Papers by Keyword: Dynamic Loading

Abstract: Damage or a loss of strength in this hip joint can occur as a result of calcification, aging, the development of illnesses such as osteoporosis, arthritis, and bone cancer, and it can also be permanently destroyed by accidents. As a result, an artificial hip prosthesis can be implanted to prevent undesirable outcomes. Throughout the jumping, running, and walking cycles, the hip joint is the most essential load-bearing and shock-absorbing component in the lower half body. As a result, using a finite element analysis technique, this work simulates the design of an Artificial Hip Joint with holes and thickness as variables, using CoCrMo acetabular implant material. ANSYS 19.1 software with transient structural characteristics will be used to simulate providing the load with the activity of climbing stairs. According to the findings of this study, the acetabular design with a thickness of 3 mm and 5 holes is the most optimal. This is due to the design's distribution of stress, strain, and total deformation being the most ideal and having a relatively low weight with appropriate usage period and safety factor forecasts.

Abstract: The present study aims to carry out a parametric investigation on a pile made of different materials, and subjected to static and dynamic loading resulting from the weight of the structure and the shear force acting on the head of the pile. It is worth specifying that the pile is anchored in the ground on a Winkler-Pasternak elastic foundation that is made up of five different layers. In this study, the equilibrium equations were treated using the high-order theory with a new shear deformation shape function of a cylindrical pile made of an isotropic material and a sandwich functionally graded material.The results obtained with a numerical study based on the minimization of energies by the Rayleigh-Ritz method was carried out in order to highlight the influence of the geometric ratio, the volume fraction of the functionally graded material, and the type of loading on the vibration frequencies and the admissible stresses in order to determine the most appropriate material for the pile so that extreme stresses can be absorbed. The precision and the applicability of the method with new solution of the transverse shear deformation are demonstrated through this study with modeling of the layered property of the soil, were then compared with those reported in previous work available in the literature. It turned out that these results are in good agreement with each other, for the different materials of pile and for all boundary conditions considered. The results of pile with sandwich functionally graded material, it is revealed that the role of this material has an influence on the type of loading, especially, in the case statique of a pile subjected to a compound bending weight and the shear effect, in case dynamique the pile with vibration flexible or rigid .

Abstract: In this study, dynamic temperature field in a dissimilar steel joint specimen was numerically analyzed by means of three-dimensional explicit finite element analysis. Fully coupled thermal stress analysis was performed by using FE-code Abaqus/Explicit ver. 6.12. It was assumed that 90% of the plastic work was transferred to heat. Furthermore, dynamic loading tests were conducted with three-point bending specimen extracted from the dissimilar steel joint between a mild steel and a high tensile strength class steel. The specimen included a U-shape notch in the bonded interface. A high-speed infrared camera was used to measure the temperature field near the bonded interface. The temperature field was recorded at a frame rate of 200 Hz during the dynamic loading test. The numerically calculated temperature field near bonded interface showed reasonable agreement with the temperature field measured by the high-speed infrared thermography. The temperature in the soft steel particularly increased during the dynamic loading. On the other hand, the increase in temperature in the hard steel area was relatively few.

Abstract: This paper presents a summary of a preliminary research aimed at producing ultrafine-grained (UFG) and heterogeneous microstructure in microalloyed steel and testing these materials under dynamic loading conditions (strain rates 800 s^-1 and 1800s^-1). The UFG and bimodal-structures, due to grain size, structural composition or morphology of structural components, were produced by an advanced thermomechanical processing, namely rolling in: hot, two-phase and cold-hot combined conditions. The advantage of bimodal microstructures is their maximization of mechanical behavior under extreme loading conditions due to promoted accumulation and interactions of geometrically necessary dislocations. The dynamic work-hardening behavior has been studied as a function of solute atoms and fine-scale, second-phase particles in the UFG and bimodal-structures. The substantial complexity of the phenomena, which occur through the evolution of microstructure and texture in response to dynamic loading, presents formidable challenges to theoretical model development of plastic deformation of UFG and bimodal-structures. Such an extraordinary work hardening provides an attractive strategy to develop optimal combination of mechanical properties i.e. strength/ductility ratio. A multi-scale analysis capable of including material behavior in different scales should be applied to discuss mechanical response of mentioned above microstructures and to help to analyze their influence on mechanical behavior under dynamic loading. The investigation was performed for a material of common application: high strength microalloyed steel X70. The experimental results show that strain rate sensitivity of the heterogeneous microstructures obtained by various thermomechanical rolling routes are significant, but not by a similar magnitude with the microstructure compositions and increasing strain rate.

Abstract: This paper presents a qualitative study on different loadings – quasi-static or shock – of theoretical shape of cranium itself and of the injured cranium restoration using different theoretical shapes of implant plates. Simulations were made in DEFORM 2DTM. Some comparisons were made and conclusions about shape and fixture of the implant plates were stated.

Abstract: Heavy industry, industrial plants and technology facilities use really big manufacturing units or assemblies with the weight of tens of tons. In case of rotary kilns, the weight can reach hundreds of tons. During the production process, those units move, creating, in addition to considerable static effects, big dynamic effects. Industrial facilities often face failures of the reinforced concrete foundation which is loaded dynamically by a rotating machine. Such failures typically result in cracks and failures of any of the foundation cross-section. Thus, a part of the foundation starts deviating, the rigidity goes down, geometry of the machine position is changing and an accident may occur - for instance, bearings may fail or malfunctions may occur in the machine. This has also happened in the case described in this article. The subject of the article is the large foundation structure of the rolling device in the Block Mill I in Třinecké železárny a.s. The slab of the foundation structure is approximately a T-shape, which has nearly 43 m in one direction and over 30 m in the other direction. The monolith foundation slab will be 2.0 m thick, the whole foundation structure will be 2.0 - 8.0 m thick. With such an extensive foundation, considerable attention must be paid not only to the design and realization, but also to the effect of the hydration heat.

Abstract: The paper presents the development results of "smart" pressure-sensitive fibre-cement compositematerials as well as thin-film coating sensors designed to detect disruptions of the base materialstructure. Basic material characteristics of fine-grained and coarse-grained cement matrices wereacquired during the research. The benefits and influence of conductive inorganic components,metallic components in the form of iron fillings and steel wires, and last but not least carbon-basednon-metallic fibrous reinforcement, have been verified. Thin-film epoxy resin coatings were enrichedwith amorphous carbon black, multi-walled carbon nanotubes (MWCNT) and natural micronizedgraphite. The article closely describes the measurement of electrical and electro-mechanical(piezoresistive) properties of conductive fibre-cement composites and thin-film organic coatings in anon-loaded state, during static loading and especially during dynamic ballistic and shock tests on thefall tower. Specific electrical characteristics and the course of change in electric conductivity wasexpressed as electrical resistivity (the real component of the impedance).The performed experiments confirmed excellent electrical conductivity of dense steel-fibrereinforced composites and graphite-doped hybrid fibre reinforced concrete. The coatings showedsignificant and permanent changes in impedance in the order of tens of ohms. The newly developedfibre composites and coating layers change the impedance during destructive and non-destructivedynamic loading tests. The impedance changed not only during failure of the matrix, but also in thecase of indirect impact. Moreover, carbon reinforced concrete with incorporated graphite showedsome piezoresistive properties. These detection materials were intended to be part of a ballistic-resistant monitoring system.

Abstract: An efficient implementation of lightweight design is the use of continuous carbon fiber reinforced plastics (CFRP) due to their outstanding specific mechanical properties. Embedded metal elements, so-called inserts, can be used to join metal-based attachments to structural CFRP parts in the context of multi-material design. They differ from other mechanical fasteners and have distinctive benefits. In particular, drilling of the components to be joined can be avoided and, depending on the preforming, fiber continuity can be maintained using such elements. Thus, no local bearing stress is anticipated. Previous work published by the authors [1] dealt with a systematic research of the influence of different types of stresses on the load bearing capacity of welded inserts. This contribution aims at the investigation of the performance of shape-optimized inserts under the same types of loading to compare with the results of the welded inserts serving as a reference. For that purpose, the respective load bearing capacities were evaluated after preinduced damages from impact tests and thermal cycling. In addition, dynamic high-speed tensile tests (pull-out) were conducted under different loading velocities. It is shown that the load bearing capacities increased up to 19% for high velocities (250 mm/s) in comparison to quasi-static loading conditions (1.5 mm/min) showing an obvious strain rate dependency of the CFRP. Quasi-static residual strength measurements under tensile loading identified the influence of the respective preinduced damages of the insert. Influence of the thermal loading condition was evaluated by placing the specimens in a climate chamber and exposing it to various numbers of temperature cycles from-40 °C to +80 °C with a duration time of 1.5 hours each. Here, it turned out that already 10 temperature cycles decreased the quasi-static load bearing capacity up to 31%. According to DIN EN 6038 the specimens were loaded with different impact energies and the residual strength were measured carrying out pull-out tests. It could be shown that the damage tolerance is significantly lower for the shape-optimized insert due to failure-critical delamination. The optimized insert also endured lower impact energies and the influence on the performance was higher.

Abstract: Stable osseointegration between implant threads and the surrounding marginal bone provides the mechanical base of an implant for daily chewing activity. The contact area of implant-bone interfaces and the concentrated stresses on the marginal bones are principal concerns of implant designers. In this work we numerically analyze by the finite element method the distribution of the equivalent stress and their level in the bone the most fragile element of the dental prosthesis. Each set of the model contained a crown, framework, abutment, implant and bone, subjected to variable dynamic loading according to time.

Abstract: A variety of micro forming processes has been invented, and the size effects have become a research hotspot at home and abroad. Micro bending molds with different feature sizes were designed. Quasi-static tester loading and dynamic laser shock loading with soft punch for micro bending forming was studied by numerical simulation respectively based on ANSYS implicit analysis and LS-DYNA explicit analysis. The constitutive models of workpiece are bilinear kinematic hardening model and Johnson-cook model respectively. The effects of different loading conditions and feature sizes of the die on the forming depth, equivalent plastic strain and equivalent plastic strain rate were studied. The results of numerical simulation show that, with the increasing of feature size of the mold, the forming depth under two kinds of loading conditions shows a tendency to increase. In dynamic laser shock loading, the equivalent plastic strain and equivalent plastic strain rate of the key position of the bent part would decrease with the increasing of the feature size of the die. While in quasi-static loading, the opposite law is shown. The research shows that, the flexible micro-bending processes with different loading models showed similar size effect. However, compared with quasi-static loading, in dynamic loading, the strain of forming parts is more centralized, and there is a high strain rate and better formability of the workpiece.