Anvil Face Research Articles

Analysis of the oscillation behavior during ultrasonic welding of EN AW-1070 wire strands and EN CW004A terminals

For fulfilling the demand of durable yet lightweight electrical connections in transportation industries, ultrasonic metal welding (USMW) sees widespread use in these branches. As the ultrasound oscillations utilized in the welding procedure occur at a range of only a few micrometers at frequencies of 20–100 kHz for an overall duration of only 50–1500 ms, it is not possible to observe the compaction behavior with the bare eye. This paper focusses on investigating the oscillation behavior of the horn, the anvil, and the joining partners during the welding procedure by utilizing an array of synchronized laser vibrometers and performing welds with incrementing time stages. The oscillation data is correlated with temperature measurements in the welding zone as well as tensile testing results. Inter alia the formation of sidebands at the fundamental frequency as well as 2nd- and 3rd-order harmonics has been observed for the anvil, terminal, and wire front face when exceeding optimal weld time which would lead to maximum joint strength. Following the assumption of other research groups, the cause of these sidebands could be a change in relative motion of these components. As the terminal is slipping with increasing weld time, it could be assumed that the reason for the sidebands is low-frequency movement of the anvil, modulated onto the fundamental frequency, additionally indicating successful bonding of the stranded wire and the terminal. Furthermore, this slipping of the terminal on the anvil could lead to increased wear of the anvil knurls.

Practical effects of pressure-transmitting media on neutron diffraction experiments using Paris–Edinburgh presses

ABSTRACT To understand the practical effects of pressure-transmitting media (PTM) on neutron diffraction using Paris–Edinburgh presses, diffraction patterns of MgO were collected to approximately 20 GPa using PTMs of Pb, AgCl, 4:1 methanol–ethanol (ME) mixture with and without heating, N2, and Ar. Hydrostaticity in the sample chamber estimated from the MgO 220 peak width improves in the order of Pb, AgCl, Ar, ME mixture, N2, and the heated ME mixture. Unlike previous results using diamond anvil cells, the unheated ME mixture is superior to Ar even after freezing, probably due to the cup on the anvil face. Considering these results and the sizable coherent scattering of Ne, which would show good hydrostaticity, we conclude that the ME mixture (preferably the heated one) is the best PTM in neutron experiments up to 20 GPa, while Ar can be substituted when a sample is reactive to alcohols.

A Novel, Easy-to-Use Staple Line Reinforcement for Surgical Staplers.

BackgroundStaple line reinforcement (SLR) is a popular tool used by surgeons to increase staple line strength and improve peri-operative hemostasis. However, currently marketed buttress materials require special attention in attachment to the staple anvil and cartridge and may come loose during typical maneuvering of stapling procedures. We have evaluated a new SLR that has an attachment material that affixes buttress across the entire anvil and cartridge face to prevent slipping, twisting, sliding and/or bunching.MethodsIn benchtop and preclinical testing, the new buttress material (ECHELON ENDOPATH™ Staple Line Reinforcement) was compared to a commercially available SLR for physical characteristics, including strength, absorption, security on the anvil and cartridge during stapler manipulation, impact on the tissue healing response and tissue abrasion. The two SLR’s were also compared to a staple line without buttress for hemostasis.ResultsThe new SLR was 180% stronger initially and maintained a greater strength for up to 14 days of exposure to an in vitro solution (p≤0.001), even though it was lighter and exhibited a faster rate of degradation. The new buttress material maintained complete adherence to the anvil and cartridge throughout tissue manipulation, whereas the commercial product lost substantial coverage in 72% of samples. Both SLR’s provided superior hemostasis to the non-buttress control, with minimal impact on tissue healing or abrasion.ConclusionBecause the new buttress material comes with attachment material affixed across the entire anvil and cartridge face of the stapler and maintains coverage during manipulations, it should be much easier to use. The physical characteristics of the new SLR were as good as or better than current product that requires the buttress to be applied to the cartridge and anvil. In addition, the new SLR is similar in hemostasis to standard products and superior to stapling without the use of buttress. Further research is needed to determine whether these preclinical benefits carry over into a clinical setting.

A Breakthrough in Pressure Generation by a Kawai-Type Multi-Anvil Apparatus with Tungsten Carbide Anvils

Expansion of the pressure range of Kawai-type multi-anvil presses (KMAPs) with tungsten carbide (WC) anvils is called for, especially in the field of Earth science. However, no significant progress in pressure generation has been made for 40 years. Our recent studies have expanded the pressure generation of a KMAP with WC anvils to 65 GPa, which is the world record for high-pressure generation in this device and is more than 2.5 times higher than conventional pressure generation. We have also successfully generated pressures of about 50 GPa at high temperatures. This work reviews our recently developed technology for high-pressure generation. High-pressure generation at room temperature and at high temperature was attained by integration of the following techniques: ① a precisely aligned guide-block system, ② a high degree of hardness of the second-stage anvils, ③ tapering of the second-stage anvil faces, ④ a high-pressure cell consisting of materials with a high bulk modulus, and ⑤ high thermal insulation of the furnace. Our high-pressure technology will facilitate investigation of the phase stability and physical properties of materials under the conditions of the upper part of the lower mantle, and will permit the synthesis and characterization of novel materials.

The shear-driven transformation mechanism from glassy carbon to hexagonal diamond

Hexagonal diamond, a potentially superhard material, forms from a glassy carbon precursor at pressures of ∼100 GPa at the relatively low temperature of 400 °C. The formation mechanism of the hexagonal diamond phase was investigated by performing microstructural analysis on cross-sections of the recovered samples. Three distinct structures have been observed, a graphitic region near the centre of the sample with low density, a hexagonal diamond region at the edge of the sample with high density, and a mixed region containing significant proportions of both the graphitic structure and hexagonal diamond. The hexagonal diamond was more likely to occur at greater radial distance from the centre of the sample with some evidence for greater amounts also near the diamond anvil faces. The observed distribution of the hexagonal phase correlates well to regions of greatest shear strain expected from modelling studies of strain fields in diamond anvil cells. The findings support the proposition that shear strain plays an important role in the formation of hexagonal diamond, and that it may be a driving force for the natural occurrence of hexagonal diamond in the shear zone of meteorite impact craters.

Force analysis and pressure quantitative measurement for the high pressure cubic cell

Large volume cubic press is one of the most popular high pressure devices which can produce pressures up to about 7 GPa. It is well known experimentally that the enhancing of the maximum pressure generated in the large volume cubic press has attracted wide attention among scientists and engineers because the higher pressure is capable of synthesizing some materials with interesting properties. In the large volume cubic press, pyrophyllite is typically used as a pressure-transmitting medium. A specimen immersed in such a solid experiences a generalized stress state. The pressure distribution in pyrophyllite is an important parameter for characterizing the sample environment and designing the experiments at high pressure. There is a need for the quantitative measurement of pressure gradients in the pyrophyllite pressure medium, so that the accurate experimental data under high pressure can be obtained. In the large volume cubic apparatus (68 MN), we put a circuit into the high pressure cubic cell, so that the pressures at various positions can be measured by using the phase transitions in Bi, Tl and Ba. In the present work, the relationship between the total press load and the press load allocated to the anvil face, and the relationship between the total press load and the press load allocated to gaskets are established at room temperature. The results show that with the increase of the total press load, the load allocated to the gaskets is increased sharply, while the curve of load allocated to the anvil face versus total press load reaches a plateau, which results in the cell pressure reaching upper limit when the cell pressure reaches up to about 5 GPa. According to the experimental results, the stress state of the cubic cell under high pressure is analyzed and the reason why the pressure generated in the large volume cubic chamber is difficult to exceed 7 GPa is explained. Based on the geometrical structure of the cubic cell, the scheme to increase the upper pressure limit for cubic cell by using the material with high bulk modulus as the pressure transmitting medium and the material with low bulk modulus as the gasket, is proposed. Additionally, the method of calculating the pressure values at different positions along the axis of symmetry in the cubic cell is given through the quantitative calibration of the pressure gradient in the axial direction of the cubic cell. This method can provide more accurate pressure data for high pressure experiments.

An improved hydrothermal diamond anvil cell.

A new type of HDAC-V hydrothermal diamond anvil cell (HDAC-VT) has been designed to meet the demands of X-ray research including X-Ray Fluorescence, X-ray Absorption Spectroscopy, and small angle X-ray scattering. The earlier version of HDAC-V that offered a large rectangular solid angle used two posts and two driver screws on both sides of a rectangular body. The new version HDAC-VT in a triangular shape has two alternative guide systems, either three posts inserted into bushings suitable for small anvil faces or linear ball bearings suitable for large anvil faces. The HDAC-VT having three driver screws offers the advantage of greater control and stability even though it sacrifices some of the size of solid angle. The greater control allows better sealing of samples, while greater stability results in longer survival for anvils and ceramic parts. This improved design retains several beneficial features of the original HDAC-V as well. These include the small collar that surrounds the heater and sample chamber forming an Ar + H2 gas chamber to protect diamonds and their heating parts from being oxidized. Three linear ball bearings, when used, fit to the three posts prevent seizing that can result from deterioration of lubricant at high temperatures. Positioning the posts and bearings outside of the gas chamber as in HDAC-V also prevents seizing and possible deformation due to overheating. In order to control the heating rate precisely with computer software, we use Linkam T95 and have replaced the Linkam 1400XY heating stage with the HDAC-VT allowing the HDAC to be heated to 950 °C at a rate from 0.01 °C/min to 50 °C/min. We have used the HDAC-VT and Linkam T95 to observe in situ nucleation and growth of zabuyelite in aqueous fluid and to homogenize melt inclusions in quartz from three porphyry deposits in Shanxi, China.

Generation of pressures over 40 GPa using Kawai-type multi-anvil press with tungsten carbide anvils

We have generated over 40 GPa pressures, namely, 43 and 44 GPa, at ambient temperature and 2000 K, respectively, using Kawai-type multi-anvil presses (KMAP) with tungsten carbide anvils for the first time. These high-pressure generations were achieved by combining the following pressure-generation techniques: (1) precisely aligned guide block systems, (2) high hardness of tungsten carbide, (3) tapering of second-stage anvil faces, (4) materials with high bulk modulus in a high-pressure cell, and (5) high heating efficiency.

Containment of fluid samples in the hydrothermal diamond-anvil cell without the use of metal gaskets: Performance and advantages for in situ analysis

Metal gaskets (Re, Ir, Inconel, or stainless steel) normally used to contain fluid samples in the hydrothermal diamond-anvil cell (HDAC) are sometimes undesirable due to possible contamination and to gasket deformation at high pressures and temperatures resulting in nonisochoric behavior. Furthermore, in x-ray spectroscopic experiments, metal gaskets may attenuate the incident x-ray beam and emitted fluorescence x-rays, and the interaction of scattered radiation with the gasket may produce fluorescence that interferes with the x-ray spectrum of the sample. New arrangements and procedures were tested for the operation of the HDAC without using the metal gaskets. Distilled, de-ionized water was loaded into the sample chamber, a laser-milled recess 300 microm in diameter and approximately 50 microm deep centered in the 1.0 mm face of the lower diamond anvil, and sealed by pressing the top diamond anvil face directly against the lower one without a metal gasket in between. A maximum sample pressure of 202 MPa at 617 degrees C was maintained for a duration of 10 min without evidence of leakage. A small change in fluid density was observed in one experiment where the sample was held at 266 MPa at 708 degrees C for 10 min. The gasketless HDAC was also employed in x-ray absorption spectroscopy experiments, where, in addition to the sample chamber in the lower diamond, two grooves were milled at a 90 degrees angle to each other around the sample chamber to minimize the attenuation of incident and fluorescent x rays. With a minimum distance between the sample chamber and the grooves of 80 microm, a pressure of 76 MPa at 500 degrees C was maintained for 2 h with no change in the original fluid density.

Internal resistive heating in diamond anvil cell for in situ x-ray diffraction and Raman scattering

An internal resistive heater contained completely between the anvil faces of a diamond anvil cell has been used to conduct experiments up to 10 GPa and temperatures up to 3000 K. There is evidence that pressures up to 50 GPa can be achieved with smaller anvil faces and smaller heater assembly. The technique offers a very homogeneous temperature profile and excellent time stability for studying both metallic and nonmetallic materials. Temperature is measured by spectroradiometry as an image of the incandescent sample is projected onto the end of a fiber optic cable leading to a spectrometer. A very linear relationship between temperature and power provides accurate temperature measurements even when the temperature is below incandescence. The melting of gold determined by loss of diffraction peaks occurred at temperatures in good agreement with published values. In situ Raman spectra of SiO2 revealed the conversion of quartz to coesite. This method offers a larger heating volume with more stable and uniform temperature than laser heating techniques and at temperatures much greater than those that can be achieved by external resistive heating techniques.

X-ray diffraction under non-hydrostatic conditions in experiments with diamond anvil cell: wüstite (FeO) as an example

The stress state in a solid specimen compressed between two flat and parallel anvil faces (in a diamond anvil cell, for example) is non-hydrostatic. The resulting lattice strains, measured by X-ray diffraction, exhibit certain features, which are absent if truly hydrostatic conditions prevail. We describe the method of analysis of lattice strain in non-hydrostatic stress states. This is based on the transformation of stress axis into crystal axis and further on the calculations of the strain in a given direction by taking into account the pressure dependence of elastic moduli. Application of the theory is demonstrated with an example of a study of wüstite (FeO) at pressures up to 18 GPa. We found that the pressure of phase transition is proportional to the uniaxial stress component, which rises from 10.1 GPa for compression without pressure medium to 15.4 GPa in Ar pressure medium. Extrapolation to zero stress conditions gives the value 16.8 GPa, which is in good agreement with the data of Fei (Y. Fei, in: M.D. Dyar, C. MacComman, M.W. Schaefer (Eds.), Mineral Spectroscopy, Geochemical Society, 1996 pp. 243–254) (powder diffraction data, compression in He pressure medium, P tr=17(1) GPa) and Shu (J. Shu, Eos Trans. Am. Geophys. Union 75 (1998) 203) (single crystal diffraction data, compression in He pressure medium, P tr=18(1) GPa).

Hydrothermal diamond anvil cell for XAFS studies of first-row transition elements in aqueous solution up to supercritical conditions

A hydrothermal diamond anvil cell (HDAC) has been modified by drilling holes with a laser to within 150 μm of the anvil face to minimize the loss of X-rays due to absorption and scatter by diamond. This modification enables acquisition of K-edge X-ray absorption fine structure (XAFS) spectra from first-row transition metal ions in aqueous solutions at temperatures ranging from 25°C to 660°C and pressures up to 800 MPa. These pressure–temperature ( P– T) conditions are more than sufficient for carrying out experimental measurements that can provide data valuable in the interpretation of fluid inclusions in minerals found in ore-forming hydrothermal systems as well as other important lithospheric processes involving water.

New diamond anvil cells for gigahertz ultrasonic interferometry and X-ray diffraction

Two new diamond anvil cells have been designed for ultrasonic and X-ray diffraction measurements on a single crystal sample up to 6 GPa and 250 °C. Advances in the generation and transmission of coherent GHz ultrasonic signals with wavelengths of the order of micrometers now make it practical to measure elastic properties of samples small enough to be subjected to pressure and temperature in diamond anvil cells. The signal is carried from a thin transducer through a sapphire buffer rod coupled to one of the diamond anvils by means of force. The signal traverses the diamond anvil and enters the single crystal sample which is coupled to the anvil face by cement, adhesion, or by a normal force. Interference of superimposed waves reflected from the near and far faces of the single crystal is used to measure travel time of the sound waves in the sample. One of the diamond anvil cells employs the conventional geometry in which access for the X-rays is through the diamond anvils. The other provides access for X-rays at high angles to the load axis so that they do not need to pass through the diamond anvils and can therefore have access to the sample while the buffer rod is in place. Both diamond anvil cells make it possible to measure d-spacings at several different orientations using a four-circle goniometer. This capability is used for detecting and correcting displacement of the sample from the center of the goniometer. Measurement of travel times and lattice parameters at the same pressure-temperature conditions allows conversion of travel times to velocities and can provide simultaneous equations of state, which EOS can then be used to make an independent determination of pressure vs. lattice parameter. This provides a primary pressure scale

Measurement of infrared absorptivities and line shapes and the distortion of anvils in diamond-anvil cells

The infrared transmission of diamond and other transparent anvil apparatuses that contain absorbing samples, has been calculated as a function of frequency for planar anvils that are inclined to one another or that are distorted into parabolic shapes. At frequencies where the samples are completely transparent, the height of the interference fringes decreases with increase of frequency at nearly the same rate for both parabolically distorted and inclined anvils for which the maximum difference in optical path length of the sample is the same. Hence, the distortion of anvils in a typical experimental configuration have been measured up to a mean pressure on the anvil faces of 60 kbar. They are consistent with the predictions of elasticity theory that distortions occur at the rate of about 20 μm in 500 kbar. The predicted effect of such distortions on the absorbance, integrated area, and time autocorrelation function of the dipole moment is insignificant in a well-designed experiment, and so all these properties can now be measured accurately at high pressures.

Measurement of anisotropic stress field in a gasketed diamond-anvil cell

A new technique is proposed to evaluate the axial and lateral stress components, p z and p r , separately within the solid pressure medium of a gasketed diamond cell. The values of p z and p r are obtained from shifts of the R-line of two ruby plate fragments placed in a pressure chamber, one having crystal plane (11 2 0) and the other (0001) parallel to the anvil face.

Melting of Diamond

Radiation from a Q-switched YAG laser, focused on the (100) face of a single crystal diamond anvil in a high-pressure diamond cell, caused a portion of the diamond anvil face to melt. Potassium bromide mixed with graphite was under pressure between the anvils when melting occurred. The diamond surface melted at pressures greater than approximately 120 kilobars and graphitized at lower pressures. Evidence for the melting and graphitization of the diamond was obtained by optical and scanning electron microscopy.

Stress analysis of a beveled diamond anvil

A finite element stress analysis has been performed on a brilliant cut high-pressure diamond anvil. The analysis includes the presence of a metal gasket. A perfectly cohesive interface is assumed to exist between the diamond and metal. Different configurations of the anvil face were studied. The stress distribution resulting from various beveled angles has been analyzed. It has been found that for a flat anvil, with a center normal pressure of about 210 kbar, an octahedral shearing stress of about 90 kbar is present near the center and monotonically increases radially to about 208 kbar along the outer edge. When the anvil surface is beveled, the octahedral shearing stress at the outer corner decreases significantly. The optimum beveled angle necessary to minimize these stresses seems to lie in the neighborhood of 15°. The assumptions made and other stress considerations are discussed.

A Raman Microscope Technique for Studying Liquids in a Diamond Anvil Cell

The diamond anvil cell (DAC) has been used extensively in the study of solids and liquids at high pressure. For liquids it is necessary to use a metal gasket to retain the sample between the anvil faces. The pressure experienced by the fluid can be measured by including a small fragment of ruby, the fluorescence spectrum of which is sensitive to pressure. Several experimental arrangements for observing Raman spectra from a DAC have been tried. For 0° scattering, in which the laser passes straight through the cell, scattered light can be collected with an off-axis elliptical mirror which focuses it onto the entrance slit of the monochromator. Another technique uses a small mirror 15° off normal incidence to the DAC by which the laser is focused onto the sample. A lens then collects the near 180° scattered light and brings it to a focus at the monochromator.

X-ray diamond-anvil press for use at high temperatures

This paper describes the design and operation of a new diamond-anvil press that can conduct x-ray diffraction investigations of polycrystalline materials at sustained pressure and temperature up to 30 GPa and 500 °C. Several improvements have been made in heating efficiency, uniformity of temperature, alignment operation of anvil faces, and elimination of preferred orientation effect. Examples of the application to the study of a high-pressure phase of phosphorus are shown.

Stress Analysis of a Beveled Diamond Anvil

ABSTRACTA finite element stress analysis has been performed on a brilliant cut high pressure diamond anvil. The analysis includes the presence of a metal gasket. A perfectly cohesive interface is assumed to exist between the diamond and metal. Different configurations of the anvil face were studied. The stress distribution resulting from various beveled angles has been analyzed. It has been found that for a flat anvil, with a center normal pressure of about 210 kbar, an octahedral shearing stress of about 90 kbar is present near the center and monotonically increases radially to about 208 kbar along the outer edge. When the anvil surface is beveled, the octahedral shearing stress at the outer corner decreases significantly. The optimum beveled angle necessary to minimize these stresses seems to lie in the neighborhood of 15 degrees. The assumptions made and other stress considerations are discussed.