Mechanical Behavior Of Components Research Articles

Effect of cyclic hydrothermal accelerated ageing on the mechanical behavior of components in adhesively bonded aluminum/composite joints reinforced with z-pins

This study presents an in-depth investigation into the moisture absorption and mechanical behavior of Glass Fiber Reinforced Polymer (GFRP) composites and adhesive bonded joints under hydrothermal aging conditions. The aim of this research is to assess the effects of moisture exposure and aging cycles on the performance of GFRP composites and their bonded joints. The experimental program involved preparing GFRP composite specimens and adhesive samples with specific thicknesses and subjecting them to hydrothermal aging cycles. Moisture absorption and desorption behavior of the adhesive and composite specimens were evaluated using Fick’s law, and equilibrium moisture content and diffusion coefficients were determined. Tensile tests were conducted to assess the mechanical properties of the materials, including elastic modulus, ultimate strength, and ultimate strain. The results demonstrated that both the adhesive and GFRP composite exhibited continuous moisture absorption and desorption behavior, following Fick’s law. The moisture uptake reached a saturation point, indicating equilibrium moisture content. The diffusion coefficients of the composite were found to be significantly influenced by the saturated moisture concentrations, highlighting the role of the fiber/matrix interface. Furthermore, the mechanical properties of both the adhesive and GFRP composite were evaluated under hydrothermal aging conditions. The elastic modulus of the adhesive increased after the first aging cycle, indicating the completion of the curing process. However, subsequent cycles resulted in reduced mechanical properties due to plasticization, molecular network changes, and swelling caused by moisture. The GFRP composite exhibited a reduction in ultimate strength and elastic modulus with increasing aging cycles, along with a decrease in strain. The study revealed that the moisture absorption affected the failure modes of the bonded joints, leading to a transition from fiber failure to adhesive failure. Hybrid bonded joints, incorporating pins to distribute stress, exhibited improved stability and higher ultimate loads compared to simple joints. This work contributes to the existing body of knowledge by providing a comprehensive understanding of the moisture absorption/desorption behavior and mechanical properties of GFRP composites and adhesive bonded joints under hydrothermal aging. The findings highlight the need for further investigation into the underlying mechanisms, long-term durability, and development of moisture barrier coatings to enhance the performance of GFRP composites in challenging environmental conditions.

Progressive collapse resistance of unsymmetrical steel sub-structure under a middle column-removal scenario

This paper presents an investigation on progressive collapse resistance of a type of unsymmetrical steel sub-structure. The sub-structure which consists of box-beam, H-beam and tube column is extracted from the practical project. In order to examine the effect of the unequal geometrical parameters, three specimens with different span ratio of box-beam to H-beam and depth ratio of H-beam to box-beam were designed for Pushdown test. Moreover, a numerical analysis is carried out, wherein the finite element models are established by ABAQUS, and the validation is conducted by the comparison with experimental results. Furthermore, a Beam Supporting Transfer Structure (BSTS) is considered in parametric studies, aiming to further explore the influence of extra load resulting from BSTS on unsymmetrical structure. The experimental results indicate that the ratios expressed for the span and depth under different value can easily change the overall resistance of the unsymmetrical structure, especially in the First Peak Load (FPL), Ultimate Failure Load (UFL). Regarding mechanical behavior of components, when the depth ratio is equal to 0.8, span ratio decreases from 1.5 to 1, the Catenary Action (CA) of H-beam and Flexural Action (FA) of box-beam display more sensitive to the variation of span ratio than other key results. Similarly, when the span ratio is equal to 1.5 depth ratio increases from 0.8 to 1, the FA of H-beam and CA of box-beam show more sensitive to the variation of depth ratio than other key results. Moreover, the UFLs of three specimens are observed as the ultimate load resistance in experiment, which is due to the development of the CA of beams and large residual resistance provided by the FA of box-beam. Ultimately, an advice of the span ratio and depth ratio for structure design is proposed.

A Novel Design of Torsion Spring-Connected Nonlinear Stiffness Actuator Based on Cam Mechanism

Abstract The nonlinear stiffness actuator (NSA) is a type of compliant joint with variable stiffness that is necessary for human–machine collaboration and has been the focus of extensive research attention. This academic work presents the principle of a torsion spring-connected nonlinear stiffness actuator (TSNSA), a NSA suitable for implementing revolute motions, which contrasts with existing NSAs that often have bulky mechanisms and are affected by a limited range of movement. It has a split sleeve, disc springs, and cam mechanisms (CMs) that when correctly configured, can passively and actively adjust stiffness, where the speed of stiffness regulation can be effectively improved. The mathematical model of a split sleeve inserted into a torsion spring is designed to analyze the behavior of mechanical components. Furthermore, a detailed CM profile has been designed to obtain the desired nonlinear stiffness. Its theoretical analysis includes numerical simulations with results consistent with the desired deflection–torque profile.

Modeling of thermal distributions by analyzing the heat tolerance of a robotic gripper pivot exposed to heated electronics

There are several applications in the aerospace, automotive and energy industries, for example, that often require high fidelity modeling or problems involving structural mechanics, heat transfer, or electromagnetic. Finite element analysis (FEA) is a popular method for solving the underlying partial differential equations (PDE) for these problems. 3D finite element analysis or 3D-FEA accurately captures the physics of these problems. The relevance of this study is to show how to set up finite element analysis (FEA) simulations and leverage the model of the environment to solve problems typically encountered by engineers and scientists in a variety of fields such as aerospace, automotive and energy. This study analyzes the behavior of mechanical components under different physical effects and shows a thermal analysis of a commercial KUKA YouBot robotic arm component by finding temperature distributions, figures, code, and test results for multiple materials. The developed model allows understanding and assessing the responsive component under loading, vibration or heat and determining deformation stresses among many things to select the best material and even prevent failure or undesired resonance as an example. These systems are typically modeled using partial differential equations or PDEs that capture the underlying physics of the problem and FEA is just one of the most common methodologies to solve this type of equation. The linear regression model can be a good predictive model that represents the relationship between thermal conductivity and max temperature to avoid undesired performance of the robotic arm.

Fatigue of textiles used in vascular surgery: Application to carotid endarterectomy

Fatigue is a material-based phenomenon playing a significant role in the mechanical behavior of components and structures. Although fatigue has been well studied for traditional materials, such as metals, its underlying mechanisms are not thoroughly understood in novel applications such as the case of textiles used as patches to close the arteriotomy in carotid endarterectomy. The latter is a type of vascular surgery for the treatment of carotid artery disease in which after an arteriotomy and removal of atherosclerotic plaque closure is made with a patch sutured on the artery. Completion of the operation signals the initiation of complex mechanical and hemodynamic phenomena. Fatigue performance of the patch eventually determines the successful outcome of carotid endarterectomy. In this study, we evaluate with a two-fold approach the mechanics of patch angioplasty in carotid endarterectomy. First, an analytical model for the fatigue behavior of textiles is developed, considering the microstructure and geometry of the fabric. Then, the surgical procedure is simulated and a finite element analysis of the endarterectomized and patched carotid artery is employed. Stress fields are calculated, while deformation at the site of patch angioplasty indicates a potential cause for the formation of aneurismal degeneration after the surgery. Such analysis can provide a better understanding in the establishment of follow-up protocols.

The fatigue behavior of V-notches in presence of residual stresses: recent developments and future outcomes

Residual stresses, arising from welding processes or nonhomogeneous plastic deformations, broadly influence the high cycle fatigue behavior of mechanical components. The presence of V-notches leads to singular residual stresses ahead of the notch tip and the asymptotic stress field can be described by the notch stress intensity factor (NSIF). However, plastic effects induce redistribution of residual stresses during cyclic loading and this variation is accounted in several numerical models developed for the calculation of the residual NSIFs. Due to the development of these models, the fascinating issue of predicting the fatigue strength of pre-stressed notched components has gained widely attention by the researchers and new approaches were recently developed and some of them are here reviewed.

Influence of a Variable in Time Heat Transfer Coefficient on Stresses in Model of Power Plant Components

The paper discusses the issue of the modelling of strains and stresses resulting from heating and cooling processes of components in power plants. The main purpose of the work is to determine the mechanical behavior of power plant components operating under mechanical and thermal loading. The finite element method (FEM) has been used to evaluate the temperature and stresses changes in components as a function of time. Temperature fields in the components of power plants are dependent, among parameters, on variable heat-transfer conditions between components and the fluid medium, that may change its condition, flowing inside them. For this reason, an evaluation of the temperature field and the consequent stress fields requires the use of heat-transfer coefficients as time-dependent variables and techniques for determining appropriate values for these coefficients should be used. The methodology that combines computer modelling of the temperature fields with its measurements performed at selected points of the pipelines may be used in this case. The graphs of stress changes as a function of time have been determined for the chosen plant components. The influence of the heat transfer conditions on the temperature fields and mechanical behavior of components in question have been discussed.

Life probability distribution model of mechanical components with the number of load application as life parameter

With the number of load application as the life parameter, the method for modeling the life probability distribution of mechanical components is studied. First, the failure behavior of mechanical components is analyzed, and the method for describing the failure behavior of mechanical components is developed with the stress–strength interference theory. Then, based on the failure behavior, the life probability density function, life cumulative distribution function, reliability, failure rate, and mean life of component with the number of load application as the life parameter, which can embody the effect of parameters including stress, strength and its degradation, and so on, are derived, respectively. Finally, for the cases of different parameters of stress and strength, the life probabilistic distribution characteristic, reliability, failure rate, mean life, and reliable life of components are studied. The result shows that the life probabilistic distribution characteristic of components is dependent on the specific value of parameters describing the failure behavior. With the method and model proposed in this article, as long as the parameters of strength, stress, strength degradation, and so on are known, the life probabilistic distribution functions of components can be calculated, the rules that the reliability and failure rate of component change as the number of load application can be obtained, and the mean life and reliable life of components can be determined.

Study of Mechanical Behavior of Components of Duplex Steel by Using of X-Ray Diffraction Technique

Duplex stainless steel is a material that attracts great interest of different branches of engineering and industry because of its combination of good structural and mechanical characteristics and high corrosion resistance. The microstructure of duplex steel presents an example of composite material with approximately equal amounts of austenite and ferrite phases. Physical and mechanical properties of these components are different so their behaviors under loading are different too. Therefore it is important to analyze the distribution of applied stress between ferrite and austenite phases of duplex steel. The analysis of stress distribution was made by X-ray diffraction technique. X-ray diffraction method allows separate measuring of stresses in each phase and determination of others mechanical characteristics as Young ́s modulus, yield stress of ferrite and austenite both in elastic and plastic region. In presented paper the samples of duplex steel after rolling were loaded by calibrated springs; using of Cr-Kα radiation allows carrying out of stress measurements in ferrite and austenite phases of duplex stainless steel.

Casting and stress-strain simulations of a cast ductile iron component using microstructure based mechanical behavior

The industrial demand for increased component performance with concurrent reductions in component weight, development times and verifications using physical prototypes drives the need to use the full potential of casting and Finite Element Method (FEM) simulations to correctly predict the mechanical behavior of cast components in service. The mechanical behavior of the component is determined by the casting process, and factors as component geometry and casting process parameters are known to affect solidification and microstructure formation throughout the component and cause local variations in mechanical behavior as well as residual stresses. Though residual stresses are known to be an important factor in the mechanical behavior of the component, the importance of local mechanical behavior is not well established and the material is typically considered homogeneous throughout the component. This paper deals with the influence of solidification and solid state transformation on microstructure formation and the effect of local microstructure variations on the mechanical behavior of the cast component in service. The current work aims to investigate the coupling between simulation of solidification, microstructure and local variations in mechanical behavior and stress-strain simulation. This is done by performing several simulations of a ductile iron component using a recently developed simulation strategy, a closed chain of simulations for cast components, able to predict and describe the local variations in not only elastic but also plastic behavior throughout the component by using microstructural parameters determined by simulations of microstructural evolution in the component during the casting process. In addition the residual stresses are considered. The results show that the FEM simulation results are significantly affected by including microstructure based mechanical behavior. When the applied load is low and the component is subjected to stress levels well below the yield strength of the material, the residual stresses highly affect the simulation results while the effect of local material behavior is low. As the applied load increases and the stress level in the component approaches and passes the yield strength, the effect of residual stresses diminishes while the effect of local mechanical behavior increases. In particular the predicted strain level is heavily affected by the use of local mechanical behavior. It is proposed that it is important to include both local mechanical behavior and residual stresses in stress-strain simulations to predict the true mechanical behavior of the component.

Analysis of Surface Roughness of Low Carbon Steel during Cold Rolling of Thin Strip

Surface roughness plays an important role in determining the tribological behaviour of mechanical components (e.g. gears and roller bearings etc.) under full-film and mixed (or partial) elastohydrodynamic lubrication conditions. This paper describes a detailed mechanics analysis of the surface roughness transformation of thin strip which has been cold rolled on an experimental mill. Low carbon steel strips were rolled at various speeds and reductions, and the effects of rolling parameters on surface roughness are studied. The results of surface roughness can provide important information to optimise the rolling schedule and to improve the rolled strip quality.

Characterization of yielding of sheet metal at elevated temperatures

Abstract In times of highest significance of process modeling and numerical simulation characterization of material properties is of special importance for components’ and tools’ dimensioning. Especially in fields of sheet metal forming the mechanical behavior of components highly differ according to real stress condition. In particular yield loci combine the information of beginning of yielding with biaxial stress conditions. Although these data are essential, they are unknown for many different sheet metals, mainly new materials used for light-weight constructions, e.g. aluminum and magnesium alloys. In this paper investigations done on a novel concept of experimental setup, which has been developed at the Chair of Manufacturing Technology (LFT) and which enables the determination of yield loci at elevated temperatures, are presented. The strategy for local heating is based on FE-calculations and verified afterwards. A 210 W-diode laser is used for the local heating of the specimens up to temperatures in the range of 300 °C. During forming process a constant temperature is guaranteed by a closed-loop temperature-control (CLTC), the homogeneous distribution of temperature in the forming zone is realized using a special optical system.

Novel Concept of Experimental Setup for Characterisation of Plastic Yielding of Sheet Metal at Elevated Temperatures

In times of highest significance of process modelling and numerical simulation characterisation of material properties is of special importance for tools’ and components’ dimensioning. But in general material properties depend on many different influencing variables, e.g. temperature, humidity and many others. Especially in fields of sheet metal forming the mechanical behaviour of components highly differs according to real stress condition. In particular yield loci combine the information of beginning of yielding with a biaxial stress condition, but nevertheless for many materials they have not been determined yet. For all others the existing values are available only at room temperature. In this paper a novel concept of the experimental setup is shown, with which plastic yielding of sheet metal can be examined also at elevated temperatures. In usual biaxial tension tests cruciform specimen are drawn in plane. The new machine-concept, which is presented in this paper, is based on a punch-load moving perpendicular to the sheet. By clamping the specimen restoring forces are induced, which cause in dependence of special developed tool and work piece geometries defined stress conditions. Using an optical measurement system for determination of strains with CCDcameras of very high frame rate allows exact identification of starting plastification by offline analysis. Experiments at elevated temperatures are realised by local heating with a diode laser and a special optical system to reach a homogenous distribution of temperatures in the forming zone. On the one hand these investigations are necessary for many materials to achieve further information on characteristic properties in warm forming, because their data are only known at room temperature. On the other hand some materials, e.g. magnesium wrought alloys, are mostly formed at elevated temperatures (here in the range of 200°C to 250°C), because of its significant higher formability. Thus, material behaviour must be characterised at these temperatures.

Determination of Residual Stresses in Carburized, Quenched and Tempered AISI 8620 Steel

The residual stresses (RSs), which result from processing, have a great influence on the mechanical behavior of components, particularly when these components are subject to failure mechanisms. The failure mechanisms, in turn, depend on local conditions such as fatigue, brittle fracture or stress-corrosion-cracking. In the case of carburized parts, the influence of RSs becomes particularly critical for thin walls, when overlapping carburized cases may result, having a detrimental influence on the fatigue resistance. This paper presents RSs results, obtained throug x-rays diffraction measured on the surface of carburized sheets of AISI 8620 steel, 0.5mm to 10 mm thick. The results show the influence of core hardness on the RSs on the surface, particularly when the effective case depth is larger than half the thickness. The influence of a stress relieving treatment at 180 C is also reported.

FEATURE ARTICLE: Items of special interest, tutorials, and surveys: Static and Dynamic Behav Ior of Mechanical Components Associated With Electrical Transmission Lines -- Iii (a)

FEATURE ARTICLE: Items of special interest, tutorials, and surveys: Static and Dynamic Behav Ior of Mechanical Components Associated With Electrical Transmission Lines -- Iii (a)

Literature Review : Static and Dynamic Behavior of Mechanical Components Associated With Electrical Transmission Lines - II

Literature Review : Static and Dynamic Behavior of Mechanical Components Associated With Electrical Transmission Lines - II

Static and Dynamic Behavior of Mechanical Components Associated With Electrical Transmission Lines

This article describes the behavior of transmission towers, insulator strings, conductors, and foundations as determined from theoretical analyses, model testing, and full-scale tests. Line vibration is also briefly reviewed.