基于力学机械性能调节的金属检定装置设计

基于力学机械性能调节的金属检定装置以力学理论为基础,有效调节作用于金属材料的力学作用,根据材料表现出的性能得出准确的测量结果。文章将对力学机械性能调节的金属检定装置的各项功能进行分析与阐述,如通过结构驱动,改变力学传感器拉伸情况,进而有效调整拉力;改变驱动机扭矩,有效调整装置拉力,降低力学测试过程中出现安全问题的概率等,以期确保检测工作的高效进行,提高检测工作效率。

聚丙烯模拟回收料转矩流变与力学机械性能研究

给出了一种采用简单快捷转矩流变方法评估聚丙烯回收料可用性的方法。可以用时间-转矩曲线或平衡转矩值来评估聚丙烯回收料的力学机械性能下降程度和可用情况。平衡转矩Me=0(190℃,45 g,50 r/min)可以用作聚丙烯回收料可用性的临界值。当所测回收料的平衡转矩值已经下降到零的时候,可认为这种材料已经不可直接使用。

不同含氟比例弹性义齿材料的力学性能比较

背景:患者长期戴用弹性义齿修复体后,会增加龋病和牙周病、局部义齿性口炎等疾病的发病率。在材料中添加氟化物可预防和降低上述疾病的发病率,目前国内外在口腔材料中添加氟化物防龋的研究较多,但尚无在弹性义齿材料中添加单氟磷酸钠并进行相关力学性能测试研究的相关报道。目的:评价不同含氟比例弹性义齿材料的力学性能。方法:取弹性义齿材料,分别制成长80 mm、宽51 mm、厚1 mm,长20 mm、宽5 mm、厚5 mm,长25 mm、宽2 mm、厚2 mm尺寸,每种尺寸60个试件,每组尺寸内按照添加单氟磷酸钠的质量比再分为6组,单氟磷酸钠质量比分别为0(对照组)、3%、5%、10%、15%、20%,检测试件的扯断强度、弯曲强度及邵氏硬度。结果与结论:随着弹性义齿材料中单氟磷酸钠质量比例的增加,材料的扯断强度、弯曲强度及邵氏硬度值逐渐降低,当弹性义齿材料中单氟磷酸钠质量比例增加至10%时,材料的扯断强度、弯曲强度及邵氏硬度与对照组相比虽有所降低,但差异无显著性意义(P>0.05);当弹性义齿材料中单氟磷酸钠质量比例达到15%时,材料的扯断强度、弯曲强度均低于对照组(P<0.05);当弹性义齿材料中单氟磷酸钠质量比例达到20%时,材料的扯断强度、弯曲强度、邵氏硬度均低于对照组(P<0.05)。结果表明,单氟磷酸钠含量可影响弹性义齿材料的力学指标,10%是最佳加氟比例,高于此给氟量可改变弹性义齿材料的力学性能。

Effect of ultrasonic and mechanical vibration treatments on evolution of Mn-rich phases and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys

Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV+MV treatments can significantly refine and fragmentize the microstructures.In addition,UV treatment can significantly passivate the primary Mn-rich Al15Mn3Si2 intermetallics.The formation mechanisms of refinement and passivation of the grains and non-dendrite particles were discussed.Compared with the gravity die-cast alloys,the UV and UV+MV treated alloys exhibit improved tensile and creep resistance at room and elevated temperatures.These results can be attributed to the refinement of theα(Al)grains and the secondary intermetallics,the increased proportion of refined heat-resistant precipitates,and the formation of nano-sized Si particles.The ultimate tensile strength of the UV treated alloys at 350℃ exceeds that of commercial piston alloys.This indicates the high application potential of the developed piston alloys in density diesel engines.

Microstructure and mechanical properties of die-cast AZ91D magnesium alloy by Pr additions

Mg-9Al-xPr(x=0.4,0.8 and 1.2,mass fraction,%)magnesium alloys were prepared by high-pressure die-casting technique.The effects of Pr on the microstructures of die-cast Mg-9Al based alloy were investigated by XRD and SEM.Needle-like Al11Pr3 phase and polygon Al6Mn6Pr phase are found in the microstructure.With 0.4%Pr addition,fine needle-like Al11Pr3 phase and a small amount of polygon Al6Mn6Pr phase near the grain boundary are found in the microstructure.Increasing Pr addition to 0.8%, lots of coarse needle-like Al11Pr3 phase within grain and polygon Al6Mn6Pr phase on grain boundary are observed.Further increasing Pr addition,the size of needle-like Al11Pr3 phase decreases,while the size of polygon Al6Mn6Pr relatively increases.The mass fraction of Pr at around 0.8%is considered to be suitable to obtain the optimal mechanical properties.The optimal mechanical properties are mainly resulted from grain boundary strengthening obtained by precipitates and solid solution.

Effect of addition of Si on microstructure, mechanical properties, bio-corrosion and cytotoxicity of Mg-6Al-1Zn alloy

The Mg-6Al-4Zn alloy was fabricated by mechanical alloying(MA)and hot pressing to serve as biodegradable metal implant.The influence of addition of 1%Si(mass fraction)on the microstructure,mechanical properties and bio-corrosion behavior of Mg-6Al-1Zn alloy was studied using X-ray diffractometry,transmission electron microscopy,compression test,as well as immersion,electrochemical test and MTT assay.The results showed that the addition of 1%Si to Mg-6Al-1Zn alloy led to the formation of fine Mg2Si phase with polygonal shape,and increased compressive strength,elongation and improved corrosion resistance.Furthermore,the cell viability of Saos-2 cells has been improved by addition of 1%Si to Mg-6Al-1Zn alloy.According to the results,the magnesium ions released in the methylthiazol tetrazolium(MTT)test have not shown any cell toxicity.All these indicated that the addition of 1%Si improved the properties of Mg-6Al-4Zn alloy for using as a biodegradable implant.

Artificial neural network prediction of mechanical properties of hot rolled low carbon steel strip

Conventionally, direct tensile tests are employed to measure mechanical properties of industrially pro- duced products. In mass production, the cost of sampling and labor is high, which leads to an increase of total pro- duction cost and a decrease of production efficiency. The main purpose of this paper is to develop an intelligent pro- gram based on artificial neural network （ANN） to predict the mechanical properties of a commercial grade hot rolled low carbon steel strip, SPHC. A neural network model was developed by using 7 x 5 x 1 back-propagation （BP） neural network structure to determine the multiple relationships among chemical composition, product pro- cess and mechanical properties. Industrial on-line application of the model indicated that prediction results were in good agreement with measured values. It showed that 99.2 % of the products＇ tensile strength was accurately pre- dicted within an error margin of ~ 10 %, compared to measured values. Based on the model, the effects of chemical composition and hot rolling process on mechanical properties were derived and the relative importance of each in- put parameter was evaluated by sensitivity analysis. All the results demonstrate that the developed ANN models are capable of accurate predictions under real-time industrial conditions. The developed model can be used to sub- stitute mechanical property measurement and therefore reduce cost of production. It can also be used to control and optimize mechanical properties of the investigated steel.

Effect of low temperature thermo-mechanical treatment on microstructures and mechanical properties of TC4 alloy

The effects of low temperature thermo-mechanical treatment （LTTMT） on microstructures and mechanical properties of Ti-6Al-4V （TC4） alloy were studied by optical microscopy （OM）, tensile test, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The experimental results confirm that the strength of TC4 alloy can be improved obviously by LTTMT processing, which combines strain strengthening with aging strengthening. The effect of LTTMT on the alloy depends on the microstructure of the refined and dispersed a＋fl phase on the basis of high dislocation density by pre-deformation below recrystallization temperature. The tensile strength decreases with the increase of pre-deformation reduction. The optimal processing parameters of LTTMT for TC4 alloy are as follows： solution treatment at 900 ℃ for 15 min, pre-deformation in the range of 600-700 ℃ with a reduction of 35%, finally aging at 540 ℃ for 4 h followed by air-cooling.

Study on inverter fault-tolerant operation of PMSM DTC

This paper presents an investigation of inverter fault-tolerant operation for a permanent magnet synchronous motor （PMSM） direct torque control （DTC） system under various inverter faults. The performance of a faulty standard 6-switch inverter driven PMSM DTC system is analyzed. To avoid the loss or even disaster caused by the inverter faults, a topology-modified inverter with fault-tolerant capability is introduced, which is reconfigured as a 3-phase 4-switch inverter. The modeling of the 4-switch inverter is then analyzed and a novel DTC strategy with a unique nonlinear perpendicular flux observer and feedback compensation scheme is proposed for obtaining a continuous, disturbance-flee drive system. The simulation and experimental results demonstrate that the proposed inverter fault-tolerant PMSM DTC system is able to operate stably and continuously with acceptable static and pretty good dynamic performance.

Effect of ball-milling parameter on mechanical and damping properties of sintered Mg-Zr alloy

Effects of ball-milling parameter on structures and properties of sintered Mg-l.5Zr （mass fraction, %） alloy were researched by metallographic analysis, mechanical properties tests and DMA technology. The results indicate that with 310 r/min rotation speed, the microstructure of the sintered alloy is greatly refined, and Zr-phase distributes uniformly. The micro-hardness, bending strength and damping capacities are the greatest under 310 r/min rotation speed. The damping peak of sintered Mg-l.5Zr alloy increases with increasing frequency under the testing conditions. The relaxation time meets the Arrhenius relationship, and shows the characteristics of relaxation damping.

Optimizing consolidation behavior of Al 7068-TiC nanocomposites using Taguchi statistical analysis

The fabrication of high strength Al 7068？5%TiC （mass fraction） nanocomposite was studied by mechanical alloying and hot pressing routes. Considering densification importance and grain growth effects, hot pressing process conditions for producing bulk nanocomposite were optimized using statistical Taguchi method based on compressive strength achievement. The Taguchi results indicate that 30 min hot pressing under pressure of 500 MPa at 385 °C provides high compressive strength and hardness of 938 MPa and HV 265, respectively. More interestingly, analysis of variance proves that the applied pressure is the most influential factor for hot pressing of the nanocomposite. The contribution percentages of factors in hot pressing terms are as follows： applied pressure （61.3%）, exposed temperature （29.53%） and dwelling hot pressing time （4.49%）.

Hydriding/dehydriding properties of Mg-Ni-based ternary alloys synthesized by mechanical grinding

The Mg-Ni-based ternary alloys Mg2-xTixNi(x=0,0.2,0.4)and Mg2Ni1-xZrx(x=0,0.2,0.4)were successfully synthesized by mechanical grinding.The phases in the alloys and the hydriding/dehydriding properties of the alloys were investigated.Mg2Ni and Mg are the main hydrogen absorption phases in the alloys by XRD analysis.Hydriding kinetics curves of the alloys indicate that the hydrogen absorption rate increases after partial substitution of Ti for Mg and Zr for Ni.According to the measurement of pressure-concentration-isotherms and Van't Hoff equation,the relationship between ln p(H2)and 1 000/T was established.It is found that while increasing the content of correspondingly substituted elements at the same temperature,the equilibrium pressure of dehydriding increases,the enthalpy change and the stability of the alloy hydride decrease.

Perturbation to Noether-Lie Symmetry and Adiabatic Invariants for Mechanical Systems in Phase Space

Based on the concept of adiabatic invariant,the perturbation to Noether-Lie symmetry and adiabatic invariants for mechanical systems in phase space are studied.The criterion of the Noether-Lie symmetry for the perturbed system is given,and the definition of the perturbation to Noether-Lie symmetry for the system under the action of small disturbance is presented.Meanwhile,the Noether adiabatic invariants and the generalized Hojman adiabatic invariants of the perturbed system are obtained.

Mechanical Behavior of Soybean Protein Fibers

In order to understand the relationship between the mechanical property and the effect of bleaching and dyeing to the soybean protein fibers(SPF),four mechanical models are chosen.The tensile and relaxation property of the soybean protein fibers are analyzed.The tensile and relaxation curves are fitted with the suitable model.It shows that the relaxation property of SPF is in accordance with the standard linear solid model.Estimates of the Hookean spring modulus at 8% and at 10% are different,so some structural modifications could be produced by the strain.Bleached fibers show a higher level of relaxation than raw fibers and dyed fibers.Bleaching has a remarkable influence on decreasing tenacity at break for each test modality.Knotted and looped modalities decrease fiber tenacity remarkably in all three samples.

Effect of Force Adaptation in Mechanics

Discovery of effect of force adaptation in mechanics is presented. The discovery is based on use of the mobile closed mechanical contour for force transfer from the mechanism input link to an output link, According to discovery the motion transfer can be carried out by Assur structural group in the form of the mobile closed contour, and the output link is the link with one degree of freedom. The received mechanical system includes an input link, an output link and the closed contour placed between them as fourth class Assur structural group. The kinematic chain has two degrees of freedom. However the closed contour imposes an additional constraint on relative motion of its links. The carried out discovery allows providing the variable transfer ratio only due to the variable external load. Mechanical properties of the closed contour allow providing the required transfer ratio independently, smart and automatically.

Aerodynamic Performance and Noise Characteristics of a Centrifugal Compressor with Modified Vaned Diffusers

Improvement of aerodynamic performance and reduction of interaction tone noise of a centrifugal compressor with vaned diffusers are discussed by experiments and visualization techniques using a colored off-film method. The focus of the research is concentrated on the leading edge shape of diffuser vanes that are deeply related to the generation mechanism of the interaction tone noise. The compressor-radiated noise can be reduced by more than ten decibels by using modified diffuser vanes which have 3-D tapered shapes on both pressure and suction sur- faces of the leading edge. Furthermore, by adopting the proposed modified diffuser vanes, the secondary flow which is considered to be an obstruction of diffuser pressure recovery can be suppressed, and also the pressure decrease observed in the throat part of the diffuser flow passage is reducible. Thus, the proposed diffuser vanes show a favorable result for both noise and the aerodynamic performance of the centrifugal compressor, and offer a few basic guidelines for the diffuser vane design.

Curing kinetics and mechanical properties of bio-based composite using rosin-sourced anhydrides as curing agent for hot-melt prepreg

In this study, a novel bio-based thermosetting system has been developed from epoxy resin （EP）, with rosin-sourced anhydrides （maleopimaric acid, RAM） as curing agent and imidazole type latent catalyst （two amino imidazole salt complex, IMA）, to be used as matrix for hot-melt prepreg curing at mid-temperature. For comparison, the epoxy resin system with petroleum sourced hardener methylhexahydrophthalicanhydride （MHHPA） was also examined. The curing behaviour and mechanism were investigated by non-isothermal differential scanning calorimeter （DSC） analysis and Fourier transform infrared （FTIR） spectra. The results showed that the curing course of bio-based epoxy resin system containing RAM included two stages, which were the reaction between the free carboxyl group of RAM and oxirane ring under the acceleration of IMA, and the main reaction attributed to the reaction between anhydride and oxirane. According to Kissinger method, the reaction activation energy （E,） of two stages were 68.9 and 86.5kJmo1-1, respectively. The Eo of EP/MHHPA and EP/IMA resin system were 81.04 and 77.9kJmol-I. The processing property of EP/RAM/IMA system, i.e. the relationship between viscosity-temperature-time, was characterized by cone-plate viscometer aim to decide the processing parameter ofprepreg preparation. The effect of RAM content on mechanical performance and dynamic mechanical property was investigated. Noteworthily, compared with the laminates with EP/MHHPA as matrix, the laminates with RAM as hardeners achieved a 44%, 73% and 70℃ increase in bending strength, bending modulus and the glass transition temperature, respectively, due to the bulky hydrogenated phenanthrene ring structure incorporated into the cross-linking networks. When the fiber volume fraction reached 47%, the mechanical property of the laminates prepared with hot melt prepreg was superior or comparable to that of composites with pure petroleum sourced matrix. RAM as cross-linking agent of epoxy resin holds a great potential to satisfy the requirement of composites such as structure and secondary structure parts preparation.

Coupling effects of stress and ion irradiation on the mechanical behaviors of copper nanowires

By using molecular dynamics simulations,we studied the ion irradiation induced damage in mechanically strained Cu nanowires and evaluated the effects of damage on the mechanical properties of nanowires.The stresses in the pre-strained nanowires can be released significantly by the dislocation emission from the cascade core when the strain is greater than 1%.In addition,comparison of the stress-strain relationships between the defect-free nanowire and the irradiated ones indicates that ion irradiation reduces the yield strength of the Cu nanowires,and both the yield stress and strain decrease with the increase of irradiation energy.The results are consistent with the microscopic mechanism of damage production by ion irradiation and provide quantitative information required for accessing the stability of nanomaterials subjected to mechanical loading and irradiation coupling effects.

Dynamic PIV Measurement of a Compressible Flow Issuing from an Airbag Inflator Nozzle

Among many equipment for passenger safety, the air bag system is the most fundamental and effective device for an automobile. The inflator housing is a main part of the curtain-type air bag system, which supplies high-pressure gases in pumping up the air bag-curtain which is increasingly being adapted in deluxe cars for protecting passengers from the danger of side clash. However, flow information on the inflator housing is very limited. In this study, we measure the instantaneous velocity fields of a high-speed compressible flow issuing from the exit nozzle of an inflator housing using a dynamic PIV system. From the velocity field data measured at a high frame-rate, we evaluate the variation of the mass flow rate with time. The dynamic PIV system consists of a high-repetition Nd：YLF laser, a high-speed CMOS camera, and a delay generator. The flow images are taken at 4000 fps with synchronization of the trigger signal for inflator ignition. From the instantaneous velocity field data of flow ejecting from the airbag inflator housing at the initial stage, we can see a flow pattern of broken shock wave front and its downward propagation. The flow ejecting from the inflator housing is found to have very high velocity fluctuations, with the maximum velocity at about 700 m/s. The time duration of the high-speed flow is very short, and there is no perceptible flow after 100 ms.

Microstructures and mechanical properties of SiBCNAl ceramics produced by mechanical alloying and subsequent hot pressing

Amorphous SiBCNAl powders were prepared via a mechanical alloying (MA) technique using crystalline silicon (Si), hexagonal boron nitride (h-BN), graphite (C), and aluminum (Al) as starting materials. SiBCNAl powders were consolidated by a hot pressing (HP) technique at 1800 °C under a pressure of 30 MPa in argon and nitrogen. The sintering atmosphere had a great influence on the microstructures and mechanical properties of the ceramics. The two ceramics had different phase compositions and fracture surface morphologies. For the ceramics sintered in argon, flexural strength, fracture toughness, elastic modulus and Vickers hardness were 421.90 MPa, 3.40 MPa·m1/2, 174.10 GPa, and 12.74 GPa, respectively. For the ceramics sintered in nitrogen, the mechanical properties increased, except for the Vickers hardness, and the values of the above properties were 526.80 MPa, 5.25 MPa·m1/2, 222.10 GPa, and 11.63 GPa, respectively.