长线台座预应力管芯内振拉模机结构性能及使用效果

长线台座预应力管芯内振拉模机结构性能及使用效果杨德强（上海市浦东浦航建筑钢模厂，上海２０１２０２）我厂生产长线台座预应力管芯内振动拉模机已有十多年历史，是国内最早生产拉模机的厂家。在北方大批预制构件市场中，目前大多数采用挤压机生产．根据国标Ｇ４３６预...

齿轮式内振拉模机的研制

提出了新型内振拉模机的设计思路,介绍了该型机组成及特点;通过试运行,对整机修改、调整、设计,完成了YNL-120A-500600型新型内振拉模机的研制,填补了国内空白.

基于PLC的拉模机新型控制系统的设计

利用PLC控制技术设计了新型的拉模机控制系统,以增强拉模机的性能。

一模多用的组合拉模——改进后的预应力圆孔板管芯内振动拉模机

近年来我国各地混凝土构件厂,对使用预应力圆孔板管芯内振动拉模机都比较感兴趣。因为用它生产的圆孔板各项技术指标都能达到设计要求。产品质量稳定,达到了行业标准,厂家能顺利地通过生产许可评审,获得生产许可证。但是已使用我厂拉模的构件厂或将要订货的单位,有不少提出了如下建议:在资金紧缩,产品质量要求却日益提高的新形势下,希望能推出一模多用的组合拉模。

用内振拉模机生产预应力圆孔板经验点滴

一、两种设备的选择我厂从1985年建厂投产至今,全部使用上海市川沙施湾建筑钢模厂制造的预应力长线台圆孔板管芯内振动拉模机共8套。凡是上海市民用建筑设计院设计的沪G302、303构件图集的构件,我厂均生产。任何一个企业在正式投产前,必须要引进设备。

管芯内振动拉模机的使用效果

我厂1971年建成投产,是我县投产最早规模最大的生产预应力圆孔板的厂家。现有职工150名,生产场地7000m^2,为二级构件厂。使用上海川沙施湾建筑钢模厂生产的内振拉模机后,圆孔板年产量可达6000m^3,年产值达300多万元。

预应力混凝土多孔板内振拉模机的施工技术

一、概述多孔板内振拉模机是我国近几年来兴起的一种新型多孔板成型机械。目前有十来家生产厂家,以芯管内振为主。这些内振拉模机的机械原理基本相同,它们是综合了过去的支模、简易拉模的生产设备和生产工艺,将钢模、管芯、振摇、拔管合为一体的多功能设备,是预应力多孔板长线台座生产的革新机械。改变了预应力多孔板生产用翻模。

组合式多孔板管芯内振拉模机

我厂改进设计的120型和180型系列预应力多孔板管芯内振拉模机(简称内振拉模),注册商标“水星”牌(见64页广告)。各种规格齐全,在1985年“全国砼生产设备交流交易会”上荣获优秀产品称号。一套拉模经组合后可生产2～3种规格多孔板,拉模移位采用杠杆车,牵引车采用转弯器,后端头板开合采用闸门式,因而可节约钢筋和场地,比同类设备更领先一步。目前已有10多个省市100多家构件厂使用。据调查,凡是使用我厂设备的厂家,构件质量稳定,达到行业标准要求。

预应力圆孔板管芯内振拉模机

在我国预应力构件生产行业中,相当一部分构件厂对预应力圆孔板生产仍采用手工脱模、翻板脱模工艺,它存在着生产效率低、耗能高、劳动强度大、废次品率高等弊病。

对内振拉模构件产品质量的对比分析

本文根据内振拉模构件与挤压成型构件的对比分析，对内振拉模式构件质量作了充分的肯定，为推广应用新设备，提高农房用件质区奠定了理论基础。

预应力空心板“活筋”现象的防治

目前,我国在低层住宅建设中所使用的预应力空心板,有相当一部分是由中小预制厂家生产的。这些厂家多采用拉模机进行生产。较之大型预制厂钢模、蒸汽养护车间生产,自有其优缺点,在此不加赘述。 仅以在使用拉模法生产预应力空心板的实践中是如何研究防治预应力空心板产生“活筋”现象而采取的措施和办法叙述如下:

An Autonomous Electric Powered Tractor--Simulation of All Operations on a Swedish Dairy Farmagricultural m machinery. This s study investig gated the feasib bility of an au utonomous batte ery electric tra actor through simulation. The e

For a conventional agricultural tractor the main environmental effects origina ates from the usage phase, more specifically from the diesel use and exhausts. To decre ease the environ nmental effect, it is vital to find a substitute for fossil diesel as a fuel for agricultural machinery. This s study investig gated the feasib bility of an autonomous battery electric tractor through simulation. The simulated farm is an organic dairy farm of 200 ha with five crops in the crop rotation cycle and a traditional plough among the used implements. Based on the res sult from the simulation cost calculations, sensitivity analysi is and a limited life cycle analysis （LCA） was made. The results show that it is in theory possible to replace a conventional tractor （160 kW） with two autonomous battery powered machines （36 kW engine, 113 kWh battery） with 15% lower costs. Energy consumption would be red duced by 58% a and greenhouse gas emissions by 92% compared to diesel when energy consumption and greenhouse gas emissions from battery manufacturing were included. Today the technology for autonom mous control is under fast development, but there are yet no systems on the market that can handle all machinery tasks like assumed in this study. Challenges yet to solve are , among others, legislative, relevant sensors, logistics and fleet management. Further rese earch is needed to verify the results in practical farming.

Prediction of overbreak depth in Ghalaje road tunnel using strength factor

It is well known that the overbreak caused by the blasting damage during tunnel excavation increases costs associated with filling the collapsed area with shotcrete and results in filing of a claim by the contractor. This paper outlines a new approach for prediction the overbreak depth during tunnel construction. Hence, firstly excavation damage zone(EDZ) are determined by average specific charge in each zone. Numerical modelling is used to simulate the EDZ around tunnel boundary and the overbreak depth are calculated by the rock strength factor. The predicted overbreak depth compared with observed field data from a case study. The results show that there exists an approximately up to 40% difference between the prediction and the observed volume of overbreak depth. Therefore, the method can be well used to predict the overbreak depth to estimate more precision of shotcrete and concrete volumes in tunnelling cost during design phase.

Calculation model and mechanism analysis for rain-wind-induced vibration of stay cable

Rain-wind-induced vibration of cable was studied based on previous research achievements. According to the quasi-steady assumption, the governing equation of vertical motion of the cable was derived and the criterion for unstable motion and occurrence mechanism was studied. A comparison was performed between the oscillation responses of the stay cable obtained from calculated model and previous results. The results indicate that the analysis model can reflect the main characteristics of wind-rain-induced vibrationt of the cable which is amplitude- and velocity-restricted, and it is probably related with the periodic vortex shedding of wake flow. It is essential for the occurrence of rain-wind-induced or wind-induced vibration of cable that the derivative of lift coefficient with respect to transient angle of attack is less than zero. When rain-wind-induced vibration occurs, the aerodynamic force has a dual function for the vibration, and the maximum amplitude of stayed-cable is determined by the relative value of aerodynamic exciting force and aerodynamic damping force.

Crack branching mechanism of rock-like quasi-brittle materials under dynamic stress

The cracking patterns of a thin sheet with a pre-existing crack subjected to dynamic loading are numerically simulated to investigate the mechanism of crack branching by using the FEM method.Six numerical models were set up to study the effects of load,tensile strength and heterogeneity on crack branching.The crack propagation is affected by the applied loads,tensile strength and heterogeneity.Before crack branching,the crack propagates by some distance along the direction of the pre-existing crack.For the materials with low heterogeneity,the higher the applied stress level is and the lower the tensile strength of the material is,the shorter the propagation distance is.Moreover,the branching angle becomes larger and the number of branching cracks increases.In the case of the materials with high heterogeneity,a lot of disordered voids and microcracks randomly occur along the main crack,so the former law is not obvious.The numerical results not only are in good agreement with the experimental observations in laboratory,but also can be extended to heterogeneity media.The work can provide a good approach to model the cracking and fracturing of heterogeneous quasi-brittle materials,such as rock,under dynamic loading.

Effects of porosity on tensile mechanical properties of porous FeAl intermetallics

Uniaxial tensile tests and scanning electron microscopy(SEM)experiments were carried out on the porous FeAl intermetallics(porosities of 41.1%,44.2%and 49.3%,pore size of 15−30μm)prepared by our research group to study the macroscopic mechanical properties and microscopic failure mechanism.The results show that the tensileσ−εcurves of the porous FeAl with different porosities can be divided into four stages:elasticity,yielding,strengthening and failure,without necking phenomenon.The elastic modulus,ultimate strength and elongation decrease with the increase of porosity and the elongation is much lower than 5%.A macroscopic brittle fracture appears,and the microscopic fracture mechanism is mainly intergranular fracture,depending on the Al content in the dense FeAl intermetallics.In addition,the stochastic porous model(SPM)with random pore structure size and distribution is established by designing a self-compiling generation program in FORTRAN language.Combined with the secondary development platform of finite element software ANSYS,the effective elastic moduli of the porous FeAl can be determined by elastic analysis of SPM and they are close to the experimental values,which can verify the validity of the established SPM for analyzing the elastic properties of the porous material.

Modeling and software implementation of flight system for simulator of a new fighter

Real-time modeling and simulation of flight system are the key parts of simulator. After describing the architecture of simulator for a newer fighter, author presents the composition of flight system and its mathematic models. In this paper, aircraft is regarded as an elastic flight body. And a new integrated algorithm which can remedy the shortcoming of Euler method and four-element method is used to calculate the Eulerian angles of aircraft. Finally, the software implementation of the flight system is given in the paper.

Size and spatial distribution of landslides induced by the2015 Gorkha earthquake in the Bhote Koshi river watershed

The Mw 7.8 Gorkha earthquake in Nepal on April 25, 2015, produced thousands of landslides in the Himalayan mountain range. After the earthquake, two field investigations along Araniko Highway were conducted. Then, using remote sensing technology and geographic information system(GIS)technology, 1481 landslides were identified along the Bhote Koshi river. Correlations between the spatial distribution of landslides with slope gradient and lithology were analyzed. The power-law relationship of the size distribution of earthquake-induced landslides was examined in both the Higher Himalaya and Lesser Himalaya. Possible reasons for the variability of the power exponent were explored by examining differences in the geological situations of these areas. Multi-threshold cellular automata were introduced to model the complexity of system components. Most of the landslides occurred at slope gradients of 30°–40°, and the landslide density was positively correlated with slope gradient. Landslides in hard rock areas were more common than in soft rock areas. The cumulative number-area distribution of landslides induced by the Gorkha earthquake exhibited a negative power-law relationship, but the power exponents were different: 1.13 in the Higher Himalaya, 1.36 and Lesser Himalaya. Furthermore,the geological conditions were more complex and varied in the Lesser Himalaya than in the Higher Himalaya, and the cellular automata simulation results indicated that, as the complexity of system components increased, the power exponent increased.Therefore, the variability of the power exponent of landslide size distribution should ascribe to the complexity of geological situations in the Bhote Koshi river watershed.

Path-tracking Control of a Tractor-aircraft System

An aircraft tractor plays a significant role as a kind of important marine transport and support equipment. It＇s necessary to study its controlling and manoeuvring stability to improve operation efficiency. A virtual prototyping model of the tractor-aircraft system based on Lagrange＇s equation of the first kind with Lagrange mutipliers was established in this paper, According to the towing characteristics, a path-tracking controller using fuzzy logic theory was designed. Direction control herein was carried out through a compensatory tracking approach. Interactive co-simulation was performed to validate the path-tracking behavior in closed-loop, Simulation results indicated that the tractor followed the reference courses precisely on a flat ground.