Finite element simulation of brittle fracture of bulletproof glass system

The thickness and weight of a bulletproof glass material can be reduced by using strengthened glass that possesses current protective capabilities. In this study, numerical simulations are performed to estimate the protective capability of strengthened borosilicate glass used in bulletproof glass systems. High-velocity impacts and perforation behavior are well described by a dynamic brittle fracture model. A parametric study of the material model of glass is conducted by comparing test results of individual impacts with corresponding numerical estimations; the size of back-surface spall, morphology of perforated surface, and fractured areas are compared. Material parameters of strengthened and non-strengthened borosilicate glasses are determined. Numerical simulations that use a material model considering these parameters well describe the overall fracture behavior of bulletproof glass. The main parameters that affect protective capability are initial compressive yield and fracture stresses. The protective capability of strengthened borosilicate glass is ～20% better than that of non-strengthened borosilicate glass.     

Frictional contact analysis under tangential loading using a local axes boundary element formulation

This paper presents a quadratic boundary element (BE) formulation for contact problems under normal and tangential loading using a local axes system to couple the contact variables. A brief review of the BE formulation is presented with emphasis on the coupling of contact variables to satisfy equilibrium and compatibility conditions. Four contact examples are shown to demonstrate the accuracy of the alternative BE formulation.     

The subsurface stress field caused by both normal loading and tangential loading

The subsurface stress field caused by both normal loads and tangential loads has been evaluated using the rectangular patch solution. The effect of tangential loading on the subsurface stress field has been investigated in detail for both the cylinder-on-cylinder contact and a spur gear teeth contact. For the cylinder-on-cylinder contact, the subsurface stress fields are moved more to the direction of tangential loads and the positions where the maximum stress occur are getting closer to the surface with the increasing tangential loads. The subsurface stress fields of the gear teeth contact are expanded more widely to the direction of tangential loads with the increasing tangential loads. The friction coefficient of a gear teeth contact is low because they are operated in a lubricated condition, and therefore surface tractions in the EHL condition hardly affect on the subsurface stress field.     

A unified brittle fracture criterion for structures with sharp V-notches under mixed mode loading

A unified brittle fracture criterion for cracks and V-notches under mixed mode loading is proposed by extending the maximum circumferential stress criterion and Novozhilov’s criterion. The mixed mode fracture toughness and crack orientation of PMMA plates with a sharp V-notch are predicted by the proposed criterion. Tests were also carried out in order to investigate the mixed mode fracture of the PMMA plates. The fracture criterion is validated by comparison to experimental results.     

不同加载方式下的200 t浮式起重机有限元分析

针对200t浮式起重机整机结构计算的复杂性,在Ansys有限元分析软件中对200t浮式起重机整机结构根据不同的倾斜角度,进行不同的加载力分析计算,得到不同计算工况下的计算结果,并针对结果进行对比分析研究。     

Parameters of fracture mechanics under combined loading by normal separation and In-plane shear

The methods of separable functions and finite elements have been used to generate design formulas of the J-integral for a tensing plate made of material reinforced by a deformation with a centrally inclined through crack. The crack angle allows for a variation of the loading conditions from normal separation up to the combined loading by normal separation and in-plane shear. The correcting coefficients η _pl and η _pl ^COD that enter into the formulas of the J integral depend on the relation between normal separation and in-plane shear parameters and on the deformation reinforcement factor. At the same time, the normalized correcting coefficients η _pl (θ)/η _pl (θ = 0) are practically independent of the sample geometry.     

Finite element modelling for a piezoelectric ultrasonic system

In this paper, a three-dimension (3-D) mechanical element with an extra electrical degree of freedom is employed to simulate the dynamic vibration modes of the linear piezoelectric, piezoelectro-mechanic and mechanical behaviors of a metal disc structure embedded with a piezoelectric actuator. In piezoelectric finite element formulation, a discretized equation of motion is developed and solved by using the integration scheme to explain why an adaptive boundary condition, a simple support condition with three non-equal-triangular (120°–90°–150°) fixed points near the edge, which is the asymmetric disc used as the stator of the studied ultrasonic motor, for the mechanical design of an asymmetric disc-type piezoelectric ultrasonic stator, is defined so that a lateral elliptical motion of the contact point between stator and rotor can be realized for driving the rotor. It starts from hybrid elements with displacement and electric potential as the nodal d.o.f.s model and uses Guyan reduction and Householder-Bisection inverse iteration to find the displacement profile and displacement vector flow of the stator under frequency driving. The standing wave existence is also proven by the displacement patterns of the finite element theoretical model.     

Finite element modelling of the Ilizarov external fixation system

This study describes a computational method for predicting the mechanical response of any configuration of the Ilizarov external fixation system. Mechanical testing of each of the individual components (ring, threaded rod, and wire) of the Ilizarov system was used to determine the stiffness of each component. Finite element (FE) analysis was then used to model each of the individual components. Each model was tuned to match the mechanical testing. A modular FE modelling system, using a master input file, was then developed where the tuned FE models of the individual components could be generated, positioned, and interconnected to replicate a range of fixator configurations. The results showed that the stiffness predications from the FE modelling of the fixator configurations were consistently 10 per cent higher than the stiffness values obtained from the mechanical testing. The FE modelling system can be used to predict the characteristic response of the fixator configurations and clearly shows the relative changes in that response for variations in the number of components used.     

Finite element modelling of skeletal muscles coupled with fatigue

In this study, Hill's muscle theory coupled with fatigue was proposed to describe mechanical behaviours of skeletal muscles. The force developed by a fatigued muscle was described by a muscle fatigue formula which was a time function of the activation α_a and the stretch λ. The modified Hill's muscle theory was hence incorporated into a three-dimensional (3D) finite element model using the PAK finite element code. In this paper, the theoretical derivation of the 3D muscle model was firstly described. After presenting the method of establishing the finite element programme, a case example of studying the mechanical response of a frog gastrocnemius muscle was used to illustrate the applicability of the proposed methodology. The effects of the muscle fatigue on the deformation as well as the stress and strain distribution of the frog muscle subject to a cyclic activation function have been determined. An experiment capturing the real-time shape change of a frog muscle was also conducted to assess the applicability of the proposed method. A comparison between the deformed shapes of the predictive model and the frog muscles was also made. It was shown that the method is capable of providing a reasonable model for describing the mechanical behaviour of skeletal muscles.     

Finite element modelling and experimental modal testing of a three-dimensional framework

The object of this paper is to develop a finite element model for a 1/10 scale crane rig in the laboratory, so that one may predict the dynamic behaviour of the scale crane rig based on the relevant features of the developed finite element model. To this end, the finite element modelling and experimental modal testing for the 1/10 scale crane rig are first carried out. Two kinds of coupling for the transducer and the tested structure for achieving the better experimental outcome are proposed. The finite element model is then modified, according to the experimental results, using various techniques. It has been found that the new modified finite element model, by replacing the conventional infinite rigidity for the ground-fixed nodes by the appropriate stiffness for the translational and rotational springs, can predict the vibration characteristics of the experimental crane rig with satisfactory accuracy.     

淤煤装载机螺旋滚筒的有限元分析

为了验证新型矿用水仓淤煤装载机螺旋滚筒传动的可靠性,应用有限元分析软件ANSYS对螺旋滚筒给料机构进行了刚度和强度分析,并根据分析的结果对螺旋滚筒的结构进行了优化设计,大大减轻了整个螺旋滚筒给料装置的总质量,提高了整机的使用性能.     

Cyclic tangential loading of dissimilar elastic bodies

A two-dimensional fretting fatigue problem involving normal and tangential loading of dissimilar elastic bodies in contact is analyzed. The bodies are brought into contact by a monotonic normal load and then a cyclic tangential load is superimposed with the normal load held constant. The Hertz half plane assumption is retained for each body and the region of contact is divided into a central zone of stick and two external regions of micro-slip in each of which the Amontons-Coulomb law of sliding friction is assumed to apply. The effect of the interaction between the normal and shear stresses due to the mismatch in elastic constants is quantified by comparing the present rigid-elastic numerical solution (extreme case) to the Cattaneo-Mindlin closed form solution for elastically identical materials.     

Antiwear coatings for parts that operate under cyclic loading

The outlook for the use of antiwear coatings based on titanium and aluminum nitrides to improve the performance of parts that undergo wear and cyclic loading is considered.     

Finite element analysis of the thermal effect in high-speed blanking of thick sheet metal

Investigating the shear zone temperature is one of the major challenges in the study of high-speed blanking in thick sheet metals. Several studies have shown that a clear temperature change occurs even at low speed and that this significantly influences the blanked edge quality and die life; however, the thermal effects of high-speed blanking of thick sheet metals have received comparably little attention. This study proposes a methodology to predict the temperature distribution in the blanking process using a coupled thermo-mechanical finite element method for thin phosphorous bronze. The finite element model of blanking was developed to characterize the quality of the blanked edge for different punch speeds. The effect of material softening due to the heat generated during plastic work was considered in the blanking simulations. To verify the validity of the proposed model, several simulations were performed and the results, such as the blanking force and proportion of sheared area, were compared with those obtained from experimental studies. It was found that the thermal effect in thin phosphorous bronze at high punch speeds does not significantly affect the product quality. Therefore, a higher productivity can be attained while maintaining a high quality of the finished product using high-speed blanking.     

Strip yield modelling of fatigue crack under variable amplitude loading

The results from ‘strip yield’ approach of the FASTRAN type models of plasticity induced crack closure effects of fatigue cracks subjected to variable amplitude loadings are presented. The strip yield results are compared with authors’ finite element (FE) and experimental results. It has been observed that the strip yield model is seen to be fundamentally limited by choice of α (constraint factor) and corresponding to treat baseline closure effects. Double overload closure behavior is functionally similar for both strip yield and FE models. Under multiple overloads, an important functional difference is seen between FE and strip yield models. This has been linked to the absence of in-plane constraint in the strip yield model, which is seen to have a distinct decreasing influence on on-going closure effects.     

Properties of thick galvanic steel coatings

The properties of thick steel coatings applied galvanically with mechanical action in different conditions in an electrolyte flux are investigated; the electrolyte is based on iron chloride. On the basis of the results, the utility of this process in repairing large and expensive worn components is assessed.     

岸边集装箱起重机大车平衡梁结构开裂的有限元分析

应用有限元软件Ansys对岸桥大车平衡梁结构进行三维建模及计算,分析结构裂纹区域的应力分布情况,找出导致结构疲劳开裂产生的主要原因,并以此为依据提出了避免开裂的结构改进方法。     

FE modelling of surface stresses in erosion-resistant coatings under single particle impact

A finite element methodology was developed to investigate tensile stresses in the surface of multilayered coatings under single particle impact, simulating particulate erosion conditions. Eight different coating architectures were analyzed to determine reduction in tensile stresses obtained through a combination of layering patterns and material property selections. Depending on actual layer configuration and materials properties used in the calculations, differences in tensile stresses up to 3.6 times were observed. In addition, the role of a bond coat and a load-spreading layer were analyzed to assess their effectiveness in erosion-resistant coatings. Overall, the best coating architecture, from the standpoint of maximizing tensile stress reduction, was the one with a thin, low-modulus top layer and a thick, high-modulus bottom layer.     

UG环境下齿轮弯曲强度的有限元仿真

通过理论计算能够得到齿轮齿根弯曲疲劳强度,但理论计算方法未考虑径向压应力对齿根弯曲强度的影响.在UG NX 2环境中建立标准渐开线圆柱直齿轮,在UG结构分析模块中对轮齿进行静态结构分析并得到应力分布图,仿真精度与解算器和网格划分关系密切.理论计算与虚拟仿真结果均满足许用应力要求.该方法在同一软件环境中实现了对象CAD与CAE的结合,能够辅助模型结构的优化设计,有助于提高设计效率和产品质量.     

Finite element analysis of buckle propagation in pipelines under tension

Using a novel finite element technique, results are obtained regarding the effects of tension on buckle propagation in pipelines. The unique feature of the technique, which is otherwise built within the framework of large-deformation, elastoplastic finite element analysis, is that the steady-state nature of buckle propagation is exploited in the formulation. Parametric studies can be conducted easily, since the computational requirements of the procedure are low compared with those of conventional finite element analysis. In this paper, the technique and its implementation are reviewed briefly. In order to demonstrate the predictive capability of the technique, results for aluminum Al-6061-T6 are compared with experimental data for a wide range of values of the diameter-to-thickness ratio. Calculations are then carried out in order to examine the effects of tension on buckle propagation.