Orthogonal Load Research Articles

Study of the Micro-Vibration Response and Related Vibration Isolation of Complex Traffic Load-Induced Experimental Buildings

In view of the high-sensitivity vibration effect of precision instrument laboratory buildings under the influence of surrounding traffic loads, field micro-vibration tests under various working conditions were carried out based on actual projects. Combined with numerical simulation, measured data served as input loads to simulate the vibration effect of various traffic loads on the floor of a building structure, and the structural vibration laws under the comprehensive action of various loads were analyzed. The vibration isolation effect of the isolation ditch on the oblique orthogonal load was investigated according to the corresponding safety index. The results show that the main frequency components of the site vibration frequency caused by various traffic loads are approximately 25 Hz and that the root-mean-square speed value is stable below VC-E, which meets the design requirements. Under the comprehensive action of multiple loads, the site structure will produce a vibration amplification effect, which is obvious when all types of loads are distributed symmetrically and the curve distribution is controlled by load factors with large amplitudes. The isolation effect of a small isolation ditch is best when it is located close to the source and the building. The depth of the isolation ditch must be greater than the maximum depth of the source to achieve better results, and the width has little influence. The effect of a small isolation trench on vertical vibration is poor, and the oblique orthogonal triaxial load has a counteracting effect on the vertical component. Thus, additional structural vibration isolation measures are needed. The research results provide a reference for engineering vibration isolation, damping measures, and structural design.

Short arm splints for wrist stabilization: A mechanical material test and cadaveric radiography study.

Documentation of the wrist stabilizing effect and mechanical properties of common splinting materials is warranted to support evidence-based condition-specific recommendations for wrist immobilization. The objectives of this study were to assess the wrist stabilizing properties of volar and dorsal short-arm splints made of four different materials and evaluate the mechanical properties of the splinting materials. Dorsal and volar short arm splints made of plaster of Paris (PoP) (eight layers), Woodcast (2 mm, rigid vented), X-lite (classic, two layers) or a 3D-printed material (polypropylene) were sequentially mounted on 10 cadaveric arm specimens and fixed in a radiolucent fixture. This enabled the evaluation of maximum wrist flexion and extension relative under an orthogonal load of 42 N via radiographic images. In addition, a three-point bending test was performed on ten sheet duplicates of each of the four splinting materials. When applied as a volar splint, PoP had the highest capability to resist wrist flexion and extension. However, when applied as a dorsal splint, Woodcast exhibited a lower wrist flexion and a similar wrist extension. The 3D-printed splints-both volar and dorsal-showed the highest mean wrist flexion and extension. The mechanical properties of the Woodcast, X-lite and 3D-printed splinting materials were very similar. PoP exhibited distinct properties with a stiffness of 146 (95% confidence interval [CI]: 120-173) N/mm and a deflection at F max of 0.6 (95% CI: 0.5-0.7) mm compared to ≤7.7 (95% CI: 7.4-7.9) N/mm and ≥20 (95% CI: 18-22) mm for the other materials. PoP displayed better wrist stabilizing properties and material stiffness than Woodcast, X-lite and 3D-printed polypropylene. When considering wrist stabilizing properties, PoP may still prove to be the preferred choice for wrist immobilization. Not applicable.

Orthogonal impact load in 6061-T651 and 7075-T651 aluminum alloy plates

Orthogonal impact load in 6061-T651 and 7075-T651 aluminum alloys was evaluated. Clamped square plates with the dimensions of 300 × 300 × 6.35 mm were experimentally impacted at 200, 400 and 600 J with different velocities by means of a drop tower-device. Impacted force-time and -displacement curves were obtained to evaluate the absorbed energy. Also, the impact damage was evaluated in terms of the transverse displacement and overall crack length induced to the plate. Further, explicit finite element and analytical approaches were used to compare against the experimental results. Considering the absorbed energy as a direct function of the induced damage, it was observed that the 7075-T651 alloy had a better performance than 6061-T651 for the 200 J impact test. Even though both alloys had a similar response for the 400 J impact test, it was not the case at 600 J where the absorbed impact energy for the 6061-T651 alloy was higher than for the 7075-T651. The induced damage (crack length) tends to increase with the strain rate for a given impact energy level.

Design of a Test Setup for Measuring all Load Components Acting on Tillage and Planting Implements

This project entailed the design, manufacture, and testing of a test setup with the ability to measure all load components acting on tillage and planting implements. In future, data obtained with the test setup can be used to perform accurate design calculations, as input into finite element simulations, and to perform accurate fatigue analysis. The design of implements can therefore be improved to better withstand the loads under various operational conditions and to minimise fatigue cracking. Laboratory controlled testing, and subsequent field tests, proved that the designed test setup was able to isolate and accurately measure each of the three orthogonal load components, as well as the main moment. It was further shown that the remaining two moments could be accurately calculated using the measured load components and fixed geometric lengths. The conclusion was drawn, based on field tests, that an increase in speed with the tine ripper had no significant effect on the mean load. Further, an increase in the working depth, resulted in an increase in the load, especially in the draught and vertical directions. Finally, it was shown that a decrease in turning radius (a tighter turn), resulted in an increase in the lateral force component.

Mitigation of Load Mismatch Effects Using an Orthogonal Load Modulated Balanced Amplifier

This article presents an orthogonal load-modulated balanced amplifier designed to mitigate the effects of the load mismatch on the power-added efficiency and output power of the amplifier. This is achieved by electronically adjusting the ratio between the two input signals of the power amplifier (PA) (in phase and amplitude) and the reactive termination at the output nominally isolated port. The mode of operation of the PA is described using a theoretical analysis that highlights the role of the different tuning parameters and is confirmed by simulations using a simplified transistor model. The design and characterization under load mismatch of a prototype PA, working in the 1.6–3.2 GHz band are described and the experimental results compared to those of an analogous balanced PA, where it is shown that the orthogonal balanced amplifier is able to increase substantially the mismatch region on which a given target performance is achieved.

Development of a True-Biaxial Split Hopkinson Pressure Bar Device and Its Application.

Although highly desirable, the experimental technology of the dynamic mechanical properties of materials under multiaxial impact loading is rarely explored. In this study, a true-biaxial split Hopkinson pressure bar device is developed to achieve the biaxial synchronous impact loading of a specimen. A symmetrical wedge-shaped, dual-wave bar is designed to decompose a single stress wave into two independent and symmetric stress waves that eventually form an orthogonal system and load the specimen synchronously. Furthermore, a combination of ground gaskets and lubricant is employed to eliminate the shear stress wave and separate the coupling of the shear and axial stress waves propagating in bars. Some confirmatory and applied tests are carried out, and the results show not only the feasibility of this modified device but also the dynamic mechanical characteristics of specimens under biaxial impact loading. This novel technique is readily implementable and also has good application potential in material mechanics testing.

Femtosecond laser–assisted capsulotomy with capsular marks for toric IOL alignment: Comparison of tensile strength with standard femtosecond laser capsulotomy

To compare the capsulotomy rim strength with capsular marks (CMs) to the rim strength without CMs in porcine eyes, and to demonstrate the practicality of CMs for intraoperative toric intraocular lens (IOL) alignment. LENSAR facility, Orlando, Florida, USA. Laboratory study. The biomechanical strength of the capsulotomy with CMs was tested under two different load orientations (orthogonal to or in-line with CMs). Thirty-six porcine eyes were randomly assigned to three treatment cohorts: (1) standard capsulotomy with no CMs, (2) capsulotomy with CMs for in-line tensile testing and (3) capsulotomy with CMs for orthogonal tensile testing. Study parameters were capsulotomy break force and maximum extensibility. The ease of using CMs for toric IOL alignment was also evaluated. There was no significant difference between the mean break force for standard capsulotomy (180.57mN±22 [SD]), capsulotomy with CMs with orthogonal load (178.04±20mN, P=1.000), and with in-line load (181.05±15mN, P=1.000). Likewise, the mean extensibility at the break point for standard capsulotomy (6.47±0.33mm) was equivalent to the mean extensibility with CMs with orthogonal load (6.49±0.45mm, P=1.000) and with in-line load (6.3±0.47mm, P=.960). In the implanted eyes, toric IOLs were found to be easily aligned with the CMs. The femtosecond laser capsulotomies with CMs were equivalent in tensile strength and extensibility to standard femtosecond laser capsulotomies and showed high potential for effective alignment of toric IOLs.

A Practical Approach for the Estimation of Strength and Resilient Properties of Cementitious Materials

Cementitious stabilization of granular soils has been proven to be a cost-saving option for the use of materials with marginal quality in the construction and rehabilitation of pavement structures. The orthogonal load distribution capacity of the Cement-Stabilized Materials (CSM) is typically characterized by Unconfined Compressive Strength (UCS), Indirect Tensile Strength (IDT), and Resilient Modulus (Mr) tests in the laboratory. The aforementioned parameters and properties are integral components of the analysis and design of pavements with stabilized layers. Time and budget constraints make it impractical for many state agencies to complete the full laboratory characterization protocols to determine all the design input parameters. Therefore, in many cases, the design engineers opt out of laboratory testing and primarily rely on past experience and engineering judgments to assign design input parameters. Such an approach compromises the reliability of the pavement life predictions, and can potentially incur unforeseen costs to the traveling public. This study was designed to bridge this gap by developing a series of statistically robust relationships between the laboratory achived data to provide an estimate of the design input parameters. To accomplish this objective, 570 stabilized cylindrical specimens were prepared and subjected to UCS, IDT, and submaximal modulus tests at three strength ratio levels. Subsequently, the relationships between the IDT, UCS, and resilient modulus at small-strain and intermediate strain levels were developed in this study. Such relationships can serve as a valuable means for the estimation of the tensile and compressive strength of the CSM for pavement design.

Neural network based model for estimation of the level of anisotropy of unbound aggregate systems

Abstract Directional dependency of the materials properties in granular soils is an integral component of the analysis and design of pavement foundations. Laboratory determination of such anisotropic properties is often overlooked by design engineers due to the lack of available protocols, equipment, time constraints, and budgetary issues. This research strives to bridge this gap by investigating an alternative approach to provide a practical and reliable framework to estimate the level of anisotropy of unbound granular materials. To achieve this objective, an experiment design was developed to establish a comprehensive aggregate feature database. Nonlinear and cross anisotropic material properties were determined using Variable Dynamic Confining Pressure (VDCP) stress path tests in the laboratory. Particle geometry was characterized using the Aggregate Imaging System (AIMS). Scale parameters and shape parameters of the form, angularity and textural properties of the particles were incorporated in the aggregate database to account for the shape-induced anisotropy of particulate soils. Moisture state and density parameters were also incorporated in the database for further post processing. Several neural network models with different architectures were developed, and the performances of the models were assessed based on an unseen set of data. The impact of the neural network topologies on the performance of the models were also investigated in this research effort. The results indicate that increasing the number of hidden layers has negligible impact on the performance of the models. Additionally, a series of sensitivity analyses were performed to investigate the level of contribution of aggregate features on the anisotropic behavior of unbound granular materials. The results of the sensitivity analysis underscores the influence of aggregate angularity, fines content, surface macro-texture, as well as the parameters of the stress path tests, on the orthogonal load distribution capacity of aggregate layers.

A Markov model to estimate mortality due to HIV/AIDS using CD4 cell counts based states and viral load: a principal component analysis approach

Background: Improvement of health in HIV/AIDS patients on Highly Active Antiretroviral Therapy (HAART) is characterised by an increase in CD4 cell counts and a decrease in viral load to undetectable levels. In modelling HIV/AIDS progression in patients, researchers mostly deal with either viral load only or CD4 cell counts only as they expect these two variables to be collinear. Methods: In this study, a cohort of 320 HIV/AIDS patients under HAART follow-up from a wellness clinic in Bela-Bela, South Africa is used. A time homogeneous Markov model is developed to explain and predict probability of death from HIV/AIDS. Principal component variables are created by fitting a regression model of viral load on CD4 cell counts. Results: Inclusion of a viral load principal component improves the efficiency of the model. The new viral load covariate helps to explain the component of mortality/transition, which could not be explained by the CD4 cell counts alone. CD4 cell counts are categorised to define the states for the Markov model. Results show that the expected percentage prevalence gives almost a perfect fit of the observed data. Conclusion: The orthogonal viral load covariate along with CD4 baseline, gender, non-adherence to treatment and age in years (y) variables play a significant role in modelling HIV/AIDS progression based on both CD4 cell counts and viral load monitoring.

Solution of the ratchet-shakedown Bree problem with an extra orthogonal primary load

The complete shakedown and ratcheting solution is derived analytically for a flat plate subject to unequal biaxial primary membrane stresses and a cyclic secondary bending stress in one in-plane direction (x). The Tresca yield condition and elastic-perfectly plastic behaviour are assumed. It is shown that the results can be expressed in the form of a “universal” ratchet diagram applicable for all magnitudes of orthogonal load. For sufficiently large cyclic bending stresses, tensile ratcheting can occur in the x direction if the x direction primary membrane stress exceeds half that in the orthogonal direction. Conversely, for sufficiently large cyclic bending stresses ratcheting in the x direction will be compressive if the x direction primary membrane stress is less than half that in the orthogonal direction. When the x direction primary membrane stress is exactly half that in the orthogonal direction ratcheting cannot occur however large the cyclic secondary bending stress.

Hearing loss impacts neural alpha oscillations under adverse listening conditions.

Degradations in external, acoustic stimulation have long been suspected to increase the load on working memory (WM). One neural signature of WM load is enhanced power of alpha oscillations (6–12 Hz). However, it is unknown to what extent common internal, auditory degradation, that is, hearing impairment, affects the neural mechanisms of WM when audibility has been ensured via amplification. Using an adapted auditory Sternberg paradigm, we varied the orthogonal factors memory load and background noise level, while the electroencephalogram was recorded. In each trial, participants were presented with 2, 4, or 6 spoken digits embedded in one of three different levels of background noise. After a stimulus-free delay interval, participants indicated whether a probe digit had appeared in the sequence of digits. Participants were healthy older adults (62–86 years), with normal to moderately impaired hearing. Importantly, the background noise levels were individually adjusted and participants were wearing hearing aids to equalize audibility across participants. Irrespective of hearing loss (HL), behavioral performance improved with lower memory load and also with lower levels of background noise. Interestingly, the alpha power in the stimulus-free delay interval was dependent on the interplay between task demands (memory load and noise level) and HL; while alpha power increased with HL during low and intermediate levels of memory load and background noise, it dropped for participants with the relatively most severe HL under the highest memory load and background noise level. These findings suggest that adaptive neural mechanisms for coping with adverse listening conditions break down for higher degrees of HL, even when adequate hearing aid amplification is in place.

Analysis of elastic–plastic behavior and plastic front evaluation in spot welded joints

A new analytical procedure for the evaluation of the elastic–plastic stiffness behaviour and of the plastic front in spot welded joints is presented. The spot weld joint is modelled with a new theoretical model, a circular finite plate having variable thickness and with central rigid nugget. The closed form solution of the new reference theoretical model, while plasticity effect is considered, leads to the definition of a joint element useful to FE models of multi-spot structures. This solution allows to evaluate the variation of the stiffness of the spot nugget, when the finite plate is subjected to orthogonal load, while plasticity and moderate deflections are present. Furthermore, using the new analytical procedure it is possible to determine a good accuracy in the estimation of the evolution of plastic front, with the goal of studying the local behaviour of the junction, in terms of evaluation of plasticity radius and in terms of global stiffness of the joint. The procedure can be used as the basis to develop a spot weld element in FE analysis of multi spot welded structures, able to precisely evaluate both local and overall stiffness of spot joints, even when plasticity is accounted. The theoretical procedure leads to results that match those obtained analysing the actual spot weld region by reference FE models.

A new analytical model for the elastic–plastic behaviour of spot welded joints subjected to orthogonal load

An analytical procedure for the evaluation of the elastic–plastic stiffness behaviour of spot welded joints is presented. The procedure is based on a new model of spot weld region: a circular plate having variable thickness with a central rigid nugget, which is resolved using an original analytical method. The closed-form solution allows to describe the displacement of a rigid nugget when an axial orthogonal load is applied on the plate while plasticity and large deflections are present. The goal is to reach a reliable spot weld region model which can be used as the basis to develop a spot weld element in FE analysis even when plasticity and large deflections are in effect. The procedure is as completely original as no other can be found in the technical literature, and it has been applied to some examples of plates usually employed for spot weld analysis. The analytical results obtained by using the new general relations precisely match those obtained modelling spot weld area by FEA.

Ramp Position Influences Lower Extremity Biomechanics while Exercising on the Elliptical Trainer

The elliptical trainer, developed to simulate running while minimizing joint loads, elicits a unique lower extremity biomechanical response. PURPOSE: To examine the angular kinematics, peak net joint moments, and peak joint powers at the hip, knee and ankle joints while exercising at three different ramp settings on the elliptical trainer exercise machine (Precor EFX). METHODS: Twenty-six healthy individuals with no history of lower extremity injury and with previous experience exercising on an elliptical trainer volunteered for this study (age: 22.19 ± .85 y, 169.9 ± 9.8 cm, 74.0 ± 19.3kg). Motion was captured with two cameras as subjects performed exercise (120 steps/min) at three ramp conditions (13, 25, and 40 degree incline). The pedal resistance was kept constant at the lowest setting. The pedals of the elliptical were fitted with three orthogonal load cells. Video (60Hz) and force data (600Hz) were synchronized and used to perform a 2D inverse dynamics analysis. RESULTS: As the ramp inclination increased, subjects demonstrated greater amounts of ankle dorsiflexion, knee flexion, hip flexion and lesser degrees of plantar flexion and hip extension (p<.000). Mean peak moments at the ankle joint were not significantly different across the three ramp settings. Peak knee extensor and hip flexor moments increased (knee=.05 to .28 Nm/kg; hip=.20 to .56 Nm/kg) and flexor moments at the knee and extensor moments at the hip decreased (knee:2.27 to .49 Nm/kg; hip:2.08 to .27 Nm/kg) as the ramp settings increased (p<.000). While both peak positive and negative ankle joint powers reached statistical significance across the three ramp settings, the effect size of the ramp on power generation was small. As the ramp increased, peak positive power at both the knee and hip significantly decreased (knee:2.86 to .41 watts/kg; hip:4.25 to 0.98 watts/kg) and negative power decreased at the knee joint (1.13. to 0.44 watts/kg) (p<.000). CONCLUSIONS: Distinct from running, where the ankle joint contributes significantly to the overall power for forward propulsion, the hip and knee joints were observed as the primary sources of power during exercise on the elliptical trainer. This report on mechanics of the elliptical stride makes a valuable contribution to the fitness and rehabilitative arenas. Pedal load cells provided by Precor, Inc.

Experimental measurement and finite element analysis of the deformation of a high-pressure sluice gate

The deformation of a high-pressure sluice gate under an orthogonal water pressure load of 0.539 MPa (i.e., 55 m water height), acting upon the upstream side of a gate leaf, was studied numerically and experimentally. The sluice gate was installed at the end of a water-release tunnel in the Nan-Hwa Reservoir, Nan-Hwa, Taiwan, R.O.C. The numerical results obtained using the ANSYS 5.5.2 finite element program agreed reasonably well with the experimental data. The deformation of this high-pressure sluice gate under water pressure loads of 0.736 MPa (i.e., 75 m water height) and 0.931 MPa (i.e., 95 m water height) was predicted by ANSYS 5.5.2. The research reported here may provide a method for establishing a safety monitoring system for any high-pressure gate and provide engineers with useful information to evaluate the possibility of increasing the capacity of an existing reservoir.Key words: sluice gate leaf, finite element method (FEM), strain gauge, water pressure.

Experimental measurement and finite element analysis of the deformation of a high-pressure sluice gate

The deformation of a high-pressure sluice gate under an orthogonal water pressure load of 0.539 MPa (i.e., 55 m water height), acting upon the upstream side of a gate leaf, was studied numerically and experimentally. The sluice gate was installed at the end of a water-release tunnel in the Nan-Hwa Reservoir, Nan-Hwa, Taiwan, R.O.C. The numerical results obtained using the ANSYS 5.5.2 finite element program agreed reasonably well with the experimental data. The deformation of this high-pressure sluice gate under water pressure loads of 0.736 MPa (i.e., 75 m water height) and 0.931 MPa (i.e., 95 m water height) was predicted by ANSYS 5.5.2. The research reported here may provide a method for establishing a safety monitoring system for any high-pressure gate and provide engineers with useful information to evaluate the possibility of increasing the capacity of an existing reservoir.Key words: sluice gate leaf, finite element method (FEM), strain gauge, water pressure.

On the evaluation of statical-kinematic stiffness matrix for underconstrained structural systems

Because of singularity of the elastic stiffness matrix, analysis of underconstrained systems requires the comprehensive stiffness matrix, comprising both kinds of first-order structural stiffness—elastic and statical-kinematic. The latter accounts for the role of the member forces, induced in the system by the equilibrium part of the applied load, as the source of the system resistance to the perturbation part of the same load. Evaluation of the sought member forces using orthogonal load resolution into equilibrium and perturbation components is awkward and computationally expensive. A special modification of the singular elastic stiffness matrix simplifies the procedure and makes it amenable to the conventional tools of structural analysis. The efficiency and accuracy of the procedure is illustrated by a detailed numerical example.

Modeling and Experiments for Deformation Under Load in Ni-Mn-Ga Ferromagnetic Shape Memory Alloy

AbstractA simple model is proposed to relate strain, stress, field and anisotropy in a ferromagnetic shape memory alloy (FSMA) and experiments were performed to test the validity of the model. The model is presented as applied to the case of orthogonal field and load in a NiMn-Ga FSMA. The model predicts threshold-type strain behavior as field changes at constant load or as load changes with constant field. The measured behavior of strain with stress at constant field approximated the predictions of the model. Field-induced strain remained constant at about 6% with the addition of stress until such a stress was applied that the mechanical energy overcame the anisotropy of the sample and the strain was reduced to 0. The model's predictions of critical strain behavior with applied field at constant stress were qualitatively accurate at some stress levels, but under-predicted the field necessary to produce strain.

Orthogonal load resolution and statical-kinematic stiffness matrix

The structural behavior of underconstrained systems is explored with an emphasis on statically indeterminate ones. The roles of the elastic stiffness and the statical-kinematic stiffness (induced by prestress or an equilibrium load) are investigated and compared. The linearized response of a prestressed underconstrained system is shown to go beyond the simple notion of the first-order stiffness induced by prestress and independent of the member stiffnesses. Some interesting features of structural behavior under a general load and stability under an equilibrium load are revealed and illustrated with an example of a quasi-variant pin-bar system. Finally, a comprehensive stiffness matrix with coefficients representing various sources of first-order stiffness is introduced, to replace, when necessary, the conventional elastic stiffness matrix. The comprehensive matrix is valid for structural systems of any type and is always invertible.