scholarly journals Prediction of squeal instabilities of a FEM automotive brake with uncertain structural and environmental parameters with a hybrid surrogate model

2021 ◽  
pp. 1-20
Author(s):  
Enora Denimal ◽  
Jean-Jacques Sinou ◽  
Samuel Nacivet
Keyword(s):  
Surrogate Model ◽  
Environmental Parameters ◽  
Brake System ◽  
Direct Access ◽  
Design Parameters ◽  
Meta Model ◽  
Mean And Variance ◽  
The Mean ◽  
The Stability ◽  
Automotive Brake

Abstract This study focuses on the prediction of the stability behaviour of an industrial automotive brake system under structural and environmental uncertainties. Uncertainties are modelled with a random distribution or an interval and are propagated with a hybrid surrogate model associating polynomial chaos and kriging. The objective is to create a surrogate model of each eigenvalue computed with the CEA. As the modes can be tracked only when unstable, the effective size of the training sets can become extremely small. Despite this limitation, it is shown the hybrid meta-model is still able to predict the stability of the brake system. Moreover, the hybrid meta-model gives a direct access to the mean and variance of the eigenvalues with respect to the design parameters without any additional MCS. By considering different PDF for the friction coefficient, it is shown it has a high influence on the stability and the latter should be accurately estimated.

Robust Design Through the Use of a Hybrid Genetic Algorithm

2002 ◽  
Author(s):  
Kurt Hacker ◽  
Kemper Lewis
Keyword(s):  
Robust Design ◽  
Hybrid Genetic Algorithm ◽  
Design Parameters ◽  
Optimization Approach ◽  
Engineering Systems ◽  
Local Optima ◽  
Good Design ◽  
Mean And Variance ◽  
The Mean

In this paper we present a hybrid optimization approach to perform robust design. The motivation for this work is the fact that many realistic engineering systems are mutimodal in nature with multiple local optima, and moreover may have one or more uncertain design parameters. The approach that is presented utilizes both local and global optimization algorithms to find good design points more efficiently than either could alone. The mean and variance of the objective function at a design point is calculated using Monte Carlo simulation and is used to drive the optimization process. To demonstrate the usefulness of this approach a case study is considered involving the design of a beam with dimensional uncertainty.

Reliability-Based Design of Reinforced Earth Retaining Walls

1996 ◽  
Vol 1526 (1) ◽  
pp. 64-78 ◽  
Author(s):  
Imad A. Basheer ◽  
Yacoub M. Najjar
Keyword(s):  
Order Approximation ◽  
Retaining Walls ◽  
Design Parameters ◽  
Physical Parameters ◽  
Statistical Parameters ◽  
First Order ◽  
Reliability Based Design ◽  
Reinforced Earth ◽  
Mean And Variance ◽  
The Mean

Reliability of an earth structure can be assessed from the knowledge of the governing probability distribution and its related statistical parameters, namely, the mean and variance. In this study, the mean and variance for the design parameters (width and length of the reinforcing ties) of reinforced earth retaining walls supporting sandy soils are determined using the first-order Taylor series approximation. Design diagrams that enable estimation of both mean and variance also are developed to avoid extensive computations that involve partial differentiation. Errors associated with truncating second-order terms are also evaluated. It is found that for soils with moderately variable physical parameters, the first-order approximation is adequate for estimating both the mean and variance.

Improving the Reliability of Tube Hydroforming Process by the Taguchi Method

2005 ◽  
Author(s):  
Bing Li ◽  
T. J. Nye ◽  
Don R. Metzger
Keyword(s):  
Taguchi Method ◽  
Rapid Development ◽  
Tube Hydroforming ◽  
Design Stage ◽  
Design Parameters ◽  
Forming Parameters ◽  
Hydroforming Process ◽  
Process Output ◽  
Mean And Variance ◽  
The Mean

The tube hydroforming process has undergone extremely rapid development, especially in applications for the automobile industry. In-process variation of forming parameters such as material properties, friction conditions and part geometries will directly affect the quality of forming response by causing variation in the process output. To ensure a reliable hydroforming process at the design stage, applying robust design methodologies becomes crucial to the success of the resulting process. The reliability of the tube hydroforming process based on the tube wall thickness thinning ratio is studied in this paper. In order to improve the reliability of the process, the Taguchi method, which is capable of evaluating the effects of process variables on both the mean and variance of process output, is used to determine the optimal forming parameters for minimizing the variation and average value of the thinning ratio. The Taguchi method is applied to design experimental arrays which incorporate design (i.e., controllable) parameters and noise (i.e., non-controllable) parameters. Finite element simulation is used to analyze the virtual experiments according to the experimental arrays. Through statistical analysis, the influence of each design parameter on both the mean and variance of the thinning ratio is obtained, and is used to find the optimal combination of design parameters for minimum thinning ratio, minimum variance of thinning ratio, and maximum expected process reliability. A cross-extrusion hydroformed tube is employed as an example to illustrate the effectiveness of this approach.

Control of Brake Squeal Using Shunted Piezoelectric Pads

2019 ◽  
Author(s):  
Yaqoub Abdullah ◽  
Amr Baz
Keyword(s):  
Automotive Industry ◽  
Mechanical Energy ◽  
Natural Extension ◽  
Electrical Energy ◽  
Brake System ◽  
Design Parameters ◽  
Disc Brake ◽  
Brake Squeal ◽  
Electric Networks ◽  
The Stability

Abstract Brake squeal phenomenon poses serious challenges to the automotive industry due to its technical complexity and the pressing need for mitigating its undesirable effects. More importantly, brake squeal causes significant customer dissatisfaction and adversely affects the subjective quality of the vehicles. These effects have substantial economic impact on the automotive industry. Furthermore, it is essential to properly treat the brake squeal problems in order to avoid unexpected catastrophic failure of the brake system. In this paper, it is proposed to mitigate the brake squeal problems by providing the brake pads with piezoelectric patches which are shunted by properly tuned electric networks. The shunted piezoelectric pads offer a unique ability to convert the mechanical energy induced by the brake squeal into electrical energy which can be dissipated into the network in order to enhance the damping and stability characteristics of the brake system. Accordingly, it is envisioned that the proposed approach would enable the disc brake systems to operate over broad ranges of operating parameters without experiencing the adverse effects of brake squeal. The proposed system is modeled by a simple two Degree-Of-Freedom (DOF) disc brake model. The structural DOF are integrated with the constitutive model of the shunted piezoelectric network in order to predict the threshold of brake squeal. The stability limits of the proposed brake system are established as a function of the design parameters of the shunted piezoelectric network. Numerical examples are presented to demonstrate the effectiveness of the proposed system in expanding the operating range of the brake system without experiencing squeal problems. Application of the proposed system to a distributed disc brake system model is a natural extension of the present work.

Injuries to the Coronoid Process of the Ulna with Involvement of the Lesser Sigmoid Notch

2020 ◽  
Author(s):  
Valentin Rausch ◽  
Sina Neugebauer ◽  
Tim Leschinger ◽  
Lars Müller ◽  
Kilian Wegmann ◽  
...  
Keyword(s):  
Fragment Size ◽  
Coronoid Process ◽  
Annular Ligament ◽  
Concomitant Injuries ◽  
Proximal Ulna ◽  
Sigmoid Notch ◽  
Coronoid Fractures ◽  
The Mean ◽  
The Stability ◽  
Arthritic Changes

Abstract Introduction This study aimed to describe the involvement of the lesser sigmoid notch in fractures to the coronoid process. We hypothesized that injuries to the lateral aspect of the coronoid process regularly involve the annular ligament insertion at the anterior lesser sigmoid notch. Material and Methods Patients treated for a coronoid process fracture at our institution between 06/2011 and 07/2018 were included. We excluded patients < 18 years, patients with arthritic changes or previous operative treatment to the elbow, and patients with concomitant injuries to the proximal ulna. In patients with involvement of the lesser sigmoid notch, the coronoid height and fragment size (anteroposterior, mediolateral, and craniocaudal) were measured. Results Seventy-two patients (mean age: 47 years ± 17.6) could be included in the study. Twenty-one patients (29.2%) had a fracture involving the lateral sigmoid notch. The mean anteroposterior fragment length was 7 ± 1.6 mm. The fragment affected a mean of 43 ± 10.8% of the coronoid height. The mean mediolateral size of the fragment was 10 ± 5.0 mm, and the mean cranio-caudal size was 7 ± 2.7 mm. Conclusion Coronoid fractures regularly include the lesser sigmoid notch. These injuries possibly affect the anterior annular ligament insertion which is important for the stability of the proximal radioulnar joint and varus stability of the elbow.

Instant 99mTc-Labelled Glucoheptonate Kit for Kidney Imaging

1983 ◽  
Vol 22 (05) ◽  
pp. 246-250 ◽  
Author(s):  
M. Al-Hilli ◽  
H. M. A. Karim ◽  
M. H. S. Al-Hissoni ◽  
M. N. Jassim ◽  
N. H. Agha
Keyword(s):  
Sodium Hydroxide Solution ◽  
Normal Subjects ◽  
Organ Distribution ◽  
Stable Complex ◽  
Scintillation Camera ◽  
Ph Adjustment ◽  
The Mean ◽  
The Stability ◽  
Kidney Imaging ◽  
Mean Concentration

Gelchromatography column scanning has been used to study the fractions of reduced hydrolyzed 99mTc, 99mTc-pertechnetate and 99mTc-chelate in a 99mTc-glucoheptonate (GH) preparation. A stable high labelling yield of 99mTc-GH complex in the radiopharmaceutical has been obtained with a concentration of 40-50 mg of glucoheptonic acid-calcium salt and not less than 0.45 mg of SnCl2 2 H2O at an optimal pH between 6.5 and 7.0. The stability of the complex has been found significantly affected when sodium hydroxide solution was used for the pH adjustment. However, an alternative procedure for final pH adjustment of the preparation has been investigated providing a stable complex for the usual period of time prior to the injection. The organ distribution and the blood clearance data of 99mTc-GH in rabbits were relatively similar to those reported earlier. The mean concentration of the radiopharmaceutical in both kidneys has been studied in normal subjects for one hour with a scintillation camera and the results were satisfactory.

scholarly journals The force effects of two types of polyethylene terephthalate glyc-olmodified clear aligners immersed in artificial saliva

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Biao Xiang ◽  
Xingxing Wang ◽  
Gang Wu ◽  
Yichen Xu ◽  
Menghan Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Polyethylene Terephthalate ◽  
Artificial Saliva ◽  
Orthodontic Force ◽  
The Mean ◽  
The Stability ◽  
Scanning Electron

AbstractNumerous factors can influence the force exerted by clear aligners on teeth. This study aimed to investigate the stability of the force delivered by two different material appliances. 90 clear aligners with 2 materials and three different activations were designed and fabricated. Then, a device was employed to measure the force generated by the two types of PET-G material appliances immersed in artificial saliva for 0, 3, 7, 10, 14 days. Scanning electron microscopy was applied to observe the morphologic alterations on the aligner surfaces, respectively. The forces generated by different activation appliance exhibited differently, 0.0 mm < 0.1 mm < 0.2 mm. In addition, increasing the immersion times and the orthodontic force also decreased, but the forces decreased differently. Compared with the forces of conventional PETG appliances with 0.20 mm activation, the modified PETG appliances with the same activation exhibited significantly higher mean force. When comparing the mean force for modified PETG appliances after 10 and 14 days with conventional PETG appliances, the delivery forces exhibited significant differences (P < 0.05). The force delivered by both materials decreased obviously following artificial saliva immersion, and the force generated by modified aligners exhibited better stability than conventional aligners.

scholarly journals Weighted statistical binary patterns for facial feature representation

2021 ◽  
Author(s):  
Hung Phuoc Truong ◽  
Thanh Phuong Nguyen ◽  
Yong-Guk Kim
Keyword(s):  
Comprehensive Evaluation ◽  
Facial Feature ◽  
Input Image ◽  
Feature Representation ◽  
Illumination Variation ◽  
Straight Line ◽  
Mean And Variance ◽  
The Mean ◽  
Face Datasets ◽  
Degraded Images

AbstractWe present a novel framework for efficient and robust facial feature representation based upon Local Binary Pattern (LBP), called Weighted Statistical Binary Pattern, wherein the descriptors utilize the straight-line topology along with different directions. The input image is initially divided into mean and variance moments. A new variance moment, which contains distinctive facial features, is prepared by extracting root k-th. Then, when Sign and Magnitude components along four different directions using the mean moment are constructed, a weighting approach according to the new variance is applied to each component. Finally, the weighted histograms of Sign and Magnitude components are concatenated to build a novel histogram of Complementary LBP along with different directions. A comprehensive evaluation using six public face datasets suggests that the present framework outperforms the state-of-the-art methods and achieves 98.51% for ORL, 98.72% for YALE, 98.83% for Caltech, 99.52% for AR, 94.78% for FERET, and 99.07% for KDEF in terms of accuracy, respectively. The influence of color spaces and the issue of degraded images are also analyzed with our descriptors. Such a result with theoretical underpinning confirms that our descriptors are robust against noise, illumination variation, diverse facial expressions, and head poses.

scholarly journals Groups and Individuals: Optical Flow Patterns of Broiler Chicken Flocks Are Correlated with the Behavior of Individual Birds

Animals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 568
Author(s):  
Sabine G. Gebhardt-Henrich ◽  
Ariane Stratmann ◽  
Marian Stamp Dawkins
Keyword(s):  
Optical Flow ◽  
Broiler Chicken ◽  
Average Length ◽  
Flow Patterns ◽  
Group Level ◽  
Positive Correlation ◽  
Water Test ◽  
Mean And Variance ◽  
The Mean

Group level measures of welfare flocks have been criticized on the grounds that they give only average measures and overlook the welfare of individual animals. However, we here show that the group-level optical flow patterns made by broiler flocks can be used to deliver information not just about the flock averages but also about the proportion of individuals in different movement categories. Mean optical flow provides information about the average movement of the whole flock while the variance, skew and kurtosis quantify the variation between individuals. We correlated flock optical flow patterns with the behavior and welfare of a sample of 16 birds per flock in two runway tests and a water (latency-to-lie) test. In the runway tests, there was a positive correlation between the average time taken to complete the runway and the skew and kurtosis of optical flow on day 28 of flock life (on average slow individuals came from flocks with a high skew and kurtosis). In the water test, there was a positive correlation between the average length of time the birds remained standing and the mean and variance of flock optical flow (on average, the most mobile individuals came from flocks with the highest mean). Patterns at the flock level thus contain valuable information about the activity of different proportions of the individuals within a flock.

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