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Autophagy, the process of lysosomal degradation of biological materials within cells, is often halted abnormally in proteopathies, such as tauopathy and amyloidopathy. Thus, autophagy regulators that rescue dysregulated autophagy have great potential to treat proteopathies. We previously reported that the natural small molecule kaempferide (Kaem) induces autophagy without perturbing mTOR signaling. Here, we report that Kaem promotes lysosomal degradation of microtubule-associated protein tau (MAPT) in inducible MAPT cells. Kaem enhanced autophagy flux by mitigating microtubule-associated protein 1 light chain 3 (LC3) accumulation when MAPT expression was induced. Kaem also promoted activation of transcription factor EB (TFEB) without inhibiting mTOR and without mTOR inhibition-mediated cytotoxicity. In addition, Kaem-induced MAPT degradation was abolished in the absence of mitochondrial elongation factor Tu (TUFM), which was previously shown to be a direct binding partner of Kaem. Collectively, these results demonstrate that Kaem could be a potential therapeutic for tauopathy and reveal that TUFM can be a drug target for autophagy-driven disorders.

Human colon carcinomas, including HCT116 cells, often exhibit high autophagic flux under nutrient deprivation or hypoxic conditions. Mitochondrial ROS (mROS) is known as a ‘molecular switch’ for regulating the autophagic pathway, which is critical for directing cancer cell survival or death. In early tumorigenesis, autophagy plays important roles in maintaining cellular homeostasis and contributes to tumor growth. However, the relationships between mROS and the autophagic capacities of HCT116 cells are poorly understood. Ubiquinol cytochrome c reductase binding protein (UQCRB) has been reported as a biomarker of colorectal cancer, but its role in tumor growth has not been clarified. Here, we showed that UQCRB is overexpressed in HCT116 cells compared to CCD18co cells, a normal colon fibroblast cell line. Pharmacological inhibition of UQCRB reduced mROS levels, autophagic flux, and the growth of HCT116 tumors in a xenograft mouse model. We further investigated mutant UQCRB-overexpressing cell lines to identify functional links in UQCRB-mROS-autophagy. Notably, an increasing level of mROS caused by UQCRB overexpression released Ca2+ by the activation of lysosomal transient receptor potential mucolipin 1 (TRPML1) channels. This activation induced transcription factor EB (TFEB) nuclear translocation and lysosome biogenesis, leading to autophagy flux. Collectively, our study showed that increasing levels of mROS caused by the overexpression of UQCRB in human colon carcinoma HCT116 cells could be linked to autophagy for cell survival.

Small molecules targeting autophagy have been highly implicated as new therapeutic agents to treat diseases of interest. With the increasing demand for autophagy-targeting drugs, this review attempts to provide an efficient strategy to explore major autophagy-based human disease interventions with newly explored mechanisms using small molecules and promising therapeutic approaches.Introduced in this review are direct links and applications among autophagy pathways, their modulators, and phenotypic diseases, along with recent approaches. Autophagy-related diseases, machinery, and compounds are introduced to guide the appropriate investigation of autophagy in the pharmaceutical industry. The authors then provide their expert perspectives on the subject.The self-catabolic intracellular process autophagy occurs in organisms throughout their lifetime, supporting its critical role in organismal health across life stages. Because of the detrimental influence of dysfunctional cells to an organism and their etiology in numerous diseases, maintaining cellular quality control by recycling components through autophagy is essential to prevent health decline.

Human colon carcinomas, including HCT116 cells, often exhibit high basal autophagic flux under nutrient deprivation or hypoxic conditions. Mitochondrial ROS (mROS) is known as a “molecular switch”’ for regulating the autophagic pathway, which is critical for directing cancer cell survival or death. In early tumorigenesis, autophagy plays important roles in maintaining cellular homeostasis and contributes to tumor growth. However, the relationships between mROS and the autophagic capacities of HCT116 cells are poorly understood. Ubiquinol cytochrome c reductase binding protein (UQCRB) has been reported as a biomarker of colorectal cancer, but its role in tumor growth has not been clarified. Here, we showed that UQCRB was overexpressed in HCT116 cells compared to CCD18co cells, a normal colon fibroblast cell line. Pharmacological inhibition of UQCRB reduced mROS levels, autophagic flux, and the growth of HCT116 tumors in a xenograft mouse model. We further investigated mutant UQCRB-overexpressing cell lines to identify functional links in UQCRB-mROS-autophagy. Notably, an increasing level of mROS caused by UQCRB overexpression released Ca2+ by activation of lysosomal TRPML1 channels. This activation induced transcription factor EB nuclear translocation and lysosome biogenesis, leading to autophagy flux. Collectively, our study showed that increasing levels of mROS caused by overexpression of UQCRB in human colon carcinoma HCT116 cells could be linked to autophagy for cell survival.

Polyvinylidene fluoride (PVDF) has been widely used in piezoelectric applications because of its outstanding properties such as low permittivity, high thermal stability, high chemical resistance, and flexibility. In this study, PVDF film sensors were prepared for fatigue damage monitoring of single-lap adhesive joints. PVDF films were fabricated using the solvent casting method, and post treatment, including mechanical stretching and heat setting, was conducted to increase the β-phase crystallinity of the films. Subsequently, the PVDF films were polarized to align the molecular dipoles. The crystal structures of the PVDF films were investigated using X-ray diffraction (XRD) and the thermal behaviors were analyzed using differential scanning calorimetry (DSC). The piezoelectric constants of the prepared PVDF films were measured using a d33 meter. The sensing performance of the films for fatigue damage monitoring of single-lap adhesive joints was assessed by fatigue tests under various stress levels. In addition, a fatigue failure manual based on the PVDF sensor signal, which can predict the failure of the adhesive joints, was constructed.

Although proper surface treatment is very important in adhesively bonded joints , perfectly clean surfaces have been considered in previous studies. Making the surface of an adherend clean is generally very difficult in real fields. In order to identify the minimum surface treatment that can achieve the required adhesion strength , we investigated the effects of residual oils on the adhesion characteristics of metal-carbon fiber-reinforced epoxy composites adhesive joints . We found that the amount of residual oils on the metal surfaces should be controlled to be less than 1.0 g/m 2, and that enough adhesion strength could be obtained if the flame treatment followed. Experimentation also suggested that three or four cycles of ethanol cleansing and five seconds of flame treatment was the minimum surface treatment easily adoptable in industrial fields.

Disorders of autophagy, a key regulator of cellular homeostasis, cause a number of human diseases. Due to the role of autophagy in metabolic dysregulation, there is a need to identify autophagy regulators as therapeutic targets. To address this need, we conducted an autophagy phenotype-based screen and identified the natural compound kaempferide (Kaem) as an autophagy enhancer. Kaem promoted autophagy through translocation of transcription factor EB (TFEB) without MTOR perturbation, suggesting it is safe for administration. Moreover, Kaem accelerated lipid droplet degradation in a lysosomal activity-dependent manner in vitro and ameliorated metabolic dysregulation in a diet-induced obesity mouse model. To elucidate the mechanism underlying Kaem’s biological activity, the target protein was identified via combined drug affinity responsive target stability and LC–MS/MS analyses. Kaem directly interacted with the mitochondrial elongation factor TUFM, and TUFM absence reversed Kaem-induced autophagy and lipid degradation. Kaem also induced mitochondrial reactive oxygen species (mtROS) to sequentially promote lysosomal Ca2+ efflux, TFEB translocation and autophagy induction, suggesting a role of TUFM in mtROS regulation. Collectively, these results demonstrate that Kaem is a potential therapeutic candidate/chemical tool for treating metabolic dysregulation and reveal a role for TUFM in autophagy for metabolic regulation with lipid overload., Kim, Hwang et al. use in vitro and in vivo models of autophagy disorder/metabolic dysfunction to show that in this context, the natural compound kaempferide is an autophagy enhancer and reveal that one of the underlying mechanisms governing this is mediated by the mitochondrial elongation factor TUFM. This insight may have therapeutic value in the treatment of metabolic disorders.

Manipulating autophagy is a promising strategy for treating cancer as several autophagy inhibitors are shown to induce autophagic cell death. One of these, autophagonizer (APZ), induces apoptosis-independent cell death by binding an unknown target via an unknown mechanism. To identify APZ targets, we used a label-free drug affinity responsive target stability (DARTS) approach with a liquid chromatography/tandem mass spectrometry (LC–MS/MS) readout. Of 35 protein interactors, we identified Hsp70 as a key target protein of unmodified APZ in autophagy. Either APZ treatment or Hsp70 inhibition attenuates integrity of lysosomes, which leads to autophagic cell death exhibiting an excellent synergism with a clinical drug, temozolomide, in vitro, in vivo, and orthotropic glioma xenograft model. These findings demonstrate the potential of APZ to induce autophagic cell death and its development to combinational chemotherapeutic agent for glioma treatment. Collectively, our study demonstrated that APZ, a new autophagy inhibitor, can be used as a potent antitumor drug candidate to get over unassailable glioma and revealed a novel function of Hsp70 in lysosomal integrity regulation of autophagy.

We studied effects of material anisotropy on impact mitigation in single column woodpile structures. Local vibrations and nonlinear contacts of cylindrical members are key mechanisms of wave modulation in woodpile structures. We numerically obtained wave propagations in single column woodpile structures by changing longitudinal and/or transverse stiffness different from stiffness along the stacking direction. We found that changes in longitudinal and/or transverse stiffness altered wave propagation tendency as well as impact mitigation rate. We observed compact and wide waves propagated through single column woodpile structures with small stiffness ratio, while disintegrated but narrow waves with large stiffness ratio. According to dynamic behavior under impact loadings and frequency responses of woodpiles, bending vibration changed from 3rd to 1st mode and low energy band moved to relatively low frequency region when the single column woodpile structures had small stiffness ratio. This leads to increase impact mitigation characteristics of single column woodpile structures.

This study analyzes the mechanical behaviors of conical composite tubes, considering fiber orientation errors, under static loads. Fiber orientation errors are defined as fiber orientation changes that occur due to the taper angle of conical composite tubes during the wrapping process. Such fiber orientation errors are one of many important parameters in predicting mechanical properties, and must be taken into account for the design of conical composite tubes. Thus, this study derived the theoretical equations to analyze the mechanical behaviors of conical composite tubes under static loads considering fiber orientation errors according to the laminate plate theory. For verification of the derived equations, the calculation results were compared with the results of other research that did not take fiber orientation errors into account as well as experimental results that did include fiber orientation errors. As a result, the derived equations could predict the static behaviors of conical composite tubes 5.5% errors. Also, we performed parametric studies such as taper angles, sizes, and stacking sequences. The effect of taper angles on the static behaviors was the most important and the static deformations with and without the consideration of fiber orientation errors had a 500% difference over 10 O of the taper angle.

The adhesion strength of shape-memory fibers (SMFs) embedded in adhesives can be enhanced by varying the operating conditions. The interfacial shear strength (IFSS) of an epoxy adhesive (DP460 off-white) with embedded SMFs (25 µm Ni–Ti alloy particles) was investigated using the single-wire pull-out test method; the Ansys simulation software was used to characterize the factors that affect the IFSS. With increasing pre-strain of the SMFs, the IFSS increases because of the surface roughness and phase transformation of the SMFs. At temperatures below and above the SMF phase-transformation temperature, adhesive’s property degradation and the SMF phase transformation are the factors that most strongly influence the IFSS, respectively.

Recently, origami structures have been widely studied for various applications such as mechanical, electrical, bio, and nanosystems. Unlikely paper-like materials, engineering materials have higher stiffness and thickness so the hinge-like motion of the crease of paper origami is impossible. Therefore, origami, which is not made of paper-like materials, has different characteristics from paper origami. Several researchers reported that introducing slits or holes at or near the crease can make the hinge-like motion of the origami, but investigating the effects of the crease line design was not considered. In this paper, a perforated crease line was considered and parametric studies of the crease line design were investigated by finite element analysis and experiment. It was found that the length and distance of the perforated holes were significant factors to determine the stability and the barrier force and spring constant of Kresling origami could be optimized. Finally, it was shown that special motions could be realized with a combination of two origami with the same dimension but different crease line designs.

Autophagy is a critical regulator of cellular homeostasis, dysregulation of which is associated with diverse diseases. Here we show therapeutic effects of a novel autophagy enhancer identified by high-throughput screening of a chemical library against metabolic syndrome. An autophagy enhancer increases LC3-I to LC3-II conversion without mTOR inhibition. MSL, an autophagy enhancer, activates calcineurin, and induces dephosphorylation/nuclear translocation of transcription factor EB (TFEB), a master regulator of lysosomal biogenesis and autophagy gene expression. MSL accelerates intracellular lipid clearance, which is reversed by lalistat 2 or Tfeb knockout. Its administration improves the metabolic profile of ob/ob mice and ameliorates inflammasome activation. A chemically modified MSL with increased microsomal stability improves the glucose profile not only of ob/ob mice but also of mice with diet-induced obesity. Our data indicate that our novel autophagy enhancer could be a new drug candidate for diabetes or metabolic syndrome with lipid overload., Autophagy plays an important role in metabolic functions and increased autophagic activity may be beneficial for metabolic disorders. Here the authors screen a chemical library for enhancer of autophagic flux and identify small molecules that improve the metabolic profile by increasing lysosomial functions.

The drug FK506 (tacrolimus, fujimycin) exerts its immunosuppressive effects by regulating the nuclear factor of the activated T-cell (NFAT) family of transcription factors. However, FK506 also exhibits neuroprotective effects, but its direct target proteins that mediate these effects have not been determined. To identify the target proteins responsible for FK506's neuroprotective effects, the drug affinity responsive target stability (DARTS) method was performed using label-free FK506, and LC-MS/MS analysis of the FK506-treated proteome was also performed. Using DARTS and LC-MS/MS analyses in combination with reference studies, V-ATPase catalytic subunit A (ATP6V1A) was identified as a new target protein of FK506. The biological relevance of ATP6V1A in mediating the neuroprotective effects of FK506 was validated by analyzing FK506 activity with respect to autophagy via acridine orange staining and transcription factor EB (TFEB) translocation assay. These analyses demonstrated that the binding of FK506 with ATP6V1A induces autophagy by activating the translocation of TFEB from the cytosol into the nucleus. Because autophagy has been identified as a mechanism for treating neurodegenerative diseases and because we have demonstrated that FK506 induces autophagy, this study demonstrates that FK506 is a possible new therapy for treating neurodegenerative diseases.

Identifying the target proteins of bioactive small molecules is a key step in understanding mode-of-action of the drug and addressing the underlying mechanisms responsible for a particular phenotype. Proteomics has been successfully used to elucidate the target protein profiles of unmodified and ligand-modified bioactive small molecules. In the latter approach, compounds can be modified via click chemistry and combined with activity-based protein profiling. Target proteins are then enriched by performing a pull-down with the modified ligand. Methods that utilize unmodified bioactive small molecules include the cellular thermal shift assay, thermal proteome profiling, stability of proteins from rates of oxidation, and the drug affinity responsive target stability (DARTS) determination (or read-out). This review highlights recent proteomic approaches utilizing data-dependent analysis and data-independent analysis to identify target proteins by DARTS. When combined with liquid chromatography/tandem mass spectrometry, DARTS enables the identification of proteins that bind to drug molecules that leads to a conformational change in the target protein(s). In addition, an effective strategy is proposed for selecting the target protein(s) from within the pool of analyzed candidates. With additional complementary methods, the biologically relevant target proteins that bind to the small bio-active molecules can be further validated.

In recent years, development of novel bioactive small molecules targeting autophagy has been implicated for autophagy-related disease treatment. Screening new small molecules regulating autophagy allows for the discovery of novel autophagy machinery and therapeutic agents. Areas covered: Two major screening methods for novel autophagy modulators are introduced in this review, namely target based screening and phenotype based screening. With increasing attention focused on chemical compound libraries, coupled with the development of new assay systems, this review attempts to provide an efficient strategy to explore autophagy biology and discover small molecules for the treatment of autophagy-related diseases. Expert opinion: Adopting an appropriate autophagy screening strategy is important for developing small molecules capable of treating neurodegenerative diseases and cancers. Phenotype based screening and target based screening were both used for developing effective small molecules. However, each of these methods has many pros and cons. An efficient approach is suggested to screen for novel lead compounds targeting autophagy, which could provide new hits with better efficiency and rapidity.

The PVDF (polyvinylidene fluoride) fibers were prepared using the wet spinning processing. To improveβ-phase crystalline which closely related piezoelectric property PVDF wet spun fibers conducted post treatment. Posttreatment is consisted of heat stretching and annealing process. The heat stretching and annealing conditions werecontrolled by changing temperature between glass transition temperature and melting temperature. From theseexperimental data, the resulting crystal structure of the β-phase crystalline was confirmed by FT-IR and XRDexperiments. From these analysis results, optimum stretching and annealing conditions of the wet spun PVDF fiberswere founded to increase high β-phase crystalline. Furthermore results showed that thermal processing had a directeffect on modifying the crystalline microstructure and also confirmed that heat stretching and annealing couldincrease the degree of crystallinity and β-phase crystalline. Finally, piezoelectric constant ( d 11 ) of the post heat treatedPVDF fibers reinforced composite were measured to investigate the feasibility for the sensing materials.초록

Because crack detection for laminated composites in-service is an effective method for improving structural reliability, various nondestructive methods have been studied to detect cracks in laminated composites. A recent study on the damage monitoring of composite materials using the piezoelectric method, which uses the piezoelectric characteristics of polymeric materials for the matrix of composite materials, concluded that the piezoelectric method can be a useful, nondestructive method for the damage monitoring of glass fiber epoxy composites. The dielectric and piezoelectric properties of composites are the basic properties used for the analysis of electromechanical coupling systems, along with the mechanical properties. In this research, therefore, the electromechanical characteristics of unidirectional glass fiber epoxy composites as well as their electric and mechanical characteristics were investigated. The dielectric, piezoelectric, and mechanical properties of unidirectional glass fiber epoxy composites were measured experimentally with respect to the fiber orientation, and the relationship between the piezoelectric and mechanical characteristics of unidirectional glass fiber epoxy composites was analyzed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

The objective of this study was to investigate 3D woodpile metamaterials for mitigating impact-induced vibrations by leveraging their local resonant and nonlinear contact characteristics. For experimental demonstrations, we designed, fabricated and tested prototypes of sandwich-structured woodpile metamaterials consisting of two plates, slender cylindrical rods and fasteners. We experimentally and numerically obtained impact responses of sandwich-structured woodpile metamaterials under various geometries and boundary conditions. We found that sandwich-structured woodpile metamaterials could efficiently manipulate and attenuate the impact vibrations due to their local bending motions and nonlinear contact between members. In addition, sandwich-structured woodpile metamaterials could have high damping as well as high stiffness by controlling the rod spacing. The findings from this study suggest sandwich-structured woodpile metamaterials can be used as structural components for impact-induced vibration mitigation.

In this work, a smart curing method for the co-cured aluminum/composite hybrid shaft which can reduce the thermal residual stresses generated during co-curing bonding operation between the composite layer and the aluminum tube was applied. In order to reduce the thermal residual stresses generated during co-cure bonding stages due to the difference of coefficients of thermal expansions (CTE) of the composite and the aluminum tube, a smart cure cycle composed of cooling and reheating cycles was applied. The heating and cooling operations were realized using a pan type heater and water cooling system. The thermo-mechanical properties of the high modulus carbon epoxy composite were measured by a DSC (differential scanning calorimetry) and rheometer to obtain an optimal time to apply the cooling operation. Curvature experiment of the co-cure bonded steel/composite strip was performed to investigate the effect of cure cycle on generation of the thermal residual stress. Also, the thermal residual stresses of the aluminum/composite hybrid shaft were measured using strain gauges with respect to cure cycles. Finally, torsional fatigue test and vibration test of the aluminum/composite hybrid shaft were performed, and it has been found that this method might be used effectively in manufacturing of the co-cured aluminum/composite hybrid propeller shaft to improve the dynamic torque characteristics.

Wear debris generated on the sliding surface of carbon composite bearings should be removed quickly for stable sliding movement because it induces severe damage on the contact surface. In order to remove the wear debris generated, composite bearing specimens with many micro-grooves on their surfaces were fabricated using a newly developed molding method. The wear characteristics of carbon/epoxy composites with micro-grooves were investigated by dry sliding test with respect to applied pressure and compared to those of carbon/epoxy composites without micro-grooves. Using the measured friction coefficient and wear rate, a model for the effect of wear debris on the friction and wear of carbon composites was proposed.

As adhesive joints have been widely used for fastening thin adherends, the damage tolerance design of adhesive joints has become important, and the estimation of initiation and propagation of a fatigue crack in the adhesive has become necessary. However, the measurement of crack length of tubular joints has been difficult because the observation of crack initiation and growth in the adhesive layer by conventional methods is not easy. In this work, a prediction method for the fatigue crack length in the adhesive layer of tubular single-lap adhesive joints was developed by the piezoelectric method. In order to obtain the relationship between the fatigue crack length and the piezoelectric signal, finite element analysis was conducted and verified by experiments. The damage of the adhesive joints was monitored by the piezoelectric method during torsional fatigue tests on tubular single-lap adhesive joints. Using the damage monitoring signals and the relationship between the fatigue crack length and the piezoe...

Adhesive joints have been widely used for fastening thin adherends because they can distribute the load over a larger area than mechanical joints, require no holes, add very little weight to the structure and have superior fatigue resistance. Since the reliability of an adhesive joint is dependent on many parameters, such as the shape of joint, type of applied load and environment, an accurate prediction of the fatigue life of adhesive joints is seldom possible, which necessitates an in situ damage monitoring of the joints during their operation. Recently, a piezoelectric method using the piezoelectric characteristics of epoxy adhesives has been successfully developed for adhesive joints because it can continuously monitor the damage of adhesively bonded structures without producing any defects induced by inserting a sensor. Therefore, in this study, the damage of adhesive joints was monitored by the piezoelectric method during torsional fatigue tests in order to develop the diagnosis criterion for damage...

Mechanical design can be classified into stiffness design and strength design. In the stiffness design, the stiffness or deformation of members is concerned, and the enhancement of dynamic characteristics such as natural frequency or damping capacity of members or systems is also important. While, in the strength design, the primary concern is the enhancement of load carrying ability of members or systems. Fiber reinforced composite materials offer a combination of strength and modulus that are either comparable to or better than many traditional metallic materials. Because of their low specific gravities, the strength-weight ratios, and modulus-weight ratios of these composite materials are much superior to those metallic materials. Composite materials can be tailored to meet the specific requirements of each particular design. Available design parameters are the choice of materials (fiber, matrix), the volume fraction of fiber and matrix, fabrication method, number of layers in a given direction, thickness of individual layers, type of layer (unidirectional or fabric), and the layer stacking sequence. The greatest disadvantages of composite materials are the costs of the materials and the lack of well-defined design rules, therefore, composite materials should be applied in the right place with appropriate design rules. Up to now, the fiber reinforced composite structures are mainly employed in the strength design such as aircraft, spacecraft and vehicles. In this paper, the novel application examples of composite structures to components for the robots, machine tools and automobiles are addressed considering the stiffness design issues of composite structures.

Substituting composite structures for conventional metallic structures has many advantages for structural dynamic characteristics because composite materials have the higher specific stiffness and damping characteristics than conventional materials. However, the dynamic characteristics such as the fundamental natural frequency and damping of composite structures are influenced much by their joints. In this work, the effects of clamping conditions on the dynamic characteristics of cantilever type composite machine tool structures with clamped joint were investigated to increase the natural frequency and damping of structures. In order to improve the shear property of the clamping part of composite machine tool bar, a new method for the clamping part was developed with metal core or sleeve inserted in the composite body at the clamping part. From the finite element and experimental results, suitable clamping conditions for the maximum dynamic stiffness were obtained for the composite structures with clamped joint.

Power transmission shafts such as driving shafts or automotive propeller shafts should transmit static and dynamic torques with vibrational stability. Hybrid shafts made of unidirectional fiber-reinforced composite and metal have high fundamental bending natural frequency as well as high torque transmission capability: composite increases the fundamental bending natural frequency due to its high specific stiffness and metal such as aluminum or steel transmits the required torque. However, fabrication-induced thermal residual stresses due to the coefficient difference of thermal expansion of the composite and the metal are developed during manufacturing hybrid shafts so that the high residual stresses decrease fatigue resistance of the hybrid shafts, especially at low operating temperatures. In this paper, the torsional fatigue characteristics of aluminum–composite co-cure joined shafts with axial compressive preload were investigated. To change the thermal residual stresses, an axial compressive preload was given to the aluminum tube by a compressive jig during the co-cure bonding operation. In order to determine the thermal residual stresses with respect to the preload and temperature difference, stress analyses were performed by simple equations from mechanics of materials and finite element method. Then the static torque capacities and fatigue strengths of the hybrid shafts from static and fatigue torsional tests were correlated with the calculated thermal residual stresses. The fatigue strength of the hybrid shaft was much improved by the axial compressive preload, exceeding that of a pure aluminum shaft. Also, the degradation of the fatigue resistance of the hybrid shaft at subzero operating temperature was overcome by the axial compressive preload.

Rubber-toughened structural epoxy adhesives are widely used for bonding structures because of their high toughness characteristic. However, the mechanical properties of structural epoxy adhesives degrade much at high environmental temperature, which affects the performance of the adhesive joints severely. Therefore, in this study, the temperature effects on the static and fatigue characteristics of adhesively-bonded tubular single-lap joints were measured. Then the relations between the parameters of S-N curves and the static strength of adhesively-bonded tubular singlelap joints were obtained, from which a fatigue life prediction model for the adhesively-bonded tubular single-lap joints at elevated temperatures was developed.

High-speed air spindles are appropriate for high-speed and high-precision machining such as small hole drilling of printed circuit board (PCB) or wafer cutting for manufacturing semiconductors. The axial load capability and stiffness of the air spindles for drilling operation are dependent on the thrust bearings. The thrust bearings are composed of an air supply part in the housing and a rotating part. Since stresses induced in the rotating part of thrust bearing by centrifugal force are very high at high-rotational speed, the axial stiffness and load capability of an air spindle should be designed considering stresses due to centrifugal force as well as the natural frequency of the rotating shaft to avoid the resonant whip vibration of the spindle. In this work, the air supply part and the rotating part of a thin thrust bearing were designed for a high-speed carbon fibre composite air spindle using the stiffness map to maximize the stiffness of the thrust bearing under axial and centrifugal forces.

High speed boring operations of deep holes with steel or tungsten boring bars are often hindered by the chatter vibration of boring bars because of their low dynamic stiffness and natural frequencies. The chatter is a self-excited vibration that occurs in metal cutting if, either the chip width is too large with respect to the dynamic stiffness of the system, which is proportional to the damping and static stiffness of the boring bar, or the rotating speed of the boring bar approaches one of its natural frequencies, which is proportional to the specific stiffness (E/ρg) of the material used. In this study, a rotating boring bar was designed and manufactured with high stiffness pitch-based carbon fiber epoxy composite to meet the requirements of boring at high rotating speed because carbon fiber epoxy composite materials have a much higher specific stiffness and higher damping than conventional boring bar materials. The optimum design parameters for the composite boring bar were experimentally determined with respect to material types and dimensions of the boring bar through vibration tests. The dynamic characteristics of the composite boring bar developed were measured by the boring operation of aluminum engine blocks. From experiments, it was found that the dynamic stiffness of the composite boring bar was about 30% higher than that of the tungsten carbide boring bar. Also, chatter did not occur up to the ratio of length to diameter (l/d) of 10.7, which is about a 30% improvement compared to the tungsten boring bar of l/d of 8.0.

Poly(vinylidene difluoride) (PVDF) has been widely used in piezoelectric applications as films and nanofiber mats, but there are limited publications on piezoelectric wet-spun fibers. In this work, PVDF fibers were prepared using the wet spinning method, and the processing parameters, including the drawing ratio and heat setting temperature, were controlled in the continuous wet spinning system to increase the β-phase crystallinity of the fibers. In addition, the wet-spun PVDF fibers were compressed by a rolling press to eliminate voids in the fibers. Then, the compressed PVDF fibers were poled to align the molecular dipoles. The crystal structures of the PVDF fibers were investigated using X-ray diffraction and Fourier-transform infrared spectroscopy. Single filament tensile tests were performed to measure the tensile strength of the fibers. The morphologies of the PVDF fibers with respect to the processing parameters were observed by scanning electron microscope (SEM) and polarization optical microscopy. The piezoelectric constant of the prepared PVDF fibers was then measured using a d33 meter. The wet-spun PVDF fibers showed the highest β-phase and piezoelectric constants when the drawing ratio and heat setting temperature were 6 and 150 °C, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45712.

This study suggested a tactile sensor with piezoelectric sensors in a fibrous shape to detect multi-axial loads (vertical load and horizontal load) simultaneously for the skins of unmanned robots. The sensor was designed by finite element analyses. A simple detecting scheme of the multi-axial loads was constructed by lab-scale experiments. Verification tests of the developed tactile sensor confirmed that applied vertical and horizontal loads could be detected with less than 4% error.