder is loaded with a constant axial force and subjected to cyclic shear and cyclic internal pressure. In general, for structures exhibiting ratcheting, hundreds or more load cycles must be analysed via step-by-step calculations until the shakedown state is reached. Using the STPZ, post-shakedown quantities, including strain ranges and accumulated strains can be estimated efficiently and the structure can be designed according to the rules of the ASME Codes. The computational effort and the quality of the results of the STPZ are compared with a step-by-step calculation.

scholarly journals A Smart Many-Core Implementation of a Motion Planning Framework along a Reference Path for Autonomous Cars

Electronics ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 177 ◽  
Author(s):  
Gianpiero Cabodi ◽  
Paolo Camurati ◽  
Alessandro Garbo ◽  
Michele Giorelli ◽  
Stefano Quer ◽  
...  
Keyword(s):  
Real Time ◽  
Graphics Processing Units ◽  
Data Communication ◽  
Computational Effort ◽  
Random Trees ◽  
Sequential Algorithm ◽  
Original Algorithm ◽  
Reference Path ◽  
Autonomous Cars

Research on autonomous cars, early intensified in the 1990s, is becoming one of the main research paths in automotive industry. Recent works use Rapidly-exploring Random Trees to explore the state space along a given reference path, and to compute the minimum time collision-free path in real time. Those methods do not require good approximations of the reference path, they are able to cope with discontinuous routes, they are capable of navigating in realistic traffic scenarios, and they derive their power from an extensive computational effort directed to improve the quality of the trajectory from step to step. In this paper, we focus on re-engineering an existing state-of-the-art sequential algorithm to obtain a CUDA-based GPGPU (General Purpose Graphics Processing Units) implementation. To do that, we show how to partition the original algorithm among several working threads running on the GPU, how to propagate information among threads, and how to synchronize those threads. We also give detailed evidence on how to organize memory transfers between the CPU and the GPU (and among different CUDA kernels) such that planning times are optimized and the available memory is not exceeded while storing massive amounts of fuse data. To sum up, in our application the GPU is used for all main operations, the entire application is developed in the CUDA language, and specific attention is paid to concurrency, synchronization, and data communication. We run experiments on several real scenarios, comparing the GPU implementation with the CPU one in terms of the quality of the generated paths and in terms of computation (wall-clock) times. The results of our experiments show that embedded GPUs can be used as an enabler for real-time applications of computationally expensive planning approaches.

A Study Effect of Shooting 2 Balls in a Ball Swaging Process on Gram Load Parameter Using Finite Element Analysis

2014 ◽  
Vol 1061-1062 ◽  
pp. 421-426 ◽  
Author(s):  
Panupich Kheunkhieo ◽  
Kiatfa Tangchaichit
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Radial Direction ◽  
Base Plate ◽  
Element Model ◽  
Load Parameter ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Main Component

The purposes of this research are to explore the baseplate and actuator arm deformation which effect to the gram load which occur in the ball swaging process, the main component determining quality of assembly the head stack assembly with the actuator arm. By shooting a ball though the base plate, the component located on the head stack assembly, the base plate plastic deformation takes place and it in expand in radial direction. The base plate then adjoins with the actuator arm. Using the finite element method to reproduce the ball swaging process, we repeated to study effect of the swage press clamp and velocity. The study done by creating the three dimensionals finite element model to analyze and explain characteristics of the baseplate and actuator arm deformation which effect to gram load which effect to the ball swaging process.

SIFs for Radial Cracks in Annular Discs Under Internal and External Shrinkage Pressure and Constant Angular Velocity

2007 ◽  
Author(s):  
A. Sakhaee-Pour ◽  
A. R. Gowhari-Anaraki ◽  
S. J. Hardy
Keyword(s):  
Finite Element ◽  
Angular Velocity ◽  
Constant Angular Velocity ◽  
Coefficient Of Determination ◽  
Linear Elastic ◽  
Crack Configuration ◽  
Wide Range ◽  
Elastic Fracture ◽  
Radial Cracks

Finite element method has been implemented to predict stress intensity factors (SIFs) for radial cracks in annular discs under constant angular velocity. Effects of internal and external uniform pressure on the SIFs have also been considered. Linear elastic fracture mechanics finite element analyses have been performed and results are presented in the form of crack configuration factors for a wide range of components and crack geometry parameters. These parameters are chosen to be representative of typical practical situations. The extensive range of crack configuration factors obtained from the analyses is then used to develop equivalent prediction equations via a statistical multiple non-linear regression model. The accuracy of this model is measured using a multiple coefficient of determination, R2, where 0 ≤ R2 ≤ 1. This coefficient is found to be greater than or equal to 0.98 for all cases considered in this study, demonstrating the quality of the model fit to the data. These equations for the SIFs enable designers to predict fatigue life of the components easily.

Study on Bridge Deck Link Slabs of Simply Supported Girder Bridges

2014 ◽  
Vol 1079-1080 ◽  
pp. 280-285
Author(s):  
Han Yong Liu ◽  
Shang Chuan Zhao ◽  
Long Li
Keyword(s):  
Bridge Deck ◽  
Maximum Tensile Stress ◽  
Internal Force ◽  
Early Disease ◽  
Factors Affecting ◽  
Linear Elastic ◽  
Girder Bridges ◽  
The Status ◽  
Suitable Structure

Accordingto the status of seriously early disease, the diseases investigation and causesanalysis were performed on bridge deck link slabs. The results show thattransverse cracks and pot holes are the main forms of diseases of bridge decklink slabs. The main reason of diseases for bridge deck link slabs is the lightstructure, mechanical complex, unclearly to the performance under force, anddifficult to guarantee the quality of construction. According to the causes ofdiseases, the linear elastic analysis was performed on bridge deck link slabunder loading. The formula of maximum tensile stress of concrete in bridge decklink slab is derived. The main factors affecting the internal force of bridgedeck link slab were analyzed. The suitable structure of bridge deck link slabsis proposed.

scholarly journals Home-based pulmonary rehabilitation in people with bronchiectasis, a randomised controlled trial

2021 ◽  
pp. 00021-2021
Author(s):  
Anderson José ◽  
Anne E. Holland ◽  
Jessyca P. R. Selman ◽  
Cristiane Oliveira de Camargo ◽  
Diogo Simões Fonseca ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Muscle Strength ◽  
Pulmonary Rehabilitation ◽  
Controlled Trial ◽  
Quadriceps Muscle ◽  
Step Test ◽  
Control Group ◽  
Test Quality ◽  
Incremental Step

AimTo investigate the short- and long-term effects of Home-based Pulmonary Rehabilitation (HBPR) on functional capacity, quality of life, peripheral muscle strength, dyspnea and daily physical activity in people with bronchiectasis.MethodsRandomised controlled trial with 63 participants with bronchiectasis. The HBPR group performed three sessions per week for 8 weeks (aerobic exercise: step training for 20 min; resistance training: exercises for quadriceps, hamstrings, deltoids, and biceps brachii with elastic bands). The control group received recommendation to walk at moderate intensity, three times per week. A weekly phone call was conducted for all participants, and the HBPR group received a home visit every 15 days. The primary outcome was distance in the incremental shuttle walk test (ISWT). Secondary outcomes were time in the endurance shuttle walk test (ESWT), number of steps in the incremental step test, quality of life, quadriceps muscle strength and daily physical activity. Measures were taken before and after intervention and 6 months later.ResultsAfter the intervention, the HBPR group had increased the distance in ISWT compared with the control group with between-group difference: 87.9 m (95% CI 32.4 to 143.5). Between-group differences was found in ESWT, incremental step test, quality of life and quadriceps muscle strength in favor to HBPR group too. After 6 months, no differences were observed between the groups.ConclusionHBPR is an effective alternative for offering pulmonary rehabilitation for people with bronchiectasis. However, the program was not effective in maintaining the benefits after 6 months of follow-up.

scholarly journals Examination of a Low-Profile Spinal Implant

2017 ◽  
Vol 11 (6) ◽  
pp. 895-901
Author(s):  
Takuto Iwade ◽  
Noriyuki Hisamori ◽  
Junichi Fujita ◽  
Kenji Yamaya ◽  
◽  
...  
Keyword(s):  
Contact Area ◽  
Cyclic Load ◽  
Load Test ◽  
Screw Thread ◽  
Static Load Test ◽  
Spinal Implant ◽  
Thread Surface ◽  
Low Profile ◽  
Screw Threads

Most spine implant devices are fabricated outside Japan, and therefore do not always fit the bodies of Japanese people. This causes a quality-of-life (QOL) problem in which patients feel the embedded implant devices on their back. The aim of this study was to develop more compact and lower-profile spine implant devices. Three types of devices with different heights and different screw threads were created, and the removal torque (fitting force) of the devices was measured after a static load test and cyclic load test. In addition, the screw thread surface was observed in detail after the tests. The results indicated that the mechanism of the reduction in the fitting force was related to partial contact due to abrasion or plastic deformation of the screw thread surface and decrease in the contact area between the screw threads caused by the increased diameter of the upper opening of the implant device after tightening. Therefore, we concluded that lowering the height of the implant device, securing the number of the screw threads, and securing the contact area of the threads are important in developing a low-profile spine implant.

scholarly journals Subgrid Parameterizations of the Eddy–Eddy, Eddy–Mean Field, Eddy–Topographic, Mean Field–Mean Field, and Mean Field–Topographic Interactions in Atmospheric Models

2019 ◽  
Vol 76 (2) ◽  
pp. 457-477 ◽  
Author(s):  
Vassili Kitsios ◽  
Jorgen S. Frederiksen
Keyword(s):  
Baroclinic Instability ◽  
Mean Field ◽  
Three Dimensional ◽  
Computational Effort ◽  
Atmospheric Flows ◽  
Large Eddy ◽  
Subgrid Scales ◽  
High Level ◽  
Jet Structure

Abstract Parameterizations are developed for each of the subgrid turbulence interaction classes in fully three-dimensional global atmospheric flows over topography, typical of January and July climate states. Stochastic and deterministic parameterizations are developed for the eddy–eddy interactions and deterministic parameterizations for eddy–mean field, eddy–topographic, mean field–mean field, and mean field–topographic interactions. All parameterizations are calculated from the statistics of higher-resolution reference direct numerical simulations (DNSs) truncated into resolved and subgrid scales and employed without tuning coefficients. This parameterization framework is validated by performing large-eddy simulations (LESs) that closely agree with the reference DNSs in terms of time-averaged kinetic energy spectra, zonal jet structure, and nonzonal streamfunction fields. Both the DNSs and LESs are formulated in such a way that the usual problem of a long artificial dissipation range does not occur. Successful LESs are produced with truncation wavenumbers 31 and 15, using, respectively, only 11.9% and 1.3% of the DNS computational effort at truncation wavenumber 63. The lower-resolution LESs show that the parameterizations are successful even when the energy injection due to baroclinic instability is not completely resolved. The contribution of each of the parameterized interaction classes to the quality of the LES is identified. The best agreement is achieved when all subgrid components are included. There is a very high level of agreement between the LESs and DNSs with typical streamfunction pattern correlations of r = 0.962 for the nonzonal components and r = 0.999 for the total fields when the complete sets of parameterizations are used.

scholarly journals Addressing cluster-constant covariates in mixed effects models via likelihood-based boosting techniques

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0254178
Author(s):  
Colin Griesbach ◽  
Andreas Groll ◽  
Elisabeth Bergherr
Keyword(s):  
Mixed Models ◽  
Fixed Effects ◽  
Regression Models ◽  
Computational Effort ◽  
Likelihood Inference ◽  
Gradient Boosting ◽  
Current State ◽  
Selection Step ◽  
Boosting Algorithm

Boosting techniques from the field of statistical learning have grown to be a popular tool for estimating and selecting predictor effects in various regression models and can roughly be separated in two general approaches, namely gradient boosting and likelihood-based boosting. An extensive framework has been proposed in order to fit generalized mixed models based on boosting, however for the case of cluster-constant covariates likelihood-based boosting approaches tend to mischoose variables in the selection step leading to wrong estimates. We propose an improved boosting algorithm for linear mixed models, where the random effects are properly weighted, disentangled from the fixed effects updating scheme and corrected for correlations with cluster-constant covariates in order to improve quality of estimates and in addition reduce the computational effort. The method outperforms current state-of-the-art approaches from boosting and maximum likelihood inference which is shown via simulations and various data examples.

scholarly journals When is shared sanitation acceptable in low-income urban settlements? A user perspective on shared sanitation quality in Kumasi, Kisumu and Dhaka

2020 ◽  
Vol 10 (4) ◽  
pp. 959-968
Author(s):  
Vasco Schelbert ◽  
Dario Meili ◽  
Mahbub-Ul Alam ◽  
Sheillah Simiyu ◽  
Prince Antwi-Agyei ◽  
...  
Keyword(s):  
Low Income ◽  
Group Discussions ◽  
The Sustainable Development ◽  
Acceptable Quality ◽  
Urban Settlements ◽  
Individual Household ◽  
Development Goals ◽  
Joint Monitoring ◽  
Incremental Step

Abstract Shared sanitation facilities (SSFs) have contributed considerably to sanitation access in many low-income settlements. While many SSFs are of unacceptable quality, others have been found to be a hygienically safe and a socially and economically viable sanitation option. Within its framework, the WHO/UNICEF Joint Monitoring Programme (JMP), evaluating progress on the Sustainable Development Goals, considers shared sanitation as ‘limited sanitation’. Overall, there is uncertainty about the criteria to distinguish between unacceptable and acceptable quality of SSF. In our study, we used a user-centred qualitative approach in low-income urban settlements in Kumasi (Ghana), Kisumu (Kenya) and Dhaka (Bangladesh) and conducted 17 focus group discussions to evaluate how SSF users define the quality of an SSF and which aspects they consider as essential priorities for good-quality SSF. In descending order, the user priorities identified are: immediate water access, cleanliness, gender-separated toilets, flush toilets, lighting for use at night, lockable/functional doors, tiling, handwashing stations and privacy. This list can serve as input to the sanitation guidelines, local building codes and the establishment of minimum national sanitation standards. SSFs that meet these minimal criteria can then be promoted as an incremental step when individual household facilities are not feasible.

scholarly journals Non-linear methods based on ultrasonic waves to analyse disbonds in single lap joints

2017 ◽  
Vol 231 (16) ◽  
pp. 3066-3076 ◽  
Author(s):  
G Scarselli ◽  
F Ciampa ◽  
F Nicassio ◽  
M Meo
Keyword(s):  
Adhesive Layer ◽  
Lap Joints ◽  
Ultrasonic Waves ◽  
Destructive Testing ◽  
Linear Elastic ◽  
Single Lap Joints ◽  
Non Linear ◽  
Structural Responses ◽  
Non Destructive

Adhesive bonded lap joints are widely used in the aerospace field and non-destructive testing (NDT) techniques are critical in evaluating the quality of adhesion before and during use. Two types of bonded samples have been experimentally investigated in order to verify the reliability of non-linear elastic wave spectroscopy (NEWS) based on the use of ultrasound. Piezoelectric sensors have been attached to the samples and used as generators and receivers. Both the samples have shown non-linearities in their dynamic behaviour. Non-linear metrics have been applied to their structural responses over an assigned range of excitation frequencies based on higher order harmonic analysis in order to evaluate the degree of non-linearity of the samples. Possible interpretations of the experimental behaviour are provided in the paper based also on tomographic testing of the adhesive layer that showed the presence of microbubbles in the bond due to manufacturing process.

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