拉伸测试速率控制方式优劣分析

为了找出更易于日常测试的拉伸测试方式,通过拉伸测试对应变控制与位移控制两种方式进行了试验对比,试验结果表明:拉伸测试应变速率控制方式是更符合标准和实际拉伸测试速率的控制方式。     

Cr17铁素体不锈钢的应变速率脆性

研究了Cr17铁素体不锈钢在高温拉伸试验过程中应变速率对合金断面收缩率的影响,并对其发生机制进行了分析。合金在500℃下以不同应变速率(1.43×10-6~1.33s-1)拉伸至断裂,测试断面收缩率,并利用电子探针对晶界成分进行了观察测试。结果表明:应变速率从1.43×10-6 s-1升高至1.43×10-2 s-1,断面收缩率降低,约在1.43×10-2 s-1时达到最低值。然后,随着应变速率增加至1.33s-1,断面收缩率升高。经电子探针测试证实,断面收缩率达到最低值的样品,硫在晶界上偏聚,其他应变速率拉伸的样品没有观察到硫的晶界偏聚。基于多晶金属弹性变形的微观理论,分析这些试验结果,证实了此合金在拉伸试验中具有应变速率脆性的基本特征——临界应变速率。     

测试条件对冷轧薄板力不性能测试结果的影响

应用ＩＮＳＴＲＯＮ５５６９型电子拉力试验机,在不同测试条件下,对冷轧薄板力学性能进行了测试分析．结果表明,设置试验机的控制参数、拉伸速度、试样尺寸等均对力学性能测试结果有影响。其中,提高拉伸速度使规定非比例伸长应力σ０．２增加,应变硬化指数ｎ值减少,塑性应变比ｒ值无明显变化规律,试样尺寸对ｒ值有影响。     

拉伸试验速度对屈服强度的影响及控制

通过理论分析及实验数据，表明金属拉伸试验速度对屈服强度的影响。并依据国家标准，巾平均应力速率推导负荷速率计算公式，根据负荷速率可以简单、直观、方便地进行日常拉伸试验。确保试验结果的准确性。     

汽车薄板钢应变速率敏感性影响有新论

日前，德国学者研究了汽车薄板钢在碰撞条件下，应变速率、温度、应变和显微组织对其应变速率敏感性的影响。 该研究通过液力伺服动态拉伸实验阐述了各参数对汽车薄板用钢应变速率敏感指数m值的影响。研究主要结论如下：汽车碰撞实验中，在应变速率为10^-3s^-1～200s^-1、温度在233K～373K范围内，汽车薄板用钢的动态变形行为是一个热激活过程，流动应力随着应变速率的增加或者是温度的降低而增加。     

双相钢780DP的动态拉伸性能

本文对双相钢780DP进行了不同应变率的动态拉伸试验,对试样的断口形貌和显微组织进行了检测和分析。结果显示,780DP钢的强度随着应变率的提高而增加,并且具有明显的应变速率敏感性,在高应变率的条件下,780DP钢强度提高的主要原因是形变硬化和位错运动机制的改变,同时具有形变微区的绝热升温效应。     

冷轧薄钢板基本成形性能指标影响因素分析

探讨了试样尺寸对冷轧薄钢板基本成形性能的影响,结果表明不同尺寸试样对σｐ０．２、σｂ、ｒ、ｎ值的测试结果影响不大,对δ值的测定结果有明显的影响;确定了冷轧薄钢板不同试样尺寸之间的换算因子;还探讨了拉伸速度、不同应变量的取值对ｒ、ｎ值测定结果的影响。     

应变速率对钛合金室温拉伸性能的影响

拉伸速率对金属材料的室温拉伸性能影响很大,文章介绍了不同应变速率对钛合金Ti6Al4V(TC4)、TA15和Ti1023室温拉伸性能影响的研究进展,并通过分析和归纳,阐述了第一应变速率和第二应变速率对钛合金的抗拉强度、屈服强度、断后伸长率及断面收缩率的影响程度和规律,最后对应变速率对钛合金室温拉伸性能影响研究的发展方向进行了展望。     

材料的成分组织对动态拉伸性能的影响

本文通过分段Ｈｏｐｋｉｎｓｏｎ杆拉伸装置，在１０＾２－１０＾３Ｓ＾－１应变率范围内测试了５８ＳｉＭｎ钢、４５钢、ＰＣｒＮｉ３ＭｏＶＡ钢、Ｄ６０钢、６０３钢、６１７钢和２８ＣｒＭｏＶＡ钢的动态拉伸性能，以研究的应变速率敏感性。     

300M超高强度钢的应力腐蚀开裂

利用慢应变率拉伸试验技术研究了３００Ｍ超高强度钢的应力腐蚀开裂（ＳＣＣ），结果表明，３００Ｍ钢在３．５％ＮａＣｌ水溶液和蒸馏水中均对ＳＣＣ敏感，随温度增加和拉伸应力变速率的降低钢的ＳＣＣ敏感性增加，并且阴极极化和阳极极化均提高钢的ＳＣＣ敏感性，除氧和降低溶液ｐＨ值均提高钢的ＳＣＣ敏感性。     

应变分析方法在金属薄板拉深成形中的应用

用应变分析方法测量和分析接深试验过程中拉深杯件各个区域的应变分布情况和应变变化历史,还分析了典型实物拉深零件JD90型摩托车油箱的应变分布特点,最后提出了确定接深成形零件危险部位的方法。     

邯钢400m2烧结机工艺参数的优化研究与效果

为了使400m^2烧结机生产水平尽快达到一个新的台阶，邯钢就优化400m^2烧结机工艺参数进行了实验室研究。分别对4种碱度的烧结矿进行混合料配煤、混合料水分、抽风负压和点火温度的试验研究，通过对试验烧结矿的各项技术指标、冶金性能等分析确定了各种烧结矿最佳生产工艺参数。并将研究结果应用于生产实践，在生产中获得了生产率提高，能耗降低的效果。     

Numerical Simulation of Influence of Casting Speed Variation on Surface Fluctuation of Molten Steel in Mold

The influences of casting speed variation on surface fluctuation of the molten steel in mold during continuous casting were investigated with numerical simulation method.It was found that when the casting speed was evenly decreased from 1.4 m·min-1 to 0.6 m·min-1,the increase of the surface fluctuation of the molten steel in mold was observed only on time that was at the start of casting speed change.While,in experiment of increasing casting speed evenly from 0.6 m·min-1 to 1.4 m·min-1,the increase of the surface fluctuation of the molten steel in mold was observed only at the time when the casting speed was stopped to increase after it had been increased to 1.4 m·min-1.For surface fluctuation of the molten steel in mold which was produced during the casting speed evenly increasing or decreasing period and at the time when increasing or decreasing the casting speed at low casting speed level(0.6 m·min-1),the influence of casting speed change is very small.In addition,it is found that,at high casting speed level(1.4 m·min-1),even a little change of casting speed could result in remarkable increase of the surface fluctuation.Thus,at high casting speed,changing casting speed should be avoided or much slower speed changing rate should be used.     

Calculations of forming limit diagrams

The right-hand side of the forming limit diagram (FLD) was calculated using a Marciniak-Kuczynski analysis with a nonquadratic anisotropic yield criterion. Effects of changing the strain-hardening exponent, n, strain-rate exponent, m, strain ratio, R, stress exponent in the anisotropic yield criterion, a, and the inhomogeneity factor, f, were explored. For a ≥ 6, the effect of R is negligible. The calculated forming limit for plane strain is raised by increased values of n, m, and f and is unaffected by R and a. The slope of the right-hand side is decreased by increased values of n, m, and a, whereas the slope increases with higher f The calculated FLDs agree well with experimental ones determined by in-plane stretching.     

Non-Metallic Inclusion Distribution in Surface Layer of IF Steel Slabs

Non-metallic inclusion distribution in the surface layer of IF steel slabs during unsteady casting was investigated using the original position statistic distribution analysis（OPA）method.It was found that most non-metallic inclusions larger than 10 μm existed in the subsurface layers of 0.5-3.5 mm from the slab surfaces and very few large non-metallic inclusions were found in the inner regions（≥4.5 mm from slab surfaces）.In addition,it was found that at high casting speed level（1.4 m/min）,even a slight change of casting speed could result in a remarkable increase of the non-metallic inclusions.Thus,at high casting speed,changing the casting speed should be avoided or considerably lower speed changing rate must be used.     

钒钛铁精矿内配碳球团压团工艺研究

内配碳球团性能(落下次数、抗压强度等),对于直接还原生产海绵铁时获得较高金属化率极为重要.首先初步确定每个因素的基准参数,通过改变其参数值进行一系列单因素试验,然后根据正交试验原理,设计了四因素三水平试验条件,采用769YP-60E型手动压片机对钒钛铁精矿内配碳球团压团工艺参数进行试验研究,最后运用极差分析法和方差分析法对试验数据进行处理,对影响球团性能的各因素进行显著性检验.结果表明:利用实验结果和极差分析综合比较确定了使生球落下次数较高的工艺条件分别为A282C3D2,即矿煤粒度比(200:60)、水分8%、粘结剂0.3%、压力为10 MPa;方差分析将因素水平变化所引起的结果差异与误差波动带来的试验结果间的差异区分开来,得出影响落下次数的主次因素分别B2A2D2G3,即球团水分是影响球团性能或压团工艺参数的主要因素,矿煤粒度比对球团性能有较大影响,压团压力和粘结剂浓度对各项指标的影响最小;生球团要进行干燥处理,干燥温度为105℃,干燥时间控制在2 h左右,所得球团的抗压强度为98N/个、高温爆裂性能小于20%,能满足转底炉直接还原工艺的要求.     

高线精轧机辊缝补偿技术创新与实践

分析了宣钢公司高线厂生产事故频发、作业率低、成品尺寸超差、螺纹钢横肋不够的原因,认为精轧机内各架次轧槽磨损不均是主要原因。以解决精轧机烧导卫堆钢事故为突破口,修订了精轧机辊缝补偿标准,调整优化了精轧机换辊次序,减少日检修换辊架次,大幅压缩日检修时间,并辅以主控台速度设定与预加张力优化、活套系统改造。优化后,作业率及成品质量明显提高,达到了同行业领先水平。     

应用射钉法测量板坯凝固坯壳的厚度

结合鞍钢连铸机的生产实际情况,采用射钉法测定二冷区内的凝固坯壳厚度,并计算铸坯凝固系数.测量结果表明,两个测量钢种在2.6m/min拉速下,连铸坯坯壳厚度的实际测量结果与连铸机二级系统的计算结果基本一致.整个凝固过程坯壳厚度生长符合平方根定律.     

Lumbosacral movement in the sit-and-reach and in Cailliet's protective-hamstring stretch

STUDY DESIGN: This study analyzed movement characteristics of subjects as they performed two different hamstring stretching activities. OBJECTIVES: The study determined if there were differences in lumbosacral movement as the subjects performed the two stretches. SUMMARY OF BACKGROUND DATA: Cailliet contends that his protective hamstring stretch is less apt to be stressful to the structures of the spine than is a more commonly done sit-and-reach stretching activity. No previous biomechanical investigation has tested his contention. METHODS: Lumbosacral movement was measured with an Ady-Hall lumbar monitor as 40 university students (20 males, 20 females) performed a popular sit-and-reach test and a sit-and-reach test that subscribed to Cailliet's protective hamstring stretch protocol. RESULTS: Lumbosacral movement was almost identical in the two stretching activities. CONCLUSIONS: If lumbosacral movement is the only criterion to consider in evaluating the safety of these two stretching activities, it makes little difference which activity is chosen. If moment of inertia were the dependent variable rather than lumbosacral movement, possibly one activity may be less stressful to the structures of the spine than the other.     

连铸厚板坯轻压下技术的应用

 对首秦2号板坯连铸机轻压下工艺进行了细致的研究。通过连铸坯射钉试验对首秦2号连铸机二级冷却模型进行了校验;通过不同轻压下率试验条件下连铸坯中心偏析的程度确定了合理的、能够有效改善连铸坯中心偏析的轻压下率;通过连铸坯厚度方向不同部位碳硫元素的分析对轻压下工艺改善前后连铸坯中心偏析度进行了对比。结果表明：首秦2号连铸机二级冷却模型能够准确反映连铸坯凝固末端的位置。在拉速为0.70m/min的连铸工艺条件下,320mm厚连铸坯轻压下段为第9和第10段,合理的轻压下率应该保持在0.85～1.0mm/m之间。采用合理的轻压下工艺后,连铸坯中心偏析得到了明显改善,满足了首秦高品质中厚板对连铸坯内部质量的严格要求。