Using the Weibull distribution to characterise road transport vibration levels

This paper reviews the various ways that have been proposed to characterise road transport vehicle vibrations and recommends a new approach to characterise the vibrations levels during a transport journey. Some 47 road vehicle vibration records, obtained from a broad range of conditions, were analysed, and results show that the root-mean-square (rms) distribution of the vibrations can be accurately modelled with a reduced version of the three-parameter Weibull distribution (shape parameter set to 2). This statistical approach to characterising road vehicle vibrations takes into account the random fluctuations in rms levels that occur naturally during a road journey and can be used to classify the severity of RVV. This offers significant improvement on the simplistic mean rms value that has, so far, been the sole parameter to describe vibration levels during transport. The Weibull location parameter represents the low threshold of the rms level in the record (except when xo is less than zero, in which case the low rms threshold is zero), whereas the Weibull range parameter is proportional to the range of rms level. Results also reveal a strong relationship between the rms mean and the sum of the location and scale parameters. In addition, this enables generation of rms distributions from the mean power density spectrum (PDS) alone. The modified (fixed-shape) Weibull distribution can be used to faithfully describe the entire statistical distribution of the rms level of a journey or transport mode with just two parameters. This new approach can be used in a practical way for quantifying and comparing transport vibration rms levels for design and testing purposes.     

On the time compression (test acceleration) of broadband random vibration tests

Many broadband random vibration tests are time compressed. This is done by increasing test intensity according to the Basquin model of cyclic fatigue. Conventionally, the test level is accelerated from the root mean acceleration and an assumed power constant (k = 2) is applied. Using conventional analysis the potential error in test severity can be very large if k is incorrect. The Miner–Palmgren hypothesis of accumulated fatigue is used to re‐assess the potential error in test severity accounting for the non‐stationarity found in road distribution. This shows a substantially reduced sensitivity to the value of k depending on the distribution of actual vibration intensities around the time‐compressed test intensity. Using an example of a leaf‐sprung vehicle, the conventional level of time compression is shown to have low sensitivity to errors in k, whereas for an example of an air‐ride vehicle a lower level of time compression is needed to reduce error sensitivity. Copyright © 2010 John Wiley & Sons, Ltd.     

独立卡尔曼滤波器全加速度计复杂振动角速度解算

对于运动体的多自由度振动测试,准确的振动角速度是复杂振动参数解算的关键。针对目前解算角速度单一方法测试精度不理想的问题,分析由4个三轴加速度计组成传感器阵列,测试角速度解算算法,设计一种独立的卡尔曼滤波器用于角速度解算。通过仿真及实验证明:该方法解算结果的误差最大值和标准差相对于单一方法可提高1个数量级,其得到的角速度幅值准确性和曲线平滑度也优于其他单一解算方法。     

Measurement and analysis of truck transport vibration levels and damage to packaged tangerines during transit

The purpose of this study was to measure the vibration levels in commercial truck shipments in Thailand and observe the effects on packaged fruit. The study measured the vibration levels in two of the most commonly used truck types to ship packaged goods as a function of road condition and vehicle speed. The suspension type on the trailers studied was leaf‐spring. The results of damage to packaged tangerine fruit as a function of location in the payload are also presented. The data presented in this study will assist product and package designers to reduce damage in transit. The results showed that vibration levels increased with speed and as a result of road condition. Analysis of variance indicated that three controlling factors, road surface, truck speed and truck type, significantly affected (p ≤ 0.05) peak PSD, PSD* (root mean square) over the frequency range 2–5 Hz, and fruit damage. As expected, based on previous work, an increase in truck speed resulted in an increase in vibration levels and damage to packaged fruit. The laterite road condition produced the highest vibration level for a given truck and travelling speed followed by concrete highway and asphalt road conditions. Fruit damage was found to be greatest in the uppermost container for every combination of road, truck type and travelling speed, which also corresponded to the highest vibration levels recorded. The results showed that a significant amount of damage can occur on unpaved roads (laterite), while the packages are transported from farms and harvesting areas to regional truck terminals. Damage on asphalt road conditions was minimal. This paper provides an updated history of measured and quantified levels of vibration for these specific trucks and road conditions. Copyright © 2005 John Wiley & Sons, Ltd.     

Application of a photoelectric method to vibration testing

Measurement Techniques -     

Transverse vibration of a cylindrical shell with torispherical head: model tests and stress analysis

As an aid in the design of vessels or containers in a process undergoing dynamic loading, the dynamic characteristics of a cylindrical scale model vessel have been investigated by the method of resonance testing. The scale model is 1/10th scale of a vessel in a process, comprising a cylinder and torispherical head of steel.
The dynamic characteristics of the scale model vessel and the normalised principal bending stresses are calculated and tabulated for a number of circumferential modes of vibration, for an empty vessel.
Practical problems associated with the method of vibration testing are discussed and a practical example shown of the use of the method of dynamic similarity and the scale model results, as an aid in the design of a full scale vessel.     

Risk evaluation and mitigation of sustainable road freight transport operation: a case of trucking industry

Road freight transportation sustainability is gaining increasing importance due to an ever-increasing freight movement, globalisation and operational flexibility. The transport managers across the globe are finding it difficult to manage the increasing risks in its operation and implementation of risk-mitigation strategies under economical sustainability. However, very few literatures have examined the impact of sustainable risk management practices on road freight transportation. Our study addresses this important gap in the literature by proposing an integrated fuzzy failure mode and effects analysis (FMEA) approach in the selection of risk-mitigation strategy on the trucking industry. Our findings direct to the managers that risk-mitigation strategies must be selected considering the criticality of risks along with the limited budget. In addition, we find that considering subjective evaluations of expert’s judgment and cost benefit justification gives a convincing outcome while calculating of risk-mitigation number in FMEA approach. Proposed approach provides supportive guidelines to the manager to improve the decision-making process.     

Application of the simultaneous iteration method to undamped vibration problems

The simultaneous iteration method of obtaining eigenvalues and eigenvectors is employed for the solution of undamped vibration problems. This method is of significance when a few of the dominant eigenvalues and eigenvectors are required from a large matrix, and hence is particularly suitable for vibration problems involving a large number of degrees of freedom. It is shown that advantage may be taken of both the symmetry and the band form of the mass and stiffness matrices, thus making it feasible to process on a computer larger order vibration problems than can be processed using transformation methods. A method of allowing for body freedom is given and some numerical tests are discussed.     

Intelligent transport systems and effects on road traffic accidents: state of the art

The results from several reviews have been presented and the aspects of road safety associated with intelligent transport systems (ITS) applications have been addressed. The attempt is to make a state-of-the-art regarding effects on accidents by categorising systems according to levels of evaluations methods that have been applied. These categories are effects on behaviour, effects on accidents by proxy/surrogate methods, accident studies from real traffic, effects on accident types and finally by meta-analysis where weighted estimates of effects on accidents can be calculated. Thirty-three IT systems including driver assistance systems/advanced driver assistance systems, in-vehicle information systems, in-vehicle data-collection systems and road telematics have been listed. Effects based on meta-analysis are estimated for 11 systems, and single accident studies are found for an additional 2 systems. For the remaining 20 systems, no studies from real road traffic have been identified. Effects on accidents of antilocking brake systems and electronic stability control (ESC) are presented in more detail according to their effects on certain accident types. ESC appears to be very efficient in reducing the number of accidents. Behavioural adaptations to ITS are considered and discussed, especially in terms of compensation mechanisms. Four hypotheses regarding prediction of effects on accidents are stated according to whether systems increase or decrease 'windows of opportunities' by calling upon a driver behaviour model where emotions play a central role     

Sharing the responsibility for driver distraction across road transport systems: A systems approach to the management of distracted driving

Distracted driving is acknowledged universally as a large and growing road safety problem. Compounding the problem is that distracted driving is a complex, multifaceted issue influenced by a multitude of factors, organisations and individuals. As such, management of the problem is not straightforward. Numerous countermeasures have been developed and implemented across the globe. The vast majority of these measures have derived from the traditional reductionist, driver-centric approach to distraction and have failed to fully reflect the complex mix of actors and components that give rise to drivers becoming distracted. An alternative approach that is gaining momentum in road safety is the systems approach, which considers all components of the system and their interactions as an integrated whole. In this paper, we review the current knowledge base on driver distraction and argue that the systems approach is not currently being realised in practice. Adopting a more holistic, systems approach to distracted driving will not only improve existing knowledge and interventions from the traditional approach, but will enhance our understanding and management of distraction by considering the complex relationships and interactions of the multiple actors and the myriad sources, enablers and interventions that make up the distracted driving system. It is only by recognising and understanding how all of the system components work together to enable distraction to occur, that we can start to work on solutions to help mitigate the occurrence and consequences of distracted driving.     

应用热分析技术研究菱镁石矿轻烧过程动力学

以辽宁大石桥晶质菱镁石矿为原料,采用TG、DSC热分析技术研究菱镁石粉末分解动力学.实验研究表明,菱镁石在500～700℃发生分解,失重率为43.13%.由TG曲线得出菱镁石分解反应表现活化能E=172.32kJ/mol,反应级数n=0.78;DSC曲线表明反应活化能E=199.44kJ/mol,反应级数n=0.87.TG、DSC曲线研究结果有较好的一致性,表明热分析技术在菱镁石分解动力学中可以得到良好的应用.     

振动荷载下路基的能量耗散率空间分布规律的研究

为研究振动荷载作用下的路基内部的能量状态分布,基于Parseval定理,分别以动应变/加速度为变量,推导建立了周期性和非周期性的路基内振动信号的能量耗散率计算公式;根据土体的动力互易性原理,进行了振动荷载下路基动力响应现场试验,利用试验测试结果,分析研究了该路基的能量耗散率空间分布规律.研究结果表明:①能量耗散率沿深度...     

Application of the Wigner distribution to nonlinear systems

A new way to study nonlinear oscillations is presented, based on Time—Frequency Analysis, a technique that allows the representation and study of the instantaneous spectral content of a signal. The investigation of nonlinear oscillations is an interesting subject in many areas of physics and engineering, especially in nonlinear optics where this phenomenon arises directly from the interaction of electromagnetic waves and matter. Here it is shown how Time—Frequency Analysis can clarify the nature of a free nonlinear oscillation, which is proven to have a peculiar yet physically reasonable instantaneous spectrum.     

Determinantal method for locally modified structures. Application to the vibration damping of a space launcher

In order to improve the dynamic behaviour of an existing or already designed structure, local modifications can be performed by taking advantage of the relative displacement between two points of the structure. A stiffner, damper or viscoelastic rod may be added and its effect on the initial structure must be assessed. A new formulation is developed, based on the response of the initial structure at the attachment points of the local modification. A determinantal equation results, whose roots are the eigenvalues of the modified structure. The equation is solved numerically with a dedicated algorithm and it is shown that this is faster than performing an eigenvalue problem reanalysis. The method is able to deal with both undamped and damped systems, and can handle several modifications simultaneously. It is applied on the last stage of a space launcher, along with a double modal synthesis method.     

Planning and implementing field operational tests of intelligent transport systems: a checklist derived from the EC FESTA project

To date, the main focus of intelligent transport systems (ITS) research programmes has been on technology development and proof of concept, rather than on understanding the implications of system implementation. Improved knowledge is needed about the ways in which drivers use ITS, their short- and long-term effects and how system performance can be optimised. The field operational test, or FOT, is a sophisticated evaluation method that can be used to answer these and other critical questions, and to stimulate market acceptance and demand for ITS. Although the large-scale FOTs conducted to date have yielded important insights into both the positive and potentially negative impacts of ITS, there is considerable scope for improving the design and implementation of FOTs. There are many advantages in doing so. The authors outline, in the form of a checklist, the critical steps and considerations involved in successfully planning and implementing an FOT, drawing on work undertaken in the EC-funded FESTA (Field opErational TeSt support Action) project.     

Long-term reactive transport modelling of stabilized/solidified waste: from dynamic leaching tests to disposal scenarios

Environmental impact assessment of hazardous waste disposal relies, among others, on standardized leaching tests characterized by a strong coupling between diffusion and chemical processes. In that respect, this study shows that reactive transport modelling is a useful tool to extrapolate laboratory results to site conditions characterized by lower solution/solid (L/S) ratios, site specific geometry, infiltration, etc. A cement solidified/stabilized (S/S) waste containing lead is investigated as a typical example. The reactive transport model developed in a previous study to simulate the initial state of the waste as well as laboratory batch and dynamic tests is first summarized. Using the same numerical code (HYTEC), this model is then integrated to a simplified waste disposal scenario assuming a defective cover and rain water infiltration. The coupled evolution of the S/S waste chemistry and the pollutant plume migration are modelled assessing the importance of the cracking state of the monolithic waste. The studied configurations correspond to an undamaged and fully sealed system, a few main fractures between undamaged monoliths and, finally, a dense crack-network in the monoliths. The model considers the potential effects of cracking, first the increase of rain water and carbon dioxide infiltration and, secondly, the increase of L/S ratio and reactive surfaces, using either explicit fracture representation or dual porosity approaches.     

Biomaterials innovation: it’s a long road to the operating room

 An innovative process for forming a wide variety of porous biomaterials was conceived of and developed over several years at a University and later by a company that licensed the early patents. The family of patents formed the basis for several promising innovative biomaterials devices. However, only one commercial product has been realized. That product is the very successfull coralline hydroxyapatite (HA) now widely used in orthopaedic surgery, oral and maxillofacial bone repair and plastic surgery. This paper challenges the equation of discovery with a genuine innovation which reaches the marketplace. The paper reviews several aspects of the innovation and development history with an emphasis on the challenges of bringing any new biomaterial through all the conceptual, developmental, business and regulatory hurdles. New class three medical devices require huge investments of time and money typically requiring a minimum of eight years and 15–20 million dollars per new device to take it from concept to an approved product. These hurdles are so high that most research innovations in biomaterials never get put into the developmental pipeline. This paper is presented from an anecdotal perspective of an innovator who has had a continuous research and development involvement in the technology but has no significant management involvement beyond the early startup activities. It differs from predecessors is that it deals not only with the initial step of discovery but in the very difficult steps that follow on the road to a real innovation. Several strategies that may help other R&D groups outside the biomedical industry shorten the development cycle and increase the probability that a given biomaterials innovation can be seen through to approved product are discussed. Guidelines are suggested for culling out ideas that are technically sound but that likely won’t lead to successful products. Received: 2 January 1997 / Accepted: 27 March 1997     

Application of the finite element–difference method to vibration problems

The so-called finite element–difference method introduced in References 1 and 2 yields a continuous stress field by finite difference operations and finite element interpolations. In the present paper, applications of the method to vibration problems are discussed. The inverse iteration procedure is modified for this method. Numerical results show that the accuracy of solutions depends strongly on the type of finite difference operator chosen: for reliable and accurate solutions in modal analysis problems, element internal strains must be included in the strain field used to compute nodal forces associated with element deformations.