Pendulum Device Research Articles

Protective Coating Based on Organic Silicon Polymer of Ladder Structure Nanostructured with Alkoxysilane

New materials based on oligooxidridsilmethylensiloxysilane nanostructured with ethyl ester of orthosilicic acid – tetraethoxysilane have been studied in the research. Tetraethoxysilane introduction into the composition is supposed to cause its decomposition up to nanoparticles of silicon oxide. The alkoxysilane hydrolytic destruction kinetics and the impact of the composition and nature of the polymer composition components on the physical properties have been studied. Atomic force microscopy was used to study the structurization kinetics of the polymer composition. The composition hydrophobicity was determined by the edge wetting angle. To study the adhesion characteristics of the obtained material, the method of disc separation from the substrate has been used. The relative rigidity has been determined by a pendulum device M3. Atomic force microscopy revealed the presence of nanoscale neoplasms (at average of one hundred twenty per one square micrometer) in diameter from two to five nanometers in the surface structure of the composition, modified with tetraethoxysilane. Herewith the physical properties of the material change: rigidity increases, the edge angle of wetting increases as well. The studied nanostructured compositions can also be applied. For example – they can be used as a protective coating with a set of special properties, such as high hydrophobicity.

Evaluation of litchi impact damage degree and damage susceptibility

Mechanical damage induced by impact during shaking harvesting or transportation debases the quantity and shortens the shelf life of litchi fruit. In this paper, ‘Nuomici’ and ‘Guiwei’ litchis were used to study the impact behavior between fruit and a rigid plate with a new measuring method in order to achieve an approach to evaluate the damage degree and the damage resistance. Impact tests were conducted on a pendulum device and the impact force, compressed depth and contact length were recorded with a force sensor and a high-speed camera. Based on these data, a method was introduced to calculate the contact area, average surface pressure and compressed volume at any given moment of the impact. Analysis of the impact process indicated that the end of deformation phase was the most dangerous moment for a fruit during the impact in all cases. For both cultivars, as the drop height increased from 200 mm to 800 mm, the percentage of absorbed energy, the maximum contact area and the damage degree increased, while the contact time decreased. The maximum surface pressure remained stable as the drop height ranged from 400 mm to 800 mm, so that surface pressure was not a main factor affecting the damage degree. The damage degree of ‘Guiwei’ and ‘Nuomici’ were 13.34% and 13.27% at drop height of 200 mm and 27.89% and 23.74% at 800 mm. Respectively, 70% and 79% damage degree happened at drop height of 400 mm. The difference of litchi cultivar has low effect on contact area and contact time, but significant effect on damage degree when drop height was 600 mm and 800 mm. Based on elastic theory, power models with high coefficient of determination were successfully used to fitting the relationship between impact energy and compressed depth for both cultivars. Combined with the good linear fittings between compressed volume and damage degree, the damage degree could then be predicted with impact energy. Furthermore, the damage susceptibility (DS) was introduced to describe the susceptibility of impact damage of litchi fruit. The results show that DS decreased with the increase of drop height. ‘Nuomici’ was more resist to impact damage than ‘Guiwei’ as drop height changed from 600 mm to 800 mm. The new method presented in this study can be used to evaluate the damage of litchi fruit and optimize the design of litchi shakers.

Device and Measuring Method the Moments of Rolling Resistance Forces on the Contact Spot

Currently, the study of rolling friction is one of the main directions in the study of the laws of contact interaction of solids. The complexity of solving the problems existing in this area is evidenced by the practically vast number of publications, the list of which is constantly growing.In this paper, attention is paid to studies of the moments of rolling resistance at displacements from the equilibrium position of a ball-shaped body that are substantially smaller than the size of the contact spot. The purpose of the present work is to describe the design of the single-contact pendulum device developed by the authors, in which the physical pendulum, resting on the flat surface of the body under study with only one ball, makes free small stable swings in a vertical plane, as well as in the description of a special measurement technique with high sensitivity and accuracy rolling resistance forces, including adhesion forces and frequency-independent forces of elastic deformations. It is assumed that the adhesion forces can exhibit both dissipative properties and elastic properties, while elastic forces are independent of the strain rate.The originality of the method of measuring rolling resistance in this paper consists in using the method of nonlinear approximation of the dependence of the amplitude and period of swing of the pendulum on time. The approximation is carried out on the basis of the proposed laws of amplitude decay and period variation, which differ from the usual exponential law.It is assumed that this approach allows one to evaluate the surface tension of a solid and evaluate the pressure of adhesion forces between the surfaces of the contacting bodies, as well as to establish an analytical form of the moment of rolling resistance. The curves of the dependence of the rolling resistance moment on the swing amplitude of the pendulum are constructed. Experiments were performed for the following pairs of contacting bodies: steel-steel, steel-glass, steel-electritechnical silicon. It was assumed that the pressure at the contact spot did not exceed the elastic limit.The developed single-ball pendulum device and the proposed measurement procedure open up new wide possibilities for studying the laws of mechanisms of rolling resistance under conditions of microand mesoscale displacements of a rolling body from a state of rest.

FINE-TUNING OF MODELLING STRATEGY TO SIMULATE THERMO-MECHANICAL BEHAVIOUR OF DOUBLE FRICTION PENDULUM SEISMIC ISOLATORS UST ESTIMATOR

The use of friction pendulum devices has recently attracted the attention of both academic and professional engineers for the protection of structures in seismic areas. Although the effectiveness of these has been shown by the experimental testing carried out worldwide, many aspects still need to be investigated for further improvement and optimisation. A thermo-mechanical model of a double friction pendulum device (based on the most recent modelling techniques adopted in multibody dynamics) is presented in this paper. The proposed model is based on the observation that sliding may not take place as ideally as is indicated in the literature. On the contrary, the fulfilment of geometrical compatibility between the constitutive bodies (during an earthquake) suggests a very peculiar dynamic behaviour composed of a continuous alternation of sticking and slipping phases. The thermo-mechanical model of a double friction pendulum device (based on the most recent modelling techniques adopted in multibody dynamics) is presented. The process of fine-tuning of the selected modelling strategy (available to date) is also described.

Approximate neural optimal control with reinforcement learning for a torsional pendulum device

A torsional pendulum device containing hyperbolic tangent input nonlinearities can be formulated as a nonaffine system. Unlike basic affine systems, the optimal feedback control of complex nonaffine plants is difficult but quite important. In this paper, the approximate optimal control design of continuous-time nonaffine nonlinear systems is investigated with the help of reinforcement learning. For addressing the learning algorithm conveniently, an effective pre-compensation technique is adopted to perform proper system transformation. Then, the integral policy iteration strategy is incorporated to relieve the demand of system dynamics. Moreover, the actor–critic structure is implemented by virtue of neural network approximators. Finally, the experimental verification for the proposed torsional pendulum plant is conducted after a learning process of 20 iterations and the stability performance with basic robustness guarantee can be observed during two case studies.

Damage caused by multiple impacts of litchi fruits during vibration harvesting

Mechanical damage caused by fruit-to-fruit impact is a major challenge for mechanical harvesting of litchi (Litchi chinensis Sonn) fruits. Guiwei litchi fruits were used to study the impact behavior and damage degree due to multiple fruit-to-fruit impacts. The effect of impact times and impact energy absorbed by fruits on fruits damage degree were studied by using a pendulum device. The damage degree of fruits was determined with the modulus of elasticity of fruits. A comb-shaped shaker was used for mechanical detaching tests while the detaching time, impact times and impact energy absorbed of litchi fruits during vibration process at three frequencies of 18 Hz, 25 Hz and 32 Hz were investigated based on a high-speed camera. The results of the pendulum tests showed that the damage degree of litchi fruits increased with the increase of the string length from 0.1 m to 0.35 m at all impact times and most of the damage was caused before 10 times of impacts. Furthermore, the damage degree increased according to a power function (R2 = 0.9433) with the total impact energy absorbed of all impacts, which can be used to estimate the damage degree of a fruit after multiple impacts. The mechanical detaching tests showed that 90% fruits were detached in 1.2 s, 0.9 s and 0.5 s at 18 Hz, 25 Hz and 32 Hz respectively and the average impact times decreased from 13.1 times to 6.6 times with the increase of frequency. The calculation results showed that a vibration frequency of 32 Hz induced the lowest average estimated damage degree, which was 5.69%. Therefore, harvesting litchi fruits mechanically at high rate and low damage might be feasible with a proper shaking frequency.

Original Techniques of the High Precision Automatic Impact Test Device

Abstract Irradiation embrittlement testing of reactor pressure vessel (RPV) steel is essential to the surveillance experiment of nuclear power plant safety and requires high precision, high reliability, high repeatability, and high stability (4-High). It is very difficult to achieve the 4-High requirements of the remote control automatic impact test device in the hot cell. This article introduces our original designs of the obverse straight transfer specimen: the direct centering of the specimen notch and solid bath furnace. Aside from the common motor and automatic release pendulum device of automatic impact testing, the original new techniques of the automatic impact test consist of only two actuators (the push specimen plate and the notch automatic centering device). This innovative technique has successfully guaranteed the 4-High test results; it has simplified the track, reduced the number of steps, minimized the number of actuators of the automatic impact test, shortened transfer specimen time, and improved the precision of temperature control and notch centering. Through the successful use of this original technique, we have replaced the usual lateral transfer specimen and indirect centering of specimen notch with the obverse straight transfer specimen and direct centering of specimen notch. By adopting only one actuator, our technique has easily resolved the difficulties of terminal rebound and the disturbance and dislocation of the specimen. The operation has combined specimen transfer and centering into one step, which has smoothly overcome the difficult problems of instant specimen transfer, notch centering, and compression so that the specimen touches the test anvil closely. In sum, these innovative techniques have streamlined the complicated and rapid process of automatic impact testing into a simple and easy process.

A discrete element model (DEM) for predicting apple damage during handling

Apples can suffer from significant mechanical injury in the form of bruise damage. The discrete element method (DEM) allows for individual particle contacts and the dynamic behaviour of a group of particles to be studied. Successfully applying this method to apples allows for future investigations into postharvest mechanical damage to be performed on a range of fruit and vegetables. A contact model that closely replicated the visco-elastic nature of apples was used and the material properties were successfully determined using a pendulum device. Bruise damage models (in the form of bruise volume, bruise area and bruise depth) were coupled to the peak impact forces available through DEM. Bruise formations resulting from multiple impacts and variable time durations between impacts were studied. A detailed multi-sphere particle shape representation along with a realistic contact point loading scheme was implemented. Overlapping bruises were studied and accounted for on a post process level. The resulting DEM model was successfully validated and extended to include run-time bruise visualisation. Qualitatively the model accurately predicted the dynamic bulk behaviour of the apples. Quantitatively, the model succeeded in predicting the contact forces experienced by apples to within 11%. The model predicted the mean bruise damage of a single apple for realistic situations within an accuracy of 47% in terms of mean bruise volume, 35% for bruise area and 30% for bruise depth.

A point of application study to determine the accuracy, precision and reliability of a low-cost balance plate for center of pressure measurement

Changes in postural sway measured via force plate center of pressure have been associated with many aspects of human motor ability. A previous study validated the accuracy and precision of a relatively new, low-cost and portable force plate called the Balance Tracking System (BTrackS). This work compared a laboratory-grade force plate versus BTrackS during human-like dynamic sway conditions generated by an inverted pendulum device. The present study sought to extend previous validation attempts for BTrackS using a more traditional point of application (POA) approach. Computer numerical control (CNC) guided application of ∼155 N of force was applied five times to each of 21 points on five different BTrackS Balance Plate (BBP) devices with a hex-nose plunger. Results showed excellent agreement (ICC > 0.999) between the POAs and measured COP by the BBP devices, as well as high accuracy (<1% average percent error) and precision (<0.1 cm average standard deviation of residuals). The ICC between BBP devices was exceptionally high (ICC > 0.999) providing evidence of almost perfect inter-device reliability. Taken together, these results provide an important, static corollary to the previously obtained dynamic COP results from inverted pendulum testing of the BBP.

Rotations of Pendulum When Its Pivot Oscillates Chaotically

This paper investigates the possibility of energy generation via pendulum rotations when the source of vertical excitation is chaotic in nature. The investigations are conducted using an additional height-adjustable mechanism housing a secondary spring to optimize a configuration of experimental pendulum setup. Chaotic oscillations of the pendulum pivot are made possible at certain excitation conditions due to a piecewise-linear stiffness characteristic introduced by the modification. A velocity control method is applied to maintain the rotational motion of the pendulum as it interacts with the vertical oscillator. The control input is affected by a motor, and a generator is used to quantify the energy extraction. The experimental results imply the feasibility of employing a pendulum device in a chaotic vibratory environment for energy harvesting purpose.

Validating the BTrackS Balance Plate as a low cost alternative for the measurement of sway-induced center of pressure

The BTrackS Balance Plate (BBP) is a low-cost force plate that provides objective balance assessment and true portability for the user. Given that this technology is relatively new, the purpose of the present study was to provide the first center of pressure (COP) validation of the BBP. Two BBP devices (one new and one used) were compared with a laboratory-grade force plate (LFP) during simultaneous collection of COP that was induced by an inverted pendulum device with human-like sway characteristics. The results of this study showed almost perfect agreement between the BBP devices and the LFP (ICC>0.999), as well as a high degree of BBP accuracy (<1% error magnitude) and precision (<0.2mm regression residuals). These results suggest the BBP can serve as an effective, low-cost solution for objective balance testing in the laboratory or clinic.

Development of a new testing equipment that combines the working principles of both the split Hopkinson bar and the drop weight testers.

In the current work, a new high strain rate tensile testing equipment is proposed. The equipment uses a pendulum device to generate an impact load and a three-bar mechanism to bring that load to act upon a specially designed specimen. As the standard impact testing apparatus uses pendulum device and the well-known SHB high strain rate tester adopts the above-mentioned mechanism, the introduced equipment can be dealt with as an impact apparatus in which the base that supports the V-shape specimen is replaced with the three-bar configuration that the traditional SHB uses. In order to demonstrate the applicability of the new tester, virtual design tools were used to determine the most appropriate configuration for it. Then, a detailed design was created, and a full-scale prototype was produced, calibrated, instrumented and tested. The obtained results demonstrate that the new tester is capable of axially straining steel specimens up to failure at a maximum rate of about 250 s−1, which is reasonable when compared with a more established high strain rate testers.

Orthodontic Protocol Using Mini-Implant for Class II Treatment in Patient with Special Needs.

Improving facial and dental appearance and social interaction are the main factors for special needs (SN) patients to seek orthodontic treatment. The cooperation of SN patients and their parents is crucial for treatment success. Objective. To show through a case report the satisfactory results, both functional and esthetic, in patients with intellectual disability, congenital nystagmus, and severe scoliosis. Materials Used. Pendulum device with mini-implants as anchorage unit. Results. Improvement of facial and dental esthetics, correction of Class II malocclusion, and no root resorption shown in the radiographic follow-up. Conclusion. Knowing the limitations of SN patients, having a trained team, motivating and counting on the cooperation of parents and patients, and employing quick and low-cost orthodontic therapy have been shown to be the essential factors for treatment success.

Analysis of Free Pendulum Vibration Absorber Using Flexible Multi-Body Dynamics

Structures which are commonly used in our infrastructures are becoming lighter with progress in material science. These structures due to their light weight and low stiffness have shown potential problem of wind-induced vibrations, a direct outcome of which is fatigue failure. In particular, if the structure is long and flexible, failure by fatigue will be inevitable if not designed properly. The main objective of this paper is to perform theoretical analysis for a novel free pendulum device as a passive vibration absorber. In this paper, the beam-tip mass-free pendulum structure is treated as a flexible multibody dynamic system and the ANCF formulation is used to demonstrate the coupled nonlinear dynamics of a large deflection of a beam with an appendage consisting of a mass-ball system. It is also aimed at showing the complete energy transfer between two modes occurring when the beam frequency is twice the ball frequency, which is known as autoparametric vibration absorption. Results are discussed and compared with findings of MSC ADAMS. This novel free pendulum device is practical and feasible passive vibration absorber in the mitigation of large amplitude wind-induced vibrations in traffic signal structures.

Evaluation of a dentoalveolar model for testing mouthguards: stress and strain analyses

Custom-fitted mouthguards are devices used to decrease the likelihood of dental trauma. The aim of this study was to develop an experimental bovine dentoalveolar model with periodontal ligament to evaluate mouthguard shock absorption, and impact strain and stress behavior. A pendulum impact device was developed to perform the impact tests with two different impact materials (steel ball and baseball). Five bovine jaws were selected with standard age and dimensions. Six-mm mouthguards were made for the impact tests. The jaws were fixed in a pendulum device and impacts were performed from 90, 60, and 45° angles, with and without mouthguard. Strain gauges were attached at the palatal surface of the impacted tooth. The strain and shock absorptionof the mouthguards was calculated and data were analyzed with 3-way anova and Tukey's test (α=0.05). Two-dimensional finite element models were created based on the cross-section of the bovine dentoalveolar model used in the experiment. A nonlinear dynamic impact analysis was performed to evaluate the strain and stress distributions. Without mouthguards, the increase in impact angulation significantly increased strains and stresses. Mouthguards reduced strain and stress values. Impact velocity, impact object (steel ball or baseball), and mouthguard presence affected the impact stresses and strains in a bovine dentoalveolar model. Experimental strain measurements and finite element models predicted similar behavior; therefore, both methodologies are suitable for evaluating the biomechanical performance of mouthguards.

Depression-like behavior changes after one and triple times cerebral concession in rats by forced swimming test

Objective To observe the changes of depress-like behavior characteristics in different period of the forced swimming test(FST) after pure cerebral concussion(PCC)and multiple cerebral concussion(3MCC) model rats. Methods 24 adult healthy male SD rats were chosen. A brain concussion model was produced in rats using a simple pendulum device, according to the impacting times (one or three times) and impacting interval(24 h or 48 h). The rats were randomly assigned to the one time PCC group, triple MCC 24 h group(3MCC 24 h) and triple MCC 48 h group(3MCC 48 h), and one normal control group was used(8 rats in each group). FST was used to assess the change of depress-like behavior characteristics in rats. Results The following depress-like behavior changes of FST ( climbing; swimming; motionless) were observed at the 3rd, 7th, 15th, 30th day after injury were as follows: (1) Compared with the normal control group, the decline of climbing behavior frequency had statistically significant(P 0.05). Conclusion There are some depress-like behaviors after one time CC and triple CC in rats, while the severity of triple CC is more severe than one time CC, and the short time interval strike triple CC is more severe than the long time interval triple CC. Key words: Pure cerebral concussion; Triple cerebral concussion; The depression-like behavior; Forced swimming test

Effects of Enzymatic Degradation after Loading in Temporomandibular Joint

Synovial fluid of the joint decreases friction between the cartilage surfaces and reduces cartilage wear during articulation. Characteristic changes of synovial fluid have been shown in patients with osteoarthritis (OA) in the temporomandibular joint (TMJ). OA is generally considered to be induced by excessive mechanical stress. However, whether the changes in synovial fluid precede the mechanical overloading or vice versa remains unclear. In the present study, our purpose was to examine if the breakdown of joint lubrication affects the frictional properties of mandibular condylar cartilage and leads to subsequent degenerative changes in TMJ. We measured the frictional coefficient in porcine TMJ by a pendulum device after digestion with hyaluronidase (HAase) or trypsin. Gene expressions of interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2), matrix metalloproteinases (MMPs), type II collagen, and histology were examined after prolonged cyclic loading by an active pendulum system. The results showed that the frictional coefficient increased significantly after HAase (35%) or trypsin (74%) treatment. Gene expression of IL-1β, COX-2, and MMPs-1, -3, and -9 increased significantly in enzyme-treated TMJs after cyclic loading. The increase in the trypsin-treated group was greater than that in the HAase-treated group. Type II collagen expression was reduced in both enzyme-treated groups. Histology revealed surface fibrillation and increased MMP-1 in the trypsin-treated group, as well as increased IL-1β in both enzyme-treated groups after cyclic loading. The findings demonstrated that the compromised lubrication in TMJ is associated with altered frictional properties and surface wear of condylar cartilage, accompanied by release of pro-inflammatory and matrix degradation mediators under mechanical loading.

Mood regulation in bipolar disorders viewed through the pendulum dynamics concept.

Bipolar disorders have been characterized by powerful fluctuations of energy, mood, and thinking patterns. Mood episodes (manic or depressive) could be considered as deviations of a psycho-physiological index above or below a conventionally defined value called ‘normothymia’. In the present study, we analyzed the feedback techniques used to suppress the oscillatory activity exhibited on an inverted pendulum device. Subsequently, we examine the degree that this multimodal feedback design could be considered on a hypothetical pendulum where the mood plays the role of the suspended mass, and the force balance compensation circuitry is substituted by drug-specific therapeutic interventions. The study does not concern a model of bipolar illness that could simulate numerically various phases of mood episodes but focuses on the functional similarities regarding the correction treatments applied on the two different oscillating systems giving a potential perspective of how techniques of feedback control may enhance the conceptualization of the treatment schemes followed in recent guidelines for biological treatment of bipolar disorders. Our theoretical consideration, along with observations on clinical level, gives support to the concept that the compensation of the mood oscillations should be adaptive with selective therapeutic interventions that compensate the excited system in different time scales.

Design, construction, and evaluation of a modified rolling pendulum to measure energy dissipation in rubber

A practical method to measure the energy dissipation in rubber vulcanizates under rolling condition has been considered. For this purpose, a modified rolling pendulum device was designed and constructed to eliminate the shortcomings of an initial design by Gent. This modified device has a working table, heated rolling plate, symmetric pendulum and an ultrasonic sensor for accurate measurement of the roller travel distance and calculation of rolling resistance parameters for rubber. Performance of this new device was evaluated by measurement of the rolling resistance force and coefficient for rubber vulcanizates containing un-modified and silane-modified nano-silica under different conditions. The device could successfully show the effects of strain, temperature and silica surface modification on rubber rolling resistance parameters, as reported by other researchers.

Mechanical resistance of coppice stems derived from full‐scale impact tests

ABSTRACTBroadleaf coppice forests have the capacity to mitigate the threat posed by rockfall in many mountainous regions. Other forest types alike the rockfall protective effect is determined by the mechanical resistance of the coppice tree stems. In addition, the rockfall protective function of coppice forests is enhanced by specific stem aggregations (clumps) that have a rock interception and retention effect difficult to evaluate. The main objectives of this study are to quantify the mechanical resistance of small diameter coppice stems and to gain qualitative insight on breakage behavior. The aim is to supply data for more reliable assessments of the rockfall protective function of coppice forests with rockfall simulation models and to provide a basis for better estimating the rockfall protective effect of coppice clumps. To achieve these objectives we assessed the mechanical resistance of 73 beech (Fagus sylvatica L.) coppice stems using an impact pendulum device. We found an exponential relationship between the stem diameter at breast height (DBH) and mechanical resistance (loss of momentum or kinetic energy of the impactor during impact). Moreover, the results show that the high flexibility of the stems leads to relatively long lasting impacts and only negligible damage at the point of impact on the stem. As a result, the mechanical resistance of the stems is partly determined by impactor velocity and mass. These findings question the practicality of defining mechanical resistance by means of the change of momentum or energy of the impactor. Moreover, the results highlight the limits of upscaling or downscaling the data of this study to conclude for the mechanical resistance of beech trees of other than the tested dimensions. For the target DBH range the obtained dataset is nevertheless more reliable than data of previous studies, because the DBH specific impact process could be considered. Copyright © 2013 John Wiley &amp; Sons, Ltd.