Humanoid Based Intelligence Control Strategy of Plastic Cement Die Press Work-Piece Forming Process for Polymer Plastics

The plastic cement belongs to a sort of polymer material, the chemical composition is very complex, and the plastic cement work-piece is generally manufactured by die press forming. Aimed at being difficult to control in parameters of forming process, the paper explored the humanoid based intelligence control strategy. In the paper, it made the anatomy in control puzzle resulted in uncertainty such as chemical component of plastic cement etc., summarized up the characteristic of cybernetics in forming process, researched on the humanoid based intelligence control strategy, and constructed the control algorithm of forming process in plastic cement work-piece. Taking the process experiment of temperature and pressure control as an example, it validated the good dynamic and static control quality through simulation of control algorithm constructed in this paper. The experimental results show that the control algorithm explored in this paper is reasonably available.

Rheological Behaviors of Fresh Cement Pastes with Polycarboxylate Superplasticizer

The rheologicalbehaviors of fresh cement paste with polycarboxylate superplasticizer were systematically investigated.Influentialfactors including superplasticizer to cement ratio（Sp/C）,water to cement ratio（w/c）,temperature,and time were discussed.Fresh cement pastes with Sp/Cs in the range of 0 to 2.0% and varied W/Cs from 0.25 to 0.5 were prepared and tested at 0,20 and 40 °C,respectively.Flowability and rheologicaltests on cement pastes were conducted to characterize the development of the rheologicalbehavior of fresh cement pastes over time.The exprimentalresults indicate that the initialflowability and flowability retention over shelf time increase with the growth in superplasticizer dosage due to the plasticizing effect and retardation effect of superplasticizer.Higher temperature usually leads to a sharper drop in initialflowability and flowability retention.However,for the cement paste with high Sp/C or w/c,the flowability is slightly affected by temperature.Yield stress and plastic viscosity show similar variation trends to the flowability under the abovementioned influentialfactors at low Sp/C.In the case of high Sp/C,yield stress and plastic viscosity start to decline over shelf time and the decreasing rate descends at elevated temperature.Moreover,two equations to roughly predict yield stress and plastic viscosity of the fresh cement pastes incorporating Sp/C,w/c,temperature and time are developed on the basis of the existing models,in which experimentalconstants can be extracted from a database created by the rheologicaltest results.

Elastoplastic cup model for cement-based materials

Based on experimental data obtained from triaxial tests and a hydrostatic test, a cup model was formulated. Two plastic mechanisms, respectively a deviatoric shearing and a pore collapse, are taken into account. This model also considers the influence of confining pressure. In this paper, the calibration of the model is detailed and numerical simulations of the main mechanical behavior of cement paste over a large range of stress are described, showing good agreement with experimental results. The ease study shows that this cup model has extensive applicability for cement-based materials and other quasi-brittle and high-porosity materials in a complex stress state.

Study of elastic-plastic damage model of cement consolidated soil with high organic content

On the basis of elastic-plastic damage model of cement consolidated soil,the authors took organic contents into reasonable damage variable evolution equation in order to seek relation between the organic contents and parameters in the equation,and established the elastic-plastic damage model of cement consolidated soil considering organic contents.The results show that the parameters change correspondingly with difference of the organic contents.The higher the organic contents are,the less the valves of the parameters such as elastic modulus(E),material parameters(K,n) and damage evolution parameter(ε) become,but the larger strain damage threshold value(εd) of the sample is.Meanwhile,the calculation results obtained from established model are compared with the test data in the condition of common indoors test,which is testified with reliability.

Effect of Polyethylene Terephthalate Plastic Waste on the Physico-Mechanical and Thermal Characteristics of Stabilized Laterite Bricks

The present work investigated the effect of polyethylene terephthalate (PET) plastic waste on the physico-mechanical and thermal properties of cement-stabilized laterite bricks to see the durability of the modified bricks (CSLB). Samples were formulated by mixing laterite, cement, and different percentages of PET (0%, 3%, 5%, and 7%) by volume. The bricks were produced using the M7MI Hydraform standard interlocking block and kept in the shade for a curing period of 28 days. The addition of 3% to 5% PET to the laterite stabilized with 10% cement results in a decrease in both dry and wet compressive strength, which is determined using the Controlab compression machine. However, the obtained results are in concordance with the standards. The thermal conductivity of CSLB, determined using the box method with the EI700 measurement cell, decreases as the PET content of the mixture increases. A decrease in bulk density from 1.67 to 1.58 g/cm3 was observed.

泵送碱式硫酸镁水泥混凝土的制备和性能

碱式硫酸镁水泥混凝土是新开发出来不久的混凝土材料,具有高抗拉强度、抗冲击和耐腐蚀等优点,但由于其较小的塌落度,限制了其工程应用。本文试验研究了不同掺量萘系减水剂对泵送碱式硫酸镁水泥混凝土塌落度和强度的影响,确定强度等级C30、C40、C50和C60的萘系高效减水剂适宜掺量分别为2.0%、1.2%、1.5%和1.8%。分别研究了掺粉煤灰型和矿渣型泵送碱式硫酸镁水泥混凝土基本力学性能及在海水浸泡、淡水浸泡1280 d后的强度保留率并进行机理分析,发现粉煤灰型泵送碱式硫酸镁水泥混凝土抗海水腐蚀性较好,适合东部沿海地区应用;随着海水暴露时间的延长,泵送碱式硫酸镁水泥混凝土的Df值呈现幂函数的降低关系。本文还对大气中暴露2400 d的钢筋泵送碱式硫酸镁水泥混凝土小梁进行观测,未有锈涨现象。本文为碱式硫酸镁水泥混凝土在工程领域的应用具有重大意义。

减缩剂对水泥砂浆及超高性能混凝土收缩性能的影响

研究了不同掺量的减缩剂(SRA)对水泥砂浆塑性收缩开裂、水泥水化热、水泥砂浆毛细管负压的影响,以及SRA掺量(1%、3%、4%)对超高性能混凝土(UHPC)抗压强度和收缩性能的影响。结果表明:SRA可显著降低水泥砂浆的开裂面积、平均和最大裂缝宽度,当SRA掺量为4%时,缓解塑性收缩开裂的效果最佳,开裂面积、平均和最大裂缝宽度与基准组相比分别降低了52.1%、35.0%和48.4%;SRA通过延缓毛细管负压的发展,降低了水泥砂浆的塑性收缩开裂;随着SRA掺量的增加,UHPC的抗压强度提高越明显,UHPC的收缩显著降低;当减缩剂掺量为4%时,UHPC的28 d抗压强度达140.0 MPa,收缩率最低。

软弱土地区城市道路河道生态护岸设计

南充市顺庆区荆溪河沿岸滨河路及护岸建设过程中,大部分河段存在较厚的软塑粉质黏土。该层土物理力学性质较差,对道路建设和护岸稳定极为不利。滨河路是拟建的休闲景观大道,因此该工程在保证道路和护岸安全的前提下,提出生态需求。根据场地工程地质情况,选取了斜坡式生态护岸形式,即表面采用绿化混凝土护坡与客土绿化,坡脚采用格宾石笼护脚,针对较厚的软塑粉质黏土区域采取水泥土搅拌桩进行加固处理。监测结果表明护岸方案整体稳定性及不均匀沉降满足要求。

CO_(2)腐蚀-应力耦合下固井水泥环密封完整性

CO_(2)地质封存过程中,与地层围岩中的水反应后腐蚀着固井水泥环,腐蚀损伤和套管内压(应力)耦合作用极大地影响着水泥环的密封完整性。基于CO_(2)腐蚀实验,获得不同腐蚀程度水泥石材料力学性能参数,采用混凝土损伤塑性(CDP)本构模型和Mohor-Coulomb准则描述腐蚀前后水泥环的应力-应变行为,利用ABAQUS软件建立考虑CO_(2)腐蚀与应力耦合作用的井筒组合体(套管-水泥环-地层围岩)有限元分析模型,分析和探讨了套管内压和腐蚀时间对水泥环完整性的影响。结果表明,较高套管内压下,井筒水泥环发生弹塑性变形,出现结构损伤,套管与水泥环界面易形成微间隙;受腐蚀和套管内压的耦合作用,水泥环更易于出现完整性失效问题,相比较于未腐蚀水泥环,腐蚀水泥环受压后径向应力、等效塑性应变、微间隙以及拉伸和压缩损伤均较大,与之相反,塑性半径是减小的;微间隙与拉伸和压缩损伤受腐蚀时间的影响不明显。

高速分散对水泥基浆体流变行为的影响研究

为研究高速分散速率与时长等参数对水泥基浆体流变行为的影响,采用涡流式高速分散设备,设计不同速率与时长,分别对不同水胶比、不同硅灰掺量的水泥基浆体进行分散,再通过流变仪测试浆体的流变性能。试验结果表明:分散速率对于较低水胶比水泥浆体屈服应力、触变性的影响大于较高水胶比浆体;不同水胶比水泥浆体样品的塑性黏度均随分散速率的提高迅速降低后趋于稳定,塑性黏度变化的转折点大致出现在分散速率为1 000~1 500 rpm处。硅灰的掺入显著提高了各浆体的屈服应力、塑性黏度与触变性,但当采用较高的速率进行分散时,浆体间流变参数的差异总体上呈缩小趋势。掺硅灰等超细粉体的水泥基浆体的高速分散时长建议控制在2 min左右。

Constitutive model for monotonic and cyclic responses of loosely cemented sand formations

This paper presents a model to simulate the monotonic and cyclic behaviours of weakly cemented sands.An elastoplastic constitutive model within the framework of bounding surface plasticity theory is adopted to predict the mechanical behaviour of soft sandstone under monotonic and cyclic loadings. In this model, the loading surface always passes through the current stress state regardless of the type of loading. Destruction of the cementation bonds by plastic deformation in the model is considered as the primary mechanism responsible for the mechanical degradation of loosely cemented sands/weak rock.To model cyclic response, the unloading plastic and elastic moduli are formulated based on the loading/reloading plastic and elastic moduli. The proposed model was implemented in FLAC2D and evaluated against laboratory triaxial tests under monotonic and cyclic loadings, and the model results agreed well with the experimental observations. For cyclic tests, hysteresis loops are captured with reasonable accuracy.

硬化促进剂对水泥基泡沫混凝土性能影响

为分析硬化促进剂对水泥基泡沫混凝土性能的影响,对加入不同硬化促进剂的水泥基泡沫混凝土进行试验。以水泥质量为基准,分别添加2.0%的氯化钙和0.5%的草酸钙作为硬化促进剂,降低混凝土混合物的收缩变形,增加硬化泡沫混凝土的抗压强度。结果表明,集料稳定性显著提升,泡沫混凝土混合物的塑性收缩降低了47%~65%。在含有硬化促进剂的泡沫混凝土中,28 d龄期D400的抗压强度从0.31 MPa增至0.47 MPa, D600的抗压强度从0.96 MPa增至1.44 MPa,同时密度保持为D400和D600的平均密度。添加硬化促进剂可以有效提升水泥基泡沫混凝土的性能,满足实际工程的要求。

Underground void filling by cemented mill tailings

Underground mining always create voids.These voids can cause subsidence of surface.So it is always a demand to fill the void in such a manner that the effect of underground mining can be minimized.Void filling using mill tailings especially in metal mining is one of the best techniques.The tailings produced in milling process have traditionally been disposed in tailing ponds creating a waste disposal and environmental problems in terms of land degradation,air and water pollution,etc.This disposal practice is more acute in the metal milling industry where the fine grinding,required for value liberation,results in the production of very fine tailings in large percentage.This paper includes discussions on the effectiveness of different paste mixes with varying cement contents in paste backfilling operations.The results revealed that material composition and use of super plasticizer strongly influenced the strength of cemented backfill.

Stress distributions on crown-luting cement-substrate system with finite element method

The aim of this work is to analyze the stress distributions on a crown-luting cement-substrate system with a finite-element method in order to predict the likelihood of interfacial micro cracks, radial or circumferential cracks, delamination, fracture and delamination with torsion. The contact and layer interface stresses in elastic layered half-space indented by an elastic sphere were examined using finite element method. The model consists of crown, luting cement and substrate. The solutions were carried out for three different elastic moduli of luting cement. It was placed between the cement and the substrate as a middle layer and its elastic module was chosen lower than the elastic module of crown and higher than the elastic module of dentin. An axisymmetric finite element mesh was set up for the stress analysis. Stress distributions on the contact surface and the interfaces of crown-luting cement and luting cement-dentin have been investigated for three different values of luting cement by using ANSYS. The effects of the luting cement which has three different elastic moduli on the pressure distribution and the location of interfacial stresses of the multi-layer model have been examined. The mechanism of crack initiation in the interfaces and interfacial delamination was also studied quantitatively. For each luting cement, the pressure distribution is similar at the contact zone. Stress discontinuities occur at the perfect bonding interfaces of the crown-luting cement and the substrate-luting cement. The maximum stress jumps are obtained for the highest and the lowest elastic module of the luting cement. In the crown-luting cement-substrate system, failures may initiate at crown-luting cement region for luting cement with the lowest elastic module value. In addition, failures at luting cement-substrate region may occur for luting cement with the highest elastic module. In the luting cement, the medium elastic module value is more suitable for stress distribution in crown-luting cement-substrate interfaces.

Plastic Sealed Thermal Expansion Packer for Thermal Recovery

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Effects of Curing Temperature on Rheological Behaviour and Compressive Strength of Cement Containing GGBFS

The viscoplasticity and compressive strength of cement with high erosion performance were studied. The influences of curing temperature and content of ground granulated blast furnace slag(GGBFS) on these performances of the medium heat cement(including high iron and low calcium phase) were also investigated. The results indicate that the medium heat cement with high iron phase can maintain better fluidity and low temperature sensitivity than that of ordinary Portland cement at high temperature. GGBFS can play an important role in improving the fluidity and stability of the slurry, and avoid the cement setting and hardening prematurely at high temperatures. The microstructure analysis shows that a large amount of CH with layer shape appear in the slurry. The amount of this gel layer in the slurry increased as the curing temperature elevated. The layer can make the cement stone structure more denser, so that the compressive strength of samples are enhanced in the later stage. When the medium heat cement contains 40% GGBFS, the system has the best flow performance and stability under high temperature environment, and can be applied to mass concrete with excessive internal temperature.

Failure Analysis of WC-3.5wt%Co Cemented Carbides in Mining Applications

In order to further understand the wear mechanisms of cemented carbide cutter head of conical pick, six wornout cutter heads were investigated detailedly through scanning electron microscopy（SEM） and energy dispersive spectrometry（EDS）. Abrasion wear and tipping were found to be the main wear mechanisms of the worn out cutter heads. Thermal stress and impact load played important roles in the wearing process of cutter heads. The intermixed mineral particles in the worn out areas aggravated the wear on the surface of cemented carbide. The spherical particles and vine-like structures were found to distribute in the wornout areas arbitrarily, and the compositions of which were detected using EDS.

改性废塑料纤维水泥稳定碎石性能与应用研究

为研究掺入改性废塑料纤维材料的水泥稳定碎石混合料的力学性能及变形特性,依托怀芷高速公路工程,铺筑了试验路,验证废旧塑料纤维应用于水泥稳定碎石基层的可行性,提出废塑料纤维水泥稳定碎石混合料拌合工艺。研究结果表明:掺入适量的改性废塑料纤维,可以显著提升水泥稳定碎石材料的劈裂抗拉强度和弯拉强度。当掺入0.30%的改性废塑料纤维时,7 d龄期的水泥稳定碎石的劈裂抗拉强度提高了71.4%,弯拉强度提高了13.1%。掺入0.30%的改性废塑料纤维可有效降低水泥稳定碎石的干缩变形系数和温缩变形系数。通过调查铺筑的试验路发现,芯样无侧限抗压强度合格,废旧塑料纤维水泥稳定碎石基层的抗裂性能得到了显著提高。

The Cementing Techniques Of Salt Formation

This paper analyzes mechnasim of casing failure and collapse by salt formation,discusses cementing techniques of salt zone about casing programme, casing design, preparation of well condition, mud and slurry properties required, cementing technology, and puts forward the measures for solving problems posed when cementing through salt sequences, and illustrates with examples.