Minimum Deflection Research Articles

On the correlation between minimum thickness and central deflection during small punch test

Present paper deals with a detailed study on the correlation between minimum thickness (t/t0) and central deflection (δ/t0). Such data are obtained during the deformation of a small punch test of miniaturized specimen. Finite element studies have been carried out to investigate the effect of various parameters which are expected to influence this correlation. The parameters under consideration are material hardening, material yield stress, coefficient of friction and initial thickness of the specimen. It is shown that the correlation remains unaffected with respect to change in material parameters. Similarly, the coefficient of friction beyond 0.2 also does not affect the correlation. However, change in thickness has significant effect on the correlation. A modification has been suggested in the existing correlation to consider the influence of thickness change. The modified correlation is then used to calculate fracture toughness using the experimental results quoted in the literature. It is shown that the modified correlation improves the fracture toughness prediction considerably.

Efficient thermal infrared emitter with high radiant power

Abstract. Sensitive and selective gas measurements are crucial for a large variety of applications, e.g., explosion protection. Optical gas detection is usually based on the gas' absorption of infrared radiation (IR). It is the leading technique in terms of accuracy, reliability, and economic efficiency. Since most gas measurements are made in the two wavelength ranges of (3 ... 5) and (8 ... 14) μm, a broadband IR source is necessary. In this paper, we report on a novel thermal IR emitter with high radiant power and a near-blackbody emission characteristic that can be modulated electrically. The layout of the IR source had been optimized by use of finite element analyses (FEA) in order to get an adequate electrical resistance as well as a homogeneous temperature distribution and a minimum deflection of the radiating element. Due to its excellent thermal isolation from the heat sink, the electrical power consumption is very low. Operating temperatures of up to 1400 K are possible, so that the fabricated IR source features a very high radiant power. Its application in gas analysis will improve the performance and efficiency of gas measurement systems.

The Etiology of chatter in the Himalayan singing bowl

The Himalayan singing bowl is a nearly symmetric idiophone played by rotating a wooden stick called a puja around the outer rim of the bowl. The vibrations of the bowl are excited by a stick-slip mechanism, which produces a radial motion of the bowl with a deflection shape similar to the (2,0) mode. We present experimental evidence that the position of the puja coincides with the point of minimum displacement on the bowl, indicating that it imposes a node in the deflection shape that rotates around the bowl with the puja. However, in many cases the puja is forced off of the bowl and an audible chatter is produced as the puja repeatedly strikes the bowl several times per second. This indicates that the position of the puja is not a node, but rather merely a point of minimum deflection. Examination of high-speed electronic speckle pattern interferograms and time-resolve acoustic spectra provide insight into the mechanics of the singing bowl and the origin of the chatter.

Creep Properties Assessment of P92 Steel by Small Punch Creep Tests

Small punch creep (SPC) tests have the potential as an alternative to conventional uniaxial creep tests when limited amount of material is available. This paper investigates the applicability of SPC to evaluate the creep deformation behavior of P92 steel. SPC results have been compared with uniaxial creep test results in order to establish the correlation between the two tests. Small punch tests on P92 steel have been performed at 600 °C in the load range of 1000–400 N. The load dependence of minimum deflection rate was found to obey Norton’s power law but with a two slope behavior exhibiting distinct values of load exponents in the low and high load regimes. Transition in fracture mode of SPC specimens from ductile transgranular at high loads to brittle intergranular fracture at low loads was in accordance with the large variation in load exponent values. Monkman–Grant equation interrelating minimum deflection rate with rupture time has been found to be valid for SPC data. Correlations between SPC load and minimum deflection rate with uniaxial creep stress and minimum creep rate respectively, established based on empirical relations suggest the relevance of SPC for evaluating creep properties in relatively short time.

Optimum design of concrete cable-stayed bridges

The design of cable-stayed bridges involves a significant number of design variables and design objectives. The concrete cable-stayed bridge optimization is formulated here as a multi-objective optimization problem with objectives of minimum cost, minimum deflections and minimum stresses. A numerical method is developed to obtain the optimum design of such structures. This numerical method includes: structural analysis, sensitivity analysis and optimization. The structural analysis accounts for all the relevant effects (concrete time-dependent effects, construction stages and geometrical nonlinear effects). The structural response to changes in the design variables is achieved by a discrete direct sensitivity analysis procedure, and an entropy-based approach was used for structural optimization. The features and applicability of the proposed method are demonstrated by numerical examples concerning the optimization of a real-sized concrete cable-stayed bridge.

Deflection monitoring and assessment for a suspension bridge using a connected pipe system: a case study in China

Summary This paper discusses the application of a connected pipe system (CPS) to a suspension bridge in China for the purpose of vertical deflection monitoring and assessment. The CPS mainly consists of three main parts: the pressure transmitters to detect the height change of liquid, the pipes to connect the reference point and measurement points, and the liquid to fill the connected pipes. Multiple pressure transmitters, taken as the measurement point, were mounted inside of the girder. A reference transmitter was mounted inside of a tower, taken as a fixed point. To verify the performance and reliability of the CPS, a controlled load test after the completion of the bridge construction and an uncontrolled load test under the actual traffic loading were carried out. The results showed that the CPS exhibited excellent capability in real-time measurement of vertical deflection of the suspension bridge. With the long-term deflection data monitored by the CPS, the extreme deflections with respect to vehicle loads were predicted by extreme value analysis. The generalized extreme value distribution was adopted to establish the probability models of the daily maximum and minimum deflection sequences, and then the extreme deflections within the design reference period of 100 years were determined based on the probability models. Comparison of the extreme deflections and the deflection thresholds was carried out. The deflection monitoring and assessment method proposed in this paper have shown high potential of applicability in the practice of health monitoring for long-span bridges. Copyright © 2015 John Wiley & Sons, Ltd.

Optimized design of linear cascades for turbomachinery applications

This paper presents a cascade optimization methodology for representing axial turbomachinery profiles of series NACA-65. In geometrical parameterization scheme of the cascade the following are considered as design variables: the stagger angle, cascade pitch, and camber line. For the calculation of the flow, the panel method of Hess and Smith with modifications is used to introduce the viscous effects by calculating the boundary layer. This methodology used a viscous/inviscid interaction and has as advantage the low computational cost and being favorable for the optimization process. The maximization of the relationship between the lift and the drag coefficient was defined as objective function and was added a penalty function, given by the minimum deflection angle of the flow in the cascade. For the optimal solution, a controlled random search algorithm is used. On the other hand, is also constructed a response surface by interpolation of radial basis functions to obtain comparative analysis of the solutions. Results of pressure distributions and aerodynamic coefficients are also obtained for the optimal cascades.

초고밀도 고층복합빌딩시스템의 최적설계

In this study, we propose an innovative lateral force distribution building system between tall buildings by utilizing the difference of moment of inertia, as the alternative design for highly integrated city area. Considering a tri-axial symmetric conditions and boundary conditions for the three-dimensional building structure system, a two-dimensional model is composed. In the proposed indeterminate structural model, important design variables are determined for obtaining minimum horizontal deflections, reactions and bending moments at the ground level of the buildings. Regarding a case of the provided two spatial structures connected to 4 buildings, the optimum location of middle located spatial structure is 45% from the top of the building, which minimize the end moments at the bottom of the buildings. In the considered verification examples, reduced drifts at the top location of the building systems are validated against static wind pressure loads and static earthquake loads. The suggested hybrid building system will improve the safety and reliability of the system due to the added internal truss-dome structures in terms of more than 30% reduced drift and vibration through the development of convergence of tall buildings and spatial structures.

Geometric interpretation of synthesis of a quasi-optical distribution system for multibeam phased array antennas

A geometric interpretation is proposed for synthesis of a quasi-optical system employed in multi-beam active phased array antennas (APAAs). Relationships are obtained for the angles of deflections of APAA beams and for optimum positions of the probes of the distribution system. The optimization is performed according to two criteria: the minimum mean deflection and the minimum local deflection. The example of construction of a quasi-optical distribution system for a five-beam APAA is presented. Dependences of phase errors on the positions of radiators and patterns of an APAA with a sidelobe level not exceeding 40 dB are obtained.

Optimization of cutter posture based on cutting force prediction for five-axis machining with ball-end cutters

In process planning for five-axis machining, the key issue is the determination of cutter postures (orientations). In this paper, a simulation-based method is proposed to identify cutter postures that produce minimum deflection cutting force. The method applies to the finish machining process, where only the ball part of the cutter will be engaged with the workpiece. For ball-end cutters, with change of cutter postures, the shape of the engagement region between the cutter and workpiece remains the same. Only the distribution of the engagement region on the cutter surface will change. Based on this principle, a method to transform engagement information between cutter postures is proposed, to eliminate the demand for repeated engagement calculation for different cutter postures. As a result, the computational loads of cutting force calculation for different cutter postures are greatly reduced, which enables us to deploy evolutionary algorithms to search for the optimal cutter posture at a reasonable computational cost.

Effect of Three-wall Bony Defect along Various Root Surfaces on Position of Center of Resistance: A 3D Finite Element Analysis.

Increase in adult orthodontic patients has increased the challenges faced by orthodontists, as they often present themselves with a varying degree of dental and peri-odontal compromise, in which the entire orthodontic treatment planning will revolve around maintenance and augmentation of supporting apparatus. One of the many factors to be considered during treating an adult patient is the height of alveolar bone and its effect on center of resistance (CRes). Eight 3D analytical models of upper central incisor were designed using 'Solid Works Office Premium'. The models were subjected to 3 and 6 mm bone loss along all four surfaces, i.e. labial, lingual, mesial and distal. One Newton of retraction force was applied on labial surface of tooth on model number 1, 2, 5 and 6 and 1N of distalization force was applied to model number 3, 4, 7 and 8. The relative location of the CRes to the total root length was taken as 41.8% of total root length from the root apex. The ANSYS software was used to evaluate the change in CRes on all the models. It was observed that CRes shifted apically from its relative location (41.8% from apex); however, this shift was clinically insignificant. Minimum deflection of CRes, 0.0122 mm, was seen when a distalization force was applied on model with 6 mm bone loss on distal surface, while maximum deflection of 0.0245 mm was seen when retraction force was applied on model with 6 mm bone loss on labial surface. The resultant displacement in position of center of resistance is negligible; hence, there is no need of changing biomechanics during orthodontic treatment for a tooth with three wall infrabony defects. However, it is necessary to further study other infrabony defects like two wall or one wall defect, and their effect on position of CRes.

Variability of Deflections for Reinforced Concrete Flat Plate

The deflection of reinforced concrete members can be highly variable, due to uncertainties in the characteristics of the concrete. However, current standards do not take this problem into account, instead recommending only the minimum thickness and maximum allowable deflections based on empirical data. This paper is aimed at evaluation deflection variabilities by applying a probabilistic analysis model to a finite element analysis model. To evaluate the variabilities of deflections, a Monte Carlo simulation, which incorporated the eight parameters related to concrete, reinforcement, member size, and tension stiffening. The results showed that lager spans were more sensitive to the deflection due to loads and that as the applied live loads were increases and the slab thickness were decreased, the deflection variability increased.불확실성을 가지는 콘크리트의 특성으로 인해 철근 콘크리트 부재의 처짐에는 높은 변동성이 발생할 수 있다. 그러나 현행 설계규준은 이를 고려하지 않고 경험적인 데이터에 바탕을 두고 있으며, 부재의 최소 두께 또는 최대 허용 처짐만을 제시하고 있다. 본 논문에서는 철근 콘크리트 플랫 플레이트의 처짐 예측이 가능한 유한요소해석 모델에 확률해석 모델을 적용하여 철근 콘크리트 플랫 플레이트 처짐의 변동성을 평가하고자 하였다. 이를 위해 콘크리트, 철근, 부재치수, 인장강성에 관련된 8개 요소를 변수로 한 몬테카를로 시뮬레이션을 수행하였다. 해석결과, 스팬의 크기가 증가할수록 하중으로 인한 처짐에 더 민감하게 반응하는 것으로 나타났으며, 재하되는 활하중의 크기가 클수록, 슬래브의 두께가 작을수록 처짐의 변동성이 큰 것으로 나타났다.

Minimize the Deflection of Laminated Composite Plates under the External Load Using Fiber Orientation Angle

Optimization of fiber orientation angle is studied to minimize the deflection of the laminated composite plates by the genetic algorithm. The objective function of optimization problem is the minimum deflection of laminated composite plates under the external load; optimization parameters are fiber orientation angle of laminated composite plates. The results for the optimal fiber orientation angle and the minimum deflection of the 4-layer plates are presented to demonstrate the validity of present method.

Long-term flexural cracking control of reinforced self-compacting concrete one way slabs with and without fibres

In this study experimental result of a total of eight SCC and FRSCC slabs with the same cross-section were monitored for up to 240 days to measure the time-dependent development of cracking and deformations under service loads are presented. For this purpose, four SCC mixes are considered in the test program. This study aimed to compare SCC and FRSCC experimental results with conventional concrete experimental results. The steel strains within the high moment regions, the concrete surface strains at the tensile steel level, deflection at the mid-span, crack widths and crack spacing were recorded throughout the testing period. Experimental results show that hybrid fibre reinforced SCC slabs demonstrated minimum instantaneous and time-dependent crack widths and steel fibre reinforced SCC slabs presented minimum final deflection.

Topography and Surface Roughness of Floor in Groove Micro Milling

AbstractMicro milling operation is a fabrication process to create 3D parts from tens of micrometers to a few millimeters in size using a tool with diameter less than 1mm. Micro groove is one of the common features observed in the micro parts. The surface roughness of micro grooves plays an important role in their performance. Since most of the finishing processes could not be easily performed on the micro grooves, it is of extreme importance to find a relationship between micro milling parameters and the surface roughness profile. In this paper, in order to anticipate the profile and surface roughness of the groove floor a model is proposed based on the kinematic of cutting process and tool geometry. The effects of minimum chip thickness, elastic recovery, size effect and tool deflection are included in the model. Relationship between position of points on the floor surface of groove and kinematics of cutting process are derived. In next step, simulations of proposed model are performed in the ACIS environment. Finally, using the DOE method surface roughness is investigated stochastically. The simulated and measured surface roughnesses are compared together that confirm the validity of proposed model.

HIGH TEMPERATURE MECHANICAL PROPERTIES OF Al-Al4C3 COMPOSITE PRODUCED BY MECHANICAL ALLOYING

A method of mechanical alloying process is described. It was proved that the transformation efficiency of carbon to Al4C3 by heat treatment of aluminium with the porous furnace black and electrographite at temperatures 723 – 873 K and time periods 1 - 10 hours is higher than that of the hard cracked graphite. The size of Al4C3 dispersed phase was measured on thin foil and it was constant and as small as 30 nm. Subgrain size measured in the range of 100 grains in thin foils depended on the carbon type.. It ranged from 0.3 to 0.7 μm. Mechanical properties were analyzed in a microstructural matrix (after extrusion) as well as in nano-matrix The temperature dependence of ductility, and reduction of area in the temperature range of 623 – 723 K and strain rate of 10-1 s-1, indicated a considerable increase of properties. In a case when the volume fraction of Al4C3 changes from lower to higher, the grain rotation mechanism dominates instead of the grain boundary sliding. Creep parameters for Al-Al4C3 systems and commercial IN9021 and IN9052 systems were compared. The dependence of the minimum deflection rate on the applied force as well as the dependence of the time to fracture on the applied force for two temperature levels (623 and 723 K) by small punch testing is depicted. The anisotropy of the creep properties and fracture using small punch tests for the Al-Al4C3 system produced by ECAP were analyzed.

Design analysis of the optimum configuration of self-anchored cable-stayed suspension bridges

This paper describes a formulation to predict optimum post-tensioning forces and cable dimensioning for self-anchored cable-stayed suspension bridges. The analysis is developed with respect to both dead and live load configurations, taking into account design constrains concerning serviceability and ultimate limit states. In particular, under dead loads, the analysis is developed with the purpose to calculate the post-tensioning cable forces to achieve minimum deflections for both girder and pylons. Moreover, under live loads, for each cable elements, the lowest required cross-section area is determined, which verifies prescriptions, under ultimate or serviceability limit states, on maximum allowable stresses and bridge deflections. The final configuration is obtained by means of an iterative procedure, which leads to a progressive definition of the stay, hanger and main cable characteristics, concerning both post-tensioning cable stresses and cross-sections. The design procedure is developed in the framework of a FE modeling, by using a refined formulation of the bridge components, taking into account of geometric nonlinearities involved in the bridge components. The results demonstrate that the proposed method can be easily utilized to predict the cable dimensioning also in the framework of long span bridge structures, in which typically more complexities are expected in view of the large number of variables involved in the design analysis.

Hydrodynamic instability and shear layer effect on the response of an acoustically excited laminar premixed flame

Combustion instabilities can cause serious problems which limit the operating envelope of low-emission lean premixed combustion systems. Predicting the onset of combustion instability requires a description of the unsteady heat release driving the instability, i.e., the heat release response transfer function of the system. This study focuses on the analysis of fully coupled two-way interactions between a disturbance field and a laminar premixed flame that incorporates gas expansion effects by solving the conservation equations of a compressible fluid. Results of the minimum and maximum flame front deflections are presented to underline the impact of the hydrodynamic instability on the flame and the shear layer effect on the initial flame front wrinkling which is increased at decreasing gas expansion. These phenomena influence the magnitude of the burning area and burning area rate response of the flame at lower frequency excitation more drastically than reduced-order model (ROM) predictions even for low temperature ratios. It is shown that the general trend of the flame response magnitudes can be well captured at higher frequency excitation, where stretch effects are dominant. The phase response is influenced by the DL mechanism, which cannot be captured by the ROM, and by the resulting discrepancy in the flame pocket formation and annihilation process at the flame tip.

Optimization of a passive vibration absorber for a barrel using the genetic algorithm

The non-linear vibrations of a barrel, induced by the interaction with a high-speed moving projectile, negatively affect the shooting accuracy of a weapon. This study presents a new method that determines the non-linear behavior of the barrel with a passive vibration absorber and optimizes the absorber using the genetic algorithm (GA). Since both the barrel geometry and its coupling with the absorber are non-linear, a new finite element method (FEM) approximation has been developed for the interaction of barrel and projectile and combined with the classical finite element method. The final coupled equation of motion of entire system has been solved by a step by step integration, and for minimum tip deflection of the barrel, a GA has been then used in order to optimize the some parameters of the absorber. The results of analyses of the proposed FEM model were compared, and a good agreement was seen with the existing literature. In another example, the FEM–GA integrated optimization procedure was also used for the optimization of a passive vibration absorber, and a more accurate result (0.5% better) was obtained when compared to the experimental study given in literature.

Balancing energy efficiency and structural performance through multi-objective shape optimization: Case study of a rapidly deployable origami-inspired shelter

For military and disaster relief housing, rapidly deployable shelters must be lightweight, be packaged in a small volume for transportability, and be erected without heavy lifting equipment. A critical design criterion is also energy efficiency in heating and cooling. To meet these priorities, the research team has utilized origami as inspiration for a thermally insulated rigid wall deployable shelter that can be erected manually through counterweighting. To enhance energy efficiency, improvements in the shape of a structure (i.e., member lengths and angles) at a design stage can lead to savings throughout its lifecycle. This is magnified in the context of mass-production of deployable shelters, where any improvements are multiplied. Structural efficiency is also critical to achieve lightweight design. This paper presents a multi-objective shape optimization methodology which balances the priorities of structural performance (i.e., minimum deflections) and energy efficiency (i.e., minimum thermal energy load). This is demonstrated for the case study of a deployable shelter. Design variables include geometric parameters. Constraints relate to the package size and capability of interfacing with existing technologies. Structural analysis is performed using a parametric finite element program. Thermal energy is calculated using EnergyPlus. An optimized solution is found and compared against existing military solutions.