Longitudinal Speed Research Articles

Adaptive slip vectoring for speed and yaw-rate control in electric vehicles with four in-wheel motors

A non model-based control architecture, called adaptive slip vectoring, is presented to regulate speed and yaw-rate in a fully electric vehicle equipped with four in-wheel induction motors. The actuators redundancy is dealt with by a Slip Vectoring strategy which, given a driving force and a driving yaw-moment as control constraints, allocates optimal slip references to each tire, so that four speed references are provided to the four in-wheel motors on the basis of vehicle accelerations, speed and yaw-rate regulation errors. In order to drive independently each in-wheel motor speed to its reference, a decentralized feedback control loop is designed which leads to exponentially convergent load torque estimates so that the torque–slip operating conditions can be monitored online and the load torque requirements are matched for each tire. As a result four decentralized current-pair reference inputs are provided to each motor. Structural sufficient conditions for local exponential stability of the speed and yaw-rate regulation are obtained for uniform rectilinear references. A new overall stability index is introduced and monitored online, and an automatic longitudinal speed reduction can be performed with the goal of keeping such a stability index within a predetermined range so that the structural sufficient conditions are met. Realistic CarSim simulations are presented: (i) a snowy uphill path illustrates the non model-based speed reduction driven by the stability index monitoring; (ii) standard moose-test maneuvers on dry and wet asphalt illustrate uniform yaw-rate tracking performance due to the continuous differential actions of the four in-wheel torques.

Trend analysis and inter-annual variability in wind speed in South Africa

Reliable forecasts of long-term longitudinal wind speed patterns may help predict air circulation changes. They are also essential for the planning and financing of wind projects for Independent Power Producers (IPPs). Long-term wind speed trends and variations in historical mean wind speed data were examined using Mann Kendall’s test and calculating inter-annual variability (IAV). The Wind Atlas for South Africa (WASA) provides high resolution quality wind data for research and applications locally. WASA has 19 meteorological stations in South Africa. The WASA project began in 2009 with the aim of mapping South Africa's wind resource, allowing stakeholders in the wind energy sector and industry to explore and prepare for utility-scale wind power generation. For the past ten years, WASA has been measuring and providing data.The results showed an increasing trend at WM01 and a decreasing trend at WM08. There was no clear trend at other wind masts. Satellite data was used to validate results and no trends were observed at most of the stations. IAV values for this study ranged between 1.088% and 3.353% which is relatively low compared to the commonly found IAV values of 5-6%, implying that mean annual wind speed variation at these stations is low. To confirm a clear trend in wind speed, it is recommended that further work be done with long term periods and substantiate our finding with the use of historical simulation and climate change scenarios.

Assessment and Non-Destructive Evaluation of the Influence of Residual Solvent on a Two-Part Epoxy-Based Adhesive Using Ultrasonics

Polymers are increasingly being used in higher demanding applications due to their ability to tailor the properties of structures while allowing for a weight and cost reduction. Solvents play an important role in the manufacture of polymeric structures since they allow for a reduction in the polymer’s viscosity or assist with the dispersion of fillers into the polymer matrix. However, the incorrect removal of the solvent affects both the physical and chemical properties of polymeric materials. The presence of residual solvent can also negatively affect the curing kinetics and the final quality of polymers. Destructive testing is mainly performed to characterize the properties of these materials. However, this type of testing involves using lab-type equipment that cannot be taken in-field to perform in situ testing and requires a specific sample preparation. Here, a method is presented to non-destructively evaluate the curing process and final viscoelastic properties of polymeric materials using ultrasonics. In this study, changes in longitudinal sound speed were detected during the curing of an aerospace epoxy adhesive as a result of variations in polymer chemistry. To simulate the presence of residual solvent, samples containing different weight percentages of isopropyl alcohol were manufactured and tested using ultrasonics. Thermogravimetric analysis was used to show changes in the decomposition of the adhesive due to the presence of IPA within the polymer structure. Adding 2, 4, and 6 wt.% of IPA decreased the adhesive’s lap shear strength by 40, 58, and 71%, respectively. Ultrasonics were used to show how the solvent influenced the curing process and the final sound speed of the adhesive. Young’s modulus and Poisson’s ratio were determined using both the longitudinal and shear sound speeds of the adhesive. Using ultrasonics has the potential to non-invasively characterize the quality of polymers in both an in-field and manufacturing settings, ensuring their reliability during use in demanding applications.

Programmable Transport of C60 by Straining Graphene Substrate

Controlling the maneuverability of nanocars and molecular machines on the surface is essential for the targeted transportation of materials and energy at the nanoscale. Here, we evaluate the motion of fullerene, as the most popular candidate for use as a nanocar wheel, on the graphene nanoribbons with strain gradients based on molecular dynamics (MD), and theoretical approaches. The strain of the examined substrates linearly decreases by 20%, 16%, 12%, 8%, 4%, and 2%. MD calculations were performed with the open source LAMMPS solver. The essential physics of the interactions is captured by Lennard-Jones and Tersoff potentials. The motion of C60 on the graphene nanoribbon is simulated in canonical ensemble, which is implanted by using a Nose-Hoover thermostat. Since the potential energy of C60 is lower on the unstrained end of nanoribbons, this region is energetically more favorable for the molecule. As the strain gradient of the surface increases, the trajectories of the motion and the C60 velocity indicate more directed movements along the gradient of strain on the substrate. Based on the theoretical relations, it was shown that the driving force and diffusion coefficient of the C60 motion respectively find linear and quadratic growth with the increase of strain gradient, which is confirmed by MD simulations. To understand the effect of temperature, at each strain gradient of substrate, the simulations are repeated at the temperatures of 100, 200, 300, and 400 K. The large ratio of longitudinal speed to the transverse speed of fullerene at 100 and 200 K refers to the rectilinear motion of molecule at low temperatures. Using successive strain gradients on the graphene in perpendicular directions, we steered the motion of C60 to the desired target locations. The programmable transportation of nanomaterials on the surface has a significant role in different processes at the nanoscale, such as bottom-up assembly.

A Study on the Evacuation of an Extra-Long Highway Tunnel Fire—A Case Study of Chengkai Tunnel

The smoke from tunnel fires spreads over long distances and is difficult to vent. Smoke accumulation leads to high temperatures, low visibility, and high concentrations of toxic gases, which greatly hinders the evacuation of people inside the tunnel. In this paper, a representative extra-long highway tunnel—Chengkai Tunnel—is selected as the engineering background, and a tunnel model is built using FDS and Pathfinder software to simulate the fire scenario and evacuation scenario under different longitudinal wind speeds. The concept of safe evacuation reliability is proposed to describe the relationship between the ASET (available safe egress time) and the RSET (required safe egress time). The simulation results show that with the increase in longitudinal wind speed, the ASET upstream of fire source increases first and then remains unchanged, while ASET downstream of fire source increases first and then decreases. The ASET upstream of the fire source is affected by visibility, while the ASET downstream of the fire source is affected by visibility when the wind speed is low, and is affected by temperature as the wind speed increases. The bottleneck effect is an important reason for the long evacuation time of people. The blockage time is a power function of the evacuation movement time, and increasing the width of the cross passage can improve the evacuation efficiency of the tunnel. The increase in the number of evacuees will reduce the reliability of the safe evacuation of personnel. Among all simulated scenarios, a longitudinal wind speed of 2.5 m/s has the highest safe evacuation reliability, with 0.79, 0.92, and 0.99 for scenarios R1, R2, and R3, respectively. Excessive wind speed reduces the safe evacuation reliability downstream of the fire source.

Ультразвуковой контроль качества пропитки стеклопластиковых элементов конструкций летательных аппаратов органическими смолами

Fiberglass products after molding and heat treatment are impregnated with the organosilicon resin to increase heat resistance followed by polymerization by heat treatment. A method for non-destructive quality control of the composite-profile products impregnation made of fiberglass plastics with the organosilicon resin is proposed. Results of experimental work are presented on the study of alteration in the longitudinal ultrasonic waves speed in structural elements of the aerial vehicles made of fiberglass before and after impregnation with the organosilicon resin, i.e. the MFSS-8 product. Besides, alteration in the longitudinal ultrasonic waves speed in the fiberglass samples violating the impregnation technology are demonstrated.

Cooperative Control of Two-Vehicle Transportation Based on Time-Varying Distance Between Vehicles

For two-vehicle cooperative transportation control, the typical methods are to keep the relative heading angle of the two vehicles constant and to realize cooperative transportation by using the characteristics of mecanum wheels. These methods do not apply to the requirements of the highway scene for the trafficability and robustness of two-vehicle transportation. To solve these problems, a cooperative control method based on a time-varying distance model was proposed. First, a multiaxis all-wheel-steering kinematic model was constructed based on the proportional steering principle. The reference rotation angles of each wheel were output by the model predictive control (MPC), which could realize trajectory tracking, with the current vehicle state and longitudinal speed prediction sequence as inputs. Second, the leader–follower strategy was adopted to build a dynamic reference distance of the path-between-vehicles model based on trajectory tracking deviation, vehicle states, and road information. On this basis, a two-vehicle cooperative prediction equation was established, and it output the longitudinal speed of the follower through the MPC. Finally, Simulink/TruckSim cosimulation was used to verify the effectiveness of the cooperative control method, which provides a new control idea for improving the efficiency of bulk transportation. The effectiveness and robustness of the collaborative control strategy were verified by Simulink/TruckSim cosimulation and a real vehicle experiment, which provides a new control idea for improving the efficiency of large cargo transportation.

All-optical, non-contact, local measurement of both Young’s modulus and Poisson’s ratio in metals using a combination of Rayleigh and leaky surface acoustic waves

In non-destructive evaluation (NDE), measuring ultrasound (US) longitudinal and shear wave speeds is the main method to determine two independent mechanical moduli (Young’s modulus and Poisson’s ratio). Most US techniques use time-of-flight measurements. However, when the local sample thickness is unknown or the sample geometry is complex, bulk-wave propagation speeds cannot be accurately defined. Here we show that a properly shaped beam of nanosecond laser pulses can be used to efficiently excite (without material ablation) two types of surface acoustic waves. In addition to a conventional surface, or Rayleigh, wave, a leaky surface wave (LSAW) can be launched in the near field of the excitation region. We present the theoretical background, numerical simulations, and experimental results clearly showing that both elastic constants can be reconstructed locally by tracking Rayleigh and LSAW waves. Spatially resolved elastic properties can be obtained using local values of wave speeds obtained by sample scanning. Non-contact optical detection of propagating waves at the sample surface, in which a fiber-optic Sagnac interferometer was used, is a key piece of the method. It does not require acoustic coupling and allows remote measurements in the near field of the laser source with micron-scale resolution.

Cooperative vehicle platoon control considering longitudinal and lane-changing dynamics*

This paper presents a distributed cascade Proportional Integral Derivate (DCPID) control algorithm for the connected and automated vehicle (CAV) platoon considering the heterogeneity of CAVs. Furthermore, a real-time cooperative lane-changing model for CAVs, which can seamlessly combine the DCPID algorithm and sine function is developed. The DCPID algorithm determines the appropriate longitudinal acceleration and speed of the lane-changing vehicle considering the speed fluctuations of the front vehicle on the target lane (TFV). In the meantime, the sine function plans a reference trajectory which is further updated in real time using the model predictive control (MPC) to avoid potential collisions. Simulation results indicate that the DCPID algorithm can provide robust control for tracking and adjusting the desired spacing and velocity for all 400 scenarios. Besides, the proposed cooperative lane-changing model can guarantee effective and safe lane changing with different speeds and even in emergency situations.

Intelligent electric vehicle trajectory tracking control algorithm based on weight coefficient adaptive optimal control

The track tracking effect of intelligent vehicle directly affects the safety of vehicle and passengers. In the process of intelligent vehicle track tracking, the track tracking accuracy is related to many factors such as track curvature, road friction coefficient, and longitudinal speed change. In this paper, a new lateral and longitudinal coupling control algorithm is proposed. Based on the vehicle dynamics model and the optimal control theory, combined with the fuzzy control theory, the Fuzzy Linear Quadratic Regulator (FLQR) lateral optimal controller is designed, and feed-forward control and predictive controller are added. According to the real-time tracking lateral error and fuzzy control algorithm fed back by the system, the weight coefficient of the lateral displacement deviation in the cost function is dynamically adjusted; considering the coupling effect of lateral and longitudinal controllers of vehicle trajectory tracking control, a model predictive control (MPC) longitudinal speed controller is designed based on MPC theory, considering acceleration constraint and acceleration variation constraint, and taking lateral stability as evaluation index. A joint simulation platform is built based on CarSim and Simulink. The simulation results show that the designed lateral and longitudinal coupling controller of FLQR + MPC has better track tracking accuracy and can improve the driving stability of the vehicle; finally, the tracking effect of the designed algorithm is verified by real vehicle experiments. The maximum error of the designed controller algorithm in real vehicle tracking is 0.56 m, and the tracking effect is good.

Design of Nonlinear Control Systems for Autorobots

Currently, various types of robots are increasingly being used to solve different tasks. Most often, these are mobile robots that move on the earth’s surface performing the assigned tasks, in particular, they are four-wheeled robots similar to a car — autorobots. As control objects, the robots are essentially nonlinear, which requires the use of nonlinear methods for the control system design. At the same time, it is difficult to apply traditional methods for designing nonlinear control systems due to a complex type of nonlinearities in the equations of mobile robots and, in particular, autorobots. In this paper, the design problem is solved using a discrete-continuous quasilinear model, which is created on the basis of the nonlinear differential equations in the Cauchy form. Due to the great complexity of the nonlinearities of the autorobot equations, the corresponding quasilinear model is created by the numerical method. The quasilinear model obtained by this method is discrete-continuous and controllable, moreover, its state variables are measurable. The discrete autorobot control system includes two practically independent control subsystems: longitudinal speed and turns. A discrete PI control law is used to control the speed, and the discrete turn control subsystem is designed by the method of desired dynamics. The resulting autorobot control system provides a stable movement along the trajectory, which can be set as a function of time or as a function of the coordinates of the moving autorobot’s position.The suggested approach can be used to design control systems for nonlinear objects of various purposes with complex differentiated nonlinearities. However, the design problem has a solution if the corresponding discrete-continuous quasilinear model of the object is controllable, and the state variables are measurable.

Interface-independent sound speed and thermal conductivity of atomic-layer-deposition-grown amorphous AlN/Al2O3 multilayers with varying oxygen composition

Dielectric amorphous multilayers (AMLs) play a critical role in a wide array of technologies such as optical coatings, nanoelectronics, energy harvesting, and recovery devices. However, despite their wide applications, a robust understanding of the effect of the interplay between chemical and structural disorder on the thermal properties of AMLs is still lacking. Therefore, in this paper, we experimentally and numerically investigate the effects of composition and interface density on the sound speed and thermal conductivity of a series of amorphous aluminum nitride and aluminum oxide multilayers grown via plasma-enhanced atomic layer deposition. To systematically change the composition, the oxygen content of the AMLs is proportionally varied with interface density during growth. We find that the longitudinal sound speed of these AMLs is dictated by the oxygen content instead of the number of interfaces. The thermal conductivity, in contrast, is dictated by both interface density and oxygen content. The interfaces act to decrease the thermal conductivity, whereas the oxygen content increases the thermal conductivity. Due to the competing influence of the interfaces and oxygen content, the thermal conductivity of the AMLs remains nearly constant as a function of interface density. Our study provides crucial insights into the effect of the interplay of composition and interfaces on the sound speed and thermal conductivity of AMLs.

Characterizing Viscoelastic Polyvinyl Alcohol Phantoms for Ultrasound Elastography.

Ultrasound phantoms mimic the acoustic and mechanical properties of native tissues. Polyvinyl alcohol (PVA) phantoms are used extensively as models for validating ultrasound elastography approaches. However, the viscous properties of PVA phantoms have not been investigated adequately. Glycerol is a viscous liquid that has been reported to increase the speed of sound of phantoms. This study aims to assess the acoustic and viscoelastic properties of PVA phantoms and PVA mixed with glycerol at varying concentrations. The phantoms were fabricated with 10% w/v PVA in water with varying concentrations of glycerol (10%, 15% and 20% v/v) and 2% w/v silicon carbide particles as acoustic scatterers. The phantoms were subjected to either one, two, or three 24-h freeze-thaw cycles. The longitudinal sound speeds of all PVA phantoms were measured, and ranged from 1529 to 1660 m/s. Attenuation spectroscopy was performed in the range of 5 to 20 MHz. The measured attenuation followed a power-law relationship with frequency, wherein the power-law fit constants and exponents ranged from 0.02 to 0.1 dB/cm/MHzn and from 1.6 to 1.9, respectively. These results were in agreement with previous reports for soft tissues. Viscoelasticity of PVA phantoms was assessed using rheometry. The estimated values of shear modulus and viscosity using the Kelvin-Voigt and Kelvin-Voigt fractional derivative models were within the range of previously-reported tissue-mimicking phantoms and soft tissues. The number of freeze-thaw cycles were shown to alter the viscosity of PVA phantoms, even in the absence of glycerol. Scanning electron microscopy images of PVA phantoms without glycerol showed a porous hydrogel network, in contrast to those of PVA-glycerol phantoms with non-porous structure. Phantoms fabricated in this study possess tunable acoustic and viscoelastic properties within the range reported for healthy and diseased soft tissues. This study demonstrates that PVA phantoms can be manufactured with glycerol for applications in ultrasound elastography.

Plastic deformation behavior of a Cu–10Ta alloy under strong impact loading

In this work, a Cu–10Ta alloy with a copper to tantalum mass ratio of 9:1 is prepared using powder metallurgy technology. Physical properties of the alloy, including density, microstructure, melting point, and constant-volume specific heat, are tested. Via the split Hopkinson pressure bar (SHPB) and flyer-plate impact experiments, the relationship between equivalent stress and equivalent plastic strain of the material is studied at temperatures of 298–823 K and under strain rates of 1 × 10−3–5.2 × 103 s−1, and the Hugoniot relationship at impact pressures of 1.46–17.25 GPa and impact velocities of 108–942 m/s is obtained. Evolution of the Cu–10Ta microstructure that occurs during high-strain-rate impact is analyzed. Results indicate that the Cu–10Ta alloy possesses good thermal stability, and at ambient temperatures of up to 50% its melting point, stress softening of less than 15% of the initial strength is observed. A modified J-C constitutive model is employed to accurately predict the variation of yield strength with strain rate. Under strong impact, the copper phase is identified as the primary source of plastic deformation in the Cu–10Ta alloy, while significant deformation of the high-strength tantalum particles is less pronounced. Furthermore, the longitudinal wave speed D is found to correlate linearly with the particle velocity u upon strong impact. Analysis reveals that the sound speed and spallation strength of the alloy increase with increasing impact pressure.

Сравнение численных схем для задачи ламинарного течения во внезапно расширяющемся канале

The paper studies fluid flow in a two-dimensional channel with sudden expansion (x/h = 2). Calculations were made for the laminar flow mode based on numerical integration of the nonstationary Navier --- Stokes equations. Various flow characteristics were determined at Re = 100--800. Results were obtained for the longitudinal speed profiles in various channel sections and lengths of the primary and secondary vortices at various values of the Reynolds number after the step. The friction coefficient distribution on the channel lower side along its length is presented for various values of the Reynolds number. For the difference approximation of the initial equations, the control volume method was applied; relationship between speed and pressure was found using the SIMPLE procedure. For numerical solution of the problem, the following QUICK schemes were introduced: McCormack's second-order accuracy, Warming --- Cutler --- Lomax's third-order accuracy and Abarbanel --- Gotlieb --- Turkel's fourth-order accuracy. To confirm correctness, numerical results were compared with the experimental data taken from the literature sources

Experimental study and machine learning on the maximum temperature beneath tunnel ceiling induced by adjacent tandem fires in longitudinally ventilated tunnel

This study experimentally investigated the effects of longitudinal ventilation on the maximum temperature rise under tunnel ceilings induced by adjacent tandem fires. Because the tunnel is a narrow building structure, the fire source may ignite the surrounding flammable materials (such as adjacent vehicles, etc.), causing the simultaneous burning of multiple fires. The experiments were conducted in a 1:8 reduced-size tunnel. The ceiling temperature were measured for 60 repeatable test conditions, including five separation distances between adjacent fire sources at various heat release rates with different longitudinal wind speeds. As regards the effect of fire separation distance, the maximum ceiling temperature rise was recorded and measured for five different fire separation distances; as the fire separation distance increased to 0.9 m for a given test condition, the maximum ceiling temperature rise gradually decreased. Meanwhile, the maximum ceiling temperature rise decreased as the crosswinds increased. A new correlation was proposed between the maximum ceiling temperature rise as a function of the change in fire plume due to the fire separation distance and the Froude number representing flame tilting caused by crosswinds. Meanwhile, machine learning algorithm is used to predict the fire heat release rate. The model was shown to be able to effectively explain the experimental results and can provide a reference for examining the evolution of tunnel fire situations.

Evaluation of the acoustic and environmental performance of different wall structures with particular emphasis on straw

The building material straw as a renewable and almost endlessly available by-product could contribute to lower greenhouse gas emissions and primary energy consumption in the building construction sector. Straw as building material, is used as insulation material in metal stud walls and timber frame constructions. Additionally, whole straw bales can be used as insulation and bearing structure in combination with a timber frame. The state of the art provides an inconsistent data conglomerate on the acoustical and environmental performance of different wall structures, test setups and assessment methods. The presented research shows results of a parallel evaluation of the acoustic and environmental performance of wall structures with a consistent approach in measurement and calculation methods. The results of building acoustic measurements are used to quantify the acoustic potential for of straw in those wall constructions. The results show that the building acoustic performance of wall constructions with straw is comparable to the performance of already on the market established wall constructions. The influence of parameters like density, dynamic stiffness, air flow resistivity and longitudinal wave speed of used materials on the measured sound reduction index is discussed. Especially the density and the dynamic stiffness are important material parameters to achieve a high sound reduction index of the wall constructions. Since straw is a renewable material, the environmental impacts of the different acoustically analyzed wall constructions were investigated additionally. Standardized assessment methodologies were applied on the different components and a comparison with different insulation materials was carried out. It could be shown that the use of straw leads to lower environmental impacts (demonstrated in the Global Warming Potential indicator), though, the insulation material is not the most relevant parameter of the structures. Significantly higher environmental impacts are caused by the bearing structure (metal and timber frame studs) and the planking materials. Finally, an overall comparison together with standard concrete and brick wall structures underlines the beneficial environmental properties of walls made of renewable materials with straw.

Shock-induced melting of [100] lithium fluoride: Sound speed and Hugoniot measurements to 230 GPa

Although [100] lithium flouride (LiF) is the most widely used optical window material in dynamic compression experiments, its high stress ($>100\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$) shock compression response, including melting, is not well understood. To address this need, we measured wave profiles in plate impact experiments to determine the Hugoniot states and longitudinal sound speeds in [100] LiF crystals shock compressed to 231 GPa. The measured peak states are fitted well by a linear shock velocity--particle velocity relation, providing an accurate determination of the LiF Hugoniot curve to significantly higher stresses than previous experiments. The longitudinal sound speeds show a near linear increase with density compression to 182 GPa. Between 182 GPa and 195 GPa, the sound speed and the longitudinal modulus decrease abruptly, due to shock-induced melting. The increasing sound speeds and moduli at higher stresses suggest that shock compressed LiF is fully liquid at 195 GPa and above, allowing determination of the Gr\"uneisen parameter for liquid LiF. The melt stress determined here differs from that predicted by current multiphase equations of state for LiF. Our results provide important insight into the high stress solid and liquid states of shock compressed LiF and point to the need for an improved multiphase equation of state at high pressures and high temperatures.

Mechanism-driven analytical modelling of UHMWPE laminates under ballistic impact

Ultra-high molecular weight polyethylene (UHMWPE) fiber reinforced composite laminates have been widely used to defend against projectiles and fragments. Although the ballistic performance of UHMWPE composites has been extensively characterized both experimentally and numerically, analytical modelling remains a challenge. This study develops a mechanism-based analytical model of UHMWPE cross-ply laminates, with the progressive process of projectile penetration divided into two sequential stages of local failure and bulging deformation: the former is characterized with the strain concentration model under local shock compaction, and the latter is described using a modified membrane stretching model. Compared with existing energy-based models, the current model enables revealing physical mechanisms underlying the deformation/failure processes of UHMWPE laminate subjected to projectile impact, with relevant parameters correlated with material properties. Further, without using any fitting parameter, the proposed analytical model can predict both the ballistic limit and residual projectile velocity. For validation, the model predictions are compared with existing test data, with good agreement achieved for varying projectile mass, projectile size, laminate type, and laminate thickness. It is demonstrated that the maximum strain under a penetrating projectile is controlled by the thickness of un-penetrated laminate and the growth of bulge, and that the longitudinal wave speed and maximum tensile strain in the UHMWPE laminate dictate its ballistic limit.

Similar ratio experiment and characteristic analysis of quasi-sandstone

The stability control of surrounding rock in deep roadway is becoming more and more difficult, and grouting reinforcement support has become the mainstream of roadway control. In order to obtain the ratio of quasi-sandstone material corresponding to the grouting body, this paper uses river sand as aggregate, cement and gypsum as cementing agent, retarder and defoamer as additives, and carries out orthogonal proportioning tests with three influencing factors: water-binder ratio (ratio of water to mass of cementing agent), gypsum-cement ratio (ratio of gypsum to mass of cement) and binder-aggregate ratio (ratio of cementing agent to aggregate mass), and compares and analyzes the sensitivity of each factor on the density, compressive strength, tensile strength, elastic modulus, Poisson’s ratio, longitudinal wave velocity, elasticity index and brittleness index of quasi-sandstone material. The results show that 1) the Water-binder ratio has the greatest effect on the sensitivity of material compressive strength, tensile strength, elastic modulus, Poisson’s ratio and longitudinal wave velocity; the gypsum-cement ratio has the greatest effect on the sensitivity of material deformation index and brittleness index; the binder-aggregate ratio has the greatest effect on the sensitivity of material density. 2) Reducing the Water-binder ratio can improve the density, compressive strength and tensile strength of the material; reducing the paste ratio can improve the modulus of elasticity, Poisson’s ratio and longitudinal wave speed of the material; as the gypsum-cement ratio increases, the deformation index first decreases and then increases and then decreases; as the binder-aggregate ratio increases, the brittleness index first increases and then decreases and then increases. 3) The empirical equations between physical and mechanical properties of sandstone-like materials and Water-binder ratio, gypsum-cement ratio and binder-aggregate ratio were established based on multiple linear regression analysis, and more reasonable material ratios were quickly obtained by physical and mechanical parameters of materials. The results of the study provide theoretical references for similar material simulation tests for quasi-sandstone grouting.