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在制造业中,夹具是产品在制造各个工艺阶段中地位处在非常重要的工艺装备之一.在生产中,厂家所使用到的夹具的工作效率、质量、精度及夹具的使用的可靠性和安全性,都会对所要生产的产品的加工质量及生产效率造成决定性的影响.因此夹具选择,使用对于厂家非常重要.夹具用于对加工对象的固定,使工件处在正当的加工位置上,以便于下一步的加工需要.夹具的类型分为普通夹具,专用夹具,组合夹具,标准夹具,可调夹具等.本文是针对半轴轴承套设计的专用夹具,主要参考了《机床夹具设计》和《机床夹具及应用》里面所介绍的一系列方法,并大量查阅了《机床夹具设计手册》中的设计参数从而设计出来.通过对夹具进行合理化的设计,保证夹具的精度,可靠性和生产率. 相似文献
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本文详细介绍了滚珠挡条的数控加工及夹具设计,通过设计出一种合理的夹具可以解决加工滚珠挡条过程中出现的难点问题.重点是对利用设计的夹具保证安装固定滚珠挡条五个槽面和安装传输轴的24个孔φ1 1mm必须达到图纸的形位精度和表面粗糙度的要求,同时能快速控制滚珠挡条的总长度以及提高加工效率等作了较为详细的介绍,通过作者的实践,成功完成了滚珠挡务数控铣削的加工及夹具设计. 相似文献
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根据多路阀的特点制作了加工工艺,设计了刀具和夹具.在工艺方面,选用了珩磨加工方法.设计的珩磨刀是专用成型刀具,在刀具前头加了一段导向头,在刀柄上使用的是用万向接头与主轴连接的.设计夹具时对阀组进行了粗定位设计.从阀组外形和重量分析,设计了使用手柄和丝杆为传动的夹具. 相似文献
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在碳纤维增强复合材料(CFRP)的钻削制孔加工中,分层损伤是最重要的一类缺陷,严重影响孔的连接装配性能及材料的使用寿命。本文探讨了高强度型T800/X850 CFRP钻削加工中制孔分层缺陷的形成机理,通过试验研究了钻削参数对CFRP制孔分层缺陷的影响规律。结果表明选择高转速、低进给的钻削参数来进行钻削加工,有利于降低分层损伤。在相同的轴向力作用下,无涂层匕首钻表现出更优异的切削性能。 相似文献
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数控铣床的夹具较多,在需要加工轴类工件时,我们可以使用万能分度头对零件进行装夹,然而在数控铣床上进行一些特殊要求的轴类加工时,轴类零件常需要被牢固的定位的角度旋转需要人工分度,所以万能分度头的分度精度对分度类工件的铣削起着至关重要的作用,而在传统的万能分度头的使用过程中,作者发现孔盘中的小孔比较难数,经常会发现点错的情况,直接造成加工误差的产生。现设计出新型的分度盘介绍如下。 相似文献
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在数控铣床加工过程中,为使机床、工件、刀具保持正确相对位置需要采用夹具这一工艺装置。工装夹具是数控铣床加工中不可或缺的组成部分之一,特别是随着数控机床技术不断向着精密、高速、高效、复合、智能方向发展的背景下,夹具技术也必须不断改进和完善,以满足数控机床发展的需求。 相似文献
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麻花钻对于机械加工来说,是一种常用的钻孔工具。其结构简单,操作方便,是机械加工方面不可或缺的工具之一。钻孔加工是生产过程中一个最基本的工序,也是保质保量完成生产加工任务的基础。全面了解钻头的结构特点和钻削原理,掌握好刃磨的方法和技巧,通过对钻头刃口的修磨和强化来改善钻削加工条件,从而保证产品质量并大大提高工作效率。 相似文献
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数控铣床工装夹具的设计对于其工作的效率与精确度而言都具有十分重要的影响，而随着科技的不断进步发展，也有必要对于传统的工装夹具设计内容加以改进。在这种背景下，本文首先探讨了数控铣床工装夹具的应用现状，进而分析了数控铣床工装夹具的设计内容，最后给出了数控铣床工装夹具的设计改进方向。 相似文献
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本文通过对轴承密封圈防尘盖的用途及作用的研究,本作简单实用的原则对现有压装防尘盖的工装模具进行改进,设计出一套简单实用的、专用的装配模具,此模具的设计内容主要有定位元件,装夹机构及装配模具的设计,该模具在实际应用中,既保证了产品的加工精度,降低产品的不良率,又极大地提高了生产效率,更实用于装配生产线,降低了工人的劳动强度。 相似文献
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This study examined the effect of carbohydrate ingestion on metabolic and performance-related responses during and after a simulated 1h cycling time trial. Eight trained male cyclists (VO 2 peak = 66.5ml kg -1 min -1 ) rode their own bicycles mounted on a windload simulator to imitate real riding conditions. At a self-selected maximal pace, the cyclists performed two 1h rides (separated by 7 days) and were fed either an 8% carbohydrate or placebo solution. The beverages were administered 25 min before (4.5ml kg -1 ) and at the end (4.5ml kg -1 ) of the ride. With carbohydrate feeding, plasma glucose tended (P = 0.21) to rise before the time trial. Compared with rest, the plasma glucose concentration decreased significantly (P < 0.05) at the end of both rides, with no statistically significant difference being observed between treatments. Thereafter, plasma glucose increased significantly (P < 0.05) at 15 and 30 min into recovery, and was significantly higher at 30 min during the carbohydrate trial compared with the placebo trial. No significant changes in plasma free fatty acids were observed during the ride. However, a significant increase (P < 0.05) in free fatty acids was found at 15 and 30 min into recovery, with no difference between trials. Mean power output was significantly (P < 0.05) greater during the carbohydrate compared with the placebo trial (mean - S.E.: 277-3 and 269-3W, respectively). The greater distance covered in the carbohydrate compared with the placebo trial (41.5-1.06 and 41.0–1.06km, respectively; P < 0.05) was equivalent to a 44s improvement. We conclude that pre-exercise carbohydrate ingestion significantly increases endurance performance in trained cyclists during a 1h simulated time trial. Although the mechanism for this enhancement in performance with carbohydrate ingestion cannot be surmised from the present results, it could be related to a higher rate of carbohydrate oxidation, or to favourable effects of carbohydrate ingestion on the central component of fatigue. 相似文献
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Roy J. Shephard 《Journal of sports sciences》2013,31(7):603-620
The biology and medicine of rowing are briefly reviewed. Effort in a 2000 -m race is about 70% aerobic. Because the boat (and in some instances a cox) must be propelled, successful competitors are very tall, with a large lean mass and aerobic power. Large hearts may lead to erroneous diagnoses of a cardiomyopathy. Large respiratory minute volumes must be developed by chest muscles that are also involved in rowing. The vital capacity is typically large, and breathing becomes entrained. Expiration cannot be slowed relative to inspiration (as normally occurs at high rates of ventilation) and the limiting flow velocity may be reached, with the potential for airway collapse. Performance is strongly related to the power output at the ‘anaerobic threshold’, and lactate measures provide a guide to an appropriate intensity of endurance training. Peak blood lactate levels are higher in males (commonly 11–19 mmol·l -1 and occasionally as high as 25 mmol·l -1) than in females (9–11 mmol·l -1), probably because males have a greater muscle mass in relation to blood volume. The skeletal muscles are predominantly slow twitch in type, developing an unusual force and power at low contraction velocities. Many rowers have a suboptimal diet, eating excessive amounts of fat. Lightweight rowers also have problems of weight cycling. Aerobic power and muscle endurance often change by 10% over the season, but such fluctuations can be largely avoided by a well-designed winter training programme. Injuries include back and knee problems, tenosynovitis of the wrist and, since the introduction of large blades, fractures of the costae. 相似文献
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Alan M. Nevill Roger L. Holder Andrew Bardsley Helen Calvert Stephen Jones 《Journal of sports sciences》2013,31(4):437-443
A regression analysis of competitors' tournament results in relation to their world rankings was proposed to identify the effect of home advantage in international ‘grand-slam’ tennis and ‘major’ golf tournaments. The results provided little evidence of home advantage in either the grand-slam tennis or the golf tournaments held in 1993. The only possible evidence of home advantage was found in the Wimbledon tennis and the US Open golf championships. Even these findings can be explained, at least partially, by (1) the availability of information concerning the low world rankings of the British tennis players competing at Wimbledon, and (2) selective entry, allowing only the world's top-ranked foreign golfers into the US open golf tournament. In both cases, the lower ranking home competitors have a greater opportunity to perform above their anticipated world rankings. Therefore, provided entry into tennis and golf tournaments is truly ‘open’ to both the host nation's representatives and foreign competitors alike, home advantage does not appear to be a major factor influencing the competitors' performance in such competitions. These findings may be explained by the relatively objective nature of the scoring systems used in tennis and golf, unlike the subjective influence of refereeing decisions on the results of team-games such as soccer. 相似文献
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许良 《体育科技文献通报》2011,19(2):1-4
基于1985、1995和2005年全国学生体质调研数据,对各时期我国城乡学生形态、机能、体能发展水平进行系统地定量研究,动态分析20年全国城乡学生体质发展的特点与规律。主要研究结果：（1）近20年城乡学生生长发育持续提前,城市学生各项形态指标生长水平高于乡村,身高城乡差距缩小,体重、胸围城乡差距加大;（2）城市学生肺活量水平高于乡村,城乡学生肺活量20年持续下降,前10年乡村学生下降快、后10年城市学生下降快;（3）乡村学生800m、1000m跑水平高于城市,城市女生50m跑、仰卧起坐水平高于乡村,其他素质城乡学生水平波动较大;（4）城市女生50m跑20年持续下降,城乡学生800m和1000m跑、城市学生50m×8往返跑20年加速下降,其他素质20年间有增有降发展极不平稳。 相似文献
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采用测量、问卷调查、数理统计等方法,分析定向运动学习前后对大学生身心健康的影响.结果经T检验和x2检验且表明：定向运动不仅能增强学生体质健康水平,而且有助于学生的情绪调节,增强自信心与创新意识,培养勇敢顽强的意志品质,建立良好的人际关系,能有效地促进学生身心健康发展.为了全面提高大学生整体素质,积极实践,构建定向运动课内外一体化教学模式,进行定向运动课程模块化教学,以满足学生的多元化需求. 相似文献
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重新认识体育的社会关联 总被引：3，自引：1，他引：2
体育与政治之间存在一个悖论，体育的发展与经济实力之间没有直线相关，体育与教育部分重叠，体育与宗教最为近缘，体育可借用科学手段，体育的艺术禀性日益明显，体育与养生反映着两种人生观。 相似文献
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本文在专家访谈、问卷调查、数理统计和文献资料分析的基础上,探析了上海社区体育竞赛参与者的特点、参与者对社区体育赛事运作管理的看法等问题。在此基础上从引进社区体育赛事的志愿者、整合社区体育赛事的各种资源、开发社区体育竞赛的无形资产、组建非营利性的专业团队、规范社区体育赛事的服务管理等方面提出了进一步满足上海社区居民日益增长的体育竞赛参赛需求的对策与措施。 相似文献
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对全面把握游泳训练环节的探讨 总被引：4，自引：0，他引：4
从系统观点出发,结合训练实践,对全面把握游泳训练环节进行探讨。认为应强化非智力因素在运动员多年训练中的作用,在育材全过程中不断选材,从整体上把握动态训练的全过程,把培养高水平运动员的整个过程置于一个严格的科学控制之下。 相似文献