forming mechanism
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2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Juan Wang ◽  
Xiongrong Huang ◽  
Wei Wang ◽  
Haosheng Han ◽  
Hongyu Duan ◽  
...  

Purpose The purpose of this study is to determine the tribological behavior and wear mechanism of a polytetrafluoroethylene (PTFE)/polyester (PET) fabric composite for application as a self-lubricating liner suitable for high-speed and low-load friction conditions. Design/methodology/approach The effects of different loads and sliding speeds on the friction coefficients and wear characteristics of the composite were studied using reciprocating friction tests. Scanning electron microscopy, extended depth-of-field microscopy, and energy-dispersive X-ray spectrometry was used to analyze the worn surface morphology, wear depth and elemental content of the lubrication films, respectively. Findings The friction coefficient curves of the composites presented a long-term steady wear stage under different sliding conditions. With increasing sliding speed, the friction coefficient and wear depth of the composite slowly increased. The film-forming mechanism of the composite revealed that the PTFE/PET ply yarn on the composite surface formed complete PTFE lubrication films at the initial sliding stage. Originality/value The PTFE/PET fabric composite maintained good friction stability and high-speed adaptability, which demonstrates that the composite has broad application prospects as a highly reliable self-lubricating bearing liner with a long lifespan.


2022 ◽  
Vol 2022 ◽  
pp. 1-18
Author(s):  
Guofeng Yu ◽  
Yunchun Han ◽  
Xiaoyang Yu ◽  
Ren Bao ◽  
Jiaxing Guo ◽  
...  

Gangue materials have been used to solve mine disasters with a support tunnel along the goaf and filling mining. Mastering the properties and damage characteristics of filling materials is an important basis for effective implementation. Based on the conventional uniaxial compression acoustic emission (AE) test, the effects of cementitious materials, ratio between water and cementitious material, gangue particle size, and grading parameters on the mechanical properties of gangue-cement samples were analyzed. The stage characteristics of compression deformation were studied. The fracture propagation characteristics and rock mass failure types induced by different graded gangues were revealed. The fracture forming mechanism from clustered damage and failure was interpreted. The results show that the compressive strength of the backfill increases with the increase of cementitious material; however, it decreases with the increase of water binder ratio. Controlling the proportion and dosage of materials was the key factor to realizing pumpability and stability. Combined with the deformation and AE characteristics, the failure stage of the backfill body is divided into three stages: linear deformation-low energy changing, block compression-high energy changing, and gentle stability-stable energy changing. Affected by the gangue distribution, the load in each stage will induce fracture to produce five distribution modes of single, turning, breakthrough, bifurcated, and collapsed surrounding gangue. In the process of loading failure, different gradation and particle sizes will also change its stress concentration characteristics, resulting in the transformation of rock failure types. The surface structure and roughness of gangue play an important role in the compressive performance of cement paste. The research results try to provide some guidance for efficient filling mining.


2022 ◽  
Author(s):  
Jiang Liuyun ◽  
Bingli Ma ◽  
Zhihong Jiang ◽  
Yingjun Ma ◽  
Yue Wen ◽  
...  

Abstract A novel nano-hydroxyapatite/bamboo fiber (n-HA/BF) bioactive composite membrane was obtained by a simple casting technique. The membrane forming mechanism and the effects of different forming membrane methods, drying methods and n-HA amounts on the properties of n-HA/BF membrane were investigated by Fourier Transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle, electromechanical universal tester, in vitro soaking in simulated body fluid (SBF) and in vitro cell cultureexperiment. The results demonstrated that the n-HA dispersity in BF matix was not affected by the prepartion condition, however, the morphologies of membrane was determined by the different preparation conditions owing to different hydrogen bond shrinkage. Moreover, the hydrophilicity of the composite membrane was improved under the condition of the membrane formation in oven, freeze drying and high addition content of n-HA, and the mechanical properties of composite membrane depended on n-HA content. In vitro soaking behavior indicated that the degradability and bone-like apatite deposition could be controled by differentpreparation conditions. And the cell proliferation experiment showed that the n-HA/BF composite membranes obtained under different preparation conditions were all non-toxic. The above results indicated that the n-HA/BF composite membrane could be obtained by a simple casting technique, and the properties could be controlled by adopting different preparation conditions, which would have a great promising as guide bone tissue regeneration (GBR) membrane, and the study would provide a new application for BF in biomedical field.


Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4333
Author(s):  
Feiyue Wang ◽  
Hui Liu ◽  
Long Yan

Three types of shell bio-fillers, including eggshell (CES), conch shell (CHS) and clamshell (CMS), were prepared by cleaning, ultrasonication and pulverizing processes of biowastes, and then applied to intumescent fire-retardant coatings. The effects of shell bio-fillers with different polymorphs on the fire resistance and char-forming of intumescent fire-retardant coatings were investigated by cone calorimeter test, fire protection tests, smoke density test, thermogravimetric analysis (TG), and the fire resistance and char-forming mechanism of bio-fillers in intumescent fire-retardant coatings were proposed. The results show that three kinds of bio-fillers exert an excellent synergistic effect on enhancing the fire resistance and char-forming properties of the intumescent fire-retardant coatings, while clamshell has the best synergistic efficiency among the bio-fillers. Especially, IFRC-CMS coating containing 3 wt% clamshell shows the best fire protection performance and lowest smoke production and heat release, which offers an equilibrium backside temperature of 134.6 °C at 900 s, a flame-spread rating of 14.4, and a smoke density rating value of 22.8%. The synergistic efficiency of bio-fillers in the intumescent coatings depends on the polymorphs of CaCO3 in bio-fillers, and aragonite CaCO3 shows a higher synergistic efficiency compared to calcite CaCO3 and the mixture of aragonite and calcite CaCO3. The CMS composed of aragonite shows the best synergistic effect, CHS composed of aragonite and calcite comes second, and CES composed of calcite has the weakest synergistic effect.


2021 ◽  
Vol 11 (23) ◽  
pp. 11552
Author(s):  
Chen Qiao ◽  
Fenglin Xu ◽  
Pengcheng Su ◽  
Yang Liu ◽  
Yifang Zhang ◽  
...  

The shear failure of rock is a major cause of rock slope instability and consequent landslides. To determine the forming mechanism of infrasonic waves during the loss of stability of sandstone slopes, experiments were carried out using a shear loading device and an infrasonic monitoring device. In the experiments, infrasonic wave events were identified, and the characteristic parameters of infrasonic waves were extracted to analyze the features of the infrasonic wave response during the shear failure of sandstone. The study results show that: (1) the whole process of shear failure was associated with infrasound events. A normalized energy cumulative coefficient of over 0.6 and a normalized infrasound rate of over 0.89 are the key time nodes for alarming landslide; (2) with an increase in sample size, the shear resistance of the sample increases logarithmically, the total energy of infrasound events increases exponentially, and the average dominant frequency of infrasound events decreases linearly; and (3) with an increase in axial pressure, the shear of the rock increases almost linearly, the number of infrasound events increases linearly, and the average dominant frequency of infrasound events increases exponentially. The research results provide important guidance for the dynamic monitoring and evaluation of the stability of sandstone slopes and can provide a theoretical reference for landslide alarming of sandstone slopes using infrasonic waves.


2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Xincun Zhuang ◽  
Meile Liang ◽  
Shengfa Zhu ◽  
Yin Zhu ◽  
Zhen Zhao

AbstractSheet-bulk metal forming (SBMF) is a promising process for manufacturing complex sheet components with functional elements. In this study, the entire forming process for a typical thin-walled component with external gearing is investigated, including sheet forming and bulk forming processes. Deep drawn cups are prepared during sheet forming; subsequently, upsetting is performed on the sidewall to form external gearing. The upsetting method performed is known as upsetting with a controllable deformation zone (U-CDZ). Compared with the conventional upsetting method, a floating counter punch with a counter force is used in the U-CDZ method such that the forming mechanism is changed into the accumulation of the deformation zone instead of deformation throughout the entire sidewall. The effects of the counter force and material flow are investigated to understand the mechanism. The forming quality, i.e., the formfilling and effective strain distribution, improved, whereas a high forming load is avoided. In addition, a punch with a lock bead is used to prevent folding at the inner corner during the experiment.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shun-Li Shang ◽  
Hui Sun ◽  
Bo Pan ◽  
Yi Wang ◽  
Adam M. Krajewski ◽  
...  

AbstractForming metallurgical phases has a critical impact on the performance of dissimilar materials joints. Here, we shed light on the forming mechanism of equilibrium and non-equilibrium intermetallic compounds (IMCs) in dissimilar aluminum/steel joints with respect to processing history (e.g., the pressure and temperature profiles) and chemical composition, where the knowledge of free energy and atomic diffusion in the Al–Fe system was taken from first-principles phonon calculations and data available in the literature. We found that the metastable and ductile (judged by the presently predicted elastic constants) Al6Fe is a pressure (P) favored IMC observed in processes involving high pressures. The MoSi2-type Al2Fe is brittle and a strong P-favored IMC observed at high pressures. The stable, brittle η-Al5Fe2 is the most observed IMC (followed by θ-Al13Fe4) in almost all processes, such as fusion/solid-state welding and additive manufacturing (AM), since η-Al5Fe2 is temperature-favored, possessing high thermodynamic driving force of formation and the fastest atomic diffusivity among all Al–Fe IMCs. Notably, the ductile AlFe3, the less ductile AlFe, and most of the other IMCs can be formed during AM, making AM a superior process to achieve desired IMCs in dissimilar materials. In addition, the unknown configurations of Al2Fe and Al5Fe2 were also examined by machine learning based datamining together with first-principles verifications and structure predictions. All the IMCs that are not P-favored can be identified using the conventional equilibrium phase diagram and the Scheil-Gulliver non-equilibrium simulations.


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