Clamping Frame Research Articles

Setting Residual Stresses in Tensile Stress-Superposed Incremental Sheet Forming

Incremental sheet metal sheet forming (ISF) is a flexible forming process to manufacture sheet metal parts. ISF processes allow a control of residual stresses depending on the process parameters and the acting forming mechanisms. These forming-induced residual stresses highly influence the product properties. This paper presents numerical and experimental results demonstrating the influence of biaxial tensile stress-superposed incremental forming (TSSIF) on the residual stress of truncated cones. An adjustable clamping frame is used to apply defined tensile stresses over the sheet plane in biaxial direction during forming. Residual stresses are evaluated by means of x-ray diffraction on both sides of the cone wall. Tensile stress-superposition shifts the residual stress amplitudes to the tensile residual stress region, depending on the amount of initial tensile stress. TSSIF can be used to improve the product properties of compressive stress-imposed components.

Дослідження напруженого стану багатоцільового змінного бульдозерно-захватного робочого обладнання

The article is devoted to the development and presentation of the design of changeable, bulldozer-gripping, multi-purpose work equipment for the mobile hinge-united wheeled chassis of high passability, modeling the load on work equipment within the software "SolidWorks" to optimize process or to check geometric and weight parameters in order to justify the material for long-term resistance. The changeable working equipment on the basis of the mobile hinge-united wheeled chassis of high passability, namely the bulldozer dump in combination with the gripping device for performance of a wide range of working operations is presented. Changeable work equipment provides: - development and movement of soils of I-III categories at a distance of up to 100 m, digging up and backfilling of trenches and ditches; - forming of embankments, cutting of terraces, performance of planning, cleaning and preparatory works by the main dump; - capture, fixing and transportation of goods; - loosening of soils of IV-V categories; - uprooting of stumps; - extraction and movement of boulders; - installation and dismantling of vertical elements (racks, pillars), horizontal long elements (curb, paving slabs, pipeline elements,…). Also the study of the stress state of the most responsible elements of the working equipment was carried out in the software environment "SolidWorks" within the existing loads and the accepted material for their manufacture. The number of load cycles before the loss of these elements of long-term resistance beyond the yield strength of the material was determined. The conducted researches allowed to establish: - when modeling the stress state of the element of working equipment (clamping frame) in the environment "SolidWorks" at static load within 710 kN, the clamping frame material and its design withstand working loads according to all criteria of the program "SolidWorks": fatiguing destruction, loss of stability, margin of strength, deformation and displacement that occur under load. The load acting on this element in the process of work was determined using the formed calculation schemes and standard methods; - the design of the clamping frame made of steel 10HSND withstands without signs of destruction of about 1,000,000 load cycles. A further increase in the number of load cycles leads to the destruction of this structural element; - for the manufacture of elements of working equipment, it is advisable to use steel 10HSND. More durable grades of steel are inexpedient from an economic point of view, and steels with a yield strength of less than 390 H/mm2 do not have a sufficient margin of safety.

Pengaruh Clamping Frame Kayu Meranti dan ASTM A36 pada Friction Spot Joining AL 1100 dan PVC

In this paper, the effect of welding parameters on the shear strength of Al-PVC hybrid structures was discussed. This Research developed welding parameters in the form of Plunge Depth, heating time, and clamping frame materials. By these different parameters would result in different shear strength of welded materials. Following optimization of the process, a detailed comparison of the properties and microstructures of two different materials (meranti wood and ASTM A36 Steel) would affect to different values of thermal conductivity. The Aluminum used was Al 1100, which was welded by using a friction stir spot welding method with Polyvinyl Chloride (PVC). In this study, by the different heating times, the shear test was carried out with the ASTM D3163 standard. In this study, it was found that the maximum temperature of Aluminum occurs during the 2 nd second of the welding process and then decreased in the 5 th second until 60 th second. However, the optimum shear strength found at 20 th second. Following heat transfer and degradation materials, the 2mm plunge depth has a higher temperature and higher shear strength than 1,5mm plunge depth. Differences in the response of the two depth were attributed to the difference in mechanical interlocking. This study found that the ASTM A36 clamping frame maximum shear load of 182.4 N is higher than meranti wood frame of 125.5 N. Differences in these value are attributed to the differences of the thermal conductivity, which meranti wood had a lower thermal conductivity than ASTM A36. These have findings significant implications for the commercial application of welding hybrid structures. The best way to take advantage of the benefit of AL-PVC Structure Hybrid for friction stir spot welding would appear to be 20 second heating time, 2mm plunge depth with ASTM clamping frame.

Development of innovative flow visualisation methods to investigate the stages of Wet Compression Moulding (WCM) process

The WCM is a novel production technique for fibre-reinforced polymer components. This technique is increasingly adopted in industry, typically in the automotive sector for medium to large-scale production. This process reduces the cost per part significantly by reducing the number of tools and processing steps, relative to Resin Transfer Moulding. To date, the processing variables, their relations and effect on the composite quality have been established through the knowledge gained by technologists. The drive of this research is to develop a fundamental understanding of the impact of process parameters (key process timings and cavity thicknesses, mould closing speed, edge clamping frame dimensions) and material properties (fibre reinforcement compaction response, permeability, and wettability together with test fluid viscosity and surface tension) on textile wetting, impregnation, and resulting composite part quality. In this study, a 480g/m2 non-crimp unidirectional glass fibre reinforcement has been chosen and characterised for compaction response, in-plane, and through-thickness permeability. For ease of handling, motor oil (DTE heavy VG100) has been characterised and used as a test fluid. Two experimental flow visualisation setups have been developed at the CACM to investigate the influence of process and material parameters on initial resin application and textile wetting, and the subsequent compression flow stage.

Study of thermal buckling behavior of plain woven C/SiC composite plate using digital image correlation technique and finite element simulation

In this study, the thermal buckling behavior of plain woven C/SiC composite plate is investigated by a noncontact measurement based on the three-dimensional digital image correlation (DIC) technique and finite element analysis. The plain woven C/SiC composite plate is fixed by a water-cooling steel frame and one-side heated by quartz lamp array heating apparatus. The buckling temperature and the first buckling mode shape of the C/SiC composite plate are determined from the temperature-displacement curves and full-field deformation that are obtained from the DIC-based experiment. A nonlinear finite element buckling analysis with initial imperfection is performed using the ANSYS software. In order to improve the accuracy of the numerical simulation, a clamping frame model is further proposed for simulating the real clamping boundary in experiment. The results of the finite element simulation and DIC-based measurement coincide well regarding the temperature-displacement curve tendency and critical buckling temperature. Finally, a parametric study is performed using the presented numerical model to investigate the thermal buckling behavior of plain woven C/SiC composite plates with various dimension sizes.

Improving energy efficiency in friction assisted joining of metals and polymers

The influence of the clamping frame material in Friction Assisted Joining of polymer-metal sheets is investigated. An experimental campaign was conducted by varying the clamping frame material (steel and wood) and the heating time. The process was applied to join Al-Mg aluminum alloy and Polyvinyl Chloride sheets. Thermal analysis and energy measurements were conducted during the process. The morphology, fracture surface and strength of the joints were analyzed. The clamping frame made of wood enabled different advantages to be achieved, including reduction of the energy loss towards the clamping frame, faster heating of the materials being joined, and more uniform distribution of the temperature over the joining area, which resulted in increased mechanical strength. Under optimal conditions the joint efficiency approached 97%.

Variation in mouthguard thickness according to heating conditions during fabrication Part 2: sheet shape and effect of thermal shrinkage.

The aim of this study was to investigate the influence of the thermal shrinkage to thickness of the mouthguard with the heating method by the setting position of a sheet and the working model using an ethylene vinyl acetate sheet prepared by extrusion. Mouthguards were fabricated with EVA sheets (4.0mm thick) using a vacuum-forming machine. Two forming conditions were compared: the square sheet was pinched by the clamping frame attached to the forming machine (S); and the round sheet was pinched at the top and bottom and stabilized by the circle tray (R). The sheet was aligned to make the sheet's extrusion direction vertical (V) or parallel (P) to the midline of the working model. The following two heating conditions were compared: (i) the sheet was molded when it sagged 15mm below the level of the sheet frame measured at the top of the post in condition S (S-0), or that sagged 10mm in condition R (R-0) in the usual position; (ii) the sheet frame was lowered by 50mm from the ordinary height (S-50, R-50). Postmolding thickness was determined using a measuring device. Measurement points were the incisal and molar portion. Differences in the change of thickness of mouthguards molded under different heating conditions and extrusion directions for each sheet shape were analyzed by two-way analysis of variance (anova). The results of this study showed that by lowering the height of the sheet frame, the difference of the sheet temperature of each part was reduced. Among all sheets, condition V produced under S-50 and R-50 had the largest thickness independently of shape sheet. Furthermore, thickness reduction is effectively suppressed by aligning the direction of the extruded sheet to be vertical to the midline of the model.

Optimal heating conditions for forming a mouthguard using a circle tray: Effect of different conditions on the thickness and fit of formed mouthguards

PurposeThe aim of this study was to determine the optimal heating conditions for sheet forming using a circle tray by comparing the thickness and fit of mouthguards formed under different conditions. MethodsMouthguards were fabricated using ethylene vinyl acetate sheets (4.0mm thick) and a vacuum forming machine. The working model was trimmed to a height of 20mm at the incisor and 15mm at the first molar. Two forming conditions were compared: square sheets were pinched by the clamping frame attached to the forming machine; and round sheets were pinched at the top and bottom and stabilized by a circle tray. Each condition was defined when the sheet sagged by 10-mm or 15-mm below the level of the clamp. The thickness of the sheet was determined for the incisal and molar portion. Additionally, the difference in fit according to the forming conditions was measured by examining the cross section. Differences in the thickness or the fit due to forming conditions were analyzed using two-way analysis of variance (ANOVA) followed by Bonferroni's multiple comparison tests. ResultsThe thickness after formation was thicker at the 10-mm condition than that of 15-mm, and the fit at the 15-mm condition was better when that of 10-mm with square and round sheets. ConclusionWithin the limitation of this study, it was suggested that when forming a mouthguard using a 4.0-mm EVA sheet and a circle tray on a vacuum forming machine, the sheet should be formed at a sagging distance of 10-mm.

Influence of sheet material shape on the thickness and fit of mouthguards

The aim of this study was to evaluate the influence of sheet material shape on the thickness and fit of mouthguards. Mouthguards were fabricated using ethylene vinyl acetate sheets (4.0 mm thick) and a vacuum-forming machine. The working model was trimmed to a height of 20 mm at the incisor and 15 mm at the first molar. Three forming conditions were compared: Square sheets were fabricated while being secured by the clamping frames attached to the forming machine; round sheets were fabricated while secured by a circle tray; and square sheets were fabricated while secured by a circle tray. Each condition was defined when the sheet sagged by 15 mm below the level of the clamp. The thickness of the sheet was determined for the incisal and molar portion. Additionally, the difference in fit according to the forming conditions was analyzed. Differences in the material thickness or the fit due to forming conditions were analyzed using one-way analysis of variance (anova). Round sheets resulted in the thinnest mouthguard at the incisor and molar region and produced the best fit. For square sheets, no significant difference in thickness was observed between the clamping frame and circle tray methods. The fit of the mouthguard at the first molar was better when using square sheets fabricated by a circle tray than those fabricated by the clamping frame. In conclusion, when molding a mouthguard using square sheets, the thickness reduction was less and fit was better with using a circle tray, which may be clinically useful.

Incremental Sheet Metal Forming with Direct Resistance Heating Using Two Moving Tools

This paper describes new developments in an incremental, robot-based sheet metal forming process (‘Roboforming’) for the production of sheet metal components in small batch sizes. The dieless kinematic-based generation of a shape is implemented by means of two industrial robots which are interconnected to a cooperating robot system. Compared to other incremental sheet metal forming machines, this system offers high geometrical form flexibility without the need of any part-dependent tools. The industrial application of incremental sheet metal forming is still limited by certain constraints, e.g. the low geometrical accuracy and number of formable alloys. One approach to overcome the stated constraints is to use the advantages of metal forming at elevated temperatures. For the temperature input into the sheet metal, there are different approaches like heating with warm fluids, a laser beam or using direct resistance heating. This paper presents results of the research project ‘Local heating in robot-based incremental forming’, funded by the German Research Foundation (DFG), where the heating of the current forming zone by means of direct resistance heating is examined as a variation of the Roboforming process. In order to achieve a local limitation of the heating on the current forming zone, the electric current flows into the sheet at the electric contact of the forming tool and the sheet metal. Thus the forming tool is part of the electric circuit. In current literature Authors report about results from experiments using single-point incremental forming, where the forming tool and the clamping frame of the sheet are connected to the power source. In order to further limit the heating on the forming zone, a new approach will be presented in this paper, where a second tool is used to support the forming and heating process, as both tools can be connected to the power source, making a current flow through the rest of the sheet and the clamping frame unnecessary. With the use of two tools the current flow and thus the heated zone of the sheet can be manipulated. Additionally the advantages of the supporting tool, already shown in forming at room temperature, such as increased geometrical accuracy and maximum draw angle can be used. Starting with a description of the new process setup for steel forming at about 600 °C, results of experiments evaluating the influence of the supporting tool on the forming process at elevated temperatures and the resulting geometrical accuracy will be presented in this paper. Therefore, different process parameters as forming temperature, cooling and relative positioning of the both tools have been varied.

A smart panel with active damping wedges along the perimeter

This paper discusses the practical implementation of decentralized velocity feedback on athin rectangular panel using sixteen triangularly shaped piezoceramic patch actuators withthe base edges uniformly distributed along the perimeter of the panel and accelerometersensors located at the tips of the actuators. In the first part of the paper, thesensor–actuator open loop frequency response function of one feedback loop is modelledand analysed in order to study the principal stability properties of a single control unit. Inparticular an elemental model is developed for studying the bending excitation and passivestiffness and inertia effects produced by the triangular piezoceramic actuator and forinvestigating the resilient effect of the clamping frame that holds the panel. Thesimulated frequency response function is validated experimentally and contrasted withthat obtained from a conventional model of the bending excitation produced bytriangularly shaped distributed transducers. In the second part of the paper,the stability and control performance of sixteen decentralized feedback loops areinvestigated experimentally. Six rectangular panels have been built and equipped withaccelerometer sensors and piezoceramic triangular actuators of various geometriessuch that the effects of the base width, height and base area can be examined.

ID-Cut-off Grinding of Brittle Materials

The inner diameter(ID) cut-off grinding is primary used for the cutting of silicon single crystals into thin slices. These slices, so called wafers, are the basic material for the manufacturing of semiconductors. Larger wafers with an increased density of components and an improved quality can only be manufactured economically, if the basics of the slicing operation are known. The paper describes the major problems in ID cut-off grinding and derives strategies which can make the process more predictable. There is applied a special kind of tool with a centred hole. It is a 170 micron thick fine steel rod plated with diamonds on its inner diameter. The stiffness of this tool is achieved by a radial loading in a circular clamping frame; so especially the load stresses, of the blade core are of great interest. To get values of radial and tangential stresses, finite element calculations have been carried out. One possibility of measuring these stresses is to use electromagnetic methods; the necessary calibration tests are described. The process behaviour during the cutting-off is investigated on the influence of cutting speed, feed speed and the kind of coolant which is utilized.

Piezoelectric vibration exciter, especially for destructive material testing

A piezoelectric vibration exciter for generating mechanical vibrations for the purpose of destructive material or specimen testing has two equally sized disk stacks, each with an even number of piezoceramic disks. A vibration armature serving as a clamping device for the test specimen is arranged between the two disk stacks in a stiff clamping frame having a bail and a base plate. The assembly containing the disk stacks and the vibration armature is clamped in position in the stiff clamping frame. The piezoceramic disks are energized with an AC voltage so that one disk stack will axially contract in phase with the voltage, while the other disk stack will axially expand. As a result, the vibration armature and the test specimen arranged between the disks reciprocate at the frequency of the AC voltage input.

金属薄板の貫通破壊

The plastic deformation and the perforation of thin metallic plates subjected to normal impacts by a spherical projectile are studied. The aluminium plates of 0.3, 0.5 and 0.8mm thick and the copper plates of 0.3mm thick are used for the experiment.Dynamic tangential and normal loads of the plates at the clamping frame are rneasured by small load cells. The peak values of these dynamic loads are found to show the maximum at a little lower velocity than the perforation critical velocity vcr.The values of the perforation energy, the tangential and the normal load of the dynamic perforatiom are compared with the static ones. The dynamic perforation energies are found to be about twice the static ones.The dynamic deflection profiles of the plate are obtained by a still camera and a stroboscope. Both theoretical and experimental deflection profiles show a good agreement.

輻射加熱による平行四辺形平板の熱変形

The deformation of skew plate clamped along all edges under the uniform radiant heating was dealt experimentally and theoretically. The temperature rise, the deflection and strains at many points on the surface of plate were measured continuously for the case of one surface heating. The thermal buckling phenomenon was clearly observed and the mode of the buckling was determined from the observed deflection of plate. The fundamental differential equations for the thermal deformation of the skew plate were solved by the difference method, using the measured temperature distribution and considering the effect of the deformation of the clamping frame. The stress distribution, the critical temperature and the mode of the thermal buckling were calculated and compared with the experimental results.

Azimuthal Variations of the Betatron Field

The azimuthal variations in the out-of-phase fields of a 3 MeV. betatron have been measured using apparatus of improved sensitivity. The method is described and the out-of-phase field analysed giving the contributions from inhomogeneities in the iron, eddy currents between laminations and eddy currents in the laminations themselves. Also a structural steel clamping frame is shown to have a negligible effect on the field.