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This paper aims to define sports engineering through the use of historical and contemporary examples. The historical development of the technology in the sprint and in the javelin are discussed, from their introduction to the Olympics over two and a half thousand years ago to the current day. The rules pertaining to tennis racquets are described and the ways in which manufacturers and researchers attempt to maximize performance using technology are examined. Two models for a tennis racquet are shown, one in which the racquet is modelled as a rigid body and one in which it is modelled as a flexible beam. Use of the models shows that further advances in racquet technology using stiffer and lighter materials are unlikely to speed the game up. It was concluded that technology can be used by athletes and manufacturers to enhance performance. Equally, the ruling bodies of sport can also use technology to limit performance, leading to a delicate balance between technology and tradition.

The paper provides a picture of the changes and advances in the field of strain measurement, as represented by the contents of the journal “strain”, from its inception in 1965 to the present day.

This paper describes some recent work on the stress analyses and failure prediction of some typical pressurised high temperature components under creep conditions, including plain pipes, pipe bends, branch connections and welds etc, in the main steam pipework of power plant. The materials used are typically low alloy ferritic CrMoV steels. Experimental creep testing methods, and the procedures used for generating the material properties in creep and damage constitutive equations, are briefly described. Some typical numerical results are presented to illustrate the main characteristics of the behaviour of these components and to demonstrate the effects of geometry, material properties and loading modes on stress distributions and failure life predictions. The emphasis of the paper is on welded components.

This paper reports results from a stress, acoustics and vibration investigation of the ride and driveline components of a new 2-seater sports car. The work was aimed at giving design assurance information to designers and vehicle engineers working to compressed timescales. The paper focuses on two particular areas: design of the power train for NVH refinement, and design analysis of a suspension wishbone. In the first case, a dynamic model of drive shaft torsion effects was created to understand design relationships needed for high power, high torque performance car. In the second case, an investigation was made into the integrity of a suspension wishbone component when gauge thickness was reduced from 3 mm to 2 mm. The work described was carried out in a joint industry academic venture sponsored by Knowledge Transfer Partnership (KTP). It is from this background that the authors give some perspectives on vehicle development.

The design of high power ultrasonic cutting devices is based on tuning a blade to a longitudinal mode of vibration at a low ultrasonic frequency, usually in the range 20-100 kHz. To achieve the required cutting amplitude, gain is designed into the blade via profiling. It is expected that the use of higher-gain blades could enable longitudinal-mode guillotine-type cutting of a range of materials traditionally difficult to cut using this technology. Using a conventional high-gain blade, a feasibility study of ultrasonic cutting of bone is conducted using compact tension specimens of bovine femur. Finite element (FE) models are created, based on the assumption that the ultrasonic blade causes a crack to propagate in a controlled mode 1 opening. The models are compared with the experimental data collected from ultrasonic bone cutting experiments. Although the proposed cutting mechanism is supported by the data, the blade gain is insufficient to enable through cutting of long bone or other difficult to cut materials. Consequently, the paper examines the relationship between gain, profile, stress and nodal position for a range of ultrasonic cutting blades with increased gain.

In this paper, a new type of vibration structure (i.e. swing frame) of vertical dynamic balancing machine is designed, which is based on the analysis of traditional double-plane vertical dynamic balancing machine’s swing frame. The static unbalance and couple unbalance can be separated effectively by using the new dynamic balancing machine with the new swing frame. The modal and harmonic responses are analyzed by using the ANSYS7.0. By comparing the finite element modal analysis with the experimental modal analysis, the natural frequencies and vibration modes are found out, which can provide the dynamics direction for designing vertical dynamic balancing machine. The new dynamic balancing machine can measure static unbalance and couple unbalance directly, and the influence between them is faint. The practical result indicates that the new vertical dynamic balancing machine is suitable for inertial measurement of flying objects, and can overcome the shortcomings of traditional double-plane vertical dynamic balancing machines, in which the effect of plane-separation is inferior. The vertical dynamic balancing machine with the new vibration structure can be widely used in the future application.

Laminar composites have been formed from waste paper and suitable water based binders using a two stage binding technique. The new materials can have physical and mechanical properties equivalent to spruce pine and superior to other wood substitutes such as MDF. The degree of penetration of the binder into the paper is a critical factor in achieving the desired properties and there is a need for rapid assessment of the penetration of the binder. A technique based on the forcing of a probe into the laminate has been developed. Several probe geometries have been investigated and an optimum process established. By analysing the force / displacement graph generated by the probe, and applying a fast Fourier transformation the degree of binder penetration can be established.

Recent work by the authors has allowed the estimation of crack-tip SIFs by direct curvefitting of a cardioid form to measured isopachics from thermoelastic stress analysis. However, some of the curve-fits indicated that the cardioid form was inappropriate for the base model. One of the possible explanations for this is that the cardioid form is only suitable for an isolated crack-tip stress field. In the experimental data for the previous studies, a crack was placed centrally in a plate and there will therefore have been two (potentially) interacting crack-tips involved. The object of the current paper is to determine numerically, the stress field for such a crack system and to quantify the effect of any interactions on the curve-fitting procedure.

A new inverse method has been developed for the simultaneous derivation of tensile and compressive stress strain behaviour from bending tests only. This new procedure can be applied to materials having asymmetric tensile and compressive stress strain behaviour and also materials that have been previously strain hardened (Bauschinger Effect). This paper presents results obtained using the new method and compares them with experimentally obtained tensile and compressive stress strain curves. The agreement of the derived stress strain data in tension and compression is encouraging.

By combining modern surface strain measurement techniques with the traditional tensile test mechanical test, a method has been developed whereby the mechanical properties of a test sample with a heterogeneous microstructure such can be characterised in one test. In this paper the applicability to such a method of two such surface strain measurement techniques, image correlation (IC) and electronic speckle pattern interferometry (ESPI), is assessed. Two commercially available systems were used to monitor, simultaneously, the surface strain on tensile test specimens during testing. Measurements on homogeneous samples were compared with measurements made using strain gauges and excellent agreement was found. Elastic modulus and proof stress values measured in these standard samples showed that the uncertainty in the measurements was below 10%. The method was then applied to an inertia friction weld, whose strength varied linearly as a function of distance from the weld line. The values of proof stress obtained were compared with micro-hardness measurements.

This paper describes initial investigations into the use of frozen-stress photoelasticity to study the development of slippage within shrink-fitted shaft/hub pairs, with the aim of studying the residual stresses remaining after partial slippage has occurred. Results to date show the feasibility of measuring the shear stresses along the partially-slipping interface between shaft and hub.

The measurement of changes in the properties of ultrasonic Lamb waves propagating through structural material has frequently been proposed as a method for the detection of damage. In this paper we describe work that uses optical fibre sensors to detect the Lamb waves and show that the directional properties of these sensors allow us to not only detect damage, but also to locate it. We look at two types of optical fibre sensor, a polarimetric sensor and the fibre Bragg grating. The polarimetric sensor measures the change in birefringence of a fibre caused by the pressure wave of the ultrasound acting upon it. This is an integrated sensor since the fibre length bonded to the sample needs to be greater than the ultrasonic wavelength in order to obtain the required sensitivity. The maximum sensitivity of this sensor is when the fibre is positioned normal to the direction of wave propagation. Fibre Bragg gratings are essentially point sensors since the grating length needs to be a fraction of the ultrasound wavelength to obtain maximum sensitivity. Ultrasound is detected mainly through the in-plane strain it produces and maximum sensitivity is therefore produced when the grating is aligned parallel to the direction of wave propagation. Holes drilled into sample plates can be detected using both type of sensor by examining the changes in either the transmitted Lamb wave or through detection of the reflections produced by the hole. The sensitivity of the technique is shown to be determined by the relative positions of the acoustic source, the hole and the sensor. If we use fibre Bragg gratings in a rosette configuration (i.e. 3 gratings forming an equilateral triangle) then the direction of the Lamb wave can be determined using the directional sensitivities of the gratings. Using two such rosettes allows us to calculate the source of the wave from the intersection of two of these directions. If the source of the wave is the hole (which acts as a passive source), then the location of that hole can be determined.

Data from tension and compression tests at quasi-static and impact strain rates of up to 50s −1 (corresponding to impact speeds of up to 7ms −1) are presented to characterise the effect of strain rate on mechanical properties of triaxially braided carbon/vinyl ester. Three braid architectures were studied; 0°/±30°, 0°/±45° and 0°/±60° where the 0° was an 80k tow and the ±30° to ±60° braid tow was 12k. The methodologies and apparatus used were developed for testing composite materials with a large unit cell size at a range of strain rates and are based on novel tensile and compressive loading rigs in conjunction with a modified instrumented falling weight machine (drop tower). In the paper, the effects of increase in strain rate on fibre and matrix dominated material properties are presented. The ultimate tensile and compressive strengths were found to vary with rate. The axial properties of the braided carbon/vinyl ester, dominated by the 80K carbon fibre tow, were relatively insensitive to rate, but strong rate dependency was seen in the transverse directions where the effects of the polymer resin were more significant.

This paper is based on the experimental and numerical analysis work carried out as part of an international round robin aimed to predict the limit load of the ¼ scale Pre-stressed Concrete Containment Vessel (PCCV) which was tested at Sandia National Laboratories (SNL) in USA. The design pressure, Pd, for the PCCV was 0.39MPa. Pressurisation test was conducted causing global collapse of the PCCV structure, which occurred at the pressure of 1.423MPa (3.65 Pd). Displacements, loads and strains were monitored at 55 standard locations giving a unique opportunity to assess the accuracy and reliability in predicting failure modes and limit loads of PCCV structures. To simulate the inelastic response of the structure with extensive concrete cracking requires specialist numerical models and detailed geometric representation of the main structural features. One of the most important structural features was the prestressed hoop tendon system. The paper presents a brief explanation of the test, the instrumentation used to monitor the tendon behaviour and describes the analytical models employed to predict the tendon behaviour.

Aircraft engineers in the design phase often use practical solutions and results of the elementary theory of structures under the classical hypotheses assumed for shear, torsion and bending behaviour of structural elements that can be studied as "beams". This assumption, very powerful in general, under particular situations (for example: the modification of loading conditions in the development of new aircraft versions) can be inadequate to represent real distributions of stress and strain. This is particularly true when local behaviour of structures depends on secondary phenomena such as warping produced by non-uniform bending and torsion acting on structural elements with variable stiffness along their flexural axis. In this paper the results of analytical and experimental studies carried out for a metallic tail rotor blade of a helicopter are summarised; this research activity was born during a collaboration between the Department of Aerospace Engineering of Pisa and an aeronautical industry. Local strain distributions under real loading conditions have been obtained by means of finite element analyses and by means of strain gauge measurements. To describe warping mechanisms accurately, also caused by the presence of a reinforcing plate of the blade structure, sub-modelling technique has been used and during a fatigue test, the blade was instrumented with an appropriate number of rosettes. Numerical and experimental results show, with a good agreement, that local geometry of the blade and the severe loading condition produce a considerable increase of strains that elementary theory can not predict; moreover, numerical results and above all strain measurements have proved that local yielding of the material can occur during the service life with detrimental effects on the fatigue endurance of the tail rotor blade.

The RNLI has been using composites for the construction of some of its lifeboats since the early 1970s and in the late 1980s a decision was taken to adopt a newer advanced form of composite construction with a view to saving overall structural weight whilst maintaining the requisite structural strength. This paper presents a broad discussion of the history of the use of composites in the RNLI, the structural design and development of lifeboats and the challenges currently faced in the identification of damage and repair methods for fibre-reinforced plastic sandwich structures, operating in the marine environment.

This paper emphasises the importance of the knowledge of service loads to both the initial design process and the maintenance of structural integrity during the lifetime of engineering components and structures. Three case studies are presented. All involve accidents which caused major loss of life: the Hillsborough Stadium disaster in Britain, the German ICE train crash at Eschede and the China Airlines disaster off Taiwan.

An application of the elastic-plastic problem by the photoelastic coating method is presented in this paper. A general procedure of this experiment, such as image processing and separation of the difference of principal strain to obtaine stresses from isochromatic fringes is referred. The methodology to extract centre lines of coloured isochromatic fringes is explained. Experiments are conducted with cross-shaped aluminum specimens with a circular hole subjected to uniaxial tension and equi-biaxial tension. Results of image processing are shown, and the distribution of difference of principal strains and separated principal strain are shown in the case of equi-biaxial tension.

Self-expanding stents are small medical devices used to treat vascular disease and are typically fabricated from a super-elastic, shape memory alloy known as Nitinol and have a fine mesh structure. This paper describes preliminary work on the application of Thermoelastic Stress Analysis (TSA) to Nitinol stents. Uniaxial tensile tests were conducted on thin tubes of Nitinol to characterise the material mechanical properties. TSA calibration exercises were conducted, which showed that Nitinol exhibits a non-uniform thermoelastic response through its elastic region that corresponded to the superelastic behaviour. Initial TSA demonstrated that a viable thermoelastic signal could be obtained from the stents. In high resolution tests the effect of motion and noise were considerable but it was still possible to obtain a readable thermoelastic signal.

This paper describes a development of a new method (: Cantilever Method) to measure Young’s modulus of flexible materials. The method is based on a nonlinear deformation theory that takes into account large deformation behaviors. A set of testing devices was designed and machined. Measurements were carried out on two kinds of flexible materials (PVC: a high-polymer material and SWPA: a steel material). The modulus measured by this method is “Secant modulus”. The results of my evaluation confirm that the new method is suitable for flexible thin plates or rods. Based on the assessments made the method can be further applied to thin sheet and fiber materials (e.g., steel belt, glass fiber, carbon fiber, optical fiber, etc.).

This paper presents three kinds of high-temperature test methods for three different materials along with the results. Resistively heated polysilicon film 3.5 micron thick shows ductile behavior at 500°C. Resistively heated nickel 200 microns thick shows decreasing strength at 400°C. Furnace heated silicon carbide 200 microns thick maintains its strength at 1000°C. Strain is measured by laser-based interferometry in the first two cases to obtain complete stress-strain curves, while force-displacement is measured in the third case.

Electroless plating can uniformly plate a material on irregular and non-conducting surfaces. Consequently, it has been utilized widely for printed circuit boards in the electronics industry. During the plating process, internal stress is frequently incorporated into the film and this often results in detachment from the substrate. In order to investigate the origins of stress in the films, measurements of film stress are required during the early stages of growth. In this study, TV holography, which can capture holographic images at TV frame rates, was used to sensitively measure the deflection of the cantilever beam during deposition. By substituting the deformation data in Stoney’s equation, it is possible to calculate internal stresses in-situ. The internal stress created by electroless plating from a Cu plating solution on a Be-Cu substrate is discussed. It is assumed that the internal stress is generated in the initial stage in which the plating grains with a thickness of about 0.01µm deposit. This paper shows that the present method can be very useful for in-situ measurement of initial internal stress.

Damaging temperature effects observed during ultrasonic cutting operations are typically a result of friction between the vibrating blade and material, and combustion of debris. In order to prevent the high temperatures causing damage, the ultrasonic blade has to cut with a sufficient speed. This can be achieved either by applying a relatively high static load or by increasing the working vibration amplitude of the cutting edge, however, the result can be poor operational control and exceeding the fatigue limit of the blade, respectively. In this paper, the effect of blade tip profile is considered, particularly with reference to the influence of the cutting edge contact area on temperature under different static loading conditions. Titanium blades, with different cutting edge profiles are tested in a series of experiments that monitor cutting speed, static load, temperature around the cut site, and vibration amplitude at the cutting edge. The blades are tested cutting bovine femur and artificial bone material, and the cut surfaces are examined for signs of damage after each test. The experimental data reveal that blades with a small cutting edge contact area cut at a lower temperature, and that signs of thermal damage are less evident.

This paper describes a study of laser generated ultrasonic waves in an 2-layer elastic, isotropic biomaterial model, in order to establish a modelling technique to simulate the thermoelastic response of high-power short pulse laser beams in human skin. The theory proposed in this paper takes into consideration the fundamental understanding of the laser/material interface. A finite element model using the commercial finite element code ANSYS is used to study the effects of laser pulse duration and energy flux contribution to the surface waves. The simulation comprises a set of boundary conditions that approximate a heat flux point source located on top of the surface of the material. Because of the time scale of interest, the elastic effects do not feed back into the thermal problems, so that a sequential coupled-field analysis was performed where the thermal and elastodynamic fields are uncoupled and treated separately. The initial finite element analysis involves a transient thermal analysis using a heat flux with Gaussian spatial variation to simulate the laser pulse heating. The results from the thermal analysis were read and applied to the structural analysis where the out-of-plane displacements histories are analyzed in the skin model with varying thicknesses

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.

A study is presented into the effect of ultrasonic activation of the platen on the stressstrain relationship in compression tests on aluminium specimens. The aim is to gain some insights into the reported beneficial effects of ultrasonically excited tools in metal forming operations. The paper investigates the compression of aluminium specimens using a variety of different lubricants under conditions of constant crosshead velocity and superimposed longitudinal ultrasonic excitation of the platen. The study shows that the changes in the stress-strain relationship under ultrasonic excitation can be explained in terms of the superimposed oscillatory stress condition and that there is some evidence of small changes in the interfacial friction condition.

Hole drilling is one of the most widely used techniques for measuring residual stress, but the conventional approach is limited in the near surface detail that can be resolved. Because of concerns about the levels of induced residual stress that might develop during machining and surface treatment processes, there is significant interest in developing a technique that can obtain near-surface residual stress information by the application of fine-increment hole drilling. Critical information can be lost if conventional, large depth increments are used and the fine incremental hole drilling approach, using depth increments as small as 20µm, offers a cost effective and rapid solution, with the possibility of measuring near surface stresses. Results focus on three different machining studies and a shot peened specimen, all cases where the stress field changes rapidly through the depth, particularly close to the surface. A systematic assessment of machining parameters is not within the scope of this paper and is not presented, but work has focused on highlighting the application and potential of the fine increment hole drilling approach.

The development of aeroengines with increasing thrust capabilities requires the development of shaft technology to deal with this greater power transmission, whilst still restricting their dimensions and weight. Modern aerospace drive shafts are predominantly of a single-alloy design and significant benefits could be obtained from using a dual alloy shaft, where a high temperature alloy is used at the turbine, i.e. hot, end of the shaft and a high strength alloy is used for the spline end of the shaft, where high strength is required, rather than high temperature performance. Whilst the processes of joining dissimilar materials are widely used the evolution of the joint and its strength characteristics are not fully understood. A program of research has been instigated to lead to an improved understanding of friction welds and their behaviour under monotonic and cyclic loadings with the overall objective to establish confidence in the welding parameters for these material combinations and the associated post-weld heat treatments. This paper presents an overview of the mechanical testing program and the aims of this work, illustrated with some examples from the monotonic and cyclic test work carried out on inertia friction welded dual alloy shaft components.

The marine industry at present employs the use of aluminium extrusions in the construction of decks and superstructures that could be replaced with pultruded glass reinforced plastic (GRP) profiles. The length of the pultruded section is limited and therefore, efficient and economic jointing techniques must be developed that can withstand the loads applied to ship structures. This paper evaluates a novel means of adhesively bonded connection for GRP structures known as a finger joint. Various joint geometries are examined, load displacement behaviour is established and Thermoelastic Stress Analysis (TSA) is used to provide the full field stress distribution over the joint. The results of the TSA are compared with the load displacement behaviour. It is shown that by increasing fingertip angle there is a decrease in load carrying capacity, a decrease in shear stress and an increase in stress concentration factor at the finger joint tip.

The characterisation of composite plates used in structural work in the field of aeronautics is approached by associating ultrasound and speckle interferometry measurements. The reduced thickness of the specimens does not allow for gauge instrumentation to measure out-of plane deformation. A system was therefore used which makes it possible to obtain the cartography of the deformations in and out of-plane. This paper describes an application of electronic speckle interferometry in the measurement of through thickness deformation in composites.

This paper deals with the simultaneous identification of the four through-thickness orthotropic rigidities of a thick composite tube. A diametral compression test has been carried out on a glass/epoxy ring cut from the tube. The full strain field has been measured over one face of the sample with the grid method. The measured fields have been processed with the Virtual Fields Method to identify the rigidities of the material. At the beginning, discrepancies and significant variations occurred in the identified moduli due to inhomogeneous distribution of the strains through the thickness. A method based on a simultaneous measurement on both sides of the ring has been adopted. Very satisfactory results have been obtained using this methodology.

Facing compressive failure, facing wrinkling and core shear failure are the most commonly encountered failure modes in sandwich beams with facings made of composite materials. The occurrence and sequence of these failure modes depends on the geometrical dimensions, the form of loading and type of support of the beam. In this paper the above three failure modes in sandwich beams with facings made of carbon/epoxy composites and cores made of aluminum honeycomb and two types of foam have been investigated. Two types of beams, the simply supported and the cantilever have been considered. Loading included concentrated and uniform. It was found that in beams with foam core facing wrinkling and core shear failure occur, whereas in beams with honeycomb core facing compressive failure and core shear crimping take place. Results were obtained for the dependence of failure mode on the geometry of the beam and the type of loading. The critical beam spans for failure mode transition from core shear to wrinkling failure were established. It was found that initiation of a particular failure mode depends on the properties of the facing and core materials, the geometrical configuration and loading of composite sandwich beams.

This paper is related to the understanding of the relationship between the apparent interlaminar shear strength and the temperature-moisture content by the analysis of the dominant failure mode. It assesses the fracture mode of laminates with carbon fiber fabrics in (0, 90, 45)S ply orientation reinforced Polyphenylenesulphide (PPS) polymer matrix, tested for Interlaminar Shear Strength by the Short Beam method. Tests were conduced at different temperatures: (+20ºC), (+0ºC), and (-55ºC), under various moisture-absorbed contents, namely Dry, 25%, 50%, and 75% of the saturated condition. Fractographic analyses were made and reveal, by the analysis of the fracture surface, the dominant mode of failure in every temperature-moisture content pair. As expected it is verified that temperature is a degradation factor. It is also found that humidity is not a degradation factor and, above the water freezing temperature, the moisture content even becomes a strengthening factor on this thermoplastic composite

The paper focuses on the structural integrity of the corner radius of the carbon fibre composite, ‘C’-section spar for the Airbus A400M wing. The corner radius is subject to opening moments generated by internal wing box fuel pressures. The low inter-lamina strength of composites makes de-lamination of the corner of prime concern. The paper describes initial development of analytical techniques to calculate the through-thickness tensile stresses and inter-lamina shear stresses developed in a corner radius under applied bending moments and transverse shear forces. A test programme is also described, aimed at the determination of the failure moment of curved laminates under pure bending moments. Using the analytical expressions developed, a through-thickness failure stress is calculated from the failure moments. A variation of the failure stress with specimen thickness is indicated, showing that thicker specimens fail at higher inter-lamina stresses – a characteristic that must be exploited in the design of the spar. Using finite element analysis of the test configuration, in conjunction with virtual crack extension techniques, it is demonstrated that, at the failure load, a constant rate of strain energy release accompanies inter-lamina crack growth in the different test specimens. A critical energy release rate for uncontrolled crack growth is thus established, which is used, in conjunction with further finite element analysis, to predict the failure stress of specimens with different values of thickness and corner radius. It is concluded that this fracture mechanics approach to integrity can be applied to the A400M spar corner and to similar aircraft structures. Recommendations for further testing and correlation with analysis are proposed to strengthen the theoretical basis for such integrity assessments.

In this paper the combined use of both RGB and phase stepping photoelasticity is proposed. The method is characterised by the following features: maximum measurable order greater than that of the RGB method, ability to determine the total fringe order without necessity of unwrapping.

Displacement measurement can be performed with high accuracy using phase-shifting method. In phase-shifting method, it is often used four steps of phase-shifting for one cycle. In conventional method, to measure the displacement of an object by an interferometer, the phase of a reference beam should be shifted by every π/2 in the four-step phase-shifting. In this paper, a phase-shifting method with unknown intervals is proposed. This method does not need to shift a phase by every π/2. It can detect an intensity distribution and a phase distribution from five fringe images with equal intervals even if the phase-shift amount is unknown. Using this method, we propose a displacement measurement of phase-shifting digital holographic interferometry using spherical wave as reference wave.

In this paper, we apply phase-shifting digital holographic interferometry to simultaneous measurement for out-of-plane and in-plane displacements by employing two beam illuminations for an object. Phase-shifted holograms before and after displacements of the object using each of two beams are recorded by a CCD camera, separately. The complex amplitude at each pixel of the CCD plane is analyzed from the holograms taken with phase-shifting. The complex amplitude of he object is reconstructed from the complex amplitude distribution on the CCD plane using the Fresnel diffraction integral. Each directional phase difference distribution is obtained by calculating the phases before and after deformation for each directional beam. The phase distribution for out-of-plane displacements is obtained by calculating the sum of the two phase difference distributions. The phase distribution for in-plane displacements is obtained by calculating the difference of the two phase difference distributions. The phase values provide accurate displacement distribution information. Actually, when the object deforms in both out-of-plane and in-plane directions, it is possible to analyze the displacement distribution in each direction. The theory and an experiment are shown.

This paper reports recent results from a set of experimental and computational studies of ductile flat fracture in modern gas pipeline steel. Experimental data from plain and notched cylindrical tensile bars and standard C(T) specimens together with damage mechanics theories have been used to capture the flat fracture characteristics of a gas pipeline steel of grade X100. The modelling was via finite element analysis using the Gurson-Tvergaard modified model (GTN) of ductile damage development. The assumption of effective material damage isotropy was sufficiently accurate to allow the transfer of data from the notched bars to predict, in a 2D model, the crack growth behaviour of the C(T) specimen. This was in spite of the considerable ovalisation of the bars at the end of their deformation. However, it was not possible to obtain similar accuracy with a 3D model of the C(T)test, even after a large number of attempts to adjust the values of the GTN parameters. This, and the anisotropic shape change in the tensile bars, suggests very strongly that the damage behaviour is so anisotropic that conventional models are not good enough for a full engineering description of the flat fracture behaviour. Suitable averaging (of shape) in the modelling of the notched bar data, and the companion averaging associated with the 2D model of the C(T) data provide a relatively fast way of transferring engineering data in the tests. There is a discussion of potential ways in which to incorporate 3D effects into the modelling for those purposes where the considerable increase in computational time (due to the microstructurally-sized finite elements needed to capture the damage behaviour) is acceptable in order to include through-thickness effects.

This paper describes the conceptual, embodiment and detailed design of a representative test specimen to mimic fretting variables in aero-engine splined couplings. A fretting bridge design was chosen for the multi-axial representative specimen from a set of four concepts evaluated. The test specimen was intended to facilitate more rapid testing for design against fretting fatigue and wear in the complex contact geometry of the spline coupling.

The paper presents a procedure whereby the Poisson’s ratio and dynamic Young’s modulus of isotropic and homogeneous materials are determined using two of the first four frequencies of natural vibration in thin square plates. The procedure is based on suitable approximate relationships relating the resonant frequencies to the elastic constants of the material. These relations were derived from an extensive series of numerical analysis carried out by a finite element code. To measure the fundamental resonant frequencies, inexpensive computerized equipment is proposed. The procedure has been validated on Carbon Steel specimens.

A method to predict the modal density and radiation efficiency of orthogonally stiffened cylindrical shell is presented in this paper. The modal density is derived using energy method from the undamped natural frequencies of stiffened shell by treating the stiffeners as discrete elements. The band averaged radiation efficiency is estimated by categorizing the structural modes into acoustically fast and acoustically slow modes. The predicted parameters are compared with experimental results using laser vibrometer measurements. Phase-roll off has been observed in laser vibrometer measurements for which a correction procedure is applied. This prediction method can be easily extended to shells with stiffeners having different size, orientation etc.

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.

In this paper a new measurement technique to perform thermoelastic stress analysis on rotating mechanical component is proposed. The idea is to use a particular realization of the Dove prism optical system, optimized to work width infrared radiation, able to give a fixed output image of a rotating surface on where a normal thermoelastic measurement system can be applied. The realization of a first prototype of this optical system is described. First results on a test case are illustrated.

The reinforcement effect of a strain gauge installed on low modulus materials can be significant. The increasing use of low modulus materials requires therefore the evaluation of such effect. This paper concerns the relationship between the local reinforcement effect and the strain gauge stiffness. The conclusion is that the gauge stiffness alone does not allow the user a thorough evaluation of the reinforcement effect.

This work discusses application of the thermoelastic technique to the stress analysis of Rapid Prototyping (RP) models. The aim is to evaluate the possibility of conducting complete and effective structural tests on prototypes made by means of stereolithography (SLA). The analyzed material is an RP Cure 600 ND epoxy resin. A statistical approach was followed to evaluate the sensitivity of the thermoelastic behaviour of the material to some SLA characteristic parameters. In addition, the effect of load cycle frequency on thermoelastic signal was also analyzed. The experimental work included forty-eight tests on ASTM standardized specimens. A new testing procedure was developed for resin-made models. The new method is based on the application of a loading ramp to SLA standard specimens and on the acquisition of the infrared signal. The thermoelastic constant K is determined using the thermographic signal temporal slope. Results for an engine bracket are presented in the paper.

Charpy upper shelf energy is widely used as a fracture controlling parameter to estimate the crack arrest/propagation performance of gas transportation pipeline steels. The measurement of this fracture criterion particularly for modern steels and its apportion into different components, i.e. fracture and non-related fracture energy, are of great importance for pipeline engineers. This paper presents the results of instrumented Charpy impact experiments on high-grade pipeline steel of grade X100. First, the instrumentation technique including the design and implementation of a strain gauge load-cell and the details of the data-recording scheme are reviewed. Next, the experimental data obtained from the Charpy impact machine so instrumented are presented and discussed. These include the test data from full and sub-sized Charpy V-notched specimens. The instrumented Charpy machine was able to capture the load history in full during the fracture process of the test specimens resulting in a smooth load-time response. This eliminated the need for filtering used in similar test techniques. From the recorded test data the hammer displacement, impact velocity and fracture energy were numerically calculated. The results showed that there was a significant drop in hammer velocity during the impact event. This resulted in a change in the fracture mode from dynamic to quasi-static which was more appreciable for full-size Charpy test samples. As a result, sub-sized specimens might be preferable for impact testing of this steel in order to guarantee the conditions of dynamic crack propagation in the specimen ligament. Accurate analysis of the instrumented impact test data showed that the ratio of crack initiation energy to propagation energy was around 30% for the X100 steel. It can be concluded that in impact testing of high-grade pipeline steel a significant portion of overall fracture energy is consumed in non-related fracture processes. This high fracture initiation energy should be accounted for if the current failure models are going to be used for toughness assessment of highstrength low-alloy gas pipeline steels.

This paper presents the study of nested rings crushed laterally between rigid platens at 2 different velocities. In this investigation two different types of nested ring configurations are analysed: (A) In-Plane; where three rings of varying diameter are placed within each other and their axes are parallel. (B) Out of-Plane; where the rings have a 90 degree orientation. Material used was cold finished, drawn over mandrel (DIN 2393 ST 37-2) and is referred throughout the paper as mild steel. The Cowper-Symonds relation was used to predict the dynamic yield stress of the rings and this was included in the FE material model. The results obtained from experiments were compared to that of finite element method using the software package Ansys. Discussion is made on the post – collapse behaviour of these systems. It was found that the Out of-Plane ring system exhibited a more desirable force-deflection response due to its 90 degree orientation.

This paper presents some of the latest results of a research project aimed at using composite corrugated paperboard structures for protection of products against mechanical shocks and vibration during transportation and handling. Specifically, the behaviour of multi-layered corrugated paperboard (MCPB) under shock loading is investigated. Conventionally, packaging cushion design requires the determination of the maximum expected shock levels or equivalent drop which are usually determined from statistical analysis of original field measurements. With this approach, it is generally acknowledged that the cushioning element is engineered to provide adequate protection for statistically likely events but not for extreme events with low statistical likelihood. It is reluctantly accepted that, should it occur, the latter will result in damage to the product. MCPB can be formed with a broad range of compressive characteristics and with various proportions of elastic and plastic behaviour. The objective of this experimental investigation was to determine the optimum elastic/plastic proportion to extend the protective range to include large shock levels. The experimental results obtained include the effects of compression history on the stress-strain properties of MCPB as well as the behaviour of the material in both virgin and pre-compressed form under impulsive loads. The mechanism of deformation of the corrugations (flutes) was studied using high-speed video equipment. The complex acceleration signals produced during deformation of the composite corrugated paperboard cushions under shock loading were analysed by means of the shock response spectrum. Experiments have shown that inserting a sacrificial crumple element of virgin corrugated paperboard at the optimum contact area ratio dramatically lowers the overall level of the resulting shock response spectrum. This has the effect of increasing the allowable drop height for a limited number of extreme events. The main conclusion of the research is that MCPB in both virgin and pre-compressed forms can be combined to provide significantly enhanced protection to products against mechanical hazards during distribution.

There are no standard reference materials suitable for the calibration of full-field optical strain measurement systems. This is hindering the uptake of the technology by industrial end-users since optical metrology instrumentation and procedures cannot be easily integrated into quality assurance systems. The EU-funded SPOTS project is developing a physical reference material (PRM) and measurement protocol that should provide the basis of a calibration standard for establishing the traceability of strain values obtained with optical devices. This paper describes a PRM based on a parametric design of monolithic four-point bend test that can reliably generate a known strain field over a range of specimen sizes. Measurements acquired from strain gauges and LVDTs compared well with data obtained from ESPI, digital image correlation, photoelasticity and thermoelasticity studies, demonstrating excellent repeatability and inter-laboratory reproducibility.

The paper describes the work towards a set of standardised tests for the evaluation of the performance of optical systems for measuring strain. In particular, the standardised tests are designed to allow the components of a system to be evaluated both in terms of hardware and software. The intention is to allow designers of optical systems to assess the efficacy of their innovations in instrumentation and algorithms, to assist manufacturers of systems in the quality assurance process, to permit end-users to evaluate system capabilities prior to purchase, and to support both manufacturers and end-users in setting up and fault diagnosis. Two standardised tests are proposed and described of which one is physical, a disc in contact with a half-space, and the other is virtual, a pair of shrinkage-fit thick rings or cylinders.