Resistance of Polymeric Laminates Reinforced with Fabrics against the Growth of Delaminations

Dependence of the initiation values of the Strain Energy Release Rate, GCi, on the orientation of the reinforcement direction α relative to the delamination front was investigated for two laminates of different interfacial ply arrangements. In the case of the first laminate, the delamination was located at the interface of the layers reinforced with symmetric fabric and unidirectional fabric. In the case of the second laminate, the delamination was located at the interface of layers reinforced with symmetric fabric. In both laminates, the orientation of fibers in the layers separated by the delamination differed by 45° regarding the warp directions. The investigations were carried out for Mode I, Mode II, and Mixed-Mode I/II (GII/GI = 1 and GII/GI = 1.7) loadings using hybrid beam specimens. The major problem appearing in the intended tests was the inevitable lack of symmetry in the xz and xy planes of the specimens and the resulting deformation and stress–strain couplings, causing undesired loading modes. To decrease these couplings, especially designed hybrid beam specimens were used. An auxiliary finite element analysis was performed to assess the remaining effects of the reduced couplings. To ascertain whether statistically significant differences between Gci values for different α occurred, the one-way analysis of variance supplemented by Levene’s test was carried out. The dependence of Gci on α was found out for both laminates. However, it was not equally strong, and it turned out that the loading mode and the interfacial ply were arrangement sensitive.

A nonlinear fractional-order damage model of stress relaxation of net-like red soil

It is essential to precisely describe the nonlinear characteristics of the stress relaxation behavior to ensure the long-term stability of geotechnical structures in the net-like red soil. A novel damage model of variable fractional-order was discussed here to accurately analyze the progress of stress relaxation for the net-like red soil. Moreover, unsaturated triaxial experiments on stress relaxation under a step-loading mode were performed to identify model parameters and investigate the nonlinear relaxation characteristics of the net-like red soil. The feasibility and validity of the proposed model were furthermore verified by comparisons with the experimental results and fitting curves obtained from the Nishihara model and the generalized Kelvin model. Results show that the analytical result by the proposed model is consistent with the measured data, and the proposed model can better depict the nonlinear characteristics of stress relaxation relative to other analytical models. It can better exhibit the relaxation evolution of soil compared with the conventional models.

Determining the Image Base of ARM Firmware by Matching Function Addresses

Firmware is software embedded in a device and acts as the most fundamental work of a system. Disassembly is a necessary step to understand the operational mechanism or detect the vulnerabilities of the firmware. When disassembling a firmware, it should first obtain the processor type of running environment and the image base of firmware. In general, the processor type can be obtained by tearing down the device or consulting the product manual. However, at present, there is still no automated tool that can be used to obtain the image base of all types of firmware. In this paper, we focus on firmware in ARM and propose an automated method to determine the image base address. Firstly, by studying the storage rule and loading mode of the function address, we can obtain the function offset and the function address loaded by LDR instruction, respectively. Then, with this information, we propose an algorithm, named Determining image Base by Matching Function Addresses (DBMFA), to determine the image base. The experimental results indicate that the proposed method can successfully determine the image base of firmware which uses LDR instruction to load function address.

Energy characteristics of acoustic emission under various modes of uniaxial loading

Acoustic emissions were recorded in the process of uniaxial compression of samples of various geomaterials. The experiments were carried out on a low-noise lever setup with water leakage; the maximum load on the sample did not exceed 250 kN. Some of the samples were tested at a continuously increasing load, the other at its stepwise change. The energy distribution of acoustic emission signals was investigated. The energy characteristic of acoustic emission was the square of the maximum signal amplitude. The flow of AE events is considered from the standpoint of nonequilibrium thermodynamics and Tsallis statistics. A decrease in the steepness of the linear part of the repeatability plots for a particular geomaterial was revealed when changing the loading mode from linear to stepwise, which means an increase in the proportion of higher-energy events with a stepwise change in load.

Stress Evaluation in the Blank Critical Region During Extrusion of the Pipe Blank into the Hole

The study assessed the stress state of the pipe blank in the process of extrusion into the hole. A finite element formulation of the research problem with the setting of boundary conditions in displacements and surface loading conditions is presented. The calculation of the workpiece was carried out in an elastic formulation using the Nastran engineering analysis application. The assessment of the stress state in the critical region is presented in two approximations with a thickening of the grid in the stress focus area. Based on the results of the distribution of equivalent stresses, an assessment of the unevenness of the stressed state of the workpiece was carried out. The presented study is important because it allows us to predict the appearance of defects in the process of forming a pipe billet during extrusion into a hole, to evaluate the power loading mode.

Improvement of covered wagons of the “East-West” type by sectioning with a partition

The dynamic loading and strength of the frame of the “East-West” type covered wagon were determined. To increase the efficiency of operation of covered wagons in international traffic, it is proposed to improve their frames. This improvement consists in using a sectional partition in the body in order to divide it into two separate sections. This allows the transportation of different goods in one wagon, and therefore decreasing empty mileage. The longitudinal loading of the covered wagon frame was determined. The case of shunting impact was considered. The studies were carried out in a flat coordinate system. The loading mode of the frame of the covered wagon in the empty and loaded states was considered. The acceleration acting on the covered wagon frame in the loaded state was 0.37g, empty – 0.42g, which does not exceed the standard values. The wagon motion is rated “excellent”. The main strength indicators of the covered wagon frame were determined. The calculation was made by the finite element method. It was found that the maximum equivalent stresses are concentrated in the area of interaction of the center sill with the bolster beam and amounted to 340 MPa, which is lower than the yield stress of the material. Maximum displacements occur in the middle of the frame beams and are about 12 mm. The natural vibration frequencies of the covered wagon frame were calculated. The research will help to increase the efficiency of using covered wagons in international traffic. Also, the research results can be useful developments in the creation of innovative rolling stock structures

Effect of microwave and steam treatment on the thermo-hygro-plasticity of beech wood

The effects of microwave and steam treatment were analyzed relative to the immediate (thermo-hygro-plasticity) and post-assessed (permanent changes) properties of wood. The study was conducted using European beech (Fagus sylvatica L.) standard and 1.5 times up-scaled (only for microwave-heated and reference samples) bending specimens tested in a static three-point loading mode. The specimens were plasticized by heat and moisture (1) separately and (2) simultaneously by heating moist specimens using (i) various microwave regimes in continuous mode, and (ii) heated saturated steam in discontinuous mode. Oven-dried specimens tested at 20 °C served as references. The thermo-hygro-plasticity was studied immediately after treatment, whereas the permanent changes were assessed after oven-drying of plasticized specimens to 0% moisture content. Permanent structural changes were analyzed using scanning electron microscopy. Microwave treatment increased the plasticity of wood (decreasing the modulus of elasticity by 70%) comparably to steam treatment, when the output moisture content was 30% or higher. A similar degree of plasticity was found in up-scaled specimens heated by microwaves. Further analyses confirmed that microwave treatment did not cause any permanent damage to wood structure or reduce mechanical performance. The results showed that microwave treatment is an efficient alternative to steaming when plasticizing moist wood.