焊接冷裂纹临界冷却时间判据建立

用平板刚性拘束裂纹试验（ＰＲＲＣ）研究了４种国产低合金高强钢焊接冷裂敏感性，探讨了焊接接头扩散氢含量、焊接线能量、局部预热温度、拘束度的大小及局部预热产生附加应力等对钢材冷裂纹敏感性的影响。建立了国产低合金高强钢的临界冷却时间判据ｔｃｒ。实验表明此判据可靠，可用于评定现行焊接工艺条件下是否产生冷裂纹及确定合理的焊接工艺。     

低温环境下不同预热温度对T形接头焊接结果的分析

低温环境金属的焊接易导致焊接接头产生冷裂纹.为减少焊接冷裂纹的产生,需采用预热措施.采用焊条电弧焊在环境温度为-15℃下进行T形接头焊接仿真,运用Simufact-Welding软件分析焊件预热到80℃和120℃时焊缝处的残余变形和残余应力.结果表明,预热到120℃时,焊缝处的残余变形小;预热到120℃时,除焊缝起始点和终止点外,其余焊缝处的残余应力小.因此,合理控制预热温度,可减小晶粒脆化;适当增大t./5时间,有利于缓解接头的冷却速度,减小淬硬倾向.     

研究压杆稳定性应突出整体性效应

现行的材料力学教材中,大多认为临界应力的增大可以提高压杆稳定性。有不少教材将式σ_(cr)/σ≥n_w作为校核压杆稳定性的条件,笔者认为这一问题值得探讨。按此判断条件,由临界应力计算公式σ_(cr)=π~2E/λ~2知,可通过减低压杆柔度λ值来增大临界应力σ_(cro)又λ=ul/i,可设法增大i值以减低压杆柔度,从而达到提高压杆稳定性之目的。     

灰铸铁发动机缸体裂纹焊补工艺分析

灰铸铁发动机使用后出现裂纹,采用焊补修复,但由于外形尺寸比较大,结构复杂,若采用预热焊接需用专门的加热设备,焊接成本高,焊接周期长。通过对灰铸铁焊接性进行分析,提出用手工电弧焊修补发动机裂纹,选择合适的焊接参数和合理的焊接操作方法,取得预期的焊接效果,经济而实用。     

用插销法研究低碳钢和低合金钢焊接接头的应力腐蚀

插销法是焊接裂纹敏感性的试验方法。用插销法作为评定低碳钢、低合金钢焊接接头应力腐蚀破裂（Stress Corrosion Cracking，略记为SCC）性能的方法，并以施加于插销的临界初始应力σimpSCC作为评定SCC抗力的指标，用不同型号焊条焊制的20g和16MnR钢，焊接接头HAZ各区及焊缝在沸腾混合硝盐溶液（MNS）中的SCC敏感性的试验结果表明：以插销法的σimpSCC与分别以恒载拉伸法的σSCC和以悬臂弯曲法的J1SCC评定的接头各区SCC抗力的变化规律是一致的，文中还对SCC的亚临界扩展过程进行了讨论。     

高强度核电用钢厚板手工焊性能研究

介绍了武钢首批试制的高强度核电用钢厚板手工电弧焊性能研究,按照第三代核电技术(AP1000)用钢提出的焊接技术条件,对36mm和48mm两种规格的核电用厚钢板进行了手工焊焊接性能试验,研究结果表明:采用E9018-G-H4R核电专用焊条匹配WHD585E钢厚板所得焊接接头综合力学性能优良,能满足第三代核电用钢提出的焊接技术条件。     

WELDOX960E高强钢焊接接头组织与力学性能研究

通过拉伸、弯曲、冲击、硬度和金相组织分析等试验,对WELDOX960E高强钢焊接接头力学性能和组织进行了研究。研究结果表明:采用Union X96焊丝、MAG焊焊接WELDOX960E高强钢时,焊接接头具有良好的拉伸、冲击性能;弯曲性能还有待提高;WELDOX960E高强钢焊接接头粗晶区的硬度值最大,热影响区有软化现象出现;其焊缝组织为针状铁素体与贝氏体混合组织;熔合区组织为马氏体和少量M-A组元,且晶粒粗大;正火区组织为铁素体与珠光体。     

45#钢管焊接热裂纹产生的原因及对策

45#钢总体来说焊接性不算好,若焊材的选择不当或工艺处理不当都会导致焊接热裂纹的出现,热裂纹的产生主要与焊材或母材中碳、硫、磷含量过高有关,为避免热裂纹的出现,必须减少碳、硫、磷溶入焊缝,采用抗裂性好碱性焊条焊接或TIG。     

铁路车辆用GR65钢焊接性能研究

进行了29mm规格铁路车辆用GR65钢焊接性能研究,结果表明:GR65钢具有优良的抗裂性能,热影响区淬硬倾向较小。匹配WER60焊丝采用富氩气体保护焊接,焊缝组织为针状铁素体+少量的晶内先共析铁素体,焊接接头强度605MPa,焊缝-40℃冲击功达到171J,远高于技术条件要求。     

基于自蔓延反应的紫铜与钢异种接头焊接工艺研究

采用自蔓延焊接技术进行紫铜T2和Q235钢强磁场条件下焊接工艺研究,通过焊缝组织形貌观察及力学性能测试,结果表明利用自蔓延焊接工艺可克服异种金属之间性能差异,通过合金元素扩散可使焊缝形成良好的冶金熔合,其平均强度达275.8MPa。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

Western and Eastern culture differences in commercial field

The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity.     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

风的曲线

Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose.