IDENTIFICATION OF GRANULAR SOILS STRENGTH AND STIFFNESS PARAMETERS BY MATCHING FINITE ELEMENT RESULTS TO PMT DATA

2014 ◽  
Vol 11 (02) ◽  
pp. 1342001 ◽  
Author(s):  
Y. ABED ◽  
R. BAHAR ◽  
J.-C. DUPLA ◽  
DJ. AMAR BOUZID
Keyword(s):  
Finite Element ◽  
Experimental Tests ◽  
Loading Path ◽  
Soil Parameters ◽  
Model Parameters ◽  
Expansion Curve ◽  
The Difference ◽  
Strength And Stiffness ◽  
Analytical Expressions

This paper describes an efficient methodology for the identification of soil parameters using the combination of the finite element method and the in situ pressuremeter test (PMT). The objective of the procedure applied here is to identify the parameters of generalized Prager model associated with the Drucker and Prager failure criterion from a pressuremeter expansion curve. The approach consists of minimizing the function representing the difference between the experimental curve and the curve obtained by integrating the model along the loading path in the in situ testing. First, both analytical expressions governing the problem of cavity expansion and those related to the finite element modeling are given in detail. Then, a Fortran computer program called "Press-Sim" along with the solution strategy are described and clearly explained. The influence of some model parameters as well as the probe geometry on the computed pressuremeter curves is examined. The paper finishes by presenting some identification examples drawn from real experimental tests for which the targeted parameters are compared with those of other experimental procedures. Results of comparison show a very good agreement.

scholarly journals An optimization procedure for the soil behavior identification using pressuremeter results

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Younes Abed
Keyword(s):  
Comparative Study ◽  
Optimization Procedure ◽  
Loading Path ◽  
Soil Parameters ◽  
Model Parameters ◽  
Soil Behavior ◽  
Trial Test ◽  
Different Depths ◽  
The Comparative Study

AbstractThe soil parameters identification procedure is usually a trade-off between sophisticated soil model behaviour and the large number of parameters to identify. Such procedure that can accomplish both of these objectives is highly desirable, but also difficult. This paper presents a methodology for identifying soil parameters that takes into account different constitutive equations. For identifying the generalized Prager model parameters, associated to the Drucker and Prager failure criterion, using an in-situ pressuremeter curve, we have proposed a procedure that is based on an approach of inverse analysis. This approach involves the minimizing the function representing the area between the experimental curve and the simulated curve, obtained by fit in the model along the in-situ loading path. A comparative study between two optimization processes is proposed. The first is based on the technique of the simplex by Nelder and Mead, while the second is based on the decomposition of the pressuremeter curve in three distinct areas. After a brief description of an existing computer program called Press-Sim, which has been written in Fortran for analyzing a cavity expansion using the finite element method, a short explanation is given about the two optimization procedures considered in this article. Then, for a chosen site where soil strength parameters are measured, the comparative study has been performed for both methods at four different depths. For the determination of the angle of friction, the two procedures yield very close values and are in a good agreement with that given by the triaxial test, while for the cohesion, they both diverge from each other on both sides of the value measured by the trial test.

Experiment Research on Control Method and Mathematic Models during Energy Storage to the Double Function Flywheel System

2011 ◽  
Vol 291-294 ◽  
pp. 2814-2817
Author(s):  
Zhi Hua Liu ◽  
Yan Min Li ◽  
Chun Li Wang
Keyword(s):  
Energy Storage ◽  
Attitude Control ◽  
High Speed ◽  
Control Method ◽  
Experimental Tests ◽  
Model Parameters ◽  
Electrical Machinery ◽  
Wide Range ◽  
Double Function ◽  
The Difference

The mathematical models of the double function flywheel system were built based on experimental tests and theoretical analysis in the course of energy storage and attitude control. Due to significant changes of the system model parameters in the experiment, the difference between the up and down flywheel-electrical machinery unit are compensated through the cascade compensation, and then the PID compound control algorithm with integral separation and formula partition is put forward. Experiments show that overshoot is restrained effectively and stable control is realized in high speed and wide range synchronously. The angel of the platform can be stabilized within 1°, namely the attitude affection should be controlled less than 1.2′ according to the flywheels in satellite.

scholarly journals Local Buckling Characteristics of Stainless-Steel Polypropylene Deep-Sea Sandwich Pipe under Axial Tension and External Pressure

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4866
Author(s):  
Jianxing Yu ◽  
Weipeng Xu ◽  
Nianzhong Chen ◽  
Sixuan Jiang ◽  
Shengbo Xu ◽  
...  
Keyword(s):  
Finite Element ◽  
Local Buckling ◽  
External Pressure ◽  
Loading Path ◽  
Finite Element Models ◽  
Collapse Pressure ◽  
Loading Paths ◽  
Axial Tension ◽  
The Difference ◽  
Good Agreement

In this paper, the effects of different loading paths of axial tension and external pressure on the collapse pressure of sandwich tubes are studied by experiments and finite element models. The difference of the two loading paths is investigated. Eight experiments were carried out to study the influence of different loading paths on pipeline collapse pressure under the same geometric and material parameters. Parameterization studies have been carried out, and the results are in good agreement with the experimental results. The test and finite element results show that the loading path of external pressure first and then the axial tension (P→T) is more dangerous; the collapse pressure of the sandwich pipe is smaller than the other. Through parametric analysis, the influence of the axial tension and the diameter-to-thickness ratio of the inner and outer pipe on the collapse pressure under different loading paths are studied.

Finite Element Analysis Route to Achieve Accurate Resistivity Measurements in Diamond Anvil Cell

2013 ◽  
Vol 669 ◽  
pp. 279-282
Author(s):  
Xuan Guo Nan ◽  
Gang Peng ◽  
Bao Jia Wu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Diamond Anvil Cell ◽  
Resistivity Measurement ◽  
Clear Understanding ◽  
Element Analysis ◽  
Steady Current ◽  
Diamond Anvil ◽  
The Difference

To have a clear understanding of the effect of electrode resistivity on the in-situ resistivity measurement under high pressure in a diamond anvil cell (DAC), we perform finite element analysis (FEA) to simulate the distribution of the steady current field in sample. The theoretical analysis reveals the origin of the effect. It is caused by the resistivity difference between electrodes and sample. And the more the difference of their resistivity is, the more obvious the effect is. All these will result in large resistivity error. However we find that reducing the resistivity difference between the electrode and sample can improve the results.

scholarly journals Experimental and numerical study on the screw connection strength of bamboo-oriented strand board compared with wood-oriented strand board

2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Kaiting Zhang ◽  
Fuli Wang ◽  
Runmin Xu ◽  
Xinhui Fan ◽  
Bin Yan ◽  
...  
Keyword(s):  
Bending Strength ◽  
Oriented Strand Board ◽  
Numerical Study ◽  
Bending Moment ◽  
Experimental Tests ◽  
Stiffness Coefficient ◽  
The Difference ◽  
Strength And Stiffness ◽  
Von Mises ◽  
Von Mises Stresses

AbstractThe utilization of resourceful bamboo can alleviate the wood shortage problem. Bamboo-oriented strand board (BOSB) with the highest utilization of bamboo ratio and excellent mechanical properties was considered as a good engineering and furniture material. The strength of joints affects the safety of BOSB structure. This study aims to investigate the effect of screw spacing on the tensile and compressive stiffness and strength of corner joints from BOSB by experimental method combined with finite element method (FEM) compared with wood-oriented strand board (WOSB). The results showed that (1) the strength and stiffness of the corner joint was significantly affected by the screw spacing, and it affected the compressive strength and stiffness of WOSB more significantly; (2) the bending moment and stiffness coefficient of BOSB compressed joint decreased with the increase of spacing, while that of tensile joint increased first and then decreased, and it reached the maximum value, when the spacing was 48 mm; (3) compared with WOSB joint, BOSB joint had higher strength and stiffness, and the failure of the joint was due to the yielding of self-drilling screws. This was also verified by numerical analysis results; (4) the bending moment of BOSB joints was about 2.5 times that of WOSB joints, while the difference between stiffness coefficient was small; (5) the elastic deformations resulted from experimental tests and FEM are similar. It was shown that when the screw spacing is 48 mm, the Von Mises stresses on the BOSB joint were smaller, and the bending strength and stiffness were larger, which was the most suitable screw spacing.

scholarly journals Calculation of V-shaped overlaps

2021 ◽  
pp. 11-15
Author(s):  
В.А. Манухин
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress State ◽  
Reference Solution ◽  
Normal Stresses ◽  
The Finite Element Method ◽  
Approximate Methods ◽  
The Dead ◽  
The Difference ◽  
Strength And Stiffness

В статье приводится краткое описание и сравнение двух приближенных методик учета килеватости V-образных перекрытий при расчетах их прочности и жесткости. В обеих методиках килеватость учитывается введением добавочной жесткости центральной продольной балки, при этом само перекрытие рассматривается как плоское. Отличие методик заключается в различном подходе к оценке добавочной жесткости центральной балки и учете зависимости добавочной жесткости от угла килеватости, соотношения размеров перекрытия, наличия распора продольных кромок перекрытия. Расчеты по обеим методикам сравниваются с «эталонным» решением, полученным методом конечных элементов. Для простейшего V-образного перекрытия с одной продольной центральной балкой исследовано влияние на результаты вычислений угла килеватости и распора продольных кромок перекрытия. Показано, что оба приближенных подхода дают в целом надежные оценки прогиба перекрытия и напряженного состояния в середине пролета центральной балки, однако наибольшие нормальные напряжения в опорных сечениях центральной балки ими существенно занижаются. The article provides a brief description and comparison of two approximate methods for taking into account the dead-rise angle of V-shaped overlaps when calculating their strength and stiffness. In both methods, the dead-rise angle is taken into account by introducing additional rigidity of the Central longitudinal beam, while the overlap itself is considered as flat. The difference between the methods is a different approach to assessing the additional stiffness of the central beam and taking into account the dependence of the additional stiffness on the dead-rise angle angle, the ratio of the overlap size, and the presence of a emphasis of the longitudinal edges of the overlap. Calculations using both methods are compared with the "reference" solution obtained by the finite element method. For the simplest V-shaped floor with a single longitudinal central beam, the influence of the dead-rise angle and the spacer of the longitudinal edges of the floor on the results of calculations is studied. It is shown that both approximate approaches give generally reliable estimates of the overlap deflection and the stress state in the middle of the central beam span, but they significantly underestimate the maximum normal stresses in the support sections of the central beam.

Representation of bolted joints in a structure using finite element modelling and model updating

2020 ◽  
Vol 14 (3) ◽  
pp. 7141-7151 ◽  
Author(s):  
R. Omar ◽  
M. N. Abdul Rani ◽  
M. A. Yunus
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Model Updating ◽  
Complex Structure ◽  
Bolted Joints ◽  
Model Parameters ◽  
Fe Model ◽  
Bolted Joint ◽  
Fe Modelling ◽  
Joint Structure

Efficient and accurate finite element (FE) modelling of bolted joints is essential for increasing confidence in the investigation of structural vibrations. However, modelling of bolted joints for the investigation is often found to be very challenging. This paper proposes an appropriate FE representation of bolted joints for the prediction of the dynamic behaviour of a bolted joint structure. Two different FE models of the bolted joint structure with two different FE element connectors, which are CBEAM and CBUSH, representing the bolted joints are developed. Modal updating is used to correlate the two FE models with the experimental model. The dynamic behaviour of the two FE models is compared with experimental modal analysis to evaluate and determine the most appropriate FE model of the bolted joint structure. The comparison reveals that the CBUSH element connectors based FE model has a greater capability in representing the bolted joints with 86 percent accuracy and greater efficiency in updating the model parameters. The proposed modelling technique will be useful in the modelling of a complex structure with a large number of bolted joints.

Automatic Tread Gaging Machine

1979 ◽  
Vol 7 (1) ◽  
pp. 31-39
Author(s):  
G. S. Ludwig ◽  
F. C. Brenner
Keyword(s):  
Experimental Tests ◽  
Automatic Machine ◽  
Wear Rates ◽  
Handling Device ◽  
Straight Line ◽  
Component Systems ◽  
Before And After ◽  
Good Repeatability ◽  
The Difference ◽  
Straight Lines

Abstract An automatic tread gaging machine has been developed. It consists of three component systems: (1) a laser gaging head, (2) a tire handling device, and (3) a computer that controls the movement of the tire handling machine, processes the data, and computes the least-squares straight line from which a wear rate may be estimated. Experimental tests show that the machine has good repeatability. In comparisons with measurements obtained by a hand gage, the automatic machine gives smaller average groove depths. The difference before and after a period of wear for both methods of measurement are the same. Wear rates estimated from the slopes of straight lines fitted to both sets of data are not significantly different.

Comparison of Mammography and Ultrasonography for Tumor Size of DCIS of Breast Cancer

2019 ◽  
Vol 15 (2) ◽  
pp. 209-213
Author(s):  
Yu Wang ◽  
Jiantao Wang ◽  
Haiping Wang ◽  
Xinyu Yang ◽  
Liming Chang ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Correlation Coefficient ◽  
Tumor Size ◽  
Ductal Carcinoma ◽  
Pearson Correlation ◽  
Dense Breast ◽  
Pathological Examination ◽  
Negative Group ◽  
The Difference

Objective: Accurate assessment of breast tumor size preoperatively is important for the initial decision-making in surgical approach. Therefore, we aimed to compare efficacy of mammography and ultrasonography in ductal carcinoma in situ (DCIS) of breast cancer. Methods: Preoperative mammography and ultrasonography were performed on 104 women with DCIS of breast cancer. We compared the accuracy of each of the imaging modalities with pathological size by Pearson correlation. For each modality, it was considered concordant if the difference between imaging assessment and pathological measurement is less than 0.5cm. Results: At pathological examination tumor size ranged from 0.4cm to 7.2cm in largest diameter. For mammographically determined size versus pathological size, correlation coefficient of r was 0.786 and for ultrasonography it was 0.651. Grouped by breast composition, in almost entirely fatty and scattered areas of fibroglandular dense breast, correlation coefficient of r was 0.790 for mammography and 0.678 for ultrasonography; in heterogeneously dense and extremely dense breast, correlation coefficient of r was 0.770 for mammography and 0.548 for ultrasonography. In microcalcification positive group, coeffient of r was 0.772 for mammography and 0.570 for ultrasonography. In microcalcification negative group, coeffient of r was 0.806 for mammography and 0.783 for ultrasonography. Conclusion: Mammography was more accurate than ultrasonography in measuring the largest cancer diameter in DCIS of breast cancer. The correlation coefficient improved in the group of almost entirely fatty/ scattered areas of fibroglandular dense breast or in microcalcification negative group.

Sign in / Sign up

Export Citation Format

Share Document