Ed Honda, 40 years in Plastics engineering and more

Ed Honda is the owner of Honda Design LLC. Ed has been involved in plastic product development with various Chicago-area manufacturers for over 40 years. He has developed a comprehensive knowleadge base of plastics related design. This comes from development and implementation of hundreds of plastic components, and active participation in dozens of design related projects in consumer, commercial and military applications. Ed was kind enough to take some time and sit down with me, to share his vast knowledge.

What difference do you see over the years in the plastics industry?

3D CAD and injection molding simulation have taken a lot of the speculation and guesswork out of the design and development of plastic components and assemblies.  Being able to validate the part design, the fundamental tooling approach, and processing for the shop floor before allocating any resources to 3D printing or SLAs, prototype and/or production tooling, and molding trials- empowers the designer with significant abilities to get a product to market quicker and more cost-effectively.

What do you think a mold maker or part manufacturer ideally should be doing, to optimize their designs?

Since mold makers and custom molders are providing manufacturing services, as well as quality components and assemblies, it’s important for them to bring human experience and knowledge to the table. However, with all the engineering simulation tools now available, being literate and competent with injection molding simulation software is like adding another experienced member to the design team.  

Are you excited about SolidWorks Plastics?

I’ve been using SimpoeWorks, the full-featured predecessor to SolidWorks Plastics, for three years now. It has been an integral tool in validating and refining my plastic component designs by allowing me to include tooling and processing requirements into the component design as well. The ability to be able to work with both design and simulation-based refinements within the native SolidWorks environment at a mouse-click is smooth, efficient and, well, great! 

What services do you offer through Honda Design LLC.?

I offer forty years’ experience in the plastic product development and manufacturing industries. I work with companies in the Midwest and both coasts, developing products for the consumer, commercial, and military markets. I’m also well-versed in secondary processes such as decorating, painting, and assembly of plastics.

 Injection molding simulation services has become a large part of my business. Using SimpoeWorks for component design troubleshooting- before and after a production mold has been built, has helped my company grow the last two years. 

How do we get hold of you?

Email: ed@hondadesignllc.com

Phone: 312.391.0500

Website: www.hondadesignllc.com

Thanks Ed for your time. And good luck with all future endeavors.

Rajat Trehan

Product Manager 

Computer Aided Technology Inc.

Showing SolidWorks Simulation Results in 3dVia Composer

I was with a group of users the other day and the question came up, “Can I show stress results from SolidWorks in Composer as a view.” My first thought and others in the room was no. Then the hamster in my brain woke up and started spinning the wheels.

 

1. What is important to user to see?
•  Deformation?
• Color Plot?
• Maxium Stress location?
2. What outputs from Simulation can I leverage?
3. What inputs from Composer will give me most of what the user wanted.

Answer #1
User: “ I want them all”

Answer # 2
Eprt (eDrawing 3d results file)
Bmp (Bitmap 2d image)
Jpg (JPEG 2d image)
vrml (3d results file)
xgl (3d results file)
zgl (3d results file )

Answer #3
Out of those files about vrml was the winner.

Big Problem #1
Composers does not bring in the color of the faces from the vrml. Composer can only bring in textures from 3dxml

Redneck Work Around #1
SolidWorks can open VRML files with color and it can save 3dxml files. We have a winner. So perform your analysis and save the results plot as a VRML file. Then open the file in SolidWorks and save the files as a 3dXML

 Have fun,

Bob McGaughey, CSWE

Computer Aided Technology, Inc.

SolidWorks Plastics

SolidWorks today announced a new tool called SolidWorks Plastics. SolidWorks Plastics provides tools that help manufacturers validate and optimize the design of plastic parts and injection molds.

What is the big deal?

Optimal process settings are critical to influencing the cost, quality and productivity of plastic injection molding. The main trouble with injection molding is to have a box of good parts contaminated with scrap. For that reason process optimization studies have to be done and process monitoring has to take place. To have a good part come out of the mold the following issues are typically investigated:

- Fill phase: this can be optimized by varying screw turns per minute and back pressure. Variation of time needed to reload the screw gives an indication of stability of this phase. Injection speed is another critical factor in the fill process. Varying injection speed changes the material damage (shear rate).

-Gate location : A good position will help prevent lack of material to fill the cavity or popularly known as short shot. Injection speed and pressure will also need to be studied to prevent short shot.

- When mold and/or material temperatures are low, the material is cold when the melt front meets, so they do not bond well. This leads to developing a Weld line, also referred to as Knit line. Fill time and pressure need to be studied to reduce or eliminate weld lines.

-If the pressure applied in packing stage is low, or cooling time is too short it can lead to localized depression or Sink Marks on the part. Pressure applied and cooling time is studied to ensure sink marks are minimized.

These are just some of the issues part and mold makers need to worry about before they have a working injection molding process. Typical trouble shooting process would entail industrial CT scanning of mold. Also, multiple trial and error cycles at the machine. These are both expensive and time consuming.

SolidWorks Plastics simulates how melted plastic flows during the injection molding process to predict manufacturing related defects on your parts. Once the defects are identified, they can be easily minimized or eliminated by making changes to part design, mold design, plastic material, or processing parameters. This is all done in a friendly SolidWorks environment.

Tune in for more on this exciting new tool from SolidWorks.

Rajat Trehan

Product Manager

Computer Aided Technology Inc.

 

Flow Simulation Webcast : April 3rd

SolidWorks Flow Simulation is fully integrated within Solidworks 3D CAD software so that every designer can get the benefits of flow simulation at any stage of product development, to design with better insight.
SolidWorks Flow Simulation can quickly and easily simulate fluid flow, heat transfer and fluid forces that are critical to the success of your design.

Register now, to ensure a spot. The following topics will be covered

- Examine flow in and around components to detect
turbulence and recirculation issues.

- Optimize thermal performance of electronic components

- Find best dimensions that satisfy design goals

Rajat Trehan

Product Manager

Computer Aided Technology Inc.

Make That Drawing View Right

So you have a drawing view of maybe an odd shaped object and you wish to set it horizontal or vertical to a known edge for better reference. Sure you can rotate the view, but entering 22.33871842 degrees may still not be exactly horizontal. So how do we do it?

Well ok then, select the line to be the horizontal reference and go to the Tools drop down menu.

Once you have picked the orientation SolidWorks will rotate the view so that is the horizontal edge.

Simple enough...

John Van Engen
CATI Tech Support

Simulate a hot environment

SolidWorks Flow Simulation is a great tool, to help us understand effects of local heat in an environment. We had an interesting project at hand, we were asked to figure out, heat generated in a small furnace.

 

 

 

 

 

 

 

Once the cad model is ready all we have to do is enter basic information. For example how hot the  heating element get (power in watts) , fan speed (rpm) and ambient conditions (room pressure and temperature). We can then figure out heat generated (temperature) in the rods.

 

 

 

 

 

 

 

Also, how uniform is the temperature along the conveyor belt. This is very important  to ensure  components running through the belt get cured uniformly. In a typical furnace they have to maintain a definite temperature range.

 

 

 

 

 

 

 

Once we understand the effect of heating rod and conveyor belt temperature, we can also visualize air movement in the curing chamber. This can be done using Flow trajectories.

 

 

 

 

 

The alternative to this virtual test is to build a physical model, mount temperature gages and run smoke tests to figure out air movement.  Good luck doing all this in 15 minutes.

In these hot environments it is not only necessary to figure out the engineering aspect, but also to determine how comfortable is someone working in close proximity to these furnaces. Solidworks Flow Simulation also calculates comfort parameters as per ASHRAE standards. 

 

The image on the left is  (PMV) Predicted Mean Vote. PMV is an index on how hot or cold a person would feel based on 7 point thermal scale (-3 to 3). -3 being cold to 3 being hot. In this case the plot is taken 5 inches from the from of the furnace.The image on the right is Predicted Percent Disatisfied (PPD). PPD is an index that provides information on thermal discomfort. Since it indicates 100%, I would suggest do not stand 5 inches from the rear of the furnace.

 

 

Rajat Trehan

Product Manager

Computer Aided Technology Inc.

Tracer Study in Flow Simulation

With the tracer study in Flow Simulation you can quickly simulate a concentration source,surface condensation or evaporation of admixture fluid (e.g. water vapor or toxic gas) in the carrier fluid (e.g air).The assumption being this admixture has little or no effect on the carrier fluid flow.

Examples of tracers in air being : water vapor, carbon dioxide,etc. Any admixture whose concentration is relatively low can be considered as a tracer. This feature is very useful for designing clean rooms.

Rajat Trehan

Product Manager

Computer Aided Technology Inc. 

NAFEMS Benchmarks SolidWorks Simulation

When you install SolidWorks Simulation, NAFMES benchmarks are installed by defualt. I would highly recommend everyone to go through atleast a few of them. The goal here is to see how NAFEMS quantifies Solidworks Simulation results, and if possible to come up with a technique that will be applicable to your specific problem at hand.

Here is an example of how you can use a simple model to come up with your own benchmark.

  

You can download this model and follow the steps explained in the link.

Rajat Trehan

Product Manager

Computer Aided Technology Inc.

SolidWorks Sustainability 2012

Solidworks has built Life Cycle Assessment tools to measure environmental impact of your 3D model. Every license of SolidWorks comes equipped with SolidWorks Sustainability, try it. click on evaluate and then pick SolidWorks Sustability.

Check out this short video showcasing Sustainability.

 

Rajat Trehan

Product Manager - Design Validation

Computer Aided Technology Inc.

Simulation and Motion Optimization

SW Motion is a great tool to understand kinematics of a mechanism. The  2012 version of Motion has a great new feature. If you use actuators and sensors to control the movement of a mechanism, you can optimize the entire design virtually. Typically, to get the system correctly configured would take many trial and errors on an actual machine or many hours of hand calculations.

 

A user can simply input sensors as a variable and the optimization tool to study range of motion. In addition constraints can be given to ensure SolidWorks motion find an optimum design for you. Check out this video…let me know how this will help your design processes.

Rajat Trehan

Product Manager - Design Validation

Computer Aided Technology Inc.

SolidWorks 2012 SP0.0 is available for download

Good Afternoon

SolidWorks has released SolidWorks 2012 SP0.0 for download today.

If you are currently active on subscription/maintence you can download the software from the SolidWorks Customer Portal (https://www.solidworks.com/sw/support/downloads.htm).

You can also learn more about the 2012 release of the software by watching the video on the SolidWorks Website (http://www.solidworks.com/launch/register/solidworks-2012-b.htm).

You can also attend one of the CATI Design Summits that are going on throughout the Midwest this October to see What’s New in 2012. To register for one of these events go to http://www.cati.com/events/design-innovation-summit/cati-design-innovation-summit.php

Thanks and Enjoy SolidWorks 2012

Josh Altergott

CATI Support Manager

 

Fishing and Fatigue

 
 
 Fishing is all about enjoying nature. The calm serene water, calling you to sit back, relax, sun bathe while you catch dinner.  Every summer weekend, Rod takes a break from rigors of work and impress on his family his fishing skills.

 

This seat has experienced many joyous moments, passed on wisdom, and helped create some amazing memories. The seat is mounted to the floor using a pedestal and base.  On a recent trip, Rod was enjoying his beer and suddenly the base broke.

  
 
The curious engineer launched into an investigation. After some deliberation, he realized the root cause. While waiting for his bait to hook on, Rod rocks the chair. While this may not be as damaging once or twice, over time it will take toll on the base. This looked like a perfect job for SolidWorks.

It did not take long to create a 3D model. A close look at the supplier’s website gave me all necessary dimensions. Since SolidWorks has an analysis tool integrated to its environment. The next step was streamlined.  Few simple measurements on the boat e,g chair height, distance between base and foot rest platform and most importantly ….Rod’s weight; helped generate conditions.

 

 

 
 

 
 

A simple analysis shows, rocking once does not generate a significant load. A factor of safety of 1.4 indicates the base is very safe and Rod can continue to enjoy his beer while sharing life experiences.

So what happened? Well over time, and in this case many years; base underwent fatigue. Fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The repetitive habit of rocking, caused a localized damage at the notch. Each cycle of load fluctuation weakens the object to some extent. After a number of cycles, the object becomes so weak that it fails.

Failure due to fatigue occurs in three stages:

• Stage 1. One or more cracks develop in the material. Cracks can develop anywhere in the material but usually occur on the boundary faces due to higher stress fluctuations. Cracks can occur due to many reasons. Imperfections in the microscopic structure of the materials and surface scratches caused by tooling or handling are some of them.


• Stage 2. Some or all the cracks grow as a result of continued loading.


• Stage 3. The ability of the design to withstand the applied loads continue to deteriorate until failure occurs.

 

  

 The output of Fatigue tests gives Damage percentages. The percentage cumulative damage factor or the percentage life consumed due to applied load. Rod had to rock the chair 350000 times to make the base fail.

Rod has since replaced the base and continues enjoy his passion. As any engineering investigation, my recommendations were simple….stop rocking the chair. A simple reverse calculation showed a lighter person (~ 195 lbs) would be able to rock 1 million times before breaking the base. ….Training shoes anyone??

Rajat Trehan

Product Manager - Design Validation

Computer Aided Technology Inc.

Help your Pressure Vessel Designs meet ASME Section 8 requirments.

A Pressure Vessel study combines results of multiple loads and understand behavior of any cross section as per ASME standards. A typical load includes internal pressure, temperature rise and earthquake loads. So to start with a user will create different static studies to understand design behavior under each load type (pressure, temperature, etc).

 

Using SolidWorks Simulation users can easily study the effect of multiple loads on designs.

 

 

Once a Pressure Vessel Design is run, users can use stress linearization to separate bending and membrane stresses. Simply define a section clipping on the stress plot, then right click and pick linearize. Pick any two points on the section and click calculate. The software generates six graphs for 6 stress components. Compare the numbers generated with ASME section 8 requirement.

So there you go, no need to fret over a Professional Engineer coming down every few weeks to clear your designs. You can use SolidWorks to help you out and assure him or her your designs conform to ASME standards

Rajat Trehan

Product Manager - Design Validation

Computer Aided Technology Inc.

Valve Design using SolidWorks Flow Simulation

A designer needs to understand how a concept design performs and then quickly, study design variations to come up with most efficient design. This factor alone makes Flow Simulation the perfect tool for engineers.

 

We will use a Ball Valve as an example. The user closes the internal volume of pipe using extrusions called lids. SolidWorks Flow Simulation works with the SolidWorks geometry, hence there is no need to define a fluid volume. Based on the enclosed region between the lids, the software is able to determine the calculation region.

I enjoy the preview the software gives as the solution is running. The preview allows you to look at the results while the calculation isstill running. This helps to determine if all the boundary conditions are correctly defined and gives the user an idea of how the solution will look even at this early stage. At the start of the run the results might look odd or change abruptly. However, as the run progresses these changes will lessen and the results will settle in on a converged solution. The result can be displayed either in contour-, isoline- or vector-representation.

 
Once the solution is complete, there are multiple ways to understand design behavior.

A cut plot displays the distribution of the selected parameter on a certain SolidWorks plane. It can be represented as a contour plot, isolines, vectors, or as arbitrary combination of the above (e.g. contours with overlaid vectors).

A surface plot shows the pressure distribution on all faces of the valve in contact with the fluid. You can also select one or more single surfaces for this plot, which do not have to be planar.

 
Using Flow trajectories you can show the flow streamlines. Flow trajectories provide a very good image of the 3D fluid flow. You can also see how parameters change along each trajectory by exporting data into Microsoft® Excel®. Additionally, you can save trajectories as SolidWorks reference curves.

 
Since, SolidWorks is parametic tool user can have multiple design configurations to check for different valve openings or shapes or flow rates. Once a test is run, to check for different variations of the same design, a user can set multiple tests by cloning the existing projects onto different configurations.

 
Now the Flow Simulation project we have chosen is added to the SolidWorks project which contains the geometry that has been changed. All our input data are copied, so we do not need to define our openings or goals again. The Boundary Conditions can be changed, deleted or added. All changes to the geometry will only be applied to this new configuration, so the old results are still saved.

Imagine being the designer of this ball valve. How would you make decisions concerning your design? If you had to determine whether the benefit of modifying the design as we have just done outweighted the extra costs, how would you do this? Engineers have to make decisions such as this every day, and Flow Simulation is a tool to help them make those decisions. Every engineer who is required to make design decisions involving fluid and heat transfer should use Flow Simulation to test their ideas, allowing for fewer prototypes and quicker design cycles.

Rajat Trehan

Product Manager - Design Validation

Computer Aided Technology Inc.

CATI Design Innovation Summit

Join CATI for our first annual Design Innovation Summit! The CATI Design Innovation Summit is an interactive learning experience focusing on how you can design and make better products. The information covered at these events is too vital to your organization's success to put a price on, so registration is FREE.

>Register Today

Event Highlights:

• FREE hands-on SolidWorks Training


• Presentations from top SolidWorks World Presenters


• User focused content


• Multiple presentation tracks to customize your experience


• The latest SolidWorks Solution offerings


• 3D Printing from Objet Geometries


• See real products designed in SolidWorks


• Network with fellow SolidWorks users


• Contests and prizes

>Suggest a presentation idea

When & Where:

October 4, 2011 - The Wisconsin Auto Museum, Hartford, WI
October 5, 2011 - Harper College, Palatine, IL
October 11, 2011 - The Moto Museum, St. Louis, MO
October 13, 2011 - Indiana State Museum, Indianapolis, IN

More information will be released in the coming weeks.

>Register Here

We hope to see you there!

 

Jim TeDesco
Marketing
Computer Aided Technology, Inc.

Canned Beer Vs Bottled Beer : Can SolidWorks Sustainability help?

With summer at its peak, grilling and beer help most guys keep in good mood. Everytime I walk into store, to pick up beer, I have wondered what would make more sense glass or can? Shananigans would say why bother, but as a responsible citizen I do care about the environment. Besides, If one can contribute towards keeping the environment green, without any major effort aka $$$, why not?

So to figure out what is the right thing to do, I turned to my one of my favorite resource...Google.  I found a fellow engineer who has studied this same puzzle in great detail. Check out the video...

Using SolidWorks Sustainability as a part of our design process one can quickly figure out how green our designs are. No one needs to be a Life Cycle Assessment (LCA) expert, as Sustainable tools are part of Solidworks.

Rajat Trehan

Product Manager - Design Validation

Computer Aided Technology Inc.

One Black coffee please!

I was asked on a very sleepy morning how does the house coffee machine work and could I simulate the thermostat which works overtime in most hourseholds. So off I went to hunt for some facts. Assuming that initially, (before turning the machine on) everything pot, and surrounding air is at 72F. The initial temperature of coffee is 195 F. The coffee pot is heated at the bottom by a 2000 Watt heat power source to keep the temperature of the coffee between 190 F and 200 F.  A thermostat is placed at the top surface of the coffee machine, which turns the power off if the temperature at the thermostat location exceeds 200F. The heat power remains off until the temperature in the previous step drops below 190F.

 
Once the basic information was in place, next step was fairly simple using SolidWorks Simulation, I was able to look assign power to be bottom face of the coffee pot. The transient analysis helped simulate the thermostat.

 
 

To make sure the thermostat was working, I probed the top surface of coffee and check the temperature variation with time. The temperature at the thermostat location increases until it reaches the maximum allowed temperature. In the following calculation steps, the thermostat turns off the power source until the temperature at the thermostat location drops below the minimum allowable value. After that coffee goes through similar cycles of cooling and heating.

 

Now that I have convinced myself and a very special critque of mine….how about that coffee.?

Rajat Trehan

Product Manager - Design Validation

Computer Aided Technology Inc.

Non Linear Analysis

Nature is nonlinear. That means linear analysis can only approximate the real nonlinear behavior of parts and assemblies. Most of the time, such an approximation is acceptable, and linear analysis can provide valuable insight into product characteristics. In many cases, however, linear assumptions differ too much from reality and provide crude or misleading information.

Using the results of linear analysis to decide if a part will fail under its operating loads may lead to overdesign. For example, a bracket design analyzed only with linear analysis requires the designer to stick with a requirement that stress must not exceed the yield. But nonlinear analysis may show that some yielding is used or to choose a less expensive material without compromising structural integrity. An engineer may be concerned about too large a deflection of a flat panel as tested with linear analysis, for another example, and overdesign it to compensate for that deflection without ever knowing that linear analysis exaggerated the deformations, and it was fine as originally designed.

Snapping of buckle is a good example where non linear analysis will give prescribed results. Geometry change together with material response change can be predicted accurately using non linear testing. A linear test will not be able to predict overall behavior accounting for shape and load variation. Some examples where non linear testing will be crucial.

Diaphragm spring : The non linear spring characteristic requires a nonlinear geometry analysis to account for membrane effects.

Pulley : A stamped steel pulley may buckle under belt load before it develops excessive stresses. Although a linear buckling analysis may be enough to determine buckline load, nonlinear analysis is required to study postbuckling behavior.

Allen wrench: Contact between wrench and socket screw necessitates contact stress analysis.

 Historically, engineers were reluctant to use nonlinear analysis, because of its complex problem formulation and long solution time. That's changing now, as nonlinear FEA software interfaces with CAD and has become much easier to use. In addition, improved solution algorithms and powerful desktop computers have shortened solution times. A decade ago, engineers recognized FEA as a valuable design tool. Now they are starting to realize benefits and greater understanding that nonlinear FEA brings to the design process.

Rajat Trehan

Product Manager - Design Validation

Computer Aided Technology Inc.
 

Solidworks Sustainability and ISO 14000 certification

ISO 14000 addresses various aspects of environmental management. The standards, ISO 14001:2004 and ISO 14004:2004 deal with environmental management systems (EMS).

ISO 14004:2004 provides guidelines on the elements of an environmental management system and its implementation, and discusses principal issues involved.

ISO 14001:2004 specifies the requirements for such an environmental management system. Fulfilling these requirements demands objective evidence which can be audited to demonstrate that the environmental management system is operating effectively in conformity to the standard.

An EMS meeting the requirements of ISO 14001:2004 is a management tool enabling an organization of any size or type to

-          Identify and control the environmental impact of its activities, products or services, and to

-          Improve its environmental performance continually, and to

-          Implement a systematic approach to setting environmental objectives and targets, to achieving these and to demonstrating that they have been achieved.

How can Solidworks Sustainability help?

SolidWorks Sustainability evaluates the environmental impact of a design throughout the life cycle of a product.  A user can compare results from different designs to ensure a sustainable solution for product and environment.  By integrating Life Cycle Assessment into design process, a user can see how decisions about material, manufacturing and location (where the parts are manufactured and where they are used) influence a design’s environmental impact.  Solidworks Sustainability distills the results into environmental impact factors, which it measures and totals in terms of Carbon Emissions, Energy Consumed, Air Acidification and Water Eutrophication.

The objective behind ISO 14001:2004 is to assure management and stake holders on environmental issues, comply with regulations, support an organizations environmental policy, and actions. Because ISO 14001:2004 does not lay down levels of environmental performance, the standard can be implemented by a wide variety of organizations. SolidWorks Sustainability can provide a framework to demonstrate conformity. SolidWorks Sustainability can help support an organizations claims and communications on their environmental initiatives.

Rajat Trehan

Product Manager – Design Validation

Computer Aided Technology Inc.

Fatigue Analysis of a Landing Gear using SolidWorks Simulation

It is observed that repeated loading and unloading weakens objects over time even when the induced stresses are considerably less than the allowable stress limits. This phenomenon is known as fatigue. Each cycle of stress fluctuation weakens the object to some extent. After a number of cycles, the object becomes so weak that it fails. Fatigue is the prime cause of the failure of many objects, especially those made of metals. Examples of failure due to fatigue include, rotating machinery, bolts, airplane wings, consumer products, offshore platforms, ships, vehicle axles, bridges, and bones.

Linear and nonlinear structural studies do not predict failure due to fatigue. They calculate the response of a design subjected to a specified environment of loads and restraints. If the calculated stresses are within the allowable limits, they conclude the design is safe in this environment regardless of how many times the load is applied.

Failure due to fatigue occurs in three stages:

Stage 1: One or more cracks develop in the material. Cracks can develop anywhere in the material but usually occur on the boundary faces due to higher stress fluctuations. Cracks can occur due to many reasons. Imperfections in microscopic structure of materials and surface scratches caused by tooling or handling are some of them.

Stage 2: Some or all cracks grow as a result of continued loading.

Stage 3: The ability of design to withstand applied loads continue to deteriorate until failure occurs.

Since Fatigue cracks start (typically) on the surface of a material. Strengthening the surfaces of the model increases life of model under fatigue events.

Using SolidWorks Simulation user can study the effect of a single load. In this case we study landing gear mechanism.  Note the wheels are not modeled. A total bearing force of 6000 lbs is applied to the faces that connect the wheel to the axle.

 

S N Curve or Alternating stress versus number of cycles required to cause failure at a given stress ratio is required to define material failure due to fatigue. A SN curve is based on stress ration or mean stress. The software uses linear interpolation to extract data when you define multiple SN curves for a material. A typical SN curve is shown in figure below

 

SolidWorks Simulation enables users to define different types of fatigue events: constant amplitude and variable amplitude.

Constant Amplitude Events

All cycles of a constant amplitude event have the same alternating and mean stresses. A constant amplitude fatigue event is fully defined by an alternating stress, mean stress (or stress ratio), and the number of cycles. A fatigue event can refer to one or more static studies, or to a particular solution step from nonlinear or modal time history dynamic studies. The software calculates the worst alternating stress levels for each event.

Variable Amplitude Events

A variable amplitude fatigue event is a load history record that defines the fluctuation history of load. The time values do not play any role for fatigue studies with a single variable amplitude event. In this case, it is adequate to define the amplitude sequence.

Fatigue results

SolidWorks Simulation gages fatigue on two parameters

 
Damage factor indicate the specified event consumes x% of the life. The maximum damage show 0.016% The damage plot shows that the axle is likely to fail due to fatigue failure after 1/(max damage) = 1 / 1.6 x 10^-4 = 6,238 blocks (repeats) of the specified variable-amplitude loading event. This result is verified by the total life plot as shown in the next procedure.

Based on damage total life of the mechanism can be figured out

 
Rajat Trehan

Product Manager - Design Validation

Computer Aided Technology Inc.