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1.
为了提高TB6钛合金零件的疲劳抗力,研究了喷丸强化对TB6钛合金疲劳性能的影响,并采用白光干涉仪、X射线应力测量仪、显微硬度计及扫描电子显微镜等仪器对其表面完整性进行分析,探讨喷丸强化机制。结果表明:相比未处理的试样,喷丸处理试样的旋转弯曲疲劳寿命显著提高。喷丸强度对TB6钛合金的疲劳性能影响显著,随着喷丸强度的增加,残余压应力层和硬化层深度相应增大,对疲劳性能有利;而同时表面粗糙度也在增大,局部应力集中效应会抑制疲劳性能的改善。  相似文献   

2.
采用热模锻造方式制备出TB6与TC4钛合金行星齿轮架毛坯,并对毛坯进行热处理,然后切取试样,测试其高周疲劳性能,对比分析疲劳断口形貌。研究表明:TB6钛合金试样疲劳强度平均值为723.0 MPa,其在存活率90%、置信度95%条件下的疲劳强度下极限为677.1 MPa; TC4钛合金试样疲劳强度平均值为437.7 MPa,其在存活率90%、置信度95%条件下的疲劳强度下极限为405.8 MPa。从疲劳断口形貌上来看,TB6与TC4钛合金均以解理断裂为主,且二者均具有一定的韧性。TB6钛合金锻件疲劳强度的波动性小于TC4钛合金锻件,且高周疲劳性能更好,可以作为行星齿轮架的备选材料。  相似文献   

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激光金属沉积(LMD)是一种应用广泛的金属增材制造技术,可以快速成形复杂的结构件。以TA15钛合金粉末为原材料,采用激光金属沉积技术成形了TA15工字梁缩比件,进行了LMD TA15钛合金工字梁试样的疲劳试验和失效分析,研究了LMD TA15钛合金材料和结构的疲劳性能。对4件试样在应力比为0.06,载荷峰值为80%静力破坏载荷的交变载荷下进行四点弯曲疲劳试验,受成形缺陷影响,试样出现混合失效模式:两件试样无明显缺陷,裂纹形态为受拉缘条角裂纹,两件试样为内部气孔缺陷诱发失效,裂纹形态为受拉缘条半椭圆裂纹。起裂位置与缺陷和应力水平有关,存在明显的差异。为阐明试样疲劳失效行为,进行了有限元分析,获得起裂位置的应力水平,分析了缺陷和应力水平对疲劳寿命的影响。结果表明,缺陷是影响试样疲劳性能的主导因素,缺陷降低疲劳寿命50%以上,对于无明显缺陷试样,试样的疲劳行为受到应力水平控制。  相似文献   

4.
准确检测加工带来的残余应力,确保疲劳试样符合标准要求,对测定钛合金的疲劳性能至关重要。本文对目前常用的残余应力的测试分析技术进行了介绍,并对适合钛合金疲劳试样残余应力测试的技术进行了讨论。结果表明,X射线衍射法是目前最合适的钛合金疲劳试样残余应力测试方法。  相似文献   

5.
为了研究重熔处理对火焰热喷涂件疲劳性能的影响,本文应用火焰热喷涂技术在40Cr基体上制备出Ni60A自熔性粉末合金涂层,将热喷涂件经不同时间的火焰重熔处理后,应用疲劳试验机测试了喷涂试样及基体试样的弯扭疲劳寿命,分析了试样的宏观断口及极限应力。结果表明:重熔处理时间是影响热喷涂件疲劳寿命的关键因素之一。当重熔时间不足时,涂层表面缺陷为主要裂纹源,涂层与基体的结合力不强,极限应力随裂纹的萌生波动,裂纹在涂层中的扩展以微观第一阶段为主,断口大多为瞬断面,无疲劳辉纹,热喷涂件的疲劳寿命较短;当重熔时间过长时,涂层强度有所提高,但涂层中再次形成的缺陷为主要裂纹源,极限应力波动显著,裂纹在涂层中的扩展为微观第一阶段及第二阶段,断面有较明显的疲劳辉纹;当重熔时间合理时,缺陷对喷涂件疲劳寿命的影响减弱,构件疲劳寿命显著提高。  相似文献   

6.
基于摩擦修正的TB6合金流变应力行为研究及本构模型建立   总被引:1,自引:0,他引:1  
TB6合金是一种高强高韧近β钛合金。采用Gleeble-3500热模拟试验机对铸态TB6钛合金进行了等温热压缩变形试验,变形温度范围为700~900℃,应变速率范围为0.001~1.000 s-1,研究了铸态TB6合金热变形流变应力行为,分析了热压缩后的金相显微组织,基于摩擦修正后的流变应力曲线采用双曲正弦形式的修正Arrhenius关系对TB6钛合金的本构模型进行回归。结果表明:铸态TB6合金的热变形行为对变形温度和应变速率较为敏感,随着变形温度的降低和应变速率的增加流变应力显著增大;其热变形机制以动态回复和动态再结晶为主;得到铸态TB6钛合金热变形本构方程,比较回归模型计算的应力值与实测值其平均相对误差仅为1.48%,因此采用Z参数的双曲正弦函数形式能够较为精确地预测铸态TB6合金高温变形时的流变应力。以上研究为TB6钛合金塑性加工过程的模拟和控制提供了理论基础。  相似文献   

7.
研究了磨削、一次喷丸、二次喷丸3种表面加工方法对TC4钛合金表面完整性及高周疲劳性能的影响规律,采用白光干涉仪、X射线残余应力测试仪对经不同方法加工的试样的表面形貌、表面粗糙度和表面残余应力分布等表面完整性参数进行了表征。采用旋转弯曲疲劳试验机分别测试了不同方法加工的光滑试样(应力集中系数Kt=1)和缺口试样(Kt=2)的旋转弯曲疲劳S-N曲线。结果表明,相比磨削,一次喷丸和二次喷丸处理后TC4钛合金光滑试样和缺口试样的疲劳极限均显著提高,TC4钛合金的疲劳缺口敏感性下降。另外,二次喷丸的疲劳极限增益效果优于一次喷丸的,原因是二次喷丸在TC4钛合金表面形成了更优的残余压应力场分布和更低的表面粗糙度。  相似文献   

8.
采用拉-拉加载方式对等静压铍材进行高周疲劳试验,根据试验数据绘制了S-N曲线,获得其疲劳极限,并运用扫描电镜观察疲劳断口形貌。结果表明,等静压铍材在指定疲劳寿命10~7次下的疲劳极限为385 MPa;疲劳裂纹萌生于铍材试样边缘处,裂纹穿过晶界与相邻晶粒内的微裂纹连接合并长大;铍材试样发生瞬时解理断裂,形成主要由疲劳源和放射区构成的断口形貌;疲劳源尺寸随最大循环应力的减小而增大。  相似文献   

9.
本文通过等温锻压机对TB6钛合金进行等温锻造,锻造完成后锻坯采取水淬和空冷不同的冷却方式,冷却完成后水淬的锻坯进行时效处理,空冷的锻坯进行固溶时效处理。研究TB6钛合金等温锻后不同的固溶时效制度对钛合金组织和力学性能的影响。结果表明,TB6钛合金等温锻后水淬的α相尺寸小于等温锻后空冷的α相尺寸,水淬的钛合金β基体上无感生α相,空冷的钛合金β基体上有感生α相形成。水淬的钛合金经时效后析出的次生α相比空冷的钛合金经固溶时效后析出的次生α相更加混乱。TB6钛合金等温锻后水淬经时效的强度和塑性与等温锻后空冷经固溶时效的水平相当,但断裂韧度前者高于后者。  相似文献   

10.
硫化物夹杂对疲劳裂纹源萌生的影响有正负二重性.分析了硫化物形状、尺寸、分布和力学性能对高速钢W6Mo5Cr4V2冷轧芯辊疲劳断裂的作用.认为质软硫化物能够对脆性夹杂物起到包裹、缓冲过渡作用,减缓硬脆非金属夹杂物对基体产生的嵌镶应力,阻止疲劳裂纹的萌生.但其对基体的割裂作用依然存在.  相似文献   

11.
转炉炉壳热应力分析   总被引:5,自引:1,他引:4  
任学平  郭志强  邹家祥 《炼钢》2001,17(6):47-49
根据实际转炉建立实体模型。以有限元为手段,考虑了炉衬和炉壳材料的物性参数随温度变化的特点和炉衬与炉壳之间膨胀间隙,计算了转炉炉壳在温度载荷和炉衬膨胀压力同时作用下的热应力。所得结果可为转炉炉壳设计提供依据。  相似文献   

12.
Some theories of personality hold that an individual's perception of others is influenced by his own personality characteristics; more specifically, that a trait of low social value will be projected more into others, and that insight into the possession of these characteristics reduces this distortion. These 2 hypotheses were tested by having a group of college students rate each other (including themselves) on degree of friendliness or hostility. Agreement with group rating about self yielded the insight score. In general, the hypotheses were supported; the "friendly" Ss were most accurate in their perception of others, and insight was positively associated with accurate perception. From Psyc Abstracts 36:04:4HL16M. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

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The rates of infection of two methods of external ventricular drainage in use at Atkinson Morley's Hospital--namely, (a) percutaneous drainage with Rickham reservoirs and (b) tunnelled ventriculostomies--were compared in this retrospective review. Percutaneous drainage of CSF with Rickham reservoirs was associated with a 27% rate of infection as identified by positive microbiological cultures; tunnelled ventriculostomy catheters had a 10% infection rate. The difference in the infection rate between the two methods was statistically significant (P < 0.015). Other variables examined, including the age and sex of the patients and the reasons for ventricular drainage, were not associated with an increased rate of infection. Most infections from either method were caused by a coagulase negative staphylococcus. The average duration of ventricular drainage before identification of positive cultures was 5.7 days for Rickham reservoirs and 6.0 days for ventriculostomies.  相似文献   

17.
通过对焦炭在高炉内的历程及其变化规律的剖析,阐述焦炭热性能指标的意义,形象地把焦炭在高炉内的损耗分为三部分(M1,M2,M3)。指出M2对焦比及焦炭价格有一定的指导作用。  相似文献   

18.
Cancer of the cardia is traditionally discussed with cardiac cancer of the lower portion of the esophagus and upper gastric cancer invading the esophagus, and the specific characteristics of cancer of the cardia have never been clearly defined. We reviewed the outcome of 172 patients with adenocarcinoma of the cardia who had undergone radical surgery between 1949 and 1994 in the Division of Gastrointestinal Surgery of the Cancer Institute Hospital. The centers of the tumors were located within 2 cm above and below the boundary between the esophagus and the stomach, and their longitudinal diameter was less than 8 cm. We divided the patients into an early period (1949-1979; n = 79) and a late period (1980-1994; n = 93), and focused on the historical transition. There were no differences in patient gender or histology between the two periods. However, the late period was associated with fewer cases of esophageal invasion and shorter longitudinal diameter, as the age of the population advanced. The number of advanced cancers such as the localized and infiltrative type had decreased, and early cancer and early clinical stage had become more common, but despite the fact that the number of early cancers had increased, extended dissection, such as thoracic and paraaortic lymph node dissection, was performed more frequently. By clinical stage, the long-term outcome markedly improved in Stage I patient in the late period, and tended to improve in Stage II and III patients. This appears to have been attributable to the prevention of micrometastasis by extended dissection, although the number of early cancers is another major potential cause. There were no differences in the outcome of Stage IV patients between the two periods, and further advances in multimodality therapy must be awaited. The range of resection is basically proximal gastrectomy, and if there are adequate indications, the prognosis is favorable. In view of the status of lymphatic flow and lymph node metastasis, and long-term results, lateroaortic lymph node dissection is important. Since the number of early cancer patients has been increasing, if intraabdominal recurrence is prevented, intrathoracic lymph node dissection will contribute greatly to the outcome of such patients.  相似文献   

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Usage of quality of life of psychiatric patients' relatives as the parameter of estimation of the quality of psychiatric care is considered. By means of standard questionnaire elaborated by the authors as well as by means of both individual and group conversations the quality of life was analyzed in 40 relatives which lived together with psychiatric patients. Different spheres of their life and difficulties (financial, social-psychologic, production) were examined in families with such patients. The defects of psychiatric care that had direct influence on the quality of life of the psychiatric patients' relatives are outlined.  相似文献   

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