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Search Results: 1 - 10 of 304689 matches for " 王清远 "
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骨疲劳损伤研究
清远,Pidaparti,RM
力学进展 , 2002, DOI: 10.6052/1000-0992-2002-2-J2001-091
Abstract: 和所有人造的结构材料一样,骨在重复载荷作用下也会发生疲劳断裂.近年来,在骨疲劳损伤领域的研究已取得较大发展.本文综述了骨疲劳损伤的一些共同性研究课题,重点包括骨疲劳损伤的特性,基于骨疲劳微裂纹的损伤评估模型及骨疲劳行为的实验研究结果等.最后提出要更好理解骨疲劳损伤,修复和再生行为仍然有大量的研究工作需要开展.
复合材料修补件的强度和疲劳性能
清远,陶华
材料工程 , 2003,
Abstract: 复合材料贴片修补损伤金属结构件已被证明是一种可靠的低成本高效益结构补强延寿方法。对复合材料贴片修补前后的含裂纹7075-T6铝合金薄板进行了拉伸和疲劳性能研究。结果表明,修补后构件的强度和疲劳寿命都明显提高,随着硼-环氧复合材料补片层的增加,修补铝合金板的疲劳扩展速率显著下降,疲劳寿命可获得10倍以上的改善。基于Rose分析解发展了一个简单的疲劳寿命预测模型,通过与试验结果比较证明了该模型的简单有效。
西方国家公共图书馆治理的特点——以西方国家的文化管理体制特点为背景的分析
蒋永福,清远
图书情报工作 , 2010,
Abstract: ?西方国家文化管理体制的特点主要表现为:注重分权管理,即政策、决策、执行三个环节相分离;注重间接管理,即权力下放并在资金分配上遵循“一臂间距”原则;注重绩效管理,即在绩效评价上强调结果。西方国家的公共图书馆治理也形成了相应的特点,如在服务供给上,追求全面覆盖和普遍均等;在管理主体设置上,普遍采取理事会制;在经费投入上,以地方政府为主,中央政府予以大力支持;在治理评价上,普遍强调结果为重。西方国家公共图书馆治理的特点对我国具有重要的借鉴意义。
PBL与PZ型剪力连接件抗拉拔性能试验
薛辉,清远
- , 2016,
Abstract: 中文摘要: 本文采用12个PBL和3个PZ型剪力连接件试件,通过一套自主设计的单调加载装置,进行了极限抗拉拔承载力、相对位移、剪力键应变和破坏模式的测试试验,比较了开孔大小、埋置深度以及剪力键类型对试件极限抗拉拔承载力、初始开裂荷载和破坏模式的影响;并根据试验结果拟合了PBL剪力键极限抗拉拔承载力的计算公式。研究结果表明:加大孔径能直接提高PBL剪力键的极限抗拉拔承载力,当孔径由0mm增长到30mm,极限抗拉拔承载力增长率最大可达34.5%;埋置深度的增加较孔径能更显著地提升剪力键的极限抗拉拔承载力,当埋深由110mm增长至225mm,PBL和PZ型剪力连接件对应的极限抗拉拔承载力的增长率可分别达到224%和165%;PZ型剪力连接件较相同埋深的PBL剪力键有更大的极限抗拉拔承载力,同时由于其良好的疲劳性能,不同几何尺寸和构造的PZ型剪力连接件力学性能的研究工作有待进一步开展。
Abstract:This paper presents a study on the pull-out behavior of the PBL shear connector and the PZ shaped composite dowel, a total of 15 specimens, by using a self-designed monotonic loading equipment, aimed to study the ultimate uplift capacity, initial crack load, failure pattern and strain states of the steel web during the loading progress, the influence of the hole size, depth of embedment and form of the shear connector were considered. Based on the results of the PBL shear connectors, the calculation formula for ultimate pull-out bearing capacity was established. The results showed that the enlargement of the hole size or embedment depth could lead to direct increase on the ultimate pull-out bearing capacity of these two shear connectors. Ceteris paribus, the PZ shaped dowel had bigger bearing capacity than the PBL one, also better fatigue property based on other researchers’ work, which could lead to further study on the mechanical property of the PZ shaped dowel with various geometric dimensions.
CFRP加固混凝土短柱轴压性能研究
Performance Study on Axial Compression of CFRP-Strengthened Concrete Columns
 [PDF]

刘晓凯, 清远, 志宇
Hans Journal of Civil Engineering (HJCE) , 2015, DOI: 10.12677/HJCE.2015.43014
Abstract:
通过对6个混凝土柱的静力加载试验,本文研究了碳纤维布加固对不同截面混凝土柱的力学性能的影响,分析了碳纤维布粘贴层数及短柱截面类型对碳纤维布加固效果的具体影响。结果表明:碳纤维布可明显提高混凝土柱的刚度和极限承载力,减小柱的竖向位移,减小柱的横向应变和纵向应变;当碳纤维布粘贴层数为两层时,其影响程度比粘贴一层时更为显著,但其提高程度不与加固面积成正比;碳纤维布加固对混凝土圆柱极限承载力和刚度的提高优于对混凝土方柱的提高。
Through the static load test of six CFRP reinforced concrete columns, the paper studies the CFRP reinforced concrete columns with different cross section of the influence of mechanical properties, and analyzes the specific influence of the carbon fiber cloth paste layer and column’s section type to carbon fiber cloth reinforcement effect. The results show that: Carbon fiber cloth can obviously increase the stiffness and ultimate bearing capacity of concrete columns, reduce the vertical dis-placement of column and reduce the lateral strain and the axial strain of the columns. When the paste layer of carbon fiber cloth is two, the impact is more obvious. But the increase degree is not proportional to the reinforced area; the improvement of carbon fiber cloth reinforcement to con-crete columns’ ultimate bearing capacity and stiffness is superior to the improvement of concrete square column.
波形钢板焊接连接件的疲劳试验研究及寿命评价
志宇,清远
建筑结构学报 , 2015,
Abstract: 通过对波形钢板焊接连接件(以下简称焊接件)的等幅疲劳加载试验和有限元分析,研究此类焊接件的应力集中特性,并对其进行寿命评价。结果表明:疲劳荷载作用下该类焊接件的破坏模式可类比于焊接波形钢腹板H形钢梁(以下简称钢梁),即发生在近波形钢腹板倾斜段终点部位焊趾处的典型疲劳破坏;波形倾斜段倾角和曲率半径与波高的比值对波形钢板平直与倾斜过渡段部位的局部应力集中影响显著,应作为设计控制参数;研究提出了将以上两参数作为变量的应力集中(即仅考虑几何应力)计算式;采用该几何应力方法可以减小波形倾斜段倾角对疲劳寿命数据离散性的影响,从而使疲劳评定简化。通过引入波形钢板焊接构造细节的应力集中系数,对不同波形倾斜段倾角情况下焊接件的疲劳寿命进行预测;将规范典型焊接接头构造细节的疲劳寿命与焊接件疲劳试验结果进行了对比。结果表明:采用AASHTO-2004规范和JSSC-1993规范对波形倾斜段倾角为45°和60°的连接细节可基本采用同一寿命评价等级;从97.7%保证率的角度考虑,波形倾斜段倾角为30°、45°和60°的连接细节可分别采用与GB50017—2003规范对应的3类、4类、5类构件和连接,与TB10002.2—2005规范对应的Ⅲ类、Ⅶ类和Ⅷ类来评价其寿命。
结构金属材料超高周疲劳破坏行为
清远,刘永杰
固体力学学报 , 2010,
Abstract: 受传统试验方法的限制,结构材料的疲劳研究范围常限于107周次以内。然而,过去十年出现了一系列意料之外的破坏事件,尤其是对于认为具有明显疲劳极限的钢铁结构部件。因此,对于不同材料达到1010周次的超高周疲劳行为的研究引起了广泛关注,尤其是近年来成为了热点。本文综述了结构金属材料超高周疲劳的研究现状并介绍了其基本方面。主要内容包括加速疲劳试验方法的发展与应用、超高周疲劳引起的内部断裂的裂纹萌生机制与扩展特征、S-N曲线的形状特点、疲劳极限存在性及其预测、加载频率和环境及表面状况的影响等。在此基础上提出值得进一步研究的一些方向。
超声表面冲击对Ti6Al4V生物相容性的影响
曹小建,,清远
- , 2018, DOI: 10.15961/j.jsuese.201700325
Abstract: 中文摘要: 钛合金植入物与人骨弹性模量相差较大,易产生应力遮挡而导致假体松动和骨质变化,临床上虽然在钛合金假体表面镀生物活性膜,但膜厚度仅数微米,有必要研究能同时提高植入物组织相容性和生物力学性能,又降低应力遮挡效应的方法。在静荷载25 N、振幅30 μm、冲击数36 000 次/mm 2下对Ti6Al4V钛合金进行超声表面冲击强化(UNSM)处理,对UNSM处理后的表面形貌、强塑性变形层(表面纳米层)、模拟体液中的极化曲线、腐蚀形貌、表面沉积物、预腐蚀两周后的疲劳行为、纤维软骨细胞的黏附等进行分析,并与复合表面(UNSM+TiN镀膜)处理试样进行对比。结果表明:超声冲击后表层获得约40 μm深的纳米晶层;尽管冲击后Ti6Al4V表面的腐蚀电流密度和点腐蚀增强了,但模拟体液预浸泡两周后Ti6Al4V钛合金10 8周次的疲劳强度仍被显著提升;内部裂纹均萌生于100~250 μm深的粗晶变形层内,因为该粗晶变形层内残余压应力迅速减小,塑性和韧性较表面纳米层低;经模拟体液浸泡后,纳米表面形成的钙磷沉积物结节显著增多;表面积的增加和合适的表面粗糙度促进了软骨纤维细胞的早期黏附;UNSM处理后再覆盖TiN膜能进一步提升Ti6Al4V的生物相容性。纳米晶弹性模量的减小和晶粒尺寸的梯度变化有助于对抗应力遮挡,复合表面纳米化技术对金属植入物的发展有积极的意义。
Abstract:Because the difference of elastic modulus between titanium alloy implants and human bones is large,prosthetic loosening and osseous change usually happen due to the stress shielding.Though bioactive films are coated onto the Ti-base implants for the clinical application,the thickness is limited several microns.Therefore it is necessary to search a method,which can improve the biocompatibilities and smooth the stress gradient.Ultrasonic surface impact (ultrasonic nanocrystal surface modification,UNSM) was carried out with the condition of a static load of 25 N,vibration amplitude of 30 μm and 36 000 strikes per unit on Ti6Al4V.The surface topography,severe plastic defornation layer,polarisation curve in simulated body fluid (SBF),corrosion feature,surface depositions,corrosion fatigue behavior of Ti6Al4V which was pre-soaked into SBF for two weeks,and the adhension of fibrochondrocyte were studied.A depth of 40 μm nanocrystal surface layer is achieved.UNSM improves the fatigue strengths of Ti6Al4V in SBF though the current density of corrosion is increased and the pitting corrosion is accelerated.Inner cracks usually appear at coarse grained deformation layer between the depth of 100~250 μm,because the residual compressive stress is reduced and the toughness is lower than the surface.Calcium and phosphorus nodules are significantly enhanced on UNSMed surface.The earlier adhension of fibrochondrocyte can be promoted at the same while.Coating a TiN film on the UNSMed surface helps to improve the whole biocompatibilities of Ti6Al4V further.The gradient of elastic modulus and grain size are helpful to resist stress shielding.Hybrid surface modification has positive significance for metal implants.
2024--t3和2524--t34铝合金疲劳裂纹的萌生机制
李棠,陶俊林,清远
材料研究学报 , 2011,
Abstract: ?通过2024--t3和新型2524--t34铝合金的疲劳实验和对试样表面及疲劳断口的观测,研究了材料的微观结构和疲劳裂纹萌生机制。实验在室温下完成,应力比为0.1、加载频率为15hz。结果表明:实验材料呈现了再结晶的层状晶粒结构,晶粒沿着轧制方向被拉长,并较为平坦。2024铝合金中二相粒子的分布更为密集无序,且粗大、不规则形状的二相粒子分布更多,而2524铝合金中二相粒子多沿轧制方向呈带状分布。2524铝合金中的多数裂纹萌生于材料中含fe的粗大的$\beta$相粒子,并伴有少量的滑移带裂纹形核和材料缺陷裂纹形核等;包铝层的滑移带形成的挤入挤出为2024和2524包铝合金的裂纹多处形核提供了主要位置。
DZ125合金超高周疲劳微观裂纹萌生机制
许罗鹏 , ZHOU Min , 清远
- , 2018, DOI: 10.15961/j.jsuese.201700907
Abstract: 中文摘要: DZ125合金具有优良的综合性能表现,已被广泛应用于燃气涡轮高温部件的铸造。关于DZ125合金的疲劳问题研究已有较多文献报道,但从微观断口分析的角度系统阐述该合金超高周疲劳裂纹萌生及失效机制的研究则相对较少。通过研究发现,随着疲劳强度的降低,疲劳数据离散性有增大的趋势;较小的疲劳应力(小于220 MPa)所对应的疲劳寿命并未有明显增加,上述特征与疲劳微观裂纹萌生机制的改变直接相关。在高应力作用下,疲劳裂纹倾向于从材料的表面或次表面萌生,巨型二次裂纹成为其断口形貌的主要特征;在低应力状态下,材料内部的孔洞缺陷是疲劳裂纹萌生的主要区域,并严重影响材料的疲劳寿命。驻留滑移带(PSB)可导致表面粗糙区的形成,成为裂纹尖端的主要特征。主裂纹与其他二次裂纹存在竞争关系,并最终引起疲劳断裂的发生。基于Murakami公式,DZ125合金在裂纹萌生阶段的平均应力强度因子为3.15 MPa·m 1/2,裂纹快速扩展阶段的平均应力强度因子和材料的断裂韧性(K IC)分别为7.72和15.70 MPa·m 1/2。
Abstract:The DZ125 alloy has excellent mechanical, fatigue, and high-temperature behaviors. It has been widely used in high-temperature gas turbine components. Although a lot of researches have been carried out on the fatigue problem of the DZ125 alloy, there are still few systematical studies on the fatigue crack initiation mechanism and its failure mechanism during very high cycle fatigue (VHCF) by microscopic fracture analysis. It is found that the scatter of fatigue data increases as fatigue stress decreases, and the fatigue life does not increase significantly even at a low fatigue stress (<220 MPa). The above characteristics are directly related to the change of micro-crack initiation mechanism. Under a high fatigue stress, micro-crack tends to initiate from surface or sub-surface of specimen, and the large secondary crack is the main feature of its fracture morphology. At a low fatigue stress, micro-crack is likely to initiate from interior material defects, and the existence of these defects can seriously affect the fatigue life. Persistent slip bands (PSB) lead to the formation of rough surfaces, which is the main feature at the crack tip. The main crack competes with other secondary cracks and eventually causes fatigue fractures. The results of the Murakami equation show that the average stress intensity factor at micro-crack initiation stage is 3.15 MPa·m 1/2, the average stress intensity factor at the onset of unstable crack propagation is 7.7 MPa·m 1/2, and the average fracture toughness ( K IC) is 15.70 MPa·m 1/2.
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