| Stress sensor is an important kind of device which have wildly been used indetecting the safety of engineering and mechanical structure. Especially, stress sensorplays a significant role in some huge buildings, bridges, tunnels and pipeline transportetc. Moreover, tiny stress characteristic in structures is an important informationwhich helps us to appraise fatigue, life and initial failure of materials. In this paper, itis worked on developing a tiny stress sensitive composite film which is made ofIron-based amorphous powder and rubber.In this article, the matrix material of these composite stress sensitive films arebutyl rubber (IIR) and silicon rubber (SIR). Meanwhile, the reinforcing materials areamorphous Fe73.5Cu1Nb3Si13.5B9and Fe73Si18B9powders (Hereinafter referred to asFeCuNbSiB and FeSiB powder). Fe73Si18B9/SIR, Fe73.5Cu1Nb3Si13.5B9/SIR andFe73.5Cu1Nb3Si13.5B9/IIR (Hereinafter referred to as FeSiB/SIR, FeCuNbSiB/SIR andFeCuNbSiB/IIR composite films) composite films have been made by means ofmechanical blending and precision casting pressure heat molding. And wesystematically researched the organization structure, physicochemical properties,stress sensitive, environment applicability, macroscopic and microcosmic distributionstress sensitive of these films. And the stress sensitive property is represented bystress impedance effect.On the basis of preliminary study and the study of this article,it is summarized several conclusions:(1) The preporties of different powder content with Fe73Si18B9soft film havebeen researched, which is applied stress at continuous upload and offload. When thefilm thickness of200μm, the particle size of Fe73Si18B9powder is300mesh number,and testing frequency is1kHz. Research shows that, with the speed of continuousupload or offload below0.1mm/min, testing frequency at1kHz and pressue at0.03~1MPa, the film is of a nice stability and sensitivity. The film is more sensitivewith pressure below0.2MPa. In this pressure range, with the powder contentincreased, the tendency of stress sensitive is indential. But the sensitive is increased.When the content of powder increased to83.3wt%, and pressure increased from0.03 to0.2MPa, the SI%value is from36.51%increase to82.48%. And the value of k isreduced from42.91to1.889. When pressure from0.2~0.7MPa, and the content ofpowder is83.3wt%, the value of k is from1.889~0.6. When pressure increased to1MPa, the value of k reduced approach to0.(2) The properties of Fe73.5Cu1Nb3Si13.5B9nanocrystalline powder/rubber softfilm. For the Fe73.5Cu1Nb3Si13.5B9/SIR soft film also have been researched, resultshows that, when the content of powder is35volwt%the thickness of film is200μm,and testing frequency is1kHz the film is of nice stress sensitive property. With thespeed of continuous upload or offload below0.5mm/min, testing frequency at1kHzand pressue at0.2~1MPa, the film is of a nice stability and sensitivity. With theincrease of pressure σ, the value of impedance Z reduced nonlinear, and the value ofSI%is from6%to23%,the sensitive value k is2~0.2, The standard deviation isbetween0.02~0.05. Film is more sensitive with stress below0.2MPa. But forFe73.5Cu1Nb3Si13.5B9/IIR soft film, the result shows that stability is better with stressloaded speed at v=0.1mm/min. When the process of upload, the sensitive value of kincreased in the beginning and reduced in the end. When offload, the value of kincreased with stress reduced. The sensitive property is better with frequency at1kHzthan50kHz. In the same testing conidion, the thickness of composite is better at200μm than150μm. The temperature between39.5℃and80℃, stress sensitiveproperty is increased with temperature increased.(3) Numerical simulation about this film have been done by means of ANSYSsoftware. It is mainly worked on the stress and deformation process of micro andmacro aspects. By the analysis, it is drawn two conclusions: Firstly, the contact ofamorphous powder and rubber can regard as soft contact. The stress distribution inflexible rubber is uniformly distributed and in rigid powder is not so. Stressconcentration phenomenon have appeared in rigid powder, which may be induced bythe dimensions, shapes and positions of amorphous powder. Secondly, Aboutdeformation of stretching process, general speaking, the mechanical side is muchbigger than constraint side, and deformation is gradient decreases between these twosides.(4) Stress-strain relationship of this film is measures by means of tensile testing machine and compression testing machine. The stress-strain behavior of thiscomposite film is a typical viscoelastoplastic material. We regard it as a plasticelement, a cohesive unit and an elastic element which combined together. It can beseen as a pure elastic material with slowly and tiny stress. While the stress up to itsyield point, plastic deformation appears. The property of cohesive can be ignoredwith low velocity loading. In this paper, we also discussed about the stress-strainrelationship of this composite film by Mises yield theory, and get its constitutiverelation.(5)In aspects of stress sensitive mechanism: In the base of preliminary study, theindependence value Z and its components L, C, R and phase angle θ have been tested.These kind of film appears stress-capacitive reactance and stress-impedanceproperties with high frequency alternating current testing. We also have modified theequivalent circuit model, and attached a more accurate calculated results. This articlesuggests that, the leading function of stress-impedance effect about the compositefilm is stress-capacitive reactance effect. The other aspects such as ICR, inductivereactance, and magnetoelectriceffects lead a secondary role. The equivalent circuitmodel renewed can equivalent as an ICR and multi-capacitance series connection.Since, Iron-based amorphous powder enhanced and rubber matrix compositefilms have some unique superiority, which include good weathering resistance, highlystability, excellent repeatability, and advantages on good controls of shapes, thicknessand size of material. It will hopefully to be widely used in tiny stress sensor area. |
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