bluuebunny/crossref_metadata_2025 huggingface dataset:
A Summary of the Research on Natural Resource Assets Departure Audit on Leading Cadres
Authors: Wang Cuilin , Qi Teng , Lin Shujia
Published: August 2020

With the promulgation of relevant laws and regulations in China in 2014, the study of natural resource assets departure audit on leading cadres has become a hot topic. It can be seen that the current literature has a rich discussion of basic theoretical research on natural resource assets departure audit on leading cadres, and the discussion on specific technical applications, method models, and accountability systems is unfortunately insufficient. The follow-up should deepen theoretical research in this subject, enhance the research of disciplinary integration, further strengthen the relationship between theory and practice and conduct more relevant explorations of evaluation systems and empirical analysis.
Driving Forces of Intra-Annual Variation in Plant Spectral Beta Diversity in Inner Mongolia Grassland
Authors: Bai Lan , Tian Jialing , Peng Yu
Published: August 2020

The variation trend of plant spectral beta diversity index of different types of grasslands in Inner Mongolia and its key climate drivers were explored by analyzing the changes of monthly and annual climate variables and spectral index of plant diversity during the period from 1982 to 2017.All the study areas are located in nature reserves that provide protection for fragile ecosystems and biodiversity, so grazing and human disturbance can be ignored. The results show that the variation trends in plant spectral diversity of different types of grassland in Inner Mongolia were different. The plant diversity in Anxi nature reserve reached the highest in October, while that in West Ordos, Xilingol and Tumuji nature reserve reached the highest in April. Temperature is a key driving factor for the variation of beta diversity of all types of grassland plants, and is negatively correlated with the plant diversity. Compared with the inter-annual scale, the climatic factors on the inter-monthly scale have a greater impact on the grassland plant diversity. Understanding monthly climate variables help us monitor the dynamic change of grassland plant diversity in a timely and effective manner.
Stress Relationship between Ecological Security and Urban Expansion Suitability
Authors: Sun Yanzhi , Zhang Tongsheng
Published: August 2020

Systems integration assessment can provide the comprehensive information for practice and policy, reducing conflict in decision-making. Using Beijing city as a case study, this paper proposed a systematic stress assessment method to describe the stress relationship between urban expansion suitability and ecological security. Firstly, Minimum Cumulative Resistance Model (MCR) was adopted to depict the ecological security pattern from 2000 to 2018, and the pattern of high, moderate and low ecological security was protracted. Secondly, the index weights of urban expansion suitability were calculated by Analytic Hierarchy Process (AHP) to eliminate subjectivity, and 5 levels of urban expansion suitability were established by weighted overlay. Finally, this study evaluated the stress effect. Results showed that the overall regional ecological security of Beijing decreased first (2000-2010) and then increased (2010-2018). The suitable area for urban expansion was getting larger, but the expansion rate dropped. Stress effect on urban expansion from ecological security pattern raised from 2000 to 2010 and then dropped. However, the stress effect on ecological security from urban expansion was continuously increasing, stimulating potential risks to the natural ecosystem. The changes of stress effect were stimulated by the policy and planning, driving urban expansion in early period and ecological conservation latterly. Comprehensively, the integrated stress effect assessment improved the recognition of the spatiotemporal variation of ecological security patterns and urban expansion in Beijing.
Spatial Distribution Pattern Analysis of Unsafe Setting of Electric Wires in Urban Area Using K-function Methods: A Case Study of Guangming District
Authors: Liao Cong , Pang Xiao , Cai Heng , Tian Yuan
Published: August 2020

Hidden fire risk are important disaster-inducing factors for potential fire accidents, which provides a breakthrough point for early intervention and prevention of potential fire accidents. Unsafe setting of electric wires is a very dangerous type of hidden fire risk that could cause fire accidents. It is of great significance to analyze the distribution pattern of hidden fire risk and related factors of this type of hidden fire hazard for early intervention. However, few researches have been done in the field of hidden fire risk. In this study, two network K-function methods, the univariate network K-function method and the bivariate network K-function method, were applied to analyze spatial patterns and its related factors of unsafe setting of electric wires as a hidden fire risk. The research data came from daily inspection in urban grid management of Guangming district, Shenzhen. The results indicated that the spatial distribution of unsafe setting of electric wires is highly related to the transportation network in the study area. The distribution pattern is influenced by the distribution of residential quarters and office buildings. The methods in this study can also be used to analyze other types of hidden fire hazards.
Research on the Countermeasures of Rural Ecological Environment Governance: Taking Qingyanggang Village in Hubei Province
Authors: Peng Xianze , Zhang Yingqi
Published: August 2020

The problem of inadequate development and inadequate development in my country is evident in rural areas, especially in ecological governance. This article takes Qingyanggang Village, a village in the Jianghan Plain, a land of fish and rice as an example, to focus on analyzing and studying the difficulties and problems in its ecological governance: lack of infrastructure for domestic sewage treatment, the slow accumulation of domestic garbage, lack of environmental awareness among villagers, and serious rural agricultural pollution. In view of the existing problems, and in accordance with the basic requirements of national ecological civilization construction and rural ecological revitalization, corresponding suggestions were put forward to promote the Qingyanggang village revitalization plan as a whole, increase the effective utilization of resources, accelerate the ecological environment governance, and promote Qingyanggang village Revitalize green and sustainable development.
Economic Optimization of Multiple Microgrids System Based on Alliance Theory
Authors: Zhou Yibin , Zhou Fengquan , Liu Yang , Wang Zixuan , Li Peng
Published: August 2020

Aiming at the problem of economic operation of multiple microgrids system, a coordinated optimized operation method of multiple microgrids in integrated energy system based on alliance theory was proposed. Firstly, energy storage station was introduced into multiple microgrids optimal scheduling, the energy flow relationship between various links was studied, and an economic optimal dispatch model was established under the alliance mode of multiple microgrids and energy storage station; Secondly, constructed a Shapely value benefits distribution mechanism to carry out the initial benefits distribution of the alliance and the secondary distribution of the multiple microgrids internal benefits. Finally, taking a typical daily scenario as an example, the optimal operation scheduling strategy of multiple microgrids with the participation of energy storage station was obtained. The results showed that the method proposed in this paper can effectively improve the benefits of all participants and ensure the economic operation of multiple microgrids, at the same time, it realized the full consumption of renewable energy.
Experimental Research on Destruction Characteristics of Mud Inrush on Tunnel in Argillaceous Fault Fracture Zone
Authors: Yang Teng , Zhang Qingsong , Zhang Xiao , Wang Deming
Published: August 2020

The argillaceous fault fracture zone is a special area which bears the most concentrated stress when it forms and develops. Therefore, the tunnel under construction is subject to serious water and mud inrush when excavated through this area. In order to explore the destruction characteristics of mud inrush, a large-scale three-dimensional geological model test was carried out, which overcomes the “black box” problem of the traditional test, and a cone-shaped and parabolic body model were proposed to depict the shape of soil disturbance. In addition, the evolution law of displacement field inside medium was studied and the change regulation of actual disaster influence area also was been revealed. Finally, the tunnel mud inrush mechanics were revealed according to destroyed characteristics. As the results showed, the location of the initial mud inrush occurred at the spandrel of the tunnel face, the displacement of soil near the location of mud inrush increased with proceeding time, but there was a sudden saltation of the increasing rate when the disaster occurred. Besides, the shape of surface subsidence above the location of the inrush gradually transferred from “W” to “V” in the process of mud inrush. With the increase of the number of mud inrush, the soil disturbance develops from the local to the whole. When the local disturbance occurs, the soil form is cone, while when the whole disturbance occurs, the soil form is parabola. In addition, it is found that soil displacement is related to the seepage pressure under different disturbance modes. Finally, the conclusion of the model test may shed light on the catastrophic process and evolution law of the mud inrush in fault fracture zone. which has certain guidance and reference significance for the prevention of mud inrush in similar projects.
Description of HVAC System and Identification of Flow Rates and Pressures in HVAC Based on Collective Intelligence System
Authors: Li Huai , Yu Zhen , Li Li
Published: August 2020

The efficient control of the HVAC system is important for the reduction of energy consumption in buildings. The water and air distribution network of HVAC system not only consume energy but also determine whether the cold and heat are delivered properly in the building according to the cooling and heating loads. The optimal control of the HVAC distribution system is complex due to the scale of the network and the coupling effects between HVAC devices. This paper proposes a novel distributed control system using standard computing process nodes, which is called the Collective Intelligence System (CIS). The proposed method is validated using a typical HVAC system in a real office building. The description of the HVAC system and the identification of flow rates and pressures of the distribution network is demonstrated using the decentralized identification algorithm.
Based on Numerical Control Fold the Speed of Curved Robot System from Meet Speed with Swing to Study
Authors: She Minghui , Weng Wei , Chen Huihuang , Yang Adi , Yu Lun
Published: August 2020

In order to solve the current domestic sheet metal enterprise users has increased rapidly, but there are still most bending machine or manual operation problem, involving the employment difficult problems, according to labor shortage problem, must promote intelligent enterprise transformation, realize the exchange Labour “machine”, the development and application of nc bending robot system is the inevitable developing trend of sheet metal industry, speed adaptive speed and oscillation is important in the development and application of nc bending robot system. This paper describes the system model of the speed adaptive speed and swing of the CNC bending robot system, and analyzes the performance of the speed adaptive speed and swing system comprehensively. The results of computer simulation show the consistency between simulation and theory.
Data-Dirven Method for Wake Effect Analysis on Nacelle Anemometer
Authors: Jing Bo , Qian Zheng , Chen Tianyang , Pei Yan , Kang Dahai
Published: August 2020

For most wind turbines, blade wakes affect the measurement of nacelle anemometer, result in the inconsistency between nacelle wind speed (NWS) and free stream wind speed, which seriously affects the power forecasting and performance evaluation of wind turbine. This paper proposes a data-driven method to analyse the wake effect on nacelle anemometer. At first, we use Relevance Vector Machine to establish a site calibration model between Lidar wind speed (LWS) and NWS. After that, we can use the calibrated LWS to replace the free stream wind speed, and wake effect on nacelle anemometer can be evaluated by comparing the calibrated LWS and NWS. Then, Wind Turbine Power Curve (WTPC) is applied to make a detail analysis of wake effect on nacelle anemometer. The experimental results show that wake effect accelerates the air velocity behind the impeller. Therefore, WTPC fitted by NWS is “lower” than the real one. However, SCADA system overcorrects the wake effect, thus WTPC fitted by SCADA data is “higher” than the real power curve.
The Reducing Ambience Analysis under the Low Nitrogen Mode Operation of a Boiler
Authors: Xiang Baixiang , Huang Jun , Li Yan , Han Binqiao
Published: August 2020

In 2014, the electricity industry boilers are required to meet the ultra-low emissions standard. Specifically, the dust, SO2, NOx are required to reach 5, 35, 50 mg/m3, respectively. Hence, the boiler operated under lean oxygen will be widely and long-term existed. In this paper, the distributions of velocity, temperature and flue gas composition were simulated under different air distribution modes. The numerical simulations demonstrated that both the CO and H2S contents in the major burner zone increased with the SOFA rate increasing. However, there is almost no CO and H2S in the burnout zone due to the increase of SOFA. Besides, as the SOFA rate increasing, NO in the burnout zone slightly increased, but the NO in the main combustion zone significantly reduced.
An Approximate Analysis of Insulation Thickness of Elliptic Pipe
Authors: Shi Jinsheng , Zhang Qiaozhen
Published: August 2020

The thermal insulation characteristics of elliptic pipe were analyzed preliminarily. Thermal resistances between elliptic pipe line to surrounding ambient were studied in dimensionless form. The expression for critical insulation thickness was obtained. The lower bound thickness and heat transfer rate were researched. Influences of different factors were discussed. It is found that for cases of small Biot number, the lower bound thickness is obviously greater than the critical thickness. And the addition of insulation material upon elliptic pipe line should be conducted enough so that the insulation layer exceeds the lower bound thickness in order the insulation investment play a positive role.
Exploration on Teaching Method Improvement in the Course of Design Principle of Steel Structure
Authors: Li Qiang , Mao Jianghong , Zhang Jun , Fan Weijie , Wang Yinhui
Published: August 2020

The course “design principle of steel structure” is one of the main professional courses in civil engineering, which has the characteristics of many contents, strong theory and high requirement of innovative design ability. Based on the analysis of the present situation of the teaching of the steel structure course in the college, this paper puts forward the existing teaching problems and probes into the concrete methods of the innovation and reform of the steel structure course, which is of great practical significance to improve the teaching effect and the education quality.
Practice of Training Building Industrialization Talents under the Background of New Engineering by Course Reconstruction
Authors: Zhang Jun , Mao Jianghong , Fan Weijie , Li Qiang , Wang Yinhui
Published: August 2020

Targets of training building industrialization talents under the background of new engineering are to develop the engineering practice ability, innovation ability and cross-border ability. As a part of traditional civil engineering comprehensive experiment course, bending experiment of reinforced concrete (RC) beam was reconstructed based on PC project in this paper. By simulating the stakeholders in the actual project, students’ autonomous learning ability is well stimulated. Both traditional professional knowledge and expanded professional knowledge were involved in the new mode. Practice of this paper demonstrate that higher education should be student-centered and design of reconstructed course should conform to the most typical engineering project.
Random Seismic Response Analysis of Long-Span Steel-Concrete Composite Structure
Authors: Gu Zhenyuan , Kan Xinjia , Zhang Zhenting , Cao Xiaojian , Shen Qiangru
Published: August 2020

Considering the randomness of seismic input and the nonlinear characteristic of long-span structures, the probability density evolution method is used to study the dynamic response of the long-span steel-concrete composite structure under random earthquake. Three-dimensional structural model is established in the finite element software SAP2000, and then the displacements between layers and the response rule of vertical displacements of truss roof of the composite structure are obtained. The results show that under the input of three-dimensional earthquake, the vertical displacement of the grid roof of the isolated long-span steel-concrete composite structure is an order of magnitude larger than the horizontal direction of each layer. The probability density evolution method can offer comprehensive probability information of nodal displacements, and provide a reasonable way for the seismic reliability analysis of long-span isolated structures.
A Comparative Study on Wellbore Pressure Transmission of Water and Carbon Dioxide during Fracturing
Authors: Xiao Caiyun , Ni Hongjian , Zhao Bo , Li Ning
Published: August 2020

Hydraulic fracturing is one of the most effective ways for the development of unconventional oil and gas resources, CO2 has been regarded as an excellent alternative to water as its broad application prospects in unconventional reservoir development and benefit for CO2 utilization. The wellbore pressure will keep rising before fracture initiation during hydraulic fracturing, and fluid properties have significant influence of wellbore pressure transmission especially for CO2 fracturing. In this paper, a wellbore pressure transmission model based on the definition of fluid compressibility is established and coupled with wellbore flow model of compressible fluid to calculate the borehole pressurization rate for water-based and CO2 fracturing. The model has been verified by field data. The results show that the borehole pressurization rate for both water-based and CO2 fracturing reveal rising trend as pump rate increasing, and borehole pressurization rate of water-based fracturing is 10∼20 times that of CO2 fracturing with same pump rate. Moreover, the borehole pressurization rate increases linearly with pump rate of water-based fracturing, but excessive pump rate might reduce borehole pressurization rate of CO2 fracturing. The research results can simulate more perceptions for the optimizing design of actual hydraulic fracturing operating.
An ETA-PDE Method for the Fragility Analysis of Concrete Dam
Authors: Xu Qiang , Xu Shutong , Chen Jianyun , Li Jing , Jia Qibin
Published: August 2020

A nonlinear damage ETA-PDE method is proposed for the fragility analysis of concrete dam. The endurance time analysis (ETA) method and the generalized probability density evolution (PDE) method are constructed by optimization and the method of lines (MOL) algorithm especially for the randomness of ground motion. Then, by integrating the ETA method and generalized PDE method, a nonlinear damage ETA-PDE method is established. To verify the applicability and reliability of the proposed ETA-PDE method, by using the tensile damage model, the nonlinear damage dynamic calculation and the fragility analysis are carried out for the Koyna concrete gravity dam. The results show the proposed PDE method can capture details of the probability density distribution for the fragility indicators (such as the plastic dissipation energy, the damage dissipation energy, the damage volume and so on). The proposed ETA-PDE method has special advantages on the calculating scale and solving probability density. Thus, it is suitable for practical engineering applications.
Safety Risk of Flammable and Explosive Dangerous Goods through the Ship Lock
Authors: Xie Tiansheng , Han Chao , Wang Guobo , Fengyun Chen
Published: August 2020

Based on the analysis of the current situation on flammable and explosive dangerous goods passing through the Three Gorges ship lock, evaluate leakage, fire, and explosion hazards through typical accident simulation calculations to find out the hazardous characteristics and safety risks of flammable and explosive dangerous goods through the Three Gorges ship lock. The study indicates the main safety risks of flammable and explosive dangerous goods passing through the ship lock are ship collision, grounding, leakage, fire and explosion, as well as the facilities strength declining in lock chamber, cracks or other structural destructions due to the long-time high temperature under flame or overpressure of the explosion.
Oxidation response of additively manufactured eutectic Mo-Si-B alloys
Authors: Becker J , Fichtner D , Schmigalla S , Schultze S , Heinze C , Küsters Y , Hasemann G , Schmelzer J , Krüger M
Published: August 2020

Previous studies showed the technical feasibility of additive manufacturing (AM) of Mo-Si-B alloys using the laser powder bed fusion (L-PBF) process. The competitiveness of the properties of AM alloys was demonstrated by a comparison to literature data from conventionally processed Mo-Si-B materials. In addition to the excellent mechanical properties at ambient and elevated temperatures, the oxidation resistance in a wide temperature range is another decisive aspect for the potential use of AM Mo-Si-B alloys. The present work shows investigations on the cyclic oxidation performance of a eutectic AM Mo-16.5Si-7.5B alloy. Depending on the temperature (800 °C, 1100 °C, 1300 °C), the oxidation mechanisms are different, which is due to different reactions at the surface of the alloys accompanied with mass changes of samples. These mass changes can be explained on the basis of microstructural investigations. However, compared to a directionally solidified (DS) alloy, the AM alloy shows improved oxidation resistance.
Microstructure and surface investigations of TiAl6V4 and CoCr28Mo6 orthopaedic femoral stems
Authors: Crackau M , Harnisch K , Baierl T , Rosemann P , Lohmann C H , Bertrand J , Halle T
Published: August 2020

Total hip arthroplasties (THA) achieve very good clinical results and show annually increasing numbers of implantation. Interactions of the bone with the implants surface are of major importance for a stabile fixation and longevity of the implant. Therefore, manufacturing of the material and the implants as well as their surface properties can have a decisive influence on the functionality of the implant. The aim of the present study is the investigation of two commercially available femur stems with analytical methods. One stem is made of a TiAl6V4 wrought alloy for cementless application and the other one is made of a CoCr28Mo6 cast alloy for cemented fixation. The change of the production-related microstructure within the implant, differences between surface and bulk properties and potential correlations between the production-related changes to predict failures are addressed. Longitudinal cross sections of tested stems were prepared metallographically, investigated using optical and scanning electron microscopy including EDS and EBSD and correlated with micro hardness depth profiles. Due to production and processing, a subsurface layer is formed in both alloys. The TiAl6V4 wrought alloy stem exhibits a homogenous recrystallization microstructure with fine grains of micrometre size. The subsurface layer of the stem is deformed in parts with embedded corundum particles within the depth of 10 µm. Corundum residues were detected on the entire stem surface and partially covered by the applied calcium phosphate spray coating. The CoCr28Mo6 cast alloy stem shows a dendritic microstructure with chromium- and molybdenum-rich interdendritic precipitations and a surface layer of smaller globular grains in the size of 50 µm to 200 µm. The face centred cubic (fcc) crystal structure was predominantly detected in the phase analysis. The brittle hexagonal close packed (hcp) phase was evident at the implants surface. Similar to the TiAl6V4 alloy stem, embedded residues of corundum particles were detected on the implant surface. This study shows different surface integrities for both stems in comparison to the base material. The observed residues from the manufacturing processes are generally well-embedded into the implant surface, however if released they could impair the functionality of the endoprosthesis as the particles might negatively affect the sterilization process or might reduce metal corrosion resistance.
Preceramic polymer-derived ceramic foams with lamellar strut porosity
Authors: Dammler K , Schelm K , Kniep D , Hasemann G , Scheffler M
Published: August 2020

Open porous replica foams with additional lamellar strut pores were prepared by preceramic polymer processing combined with a freeze-drying process. Polymer foam templates were coated with an aqueous polymethylsilesquioxane system followed by freezing at - 20 °C to generate hierarchical porosity within the foam struts. The cellular structure was preserved during freeze drying, cross-linking, template removal and pyrolysis, and additional strut porosity was formed. The size of the lamellar strut pores was found to depend on the solid load of the preceramic slurry and its pretreatment procedure. The cellular materials obtained in this work possess additional lamellar strut pore channels with a thickness of approximately 40 µm and a total foam porosity of > 90 %.
Improvement of the martensitic stainless steel X46Cr13 by Q&P heat treatment
Authors: Dieck S , Ecke M , Halle T , Rosemann P
Published: August 2020

The innovative heat treatment concept of “Quenching and Partitioning” (Q&P) enables the production of high-strength martensitic steels with high ductility. Residual austenite is stabilized in the partitioning process by carbon diffusion. This enables the strain-induced phase transformation from austenite to martensite and increases the ductility without reducing the strength. So far, little research has been done on the application of the Q&P process on martensitic stainless steels and their related corrosion resistance. The present work supplements the first investigations by Yuang and Raabe with important material-technical parameters as well as the achievable corrosion resistance. The Q&P heat treatment offers enhanced mechanical properties and a higher corrosion resistance in comparison to the conventional quenching and tempering heat treatment.
On the effect of aluminum and chromium on the deformation twinning of body-centered cubic iron
Authors: Ecke M , Michael O , Halle T
Published: August 2020

This paper reports on investigations on the effect of aluminum and chromium on the formation of deformation twins in body-centered cubic iron. For this purpose, impact loading experiments (ε = 104 s−1) were carried out at room temperature on samples of iron and the alloys Fe-10at.-% Al and Fe-10at.-% Cr. Furthermore, the grain size was varied in order to consider the effect of the alloying elements for both fine-grained and coarse-grained microstructures. The investigations on twin formation were carried out by electron backscatter diffraction (EBSD) and by quantitative image processing using optical microscopy. The observations show a comparable twin portion in iron and Fe 10at.-% Cr after impact loading for both grain sizes. In the alloy Fe-10at.-% Al the portion of twins is significantly increased for fine-grain and coarse-grain state. In order to clarify the possible reason, X-ray diffraction analyses (XRD) were additionally carried out. These show a shift in the reflexes which can be attributed to an elastic distortion of the lattice. This lattice distortion due to the formation of solid solution correlates very well with the determined twin fractions.
Comparison of liquid and gel electrolytes for the investigation of pitting corrosion on stainless steels
Authors: Heyn A
Published: August 2020

Electrochemical methods have become established for the investigation and testing of stainless steels for their resistance to pitting corrosion. In contrast to liquid electrolytes, which are normally used for this purpose, gel-like electrolytes have clear advantages regarding their usability. However, it must be clarified whether both types of electrolyte lead to the same or different results. In the investigations presented here, various agar-based gel electrolytes were characterized regarding their corrosion-relevant properties, such as chemical composition, rheo-logical properties and the electrolyte film forming on the surface. To compare the two electrolyte types, electrochemical investigations were carried out with graduated agar and NaCl concentrations on the material 1.4301 (AISI 304). Pitting and repassivation potentials were determined by dynamic polarization experiments and the varied factors were statistically evaluated regarding their influence. The results show that liquid and gel electrolytes provide comparable results. However, the pitting corrosion phenomena under external polarization are shallower with gel electrolytes and therefore their repassivation is supported. Also, the use of gel electrolytes with indicators for iron ions, which at the same time act as oxidizing agents and allow polarization into critical areas, gives comparable results. Gel electrolytes are therefore a very good alternative to liquid electrolytes if the detection of corrosion-sensitive surfaces is in focus.
Recent advances in additive manufacturing of Mo-Si-B alloys – A status report on the cooperative project LextrA -
Authors: Krüger M , Schmelzer J , Fichtner D , Heinze C , Küsters Y , Rittinghaus S K , Weisheit A , Heinz R , Gerking L , Gruber K , Schmigalla S , Schultze S
Published: August 2020

Mo-Si-B alloys are potential materials for ultra-high temperature applications, e.g. as turbine blades. Due to their excellent mechanical properties they are subject to basic research for about 20 years. The next step towards industrial application of this type of alloys is to use the current knowledge on microstructure-properties relationships and combine this with innovative laser additive manufacturing (AM). This way of processing is very challenging since the melting point of Mo-Si-B materials is > 2000 °C and the brittle-to-ductile transition temperature is typically about 900 °C. The authors demonstrate that gas atomized Mo-Si-B powders of three different compositions could be successfully processed by different AM processes, namely Direct Energy Deposition (DED) and Laser Powder Bed Fusion (LPBF). It is verified that the mechanical and oxidation properties provided by the AM materials are comparable and competitive to similar alloy compositions from conventional processes.
Simulative and experimental investigations on single-sided resistance spot brazing of sheet metal tube connections as an alternative to single-sided resistance spot welding
Authors: Najuch M , Jüttner S , Schmicker D
Published: August 2020

In order to reduce the deficits in single-sided resistance welding (SSSW), single-sided resistance brazing is a promising alternative. The reason for this is a process-related reduced thermal and mechanical component impact compared to SSSW. In the underlying article, the single-sided resistance brazing process will therefore be presented. In addition to the process architecture, the process advantage is presented and the joining characteristics are clarified. Finally, the presumed process advantage is confirmed by means of a practical example.
Hydrogen diffusion and local Volta potential in high- and medium-entropy alloys
Authors: Rhode M , Wetzel A , Ozcan O , Nietzke J , Richter T , Schroepfer D
Published: August 2020

High-entropy alloys (HEAs) are characterized by a solid solution of minimum five and medium-entropy alloys (MEAs) of minimum three principal alloying elements in equiatomic proportions. They show exceptional application properties, such as high-strength and ductility or corrosion resistance. Future HEA/MEA-components could be exposed to hydrogen containing environments like vessels for cryogenic or high-pressure storage where the hydrogen absorption and diffusion in these materials is of interest. In our study, we investigated the HEA Co20Cr20Fe20Mn20Ni20and the MEA Co33.3Cr33.3Ni33.3. For hydrogen ingress, cathodic charging was applied and diffusion kinetic was measured by high-resolution thermal desorption spectros-copy using different heating rates up to 0.250 K/s. Peak deconvolution resulted in high-temperature desorption peaks and hydrogen trapping above 280 °C. A total hydrogen concentration > 40 ppm was identified for the MEA and > 100 ppm for HEA. This indicates two important effects: (1) delayed hydrogen diffusion and (2) considerable amount of trapped hydrogen that must be anticipated for hydrogen assisted cracking phenomenon. Local electrochemical Volta potential maps had been measured for the hydrogen free condition by means of high-resolution Scanning Kelvin Probe Force Microscopy (SKPFM).
Influence of modern machining processes on the surface integrity of high-entropy alloys
Authors: Richter T , Schröpfer D , Rhode M , Börner A
Published: August 2020

High Entropy Alloys (HEAs) are a recent class of materials. In contrast to conventional alloys, HEAs consist of five alloying elements in equiatomic equilibrium. The high entropy effect is due, among other things, to the increased configuration entropy, which promotes solid solution formation. Many HEAs have enormous application potential due to excellent structural property combinations from very low to high temperatures. For the introduction of HEAs in real components, however, the question of the applicability of machining production technologies for component manufacture is of central importance. This has so far received little attention in global materials research. Reliable and safe processing is essential for the demand of economical component production for potential areas of application, e.g. in power plant technology. For metals, milling is the standard machining process. This article presents the results of machining analyses. It focuses on the surface integrity resulting from the milling process on a Co20Cr20Fe20Mn20Ni20-HEA. For this purpose, investigations were carried out using ball nose end milling tools for conventional milling process in comparison to an innovative hybrid process available at BAM Berlin, Ultrasonic-Assisted Milling (USAM). USAM promises a lower degradation of the surface properties due to lower loads on the workpiece surface during machining. For this purpose, basic milling parameters (cutting speed and tooth feed) were systematically varied and cutting forces were measured during the milling experiments. The subsequent analysis of these forces allows an understanding of the mechanical loads acting on the tool and component surface. These loads cause topographical, mechanical and microstructural influences on the surface and consequently on the surface integrity. For their characterization, light and scanning electron microscopy were used, and the roughness and residual stresses via X-ray diffraction were measured. The results indicate significant advantages using USAM, especially due to reduced cutting forces compared to the conventional milling process. This causes lower mechanical loads on the tool and surface, combined with lower tensile residual stresses on and below the surface, and ultimately results in a significantly enhanced surface integrity.
KorroPad testing - applications from industry and research
Authors: Rosemann P , Kauss N , Heyn A
Published: August 2020

The pitting corrosion resistance of stainless steels can be assessed with the KorroPad test in a very simple, quick and inexpensive way. The KorroPad is therefore an interesting alternative to time-consuming long-term tests and complex electrochemical investigations for manufacturers, processors and users of stainless steels. In this article, the basic functionality of the KorroPad is described and selected examples from industry and research illustrate it´s application. The assessment of grinding processes and post-weld treatment are first presented as relevant examples regarding industrial surface treatments on the pitting corrosion resistance. Subsequently, current research to the modification of the KorroPad test is presented, which shows the specific detection limit of KorroPads on binary Fe-Cr reference alloys. Finally, modified KorroPads are used to detect microstructure related susceptibility to pitting corrosion induced by sensitizing heat treatment. The KorroPad enables the creation of a sensitization T-t diagram based on the pitting corrosion resistance.
Sensitization behaviour of the nitrogen alloyed austenitic stainless steel X8CrMnMoN18-19-2
Authors: Rosemann P , Müller C , Halle T
Published: August 2020

Austenitic stainless steels have been used in many different industrial branches. Nitrogen alloyed austenite´s with up to 20 wt. % manganese and 0.8 wt. % nitrogen have been available on the market as nickel-free grade for some years. In these steels, the austenitic matrix is stabilized without the addition of nickel, while the corrosive resistance and mechanical properties are significantly improved by addition of Mn and N. As with all stainless steels, the chemical composition and heat treatment have a decisive influence on structure, mechanical properties and corrosion resistance. Solution annealing, quenching and work hardening are applied to combine excellent mechanical properties (Rm from 900 MPa to 2,000 MPa, A5 > 50 %, Av > 350 J) with high corrosion resistance. Solution annealing is applied to eliminate undesired precipitation phases (Cr2N, M23C6 and sigma phase), distribute the alloy elements homogeneously in the austenite and assure the high corrosion resistance. If the distribution of the alloy elements (Cr, Mo and N) is impaired by suboptimal heat treatment, processing or high temperature conditions, the corrosion resistance can be reduced. Precise knowledge of the sensitization behaviour of these high nitrogen alloyed steels is necessary. Therefore, the sensitization behaviour of the nitrogen alloyed austenitic steel X8CrMnMoN18-19-2 (1.4456) was investigated by thermal ageing in the temperature rage of 500 °C to 900 °C for up to 100 h. Thermodynamic calculations were used to predict the formation of different phases. The microstructure of the various sensitization states was evaluated by scanning electron microscopy (SEM) and compared with the corrosion resistance characterized by the electrochemical potentiodynamic reactivation (EPR) test and the KorroPad method. The reduction of corrosion resistance is correlated with the occurrence of M2N nitrides in the microstructure and two sensitization diagrams were created based on the experimental results.
Einfluss des Umwandlungs- und Erstarrungsverhaltens nicht-rostender Chrom-Nickel-Stähle auf die Schweißeignung beim Hochleistungsschweißen
Authors: Schuster J
Published: August 2020

Inhalt. Die Zielstellung der vorgestellten Untersuchungen bestand in der Klärung des Einflusses der gegenüber den herkömmlichen Schweißprozessen größeren Abkühlgeschwindigkeit des Laserstahlschweißens auf das Erstarrungs- und Umwandlungsverhalten hochlegierter Chrom-Nickel-(Molybdän)Stähle. Wie nachgewiesen werden konnte, treffen für Strahlschweißprozesse u. U. die Iso-Ferritlinien im WRC-92- und im SCHAEFFLER-Diagramm nicht mehr zu. Dabei zeigt das SCHAEFFLER-Diagramm Erstarrungswechsel besser an als das WRC-92-Diagramm. So verschiebt sich im WRC-92-Diagramm der Erstarrungswechsel zu höheren Werten des Ni-Äquivalents.
First principles density functional theory calculations on the elastic properties of Mo-Si based solid solutions
Authors: Touzani R S , Krüger M
Published: August 2020

The alloy system Mo-Si-B gained a lot of attention, as it showed superior elastic properties than currently used Ni based superalloys at elevated temperatures. In the Mo-Si-B alloy system, Mo based solid solutions play an important role as a compound and one can observe a solid solution with small amounts of Si and tiny, almost negligible, amounts of B. To improve the ductility of this alloy at higher temperatures, titanium is added and as a result Mo-Si-Ti solid solutions are formed. To get an idea of the elastic properties of new Mo based solid solutions, first principles density functional theory calculations serve as a powerful method for the prediction and qualitative, often almost quantitative results for the elastic moduli are achieved. Here we show the elastic properties like bulk, shear and Young’s modulus as well as the Vickers hardness, calculated with first principles density functional theory (DFT), of Mo-Si-B-Ti based solid solutions with approximated atom concentrations Mo-1 at.% Si, Mo-3 at.% Si, Mo-2 at.% Si-1 at.% Ti, Mo-3 at.% Si-1 at.% B and Mo-3 at.% Si-1 at.% Ti.
Microstructural Characterization of Quenched and Partitioned commercial Medium Carbon Steel
Authors: Wilke A , Dieck S , Härtel M , Lampke T , Halle T
Published: August 2020

In order to achieve the desired properties, the microstructure of metals is often modified by heat treatments. A suitable combination of high strength and good ductility can be achieved by adjusting the amounts of martensite and retained austenite through a Quenching and Partitioning (Q&P) process. Controlling these material properties offers new potentials in the production of light weight steel parts. This paper presents a basic study of heat treatment conditions with subsequent microstructural characterization of quenched and partitioned commercial 0.54C-1.45Si-0.71Mn spring steel. Beginning from full austenitization, different quenching and partitioning parameters were applied. Microstructural characterization was performed using optical microscopy in combination with different etching methods as well as Scanning Electron Microscopy (SEM) and Electron Backscattered Diffraction (EBSD). It is shown that the intended dual phase microstructure with a specific phase fraction of austenite can be produced. Those results and consideration of hardness measurements show that the investigated commercial spring steel is a promising candidate for improving mechanical properties by a Q&P process.
Pyroelectric X-ray Generator for XRF in Combination with Optical Microscopy
Authors: Wilke M , Hanns L , Harnisch K , Knapp W , Ecke M , Halle T
Published: August 2020

X-ray fluorescence spectroscopy (XRF) is a method for elemental analyses of materials. In comparison to other analysing methods such as energy dispersive X-Ray spectroscopy (EDS) within a scanning electron microscope (SEM) or optical emission spectroscopy (OES) there are several advantages. This paper contains experimental investigations to improve the emission behaviour of a pyroelectric X-ray source regarding X-ray energy and output intensity. Pyroelectric lithiumtantalate (LiTaO3) was used to emit and accelerate electrons and to generate primary X-rays subsequently. Geometrical conditions were altered and the design of the X-ray source was optimized. All steps of optimization have been performed with respect to an application in a spectroscopic device in combination with an optical microscope (OM). Based on this purpose, the miniaturization of all applied components is of major importance. Different pure metals, alloys, and a coated specimen were analysed to demonstrate potential applications and current limitations of the designed system. Materials with a wide range of necessary excitation energy for chemical analyses of 1.5 to 10 keV for the Kα and Lα X-ray fluorescent lines were used to demonstrate the technical relevance of this type of application. As a result, a prototype of a spectrometer that combines XRF and OM was designed and tested.
What Can Mechanisms Underlying Derived Traits Tell Us About the Evolution of Social Behavior?
Authors: Treanore Erin , Derstine Nathan , Amsalem Etya
Published: August 2020

Social behavior, although rare, is a highly successful form of living that has reached its most extreme forms in eusocial insects. A tractable framework to understand social evolution is the study of major transitions in social behavior. This includes the transitions between solitary to social living, from species exhibiting intermediate degrees of sociality to species exhibiting true sociality, and from primitive to advanced eusocial species. The latter transition is characterized by the emergence of traits not previously found in primitive eusocial species, such as fixed morphological differences between castes and task specialization within the sterile caste. Such derived traits appear to exist in a binary fashion, present in advanced eusocial species, and absent or rare in primitive ones, and thus do not exist in a gradient that is easily tracked and compared between species. Thus, they may not be viewed as valuable to explore ultimate questions related to social evolution. Here, we argue that derived traits can provide useful insights on social evolution even if they are absent or rare in species with a lower social organization. This applies only if the mechanism underlying the trait, rather than the function it regulates for, can be traced back to the solitary ancestors. We discuss two examples of derived traits, morphological differences in female castes and primer pheromones regulating female reproduction, demonstrating how their underlying mechanisms can be used to understand major transitions in the evolution of social behavior and emphasize the importance of studying mechanistic, rather than functional continuity of traits.
A Likelihood Ratio Test for Gene-Environment Interaction Based on the Trend Effect of Genotype Under an Additive Risk Model Using the Gene-Environment Independence Assumption
Authors: de Rochemonteix Matthieu , Napolioni Valerio , Sanyal Nilotpal , Belloy Michaël E , Caporaso Neil E , Landi Maria T , Greicius Michael D , Chatterjee Nilanjan , Han Summer S
Published: August 2020

Several statistical methods have been proposed for testing gene-environment (G-E) interactions under additive risk models using data from genome-wide association studies. However, these approaches have strong assumptions from underlying genetic models, such as dominant or recessive effects that are known to be less robust when the true genetic model is unknown. We aimed to develop a robust trend test employing a likelihood ratio test for detecting G-E interaction under an additive risk model, while incorporating the G-E independence assumption to increase power. We used a constrained likelihood to impose 2 sets of constraints for: 1) the linear trend effect of genotype and 2) the additive joint effects of gene and environment. To incorporate the G-E independence assumption, a retrospective likelihood was used versus a standard prospective likelihood. Numerical investigation suggests that the proposed tests are more powerful than tests assuming dominant, recessive, or general models under various parameter settings and under both likelihoods. Incorporation of the independence assumption enhances efficiency by 2.5-fold. We applied the proposed methods to examine the gene-smoking interaction for lung cancer and gene–apolipoprotein E $\varepsilon$4 interaction for Alzheimer disease, which identified 2 interactions between apolipoprotein E $\varepsilon$4 and loci membrane-spanning 4-domains subfamily A (MS4A) and bridging integrator 1 (BIN1) genes at genome-wide significance that were replicated using independent data.