Inertial Dynamometer Research Articles

Analysis of Parameters Influencing the Formation of Particles during the Braking Process: Experimental Approach

Knowing and understanding the parameters influencing the concentration of particles created by brake wear, as one of the main contributors to non-exhaust emissions from vehicles, is important for the further development of systems on vehicles to reduce the concentration of particles, and also for further research in the field of developing new friction pairs. In this research, a brake inertial dynamometer was used to measure brake particles, and four different brake pads were examined. Based on a previous review of the applied tests and driving cycles, the braking parameters were determined, i.e., the initial simulated speed of the vehicle, the load of one-quarter of the vehicle, and the brake pressure. The ambient temperature, air humidity, coefficient of friction between friction pairs, deceleration, and braking time can have an influence depending on the brake pad. Further, during the measurement, the temperatures of the brake pads were also measured, where the initial temperature of the brake pads was always the same. In order to process the data, several methods were used, including the presentation of the obtained results in a time domain, the application of the Taguchi design of the experiment with the analysis of the parameters, and a correlation analysis using the Pearson and Spearman correlation coefficients. In this research, the authors concluded that the influences of the parameters primarily depend on the applied brake pads. The vehicle speed turned out to have a large influence in all cases, as did the load, i.e., the influence of the vehicle weight (indirectly through the kinetic energy of the vehicle). In this case, the pressure showed less influence on the particle concentration. An important braking parameter that has a significant impact on the concentrations of PM2.5 and PM10 particles is the final temperature of the brake pads.

A methodology for dynamic calibration of inertial dynamometers for wheelchairs

Every day, wheelchair users face countless obstacles that make their social inclusion a real challenge. In this way, it is important that assistive technologies be constantly developed and improved. An example is the dynamometer, which helps in training to characterize the performance of the wheelchair user. In this work, we present a methodology for the dynamic calibration of an inertial dynamometer for wheelchair users, which aims to assist in the rehabilitation and to enable them to perform day-to-day activities independently. The dynamometer is placed on a structure elevated in relation to the ground, at a known height. At the upper end, a wire is attached to the dynamometer cylinder and at the lower end, a known weight is used to enforce acceleration on the cylinder. The wheelchair is placed on top of the cylinder with known different weights corresponding to the user's weight for each repetition of the experiment. The wire is then wrapped around the cylinder and the object is dropped freely, rotating the cylinder. The measurement of the system acceleration is given by an encoder. Data collected in the tests enable to get the system inertial characteristics for each applied weight, allowing to set calibration curve and to evaluate the performance when the propulsion in the dynamometer is imposed by the wheelchair user. This work describes the methodology proposed for calibrating the complete device allowing the quantification of measured values such as power, torque and speed imposed by the user. The calibration steps can be easily reproduced at a low cost and very good performance.

Performance Validation of High-Speed Motor for Electric Turbochargers Using Various Test Methods

As environmental regulations on automotive exhaust gas are gradually strengthened to cope with climate change, internal combustion engines, including those in hybrid electric vehicles, are continuously being downsized. Supercharging technologies are essential to compensate for the reduced engine power. One of the supercharging technologies, the turbocharger, has a response delay in the low-speed region, which is known as turbo lag. Various technologies have emerged to reduce turbo lag. Recently, electric supercharging technologies capable of reducing turbo lag using high-speed motors have been developed and commercialized. However, they are difficult to obtain for high-speed motors because of the cost of load performance test equipment. For this reason, many previous studies have compared analysis and experiment results under no-load conditions, or they have estimated performance in the high-speed region from results at low speed with light loads. This makes it difficult to know exactly how the performance of the motor is affected under loads applied to an actual system. In this study, performance test evaluation was conducted using a high-speed torque sensor, eddy current brake, and inertial dynamometer. Input/output power and efficiency were calculated using the measured voltage, current and output side torque and speed, and the results were compared.

How Does Instability Affect Bench Press Performance? Acute Effect Analysis with Different Loads in Trained and Untrained Populations.

(I) The execution of different sports involves a significant number of throws, jumps, or direction changes, so the body must be as stable as possible while performing a specific action. However, there is no classification of unstable devices and their influence on performance variables. Furthermore, the effect on athletes' experience using instability is unknown. (II) The aim of this study was to analyze the power and speed parameters in bench press with different loads and unstable executions: (1) stable (SB), (2) with asymmetric load (AB), (3) with unstable load (UB), (4) on fitball (FB) and (5) on a Bosu® (BB). A total of 30 male participants (15 trained and 15 untrained) were evaluated for mean propulsive speed (MPS), maximum speed (MS), and power (PW) with different types of external load: a low load (40% of 1RM), medium load (60% of 1RM), and high load (80% of 1RM) in each condition. Variables were measured with an inertial dynamometer. (III) The best data were evidenced with SB, followed by AB (3-12%), UB (4-11%), FB (7-19%), and BB (14-23%). There were no differences between groups and loads (p > 0.05) except in the case of MS with 60% 1RM, where trained participants obtained 4% better data (p < 0.05). (IV) Executions with implements and equipment such as fitball and Bosu® do not seem to be the most recommended when the objective is to improve power or execution speed. However, situations where the load is unstable (AB and UB) seem to be a good alternative to improve stabilization work without high performance. Furthermore, experience does not seem to be a determining factor.

Tribological Behaviors of Polymer-Based Hybrid Nanocomposite Brake Pad

Although extensive improvement has been done on brake pad for vehicles, most recent materials used still encounter wear rate, friction, stopping distance, and time deficiencies. In this regards, this study developed a polymer-based nanocomposite brake pad. Here, a combination of carbon-based materials, including those at a nanoscale, was used to produce the brake pad. Tribological performance, such as friction coefficient, wear rate, and stopping distances of developed brake pad were investigated using an inertial dynamometer. The results revealed that the stopping distances, the coefficient of friction (CoF), and wear rate vary with the brake pad formation and velocity. The micrographs show changes in the structural formation after the incorporation of carbon-based fillers. It also shows smooth surface structure and uniform dispersion of the carbon fiber. The smooth surface of the worn brake pad is an indicative of a tougher structure. Hence, it was deduced that the fabricated polymer-based hybrid composite had good tribological property. This improved property is suggestive of materials that may be successfully used for brake pad application.

Processing and study of the wear and friction behaviour of discrete graded Cu hybrid composites

Discrete functionally graded composites are the novel composites which have high potential in the brake friction material applications. In this paper, we have prepared discrete functional graded Cu/10%SiC/ 20%graphite(Gr)/10%boron nitride (h-BN) hybrid composites by the layer stacking compaction and pressure sintering techniques. We have considered two types of composites based on h-BN particle sizes. The size ranges of h-BN used were 140–180 and 3–25 µm. The friction and wear properties of the composites were evaluated in a laboratory scale brake inertial dynamometer at low (5, 10 m s-1) and high sliding speeds (30, 35 m s-1) and, high braking load (2000 N) conditions. In addition, we have performed microstructure characterization, density, hardness and flexural strength measurements. Wear surface morphology studies were also carried out using stereoscope and scanning electron microscope. Our experiments lead to the following important results: (1) the large size h-BN particle improves the densification of the hybridized composite layer and provides higher wear resistance and better braking performance at all sliding speeds, (2) the wear loss (by mass) and the stopping distance/time increase with sliding speeds due to the increase in the braking energy, (3) at low sliding speeds (5, 10 m s-1), abrasive wear is the main wear mechanism, whereas many different wear mechanisms (delamination, oxidation, abrasive) are cooccuring at higher sliding speeds (30, 35 m s-1), (4) the mechanical properties (flexural strength and surface hardness) of composites are not affected by the h-BN particle size, (5) the incorporation of copper layer in the discrete layer structure deflects and arrests the crack at the copper/composite layer interface, thus improving the fracture resistance in addition to improving the bulk thermal conductivity.

Les profils musculaires inertiels permettent une définition plus précise des charges d’entraînement

Aims of the study The aim of the present study was to explore the interest of inertial load-velocity and load-power relationships for establishing resistance training zones. Materials and methods Thirty-five subjects went twice at the laboratory. The first session was used to determine bench press one repetition maximal (1RM) while the second session was used to determine load-velocity and load-power relationships by the means of an inertial dynamometer. For each subject, four major training zones (maximal velocity, power-velocity, strength-power, maximal strength), defined from the 1RM, were compared to the corresponding training zones defined from inertial load-velocity and load-power relationships. Results Training zones defined from the 1RM are significantly different ( P < 0,001) from the ones based on load-velocity and load-power relationships. According to load-power and load-velocity relationships results, maximal bench press velocity should be trained from 0 to 23% of the 1RM; power-velocity should be trained from 25 to 54% of the 1RM; strength-power should be trained from 54 to 82% of the 1RM and maximal strength should be trained with superior loads. Such muscular profiles defined with inertial dynamometers allow a more acute and individualised prescription for power-velocity resistance training.

Validité et reproductibilité d’un dynamomètre inertiel basé sur l’accélérométrie

Introduction The purpose of this study was to investigate the validity and reliability of an inertial dynamometer using accelerometry. Methods Fourteen subjects were tested during three successive sessions at four increasing loads (30, 50, 70 and 95% of the 1RM). Maximal force, velocity and power performances were simultaneously assessed by the Myotest (Myotest S.A., Switzerland), an inertial dynamometer using accelerometry, and by another control valid dynamometer witch combine accelerometer and linear position transducer. At three first loads, only minor differences appeared in between both dynamometers, correlations were excellent and coefficients of variation were good and similar. However, at 95% of the 1RM, Myotest validity and reliability became insufficient. Conclusion Bench press inertial assessment with accelerometer appeared valid and reliable at 30, 50 and 70% of the 1RM, but not at 95% of the 1RM.

Comparison of Chase and inertial brake Dynamometer testing of automotive friction materials

For effective and safe automotive brake system applications, friction materials must meet certain minimum requirements for performance, noise and durability. To ensure this, friction materials are subjected to a series of vehicle tests on a test track or on the road before they are released as commercial products. While vehicle tests are expensive, time consuming and subject to road conditions and weather variability, brake dynamometer testing in the laboratory is faster and less costly to screen or verify friction material characteristics. Furthermore, because of the capability to control test conditions precisely, a brake dynamometer serves as an excellent tool for the research and development of friction materials. In the U.S.A. two major types of brake dynamometers are commonly used: the inertial dynamometer which evaluates a full size brake or a brake system and simulates vehicle braking well, but is time consuming and expensive, or a smaller Chase dynamometer that features low capital expenditure and shorter test time using a small friction material sample against a large drum. The Chase dynamometer does not simulate brake conditions as well as the inertial dynamometer, and therefore is used primarily for rapid screening and/or for quality control only. The correlation, or the lack of it, between these two brake dynamometers is discussed in this paper. Friction and wear data from both test systems on several friction pairs under various temperature, sliding speed and load conditions are compared and discussed. The materials used were (a) non-asbestos organic disc pads against cast iron rotors, (b) semimetallic disc pads against cast iron rotors and (c) non-asbestos organic disc pads against copper rotors.

Correlation of wear with oxidation of carbon-carbon composites

The wear characteristics of carbon-carbon composites for aircraft brake materials were investigated using an inertial dynamometer. Wear rates were measured in terms of weight loss and thickness reduction. The wear rates in terms of weight loss are always greater than those in terms of thickness reduction over a wide range of braking conditions. This difference agrees with previous work carried out under a normal braking condition and, as before, is attributed to the oxidation of carbon beneath the porous friction surfaces. Good agreement was obtained between the activation energies for the oxidation of carbon (29 kcal mol −1) and for material loss on non-friction surfaces (27 kcal mol −1). Such good agreement suggests that the rate-controlling step for oxidative weight loss is the diffusion of oxygen through pores.

Microstructural changes in semimetallic disc brake pads created by low temperature dynamometer testing

A combination of commercial semimetallic disc pads and a ventilated gray cast iron rotor were tested with an inertial dynamometer according to the following schedule: 100 burnish stops plus 300 stops initiated at a rotor temperature of 120°C. Changes in friction and wear observed during this test have been related to structural and compositional changes in the pads, rotor and collected wear debris. These structural and compositional changes have been characterized by scanning electron microscopy, energy dispersive analysis of X-rays, X-ray diffraction and Knoop hardness measurements. Friction-affected zones are created in both the pads and the rotor during the initial portion of the test. In the pads the zones are denser than the bulk material; in the rotor the zones are composed of a thin layer of material permanently transferred from the pads over a thicker layer of decomposed pearlite. The removal of the rough surface of the as-ground pads and the concurrent development of friction-affected zones are responsible for the high rate of pad thickness wear observed during the initial portion of testing.

Physical and chemical changes of organic disc pads in service

Automotive organic disc pads undergo a series of physical and chemical changes at the frictional heat affected layer (FHAL) in service. To determine these changes as a function of energy absorption, a series of inertial dynamometer tests was run for a full size passenger car disc brake to different energy levels to produce a series of FHALs with progressively different compositions. The FHALs produced as wear surfaces between 238°C and 438°C were subsequently characterized by a combination of optical microscopy, X-ray fluorescence and diffraction and thermogravimetric analysis. As the temperature increased there was a decreased organic content, an increased inorganic content, a decreased asbestos content, an increased olivine content and the formation of carbonaceous residues. These formations were produced under conditions where the FHALs were undergoing increasing exponential wear as the temperature increased.

Effects of potassium titanate fiber on the wear of automotive brake linings

Asbestos reinforcing fiber in an automotive friction material was replaced by an experimental ingredient having better thermal stability and the effects on wear and friction were studied. A friction materials test machine (SAE J661a) was used to determine friction and wear, under constant energy output conditions, as a function of temperature between 121 and 343°C (250 and 650°F). When potassium titanate fiber replaced one-half of the asbestos in a standard commercial lining, with a 40% upward adjustment of phenolic resin content, wear above 204°C (400°F) was improved by 40% and friction by 30%. Tests on a full scale inertial dynamometer supported the findings of the sample dynamometer tests. It was demonstrated that the potassium titanate fiber contributes directly to the improvement in wear and friction.

Electromyographic and biomechanical study of human power production.

The present paper describes an investigation designed to examine the relationship(s) between (1) the physiological characteristics of muscles as reflected in electrical activity, and (2) the mechanical characteristics to power output in the human forearm. Electromyographic responses were recorded from the biceps, brachialis, and brachioradialis muscle groups while subjects were performing on a specially constructed inertial dynamometer. Mechanical analysis included a resolution of forces acting on the forearm. This procedure included the calculation of muscle forces through the use of geometrical considerations and the principle of moments. Results were suggestive of the existence of a linear relationship between power output and electrical activity, and (2) the mechanical characteristics to power output in the human forearm. In addition, statistical analysis revealed that power production and calculated muscle force were related at higher inertial loads.

The effect of load on muscle output.

Analytic consideration of muscle output resulted in an expression that relates the power output of a muscle to the imposed load. The simplest theory predicted that maximum power output would occur when the load impedance was equal to the impedance of the muscle system involved. Modification of this theory to accommodate the inverse type of relationship between the force generated and the speed of contraction, in agreement with physiological considerations, predicted the maximum power output at a load impedance (moment of inertia) five to ten times the impedance of the muscle system involved. Experimental observations over a wide range of loads on a specially constructed inertial dynamometer confirmed the predictions and gave a power curve similar to the predicted one.