斜搭接连接件疲劳特性分析

为了研究搭接角度对斜搭接连接件疲劳特性影响的规律,对不同搭接角度的斜搭接连接件进行了疲劳试验,并利用有限元软件对紧固孔在拉伸状态时的应力场进行了分析,采用名义应力法对紧固孔的疲劳寿命进行了估算。结果表明:失效部位发生在第一排孔边处;疲劳寿命随着搭接角度的增加而增大;搭接角度与疲劳寿命近似曲线关系为lg N=6.047-1.020×0.6601α。     

中外合资企业跨文化人力资源管理模式及应用

本文以上海大众汽车有限公司为例，运用比较管理心理学理论，从跨文化的角度详细研究和比较了中德两国在企业人力资源管理上的各自特点与具体作法，并在借鉴与吸收德国管理经验的基础上，结合中国国情和企业实际，提出在合资企业中建立＂共同管理文化＂（ＣＭＣ）的跨文化人力资源管理模式。     

GH4145激光点焊工艺及接头性能研究

目的研究不同工艺参数下高温合金的微激光点焊接头性能。方法利用Nd:YAG激光器对厚度为0.23 mm和0.13 mm的GH4145进行搭接点焊,利用微型拉伸机、金相显微镜、硬度计对接头的物理性能进行测试,并观察组织结构。结果脉宽长度为6.0 ms,输出功率百分比为20%(输出功率16 W)时,最大拉伸剪切力为178.59 N,靠近焊点中心位置两边测试点硬度分别达到HV517和HV506。结论接头表面熔化尺寸、焊接接头的拉伸剪切力和硬度随着激光功率的增大而增大,增大到一定值时停止变化,不同参数下达到不同的最大值,组织无明显规律变化。近表面处出现等轴晶,表面以下至熔合线的显微组织为树状晶。通过激光搭接点焊将两片GH4145连接,接头处拉伸剪切力、硬度均低于母材,功率增大有助于提高接头的抗拉强度。     

The Performance of Venture-Backed Firms: The Effect of Venture Capital Company Characteristics

This paper deals with the empirical investigation of the question as to which type of venture capital (VC) companies determines the growth and survival of istics of VC companies as additional factors that explain the high variation of the employment growth rate of portfolio firms and their probability of surviving. Surprisingly, venture- backed firms financed by independent VC companies are not among the most successful firms. Independent VC companies are some of those with the greatest profit orientation and hence, a high quality of the value chain process is to be expected. Significantly higher employment growth rates are evident for firms financed by locally active VCs. Changes in the board of directors do not have a positive effect on firms' performance. Syndicated investment strategy seems to be a successful strategy.     

铺层方式对CFRP-Al单搭接接头胶接性能的影响

使用热压罐制备[45/-45]_4s、[0/90]_4s和[0/45/-45/90]_2s三种铺层方式的CFRP层合板,然后在室温下与Al胶接制备出单搭接试样。使用电子万能试验机、数字图像相关法(DIC)和扫描电子显微镜(SEM)等手段测量胶接接头的拉伸载荷-位移曲线和应变分布并观察断口形貌。基于试验数据分析不同铺层方式下CFRP-Al单搭接接头的拉伸性能,研究了铺层方式对CFRP-Al单搭接接头胶接性能的影响和铺层方式胶接接头的破坏机制。结果表明,在拉伸过程中[45/-45]_4s试样出现塑性变形阶段其拉伸位移最大,而[0/45/-45/90]_2s和[0/90]_4s试样的拉伸位移较小且发生了脆性断裂。铺层方式从[45/-45]_4s到[0/45/-45/90]_2s再到[0/90]_4s,试样的极限载荷和纤维束断裂数量增加、层间剪切力减小、应变集中程度和分层破坏程度降低。     

船用铝-钢爆炸复合过渡接头性能要求及分析

对铝-钢爆炸复合过渡接头的材质及规格、制造工艺、标准规范、性能要求、焊接要求等方面进行了介绍及分析,为过渡接头的检验、验收和标准的修订提供了一定的参考。     

设周边缝对小湾高拱坝工作性态的影响

用非线性有限元对小湾高拱坝(坝高292．0m)设周边缝时的工作性态进行研究。模型中考虑了缝面应力与变位的非线性重调整,考虑了坝体、坝基材料非线性和周边缝接触非线性的耦合,模拟了缝的开裂、滑移等非线性。对设缝深度、范围、以及干缝、湿缝等对高拱坝拱冠、坝踵和坝肩等关键部位的位移场和应力场的影响进行了分析研究,并对设缝前后建基面、坝踵附近的开裂区和屈服区进行分析,研究结果表明,设周边缝可以有效地降低高拱坝坝踵的粱向拉应力,对坝踵附近应力影响较大,坝体其它部位应力和位移变化不大。     

近等原子比钛镍合金氩弧焊接接头的组织和性能

借助金相显微镜、拉伸实验和弯曲回复法等手段研究了近等原子比钛镍形状记忆合金氩弧焊接接头的组织和性能。研究结果表明,近等原子比钛镍形状记忆合金氩弧焊接接头的显微组织可分为三个区,分别是粗大柱状晶区、细小柱状晶区和热影响区。由于焊接接头显微组织与母材之间的差别,在相同的应变下,近等原子比钛镍形状记忆合金氩弧焊接接头的回复温度明显高于母材,记忆性能变差。焊接后的近等原子比钛镍形状记忆合金的屈服强度与母材相近,但抗拉强度和延伸率远低于母材。氩弧焊接近等原子比钛镍合金的显微组织在热处理后不会发生明显变化,经过形变后,焊接接头的回复温度与母材仍有差别,显微组织的不同是造成这一现象的原因之一。     

Innovation Systems and Industrial Performance Germany in International Perspective

How do national-institutional structures affect the ability of enterprises to respond to increased competitive pressures in product markets and a speeding-up of product life-cycles? The papers in this special issue explore the workings of national, regional and sectoral innovation systems of which German enterprises, universities and other organizations form part. They suggest that while some high-tech market niches are well suited to German strengths in incremental innovation, the German institutional setting tends not to favour high-risk innovation strategies in newly emerging technologies     

Ownership Increase in International Joint Ventures: The Within- and Across-Country Flexibility Perspective

We employ the real options perspective to examine how multinational corporations (MNCs) increase ownership levels in their international joint ventures (IJVs) to exploit (or utilize) both within- and across-country flexibility. This paper utilize a rich dataset of South Korean firms’ foreign affiliates to test hypotheses derived from the real options theory. It examines the roles of growth options that require small equity stakes under uncertainty as well as switching options that require controlling equity stakes to coordinate switching implementation. Specifically, we examine how the ownership of jointly-owned foreign subsidiaries changes under the influence of changing labor cost uncertainty. We utilize a two-stage model to address the sample selection bias associated with a subsidiary’s choice of joint venture under the influence of high labor cost uncertainty. In the first stage, we run a probit model with a dummy variable for JVs and wholly-owned subsidiaries (WOSs) (1: JV, 0: WOS) as the dependent variable. In the second stage, we run a panel logistic regression model (STATA command, “xtlogit”). We found that MNCs engaged in greenfield IJVs increase their initial ownership when labor cost uncertainty within their host countries is favorably resolved. We also found that MNCs’ tendency to increase their IJV ownership intensifies when their subsidiary networks are exposed to negatively correlated labor cost growth rates across countries. Taking within and across country flexibility perspective, this study adds new insights on MNC ownership changes, especially in IJVs. Based upon our findings, we conclude that MNCs make flexible ownership adjustments for their foreign subsidiaries in response to different uncertainty conditions within and across countries.     

ZK60镁合金光纤激光焊接工艺参数及接头性能研究

目的 采用光纤激光对ZK镁合金进行焊接,分析焊接工艺参数对焊接接头性能的影响规律。方法 采用正交实验方法,在焊接过程中对焊接主要的工艺参数比如:激光的功率,焊接的速度,离焦量进行三因素三水平正交实验,采用拉力实验机对焊接接头进行抗拉强度测试,得到抗拉强度最大的工艺参数组合。对焊缝微观组织及断口形貌进行分析。结果 当激光功率为1 400 W、焊接速度为40 mm/s、离焦量为3 mm时,焊缝抗拉强度达到最高的308 MPa,达到母材抗拉强度的95%。结论 在合适的工艺条件下,光纤激光焊接过程中,如果热输入较低,焊接速度过快,导致熔池冷却速度非常快,同时细化了晶粒,提高焊缝接头的综合力学性能。     

L360QCS微合金钢焊接接头抗SSCC性能分析

经过反复焊接工艺试验,确定了合理的L360QCS微合金钢焊接工艺参数,针对L360QCS微合金钢焊接接头进行了抗SSCC试验研究。结果表明,焊接接头屈服强度为410 MPa,抗拉强度为528 MPa,平均冲击功值为145J,弯曲试验、刻槽锤断试验均未见缺陷,各类力学性能指标合格;根焊层、填充层、盖面层平均硬度值分别为136.6HV、146.3HV、157.1HV;根焊层、填充层微观组织晶粒细小,为等轴铁素体+珠光体盖,盖面焊层组织晶粒较粗大,为粒状贝氏体+珠光体+针状铁素体;焊接接头SSCC试验未出现裂纹,经XRD、SEM分析,腐蚀产物膜为呈堆砌状态的四方晶系晶体FeS。L360QCS微合金钢焊接接头能够满足NACE TM0177-2005标准规定的抗SSCC性能要求。     

复合板基层厚度对激光焊接头腐蚀性能的影响

目的通过探索基层金属厚度对复合板激光穿透焊接的影响规律,分析其影响度与焊接速度、激光功率的差别,为双金属复合材料激光穿透焊接提供更多的技术支撑。方法以焊接速度、激光功率和基层金属厚度为变量,设计了三因素三水平的正交实验,对X65/DSS2205层状双金属复合材料进行激光穿透焊接实验,对不同焊接条件下接头的显微组织进行观察分析,采用EDS面扫方法对焊缝复层区进行成分扫描,测量接头复层侧动电位极化曲线,并比较了基层金属厚度的影响度较焊接速度与激光功率的大小。结果双金属复合板激光穿透焊接接头显微组织在厚度方向存在明显的分层;基层金属厚度为1.2 mm时,复层贵金属元素保留量最大;随着基层金属厚度的减小,接头综合耐腐蚀性能提高;基层金属厚度对接头耐腐蚀性能的影响小于焊接速度和激光功率2个变量;焊接速度为2.5 m/min,激光功率为3500 W,基层金属厚度为0.8 mm时,接头耐腐蚀性能最优。结论基层金属厚度对于复合板激光穿透焊接接头的焊缝复层元素含量、以及接头复层一侧耐腐蚀性能都有较为明显的影响,但相比于焊接速度与激光功率,其影响度相对较小,因此在进行复合板激光穿透焊接时,在选定基层金属厚度后,仍要对焊接速度和激光功率进行优化工艺设计。     

TA1钛合金自冲铆接头力学性能及微动行为

本工作以TA1自冲铆接头为研究对象,基于拉伸-剪切和疲劳试验分析了接头的力学性能,并采用扫描电镜从微观层面研究了接头的拉伸-剪切失效机理、疲劳失效机理及微动行为。结果表明:拉伸-剪切失效模式为铆钉腿部从下板拉脱,铆钉颈部存在不同程度的断裂。疲劳失效模式主要为上板断裂失效,其疲劳极限约为1.18 kN。疲劳裂纹从上板与铆钉头接触部位萌生,在持续微动磨损及疲劳循环应力作用下,沿板厚和板宽方向不断扩展,直至接头疲劳断裂。微动磨损的剧烈程度直接影响接头疲劳失效模式。上板与铆钉头接触区的微动磨损源于板宽W区域,随着微动过程的不断进行,逐步向板长L区域扩展。     

硅烷处理对有机涂层／金属胶接接头力学性能的影响

研究了硅烷处理的胶接接头的力学性能,分析了硅烷处理对涂层/金属界面力学性能的影响.对碳钢表面进行硅烷处理,用环氧树脂胶黏剂粘接.对疲劳后的胶接接头施加静态载荷,通过分析硅烷处理胶接接头的应力-应变曲线及接头破坏形式,得出疲劳破坏与静载破坏的区别.结果表明:硅烷处理的胶接接头经一定周次疲劳后能提高接头的粘接强度,接头的破坏形式虽然为界面断裂但却为韧性断裂;接头静拉破坏形式为界面破坏和内聚破坏的混和破坏.