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Electric vehicles are playing an increasingly important role in the agricultural sector. The selection of tyres for reducing energy loss due to rolling resistance is an important consideration in determining the viability of these vehicles. To date little is known about rolling resistance of small all-terrain vehicles. In this study a test rig was used to collect rolling resistance data for seven ATV tyres. The study verifies the relationship between normal load and rolling resistance and gives insight into some of the important considerations when selecting tyres for small off road vehicles.

A novel application of magnetostrictive actuators in underplatform dampers of bladed disks is proposed for adaptive control of the normal load at the friction interface to achieve the desired friction damping in the structure. Friction damping in a bladed disk depends on operating parameters, such as rotational speed, engine excitation order, nodal diameter normal contact load, and contact interface parameters, such as contact stiffness and friction coefficient. The operating parameters have a fixed value, whereas the contact interface parameters vary in an unpredictable way at an operating point. However, the ability to vary some of these parameters such as the normal contact load in a controlled manner is desirable to attain an optimum damping in the bladed disk at different operating conditions. Under the influence of an external magnetic field, magnetostrictive materials develop an internal strain that can be exploited to vary the normal contact load at the friction interface, which makes them a potentially good candidate for this application. A commercially available magnetostrictive alloy, Terfenol-D is considered in this analysis that is capable of providing magnetostrain up to 2 × 10-3 under prestress and a blocked force over 1500 N. A linearized model of the magnetostrictive material, which is accurate enough for a direct current application, is employed to compute the output force of the actuator. A nonlinear finite element contact analysis is performed to compute the normal contact load between the blade platform and the underplatform damper as a result of magnetostrictive actuation. The nonlinear contact analysis is performed for different actuator mounting configurations and the obtained results are discussed. The proposed solution is potentially applicable to adaptively control vibratory stresses in bladed disks and consequently to reduce failure due to high-cycle fatigue. Finally, the practical challenges in employing magnetostrictive actuators in underplatform dampers are discussed.

Understanding the shear failure mechanisms of coal mass is essential to dealing with mining issues, including roof collapses, pillar instabilities, and severe roadway closures. A numerical three-dimensional synthetic rock-mass method was used to study the shear behavior of coal mass. It was found that the peak and residual shear strength increase significantly with normal load. The shear stiffness also increases, especially at a low normal stress. The dilation decreases significantly with a normal load. Coal joints tend to reduce dilation and control the shear-rupture geometry. The effect of the joints on the shear failure decreases with a normal load.

To promote the engineering application of composite transmission of high speed curve face gear, which consists of a cylindrical gear and a high speed curve face gear, the analysis of tooth bending stress should be taken into consideration. High speed curve face gear pair is a new type of curve face gear pair. Combined with the principle of high speed cam and curve face gear pair transmission, it can transfer the axial/rotation composite motion and power between two intersecting shafts. Based on the gear engagement principle, the gear meshing coordinate system was established and the fundamental of the high speed composite transmission was expounded. Combined with the tooth profile equation of generating gear, the tooth surface equation of high speed curve face gear was gained. Tooth force, contact ratio and normal load distribution were calculated. Then the tooth bending stress of high speed curve face gear during the transmission was calculated and analyzed in detail. Influence of basic parameters on tooth bending stress was discussed. Finally, the simulation and measurement experiment of tooth bending stress was carried out. By the comparison analysis of simulation, experiment and theory, the correctness of tooth bending stress calculation method was verified, which has important guiding significance for the further research of high speed curve face gear of composite transmission.

This paper presents the effect of grinding wheel contact stiffness on the plunge grinding cycle. First, it proposes a novel model of the generalized plunge grinding system. The model is applicable to all plunge grinding operations including cylindrical, centerless, shoe-centerless, internal, and shoe-internal grinding. The analysis of the model explicitly describes transient behaviors during the ramp infeed and the spark-out in the plunge grinding cycle. Clarification is provided regarding the premise that the system stiffness is composed of machine stiffness and wheel contact stiffness, and these stiffnesses significantly affect productivity and grinding accuracy. The elastic deflection of the grinding wheel is accurately measured and formulas for representing the deflection nature under various contact loads are derived. The deflection model allows us to find the non-linear contact stiffness with respect to the normal load. The contact stiffnesses of four kinds of grinding wheels with different grades and bond materials are presented. Both cylindrical grinding and centerless grinding tests are carried out, and it is experimentally revealed that the time constant at ramp infeed and spark-out is significantly prolonged by reducing the grinding force. It is verified that a simulation of the grinding tests using the proposed model can accurately predict critical parameters like forces and machine deflection during plunge grinding operations. Finally, this paper provides a guideline for grinding cycle design in order to achieve the required productivity and grinding accuracy.

Measurements with digital image correlation of normal and tangential contact stiffness for ground Ti-6Al-4V interfaces suggest a linear relationship between normal contact stiffness and normal load and a linear relationship between tangential contact stiffness and tangential load. The normal contact stiffness is observed approximately to be inversely proportional to an equivalent surface roughness parameter, defined for two surfaces in contact. The ratio of the tangential contact stiffness to the normal contact stiffness at the start of tangential loading is seen to be given approximately by the Mindlin ratio. A simple empirical model is proposed to estimate both the normal and tangential contact stiffness at different loads for a ground Ti-6Al-4V interface, on the basis of the equivalent surface roughness and the coefficient of friction.

This paper investigates the possibility of DC-link capacitor testing in multi-leg converters. Operating conditions similar to ones expected in normal operation can be achieved with the circular power flow, which is possible in multi-leg converters. Two cases are considered. The first one is DC/DC buck converter and second one is dual three-phase drive. Based on simulation results it can be asserted that regenerative/synthetic load can be comparable to normal load with proper setup of operational parameters.

Applying accurate normal load to a specimen in direct shear tests under constant normal stiffness (CNS) is of importance for the quality of the resulting data, which in turn influences the conclusions. However, deficiencies in the test system give rise to a normal stiffness, here designated as system normal stiffness, which results in deviations between the intended and actual applied normal loads. Aiming to reduce these deviations, this paper presents the effective normal stiffness approach applicable to closed-loop control systems. Validation through direct shear tests indicates a clear influence of the system normal stiffness on the applied normal load (13% for the test system used in this work). The ability of the approach to compensate for this influence is confirmed herein. Moreover, it is demonstrated that the differences between the measured and the nominal normal displacements are established by the normal load increment divided by the system normal stiffness. This further demonstrates the existence of the system normal stiffness. To employ the effective normal stiffness approach, the intended normal stiffness (user defined) and the system normal stiffness must be known. The latter is determined from a calibration curve based on normal loading tests using a stiff test dummy. Finally, a procedure is presented to estimate errors originating from the application of an approximate representation of the system normal stiffness. The approach is shown to effectively reduce the deviations between intended normal loads and the actual applied normal loads. Funding details: BeFo 391; Funding details: Svensk Kärnbränslehantering, SKB; Funding details: Nuclear Waste Management Organization, NWMO; Funding text 1: Open access funding provided by RISE Research Institutes of Sweden. The authors would like to acknowledge the research funding granted by BeFo Rock Engineering Research Foundation (grant proposal BeFo 391) and SKB, Swedish Nuclear Fuel and Waste Management Co, Solna, Sweden. The authors would also like to thank Adjunct Professor Diego Mas Ivars at SKB, Swedish Nuclear Fuel and Waste Management Co; Associate Professor Fredrik Johansson at KTH Royal Institute of Technology; and Adjunct Professor Erland Johnson at RISE Research Institutes of Sweden AB for their valuable contribution to this work.

Foamed concrete has been widely used in tunnels where foamed concrete-rock joints are usually encountered. However, few studies have been conducted on the mechanical properties of the joint. To investigate the shear behaviors of the joint, compressive properties of foamed concrete were first studied by compression tests, and a series of direct shear tests under constant normal load condition were then conducted. Three failure types were identified during the tests: interface failure, foamed concrete failure and the mixed type. Both the normal stress and dry density of the foamed concrete can significantly influence the shear behaviors of the joint, but have little effect on the friction coefficient of the joint. Based on the results, a model was proposed for the joint, which can successfully describe the shear behaviors of the joint. The model can easily be implemented in numerical codes, and then be used to investigate the mechanical behaviors of tunnels in practical cases.

Time- and load-dependent friction behavior is considered as important for a long time, due to its time-evolution and force-driving characteristics. However, its electronic behavior, mainly considered in triboelectric effect, has almost never been given the full attention and analyses from the above point of view. In this paper, by experimenting with fcc-latticed aluminum and copper friction pairs, the mechanical and electronic behaviors of friction contacts are correlated by time and load analyses, and the behind physical understanding is provided. Most importantly, the difference of “response lag” in force and electricity is discussed, the extreme points of coefficient of friction with the increasing normal loads are observed and explained with the surface properties and dynamical behaviors (i.e. wear), and the micro and macro theories linking tribo-electricity to normal load and wear (i.e. the physical explanation between coupled electrical and mechanical phenomena) are successfully developed and tested.

This paper presents an investigation into the effect of unexpected overloading on scuffing initiation with a twin-disc test device. An existing twin-disc test device was modified to be suitable for applying overloading dynamically to the disc contact. Three test series including three pairs of discs in each series were subjected to combined normal force and rolling/sliding loading. First a base level for scuffing initiation was defined by increasing the normal load stepwise until failure, while keeping the rolling and sliding between the discs constant. In the subsequent test series, the overload cycles were applied at a significantly lower level in two different patterns leading to scuffing at both an earlier and later stage than was observed for the base level. acceptedVersion

When subjected to shear loading condition, a steel rock bolt will become bent in the field close to the loading point in situ. The bolt is deformed as the joint displacement increases, which can mobilize a normal load and a shear load on the bolt accordingly. In this work, the relationship analysis between the displacing angle and loading angle is carried out. By considering elastic and plastic states of rock bolt during shearing, the rotation of bolt extremity can be calculated analytically. Thus, the loading angle is obtained from displacing angle. The verification of analytical results and laboratory results from reference research implies that the analytical method is correct and working. In terms of in-situ condition, the direction of the load acting on steel bolt can be predicted well according to the direction of the deformed rock bolt with respect to original bolt axis.

In this paper, the effect of joint separation on the shear behavior of planar non-persistent joints under high normal load has been investigated using PFC2D. Initially, calibration of PFC was undertaken with respect to the data obtained from experimental laboratory tests to ensure the conformity of the simulated numerical models response. Furthermore, the simulated models were cross checked with the results of direct shear tests performed on non-persistent jointed physical models. Through numerical direct shear tests, the failure process was visually observed, and the failure patterns were found reasonably similar to the experimentally observed trends. The discrete element simulations demonstrated that the failure pattern was mostly influenced by joint separation, while the shear strength was linked to the failure pattern and mechanism. Исследовано влияние разъединения соединения при сдвиге плоского нестабильного соединения под действием интенсивной нормальной нагрузки с использованием программного обеспечения PFC2D. Первоначально калибровка PFC2D проведена на основе экспериментальных данных для согласования с моделируемым числовым результатом. Достоверность моделируемых моделей проверена при сравнении с результатами прямых испытаний на сдвиг, выполненных на нестабильных сочлененных физических моделях. Благодаря числовому прямому испытанию на сдвиг процесс разрушения был отмечен визуально, и разрушенные образцы отбирались подобными экспериментально наблюдаемым тенденциям. Дискретное моделирование элемента показывает, что на разрушение образца главным образом влияет разъединение соединения, в то время как прочность при сдвиге связана с моделью разрушения и механизмом разрушения. Досліджено вплив роз’єднання з’єднання при зсуві плоского нестабільного з’єднання під дією інтенсивного нормального навантаження з використанням програмного забезпечення PFC2D. Спочатку калібрування PFC2D проведено на основі експериментальних даних для узгодження з модельованим числовим результатом. Достовірність модельованих моделей перевірено при порівнянні з результатами прямих випробувань на зсув, що виконані на нестабільних зчленованих фізичних моделях. Завдяки числовому прямому випробуванню на зсув процес руйнування було відмічено візуально, і зруйновані зразки відбиралися подібними експериментально спостережуваним тенденціям. Дискретне моделювання елемента показує, що на руйнування зразка головним чином впливає роз’єднання з’єднання, тоді як міцність при зсуві пов’язана з моделлю руйнування і механізмом руйнування.

A marker layer (Au80Pd20) combined with four different techniques was used in order to estimate the real contact area between static steel–steel contact pairing (substrate: AISI304 and ball: AISI 52100). The experiments were done with polished references (substrate and ball) and with substrates having a laser-patterned line-like surface topography using two loads (1 and 5 N) and two pattern periodicities (9 and 15 µm). Irrespective of the normal load, all techniques led to the same results within the standard deviation for the polished surfaces. For the laser-patterns, only the combination of foot-printing, scanning electron microscopy and image segmentation is capable to provide meaningful results, since the other techniques significantly overestimate the real contact area.

In the present study, artificial neural network (ANN) model was developed to predict the wear characteristics of Al 2219-SiCp composite. In the development of predictive model, weight fraction of the reinforcement, sintering temperature, applied normal load on the pin and disc speed were considered as model variables. Full factorial experiments were carried out and observed wear characteristics were taken as input for the model. A feed forward back propagation hierarchical neural network was considered in the study. Out of 81 datasets, 49 sets of data were used for training, 16 sets of data for validation and 16 sets of data for testing. The results exhibit good prediction accuracy of about 85% on average of all wear characteristics and percentage error was within the acceptable limits.

In this paper, the effect of rock bridge surface on the shear behavior of planar non-persistent joints under low and high normal loads has been investigated using particle flow code in 2 Dimensions. PFC2d was calibrated with respect to the data obtained from experimental laboratory tests to ensure the conformity of the simulated numerical models response. The models consisting non-persistent joint were simulated and tested by shear loading under low and high normal loads. The discrete element simulations demonstrated that the failure pattern was mostly influenced by normal load, while the shear strength was linked to the failure pattern and failure mechanism. The failure patterns were found reasonably similar to the experimentally observed trends.

The rolling resistance of skis used in roller skiing competitions should resemble the gliding resistance of cross-country skis to allow specific training and moving patterns for cross-country skiing and to guarantee equal opportunities for athletes in roller ski races. Therefore, the purpose of this work was to develop a portable rolling resistance meter to precisely measure the rolling resistance of roller skis. Measurements were based on recordings of the angular deceleration of a flywheel due to the rolling resistance between a roller ski’s wheel and the flywheel’s steel surface. Rolling resistance coefficients of four roller ski types ranged between 0.019 and 0.025. Measurements of the rolling resistance coefficient showed a precision of 1.26%. Substantial rolling resistance coefficient variations (10%) were observed for wheels of the same type. Furthermore, the rolling resistance coefficient was found to be negatively correlated with normal load or ambient temperature. The proposed rolling resistance meter is appropriate to determine the rolling resistance coefficient of roller skis’ wheels precisely.

In this paper, a methodology was proposed and an experimental configuration was designed to investigate the fretting fatigue mechanism under complex cyclic loading condition. This condition is common and highly influences the fretting fatigue behavior. However, it is barely studied at present. A series of fretting fatigue tests shown that cyclic normal load will enlarge the slip region of contact interfaces, making the crack nucleation location moves toward the middle range of contact region. It is demonstrated that complex cyclic loads have a positive effect of fretting damage, making the fatigue life shorter than those in constant normal loading conditions.

The typical shear behaviour of rough joints has been studied under constant normal load/stress (CNL) boundary conditions, but recent studies have shown that this boundary condition may not replicate true practical situations. Constant normal stiffness (CNS) is more appropriate to describe the stress–strain response of field joints since the CNS boundary condition is more realistic than CNL. The practical implications of CNS are movements of unstable blocks in the roof or walls of an underground excavation, reinforced rock wedges sliding in a rock slope or foundation, and the vertical movement of rock-socketed concrete piles. In this paper, the highlights and limitations of the existing models used to predict the shear strength/behaviour of joints under CNS conditions are discussed in depth.

Two different methodologies for assessing the friction between plantar skin and sock textiles are compared in this study. The first approach uses a custom-built friction plate rig. The rig consists of sock material mounted on a test plate attached to two load cells that measure normal and shear loads at the skin-sock textile interface. With this methodology, participants are required to slide their foot over the test plate whilst maintaining a targeted normal load and a relatively consistent sliding speed. The second approach uses a pneumatically-driven foot probe loading device. The device includes an instrumented probe with sock material on its contact surface. Participants are instructed to stand on a platform whilst the probe is applied to, and then driven across, the plantar aspect of foot. The cyclic motion of the probe is displacement-controlled and normal and shear loads are measured using load cells. Both approaches allow friction coefficients to be calculated from load data collected during the sliding phase of movement. Data from both approaches was examined, collected from friction tests using the same six participants and sliding contact between the first metatarsal head (1MTH) region and textiles from two commercially available running socks. Both approaches were capable of measuring the friction between 1MTH skin and sock materials and good agreement was found between them. In the dry conditions tested, the cotton-rich sock was found to provide lower friction that the anti-blister sock material.

Friction is known to cause vibration in many situations and one particular kind of friction-induced vibration is in the form of stick-slip vibration, which is of fundamental significance in science due to its ubiquitous nature. In this paper, an experimental and theoretical study is performed to investigate friction-induced stick-slip vibration. An experimental setup with a sophisticated dual-pin-on-disc configuration is produced. A detailed solid model is constructed and modal tests are conducted to establish a novel, simplified 2-degree-of-freedom (DoF) theoretical model for the test rig. A series of stick-slip oscillation tests at several levels of normal load and disc velocity are performed and interesting vibration behaviour is discovered. A non-smooth Coulomb’s law of friction is adopted and identified for the 2-DoF model and the method of the Switch Model is used to deal with the non-smooth transitions from stick to slip and from slip to stick. The theoretical results predicted by the 2-DoF model agree qualitatively quite well with the experimental results. The differences between the two sets of results also suggest that there are challenges in realising regular stick-slip vibration in real machines/structures and capturing it theoretically. The main contributions of this work are the new designed test rig, the experimental findings, and the established theoretical model that can be used to reveal interesting dynamic behaviour of stick-slip vibration.

The prehension of the small objects with the human fingers is depending on the friction and adherence between finger’s skin and object’s surface. The design of finger pads for robotic and prosthetic hands must simulate both the human finger friction and adherence and elastic deformation, especially for small objects. In this paper, the authors have experimentally investigated the friction forces and friction coefficients in a dry sliding contact tribosystem using Microtribometer CETR UMT-2. A steel cylinder was sliding on the human finger with speeds between 0.5 to 10 mm/s at normal loads up to 10 N. The results showed that the friction coefficient increases with the sliding speed and decreases with the normal load. Also, it was evidenced the presence of the adherence and sliding zones during the laterally cyclic movement of steel cylinder as function of the normal loads and sliding speeds. A general equation for the friction coefficient as function of sliding speed and normal load has been obtained. Therefore, the experimental results offer important information to select the adequate artificial skin materials for robotic finger pads, often overlooked, with relatively simple shapes and mechanical properties typically used.

A study of non-Newtonian inertia squeeze film in rectangular stepped plates has been presented in this paper. Applying the momentum integral method incorporating the micro-continuum theory of non-Newtonian fluids, a non-Newtonian inertia lubrication equation is derived. It is found that the fluid inertia effects yield in a higher normal load capacity as well as a longer squeeze film time as compared to the non-Newtonian stepped squeeze film in the absence of fluid inertia forces.

Shear behaviour of rock joints can be studied under both constant normal load (CNL) and constant normal stiffness (CNS) boundary condition. CNS condition is suitable for non planar and reinforced rock joints whereas CNL condition is suitable for planar and non reinforced rock joints. In the present study shear behaviour of modelled rock joints with different asperity have been experimentally investigated under both CNL and CNS boundary conditions. Test results indicate that CNS boundary conditions gives higher shear strength as compare to CNL boundary condition when other parameter of testing is kept same. But, this effect tends to diminishes with increase in normal stress on the shearing plane and at high normal stress both CNL and CNS boundary conditions gives same shear strength. A new shear strength model is proposed for both the boundary condition and the proposed model is validated by comparing the predicted shear strength with present experimental results and results available in the literature for natural and artificial rock joints with different asperity and roughness. The new study and model will be useful for safe and economical design of underground openings in jointed rocks, stability analysis of rock slopes, design of foundation on rock and design of rock socketed piles.

Non-stationary effects in the friction-induced dynamics of a two-degree-of-freedom brake model are examined in this paper. The belt–spring–block model is designed to take into account variations of the normal load during the braking process. It is shown that due to the adiabatically slowing down velocity of the belt, the system response experiences specific qualitative transitions that can be viewed as simple mechanical indicators for the onset of squeal phenomenon. In particular, the creep-slip leading to a significant widening of the spectrum of the dynamics is observed at the final phase of the process.

This paper presents motivation and details on the development of an advanced shear tester (AST) device capable of investigating the response of 150-mm cylindrical specimens under constant normal stiffness (CNS) conditions. Based on the laboratory experience and field observations from the soil and rock engineering, CNS conditions are particularly desirable when the normal stress changes considerably during the shearing process. Such situations occur in asphalt pavement structures especially under certain loading configurations. The CNS conditions are complementary to the constant normal load conditions that are applied in the current shear-mode devices incorporated in testing of asphalt concrete (AC) and pavement interface properties. This paper demonstrates the complex state of stress in the upper AC layer of a typical pavement under moving truck wheel and shows the need for the CNS device. In addition to outlining unique AST design features, this paper presents also the verification effort conducted on ...

A novel laboratory technique has been used to measure the rolling resistance of tyres using a force transducer. The effect of inflation pressure, normal load and speed has been studied for two different bias-ply tyres—with and without treads. As anticipated, the results indicate that a treaded tyre has higher value of the rolling resistance as compared with a tyre with treads removed.

A high level of individuals on the planet is living in decentralized, rustic and remote territories which are topographically detached from lattice association. Power dissemination and consistent fuel transportation to create electrical vitality for these regions represent an awesome test. A savvy lattice mixture vitality framework has been outlined and mimicked to help a little group considering a normal load request of 72 kWh/d and a pinnacle heap of 7 kW. The recreation and enhancement procedure of the cross breed vitality framework, with the thought of meteorological information, have been finished by HOMER Software. Reenactment comes about demonstrate that the proposed framework is financially and ecologically doable, and that the Net Present Cost (NPC) and in addition CO 2 outflow are diminished by around 74% and 92% separately every year contrasted with customary power plants. The NPC of the streamlined framework has been observed to be about US$ 76,901 with the Cost of Energy (COE) of about US$ 0.198/kWh. This upgraded mixture vitality framework will be pertinent for every single other area on the planet with comparative meteorological and natural conditions.

In this work, different cognitive load situations are examined and classified in the context of a Human Computer Interaction (HCI) scenario. Machine learning methods were used to detect three cognitive load states (overload, underload, normal load) with the help of five different psychophysiological signals (ECG, EMG, Respiration, GSR, Temperature). At first it is shown, that the three regarded states can be clearly distinguished in the Valence-Arousal-Dominance space (VAD). After this comparisons between a 10-fold-valdidation and a batch-validation as well as three different classifiers (k-Nearest-Neighbour, Naive Bayes, Random Forest) are accomplished. At last the influence of gender in contrast to an overall analysis is shown.

The interface bonding condition between asphalt concrete layers is unquestioned as one of the significant factors influencing pavement performance. In order to research the interface charac...

To help reduce the costs and logistical requirements for establishing forward operating bases (FOBs), the U.S. Army investigates construction methods that use indigenous materials in place of commercial materials manufactured far away. An established construction system called the HESCO bastion, currently used in theater for force protection, derives its mass and load resistance from indigenous soils placed in manufactured steel and geotextile containment modules. Using this system for other FOB structures, such as soldier housing, could greatly reduce costs and logistical burdens for Class 4 construction materials. Before developing such applications, however, the load-resisting characteristics of HESCO units must be tested for incorporation into new engineering guidance. In this study a HESCO unit was filled with dry, coarse sand and subjected to combination of normal and lateral loads at four separate intensities. The interaction of normal and lateral loads was investigated, as well as the cyclic loading hysteresis. A lateral load capacity for HESCO bastions was determined based on the applied normal load. The results validated the suit-ability of HESCO units as load-bearing structural members for temporary soldier housing in FOBs located in remote areas of operation.

In order to successfully automate levelling processes, in particular for heavy plates, the deflection of the leveller has to be compensated based on a deflection model. In this work, a detailed mathematical deflection model of a hot leveller with bending mechanism and its experimental validation are presented. The roll intermesh profiles are calculated based on the deflection of the work rolls that are elastically supported by support rolls, frames, posts and adjustment screws. The deflection model is suited to compensate the effect of deflection on the roll intermesh and the plate flatness as well as to assess the loads of critical parts, for example the support rolls. A new experimental design to measure the deflection of a leveller is presented and successfully applied for model validation. The work roll deflection is measured directly by means of displacement sensors that are inserted in cut-outs of test plates. These test plates are modelled as linear elastic stripes. For normal load levels, the rela...

Power load consists of four components according to the law of its variation, normal load, weather-sensitive load, special-events load, random load, and we can separate the air conditioning load from power load. Then by fitting the relationship between meteorological factors and air-conditioning power consumption, can we grasp the effect of meteorology factors on power load in high-temperature seasons.

Elucidating the effects of gravity on rover/rover wheel performance is important because it can provide a basis for predicting their performance on extraterrestrial surfaces based on test results obtained on Earth. Results of previous studies by Wong (2012) and by Wong and Kobayashi (2012) indicate that if in conducting performance testing of rovers/rover wheels on Earth with identical mass to that on the extraterrestrial surface, instead of with identical normal load (force) used in the current practice, their performance on the extraterrestrial surface can be predicted based on test results obtained on Earth. As described herein, the effects of gravity on rigid rover wheel sinkage and motion resistance were investigated using the two-dimensional discrete element method. The rover wheel mass is unchanged under various gravity conditions. The results of this study substantiate the findings presented in Wong (2012) and Wong and Kobayashi (2012). Given identical mass, the sinkage of a rigid rover wheel under Earth gravity g is the same as that under a different gravity g ex : 1/6g–2g. It is also shown that the ratio of the motion resistance of a rigid rover wheel under gravity g ex to that under Earth gravity g is equal to the ratio g ex / g .

A model for interactions of a single large impurity particle with the optic and pad during pad-polishing has been developed to detailedly illustrate the scratch formation process. Equations for calculating the normal load applied on the optic by the impurity particle are provided, and the friction between the optic and impurity particle has also been considered in scratch formation. Initiation and evolution of the scratches under the combined effects of the normal and friction forces are illustrated in the model. The most important factors affecting the normal load and thus scratch formation have been analyzed and verified using published experimental results. Based on the model, the implications in reduction of scratch formed on optics during pad polishing have been analyzed.

During sliding low elastic modulus, materials can form ridges and distinct zones of contact vice the commonly observed Schallamach wave phenomena. It was shown that at low velocities (0.001 and 0.01 m/s), the contact geometry retained a single region of contact and at higher velocities (0.1 and 1 m/s) the contact separated into two distinct zones. It was also shown that this phenomenon was independent of the applied normal load.

A novel method for suppressing frictional vibration in sliding systems without using additional devices (e.g., dampers or actuators) is theoretically proposed. This method is based on the principle that yawing angular misalignment provides positive damping to sliding systems. Even if frictional vibration occurs due to a negative slope of the friction versus velocity characteristic, it can be suppressed by applying a misalignment angle φ that is larger than the critical misalignment angle φcr. To examine the basic applicability of this method to disc brake systems, a braking test at a constant normal load was simulated numerically. It was found that yawing angular misalignment can not only suppress frictional vibration but also shorten the braking time as a secondary effect of suppressing frictional vibration.

The aim of this work is to study the wear behavior of the cylinder liner of internalcombustion engines, using reciprocating wear testing machine and study the effect of operating conditions (Rotating speed, length of stroke and normal load) on the wear behavior in dry sliding. A statistical analysis method was applied to study the interaction effect of these parameters, and effect of each parameter. Results obtained showed that the wear characteristics is effected mainly by the normal load (P), and stroke length (L), and the rotating speed (R) has no significant effect on the liner wear. The study also showed an interaction effect of normal load (P), and stroke length (L) together on the wear of the liner.

The surfaces of fibrous materials like textiles are characterised by emergent superficial fibres forming hairiness. Hairiness is an important factor for the frictional and tactile properties of fabrics. In this study, we investigated the friction mechanisms of hairy fabrics by sliding probes with varying geometry over the textile surfaces. The total friction between a hairy fabric and a cuboid-shaped slider is given by two main contributions—one due to the contact of hairs with the front of the slider and the other one resulting from the hairiness underneath the slider. By changing the slider geometry, the relative importance of these two contributions can be systematically varied, so that conclusions about adhesion and deformation mechanisms involved in the friction of hairy fabrics can be drawn. For a given slider area and a given normal load, the force underneath the slider was found to be independent of the slider width while the force in front of the slider increased linearly with the slider width. The major contribution of the force underneath the slider is highlighted. This force is influenced by the material and surface roughness of the slider, indicating that adhesion mechanisms play a significant role in the friction.

The characterization of the rolling resistance is an important issue when designing mechanical systems in order to predict the force needed to run a given mechanism. Frictional forces in bearings and rolling resistance in rollers and wheels are the most important factors contributing to the overall resistance to the movement. As the rolling coefficient varies as a function of the material nature, normal load, and rolling velocity, it is desirable to test the designed system under real conditions. Mechanical testing machines, present in most mechanical laboratory tests, usually work in uniaxial mode. In this work a simple testing device to be used with uniaxial mechanical testing machines is presented.

The main objective of this research was to investigate the performance of refined, bleached and deodorized (RBD) palm olein by using a pin-on-disk tester. The pin was held to the rotating plain disk at a normal load (10 N) according to the American Society for Testing and Materials (ASTM) G99. The RBD palm olein was used as the main lubricant owing to a greater awareness of the greenhouse effect phenomenon which has lessened the usage of conventional lubricants that affect our environment. This trend has strongly encouraged the government to use eco-friendly and biodegradable lubricants in the manufacturing industry. RBD palm olein was selected due to its superior tribological properties and large production in Malaysia. The tests were carried out using a direct lubricant flow of RBD palm olein and hydraulic oil on a plain disk at two different speeds (0.4 m/s and 4 m/s). The material used for both frictional surfaces was stainless steel. The results clearly show that the wear obtained when using the RBD palm olein was lower than that of the hydraulic oil. In addition, the coefficient of friction and wear scar diameter of the sample lubricated with RBD palm olein was remarkably lower at low speeds, and approximately the same as hydraulic oil at high speeds.

A mathematical model of eight degrees freedom was built up with considering the normal load transfer due to the presence of the longitudinal, lateral acceleration for a vehicle under braking in turn condition. And the simulation model based on the mathematical model was eatablished by means of MATLAB/Simulink software. The comparison between simulation results and real vehicle test results under the snow pavement double-lane change condition is in good agreement. It can be concluded that the 8DOF vehicle dynamics model of this study is acceptable and valid.

The current practice for experimentally evaluating the performance of extraterrestrial rovers/rover wheels is to conduct tests on earth on a soil simulant, appropriate to the regolith on the extraterrestrial body of interest. In the tests, the normal load (force) applied by the rover/rover wheel to the soil simulant is set identical to that expected on the extraterrestrial surface, taking into account its acceleration due to gravity. It should be pointed out, however, that the soil simulant used in the tests is subject to earth gravity, while the regolith on the extraterrestrial surface is subject to a different gravity. Thus, it is uncertain whether the performance of the rover/rover wheel obtained from tests on earth represents that on the extraterrestrial surface. This issue has been explored previously. A method has been proposed for conducting tests of the rover/rover wheel on earth with identical mass to that on the extraterrestrial surface, instead of with identical normal load used in the current practice [1]. This paper provides further evidence to substantiate the merits of the proposed method, based on a detailed analysis of the test data obtained under various gravity conditions, produced in an aircraft undergoing parabolic flight manoeuvres [8]. In the study, the effect of slip on wheel sinkage has been evaluated. It is found that gravity has little effect on the slip and sinkage relationship of the rover wheel under self-propelled conditions.

Vegetable oil is one of the bio-oils that have been promoted to replace petroleum-based products due to its eco- friendly characteristics. Palm oil has high productivity rate, and so it could fulfil the demand for a bio-lubricant. In this paper, the influence of the normal load on friction and wear performance were investigated for a RBD palm olein and compared with paraffinic mineral oil using four-ball tribotester. The normal load was varied from 30 kg to 60 kg. All experimental works were conforming to ASTM D 4172. The results exhibited that the RBD palm olein has lower coefficient of friction compared to paraffinic mineral oil. However, the wear scar of ball bearings lubricated with RBD palm olein showed larger diameter compared to paraffinic mineral oil. As a conclusion, RBD palm olein has better performance compared to paraffinic mineral oil in terms of capability to reduce friction.

In order to increase the performance and efficiency of current tactile sensors, the study on the versatility of the human hand and tactile function could provide excellent hint. Our objective is to develop a new algorithm based on comparing the behavior of human tactile mechanism (using psychophysics experiment) vs. a robotic hand (equipped with 3-axis tactile sensor) using stainless steel (SUS) foils and 1,000-yen bills as medium. The significance of tangential load is highlighted to distinguish between material thicknesses. The result from the first experiment shows that using normal vs. angled load, the Weber fraction is high during low thickness and decreased with increase of thickness. In the second experiment, we find that the ability to distinguish between sheet numbers improves by increasing tangential load compared to just normal load. Overall, it is noted that the tangential load makes the tactile sensor distinguish extremely thin material.

Several real life reinforced soil structures such as traffic supporting embankments and pavements are subjected to cyclic loads. The behaviour of soil-reinforcement interface under cyclic load is different from that under monotonic load. In the investigation reported herein, cyclic pullout tests were conducted on geogrid embedded in sand. A load controlled pullout test apparatus complying with the dimensions suggested by ASTM D-6706-01 was designed and fabricated in-house. Modular units for applying both cyclic and monotonic load were also designed and fabricated. Cyclic load was applied through a pneumatic double acting air cylinder. In addition, the setup consisted of a signal generator and a filter lubricator regulator volume booster. The effect of normal stress and cyclic load on the pullout behaviour was studied. It was found that cyclic loads of a lower magnitude than the monotonic capacity could cause failure. In the case of cyclic loads of small magnitude, the displacements showed tendency to stabilize. In the case of higher magnitudes of cyclic loads, the displacements progressively increased to failure. An initial stiffness was noticed in the system due to the initial densification achieved near the interface due to the dynamic nature of the cyclic pullout forces. Normal load as well as cyclic load played important roles in the number of cycles to cause failure. Post-cyclic monotonic tests showed the effect of degradation of the soil-geosynthetic interface after subjecting the same to certain number of load cycles.

We present a general formulation for the stick slip behaviour of incomplete contact under oscillating loading, but with a constant normal load. An asymptotic description of the contact traction very close to the contact edges is used. The slip zones present in the steady state with cyclically varying bulk tension and shear force (with an arbitrary phase shift) are found. The range of the variation of the state of stress near both of the contact edges and the respective slip zone sizes are defined in terms of the loading parameters, including the phase angle. The quality of the approximations used by the asymptotic approach and the range of applicability of the method is also analysed in detail in this paper.