Papers by Keyword: Stamp

Abstract: The numerical method of stamp topological optimization taking into account fatigue strength is presented in the work. It is proposed to take into account the restrictions on the stress state in accordance with the curve of the dependence of the maximum stresses on the number of loading cycles in the ESO topological optimization method. An approach to the selection of the evolutionary coefficient with a step-by-step increase in the rejection coefficient is proposed when constructing an iterative scheme for the rejection of elements by the method of topological optimization. The calculation of the stamp optimal topology with a decrease in volume due to the removal and redistribution of material was carried out in the study. The new geometric model of the optimal topology stamp is based on the predicted distribution of elements with a minimum stress level. The verification calculation of the stress state of the stamp of optimal topology with an assessment of fatigue strength was carried out in the work. The numerical calculation was carried out using the finite element method in the Ansys software package. The minimized stamp volume decreased by 35% according to the calculation results. The results of the study can be further applied in the development of topological optimization methods and in the design of stamping tools of optimal topology.

Abstract: The paper presents the way the 3D scanning was used to correct miss-alignment of the tools on a metal sheet bending press. Parts obtained by bending where not conform to requirements, and the reason was unknown. In order to find the error, the shape, size, and alignment of bending board and stamp had to be checked. The particular very long tools imposed as the single appropriate method of measurement: 3D scanning. The point clouds gathered by 3D scanning were processed to get the 3D models of the tools. Analyzing the models of the tools and their relative position led to conclusions that revealed the error and allowed fixing the problem.

Abstract: The influence of forming condition on crash performance of thin-walled structures is investigated, in which high strength low alloy steel HSLA340 and dual phase steel DP590 are considered. Stamping and knife-edge-bending process were carried out respectively to form hat channels, and then, impact tests were performed on the spot-welded top-hat sections subjected to quasi-static and dynamic axial loading conditions to identify the forming effect on the crashworthiness. Regular progressive buckling (quasi-inextensional mode) was observed for knife-edge-bent specimens, while the stamped specimens showed peculiar collapse mode, especially, global instability existed for all the specimens under dynamic impacting and their energy absorption capacity was significantly reduced. The result demonstrates that for accurate assessing the structural performance detailed stamping history of sheet metal components should be taken into consideration.

Abstract: Brick used with stone in an alternate order -especially on monumental masonry buildings- is one of the basic construction materials in Ottoman classical architecture. Parallel to the announcement of Tanzimat Declaration (1839), to the political and economical relations improved with European states and to the Industrial Revolution in Europe, an effective change had been seen on design concept and construction techniques in Ottoman architecture. Many new buildings were built using modern materials and imported techniques such as solid brick (in western norms) masonry walls, steel beams at the horizontal and vertical bearers, cement and concrete. The product of modern solid bricks in western standards had been realized in Ottoman territories in the last quarter of 19th century. The base of this research is constituted on 334 imported and local product solid bricks which remain to Zihni Göğer’s (firstly documented for this research), to Uzay Yergün’s, to Aynur Çiftçi’s and to the Yıldız Techical University, Department of Architectural Conservation’s private collections. Most of the bricks are in a good condition, clean and have stamps. From the stamps one learns where they were produced, in which country or even city, the names of the plants, the logos and the dates of product. During the documentation every brick is numerated, photographed and a catalogue is prepared including the dimensions of the bricks. The demolotion of the buildings made of solid brick masonry walls-especially those which are not registered as an essential cultural asset- the interventions undertaken and the use of new materials during restoration of bearer walls have damaged the original bricks. Finally they were not conserved and documented. The aim of this paper is to determine the change of the production and the standarts of the bricks, to indicate their varieties, their fields of use and their conservation problems before and after the modernisation period of Ottoman architecture. It is intended to take into consideration the conservation and documentation of this material during renovations reflecting the original construction technique of the period that belongs to monumental and civil architecture.

Abstract: Nano-structured polymer stamps were prepared from porous anodic alumina templates. Prepolymers were poured onto the highly ordered porous anodic alumina templates, and they were cured by UV-irradiation. Simple separation of the elastic stamp from the nanoporous aluminum oxide leads to well replicated nano-stamps. The nanopatterns on the stamp were transferred as ultrahigh-density nanopore arrays on various substrates which are potentially applicable to the fabrication of ultrahigh-density metallic or semiconductor nanodot arrays for magnetic storage devices or display devices.

Abstract: Here a simple and direct method based on transfer printing has beep developed, in which rigid stamps transfer metal films deposited on the relief surface of the stamps onto patterned organic substrates. Ultra-precision machining technology is combined with conventional photolithography to fabricate patterned Si stamps and organic substrates by replica molding. Experiment results indicate that patterned metal films on Silicon stamps were successfully transferred onto PDMS substrates. Fabrication of patterned metal films on organic substrates by transfer printing may suit for fabricating sub-micrometer and nanometer scale features in a single process.

Abstract: The fabrication of nano-structured materials using nanoimprint lithography has become more prevalent in recent years, due to its cost effectiveness and readiness. However, One of the biggest drawback of this technique is the fabrication of the imprinting stamp, which is expensive and difficult to fabricate. This paper describes a method of replication original Si or quartz made imprinting template into a polymer stamp which has many advantages, such as the simplicity and low cost of the fabrication process and the flexibility of the resulting stamp. Using the hot embossing method, PVC based imprint stamp with sub 100nm patterns can be fabricated. Due to its high UV transmittance, reasonable mechanical hardness and low surface energy, PVC based nanosized template can be used as a stamp for UV-NIL and sub 100nm patterns were successfully transferred by the UV-NIL process with PVC based imprint stamp.