Papers by Keyword: Force

Abstract: Provided here is a mathematical model of the operation of backward extrusion in the mode of short-time creeping of thick-walled pipe blanks made out of orthotropic material with cylindrical anisotropy of the mechanical properties. Carried out was theoretical research of the operation of isothermal axisymmetric backward extrusion of thick-walled pipe blanks made out of anisotropic materials by conic point-tool in the mode of short-time creeping. Established were regularities regarding the change of material flow kinematics, regarding the stressed and strained condition of the blank, regarding force modes and limit possibilities of deformation depending on the technological parameters, on friction conditions on the contact surfaces of the operating tools and of the blank, regarding the geometrical dimensions of the blank and of the manufactured part, and of the anisotropy of the mechanical properties of the blank material, that on the basis of the developed mathematical model of isothermal non-radial flow of anisotropic material under conditions of axisymmetric stressed and strained conditions in the mode of short-time creeping. Experimental operations were carried out for isothermal backward extrusion of thick-walled pipe blanks made out of АМг6 aluminum and ВТ6С titanium alloys. Comparing the results of theoretical and experimental data for force modes of the operation of isothermal backward extrusion of thick-walled pipe blanks points to their satisfactory similarity (difference not exceeding 5% - 10%).

Abstract: An investigation was undertaken to explore the grinding characteristics in grinding of yttrium vanadata (YVO4) crystal by using a resin diamond wheel. The grinding forces and surface roughness were measured and the morphological features of ground workpiece surfaces were examined. The results indicate that the depth of cut is the leading factor in affecting grinding forces whereas the surface roughness is mainly governed by the grinding speed. The material removal mechanism was found to be dominated by brittle fracture mode at conventional grinding speeds, and gradually transfer to ductile flow mode under higher grinding speeds, which is greatly related to the maximum undeformed chip thickness.

Abstract: Oral adjusting of ceramic prostheses involving abrasive machining using dental high-speed rotary cutting instruments is a central process in restorative dentistry, because this process affects not only restorative quality but also patients’ comfort. However, the dental grinding process, especially dental grinding of high-strength ceramic prostheses, is less understood in clinical dentistry. This paper presents dental grinding of an innovative high-strength lithium disilicate ceramic in in vitro oral adjusting regime using a dental high-speed electric handpiece and diamond burs. The dental abrasive machining characteristics were quantitatively evaluated in terms of normal and tangential forces, force ratio, and specific grinding energy as functions of clinically relevant dental grinding variables including depth of cut and feed rate and feed direction of burs. The results showed that the dental tangential and normal forces and specific grinding energy exhibited significant dependences on depth of cut, feed rate and direction of burs, but revealed significantly small scales compared to engineering machining regime. Clinical implication was given that down grinding undoubtedly reduced the abrasive adjusting forces to relieve patients’ discomfort in oral regime. Moreover, dentists must be cautious in dental abrasive adjusting of the lithium disilicate ceramic prostheses at or beyond the specific material removal rate of 2.4 mm³/min due to significantly large forces and vibrations.

Abstract: In recent development of dental restoration, zirconia has been used as a prosthetic material due to their enhanced properties of fracture strength and toughness compared to other ceramic materials. Zirconia based ceramic materials are used in structural application in engineering, such as in the manufacture of cutting tools, gas sensors, refractories. Grinding was used as the efficient technique to finish ceramic materials. Due to the hard and brittle nature of a ceramic material, the grounded components were left with surface and subsurface damages. In this paper, the influence of the grinding parameters on the grindability of yttrium partially stabilized zirconia was carried out using a diamond grinding wheel. The resin bonded grinding wheel was used to analyze the grinding behavior of the material. The grinding force and surface roughness were measured during the grinding process and the experiments were conducted under conventional flooded conditions. The relationship between the surface finish and grinding parameters such as depth of cut, wheel speed were analyzed.

Abstract: Towbars are the main component of the assembly connection between the vehicle and the trailer. With proper use, recommended by the towbars producer, and the correct calculation and design by the manufacturer in accordance with international law, they ensure road safety.The main role of the towbars is to maintain in maximum safety conditions, the link between towing vehicle and various aggregates, namely trailers.

Abstract: The paper interprets the calculation of the size of force effects created by the reason of the effect of balled conveyor belt of pipe conveyor to the guide rollers located in the ring idler stations. Knowing them is essential for the research of dynamic resistances by pipe conveyors operations. Examined force effects were determined by the help of finite element methods. The calculation was performed by the program Abaqus. Presented calculation is realized by original calculation model. The results of the calculation present information about action of the effect force of the balled conveyor belt to the guide rolls in the ring idler station. Results became a basis for determination of postulates for identification of dynamic resistances. Their knowledge is the key element for conveyor belts lifetime increase.

Abstract: This paper proposes one of the possible techniques for interacting for shape memory alloy (SMA) actuator based tactile display, which can act as demonstrator devices. This work is focused on developing a model of a pair of antagonistic high strain SMA tension actuators with independent control of force and displacement. The technology employed utilizes two Flexinol 100 micron heat actuated wires of Titanium-Nickel (NiTi) shape-memory alloy which contract when heated under pre-stress and produces up to 5% strain recovery. This phenomenon, which provides a unique mechanism for actuation, is associated with the unique interaction between the martensite and austenite crystal structures of the SMA. Physical measurements of the behaviour of the actuator elements were performed using a laser displacement sensor to verify the fidelity of response to software commands, and to measure step response to pulse-width modulated (PWM) current control at different frequencies and duty cycles. Results yielded high accuracy across a wide range of frequencies and duty cycles, proving the SMA actuation technique has potential to present and convey useful tactile information of surface deformation for virtual environment applications.

Abstract: Continually increasing exhaust emission standards for automobiles and an increasing environmental awareness push design engineers to develop new constructive and material concepts. So-called sandwich panels, consisting of stiff facings and light-weight cores, offer the possibility to combine properties of different materials synergistically. When processing large quantities, as is the case in the automotive industry commonly used manufacturing processes for cutting sandwich panels, like sawing or milling, are not applicable. A common manufacturing process to cut metal sheets in high quantities is shear cutting. However, pre-trials of shear cutting of sandwich panels have shown that it is not possible to achieve flawless cutting surfaces with current process layouts. Characteristic types of failure like high bending of the facings, delamination effects, burr formation and an undefined cracking of the core material were ascertained. Thus, in this study, the influence of cutting parameters, such as the clearance and the punch diameter, on these types of failure is examined. Five different clearances between 0.025 mm and 0.4 mm with two punch diameters, 8 mm and 32 mm, were investigated. In order to compare the influence of different materials, three commercially available sandwich panels were studied. The chosen sandwich panels differ both in the face sheet thickness and the core material. Finally, the shear cutting force is measured to identify a possible correlation between the cutting force and the face bending. As a result, optimal clearances to minimize the face bending are derived. Additionally, the influence of the core stiffness on the cutting force is determined.

Abstract: The metal-forming processes provide a high degree of material utilization, a high working capacity, a high quality of the parts and so on. Taking in account the characteristics of these processes and the current requirements of the market economy, it is necessary to extend the research in the metal-forming field in order to develop new solutions that lead to optimization of the metal-forming technologies and, implicit, to obtain the best quality-price ratio. Also, the software for the simulation, data acquisition, data processing and computer aided design are necessary. This paper presents an application developed ​​using a graphical programming language called LabVIEW, through which, the dimensions of the sheet blank for the flanged parts are calculated based on the specifications of the work drawing, checks the hole flangeability and calculates the force required by the metal-forming processes.

Abstract: This study investigates the influences of driven rotary tool (DRT) on temperatures and forces when turning AISI 1045 steel. A set of cutting conditions was used in FE simulations to predict cutting force, stresses and temperatures developed at around the edge of tool. The material cutting speed ranges were set between 20 and 250 m min^-1. The rotary tool speed were 0 and 100 rpm.^. The feed rate and the depth of cut were set constant. Simulation results provided the predicted cutting distribution of temperatures and stresses at the chip and work piece.