•The static behaviour of notched PPS/GF specimens was investigated.•V-shaped notched specimens were manufactured and tested.•Different notch root radii and manufacturing processes were ...considered.•Different approaches for the static strength assessment were compared.
In this paper the static behaviour of polyphenylenesulfide reinforced by 40% wt. short glass fibre net-shaped plain and notched specimens was investigated. The specimen geometries were obtained by injection moulding and the experimental results were compared with data obtained from machined specimens with the same material and geometries. All data were reanalysed according to several models available in the literature for orthotropic materials, to find a rapid and efficient assessment tool for predicting the strength of short glass fibre reinforced materials in the early design stages. To this end, approaches based on orthotropic linear elastic stress analysis were considered, namely the linear elastic peak stress criterion, the nominal net-stress criterion, the point stress criterion, the average stress criterion, the strain energy density criterion, the generalized stress intensity factor-based approach, the inherent flaw model, the damaged zone criterion and the Hitchen criterion. Among the models, the average stress criterion and the generalized stress intensity factor-based approach provided the most accurate predictions of the static strength, ranging from −10% to +9% and from −19% to +2%, respectively, compared to the experimental data.
Ultrasonic Testing (UT) is one of the well-known Non-Destructive Techniques (NDT) of spot-weld inspection in the advanced industries, especially in automotive industry. However, the relationship ...between the UT results and strength of the spot-welded joints subjected to various loading conditions is unknown. The main purpose of this research is to present an integrated search system as a new approach for assessment of tensile strength and fatigue behavior of the spot-welded joints. To this end, Resistance Spot Weld (RSW) specimens of three-sheets were made of different types of low carbon steel. Afterward, the ultrasonic tests were carried out and the pulse-echo data of each sample were extracted utilizing Image Processing Technique (IPT). Several experiments (tensile and axial fatigue tests) were performed to study the mechanical properties of RSW joints of multiple sheets. The novel approach of the present research is to provide a new methodology for static strength and fatigue life assessment of three-sheets RSW joints based on the UT results by utilizing Artificial Neural Network (ANN) simulation. Next, Genetic Algorithm (GA) was used to optimize the structure of ANN. This approach helps to decrease the number of tests and the cost of performing destructive tests with appropriate reliability.
Aeronautical electronic equipment, used for data collection during flight, is usually fixed to the nose radome using mounting brackets. The stiffness and first-order frequency performance of the ...mounting brackets is studied to avoid plastic deformation and resonance during flight, which is of great engineering significance for improving flight stability. The static strength and modal analysis of the mounting bracket under inertial load are conducted, and a sensitivity analysis method is used to determine the design variables of the installation bracket. With the goal of minimizing the total weight of the structure as the optimization objective, the thickness of each component of the bracket is optimized while ensuring the stiffness and first-order modal performance of the installation bracket. The vibration tests are conducted for the optimized installation bracket structure. The results show that the stiffness of the optimized installation bracket structure remains basically unchanged, the first-order freque
The predictability of damage evolution is a challenge for mechanical joints of composite structures due to the highly nonlinear material behavior. In this study, friction riveting was investigated as ...an alternative joining technology for composite laminates by analyzing experimentally the joint mechanical behavior under different loading scenarios. The failure and fracture micro-mechanisms of composite laminate single lap joints were studied under quasi-static and cyclic loading. The joints failed mainly by rivet detachment from the composite hole, followed by adhesive/cohesive failure of the squeezed material, and rivet pull-through failure. Despite lower quasi-static strength of friction-riveted joints (6.2 ± 0.3 kN) compared to reference bolted joints (8.7 ± 0.2 kN), their fatigue life was higher by 88%. The main improving contributions were: the squeezed material, working as an adhesive between the composite parts and an additional fracture micro-mechanism, and the absence of clearance at the rivet-composite interface, which promoted an improved load transfer between the joined parts.
In order to obtain the static strength of small modulus plastic gears, a small modulus plastic gear static strength test bench is developed, which can accurately measure the static strength of ...plastic gears under different modulus, speeds and materials. The working principle, constitution and the design of tooling parts of the test bed are mainly introduced. The test bench is composed of the mechanical system, the electric control system and the measuring software. The electric control system and the measuring software mainly adopt the horizontal structure, which is of the compact structure, with small space occupation, uses simple fixture design and is easy to measure. The static strength test is carried out, and the static strength using different materials is briefly tested. The experimental equipment can realize the measurement of the static strength of the small module plastic gear, which solves the problems of inaccurate static strength test of the small module gear and the difficulty of test clamping,
•The FKM-Guideline contains an algorithm for the analytical strength assessment of machine components made of steel, cast iron, and aluminium alloys.•The algorithm covers the evaluation of non-welded ...and welded components.•The relevant component properties can be considered by appropriate influencing factors.•Current developments of the FKM-Guideline are outlined.
The FKM-Guideline “Analytical Strength Assessment” contains an algorithm for both static and the fatigue strength assessment of components made of steel, cast iron, and aluminium alloys. Designed to be advantageous for industrial applications, this guideline expresses the design stress using a straightforward linear-elastic material behaviour.
Starting with the material strength properties specified in technical standards, the relevant component properties for both static and fatigue strengths can be determined by considering all influencing factors. The safety level required for assessment can be adjusted using experience-based safety factors. The outcomes of the analytical strength assessment provide a measure of the degree of utilisation.
While the FKM-Guideline has been successfully applied since 1994, continuous further development is necessary to ensure it remains at the forefront of industry standards. Key development areas include the improvement of the critical strain curve, introduction of a coordinate-invariant fatigue strength assessment procedure, conducting investigations on the accuracy of the calculation according to the FKM-Guideline as a precondition for the development of a probabilistic safety concept, and extension of the FKM-Guideline to additional material groups such as high-strength steel.
•Ultra-high strength steel sheets were joined by mechanical clinching with dies for control of metal flow.•Static load of clinched joint was smaller than that of resistance spot welded joint.•Fatigue ...load of clinched joint was larger in large number of cycles.
Ultra-high strength steel sheets having low ductility were joined by mechanical clinching with dies for control of metal flow. The diameter and depth of the die were modified to relieve concentration of deformation of the sheets for avoidance of the occurrence of sheet fracture. As the tensile strength of the steel sheets increased, the interlock decreased due to small metal flow. Two kinds of the ultra-high strength steel sheets having different ductility were used. The ultra-high strength steel sheets having large ductility were successfully joined using die having modified shape, whereas the sheets having small ductility were not joined. The static and fatigue strengths of the mechanically clinched joint were compared with those of the resistance spot welded joint. Although the static load of the mechanically clinched joint was smaller than that of the resistance spot welded joint in both tension-shearing and cross-tension tests, the fatigue load of the clinched joint was larger in the large number of cycles. It was found that mechanical clinching has superior fatigue strength due to the large yield stress of the sheets and relaxation of the stress concentration.
Experimental tests on corroded tubular TT-joints with and without Carbon fiber reinforced polymer (CFRP) reinforcement were conducted. The failure process, load-displacement curves, and observed ...failure modes of the tested specimens under axial brace compression were obtained and discussed. Experimental results indicate that the bearing capacity and stiffness of the corroded tubular TT-joints strengthened with six layers of CFRP were improved efficiently. The improvement in the static strength was mainly produced by the constraint of CFRP to the chord deformation at the brace/chord intersection. Thereafter, finite element analysis on 80 models were conducted to investigate the influence of the number of CFRP laminates, corrosion depth, and corrosion length on the static strengths of CFRP strengthened tubular TT-joints with local corrosion. Parametric study showed that, i) more layers of CFRP laminates increase both stiffness and ultimate capacity. ii), the contribution of each layer of CFRP laminates on the bearing capacity reduces gradually with the increase of the number of CFRP laminates or corrosion depth. iii) after a certain length of CFRP, the effect of CFRP length becomes neglectable. Finally, a new equation is proposed to investigate the influence of corrosion and CFRP strengthening on the ultimate bearing capacity of the CHS tubular TT-joints.
•Static strength of CFRP-strengthened tubular TT-joint with corrosion was tested.•Improvement of static behavior of CFRP-strengthened TT-joint with corrosion was studied.•Efficiency of CFRP strengthening to corroded TT-joint was investigated numerically.
In the full-size static strength test of aircraft, the traditional balancing load scheme is used to ensure the loading accuracy to simplify the complex loading scheme, and the load in non-assessment ...area is simplified to several loading points. For the thin-wall structure, the balancing in non-assessment area has great influence on assess-ment area. Taking a front fuselage serious condition of a certain civil aircraft as an example, the balancing load scheme of full-size static strength test is studied based on the finite element model. By comparing the internal force solution of analysis mode load and traditional test mode balancing schemes, the traditional load balancing scheme of full-size static strength test is optimized. The results show that the internal force under optimized test load is basically identical with that under theoretical design load. The Saint-Venant principle is inapplicable to the thin-wall structure of civil aircraft. The load balancing of full-size static strength test should accorda
In the present paper, the effect of the collar plate on the static capacity of circular hollow section (CHS) X-joints under brace compression is experimentally and numerically investigated. For this ...aim, three X-joints reinforced with collar plate, with different values of β, and three corresponding unreinforced X-joints were tested. All of the details and results of the experimental tests are presented. The static behavior of the collar plate reinforced and un-reinforced X-joints is then evaluated from the load-displacement curves and deformed shapes. The compression between the results of reinforced and unreinforced X-joints shows that the collar plate can increase both of the initial stiffness and ultimate strength. Also, these beneficial effects of the collar plate are significant in all of the joints with small, intermediate, and big values of the brace-to-chord diameter ratio (β = 0.25, 0.54, 0.73). Moreover, the compression between deformed configurations shows that deformed shape of the reinforced specimens in the near joint intersection is more uniform than the deformed shape of the corresponding unreinforced specimens. Finally, finite element (FE) model is proposed. Results show that the present FE model can accurately predict the load-displacement curves and failure modes of the unreinforced and collar plate reinforced X-joints.
•The effect of the collar plate on the static capacity of the CHS X-joints is studied.•Six experimental tests are carried out for validating the enhancement effect.•Initial stiffness, ultimate strength, and deformed shapes of the collar plate reinforced and unreinforced X-joints are investigated.•The finite element method is validated by the experimental data.
PDF
