In order to obtain an optimal combination of welding parameters to weld an aluminum alloy (6082-T6) with MIG (Metal Inert Gas) it was used an L27 Taguchi orthogonal array. The array originated 27 different combinations that gives rise to 27 welding programs for the metal pulsed spray mode. The welds were made in aluminum bars using an industrial robot. All welds were repeated three times to ensure string repeatability. Metallographic tests were performed on the weld beads for measuring the width bead, penetration and reinforcement. Measurement data was analyzed for signal / noise and analysis of variance (ANOVA). Applying the Taguchi's method, an optimal combination of welding parameters was reached.

The present article describes an experimental analysis of a robotized Gas Metal-arc Welding (GMAW) in aluminum alloy, using Metal Inert Gas (MIG) in its transfer method variation Standard and pulsed Cold Metal Transfer (CMT+P), developed in order to optimize the penetration depth, width and reinforcement of the weld bead. The base metal was the aluminum alloy 6082-T6 and the filler metal was aluminum alloy 5754.

The drop tests of the experimental structure with explosive substitute material were carried out to study the dynamic deformation and failure of the explosive substitute. Designed the PBX simulation material as a cylindrical flat head structure, the support structure of the PBX simulation material as an aluminum support ring, and affixed a counterweight to the upper part of the PBX simulation material. The PBX simulation materials, the counterweight and the support ring, were glued together to form the drop test pieces. A special drop test system was designed, which realized the non deflection of the falling posture of the drop test pieces and the drop was pure free. The results show that in the drop impact tests, the critical height of the explosive simulant failure is about 600mm to 700mm when the counterweight of 19.62kg is used.

Geothermal bore holes and steam pipes are often in remote locations where normal powering methods for monitoring systems are difficult due to distance from the electrical grid. Solar power options are limited during the winter months, and colder temperatures are detrimental to stand-alone batteries. The authors have successfully field tested their patented thermoelectric generator in Hveragerdi at the Agricultural University of Iceland. It was retrofitted directly to the surface of a geothermal steam pipe in less than 30 minutes. The generator can produce more than 5 watts (W) in steady state in an environment which has a delta T of 130 °C between the ambient air temperature and the surface of the steam pipe. Cellular video surveillance systems, rudimentary control systems, and small robotic systems have been powered while trickle charging 12 volt (V) 9 ampere-hour (Ah) lead acid batteries. Recent applications use a standard commercially available 3G mobile broadband connection with a low power modem for a web cam. The charged batteries can be used for peak power applications. Reliability studies are in progress and additional options will be investigated.

The first-generation of autonomously healed concrete elements is under construction: beams (SIM-SECEMIN project, Belgium), one-way flat slabs (MeMC, VUB, Belgium) and wall panels (Materials4Life project, UK) are designed with the embedment of encapsulated repair agent. In the presence of cracks, capsules rupture releasing the agent that fills the crack void. The released agent seals and mechanically restores the crack discontinuity. This automatic process can be repeatable using vascular networks that carry the agent and release it at different locations into concrete. The innovative design is built up following several series of laboratory-scale beam tests configured over the last decade. This paper discusses the application of numerous experimental techniques that assess the mechanical performance of autonomously healed concrete: Acoustic Emission, Ultrasound Pulse Velocity, Optical Microscopy, Digital Image Correlation, Capillary Water Absorption, Computed Tomography. The study focuses on the performance and efficiency of each method on laboratory and real-scale tests. The techniques with the most promising output are selected and combined in order to design a sensing tool that evaluates healing on real applications.

The subsurface nature of Crack Tip Opening Displacement (CTOD) makes its direct measurement very difficult, if not impossible. During fracture toughness testing, CTOD is commonly calculated by applying a plastic hinge model using externally applied clip gauges. However, clip gauge CTOD calculations merely provide information relating to the center of the defect (which is typically the most critical point, but not always). For the case of a finite-length surface defect, CTOD will be variable over the defect front. Exact knowledge of CTOD over the entire front is useful for detailed calculations, such as crack profile evolution due to ductile tearing or calculations involving interacting defects. To experimentally measure the CTOD at locations other than the center of the crack, the authors propose a technique based on full field three-dimensional profile measurement of the notched surface by means of stereoscopic Digital Image Correlation (3D-DIC). The method is based on the plastic hinge model assuming that the crack flanks rotate in a rigid manner around a plastic hinge point in the un-cracked ligament. Having measured full-field out-of-plane displacement at the surface of the specimen around the crack using the 3D-DIC method, CTOD can be inferred over the entire crack front. Results show that, due to the acceptable agreement between the DIC based calculation and CTOD measured from cast replicas, the proposed technique has a sufficient accuracy to measure CTOD on the entire crack front in plastically deforming specimens.

This study focuses on characterizing the transient deformation of test plates which have been exposed to air blasts arising from air-backed and metal-backed explosive detonations. Four charge masses are considered, namely 10g, 15g, 20g and 25g masses of PE4 plastic explosive which were moulded into cylindrical charges of a constant 38mm diameter. The transient deformation of the test plates was captured using high speed Digital Image Correlation (DIC), which utilized two high speed cameras to record the experiments. The experimental plates exhibited plastic deformation with no tearing. The impulse imparted to the test plates increased fivefold when the charge was metal-backed. The permanent deflections from the metal-backed detonations were larger than for air, but not to the same degree as the impulse increase.

Full-field optical strain measurements as a function of temperature are difficult to perform at the micron scale. The thermal expansion mismatches result in stresses that can break interfaces and damage the parts. Digital image correlation is an ideal measurement technique for this type of application, but it requires surface features of a specific scale that can be tracked and a measurement surface that remains in focus throughout the range of temperatures. These requirements are not difficult at the centimeter scale, and have been demonstrated at the millimeter and nanometer scales, but have not been achieved at the micrometer scales that are ideal for electronic parts. The problems include the small depth of focus, movement of the specimen due to thermal expansion, damage to the microscope lens due to heating, optical distortions due to uneven air temperatures, and the application of surface features for tracking. A new test apparatus and test method has been developed to provide the conditions needed for high-quality digital image correlation measurements using a high-magnification optical microscope up to 1000x magnification over a range of several hundred degrees Celsius. In this paper, the apparatus and test methods are described, and test results are demonstrated.

Indentation test has been widely used to determine the mechanical properties of materials. In the present work, based on our previous developed inverse computation approach, we investigated the identifiability of the plastic properties of metal materials using solely the residual imprint in instrumented indentation. The indentation experiment was implemented on the Al 2024-t3 alloy, and result shows the experiment error exists unavoidably. To quantitatively investigate the influence of experiment error on the inverse derived material properties, the indentation simulation models were built, of which three different indenter shapes (conical, flat and spherical) and two different simulation set-ups (load or displacement control types) are considered. The sensitivity of the inverse problem in the relevant questions are systematically investigated. Results show the inverse problem formulated by the force control using a non-self-similar indenter is able to give more robust solution of the inverse derived material parameters. Besides, the numerical protocol was verified by application on the Al 2024-t3 alloy, and the plastic properties (yield stress and strain hardening exponent) obtained from indentation and uniaxial tests show good agreement.

The use of carbon fiber reinforced polymer (CFRP) as externally bonded reinforcement (EBR) for strengthening reinforced concrete (RC) structures loaded by a blast wave is confirmed as an efficient solution. This observation is complementary to other advantages of CFRP such as high tensile strength, light weight and durability. This paper discusses the behavior of CFRP as EBR in case two successive independent blast loads are applied on the same target. Main problems are the lack of knowledge regarding the failure modes of the CFRP strips under high strain rate and the blast response of the retrofitted structures when total debonding of the CFRP strips occurs. Four simply supported slabs with different EBR but with the same bond contact surface are tested using an explosive driven shock tube (EDST) to generate the blast wave. Digital image correlation (DIC) is used to measure the strain evolution in the concrete and the CFRP strips during the first explosion. The results show that for the first explosion, EBR increases the flexural strength and stiffness of the RC slabs. In the second explosion, total debonding of the CFRP strips occurs which initiates from the midspan of the slabs towards the supports; when the total debonding of the CFRP strips occurs, the strain distribution in the steel rebars are the same for all slabs regardless of the quantity of applied EBR.