Currently the fire protection problems for structural elements, is usually solved by means of the... more Currently the fire protection problems for structural elements, is usually solved by means of the prototype-model correlations, established by means of dimensional methods. The authors, based on a reliable state-of-art analysis, established the advantages and limits of the presently-used dimensional methods. Finally, they state that these methods have several serious shortcomings, which entirely disappear by applying the "Modern Dimensional Analysis (MDA)", conceived by Szirtes [65] [66]. The authors have used MDA since 2000, in solving several engineering problems; for instance, heat transfer modelling along steel structural elements, unprotected-, as well as protected, against the fire. They briefly describe both the obtained Model Laws and their experimental validation, based on an original electric-heated test bench. In this paper, we offer the numerical simulation (with Finite Elements Method, FEM) of the experimental-obtained thermal fields for a real structural element, as well as for its reduced scale models. The obtained simulation results are in good agreement with the experimental data and consequently, the proposed numerical model is valid.
The paper aims to determine the longitudinal Young's modulus of early-and latewood, by conducting... more The paper aims to determine the longitudinal Young's modulus of early-and latewood, by conducting global measurements for the entire wood specimen. In order to accomplish this least squares method is used as mathematical instrument, together with a global elasticity modulus investigation experimental method-where, according to the authors, there are two methods which can successfully be used in order to solve the problem: one using a tensile-compression testing machine, foreseen with the very expensive video-extensometers, and the other using Video Image Correlation method on a classical tensile-compression testing machine without any supplementary devices.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The modern steel structures use mostly the intumescent paintprotection against the fire. One of t... more The modern steel structures use mostly the intumescent paintprotection against the fire. One of the main problems of these protective paints consists of the layer's thickness in order to optimize both the fire protection's problem and the costs of this protection's procedure. The authors offer some preliminary experimental results on intumescent paints layer's thickness optimization in order to assure as soon as possible the same heat transfer-gradient and also the same strength of the joint's members material.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Possible causes of microleakage and microfractures of dental fillings are often in the center of ... more Possible causes of microleakage and microfractures of dental fillings are often in the center of many academic research and investigations. Some authors found that one important cause of microleakage is the contraction/ shrinkage of the filling materials during polymerization. The purpose of this study is to demonstrate that microcracks and consequent microleakage is influenced by mechanical stresses occurring inside of dental filling materials and at the interface of the dental cavities and dental filling materials. We also tried to evaluate the deformation of some dental filling material types during mechanical loading. Cylindrical specimens were made of different types of dental filling materials, namely microhybrid composites and glass ionomer cement. Some extracted teeth were prepared with class II cavities, and filled. The lateral swelling of the tested specimens and the deformation of the filled teeth during vertical axial loading was measured with an optical method, ESPI/ Shearography.Of the tested specimen, the least deformable dental filling materials were the composite materials. During occlusal vertical loading of the filled teeth, there were found that mechanical stresses were different inside of the filling material than inside of the walls of the dental tissues, mechanical stressed being concentrated at the restoration interface. The ESPI/Shearography meth ode proved to be very useful for investigation in this field. Due to mechanical stresses accumulating at the interface of the dental filling material and the walls of the dental cavity, it is possible that later microcracks to appear due to masticatory forces.
The authors conceived and reaHzed an original testing <levice destined to anaiyze the elastic ele... more The authors conceived and reaHzed an original testing <levice destined to anaiyze the elastic elements from a special (patented) coupling system. This coupling system allows the changing of the deteriorated elastic elements without taking to pieces of the whole coupling syslem. The analyzed elastic elements are paralelipiped shape rubber, respectively Polyurethane part. These elements' elastic properties determine the whole coupling syslem's behaviors. The original testing <levice main components are an electric strain gage transducer for force (load) evaluation, respectively a number of elastic steel lamellas, foreseen with electric strain gages, for displacement evaluation.
In literature, one can usually find experimental investigations into global mechanical behaviour ... more In literature, one can usually find experimental investigations into global mechanical behaviour of soft-wood specimens, but properties of their individual components, (namely the properties of the late-wood and the early-wood parts) are rarely presented. Therefore, information on the moisture content and on the density is presented here. In fact, the ratio of the early-and late-wood parts in the cross-sectional area represents a significant influential factor, especially in the case of soft-wood components. Based on previous experimental data bases, the authors offer an original and simple analytical method for establishing Poisson's ratios for new, untested soft-wood specimens.
Background: Dental implants are useful tools and represent a widely spread technique for oral reh... more Background: Dental implants are useful tools and represent a widely spread technique for oral rehabilitation. Their long standingness is highly influenced by the mechanical and geometrical properties of the surrounding osseous tissue in which they are placed. In some unsuccessful cases though, the dental implant is exposed to masticatory forces and other functional acts, and osseous tissue may resorb near its vicinity, leading to the dental implants loss. We investigated the strain distribution inside the fixating substrate, given certain stages of its deterioration near the dental implants. Material and methods: For our investigations we used cilindro-conical screw-type dental which were submitted to vertical forces between 0-1000 N. The dental implants were fixed inside a plastic material used in photo-elastic measurements. To evaluate the strain distribution inside the fixing substrate, we used a non-contact, experimental investigation tool, the Video Image Correlation (VIC-3D) optical system. This system allows the implementation in the dental implants optimisation from stress-strain state point of view. Results: The strain field distribution inside the fixating substrate was measured at three different levels of the dental implant, when it was loaded alone and in the case when there were loaded two dental implants simultaneously. Conclusions: The most stresses are concentrated in the neck-area of the dental implant. If there are loaded two or more dental implants simultaneously, the distance between them influences strain distribution. The measurements were conducted in vitro and do not represent the in vivo conditions, but serve further important facts regarding biomechanical properties of dental implants.
It is a well-known fact that in the field of modern manufacturing processes, additive manufacturi... more It is a well-known fact that in the field of modern manufacturing processes, additive manufacturing (AM) offers unexpected opportunities for creativity and rapid development. Compared with classical manufacturing technologies, AM offers the advantages of reducing weight and improving performance and offers excellent design capabilities for prototyping and rapid sample manufacture. To achieve its full potential regarding cost, durability, material consumption, and rigidity, as well as maintaining competitiveness, there are several research directions that have not been explored. One less frequently explored direction is the involvement of dimensional methods in obtaining an optimal and competitive final product. In this review, we intend to discuss the ways in which dimensional methods, such as geometric analogy, similarity theory, and dimensional analysis, are involved in addressing the problems of AM. To the best of our knowledge, it appears that this field of engineering has not f...
Environment Protection Using Vibration Diagnosis of Machines and Equipments
The noise pollution's reduction represents one of the most serious criteria for the modern ma... more The noise pollution's reduction represents one of the most serious criteria for the modern machines and industrial equipment. To prevent the noise pollution it is absolutely indispensable (essential) the periodical evaluation of the noise level of the different moving machine parts. In this respect, several companies developed efficient ways to prevent the noise pollution, but most of them are quite expensive. So, for small and medium industrial unit there are one other way to reduce the noise pollution: to use some relative cheep equipment, which can be used by medium qualified persons for periodical evaluation of the noise level.. The authors present some results obtained with these relative cheep and useful equipment made by SKF Company, to prove the usefulness of these equipment.
Innovative Solutions for Portable Wind Turbines, Used on Ships
The properties of a composite material are determined by the properties of the constitutive mater... more The properties of a composite material are determined by the properties of the constitutive materials. In engineering practice, there are many situations in which we have composite material, but we do not have information about the properties of each phase component. The measurements we can make in such cases are on the existing material, thus being able to determine, experimentally, the global physical properties of the composite. The possibility of realizing an estimate of the mechanical properties of each component poses a problem if we start from these measurements. The paper proposes a method to achieve this, starting from the theoretical estimates established in the literature, then illustrated by an example to determine the properties of wood. Wood is a transverse isotropic material and therefore the constitutive law has symmetries that are manifested in the decrease of the number of parameters that define the stress-strain liason, defined only by five independent parameters....
The mechanical properties of the dental filling material (DFMs) strongly influence the lifetime a... more The mechanical properties of the dental filling material (DFMs) strongly influence the lifetime and durability of the tooth reparation performed. Among the most significant mechanical characteristics, one has to mention the Poisson’s ratio and the elastic modulus (Young’s modulus). They, during the cyclic mastication load, can prevent or aid in the prevention of secondary dental decays by provoking micro-cracks, the de-bonding of the filling material from the natural dental tissue, as well as fatigue at the level of their interface. The authors performed a scoping analysis of the nowadays-involved experimental methods, together with a critical review, putting in evidence of their advantages and limits. Based on the developments, they propose a new approach in this sense by involving the electronic speckle pattern interferometry (ESPI)/shearography high-accuracy optical method. They illustrate the advantages of this method in establishment of the elastic modulus, but they also propos...
In order to foresee the response during the fire of a real symmetrical structure (prototype), now... more In order to foresee the response during the fire of a real symmetrical structure (prototype), nowadays engineers apply methods which involve the associated reduced-scale model’s behaviors, mainly dimensional analysis behaviors. Between the dimensional analysis methods, the so-called Modern Dimensional Analysis (MDA), developed by Szirtes, fulfills all engineering requirements compared with the classical one. The authors used this new proposed method to describe their original electric fire simulation testing bench, as well as the Model Law (using MDA) for the heat transfer in tubular rectangular bars. So, a validation of the Model Law was performed based on several scrupulous experimental investigations both on a real column’s segment and its associated reduced-scale models manufactured at 1:2; 1:4, as well as 1:10 scales. The original heating system, the elaborated protocol, the deduced Model Law, and the results of the experimental investigations represent the contributions of the...
In this contribution, the authors continued their initial study on the efficiency of the analysis... more In this contribution, the authors continued their initial study on the efficiency of the analysis of experimentally obtained temperature curves, in order to determine some basic parameters that are as simple and reliable as possible, such as “m”, the heat transfer coefficient. After the brief review of the previous results, on which the present article is based, the authors offered a brief argumentation of the importance of dimensional methods, especially the one called modern dimensional analysis, in these theoretical-experimental investigations regarding the propagation of the thermal field of structural elements with solid sections, and especially with tubular-rectangular sections. It could be concluded that modern experimental investigations mostly follow the behavior of models attached to the initial structures, i.e., prototypes, because there are clear advantages in this process of forecasting the behavior of the prototype based on the measurement results obtained on the attac...
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