The regions of high stress may be a source of which lead to crack failure. Cantilever snapfit performance analysis for haptic evaluation. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. The most common structural element in snapfit joints is a beam, subject to a bending load, in the form of a cantilever snapfit beam with a hook. Unlike the design and use of conventional fasteners, every snapfit used in a product must be designed fiom scratch.
The first snapfit handbook creating and managing attachments for plastic parts 2nd edition paul r. Need help in simulation of snap fit design solidworks forums. Common features snap joints are a very simple, economical. To illustrate this technique, the analysis of the simplest geometry for a latch design, a cantilever beam with a uniform rectangular crosssection, is presented.
This paper describes the design and the use of snap fit fasteners for the multilifecycle design of products. L its main purpose is to generate the finite element model, which consists mainly of nodes, elements, and material property definitions. Designing for snap fits is a complex and iterative process, but if you follow the simple engineering best practices covered in this article, you can improve the initial function of your snap fit joints and decrease your prototyping life cycles. In this paper, the snapthrough deformation of the arch shell is studied. A snapfit latch is the simplest, quickest, and most costeffective method of assembling two or more parts. If you continue browsing the site, you agree to the use of cookies on this website. Cantilever snapfit performance analysis for haptic evaluation article pdf available in journal of mechanical design 312. As strain increases, viscoelastic deformation processes appear. Simulation of snapfit insertion with nonlinear contact. The influence of effective factors on mechanical stress on fingertips during snap fit assembly hamed salmanzadeh. While designing snapfit fasteners, compiicated issues of material strength, fastener geometry, part stiffness, attachment strategy, tolerances, and manufacturability need to be addressed. The influence of effective factors on mechanical stress on fingertips during snapfit assembly hamed salmanzadeh. The algorithm revises classical physics theory on cantilever stresses because of the unique performance of plastics in such applications.
Use of snapfit fasteners in the multilifecycle design of. There is a lot of types of snapfit but im planing to use a circular one do you know what are the parameters that should be respected to make a good snap fit. Applications such as bottle caps of carbonated drinks, snap fit assemblies, sealants, electrical contacts, and gaskets are required to be designed with consideration of stress relaxation behavior of the material used to make them. In solidworks simulation, this is referred to as contact, and it is critical for accurate results. Historically the analysis of these cantilever snap fit designs has been limited to using classical beam formulas to calculate lateral stiffness and nominal stress. A snap fit is an assembly method used to attach flexible parts, usually plastic, to form the final product by pushing the parts interlocking components together. Jul 22, 2011 seminar 1 presentation on snap fit design preparedby. Snap fit analysis engineering design and analysis youtube. It also enables the student to use computing as a means of learning stress analysis because writing a program is analogous to teachingit is necessary to understand the subject matter.
Typical snap fit application dividing geometry into sweepable volumes shown in. Accordingly, the design of a snap fit joint is highly dependent on the polymeric materials. Contact is also one of the most frequently misunderstood areas of analysis. Finite element analysis of milling a copper slab with a. Some researchers use the stress relaxation phenomenon to interpret viscoelastic nature of plastics. How to design snap fit components fictiv hardware guide. Valeo engineers developed best practices for simulation of snap fits. Oct 28, 2010 if youre going to perform a stress analysis on a solidworks assembly, you must be very careful to ensure that you accurately represent how the parts interact with each other. Its useful snapfit height momentary interference can be altered by changing the crosssectional shape of the beam and, of course, by its effective snapfit length. Separating the loads into a number of small steps will aid in smooth convergence.
Jones, short cantilever beam deflection analysis applied to thermoplastic snapfit design, 1987 spe. Lets assume that you understand the mechanics of how snapfit fasteners work maximum permissible deflection, mating force, stress and strain, etc. The longitudinal stress is simply given by a forcearea, where. Pdf cantilever snapfit performance analysis for haptic. Use of snapfit fasteners in the multilifecycle design. Calculate stresses, strain based on inputs for the. Apr 28, 2018 hi, stress is defined as the result of forces which lead to reaction of internal particles. While in the past injection molding has been the only viable method for producing snap fit joints in plastics, 3d printing opens up new opportunities and challenges in their design. This method of design limits the structural usefulness of the material upto a certain allowable. Seminar 1 presentation on snap fit design preparedby. Nowadays, snapfits are used in the automotive industry as a proper alternative for mechanical joints, cabling joints, and car interior lining joints. The specific name of the snapfit is usually named after the type of stress or strain it utilizes. The influence of effective factors on mechanical stress on.
The minimum number of different test series required to characterize the bending stress response and rate of the snap was. When snap fit joints are being designed, it is important. Is the contact solution path dependent for instance a snap fit. Using the nonlinear finite element analysis, the large displacement, contact condition and elastoplastic stressstrain curves are considered. Displacement control, rather than force control, usually provides better convergence in the snapfit assembly. The snap fit design guide by basf 9 has designed snap fit calculator which utilizes all the beam formulas and calculates the stress or strain values induced by the deflection. L as described in chapter 2, an sys allows several types of stress analyses. Our snapfit design calculator is a betatool that guides you through snapfit design. The circumferential strain which equals the radial strain because c 2. Trantina, design with plastics, materials selection and design, volume 20, asm handbook, asm international, 1997, pages 639 to 647 the key to any successful part development is the proper choice of material, process, and design matched to the part performance requirements. Design calculations are done on the basis of a limiting strain that. The structural features of a snap fit joint are hooks, knobs, protrusions, or bulges on one of the parts to be joined,which after assembly engage in corresponding depressions undercuts, detents,or openings in the other part to be joined. In many unreinforced thermoplastics, it is not even possible to demonstrate by way of stressstrain experiments the existence of a range in which hookes law is obeyed. Designing components with snap fits can save you time and money in production by reducing material costs and part quantities as well as improving ease of assembly.
Engineering tools are meant to serve as a guidance to the customers in the proper design and selection of materials on various applications that they are developingenhancing specially where it is still highly recommended to test the plastic grade prior to production. The design of the snapfit determines what it can be used for. May 08, 2017 for a more indepth analysis of snap fit design and to dive deeper into the material properties, check out these guides below. Ansi hardware design data fasteners, bolt and screw size charts, american wood screws, flange design data, acme thread design data,screws and bolts.
Snapfit design using classical beam theory iii2 the integrity of the assembly can also be improved by increasing the overhang depth. When snapfit joints are being designed, it is important. For gradespecific information, the reader is referred to fortron material monographs in the area of specific interest, e. Annular snap fits arent well understood but can be a handy means of making assemblies easily disassembled or permanently joined together. Are there large movements in the model or any of the other nonlinear effects mentioned above. Displacement control, rather than force control, usually provides better convergence in the snap fit assembly. Using the nonlinear finite element analysis, the large displacement, contact condition and elastoplastic stress strain curves are considered. Fundamentals of annular snapfit joints machine design. Many snapfit assemblies experience large displacements for very small loads. Most all snap fit joint designs share the common design features of a protruding ledge and a snap foot. Each of these stresses can be calculated from static equilibrium equations. Nowadays, snap fits are used in the automotive industry as a proper alternative for mechanical joints, cabling joints, and car interior lining joints.
Stress relaxation an overview sciencedirect topics. Predicting and validating assembly forces of cylindrical snapfit joints by comparing closedform solutions to computational methods. Toosi university of technology, tehran, iran objectives. On this page, strain generated in snap fit coupling structures using our materials can be calculated.
The thickness of the optimal snap fit arm decreases linearly to 30% of the orig inal crosssectional area. This design uses 17% more material and exhibits 46% higher strain than the opti mal design. The structural features of a snapfit joint are hooks, knobs, protrusions, or bulges on one of the parts to be joined,which after assembly engage in corresponding depressions undercuts, detents,or openings in the other part to be joined. Online engineering calculators and equation tools free. Hi, stress is defined as the result of forces which lead to reaction of internal particles. Some researchers use the stressrelaxation phenomenon to interpret viscoelastic nature of plastics. Most snapfit joints have a common design of a protruding edge and a snapin area. Static transient dynamic modal spectrum harmonic explicit dynamics l. The paper emphasizes that unlike the design and use of conventional fasteners, every snap fit used in a product must be designed fiom scratch. Apr 25, 2014 download mechdat file from and the pdf file from we offer high quality ansys t.
Cantilever snapfit performance analysis for haptic evaluation this paper investigates the parametric effects, which include material properties, hook. Is there significant sliding between contact bodies in the model. Achieving a more accurate prediction of a polymer snap. A cantilever snap fit latch basically consists of a protrusion some type of bead or hook at one end of the beam and a structural support at the other end.
Then i open the home pages of those and search for snap fit. In deciding between a linear and nonlinear contact analysis it is best to ask these questions. Download mechdat file from and the pdf file from we offer high quality ansys t. Understanding contact in solidworks simulation cadalyst. Cantilever snapfit performance analysis for haptic evaluation this paper investigates the parametric effects, which include material properties, hook shape, and shear deformation, on the forcede. Design and analysis of snap fit joint in plastic part. All other items of interest will mainly depend on the. There are six different type of stresses in engineering. Plastic analysis version ii 35 1 plastic analysis 1. In order to understand the source of these high stress regions, an analysis of the process of the insertion of a pin into a hole is considered. The advantages, drawbacks and general design considerations on snap fits are listed. Page 2 of 26 snap fit joints for plastics a design guide.
Bonenberger isbns 9781569903889 1569903883 hanser hanser publishers, munich hanser publications, cincinnati sample chapter 4. The snapfit calculator employs basfs new algorithm for calculating stress and strength requirements. Most all snapfit joint designs share the common design features of a protruding ledge and a snap foot. Analysis steps lthe preprocessor called pr ep7 in ansys is where you provide the majority of the input to the program. The snap fit case of this paper figure 1 is designed as a single cycle loaded assembly snap.
The mechanics and optimization of cantilever snap joints. Ansys wb static structural fea insertion simulation of a. Files are available under licenses specified on their description page. Several assumptions have been made to derive the following equations for circumferential and longitudinal stresses. There are a number of variations in snap fits, including cantilever, torsional and annular. Trantina, design with plastics, materials selection and design, volume 20, asm handbook, asm international, 1997, pages 639 to 647 the key to any successful part development is the proper choice of material, process. Page 2 of 26 snapfit joints for plastics a design guide. The critical stress location is usually the inner diameter of the hub, where max tensile hoop stress. Historically the analysis of these cantilever snap fit designs has been limited to using classical beam formulas to calculate lateral stiffness and nominal stress levels at the root of the snap. Assembly is accomplished without the use of any additional components or fasteners. Free mechanical design, engineering calculators online engineering analysis tools and data.
If youre going to perform a stress analysis on a solidworks assembly, you must be very careful to ensure that you accurately represent how the parts interact with each other. Our snap fit design calculator is a betatool that guides you through snap fit design. Finite element analysis fea is a technique which is widely used to analyze stressstrain states in various portions of devices under inspection. Analysis setting of the snap lock is done by, fixed support at the one end of the prong and the insert snap is given a displacement in y axis direction. Many snap fit assemblies experience large displacements for very small loads. As a result, the beam has to deflect further and, therefore, requires a greater effort to clear the overhang from the interlocking hook. Calculate stresses, strain based on inputs for the snap fit beam parameters. The strain in the outer fibers is uniform throughout the length of the cantilever. Stress analysis overview lstress analysis is a general term used to describe analyses where the results quantities incl ude stresses and strains. They have introduced magnification factor q which give more accurate prediction of total allowable deflection and strain value for short beams. That means that the primary unknown will be the generalized displacements. In this paper, the snap through deformation of the arch shell is studied.
Basic stress analysis aims to help students to become proficient at basic programming by actually using it in an important engineering subject. Bolt single and double shear and tension stress analysis calculator per aisc. Home technical support design calculation tool calclation of the strain in snap fit. The geometry properties will be discussed for obtaining the design guidelines. Gradespecific information is not given in the fortron pps design manual, which is a productspecific publication. Discussion created by pranay repaka on apr 19, 2012 latest reply on jan 21. Whether the snap joint is a cantilever or a cylindrical fit, they both function similarly.
Predicting and validating assembly forces of cylindrical. Weve only scratched the surface here and if you want more indepth information, check out some of the resources below. Strain analysis of press fits the press fit has no. All structured data from the file and property namespaces is available under the creative commons cc0 license. The snap fit calculator employs basfs new algorithm for calculating stress and strength requirements. The annular snapfit utilizes hoopstrain to hold into place. On this page, strain generated in snapfit coupling structures using our materials can be calculated. Valeo engineers developed best practices for simulation of snapfits.
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