Types Of Mechanical Loading Research Articles

Numerical evaluation of transient deflection and frequency responses of sandwich shell structure using higher order theory and different mechanical loadings

The static deflection, frequency and transient responses of the layered sandwich shell (flat/curved) structure computed under the different types of mechanical loading. The higher order polynomial kinematic type of mid-plane kinematics is derived for the mathematical modeling and subsequent numerical analysis. A suitable home-made code is prepared in MATLAB for the computation of deflection (static and dynamic) parameter using the proposed mathematical model. Furthermore, the numerical solution accuracy has been verified by comparing the numerical output with those available published data including the convergence test as a priori. In addition, the influences of the variable design parameters (span-to-thickness ratios, curvature ratios, aspect ratios, core-to-face thickness ratios, lamination configurations, shell configurations, and support conditions) on the deflection, frequency, and the transient values are computed extensively and the inferences provided in details.

In Vitro Weight-Loaded Cell Models for Understanding Mechanodependent Molecular Pathways Involved in Orthodontic Tooth Movement: A Systematic Review.

Cells from the mesenchymal lineage in the dental area, including but not limited to PDL fibroblasts, osteoblasts, and dental stem cells, are exposed to mechanical stress in physiological (e.g., chewing) and nonphysiological/therapeutic (e.g., orthodontic tooth movement) situations. Close and complex interaction of these different cell types results in the physiological and nonphysiological adaptation of these tissues to mechanical stress. Currently, different in vitro loading models are used to investigate the effect of different types of mechanical loading on the stress adaptation of these cell types. We performed a systematic review according to the PRISMA guidelines to identify all studies in the field of dentistry with focus on mechanobiology using in vitro loading models applying uniaxial static compressive force. Only studies reporting on cells from the mesenchymal lineage were considered for inclusion. The results are summarized regarding gene expression in relation to force duration and magnitude, and the most significant signaling pathways they take part in are identified using protein-protein interaction networks.

In vitro mechanical stimulation facilitates stress dissipation and sealing ability at the conventional glass ionomer cement-dentin interface

ObjectiveThe aim of this study was to evaluate the induced changes in the chemical and mechanical performance at the glass-ionomer cement-dentin interface after mechanical load application. MethodsA conventional glass-ionomer cement (GIC) (Ketac Bond), and a resin-modified glass-ionomer cement (RMGIC) (Vitrebond Plus) were used. Bonded interfaces were stored in simulated body fluid, and then tested or submitted to the mechanical loading challenge. Different loading waveforms were applied: No cycling, 24 h cycled in sine or loaded in sustained hold waveforms. The cement-dentin interface was evaluated using a nano-dynamic mechanical analysis, estimating the complex modulus and tan δ. Atomic Force Microscopy (AFM) imaging, Raman analysis and dye assisted confocal microscopy evaluation (CLSM) were also performed. ResultsThe complex modulus was lower and tan delta was higher at interfaces promoted with the GIC if compared to the RMGIC unloaded. The conventional GIC attained evident reduction of nanoleakage. Mechanical loading favored remineralization and promoted higher complex modulus and lower tan delta values at interfaces with RMGIC, where porosity, micropermeability and nanoleakage were more abundant. ConclusionsMechanical stimuli diminished the resistance to deformation and increased the stored energy at the GIC-dentin interface. The conventional GIC induced less porosity and nanoleakage than RMGIC. The RMGIC increased nanoleakage at the porous interface, and dye sorption appeared within the cement. Both cements created amorphous and crystalline apatites at the interface depending on the type of mechanical loading. Clinical significanceRemineralization, lower stress concentration and resistance to deformation after mechanical loading improved the sealing of the GIC-dentin interface. In vitro oral function will favor high levels of accumulated energy and permits micropermeability at the RMGIC-dentin interface which will become remineralized.

Investigations on Flexural Fatigue Strength of Conductor Paths Fabricated by LPKF-LDS® Technology

Reliability aspects are crucial for the success of every technology in industrial application. Regarding interconnect devices, several methods are applied to evaluate reliability of conductor paths like accelerated environmental tests. Especially, molded interconnect devices (MID), which enable numerous applications with three-dimensional (3D) circuitry on 3D shaped injection-molded thermoplastic parts are often under particular stress, e.g., as component of a housing. In this study, a new test method for evaluating the flexural fatigue strength of conductor paths produced by the laser-based LPKF-LDS® technology is presented. For characterization of test samples, a test bench for flexural fatigue test was built up. A result of the flexural fatigue test is a characteristic Woehler curve of the metal layer system. Applying this new test method, essential influencing parameters on the reliability of MID under mechanical load can be identified. So, the metal layer system as well as the geometric parameters of the metal layer is crucial for the performance. Furthermore, test specimens are tested under different types of mechanical load, i.e., tensile stress and compressive stress. For a holistic view on reliability of MID, experimental results are discussed and supported by simulations. An important finding of the study is the advantage of nickel-free layer systems in contrast to the Cu/Ni/Au layer system, which is often used in MID technology.

Effects of mechanical loading on the magnetic and dynamic properties of engineering materials

The influence of strain on the magnetic and dynamic properties of ARMCO iron has been characterized by Mossbauer spectroscopy and by Nuclear Inelastic Scattering of synchrotron radiation. The Mossbauer spectra, taken in backscattering geometry, reveal that the magnetic texture in these materials is depending on the type of mechanical loading, monotonic or cyclic, respectively. The applicability of Nuclear Inelastic Scattering for the investigation of the dynamic properties of these macroscopic bulk-engineering materials is shown. The so obtained phonon density of states of a monotonically loaded specimen shows slight differences in its shape and spectral features in comparison to the initial state. An influence of dislocations is also reflected in theoretically calculated phonon density of states based on classical molecular dynamics simulations.

General theory of skin reinforcement

Macroscopic mechanical properties of human skin in vivo cannot be considered independent of adjacent subcutaneous white adipose tissue (sWAT). The layered system skin/sWAT appears as the hierarchical structural composite in which single layers behave as fiber-reinforced structures. Effective macroscopic mechanical properties of such composites are mainly determined either by the properties of the skin or by those of the sWAT, dependent on the conditions of mechanical loading. Mechanical interactions between the skin and the adjacent sWAT associated with a mismatch in the mechanical moduli of these two layers can lead to production of the skin wrinkles. Reinforcement of the composite skin/sWAT can take place in different ways. It can be provided through reorientation of collagen fibers under applied loading, through production of new bonds between existing collagen fibers and through induction of additional collagen structures. Effectiveness of this type of reinforcement is strongly dependent on the type of mechanical loading. Different physical interventions induce the reinforcement of at least one of these two layers, thus increasing the effective macroscopic stiffness of the total composite. At the same time, the standalone reinforcement of the skin appears to be less effective to achieve a delay or a reduction of the apparent signs of skin aging relative to the reinforcement of the sWAT.

The contractile adaption to preload depends on the amount of afterload.

AimsThe Frank–Starling mechanism (rapid response (RR)) and the secondary slow response (SR) are known to contribute to increases contractile performance. The contractility of the heart muscle is influenced by pre‐load and after‐load. Because of the effect of pre‐load vs. after‐load on these mechanisms in not completely understood, we studied the effect in isolated muscle strips.Methods and resultsProgressive stretch lead to an increase in shortening/force development under isotonic (only pre‐load) and isometric conditions (pre‐ and after‐load). Muscle length with maximal function was reached earlier under isotonic (L max‐isotonic) compared with isometric conditions (L max‐isometric) in nonfailing rabbit, in human atrial and in failing ventricular muscles. Also, SR after stretch from slack to L max‐isotonic was comparable under isotonic and isometric conditions (human: isotonic 10 ± 4%, isometric 10 ± 4%). Moreover, a switch from isotonic to isometric conditions at L max‐isometric showed no SR proving independence of after‐load. To further analyse the degree of SR on the total contractile performance at higher pre‐load muscles were stretched from slack to 98% L max‐isometric under isotonic conditions. Thereby, the SR was 60 ± 9% in rabbit and 51 ± 14% in human muscle strips.ConclusionsThis work shows that the acute contractile response largely depends on the degree and type of mechanical load. Increased filling of the heart elevates pre‐load and prolongs the isotonic part of contraction. The reduction in shortening at higher levels of pre‐load is thereby partially compensated by the pre‐load‐induced SR. After‐load shifts the contractile curve to a better ‘myofilament function’ by probably influencing thin fibers and calcium sensitivity, but has no effect on the SR.

Critical Parameters Affecting Mechanical Behavior of Natural Fiber Reinforced Plastics

ABSTRACTOf the numerous special properties of natural fiber composites, light weight and biodegradability are the most attractive. Also, natural fiber reinforced composites have sufficiently good mechanical properties. In the present research investigation, the mechanical properties of the natural fiber (nettle and grewia optiva fiber) reinforced thermoset and thermoplastic composites have been evaluated and compared. The morphological analysis of the fractured test specimens subjected to different types of mechanical loading has also been performed using scanning electron microscopy (SEM). Critical parameters, such as contact angle of polymers, surface roughness of the natural fibers, and twist angle of the natural fiber yarn have been evaluated in order to emphasize their importance in defining the mechanical behavior of the developed composite laminates. The results reveal that poly-lactic acid (PLA)-based natural fiber composites have superior mechanical properties as compared to the polypropylene (PP)- and epoxy-based natural fiber composites.

Gene Expression Analysis of CCN Protein in Bone Under Mechanical Stress.

To investigate mechanical-dependent bone remodeling, we had previously applied various types of mechanical loading onto the teeth of rats and mice. In vitro cultured bone cells were then used to elucidate the mechanisms underlying the specific phenomenon revealed by in vivo experiments. This review describes the techniques used to upregulate CCN2 expression in bone cells produced by different types of mechanical stress, such as fluid shear stress and substrate strain in vitro, and compression or tension force in vivo.

Vibration Response Prediction of the Printed Circuit Boards Using Experimentally Validated Finite Element Model

A spacecraft consists of a number of mechanical and electronic sub-assemblies. An electronic package is consists of printed circuit boards placed in mechanical housings which are stacked together. Electronic components are mounted on the printed circuit board (PCB). A spacecraft experiences various types of mechanical loads during its launch such as vibration, acoustic and shock loads. The understanding of dynamic behaviour provides valuable insight to a design engineer, to improve the mechanical design and product reliability when used in harsh vibration condition. Generally electronic package design for vibration loads is verified by conducting tests on actual hardware.This paper addresses on using basic FEA tool to accurately investigate the dynamic characteristics of the PCB and avoid costly testing methods which require hardware. Here the normal modes & frequency response functions (FRF) of PCB are determined and validated using vibration test on PCB. The validated model is used to predict vibration response for random vibration input. It is shown here how the responses are accurately predicted for random vibration input for a design parameter variation of PCB. The results are also validated using vibration test on PCB.

Study of the semi-conductive behavior of the passive film on carbon steel in simulated concrete pore solution under stress

Purpose – This paper aims to clarify the semi-conductive behavior of the passive layer formed in concrete environment without and with presence of chloride ions under different loading conditions. Passivation and depassivation of steel play an essential role in the subsequent stages of the corrosion process. Due to the nature of passive films on metals, they show electrochemical properties of a semi-conductor. Design/methodology/approach – A C-ring model was proposed in this experiment to induce stress on the specimens. Specimens under different levels of compressive and tensile loadings were exposed to chloride-free and chloride-contaminated solutions and their semi-conductive behavior was investigated using Mott–Schottky technique. Findings – Irrespective of the type and magnitude of the applied load, the passive film on rebars in simulated concrete pore solution is a highly disordered n-type semi-conductor. In all specimens, the presence of chloride ions decreases the slope of the Mott-Schottky plots, the donor density and the space charge layer thickness, which leads to a thinner passive film. Results indicate that steel specimens immersed in chloride-free pore solution under tensile loadings passivate more rapidly compared to those under compressive loadings. However, the situation in chloride-contaminated solution is different, and steel under tensile stress exhibits more corrosion than steel under compressive stress or under no load. Originality/value – Reinforced concrete structures inevitably experience variable mechanical loads, and continuous degradation from aggressive environments. Therefore, it is imperative to study the synergic impact of different types of mechanical loadings and exposure to chloride ions on this process. This paper fulfils this need.

Vibration analysis of angle-ply laminates composite plate under thermo-mechanical effect

The paper presents mainly the dynamic response of an angle ply composite laminated plates subjected to thermo-mechanical loading. The response are analyzed by analytically using Newmark direct integration method with Navier solution, numerically by ANSYS. The experimental investigation is to fabricate the laminates and to find mechanical and thermal properties of glass-polyester such as longitudinal, transverse young modulus, shear modulus, longitudinal and transverse thermal expansion. Present of temperature could increase dynamic response of plate also depending on lamination angle, type of mechanical load and the value of temperature.

Fractography, a Powerful Tool for Identifying and Understanding Fatigue in Composite Materials

Fractography is a tool widely used in the academic world but a little-known technique in the industrial world. This tool can be useful at most stages of the development of composite parts: prototyping characterization, industrialization, production quality problems,.. Finally when a composite part is broken during service, fractographic analysis is one of the most efficient tools for the determination of the root causes of failure. Fractography is useful for the engineer who has to determine if the failure results of a mechanical overload or of a fatigue phenomenon.The implementation of a fractographic investigation requires to follow a methodology with different steps:The first step is to determine the direction of propagation in the different zones of the rupture by recognition of features on the broken surface. From these results, the initiation area can often be identified. Then a long part of the work consists in seeking features of static or fatigue damage. Fractography also allows to determine what type of mechanical loading has caused the micro-damage in the initiation area. This information can be compared with the expected loading.Sometimes, the fatigue fractographic features are localized just along manufacturing defects. In this case, a specific study is required to establish the harmfulness of these defects. The defect acceptance criteria after manufacturing are then sometimes amended.Article will discuss these aspects through industrial examples.

Reactivity of Ti-B, Cr-S, and Mn-S powder systems during explosively-driven collapse

Metal-metal and metal-sulfur reactive powder mixtures have been previously tested for initiation of reaction via planar, normal-shock loading. In addition to reacting under shock, such powder mixtures may undergo exothermic reaction from other types of mechanical loading. The thick-walled cylinder technique was performed on samples of Ti-B (1:2 molar ratio), Cr-S (1.15:1 molar ratio), and Mn-S (1:1 molar ratio). These experiments were aimed to determine the effect of large shear strains exerted on reactive metal powder mixtures and to establish the relative effectiveness of shear loading in comparison to shock loading for initiating reaction. Recovered samples were analyzed via SEM and XRD to determine the degree of reaction.

Analysis of curaua/glass hybrid interlayer laminates

This study compares the mechanical properties of curaua, glass and hybrid curaua/glass laminates evaluated experimentally with those obtained theoretically using commercial software for composites. Hybrids laminates were produced varying the fiber layer stacking sequence with the aim of optimizing the combination of vegetable and synthetic fibers. Composites were compression molded using eight layers of glass and/or curaua fiber mats and mechanically tested as per ASTM standards. The combination of curaua and glass fibers produced a material with intermediate properties and, depending on the type of mechanical loading and the stacking sequence, some hybrids showed properties close to the pure glass fiber composites. Furthermore, hybrid composites with glass layers closer to the surfaces showed the best overall results.

Elastic stability of functionally graded rectangular plates under mechanical and thermal loadings

In this paper, the buckling of a functionally graded plate is studied. The material properties of the plate are assumed to be graded continuously in the direction of thickness. The variation of the material properties follows a simple power-law distribution in terms of the volume fractions of constituents. The plates are subjected to be under three types of mechanical loadings, namely; uniaxial compression along the x-axis, uniaxial compression along the y-axis, and biaxial compression, two types of thermal loading, namely; uniform temperature rise and linear temperature rise. The equilibrium and stability equations are derived using the classical plate theory (Kirchhoff theory) and Navier's solution. Resulting equations are employed to obtain the closed-form solution for the critical buckling load for each loading case. The results are verified with the known data in the literature. Key words: Buckling, classical plate theory, functionally graded materials, mechanical and thermal loads.

Tensile Properties of Pumpkin Peel and Flesh Tissue and Review of Current Testing Methods

<abstract> Abstract. In South and Southeast Asia, postharvest loss causes material waste of up to 66% in fruits and vegetables, 30% in oilseeds and pulses, and 49% in roots and tubers. The efficiency of postharvest equipment directly affects industrial-scale food production. To enhance current processing methods and devices, it is essential to analyze the responses of food materials under loading operations. Food materials undergo different types of mechanical loading during postharvest and processing stages. Therefore, it is important to determine the properties of these materials under different types of loads, such as tensile, compression, and indentation. This study presents a comprehensive analysis of the available literature on the tensile properties of different food samples. The aim of this review was to categorize the available methods of tensile testing for agricultural crops and food materials to investigate an appropriate sample size and tensile test method. The results were then applied to perform tensile tests on pumpkin flesh and peel samples, in particular on arc-sided samples at a constant loading rate of 20 mm min^-1. The results showed the maximum tensile stress of pumpkin flesh and peel samples to be 0.535 and 1.45 MPa, respectively. The elastic modulus of the flesh and peel samples was 6.82 and 25.2 MPa, respectively, while the failure modulus values were 14.51 and 30.88 MPa, respectively. The results of the tensile tests were also used to develop a finite element model of mechanical peeling of tough-skinned vegetables. However, to study the effects of deformation rate, moisture content, and texture of the tissue on the tensile responses of food materials, more investigation needs to be done in the future.

Hybrid Bacterial Foraging Optimization Strategy for Automated Experimental Control Design in Electrical Drives

This paper explores the automated experimental control design for variable speed drives using a novel heuristic optimization algorithm. A hybrid approach, which combines desirable characteristics of two of the most widely used biologically-inspired heuristic algorithms, the genetic algorithms (GAs) and the bacterial foraging (BF) algorithms, is studied and developed in this paper. Both the structures and parameters of digital speed controllers are optimized experimentally and directly on the drive while it is subject to different types of mechanical load; the dynamics of these load profiles are generated using a programmable load emulator. The proposed hybrid bacterial foraging (HBF) algorithm is evaluated, for the purpose of control optimization for electric drives, against GA and BF, and their performances are compared and contrasted.

Aggravation of inflammatory response by costimulation with titanium particles and mechanical perturbations in osteoblast- and macrophage-like cells

The interface between bone tissue and metal implants undergoes various types of mechanical loading, such as strain, compression, fluid pressure, and shear stress, from daily activities. Such mechanical perturbations create suboptimal environments at the host bone-implant junction, causing an accumulation of wear particles and debilitating osseous integration, potentially leading to implant failure. While many studies have focused on the effect of particles on macrophages or osteoprogenitor cells, differential and combined effects of mechanical perturbations and particles on such cell types have not been extensively studied. In this study, macrophages and osteoprogenitor cells were subjected to physiological and superphysiological mechanical stimuli in the presence and absence of Ti particles with the aim of simulating various microenvironments of the host bone-implant junction. Macrophages and osteoprogenitor cells were capable of engulfing Ti particles through actin remodeling and also exhibited changes in mRNA levels of proinflammatory cytokines under certain conditions. In osteoprogenitor cells, superphysiological strain increased proinflammatory gene expression; in macrophages, such mechanical perturbations did not affect gene expression. We confirmed that this phenomenon in osteoprogenitor cells occurred via activation of the ERK1/2 signaling pathway as a result of damage to the cytoplasmic membrane. Furthermore, AZD6244, a clinically relevant inhibitor of the ERK1/2 pathway, mitigated particle-induced inflammatory gene expression in osteoprogenitor cells and macrophages. This study provides evidence of more inflammatory responses under mechanical strains in osteoprogenitor cells than macrophages. Phagocytosis of particles and mechanical perturbation costimulate the ERK1/2 pathway, leading to expression of proinflammatory genes.

Comparative studies of mechanical and morphological properties of polylactic acid and polypropylene based natural fiber composites

In this study, natural fiber reinforced polylactic acid composites have been developed by hot pressing through film-stacking procedure. The reinforcement materials used are nettle, Grewia optiva and sisal fibers in the plain weave form. For comparison purposes, polypropylene-based composites using the same fibers have also been developed. Mechanical properties (tensile, compressive, flexural, and impact properties) of all the developed composites have been evaluated through standard test procedures. It has been found that the polylactic acid based composites have superior mechanical properties and can be a potential substitute for traditional synthetic fiber composites in many application areas. Polylactic acid/sisal composite showed overall the best performance in terms of mechanical behavior. The morphological study of the fractured surface during mechanical testing has been done using scanning electron microscopy, which provides the mechanism of failure of composites during different types of mechanical loadings.