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THE work described in this paper was undertaken to investigate the behaviour of a magnesium alloy beam clastically and plastically deformed by a uniform bending moment at…
THE work described in this paper was undertaken to investigate the behaviour of a magnesium alloy beam clastically and plastically deformed by a uniform bending moment at room temperature. The object of the work was to obtain relations between stresses and strains in the beam, to afford a basis for design, in cases where it is required to submit magnesium alloy structures to bending stresses exceeding the elastic limit.
In the course of flexible PCB manufacture where the reliability of those parts subjected to bending stresses is a matter of utmost concern, the design of the PCB should…
In the course of flexible PCB manufacture where the reliability of those parts subjected to bending stresses is a matter of utmost concern, the design of the PCB should enable the flexible interconnection parts to withstand the greatest possible bending stresses. Therefore, extensive investigations were carried out to demonstrate the relationship between the design and flexural strength. The study shows the functional correlation between bending radius, material thickness, type of material, design of the circuit and number of bending cycles. Only with a detailed knowledge of these five mentioned properties can reliable PCBs be designed and manufactured. The results of these investigations are based on a great number of bending experiments performed on a practical basis and demonstrate the numerical relation between all effects. As bending cycle results are subject to relatively high deviations, the whole problem has been investigated by means of statistical evaluation criteria.
The paper reports experiments carried out on beams in pure bending. The material used was a cast magnesium alloy AZ855. The beam sections were rectangular, circular…
The paper reports experiments carried out on beams in pure bending. The material used was a cast magnesium alloy AZ855. The beam sections were rectangular, circular, I‐section, T‐scction and diamond. One series of tests was carried out up to 1 per cent fibre strain. A second series of tests was carried out up to fracture. Tension and compression tests were also made on the material. The experimental results show conclusively that the usual theory of plastic bending is correct and that the tension‐compression stress‐strain curve of the material may be used to determine the bending moment‐curvature relationships, etc., for a beam. Measurements of neutral axis shift also confirm the predictions of plastic bending theory.
Computational elastica theory is used to model a simple test for the bending properties of fabrics. This test, entitled the “CLOAK” test, was designed to offer practical…
Computational elastica theory is used to model a simple test for the bending properties of fabrics. This test, entitled the “CLOAK” test, was designed to offer practical experimental advantages over the established cantilever bending, of bending length, test. Computational elastica theory offers a routine method for modelling fabrics in cantilever bending. In this case, the CLOAK test is simulated and shown to be equivalent to both the bending length test and to a related test method proposed in the 1960s.
There has been much discussion in the literature about the relationship between fabric “handle” and objective instrumental measurements of fabric low stress mechanical and…
There has been much discussion in the literature about the relationship between fabric “handle” and objective instrumental measurements of fabric low stress mechanical and surface properties such as fabric tensile properties, shear, bending, lateral compression, surface friction and surface roughness. But fabric “handle” is not really an inherent fabric property, rather it is a description of one of the ways in which people generally make a subjective assessment of some of the quality attributes of apparel fabrics, designed for particular end‐use applications. In contrast, fabric drape is an inherent mechanical property of a fabric. Fabric drape is that unique property which quantifies the ability of a fabric to bend simultaneously in more than one plane. In order to exhibit the property of drape, fabrics must be able to bend and shear simultaneously, thus distinguishing textile materials from paper or thin polymer films. Develops a fundamental mechanical analysis of fabrics bending under their own weight. The equations governing the shape of an elastic fabric cantilever are solved numerically. Discusses the implications for experimental measurement of fabric bending length and fabric bending rigidity in terms of these numerical solutions with negligibly small errors. Graphically presents profiles of the draped fabric cantilever. Makes a comparison of the numerical solutions with the approximate formulae derived by F.T. Peirce.
Asphalt mixture is widely used in road engineering, and its performance research is particularly important. But the study of asphalt mixture performance needs a lot of…
Asphalt mixture is widely used in road engineering, and its performance research is particularly important. But the study of asphalt mixture performance needs a lot of tests, such as bending test, splitting test and so on. It also needs a lot of time and material resources. The purpose of this paper is to obtain test results through finite element numerical simulation, and show that this saves a lot of manpower and material resources.
The mechanical parameters of the material are obtained through uniaxial compression tests. The true stress and plastic strain are calculated according to nominal stress and nominal strain. A constitutive model is established. Then a finite element model of asphalt mixture is established. The numerical simulation and performance study of asphalt mixture bending test is carried out. At the same time, according to the above method, the asphalt mixture is subjected to freeze-thaw cycles and ultraviolet aging, and the mechanical parameters are obtained by a uniaxial compression test. A numerical model is established to simulate the bending characteristics of asphalt mixture after freeze-thaw cycles and ultraviolet aging.
A uniaxial compression test of the asphalt mixture is conducted to obtain nominal stress and nominal strain. The true stress and plastic strain are calculated and the elastic modulus is established with Poisson’s ratio as the elastic part, and the true stress and plastic strain as the plastic part. The model is constructed, the finite element model is established and the bending test is numerically simulated. The verified trend is consistent, and the method is feasible. According to the above method, the concrete is subjected to freeze-thaw cycle and ultraviolet aging, and the finite element model is established by using uniaxial compression test to obtain parameters. The bending test is simulated and the verification method is feasible. With the increase of the number of freeze-thaw cycles and the increase of UV aging time, the maximum bending strain of SBS modified asphalt mixture and matrix asphalt mixture is decreased .The low-temperature performance of SBS modified asphalt mixture is better than that of matrix asphalt mixture.
A method of simulating asphalt mixture test by finite element method numerical simulation is established. By using this method, the performance of asphalt mixture is studied, which saves a lot of manpower and material resources. At the same time, this method can be used to study the characteristics of asphalt mixture under complex conditions.
Presents a study of the relationships between fabric drapeability and seam allowance, seam position and seam directions in terms of drape coefficient, bending length and…
Presents a study of the relationships between fabric drapeability and seam allowance, seam position and seam directions in terms of drape coefficient, bending length and draped profile. Concludes that by the results obtained from the sewn specimens, the draped profile of a fabric without a seam can be predicted and proved by extended experimental work. Suggests that the knowledge gained from present research on fabric drape will be useful in the determination of the drape profile on garment in practical use. Moreover, it has significant value in paving the way for establishing clothing CAD systems, and sheds light on fundamental mechanisms operating in fabric drape behaviour.
A two‐spar cantilever box beam with forty‐five degrees sweep and oblique ribs placed parallel to the root clamping section was the subject of a series of static tests…
A two‐spar cantilever box beam with forty‐five degrees sweep and oblique ribs placed parallel to the root clamping section was the subject of a series of static tests. Stress and strain distributions were determined, primarily in a region distant from the root and tip disturbances, to permit a stringent comparison with three well‐known swept wing theories and the simple theory of bending. Torsional and flexural stiffnesses were also measured and compared with these theories. The sequence of calculation for each method is presented and it is found that two of the theories provide accurate predictions of the stresses, strains and stiffnesses. The influence of rivet slip and rivet flexibility on the stiffnesses of the box is mentioned. As a secondary aim of the investigation, the distribution of normal and shear strain has been measured in the cover skin and spar webs at the root connexion. The design of swept box examined has been the subject of research in a number of establishments and a review of this other work is included.
Low‐stress mechanical properties of fabrics are very important in many applications as well as in manufacturing process control. Discusses the importance and potential…
Low‐stress mechanical properties of fabrics are very important in many applications as well as in manufacturing process control. Discusses the importance and potential applications of an on‐line mechanical property measurement system. In addition, the working principles of existing off‐ line fabric bending testers have been critically reviewed. It is suggested that the principle of a future on‐line system to evaluate fabric bending behaviour should be based on the characterisation of fabric loop shapes.
The purpose of this study was to investigate the changes in solder joint stress when subjected to mechanical bending. The analytical theory pertaining to the stresses in…
The purpose of this study was to investigate the changes in solder joint stress when subjected to mechanical bending. The analytical theory pertaining to the stresses in the solder joint between the components (including the molding compound, the chip and the substrate) was described, and the printed circuit board (PCB) with a discontinuity function when the PCB assembly is subjected to mechanical bending was developed. Thus, the findings reported here may lead to a better understanding of the solder joint failure based on the Physics of Failure model.
This paper discusses the analytical model for calculating the stress in solder joints, as well as presents a simulation model that can be used for calculating the strain energy density of solder joint. First, the multilayer plate theory is used in discussing the composite material for the component, including the molding compound, the silicon chip and the substrate, or the PCB, including the copper layers, the fiber and the epoxy. Finally, the complete structure of the analytical model developed as a part of this current work is presented.
For the analytical model of multilayer structures in which the interconnection layer is discrete, mechanical bending has been modeled with respect to varying silicon chip length. The analytical model that describes the stress of the outermost solder joint experiences is chosen, as this is the typical solder joint failure. The analytical model can be applied to discrete solder joints, which are evaluated by calculating the matrix form. Owing to its use of the matrix equation, the analytical model can be highly combinatorial and thus more capable of calculating the solution.
The analytical solution based on a simple concept was presented and validated using the finite element model for the stress experienced by solder joints subjected to mechanical bending. To verify that the simulation represents a real PCB case, the authors use the finite element method (FEM) to compare their case with the multilayer plate theory. Owing to the good agreement between the theory and simulation results, the authors conclude that the multilayer plate theory can be correctly applied in multilayer PCB and be used in an analytical model for the PCB assembly subjected to mechanical bending.
Owing to the good agreement between the theory and simulation results, the authors conclude that the multilayer plate theory can be correctly applied in multilayer PCB and be used in an analytical model for the PCB assembly subjected to mechanical bending.
The analytical model is validated with the FEM model and provides the way to physically examine the solder joint failure mechanism. In this paper, the analytical model is developed as a means to assess the solder joint stress subjected to mechanical bending.
The analytical model treats the solder joint as discrete and has been successfully validated against the finite element model. The complete structure model (the second analytical model) is presented to discuss the effects of varying silicon chip length on the normal stress in solder joints. When the silicon chip length exceeds to 80 per cent of the total package length, the stress of the outermost solder joint increases rapidly. The design analysis findings have suggested that the failure of the outermost solder joint subjected to mechanical bending on the PCB assembly can be reduced by analyzing the analytical model.