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1.
Materials (Basel) ; 17(5)2024 Feb 29.
Article in English | MEDLINE | ID: mdl-38473593

ABSTRACT

Aluminum foam has relatively low tensile and flexural strengths because it is composed of many pores with thin cell walls. One method of strengthening aluminum foam is to fabricate a composite material with a dense lightweight resin. In this study, the fabrication of composite materials by directly printing resin on an aluminum foam surface using a 3D printer was attempted. The resin was directly printed on both heated and unheated aluminum foam. It was shown that composite materials consisting of aluminum foam and resin can be fabricated by directly printing resin with a 3D printer on both heated and unheated aluminum foam. The resin was softened during the printing process in the case of directly printed resin on heated aluminum foam, allowing more resin to penetrate into the pores than in the case of directly printed resin on unheated aluminum foam. In addition, it was shown that resin can be directly printed on the aluminum foam with a high bonding strength, as a large amount of resin penetrated into the pores, resulting in an anchor effect. That is, composite materials consisting of aluminum foam and arbitrary-shaped resin with relatively high bonding strength can be fabricated when a large amount of resin is allowed to penetrate into the pore.

2.
Sensors (Basel) ; 20(11)2020 May 29.
Article in English | MEDLINE | ID: mdl-32485975

ABSTRACT

Process monitoring of woven fabric thermoplastic composite is crucial to enhance the quality of composite products. In this work, a new fiber Bragg grating based technique was proposed to achieve hybrid temperature and stress monitoring according to the changes of wavelength and reflectivity, respectively. The sensor head consisting of a pre-annealed fiber Bragg grating and a steel capillary was properly designed to overcome the challenge of high forming temperatures up to 332 °C, complex woven structure, and high forming pressure of 2 MPa, which hinder the use of the conventional fiber Bragg grating sensor during the forming process. The forming temperature changes of thermoplastic composite in the heating, dwelling, and cooling phases can be precisely measured by the proposed sensor head after using a curve-reconstruction algorithm based on cubic polynomial fitting. The measured difference from the reference thermocouple is 2.92 °C, averaged from three sets of repeated experiments. Meanwhile, the change of the residual stresses of the composite can be illustrated by using the micro-bending-caused optical power loss of the fiber pigtail commencing at the glass-transition temperature in the cooling phase. The decrease of grating reflectivity that was equivalent to the optical loss was discussed by comparing to strain change detected by strain gauges and a calculated theoretical curve. These results are beneficial for developing an advanced in situ monitoring technique and understanding the forming process of the woven fabric thermoplastic composite.

3.
Appl Opt ; 58(16): 4306-4314, 2019 Jun 01.
Article in English | MEDLINE | ID: mdl-31251234

ABSTRACT

Viscoelasticity is an effect seen in a wide range of materials, and it affects the reliability of static measurements made using fiber Bragg grating (FBG)-based sensors, because the target structure, the adhesive used, or the fiber itself could be viscoelastic. The effect of viscoelasticity on FBG-based sensing has been comprehensively researched through theoretical analysis and simulation using a finite-element approach, and a further data processing method to reconstruct the graphical data has been developed. An integrated sensor package comprising an FBG-based sensor in a polymer host and manufactured by using three-dimensional (3D) printing was investigated and examined through tensile testing to validate the approach. The application of the 3D-printed FBG-based sensor package, coupled with the data process method, has been explored to monitor the height of a railway pantograph, a critical measurement requirement to monitor elongation, employing a method that can be used in the presence of electromagnetic interference. The results show that the effect of viscoelasticity can be effectively eliminated, and the graphical system response allows results that are sufficiently precise for field use to be generated.

4.
Materials (Basel) ; 11(4)2018 Mar 21.
Article in English | MEDLINE | ID: mdl-29561831

ABSTRACT

Amorphous thermoplastics, as a type of engineering plastic material, are used in various industrial sectors. In order to manufacture high-performance products, it is important to optimize their forming process to mitigate residual stresses. However, stress in a plate is difficult to measure, therefore, modeling provides a powerful way to investigate and understand the evolution of stress. In this study, the forming process of a polyetherimide (PEI) plate was modelled using finite element analysis, and then validated through a comparison with a warpage experiment. This study reveals that the whole forming process can be divided into three stages by the glass transition temperature Tg of the PEI. The second stage, corresponding to the plate cooling from above Tg to below Tg, contributes a large portion of the residual stress in a short time. The final residual stress, the magnitude of which is affected by the cooling rate and plate thickness, shows a parabolic distribution through the thickness of the plate. These important conclusions are beneficial for improving the quality of an amorphous thermoplastic plate, while allowing highly efficient production.

5.
Materials (Basel) ; 8(10): 7161-7168, 2015 Oct 21.
Article in English | MEDLINE | ID: mdl-28793626

ABSTRACT

Recently, to further improve the performance of aluminum foam, functionally graded (FG) aluminum foams, whose pore structure varies with their position, have been developed. In this study, three types of FG aluminum foam of aluminum alloy die casting ADC12 with combinations of two different amounts of added blowing agent titanium(II) hydride (TiH2) powder were fabricated by a friction stir welding (FSW) route precursor foaming method. The combinations of 1.0-0 mass %, 0.4-0 mass %, and 0.2-0 mass % TiH2 were selected as the amounts of TiH2 relative to the mass of the volume stirred by FSW. The static compression tests of the fabricated FG aluminum foams were carried out. The deformation and fracture of FG aluminum foams fundamentally started in the high-porosity (with TiH2 addition) layer and shifted to the low-porosity (without TiH2 addition) layer. The first and second plateau regions in the relationship between compressive stress and strain independently appeared with the occurrence of deformations and fractures in the high- and low-porosity layers. It was shown that FG aluminum foams, whose plateau region varies in steps by the combination of amounts of added TiH2 (i.e., the combination of pore structures), can be fabricated.

6.
Materials (Basel) ; 8(10): 7180-7190, 2015 Oct 23.
Article in English | MEDLINE | ID: mdl-28793629

ABSTRACT

Aluminum foam is usually used as the core of composite materials by combining it with dense materials, such as in Al foam core sandwich panels and Al-foam-filled tubes, owing to its low tensile and bending strengths. In this study, all-Al foam-filled tubes consisting of ADC12 Al-Si-Cu die-cast aluminum alloy foam and a dense A1050 commercially pure Al tube with metal bonding were fabricated by friction welding. First, it was found that the ADC12 precursor was firmly bonded throughout the inner wall of the A1050 tube without a gap between the precursor and the tube by friction welding. No deformation of the tube or foaming of the precursor was observed during the friction welding. Next, it was shown that by heat treatment of an ADC12-precursor-bonded A1050 tube, gases generated by the decomposition of the blowing agent expand the softened ADC12 to produce the ADC12 foam interior of the dense A1050 tube. A holding time during the foaming process of approximately tH = 8.5 min with a holding temperature of 948 K was found to be suitable for obtaining a sound ADC12-foam-filled A1050 tube with sufficient foaming, almost uniform pore structures over the entire specimen, and no deformation or reduction in the thickness of the tube.

7.
Materials (Basel) ; 7(9): 6796-6810, 2014 Sep 19.
Article in English | MEDLINE | ID: mdl-28788213

ABSTRACT

Aluminum foam has received considerable attention in various fields and is expected to be used as an engineering material owing to its high energy absorption properties and light weight. To improve the mechanical properties of aluminum foam, combining it with dense tubes, such as aluminum foam-filled tubes, was considered necessary. In this study, an aluminum foam-filled steel tube, which consisted of ADC12 aluminum foam and a thin-wall steel tube, was successfully fabricated by friction welding. It was shown that a diffusion bonding layer with a thickness of approximately 10 µm was formed, indicating that strong bonding between the aluminum foam and the steel tube was realized. By the X-ray computed tomography observation of pore structures, the fabrication of an aluminum foam-filled tube with almost uniform pore structures over the entire specimen was confirmed. In addition, it was confirmed that the aluminum foam-filled steel tube exhibited mechanical properties superior to those of the ADC12 aluminum foam and steel tube. This is considered to be attributed to the combination of the aluminum foam and steel tube, which particularly prevents the brittle fracture and collapse of the ADC12 foam by the steel tube, along with the strong metal bonding between the aluminum foam and the steel tube.

8.
Materials (Basel) ; 7(3): 2382-2394, 2014 Mar 21.
Article in English | MEDLINE | ID: mdl-28788573

ABSTRACT

Al foam has been used in a wide range of applications owing to its light weight, high energy absorption and high sound insulation. One of the promising processes for fabricating Al foam involves the use of a foamable precursor. In this study, ADC12 Al foams with porosities of 67%-78% were fabricated from Al alloy die castings without using a blowing agent by the friction stir processing route. The pore structure and tensile properties of the ADC12 foams were investigated and compared with those of commercially available ALPORAS. From X-ray computed tomography (X-ray CT) observations of the pore structure of ADC12 foams, it was found that they have smaller pores with a narrower distribution than those in ALPORAS. Tensile tests on the ADC12 foams indicated that as their porosity increased, the tensile strength and tensile strain decreased, with strong relation between the porosity, tensile strength, and tensile strain. ADC12 foams exhibited brittle fracture, whereas ALPORAS exhibited ductile fracture, which is due to the nature of the Al alloy used as the base material of the foams. By image-based finite element (FE) analysis using X-ray CT images corresponding to the tensile tests on ADC12 foams, it was shown that the fracture path of ADC12 foams observed in tensile tests and the regions of high stress obtained from FE analysis correspond to each other. Therefore, it is considered that the fracture behavior of ADC12 foams in relation to their pore structure distribution can be investigated by image-based FE analysis.

9.
Skin Res Technol ; 19(3): 339-45, 2013 Aug.
Article in English | MEDLINE | ID: mdl-23551131

ABSTRACT

BACKGROUND/PURPOSE: The mechanical properties of the stratum corneum play an important role in protecting the body from external physical stimuli and excessive sensitivity. However, it is difficult to analyze these mechanical properties in vivo. To resolve this problem, we carried out a numerical analysis to calculate the Young's modulus of the stratum corneum. We then investigated the relationship between the Young's modulus of the stratum corneum and age. METHODS: We used a Cutometer(®) and a Dermal Torque Meter(®) for measuring skin mechanical parameters, and optical coherence tomography and an ultrasonic imaging system for measuring skin thickness. Based on these non-invasive results, liner elastic analysis was performed by the finite element method, and the Young's moduli of the stratum corneum and the dermis were calculated by solving an inverse problem. Using these techniques, we analyzed the correlation between the Young's modulus of the stratum corneum for the cheeks of seventy-eight Japanese women aged from 20 to 68 years. RESULTS: In the group study, the mean Young's moduli of the stratum corneum and dermis were calculated 1.993 MPa and 0.066 MPa, respectively. While carrying out individual analyses, there was a weak relationship between the Young's modulus of the stratum corneum and age (r = 0.337). CONCLUSION: We calculated the Young's modulus of the stratum corneum in vivo, with commercially available systems, and found that it is a weak correlation with age in this group of subjects. Future developments of our method would be beneficial in the characterization of facial skin aging and the validation of cosmetic and medical applications.


Subject(s)
Aging/physiology , Elastic Modulus/physiology , Epidermis/physiology , Models, Biological , Skin Aging/physiology , Adult , Aged , Compressive Strength/physiology , Computer Simulation , Female , Humans , Male , Middle Aged , Pilot Projects , Reproducibility of Results , Sensitivity and Specificity , Tensile Strength/physiology , Young Adult
10.
Skin Res Technol ; 18(4): 495-503, 2012 Nov.
Article in English | MEDLINE | ID: mdl-22233477

ABSTRACT

BACKGROUND/PURPOSE: Does the morphology of wrinkles alter gradually with aging or suddenly at a certain age? On the basis of the theoretic wrinkle simulation of ideal skin, we have suggested that the wrinkle morphology suddenly changes from stratum corneum wrinkling to epidermis wrinkling; the former induces shallow fine furrows, and the latter induces deep prominent wrinkles. To examine the existence of drastic change in wrinkling morphology, we developed a new measurement system for facial skin wrinkling test. METHODS: The mechanical compression test of facial skin was carried out for 102 Japanese women aged 25-56 years. The test was performed on the right temple area skin, and the area of wrinkles induced by the compression was measured using a digital video camera. The rate of increase in wrinkle area during compression was defined as the skin wrinkling rate, and it was calculated for all subjects automatically by image processing. RESULTS: The test results showed that the skin wrinkling rate underwent a step increase at the age 33, which means that the wrinkling morphologies of young and old skins are completely different, and so it changes suddenly in the early 30s. CONCLUSION: A new skin measurement system was developed to validate our theory of wrinkle formation mechanism with aging. The results demonstrated the wrinkling morphology changes suddenly at early 30s.


Subject(s)
Palpation/methods , Skin Aging/pathology , Skin Aging/physiology , Skin Tests/methods , Adult , Female , Humans , Middle Aged , Reproducibility of Results , Sensitivity and Specificity
11.
J Morphol ; 270(9): 1084-94, 2009 Sep.
Article in English | MEDLINE | ID: mdl-19378269

ABSTRACT

Determining scapular position is a major issue in reconstructing the skeletal systems of extinct quadruped archosaurs and mammals, because the proximal portion of the scapulae has no direct skeletal joint with the vertebrae or ribs. When quadrupeds stand or walk, their trunk is suspended between the forelimbs by the serratus muscles, which arises from the lateral sides of the "thoracic" ribs and inserts into the proximal portion of the costal surface of the scapula. Therefore, the "thoracic" ribs are subjected to a static or dynamic vertical compression between the lifting force from the muscle and the gravitational force from the vertebral column. To investigate the body support function of the ribs, we analyzed the mechanical strength of the ribs of extant tetrapods by the two-dimensional finite element method, and compared the degree of strength through their craniocaudal scapular positions. The result of this simulation showed that the "thoracic" ribs of quadrupeds, to which the serratus muscles attach, have a relatively higher strength against compaction than the other ribs. In bipeds, however, we did not find a similar correlation between the strength of ribs and the serratus muscle. This implies that the location of robust ribs is associated with the arrangement of the serratus muscle, and provides a probable candidate for determination of the scapular position for extinct quadruped archosaurs and mammals.


Subject(s)
Muscle, Skeletal/anatomy & histology , Ribs/anatomy & histology , Scapula/anatomy & histology , Animals , Extinction, Biological , Fossils , Muscle, Skeletal/physiology , Ribs/physiology , Scapula/physiology , Shoulder/anatomy & histology , Shoulder/physiology , Thoracic Vertebrae/anatomy & histology , Thoracic Vertebrae/physiology
12.
J Theor Biol ; 259(1): 132-41, 2009 Jul 07.
Article in English | MEDLINE | ID: mdl-19269296

ABSTRACT

A mechanism of generating passive feeding flow for the Devonian spiriferide brachiopod Paraspirifer bownockeri was theoretically elucidated through fluid dynamics simulations for flow around rigid shells. The RANS equations were used as a turbulence model, and the unsteady incompressible flow was solved using the finite volume method. Two directions of ventral and dorsal flows were investigated as typical cases where little exchange flow occurs inside the shells. The digital model of the shell was constructed using image processing of X-ray CT images of a shell replica made by molding a polycarbonate plate to a well-preserved fossil specimen of Paraspirifer. To examine the effect of flow velocity, three conditions of ambient flow velocity were adopted for both the ventral and dorsal flows. The pressure distribution along the gape showed that a relatively high pressure occurred around the sulcus in all simulated cases. This high pressure generated inflow from the sulcus and subsequent spiral internal flow, especially in fast ambient flows. This means that the sulcus generated the considerable pressure gradient around the gape passively and generated the stable intake of seawater and a spiral flow of water inside the shell for feeding. We conclude that the shell form of certain spiriferides could generate spiral flows so as to promote passive feeding, and the sulcus is interpreted as an important form for the passive intake of water.


Subject(s)
Computer Simulation , Feeding Behavior , Invertebrates/physiology , Animals , Biomechanical Phenomena , Fossils , Image Processing, Computer-Assisted , Imaging, Three-Dimensional , Models, Biological , Tomography, X-Ray Computed , Water Movements
13.
Med Eng Phys ; 30(4): 516-22, 2008 May.
Article in English | MEDLINE | ID: mdl-17681837

ABSTRACT

A wrinkle formation mechanism with cutaneous aging is addressed through a mechanical calculation of linear buckling. Skin is divided into five mechanically distinct layers in this study. In general, the outer layer is stiffer than the inner layer, so buckling occurs in the outer layer against the uniform compression caused by muscle contraction. This buckling damages the skin and affects the formation of permanent wrinkles. We propose a multistage buckling theory for evaluation of the wrinkle property, namely, the specific wrinkle size and critical strain in three stages. The specific wrinkle size is derived as the wavelength of the minimum-buckling mode for infinite-length skin. A sensitivity analysis is carried out to investigate the effect of age-related changes of the mechanical parameters on the wrinkle property. We employ some aging hypotheses and prepare two sets of mechanical parameters, one for young and one for aged skin. The numerical results show that the buckling mode switch from Stage I to Stage II is the main reason why pronounced wrinkles suddenly appear in aged skin.


Subject(s)
Aging , Skin Aging , Skin/pathology , Adult , Aged , Biomedical Engineering , Dermis/pathology , Epidermis/pathology , Equipment Design , Humans , Middle Aged , Models, Statistical , Skin Physiological Phenomena , Stress, Mechanical , Subcutaneous Tissue/pathology
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