Mechanical Properties of Copper with Dendritic Silver Inclusions:Insights from Molecular Dynamics Simulations

This study explores the mechanical behavior of single-crystal copper with silver inclusions,focusing on the effects of dendritic and spherical geometries using molecular dynamics simulations.Uniaxial tensile tests reveal that dendritic inclusions lead to an earlier onset of plasticity due to the presence of high-strain regions at the complex inclusion/matrix interfaces,whereas spherical inclusions exhibit delayed plasticity associated with their symmetric geometry and homogeneous strain distribution.During the plastic regime,the dislocation density is primarily influenced by the volume fraction of silver inclusions rather than their shape,with spherical inclusions showing the highest densities due to their larger volume and higher silver content.Stacking faults,quantified via hexagonal closed-packed atom populations,are strongly correlated with dislocation activity but exhibit transient behavior,indicating that many faults are swept out or transformed during deformation.This transfient effect is observed in all cases,independently of the inclusion size.These findings highlight the complex interplay between inclusion geometry,dislocation activity,and stacking fault evolution in shaping the mechanical properties of copper.The study underscores the need to account for inclusion morphology and defect dynamics when designing advanced copper-based materials and suggests further investigations into the role of dendrite orientation and distribution to enhance material performance in engineering applications.

Solvent transport dynamics and its effect on evolution of mechanical properties of nitrocellulose(NC)-based propellants under hot-air drying process

Appropriate drying process with optimized controlling of drying parameters plays a vital role in the improvement of the quality and performance of propellant products.However,few research on solvent transport dynamics within NC-based propellants was reported,and its effect on the evolution of mechanical properties was not interpreted yet.This study is conducted to gain a comprehensive understanding of hot-air drying for NC-based propellants and clarify the effect of temperature on solvent transport behavior and further the change of mechanical properties during drying.The drying kinetic curves show the drying time required is decreased but the steady solvent content is increased and the drying rate is obviously increased with the increase of hot-air temperatures,indicating hot-air temperatures have a significant effect on drying kinetics.A modified drying model was established,and results show it is more appropriate to describe solvent transport behavior within NC-based propellants.Moreover,two linear equations were established to exhibit the relationship between solvent content and its effect on the change of tensile properties,and the decrease of residual solvent content causes an obvious increase of tensile strength and tensile modulus of propellant products,indicating its mechanical properties can be partly improved by adjustment of residual solvent content.The outcomes can be used to clarify solvent transport mechanisms and optimize drying process parameters of double-based gun propellants.

Microscopic damage and dynamic mechanical properties of rock under freeze-thaw environment

For understanding the rock microscopic damage and dynamic mechanical properties subjected to recurrent freeze-thaw cycles, experiments for five groups of homogeneous sandstone under different freeze-thaw cycles were conducted. After freezethaw, nuclear magnetic resonance(NMR) tests and impact loading tests were carried out, from which microscopic damage characteristics of sandstone and dynamic mechanical parameters were obtained. The results indicate that the porosity increases with the increase of cycle number, the rate of porosity growth descends at the beginning of freeze-thaw, yet accelerates after a certain number of cycles. The proportion of pores with different sizes changes dynamically and the multi-scale distribution of pores tends to develop on pore structure with the continuing impact of freeze-thaw and thawing. Dynamic compressive stress-strain curve of sandstone undergoing freeze-thaw can be divided into four phases, and the phase of compaction is inconspicuous compared with the static curve. Elastic modulus and dynamic peak intensity of sandstone gradually decrease with freeze-thaw cycles, while peak strain increases. The higher the porosity is, the more serious the degradation of dynamic intensity is. The porosity is of a polynomial relationship with the dynamic peak intensity.

Dynamic mechanical properties and constitutive equations of 2519A aluminum alloy

To analyze the effects of strain rate and temperature on the flow stress of 2519A aluminum alloy, the dynamic mechanical properties of 2519A aluminum alloy were measured by dynamic impact tests and quasi-static tensile tests. The effects of strain rate and temperature on the microstructure evolution were investigated by optical microscopy （OM） and transmission electron microscopy （TEM）. The experimental results indicate that 2519A aluminum alloy exhibits strain-rate dependence and temperature susceptibility under dynamic impact. The constitutive constants for Johnson--Cook material model were determined by the quasi-static tests and Hopkinson bar experiments using the methods of variable separation and nonlinear fitting. The constitutive equation seems to be consistent with the experimental results, which provides reference for mechanical characteristics and numerical simulation of ballistic performance.

Dynamic mechanical properties and instability behavior of layered backfill under intermediate strain rates

To obtain dynamic mechanical properties and failure rule of layered backfill under strain rates from10to80s-1,impactloading test on layered backfill specimens(LBS)was conducted by using split Hopkinson pressure bar system.The results indicatethat positive correlation can be found between dynamic compressive strength and strain rate,as well as between strength increasefactor and strain rate.Dynamic compressive strength of LBS gets higher as the arithmetic average cement-sand ratio increases.Compared with static compressive strength,dynamic compressive strength of LBS is enhanced by11%to163%.In addition,theenergy dissipating rate of LBS lies between that of corresponding single specimens,and it decreases as the average cement contentincreases.Deformation of LBS shows obvious discontinuity,deformation degree of lower strength part of LBS is generally higherthan that of higher strength part.A revised brittle fracture criterion based on the Stenerding-Lehnigk criterion is applied to analyzingthe fracture status of LBS,and the average relevant errors of the3groups between the test results and calculation results are4.80%,3.89%and4.66%,respectively.

Combined effects of temperature and axial pressure on dynamic mechanical properties of granite

In order to get the dynamic mechanical properties of deep rock mass suffered both high temperature and high pressure,impact loading experiments on granite subjected to temperature and axial pressure were carried out. Furthermore, the internalstructure characteristics of granite under different temperatures were observed by scanning electron microscopy (SEM). The results show that the longitudinal wave velocity assumes a downward trend which shows a rapid drop before falling slowly as the temperature increases. The uniaxial compressive strength of the specimen decreases significantly at temperatures of 25?100 °C compared to that at temperatures of 100?300 °C. The peak strain rises rapidly before the dividing point of 100 °C, but increases slowly after the dividing point. The internal structure of the rock changes substantially as the temperature increases, such as the extension and transfixion of primary and newborn cracks. In addition, the thermal damage under axial pressure is greater than that described by the longitudinal wave velocity and the phenomenon shows obviously when the temperature increases.

Influence of dynamic recrystallization on microstructure and mechanical properties of welding zone in Al-Mg-Si aluminum profile during porthole die extrusion

The effect of dynamic recrystallization(DRX)on the microstructure and mechanical properties of 6063 aluminum alloy profile during porthole die extrusion was studied through experiment and simulation.The grain morphology was observed by means of electron backscatter diffraction(EBSD)technology.The results show that,at low ram speeds,increasing the ram speed caused an increase in DRX fraction due to the increase of temperature and strain rate.In contrast,at high ram speeds,further increasing ram speed had much less effect on the temperature,and the DRX faction decreased due to high stain rates.The microhardness and fraction of low angle boundaries in the welding zones were lower than those in the matrix zones.The grain size in the welding zone was smaller than that in the matrix zone due to lower DRX fraction.The decrease of grain size and increase of extrudate temperature were beneficial to the improvement of microhardness.

Effect of Gd content on microstructure and dynamic mechanical properties of solution-treated Mg−xGd−3Y−0.5Zr alloy

The effect of Gd content ranging from 6.5 wt.%to 8.5 wt.%on microstructure evolution and dynamic mechanical behavior of Mg−xGd−3Y−0.5Zr alloys was investigated by optical microscopy,X-ray diffraction,scanning electron microscopy and split Hopkinson pressure bar.The microstructure of as-cast Mg−xGd−3Y−0.5Zr alloys indicates that the addition of Gd can promote grain refinement in the casting.Due to the rapid cooling rate during solidification,a large amount of non-equilibrium eutectic phase Mg_(24)(Gd,Y)_(5) appears at the grain boundary of as-cast Mg−xGd−3Y−0.5Zr alloys.After solution treatment at 520℃ for 6 h,the Mg_(24)(Gd,Y)_(5) phase dissolves into the matrix,and the rare earth hydrides(REH)phase appears.The stress−strain curves validate that the solution-treated Mg−xGd−3Y−0.5Zr alloys with optimal Gd contents maintain excellent dynamic properties at different strain rates.It was concluded that the variation of Gd content and the agglomeration of residual REH particles and dynamically precipitated fine particles are key factors affecting dynamic mechanical properties of Mg−xGd−3Y−0.5Zr alloys.

Mathematical modeling for dynamic stability of sandwich beam with variable mechanical properties of core

The paper is devoted to mathematical modelling of static and dynamic stability of a simply supported three-layered beam with a metal foam core. Mechanical properties of the core vary along the vertical direction. The field of displacements is for- mulated using the classical broken line hypothesis and the proposed nonlinear hypothesis that generalizes the classical one. Using both hypotheses, the strains are determined as well as the stresses of each layer. The kinetic energy, the elastic strain energy, and the work of load are also determined. The system of equations of motion is derived using Hamilton＇s principle. Finally, the system of three equations is reduced to one equation of motion, in particular, the Mathieu equation. The Bubnov-Galerkin method is used to solve the system of equations of motion, and the Runge-Kutta method is used to solve the second-order differential equation. Numerical calculations are done for the chosen family of beams. The critical loads, unstable regions, angular frequencies of the beam, and the static and dynamic equilibrium paths are calculated analytically and verified numerically. The results of this study are presented in the forms of figures and tables.

Dynamic recrystallization and mechanical properties of high-strain-rate hot rolled Mg-5Zn alloys with addition of Ca and Sr

Effects of the sole and the combined addition of Ca and Sr on microstructure and mechanical properties of as-cast and as-rolled Mg-5 Zn alloys were carefully investigated by OM,SEM,hot-compression testing and tensile testing.Ca is more effective than Sr in the microstructural refinement of as-cast alloys.High-strain-rate rolling(HSRR)produces more deformed twins and thus provides more nucleation sites for dynamic recrystallization(DRX).The addition of Ca and Sr can promote dynamic precipitation during HSRR,the precipitation process would consume the storage energy and thus increases the critical strain value of DRX,resulting in the retarded DRX effect by the addition of Ca and/or Sr.The as-rolled Mg-5 Zn-0.4 Ca-0.2 Sr alloy exhibits a good combination of strength and ductility,with the ultimate tensile strength of 317 MPa,the yield strength of 235 MPa and the elongation to rupture of 24%.

Temperature Dependency of Dynamic Mechanical Properties of Cement Asphalt Paste by DMTA Method

We investigated the temperature dependency of the dynamic mechanical properties of cement asphalt paste by the dynamic mechanical thermal analysis（DMTA） method. The experimental results show that the dynamic mechanical properties of cement asphalt pastes are sensitive to temperature due to the inclusion of asphalt, and may go through different states within a temperature range of-40 ℃ to 60 ℃, which is different from that of pure cement and asphalt. As the temperature of the cement asphalt paste increases, a considerable change of dynamic mechanical properties, including storage modulus（E＇）, loss modulus（E＇＇） and loss factor（tand） is observed. Moreover, the influence of asphalt to cement（A/C） ratio on the temperature sensitivity of the dynamic mechanical properties of cement asphalt composites was investigated. The temperature dependency of cement asphalt composites is ascribed to the temperature dependency of the asphalt and its interaction with cement paste. A simple fractional model is proposed to describe the viscoelastic behavior of cement asphalt composites.

Dynamic recrystallization behavior and mechanical properties of bimodal scale Al2O3 reinforced AZ31 composites by soild state synthesis

In this paper,(500 nm 1%+5μm 3%)bimodal scale Al2O3p/AZ31 composites was fabricated by solid state synthesis and the effect of bimodal scale Al2O3 particulates on its dynamic recrystallization behavior and mechanical properties was investigated.The optical microscopy,scanning electron microscopy,transmission electron microscopy and electron universal strength tester composites were used to characterize the composites.The results indicate that the grains size of the composites are significantly refined and the mechanical properties are obviously improved.Due to the presence of the bimodal scale Al2o3 particulates,the high-density dislocation zone is formed around nano-Al2o3p and the particle deformation zone is formed near micron-ABOap.These zones are ideal sites for the formation of recrystallization nucleus.Meanwhile,the addition of the bimodal scale Al2o3 particulates may delay or hinder the growth of matrix grain through the pining effect on the grain boundaries,resulting in significantly improving the yield strength and tensile strength of Al2O3p/AZ31 composites.

Predicting uniaxial compressive strength of serpentinites through physical,dynamic and mechanical properties using neural networks

The uniaxial compressive strength(UCS)of intact rock is one of the most important parameters required and determined for rock mechanics studies in engineering projects.The limitations and difficulty of conducting tests on rocks,specifically on thinly bedded,highly fractured,highly porous and weak rocks,as well as the fact that these tests are destructive,expensive and time-consuming,lead to development of soft computing-based techniques.Application of artificial neural networks(ANNs)for predicting UCS has become an attractive alternative for geotechnical engineering scientists.In this study,an ANN was designed with the aim of indirectly predicting UCS through the serpentinization percentage,and physical,dynamic and mechanical characteristics of serpentinites.For this purpose,data obtained in earlier experimental work from central Greece were used.The ANN-based results were compared with the experimental ones and those obtained from previous analysis.The proposed ANN-based formula was found to be very efficient in predicting UCS values and the samples could be classified with simple physical,dynamic and mechanical tests,thus the expensive,difficult,time-consuming and destructive mechanical tests could be avoided.

Effects of dynamic cooling pre-aging treatment on mechanical properties and paint-bake hardening behavior of Al-Mg-Si alloy automotive sheets

In the industrial production, the dynamic cooling pre-aging treatment was employed to replace the isothermal pre-aging during the continuous heat treatment production of Al-Mg-Si alloy automotive sheets. The effects of dynamic cooling pre-aging treatment on mechanical properties and paint-bake hardening behavior of an Al-Mg-Si alloy sheet are proposed in this study. The scanning electron microscopy, transmission electron microscopy, tensile test, Vickers hardness test, and differential scanning calorimetry were conducted for the purpose. It was found that the dynamic cooling pre-aging treatment at low temperature region led to the decreasing of cluster II, resulting in the deterioration of the ability of the paint-bake hardening. With the increase of the cooling pre-aging temperature, the increasing of cluster II effectively improved the stability against natural aging and the paint-bake hardening ability. The optimized dynamic cooling pre-aging temperature was ~150 ℃. In this condition, the hardness increase of the alloy sheet with pre-aging treatment is low during storage at room temperature. The high yield strength increment is obtained after paint-bake hardening.

Investigation on the Mechanical Properties of Polycrystalline Mg Using Molecular Dynamics Simulation

Magnesium(Mg)and its composites have been widely used in different fields,but the mechanical properties and deformation mechanisms of polycrystalline Mg(polyMg)at the atomic scale are poorly understood.In this paper,the effects of grain size,temperature,and strain rate on the tensile properties of polyMg are explored and discussed by theMolecular dynamics(MD)simulation method.The calculated results showed that there exists a critical grain size of 10 nm for the mechanical properties of polyMg.The flow stress decreases with the increase of grain size if the average grain size is larger than 10 nm,which shows the Hall-Petch effect,and the deformation mechanism of large grain-sized polyMg is mainly dominated by the movement of dislocations.When the average grain size is less than 10 nm,it shows the reverse Hall-Petch effect that the flow stress decreases with the decrease of grain size,and the deformation mode of polyMg with small grain-size is the movement and deformation of atoms at the grain boundary.Due to the more active motion of atoms as the system temperature increases,the material can easily reach the plastic stage under tensile loading,and the mechanical properties of polyMg decrease at high temperatures.The strain rate has a hardening effect on the properties of composite.Based on our calculated results,it can provide theoretical guidance for the applications of Mg metal and Mg matrix composites.

Dynamic mechanical properties of PTFE-based composites filled with multi-component

To improve performance of PTFE-based damping material,composites with several fillers were prepared by compressing and sintering. The dynamic mechanical properties of the composites were investigated by means of viscoanalyser. Temperature-dependent loss factors,storage modulus and loss modulus were obtained. And SEM was employed to study the compatibility between PTFE and fillers. The results show that,when blending PPS and PEEK at proper content,the loss factor curve appears double peaks,which can widen the high-damping temperature region of the composites. Blending graphite or alumina can increase the storage modulus obviously,but decrease the value of loss factor. And because graphite or alumina combines with matrix poorly,glide would happen at interface when bearing external load. The interface friction can dissipate vibration energy,which increases the loss modulus of the composites. Blending PPS,PEEK and graphite or alumina at right content,PTFE-based composites can meet demands as damping material in practical engineering.

The study of measuring technology on the dynamic mechanical properties of welded joint with high strainrate

In this paper, to meet the needs of studying work of dynamic mechanical properties of welded joint, the dynamic mechanical properties of welded joint were measured by means of SHPB(Split Hopkinson Pressure Bar).The dynamic mechanical property's curves of every part of welded joint were obtained. For studying the dynamic behavior of mechanical heterogeneity of welded joint, important data were offered. The method of test creates a new way of studying dynamic mechanical properties of welded joint.

Microstructure Evolution and Dynamic Mechanical Properties of Laser Additive Manufacturing Ti-6Al-4V Under High Strain Rate

The dynamic mechanical properties of the Ti-6Al-4V(TC4)alloy prepared by laser additive manufacturing(LAM-TC4)under the high strain rate(HSR)are proposed.The dynamic compression experiments of LAM-TC4 are conducted with the split Hopkinson pressure bar(SHPB)equipment.The results show that as the strain rate increases,the widths of the adiabatic shear band(ASB),the micro-hardness,the degree of grain refinement near the ASB,and the dislocation density of grains grow gradually.Moreover,the increase of dislocation density of grains is the root factor in enhancing the yield strength of LAM-TC4.Meanwhile,the heat produced from the distortion and dislocations of grains promotes the heat softening effect favorable for the recrystallization of grains,resulting in the grain refinement of ASB.Furthermore,the contrastive analysis between LAM-TC4 and TC4 prepared by forging(F-TC4)indicates that under the HSR,the yield strength of LAM-TC4 is higher than that of F-TC4.

First-principles investigations on structural stability,mechanical,and thermodynamic properties of LaT2Al20(T=Ti,V,Cr,Nb,and Ta) intermetallic cage compounds

First principles calculations were used to explore the structural stability, mechanical properties, and thermodynamic properties of LaT2Al20(T = Ti, V, Cr, Nb, and Ta) intermetallics. The calculated formation enthalpy and phonon frequencies indicate that LaT2Al20intermetallics exhibit the structural stability. The elastic moduli(B, G, E, and Hv) indicate that these intermetallics possess the better elastic properties than pure Al. The values of Poisson’s ratio v and B/G demonstrate that LaT2Al20intermetallics are all brittle materials. The anisotropy of elasticity and Young’s modulus(three-and two-dimensional figures) indicate that LaT2Al20compounds are anisotropic. Importantly, the calculated thermal quantities demonstrate that LaT2Al20intermetallics possess the better thermal physical properties than pure Al at high temperatures.

EFFECTS OF MOLECULE AGGREGATION STATE OF HINDERED PHENOL ON DYNAMIC MECHANICAL PROPERTIES OF CHLORINATED POLYETHYLENE

Hindered phenol compound 3,9-bis{1,1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}- 2,4,8,10-tetraoxaspiro[5,5]-undecane (AO-80) is a polymorphous material with different physical structures. The initial AO- 80 is highly crystalline, whereas AO-80 obtained by cooling from its molten state is an amorphous material. Annealing treatment below the melting point of AO-80 results in structural development. The mixture of chlorinated polyethylene (CPE) and vitrified AO-80 particles exhibits a dramatic change in the dynamic mechanical properties during heat treatment at 130'C. This change can be attributed to the decomposition of the vitrified AO-80 particles and the hybridization of two constituents. The vitrified AO-80 particles can crystallize again in a CPE matrix by annealing at 100'C, but this crystal is different from that of the initial AO-80 in its microstructure. In addition, the incorporation of CPE chains caused a dramatic increase in the modulus. As a result, the AO-80 crystal particles that contain some CPE chains act as multifunctional cross- links and the CPE/AO-80 hybrid was found to be a new type of elastomer.