Porous materials are widely used in the passive noise control field as sound absorbers. Conventional models of porous materials are assumed to have a rigid frame and to satisfy finite bulk elasticity. However, it may be the case that when high-frequency sound is applied to porous materials for nanotechnology applications, the classical theory of elasticity cannot be satisfied. Generalized continuum theories, such as coupled stress theory and micropolar theory, have additional degrees of freedom compared with classical elasticity. It is hence assumed that such theories are applicable to composites with granular structure. In this study, two of the six material constants are obtained from experimental results on micropolar porous solids by Lakes. At the same time, a theoretical analysis concerning reflected and transmitted fields of an incident longitudinal plane wave propagating in elastic-micropolar porous media has been investigated. The results show that two fields are affected by micropolar porous characteristics. The boundary value problem of micro elasticity is also investigated in this paper.
Micropin head geometry significantly influences surface contact and electrical conductivity. In this paper, the preforming process of extrusion is investigated to establish it as a viable process for microforming. Here, the numerical simulations using DEFORM-3D software are used to examine the effect of preformance and pin shape on the extrusion of microbrass pins with a minimum diameter of 0.88 mm under several design parameters. These parameters are planned with the Taguchi method and help to discover better conditions for the minimum extrusion loads. For obtaining the required parameters to enable the finite element software, a compression test is first performed to determine the true stress and true strain curve of the materials. The result acquired from the experiment is compared with the simulation outcome and verified the accuracy. The consequences show that the optimal microextrusion forming conditions appear on stage rod length 0.015 mm, extruding angle 60°, upper front-end taper 60°, and bottom stage angle 60° to minimalize the forming load, and the dimensions of the deformed micropin reveal a good identification with the simulation. The study hence shows a potential tool for the combination of Taguchi method and finite element software to analyze the microforming process in the fastener industry.
Porous materials are widely used in the passive noise control field as sound absorbers. Conventional models of porous materials are assumed to have a rigid frame and show finite bulk elasticity. However, in the case of acoustical wavescharacterized by high frequencies and small wavelengths -the effect of microstructure becomes significant. This effect of microstructure has resulted in the development of new types of waves, not found in the classical theory of elasticity. Generalized continuum theories include the construction of the linear theory of micropolar elasticity that consists of deformation and microrotation with six degrees of freedom, and hence can be used to study the acoustical characteristics of composites with a granular structure. In this study, we investigated transverse wave propagation and its reflection and transmission from a plane interface between two different elastic-micropolar porous interfaces in perfect contact. The micropolar porous composite was constructed using hollow glass microbubbles embedded in an epoxy matrix with six material constants that can be used as the acoustical absorbers. It was found that there are different wave types in a micropolar porous material for the incident SV (vertical transverse) or SH (horizontal transverse) wave. It was also found that these two coupled sets of transverse waves, when traveling with different velocities, are dominated by the critical value of microinertia, showing the influence of the micropolar porous characteristics.
Cold forging has played a critical role in fasteners and has been widely used in automotive production, manufacturing, aviation and 3C (Computer, Communication, and Consumer electronics). Despite its extensive use in fastener forming and die design, operator experience and trial and error make it subjective and unreliable owing to the difficulty of controlling the development schedule. This study used finite element analysis to establish and simulate wear in automotive repair fastener manufacturing dies based on actual process conditions. The places on a die that wore most quickly were forecast, with the stress levels obtained being substituted into the Archard equation to calculate die wear. A 19.87% improvement in wear optimization occurred by applying the Taguchi quality method to the new design. Additionally, a comparison of actual manufacturing data to simulations revealed a nut forging size error within 2%, thereby demonstrating the accuracy of this theoretical analysis. Finally, SEM micrographs of the worn surfaces on the upper punch indicate that the primary wear mechanism on the cold forging die for long hex flange nuts was adhesive wear. The results can simplify the development schedule, reduce the number of trials and further enhance production quality and die life.
Abstract:The malformation of sheet metal tapping screw threads in the screw threading process increases the cost of screw threading dies and their maintenance. Die factories do not reveal their screw threading die design techniques, so production and maintenance processes are established by trial-and-error or worker experience and passing down such techniques and documenting quality control is difficult. In this study, screw thread forming design and process analysis were carried out by combining computer-aided design software with computer-aided metal forming analysis software. Simulation results were verified in an actual forming process. The sheet metal tapping screw forging size error was less than 0.90%, except at a sharp angle, which was associated with an error of 3.075%, thereby demonstrating the accuracy of the simulated forming process. The numerical analysis process can be utilized to shorten forming development time; to reduce the number of die tests, and to improve product quality and die service life, reducing the cost of development and promoting the overall competitiveness of the company.
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