An Improved Finite Element-Based Model for Reliability Assessment of a Profile-Type Automotive Body Experiencing Uncertain Loading Conditions and Material Properties

2011 ◽  
Vol 4 (1) ◽  
pp. 957-968
Author(s):  
M. Shariyat ◽  
Mahboobeh Rajabi Ghahnavieh
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Reliability Assessment ◽  
Loading Conditions ◽  
Automotive Body ◽  
Profile Type

Development of Simplified Spot Weld Models: Stiffness Prediction and Computational Performance Evaluation

2010 ◽  
Author(s):  
Noman Khandoker ◽  
Monir Takla ◽  
Thomas Ting
Keyword(s):  
Finite Element ◽  
Spot Weld ◽  
Finite Element Models ◽  
Suitable Model ◽  
Loading Conditions ◽  
Computational Costs ◽  
Automotive Body ◽  
Simple Strategy ◽  
Pull Out ◽  
Computational Performance

Simple spot weld connection models are desirable in huge and complicated finite element models of automotive body-in-white structures which generally contains thousands of spot weld joints. Hence, in this paper six different individual spot weld joint finite element models simplified in terms of their geometric and constitutive representations were developed including the one that is currently used in automotive industries. The stiffness characteristics of these developed models were compared with the experimental results obtained following a simple strategy to design the welded joint based on the desired mode of nugget pull out failure. It was found that the current spot weld modeling practice in automotive industry under predict the maximum joint strength nearly by 50% for different loading conditions. The computational costs incurred by the developed models in different loading conditions were also compared. Hence, a suitable model for spot welded joints is established which is very simple to develop but relatively cheap in terms of computational costs.

Probabilistic Models to Approximate Highly Repetitive Linear and Nonlinear Finite Element Analyses of Nuclear Components

2009 ◽  
Author(s):  
Dan Vlaicu ◽  
Mike Stojakovic
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Probabilistic Models ◽  
Nonlinear Material ◽  
Superposition Method ◽  
Loading Conditions ◽  
Finite Element Analyses ◽  
Axisymmetric Nozzle ◽  
Nonlinear Superposition ◽  
Pipe Bend

In the development and technical support of nuclear plants, Engineers have to deal with highly repetitive finite element analyses that involve modeling of local variations of the initial design, local flaws due to corrosion-erosion effects, material properties degradation, and modifications of the loading conditions. This paper presents the development of generic models that emulate the behavior of a complex finite element model in a simplified form, with the statistical representation based on a sampling of base-model data for a variety of test cases. An improved Latin Hypercube algorithm is employed to generate the sampling points based on the number and the range of the variables that are considered in the design space. Four filling methods of the approximation models are discussed in this study: response surface, nonlinear, neural networks, and piecewise polynomial model. Furthermore, a bootstrapping procedure is employed to improve the confidence intervals of the original coefficients, and the single-factor or double-factor analysis of variance is applied to determine whether a significant influence exists between the investigated factors. Two numerical examples highlight the accuracy and efficiency of the methods. The first example is the linear elastic analysis of a pipe bend under pressure loading. The objective of the probabilistic assessment is to determine the relation between the loading conditions as well as the geometrical aspects of this elbow (pipe wall thickness, outside diameter, elbow radius, and maximum ovality tolerance) and the maximum stress in the elbow. The second example is an axisymmetric nozzle under primary and secondary cycling loads. Variations of the geometrical dimensions, nonlinear material properties, and cycling loading are taken as the input parameters, whereas the response variable is defined in terms of Melan’s theorem translated into the Nonlinear Superposition Method.

An Integrated Musculoskeletal-Finite-Element Model to Evaluate Effects of Load Carriage on the Tibia During Walking

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Chun Xu ◽  
Amy Silder ◽  
Ju Zhang ◽  
Julie Hughes ◽  
Ginu Unnikrishnan ◽  
...  
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Injury Risk ◽  
Load Carriage ◽  
Body Motion ◽  
Bone Biomechanics ◽  
External Loading ◽  
Fe Model ◽  
Loading Conditions ◽  
Reaction Forces

Prior studies have assessed the effects of load carriage on the tibia. Here, we expand on these studies and investigate the effects of load carriage on joint reaction forces (JRFs) and the resulting spatiotemporal stress/strain distributions in the tibia. Using full-body motion and ground reaction forces from a female subject, we computed joint and muscle forces during walking for four load carriage conditions. We applied these forces as physiological loading conditions in a finite-element (FE) analysis to compute strain and stress. We derived material properties from computed tomography (CT) images of a sex-, age-, and body mass index-matched subject using a mesh morphing and mapping algorithm, and used them within the FE model. Compared to walking with no load, the knee JRFs were the most sensitive to load carriage, increasing by as much as 26.2% when carrying a 30% of body weight (BW) load (ankle: 16.4% and hip: 19.0%). Moreover, our model revealed disproportionate increases in internal JRFs with increases in load carriage, suggesting a coordinated adjustment in the musculature functions in the lower extremity. FE results reflected the complex effects of spatially varying material properties distribution and muscular engagement on tibial biomechanics during walking. We observed high stresses on the anterior crest and the medial surface of the tibia at pushoff, whereas high cumulative stress during one walking cycle was more prominent in the medioposterior aspect of the tibia. Our findings reinforce the need to include: (1) physiologically accurate loading conditions when modeling healthy subjects undergoing short-term exercise training and (2) the duration of stress exposure when evaluating stress-fracture injury risk. As a fundamental step toward understanding the instantaneous effect of external loading, our study presents a means to assess the relationship between load carriage and bone biomechanics.

A Validated, Specimen-Specific Finite Element Model of the Supraspinatus Tendon Mechanical Environment

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
R. Matthew Miller ◽  
James Thunes ◽  
Volker Musahl ◽  
Spandan Maiti ◽  
Richard E. Debski
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Computational Model ◽  
Material Properties ◽  
Element Model ◽  
Supraspinatus Tendon ◽  
Inhomogeneous Material ◽  
Loading Conditions ◽  
Mechanical Environment ◽  
Model Predictions

Rotator cuff tears are a significant clinical problem previously investigated by unvalidated computational models that either use simplified geometry or isotropic elastic material properties to represent the tendon. The objective of this study was to develop an experimentally validated, finite element model of supraspinatus tendon using specimen-specific geometry and inhomogeneous material properties to predict strains in intact supraspinatus tendon at multiple abduction angles. Three-dimensional tendon surface strains were determined at 60 deg, 70 deg, and 90 deg of glenohumeral abduction for articular and bursal surfaces of supraspinatus tendon during cyclic loading (5–200 N, 50 cycles, 20 mm/min) to serve as validation data for computational model predictions. A finite element model was developed using the tendon geometry and inhomogeneous material properties to predict surface strains for loading conditions mimicking experimental loading conditions. Experimental strains were directly compared with computational model predictions to validate the model. Overall, the model successfully predicted magnitudes of strains that were within the experimental repeatability of 3% strain of experimental measures on both surfaces of the tendon. Model predictions and experiments showed the largest strains to be located on the articular surface (∼8% strain) between the middle and the anterior edge of the tendon. Importantly, the reference configuration chosen to calculate strains had a significant effect on strain calculations, and therefore, must be defined with an innovative optimization algorithm. This study establishes a rigorously validated specimen-specific (both geometry and material properties) computational model using novel surface strain measurements for the use in investigating the function of the supraspinatus tendon and to ultimately predict the propagation of supraspinatus tendon tears based on the tendon's mechanical environment.

Design of Pipeline Composite Repairs: From Lab Scale Tests to FEA and Full Scale Testing

2014 ◽  
Author(s):  
Remy Her ◽  
Jacques Renard ◽  
Vincent Gaffard ◽  
Yves Favry ◽  
Paul Wiet
Keyword(s):  
Finite Element ◽  
Full Scale ◽  
Combined Loading ◽  
Material Strength ◽  
Repair System ◽  
Loading Conditions ◽  
Original Design ◽  
Composite Repair ◽  
Repair Systems ◽  
Composite Properties

Composite repair systems are used for many years to restore locally the pipe strength where it has been affected by damage such as wall thickness reduction due to corrosion, dent, lamination or cracks. Composite repair systems are commonly qualified, designed and installed according to ASME PCC2 code or ISO 24817 standard requirements. In both of these codes, the Maximum Allowable Working Pressure (MAWP) of the damaged section must be determined to design the composite repair. To do so, codes such as ASME B31G for example for corrosion, are used. The composite repair systems is designed to “bridge the gap” between the MAWP of the damaged pipe and the original design pressure. The main weakness of available approaches is their applicability to combined loading conditions and various types of defects. The objective of this work is to set-up a “universal” methodology to design the composite repair by finite element calculations with directly taking into consideration the loading conditions and the influence of the defect on pipe strength (whatever its geometry and type). First a program of mechanical tests is defined to allow determining all the composite properties necessary to run the finite elements calculations. It consists in compression and tensile tests in various directions to account for the composite anisotropy and of Arcan tests to determine steel to composite interface behaviors in tension and shear. In parallel, a full scale burst test is performed on a repaired pipe section where a local wall thinning is previously machined. For this test, the composite repair was designed according to ISO 24817. Then, a finite element model integrating damaged pipe and composite repair system is built. It allowed simulating the test, comparing the results with experiments and validating damage models implemented to capture the various possible types of failures. In addition, sensitivity analysis considering composite properties variations evidenced by experiments are run. The composite behavior considered in this study is not time dependent. No degradation of the composite material strength due to ageing is taking into account. The roadmap for the next steps of this work is to clearly identify the ageing mechanisms, to perform tests in relevant conditions and to introduce ageing effects in the design process (and in particular in the composite constitutive laws).

Determination of Charge Coefficient of Piezoelectric Films Using a Combined Finite Element Model and Dynamic Loading Technique

2020 ◽  
Vol 835 ◽  
pp. 229-242
Author(s):  
Oboso P. Bernard ◽  
Nagih M. Shaalan ◽  
Mohab Hossam ◽  
Mohsen A. Hassan
Keyword(s):  
Finite Element ◽  
Dynamic Loading ◽  
Material Properties ◽  
Accurate Determination ◽  
Substrate Material ◽  
Experimental Results ◽  
Piezoelectric Composite ◽  
Piezoelectric Film ◽  
Piezoelectric Charge

Accurate determination of piezoelectric properties such as piezoelectric charge coefficients (d33) is an essential step in the design process of sensors and actuators using piezoelectric effect. In this study, a cost-effective and accurate method based on dynamic loading technique was proposed to determine the piezoelectric charge coefficient d33. Finite element analysis (FEA) model was developed in order to estimate d33 and validate the obtained values with experimental results. The experiment was conducted on a piezoelectric disc with a known d33 value. The effect of measuring boundary conditions, substrate material properties and specimen geometry on measured d33 value were conducted. The experimental results reveal that the determined d33 coefficient by this technique is accurate as it falls within the manufactures tolerance specifications of PZT-5A piezoelectric film d33. Further, obtained simulation results on fibre reinforced and particle reinforced piezoelectric composite were found to be similar to those that have been obtained using more advanced techniques. FE-results showed that the measured d33 coefficients depend on measuring boundary condition, piezoelectric film thickness, and substrate material properties. This method was proved to be suitable for determination of d33 coefficient effectively for piezoelectric samples of any arbitrary geometry without compromising on the accuracy of measured d33.

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