Fatigue behaviour and life prediction of filament wound CFRP pipes based on coupon tests

This paper investigates the fatigue behaviour of filament wound Toray T700/Epotech X4201 composite pipes with different lay-ups. The present work compares the fatigue behaviour of coupon specimens manufactured with two different fiber orientations under tension-tension and tension-compression cyclic actions. The test results show that the lay-up and stress ratio have significant effect on the failure mechanism and fatigue life of carbon fiber reinforced polymer (CFRP) composite coupons. This paper develops an empirical model, which integrates the effect of stress ratio in a fatigue damage parameter, to evaluate the fatigue life of the CFRP filament wound coupons. Combined with the numerically calculated stresses at the critical locations corresponding to the fatigue damage locations, the proposed empirical model developed from the coupon test database predicts successfully the fatigue life of full diameter CFRP pipes, using stresses computed at critical locations in the CFRP pipe.     

基于注意力机制的CNN-LSTM剩余寿命预测研究

机械设备剩余寿命的准确预测可以降低昂贵的维护费用,提高机械设备的安全性。随着深度学习的发展以及注意力机制被广泛应用于各个领域,基于数据驱动的剩余寿命预测方法为机械设备寿命预测提供了众多的方法。文章提出了一种基于注意力机制的CNN-LSTM剩余寿命预测方法,该方法利用不同的注意力机制包括通道注意力、CBAM机制和自注意力等进行剩余寿命预测试验。注意力机制可以向CNN-LSTM提取的特征信息分配不同的权重,突出关键的特征信息,过滤无用信息,进而更准确地表示设备的退化特征信息,最终得到设备的剩余寿命。文章对NASA发动机数据集进行了剩余寿命预测试验,同时研究了不同注意力机制影响,试验结果表明,基于注意力机制的方法可以有效地进行剩余寿命预测,所提方法具有一定的应用价值。     

少学时“机械零部件识图”课程的线上线下融合教学模式探讨

"机械零部件识图"是汽车类专业的一门必修专业基础课,本文基于现有"机械零部件识图"在线开放课程资源,探讨线上与线下交互融合教学模式在少学时"机械零部件识图"课程中的应用。     

Determinants of airport retail revenue: a review of literature

ABSTRACT

As the airport retail industry continues to grow due to increasing travel demands, airport operators are increasingly developing their retail revenue potential to ensure financial viability. This study aims to provide a review of airport retail literature and identify the salient factors associated with passenger shopping behaviour. The paper presents a review of contemporary airport retail literature, covering a total of 50 studies from 1998 to 2018. The review identified 26 factors, which could broadly be grouped into five categories: airport/operator related; passengers' demographic related; passengers’ travel related; passengers’ psychological related and passengers’ resources related. In addition to providing a summary of the statistically significant factors across studies, the review identifies and discusses potential approaches for future research. These include the importance of considering both “to spend or not” decision and how much to spend and how most empirical studies focussed on the former; the gap in empirical analysis on the impact of airport terminal design layout on retail performance; and the gap in application of general consumer shopping behavioural models to airport retail problems. The paper concludes with the suggestion that we can build on the existing studies to develop a hybrid approach to solve several of the identified gaps simultaneously.     

Modelling users’ behaviour in inter-urban carsharing program: A stated preference approach

In this paper, the effects of a inter-urban carsharing program on users’ mode choice behaviour were investigated and modelled through specification, calibration and validation of different modelling approaches founded on the behavioural paradigm of the random utility theory. To this end, switching models conditional on the usually chosen transport mode, unconditional switching models and holding models were investigated and compared. The aim was threefold: (i) to analyse the feasibility of a inter-urban carsharing program; (ii) to investigate the main determinants of the choice behaviour; (iii) to compare different approaches (switching vs. holding; conditional vs. unconditional); (iv) to investigate different modelling solutions within the random utility framework (homoscedastic, heteroscedastic and cross-correlated closed-form solutions). The set of models was calibrated on a stated preferences survey carried out on users commuting within the metropolitan area of Salerno, in particular with regard to the home-to-work trips from/to Salerno (the capital city of the Salerno province) to/from the three main municipalities belonging to the metropolitan area of Salerno. All of the involved municipalities significantly interact each other, the average trip length is about 30 km a day and all are served by public transport. The proposed carsharing program was a one-way service, working alongside public transport, with the possibility of sharing the same car among different users, with free parking slots and free access to the existent restricted traffic areas. Results indicated that the inter-urban carsharing service may be a substitute of the car transport mode, but also it could be a complementary alternative to the transit system in those time periods in which the service is not guaranteed or efficient. Estimation results highlighted that the conditional switching approach is the most effective one, whereas travel monetary cost, access time to carsharing parking slots, gender, age, trip frequency, car availability and the type of trip (home-based) were the most significant attributes. Elasticity results showed that access time to the parking slots predominantly influences choice probability for bus and carpool users; change in carsharing travel costs mainly affects carpool users; change in travel costs of the usually chosen transport mode mainly affects car and carpool users.     

Experimental field study of floater motion effects on a main bearing in a full-scale spar floating wind turbine

In this paper we present a full-scale experimental field study of the effects of floater motion on a main bearing in a 6 MW turbine on a spar-type floating substructure. Floating wind turbines are necessary to access the full offshore wind power potential, but the characteristics of their operation leave a gap with respect to the rapidly developing empirical knowledge on operation of bottom-fixed turbines. Larger wind turbines are one of the most important contributions to reducing cost of energy, but challenge established drivetrain layouts, component size envelopes and analysis methods. We have used fibre optic strain sensor arrays to measure circumferential strain in the stationary ring in a main bearing. Strain data have been analysed in the time domain and the frequency domain and compared with data on environmental loads, floating turbine motion and turbine operation. The results show that the contribution to fluctuating strain from in-plane bending strain is two orders of magnitude larger than that from membrane strain. The fluctuating in-plane bending strain is the result of cyclic differences between blade bending moments, both in and out of the rotor plane, and is driven by wind loads and turbine rotation. The fluctuating membrane strain appears to be the result of both axial load from thrust, because of the bearing and roller geometry, and radial loads on the rotating bearing ring from total out-of-plane bending moments in the three blades. The membrane strain shows a contribution from slow-varying wind forces and floating turbine pitch motion. However, as the total fluctuating strain is dominated by the intrinsic effects of blade bending moments in these turbines, the relative effect of floater motion is very small. Mostly relevant for the intrinsic membrane strain, sum and difference frequencies appear in the measured responses as the result of nonlinear system behaviour. This is an important result with respect to turbine modelling and simulation, where global structural analyses and local drivetrain analyses are frequently decoupled.     

马来西亚ETS米轨干线动车组概述

文章介绍了马来西亚ETS米轨干线动车组的运行线路及运用环境情况,着重分析了车辆主要技术特点及总体性能参数,详细阐述了其主要机械、电气系统与转向架等的设计方案和技术特点。     

新型锌铝合金在阀门生产中的应用

在分析阀杆螺母服役条件的基础上，对用价格低廉的锌铝合金生产阀杆螺母进行了成分设计，确定了新型的锌铝合金－ZA33－3，并对其了力学性能及耐磨性能试验，结果表明，新型ZA33－3合金的各项性能指标全面超过铜合金，是替代铜合金生产阈杆螺母的理想材料，而其价格仅为铜合金的1／3。     

从机会成本的角度谈稳定层摊铺机械的选型

从经济学观点出发 ,利用机会成本原理 ,结合本公司承建的电湛高速公路路面工程特点 ,对该路面工程所应用的基层摊铺机的选型方案进行分析     

滑油运动粘度对尾轴轴颈振动的影响研究

船舶尾轴的振动与尾轴承油膜的动态支承刚度和阻尼密切相关,互相耦合,相互激励,影响船舶航行安全性.润滑油运动粘度是影响润滑油膜的动态特性的重要因素之一,粘度的改变对尾轴的振动行为产生重要影响.文中从动力学方面研究了滑油粘度对尾轴轴颈振动的影响,得出提高润滑油粘度有利于抑制轴颈振动的结论.