Electromechanical impedance based debond localisation in a composite sandwich structure

An electromechanical impedance (EMI) based structural health monitoring (SHM) approach is proposed for the localisation of skin-core debonds in composite sandwich structure (CSS). Towards this, laboratory experiments and numerical simulations of EMI in a CSS with core to bottom face-sheet debond have been carried out using a network of piezoelectric transducers (PZTs). The frequency-domain analysis of the registered EMI signals shows that the presence of inter-facial debonds in the CSS significantly influences the conductance magnitudes of the registered EMI data. It was also noticed that the conductance magnitudes of the signals are dependent on the debond-to-PZT distances. In all the study cases, an agreement between the simulation and experimental results is observed. Eventually, a simulated SHM approach is proposed that uses a debond detection algorithm to calculate the changes in conductance magnitudes to effectively locate such debonds in CSS. The study is further extended for the detection of debonds at different locations in the CSS, including a debond located at the edge to assess the potential of the proposed SHM approach.

Nodule Deformation of PVA Roller Brushes on a Rotating Plate: Optimum Cleaning for Nanosized Particles due to Liquid Absorption and Desorption of Sponge Deformation

It is very difficult to remove extremely small particles from the surface of the wafer. Here, we proposed a new cleaning strategy using brush scrubbing, namely, nodule deformation induced fluid flow. Liquid absorption and desorption due to brush deformation enhance the mixing of liquids containing small particles. In this study, we developed a setup that reproduced the actual movement of PVA roller brushes on a rotating wafer and observed the contact surface of the brush nodule. We modeled the brush nodule deformation for each rotating condition. As a result, three types of nodule deformation were observed. In most cases, the nodule side face, rather than the bottom face was mainly in contact with the wafer surface. Moreover, we compared two types of roller brushes, normal cylindrical nodules, and edge treated nodules and found that the deformation can be significantly changed by chamfering nodule edge.

DEVELOPMENT OF THERMAL INSULATION TILE WITH NON-VENTILATED AIR LAYERS SHIELDED BY FOIL MATERIAL

A heat-insulating tile consisting of a back, side and front wall made of extruded expanded polystyrene and a polymer-sand mixture has been developed. Inside there are two unventilated air layers, separated by a heat-reflecting screen. In order to exclude cold bridges, the thermal insulation tile is made of two parts, offset in the horizontal direction. Fixing of tiles among themselves is carried out by means of occurrence of ledges on the top face of one tile with hollows on the bottom face of another. This type of joining plates ensures the absence of cold bridges and facilitates their installation. The problem is solved by the fact that in the facade thermal insulation panel containing the front, rear walls, side faces and locking elements in the form of protrusions and recesses arranged in a checkerboard pattern, and made with the possibility of mounting, the front and rear walls form a frame with a cavity , filled with insulating material, characterized in that the locking elements are placed on the front faces of the frame. Shielded layers of air are used as heat-insulating material. The frame of the panel is made of polymer-sand material, and for its fastening use an adhesive solution. This is achieved by making a panel of polymer-sand frame, in the middle of which there are shielded air layers, which provide resistance to heat transfer and infrared radiation of the material.

The optimization of friction disc gear-shaping process aiming at residual stress and machining deformation

Friction disc is the key part of the frictional clutch. But there is a lack of in-depth studies on the effect of the cutting parameters on residual stress and machining deformation. In this study, the simulation model for friction disc gear shaping was established and the effect of the typical cutting parameters on surface residual stress and machining deformation was studied. Based on the study’s results, the optimization experiment of friction disc gear shaping was carried out and a method was proposed to reduce machining deformation and to improve the fatigue life. Applying the proposed method, the residual stress on the tooth bottom increased from −122.50 to −371.33 MPa, an increase of 203.13% that increases the fatigue life greatly. Meanwhile, the front and bottom face deformation of the outer ring as well as the deformation of the front and bottom tooth tip can be decreased effectively. This study can provide technical support for improving the comprehensive performance of the friction disc and transmission system.

Finite Element Analysis for the Behavior of Reinforced Concrete T-Section Deep Beams Strengthened with CFRP Sheets

This paper presents a numerical investigation for the behavior of simply supported T-section deep beams, which strengthened with Carbon Fiber Reinforced Polymer (CFRP) sheets. The used specimens were (1.8 m length), (450 mm width and 100 mm depth) flange dimensions, and (180 mm width and 360 mm depth) web dimensions. The specimens were divided into four groups. Mainly, the difference between specimens in each group is in the main reinforcement details. The control group consisted of six beams unstrengthen with CFRP, the other groups were similar to the control group but externally strengthened with CFRP sheets, which were (0.131 mm) thickness. In detail, the second group was strengthened with CFRP sheet at the bottom surface of the web. The third group was strengthened horizontally with CFRP sheets at both sides of the specimen's web. The last group was strengthened with three sheets of CFRP; one at the bottom face of the web and the others at the web sides. The results show that using CFRP at the bottom slightly increased the ultimate strength and changed the failure mode from flexural to shear. Using CFRP at the sides significantly increased both flexural and shear strength, while using CFRP at the sides and bottom of the web did not significantly enhanced the ultimate strength in comparison with using CFRP at the sides only.

Pilot Pipe and Damping Orifice Arrangements Analysis of a Pilot-Control Globe Valve

Compared to conventional globe valves, the pilot-control globe valve (PCGV) possesses advantages of lower energy consumption and higher space utilization. In order to analyze the effects of pilot pipe and damping orifice arrangements, this work proposes four PCGVs and conducts simulations to compare their overall performances, overall flow characteristics, and local flow characteristics around the valve core. In general, the arrangement of the pilot pipe has larger effects on the hydroperformances of PCGVs than the arrangement of the damping orifice. The pipe-parallel-mounted type PCGV performs better in hydroperformance than the pipe-perpendicular-mounted type PCGV, and thus is recommended in practice. As the specified valve core travel increases, the flow resistance of PCGVs decreases and the flow capacity of PCGVs increases. However, overlarge specified valve core travel has little effects on the flow resistance and flow capacity of PCGVs. Besides, the increased specified valve core travel could effectively reduce the wear induced by the uneven pressure distribution on the external lateral face of valve core, but it has little effect on the wear induced by the uneven pressure distribution on the bottom face. For all pipe-perpendicular-mounted type PCGVs, the variation of axial force imposed on the valve core relative to the specific valve core travel presents similar tendencies under different incoming flow velocity within the scope of the investigation, which could be concluded into a fitting equation. This work could be referred for the optimization of PCGVs and other similar valves.

First observation of the "double-faced X-framed cup ossicle" extracted from a deep sea holothurian in Japan

A New type ossicle form, “double-faced x-framed cup ossicle” is discovered from the undescribed deep sea holothuroid. To give a definite view on the substantial qualities of this ossicle, a SEM observation on the ossicles and a DNA barcoding analysis are conducted. Although the most internal and external morphologies of the present species agree well with the characteristics of the family Cucumariidae Ludwig, 1894, the ossicles morphologies mostly does not agree with the congeners of Cucumariidae. On the other hand, our molecular study indicates a possibility that the specimens are not cucumariids, but belong to a sister group of Cucumariidae. In our present observation, some of the peri-oral ossicles show a very similar property with the small x-framed cup-shaped structures (which sometimes occurs in cucumariids). Therefore, the double-faced x-framed cup ossicle probably could be considered as the results of derivation from the x-body: in which four extra-arms developed on the bottom face of a cup ossicle, and finally these arms equipped with an extra-rim.

The Structural Performance of Externally Strengthened RCC Beams Made with GPC

Cement is one of the prime ingredients in construction but at the same time a source of CO2 emission during its manufacture. In order to create a sustainable building material, Geopolymer concrete (GPC) was proposed by Davidovits in 1988 which could be viable substitute for conventional concrete production. In this study, totally 21 beam specimens were prepared with GPC of M30 grade which were externally strengthened by two systems of strengthening namely Externally Bonded Reinforcement System (EBR) and Near Surface Mounted System (NSM). Strengthening of existing beams will enhance the service life and service loading conditions of beams. In EBR system, 2 numbers of 6, 8 and 10mm diameter bars are bonded at the bottom face of RCC beams and in NSM system, different types of polymer sheets are attached at the bottom face of the beam such as Carbon, Glass and Aramid. Results show that, the beam specimens made with Carbon Fiber Reinforced Polymer (CFRP) sheets perform better than the other strengthening methods, and have 67% better load-carrying capacity than the control beam (beams without strengthening applications).

Distortion in Induction-Hardened Cylindrical Part

This article concerns distortion of a workpiece after induction-hardening under various conditions. It focuses particularly on the effects of quenching water temperature, PAG polymer concentration and the rotation speed of the workpiece during induction hardening. Electrical as well as non-electrical quantities which affect the process were monitored. They included the current passing through the inductor, the power frequency, quenching water temperature, the flow rate of the quenchant through the spray-quench device, the speed of rotation of the workpiece and some others. The workpiece was a cylinder 70 mm in length which contained a drilled off-axis through hole. Prior to hardening, dimensions of the workpiece and the hole were measured on three planes set in different distances from the bottom face. The measurement was repeated after induction hardening and the findings are reported in this article. Post-process hardness was measured on the cylindrical surface of the workpiece. Hardening depths obtained with different quenchants were measured.

Mechanical Properties of Laminated Veneer Lumber Beams Strengthened with CFRP Sheets

This paper presents the results of the static work analysis of laminated veneer lumber (LVL) beams strengthened with carbon fabric sheets (CFRP). Tested specimens were 45mm wide, 100 mm high, and 1700 mm long. Two types of strengthening arrangements were assumed as follows: 1. One layer of sheet bonded to the bottom face; 2. U-shape half-wrapped reinforcement; both sides wrapped to half of the height of the cross-section. The reinforcement ratios were 0.22% and 0.72%, respectively. In both cases, the FRP reinforcement was bonded along the entire span of the element by means of epoxy resin. The reinforcement of the elements resulted in an increase in the bending strength by 30% and 35%, respectively, as well as an increase in the global modulus of elasticity in bending greater than 20% for both configurations (in comparison to the reference elements).