Papers by Keyword: Fracture Strength

Abstract: The paper presents some general aspects of adhesives used in the automotive industry, the method used to determine mechanical properties, and the advantages compared to the traditional technology used. Adhesives are substances capable of permanently bonding to surfaces by an adhesive process. This process implies that two different bodies are in contact so that the mechanical forces or work can be transferred across the interface region. Since their discovery, researchers have made great efforts to obtain more ecological and high-performance adhesives. Substances such as bitumen or beeswax have been replaced by synthetic types of adhesives. Today, adhesives have two purposes: to join two different bodies, in creating a permanent assembly, and to seal. In this paper, the type of adhesive used to fix the windshield directly to the car body which is made of metal is presented. Compared to traditional technology that involves a rubber gasket attached to the body of the car and the windshield that is fixed on it, adhesives have the role of sealing and bonding directly to the metal surface. The first part of the paper focuses on the determination of the mechanical properties of adhesives used in the automotive industry. The next step was to realize the bonding between glass and steel using windshield adhesive with different drying times.

Abstract: As the ceramic substrate materials in automobile oxygen sensor, 5YSZ/Al₂O₃ matrix composite ceramic with different amount of silica are prepared by ball-milling,tape casting and sintering.They are investigated for their microstructure and mechanical properties.The microstructure of the sample is analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX).Fracture strength is measured by ring-on-ring method. It is found that adding 1 wt.% SiO₂ into 5YSZ/Al₂O₃ matrix can improve the strength of composite ceramics.

Abstract: A newly developed process chain enables the production of active structural components. Thereby lead zirconate titanate (PZT) fibres are integrated in metal sheets by joining by forming. For the further development of the process chain to a high volume production the fracture strength of PZT should be increased. This paper pursues the approach to increase the strength by selected electrode layers. For this purpose, various electrode layers are tested on PZT plates in strength tests with the ball on three balls test (B3B-test). The evaluation of the recorded values is carried out according to statistically methods. The results show that the strength of PZT can be increased by electrode layers up to 30%. In addition, it was established that a high tensile strength and a high Young’s modulus of the electrode layers do not have a positive effect on the strength of PZT.

Abstract: To explore the effect of thickness on the fracture strength and failure modes of zirconia crowns, four crown models with different thickness (1.2 mm, 1.0 mm, 0.8 mm, 0.6 mm) with the same shape were designed by Dental Designer software in CAD/CAM system. They were manufactured to 40 zirconia crowns by CAM carving machine. The fracture strength and the failure modes of each crown was measured, while porcelain fused to metal (PFM) crowns as control. The average fracture strength of different zirconia crowns were recorded as below: 1308.38 ± 111.38 N (Group 0.6 mm), 1841.60 ± 68.21 N (Group 0.8 mm), 2429.88 ± 315.03 N (Group 1.0 mm), 3068.31 ± 233.88 N (Group 1.2 mm). There was no significant difference between Group 1.0 mm and Group 1.2 mm (P > 0.05), and statistical significance was obtained among every other two groups (P < 0.05). The failure modes of different thickness zirconium crowns are similar. There are more broken pieces from thicker crowns compared to thinner ones. It is concluded that the thickness can influence the fracture strength of zirconia crown. With the increase of the thickness, the fracture strength of the zirconium crowns also increases. We recommend zirconia crowns thicker than or at least 1.0 mm in dental practice.

Abstract: In this paper we propose novel techniques of ceramic shell mold production with lost-wax method of cast as well as technological methods aimed at fracture strength improvement. The distinguishing characteristic of application of these molds is the possibility to use them without buckling agent resulting in decrease of prime cost in casting.

Abstract: Development of Fe-based bulk metallic glasses (BMG) with good mechanical and soft magnetic properties has become a major objective in the materials science field. Bulk metallic glasses present an interesting combination of properties. They exhibit very high strength (both in tension and compression), large elastic elongation limit, high hardness, excellent corrosion resistance, and good soft magnetic properties. These properties makes them suitable for many applications like high resistant control cables, pressure vessels, micro-components, pressure sensors, microgears for motors, magnetic cores for power supplies and hard fibers in composite materials. Multi-component Fe₆₀Co₁₄Ga₂P₁₀B₅Si₃Al₃C₃ bulk metallic glass was synthesized in rod form with a diameter of 1 mm by copper mould casting technique using raw industrial materials. The obtained alloy was analyzed by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM) techniques, in order to determine the phase constituent, the thermal stability and the fracture surfaces of as-cast samples. The mechanical behaviour was investigated by microhardness and compression tests. The values recorded for hardness and fracture strength includes this alloy in the category of high resistant materials.

Abstract: The tensile and fracture strength of a medium carbon steel containing 0.2wt%C were determined after austenitisation at 1100^oC for 1 h and subsequent isothermal transformation at 700^oC for 0.5, 2, 6 and 8 h. Only the specimens transformed for 0.5 and 2 h contained martensite and these were l5.67 and 7.20%, respectively. The maximum measured tensile and fracture strength were 91l and 852 MPa, respectively and these were obtained in the specimens with the most martensite (0.5 h). Although after austenitisation and subsequent isothermal transformation there was a loss in ductility, this was accompanied by a very significant improvement in tensile and fracture strength.

Abstract: Total dentures are made of acrylic resins and artificial teeth. Among the prevalent fracture types of the dentures, 29% was a mid-line fracture, in which 68% were observed in maxillary complete dentures and 28% in mandibular complete dentures. Due to the large number of failures recorded on the maxillary dentures, several studies were conducted to establish the causes that produce these failures but also to find solutions for their prevention. One source of information about the strength of a maxillary denture under the applied load, is represented by the establishment of the stress and strain state during the loading. Different methods have been used for investigating the strain or stress distribution during deformation of dentures. The purpose of this paper is to evaluate the stress and strain state of a maxillary denture loaded in compression until the final fracture. For this study, electrical resistance strain gage were used for evaluation the strain and stress distribution in the maxillary denture made of different acrylic resins. Based on observations from practice, the strain gages were applied on the middle line of the denture at the base of the incisors and respectively on the sides of the denture, under molars. The dentures were loaded until failure and were registered the strains in the located strain gages. Also, for each type of acrylic resin were determined separately the mechanical properties of elasticity and strength. Based on the tests conducted were determined the critical stress and strain in the areas of interest. In all the tests carried out the fracture occurred in the median area of the denture and the crack was initiated between the incisor teeth. The stress and strain field associated with the crack initiation mode showed a strong influence of geometry on the fracture strength of denture. Also the type of acrylic resin has a significant effect on the fracture strength of complete denture either by strength capacity but especially by their ability to elasticity. Based on this analysis have been established new criteria for selection of acrylic resins, not only for aesthetic reasons but also for elasticity and strength reasons.

Abstract: During the last period the interest on the sandwich structures has became more favorable due to the strength to weight ratio. In the same manner, in ship building field the lightweight structures became more and more attractive. With increasing the usage fields has increased the need to study the behavior of these structures. In general all the sandwich structures loaded in bending shows an effect of the secondary bending moment. In the case of web core sandwich panels used in ship structures has been observed a pronounced effect of the secondary bending moment on laser welded joints. Considering this, the paper presents an analysis of the fracture strength of laser welded joints of a web core sandwich structure, due to the effect of secondary bending moment. In the first part, the paper analytical formulation of the secondary bending moments and their effect on welded joints. This effect is explained on the basis of angle α defined in the paper and which depends on the thickness of the face plate, the thickness of the web plate and respectively the height. The paper continues with a numerical analysis of the stress and strain state from a web core sandwich beam and where also it is analyzed the effect of the secondary bending moment on the fracture strength of laser welded joints. Based on the carried out study it was observed that for high thickness of the web plate the effect of secondary bending moments is the overloading of the welded joints, instead for small thickness of the web plate the effect of the secondary bending moments can be of the unloading the welded joints. However, a small thickness of the web plate can affect the rigidity of the structure. Therefore, based on this study was proposed a solution to reduce the secondary bending moment without reducing the stiffness of the sandwich panel. The analysis conducted in this paper can be a design criterion for the web core sandwich structures.

Abstract: The effects of different concentrations of the mixed solution, different test temperature conditions for corrosion rate of 316L stainless steel wires by using the weight loss method, discussion on fracture strength of 316L stainless steel wires changes after corrosion. The results showed that the higher the concentrations of the mixed solution, test temperature, the larger corrosion rate of 316L stainless steel wires, the smaller fracture strength of 316L stainless steel wires. During the test, the surface of 316L stainless steel wires occurred passivation. Though Cl^- of the mixed solution didnt take direct part in the reaction, it prompted passive film rupture, accelerated the corrosion rate of 316L stainless steel wires. Meanwhile, the stress-strain curve of 316L stainless steel wires after corrosion no obvious yield phenomenon, showing the form of brittle fracture. And test temperature factors on the corrosion rate of 316L stainless steel wires and mechanical properties of the most obvious effect.