胶乳对水泥石三轴力学形变能力的作用

针对套管、水泥环、地层三者间形变不协调而引起油气井生产后期层间封隔失效的问题,采用美国GCTS公司三轴岩石力学测试系统RTR-100,准确地测定了在三轴应力直接加载及三轴应力多周循环两种加载方式下水泥石的力学形变能力。实验结果表明,水泥浆中添加一定量的SBR胶乳,在降低油井水泥石抗压强度的同时增大了油井水泥石在低应力作用下的弹性形变和在高应力下的塑性形变,提高水泥石抗冲击破坏的能力。

测定高聚物动力学结晶能力的非等温DSC方法

研究了从非等温ＤＳＣ结晶曲线计算高聚物动力学结晶能力的方法．从高聚物非等温结晶动力学微分方程出发导出了计算高聚物动力学结晶能力的新方程．以含有不同催化剂的聚对苯二甲酸乙二酯为例，对其结晶进行了测试与计算．发现合理地选定最快结晶速率温度是计算动力学结晶能力的关键．

系统动力学视角下政府回应网络舆情的能力提升研究

我国政府对网络舆情日益重视,但在回应过程中,仍存在诸多问题。鉴于政府回应网络舆情的效果是多个因素相互作用的结果,本文构建了政府回应网络舆情能力的系统动力学模型。采用Vensim PLE软件对模型进行仿真分析,验证并分析模型的有效性和灵敏度。仿真结果表明,提高政府对网络舆情的重视程度、响应速度及政府自身公信力,能有效提升政府的回应能力。同时,网络舆情服务机构应及时准确地为政府供应其回应公众所需的知识,从根本上提升政府回应的效率和效果。

浅谈《工程力学》课程教学中力学检算能力的培养

在工程力学课程教学中,结合工科专业特点改进教学方法,理论联系实际,通过引入工程案例和有限元计算软件来培养学生的力学检算能力。

谈《工程力学》教学中的一些体会

《工程力学》课程是高职高专机械类专业的一门重要专业基础课,课程教学质量的好坏会直接影响到后续所开的其他专业课的学习,同时对今后工作能力有至关重要的影响,这就要求教师采取多种教学方法,努力提高教学质量。本人在教学实践过程中以培养学生学习的主动性为主,充分利用多种教学手段,在培养学生对工程力学的应用方面取得了较好成效。

泡沫铝复合材料压缩力学性能的试验研究

为了实现功能结构一体化,提高泡沫铝复合材料的力学性能,制备了硅橡胶改性环氧树脂的高分子材料填充泡沫铝的复合材料。对其进行静力学及径对力学性能影响分析,结果表明:泡沫铝复合材料的力学性能大大提高且孔径越小力学性能越好。研究结果有助于泡沫铝的应用范围拓展。

短跑跨栏摆动训练的运动传感器监测和能力评价研究

田径短跨运动是许多竞技运动的基础,是典型的周期性运动。运动员肢体的高速摆动能力是一个重要的专项能力。训练现场的实时定量化的测试评价和监控,对当前高水平运动训练有迫切需求。运动传感器检测技术的发展为运动训练的测试分析提供了有效的工具。本研究探讨了力学传感器对短跨运动员摆动训练的定量检测方法,建立了训练过程的专项能力与力学参数之间的联系,实现了运动能力的定量评价和训练效果的实时反馈,初步创建了"信号回馈"式辅助训练的方法。

第6届全国周培源大学生力学竞赛题型变化——浅谈大学生力学竞赛辅导中应加强的方面

通过对第6届全国周培源大学生力学竞赛题型变化的分析,指出在力学竞赛辅导中应对大学生加强培训或培养的方面,最后对辅导老师提出相应的要求.

试论纳米压痕技术在材料力学测试中的应用

本文以纳米压痕技术为研究对象,分析了纳米压痕技术在力学测试中的应用情况,并从多个维度,对纳米压痕技术在力学测试中的应用策略进行了研究。从本次研究结果可知,纳米压痕技术在材料力学测试中占据着重要位置,能够有效满足材料力学测试的要求,应该得到相关人员的重视。

有限元分析软件MIDAS助力工程力学课程模块化教学

为适应高职教育发展,针对传统工程力学课程教学中存在的问题和不足,本课程将内容整合为7个工学项目并采用模块化教学。同时,依托实际工程案例将有限元分析软件MIDAS引入教学过程中,对课程教学方法、教学内容与实验方式进行改革和创新,极大的提高了学生的学习兴趣和有效的提升了课堂教学效果,同时,培养了学生对实际工程结构的力学分析与检算能力。

机械制造类专业理论力学教学改革的研讨

理论力学是一门重要的专业基础课,学习效果影响今后的学习和工作。课程内容具有多、难、杂的特点,教和学都有很大的难度。本文根据课程特点、授课专业和授课对象整理和分析了教学中的常见问题,并进行了教学改革和创新。改革后,学生的学习积极性、自学能力、学习效率和效果都有了显著的提高,达到了提高综合素质的教育教学目的。

定性结构力学在高职教育教学中的研究与实践

高等职业教育的课程要以工作过程为导向。结合高职学生的应用要求及所具备的工程实践能力,指出定性分析在实际工程中的重要性,并因材施教地尝试定性结构力学的教育教学实践,训练学生定性分析问题的能力,掌握正确的学习方法,提高教与学的效率。为生产一线管理所具备的发现问题、解决问题的能力奠定基础。

Effect of quenching cooling rate on residual stress and microstructure evolution of 6061 aluminum alloy

In this study,the cooling rate was manipulated by quenching with water of different temperatures(30,60 and 100℃).Surface and internal residual stresses in the quenched 6061 aluminum alloy samples were measured using hole-drilling and crack compliance methods,respectively.Then,the processability of the quenched samples was evaluated at cryogenic temperatures.The mechanical properties of the as-aged samples were assessed,and microstructure evolution was analyzed.The surface residual stresses of samples W30℃,W60℃and W100℃is−178.7,−161.7 and−117.2 MPa,respectively along x-direction,respectively;and−191.2,−172.1 and−126.2 MPa,respectively along y-direction.The sample quenched in boiling water displaying the lowest residual stress(~34%and~60%reduction in the surface and core).The generation and distribution of quenching residual stress could be attributed to the lattice distortion gradient.Desirable plasticity was also exhibited in the samples with relatively low quenching cooling rates at cryogenic temperatures.The strengthes of the as-aged samples are 291.2 to 270.1 MPa as the quenching water temperature increase from 30℃to 100℃.Fine and homogeneous β"phases were observed in the as-aged sample quenched with boiling water due to the clusters and Guinier-Preston zones(GP zones)premature precipitated during quenching process.

Effect of interrupted aging on mechanical properties and corrosion resistance of 7A75 aluminum alloy

The effects of interrupted aging on mechanical properties and corrosion resistance of 7A75 aluminum alloy extruded bar were investigated through various analyses,including electrical conductivity,mechanical properties,local corrosion properties,and slow strain rate tensile stress corrosion tests.Microstructure characterization techniques such as metallographic microscopy,scanning electron microscopy(SEM),and transmission electron microscopy(TEM)were also employed.The results indicate that the tensile strength of the alloy produced by T6I6 aging is similar to that produced by T6I4 aging,and it even exceeds 700 MPa.Furthermore,the yield strength increases by 52.7 MPa,reaching 654.8 MPa after T6I6 aging treatment.The maximum depths of intergranular corrosion(IGC)and exfoliation corrosion(EXCO)decrease from 116.3 and 468.5μm to 89.5 and 324.3μm,respectively.The stress corrosion factor also decreases from 2.1%to 1.6%.These findings suggest that the alloy treated with T6I6 aging exhibits both high strength and excellent stress corrosion cracking resistance.Similarly,when the alloy is treated with T6I4,T6I6 and T6I7 aging,the sizes of grain boundary precipitates(GBPs)are found to be 5.2,18.4,and 32.8 nm,respectively.The sizes of matrix precipitates are 4.8,5.7 and 15.7 nm,respectively.The atomic fractions of Zn in GBPs are 9.92 at.%,8.23 at.%and 6.87 at.%,respectively,while the atomic fractions of Mg are 12.66 at.%,8.43 at.%and 7.00 at.%,respectively.Additionally,the atomic fractions of Cu are 1.83 at.%,2.47 at.%and 3.41 at.%,respectively.

Iron reduction in aluminum by electroslag refining

The effect of electroslag refining on iron reduction from commercial aluminum was investigated.Cast electrodes of commercial aluminum were electroslag refined using KCl-NaCl-Na3AlF6 slag containing Na2B4O7.Experimental results indicate that the iron content decreases with increasing Na2B4O7 addition and remelting time,and the iron content decreases from 0.400% to 0.184% under 9% Na2B4O7 addition for 30 min remelting.The elastic modulus,yield strength and ultimate tensile strength commercial aluminum are improved,and the tensile elongation is increased by 43% after electroslag refining.The chemical reaction between melt and slag to form Fe2B is the main reason for iron reduction and the thermodynamic calculation of the chemical reaction theoretically accounts for the formation of Fe2B.

Effect of minor Fe addition on glass forming ability and mechanical properties of Zr_(55)Al_(10)Ni_5Cu_(30) bulk metallic glass

A series of rod samples with diameter of 3 mm（Zr0.55Al0.10Ni0.05Cu0.30）100-xFex（x=0,1,2,3,4） were prepared by magnetic suspend melting and copper mold suction casting method.The effects of a small amount of Fe on glass forming ability（GFA） and mechanical properties of Zr55Al10Ni5Cu30 bulk metallic glass（BMG） were investigated.The results show that the addition of an appropriate amount（less than 3%,mole fraction） of Fe enhances GFA,as indicated by the increase in the reduced glass transition temperature Trg（=Tg/Tl） and the parameter γ（=Tx/（Tg＋Tl）） with increasing Fe content,and GFA gets deteriorated by further Fe addition（4%）.The addition of Fe also effectively improves the compressive plasticity and increases the compressive fracture strength in these Zr-based BMGs.Compressive tests on BMG sample with 3 mm in diameter and 6 mm in length reveal work-hardening and a certain plastic strain in the alloy containing 2% Fe.The BMG composite containing 4% Fe also exhibits a high fracture strength along with significant plasticity.

Preparation and properties of novel Cu-based bulk metallic glasses Cu_(55-x)Zr_(37)Ti_8In_x

The glassy rods were successfully fabricated in the Cu-Zr-Ti-In alloy system by casting into a copper mold. The value of ATx reaches a maximum of 66 K for the BMG CusoZraTTi8In5 alloy. The reasons for enhancing glass forming ability of Cu-based BMGs with the addition of indium were discussed from atomic size and thermodynamics. Alternatively, the BMG Cu52Zra7Ti8In3 exhibits the highest compressive strength （1981 MPa） and the best plasticity among glassy Cu55-xZra7TisInx （x_〈5）. The total plastic deformation of Cu52Zr37TisIn3 before fracture approaches 1.2%.

Microstructure and mechanical properties of 2A12 aluminum alloy after age forming

The comparative experiments of age forming and artificial aging of 2A12 aluminum alloy were carried out. The effect of the age forming on the microstructure and mechanical properties was investigated. The results demonstrate that the grains are further squashed and elongated compared with artificial aging due to the existence of the applied stress during the age forming. Meanwhile, the precipitated phases change from circle shape with random orientation of age forming to long strip shape with uniform orientation of artificial aging. The dislocation configuration in samples changes from ring dislocation or helical dislocation of the artificial aging to long and straight dislocation of the age forming. Otherwise, age forming slightly reduces the tensile properties and fracture toughness of the alloy and enhances its fatigue crack growth rate.

Design of high strength Fe-(P,C)-based bulk metallic glasses with Nb addition

Bulk metallic glass（BMG） rods Fe71Mo5-xNbxP12C10B2（x=1,2,3,4 and 5） with diameter of 1 or 2 mm were synthesized by copper mold casting.The effects of Nb substitution for Mo on the structure,thermal and mechanical properties of Fe71Mo5-xNbxP12C10B2 alloys were studied by X-ray diffraction,differential scanning calorimetry and compressive testing.The results show that the substitution of Nb for Mo leads to a decreased glass forming ability,but with plasticity of 1.0%,the fracture strength of Fe71Mo2Nb3P12C10B2 alloy increases up to 4.0 GPa.The improvement of the fracture strength is discussed in terms of the enhancement of atomic bonding nature and the favorite formation of a network-like structure due to the substitution of Nb for Mo.

Aging behavior and mechanical properties of 6013 aluminum alloy processed by severe plastic deformation

Structural features, aging behavior, precipitation kinetics and mechanical properties of a 6013 Al–Mg–Si aluminum alloy subjected to equal channel angular pressing （ECAP） at different temperatures were comparatively investigated with that in conventional static aging by quantitative X-ray diffraction （XRD） measurements, differential scanning calorimetry （DSC） and tensile tests. Average grain sizes measured by XRD are in the range of 66-112 nm while the average dislocation density is in the range of 1.20×10^14-1.70×10^14 m^-2 in the deformed alloy. The DSC analysis reveals that the precipitation kinetics in the deformed alloy is much faster as compared with the peak-aged sample due to the smaller grains and higher dislocation density developed after ECAP. Both the yield strength （YS） and ultimate tensile strength （UTS） are dramatically increased in all the ECAP samples as compared with the undeformed counterparts. The maximum strength appears in the samples ECAP treated at room temperature and the maximum YS is about 1.6 times that of the statically peak-aged sample. The very high strength in the ECAP alloy is suggested to be related to the grain size strengthening and dislocation strengthening, as well as the precipitation strengthening contributing from the dynamic precipitation during ECAP.