拉伸载荷作用下基体表层激光离散预处理对铬镀层／45钢基开裂行为的影响

采用激光离散预处理钢基体再电镀铬层技术得到了一种新型复合结构，研究了这种新型复合结构在拉伸载荷作用下的开裂行为特征，并与无激光处理钢基体的试样在同样试验条件下的开裂特征进行了对比分析。结果表明：有激光离散预处理钢基体试样的承载能力要高于无激光预处理钢基体试样的承载能力，且有激光处理的试样开裂区域在两个激光带之间（无激光处理区），主裂纹呈现明显的周期性特征。本研究结果可归结为激光预处理钢基体不仅改善了基体表层的应力状态和力学性能，而且还改善了后续铬镀层的力学性能。     

Shaped charge penetration into high- and ultrahigh-strength Steel–Fiber reactive powder concrete targets

Experiments on shaped charge penetration into high and ultrahigh strength steel-fiber reactive powder concrete (RPC) targets were performed in this paper. Results show that the variation of penetration depth and crater diameter with concrete strength is different from that of shaped charge penetration into normal strength concrete (NSC). The crater diameter of RPC is smaller than that of NSC penetrated by the shaped charge. The jet particles are strongly disturbed and hardly reach the crater bottom because they pass through the narrow channel formed by jet penetration into the RPC. The effects of radial drift velocity and gap effects of jet particles for a shaped charge penetration into RPC target are discussed. Moreover, a theoretical model is presented to describe the penetration of shaped charge into RPC target. As the concrete strength increases, the penetration resistance increases and the entrance crater diameter decreases. Given the drift velocity and narrow crater channel, the low-velocity jet particles can hardly reach the crater bottom to increase the penetration depth. Moreover, the narrow channel has a stronger interference to the jet particles with increasing concrete strength; hence, the gap effects must be considered. The drift velocity and gap effects, which are the same as penetration resistance, also have significant effects during the process of shaped charge penetration into ultrahigh-strength concrete. The crater profiles are calculated through a theoretical model, and the results are in good agreement with the experiments.     

自我革新的坚实逻辑起点——解读“党的先进性是具体的历史的”

十六大报告指出 :“党的先进性是具体的、历史的” ,这是江泽民同志和党中央在深深的忧患意识支配下对我们党自身前途和命运深刻反思的结果 ,是我们党在新的历史条件下自我批判自我革新的宣言 ,为我们坚持党的先进性找到了一个坚实的逻辑起点和实践上的切入点、着力点。进步从来不是抽象的 ,工人阶级的先进性、党的先进性也从来不是抽象的 ,这不仅因为是否先进要看实践 ,更因为党的实践是具体的历史的 ,社会进步的标准是具体的、历史的、全面的和相对的     

917低磁钢与铝合金爆炸焊接复合实验研究

采用异种金属爆炸焊接复合技术 ,研制了 91 7低磁钢与LF5、LF2 1、LF1 1等铝合金的爆炸焊接复合板 ,并对该铝—钢复合板力学性能进行了实验研究 ,对复合界面进行了金相分析 .实验结果表明 ,该铝—钢复合板复合界面物理结合良好 ,其抗剪和抗弯强度满足实船使用要求     

回弹法评定火灾后混凝土强度的试验研究

火灾高温作用后，混凝土的强度将发生变化。通过试验，对影响混凝土强度的因素进行了分析，并建立了利用回弹法评定火灾后混凝土抗压强度的专用测强曲线及计算公式，为编制火灾后混凝土结构检测评估技术规程提供试验依据和数据。     

Physical and damping properties of kenaf fibre filled natural rubber/thermoplastic polyurethane composites

The paper presents the investigation of the effect of alkaline treatment of sodium hydroxide (NaOH) on physical and dynamic mechanical analysis (DMA) viscoelastic properties of kenaf fibre filled natural rubber (NR)/thermoplastic polyurethane (TPU) composites. The treated kenaf fiber, NR and TPU were weighed and proportioned according to the required compositions and were blended using hot mixed Brabender machine. The polymer composites were then fabricated using the hot press to form a sample board. The sample was cut and prepared and water absorption, density, thickness swelling and DMA tests were performed. As far as physical properties are concerned, composites with the highest NR amount of shows the best results, which indicates good fiber bonding adhesion. The polymer composites with the highest amount of TPU shows the highest damping properties at high temperature.     

低活性粉煤灰在混凝土中的应用研究

为提高低活性粉煤灰在混凝土中的利用，依据《水泥胶砂强度检验方法》和《普通混凝土力学性能试验方法标准》，通过复掺CaO、CaSO4及防水剂、减水剂等材料对低活性粉煤灰进行了活化实验研究和混凝土性能测试研究，试验结果表明：经过活化处理后的粉煤灰重新获得了活性，提高了混凝土的强度、降低了泌水率、减小了坍落度经时的损失，从而有助于低活性粉煤灰的开发利用。     

Effect of bending temperatures on the microstructure and springback of a TRIP steel sheet

Transformation-induced plasticity (TRIP) steel possesses high strength and formability, enabling the use of a thinner gauge material and allowing for the fabrication of complex shapes. In this research, we measured the effect of bending temperatures on the microstructure and air-bending springback angle of TRIP steel at temperatures from 25 to 600 °C. Real-time in situ X-ray diffraction and scanning electron microscopy were used for pre- and postbending analysis. As the prebending temperature increased from 25 °C to 600 °C, the retained austenite (RA) volume fraction decreased, and the RA transformed to bainite at temperatures above 400 °C. The springback angle was positively correlated with the prebending RA volume fraction, with the smallest springback angle achieved at 400 °C. Additionally, the springback angle was positively correlated with the bending angle, because the RA transformation ratio contributed to increased strain hardening. Further microstructure analysis revealed that the RA became elongated in the tension direction as the bending temperatures increased.     

Polyurea coating for foamed concrete panel: An efficient way to resist explosion

Autoclaved aerated concrete (AAC) panels have ultra-light weight, excellent thermal insulation and energy absorption, so it is an ideal building material for protective structures. To improve the blast resistance of the AAC panels, three schemes are applied to strengthen the AAC panels through spraying 4 mm thick polyurea coating from top, bottom and double-sides. In three-point bending tests, the polyurea-coated AAC panels have much higher ultimate loads than the un-coated panels, but slightly lower than those strengthened by the carbon fiber reinforced plastics (CFRPs). Close-in explosion experiments reveal the dynamic strengthening effect of the polyurea coating. Critical scaled distances of the strengthened AAC panels are acquired, which are valuable for the engineering application of the AAC panels in the extreme loading conditions. Polyurea coatings efficiently enhance the blast resistance of the bottom and double-sided polyurea-coated AAC panels. It is interesting that the polyurea-coated AAC panels have much more excellent blast resistance than the CFRP reinforced AAC panels, although the latter have better static mechanical properties.     

SFPB处理的38CrSi钢表面纳米化层微观结构特征

采用超音速轰击技术（Supersonic Fine Particles Bombarding，SFPB）对调质态合金钢38CrSi进行表面纳米化处理，在材料表面制备了纳米结构表层；利用X射线衍射、扫描电镜和透射电镜等分析技术研究了表面纳米层的微观结构特征。结果表明：经SFPB处理后，材料表层发生了严重的塑性变形，表面形成了晶粒尺寸约为15nm的纳米结构层，微观应变约为0．19％；表面纳米层的厚度约为20μm（晶粒尺寸〈100nm），纳米晶粒的尺寸随着距表面距离的增加而增大；在距表面40μm的范围内，高密度的位错墙和位错缠结将晶粒分为了尺寸为200～400nm的胞块结构，分析表明表面纳米化主要是位错运动的结果。