The size effect of martensite laths and precipitates on high strength wear-resistant steels

Low alloy high strength wear resistant steels are with high toughness, low cost and good abrasion resistance. It can effectively resist the propagation of wear cracks and prolong the service life of machine components. This paper focuses on the internal relationship between macroscopic physical properties and microscopic martensite lath and precipitate size throughout thickness of wear resistant steel. Four kinds of 40mm thickness wear resistant steels with different alloy chemical composition were produced and investigated. Results show the strength and hardness performance of ARIV are obviously higher than other three steels. ARI have a relatively large strength difference through thickness. The impact toughness of ARIV is relatively uniform, which is greater than that of the ARIII at middle layer and lower than that of the ARIII at 1/4 layer. The width of martensite lath of ARIV is relatively small, mainly 100 ~ 300 nm，while that of ARII and ARIII is mainly 200 ~400 nm. ARIV steel has shorter martensite lath band and more precipitates below 50 nm. It indicates that the size of martensite laths and precipitates of wear-resistant steels are important factors to determine its performance throughout thickness.

Longitude and Latitude Based Received Signal Strength Difference Localization Models

In order to use the latitude and longitude coordinates for received signal strength difference (RSSD) localization, the errors of several spherical distance calculation methods and the error of arc length relative to string length were compared. The distance-calculation RSSD localization equations were established, including spherical accurate calculation RSSD, spherical approximate calculation RSSD, and normal cylindrical projection RSSD. And then, the optimization RSSD localization models based on geodetic coordinates and corresponding to the above equations were established, and the models were verified using the point by point search method with good convergence. The numerical results show there are a lot of weak localization areas for the RSSD localization networks lack of central stations with 4,5,6 stations. Among networks with central stations, there are only a small number of weak-localization areas for the concave 4 stations network, while there are no weak-localization areas for the networks composed of more stations. When the measurement errors and the additional losses of radio wave propagation are not considered, the localization errors of the spherical accurate model, the spherical approximate model and the equianglular projection model are very small, among which the second model has the shortest localization time. The localization errors of equidistance projection model and equal-area projection model are large, neither of which is suitable for the middle latitude and high latitude areas.

Research on the Minimum Size of Received Signal Strength Difference Localization Network

The received signal strength difference (RSSD) localization is a kind of method to locate emission sources by measuring the differences of received signal strength level between the monitoring stations and is essentially the truth value ratios of measured signal strength. In the existing literatures, only the rule of RSSD localization circle of two monitoring stations and the geometric relation of RSSD localization circle of five monitoring stations were analyzed, but the number and the station layout of the minimum RSSD localization network have not been investigated. In the present work, first, based on the existing RSSD localization equation, the constants of the commonly used wave propagation models are provided. Then, the minimum RSSD localization network is proved through algebraic analysis, which is that four monitoring stations not distributed on a straight line can locate the signal source at one point. The relationship between the localization accuracy and the signal strength error of the RSSD location network with different scales is studied further and formulated as a nonlinear programming optimization problem. It is found that the localization stability of the network with four stations is poor, and there is a serious localization deviation outlier phenomenon. Therefore, the network with four stations is not available for radio monitoring networks with a signal strength error of ± 5 to ± 10 dB. The RSSD network with five stations is basically the minimum available size, and the RSSD network with nine stations can approach the localization accuracy of the angle of arrival (AOA) network with three stations.

Tests and Finite Element Simulation of Yield Anisotropy and Tension-Compression Strength Difference of an Extruded ZK60 Mg Alloy

Multiroute yield experiments were carried out on extruded ZK60 magnesium alloy samples under 200 °C and strain rate of by a thermomechanical simulator [...]

Comparative fatigue properties estimation of composite structural nodes

Purpose The purpose of this paper is to present the concept of the author’s method of fatigue properties assessment of polymer composite structures, especially structures having nodes of concentrated force introduction (NCFI) using fatigue test data of coupons of similar composites and the ratio of their structural stress rate factors. Design/methodology/approach Basing on fatigue properties of pure composite shells coupons subjected to cyclic loads, and basing on the static strength difference between pure composite shells and shells having the structure affected by NCFI – (considered here as not only a manner of load introduction but also a kind of structural discontinuity), a method of relative fatigue properties reduction (RFPR) was developed. In the RFPR evaluation process, the author used the results of experiments on a special type of an NCFI named “a labyrinth non-adhesive node of concentrated force introduction” (LNA-NCFI) applied in certain composite gliders for fitting glider wings with the fuselage and also referred to design directives relating to primary structure of composite gliders, which are presented in the form of lightness factors linking stress with a structural mass. Findings The result of RFPR method application matched well with the results of fatigue tests of the LNA-NCFI type of a NCFI. The RFPR method may significantly facilitate the estimation of fatigue life of a structure with a structural discontinuity or an NCFI. Practical implications The RFPR method may significantly facilitate the estimation of fatigue life of a structure with a structural discontinuity or an NCFI. Originality/value The paper presents a proposal of a novel simplified method for fatigue life estimation of composite structures having a kind of structural discontinuity or an NCFI.

Quantifying Treatment-Related Fluctuations in CIDP

ObjectiveThe objective of this study was to explore the extent of IV immunoglobulin (IVIG) treatment-related fluctuations (TRFs) by using home collection of daily grip strength in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and to use that information to develop evidence-based treatment optimization strategies.MethodsThis prospective observational study included 25 patients with well-defined CIDP. Participants recorded grip strength daily for 6 months. Disability and gait metrics were collected weekly. Serum immunoglobulin G levels were obtained at peak, trough, and midcycle IVIG intervals. Day-to-day grip strength changes <10% were considered random. To identify patients with TRFs, 3-day averaged grip strength was calculated on each consecutive day after an IVIG infusion. TRFs were defined as ≥10% 3-day averaged grip strength difference compared to the pre-IVIG baseline.ResultsParticipants successfully recorded grip strength on all but 9% of recordable days. Twelve patients (48%) were classified as low/no fluctuaters and 13 (52%) as frequent fluctuaters. In the frequent fluctuating group, grip strength improved over 1 week and thereafter was relatively stable until the third week after infusion. Grip strength was significantly correlated with measures of disability.ConclusionsGrip strength collection by patients at home is reliable, valid, and feasible. A change in grip strength by ≥10% is a useful, practical, and evidence-based approach that may be used to identify clinically meaningful TRFs. From these data, we propose a treatment optimization strategy for patients with CIDP on chronic IVIG that may be applied to routine clinic care during both face-to-face and virtual video or telephone patient encounters.Trial Registration InformationClinicalTrials.gov Identifier: NCT02414490.

Effect of Different Nd:YAG Laser Power Outputs on Bond Strength of Resin Cement to Zirconia in Comparison to Sandblasting

Introduction: This study investigated the effect of various laser powers on the shear bond strength (SBS) of resin cement to the zirconia surface. Methods: Seventy-five zirconia disks were prepared and assigned to five groups including no surface treatment (control group), sandblasting with 50 µ Al2 O3 particles (second group), and Nd:YAG laser treatments with 2 W, 2.5 W and 3 W powers respectively (third, fourth and fifth groups). Afterwards, composite resin cylinders were cemented on zirconia disks using dual-curing resin cement. Before thermocycling (2000 cycles, 5-55°C), all samples were placed in distilled water at 37°C for 24 hours. Using a universal testing machine at the crosshead speed of 0.5 mm/min, the SBS was examined. Also, using a stereomicroscope, the failure type was determined. Data analyses were performed using Welch and Games-Howell tests (P< 0.05). Results: The mean bond strength difference between the control group and the other groups was significant. The respective bond strength from the highest to the lowest was observed in the sandblast group, the laser group with 2.5 W power, the laser group with 3 W power, the laser group with 2 W power, and finally the control group. However, no significant difference was observed between different laser groups (P< 0.05). Also, there was no significant difference between the sandblast and laser groups with 2.5 W and 3 W power (P< 0.05). Most of the failures in the sandblasting and laser groups with powers of 2.5 W and 3 W were mixed, but in the control and 2 W laser groups, most of the failures were of adhesive nature. Conclusion: The highest bond strength was achieved by sandblasting with Al2 O3 particles and then using an Nd: YAG laser with a power of 2.5 W.