Lightweight Design of Automobile Drive Shaft Based on the Characteristics of Low Amplitude Load Strengthening

There are two kinds of internationally recognized approaches in terms of lightweight design.One is based on fatigue accumulated damage theory to achieve better reliability by optimal structural design; another is to use high performance lightweight materials.The former method takes very few considerations on the structural strengthening effects caused by the massive small loads in service.In order to ensure safety,the design is usually conservative,but the strength potential of the component is not fully exerted.In the latter method,cost is the biggest obstacle to lightweight materials in automotive applications.For the purpose of light weighting design on a fuel cell vehicle,the new design method is applied on drive shafts.The method is based on the low amplitude load strengthening characteristics of the material,and allows the stress,corresponding to test load,to enter into the strengthened range of the material.Under this condition,the light weighting design should assure that the reliability of the shaft is not impaired,even maximizes the strength potential of machine part in order to achieve the weight reduction and eventually to reduce the cost.At last,the feasibility of the design is verified by means of strength analysis and modal analysis based on the CAD model of light weighted shaft.The design applies to the load case of half shaft in independent axle,also provides technological reference for the structural lightweight design of vehicles and other machineries.

STRENGTHENING MECHANISMSIN TiAl BASED ALLOYS

The influence of heat treatment and of thermomechanical processing on the structure and properties of a range of TiAl based alloys has been assessed and in agreement with other reports it has been found that increased refinement of the microstructure leads to improved mechanical strength at room temperature, both for the lamellar and the duplex structures. In the case of alloys cooled rapidly from the alpha phase field the increased refinement in lamellar spacing leads to significant increases in room temperature strength but thermomechanical processing can lead to far greater increases. The origin of this increase in strength in samples with a lamellar structure has been assessed in terms of the ability of dislocations to cross gamma/gamma and gamma/alpha 2 lamellar interfaces. It was concluded that the alpha 2 gamma interfaces and the alpha itself are important factors in strengthening the lamellar alloys. The stability of the various structures developed either by appropriate heat treatments or by thermomechanical processing has been investigated by exposing samples for a range of times at temperatures between 700 and 1 000 ℃. It has been found that the yield strength and the ultimate tensile strength generally decreased by about 20% during high temperature exposure at 700 ℃ for 3 000 h. The detailed behaviour on exposure at 700 ℃ has been found to be a function of alloy composition, with complex precipitates being formed in some alloys, but in all cases the amount of alpha 2 decreased with increased heat treatment time. It has been found that during exposure the alpha 2 lamellae decomposed to gamma phase by a mechanism that can involve the formation of thin gamma lamellae within the original alpha 2 lamellae.

Strengthening mechanisms based on reinforcement distribution uniformity for particle reinforced aluminum matrix composites

A modified mixed strengthening model was proposed for describing the yield strength of particle reinforced aluminum matrix composites.The strengthening mechanisms of the composites were analyzed based on the microstructures and compression mechanical properties.The distribution uniformity of reinforcements and cooperation relationship among dislocation mechanisms were considered in the modified mixed strengthening model by introducing a distribution uniformity factor u and a cooperation coefficient fc,respectively.The results show that the modified mixed strengthening model can accurately describe the yield strengths of Al3Ti/2024Al composites with a relative deviation less than1.2%,which is much more accurate than other strengthening models.The modified mixed model can also be used to predict the yield strength of Al3Ti/2024Al composites with different fractions of reinforcements.

Strengthening mechanisms of indirect-extruded Mg-Sn based alloys at room temperature

The strength of a material is dependent on how dislocations in its crystal lattice can be easily propagated.These dislocations create stress fields within the material depending on their intrinsic character.Generally,the following strengthening mechanisms are relevant in wrought magnesium materials tested at room temperature:fine-grain strengthening,precipitate strengthening and solid solution strengthening as well as texture strengthening.The indirect-extruded Mg-8Sn(T8)and Mg-8Sn-1Al-1Zn(TAZ811)alloys present superior tensile properties compared to the commercial AZ31 alloy extruded in the same condition.The contributions to the strengthen of Mg-Sn based alloys made by four strengthening mechanisms were calculated quantitatively based on the microstructure characteristics,physical characteristics,thermomechanical analysis and interactions of alloying elements using AZ31 alloy as benchmark.

EFFECT OF Nb ON STRENGTHENING OF Fe-BASE SUPERALLOY AT INTERMEDIATE HIGH TEMPERATURES

Because Nb accelerates the uniform distribution of MC phase and the grain refinement,as well as,increases the amount and stability of γ-phase,the tensile strength,ductility,stress rupture life and fatigue limit of Fe-30Ni-13Cr-1.2W-1.5Mo-2.5Ti-0.4AI superalloy at 650℃ can be improved with increase of Nb content up to 1.22 wt-%.The precipitation of small Laves phase particles dispersed along grain boundaries may be favourable to combined properties of the superalloy containing 1.22 wt-% Nb.It will be worsened only that the pre- cipitation of Laves phase particles'dispersed along grain boundaries may be favourable for combined properties of the superalloy containing 1.22 wt-% Nb.It will be worsened only that the precipitation of Laves phase is too more because of too high Nb content existhing.

Towards high strength cast Mg-RE based alloys:Phase diagrams and strengthening mechanisms

Mg-rare earth(RE)based systems provide several important commercial alloys and many alloy development opportunities for high strength applications,especially in aerospace and defense industries.The phase diagrams,microstructure,and strengthening mechanisms of these multicomponent systems are very complex and often not well understood in literature.We have calculated phase diagrams of important binary,ternary,and multicomponent RE-containing alloy systems,using CALPHAD(CALculation of PHAse Diagrams).Based on these phase diagrams,this paper offers a critical overview on phase equilibria and strengthening mechanisms in these alloy systems,including precipitation,long period stacking order(LPSO),and other intermetallic phases.This review also summarized several promising Mg-RE based cast alloys in comparison with commercial WE54 and WE43 alloys;and explored new strategies for future alloy development for high strength applications.It is pointed out that the combination of precipitation and LPSO phases can lead to superior strength and ductility in Mg-RE based cast alloys.The precipitates and LPSO phases can form a complex three-dimensional network that effectively impedes dislocation motion on the basal and non-basal planes.The LPSO phases can also prevent the coarsening of precipitates when they interact,thus providing good thermal stability at elevated temperatures.Future research is needed to determine how the combination of these two types of phases can be used in alloy design and industrial scale applications.

Strengthening mechanism of T8-aged Al-Cu-Li alloy with increased pre-deformation

The microstructure evolution and mechanical properties of a T8-aged Al-Cu-Li alloy with increased pre-deformation(0-15%) were investigated,revealing the microstructure-strength relationship and the intrinsic strengthening mechanism.The results show that increasing the pre-deformation levels remarkably improves the strength of the alloy but deteriorates its ductility.Dislocations introduced by pre-deformation effectively suppress the formation of Guinier-Preston(GP) zones and provide more nucleation sites for T1 precipitates.This leads to more intensive and finer T1 precipitates in the samples with higher pre-deformation levels.Simultaneously,the enhanced precipitation of T1 precipitates and inhibited formation of GP zones cause the decreases in number and sizes of θ′ precipitates.The quantitative descriptions of the strength contributions from different strengthening mechanisms reveal that strengthening contributions from T1 and θ′ precipitates decrease with increasing pre-deformation.The reduced diameters of T1 precipitates are primarily responsible for their weakened strengthening effects.Therefore,the improved strength of the T8-aged Al-Cu-Li alloy is mainly attributed to the stronger strain hardening from the increased pre-deformation levels.

Enhanced mechanical properties of molybdenum alloy originating from composite strengthening of Re and CeO_(2)

To enhance the mechanical properties of molybdenum alloys at both room and high temperatures,Mo-14Re-1CeO_(2)alloy was synthesized using the powder metallurgy method,and the corresponding microstructure and mechanical properties were characterized.The results indicate that the ultimate tensile strength of Mo-14Re-1CeO_(2)reaches 657 MPa,with a total elongation of 35.2%,significantly higher than those of pure molybdenum(453 MPa,and 7.01%).Furthermore,the compression strength of Mo-14Re-1CeO_(2)at high temperature(1200℃)achieves 355 MPa,which is still larger than that of pure molybdenum(221 MPa).It is revealed that there is a coherent interface between CeO_(2)and the Mo-14Re matrix with CeO_(2)particles uniformly distributed in both intergranular and intragranular regions.The improvements in mechanical properties are primarily attributed to the formation of Mo-Re solid solution,grain refinement,and dispersion strengthening effect of CeO_(2).

Significant strengthening of copper-based composites using boron nitride nanotubes

Nanotubes, such as boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs), exhibit excellent mechanical properties. In this work, high-quality BNNTs were synthesized by ball milling and annealing. Subsequently, well-dispersed 3vol%BNNTs/Cu and 3vol%CNTs/Cu composites were successfully prepared using ball milling, spark plasma sintering, and followed by hot-rolling. Moreover, the mechanical properties and strengthening mechanisms of BNNTs/Cu and CNTs/Cu composites were compared and discussed in details. At 293 K,both BNNTs/Cu and CNTs/Cu composites exhibited similar ultimate tensile strength (UTS) of~404 MPa, which is approximately 170%higher than pure Cu. However, at 873 K, the UTS and yield strength of BNNTs/Cu are 27%and 29%higher than those of CNTs/Cu, respectively.This difference can be attributed to the stronger inter-walls shear resistance, higher thermomechanical stability of BNNTs, and stronger bonding at the BNNTs/Cu interface as compared to the CNTs/Cu interface. These findings provide valuable insights into the potential of BNNTs as an excellent reinforcement for metal matrix composites, particularly at high temperature.

New construction of mutually unbiased bases for odd-dimensional state space

We study the construction of mutually unbiased bases in Hilbert space for composite dimensions d which are not prime powers.We explore the results for composite dimensions which are true for prime power dimensions.We then provide a method for selecting mutually unbiased vectors from the eigenvectors of generalized Pauli matrices to construct mutually unbiased bases.In particular,we present four mutually unbiased bases in C^(15).

EFFECT OF RARE EARTH ELEMENT Er ON STRENGTHENING OF INTERFACE OF Ti（C，N） BASED CERMETS

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Experimental investigation of engineered geopolymer composite for structural strengthening against blast loads

The recent increase in blast/bombing incidents all over the world has pushed the development of effective strengthening approaches to enhance the blast resistance of existing civil infrastructures.Engineered geopolymer composite(EGC)is a promising material featured by eco-friendly,fast-setting and strain-hardening characteristics for emergent strengthening and construction.However,the fiber optimization for preparing EGC and its protective effect on structural elements under blast scenarios are uncertain.In this study,laboratory tests were firstly conducted to evaluate the effects of fiber types on the properties of EGC in terms of workability,dry shrinkage,and mechanical properties in compression,tension and flexure.The experimental results showed that EGC containing PE fiber exhibited suitable workability,acceptable dry shrinkage and superior mechanical properties compared with other types of fibers.After that,a series of field tests were carried out to evaluate the effectiveness of EGC retrofitting layer on the enhancement of blast performance of typical elements.The tests include autoclaved aerated concrete(AAC)masonry walls subjected to vented gas explosion,reinforced AAC panels subjected to TNT explosion and plain concrete slabs subjected to contact explosion.It was found that EGC could effectively enhance the blast resistance of structural elements in different scenarios.For AAC masonry walls and panels,with the existence of EGC,the integrity of specimens could be maintained,and their deflections and damage were significantly reduced.For plain concrete slabs,the EGC overlay could reduce the diameter and depth of the crater and spallation of specimens.

Squeeze-Strengthening Effect of Silicone Oil-based Magnetorheological Fluid

In order to study the squeeze-strengthening effect of silicone oil-based magnetorheological fluid （MRF）, theoretical basis of disc squeezing brake was presented and a squeezing braking characteristics test-bed for MRF was designed. Moreover, relevant experiments were carded out and the relationship between squeezing pressure and braking torque was proposed. Experiments results showed that the yield stress of MRF improved linearly with the increasing of external squeezing pressure and the braking torque increased three times when external squeezing pressure achieved 2 MPa.

CALCULATION ON THE YIELD STRENGTH OF A PRECIPITATION STRENGTHENING Ni－BASE ALLOYS

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Antiphase Boundary Strengthening in a Single Crystal Nickel-base Superalloy

An investigation has been made into strengthening mechanism in a single crystal nickel-base superalloy DD8 by transmission electron microscopy. The results show that the stress rupture strength of the alloy increases with decreasing misfit, and the antiphase boundaries (APBs) formed in the ordered γ' phase, rather than the misfits, play a dominate role in strengthening of the single crystal Ni-base superalloy DD8.There are three kinds of mechanisms for forming the APBs which were observed in the present materials. One is mis-arrangement of the local ordered atoms in the γ' precipitates due to the local strain; the second arises from the 1/2<110> dislocations cutting into the γ', and the third is the formation of the APBs induced by the 1/2<110> matrix dislocation network. The contribution of the antiphase boundary energy to the strength of the alloy can be expressed by:where τ is the resistance to deformation provided by the APB energy; S is the long-range order degree in γ'; Tc is the transition temperature from order to disorder; f is the volume fraction of γ'; rs is the radius of γ'; b is the Burgers vector; a is the lattice constant; G is the shear modulus, and k is the proportional constant.

COMPARISON OF THE EFFECTS OF DIFFERENT STRENGTHENING NETS IN MAXILLARY COMPLETE DENTURE RESIN BASE BY THREE-DIMENSIONAL FINITE ELEMENT METHODS

Diastema often occured in maxillary complete denture resin base in the clinic,although " Lucitone 199" had been used with more tensile strength.Mechanical ex-periments have proved the high transverse tensile stress (σ_x^+) concentrating in anteri-or teeth region and their palatal surface of maxillary complete denture resin basewhile it was exposed to vertical loading in center occlusion.Setting strengtheningnet in resin base has achieved better results.For evaluating purpose,twenty

Research on the Construction and Development of Aesthetic Education Bases in Higher Education Institutions

In order to implement the national aesthetic education policy,it is essential to organically integrate relevant aesthetic education resources,promote interdisciplinary education,and carry out extracurricular practical activities centered on aesthetic education.Strengthening the foundation of aesthetic education theory,addressing practical challenges in the teaching process,and closely linking research with teaching will create a feedback loop that benefits drama education.This article provides an in-depth analysis of the construction strategies,resource advantages and disadvantages,and development of aesthetic education bases,offering countermeasures and suggestions for their construction in universities.It aims to provide a solid research foundation for the growth and development of aesthetic education bases in higher education institutions.

Quantifying Solid Solution Strengthening in Nickel-Based Superalloys via High-Throughput Experiment and Machine Learning

Solid solution strengthening(SSS)is one of the main contributions to the desired tensile properties of nickel-based superalloys for turbine blades and disks.The value of SSS can be calculated by using Fleischer’s and Labusch’s theories,while the model parameters are incorporated without fitting to experimental data of complex alloys.In thiswork,four diffusionmultiples consisting of multicomponent alloys and pure Niare prepared and characterized.The composition and microhardness of singleγphase regions in samples are used to quantify the SSS.Then,Fleischer’s and Labusch’s theories are examined based on high-throughput experiments,respectively.The fitted solid solution coefficients are obtained based on Labusch’s theory and experimental data,indicating higher accuracy.Furthermore,six machine learning algorithms are established,providing a more accurate prediction compared with traditional physical models and fitted physical models.The results show that the coupling of highthroughput experiments and machine learning has great potential in the field of performance prediction and alloy design.

Homogenization Construction of Three-Level Teaching Bases for General Practice Medicine Under the Internet+Model

With the continuous expansion of medical student enrollment,the number of clinical teaching bases is gradually increasing.However,there are significant differences in clinical teaching management models and teaching levels among different bases.Most clinical teaching bases have incomplete teaching management systems,inadequate teaching management institutions,insufficient teaching personnel,and inadequate implementation of teaching rules and regulations.This article combines the construction practice of three-level clinical teaching base of the General Medicine College and the First Affiliated Hospital of Xi’an Medical University.We establish a standardized management system for the three-level clinical teaching base;implement a teaching supervision system and strengthen the monitoring of teaching quality;adopt multiple evaluations to test the effectiveness of clinical teaching implementation;explore the path of homogenization construction of teaching bases in terms of unified teacher training,promoting the development of teacher teaching abilities with equal quality and excellence,and providing a reference for improving the quality of medical talent training.

Interfacial structure and joint strengthening in arc brazed galvanized steels with copper based filler

Galvanized steel sheets were joined by tungsten inert gas(TIG) and metal inert gas(MIG) brazing process using copper based filler. The results show that the joint zone hardness is higher than that of the base material or copper filler from the microhardness tests of TIG brazing specimens, and the fracture spot is at the base materials zone from the tensile tests of MIG brazing specimens. Examination using energy dispersive X-ray analysis reveals the presence of intermetallic compound Fe5Si3(Cu) in the joint. The dispersal of fine Fe5Si3(Cu) particles is the main strengthening factor for the joint. The Fe5Si3(Cu) particles are determined to arise from three sources, namely, spot micro-melt, whisker-like fragmentation and dissolve-separation actions.