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The process of twin-roll casting including pouring, solidifying, rolling and cooling can be accomplished in a very short time. Consequently, some important process parameters in the twin-roll casting that are difficult to be obtained in experiment can be acquired using numerical simulation. In this paper, a numerical simulation based on a 2D finite element model of vertical twin-roll strip casting of magnesium alloy has been conducted, and the thermal stress fields are significantly discussed. The influences of key process parameters consisting of submerged nozzle depth and nozzle spray angle have been studied. The thermal cracks on the surface of the strip are analysed according to the thermal stress distribution. © (2012) Trans Tech Publications, Switzerland.

This paper shows the identification of material parameters for a DC06 IF steel sheet of 0.8 mm by mechanical tests. The experimental equipment used consists of a tensile test machine, a bi-axial test machine able to perform plane-strain and simple shear tests separately or simultaneously and an optical strain gauge. Tensile, plane-strain and simple shear tests were performed at 0°, 45° and 90° from the sheet rolling direction in order to identify Hill 1948 and Hosford 1979 yield criteria. Two identification methods are used: one based on strain measurements (anistropy coefficients) and the other one based on stress measurements (plastic contours). The results confirm that mechanical tests applying other stress-states than tensile are required to obtain accurate material parameters identification.

An inverse artificial neural network (ANN) assessment for locating defects in bars with or without notches is presented in the paper. Postulated void defects of 1mm x 1mm were introduced into bars that were impacted with an impulse step load; the resultant elastic waves propagate impinging on the defects. The resultant transient strain field was analyzed using the finite element method. Transient strain data was collected at nodal points or sensors locations on the boundary of the bars and used to train and assess ANNs. The paper demonstrates quantitatively, the effects of features such as the design of ANN, sensing parameters such as number of data collection points, and the effect of geometric features such as notches in the bars.

This paper is concerned with the modelling of gear rattle in Roots blower vacuum pumps. Analysis of experimental data reveals that the source of the noise and vibration problem is the backlash nonlinearity due to gear teeth losing and re-establishing contact.We develop non- smooth ordinary differential equation models for the dynamics of the pump. The models include a time-dependent forcing term which arises from the imperfect, eccentric mounting of the gears. We use a combination of explicit construction, asymptotic methods and numerical techniques to classify complicated dynamic behaviour in realistic parametric regimes. We first present a linear analysis of motions where the gears do not lose contact, and develop upper bounds on eccentricity for quiet operation. We then develop a nonlinear analysis of ‘backlash oscillations’, where the gears lose and re-establish contact, corresponding to noisy pump operation. It is found that noisy solutions can coexist with silent ones, explaining why geared systems can rattle intermittently. We then consider several possible design solutions, and show their implications for pump design in terms of the existence and stability of silent and noisy solutions. Finally, we present conclusions and possibilities for future work.

ISO 14649 standard, commonly recognized as STEP-NC is a data model interface for computer numerical controllers. STEP-NC goes much further that G codes and has a more comprehensive data model that overcomes the lack of process information in ISO 6983 files (G codes programming). The STEP compliant approach brings the possibility to integrate the machine controller to the overall enterprise information network, with the intention of having bi-directional data flow. This will provide the novel capability for upstream feedback of information from the numerical controller to the design and process areas in the process planning and manufacturing. This paper presents the key concepts of the proposed STEP Convertor of the STEP-CNC Mapping System. The objective of the main system is to take a generic STEP file as the input to drive a CNC machine tool. The main system is broken down into two main sub-systems, STEP Convertor and STEP-NC Translator. This paper will focus solely on the information structure and conceptualization of the STEP Convertor.

This paper presents a short overview of the state of the art and future challenges of the use of full-field measurements and inverse procedures to identify the constitutive mechanical parameters of a wide range of materials. It concentrates on the so-called Virtual Fields Method (VFM) which is a tool fully dedicated to the processing of full-field measurements. Some of the future challenges are briefly covered here, namely the design of test configurations and the application to damage assessment, high strain rate testing and biomaterials. Some examples are given and the main scientific issues briefly discussed.

Applications of power ultrasonics in engineering are growing and now encompass a wide variety of industrial processes and medical procedures. In the field of power ultrasonics, ultrasonic vibrations are used to effect a physical change in a medium. However, the mechanism by which a process can benefit from power ultrasonics is not common for all applications and can include one or more of such diverse mechanisms as acoustic cavitation, heating, microfracture, surface agitation and chemical reactions. This paper presents two applications of power ultrasonics involving some of these different characteristics by concentrating on two case studies involving material failure (ultrasonic cutting) and acoustic cavitation (bacterial inactivation).

This paper presents the modelling of the effects due to load conditions on the cervical section defined between C3 and C5 after a cervical plate implant is used to transfer the compression loads from C3 to C5 as C4 is considered to be damaged as a result of a medical condition. For this study, three different scenarios which describe the common motion condition of the head-neck system are modelled. The first one refers to the effect of the head weight over the considered section. In the second case the average patient weight is supported by C3 and C5 vertebrae. The last case simulates extreme loading conditions as vertebrae lesions occur when these are compressed beyond its failure limit; the ultimate stress to compression load failure value is applied to C3. The stability and mechanical behaviour of cervical plates under compression loading conditions is evaluated using the Finite Element Method (FEM). Cervical plates are useful to restore stability of the spine by improving the inter-vertebral fusion, particularly when the cervical body has been damaged. The results show that the stresses on the plate and fixation screws, for the three cases, are within the elastic range. Conversely, it has to be considered that cortical and trabecular bone densities vary from one patient to another due to a number of factors, which can influence the fixation conditions of the screws. In the case of this analysis, healthy bone conditions were considered and the obtained results show that the risk of the integrity of the screwimplant- vertebrae system is not compromised.

This paper discusses the penetration behavior of fully supported sandwich panels with micro-lattice and foam cores, and composite skins. This behaviour is of importance during foreign object impact and perforation of sandwich structures. Experimental results are given for quasi-static penetration of micro-lattice and foam blocks, and it is shown that these two cellular materials are comparable. Experimental results are also given for drop weight penetration of fully supported skinned panels, and it is shown that skin failure and core penetration are also similar for the two core materials. It is concluded that there is scope for improving the performance of micro-lattice structure and so making such material superior to that of aluminium foam.

The sensitivity of the thermoelastic response to variations in the fibre volume fraction, resin material and manufacturing route is assessed. To quantify any effects a comprehensive materials testing programme has been conducted to obtain coefficients of thermal expansion, specific heat, density and the elastic properties, which is described in detail in the paper. The work is focused on attempting to ascertain if the source of the response is from the isotropic resin rich layer or from the orthotropic substrate. It is also demonstrated that small variations in material properties can have a significant effect on the calculated thermoelastic response.

This paper presents the experimental results obtained of flexurally loaded wind turbine blade cross section material. All material was extracted from a wind turbine blade box girder and testing was conducted in four point configuration. The aim was to gain an understanding of the structural integrity of this lightweight material as it deforms in flexure. To allow for thorough analysis, digital image correlation (DIC) was used to produce full field strain maps of the deforming specimens. Results highlight the capability of the DIC technique to identify regions of failure, as well as the aspects responsible for them. Overall, the results present a foundation for tests on larger substructure, and eventually integration into manufacturing and maintenance aspects of the industry.

The goal of this paper is to present the results obtained from damage evaluation in automotive axles, which are under torsion fatigue. For this purpose, a Nonlinear Damage Model is used. The mentioned shafts have to satisfy geometry requirements and their material has to be heat treated in order to improve their performance. One has to keep in mind that fatigue strength depends on material properties and geometry. In order to make a precise evaluation of the accumulated damage, the manufactured shafts were tested. In the first instance, the mechanical properties of the material were evaluated with static torsion tests. In the next step, the S-N curves were obtained with torsion fatigue tests. In all these cases, temperature was controlled. Experimental data at different load levels was gathered with strain gages in conjunction with a data acquisition system. The life cycle history of each tested shaft was stored and with this experimental evidence, damage curves were obtained and the cumulative damage of the axle was established. With these damage curves, it is possible to define the relation between damage rate and life for different stress levels.

This work assesses the Crack Compliance Method (CCM), which has been extensively used for the experimental evaluation of residual stresses, by the Finite Element Method (FEM) to validate its experimental applicability through numerical evaluation. The CCM is a very powerful method that is based on Fracture Mechanics theory, but its experimental application and set up has not been totally scientifically validated. In this paper, a numerical evaluation is presented on the basic applications of the CCM. The assessment of the CCM is performed on bending beams with and without prior straining history. To determine the best position and orientation of the strain gages, as well as the optimum number of readings, a number of numerical simulations where also performed for the correct performance of the experimental evaluation of the CCM. The prior straining history condition, in the analyzed components, is induced by an axial pulling before the beam is bent. Three levels of preloading are considered: low, medium and high (which are related to the yield strain of the simulated material); Isotropic and Kinematic hardening rules are also considered. After the residual stress field is induced by bending, a slot cutting is simulated and the strain relaxation produced is captured, which is used later in the CCM program for the quantification of the original residual stress field. The results obtained in this work, provide a quantitative demonstration of the effect of hardening strain on the distribution of the residual stress in beams. In the same manner, the theoretical formulation of the CCM has been evaluated validating the application of this method for the determination of residual stress fields in mechanical components.

The material assumptions made to facilitate Thermoelastic Stress Analysis (TSA) are linear elasticity, material homogeneity and isotropy, and mechanical properties that are independent of temperature. The unusual shape memory and superelastic properties of near equiatomic NiTi alloys complicate the application of any experimental stress analysis technique, and in the case of TSA, make these assumptions invalid. This paper describes a detailed analysis conducted to characterise the material properties of NiTi shape memory alloys and to identify loading conditions suitable for quantitative stress analysis using TSA. The mechanical behaviour of the material in three distinct regions is considered and the suitability of each region for TSA is discussed. It is shown that the thermoelastic response is dependent on the mean stress when tested at room temperature in the pre-martensitic phase, due the presence of an intermediate R-phase. Theoretical calculations are used to confirm that this effect is related to the high temperature dependence of the material’s Young’s modulus.

In this paper, we demonstrate that a dynamic stress concentration around Lüders band can be directly displayed using mechanoluminescence (ML) sensing film of SrAl2O4:Eu (SAO) coated on the surface of metal. Uniaxial tensile test of an aluminum alloy (2.5% Mg) plate coated with the SAO sensing film was performed and the ML images were recorded using a high-speed camera. Captured ML images confirmed the formation and propagation of Lüders band clearly in real time.

This paper details progress in the application of a methodology for acoustic emission (AE) detection and interpretation for the monitoring of fatigue fractures in large-scale industrial environments. The approach makes use of a number of novel signal processing techniques. An online radius-based clustering algorithm (ORACAL) is used to identify clusters of data, both in the spatial domain (locating AE sources) and in the feature domain (identifying candidate fracture processes). The paper proposes a new approach to the identification of AE waveforms produced by crack propagation; rather than seeking to identify the waveform features characteristic of a fracture event, the new method looks for specific patterns of clustering in the feature space. The approach is validated by a full-scale experiment. An artificial acoustic emission source, representative of a fatigue fracture, was injected into a test of a substantial landing gear component. A commercial AE monitoring system was then used to successfully locate and identify the source in a blind test using the new signal processing methodology. The method was successful on two of three experiments performed and the position of the artificial source was determined accurately; further analysis shows that the unsuccessful test appears to have occurred due to incorrect mounting of the artificial source.

There is no simple linear relationship between strain and potential in strain measurement with strain gauges, especially for large strain measurements. In this paper, a modified algorithm was proposed to improve the accuracy of strain obtained from measured voltage. The strain was calculated from a nonlinear relationship between voltage and strain rather than a linear simplification. Moreover, the corrections for different sensitivity factors of strain gauges and lead wire resistance were considered. The proposed method was suitable for both large and small strain measurements using a quarter bridge, and validated by experimental tests. It is also very easy to be implemented as a software form and used in scientific tests and engineering applications.

This paper reports on theoretical and experimental investigations into the buckling characteristics of a series of six ring-stiffened circular cylinders that experienced general instability when subjected to external hydrostatic pressure. Each study used between 3-5 designs with the same internal and external diameters, but with different numbers and sizes of ring-stiffeners. Four used designs that were machined to a high degree of precision from steel, while the other two were machined from aluminium alloy. The theoretical investigations focused on obtaining critical buckling pressure values, namely Pcr, for each design from the well-known Kendrick’s Part I and Part III theories, together with an ANSYS finite element prediction. The thinness ratio λ1, which was originally derived by the senior author, was calculated together with a dimensionless quantity called the plastic knockdown factor (PKD), for each model. The plastic knockdown factor was calculated by dividing the theoretical critical buckling pressures Pcr, by the experimental buckling pressures Pexp. The thinness ratio was used because vessels such as these, which have small but significant random out-of-circularity, defy “exact” theoretical analysis and it is because of this that the design charts were produced. Three design charts were constructed by plotting the reciprocal of the thinness ratio (1/ λ1) against the plastic knockdown factor (Pcr / Pexp), using results from Kendrick Part I, Kendrick Part III, and ANSYS. Comparison of the results obtained using Kendrick’s theories and experimentally obtained results was good.

The frequent and excessive fluctuation of agricultural and livestock products price is not only harmful to residents’ living, but also affects CPI (Consumer Price Index) values, and even leads to social crisis, which influences social stability. Therefore it is important to forecast the price of agriculture and livestock products. As a result, we made a research on the factors affecting agricultural and livestock products price, established a forecasted model of agricultural and livestock products price, and developed its early-warning system which is suitable to China. Considering the direct relationship between the price and the output, multiple linear regression method was adopted to study this problem. The model is composed of three sub-models. This paper puts forward the concept of price equilibrium coefficient C0, which describes the degree to which people accepting the forecasted price. With the establishment of the standard for the influence of price fluctuation, the influence of price fluctuation is measured. Each range of the C0 value corresponds with a specific result, which may informs the government with the danger of price fluctuation. As a result, the model can early-warn the price rising caused by crop reduction due to sudden natural disaster, which may induce social turmoil and crisis. If the forecasted price rises heavily, the government should take measures to avoid crisis. This paper offers the method to control future price. Finally, a forecasted model of pork price is calculated with simulated data. The forecasted result is in good agreement with actual situation.

Higher power consumption in data centers results in more heat dissipation, cooling costs and degrades the system reliability. Conventional power reduction techniques such as dynamic voltage/frequency scaling (DVS/DFS) have disadvantages when they are ported to current data centers with virtualization deployments. In this paper, we give a short survey and discussion on some issues and aspects of DVS/DFS in data centers. This paper also presents a simple comparison of four power management schemes in virtualization environments.

This paper concerns the analysis of how uncertainty propagates through large computational models like finite element models. If a model is expensive to run, a Monte Carlo approach based on sampling over the possible model inputs will not be feasible, because the large number of model runs will be prohibitively expensive. Fortunately, an alternative to Monte Carlo is available in the form of the established Bayesian algorithm discussed here; this algorithm can provide information about uncertainty with many less model runs than Monte Carlo requires. The algorithm also provides information regarding sensitivity to the inputs i.e. the extent to which input uncertainties are responsible for output uncertainty. After describing the basic principles of the Bayesian approach, it is illustrated via two case studies: the first concerns a finite element model of a human heart valve and the second, an airship model incorporating fluid structure interaction.

The detection of damage in gear teeth is paramount to any condition monitoring or structural health monitoring (SHM) tool for aerospace power transmissions such as those used in helicopters. Current inspection techniques include vibration analysis and time-inefficient visual inspection. Acoustic Emission (AE) is a very sensitive detection tool that has been successfully used in many SHM systems. Successful application of AE for damage detection in gear teeth will enable the optimisation of gear box design (and hence weight saving) in addition to safety improvements. This paper details a small aspect of a larger project designed to demonstrate automatic detection and location of common gear tooth defects. A novel test rig was designed to allow the fatigue loading of an individual gear tooth which was monitored using AE. The gear tooth was static in order to exclude the detection of AE signals arising from rotation; this allows initial development of the methodology prior to investigating rotating gears. Digital Image Correlation was used to determine the onset of cracking for comparison with the detected AE. Preliminary results of the investigation show that the developed methodology is appropriate for developing an automated gear health monitoring system and that future work should concentrate on the development of sensors and data acquisition methods associated with obtaining signals from rotating machinery.

The thermoelastic response obtained from an infra-red (IR) detector contains two components: the magnitude of the small stress induced temperature change caused by the thermoelastic effect and the phase angle of the temperature change relative to a reference signal generated by an application of a stress change. The phase angle is related to nonlinearity in the thermoelastic response and departures from the simple linear relationship that underpins thermoelastic stress analysis (TSA). The phase data could be used to make an assessment of temperature evolutions caused by viscoelastic behaviour resulting from damage and provide a basis for its evaluation. In the current paper the physics of other infra-red techniques used for non-destructive evaluation is used to better understand the nature of the thermoelastic response. The objective is to provide better exploitation of TSA by alternative processing of the IR measurements. Three case studies are presented that demonstrate the potential of the alternative processing for evaluating damage.

To improve the efficiency of printing or coating processes for paper products the velocity of the web and the roller width can be increased. However, these measures bring about deformations of the rollers, heating effects and streak print defects due to undesirable oscillations. This paper presents new sensor technologies for measuring the axial and circumferential distribution of contact pressure along the nip. This work is required for further research on active vibration damping of rollers. The sensors are applied underneath the elastomer covering of the rollers and must be applied without affecting mechanical features or causing a fall off in the quality of the product. In the paper different new measurement techniques are evaluated and compared to state-of-the-art technologies considering dynamic behaviour, sensitivity, linearity, applicability and accuracy. The sensors are integrated into a test rig simulating the rollers of a printing or coating machine. The results are presented in detail and an outlook is given on further research towards active vibration damping.

The paper describes initial work on using 2D digital image correlation (DIC) and thermoelastic stress analysis (TSA) to obtain data from edge cracks in cross-ply laminates. It is demonstrated that detailed data related to the crack tip stresses can be obtained using TSA. The work reveals some of the limitations experienced when using DIC in applications where high spatial resolution is required. A detailed discussion is provided along with an outline for future work.

This paper studies the effect of delaminations on strain maps for a simple cantilever beam. The aim is to build an experimental set-up which allows detecting very slight modifications in the strain maps. The case studied is a single delamination on the mid-plane. The measurement method is the deflectometry technique which enables direct slope measurements on a reflective specimen. The comparison with finite element models clearly indicated that the surface strains bear the information of the extent of the delamination. The second step is to use these surface strains to identify a stiffness reduction map for real impact damages.

This paper details work undertaken towards the development of a standard test method for the biaxial response of planar cruciform specimens manufactured from carbon fibre-reinforced plastic (CFRP) laminates and subject to tension-tension loading. Achieving true biaxial failure in a cruciform specimen without the need for the inclusion of a stress raiser, such as a hole, in the gauge-section, is a subject attracting much research globally and is by no means a trivial exercise. Coupon designs were modelled using finite element analysis (FEA) in order to predict the stress and strain distributions in the central region of the specimen. An Instron biaxial strong-floor test machine was used to test the specimens. Strain gauges were used to measure the strain in the specimen arms and to assess the degree of bending. Digital image correlation (DIC) was used to measure the full-field strain distribution in the central gauge-section of the specimen and this was compared to values measured using strain gauges. The strain readings obtained from strain gauges, DIC and FEA predictions were in good agreement and showed that the strain distribution was uniform in the central gauge-section, but that strain concentrations existed around the tapered thickness zone. These regions of strain concentration resulted in interlaminar failure and delamination of the laminate propagating into the specimen arms.

The effect of lightning attachment to structures and vehicles is a cause of major concern to a number of different industries, in particular the aerospace industry, where the consequences of such an event can be catastrophic. In 1963, a Boeing 707 was brought down in Maryland killing 81 people on board, triggering the improvement of lightning protection standards. However, commercial jets are still struck on average once every 10,000 hours of flight time and between 1963 and 1989 forty lightning related accidents were recorded within the U.S.A alone. The rapid increase in the use of composite materials in aircraft design and the consequent increase in complexity when determining the effects of a lightning strike, has led to new challenges in aircraft protection and the requirement for improved understanding and standardisation. The attachment of lightning to a structure causes damage through three mechanisms. Primarily a supersonic acoustic shock wave, caused by rapid heating of the arc channel during initial attachment, resulting in a large and rapid overpressure. Secondly a magnetic force generated by the fields developed in the high current areas around the lightning attachment point. Finally a mechanism specifically related to composite materials, where the rapid vaporisation of an expanded copper foil layer (designed to quickly transmit current across a structure, thus reducing its focus) trapped between the composite material and the protective paint layers causes an additional overpressure, which is exacerbated by additional paint layers acting to contain the explosion and direct it inwards. The work described in this paper looks to develop a technique to measure these forces in order to better understand and assess their effects. A novel methodology has been developed to allow the estimation of peak overpressure forces produced by the acoustic shock wave resulting from the attachment. The methodology utilises Digital Image Correlation and ultra-high speed photography to acquire full-field displacement measurements of panel deflections at frame rates of up to 1,000,000 frames per second. The experimental results are used in the optimisation of a finite element model, outputting the parameters of an acoustic shock that produces representative displacements, velocities and accelerations. The method is currently being validated by performing a series of tests on aluminium panels subject to instrumented impact testing. The next stage will be to use the technique developed to aid a program of investigation into the effects of artificial lightning strike events on aluminium and composite panels.

Compared with the extensive research on properties of the fracture process zone (FPZ) under quasi-static loading conditions, much less information is available on its dynamic characterization, especially for high-strength concrete (HSC). This paper presents the very recent results of an experimental program aimed at disclosing the loading rate effect on the size and velocity of the (FPZ) in HSC. Eighteen three-point bending specimens were conducted under a wide range of loading rates from from 10-4 mm/s to 103 mm/s using either a servo-hydraulic machine or a self-designed drop-weight impact device. Four strain gauges mounted along the ligament of the specimen were used to measure the FPZ size. Surprisingly, the FPZ size remains almost constant (around 20 mm) when the loading rate varies seven orders of magnitude.

The paper describes recent use of Digital Image Correlation (DIC) for in-situ measurements of deformation and cracking of large civil engineering structures like bridges and power plant. Recent work at NPL has demonstrated the potential of DIC as a novel NDT tool for measuring deformation and cracking in reinforced concrete structures. This has particular application where the area of interest is in a region where inspection is difficult or costly and where direct access may have safety implications. In this case accurate measurements from pairs of images can be very cost effective.

Current trends in the wind turbine industry demand that manufacturers and related research facilities increase development efficiency whilst minimizing production costs. A key component developed is the blade, which needs to efficiently capture the wind energy whilst being able to survive severe weather conditions. More recently larger blades have been used, where main advantages include an increase in wind capture efficiency, a reduction in the installation and reduction in maintenance costs per MW. This paper outlines the main principles behind optical measurement techniques employed, influencing factors for using this technology, and presents the importance of the results achieved thus far and describes ongoing development activities.

This paper is part of ongoing structural health monitoring in the National Physical Laboratory. The work is aimed at improving reliability of sensors and increasing the uptake of monitoring systems by improving the understanding of the fundamental interactions between the sensors and their environments. It is important to optimize and validate the selection of the sensors for each application in order to ensure that the results are meaningful. An example of unexpected aspects of a sensor performance exposed to temperature and solar radiation is demonstrated and the importance of temperature compensation is highlighted. More work is required fully to explain this phenomenon.

This research deals with the sensitivity of eight types of performance-designed high-strength concrete to the loading rate. Variations in the composition of the concrete produce the desired performance, for instance having null shrinkage or being able to be pumped at elevated heights without segregation, but they also produce variations in the fracture properties that are reported in this paper. We performed tests at five loading rates spanning six orders of magnitude in the displacement rate, from 1.74  10-5 mm/s to 17.4 mm/s. Load-displacement curves show that their peak is higher as the displacement rate increases, whereas the corresponding displacement is almost constant. Fracture energy also increases, but only for loading rates higher than 0.01 mm/s. We use a formula based on a cohesive law with a viscous term to study the results. The correlation of the formula to the experimental results is good and it allows us to obtain the theoretical value for the fracture energy under strictly static conditions. In addition, both the fracture energy and the characteristic length of the concretes used in the study diminish as the compressive strength of their aggregates increases.

Ratcheting is one of the challenging phenomena that needs to be investigated for the Fast breeder reactor (FBRs), to arrive at the optimum structural dimensions that are safe and yet do not have undue redundancy. Austenitic stainless steel is the principal structural material for Indian FBR. Preliminary assessment indicates that there is a need to demonstrate that the main load carrying vessel made of this material can provide sufficient safety margin against ratcheting under biaxial loading conditions. This exercise calls for carrying out many simulated experiments, particularly with biaxial tension torsion specimens to generate adequate data for developing robust constitutive models to predict ratcheting. Accordingly, many biaxial tension-torsion experiments for austenitic stainless steel pipes were conducted and the best results have been reported here. The mechanical behavior of this material has been reported for a given axial tensile stress superimposed with a given range of cyclic shear stress for many cycles of loading. Rectangular rosette is used for capturing the biaxial response. Important material responses like cyclic hardening and biaxial ratcheting have been experimentally observed. Maximum accumulation of 2700 μ axial strain has been observed for a loading condition of constant axial stress of 102 MPa super imposed with a cyclic variation of shear stress amplitude of 120 MPa over 2450 cycles. The amount of progressive accumulation of axial strain was found to be directly dependent on the number of cycles. The observed rate of axial strain accumulation found decreased with increase in number of cycles. All these results are presented in detail in this paper and important conclusions that are useful in modeling the observed behavior are discussed.

Thermoelastic Stress Analysis (TSA) is a well-established full-field technique for experimental stress analysis that has proved to be extremely effective for studying stress fields in the vicinity of cracks. Recently, work has focused on the observation that the stress-sum contours (isopachics) obtained from TSA take the form of a cardioid. Genetic Algorithms (GAs) and Differential Evolution (DE) have proved successful for accurate parameter estimation of the cardioids, thus allowing the SIFs to be calculated. Originally, some curve-fits indicated that a pure cardioid form is inappropriate for the base model, especially for mixed-mode cracks. The deviation from the cardioid form has been shown to be due to higher-order terms within the stress function. The objective of the current paper is to use a modified version of the original methodology (that fitted parameters to a single isopachic) to find the higher-order parameters from the entire data field obtained from the TSA.

One of our main research areas is the trans-scale modelling of damage in composite materials, which consist of a polymer matrix and carbon or glass fibres in different material combinations and geometrical arrangements. From the local stress redistribution in the fibre-matrix interphase and in the surrounding matrix material information on the parameters of microscopic damage models for composite materials can be obtained. Owing to the difficult interface characterisation based on the properties of the single material components, a photoelastic analysis of single fibre fragmentation tests is performed. In addition to the qualitative visual interpretation in polarized light, an enhanced quantitative analysis in combination with digital photoelasticity using a four image phase shifting method will be applied [1]. As the sequential capturing of images might cause incorrect results, these four pictures are grabbed simultaneously. This allows for continuous testing. Additionally, errors due to the relaxation behaviour of the matrix material can be avoided. To this, a modular optical system consisting of a variable long distance microscope and a beam dividing module proposed by [2] was developed. It allows for the simultaneous projection of four different filtered images of one microscopic scene to the four quadrants of a CCD chip. This special equipment gives the possibility to apply quantitative photoelasticity to tensile tests performed on standard testing machines. This paper explains the measurement hardware and discusses the main problems and realised solutions from picture capturing through image processing to real-time photoelastic analysis at the present state of development. Exemplary results for the qualitative analysis of selected material combinations and different manufacturing processes are shown.

Laser ultrasonics opened possibilities to measure thermal and mechanical property of skin which occupies an essential position and is beneficial in industrial and medical applications. This paper focuses on the thermal effect in the thermal section of the laser ultrasonic technique. A transient thermal analysis is developed and promoted to simulate the interaction between the laser pulse and human skin, using a multilayered finite element model (FEM). Chicken leg had been used and irradiated by KrF laser, the thermal reactions were detected and recorded by a thermal camera. By comparison, the thermal result of experiments and simulation matches.

In this paper the biomechanical behavior and numerical evaluation results of three C3-C5 porcine cervical models created with different modeling techniques are shown. The objective of this evaluation is to know the differences between the biomechanical effects on a bone graft, which replaces a damaged C4 vertebral body, a titanium alloy (Ti-6A1-4V) cervical plate, used to isolate the C4 damaged vertebra, and the influence on the compressive loads on the complete and instrumented C3-C5 cervical model. The biomechanical integrity of the healthy C3 and C5 vertebral body after the fixation of the cervical plate using titanium alloy screws is considered. Besides, 2-D Computer Tomography classic technique, 3-D Scanner Z-Corp 700 and a CT scanning Philips Brilliance system was used to create the three FEM models. In addition, 3-D Software as Pro-E Wildfire 4.0, ScanIP 3.1, UGS NX-4 and Geomagics R 10.0 was used to create specific numerical model. Main displacements and von Misses stresses between the upper and lower surfaces of the vertebral bodies and the bone graft and the influence of the titanium alloy (Ti-6A1-4V) screws on the vertebral body of C3 and C5 were evaluated. The contribution of this study is to optimize the actual surgical technique once the numerical results on the FEM model have been analyzed. In other words, the numerical disparity between classic CT techniques versus 3-D modern techniques is established.

This paper describes an innovative way to characterize the strength of spot welds. A wedge test has been developed to generate interfacial failures in weldments and observe in-situ the crack propagation. An energy analysis quantifies the spot weld crack resistance. Finite Element calculations investigate the stresses and strains along the crack front. A comparison of the local loading state with experimentally observed crack fronts provides the necessary data for a failure criterion in spot weld fusion zones. The method is applied to spot welds of Advanced High Strength steels.

For a structure subjected to an intermediate velocity impact in which the duration of loading is in the order of milliseconds and in excess of the period of it’s first free vibration mode there is a relationship between impact duration and buckling load. Although this relationship results in higher buckling loads for shorter duration impacts, the precise nature of the correlation depends on a number of other factors, one of which is geometry. Since the design of many lightweight structures subject to dynamic loading in this intermediate range is based on the use of a static buckling load to which a load factor is then applied, it is essential that this factor accurately represents the relationship between the two and takes of account of any variations. Failure to do so will at least result in an over designed structure and at worst in catastrophic failure. A series of finite element analyses (FEA) have been performed in order to determine the relationship between dynamic and static buckling loads for a range of stiffened panels with differing radii of curvature. This paper describes preliminary tests performed to determine the feasibility of using high speed digital image correlation (DIC) to study such an impact and hence provide validation of the earlier FEA analyses. These are performed on a longitudinally stiffened panel subject to uniaxial compression, clamped within a rig designed to provide built-in end conditions and allow motion of one end in the direction of loading only. The specimen is tested using an accelerated drop test rig. Impact load is monitored throughout using a load cell. Full field displacement contours are obtained using a high speed DIC system. Results are presented which demonstrate deflection contours during and after impact enabling the path of the shock wave through the specimens to be determined. An initial comparison is then made the FEA results.

Simulation result of a structural dynamics problem is dependent on the techniques used in the finite element model and the major task in model updating is determination of the changes to be made to the numerical model so that dynamic properties are comparable to the experimental result. In this paper, the dynamic analysis of a thin wall structure ( approx. 1.5±0.1 mm thick) was realized using the Lanczos tool to extract the modes between 0 and 200 Hz, but the interest was to achieve a good aggreement between the first ten natural frequencies. A shell element with mid size nodes was used to improve the finite element result and the model was tunned using the damping constant, material properties and discretization. The correlation of the results from the impact excitation response test and the finite element was significantly improved. A correlation coefficient of 0.99 was achieved after tunning the model.

The achievement of high levels of confidence in finite element models involves their validation using measured responses such as static strains or vibration mode shapes. A huge amount of data with a high level of information redundancy is usually obtained in both the detailed finite element prediction and the full-field measurements so that achieving a meaningful validation becomes a challenging problem. In order to extract useful shape features from such data, image processing and pattern recognition techniques may be used. One of the most commonly adopted shape feature extraction procedures is the Fourier transform in which the original data may be expressed as a set of coefficients (coordinates) of the decomposition kernels (bases) in the feature space. Localised effects can be detected by the wavelet transform. The acquired shape features are succinct and therefore simplify the model validation, based on the full-field data, allowing it to be achieved in a more effective and efficient way. In this paper, full-field finite element strain patterns of a plate with a centred circular hole are considered. A special set of orthonormal shape decomposition kernels based on the circular Zernike polynomials are constructed by the Gram-Schmidt orthonormalization process. It is found that the strain patterns can suitably be represented by only a very small number of shape features from the derived kernels.

The paper describes a novel method based on Digital Image Correlation (DIC) for measuring the static modulus of active PGA graphite specimens during conventional four-point bend strength tests. DIC has been used in combination with finite element and numerical modelling to monitor the displacement fields developing in the specimen during testing, and calculate representative modulus values. Details of the model and results are presented for two specimen geometries and a range of materials with different levels of exposure and density, tested in the perpendicular and parallel orientations. The calculated static modulus values from the DIC measurements confirm the trend between modulus, flexural strength and density. Comments and observations on the uncertainty in the measurement are also presented.

In this paper the effect of delamination position on the critical buckling load and buckling mode of hybrid composite beams is investigated. Experimental and numerical studies are carried out to determine the buckling load of delaminated composite beams. The laminated composite beams with various laminate designs of [G90]6, [C90]8, [C0/G0]4 and [C90/G90]4 were manufactured and tested to find the critical buckling load. Three different defect positions were placed through the thickness to find three main buckling modes. It was found that delamination position and lay-up can affect the buckling mode and also the critical buckling load. By approaching the delamination position to the outer surface of the specimen the buckling load decreases. The buckling process of hybrid and non-hybrid composite beams was also simulated by finite element software ANSYS and the critical buckling loads were verified with the relevant experimental results.

This paper is a study of the drop weight impact behaviour of small sandwich panels of carbon epoxy skins with aluminium honeycomb and titanium alloy micro-lattice cores. A series of experimental tests have shown that the specific impactor penetration behaviours are similar for both cores. The reasons for this are a result of the detailed deformation and rupture behaviour of the two types of core. The deformation and rupture mechanisms of honeycomb and micro-lattice structures will be discussed in general terms, and these observations will be used to inform discussion of actual deformation and rupture in the panel tests. In this way, micro energy absorbing mechanisms will be related to panel performance, and conclusions on the way forward for improved penetration performance using other core materials and geometries will be identified.

This paper presents an alternative to the theoretical classic teaching methods generally used in Strength of Materials or Solids Mechanics. It introduces a dynamic and interactive process, with emphasis in the use of ESA-Experimental Stress Analysis, especially strain gauges and photo-elasticity. In addition to the didactic and practical experiments, the students used all their energy and creativity to develop the interesting results presented here, such as, experimental device for measuring displacement, Buckling, Spaghetti and Popsicle sticks Bridges, Stress analysis in a cylinder block and Mini Baja project.

This article reports an accurate analysis approach of finite element modeling and optical modeling. It has been used for design and analysis of many opto-mechanical systems such as large telescopes and laser systems. The approach is to represent mirror surface deformation derived from finite element analysis (FEA) by Zernike polynomials, such that the impact of deformation on optical system performance can be evaluated by optical design and analysis program. The methodology of shell-based and solid-based finite element modeling and the comparison of their results have been described in this paper. The result shows that the deformation of the light-weighted mirror designed by this approach fulfills the requirements of optical design. The simulation results of shell based FE model are in good agreement with those of solid based FE model.

The extraction of event that cannot be detected with conventional equipment can be considered to be a precise measurement in the wide sense. In this paper, the measurement in social life is introduced. It is divided into three fields (global environment, living conditions, and life support and welfare). In each field, the method is introduced. Especially, an intelligent sensing technology is important. It is not only a measurement system for extraction of physical value, but also a system that acquires the information which human perceives and requires. The information is obtained by processing a physical value, judging, and recognizing. It is also important to examine the correlation of a physical value and a psychological value for the extraction of the information. Some examples on the study are shown. A comfortable and safe life is expected to be achieved because the measurement technology in social life advances further.

Sensors that detect the distance and the position of an object are used in a lot of fields. Among of them, the sensors that measure the shift value of an object are a large scale system, furthermore, an accurate mounting of these sensors is required. To solve these problems, this paper proposes an optical linear sensor using one-side frosted glass. This sensor can detect the position of the light irradiation point only by putting it directly on the target. For a parallel light, it is irrelevant to the distance between this sensor and the source of light because the size of light beam is unchanged according to the distance. This sensor assumes that the sensor’s surface irradiated roughly vertical with the light, and does not need a high accurate mounting. Therefore, it can be easily used.