STUDY ON STRENGTH AND PETROGRAPHIC STRUCTURE OF CLINKER BY LOW-TEMPERATURE BURNING

In this paper,the strength and petrographic structure of clinker by low-temperature burning are studied. The results show that both the calcining temperature of Ca-CO3 and sintering temperature clinker decreases by 150 degrees C compared with those in traditional rotary kiln,the rate of f-CaO in the clinker sintered at 1300 degrees C is 0.29% similar to 2.81%, the strength of the clinker is 62. 5MPa with maximum 69. 4MPa at a specific area of 2900 similar to 3400cm(2)/g. The results also show that the types of petrographic structure of the clinker can be classified as: homogeneous structure, inlaid or edged structure,stain-melting structure and porous structure. The clinker sintered at 1300 +/- 15 degrees C temperature and with enough retention period is mainly in homogeneous structure.

Application of Hot Forming High Strength Steel Parts on Car Body in Side Impact

Lightweight structure is an important method to increase vehicle fuel efficiency. High strength steel is applied for replacing mild steel in automotive structures to decrease thickness of parts for lightweight. However, the lightweight structures must show the improved capability for structural rigidity and crash energy absorption. Advanced high strength steels are attractive materials to achieve higher strength for energy absorption and reduce weight of vehicles. Currently, many research works focus on component level axial crash testing and simulation of high strength steels. However, the effects of high strength steel parts to the impact of auto body are not considered. The goal of this research is to study the application of hot forming high strength steel（HFHSS） in order to evaluate the potential using in vehicle design for lightweight and passive safety. The performance of HFHSS is investigated by using both experimental and analytical techniques. In particular, the focus is on HFHSS which may have potential to enhance the passive safety for lightweight auto body. Automotive components made of HFHSS and general high strength steel（GHSS） are considered in this study. The material characterization of HFHSS is carried out through material experiments. The finite element method, in conjunction with the validated model is used to simulate the side impact of a car with GHSS and HFHSS parts according to China New Car Assessment Programme（C-NCAP） crash test. The deformation and acceleration characteristics of car body are analyzed and the injuries of an occupant are calculated. The results from the simulation analyses of HFHSS are compared with those of GHSS. The comparison indicates that the HFHSS parts on car body enhance the passive safety for the lightweight car body in side impact. Parts of HFHSS reduce weight of vehicle through thinner thickness offering higher strength of parts. Passive safety of lightweight car body is improved through reduction of crash deformation on car body by the application of HFHSS parts. The experiments and simulation are conducted to the HFHSS parts on auto body. The results demonstrate the feasibility of the application of HFHSS materials on automotive components for improved capability of passive safety and lightweight.

Effect of short-time low-temperature austenitizing on microstructure and mechanical properties of DT300 ultra-high strength steel fabricated by laser powder bed fusion

To address the inhomogeneous microstructure and improve the mechanical properties of DT300 ultra-high strength steel specimens fabricated by laser powder bed fusion,different post-heat treatment schedules are performed.With the increase in austenitizing temperature and time,the migration rate of austenite grain boundaries continuously increases with the dissolution of nano-carbides,and the formation of nano-oxides and twin martensite is also inhibited accordingly.The rapid growth in the size of prior austenite grains and martensite laths,as well as the decrease in the content of nano-oxides and twin martensite,led to a rapid decrease in the strength(yield strength and ultimate tensile strength)from HT2 to HTF specimens.The HT1 specimens(austenitizing at 830℃for 30 min,then oil quenching and tempering at 300℃for 120 min and finally air cooling)display excellent mechanical properties of yield strength of 1572 MPa,ultimate tensile strength of 1847 MPa,elongation of 9.84%,and fracture toughness of 106 MPa m^(1/2),which are counterparts to those of conventional DT300 steel forgings after heat treatment.

An experimental analysis on the turnover time of railway freight transportation based on the impact strength of factors

Based on the factors impact strength model(FISM), we studied on calculation formulas of influence strength and key elements of FISM, and analyzed the turnover time of railway freight transportation of China. The results show that wagon transfer time is the most critical factor among the three subjective factors of wagons turnover time. The FISM based analysis of wagon transfer time show that the wagon turnover time is significantly correlated with transit time with resorting. Among the seven factors of detention time of transit time with resorting, the time of waiting to departing, converging, and waiting to break-up are key factors, while the time of make-up, break-up, arrival and departure are general factors. We carried out one empirical research based on the data of Baoji East Railway Station in 2015. The results of empirical research and FISM are consistent completely.

EFFECT OF PROCESSING METHOD ON THE IMPACT STRENGTH OF POM/TPU/CaCO_3 TERNARY COMPOSITES

Polyoxymethylene （POM）/elastomer/filler ternary composites were prepared, in which thermoplastic polyurethane （TPU） and inorganic filler, namely, CaCO3, were used to achieve balanced mechanical properties of POM. The dispersion and phase morphology of POM/elastomer/filler composites were found to depend largely on processing method, CaCO3 content in masterbatch and the filler size. Two processing methods were employed to prepare POM/elastomer/filler ternary composites. One is called the one-step method, in which elastomer and the filler directly melt blended with POM matrix. The other is called the two-step method, in which the elastomer and the filler were mixed to get masterbatch first, which was then melt blended with pure POM of different content. The effect of phase morphology and processing method on impact strength was investigated. It was found that the two-step method results in an increase in impact strength but not for the one-step method. Additionally, the impact strength of POM ternary composites decreases with the increase in the size of CaCO3 particles.

Microstructure,texture evolution and yield strength symmetry improvement of as-extruded ZK60 Mg alloy via multi-directional impact forging

Multi-direction impact forging(MDIF)was applied to the as-extruded ZK60 Mg alloy,and the microstructure,texture evolution and yield strength symmetry were investigated in the current study.The results showed that the average grain size of forged piece was greatly refined to 5.3μm after 120 forging passes,which was ascribed to the segmenting effect of{10–12}twins and the subsequent multiple rounds of dynamic recrystallization(DRX).A great deal of{10–12}twins were activated at the beginning of MDIF process,which played an important role in grain refinement.With forging proceeding,continuous and discontinuous DRX were successively activated,resulting in the fully DRXed microstructure.Meanwhile,the forged piece exhibited a unique four-peak texture,and the initial<10-10>//ED fiber texture component gradually evolved into multiple texture components composed of<0001>//FFD(first forging direction)and<11–20>//FFD texture.The special strain path was the key to the formation of the unique four-peak texture.The{10–12}twinning and basal slip were two dominant factors to the evolution of texture during MDIF process.Grain strengthening and dislocation strengthening were two main strengthening mechanisms of the forged piece.Besides,the symmetry of yield strength was greatly improved by MDIF process.

Effect of roughness on the shear behavior of rock joints subjected to impact loading

The shear behavior is regarded as the dominant property of rock joints and is dramatically affected by the joint surface roughness.To date,the effect of surface roughness on the shear behavior of rock joints under static or cyclic loading conditions has been extensively studied,but such effect under impact loading conditions keeps unclear.To address this issue,a series of impact shear tests was performed using a novel-designed dynamic experimental system combined with the digital image correlation(DIC)technique.The dynamic shear strength,deformability and failure mode of the jointed specimens with various joint roughness coefficients(JRC)are comprehensively analyzed.Results show that the shear strength and shear displacement characteristics of the rock joint under the impact loading keep consistent with those under static loading conditions.However,the temporal variations of shear stress,slip displacement and normal displacement under the impact loading conditions show obviously different behaviors.An elastic rebound of the slip displacement occurs during the impact shearing and its value increases with increasing joint roughness.Two identifiable stages(i.e.compression and dilation)are observed in the normal displacement curves for the rougher rock joints,whereas the joints with small roughness only manifest normal compression displacement.Besides,as the roughness increases,the maximum compression tends to decrease,while the maximum dilation gradually increases.More-over,the microstructural analysis based on scanning electron microscope(SEM)suggests that the roughness significantly affects the characteristics of the shear fractured zone enclosing the joint surface.

Low temperature impact strength of heavy section ductile iron castings:effects of microstructure and chemical composition

A foundry research project has been recently initiated at RTIT in order to better understand the fabrication of as-cast heavy section DI parts meeting high impact energy requirements at low temperatures.The experimental castings have the following dimensions 180 mm x 180 mm x 190 mm.The achieved as-cast Charpy impact strengths were as follows:17 J (RT),16 J (-20℃) and 11 J (-40℃).The foundry process,the chemical composition and the microstructure of this experimental casting are compared to the ones of various examples in order to show the detrimental effects of residual elements,microshrinkage and microcarbide on the impact properties.Finally,quality index empirical models (based on casting chemical compositions) are used to analyse the impact tests results.This paper illustrates that an adequate nodule count can contribute to reducing the detrimental effects of the residual elements and microsegregation.

Low temperature impact toughness of laser hybrid welded joint of high strength low alloy steel

High strength low alloy steel with 16 mm thickness was welded by using high power laser hybrid welding. Microstrueture was characterized by using optical microscopy, scanning electron microscopy （ SEM ） , transmission electron microscopy （TEM） and selected area electron diffraction （SAED）. Low temperature impact toughness was estimated by using Charpy V-notch impact samples selected from the upper part and the lower part at the same heterogeneous joint. Results show that the low temperature impact absorbed energies of weld metal are （202,180,165 J） of upper samples and （178,145,160 J） of lower samples, respectively. All of them increase compared to base metal. The embrittlement of HAZ does not occur. Weld metal primarily consists of refined carbide free bainite and a little granular bainite since laser hybrid welding owns the character of low heat input. Retained austenite constituent film ＂locates among the lath structure of bainitie ferrite. Refined bainitic ferrite lath and retained austenite constituent film provide better low temperature impact toughness compared to base metal.

某型舰船设备大负载复合材料支承冲击强度试验方法研究

舰船设备支承件的冲击特性研究受到各国海军的重视,然而超过常规冲击机能力范围的冲击载荷等要求,使得开展大负载支承件冲击强度试验成为难题。以某型动力设备的大负载复合材料支承为对象,采用水下非接触爆炸的方式,以标准浮动冲击平台冲击环境为输入参数设计其冲击强度试验方法:在低速冲击条件下,通过保证冲击载荷、降低试验负载质量、提高系统安装频率的途径来设计试验装置,依据冲击谱和冲击载荷计算对应的试验冲击因子来设计强度试验工况,并得出了实际试验与设计参数之间因试验系统多个结合面对冲击载荷传递影响的折减系数。试验结果表明,复合材料支承承受的冲击载荷与要求值之间的偏差在5%以内,为今后开展类似试验提供了参考。

SiC/SiC复合材料层板低速冲击及其剩余强度试验研究

高速飞行器中的陶瓷基复合材料结构在服役过程中不可避免地会遇到低速冲击问题,低速冲击后的损伤形式以及剩余承载能力是影响飞行器结构安全的关键问题。本研究以二维编织SiC/SiC复合材料板件为研究对象,在不同能量下开展了低速冲击试验,分析了低速冲击载荷下试验件的表面损伤状态,通过计算机断层扫描技术观察了试验件内部的损伤形貌,结合冲击过程中的冲击响应曲线以及应变历史曲线,分析了SiC/SiC复合材料低速冲击过程的损伤机理。针对含勉强目视可见损伤的试验件开展了冲击后剩余强度试验,研究了勉强目视可见损伤对SiC/SiC复合材料剩余承载性能的影响。结果表明,在低速冲击载荷的作用下,试验件的表面损伤主要包括无表面损伤、勉强目视可见损伤、半穿透损伤以及穿透损伤,试验件的内部损伤主要有锥形体裂纹、纱线断裂以及分层损伤。低速冲击损伤会严重影响SiC/SiC复合材料的剩余性能,虽然试验件损伤勉强目视可见,但其剩余压缩强度为无损件81%,剩余拉伸强度仅为无损件的68%。

冲击速度及骨料率对混凝土动强度的影响研究

混凝土结构抗爆炸冲击能力研究具有很重要的军事防护意义.国内外学者已对混凝土动强度的提高机理进行了大量研究,但大多探讨单个因素对混凝土动强度的影响,缺乏对多因素耦合作用下混凝土动强度规律的研究,并且对混凝土抗压动强度和抗拉动强度间的关系研究也较少.通过霍普金森压杆试验仪的单轴压缩试验和巴西圆盘劈裂试验,测定了不同骨料率和冲击速度下混凝土的抗压动强度和抗拉动强度,再对试验结果进行研究分析,得到混凝土动强度的理论表达式,并将混凝土抗拉抗压动强度进行了对比分析.结果表明:混凝土抗压动强度与混凝土骨料率和冲击速度呈正相关,且随着混凝土骨料率的增大,冲击速度越小,混凝土抗压动强度增加幅度越大,受动载时,混凝土抗压动强度提高幅值大于抗拉动强度提高幅值.

热冲击高强钢焊接接头的低周疲劳及断裂机理研究

为了研究热冲击下高强钢焊接接头的低周疲劳性能及断裂机理,用电弧焊焊接Q345结构钢,分别在-20~400℃、-40~650℃、-60~900℃下对焊接接头进行循环冲击,用疲劳试验机加载低周疲劳载荷,分析热冲击温度对低周疲劳性能及疲劳强度的影响,并用扫描电子显微镜等分析焊接接头的断裂机理。结果表明:相同疲劳加载次数下,焊接接头的总应变幅值随热冲击循环次数的增加匀速下降;相同热冲击循环次数下,疲劳加载次数越多,焊接接头的应变幅值越小;相同疲劳加载次数和相同热冲击循环次数下,随冲击温度范围的扩大,焊接接头的总应变幅值逐渐减小,但总应变幅值整体变化与冲击温度范围正相关。

含硫酸盐废水对磷石膏胶结充填体材料性能的影响

鉴于矿山废水处理工艺具有一定的局限性,且磷石膏充填工艺需要消耗大量的水资源,将矿山含硫酸盐废水作为磷石膏充填用水并探讨其可行性。结果表明:废水中的硫酸盐能够促进磷石膏充填体的早期水化反应,进而提升充填体早期强度。当SO_(4)^(2-)浓度从0增加至30 000 mg/L时,充填体7 d强度由0.46 MPa升高至0.63 MPa,提高了37%;14 d强度由0.64 MPa升高至1.03 MPa,提高了61%。这主要跟水化产物钙矾石(AFt)和水化硅酸钙(C-S-H)的形成有关;但随着养护时间的增长,充填体28,60,90 d强度均在硫酸盐浓度为15 000 mg/L时达到最高。过量的SO_(4)^(2-)会干扰水化硬化过程,充填体后期强度因受到钙矾石的膨胀特性以及Na2SO4重结晶等影响而出现下降。研究结果可为矿山废水治理和磷石膏充填工艺优化提供新思路。

冲击力下薄壁内衬复合管界面黏结强度效应分析

【目的】研究薄壁内衬复合管在受冲击力作用下的界面黏结强度对层间剥离屈曲的影响。【方法】建立薄壁内衬复合管在弹性阶段的非线性分析模型,对薄壁内衬复合管材模态试验与分析模型的分析结果进行对比,验证有限元分析模型可靠性。通过改变衬层与原基层管壁间的界面黏结强度,研究复合管在冲击力下的动态特征。【结果】研究结果表明,当冲击荷载较小、管道变形处于弹性阶段时,薄壁内衬复合管的损伤大都集中在层间界面处。界面黏结强度对层间剥离屈曲有较大的影响,随着层间界面黏结强度的增加,外基层管与内衬层的最大等效应力差值减少。此外,外基层管和内衬层的变形协调性能力随着黏结强度增加而增大,径向层间位移减小,增加了复合管的整体性和连续性。【结论】研究结果可为薄壁内衬修复管道设计方法及层间界面效应分析提供参考。

Ti微合金化热轧高强钢带性能试验研究

针对Ti微合金化高强钢带力学性能波动的问题,进行炼钢生产工艺优化,开展不同工艺对低合金高强钢热轧钢带力学性能影响的研究。原炼钢工艺为先将钢水在氩站进行钛合金化,然后直接送连铸机浇铸。为了进一步提高钢水洁净度、改善产品质量、增强力学性能稳定性,在原炼钢工艺中增加LF精炼工序,并进行新工艺试验。结果表明:钢水经过LF精炼处理,钢中硫含量从0.010%左右降低到0.005%左右,TiN夹杂物颗粒尺寸减小到10μm以内,能够使Ti微合金化高强钢热轧钢带的纵向冲击功提高43 J、横向冲击功提高38.9 J,并且具有良好的0℃低温冲击性能,保持产品力学性能稳定。

新型冷作模具钢9Cr5Mo2V不同热处理下的性能研究

以新型冷作模具钢9Cr5Mo2V为研究对象,通过淬回火温度对硬度的影响规律,选出5种不同的热处理工艺,对比不同工艺下模具钢的横、纵向冲击韧性、抗弯强度和耐磨性能,并与7Cr5Mo2V钢进行对照。结果表明,9Cr5Mo2V钢在1030℃淬火、520℃回火热处理下具有极佳的硬度(63.6 HRC)和耐磨性能(260.16 min/mm3);970℃淬火、520℃回火热处理后,其纵向平均冲击功最高,达62.83 J;经970℃淬火、210℃回火热处理后,9Cr5Mo2V钢具有优良的抗弯性能,纵向抗弯强度为3621.9 MPa。9Cr5Mo2V钢的纵向冲击功和抗弯强度均高于横向的纵向冲击功和抗弯强度。

SEBS与β-NAs对PP的协同增韧作用及增韧机理研究

本研究以聚丙烯(PP)为基体、氢化苯乙烯-丁二烯嵌段共聚物(SEBS)和β成核剂(β-NAs)为增韧剂,采用熔融共混法制备了PP/SEBS/β-NAs共混物,研究了SEBS和β-NAs对PP的协同增韧作用并探究了增韧机理。结果表明:当添加20%SEBS和0.05%β-NAs时,得到的PP/SEBS/β-NAs共混物样品的冲击强度达到了76.1 kJ/m2,较纯PP(3.9 kJ/m2)提高了1851.3%。SEBS和β-NAs的协同效应不仅能够增韧PP,还能够提高其加工性能。β-NAs的加入会诱导所得样品的脆-韧转变行为在低SEBS含量下提前发生。增韧机理为,由于β-NAs的加入,PP/SEBS/β-NAs共混物体系中大部分α晶转化为β晶,致使PP晶粒细化,SEBS相尺寸变小、分散更均匀。在外力作用下样品中的SEBS相充当应力集中点,不仅SEBS相内部及SEBS相和PP的界面层会发生空穴化,还会诱导样品中的PP基体发生大量的剪切屈服形变,这些过程会吸收大量能量,赋予PP/SEBS/β-NAs共混物良好的韧性。