共查询到20条相似文献,搜索用时 31 毫秒
1.
Ouk Sub Lee Dong Hyeok Kim Yong Hwan Han Yeon Chang Park 《Journal of Mechanical Science and Technology》2008,22(9):1692-1698
The conventional split Hopkinson pressure bar (C-SHPB) technique with a special experimental apparatus is used to obtain a
dynamic deformation material behavior under a high strain rate loading condition. An experimental modification is introduced
to reduce the non-equilibrium on the dynamic material response during a short test period for two polymeric materials. The
proposed method uses aluminum pressure bars to achieve a closer impedance match between the pressure bars and the specimen
materials such as hot temperature degraded POM (Poly Oxy Methylene) and PP (Poly Propylene) to obtain more distinguishable
experimental signals. In addition, a pulse shaper technique is used for increasing the rise time of the incident pulse to
ensure the dynamic stress equilibrium and the homogeneous deformation in the specimen under dynamic compression loading condition.
The details on the dynamic stress equilibrium and the duration of uniform strain rate during the dynamic deformation of the
specimen are experimentally investigated. The effects of degradation at a few different hot temperatures on the maximum compressive
stresses are also experimentally studied under varying impulsive loading conditions. 相似文献
2.
3.
The problem of a crack approaching a circular hole in cross-ply laminates under uniaxial and biaxial loading is investigated
in this paper. The effects of material orthotropy, geometry [R/d and a/d], and loading conditions on crack tip singularity
are investigated. The stress intensity factors are obtained by the modified mapping collocation method. The present results
for an isotropic infinite plate show good agreement with existing solutions. The results for cross-ply laminates show that
the stress intensity factors strongly depend on material orthotropy, geometry, and loading condition. The stress intensity
factors for cross-ply laminates exist between those for θ=0° and those for θ=90° in the whole range of crack length and decrease
as the percentage of 0° plies increases. In the range of small crack length the stress intensity factors for biaxial tension
are higher than those for uniaxial tension. In the range of large crack length the stress intensity factors for uniaxial tension
are higher than those for biaxial tension. 相似文献
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5.
Alunda Bernard Ouma Jeonghwan Nam Lim Hyun Seok Jai Sug Hawong 《Journal of Mechanical Science and Technology》2012,26(8):2617-2626
The square ring has over the past few years been used as an alternative sealing element to the O-ring, which has been used widely for a long time. The square ring geometry is believed to be especially suitable for axial static applications because its square form remains practically constant under high pressures, has a high resistance to extrusion, not sensitive to gap extrusion and high leak tightness. Some of these fundamental properties that are crucial in the design of a square ring can be justified by analysis of the stress distribution of the square ring under various loading conditions, especially under a combined loading of uniform squeeze and internal pressure. In order to justify these properties a stress frozen square ring under this combined loading condition of uniform squeeze rate and internal pressure was analyzed using the photoelastic experimental hybrid method to obtain the contact and internal stresses. This research confirmed that contrary to the established theory, the square ring extrudes at a lower pressure of 1.96 MPa. The photoelastic experimental hybrid method can adequately be used for stress analysis of square ring seals. Internal pressure plays a significant role in the design of the seals. As the internal pressure increases, the internal stresses also increase. Maximum internal stresses were observed in the region close to the extrusion gap at points 2 and 2??. The square ring experienced contact stress singularity on the upper end of the contact surface (point 2??) on the front side and at point 2 on the upper side. The upper region experienced the largest contact stresses as well as internal stresses and so the fracture criterion of maximum shear stress should be applied in this region. 相似文献
6.
Surja Kumari 《International Journal of Mechanical Sciences》1975,17(1):23-30
The problem of dynamic expansion of a finite circular hole in an infinite plate, of uniform initial thickness, in a state of plane stress is worked out by solving the equation of motion. A numerical solution is obtained for a strain-hardening material using (i) a continuous three-parameter stress-strain relation and (ii) Nadai's J2-deformation theory of plasticity. The solution is obtained by the method of characteristics for both ramp velocity and ramp pressure prescribed at the hole boundary. 相似文献
7.
《International Journal of Mechanical Sciences》1999,41(4-5):527-546
The stresses in the region of an oblique hole in a flat plate are analysed using the thermoelastic stress analysis technique. Particular attention is given to the obliquity of the hole and to the line of action of the applied load in relation to the hole axes. The effects of varying plate thickness are also studied. The data from around the rim and along the internal axis of the hole are presented as a series of stress concentration factors. The results are compared to those from previous studies and discussed in detail. These confirm the findings of the previous work in that increases in hole obliquity increase the stress at the hole, the maximum principal stress is obtained when the load is applied normal to the major axis of the surface ellipse and that as the thickness of plate increases the stresses on the surface of the plate decrease. Issues such as differences in the material’s Poisson’s ratio value are also discussed. The effect of any non-adiabatic behaviour on the thermoelastic output is described. 相似文献
8.
Kwang-Hee Im Kim Sun-Kyu In-Young Yang 《Journal of Mechanical Science and Technology》1994,8(3):303-313
In this paper, a new method is proposed to analyze impulsive stresses at an impact loading point, which cannot be solved by the classical plate theory. Particularly, impulsive stresses at an impact loading point under any impact conditions (regardless of mass of impactor, velocity of impactor, stiffness of plate, etc.), can be obtained by the three-dimensional dynamic theory of elasticity and potential theory of displacement. In addition, by using the Hertzian contact theory, impact loading can be analyzed to account for the local deformation, and this load is applied to the impulsive stress analysis by approximating the impact loading to an analyzable function. In the numerical analysis, the Fourier transform (FFT) algorithm and the numerical inverse Laplace transformation are utilized. Using a new equation, it was possible to analyze impulsive stresses at an impact loading point, and good agreement between the experimental and theoretical results was established. 相似文献
9.
Kyoung Ho Lim John W. Bull Hyun Kang Kim 《Journal of Mechanical Science and Technology》2001,15(4):413-421
A simple procedure to add and remove material simultaneously along the boundary is developed to optimize the shape of a two dimensional elastic problems and to minimize the maximum von Mises stress. The results for the two dimensional infinite plate with a hole, are lose to the theoretical results of an elliptical boundary and the stress concentration is reduced by half for the fillet problem. The proposed shape optimization method, when compared with existing derivative based shape optimization methods has many features such as simplicity, applicability, flexibiity, computational efficiency and a much better control on stresses on the design boundary. 相似文献
10.
G.B. Sinclair 《International Journal of Mechanical Sciences》1980,22(12):731-734
Two three-dimensional (axisymmetric) elastic stress fields are considered: one for a circular hole passing through a plate perpendicular to its faces and under uniform tension in the plane of the plate remote from the hole—the sharp edge problem; the other for a plate with the same size hole at its midplane and under the same type of loading but having a hole surface which smoothly blends into the plate faces—the round edge problem. The first problem has a classical solution, the second admits to analysis in oblate spheroidal coordinates. Together the closed form solutions provide a means of quantifying the effects of rounding or blending the exit edges of a hole through a plate and show increases in a stress concentration factor of 50% are possible as a result of rounding. 相似文献
11.
Mahir H. Es-Saheb Abdulmohsen Albedah Faycal Benyahia 《The International Journal of Advanced Manufacturing Technology》2011,57(5-8):501-509
The validation of the diametral disk compression test with a small flat ground and soft pad utilization has been established. The stress distribution was determined by the finite element analysis for a range of loading conditions. The results showed that for the case of a point load, the fracture is due to shear and compressive stresses at the loading point. The application of the diametral disk test for a flat ground, as well as the use of soft pads at loading regions were proposed and tested. The results showed that both grounds, flat areas and soft pads, have a significant effect on the stress distribution patterns and values in the compression disk test. The stress distributions obtained in both cases, as loading continued, are found to deviate immediately from the assumed ideal point load condition. The obtained results and data, particularly at the disk center, were manipulated in order to obtain a correction equation. Thus, the maximum tensile stress variations, at the center, with the different loading conditions over a wide range ratio of the width of the loading area to the diameter of 0.5 were recorded. Consequently, the stress differences from the ideal case (i.e., the point loading condition) were calculated and fitted with a correction equation. The use of this correction equation can be used to obtain accurate results of the diametral compression test. 相似文献
12.
Ballising, involving pushing a slightly over-sized ball made of hard material through a hole, is a kind of cold working process. Applying ballising process to fastener holes produces compressive residual stress on the edge of the holes, and therefore increases the fatigue life of the components or structures. Quantification of the residual stress field is critical to define and precede the ballising process. In this article, the ballised holes are modeled as cold-expanded holes. Elastic-perfectly plastic theory is employed to analyze the holes with cold expansion process. For theoretical simplification, an axially symmetrical thin plate with a cold expanded hole is assumed. The elasticplastic boundaries and residual stress distribution surrounding the cold expanded hole are derived. With the analysis, the residual stress field can be obtained together with actual cold expansion process in which only the diameters of hole before and after cold expansion need to be measured. As it is a non-destructive method, it provides a convenient way to estimate the elastic-plastic boundaries and residual stresses of cold worked holes. The approach is later extended to the case involving two cold-worked holes. A ballised hole is looked upon as a cold expanded hole and therefore is investigated by the approach. Specimens ballised with different interference levels are investigated. The effects of interference levels and specimen size on residual stresses are studied. The overall residual stresses of plates with two ballised holes are obtained by superposing the residual stresses induced on a single ballised hole. The effects of distance between the centers of the two holes with different interference levels on the residual stress field are revealed. 相似文献
13.
The study of thermal stresses on pressure vessels has a great significance from the theoretical and practical point of view due to their importance in many applications. This paper presents a complete analysis of thermal stresses within a thick-walled cylinder under dynamic internal temperature gradient. A complete evaluation of temperature and stress distributions, in a non-steady state, is obtained using a numerical model. In this model the temperature of the inside surface of the thick-walled cylinder is considered to change according to certain boundary conditions. The harmonic and periodic loading conditions are also studied. 相似文献
14.
The topography, morphology, structure and residual stress state at the surface of a rail with severe longitudinal ripples was characterized using a combination of spectrometry, microscopy, scattering and diffraction methods. The investigations reveal that white etching layers develop at the ripple hills, while the ripple valleys contain a severely plastic deformed layer. While the structure in the ripple valleys remains pearlite, the structure of the white etching layers on top of the ripple hills is nanocrystalline martensite containing cementite particles of a few nanometer size. The microhardness of the white etching layers on top of the ripple hills is about three times higher than the microhardness in the ripple valleys. The microhardness throughout the white etching layer is not homogeneous due to the non-uniform amount of carbon in solute solution and also due to differences in the amount and the size of the fine carbide particles. The whole running surface is under biaxial compressive residual stresses. In the ripple valleys the direction of the principal residual stresses nearly coincides with the longitudinal and the transverse direction on the rail. On the ripple hills the compressive residual stresses due to the martensite formation are significantly higher and the stress state is nearly homogeneous. 相似文献
15.
压缩载荷对冷胀孔残余应力的影响 总被引:1,自引:0,他引:1
用考虑组合强化、增量理论的有限元法计算了2124-T851 板件开缝衬套冷胀孔的残余应力场及其在压缩载荷作用下的变化情况。结果表明冷胀之后的压载循环将引起冷胀残余应力的衰减。一个足够大的压缩载荷能够使冷胀工艺给疲劳寿命带来的增益完全丧失。文中说明压缩载荷对冷胀的作用可以和超载后半周压载对裂纹的作用相比拟,建议在确定合理胀孔量时应当把它对所承受的载荷谱中压缩载荷的敏感性考虑在内,应当加强有关的疲劳对比试验研究及残余应力场测量研究。 相似文献
16.
工字型吊钩优化设计研究 总被引:1,自引:0,他引:1
利用有限元方法模拟了吊钩在不同载荷角下吊起1000t重物的过程,并计算了吊钩内部的应力分布,确定了最大应力位置和最危险工况。在保证原有形状尺寸的基础上,将吊钩截面改为工字型,并在腹板增加圆孔。利用有限元优化模块对工字型截面和孔径进行多参数优化,在满足强度要求下使吊钩的重量最小化。 相似文献
17.
机械零件形状优化设计的仿生学方法 总被引:1,自引:0,他引:1
基于相对性原理重新分析了生物适应性生长行为,提出了新的生物生长规律:生物局部区域生长行为只需根据其周边应力大小进行调整,不需要人为确定参考应力。在此基础上,提出了一种模拟生物适应性生长过程的相对应力优化法,该方法的主要特点是不需要人为确定参考应力。所提出的优化方法不但具有较高的优化效率,还能按给定的误差精度要求获得优化结果。最后,给出了受双向载荷作用平板的最优中心孔形状优化设计和给定许用应力下连杆形状优化设计的实例。 相似文献
18.
基于有限元的轴流式水轮机转轮体刚强度分析 总被引:3,自引:1,他引:2
针对轴流式水轮机,因其转轮体的结构及受力情况的复杂性,进行精确的刚强度计算是相当困难的。为了研究轴流式水轮机转轮体在工作状态下的应力状态及位移情况,采用周期性边界条件,选取包含一个完整枢轴孔在内的扇形区域作为分析模型,对弹性体结构的动力平衡方程,采用三维有限元技术进行求解,分别对额定工况、最大水头工况和两种飞逸工况下的轴流式水轮机转轮体进行了刚强度分析。结果表明:轴流式水轮机转轮体在运行时,飞逸工况下的应力水平要远远大于正常运行工况下的应力水平;转轮体的最大位移及最大应力点位于大枢轴孔的下端处,与实际转轮体最大应力位置一致,同时也说明了该方法的有效性。 相似文献
19.
层合板多钉机械连接载荷分配三维有限元分析 总被引:3,自引:0,他引:3
用三维有限元方法对层合板单排四钉机械连接钉载分配进行了分析。计算了复材板与钢板、铝板双搭接时的载荷分布。结果表明,在最大承载孔上理论值与试验值误差不大于16%。各孔的载荷分配主要取决于连接板的刚度,与孔径关系不大。 相似文献
20.
作者采用统计学的实验和数据处理方法,研究复合应力对接触疲劳的影响。实验结果表明,附加拉伸弯曲应力显著地缩短接触疲劳寿命。而压缩弯曲应力的影响,则取决于它的数值大小。较小的附加压缩应力能够增加疲劳寿命,而大的压缩应力将促进疲劳发生。存在一个临界压缩弯曲应力值,此时疲劳寿命为最大值。根据实验结果,作者就通常计算接触疲劳强度所采用的几种决定应力的适用性提出分析和评价。以最大的表面剪切应力作为决定应力更适合于接触疲劳问题,复合应力作用下的接触疲劳裂纹可能发源于金属表面。 相似文献