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Design and Analysis of Snap Fit Joints Download Report -Mechanical Projects

抽象的：

Snap fits are the simplest, quickest and most cost effective method of assembling two parts. Basically, a molded undercut on one part engages a mating lip on the other. This method of assembly is uniquely suited to thermoplastic materials due to flexibility, high elongation and ability to be molded into complex shapes. In this research paper a 2D model of snap lock is generated in ANSYS software to study the non linear contact analysis between the mating lips. Result generated by the FEA software ANSYS, allows to evaluate and optimize the snap joint prior to committing costly prototypes and tooling.

介绍：

Snap-fits are the simplest, quickest and most cost effective method of assembling two parts. When designed properly, parts with snap-fits can be assembled and disassembled numerous times without any adverse effect on the assembly. Snap-fits are also the most environmentally friendly form of assembly because of their ease of disassembly, making components of different materials easy to recycle.

尽管可以使用许多材料设计快照，但理想的材料是热塑性的，因为它具有很高的柔韧性和容易且廉价地成型为复杂几何形状的能力。其他优势包括其相对较高的伸长率，低摩擦系数以及足够的强度和刚性，以满足大多数应用的要求。

设计师应意识到，由于对两个交配零件的公差堆叠，组件可能会具有一些“播放”。由于需要模具中的幻灯片，因此某些快速拟合也可以增加注入成型工具的成本。经验丰富的设计师通常可以通过在底切正下方的墙壁上添加一个插槽或将快照放在零件边缘，从而消除幻灯片的需求，从而使它们向外朝外。

Types of Snap-Fits

Most engineering material applications with snap-fits use the cantilever design. The cylindrical design can be employed when an unfilled thermoplastic material with higher elongation will be used (a typical application is an aspirin bottle/cap assembly).

可以使用的其他类型的快照是“ U”或“ L”形悬臂式快照（有关更多详细信息，请参见V部分）。

These are used when the strain of the straight cantilever snap cannot be designed below the allowable strain for the given material.

快照拟合设计考虑

吸附联合处理各种类型的共同之处issues like stress concentration, creep and fatigue. This should be resolved during designing a joint. To resolve these issues there are some guidelines to be followed during design practice. Most of the snap joint are formed by the material commonly used is thermoplastic. We know that due to sharp edges or corners common failure is stress concentration, to avoid this failure we have one solution to incorporate fillet in a desired manner. If sink marks are an issue, a smaller radius can be used, but it may increase the stress in this area. The stiffness of thermal plastic can be improved by adding glass fiber or composite to the base resin. Creep or more accurately stress relaxation, can result in a reduction of the holding force between the two components connected by the snap fit. To avoid creep there should be relaxation in tension and relaxation in bending. To avoid fatigue failure, choose a material which can perform well in fatigue. This material can be chosen by comparing their S/N curves prior to the snap joint application. Reducing these issues is a major challenge by considering all the parameters in their desired form of a snap fit joint.

DEVELOPMENT OF SNAP JOINT IN FINITE ELEMENT MODEL

开发了锥形快照锁的二维有限元模型，以研究影响SNAP FIT拉力强度的各种因素。该模型是在FEA软件ANSYS中生成的，该模型允许非线性触点分析和进行数百个迭代的结果。制定了调节捕获镜头角，快照束支撑区域的尺寸以及梁锥度或锥度比的量。由于快照束的挠度行为主要是二维。为了有效的结果，完成了细节。该垫子区域外围的节点通过边缘夹带固定。两个交配表面之间的摩擦系数也定义为材料恒定元件。模型中还包括了扣子梁底部周围的支撑区域，以捕获支撑刚度的影响。通过在y方向上垂直移动交配触点表面，直到发生快照束捕获表面的总cAM出口来进步。高端个人计算机上的典型运行将需要大约200-500次迭代，并且大约需要2-10分钟。

CONCLUSION

在塑料部位的Snap Fit关节设计领域进行了广泛的研究。从这些纸上可以注意到，影响悬臂快照拟合的推动力或拉拉强度的最重要因素是快照束锥度比，捕获耙角和交配表面之间的摩擦系数。为了优化使用可靠的SNAP拟合的塑料成型组件，有限元分析软件（如ANSYS）起着至关重要的作用。为了进一步研究，可以扩展这种方法，以分析更复杂的三维快速拟合，而无需制造其原型。