Identification of the Critical Stiffnesses of Motorcycles in Static and Dynamic Conditions

2016 ◽  
Author(s):  
Alberto Doria ◽  
Luca Taraborrelli
Keyword(s):  
Specific Method ◽  
Structural Elements ◽  
Single Track ◽  
Structural Element ◽  
Dynamic Conditions ◽  
Lumped Element ◽  
Novel Method ◽  
Stiffness Characteristics ◽  
The Stability ◽  
Static Conditions

Stiffness of structural elements has a significant effect on the dynamics of single-track vehicles, because it influences the stability of the typical modes of this class of vehicles (weave and wobble). Up to date no specific method for measuring the critical stiffnesses of front fork, chassis and swingarm is universally recognized. This measurement is difficult chiefly for two reasons. When a structural element of a single-track vehicle is loaded at one end it undergoes both bending and torsion deformation and stiffness has to be decomposed into the bending and torsion components. The stiffness characteristics measured in static conditions may be rather different from the ones measured in the presence of dynamic loads, owing to the excitation of vibration modes. The concept of Mozzi or twist axis is used in this paper for giving a lumped element representation of stiffness of structural elements of single-track vehicles. Then the differences between stiffness characteristics measured in static and dynamic conditions are highlighted and analyzed. Finally, a novel method is proposed for the decomposition of stiffness, it makes use of the axes of the bending and torsion modes. These axes are identified by means of impulsive tests measuring the frequency response functions of three points of a rigid plate that moves with the loaded end of the structural element. Experimental results dealing with swingarm, chassis and front fork are presented.

The Modal Twist Axis: A Method for Describing the Dynamical Characteristics of Single Track Vehicles

2015 ◽  
Author(s):  
Alberto Doria ◽  
Luca Taraborrelli
Keyword(s):  
Natural Frequencies ◽  
Resonance Condition ◽  
Dynamic Properties ◽  
Point Of View ◽  
Experimental Results ◽  
Single Track ◽  
Structural Element ◽  
Lumped Elements ◽  
Axis Position ◽  
The Stability

Static and dynamic properties of single-track vehicles components (such as frames, front forks and swing-arms) play a fundamental role from the point of view of vehicle stability, which is a key issue of single-track vehicles dynamics and safety. Nowadays, the stability of a vehicle is studied by means of multi-body codes, in which it is possible to implement models of the tires and of the components of the vehicle. Actually, the chassis and the forks of motorcycles are mechanical systems with distributed mass and stiffness properties, but in most simulation codes the elastic properties of the structural elements are modeled with lumped stiffness and damping elements. Very few research has been carried out on the identification of the lumped elements, of their natural frequencies and damping from laboratory tests. In the first section of the paper, the concept of modal twist axis is proposed to characterize the dynamic deformability of a structural element. The twist axis is defined as the intersection between the un-deformed plane of the structural element and the plane tangent to the free end of the structural element in deformed condition. If the identification of the twist axis is carried out in resonance condition, the modal twist axis is found. A method for measuring the modal twist axis position and orientation is described. It is based on impulse excitation by means of a modally tuned hammer and three accelerometers which are used for defining the deformed plane. In the second section of the paper, experimental results obtained on two motorcycle frames are shown. In order to know the modal shapes of the components at the measured natural frequencies, modal analysis is carried out. A correlation between the modal twist axis position and the mode of vibration is shown and discussed. In order to study the influence of the constraints on dynamic properties, the frames are tested in two different constraint conditions: rear constrained and front constrained. The last section of the paper shows the experimental results obtained by applying the proposed method to other motorcycle components, such as a front fork and a frame with the engine.

scholarly journals RESEARCH ON THE STABILITY OF BUILDING MIXTURE STRUCTURE/STATYBINIŲ MIŠINIŲ STRUKTŪROS TYRIMAS

2001 ◽  
Vol 7 (6) ◽  
pp. 441-445
Author(s):  
Juozas Deltuva
Keyword(s):  
Materials Science ◽  
Interface Layer ◽  
Medium Size ◽  
Uniform Structure ◽  
Structural Elements ◽  
Structural Element ◽  
Entire Volume ◽  
The Stability ◽  
And Function ◽  
Production Period

The aim of this work is to establish the system of quantities that would be suitable to evaluate the stability of the structure of concrete in order to assure that the structure of mixtures and building articles is uniform during the given production period. Concrete is a polystructured material and therefore its structure must be analyzed at all levels. According to concept of the materials science, the spatial structure of such a material is defined by the arrangement and interconnections of component particles or component blocks that can be considered as discrete structural elements. A structural element is the smallest cell of material that contains all the material ingredients at the same proportions as the entire volume. A structural element is formed by a large particle of medium size and the interface layer is of small particles and liquid components. The presented method may be applied when it is desirable to compute, compare or model the structures of concrete and other building mixtures and calculate the structural uniformity indices. According to given uniformity of macro structure, it is possible to determine by the use of structural elements the admissible aggregate grain-size tolerances, in order to achieve the uniform structure, the strength and deformability. The reliability of the uniformity of a concrete structure must be regulated according to its type and function; it is especially important for load bearing reinforced concrete where a real deformation of concrete must conform to the calculated allowable one.

The Effect of Front Fork Compliance on the Stability of Bicycles

2015 ◽  
Author(s):  
Alberto Doria ◽  
Luca Taraborrelli ◽  
Nicola Segliani
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Experimental Tests ◽  
Specific Method ◽  
Lumped Element ◽  
Small Influence ◽  
Element Approach ◽  
Speed Stability ◽  
The Stability ◽  
Stiffness And Damping

In this paper the effect of front fork compliance on uncontrolled bicycle stability is analyzed. First the benchmark model of a bicycle is improved to take into account either torsion compliance or bending compliance of front fork, a lumped element approach is adopted introducing additional joints restrained by rotational springs and dampers. Two models having three degrees of freedom are developed and implemented in MATLAB codes to perform stability analysis. Then series of experimental tests are carried out on an advanced carbon fork and a standard steel fork, the modal analysis approach is adopted. Experimental methods and results are presented and discussed. A specific method is developed for identifying the stiffness and damping properties from the bending and torsion modes of the forks. Results obtained with the proposed method agree with data presented in literature. Finally, the identified stiffness and damping parameters are implemented in the simulation codes and some numerical simulations are carried out. Results presented in the paper show a small influence of torsion compliance on stability and a large influence of bending compliance on high speed stability.

STRUCTURAL RELIABILITY ANALYSIS BASED ON P-BOXES

2020 ◽  
Vol 92 (6) ◽  
pp. 51-58
Author(s):  
S.A. SOLOVYEV ◽  
Keyword(s):  
Probability Distribution ◽  
Reliability Analysis ◽  
Structural Reliability ◽  
Epistemic Uncertainty ◽  
Random Variable ◽  
Strength Criterion ◽  
Structural Elements ◽  
Structural Element ◽  
Limit States ◽  
Distribution Shape

The article describes a method for reliability (probability of non-failure) analysis of structural elements based on p-boxes. An algorithm for constructing two p-blocks is shown. First p-box is used in the absence of information about the probability distribution shape of a random variable. Second p-box is used for a certain probability distribution function but with inaccurate (interval) function parameters. The algorithm for reliability analysis is presented on a numerical example of the reliability analysis for a flexural wooden beam by wood strength criterion. The result of the reliability analysis is an interval of the non-failure probability boundaries. Recommendations are given for narrowing the reliability boundaries which can reduce epistemic uncertainty. On the basis of the proposed approach, particular methods for reliability analysis for any structural elements can be developed. Design equations are given for a comprehensive assessment of the structural element reliability as a system taking into account all the criteria of limit states.

Stability as a constraint in sagittal plane human force exertion modeling

1998 ◽  
Vol 1 (1) ◽  
pp. 23-39
Author(s):  
Carter J. Kerk ◽  
Don B. Chaffin ◽  
W. Monroe Keyserling
Keyword(s):  
Muscle Strength ◽  
Ankle Joint ◽  
Coefficient Of Friction ◽  
Sagittal Plane ◽  
Biomechanical Model ◽  
Whole Body ◽  
The Stability ◽  
Joint Center ◽  
Static Conditions ◽  
Stability Limits

The stability constraints of a two-dimensional static human force exertion capability model (2DHFEC) were evaluated with subjects of varying anthropometry and strength capabilities performing manual exertions. The biomechanical model comprehensively estimated human force exertion capability under sagittally symmetric static conditions using constraints from three classes: stability, joint muscle strength, and coefficient of friction. Experimental results showed the concept of stability must be considered with joint muscle strength capability and coefficient of friction in predicting hand force exertion capability. Information was gained concerning foot modeling parameters as they affect whole-body stability. Findings indicated that stability limits should be placed approximately 37 % the ankle joint center to the posterior-most point of the foot and 130 % the distance from the ankle joint center to the maximal medial protuberance (the ball of the foot). 2DHFEC provided improvements over existing models, especially where horizontal push/pull forces create balance concerns.

scholarly journals Stability charts based on the finite element method for underground cavities in soft carbonate rocks: validation through case-study applications

2019 ◽  
Vol 19 (10) ◽  
pp. 2079-2095 ◽  
Author(s):  
Michele Perrotti ◽  
Piernicola Lollino ◽  
Nunzio Luciano Fazio ◽  
Mario Parise
Keyword(s):  
Finite Element ◽  
Safety Margin ◽  
Structural Elements ◽  
The Finite Element Method ◽  
Geometrical Features ◽  
Overall Stability ◽  
Underground Cavities ◽  
The Stability ◽  
Rock Mechanical Properties

Abstract. The stability of man-made underground cavities in soft rocks interacting with overlying structures and infrastructures represents a challenging problem to be faced. Based upon the results of a large number of parametric two-dimensional (2-D) finite-element analyses of ideal cases of underground cavities, accounting for the variability both cave geometrical features and rock mechanical properties, specific charts have been recently proposed in the literature to assess at a preliminary stage the stability of the cavities. The purpose of the present paper is to validate the efficacy of the stability charts through the application to several case studies of underground cavities, considering both quarries collapsed in the past and quarries still stable. The stability graphs proposed by Perrotti et al. (2018) can be useful to evaluate, in a preliminary way, a safety margin for cavities that have not reached failure and to detect indications of predisposition to local or general instability phenomena. Alternatively, for sinkholes that already occurred, the graphs may be useful in identifying the conditions that led to the collapse, highlighting the importance of some structural elements (as pillars and internal walls) on the overall stability of the quarry system.

scholarly journals Current Practices for Reference Gene Selection in RT-qPCR of Aspergillus: Outlook and Recommendations for the Future

Genes ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 960
Author(s):  
Meagan Archer ◽  
Jianping Xu
Keyword(s):  
Gene Expression ◽  
Reference Gene ◽  
Reference Genes ◽  
Gene Selection ◽  
Quantitative Polymerase Chain Reaction ◽  
Specific Method ◽  
Experimental Conditions ◽  
Reference Gene Selection ◽  
Physiological Processes ◽  
The Stability

Aspergillus is a genus of filamentous fungi with vast geographic and ecological distributions. Species within this genus are clinically, agriculturally and biotechnologically relevant, leading to increasing interest in elucidating gene expression dynamics of key metabolic and physiological processes. Reverse-transcription quantitative Polymerase Chain Reaction (RT-qPCR) is a sensitive and specific method of quantifying gene expression. A crucial step for comparing RT-qPCR results between strains and experimental conditions is normalisation to experimentally validated reference gene(s). In this review, we provide a critical analysis of current reference gene selection and validation practices for RT-qPCR gene expression analyses of Aspergillus. Of 90 primary research articles obtained through our PubMed query, 17 experimentally validated the reference gene(s) used. Twenty reference genes were used across the 90 studies, with beta-tubulin being the most used reference gene, followed by actin, 18S rRNA and glyceraldehyde 3-phosphate dehydrogenase. Sixteen of the 90 studies used multiple reference genes for normalisation. Failing to experimentally validate the stability of reference genes can lead to conflicting results, as was the case for four studies. Overall, our review highlights the need to experimentally validate reference genes in RT-qPCR studies of Aspergillus.

scholarly journals The Effect of Various Hydroxide and Salt Additives on the Reduction of Fluoride Ion Mobility in Industrial Waste

2021 ◽  
Vol 13 (3) ◽  
pp. 1554
Author(s):  
Tadas Dambrauskas ◽  
Kestutis Baltakys ◽  
Agne Grineviciene ◽  
Valdas Rudelis
Keyword(s):  
Liquid Medium ◽  
Silica Gel ◽  
Ion Mobility ◽  
Fluoride Removal ◽  
Dynamic Conditions ◽  
Treatment Conditions ◽  
Medium Flow ◽  
Silica Gel Waste ◽  
Fluorine Ions ◽  
Static Conditions

In this work, the influence of various hydroxide and salt additives on the removal of F− ions from silica gel waste, which is obtained during the production of AlF3, was examined. The leaching of the mentioned ions from silica gel waste to the liquid medium was achieved by the application of different techniques: (1) leaching under static conditions; (2) leaching under dynamic conditions by the use of continuous liquid medium flow; and (3) leaching in cycles under dynamic conditions. It was determined that the efficiency of the fluoride removal from this waste depends on the w/s ratio, the leaching conditions, and the additives used. It was proven that it is possible to reduce the concentration of fluorine ions from 10% to <5% by changing the treatment conditions and by adding alkaline compounds. The silica gel obtained after the leaching is a promising silicon dioxide source.

A New Technical Standard Procedure to Measure Stimulation and Gravel-pack Fluid Leak-off under Dynamic Conditions

2015 ◽  
Author(s):  
Mahmoud Asadi ◽  
Brain Ainley ◽  
David Archacki ◽  
Eric Aubry ◽  
Harold Brannon ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Standard Procedure ◽  
Oil And Gas Industry ◽  
Testing Procedure ◽  
Technical Standard ◽  
Gas Wells ◽  
Dynamic Conditions ◽  
Oil And Gas Wells ◽  
Static Conditions ◽  
Gravel Pack

Abstract Historically, leak-off analyses of stimulation fluids have been performed using in-house laboratory procedures. The lack of industry standard procedures to perform leak-off and wall building coefficient analyses of stimulation fluids has introduced inconsistency in both results and reporting for many years. A technical standard adopted in 2006 by both API and ISO for static conditions has provided the oil and gas industry with the first standardized procedure to measure and report leak-off1. However, the more complex testing under dynamic conditions was not addressed. As a result, a group of industry experts have compiled their years of experiences in developing a new technical standard to measure the leak-off characteristics of stimulation and gravel-pack fluids under dynamic flow conditions. Stimulation and gravel-pack fluids are defined, for the purpose of this technical standard, as fluids used to enhance production from oil and gas wells by fracturing and fluids used to place filtration media to control formation sand production from oil and gas wells. Leak-off is the amount of fluid lost to porous media during these operations. The leak-off procedure was developed through the colaberation of several industry companies by evaluating numerous in-house laboratory techniques and conducting round robin testing to ensure that any modifications to these procedures were reliable and repeatable. The new standard provides a step-by-step procedure that includes fluid preparation, experimental equipment design, testing procedure and data analyses for fluids exhibiting viscosity controlled leak-off or wall building characteristics. Example calculations are reviewed within this paper.

scholarly journals Static and Dynamic Performance of Vector Control on Induction Motor with PID Controller: An Investigation on LabVIEW

2021 ◽  
Vol 4 (2) ◽  
pp. 83-96
Author(s):  
Abdillah Aziz Muntashir ◽  
Era Purwanto ◽  
Bambang Sumantri ◽  
Hanif Hasyier FAkhruddin ◽  
Raden Akbar Nur Apriyanto
Keyword(s):  
Vector Control ◽  
Induction Motor ◽  
Pid Controller ◽  
High Reliability ◽  
Load Torque ◽  
Set Point ◽  
Dynamic Conditions ◽  
Low Speed ◽  
Three Phase ◽  
Static Conditions

A three-phase induction motor is often used in everyday life because of its high reliability. However, it is associated with some disadvantages, including difficulties in maintaining constant speed during load changes and speed regulation due to the decoupled system. Therefore, this study aims to adjust the three-phase induction motor control to become a separate amplifier DC motor by setting the vector control using the IFOC method, which changes the coupled to the decoupled system. The speed settings are equipped with a PID controller where its parameters, which are obtained using Ziegler Nichols, produce speed output with fast research time and small steady-state errors. This research was conducted to observe and analyze the performance of a controller based on the IFOC approach with a PID controller at speed differences, with static and dynamic conditions in the entire speed working area. In the first stage of the research, simulation is carried out with static conditions, namely changes in speed variations throughout the work area (low speed to high speed), the next stage is a simulation with dynamic conditions, which is to provide changes in the value of the load torque when the system is operating. The simulation result carried out with LabVIEW shows a response time of 1.13 ms, a settling time of 9.9 ms, and a steady error of 0.4% at the 500 Rpm set point. It also indicated dynamic characteristics with a recovery time of 4.9 ms at the 300 Rpm set point. When operated at low speed, IFOC with PID controller has a stable response. But In dynamic conditions, the use of a PID controller is considered unsuitable. This is because the PID controller is less fast and less robust in responding to the system when conditions change in the value of the load torque.

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