Design Nomographs of Compression Helical Springs for Predetermined Reliability Levels

1981 ◽  
Vol 103 (2) ◽  
pp. 268-273
Author(s):  
My Dao Thien ◽  
M. Massoud
Keyword(s):  
Probabilistic Approach ◽  
Design Procedure ◽  
Axial Loading ◽  
Geometric Parameters ◽  
Computer Algorithms ◽  
Mean Values ◽  
Helical Springs ◽  
Reliability Level ◽  
Classical Design ◽  
Mission Success

This paper discusses a probabilistic approach for the design of Compression Closely Coiled Helical Springs subjected to periodic axial loading. The classical design procedure results in deterministic geometric parameters with tolerances normally chosen according to standards without due regard to their effects on the mission success as normally expressed by a reliability level. With the proposed design procedure, the engineer can specify nominal mean values for the geometric parameters and their tolerances according to a predetermined reliability level. Design nomographs are presented to help the engineer, in the early stages of design, to choose between many alternatives. Computer algorithms can easily be written to verify the final or optimum design.

Reliability Design of Flexible Airfield Pavements: Elastic Layered Method

1997 ◽  
Vol 1568 (1) ◽  
pp. 124-130 ◽  
Author(s):  
Yu T. Chou
Keyword(s):  
Prediction Models ◽  
Design Procedure ◽  
Design System ◽  
Mean Values ◽  
Reliability Design ◽  
Reliability Level ◽  
Lack Of Fit ◽  
User Friendly ◽  
Pavement Thickness ◽  
Independent Parameters

A design procedure was developed for layered elastic flexible airfield pavement systems in terms of probability and reliability. A user-friendly computer program, RELIFLEX, was prepared to carry out the computations. The Rosenblueth method is used to estimate the expected value and variance of the computed strains (dependent parameters) on the basis of the input mean values of independent parameters (i.e., aircraft load, layer thicknesses, and material moduli). RELIFLEX has the capability of considering the strain distribution to be normal, lognormal, or beta, and a capacity-demand analysis is included. Only normal distribution is presented. Environmental effects and the lack of fit of the prediction models are not considered in RELIFLEX. The relationships between the reliability level and the allowable strain repetition of the designed system, established using RELIFLEX, provide a decision-making tool for engineers to design pavement at the desired reliability level. For a desired reliability level of the design system, pavement thickness can be varied to agree with the designed coverage or the allowable coverage can be modified for a given pavement thickness.

scholarly journals Probabilistic Approach to Conditional Probability of Release of Hazardous Materials From Railroad Tank Cars During Accidents

2009 ◽  
Author(s):  
D. Y. Jeong
Keyword(s):  
Sensitivity Analysis ◽  
Conditional Probability ◽  
Impact Velocity ◽  
Probabilistic Sensitivity Analysis ◽  
Probabilistic Approach ◽  
Hazardous Materials ◽  
Relative Effect ◽  
Distribution Functions ◽  
Mean Values ◽  
Effective Collision

This paper describes a probabilistic approach to estimate the conditional probability of release of hazardous materials from railroad tank cars during train accidents. Monte Carlo methods are used in developing a probabilistic model to simulate head impacts. The model is based on the physics of impact in conjunction with assumptions regarding the probability distribution functions of the various factors that affect the loss of lading. These factors include impact velocity, indenter size, tank material, tank diameter, effective collision mass, and tank thickness. Moreover, each factor is treated as a random variable characterized by its assumed distribution function, mean value, and standard deviation (or variance). Reverse engineering is performed to back-calculate the mean values and standard deviations of these random variables that reproduce trends observed in available accident data. The calibrated model is then used to conduct a probabilistic sensitivity analysis to examine the relative effect of these factors on the conditional probability of release. Results from the probabilistic sensitivity analysis indicate that the most significant factors that affect conditional probability of release are impact velocity, effective collision mass, and indenter size.

Reliability Analysis of Robot Manipulators

1987 ◽  
Author(s):  
P. K. Bhatti ◽  
S. S. Rao
Keyword(s):  
Reliability Analysis ◽  
Robot Manipulators ◽  
Probabilistic Approach ◽  
Geometric Parameters ◽  
Robot Kinematics ◽  
Numerical Illustration ◽  
Accuracy And Repeatability

Abstract A probabilistic approach to robot kinematics is presented and the concept of manipulator reliability is introduced to obtain a better evaluation of the performance of manipulators. Techniques are presented to compute this reliability and its relationship to the geometric parameters such as tolerances and arm configuration are discussed. The aspects of accuracy and repeatability of manipulators are explained in terms of manipulator reliability. The reliability of a two-link planar manipulator and the Stanford arm are considered for numerical illustration.

Reliability-based optimized design of hybrid tether

2020 ◽  
Vol 92 (8) ◽  
pp. 1141-1147
Author(s):  
Anil Kumar Agrawal ◽  
Mahendra Pratap ◽  
Subhash Chandra Sati ◽  
Rajeev Kumar Upadhyay
Keyword(s):  
Probabilistic Approach ◽  
Population Data ◽  
Operational Reliability ◽  
Design Approach ◽  
Optimized Design ◽  
Limited Data ◽  
Content Type ◽  
Reliability Based Design ◽  
Classical Design ◽  
Sample Test

Purpose The purpose of this paper is to optimize the design of a hybrid tether using probabilistic approach considering inherent random variation in the stress developed and the strength it has. The variation in strength is mostly because of variation in diameter of the tether and the properties of the material along the length of the tether. As a result, classical design approach for the tether may not serve the purpose. For this purpose, a reliability-based design of hybrid tether is discussed in this paper. Design/methodology/approach A literature review was carried out on the design of tether and its operational reliability. It has been shown that the classical design approach does not serve the purpose, as the strategic operation has to be reliable enough, often requiring a measure of reliability required. A reliability-based approach has been presented to achieve the optimum design of a hybrid tether. Findings The optimization problem was carried out for different values of the safety factor to investigate the effect on the optimal design of tether. An analysis is carried out to show that one should not target a very high value of reliability or factor of safety, as it causes the self-weight of the tether to increase tremendously and its cost significantly. Research limitations/implications The present work has been carried out considering the limited data and can further be extended to determine more accurate reliability measures by considering more number of sample test data. The measured data is collected from limited required trials for demo; do not represent the exact population data. Originality/value Lab strength test and flight trials were conducted to acquire data for the present analysis. In field use, it was noticed that the tether degraded from top portion attached toward the balloon end because of maximum exposure and repeated usage.

Probabilistic Elastic Element Design for Robust Natural Dynamics of Structure-Controlled Variable Stiffness Actuators

2017 ◽  
Vol 10 (1) ◽  
Author(s):  
Florian Stuhlenmiller ◽  
Jochen Schuy ◽  
Philipp Beckerle
Keyword(s):  
Elastic Element ◽  
Material Selection ◽  
Probabilistic Approach ◽  
Design Procedure ◽  
Variable Stiffness ◽  
Actuation System ◽  
Lumped Parameter ◽  
Stiffness Properties ◽  
Natural Dynamics ◽  
Variable Stiffness Actuators

This paper proposes a probabilistic approach for the design of elastic elements to be used in structure-controlled variable stiffness actuators (VSA) for robotic applications. Considering the natural dynamics of the elastic actuation system, requirements are defined and material selection as well as geometry calculation are performed using lumped parameter models. Monte Carlo simulations are integrated in the design procedure to ensure a robust implementation of the required dynamical characteristics. Thereby, effects of uncertainties that might be caused by manufacturing or deviations of material properties are taken into account. To validate the suitability of the overall approach and the particular methods, a torsional elastic element is implemented and experimentally evaluated. The evaluation shows a fulfillment of the key requirements, i.e., specific natural dynamic behavior, that is only achieved due to considering uncertainties. Further, the transferability of the approach to other structure-controlled elastic actuators is discussed and implications are given. Only the governing equations of stiffness properties in certain load situation need to be adapted, e.g., from torsion to bending. Due to the simple transfer, the proposed probabilistic and model-based approach is promising for application to various actuator concepts with structure-controlled variable stiffness.

Reliability Analysis of Robot Manipulators

1988 ◽  
Vol 110 (2) ◽  
pp. 175-181 ◽  
Author(s):  
P. K. Bhatti ◽  
S. S. Rao
Keyword(s):  
Reliability Analysis ◽  
Robot Manipulators ◽  
Probabilistic Approach ◽  
Geometric Parameters ◽  
Robot Kinematics ◽  
Numerical Illustration ◽  
Accuracy And Repeatability

A probabilistic approach to robot kinematics is presented and the concept of manipulator reliability is introduced to obtain a better evaluation of the performance of manipulators. Techniques are presented to compute this reliability and its relationship to the geometric parameters such as tolerances and arm configuration are discussed. The aspects of accuracy and repeatability of manipulators are explained in terms of manipulator reliability. The reliability of a two-link planar manipulator and the Stanford arm are considered for numerical illustration.

Design Procedure for a Turgo Type Turbine Using a Three-Dimensional Potential Flow

2012 ◽  
Author(s):  
Jorge Luis Clarembaux Correa ◽  
Jesús De Andrade ◽  
Ricardo Noguera ◽  
Sergio Croquer ◽  
Freddy Jeanty ◽  
...  
Keyword(s):  
Potential Flow ◽  
Design Methodology ◽  
Three Dimensional ◽  
Design Procedure ◽  
Expected Value ◽  
Geometric Parameters ◽  
Flow Profile ◽  
Geometric Conditions ◽  
Global Efficiency

A useful methodology in the design of a Turgo Type Turbine (TTT) has been accomplished through the study of a particular three dimensional potential flow, known as Rankine Ovoids. The obtained streamlines solution for this flow was modified implementing several algorithms in order to select a suitable flow profile that could be adapted as a prediction of the flow passing through the buckets of a Turgo runner. Afterwards, the selected profile was incorporated with other geometric parameters, which were based on the hydrodynamic and geometric conditions presented in a TTT, in the design methodology proposed for this investigation. In addition, the equations to calculate power and efficiency of this kind of turbines are included. The global efficiency in the 3DT methodology was reported to be 80.8% for the designed TTT, which it is an expected value for this kind of turbines.

scholarly journals Effect of geometric parameters and combined loading on stress distribution of tubular T-joints

Mechanika ◽  
2019 ◽  
Vol 25 (5) ◽  
pp. 350-356
Author(s):  
Samira Belhour ◽  
Hafida Kahoul ◽  
Ahmed Bellaouar ◽  
Sébastien Murer
Keyword(s):  
Axial Loading ◽  
Computation Time ◽  
Geometric Parameters ◽  
Combined Loading ◽  
Offshore Platforms ◽  
Tubular Structures ◽  
Stress Concentrations ◽  
Standard Samples ◽  
T Joints ◽  
Modeling And Analysis

Steel tubular structures are widely used in the construction of offshore platforms and T-type junctions are extensively used in this domain. The tubular members are welded, which generates significant stress concentrations at the edges. The stress levels reached in these critical places are used to assess lifetimes based on fatigue curves from tests conducted on standard samples. This study is devoted to the modeling and analysis of T-type welded tubular structures for the determination of hot spots stresses (HSS) at the chord/brace intersection, A numerical analysis was carried out to study the effect of a combined loading composed of an axial loading and a continuation of rational bending, that best assimilate real conditions, as well as the effect of normalized geometric parameters α, β, g on the distribution of stress concentration (area and values) of T-joints. The mechanical behaviour has been modeled in 2D using quadrangular and triangular thin-shell elements by the finite element method (FEM). It is the most appropriate approach because it considers all geometric complexities and singularities of the structure, while the efforts as well as the computation time are considerably reduced compared to an experimental study or to complex FE models implementing solid elements. In this study, we use the COMSOL-MULTIPHYSICS® software...

An in vitro biomechanical comparison between bone plate and interlocking nail

2002 ◽  
Vol 15 (02) ◽  
pp. 57-66 ◽  
Author(s):  
A. Diop ◽  
N. Maurel ◽  
E. Viguier ◽  
A. Bernardé
Keyword(s):  
Electronic Device ◽  
Dynamic Compression ◽  
Strain Analysis ◽  
Axial Loading ◽  
Fracture Repair ◽  
Transverse Motion ◽  
Mean Values ◽  
Interlocking Nail ◽  
Bone Strains

SummaryIn order to compare the interfragmentary motion and bone strains in ostectomized canine femurs, stabilized with either an 8 mm interlocking nail system (IN) or a 10-hole 3.5 mm dynamic compression broad plate (DCP), ten pairs of adult canine femurs with a 25 mm mid-diaphyseal gap were used. The left femurs were implanted with a DCP and eight bi-cortical screws, and the right femurs were implanted with an IN and three screws. Eccentric axial loading and cranio-caudal bending were successively performed on every specimen. Employing an opto-electronic device, interfragmentary (axial, transverse and rotational) motion was measured during non-destructive tests. Bone strains were measured at three elective sites, with strain gauges in four pairs of the specimen. The mean values of axial and transverse motion were compared using a paired t-test within each group (P <0.05). Strain values were compared using a numerical scale and a qualitative analysis. Transverse motion was higher with DCP, whereas axial motion was higher with IN. Bone strain analysis demonstrated lower “stress protection” near the gap with IN. Those comparative results are interpretative: IN may be an interesting alternative implant for unstable diaphyseal femoral fracture repair in dogs.

scholarly journals ELASTO-KINEMATIC COMPUTATIONAL MODEL OF SUSPENSION WITH FLEXIBLE SUPPORTING ELEMENTS

2016 ◽  
Vol 56 (2) ◽  
pp. 147 ◽  
Author(s):  
Tomáš Vrána ◽  
Josef Bradáč ◽  
Jan Kovanda
Keyword(s):  
Multibody System ◽  
Geometric Parameters ◽  
Deformation Characteristics ◽  
Helical Springs ◽  
Shock Absorbers ◽  
Camber Angle ◽  
Simulation Results ◽  
The Stability ◽  
The Impact ◽  
Flexible Models

This paper analyzes the impact of flexibility of individual supporting elements of independent suspension on its elasto-kinematic characteristics. The toe and camber angle are the geometric parameters of the suspension, which waveforms and their changes under the action of vertical, longitudinal and transverse forces affect the stability of the vehicle. To study these dependencies, the computational multibody system (MBS) model of axle suspension in the system HyperWorks is created. There are implemented Finite-Element-Method (FEM) models reflecting the flexibility of the main supporting elements. These are subframe, the longitudinal arms, transverse arms and knuckle. Flexible models are developed using Component Mode Synthesis (CMS) by Craig-Bampton. The model further comprises force elements, such as helical springs, shock absorbers with a stop of the wheel and the anti-roll bar. Rubber-metal bushings are modeled flexibly, using nonlinear deformation characteristics. Simulation results are validated by experimental measurements of geometric parameters of real suspension.

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