Static Tensile Experiments Research Articles

Static properties evaluation for laser deposition repaired TA15 components based on a constitutive model considering annealing heat treatment

In remanufacturing field, the laser deposition repair technology combined with annealing heat treatment is widely used for repairing the damaged TA15 titanium alloy components owning to its low cost and high efficiency. But evaluating the properties of repaired components is still a challenging due to the damage test of the continued used components. To solve this, a new evaluation method for the static properties of the laser deposition repaired TA15 components is proposed in this study based on a new constitutive model (named as LRA constitutive model) with considering the annealing temperature and holding time in annealing heat treatment. The physical meanings of the model parameters are analyzed and illustrated from the static tensile experiments of several laser deposition repaired TA15 materials with different annealing heat treatment. In comparison with the experimental results and the predictions from the traditional constitutive model, the LRA constitutive model is validated and shows higher precision (>94 %) than the traditional constitutive model. After the application in the evaluation of static properties of a laser deposition repaired TA15 aircraft panel, the results exhibit that the proposed method has the advantage of low cost and high efficiency.

Static tensile mechanical properties and engineering application of constant resistance and large deformation anchor cable

Deep engineering is faced with mechanical phenomena, such as substantial soft rock deformation and in situ stresses, that results in frequent disasters because the energy of the surrounding rock cannot be released normally after excavation. Traditional support materials have low elongation and safety reserves, cannot adapt to large deformations of the surrounding rock, and cannot apply high preload, making it difficult to absorb energy. This study introduces a new type of constant resistance and large deformation (CRLD) cable through static tensile experiments, and compared the results of which with those of ordinary high-strength (HS) cables. Our results showed that the CRLD cable had an obvious constant resistance stage, with a constant resistance value of approximately 415 kN and an elongation rate as high as 25%, which is 3.9 times that of the HS cable. Furthermore, the energy absorption of the CRLD cable was 3.5 times that of the HS cable. Before the first steel strand broke, the temperature of the entire cable was approximately 33 °C, and the energy was absorbed evenly without obvious energy concentration. After breaking, the standard deviation of the segmental elongation of the steel strand was 4.16 mm, with a small degree of dispersion. The deformation of each section of the steel strand was uniform lengthwise and the necking rate of the fracture was 8.5%, indicating that there was no obvious necking. On this basis, a comprehensive mechanical performance evaluation index of the cable, that is, the static toughness UT, was proposed, reflecting the strength, elongation, and energy absorption density of the cable. Compared with the HS cable and another widely used He cable with excellent energy absorption characteristics, the UT of the CRLD cable was 117% higher than that of the HS cable and 38.1% higher than that of the He cable. This study also proposes a support and design principle for the CRLD cable and applies a CRLD cable to a roadway with a buried depth of 1050 m. Our results show that, owing to the high-strength reserve of the CRLD cable, the applicable preload can reach more than 85% of the breaking load of the cable, which is 2.3 times that of the HS cable. After this new support was adopted, the maximum deformation of the surrounding rock of the roadway was 180 mm, which is 36% of that of the traditional support. The deformation of the roadway was controlled and the surrounding rock was stable.

A New Type of Nanomaterial Traditional Martial Arts Training Body Protector with Buffering Effect

With the development of people’s living standards, the growing prosperity of the motherland, the traditional culture has been paid more and more attention, and traditional martial arts as a part of traditional culture is not only good for viewing but also strengthens the body, so it has been loved by many people. Traditional martial arts training is a high‐collision, injury‐prone sport, and making a good buffer protector can improve the safety of martial arts trainers and reduce the concept or degree of injury to athletes. Nanomaterials are materials produced by nanotechnology that are extremely small in one‐dimensional, two‐dimensional, or even three‐dimensional directions, and are several nanometers long in at least one direction. The purpose of this paper is to study a new type of nanomaterial with buffering effect, so as to understand the actual protective effect of body protectors made of this material on martial arts trainers. In this paper, a net‐like plant fiber nanobuffer material is proposed, and the relevant mechanical experimental tests are carried out on the material. According to static tensile experiments, the mesh nanofiber material can withstand a pressure of 1.2 million Pa under 90% strain, while ordinary fiber materials can only withstand a pressure of 700 thousand Pa under 80% strain. And the resilience of the mesh nanofiber material reaches 1.8 mm/s, while the maximum of ordinary fiber material is only 0.6 mm/s, which means that the protective gear made of mesh nanofiber material can significantly improve the stress bearing capacity of the protective gear and improve the rebound effect.

Experimental and semianalytical investigation of X850 ± IM190 CFRP bolted joints

Considering the fact that the foundation data for a new X850 ± IM190 carbon/epoxy material system adopted in commercial aircraft industry are extremely scarce in the literature, an in-plane, static tensile experiment was carried out to investigate the bearing performance of double-lap, single-bolt joints in X850 ± IM190 carbon fiber-reinforced polymer (CFRP) composites. The effects of ply ratio, 0° layers’ combination percentage, bolt diameter, and curing method were considered. Then, special attention was paid to determine the design parameters of X850 ± IM190 CFRP bolted joints, such as tensile strength of un-notched laminate and stress concentration relief factor. Based on these design parameters, an efficient semianalytical approach was established to obtain the ultimate bearing strength of the joints. The failure prediction exhibited excellent agreement with the experimental data. These results will play an important role in design and strength evaluation of X850 ± IM190 CFRP bolted joints.

Tensile Capacity of Concrete-filled Square Tubular Columns Connection with External Stiffening Ring

A static tensile experiment was carried out to investigate the flexural bearing capacity of external stiffening ring joints between concrete-filled square steel tubular column and steel beam. All of four specimens showed similar failure modes that external stiffening ring and tube flange were torn up. Nonlinear finite element model was developed with ABAQUS software to simulate the test and analyze the mechanism properties of specimens. Comparison of yield and ultimate capacity indicated that finite element analysis is valid. Moreover, on the basis of the failure modes, the distribution of stress, the deformation features and load transferring paths, which were achieved from experiments and numerical simulation, a theoretical method taking tensile membrane action of tube faces into consideration to evaluate the bearing capacity was proposed with help of yield line theory. The outcome of comparison between theoretical and experimental values clarify good applicability of this analytical method.

Collagen fibre orientation and dispersion govern ultimate tensile strength, stiffness and the fatigue performance of bovine pericardium

The durability of bovine pericardium leaflets employed in bioprosthetic heart valves (BHVs) can significantly limit the longevity of heart valve prostheses. Collagen fibres are the dominant load bearing component of bovine pericardium, however fibre architecture within leaflet geometries is not explicitly controlled in the manufacture of commercial devices. Thus, the purpose of this study was to ascertain the influence of pre-determined collagen fibre orientation and dispersion on the mechanical performance of bovine pericardium.Three tissue groups were tested in uniaxial tension: cross-fibre tissue (XD); highly dispersed fibre-orientations (HD); or preferred-fibre tissue (PD). Both the XD and PD tissue were tested under cyclic loading at 1.5 Hz and a stress range of 2.7 MPa.The results of the static tensile experiments illustrated that collagen fibre orientation and degree of alignment significantly influenced the material's response, whereby, there was a statistically significant decrease in material properties between the XD groups and both the PD and HD groups for ultimate tensile strength and stiffness (p < 0.01). Furthermore, HD tissue had a stiffness of approximately 58% of the PD group, and XD tissue had a stiffness of approximately 18% of the PD group. The dynamic behaviour of the XD and PD groups was extremely distinct; for example a Weibull analysis indicated that the 50% probability of failure in specimens with fibres orientated perpendicular (XD) to the loading direction occurred at 375 cycles. Due to this failure, XD specimens survived on average less than 20% of the cycles completed by those in which fibres were aligned along the loading direction (PD).The results from this study indicate that fibre architecture is a significant factor in determining static strength and fatigue life in bovine pericardium, and thus must be incorporated in the design process to improve future device durability.

Effects of Hole Perpendicularity Error on Mechanical Performance of Single-Lap Double-Bolt Composite Joints

Static tensile experiments and numerical simulations were carried out to study effects of hole perpendicularity error on mechanical performance of single-lap double-bolt composite joints. Hole tilting angle, varying from 1 to 4 degrees, and hole tilting direction to account for anisotropic properties of composite material were investigated. Progressive damage model (PDM) based on Chang-Lessard type criterion with an extension by Olmedo was created, which involved seven failure modes and made material properties be a direct function of predefined field variables. The model was implemented in ABAQUS/Standard using a UMAT subroutine. Good agreement was found when comparing numerical simulation results with experimental outcomes. In addition, the results demonstrate that, with increasing of hole tilting angle, damage is prone to arise and the load path of the composite bolted joints alters with changing of hole tilting direction, which result in severe stress concentration around the edge of hole and joint failure in advance.

Secondary bending effects in progressively damaged single-lap, single-bolt composite joints

Static tensile experiments and progressive failure simulations of single-bolt, single- and double-lap joints were carried out to comparatively investigate secondary bending effects, which present significant eccentric-loading phenomena in single-lap joints but are almost non-existent in symmetric double-lap joints. Progressive damage models of single-lap and double-lap joints were established, from which the numerical predictions were found to be in good agreement with the experimental outcomes. Experimental macro-scope failure patterns and seven numerical micro-scope failure modes obtained from the progressive damage analyses were presented for the two types of joints. The effects of secondary bending on the mechanical degradation and failure mechanism of single-lap joints were revealed. Some characterizations of secondary bending in the joints, such as a characterized parameter on the AGARD points, joint deformations and contact states, were quantitatively traced during the total progressive damage process. All these characterizations increased the understanding of the effects of secondary bending on the failure process of a single-bolt, single-lap joint.

Crack monitoring method based on Cu coating sensor and electrical potential technique for metal structure

Advanced crack monitoring technique is the cornerstone of aircraft structural health monitoring. To achieve real-time crack monitoring of aircraft metal structures in the course of service, a new crack monitoring method is proposed based on Cu coating sensor and electrical potential difference principle. Firstly, insulation treatment process was used to prepare a dielectric layer on structural substrate, such as an anodizing layer on 2A12-T4 aluminum alloy substrate, and then a Cu coating crack monitoring sensor was deposited on the structure fatigue critical parts by pulsed bias arc ion plating technology. Secondly, the damage consistency of the Cu coating sensor and 2A12-T4 aluminum alloy substrate was investigated by static tensile experiment and fatigue test. The results show that strain values of the coating sensor and the 2A12-T4 aluminum alloy substrate measured by strain gauges are highly coincident in static tensile experiment and the sensor has excellent fatigue damage consistency with the substrate. Thirdly, the fatigue performance discrepancy between samples with the coating sensor and original samples was investigated. The result shows that there is no obvious negative influence on the fatigue performance of the 2A12-T4 aluminum alloy after preparing the Cu coating sensor on its surface. Finally, crack monitoring experiment was carried out with the Cu coating sensor. The experimental results indicate that the sensor is sensitive to crack, and crack origination and propagation can be monitored effectively through analyzing the change of electrical potential values of the coating sensor.

3D Gradual Material Degradation Model for Progressive Damage Analyses of Unidirectional Composite Materials

A new 3D constitutive model for progressive damage analyses of unidirectional composite materials is presented, in which several important damage phenomena for the composite materials, such as the interfiber crack orientation, coupling of fiber failure and interfiber failure under longitudinal loads, closure effect for interfiber cracks, and longitudinal compressive behaviors under transversal constraints, have been considered comprehensively. A modified maximum stress failure criterion has been used for the damage onset prediction and a linear damage model has been adopted to establish the evolution rules of different damage. Numerical analyses with the model proposed have been implemented by using the subroutine UMAT in commercial software ABAQUS. Progressive damage analyses and static tensile experiments of a group of double-lap composite bolted joints have been carried out to validate the model proposed. Good agreements between the numerical and experimental results have been obtained.

Numerical Characteristic Length Model for Mechanical Composite Joints in Mechanical Manufacturing Engineering

According to the progressive damage analysis based numerical characteristic length scheme presented by Zhang, a progressive damage model established by Liu is adopted here to calculate characteristic lengths for mechanical composite joints. Four groups of specimens with different lay-ups and geometries were designed and fabricated and static tensile experiments were carried out to verify the suitability of the numerical characteristic length model. Good agreements between the predicted ultimate failure loads of the specimens and experimental outcomes are obtained. In addition, the characteristic lengths calculated from the experimental ultimate failure loads are in accordance with that obtained from numerical ultimate failure loads, which give evidence of the feasibility and suitability of the numerical characteristic length model.

Influence of π overlaminates on the mechanical behavior of all-composite adhesively bonded π joints

An all-composite out-of-plane adhesively bonded π joint is an effective structural connector for integrated aircraft structures. Its application can not only enable both the weight and assembly cost benefits, but also enhance the load-carrying capability. In composite π joints, the π shaped overlaminate is a significant kernel and thus attracts more attention of designers. With progressive damage analyses, the influences of π overlaminates with different configurations, lay-ups and geometric dimensions on the mechanical behaviors of composite π joints are obtained. The failure mechanisms and final failure loads of composite π joints with different π overlaminates are compared to provide more knowledge for the optimal design of such joints. Final failure loads stemmed from the static tensile experiments and physical failure phenomena of three types of π joints are presented. The good agreements between the numerical and experimental results not only validate the effectiveness of the numerical models, but also give evidence of the predicted tendency of strength improvement for composite π joints.

Battery-less wireless interrogation of microstrip patch antenna for strain sensing

This paper presents a battery-less wireless interrogation system that can measure the resonant frequency of a microstrip patch antenna with a fine resolution. Since the antenna resonant frequency is sensitive to strain-induced deformations, wireless interrogation of the antenna sensor for strain measurement was demonstrated. By implementing a microwatt impedance switching circuit at the sensor node, the antenna backscattering is amplitude modulated at the sensor node so that it can be separated from the structural backscattering at the interrogator. The sensor node can be powered by a small photocell and thus achieve battery-less operation. The operating principle of the wireless interrogation system is first described, followed by the implementation and characterization of the wireless interrogation system. The antenna resonant frequency shifts were correlated to the applied strains through a static tensile experiment. An excellent agreement between the experimental results and the analytical prediction was obtained. A power transmission model was established and validated with experimental measurements. Based on this power transmission model, we estimated that the maximum interrogation distance of the wireless strain measurement system is 26 m.

Experimental Research of Prestrain Effects on Mechanical Behavior of Dual Phase Steel

Dual phase (DP) steel is increasingly utilized in automotive industry to match the requirement of both performance and lightweight of autobody for economical and ecological considerations. Most of autobody structures are manufactured by stamping process which imports prestrain effects into original material and alters its static and cyclic mechanical behaviors. In this study, mechanical behavior of prestrained DP steel was researched. Firstly, microstructure of commercial DP steel with different prestrain levels was examined with optical microscope of 500X magnification. Then, static tensile experiments and strain-controlled fatigue experiments were carried out at room temperature. Test results of differenet prestrain levels were compared. Static stress-strain relationship and local strain-life model were determined using linear regression method. Furthermore, fatigue performance and notch fatigue resistance capability were compared with prestrain level based on Neuber factor. Finally, explanation of the change with prestrain was presented with crack closure theory.

G0300-9-2 異種材料の被着体を有する波型突き合わせ接着継手の引張強度特性([G0300-9]材料力学部門一般講演(9):構造強度)

In this paper, static tensile experiments to clarify the joint strength for adhesive waved butt joints with dissimilar adherends were carried out, using epoxy structural adhesive. In addition, effects of adhesive thickness and combination of adherend material on joint strength were examined in the experiments, where the adhesive thickness was changed from 0.05 to 0.1, 0.2, 0.5 mm, with the three kinds of combination of adherend materials "aluminum alloy A5052-mild steel SS400, aluminum alloy A5052-brass C3604, mild steel SS400-brass C3604". It proved that the case of similar adherend shows tendency in opposite for strength characteristics, from the result that the joint strength increases as the adhesive thickness increases in case of dissimilar adherend. The joint strength of specimen using brass C3604 as material of one side adherend proved to be the highest in the three kinds of combination of the adherend materials.

Stress cracking e ataque químico do PET em diferentes agentes químicos

A análise de resistência ao stress cracking (ESCR) do PET foi feita em corpos de prova de tração moldados por injeção, utilizando vários agentes químicos (metanol, etanol, propanol, butanol e soluções de hidróxido de sódio em diferentes concentrações). Foram realizados ensaios dinâmicos e estáticos de tração. Durante os testes os corpos de prova foram mantidos em contato com os agentes e as propriedades mecânicas monitoradas. Os resultados evidenciam que todas as soluções de hidróxidos de sódio testadas são agentes agressivos de ESC por diminuírem as propriedades mecânicas do polímero, ocasionando falha catastrófica. Já os demais fluidos, apesar de não terem efeito significativo nas propriedades do PET, afetam drasticamente sua aparência superficial. Observou-se também a ocorrência de ataque químico nos ensaios com NaOH, resultando em redução nas massas molares.

Laminated Composites Containing an Elliptical Opening. II. Experiment and Model Modification

Static tensile experiment was performed for orthotropic composite laminates containing an elliptical opening. Based on the extended point stress fracture criterion and the ex tended average stress fracture criterion, a modified model is presented that expresses the characteristic damage zone size as functions of the opening length and opening aspect ratio. The predictions for the notched strength of orthotropic laminates, containing either a circular hole, an elliptical opening, or a center crack, agree very well with experimental data and are written in a tractable form.

The onset of crack growth in aluminium alloy due to impact tension.

The purpose of this paper is to confirm the effect of specimen length and the microstructure on the onset of precrack growth when an impact load is imposed on it. Impact, impact under static pretension and static tensile experiments were carried out using high strength aluminium alloy at 288 K and 77 K. The effect of specimen length on the critical condition for crack growth was discussed, based on the static stress intensity factor (K1)pre and the impact fracture stress σcd defined by the onset of crack growth. A linear relation between (K1)pre and Df which was a summation of (K1)pre and σcd√(πa), where a was a precrack length, could be seen and this relation was independent of specimen length and temperature. Microstructural aspects near the crack tip region were also observed on the fracture surfaces. The results of microscopic deformation measured by the X-ray micro beam diffraction method and the dislocation distribution observed by TEM showed that they were almost the same at the same temperature and were independent of loading type and specimen length. Comparing above results with our previous ones for steel specimens, it is concluded that the effect of specimen length on crack growth is negligiable in the case of impact fracture when the microscopic deformation behavior at a crack tip is insensitive to a rapid stress rise, which depends on specimen length.