Effect of indenter tip radius on indentation hardness by finite element analysis

In this study, the indentation hardness test is performed by elastic-plastic finite element (FE) analysis. In order to investigate the effect of the wear of indenter tip on the load-penetration depth curve ([Formula: see text] curve), indentation simulation is made by changing the indenter tip radius. The [Formula: see text] curve obtained by finite element method (FEM) is in good agreement with the experimental results. The calculation shows that the indentation plastic work [Formula: see text] corresponding to the area in the [Formula: see text] curve is hardly affected by the indenter tip radius.

The Effect of Blast Exposure Distance on Hardness and Reduced Modulus Properties of Lead-Free Solder

This study discussed the effect of blast exposure distance of lead-free solder on micromechanical properties. Sn-Ag-Cu solder samples were exposed to 1000 g of Plastic Explosive. The soldered samples were placed at a distance of 1 m, 2 m and 4 m distance from the blast source. In order to study micromechanical properties in localized and more details, the nanoindentation approach was used. The indentation was performed at the center of the solder to examine the hardness and reduced modulus properties. The load-depth curve of indentation for 1 m distance from the blast source has apparent the discontinuity during loading as compared to the control sample. The hardness value increased as the distance from the blast source increased. The shortest distance from the blast source gives a high impact on the degradation of hardness properties as compared to others. This result is important in assessing the effect of exposure distance from the blast source.

Acoustic Velocity Correcting Method for the Tilted Acoustic Tube in Testing of Pile by Ultrasonic Transmission

The finite element software ABAQUS was used to simulate the detection of piles by ultrasonic transmission. The influence of the tilted acoustic tube on the testing results of the pile was analyzed. The results showed that, when the pile was complete, the velocity of the sound-depth curve of the received signal was inclined to one side due to the inclination of the acoustic tube and the velocity of the sound seriously deviated from the normal value; when there was a defect in the pile, the signal of the defect was not obvious due to the tilt of the acoustic tube, which was easy to miss or misjudge the defects of the pile. To solve the problem of the inclined acoustic tube, the mathematical model of the position relation of the acoustic tube was established, and the method for correcting the velocity of the sound based on the angle of the acoustic tube was derived. Numerical simulation and engineering examples were used to verify the modified method; the verification showed that the corrected acoustic signal could accurately determine the defects and their positions in the pile, and this method effectively reduced the influence of the tilted acoustic tube on the detection signal, which was beneficial to improve the accuracy of the testing for the pile.

ARM based Telemetry Subsystems Qualification for Micro-Satellite

Developing spacecraft telemetry subsystem utilizing commercial of the shelf (COTs) components to meet the technical design requirements with low-cost is big challenge for designers, due to the considerations of harmed ionizing space radiation effect, specially the total ionizing dose effect (TID). This effect induces performance degradation and failure in satellite electronic components (ECs). Because of the complexity of microcontrollers and their various integrated functionality, they present a hardness assurance encounter. A careful technique was followed in analyzing the space radiation effects. Then rigorous tests should be conducted to test the performance of the candidate microcontrollers under these effects. This paper presents the predicted dose depth curve and the total ionizing does test results for a commercial ARM microcontroller for Low Earth Orbit (LEO) satellites. Such test results help estimate the effect of space environment on the microcontroller and decide if such microcontroller is an accepted candidate for LEO missions or not.

Rail Corrugation Characteristics of Cologne Egg Fastener Section in Small Radius Curve

By analyzing the measured data of rail corrugation in a small radius curve track with Cologne fasteners, the typical passing frequencies of corrugation were obtained. Then, according to actual line conditions, the vehicle-track coupled model and rail material friction and wear model were established and simulated, and rail corrugation characteristics of the curved section were studied. The results show that the variation amplitude of creep force on the inside of a guiding wheelset is large, and it coincides with that of the saturated creep force partially and the coincident part appears periodically. The variation amplitude of creep force on the outside of the guiding wheelset is small, and it is approximately equal to that of the saturated creep force. In addition, the variation range of the wear depth curve on inner rail is mainly changing from 0 μm to 0.0014 μm, showing periodic wavy wear, and when the creep force is equal to the saturated creep force, the wear depth reaches the peak. The variation range of the wear depth curve on outer rail is mainly changing from 0.0005 μm to 0.0008 μm, showing uniform wear. Combined with the predicted profile of rail wear, it can be seen that the inner rail mainly suffers from corrugation on the top of rail and the outer rail mainly suffers from uniform wear on the side, which results in serious corrugation on inner rail and slight corrugation on outer rail. The frequency characteristics analysis of wear shows that the inner rail wear has characteristic frequencies similar to the passing frequencies. Modal analysis results show that the vibration of inner rail at the characteristic frequencies is greater than that of outer rail, which lead to the corrugation of the corresponding frequencies more easily. The wear growth rates at the characteristic frequencies are relatively large, which indicates that the wear at the corresponding frequencies will continue to develop and eventually form corrugation.

Implant Diameter, Length, and the Insertion Torque/Depth Integral: A Study Using Polyurethane Foam Blocks

The amount of energy necessary to place an implant in its seat, described as the integral of the torque-depth curve at insertion (I), has been validated as a reliable measure of primary stability. This study aimed to investigate whether (I) may detect the variations in primary stability caused by changes in the implant length or diameter better than the insertion torque (IT). Cylindric implants featuring a double-etched, sandblasted surface with different diameters or lengths were placed into monolithic polyurethane foam blocks with different densities that mimicked human bone. (I)-, (I)*-, IT-, IT*-diameter and -length plots ((I)* and IT* were the derived values corrected for undersizing) were drawn and the relation between (I), (I)*, IT, and IT* and the fixture diameter or length was investigated with correlation analysis. (I)* and IT* correlated better than (I) and IT with the fixture diameter; (I), (I)*, IT, and IT* correlated equally well with the fixture length. In all cases, the slopes of the lines best fitting the experimental data were greater for (I) or (I)* than IT or IT*, respectively. (I) or (I)* were better detectors than IT or IT* of the changes in primary stability that can be achieved by increasing the fixture diameter or length.

Effects of Bionic Curves on Penetration Force under Difference Soils

Soil penetration is the most important process during soil tilling. To optimize the soil penetration process, six specimens were designed and fabricated based on the badger teeth outlines. Both experimental investigation and numerical analysis were conducted with three types of soil. Results showed the specimen C, B, and D got the lowest penetration force and reduced the force by 26.15%, 22.68%, and 25.86% compared with that of specimen A under soil 1, soil 2, and soil 3, respectively. Depth-force curve analysis showed that the bionic specimens can slow down the force increase rate by reducing the coefficient of the force-depth curve equations. The bionic specimens obtained a lower increase of internal friction angle and cohesion after penetration, indicating the soil strength after penetration was lower. Furthermore, the rise in soil surface was observed after the penetration, and the penetration with the bionic specimens got a higher rise. Simulation analysis showed that the mechanism for the force reduction was because the force direction was changed, which brought a better flowability and less strength for the soil. It concludes that the badger teeth outlines reduce the penetration force by changing the force directions and optimizing the soil properties. Based on research results, the optimal bionic curve for penetration in different types of soil was determined.

Correlation between Implant Geometry, Bone Density, and the Insertion Torque/Depth Integral: A Study on Bovine Ribs

During insertion of dental implants, measurement of dynamic parameters such as the torque-depth curve integral or insertion energy might convey more information about primary stability than traditional static parameters such as the insertion or removal torque. However, the relationship between these dynamic parameters, bone density, and implant geometry is not well understood. The aim of this investigation was to compare static and dynamic implant stability measurements concerning three different implant designs when implants were inserted into bovine bone ribs and dynamic parameters were collected using an instantaneous torque measuring implant motor. Standard implant osteotomies were created in segments of bovine ribs. After measuring the bone density using the implant motor, 10 cylindrical, 10 hybrid tapered-cylindrical, and 10 modified cylindrical implants were placed, and their primary stability was assessed by measuring the torque–depth curve integral, along with insertion and removal torque. The relationship between these quantities, bone density, and implant geometry was investigated by means of regression and covariance analysis. The regression lines describing the relationship between the torque–depth integral and bone density differed significantly from those describing the relationship between insertion torque, removal torque, and bone density for all three designs. The torque–depth curve integral provides different information about immediate primary stability than insertion and removal torque and in certain clinical conditions might be more reliable than these static parameters for assessing implant primary stability. Further research should be carried out to investigate the findings of the present study.