Mechanical deformation properties of Continuous Welded Rail on kilometer-span suspension bridge for high-speed railway

The complex bridge-track interaction between kilometer-span bridges and continuous Welded Rail(CWR)brings great challenges to CWR designing.Taking a suspension bridge with laying CWR as a case,the mechanical properties of CWR on the bridge are analyzed to reveal the sensitive areas of the track,and the design method of CWR and track structures on the beam ends are proposed.The results show that the unidirectional Rail Expansion Joints(REJ)need to be installed on the beam end of the kilometer-span bridge to reduce rail longitudinal force.Due to the bridge characteristics,there is no CWR fixed area on the kilometer-span bridge,and rail longitudinal force on the main span caused by bending loads needs to be concerned.The deformation of track on the beam end is complex,which is the weak area on the kilometer bridge,the large relative displacement between the stock rail of REJ and the main beam can cause poor stability of ballast bed on beam end,small resistance fasteners need to be laid on the sides of stock rail on the main beam to increase the stability of ballast and fasteners on the beam end.To improve the driving safety and comfort of beam end,the Sleeper-Supporting Apparatus(SSA)should be specially designed to ensure the uniform transition of track on beam ends.Temperature and wind loads have a significant impact on track regularity on the kilometer span bridge,the dynamic response of trains and bridges under those loads needs to be attended to.

Comparison of mechanical properties in high temperature and thermal treatment granite

Static mechanical experiments were carried out on granite after and under different temperatures using an electro-hydraulic and servo-controlled material testing machine with a heating device. Variations in obvious form, stress-strain curve, peak strength, peak strain and elastic modulus with temperature were analyzed and the essence of rock failure modes was explored. The results indicate that, compared with granite after the high temperature treatment, the brittle-ductile transition critical temperature is lower, the densification stage is longer, the elastic modulus is smaller and the damage is larger under high temperature. In addition, the peak stress is lower and the peak strain is greater, but both of them change more obviously with the increase of temperature compared with that of granite after the high temperature treatment. Furthermore, the failure modes of granite after the high temperature treatment and under high temperature show a remarkable difference. Below 100 ℃, the failure modes of granite under both conditions are the same, presenting splitting failure. However, after 100 ℃, the failure modes of granite after the high temperature treatment and under high temperature present splitting failure and shear failure, respectively.

Static Performance and Fracture Numerical Analysis of 301L/Q235B Dissimilar Steel Resistance Spot Welded Joints

This paper presents an experimental study on the static tensile test of resistance spot welding between 2.0 mm thick dissimilar 301L⁃DLT and Q235B in tensile⁃shear specimens with different welding nugget diameters.Force⁃displacement curves of the specimens were compared with simulation curves by the finite element software.The stress⁃strain distribution and fracture evolution process during the tensile process were analyzed.The hardness of the nugget was higher than that of the base material and the heat affected zone.Under static tensile load,the stress and strain in the spot welded joints increased exponentially with the increase of displacement,and the maximum stress was located at the nugget edge of the 301L plate loading side.The static tensile strength and plastic deformation of the spot welded joint failure by the nugget pulled⁃out fracture mode was better than that by the interface fracture mode.The critical nugget diameter of Q235B for the transition from nugget interfacial fracture to the pull⁃out fracture was 7.12 mm,and that of 301L was 7.81 mm,which was about 5√t.

Effects of Interface on the Dynamic Hysteresis Loss and Static Mechanical Properties of Illite Filled SBR Composites

Despite growing interest in nano-sized fillers,micro-sized fillers with desired compatibility are still used for reinforcing rubbers,owing to their lower production cost and easier processing relative to nano-sized fillers.Especially,the abundant and eco-friendly clay minerals are recognized as the materials of the twenty-first century.Herein,illite,a naturally occurring clay having dimension in micrometric scale,has been selected as filler to reinforce the SBR.To improve the compatibility of illite with SBR,the illite was modified by either bis[3-(triethoxysilyl)propyl]tetrasulfide(Si69-illite)or 3-mercaptopropyltriethoxysilane(KH580-illite).The interfacial interactions of SBR composites filled with pristine illite(illite/SBR)and Si69-illite(Si69-illite/SBR),or KH580-illite(KH580-illite/SBR)were characterized by bound rubber content and Payne effect measurements,while dynamic hysteresis losses of these uncured and cured composites were also analyzed under various strain amplitudes.It was found that the filler-rubber interactions were greatly improved for Si69-illite/SBR and KH580-illite/SBR systems compared to the illite/SBR composite.This leads to an increment of modulus at 300%strain of the composites from 3.46 MPa for illite/SBR to 7.70 MPa for Si69-illite/SBR and12.96 MPa for KH580-illite/SBR.Moreover,lower rolling resistance and better wear resistance without compromising wet traction of Si69-illite/SBR and KH580-illite/SBR have been achieved.This demonstrates the high possibility of Si69 and KH580 modified illites as promising alternative fillers for reinforcing rubbers.

Mechanical behavior of salt rocks: A geomechanical model

The geomechanical behavior of salt rocks is a significant concern during drilling and development operations in some hydrocarbon reservoirs and underground gas storage sites.In this study,the static and dynamic salt rock geomechanical properties from a field in southwest Iran were evaluated using experiments such as waves'velocities,and thermo-mechanical coupled uniaxial and triaxial compression tests.As a result and by considering both the petrophysical well logs and laboratory data of the waves’velocities,it is observed that the elastic properties of the core samples are concentrated within a narrow range unless an abnormality causes scatter.The results of uniaxial compression tests showed that rock strength decreases with increasing temperature linearly.In addition,the reduction of rock strength was observed with increasing porosity of the core samples as expected.In the case of triaxial compression tests,applying confining pressure on the core sample caused an increment in rock strength,while temperature decreased rock strength.The temperature also increased cohesion and decreases friction angle.The ratio of changes in stress to strain was used to investigate the dynamic changes in the geomechanical state.The maximum 0.25 damage factor was observed for the core samples for different definitions of the damage factor.Finally,we propose a novel analytical model to predict the stress-strain behavior of salt rocks at different conditions.The model was validated using experimental results and indicated a satisfactory accuracy.