Static tests on double-lap and T-type adhesive joints were performed. We developed a device that applies contact pressure to glass-fiber reinforced plastics/stainless-steel double-lap adhesive joints. The device contains a bolt with which a strain gauge is bonded for controlling contact pressure. Using this device, we investigated the effect of contact pressure on the delamination strength of double-lap adhesive joints. We applied tensile shear loading to double-lap adhesive joints under contact pressure to their adhesive interfaces. We found that the delamination strength of the double-lap adhesive joints increased with increasing contact pressure. On the contrary, when we applied compressive shear stress to them, the delamination strength stayed constant. Therefore the delamination strength of double-lap adhesive joints is dominated by normal stress when contact pressure under tensile shear loading is applied. On the other hand, it was dominated by shear stress when contact pressure under compressive shear loading was applied. Then stress singularity parameters for double-lap and T-type adhesive joints were performed by the FEM. Stress distributions near the bonding edge could be expressed by the stress singularity parameters. Finally, a delamination evaluation diagram using stress singularity parameters was developed. This diagram enables us to evaluate the delamination strength of adhesive joints.

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We consider an elongated bi-material assembly with a continuous compliant attachment (bonding layer). The assembly is subjected to external tensile forces and bending moments applied to the ends of one of the assembly components. The objective of the analysis is to develop a simple and physically meaningful predictive analytical (“mathematical”) model for the evaluation of the interfacial shearing and peeling stresses in the bonding material, as well as the stresses acting in the cross-sections of the assembly components, with consideration of the effect of the compliance of the bonding layer. The model can be helpful in the stress-strain analysis and physical design of various assemblies of the type in question, such as, for instance, printed-circuit-board (PCB)/surface-mounted-device (SMD) assemblies. With some minor modifications the model can be applied also to die/carrier assemblies in “stretchable” (large area) electronics and photonics. The developed model enables one particularly to evaluate the induced stresses from the measured strains in the PCB in the vicinity of the SMD package. The numerical example carried out for a PCB experiencing bending in a concave fashion indicated that the interfacial shearing stresses computed with consideration of the assembly bow were lower, and the peeling stresses calculated with taking into account the effect of tension were higher, than the stresses predicted for the situation, when the assembly was subjected either to tension only, or to bending only. We explain the physics of this phenomenon. We show, as an illustration, how the developed stress model can be used for the evaluation of the dynamic response of a PCB/SMD assembly to an impact load applied to the PCB support contour in drop or shock tests.

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In this research, collision of a glass bead particle onto a ceramic beam is analyzed by the hybrid method that combines discrete element method (DEM) and finite element method (FEM), developed by the authors. Contact forces between the particle and the beam are analyzed by the Penalty method and Christensen failure criterion is used for dealing with the initiation and propagation of cracks in the glass bead particle. Numerical analysis is executed to examine the initiation and propagation of cracks and fragmentation appearance in the particle, behaviors of stresses of elements at the contact center of the particle and the beam, and stress evolution beneath the surface of the beam by particle impact and its fragmentation.

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Intelligent tires, also known as smart tires, are equipped with sensors to monitor the strain of the interior surface and the rolling radius of tire, and are expected to improve the reliability of tires and tire control systems such as anti-lock braking systems (ABS). However, the high stiffness of an attached sensor like a strain gauge causes sensors to debond from the tire rubber. In the present study, a novel optical method is used for the concurrent monitoring of in-plane strain and out-of-plane displacement (rolling radius) utilizing the non-planar surface of the monitoring object. The optical method enables noncontact measurement of strain distribution. The in-plane strain and out-of-plane displacement are calculated by using image processing with an image of the interior surface of a tire that is taken with a single CCD camera fixed on the wheel rim. This new monitoring system is applied to an aluminum beam and a commercially available radial tire. As a result, the monitoring system provides concurrent measurement of in-plane strain, out-of-plane displacement and tire pressure, and is shown to be an effective monitoring system for intelligent tires.

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The forces working at the contact interface between the metal and resin of a resin mold, which was made of metal cylinders covered with resin mold, were experimentally investigated. The forces discussed in this paper were modeled by friction force, adhesive force, and contact pressure based on residual stress. A new coefficient for adhesion was introduced by describing adhesion force. Moreover, FEM model of the forces acting on the contact interface was developed. The excellent agreement between the calculated and measured forces in applying the model to the design of an actual industrial product, i.e., an insulated rod, verified its accuracy.

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Wide range compact sensor is preferably sought for force sensing in testing of micro objects or local area of macro objects with the observation of high resolution microscope. This paper presents the design and development of an integrated passive cantilever type force sensing unit with the specificities of range variation, interchangeability of components and compact size by incorporating with cantilever, probe and a capacitive sensor for measurement of large range micro-newton forces in wide scope of application. In the design, the tactile force at the probe perpendicularly attached to the cantilever is converted as cantilever deflection, which is measured by the capacitive sensor. In connection to a tiny capacitive sensor a compatible cantilever with double-beam structure is considered. Cantilever length variation facility is incorporated in the unit for obtaining different force measurement ranges by using the same cantilever. Characterization of the cantilever is performed against a standard load cell. The force resolution with a typical cantilever is estimated as 10 nN. The elastic property of human hair is efficiently determined by testing with the combination of a digital microscope and the developed sensor system. The utility of the unit for different resolution/range by the interchangeability of cantilevers is also demonstrated. Experimental results show that this integrated force sensing unit achieves good sensitivity and linearity, and wide measurement range.

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Strain monitoring of CFRP structure by measuring electrical resistance change has attracted attention over the years. High electrical conductivity of carbon fibers enables to measure the strain by making electrodes on the structure’s surface and using bridge circuit as conventional strain gauge. Electrical resistance change method, however, is difficult to specify the gauge length because electric current is applied directly to the structure, and the current path depends on the stacking sequences, fiber volume fraction, and electrode’s location. It is also difficult to measure the electrical resistance changes at different parts simultaneously because the outputs may interfere with each other due to overlapping of current paths inside the structure. In this study, three electrodes are connected to each bridge circuit to prevent electrical interference when the electrical resistance changes are measured simultaneously, whereas electrical resistance measurements normally use two electrodes. The proposed method puts ground electrodes every other so that current path could be limited between the ground electrodes. Only the strain between ground electrodes affects the electrical resistance output, and it makes simultaneous measurements at different position possible.

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