Effect Of Loading Type Research Articles

Acute cardiac autonomic and hemodynamic responses to resistive breathing: Effect of loading type and intensity.

This study aimed to assess the acute impact of distinct loading breathing types and intensities on cardiac autonomic function and hemodynamic responses in healthy young adults. A randomized, crossover trial involved 28 participants who underwent inspiratory resistive breathing, expiratory resistive breathing (ERB) and combined resistive breathing, each at 30% and 60% of maximal respiratory pressures. Data on heart rate variability (HRV) and hemodynamic parameters were collected during each trial. The study revealed significant main and interaction effects for both the performed task and the intensity across all measured variables (all p < 0.001). ERB at 60% load demonstrated significantly higher HRV values in the standard deviation of normal-to-normal RR intervals, the square root of the mean squared difference of successive normal-to-normal RR intervals and high-frequency power, as well as significantly lower values in heart rate, stroke volume, stroke volume index, cardiac output, cardiac index, end-diastolic volume and end-diastolic volume index, compared to other loaded protocols (all p < 0.001). These findings highlight the acute effect of type-specific and load-dependent resistive breathing on cardiac autonomic and hemodynamic functions, where ERB at 60% intensity showed the most significant cardiovagal modulation while causing the least hemodynamic alterations.

Effect of loading type in concrete deep beam with strut reinforcement

Abstract This study examined eight specimens of two groups of deep beam (DB) with the same dimensions and reinforcement quantity, where the first group had four specimens tested under two-point loads and the second group had four specimens tested under one-point load (Ammash HK, AL-Mousawi MM. Experimental investigation of deep beam reinforced with different types of reinforcement. Eng Technol Appl Sci Res. 2021;11(2):7585–90.) where both groups have the same reinforcement and the dimensions and difference between the groups was only the type of load. Digital image correlation technology software was used to verify the results. Upon examining the results, each group had one reference specimen with conventional reinforcement and the other three specimens were with strut reinforcement. It was observed that the strut reinforcement technique was more effective than the conventional reinforcement. This study also found that the load capacity was decreased at two-point loads from one-point load. The results from the present study were compared to those from a prior study (Ammash HK, AL-Mousawi MM. Experimental investigation of deep beam reinforced with different types of reinforcement. Eng Technol Appl Sci Res. 2021;11(2):7585–90.) that only employed a one-point load. The concrete type, its dimensions, and its method of reinforcing were the same as Ammash and AL-Mousawi’s (Experimental investigation of deep beam reinforced with different types of reinforcement. Eng Technol Appl Sci Res. 2021;11(2):7585–90.) study. The maximum load capacity for SC (Reference DB specimen) and S10 (the deep strut beam employed a specimen with 100% reinforcement from the reinforced web) specimens for one-point load were more tolerant to stress than the two-point loads, with 15% for SC and 27% for S10 as both specimens had comparable amounts of reinforcement. When a force is applied that is less than the sum of the two load points, cracks occur in the shear and flexural zones at one load point. We have found that the use of two-point loads leads to a decrease in the maximum load capacity of specimens when compared with a one-point load. It was also noted that cracks are formed in the shear and flexural zones at one-point load when a load less than the two-point load is applied. It was also observed that when two-point loads were applied to a specimen, the displacement was less than half of what it was when tested under a one-point load, and the strain in specimens examined under two-point load was lower than in specimens examined under one point load.

Experimental and numerical investigations on flexural–torsional buckling of roller bent steel I-section arches

The flexural–torsional buckling (FTB) behavior of a freestanding circular steel I-section arch subjected to static load is systematically investigated under residual stresses, geometric imperfections, and load type effects through experimental and numerical simulation analyses. In particular, a loading rig that allows lateral deformation and twist is designed for the experiment, and a 3D scanner is used to measure the geometric imperfections and the final shape to reflect the out-of-plane buckling response better. The buckling behavior is sensitive to the loading form and the imperfection. Thus, the specific structure of the loading system, complex geometric imperfections based on measurement data, and residual stresses based on roller bending process analysis are included in the finite element model (FEM). The accuracy of the FEM is confirmed by comparing the results with the experimental findings, and a comprehensive parameter study is conducted. Results show that the transition of buckling mode will be caused by out-of-plane geometric imperfections. These imperfections significantly affect the critical load of FTB when the amplitude is greater than S/500, while the residual stress of roller bent arch has a small influence on the FTB behavior. The parametric study also finds that the arch has a large critical load of FTB under nondirectional load compared with directional load. The out-of-plane slenderness ratio, the rise-to-span ratio, and the local plastic zone also significantly affect the FTB behavior.

切削摩擦加工材の疲労特性に及ぼす負荷形式の影響

Aiming for a result to improve fatigue strength, “cutting and rubbing process” which is a kind of surface treatment was used for forming a round-bar smooth-specimen, showing drastically enhanced rotating-bending fatigue strength. On the other hand, actual machine components and structures invariably contain geometrical irregularities, such as fillets, keyways, screw threads, and holes. Fatigue cracks initiated from such stress raisers, indicating that the validity of the cutting and rubbing process on fatigue strength of specimen with a stress raiser should be examined. In this study, fatigue tests of smooth and notched specimens finished by the cutting and rubbing process were conducted under some loading types including rotating-bending, tension-compression and torsion loading. Results showed that fatigue strength of notched specimens was significantly enhanced compared to that of smooth specimens under rotating-bending and tension-compression loads. In other words, the cutting and rubbing processing was more effective in stress raisers than the smooth surface. The physical background on the effect of loading type on the fatigue strength of the cutting and rubbing processed specimen was discussed based on the fracture origin, microstructure in the surface layer, stress gradient caused by both loading type and notch.

Experimental and numerical study on a novel bamboo joint for furniture considering effect of loading type on mechanical parameters used in finite element method

The effect of loading type (tension, compression and bolt-bearing) on mechanical properties (elastic modulus, Poisson’s ratio and ultimate strength) of Moso bamboo (Phyllostachys heterocycla var. pubescens) in longitudinal direction was evaluated in this study. In addition, experimental and numerical tests were conducted to evaluate withdrawal force capacity and bending moment resistances of a novel demountable bamboo-bolt joint considering effect of loading type on mechanical parameters used in finite element method. The results showed that 1) loading type had significant effect on mechanical properties of Moso bamboo, especially, for ultimate strength; 2) the values of mechanical properties evaluated in this study measured in tension were all much higher than those measured in bolt-bearing state and followed by compression accordingly; 3) in tension, the tensile elastic modulus and Poisson’s ratio measured at outer surface were bigger than those at inner surface, respectively; 4) finite element method got more accurate results using the mechanical parameters measured in compression than those in tension and bolt-bearing states; 5) the bamboo-bolt joint proposed in this study can be used in lightweight bamboo structures through improving the embedding strength of beech wood in bamboo culm. In conclusion, one should consider the loading type used to obtain the mechanical parameters inputted in finite element method. In addition, further studies will focus on effect of size and geometry of samples used to determine mechanical properties used in finite element method, and the method of improving embedding strength of beech wood in bamboo culm to increase withdrawal force capacity and bending moment resistances of the demountable bamboo-bolt joint proposed in this study

Methods to test and generate the wear load spectrum of journal bearing in concrete pump

Load spectrum is the basis of wear analysis and life prediction in journal bearing. This paper proposed a method to generate the wear load spectrum from the measured loads that avoiding the errors introduced by the assumptions of traditional constant load. An axle pin load sensor that can recognize the load value and its orientation is developed to test the original wear loads of journal bearing in a concrete pump under working conditions. The interactive influence of perpendicular components in the measured loads is involved by introducing two effect coefficients. Subsequently, the amplitude distribution of the wear load and its lasting time are extracted from the measured complex load-time history using the rain-flow counting method and Weibull distribution. The wear load spectrum is generated by dividing the continuous load into eight load steps. The validity of the approach is supported by finite element analysis on the wear simulation of journal bearing using the generated load spectrum and the measured load. In addition, the effects of load types and load sequence on the wear are discussed based on the proposed method and the FE model. This study provides guidelines to efficiently generate the wear load spectrum for journal bearing, and enhances its reliability of wear prediction in the experimental tests and theoretical analysis.

Effects of load types and critical molar ratios on strength properties and geopolymerization mechanism

Abstract In this study, the effect of SiO2/Al2O3 (S/A), Na2O/Al2O3 (N/A) and H2O/Na2O (H/N) molar ratios on bending and compressive strength of geopolymer were investigated. The geopolymerization mechanism was also analyzed from microstructure difference by FTIR. The experimental results showed that compressive strength and bending strength of geopolymer has an opposite reaction under different critical molar ratios. The increase of S/A molar ratio and the decrease of N/A and H/N molar ratios have resulted in an increase of the compressive strength. However, it caused a noticeable decrease in bending strength. The microstructure of geopolymer indicated that the degree of polymerization and cohesion of geopolymer have systematical depending on these critical molar ratios, making the mechanical properties of geopolymer susceptible to different types of loads. This paper reveals the relationship between the microstructure of geopolymer and different mechanical properties and helps to selectively prepare corresponding geopolymer for different loading patterns.

Load Ratios Carried by Each Constituent for Some Problems of a Particulate Composite Modeled as a Mixture of Two Linear Elastic Solids

ABSTRACTThe basic constitutive equations of theory of mixtures obtained for a mixture of two linear elastic solids can be used as an alternative way to describe the mechanical behavior of binary composite materials. Determining the load ratios carried by each constituent solid of a binary composite is one of challenges of this theory. In this study, the results of directly calculating the ratios of external load carried by each constituent solid for the case of perfectly bonded interface between binary mixture constituents are discussed. Thus, the effects of loading type and volume fraction of the constituent solids to the load ratios carried by each constituent solid are investigated by using three different loading cases and three different volume fractions. Finally, displacement, stress and diffusive force results of two constituent solids using the calculated load ratios are given.

The Effect of Loading Type on the Amount of Effect of Loading on the Surface Settlement During Forepoling Tunnel Excavation in Different Geotechnical Conditions

Abstract Among the important phenomena caused by tunnel excavations, the settlements on the ground surface can be mentioned, which are particularly important for shallow tunnels excavated in urban areas, and especially when passing under residential areas of cities. Numerous methods such as mathematical (numerical and analytical) ones can be used to predict surface settlement. This study was conducted aimed at using modern techniques such as artificial neural networks to analyze the parameters affecting the occurrence of surface settlement during forepoling tunnel excavation. Tabriz Subway project is a good opportunity to examine the effect of forepoling tunnel excavation the surface settlement in a granular soil with average groundwater level offers. None of the performance parameters (such as the features of the forepoling protective umbrella) and the environmental features (such as the geological effects and tunnel geology) establish a unique relationship with the surface settlement, but several factors together do so. In this study, the forpolling tunnel was modeled using Plaxis software and analyzed in various geotechnical conditions (drained, partially saturated and saturated) under static and dynamic loading. Finally, the values of the surface settlements were examined.

The Effect of Loading during Martensitic Transformation of a Maraging Steel after Prior Austenite Grain Size Refinement by Thermal Cycling

Abstract This work demonstrates the efficiency of microstructural tuning by external loading during the martensitic phase transformation of a 12Cr-9Ni-2Mo-0.7Al-0.35Ti maraging steel. Additional prior austenite grain size refinement is achieved by thermal cycling yielding industrially relevant grain sizes, for which not the full set of all 24 characteristic Kurdjumov-Sachs orientation relation variants of martensite is obtained within each grain. For the last thermal cycle three different cases are investigated: i) one specimen is annealed at a higher temperature before the last cooling, ii) one specimen is loaded with a tensile stress of 120 MPa and iii) one specimen with an equivalent 120 MPa Mises stress in torsion during the transformation. This study is one of the first combining the effects of a small grain size, a high dislocation density and external loadings. Orientation imaging microscopy data is presented, revealing the effect of loading type during transformation on the final texture and interface/boundary character.

Nonlinear dynamic response of sandwich beams with functionally graded negative Poisson’s ratio honeycomb core

This paper investigates the nonlinear dynamic response of sandwich beams with functionally graded (FG) negative Poisson’s ratio (NPR) honeycomb core in thermal environments. The novel constructions of sandwich beams with four FG configurations of re-entrant honeycomb cores through the beam thickness direction are proposed for the first time. The temperature-dependent material properties of both face sheets and core of the sandwich beam are considered. 3D full scale finite element analyses are conducted to investigate the nonlinear dynamic response, and the variation of effective Poisson’s ratio (EPR) of the sandwich beam in the large deflection region. The numerical simulations are carried out for the sandwich beam with FG-NPR honeycomb core, from which results for the same sandwich beam with uniform distributed NPR honeycomb core are obtained as a comparator. Present results indicate that, when subjected to transverse dynamic pressure, the induced dynamic bending moment of the sandwich beam with core of positive EPR is much bigger than that of the sandwich beam with NPR core, and the thickness of which will extraordinarily increase. The effects of loading types, functionally graded configurations, temperature changes, boundary conditions, and length-to-thickness ratios on the deflection-time curves and EPR-deflection curves of sandwich beams are discussed in detail.

Size effect on shear failure at core region of reinforced concrete connections: Experimental study

Fourteen geometrically-similar interior reinforced concrete (RC) beam-to-column connections whose maximum structural sizes were 700 mm ×700 mm were designed. The seismic performances of these RC beam-to-column connections subjected to monotonic and low-cycle loading were tested. The effects of loading type, structural size and stirrup ratio on the shear failure behavior at the core region of the connections were studied. Moreover, the size effect on the nominal shear strength of the core region of RC connections was examined, and the sources of size effect were also discussed. The test results and analyses indicate that: (1) all the RC beam-to-column connections under monotonic and low-cycle loading failed by shear; (2) due to the existence of low-cycle fatigue damage characteristics, the nominal shear strength of the joints under cyclic loading is lower, and the deformation capacity is weaker; (3) the nominal shear strength decreases with the increase of the structural size of RC connections, and size effect phenomenon is obvious; (4) with the increase of stirrups ratio, the shear bearing capacity and deformation capacity of RC connections increases, at the same time the size effect in shear strength is weakened. In this experiment, the dominant effect of concrete failure and the low-cycle fatigue characteristic of loading are the main reasons for the size effect of shear failure.

Effect of Loading Type on Fatigue Lifetime of Sintered-Silver Die Attach

The effect of loading type on the fatigue lifetime of sintered-silver die attach was investigated. The fatigue lifetime was measured by fatigue testing with micro-load testing equipment. The fatigue tests were conducted under displacement control with (reversed loading (stress ratio ${R}= -1$ ), pulsating-tensile loading ( ${R} =0$ ), and pulsating-compression loading ( ${R} = -\infty $ )) at room temperature. The strain of the fatigue test was estimated by strain-displacement relation obtained from previous tensile test using the strain gauge. Sintered-silver specimens were made from prebaked microscale silver paste and pressurized at 10 MPa for 10 minutes in air atmosphere at 573 K. The fatigue lifetime of reversed-loading case was 1000 cycles, that of pulsating-tensile-loading case was 4000 cycles, and the pulsating-compression-loading case remained unbroken. This suggests that compression load does not contribute to the destruction of the sintered silver. These measured fatigue lifetimes were aligned in a row when these are organized by maximum stress (tensile stress range). For fatigue lifetime evaluation of sintered silver, evaluation focusing on tensile stress seems to be important.

Experimental investigation of cold-formed steel shear walls with self-piercing riveted connections

With the purpose of introducing a new connection to cold-formed steel structure, this paper presents an experimental investigation of cold-formed steel (CFS) shear walls with self-piercing riveted (SPR) connections under monotonic and reversed cyclic loading. The effects of loading type (Monotonic and Cyclic), rivet spacing at the steel sheet edges, rivet number at CFS framing joints, axial compression ratio, and the steel sheathing types (steel sheet sheathing and corrugated steel sheathing) on mechanical behavior and failure modes of CFS shear walls were investigated. The shear strength, initial stiffness, and ductility of CFS shear walls with SPR connections were evaluated by comparing to the results of CFS shear walls with self-drilling screw connections under the same condition. Lateral loading, safety factor, and resistance factor under the wind and seismic loads were determined in accordance with test results of CFS shear wall with SPR connections. The research indicated that the rivet spacing at the sheet edges was a key factor affecting failure modes and mechanical properties of CFS shear walls. The relationship of shear strength and ultimate deformation decreased linearly with the increase of the rivet spacing. Compared to CFS shear walls with self-drilling screw, CFS shear walls with SPR have significantly improved shear strength and stiffness. Safety factor and resistance factor recommended by AISI Seismic Design Standard are conservative for the wind and seismic design of CFS shear wall using SPR connections.

Structural behavior of non-prismatic mono-symmetric beam

This paper attempts to understand the structural behavior of non prismatic channel beams subjected to bending through finite element(FE) analysis. The present study aims at shedding some light on how tapered channel beams behave by studying the effect of taper ratio on structural behavior. As a weight reduction is always desired in aerospace structures beams are tapered in order to obtain highest structural efficiency. FE analysis has been performed to study the effect of taper ratio on linear deflection, lateral torsional buckling, non-linear parameters and dynamic parameters. Taper ratio tends to affect the mechanics of tapered beams innocuously and adversely. Consequently it becomes important to understand and document the mechanics of channel tapered beams. Channel beams generally have low torsional rigidity due to the off-shear loading. The effect of loading type and location of applied load have been studied for flange taper, web taper and symmetric taper for different conditions. Among these, as the taper ratio is increased, the torsional angular deflection increases but begins to decrease when the beam is web tapered and symmetrically tapered for a mid web loaded beam. But when loaded through the shear center, an increase in the torsional angular deflection can be observed with increase in taper ratio. This indicates that a flange taper could cause an increase in torsional angular deflection with an increase in taper ratio.

The mechanical behaviour of drainage pipeline under traffic load before and after polymer grouting trenchless repairing

Polymer grouting technology is an economical and efficient trenchless way to repair leakage and settlement of drainage pipeline. In this paper, the mechanical behaviours of drainage pipeline under traffic load before and after polymer grouting and cement grouting trenchless repairing are investigated through three-dimensional (3D) finite element method (FEM). Four different working conditions, including normal pipeline, disengaging pipeline, polymer-repaired pipeline, and cement-repaired pipeline are considered. The effects of load type, load location, buried depth on the mechanics of pipe are discussed in detail. The results show that the traffic load has great impact on both sides of the load position within 4 m, and the dangerous points of the pipeline are located at the bell and spigot joints. The most unfavorable condition occurs when the location of the disengaging corresponding to the load position. The greater influence on the disengaging pipeline with deeper buried depth applied. The disengaging pipeline can be repairing effectively and reliably by both the polymer and the cement grouting technology. However, the polymer material is more valuable than the cement material in terms of the Mises stresses after repairing.

Optimal Offering of Demand Response Aggregation Company in Price-Based Energy and Reserve Market Participation

This paper investigates the combined price-based scheduling/participation of generation company (GENCO) and demand response aggregation company (DRACO) in energy and reserve markets. The temporally coupled customer behavior can be better represented using the load profile attributes, when compared to the traditional approach with random willingness assignment. The proposed cost models for energy and reserve offerings consider the effect of load type, load pattern consumption, and availability/flexibility patterns of each type of load with time of use constraints. The load curtailment (LC) cost model accounts for criticality and willingness of the responsive loads via utilization factor and availability factors, respectively. The proposed cost models present a realistic picture of LC cost by eliminating the random willingness factor of the existing LC cost models. Thereafter, various cases of market participation with different reserve payment policies are formulated for combined participation of GENCO and DRACO. In addition, the sensitivity of participation decision of various entities to the seasonal load variation is examined for summer and winter loading profiles. The proposed cost models and scheduling framework is simulated using GENCO with ten thermal units and DRACO with various load types, profiles distributed across different load sectors comprising of commercial, residential, industrial, municipal, and agricultural loads. The combined participation resulted in improved market surplus with reduced GENCO surplus. Also, the energy and reserve market surplus dependence on seasonal load patterns is observed across different test cases and payment policies.

Transient response of a transversely isotropic multilayered half-space due to a vertical loading

• Governing equations are transformed into the fourth-order ordinary differential equations. • Solutions for displacements are obtained by using the analytical layer-element method. • The analytical layer-element excludes the positive exponential terms. • Effect of loading type, anisotropy and layering of media on the transient response is investigated. This paper investigates the transient response of a transversely isotropic multilayered half-space under vertical loadings. With the aid of a Laplace–Hankel transform, the global stiffness matrix for a multilayered half-space is acquired by assembling the analytical layer-element of each layer medium. The solutions for the displacements in the time domain are obtained by using the global stiffness matrix equations and a numerical inversion procedure. The accuracy of the proposed method is verified through comparisons with existing solutions for displacements induced by a step and rectangular pulse loading. In addition, selected numerical results for displacements induced by the buried loading are presented to illustrate the effect of transient loading type and material anisotropy on the transient response.

Fatigue assessment and stress analysis of cope-hole details in welded joints of steel truss bridge

Specimens testing and finite element analysis were conducted to investigate the fatigue performance of cope-hole details in welded integral joints of a steel truss bridge. A recommended nominal stress S-N curve of cope-hole details was obtained based on the evaluation of existing experimental results and comparison of different design specifications. The fatigue strength of the cope-hole details was evaluated via structural hot spot stress approach, which showed that the fatigue strength for the cope-hole details approaches that for FAT80. The effect of load type on local stress distribution was also identified by finite element parametric analysis. A simple equation was then proposed to estimate the stress concentration factor of cope-hole details in the tension member.

Computational homogenization for thermal conduction in heterogeneous concrete after mechanical stress

Concrete structures are subjected to various loadings during their service life and their internal structures will be changed, resulting variations in mechanical and thermo-physical properties. To investigate the effect of mechanical stress on thermal conduction, a computational homogenization method from a mesoscopic perspective was proposed in the present work. In the simulations, concrete was considered as a three-phase composite material consisting of aggregate, mortar matrix and the interfacial transition zones (ITZs) between them. The mechanical analysis was conducted firstly to study the damage distribution within concrete. The outcomes of mechanical computation were then used as the initial input data in the thermal conduction computation. The equivalent thermal conductivity of damaged element was homogenized by a composite mechanical method based on damage and the initial thermal conductivity of sound material. Accordingly, a meso-scale model in which the mechanical and thermal behavior were one-way coupled was built. The method was calibrated by comparing the numerical results with the available experimentally measured ones. Based on the verified simulation method, effective thermal conductivity (ETC) and temperature field of concrete subjected to different loading levels were calculated. Besides, the effects of loading type (compressive and tensile loadings) on ETC and temperature field of concrete were studied. It is found that ETC of concrete decreases with an increasing loading level. In addition, the effect of tensile loading on thermal behavior depends on whether the direction of thermal conduction is parallel or perpendicular to loadings.