Spring Load Research Articles

Analysis of the Leaf Spring Failure in Light Duty Dump Truck

This research analyzed the causes of failure in the leaf spring of a cold diesel Dump Truck. The test was conducted in the form of hardness using the Rockwell method and a hardness value of 104.8 HRB while microstructure analysis was used to view and identify fracture surfaces through SEM and optical microscope. Furthermore, the distribution of each spring load was determined by analytical analysis and found to be 28983 N while the chemical composition was analyzed by comparing the spring microstructure with the AISI 5150 standard. The finite element analysis conducted with the FEMAP software showed the maximum stress and strain values in the leaf spring were recorded on the left and right sides. The stress intensity factor (KI) around the end of the initial crack was also found to be greater than the fracture toughness of the material (KIC), thereby, causing the initiation and propagation of cracks in the leaf springs. It was, therefore, concluded that the failure in the spring was due to an initial defect caused by the dynamic load experienced by the spring, thereby, leading to the initiation and propagation of cracks up to the final fracture.

Optimizing Template Models to Quantifiably Assess Center of Mass Kinematic Reconstruction.

The center of mass (COM) plays a fundamental role in human ambulation, but the redundant nature of the human body adds complexity to mathematically modeling its dynamics. Template models like the Bipedal Spring Loaded Inverted Pendulum (B-SLIP) and the Virtual Pivot Point (VPP) address this complexity by removing the redundancy while retaining desired salient characteristics, such as the COM evolution. However, template models for the COM during human walking have mostly been used for qualitative analysis due to issues such as overestimation of COM vertical displacement. This paper considers a quantifiable template-based analysis of human walking by using an optimization framework to set the model parameter values for matching both explicitly and implicitly considered gait characteristics. Furthermore, it is shown that allowing the leg stiffness of the B-SLIP and VPP model to vary throughout the gait cycle better matches vertical COM trajectories with 54%-63% error reduction. These optimized template models show promise in retaining ground reaction force (GRF) information, which is not explicitly considered during the optimization process. Future work looks to incorporate these optimized trajectories as a reference for control of a lower-limb knee-ankle prosthesis.

Muscle fatigue in the latch-mediated spring actuated mandibles of trap-jaw ants.

Muscle fatigue can reduce performance potentially affecting an organism's fitness. However, some aspects of fatigue could be overcome by employing a latch-mediated spring actuated system (LaMSA) where muscle activity is decoupled from movement. We estimated the effects of muscle fatigue on different aspects of mandible performance in six species of ants, two whose mandibles are directly actuated by muscles and four that have LaMSA "trap-jaw" mandibles. We found evidence that the LaMSA system of trap-jaw ants may prevent some aspects of performance from declining with repeated use, including duration, acceleration and peak velocity. However, inter-strike interval increased with repeated strikes suggesting that muscle fatigue still comes into play during the spring loading phase. In contrast, one species with directly actuated mandibles showed a decline in bite force over time. These results have implications for design principles aimed at minimizing the effects of fatigue on performance in spring and motor actuated systems.

Overcharge to Remove Cathode Passivation Layer for Reviving Failed Li–O 2 Batteries

Overcharge to Remove Cathode Passivation Layer for Reviving Failed Li–O ₂ Batteries

Methods for editing random load spectra based on multi-parameter index preservation for accelerated durability testing

Herein, a multi-parameter index preservation-based (MPIP) load spectrum editing method is proposed for improving the efficiency of the accelerated durability testing of mechanical components. The editing process was conducted in the frequency domain by adopting a wavelet transform to decompose the load spectrum into different wavelet levels. The high-frequency wavelet levels were squared and summed at each time interval to obtain the wavelet energy distribution. The damage segments with large amplitude cycles were identified and extracted from the load spectrum based on the wavelet energy distribution. A shorter spectrum was obtained without significant changes in the indexes (the damage index, statistical index, and power spectrum density index). The effectiveness of the MPIP-based load spectrum editing method was demonstrated through the editing process of a coil spring load spectrum, along with a fatigue and damage assessment. The results show that the time duration reduction ratio of the load spectrum after editing was considerably lower than that of the load spectrum before editing. Further, the statistical indices (i.e., the mean, root mean square, and kurtosis) and power spectrum density Pearson correlation coefficient of the MPIP-based edited load spectrum were comparable to those of the original load spectrum. The results also demonstrate that the MPIP-based edited load spectrum indices and time-domain-based edited load spectrum have certain differences. However, the proposed method is more effective for accelerated durability tests. The results regarding the coil spring fatigue damage and lifetime assessment further validated this conclusion.

Development of Grating and Dewatering Units of a Cassava Processing Machine

The cassava processing machine that combines two units’ major operations of grating and dewatering was developed. The development of the machine prototype involved design, fabrication and performance evaluation. The machine which is simple to operate and maintain was powered by 2.2 kW (3.8 hP) single phase, electric motor. The machine was tested with five grater speeds (1100, 1200, 1300 1400 and 1500 rpm), dewatering with five speeds (150, 200, 250, 300, and 350 rpm) and five compression spring loads (100, 200, 300, 400 and 500 N). The recommended cassava variety TMS 30110 was also used. The results obtained from the performance of the machine showed a significant improvement over similar machines. The results from performance evaluation of the cassava processing machine showed that, 1400 rpm grater speed has the highest grating capacity and efficiency. Also in the combine machine (grating and dewatering) experiment, 1400 rpm grater speed, 300 rpm screw expeller speed and 400 N compression spring load has the highest machine capacity, throughput and efficiency of 114.23 kg/h, 95. 88 kg/h and 83.9% respectively from 10 kg cassava tuber. The moisture content 46% wb obtained was within the recommended value. The losses recorded during machine operation was minimal.

Experimental Investigation of the Dynamics of a Slider-Crank Mechanism With Local Linear Force Input

Abstract Conventional implementation of slider-crank mechanisms result in high loads transmitted through the mechanical structure, inhibiting the design of compact and oil-free machines. Therefore, this research proposes to step away from the conventional, i.e., rotative, actuation and to investigate local linear actuation on the slider-component directly, while maintaining the kinematic link of the slider-crank configuration. In this work, the local linear actuating principle is evaluated experimentally where the goal is to obtain a continuous movement of the slider mechanism where Top Dead Center & Bottom Dead Center are reached and to minimize the loads transmitted through the mechanical structure. The non-isochronous transient behavior of a slider-crank mechanism loaded with a spring-damper element is detailed as well as the optimal working conditions at steady-state to achieve a reduced loading of the kinematic structure. By matching the operating frequency and resonance frequency of the system, a reduction of the loads transmitted through the system by 63% of the nominal spring load can be achieved. Further experimental (and multibody mechanical) investigation on the influence of flywheel exposes a clear trade-off between the sensitivity of the system and the transmission of the actuation force through the kinematic link.

Electric Spring and Smart Load: Technology, System-Level Impact, and Opportunities

The increasing use of renewable energy sources to combat climate change comes with the challenge of power imbalance and instability issues in emerging power grids. To mitigate power fluctuation arising from the intermittent nature of renewables, electric spring (ES) has been proposed as a fast demand-side management technology. Since its original conceptualization in 2011, many versions and variants of ESs have emerged and industrial evaluations have begun. This article provides an update of the existing ES topologies, their associated control methodologies, and studies from the device level to the power system level. Future trends of ESs in large-scale infrastructures are also addressed.

On-Site Safety-Valves Testing in Thermal Power Plants

Abstract The paper describes the function and importance of safety devices on pressure equipment, legal regulations for the necessary scope and periods of functional inspections of safety valves in thermal power plants. The mode of operation of the apparatus for in-site testing and adjustment of safety valves on pressure vessels is described, as well as a comparative presentation of the obtained test results compared to the results obtained by the conventional method that uses hydraulic pressure of the medium for valve spring load. The on-site method uses a motor drive to load the valve spring, and uses sensitive displacement, force and sound sensors to generate signals, which are processed in a suitable software application to obtain test results. Unlike the conventional method, the on-site method allows testing of safety valves without their disassembly from the installation site. A comparison of the test results obtained by the modern method with the test results by the conventional method was made on several safety valves. It has been shown that in addition to better precision, which is important for valves with lower operating pressures, the application of the on-site method shortens the test time several times.

Unintentional Force Drifts as Consequences of Indirect Force Control with Spatial Referent Coordinates

We explored the phenomenon of unintentional force drifts in the absence of visual feedback. Based on the idea of direct force control with internal models and on the idea of indirect force control with referent coordinates to the involved muscle groups, contrasting predictions were drawn for changes in the drift magnitude when acting against external spring loads. Fifteen young subjects performed typical accurate force production tasks by pressing with the Index finger at 20% of maximal voluntary contraction (MVC) in isometric conditions and while acting against one of the three external springs with different stiffness. The visual feedback on the force was turned off after 5 s. At the end of each 20-s trial, the subjects relaxed and then tried to reproduce the final force level. The force drifts were significantly smaller in the spring conditions, particularly when acting against more compliant springs. The subjects were unaware of the force drifts and, during force matching, produced forces close to the initial force magnitude, which were not different across the conditions. There was a trend toward larger drifts during performance by the dominant hand. We view these observations as strong arguments in favor of the theory of control with spatial referent coordinates. In particular, force drifts were likely consequences of drifts of referent coordinates to both agonist and antagonist muscles. The lack of drift effects on both perception-to-report and perception-to-act fit the scheme of kinesthetic perception based on the interaction of efferent (referent coordinate) and afferent processes.

Deficits in Performance on a Mechanically Coupled Asymmetrical Bilateral Task in Chronic Stroke Survivors with Mild Unilateral Paresis

Typical upper limb-mediated activities of daily living involve coordination of both arms, often requiring distributed contributions to mechanically coupled tasks, such as stabilizing a loaf of bread with one hand while slicing with the other. We sought to examine whether mild paresis in one arm results in deficits in performance on a bilateral mechanically coupled task. We designed a virtual reality-based task requiring one hand to stabilize against a spring load that varies with displacement of the other arm. We recruited 15 chronic stroke survivors with mild hemiparesis and 7 age-matched neurologically intact adults. We found that stroke survivors produced less linear reaching movements and larger initial direction errors compared to controls (p < 0.05), and that contralesional hand performance was less linear than that of ipsilesional hand. We found a hand × group interaction (p < 0.05) for peak acceleration of the stabilizing hand, such that the dominant right hand of controls stabilized less effectively than the nondominant left hand while stroke survivors showed no differences between the hands. Our results indicate that chronic stroke survivors with mild hemiparesis show significant deficits in reaching aspects of bilateral coordination, but no deficits in stabilizing against a movement-dependent spring load in this task.

Sediment Nutrient Flux Rates in a Shallow, Turbid Lake Are More Dependent on Water Quality Than Lake Depth

The bottom sediments of shallow lakes are an important nutrient sink; however, turbidity may alter the influence of water depth on sediment nutrient uptake by reducing light and associated oxic processes, or altering nutrient availability. This study assessed the relative influence of water quality vs. water depth on sediment nutrient uptake rates in a shallow agricultural lake during spring, when sediment and nutrient loading are highest. Nitrate and soluble reactive phosphorus (SRP) flux rates were measured from sediment cores collected across a depth and spatial gradient, and correlated to water quality. Overlying water depth and distance to shore did not influence rates. Both nitrate and SRP sediment uptake rates increased with greater Secchi depth and higher water temperature, and nitrate and SRP rates increased with lower water total N and total P, respectively. The importance of water temperature on N and P cycling was confirmed in an additional experiment; however, different patterns of nitrate reduction and denitrification suggest that alternative N2 production pathways may be important. These results suggest that water quality and temperature can be key drivers of sediment nutrient flux in a shallow, eutrophic, turbid lake, and water depth manipulation may be less important for maximizing spring runoff nutrient retention than altering water quality entering the lake.

Failure Analysis of Engine Valves and its Performance Evaluation under Various Titanium Based Composite Coatings Using FE Analysis

In an internal combustion engine poppet valve is the crucial component which often opens and closes, thereby regulating gas flow in an engine cylinder. During engine operation, the valve is exposed to high temperature gases (thermal load) along with spring and cam loads (mechanical load). Due to high temperatures and fatigue loads, the valves are subjected to metallurgical changes and leads to failure. In order to resist these extreme conditions of high temperature and mechanical loads, the engine valve should possess special properties such as high surface hardness, a good amount of thermal conductivity, and fatigue strength. In this work, the reasons for the failure of two wheeler engine valve were evaluated and found that failure takes place due to change in the chemical composition mainly due to thermal diffusion at the interfaces. Thermal barrier coatings on the valve surface arrest the temperature load and increase its life. In this work, the performance of various titanium based composite coatings, i.e., TiN, TiC, TiC-Al2O3, TiCN, TiAlN, TiN- Al2O3, DLC, and uncoated valves of two wheeler engine was simulated using Finite Element Analysis. The simulation results indicated that coated valves have less thermal and fatigue loading and have more life than the uncoated valve. The Finite element simulation results of both coated and uncoated valves are presented and analyzed in this paper.

DIMENSIONAREA UNEI ÎNFĂȘURĂRI DE AMORTIZARE CU AJUTORUL MODELĂRII NUMERICE, PENTRU ATENUAREA OSCILAȚIILOR UNUI ACTUATOR CU UNGHI LIMITAT

"This paper presents a computer-aided-design (CAD) of a dumping coil of an actuator producing a limited angular displacement proportional to intake current. Initially, a 2D FEM magnetic field model was developed for studying and optimizing the actuator. Subsequently, the model was coupled with the dumping coil short circuit and mechanical motion equations describing the dumping process. The rotor dumping was analyzed by modelling the rotor movement from the maximum angle position to zero under spring load action, when no current passes through field coil. Several practical aspects regarding numerical model built in COMSOL Multiphysics v5.3 are also presented. Paper purpose: Describing the optimization process of an actuator with limited angle, as well as implementing a magnetic field FEM model coupled with electric circuit and mechanical movement equations. Elements of originality: 1. Developing a complex numerical FEM model coupled with electric circuit and movement equations. 2. Practical interpretation of the results and experience gained in using such damping solutions for limited angle actuators."

An Experimental Study of Contact Temperatures at Sealing Interface against Varying Shaft Surfaces

Increased temperatures at the sealing interface between the seal and shaft can reduce the working life of a seal through elastomer aging, swelling and increased friction. Degradation of the seal due to increased temperatures can cause pre-mature failure, wear and leakage. There is no such thing as a perfect seal; each application has requirements to cater to the needs of each system. For radial oil seals in helicopter gearboxes, the contact temperatures at the sealing interface are a critical parameter to consider. In this manuscript, investigating the factors that influence the temperatures at the contact interface shed light on the operating parameters that cause an increase in contact temperatures. Four varying shaft coatings are tested against three seal spring loads for a range of sliding velocities between 5–25 ms−1 to reproduce conditions of the gearbox. The study reveals an optimum seal spring of 12 oz, with a circumferential load of 3.34 N for lowest temperatures at the interface. Higher springs of 14 oz and lower springs of 8.5 oz both cause increased temperatures at the interface. Additionally, the need for surface coatings on the shaft is re-enforced through experimental evidence demonstrated by comparing temperatures reached between a plain stainless steel shaft and three surface coated shafts. Chrome plating shafts are undesirable due to the ‘polishing’ in effect they experience. The results of this study build on this by showing that chrome plated shafts have higher temperatures at the interface, aggravating any wear or polishing in of that surface. Contact temperatures with Tungsten carbide and Chrome oxide coatings remain within the expected temperature rise. Lastly, microscopically ‘rougher’ surfaces result in increased temperatures in contrast to surface coatings within the specified range of roughness as provided by DIN 3760/61/ISO 6194.

Real-time computing of pavement conditions in cold regions: A large-scale application with road weather information system

Pavement conditions including pavement temperatures, freezing and thawing depths, and the consequent mechanical performance are the key to the performance and longevity of the pavement. For example, thaw-weakening is a major cause of pavement damage in seasonally-frozen areas covering half of the U.S., leading to huge financial costs for taxpayers. In recent years, the damage has been lessened due to improved practices with Spring Load Restriction (SLR) policies. However, prevalent SLR date prediction methods/tools are still primitive from the perspective of information technology. Such methods/tools are obtained and/or implemented manually with small amounts of data, labor-intensive observations, and/or subjective experience. The paper reports what has been learned from a recent project supported by the Michigan Department of Transporation for the development of a web-based pavement condition prediction and SLR decision support tool: a web-based app called MDOTSLR. MDOTSLR enables access to much more data with little latency and automates data acquisition, processing, and decision making. In this paper, the data innovations and new models that support the functions of the tool will be first introduced. Followed will be the major functions (or services) of the app including software engineering details. Compared with traditional tools without web delivery, this web-based tool automates the acquisition and processing of weather data, GIS data, road weather information system data, and field measurements in real time and thus enables more accurate and convenient SLR predictions. The tool can be easily extended or modified for other road agencies for immediate financial savings in road maintenance and less disturbance to local transportation and economy.

Bulk Electric Power System Risks From Coordinated Edge Devices

As smart load adoption grows on the electric power system, potential for losing load diversity increases, possibly in ways that impact system stability. Cloud computing resources are able to coordinate large amounts of behind-the-meter loads and resources. Inadvertent or malicious actions could potentially result in gigawatts of load, distributed across large regions, acting nearly simultaneously. We study the resulting impacts of such a perturbation, which were previously recognized, with improved fidelity and granularity using a physically-based power system and demand model. The ResStock tool was used to calculate residential air conditioning load at more than 3,000 locations across the Western Interconnection, corresponding in time to heavy summer and light spring loading. Under an assumption that one cloud platform managed smart thermostats controlling 10%, 15%, or 20% of residential air-conditioning, calculated load steps could be injected into Positive Sequence Load Flow dynamic simulations. These load-driven effects were coupled with two classes of distributed generation ride-through to evaluate the potential for cascading outages. We found frequency deviations in the spring case far exceed the credible contingency event, leading to widespread distributed generation loss, while voltage depressions during the summer loading lead to widespread distributed generation loss and system separation.

Co-simulations of a semi-passive oscillating foil turbine using a hydraulic system

Turbines based on oscillating foils possess obvious advantages in shallow waters. In this study, a hydraulic system was designed for the semi-passive oscillating foil, which is more suitable for practical applications than the traditional spring-damper system. Co-simulations using software Fluent® and AMESim™ were carried out to examine the performance of the hydraulic system. Based on the results of the spring-damper system, three typical cases were analyzed for each variable to study the effects of kinematic and mechanical parameters. The results demonstrated that the oscillating foil based on the hydraulic system could achieve a regular heaving response. However, a significant feature of the developed system is that the foil stops briefly at the endpoint of the heaving motion. The kinematic parameter had a significant effect on both the hydrodynamic characteristics and the heaving response. Maximum energy is harvested at reduced frequency f ∗ = 0.10, while the maximum efficiency occurred at f ∗ = 0.125. The mechanical parameters, including the spring, cylinder radius, and rotary load, affected the hydrodynamic characteristics slightly. However, the parameters of the cylinder and the rotary load had a significant impact on the heaving response and the power output performance. The results also indicated that the unstable heaving response should be avoided, as it would decrease the energy harvesting efficiency.

Dynamic performance analysis and parameters perturbation study of inerter–spring–damper suspension for heavy vehicle

Inerter, a new type of mass element, can increase the inertia of motion between two endpoints. In order to study the dynamic inertia effect of inerter–spring–damper suspension for heavy vehicle on ride comfort and road friendliness, the inerter–spring–damper suspension is applied and its mechanism is studied. This paper establishes a half vehicle model of inerter–spring–damper suspension for heavy vehicle. The parameters of inerter–spring–damper suspension for heavy vehicle are optimized by multi-objective genetic algorithm and system simulations are carried out. The parametric influence of different spring stiffness, damping coefficient, inertance, and load on suspension performance is also studied. The simulation results demonstrate that the centroid acceleration and pitch angular acceleration are improved by 24.90% and 23.54%, respectively, and the comprehensive road damage coefficient is reduced by 4.05%. The results illustrate that the inerter–spring–damper suspension can decrease the vertical vibration of vehicle suspension especially in low frequency and reduce the road damage. The analyses of suspension parameters perturbation reveal their different effect laws of the different wheels on vehicle ride comfort and road friendliness, which provide a theoretical basis for setting parameters of inerter–spring–damper suspension.

Evaluation of fretting wear occurrence on the surface of nuclear fuel rods of Zr–1Nb–1Sn-0.1Fe alloy: Effects of assembly misalignment and grid spring loading

A mechanical apparatus was developed to investigate the grid-to-rod fretting on nuclear assembly of Zr–1Nb–1Sn-0.1Fe alloy. Test apparatus allowed the performing of fretting tests on fuel rods at a frequency to 30 Hz, which was evaluated as the first natural frequency of a fuel rod. In addition, strain-gauges was employed to evaluate the misalignment effect on the mechanical behavior of the testing material. The surface damage intensity decreased from the central part, to the extremity of wear areas. The variation of wear areas revealed that the misalignment promoted premature wear because the intensification of fretting wear occurred by the appearance of complementary efforts. The confocal method suggested that wear residues under dry conditions remained adhered to the fretting surface.