Papers by Keyword: Screw

Abstract: Today, an artificial tooth root called a dental implant is used to replace lost tooth function. Treatment with dental implants is considered an effective and safe method. However, in some cases, the use of dental implants had some failures. The success of dental implants is influenced by several biomechanical factors such as loading type, used material properties, shape and geometry of implants, quality and quantity of bone around implants, surgical method, lack of rapid and proper implant surface's integration with the jaw bone, etc. The main purpose of functional design is to investigate and control the stress distribution on dental implants to optimize their performance. Finite element analysis allows researchers to predict the stress distribution in the bone implant without the risk and cost of implant placement. In this study, the stresses created in the 3A.P.H.5 dental implant's titanium fixture and screw due to the change in abutment angles tolerance have been investigated. The results show that although the fixture and the screw's load and conditions are the same in different cases, the change of the abutment angle and the change in the stress amount also made a difference in the location of maximum stress. The 21-degree abutment puts the fixture in a more critical condition and increases the chance of early plasticization compared to other states. The results also showed that increasing the abutment angle to 24 degrees reduces the stress in the screw, but decreasing the angle to 21 degrees leads to increased screw stress and brings it closer to the fracture.

Abstract: Material used for screw production was investigated due to its inconvenient properties which caused the screw breaking on threads or in the head during the installation. Chemical composition of analyzed material corresponded with standard STN 17153 according to technological drawing for specific product. The metallographic analysis showed that failure of screws happened due to improper microstructure resulting from unsuitable thermal treatment of material. Fine inclusions based on aluminum nitride (AlN) and chromium carbonitride (Cr(C,N)) were segregated along the ferritic grain boundaries. Coarse aluminum nitride inclusions (AlN) in ferritic matrix affected the character of present fracture surface characterized by cleavage facettes. The fracture was propagated step by step following the planes with the increased concentration of inclusions across the whole cross-section of the screw.

Abstract: This paper compares the stress and strain behaviour of mechanical fasteners and elastic adhesive connections in timber façade applications. Two common designs with timber cladding are introduced. The traditional façade planks and multilayer large-format solid wood panels were selected. The resistance of a reference façade section with mechanical fasteners or adhesive bond to wind suction is determined according to the recommendations of European guideline ETAG 034. The pressure/suction chamber allowing hermetic closure was used. The sample deformation was measured at 15 locations, this also allowed to determine the elongation of the adhesive layer at break. The failure loads reached with the adhesive joint exceeded 20 kN/m² in both combinations of façade cladding. On the other hand, the sample with a large-format panel and mechanical fasteners showed the lowest failure load at 12 kN/m². The results confirmed that bonded joints are a suitable solution for large-format cladding, whereas an increase in the number of mechanical fasteners will be a more convenient solution for façade plank applications.

Abstract: Magnesium alloys have shown potential as biodegradable metallic materials for oral and maxillofacial surgery applications due to their degradability. Biodegradable magnesium are advantageous over existing biodegradable materials such as polymers, ceramics and bioactive glasses in load-bearing applications where sufficient strength and Young’s modulus close to that of the bone are required.

Abstract: The research deals with determination of the breaking cause of the screws used to attach the truck cabins. Scanning electron and light optical microscopy were used for engineering investigation of the fracture cause. Fractographical and structural analysis revealed fatigue mechanism of the screw fracture with morphology corresponding to the combination of tensile and bending stresses. Based on the acquired results a structural adjustment was recommended to the customer.

Abstract: This paper (Part 2 of 2) presents a study of the structural behavior of tension-loaded screws installed in screw chases in extruded aluminum profiles. This connection is commonly used to resist outward wind load on glass in curtainwalls and skylights. See Part 1 for details of the pull-out testing. Two types of chase, each with 1/4 in. (6.35 mm) diameter stainless steel screws were used: a flat chase with AB tapping screws (1/4-14; 14 threads per 25.4 mm) and F tapping screws (1/4-20; 20 threads per 25.4 mm), and a longitudinally ribbed chase with UNC-thread machine screws (1/4-20). The extrusions included six cross-section shapes (three with flat chases and three with ribbed chases) and three alloy-tempers.

Abstract: This paper presents test results and a proposed pull-out strength equation for tension-loaded screws installed in chases in extruded aluminum profiles. The screws are perpendicular to the extrusion's length. This connection is commonly used to resist outward wind load on glass in curtain walls and skylights. Two types of chase, each with 1/4 in. (6.35 mm) diameter 300 series stainless steel screws were used: a flat chase with AB tapping screws (1/4-14; 14 threads per 25.4 mm) and F tapping screws (1/4-20; 20 threads per 25.4 mm), and a longitudinally ribbed chase with UNC-thread machine screws (1/4-20). The extrusions included six cross-section shapes (three with flat chases and three with ribbed chases) and three alloy-tempers. Pull-out tests of 150 single screws were conducted. The Aluminum Design Manual [1] does not include pull-out strength equations for screws in chases; this research was intended to develop such equations. Pull-out strength increased with an increase in engaged length of screw threads with the chase. The shape and dimensions of the chase also affected the pull-out strength.

Abstract: Anterior cruciate ligament (ACL) reconstruction technique was under tremendous improvement during last 10 years; anatomical versus transtibial technique gradually increased, with soft tissue graft overcoming bone-tendon-bone, and biodegradable exceeding metallic implants. Still, complications related to ACL reconstruction are reported; one of it is pretibial cyst formation. Pretibial cyst formation is reported to develop between 2 and 5 years post-operation. We report a case in which the cyst was developed at 2 years after surgery; a biocomposite screw was used for fixation on tibial site, in an ACL reconstruction done with soft tissue autograft. The MRI examination suggested the diagnostic, which was confirmed by histological examination of the cyst. The screw suffered multiple fragmentation; the remnants were retrieved and analyzed. The knee stability was not affected by the cyst development. After retrieval of the screw and appropriate rehabilitation, the patient recovery was complete. The presented case confirms that even biocomposite screw may be related to these sorts of complications, mainly related to plain biodegradable screws. The case offers a point of start for analysis of the literature. A precise ethology of this kind of complications is still unknown; a lot of theories have been developed, two of them seem to be related to our case. Technical improvement together with long time surveillance of cases in which biocomposite implants were used may improve our knowledge concerning the fate of these implants.

Abstract: This work is devoted to the development of design methods for flexible rotor lines that will combine several large-scale productions of products of different sizes in the mass diversified flow of goods by processing several sizes of goods in each group tool module. Performed work provides an opportunity to increase productivity of flexible rotor lines in 3-4 times by increasing the number of goods in 2-8 times by processing several sizes of products in each group tool module. The developed design methods for flexible rotary machines and group tool modules allows you to create high-performance systems based on combining a group-volume production of products of several sizes in the mass diversified flow of goods. Organizational and technological bases of flexible rotary machines creation are first developed in this paper. Every tool module handles multiple sizes products in these new machines. New links have been established between the structural elements of flexible rotary line with the group tool module and a combination of flow characteristics. That allows us to determine the structure of the flow of goods by combining several large-scale productions of products of several sizes in the mass diversified flow of goods.

Abstract: We examine the method to determinate the kinematic characteristics of the RSM, Classification of mechanisms of this class to convert rotational motion into linear motion is introduced. At the same time, we have developed some formulas to determinate the kinematic transfer functions of the RSM of different types depending on the geometrical parameters of this kind of screw mechanism.