Pad Material Research Articles

APPLICATION OF VARIABLE PITCH OF REINFORCEMENT OF GEOSYNTHETIC MATERIALS IN FOUNDATION PADS FROM CONTINUOUS SOILS

The results of the study of the nature of the work of reinforced foundation pads from cohesive soil. Compacted soft-plastic loam is considered as the pad material, woven geotextile is used as a reinforcing element. Such a constructive solution of the foundation pad, as a rule, is associated with the impossibility or high cost of using classical inert materials for these structures. Previous studies have shown the high efficiency of the rational arrangement of reinforcing horizontal geosynthetic elements in sand pads. The main purpose of this study was to test the well-known approach to the use of variable reinforcement spacing for foundation pads made of cohesive soils. The goal was achieved by a numerical experiment (solving test problems) in the Plaxis 2D software package with various types of reinforcement, 4 types of reinforcement were considered. The main results of the research are the obtained schemes of vertical stresses, as well as the values of the maximum load that the base can withstand without destruction. Based on the results of the research, the formula for determining the position of the reinforcing layers with a variable reinforcement step in pads of cohesive soils was corrected. It was also found that when the layers are arranged in steps of 200 mm or less, the reinforcing effect in cohesive soils practically does not occur. It is confirmed that the variable reinforcement spacing allows achieving the maximum «inclusion in the work» of geosynthetics in comparison with other types of reinforcement considered in the framework of this study. In addition, it has been proven that in the study under consideration, the variable reinforcement spacing in cohesive soil pads is the most effective in terms of perceived load and the number of reinforcing layers applied.

Study on the Wear Performance of Brake Materials for High-Speed Railway with Intermittent Braking under Low-Temperature Environment Conditions.

The pin on the disc friction tester was used to conduct the intermittent braking testing of train brake materials with a low-temperature environment simulation device at temperatures 20 °C, 0 °C, -10 °C, -20 °C, and -30 °C. The results show that intermittent braking presents different wear characteristics of braking materials at low temperatures. Under different ambient temperature conditions, the most volatile friction coefficient caused by intermittent braking happens at 0 °C, and the wear rate of brake materials reaches its maximum at 0 °C. The wear surface morphology of the brake pad material mainly includes scratches, furrows, adhesions, and abscission pits, while the surface of the brake disc material was dominated by scratches, furrows, and adhesions. With the decrease in temperature, the adhesion damage of the brake pad/disc material increases. At 0 °C, the brake pad material has crack damage.

Research progress on friction and wear properties of powder metallurgy brake pad

The terrain of China is relatively complex, which leads to the complex and changeable working conditions of high-speed trains during braking. Studying the influence under different braking conditions on the performance of train brake pads is a problem worthy of in-depth discussion. In order to explore the performance changes of powder metallurgy brake pads during train braking, this paper summarizes the friction and wear properties and wear mechanism of powder metallurgy brake pads under different braking conditions; combined with the research status of powder metallurgy brake pad materials, it provides directions for the research of new powder metallurgy materials. Provide reference for the improvement of brake pads of high-speed train in the future.

Development of indirect evaporative cooler based on a finned heat pipe with a natural-fiber cooling pad

Evaporative cooler is one of the methods that have been used to keep buildings at a comfortable temperature since ancient times. This type of cooler is particularly suitable for hot and arid areas. This research examines the design and testing of an indirect evaporative cooler system utilizing heat pipes as heat exchangers and natural fibers as cooling pads. An experiment was performed on a laboratory scale with three different types of natural fiber cooling pad materials: pineapple leaf, ramie, and luffa fibers. The air temperatures to be conditioned was 40 °C, with three variations of the intake airflow velocities of 0.4, 1.1, and 1.8 m/s. According to the results of this experiment, an indirect evaporative cooler system utilizing pineapple leaf fiber as a cooling pad performs better than those employing luffa and ramie fibers as cooling pads. The maximum wet bulb effectiveness of the system using pineapple fiber was 85%, maximum dew point effectiveness was 65%, and maximum energy efficiency ratio was 52.5 Btu/W.As a passive heat exchanger, the performance of finned heat pipes is also investigated, with a maximum heat absorption of 527.6 W and a temperature reduction of 9.9 °C.

Analysis of sheet pile in dense and loose soil using finite element method

Sheet pile wall acts as a support system for soils in excavation or backfill structures of a wall. There is different loading condition on a sheet pile wall depending upon the different type of soil. The study is carried out to check the stability of sheet pile walls using finite element analysis software PLAXIS 2D. Different types of soil combinations are considered in this study, such as DD (Dense backfill and Dense foundation soil), LL (Loose backfill and Loose foundation soil), DL (Dense backfill and Loose foundation soil), and LD (Loose backfill and Dense foundation soil). The embedment depth of the sheet pile varies along with the thickness of the pile. The PZ35 sheet pile is used as the optimum sheet pile because of the reduction in horizontal displacement in all soil combinations and its lesser thickness compared to the PZ40 sheet pile. The approximate cost analysis of steel used in PZ27 and PZ35 sheet pile shows that the with PZ35 sheet pile cost is increased by 20 % with 50 % reduction in horizontal displacement. The cushion material (well-graded sand) below the building load causes a decrease in the horizontal deflection of the sheet pile.

Characterization of Brake Pads by Variation in Composition of Teak Wood Powder and Rice Husk Ash

Motorcycles in Indonesia have increased. So, part of the motorcycle increases, especially for brake pads. Asbestos brake pads are prohibited because they have the potential to cause lung cancer. Therefore, alternative brake pads material is needed that are more environmentally friendly. Teak wood powder and rice husk ash are underutilized waste to be used as alternative materials for making brake pads. This research is to determine the characteristics of the mechanical properties of composite materials made from rice husk ash and teak wood powder. The research method used is experimental. The manufacture of brake pads includes mixing materials, pressing, and heating processes. Brake pads are subjected to hardness testing, heat resistance testing, density testing, wear testing, and braking distance testing. The results of this study get the highest hardness test value of 5.821 HV, the highest density of 1.32 gr/cm3, the results of the braking distance test are 4.12 m with a retarding value of 3.67 m/s2, and the wear test results are 2.22 X 10 -6 mm2/kg. Special heat resistance test that meets the SAE J7661 standard with a heat resistance of 3600C for 1 hour.

Experimental investigation of a novel evaporative cooling pad made of cement-free porous concrete

Greenhouse overheating is a major problem for dry climate agricultural setups during the summer months. Evaporative cooling is a convenient solution for controlling indoor temperature on hot and dry days. However, conventional evaporative cooling pad materials such as polymers, cellulose, and organic fibres present problems in terms of high carbon footprint, after-use disposal, and/or very limited lifespan. In this study, porous concrete was tested as a novel evaporative cooling pad material in an experimental wind tunnel with different inlet air temperatures at a constant air velocity (2.5 m s−1). The porous concrete evaporative cooling pad demonstrated the highest evaporative cooling capacity at −11.46 kW sensible cooling with 10.17 kW m−2 °C−1 cooling coefficient. It further exhibited an evaporation rate of 5.84 g s−1 with an evaporation coefficient of 1.56 m s−1. The average cooling effectiveness was obtained as 0.97, where some inlet air conditions demonstrated negative enthalpy changes after evaporation. However, the maximum average enthalpy change was 10.97 kJ kg−1. This novel evaporative cooling pad material showed the highest effectiveness when compared to conventional evaporative cooling pad systems reported in other studies.

Characterization of the contacting area of spacer fabric under spherical compression

Spacer fabrics have been developed into a variety of special textile mattress products due to their outstanding pressure distribution performance. It may be that the contacting area of spacer fabrics can be expanded under spherical compression. The total compression force and distance curve is currently used to test the compression of spacer fabrics; however, there are few detailed reports about expanding the contacting area under the spherical intender. Therefore, this paper developed a test method for the contacting area between the spacer fabric and the spherical indenter under spherical compression. The spherical indenter was specially designed by using serial resistors method. The contacting area was easily obtained by detecting the resistance change through 12 resistors pasted on the surface of the spherical indenter and calculating the surface of the spherical indenter under dynamic movement. This method can be used to effectively characterize the pressure-relief property of textile soft materials in pad materials.

Study on the wear performance of high-speed railway brake materials at low temperatures under continuous braking conditions

A simulated test was completed using pin-on-disc friction and wear test machine to simulate the wear performance of the high-speed railway braking disc and braking pad materials at different temperatures (20, 0, −10, −20, −30 °C) under continuous braking conditions. The results show that the low temperature has a significant effect on the wear characteristics of the brake material under continuous braking conditions. At the initial stage of continuous braking, the instantaneous coefficient of friction at low temperature reaches its maximum value at approximately 500 s, which is almost one half of the time of that at room temperature (20 °C). At each temperature, the instantaneous friction coefficient shows a trend of increasing firstly and then decreasing, and with the decrease in temperature, the average friction coefficient of brake disc material tends to increase at the stable stage of instantaneous friction coefficient. As the continuous braking time increases, the average coefficient of friction at low ambient temperatures is greater than that at room temperature (20 °C). As the temperature decreases, the wear rate of the brake material shows a trend of increasing and then decreasing. With the fall of temperature, the damage form of brake pad material changes from adhesion damage to abscission damage, while the brake disc damage changes from abrasive wear and adhesion wear to damage mixture of abrasive wear, adhesion wear and crack.

A novel reliability index approach and applied it to cushioning packaging design

This paper is aimed at proposing a new approach to Reliability-based Design Optimization (RBDO) and applying it to cushioning packaging design with a highly nonlinear system. The problem is formulated as an RBDO problem, which is included a minimizing cost function and probabilistic constraints. Here, the thickness of the cushion material is dealt with uncertainty and uncontrolled parameters. The traditional reliability index approach (RIA) has evolved as a powerful tool to solve the RBDO problem; however, due to its convergence problem, the modified reliability index approach (MRIA) is proposed. Although the MRIA method solves the problems of the traditional RIA, it inherits the low efficiency of searching for the most probability point (MPP). Thus, we developed a novel RIA based on MRIA to improve the efficiency and robustness during the RBDO process. The innovation active set strategy is developed in reliability assessment, which is a strict inequality to determine whether the current constraint is active or inactive. An application example is presented, and the results are compared with MRIA to assess cost-effectiveness and efficiency. Results indicate the proposed method is feasible to solve the uncertainty problem of packaging materials in the processing process and is also an efficient RBDO method.

Testing the shearing creep of composite geomembranes-cushion interface and its empirical model

An accurate description of composite geomembranes (CGs)–cushion interface behaviour (particularly creep behaviour) is of great importance. This paper presents a creep experiment method for studying the shearing creep characteristics of CGs–cushion interfaces. In this study, natural sand and sandy gravel cushion materials were tested for their creep characteristics with CGs. In the proposed method, the shearing creep curves of CGs–cushion interfaces in multi-stage loading are obtained, and they can be transformed to the creep curve at each specific loading level with Chen’s method. The results show that the power function and modified hyperbolic function exhibit perfect performance in fitting the displacement–stress and displacement–time relationships, respectively. An original empirical creep model for the CGs–cushion interface was established on the basis of these fitting means; it was found to exhibit superior performance in fitting and predicting the attenuation creep curve at each stress level. An accelerating creep model applicable to the accelerating creep phase is presented by using the Kachanov damage factor to reflect the accelerating creep damage to CGs–cushion interface. The study provides enhanced guidance for the engineering design and construction of structures incorporating CGs.

Correction to: Comparative study of airborne particles on new developed metal matrix composite and commercial brake pad materials with ANN and finite element analysis

Correction to: Comparative study of airborne particles on new developed metal matrix composite and commercial brake pad materials with ANN and finite element analysis

Condition monitoring of train wheels using a cost-effective smart rail pad

This present paper focuses on the condition monitoring of train wheels utilizing an 3D printed rail pad that is embedded with widely available accelerometers and a strain gauge. This smart rail pad was used on a heavy haul railway line to monitor train wheels by identifying any wheel defects and measuring the respective wheel loads. A series of laboratory material tests were conducted on various 3D printing materials to identify the most suitable material for the smart rail pad. Dynamic and static loading tests were carried out to determine whether the 3D printed rail pads could withstand the typical forces exerted by a passing train. Field tests were done to determine the performance of the smart rail pads in operational conditions. Results indicated that the smart rail pads were able to identify 60% of the wheel flats and were able to measure the wheel loads with an average percent error of 6% by comparing it to the control measurements. In summary, the smart rail pads presented a good correlation between the measured wheel loads and the true values, while the identification of wheel flats was influenced by the low sampling rate of the system.

DYNAMIC RESPONSE OF A FRACTAL CUSHIONING PACKAGING SYSTEM

This paper focuses on predicting the shape, duration, and peak magnitude of the displacement, velocity, and acceleration curves while dropping weight over a viscoelastic fractal cushioning packaging system. Furthermore, to capture high-frequency harmonic components observed during the impact time span, the approximate frequency–amplitude expression of the governing equation of motion will be obtained via an ancient Chinese algorithm and He’s formulation by assuming initial trial solutions based on Jacobi elliptic functions. Numerical simulations confirmed the ability of the Jacobi elliptic functions to capture high-frequency harmonics observed during the cushioning packaging system dynamic response with a root mean square error (RMSE) value that does not exceed 0.0218, which is an indication of the great accuracy attained from our derived solution when compared to the exact numerical one. Furthermore, our derived approximate solution predicts that when a weight is dropped over the cushioning packaging, the cushion material with smaller porosity will absorb the produced kinetic energy faster.

Braking-experimental study on the relationship between friction material type and brake disc temperature

PurposeThis study aims to clarify the relationship of friction material type and brake disc temperature through braking experiment.Design/methodology/approachThe braking performances of resin materials (RM), semimetallic materials (SM) and copper-based powder metallurgy materials (PM) friction blocks mating with forged steel brake disc were examined based on TM-I-type reduced-scale inertial braking dynamometer. The brake disc surface temperature was recorded by infrared thermal camera during braking.FindingsExperimental results indicate that the thermal wear resistance of three friction materials differs with mental content, resulting in the deviation of pad-disc system contact state during braking, thus forming different temperature distribution on the brake disc surface. The peak temperature on the disc face of RM (190°C) is 36.6% and 45.4% lower than that of PM (300°C) and SM (348°C) at 160 km/h. The maximum radial temperature deviation of PM (35°C) is approximately three times than that of RM (12°C) and 40% higher than that of SM (25°C) at 50 km/h, whereas the maximum temperature deviation of SM (97°C) is six times than that of RM (16°C) and 31% higher than that of PM (74°C) at 160 km/h.Originality/valueThe effect of friction material type on the disc surface temperature distribution is revealed, which provides a meaningful reference for the design of brake friction pairs and choice of brake pad materials.

Experimental investigation of air cooler using local palm tree waste

Middle Saudi Arabia has weather conditions where the temperature is high in summer with low humidity. Conventional air conditioning systems operated by a vapor compression cycle are not economical because of the high electrical power consumption. Therefore, evaporative cooling through evaporative coolers is one of the best and most economical solutions. The present study experimentally investigates the factors affecting the performance of evaporative coolers. Pad materials and airflow rate are the main variables to investigate the evaporative cooler's performance in terms of saturation effectiveness, pressure drop across the pads, and coefficient of performance (COP). Pads material are the local palm tree “Nakheel” waste that are leaflet, leaf base, bulb, and roots. The maximum COP of the cooling system in the case of bulb pad material is 80% more than that of leaflet pad material. The saturation effectiveness of the bulb pad was a maximum which is 61.93% at an airflow of 2.25 m/s, which is more than two times that of the saturation effectiveness of the leaflet pad. The pressure drop across the bulb pad is almost 2.5 times to 9.5 times than that of leaflet pad. Results show that bulb pad performance best, whereas the leaflet pad material has the lowest performance in terms of pressure drop, saturation effectiveness, and COP.

Tribological Properties of Brake Disc Material for a High-Speed Train and the Evolution of Debris

The stability and reliability of braking system are essential factors for the safe operation of high-speed trains. In the proposed work, tribological properties of a newly developed brake disc material namely BD-1 were studied considering the thermal-mechanical effects, as well as the evolutions of wear debris, were particularly examined. The tribological properties were also compared with an existing commercial brake disc material namely BD-2 in text. Friction and wear tests were carried out on BD-1 and BD-2 against a commercial brake pad material (BP) to simulate the real emergence braking conditions of a 350 km/h high-speed railway. The thermal-mechanical coupling effects of the friction velocity, wear mass, temperatures and the friction coefficient were investigated. Local wear track and wear debris were analyzed by using SEM and EDS. Results show that the shape and size of wear debris evolve as the dominant wear mechanism varies during braking tests. As the sliding speed increases from 250 to 1250 rpm, the debris may become fine particles, then into a mixture of lamellar shape and flake shape, and finally becomes fine particles again at high speed. The maximum size of wear debris is first from 20 μm to 65 μm, and then down to 10 μm. As the local area temperature increased by more than 400 °C, debris adhere to the surface forming an adhesive layer that may act as a lubricant. Debris may help to form an adhesive lubrication layer and undertake plastics defor-mation at the speed range of 500–1000 rpm. The local area temperatures prompted the wear debris adhesion and oxidation. After reaching a certain speed limit, a uniform third body appears to protect the material surface from high speed and high temperature. Results suggested that the BD-1 could be a good candidate braking material for high-speed railway applications.

Comparative study of airborne particles on new developed metal matrix composite and commercial brake pad materials with ANN and finite element analysis

Comparative study of airborne particles on new developed metal matrix composite and commercial brake pad materials with ANN and finite element analysis

Compressive Properties of Polyurethane Fiber Mattress Filling Material

There is an inevitable trend toward exploring new, environmentally friendly fibers that can be used as raw material for mattresses with moderate hardness and air-permeable characteristics. Ethylene-propylene side by side (ES), high-shrinkage fibers, and thermoplastic polyester elastomer (TPEE) chips were introduced into polyethylene glycol terephthalate (PET)/polybutylene terephthalate (PBT) chip by melt blending to modify PET/PBT fiber. The modified PET/PBT (hereinafter referred to as PLON) is more suitable for mattress filling material than PET/PBT. To explore the compressive properties of PLON cushion made of PLON fiber and expand the scope of the PLON cushion’s application, a layered hardness test, hardness classification test and variance analysis were used to comprehensively evaluate the surface hardness, core hardness, bottom hardness and hardness classification of the mattress made of PLON cushion. The conclusions are: (1) The materials of the support layer have a significant effect on the hardness grade S. The hardness of the mattress with PLON as the support layer is between the spring and the coir; (2) when PLON is used as the material of the support layer, it possesses higher supporting force than coir and the characteristics of light weight and high resilience, which coir does not have; it is also softer than a spring mattress. As cushion material, it provides higher support for mattresses than foam. Practical applications, densities and structure were clarified through the above research, with implications for broader applications for PLON blocks in mattress products.

Nonlinear effects of a new mesh-type rail pad on the coupled vehicle-slab track dynamics system under extremely cold environment

Nonlinear dynamic behavior of a new mesh-type rail pad on the vehicle-slab track coupled system is investigated considering the influences of frequency and amplitude dependence in extremely cold environment. The frequency dependence of the new mesh-type rail pad is modeled by a fractional derivative viscoelastic element while a frictional component considers the amplitude dependence. Laboratory tests are performed to investigate the frequency and amplitude dependent performance of the rail pad and to determine key model parameters. Temperature factor and Mooney-Rivlin strain energy density are also introduced to simulate the mechanical properties of the rubber material of rail pad in low temperature environments. Further, the proposed nonlinear model for the rail pad is implemented in a coupled vehicle-slab track dynamics model to investigate the complicated nonlinear effects of the rail pad due to the dependence of the temperature, amplitude and frequency. The analysis indicates that the dynamic stiffness and damping of the mesh-type rail pads increase with the frequency increases. The proposed model for the mesh-type rail pad enables a more accurate dynamic simulation of vehicle-slab track system in extremely cold environment than the traditional Kelvin-Voigt model which overestimates the wheel rail force, rail vibration acceleration and other indicators at 3.15 Hz–40 Hz and 250 Hz–500 Hz, while underestimates these indicators at 50 Hz–125 Hz.