Straight Shape Research Articles

Effect of various multiple strip inserts and nanofluids on the thermal–hydraulic performances of parabolic trough collectors

The thermal performance of the parabolic trough collectors can be improved by the use of swirl generator inserts added to the solar receiver. These inserts help improve the energy capture from the internal receiver walls and reduce the external wall thermal losses. If nanoparticles are added to the heat transfer fluid of the solar receiver tube, then this also increases the output working fluid temperature thereby reducing the outer wall’s temperature. The main objective of the current study is to assess the effect of various straight strip shapes with and without nanofluids. Four different strip arrangements were considered; large conical-shape strips, small conical-shape strips, rectangular-shape strips and elliptical-shape strips. All of these configurations were then also tested in 6% of SiO2 nanoparticles mixed in Therminol® VP-1 (TO) forming the nanofluid. Results showed that the straight large conical strips lead to the maximum enhancement in the Nusselt number (up to 57.49% for the pure base fluid and up to 62.53% for the nanofluid). The thermal efficiency improvement for this optimal configuration with nanofluid was found to be 15.41% with a thermal loss reduction of around 26%. A similar trend was found for the thermal exergy efficiency which showed an improvement of 15.32% for this optimal configuration with the use of nanofluid.

Effective reduction of magnetisation losses in copper-plated multifilament coated conductors using spiral geometry

We wound copper-plated multifilament coated conductors spirally on a round core to decouple filaments electromagnetically under ac transverse magnetic fields and measured their magnetisation losses. Although the coated conductors were plated with copper, which connects all filaments electrically and allows current sharing among them, the spiral geometry decoupled filaments similar to the twist geometry, and the magnetisation loss was reduced effectively by the multifilament structure. The measured magnetisation loss of a 4 mm wide, 10-filament coated conductor with a 20 μm thick copper wound spirally on a 3 mm core was only 7% of that of the same 10-filament coated conductor with a straight shape under an ac transverse magnetic field with an amplitude and frequency of 100 mT and 65.44 Hz, respectively. We separated the measured magnetisation losses into hysteresis and coupling losses and discussed the influence of filament width, copper thickness, and core diameter on both losses. We compared the hysteresis losses with the analytical values given by Brandt and Indenbom and compared the coupling losses with the values calculated using a general expression of coupling loss with the coupling time constants and geometry factors.

ИССЛЕДОВАНИЕ ВЛИЯНИЯ ФОРМЫ РЕЖУЩЕЙ КРОМКИ НОЖЕВОГО ИСПОЛНИТЕЛЬНОГО ОРГАНА ГЕОХОДА НА ЭНЕРГОЕМКОСТЬ РАЗРУШЕНИЯ ПОРОДЫ ЗАБОЯ

The increase in the population creates prerequisites for the use of new undeveloped places, which include underground space. The development of underground space is associated with the construction of underground structures. A promising technology for the construction of underground structures is geokhodnaya. The basic element of which is a geokhod. As a rule, structures are built at shallow depths, which are characterized by rocks with a strength coefficient up to f = 1 on the scale of Professor M.M. Protodiakonov. Traditionally, the sinking of workings in these rocks is carried out by knife executive bodies. During the development and executive body design, one of the main indicators for evaluating its work is the energy intensity of the face rock destruction. As a result, a promising direction is to study the influence of the shape of the cutting edge of the knife executive body of the geokhod on the energy intensity of the destruction of the face rock. The article presents variants of schematic solutions of the geokhod knife executive body with a different shape of the knife cutting edge, developed on the basis of a functional and constructive approach to the development of constructive solutions and requirements for the geokhod executive bodies. It is established that the geokhod executive body geometric parameters, depending on the knife cutting edge shape, include: the angle of inclination of the knife with an inclined shape of the knife cutting edge; the radius of curvature of the knife cutting edge with a semi-convex and knife convex shape. The previously developed method of determining the face rock destruction energy intensity by the knife executive body of the geokhod is presented. For a promising direction of studying the influence of the geokhod knife executive body cutting edge shape on the energy intensity of the face rock destruction, the article provides initial data, which include the physical and mechanical properties of rocks and geokhod geometric parameters. As a result of the study, it was found that: the angle of inclination of the knife to the plane perpendicular to the axis of rotation does not significantly affect the face rock destruction energy intensity by the geokhod knife executive body; an increase in the knife cutting edge radius of curvature by the executive body of the geokhod leads to an increase in the energy intensity of the face rock destruction; given the physical and mechanical properties of the destroyed rock and the geometric parameters of the geokhod, it was found that with a knife cutting edge semi-convex shape and rкр = rг, the energy intensity of the face rock destruction is 1.4% less than with a straight shape. With a convex shape of the knife cutting edge and rкр = rг /2, the energy intensity face rock destruction is 8.3% less than with a straight shape.

Quantum Buckling in Metal-Organic Framework Materials.

Metal–organic frameworks are porous materials composed of metal ions or clusters coordinated by organic molecules. As a response to applied uniaxial pressure, molecules with a straight shape in the framework start to buckle. At sufficiently low temperatures, this buckling has a quantum nature described by a superposition of degenerate buckling states. Buckling states of adjacent molecules couple in a transverse field Ising type behavior. Based on the example of the metal organic framework topology MOF-5, we derived the phase diagram under applied strain, showing a normal phase, a parabuckling phase, and a ferrobuckling phase. At zero temperature, quantum phase transitions between the three phases can be induced by strain. This novel type of order opens a new path toward strain induced quantum phases.

In-Process Error-Matching Measurement and Compensation Method for Complex Mating.

This study proposed an error-matching measurement and compensation method for curve mating and complex mating. With use of polynomial curve fitting and least squares methods for error analysis, an algorithm for error identification and error compensation were proposed. Furthermore, based on the proposed method, an online error-matching compensation system with an autorevising function module for autogenerating an error-compensated NC program for machining was built. Experimental verification results showed that the proposed method can effectively improve the accuracy of assembly matching. In a curve-type mating experiment, the matching error without compensation was 0.116 mm, and it decreased to 0.048 mm after compensation. The assembly accuracy was improved by 28%. In a complex-type mating experiment, the verification results showed that the error reductions after compensation for three mating shapes (straight line, triangle, and curve shape) were 81%, 87%, and 79%, respectively. It showed that the proposed method can improve the assembly accuracy for complex mating shapes, which would also be improved without losing production efficiency.

Phenotypic Characterization for Identification, Conservation and Sustainable Utilization of Boset and Minjar Shenkora Goats of Ethiopia

This study was conducted on a total of 776 goats (part of Central highland goat breeds of Ethiopia), 306 from Boset district of Oromia region and 470 were from Minjar Shenkora district of Amhara region. A format developed by using food and agriculture organization discerption list was used for recording of morphological traits, bodyweight and linear body measurements. Both qualitative and quantitative traits were recorded from randomly sampled mature goats and the data were analyzed using SAS software. The goat type in the study area was characterized by a higher proportion of plain coat color patterns (62.5). Ingeneral, the majority (98.4%) of the studied goats were horned and characterized by backward orientation (67%) with a straight shape (49.3%). They presented a concave facial profile (73.8%), slop up toward the rump back profile (66.2%), no wattle (99.6%), no toggle (90.7%), no ruff (85.9%) and no beard (57.3%). The location had a significant effect on body weight and some other linear body measurements. Traits like body length, rump length, horn length, head length, head width and shin circumference were significantly higher in Boset district. In contrast, rump width and cannon bone length were significantly lower. The mean body weight of male goats in Boset and Minjar Shenkora district were 30.5±1.05 kg with a range of 16 to 47 and 27.5±0.56 with a range of 13 to 57, respectively. While for female counterpart mean body weights (kg) were 28.4±0.35 with a range of 17 to 45 for Boset and 27.5±0.33 with a range 15 to 57 for Minjar Shenkora district. Heart girth had the highest correlation with body weight in both sexes and shoulder width in Boset male goats. The wider variation in most quantitative measurement traits would open an opportunity for further improvement, conservation and utilization work.

Wettability and Its Controlling Factors of Mixed Shale Oil Reservoirs: A Case Study of Permian Lucaogou Formation in Jimusar Sag

Abstract Due to diverse mineral composition and complex lithology, mixed shale oil reservoir wettability features and the associated controlling factors remain unclear, limiting the evaluation of the oil-bearing property and sweet spot distribution. This paper examined mixed shale oil samples from the Jimusar Sag in the Lucaogou Formation. Casting thin sections, X-ray diffraction, geochemical characteristics, argon ion polishing scanning electron microscope, and high pressure mercury injection were used to analyze lithologic characteristics, mineral compositions, and pore-throat structures within the mixed shale oil reservoir. Using spontaneous imbibition and nuclear magnetic resonance, the wettability characteristics were analyzed. Impacts of organic matter abundance, mineral composition, pore-throat structure, and source-reservoir combination on wettability were discussed. The Lucaogou mixed shale oil reservoir primarily contains intergranular dissolved pores, intragranular dissolved pores, and intercrystalline pores. Three types of mercury intrusion cures were observed, including a weak platform shape (type I), gentle straight line shape (type II), and upward convex shape (type III), corresponding to intergranular, dissolved, and dissolved-intercrystalline dominant pore-throat systems, respectively. Mixed shale oil reservoirs show dual wet properties, containing both oil-wet and water-wet pores. Oil-wet pores (large pores with T2>1 ms) are more common and have better connectivity than water-wet pores (small pores with T2<1 ms). Dolomite-bearing siltstone and mudstone are primarily strongly oil-wet, while siltstone is primarily mixed wet. Type II and type III pore-throat systems are more oil-wet than type I for the same source-reservoir combination. Mixed shale oil reservoir wettability is primarily controlled by three factors, including organic matter abundance, source-reservoir combination, and dolomite content. The influence of the pore-throat structure is weak. High organic matter abundance, an integrated source-reservoir or adjacent source-reservoir, and appropriate dolomite content are necessary conditions for forming a strong oil-wet shale oil reservoir in the Lucaogou Formation. Stronger oil-wet is beneficial for shale oil charging and enrichment.

Study on the Flow State of Circulating Cooling Water for the Industrial Heat Exchange Tube in the Electromagnetic Anti-Fouling Process.

Comparing with the traditional chemical and physical method, the electromagnetic water treatment technology draws more attention of researchers for its advantages of easy application, small investment, low cost, and being pollution free in recent years. However, due to the less study of the formation process and adhesion of fouling on the surface of heat exchange equipment, the electromagnetic anti-fouling performance cannot be well evaluated. This paper studies the numerical simulation of the flow states of circulating cooling water in heat exchange tubes with a straight shape and U-shaped ones and analyzes the experimental data of fouling resistance on heat transfer surface under the action of 0.5, 0.75, 1, and 1.5 kHz electromagnetic fields. The variations in the velocity field and pressure field at various points in heat exchange tubes declare that the velocity of the circulating cooling water is smaller in the outlet of the pipeline. The change of the circulating cooling water flow state with the pipeline shape causes a certain impact on fluid velocity, and the pressure value at the outlet is larger. It is obtained that the flow velocity in the area with high surface pressure of circulating cooling water is relatively small. The experimental results indicate that the fouling resistance on the surface of the magnetic heat exchange tube is smaller than that of the nonmagnetic one. The anti-fouling efficiency in 0.5, 0.75, 1, and 1.5 kHz magnetic and contrast experiments are 46.8, 84.8, 91.2, and 63.6%, respectively. Better anti-fouling performances are obtained under the action of about 1 kHz electromagnetic frequency. The induction period of fouling on the heat exchange surface is lengthened under electromagnetic fields. All these studies are of significant importance to further understand the formation process and adhesion of fouling on the surface of heat exchange equipment, as well as to better evaluate the electromagnetic anti-fouling performance.

Effect of Fiber Shape on the Tribological, Mechanical, and Morphological Behaviors of Sisal Fiber-Reinforced Resin-Based Friction Materials: Helical, Undulated, and Straight Shapes.

In this paper, we aim to evaluate the tribological, mechanical, and morphological performance of resin-based friction composites reinforced by sisal fibers with different shapes, namely helical, undulated, and straight shapes. The experimental results show that the shape of the sisal fibers exerts a significant effect on the impact property of the composite materials but no obvious influence on the density and hardness. The friction composite containing the helical-shaped sisal fibers exhibits the best overall tribological behaviors, with a relatively low fade (9.26%), high recovery (98.65%), and good wear resistance (2.061 × 10−7 cm3∙N−1∙m−1) compared with the other two composites containing undulated-shaped fibers and straight-shaped fibers. The impact fracture surfaces and worn surfaces of the composite materials were inspected by scanning electron microscopy, and we demonstrate that adding helical-shaped sisal fibers into the polymer composites provides an enhanced fiber–matrix interface adhesion condition and reduces the extent of fiber debonding and pullout, effectively facilitating the presence of more secondary plateaus on the friction surface, which are responsible for the enhanced tribological and mechanical properties. The outcome of this study reveals that sisal fibers with a helical shape could be a promising candidate as a reinforcement material for resin-based brake friction composite applications.

On the Free Recovery Bending Shape Memory Effect in Powder Metallurgy FeMnSiCrNi

This paper presents the results of an original experimental study on the training capacity of a powder metallurgy (PM) FeMnSiCrNi shape memory alloy (SMA). The specimens were sintered under protective atmosphere from blended elemental powders, 50 vol.%. of alloy particles being mechanically alloyed. Lamellar specimens, hot rolled to 1 mm thickness, were bent against cylindrical calibres with five decreasing radii, to induce cold shapes with higher and higher deformation degree, as compared to the straight hot shape. During the training procedure, bent specimens were heated with a hot air gun, and developed free-recovery shape memory effect (SME) and partially deflected, by reducing their curvature. The first set of experiments involved fastening the specimens at one end, heating it and monitoring free end’s displacement by means of cinematographic analysis. Within the second set of experiments, both cold and hot shapes were recorded and digitalized and their chord’s length (b) and circle segment height (a) were measured and the radius was determined as R = a/2 + b2/8a for the cold (Rc) and hot shapes (Rh). Finally, the shape recovery degree was calculated for the nth calibre as Δrecn = (Rhn-Rrn)/(Rhn-1-Rrn) and the variation of Δrecn with calibre’s radius was discussed.

Types and Quantitative Characterization of Microfractures in the Continental Shale of the Da’anzhai Member of the Ziliujing Formation in Northeast Sichuan, China

A number of wells in the Sichuan Basin of China have tested industrial gas flow pressure arising from the shale of the Da’anzhai section of the Ziliujing Formation, revealing good exploration potential. Microfractures in shales affect the enrichment and preservation of shale gas and are important storage spaces and seepage channels for gas. In order to increase productivity and to reduce the risks associated with shale gas exploration, the types, connectivity, and proportion of microfractures in the Da’anzhai Member have been studied in this work by core and thin section observations, micro-CT, scanning electron microscopy, nitrogen adsorption, and high-pressure mercury intrusion. The results show that four types of fractures have developed in the shale of the Da’anzhai section: microfractures caused by tectonic stress, diagenetic shrinkage fractures of clay minerals, marginal shrinkage fractures of organic matter, and microfractures inside mineral particles. Among these, structural fractures and organic matter contraction fractures are the main types and are significant for shale reservoirs and seepage. The structural microfractures are mainly opened and are well-developed in the shale, with a straight shape, mainly between bedding, with the fracture surface being curved, fully opened, and mainly tensile. Organic matter fractures often develop on the edge of the contact between organic matter and minerals, presenting a slit-like appearance. The fractures related to bedding in the shale are particularly developed, with larger openings, wider extensions, intersecting and expanding, and forming a three-dimensional interconnected pore-fracture system. Based on image recognition, generally speaking, microfractures account for about 20% of the total pore volume. However, the degree of the microfractures’ development varies greatly, depending upon the structural environment, with the proportion of microfractures in fault-wrinkle belts and high-steep zones reaching 40% to 90% of the total pore space. On the other hand, micro-fractures in areas with underdeveloped structures account for about 10% of the total pore space.

Bragg coherent diffraction imaging allowing simultaneous retrieval of three-dimensional shape and strain distribution for 40–500 nm particles

We report the improvement of an apparatus for Bragg coherent X-ray diffraction imaging (Bragg-CDI) at BL22XU in SPring-8 to expand the applicable particle size and the application of the Bragg-CDI technique for Pd and ferroelectric barium titanate (BaTiO3) fine crystals with particle sizes of 40–500 nm. Preparing a vacuum environment around the sample enabled us to obtain the high-contrast diffraction pattern of a 40 nm particle. The reconstructed three-dimensional image showed the outer shape, size, and internal phase (strain) for a single particle. A single 500 nm BaTiO3 particle showed a straight and sharp antiphase-boundary shape, whereas smaller BaTiO3 particles showed different phase boundary shapes. The present Bragg-CDI apparatus, thus, allows the observation of the outer shape, size, and inner phase distribution for a single particle with a size of 40–500 nm.

Analytical model and energy harvesting analysis of a vibrating slender rod with added tip mass in three-dimensional space

In the paper, a new 3D energy harvesting system is provided. This work discussed the Lagrange approach to derive the differential equations of motion in the case of energy harvesting systems. An electromechanical system consists of a mechanical resonator, a piezoelectric transducer and electrical circuit with the load resistor. A flexible slender rod clamped at the bottom and loaded by the tip mass is proposed as the resonator. Moving in the 3D space, it enables the system to avoid the gravitational potential barrier of the straight vertical shape in case of buckling. This paper investigates the response of the rod deflection and the root mean square power output of selected vibration mode shapes with an attached tip mass.

On the Pull-out Behavior of Hooked-End Shape Memory Alloys Fibers Embedded in Ultra-High Performance Concrete

This study presents a three-dimensional non-linear finite element investigation on the pull-out behavior of straight and hooked-end Shape Memory Alloys (SMA) and steel fibers embedded in Ultra-High Performance Concrete (UHPC) using a single fiber pull-out model. A bilinear cohesive zone model is used to characterize the interfacial traction separation relationships. The Concrete Damage Plasticity (CDP) model is used to simulate UHPC, and the mechanical behavior is obtained through experimental tests. Parametric studies are conducted to evaluate the effects of fiber materials, fiber diameters, and hook angles on the load-displacement behavior. A good agreement between the numerical and experimental results is obtained. It is found that the hooked-end fibers with a smaller diameter and a hook angle of 40° can be a better choice for structural application. Furthermore, it is observed that the use of SMA fibers significantly improves the pull-out performance between fibers and UHPC.

Influence of Pet Fiber Geometry on Properties of Concrete Using Partial Replacement of Fine Aggregate with Copper Slag

In the last few years with the growth of population, development of industry and technology there has been rapid increment in the waste materials and by-products production. The basic strategy to decrease solid waste and plastic waste bottle disposal problems have been focused at the reduction of waste production and retrieval of usable materials from waste as raw materials . In present study, the PET fibers were achieved by manually hand cutting from Kinley polyethylene terephthalate (PET) plastic drinking water bottles. Three different geometrical shape Straight shape fiber, Flattened shape fiber and ‘O’ shape polyethylene terephthalate (PET) fibers 0.5% by weight of cement were used. Fine aggregate were partially replaced with copper slag at percentages of 0%, 20%, 40% and 60%. Effect of different geometry of PET fiber and copper slag on fresh and hardened properties of concrete was investigated. Test result revealed that geometry of fiber and copper slag has good effect on fresh properties of concrete. Without use of super plasticizer workability was increasing. The combination of O shape fiber with 60% copper slag demonstrate enhancement in compressive strength, split tensile strength and flexural strength up to 25.85%,26.39% and 28.09% respectively compared to standard mix M 25 grade concrete. With the Increment of copper slag enhancement in strength was observed it was due to the friction developed between copper slag and PET fiber surface. Development of friction was due to the angularity of copper slag particles and bridging action of PET fiber. From water absorption test result it was concluded that water absorption is less in O shape fiber. It is due to the less water absorption properties of PET fiber and copper slag and also the O shape fiber provide good interlocking property in concrete matrices compare to other two geometrical shape fiber.

The Reinforcement of Sand by Fibres with a Non-Uniform Shape

Abstract The reinforcement of soil is used to improve its strength and stiffness. The standard method of soil reinforcement is an application of geosynthetics. Soil reinforcement by distributed discrete fibres represents an alternative to those techniques. Currently used fibres have a straight shape, uniform cross-section, and smooth surface, which is not optimal in terms of the fibre-soil interaction. In this study, fibres with a variable shape were utilized. The fibres were fabricated using a fused deposition modelling technology. Firstly, a brief theoretical background is presented. Then, the proposed shapes of the fibres and their manufacturing process are described. The mechanical properties of the soil-fibre composite were investigated through consolidated drained triaxial tests. Well-graded coarse sand and poorly-graded fine sand were used. A higher peak shear strength was observed in the case of fibres with a variable shape. The effect of the variable shape of the fibres on the peak shear strength was higher in the case of the coarse sand.

Application of Scale Adaptive Simulation Model to Studying Cooling Characteristics of a High Pressure Turbine Blade Cutback Trailing Edge With Different Cooling Configurations

Abstract Effective cooling structure design in the trailing edge (TE) of a high pressure turbine (HPT) blade is essential to increase turbine efficiency and maintain structural integrity. To obtain efficient cooling structures and understand clearly cooling mechanism, this paper adopted numerical simulation methods to investigate fluid flow and cooling characteristics in detail downstream of an HPT blade TE cutback region. The effects of typical TE configurations on cutback cooling performance are investigated including three types of internal turbulators (cylindrical pin fins and elliptic pin fins arranged in streamwise and spanwise orientations), the cutback with/without land extensions and three kinds of ejection lip profiles (one straight lip shape marked as “A” and two rounded lip shapes marked as “B” and “C,” respectively). The scale adaptive simulation (SAS) is implemented to study the complex unsteady mixing process downstream of the cutback under operating condition of blowing ratio M = 0.65. The results from the shear stress transport (SST) k–ω model are compared as well. SAS is capable to reproduce the periodical vortex shedding phenomena and resolve the vortices coherent structures. Compared with the experimental data, SAS provides more accurate predictions in terms of laterally averaged adiabatic cooling effectiveness ηaw and discharge coefficient Cd than the SST k–ω model. At the rear part of the cutback surface, large deterioration in ηaw is predicted by SAS for all configurations, but ηaw is considerably overpredicted by the SST k–ω model except for the case of elliptic pin fins with spanwise orientation. The elliptic pin fins with streamwise orientation significantly improve ηaw at the rear part of the cutback surface over the baseline model with cylindrical pin fins and slightly increase Cd. However, the elliptic pin fins with spanwise orientation drastically reduce the ηaw and Cd. Downstream of the cutback, the coherent structures are strongly disturbed and become chaotic compared with the TE with cylindrical and streamwise oriented elliptic pin fins. The application of land extensions only causes an evident change to the coherent structure immediate downstream of the lip and slightly improves ηaw and reduces Cd over the baseline model at the rear part of the cutback surface. Rounded lip shapes B and C also show an obvious increase in ηaw at the rear part of the cutback surface but only a minor increase in Cd compared with the straight lip shape A. The rounded lip helps the coolant diffuse into the TE cutback and reduce the intensity of mixing. Due to larger rounding radius of shape B, the cooling effectiveness predicted by shape B is slightly better than shape C.

Using ground-penetrating radar to investigate the thickness of mollic epipedons developed from loessial parent material

The information of mollic epipedon (ME) thickness was essential for evaluation and protection of Mollisol resource. However, the traditional methods including the soil profile method, soil probes, and the drilling method, are low efficient and accurate for large area survey of soil thickness. In this study, the ground penetrating radar (GPR) was employed to detect the thickness of ME with underlying loessial parent material (LPM) along three slopes in straight, convex, and concave shapes in northeast China. The accuracy of GPR for measuring the ME thickness was verified by using excavation profile and pre-buried iron pipes. The effects of soil moisture and bulk density on soil permittivity were also investigated based on indoor experiments. The results indicated that the soil permittivity increased and decreased with the increase of bulk density and soil moisture, respectively. The relationships among soil moisture, bulk density and permittivity of both Mollisol and LPM could be described by two fitted equations, and the errors of the prediction equations was in the range of 0.32 %–5.10 %. The errors of GPR to measure the ME thickness was in the range of 3.72 %–10.64 %. The spatial distribution of the ME thickness along the three slopes varied, and the concave slope had a thicker ME than the convex and straight slope. Meanwhile, similar trends were shown that the sedimentation at the slope foot led to the thickest ME, while soil erosion at the slope shoulder and back resulted in the thinnest ME. This study could provide an efficient and accurate method to investigate soil thickness for further evaluation and protection of soil resources.

Low-velocity impact damage detection and characterization in composite sandwich panels using infrared thermography

This paper presents an experimental investigation into the impact damage detection of Paulownia wood core sandwich structures. The structures were impacted by a hemispherical-nosed head with a of diameter 16 mm at impact energies ranging from 22 to 77 J, and infrared thermography (IRT) was used to characterize the impact damage types and extents of the impacted specimens. The test results showed that it is possible to acquire damage information from the temperature distribution images acquired by IRT. Matrix cracking, delamination and fiber breakage damage were effectively characterized by a continuous dark region with a straight shape, a continuous white hot spot in the impact region and a continuous dark spot perpendicular to the fiber direction, respectively. Infrared detection can be used to detect subsurface defects and damage. The effects of different impact energy levels, fiber thicknesses and fiber stacking sequences on the damage induced in the structures were also discussed.

On the dynamic response of a hingeless helicopter rotor blade

The intense nature of the aerodynamic environment surrounding a helicopter can cause excessive deflection of the rotor blades. Therefore, proper prediction of the aerodynamic loading and the blade deflection are necessary for monitoring the blade health. Compared to a rigid blade, the dynamics of a hingeless rotor blade is of particular interest for its inherent flexing tendency and strong coupling between different degrees-of-freedom of motion. With small-angle assumption, the deformed blade resembles a straight shape with constant flapping angle. However, in reality, the blade deforms with variable flapping angle with dynamic blade twist. In this paper, the coupled, steady-state dynamic response of the Bo 105 hingeless helicopter rotor blade is investigated at forward flight for different advance ratios without small-angle assumption. The velocity distributions are generalized and the torsional deformation is introduced to modify the total blade twist for deriving the corresponding angle of attack. The solution to the resulting nonlinear equations is obtained by formulating the generalized method of lines for coupled, flap-lag-torsion degrees-of-freedom in terms of time-varying deflections and other aerodynamic parameters. The deflections and other parameters obtained from this analysis differ significantly than that of the small-angle assumption. The model is validated by comparing the method of lines solutions with finite element and published results.