Clamping Apparatus Research Articles

In vitro skin puncture methodology for material characterization

Quantifying the mechanical behavior of skin has been foundational in applications of cosmetics, surgical techniques, forensic science, and protective clothing development. However, previous puncture studies have lacked consistent and physiological boundary conditions of skin. To determine natural skin tension, excision of in situ porcine skin resulted in significantly different diameter reduction (shrinkage) in leg (19.5 %) and abdominal skin (38.4 %) compared to flank skin (28.5 %) (p = 0.047). To examine effects of initial tension and pre-conditioning, five conditions of initial tension (as percentage of diameter increase) and pre-conditioning were tested in quasistatic puncture with a 5 mm spherical impactor using an electrohydraulic load frame and custom clamping apparatus. Samples with less than 5 % initial tension resulted in significantly greater (p = 0.011) force at failure (279.2 N) compared to samples with greater than 25 % initial tension (195.1 N). Eight pre-conditioning cycles of 15 mm displacement reduced hysteresis by 45 %. The coefficient of variance was substantially reduced for force, force normalized by cutis thickness, displacement, stiffness, and strain energy up to 46 %. Pre-conditioned samples at physiological initial tension (14–25 %) resulted in significantly greater (p = 0.03) normalized forces at failure (278.3 N/mm) compared to non-conditioned samples of the same initial tension (234.4 N/mm). Pre-conditioned samples with 14–25 % initial tension, representing physiological boundary conditions, resulted in the most appropriate failure thresholds with the least variation. For in vitro puncture studies, the magnitude of applied initial tension should be defined based on anatomical location, through a shrinkage experimentation, to match natural tension of skin. Characterizing the biological behavior and tolerances of skin may be utilized in finite element models to aid in protective clothing development and forensic science analyses.

Wrinkling Determination in Sheet Metal Loaded by Shear Stresses

Lightweight concept approach in sheet metal forming requires, among others, thickness reduction and geometry complexity. This combination dramatically promotes the wrinkling occurrence, which can be considered as one of main failure mode that toolmakers must consider. The sheet metal wrinkling determination research usually considers the wrinkling in flange and conical area of a cylindrical cup. For complex geometries the loadings are more diverse than in the deep drawing of a cylindrical cup involving shear stress states. In this context, the present work proposes the application of two different wrinkling determination methodologies in an experimental sheet metal specimen loaded by shear in an aluminum alloy. One of the methodologies involves geometrical parameters to trigger the onset of wrinkling and the other methodology is physically based and considers the evolutions of the in-plane minor strain and its strain rate. The experimental formability test requires a dedicated clamping apparatus to allow its kinematics to be similar to a tensile test. Results allowed the identification of the stress state that triggered the wrinkling occurrence, and the determination of the critical strains that allow plotting the wrinkling limit curve of the sheet material.

Cold butt welding of dissimilar aluminum alloys: Characterization and interface bonding conditions

Cold Butt Welding (CBW) exploits plastic deformation to enable room temperature fabrication of joints with comparable strength to their base metals. Challenges arise when CBW involves alloys with very different mechanical properties, where the necessary conditions to reach their plastic regime differ significantly. The present study unravels the conditions at the interface under which dissimilar AA1070 and AA6082 aluminum wires achieve bonding. Statistical studies were performed to establish a minimum deformation threshold required for successful bonding. The joints were characterized through optical light microscopy, scanning electron microscopy, and micro and nano hardness examinations. In-situ tensile testing was conducted to evaluate the bond strength and failure mechanism. It was found that during the CBW process, at increasing force, the constraints generated by the clamping apparatus on the wires are such that the soft alloy can exceed its ultimate strength and eventually reach the yielding stress of the hard alloy at the interface, allowing both materials to plastically deform and bonding to occur. Moreover, the deflection in the flow of both materials leads to grain refinement and crystalline reorientation inside a region centred around the bonded interface. The severely deformed area was proven by hardness and tensile testing to be the strongest part of the weld, typically identified as the mechanically affected zone.

Tensile behavior of the titanium-steel explosive welded interface under quasi-static and high-strain rate loading

Explosive welding is well known for its capability to join a wide variety of both similar and dissimilar metals. The strengths of the welded composite plates are largely influenced by the bonding strengths of the welding interfaces, which generally exhibit a periodic wavy shape. The measurement of the tensile properties of the bonding interface is challenging due to the difficulties in preparing conventional direct tensile specimens arising from the millimeter-sized thickness of the flyer plate. In this paper, a novel small-sized (15 mm × 14 mm × 8 mm) double-T-shaped specimen was designed to study the tensile properties and failure mechanisms of the titanium/steel bonding interface, in which a clamping apparatus was used to apply compressional load on the specimen to generate tensile stress. The quasi-static (∼0.001/s) tension was conducted using the Instron MTS and the high strain rate (2000–5000/s) tension was performed using the split Hopkinson pressure Bar apparatus. Further, the microstructure of interfacial zone was characterized by optical microscopy, scanning electron microscopy and energy dispersive spectrometer. The experimental results indicated that the interface strength increased with increasing strain rate, showing an obvious positive strain rate effect. The fluctuation in tensile strengths and failure strain of the titanium/steel bonding interface were due to the presence of non-uniform defects, (e g. cavities, cracks and brittle intermetallic etc.) formed on the bonding interface. Those defects as discontinuities and stress concentration points would result in degraded mechanical properties. The fracture morphology mainly reveals brittle fracture under quasi-static, while ductile fracture existed in some zone at high strain rate. Failure mainly occurred in the bonding interface near the steel side from the interface, which showed microcracks, cleavage plane, tearing ridges, dimples, fragmentation of brittle intermetallic compounds. Meanwhile, the double-T-shaped specimen has proven to be effective to measure the tensile mechanical properties of the interface of materials with small thickness.

Analysis and design of carbon fibre clamping apparatus for replacement of insulator strings in ultra‐high voltage transmission line

Analysis and design of carbon fibre clamping apparatus for replacement of insulator strings in ultra‐high voltage transmission line

Optomechanical analysis and performance optimization of large-aperture KDP frequency converter

Surface characteristics of large-aperture potassium dihydrogen phosphate (KDP) frequency converter have direct and significant impacts on the performance of high-power solid-state laser in Inertial Confinement Fusion (ICF) facility. In this study, we analyze the close relationships between the phase gradient and the optical performances including type-I phase matching capacity and focusability of KDP frequency converter theoretically. Moreover, the influences of external forces are studied with field interferometry and finite element method (FEM). An edge-adaptive clamping apparatus with two-stage preload controllers (TSPCs) is proposed to mitigate the gravitational effect. With the proposed integrated optomechanical method and principle verification experiment, new clamping method is proved to be effective to perform offline precision calibration, improve frequency conversion efficiency and has potential for use in online surface control of this large-aperture transmission optics. The coupled effects of preload and gravity on optical performance are analyzed for identifying the characteristics of new clamping method, and the optimal preloads at typical installation attitudes are determined.

Precipitation of CaCO3 in pressure solution experiments: The importance of damage and stress

Pressure solution (PS) is a widespread phenomenon in the Earth's upper crust, which influences many important natural processes, including porosity evolution of sedimentary rocks and fault healing. PS is a creep process effecting porous rocks, involving microscale dissolution and precipitation reactions mediated by diffusion of solutes in the fluid phase. This paper presents an experimental study in carbonates, aiming to advance basic understanding of the physical chemistry controlling PS. The experiments utilize a newly developed method which enables imaging the precipitation stage of PS with a confocal microscope, via a fluorescent marker that binds to precipitating carbonate. We use this method to study the relative role of the various driving forces and the dominant mechanisms controlling the amount and spatial distribution of precipitation in carbonates undergoing PS.Using a clamping apparatus we performed dozens of experiments in which carbonate samples were indented by quartz grains in the presence of water. Carbonate precipitation was observed to occur relatively fast (hours–days), within and around all indented pits, irrespective of the imposed experimental conditions such as stress and fluid saturation, yet the amount and distribution of the precipitation varies between experiments. Two major factors were found to control the amount of precipitation: degree of damage inflicted by pitting and the application of stress. Fluid saturation was seen to affect the spatial distribution of precipitates. In light of these results, we reexamine the traditional chemical potential equations of PS in order to explain the comparable effects of damage and stress on precipitation.

Experiment and simulation study on concentrated magnetic field-assisted ECM S-03 special stainless steel complex cavity

A novel concentrated magnetic field-assisted electrochemical machining (ECM) technology is proposed in this paper to machine contemporaneously seven workplaces’ complex cavity with high efficiency and good precision. An ECM clamping apparatus with concentrated magnetic field, periodic magnetic field, and no magnetic field was designed. The magnetic field simulation was carried out. Comparing the results of the concentrated magnetic field to the periodic magnetic field, the magnetic field intensity of the former is increased by 9.8 % than the latter. The ECM cathode with the same gap was designed and manufactured. Under the conditions of 12 % NaNO3, 14-V voltage, 0.8-MPa electrolyte pressure, temperature 32 °C, cathode feed rate 0.9 mm/min, initial machining gap 0.1 mm, and the S-03 special stainless steel workpiece material, the experiments with concentrated magnetic field, periodic magnetic field, and no magnetic field were carried out. The results show that the gap magnetic field strength was increased by 16.7 % in the concentrated magnetic field than in the periodic magnetic field. Through a sectioning test, the precision in the concentrated magnetic field is increased by 33.3 % compared with no magnetic circuit and increased by 14.8 % compared with the periodic magnetic field. The concentrated magnetic field-assisted ECM technology cannot only reduce the cathode design cycle and cost but also increase the process accuracy.

Process Analysis of Oblique Gibs

Through analyzing the structure feature of long oblique strip and requirement of machining precision, We introduce a new means of planing to ensure the quality of work-piece. By studying process feature of long oblique strip , Give the method of designing clamping apparatus for planing.

Design of an Experimental Device for Biaxial Tension Tests Used in a Uniaxial Test Machine

In the present study, a set of novel clamping apparatus that could deliver biaxial stretching motions with the use of a uniaxial tensile testing machine was designed and manufactured. The conversion of uniaxial motion into biaxial stretching motions is achieved by a sliding mechanism that consists of two blocks sliding in two mutually perpendicular grooves, respectively. During the biaxial tension test, a cross-shaped specimen sitting in the grooves are stretched by the two blocks driven by a pulling rod. The different stress ratios could be obtained by adjusting the groove surface shape and the lengths of specimen wings. In the clamping apparatus design stage, the finite element simulations were performed to examine the validity of the sliding mechanism and the frictional force generated between the sliding blocks and the grooves. The coefficient of friction was determined afterwards from the comparison of the pulling forces obtained in the experiments with those calculated by the finite element simulations. In addition, the optimum geometry and dimension of the cross-shaped specimen used in the biaxial tension tests were investigated by the finite element analysis as well. The slotted specimen proposed by Kuwabara et al. was taken as the basic design. A sufficiently large area in the central region of specimen where the principal stress directions aligned with the groove direction was obtained for gluing the strain gauges to the specimen for the biaxial stretching tests. The number of slots and associated slot widths were also examined to optimize the shape of the specimens. The proposed clamping apparatus was manufactured and the biaxial tension tests were conducted with cross-shaped specimens made of advanced high strength steel sheets. The validity of the designed clamping apparatus used for biaxial tension tests was confirmed and the congruence of various yield criteria applied to the advanced high strength steel sheets subjected to biaxial stress states was discussed.

Toluene Diisocyanate Emission to Air and Migration to a Surface from a Flexible Polyurethane Foam

Flexible polyurethane foam (FPF) is produced from the reaction of toluene diisocyanate (TDI) and polyols. Because of the potential for respiratory sensitization following exposure to TDI, concerns have been raised about potential consumer exposure to TDI from residual 'free TDI' in FPF products. Limited and conflicting results exist in the literature concerning the presence of unreacted TDI remaining in FPF as determined by various solvent extraction and analysis techniques. Because residual TDI results are most often intended for application in assessment of potential human exposure to TDI from FPF products, testing techniques that more accurately simulated human contact with foam were designed. To represent inhalation exposure to TDI from polyurethane foam, a test that measured the emission of TDI to air was conducted. For simulation of human dermal exposure to TDI from polyurethane foam, a migration test technique was designed. Emission of TDI to air was determined for a representative FPF using three different emission test cells. Two were commercially available cells that employ air flow over the surface of the foam [the Field and Laboratory Emission Cell (FLEC®) and the Micro-Chamber/Thermal Extraction™ cell]. The third emission test cell was of a custom design and features air flow through the foam sample rather than over the foam surface. Emitted TDI in the air of the test cells was trapped using glass fiber filters coated with 1-(2-methoxyphenyl)-piperazine (MP), a commonly used derivatizing agent for diisocyanates. The filters were subsequently desorbed and analyzed by liquid chromatography/mass spectrometry. Measurement of TDI migration from representative foam was accomplished by placing glass fiber filters coated with MP on the outer surfaces of a foam disk and then compressing the filters against the disk using a clamping apparatus for periods of 8 and 24 h. The sample filters were subsequently desorbed and analyzed in the same manner as for the emission tests. Although the foam tested had detectable levels of solvent-extractable TDI (56ng TDI g(-1) foam for the foam used in emissions tests; 240-2800ng TDI g(-1) foam for the foam used in migration tests), no TDI was detected in any of the emission or migration tests. Method detection limits (MDLs) for the emissions tests ranged from 0.03 to 0.5ng TDI g(-1) foam (0.002-0.04ng TDI cm(-2) of foam surface), whereas those for the migration tests were 0.73ng TDI g(-1) foam (0.16ng TDI cm(-2) of foam surface). Of the three emission test methods used, the FLEC® had the lowest relative MDLs (by a factor of 3-10) by virtue of its high chamber loading factor. In addition, the FLEC® cell offers well-established conformity with emission testing standard methods.

Effects of Compression Distribution on PEMFC Stacks Using Reformate as Fuel

A PEM fuel cell stack is usually integrated with a reformer into a stationary fuel cell power system. Reformate may cause a phenomenon of voltage vibration in some cells of a stack, and these cells are usually close to end plates. In this work, we studied the instability phenomenon within a 10-cell stack. The instability was observed by monitoring the voltage variation of each cell at high currents. From the test of the assembly pressure distribution, it was found that the pressure distribution of cells close to the end plates was more uneven than others. The scanning electron microscopy (SEM) was used to observe the microstructure of gas diffusion layers within these cells. These scanning electron microscopy images showed that the gas diffusion layers close to end plates suffered more fibers damage, i.e. disabling the hydrophobic structure. The contact angle test results supported this concept as well. In this study, we interpreted that the instability was caused by flooding. If a stack clamping apparatus, providing uniform compression, was used to clamp the stack during testing, the performance of each cell remained stable even in harsh operational conditions. In this paper, it is considered that the pressure distribution of gas diffusion layers is intensely related with water removal ability as reformate is fuel for a proton exchange membrane fuel cell stack.

Development of a neutron tomography system using a low flux reactor

Abstract A neutron tomography instrument was designed and developed at the Royal Military College (RMC) of Canada with Queen's University to enhance these institutions' non-destructive evaluation capabilities. The neutron imaging system was built around a Safe Low-Power C(K)ritical Experiment (SLOWPOKE-2) nuclear research reactor. The low power and physical geometry of the reactor required that a novel design be developed to facilitate tomography. A unique rotisserie style rotary stage and clamping apparatus was developed. Furthermore, the low flux at the image plane (3×104 n cm−2 s−1), necessitated that the image acquisition and reconstruction processes be optimized. Tomographs of numerous samples were obtained using the new tomography instrument at RMC.

Use of micro ultrasonic vibration lapping to enhance the precision of microholes drilled by micro electro-discharge machining

In microhole machining of metal, micro electro-discharge machining (MEDM) is an effective method that can easily create a hole with a diameter under 100 μm. Due to the poor surface quality and shape of MEDM, a machining method that compounds MEDM and micro ultrasonic vibration lapping (MUVL) is proposed here to allow the production of high precision microholes with high aspect ratios. In our investigations, first, a circular or stepped circular microtool was made by the MEDM process, and the tool was used to create a microhole on a small piece of titanium plate in the same machining process. Finally, the abrasive particles driven by the same tool were utilized to grind this hole in the MUVL procedure, and a hole with a diameter about 100 μm can be obtained. Owing to the microtool and workpiece not taking apart from the clamping apparatus during different machining steps, the microhole was processed in the co-axial situation, so the precise shape and perfect surface can be obtained easily. For example, the diameter variation between the entrances and exits of the microholes could reach a value of about 5 μm when the workpiece had a thickness of 500 μm, if the circular microtools was used. Meanwhile, the roundness of the microholes clearly improved, regardless of whether circular or stepped tools were used. However, owing to the perfect grinding effect between the microholes and microtools, the stepped circular tools produced high quality surfaces more easily than the circular tools.

Experimental Investigation of Single-Mode Responses in a Fixed-Fixed Buckled Beam

The nonlinear, single-mode responses of a fixed-fixed, buckled beam are investigated under the case of a uniform, transverse, harmonic excitation. In order to avoid axial slipping and to obtain meaningful data, a clamping apparatus was designed to maximize the clamping force applied to the beam. To fully characterize the single-mode responses, data were obtained at various levels of buckling up to 3.3 times the thickness of the beam. The data demonstrate that at a low level of buckling, supercritical period doubling occurs during an amplitude sweep in which the first mode is directly excited. However, as the buckling level increases, the period-doubling bifurcation becomes subcritical during such amplitude sweeps. In addition, a period-five motion, broadband responses, and responses with an unexplained sideband structure were observed.