新疆天湖花岗岩的一维动静组合拉伸特性研究

基于SHPB装置,设计了岩石动静组合加载试验系统。根据SHPB装置的理论基础,即弹性杆中一维应力波传递及试件应力均匀化,系统阐述了基于SHPB装置岩石在动静组合加载下的适用性,并针对高放废物地质处置新疆预选区天湖地段的钻孔花岗岩岩芯,开展了一系列的动静组合加载试验。动静组合拉伸加载下,随着轴向静压的增大,岩石的抗冲击强度呈现出先增大的趋势。大约在静载抗拉强度的50%时,抗冲击拉伸强度达到最大值。并且,随着轴向静压的增大,岩石的动静组合拉伸强度亦随之快速增大,最大可达到静载强度的3倍,抗冲击动载的1.5倍。试验结果表明,在冲击破坏情况下,岩石组合加载破坏模式呈现拉伸破坏,与静态拉伸破坏及一般冲击下的劈裂破坏特征基本一致。通过系列的动静组合拉伸加载,能够得到不同轴向静压及不同冲击动载下,岩石承受的临界动载荷值,进而可以确定一个施加动载荷大小的安全范围,这对于深部地下工程的爆破开挖,具有一定的理论指导意义。

拉伸-弯曲组合作用下高强钢丝受力行为研究

为研究拉伸-弯曲组合作用下高强钢丝的受力行为,开展了拉伸-弯曲组合作用下高强钢丝的应力测试试验,测试了高强钢丝在不同轴向荷载和弯曲角度下的应力值。建立了拉伸-弯曲组合作用下高强钢丝的有限元模型,分析了高强钢丝的应力分布情况,模拟结果与试验结果吻合较好,验证了数值模型的准确性和合理性。基于该有限元模型,进一步研究了高强钢丝表面和截面内的应力分布情况,以及弯曲作用对应力范围的影响。结果表明,存在弯曲角度时,高强钢丝的应力分布会变得不均匀。相同轴向荷载时,高强钢丝应力值和应力范围都随弯曲角度的增加而增大。拉伸-弯曲组合作用会显著影响高强钢丝中部和两端区域的应力变化,使得这些区域内应力沿轴向和径向都存在较大的应力梯度,拉伸-弯曲组合作用效果在这些区域内应重点考虑。

硬质合金拉伸组合凹模设计

对硬质合金拉伸凹模结构及设计要点作了详细介绍,对同类型模具设计提供了参考。

拉伸扭转组合作用下泡沫铝力学性能

泡沫铝是工程中广泛使用的塑性材料之一,对泡沫铝在拉伸扭转复合载荷作用下的力学性能进行研究,确定其极限应力状态。比较剪应力和拉应力比值变化时,对其力学性能的影响。总结规律,为工程实践中相应的问题提供可靠的参考。同时对单向拉伸破坏试验及扭转破坏实验的结果进行了分析,验证强度理论。

不同拉伸对下肢爆发力的急性影响

目的:探究动态拉伸、PNF拉伸、PNF+动态组合拉伸对下肢爆发力的急性影响,为运动员在赛前准备活动中选择合理的拉伸方式提供科学依据。方法:选取具有2年以上力量训练经验的17名男性受试者,采用被试内设计,在不同的4天内安排4次分别包含无拉伸、动态拉伸、PNF拉伸和组合拉伸的实验任务。实验流程为受试者慢跑5分钟后进行拉伸干预,结束即刻通过测力台进行CMJ测试获取纵跳高度和起跳功率数据以评价下肢爆发力,通过无线表面肌电测试仪同步记录CMJ过程中下肢肌肉的表面肌电信号,并通过测量不同肌群的最大肌力,结合CMJ指标进一步了解不同拉伸对爆发力的影响特点。采用单因素重复测量方差分析处理上述数据。结果:3种拉伸后即刻CMJ指标无明显变化;动态拉伸后即刻股外侧肌、腓肠肌内侧头和腓肠肌外侧头IEMG显著下降,股内侧肌IEMG显著上升;PNF拉伸后即刻股内侧肌、股外侧肌IEMG显著上升,股二头肌、腓肠肌外侧头IEMG显著下降;组合拉伸后即刻腓肠肌外侧头IEMG显著下降,股内侧肌IEMG显著上升。其余肌电活动均无显著变化。结论:适当拉伸可对下肢神经肌肉功能产生有利影响,具有提高下肢爆发力的潜在可能性,适合在爆发力类运动前进行练习。

双向拉伸聚酯薄膜纵向拉伸方式及预热技术

介绍了双向拉伸聚酯薄膜单点和两点、小间隙和大间隙、低温和高温等纵向拉伸方式及组合的工艺技术特点;对纵向拉伸的预热辊配置和预热时间作了探讨。

闸阀关闭组件抗拉性能分析及试验研究

介绍了闸阀关闭组件批量抗拉试验方法,分析了试验结果,阐明了其拉伸性能不合格的原因,提出了改进方法。

不同应变速率下HTPB固体推进剂低温力学性能试验研究

为研究在-50℃低温下HTPB推进剂的力学性能与装药结构完整性的相关性,开展了推进剂不同应变速率下的拉伸试验,并通过快慢组合拉伸试验测试发动机低温点火条件下的力学性能。结果表明:在-50℃低温下,随着应变速率的增大,推进剂应力-应变曲线的“双峰”现象越来越明显;在快慢组合拉伸试验中,由于低应变速率拉伸时产生的初始损伤和高应变速率拉伸时的损伤累积,使得高应变速率下的延伸率增量仅为11%左右,与单应变速率下的拉伸结果差异较大。

SDA1型内燃机车门板模具成型工艺分析及解决措施

分析了SDA1型内燃机车侧墙门板成型难点,提出了整体模具成型和局部模具成型两种工艺方案。设计一种可替换、组合式拉伸模具成型方案(局部模具成型方案),既能保证翻边角度,又能保证折弯高度,产品质量达到设计要求,从而高效又经济地解决了产品质量问题。

锈蚀对承插式接头管道震害预测结果影响的分析

介绍了地下管道震害分析的方法、管道锈蚀作用的原因及危害,并从数值分析的角度出发,分析了震害预测中埋深、壁厚、水压力等参数变化对预测结果的影响。结果表明,管道的组合轴向变形与管长和水内压呈线性正相关,与管道埋深呈线性负相关;地下管道的锈蚀作用使管道壁厚变小,地震发生时更易遭到破坏,需要采取相应的措施减小管道锈蚀带来的震害影响。

Microstructure and tensile properties of containerless near-isothermally forged TiAl alloys

Ti-47Al-2Nb-2Cr-0.4（W, Mo） （mole fraction, %） alloy ingot fabricated using vacuum consumable melting was containerless near-isothermally forged, and the high temperature forgeability, microstructure and tensile properties were investigated. The results show that the TiAl ingot exhibits good heat workability during containerless near-isothermally forging process, and there are not evident cracks on the surface of as-forged TiAl pancake with a total deformation degree of 60%. The microstructure of the TiAl ingot appears to be typical nearly-lamellar（NL）, comprising a great amount of lamellar colonies （α2＋γ） and a few equiaxed γ grains. After near-isothermally forging, the as-forged pancake shows primarily fine equiaxed γ grains with an average grain size of 20 μm and some broken lamellar pieces, and some bent lamellas still exist in the hard-deformation zone. Tensile tests at room temperature show that ultimate tensile strength increases from 433 MPa to 573 MPa after forging due to grain refinement effect.

Microstructure and tensile properties of AE42-based magnesium alloys with calcium addition

The as-cast microstructure of AE42 was of typical dendritic and composed of the a matrix and some needle-shaped interphases Al11RE3. A small mount of Ca addition results in significant microstructural refinement and formation of a Al2Ca phase, which showed two kinds of morphologies, lamellar and tiny granular. The former distributes on grain boundaries and the later is within the matrix grains. With the increase of Ca addition the volume fraction of Al-RE compound (Al11RE3) decreases, but Al2Ca increases. Addition of Ca causes a significant increase of yield strength of the alloy both at ambient and elevated temperatures, but a little decrease of the ductility. With calcium addition the ultimate strength decreases at ambient temperature and 150°t, but increases at 175°C and 200°C.

Microstructure characterization and mechanical properties of TC4-DT titanium alloy after thermomechanical treatment

Influence of thermomechanical treatments （mill annealing, duplex annealing, solution treatment plus aging and triple annealing） on microstructures and mechanical properties of TC4-DT titanium alloy was investigated. Results showed that thermomechanical treatments had a significant influence on the microstructure parameters and higher annealing and aging temperature and lower cooling rate led to the decrease of the volume fraction of primaryαand the size of prior-βand the increase of the width of grain boundary αand secondary α. The highest strength was obtained by solution treatment and aging due to a large amount of transformedβand finer grain boundaryαand secondaryαat the expense of slight decrease of elongation and the ultimate strength, yield strength, elongation, reduction of area were 1100 MPa, 1030 MPa, 13%and 53%separately. A good combination of strength and ductility has been obtained by duplex annealing with the above values 940 MPa, 887.5 MPa, 15%and 51%respectively. Analysis between microstructure parameters and tensile properties showed that with the volume fraction of transformedβphase and the prior-βgrain size increasing, the ultimate strength, yield strength and reduction of area increased, but the elongation decreased. While the width of grain boundary α and secondary α showed a contrary effect on the tensile properties. Elimination of grain boundaryαas well as small prior-βgrain size can also improve ductility.

Tensile properties and microstructure of Ti14 alloy after semi-solid forging

Tensile properties of a new α＋Ti2Cu alloy after solid forging at 950 °C and semi-solid forging at 1 000 °C and 1 050 °C were investigated over the temperature range of 20-600 °C. The results reveal that high strength and low ductility are obtained in all semi-solid forged alloys. Tensile properties decrease as the semi-solid forging temperature increases, and cleavage fractures are observed after semi-solid forging at 1 050 °C. The variations in tensile properties are attributed to the coarse microstructures obtained in the semi-solid alloys. It is found that the elevated semi-solid temperatures lead to more liquid precipitates along the prior grain boundaries, which increases the peritectic precipitation and formation of Ti2Cu precipitation zones during re-solidification. Recrystallization heat treatment leads to fine microstructure of semi-solid forged alloys, resulting in improvement of tensile properties.

Microstructural evolution and mechanical properties of laser melting deposited Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy

A rectangular plate of Ti-6.5A1-3.5Mo-I.5Zr-0.3Si titanium alloy was fabricated by laser melting deposition （LMD） technology. Macrostructure and microstructure were characterized by optical microscope （OM） and scanning electron microscope （SEM）. Room temperature tensile properties were evaluated. Results indicate that the macro-morphology is dominated by large columnar grains traversing multiple deposited layers. Two kinds of bands, named the wide bands and the narrow bands, are observed. The wide band consists of crab-like a lath and Widmanstatten a colony. The narrow band consists of a lath and transformed ft. The formation mechanism of the two bands was explored. The influence of heat effect caused by subsequent deposition layers on microstructural evolution during deposition process was discussed. The room temperature tensile test demonstrates that the strength of laser deposited Ti-6.5A1-3.5Mo-I.5Zr-0.3Si is comparable to that of wrought bars.

Microstructural evolution of(TiAl)+Nb+W+B alloy

A newly designed TiAl alloy containing W,Nb,and B was produced through magnetic-flotation-melting method.Mass production of this TiAl-based alloy,15 kg ingot size,which is quite different from the 0.05 kg small ingot produced by arc-melting,has a large effect on the metallurgical properties,such as the grain size and the phase structures of the alloy.Heat treatments were carefully designed in order to reduce the amount of the high-temperature remaining β phase in the alloy,and to obtain optimal microstructures for mechanical behavior studies.A room-temperature ductility of 1.9% was obtained in the cast TiAl-based alloy after the appropriate heat treatment.The mechanical behavior of the large ingot through mass production of the TiAl-based alloy was largely improved by the alloy design and subsequent heat treatments.

PA6材料拉-扭组合的力学特征及屈服准则的试验研究

为了研究PA6在拉-扭组合作用下的力学特征、屈服准则及强度条件,利用电子拉-扭试验机对PA6材料进行了6种加载速率下的拉-扭组合变形试验,得到了相应的正应力与正应变、切应力与切应变的关系曲线;通过试验验证了Mises屈服准则可作为PA6材料的拉-扭屈服准则;基于最小二乘法建立Mises屈服准则中应力偏张量的第二不变量关于PA材料密度、声波速率、拉伸加载速率、扭转加载速率的拟合模型。由该拟合模型,可以不做加载破坏试验,即可建立PA6的拉-扭屈服准则,得到拉-扭屈服时的相当应力,并通过该屈服准则建立强度条件,可进行相应的PA6拉-扭强度计算。

Enhancement of mechanical properties of duplex Mg-9Li-3Al alloy by Sn and Y addition

For enhancement of mechanical properties in Mg-9Li-3Al alloys,Mg-9Li-3Al duplex alloys were alloyed by addition of Sn and Y.Microstructure evolution and mechanical property response of as-cast Mg-9Li-3Al alloys by alloying with Sn and Y were investigated by optical microscopy,scanning electron microscopy,X-ray diffractometry and tensile tests.The results indicate that considerable blocky dendrites of primaryαphase in Mg-9Li-3Al alloys become lath-like due to the addition of Sn.With addition of Y,Mg-9Li-3Al alloy consists of both block-like and lath-likeα-Mg dendrites.The as-cast Mg-9Li-3Al-1Sn-1Y alloy shows a yield strength of118MPa,ultimate tensile strength of148MPa and the elongation to failure of21%.Improvement in both strength and elongation of Mg-9Li-3Al alloys with Sn and Y addition is attributed to the combined action of MgLi2Sn and Al2Y intermetallic compounds.

Microstructure and tensile properties of friction stir welded dissimilar AA6061-AA5086 aluminium alloy joints

The fusion welding of dissimilar heat treatable and non-heat treatable aluminium alloy faced many problems related to solidification. The difficulties can be overcome to achieve the combined beneficial properties of both aluminium alloys using friction stir welding(FSW). The microstructural features and tensile properties of friction stir welded(FSW) similar and dissimilar joints made of AA6061 and AA5086 aluminium alloys were investigated. The microstructures of various regions were observed and analyzed by means of optical and scanning electron microscopy. Microhardness was measured at various zones of the welded joints. The tensile properties of the joints were evaluated and correlated with the microstructural features and microhardness values. The dissimilar joint exhibits a maximum hardness of HV 115 and a joint efficiency of 56%. This was attributed to the defect free stir zone formation and grain size strengthening.

Effect of thermomechanical processing on microstructure and mechanical properties of CoCrFeNiMn high entropy alloy

The CoCrFeNiMn high entropy alloy was produced by homogenization, cold rolling and recrystallization. The effects of thermomechanical processing on microstructures and tensile properties at different temperatures were investigated using X-ray diffractometry（XRD）, optical microscopy（OM）, scanning electron microscopy（SEM） and multi-functional testing machine. The results show that dendritic structures in cast alloy evolve into equiaxed grains after being recrystallized, with single face-centered cubic（FCC） phase detected. The most refined alloys, stemming from the highest rolling ratio（40%）, exhibit the highest strength due to the grain boundary strengthening, while the variation of elongation with temperature shows a concave feature. For the coarse-grained alloys, both the ductility and work hardening ability decrease monotonically with increasing temperature. Serrated flow observed at intermediate temperatures is attributed to the effective pinning of dislocations, which manifests the occurrence of dynamic strain hardening and results in the deterioration in ductility. Besides, dimples on the fracture surfaces indicate the typical ductile rupture mode.