Engineering workshop #2: Forces, moments and free-body diagrams
10 March 2010
Process type: Design
Bob Johnson, Technical Director of consultancy and training company DAMT, goes back to basics on forces and moments, using his trusty bike as an example
Welcome to part two of a series of ‘engineering workshop’ articles revising the basics of engineering. The subject for this month’s piece is: forces, moments and free body diagrams. The first thing to address is the difference between mass and force – mass is proportional to the summation of the number of particles in the material that you are considering (i.e. all atomic nuclei – protons plus neutrons) and a force is a “push” or a “pull”.
The important features of mass are (a) it doesn’t want to move when “pushed” (it has “inertia”) and (b) two masses are attracted to each other by an inverse-square-rule relationship. With regard to this second point, Newton identified that the force of attraction was proportional to the product of the two masses divided by the distance of separation squared.
Every day, we experience this force of attraction between the mass of our own bodies and the mass of the earth. Scientists are not really sure why two masses should attract each other, but still!
{fig.1}
{fig.1} shows a block of steel of mass “M”. If we represent the earth’s “pull” by an acceleration field then we can express the weight force of the mass as “Mg” (mass-times-acceleration). When the block of steel is supported on a concrete plinth (1a) the contact pressure is such that the top surface of the plinth deforms slightly and a reaction force, R, is generated. We therefore have a simple equation in the vertical direction: the reaction force equal to the weight force of the mass (R=Mg). We have shown the mass as a “free-body diagram” – the mass suspended in space with all applicable forces acting on it – it’s as simple as that.
{figs.1b, 1c, 1d} now examine what happens when we remove the support of the plinth – obviously it accelerates towards the centre of the earth until it hits something. At the moment of release (when the mass is still stationary) {fig.1b} we can show the weight force downwards (Mg) and the inertia force (Ma) upwards, where “a” is the acceleration experienced by the mass. [It is important to realise that we can include inertia effects as imaginary forces and treat them like any other force]. Initially, therefore, the acceleration of the particle is equal to the acceleration due to gravity.
After say two seconds {fig.1c} the particle has now gained speed and, because of air resistance, a drag force (Fd) is developed and the acceleration is reduced (to a’). Eventually the particle reaches its terminal velocity {fig.1d} and the downward force, Mg, is matched entirely by the drag force (Fd). Thus we have a set of free-body diagrams that help us understand a simple free-fall. [Note that the buoyancy force of the mass submerged in air has been neglected – this simplification may not be appropriate if submerged in water!].
{Fig.2}
Crank it up
{fig.2} shows the author’s cyclo-cross bike with a pedal force of 250N applied to the chain-side crank while static in the horizontal (3 o’clock) position. Figure 3 shows the corresponding free-body diagram for the crank assuming that there is no rotation (let us assume that the rider has jammed the back brake on). The free-body diagram shows the joggled crank (A-B) and the pedal (B-D) with the load being applied at a point halfway along the pedal (point C).
To represent the loaded pedal as a free-body diagram we must take away its connection to the crank and replace it with the (internal) loads at that joint. It can be seen therefore {fig.3} that the joint must supply a shear force of 250N and a bending moment of 9,000Nmm. If further cuts are made in the pedal then the reader will see that the shear force is constant at 250N between B and C and the moment increases from zero at C to 9,000Nmm at point B in a linear variation.
{Fig.3}
Similarly we can separate the crank arm from the pedal and chainwheel in order to represent the crank as a free-body diagram. Firstly, for equilibrium of the threaded joint at B, we replicate the pedal forces and moments at B, except we reverse the signs and apply these to the pedal end of the crank. We then put the crank into equilibrium by imposing the forces and moments at the bottom bracket bearing (point A). The bottom bracket end of the crank sees a shear force of 250N, a “torsional” moment of 14,000Nmm and the main bending moment of 43,750Nmm. It can be seen that the 20mm joggle in the crank causes the “torsional” (twisting) moment to increase from 9,000Nmm at the pedal end to 14,000Nmm at the bottom bracket end.
If you do a simple check you will see that the pedal (B-D) has no net load in the X, Y or Z directions (force equilibrium). Furthermore there is no net moment about the X, Y or Z directions (moment equilibrium). The same can be seen for the crank (A-B) – there is no net load in the X, Y or Z directions and no net moment about the X, Y or Z directions. Check these - the two components are floating in space under a set of perfectly balanced forces and moments.
More next time when we will attempt to calculate some stresses from the free-body diagrams derived here. In my old days at university the student would get 50% of the mark for a correct free-body diagram so be assured we’ve got it cracked already!
Bob can be contacted at .(JavaScript must be enabled to view this email address)
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Solidworks: The next generation
05 March 2010
Process types: Design and Manage
At SolidWorks World, the CEOs of SolidWorks and its parent company Dassault Systèmes, presented a future vision of SolidWorks. The big news was it looked like it was built on the backbone Catia V6. Al Dean reports
Ever since Dassault Systèmes, the developer of Catia, acquired SolidWorks in 1997, there has been constant speculation about the future of SolidWorks. Many predicted that it would be replaced with a ‘mini Catia’ and this certainly made sense as it meant that Dassault would be able to effectively service different levels of the supply chain.
However, when you have a product as successful as SolidWorks, the old adage of ‘if it ain’t broke don’t fix it’ is always there. And this argument must have held much weight in any Dassault/SolidWorks boardroom discussions over the years, as there have never been any clear signs that the two products would follow similar development paths. Until now, that is.
There’s a dump-truck load of technology coming your way. Brace yourselves for the mother lode
At the recent SolidWorks World Event, held in California last month, SolidWorks CEO Jeff Ray was joined on stage by Dassault Systèmes CEO, Bernard Charlès. This was the first time this had happened and it soon became clear why. Charlès and Ray were about to present a future vision of SolidWorks based on technology from Dassault’s V6 platform, which includes Catia V6 for design and Enovia V6 for data management.
While neither Dassault Systèmes nor SolidWorks confirmed that this ‘new generation’ SolidWorks was based on V6 technology there were more than a few clues. The demonstration was live, using a hosted version of the technology accessed over the web. It showed a platform independent technology with talk of Mac, Windows, and Linux to name but a few. It demonstrated live access to data, hosted “in the cloud”, providing quick response search tools to enable data reuse. It featured direct manipulation of geometry, combined with more traditional modelling tools. Oh, and in addition to that, at the top of the modern, clean looking user interface it said SolidWorks V6.
Modelling with “SolidWorks V6”
From the brief on stage demonstration of the core modelling tools, it was clear that the SolidWorks R & D team is using the geometry-modelling kernel from Catia V6. The tools for geometry creation and modification, for data search and reuse, match the same shown in V6 demonstrations, both in terms of capability and focus. What differentiates the two appeared to be down to one thing: user experience.
The user interface and user experience surrounding those interactions was dramatically different to Catia V6, and this is very important. Many predicted that Catia (or a cut down version of it) would eventually be sold into the SolidWorks user base. But from what was shown on stage at SolidWorks World it would appear that this is not the case.
The demo was of a platform independent technology and Mac, Windows, and Linux to name but a few, were all mentioned
While typical Catia and SolidWorks users have similar requirements, they are fundamentally different in many regards. And if the V6 technologies become a common platform, one would assume that the two products will remain separate, with each having its own user interface, own methodologies and own target markets.
It is fair to assume that Catia will continue to focus on the strategic user where business process goes hand in hand with complexity (relating to product, of teams, of supply chain, etc), while SolidWorks will continue to focus on the mainstream community, where cost versus functionality continues to reign supreme.
The unity of V6
Dassault Systèmes’ V6 platform is arguably the first product development system to have its data management backbone so tightly integrated with the authoring tools. Not just 3D and 2D design tools, but everything - mechatronics, digital factory, simulation etc.
In most product development systems there is a disconnect between the two disciplines. This includes SolidWorks and EPDM, Siemens NX and Teamcenter, Pro/E Wildfire and Windchill. The 3D tool creates the data and the data system manages it. It’s a tightly linked system, but one that is built up of separate entities.
It featured a hosted version of the technology accessed over the web
Dassault’s Enovia V6 is starting to remove that distinction and within V6 everything is managed to a highly granular level. We’re not talking about revisions of parts and assemblies, it’s the live tracking of data to feature and sub-feature level on a massive scale - not only in terms of its ability to handle huge datasets (which are inherent in the granularity), but also in terms of the people who create, edit and access that data. Implementing this level of data management directly into SolidWorks would be an extremely interesting proposition.
The Cloud
One term that was everywhere at the event was “The Cloud”. This is possibly one of the most hideously over used phrases since “Innovation” became popular and lost its meaning entirely. I’ll not dwell on the subject because in this space “The Cloud” refers to a software product running on a web-server. That’s all.
The V6 platform is a server-based architecture. Data is stored and served from that server and is managed centrally. Users can interact with and access this data using a browser-based tool, a mobile device, or via a thicker client installed on a local workstation, it doesn’t really matter.
Following the SolidWorks demo it was clear that many seemed uncomfortable with the idea of a Cloud-based application and asked, “Does that mean I don’t own my own data?” Let’s be clear. No. It doesn’t.
With V6 whether you opt for the hosted service, one that’s installed in a privately maintained server from the vendor (Dassault is gearing up for this) or you have everything behind your firewall - it doesn’t really matter. There are many options. Think of it more as “A Cloud”, rather than “The Cloud.” When you do, it becomes far less intimidating.
Alongside the pure management of data, there’s also huge potential for compute intensive tasks such as simulation and rendering. For those working on a server-farm with 100s of available cores, assets can be generated immediately, as soon as they are required, on demand if you will.
It showed direct manipulation of geometry, combined with more traditional modelling tools
Rendering was demonstrated with Luxology’s Nexus engine (the same one powering PhotoView 360) and this was used to create photo real images in real time. The potential for design exploration in this type of environment, with massive compute capabilities available, is phenomenal.
Change and fear
For the ardent SolidWorks community that has been using its 3D product of choice for many years, the suggestion that SolidWorks could be set to undergo a major change is likely to come as something of a shock. And this is probably why SolidWorks decided to present its future vision now, to let its users get used to the idea, rather than spring it on them with a close to shipping product. But before panic ensues, let’s take a closer look at things.
SolidWorks is fifteen years old and we’ve all seen what happens once software reaches a certain age - it starts to clunk, look clunky and perform in a clunky manner. Fixing and more importantly advancing that code becomes a herculean task, and it becomes harder to stay competitive with newer, more agile systems. In saying that, deciding to build something new, with new technologies, is a brave decision to make.
That’s what Dassault did with V5, and now with V6, and while the transition continues to cause problems for some of its customers for others the results have been very rewarding.
To my mind the fact that SolidWorks is working with Dassault on a future incarnation of SolidWorks is good news. I’ve been covering Dassault and Catia for long enough to know that while the French company doesn’t like to talk about ‘product’, the things Catia can achieve are quite simply breathtaking. It can capture a product, in a digital form, in the most holistic manner. And coupled with Enovia manage the information very efficiently.
The coming years are likely to ones of transition for SolidWorks and its users (as it will for the IT world in general) and I don’t predict for a minute that it will be a smooth ride. But if you’re a SolidWorks user, don’t be afraid. Be excited. Because if this stuff comes to market, I am sure it will be incredible.
www.solidworks.com / www.3ds.com
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Solidworks World report 2010
05 March 2010
Process types: Design and Manage
Al Dean attends his 11th SolidWorks World and finds a company in a state of transition, but one that hasn’t forgotten to put on an industry bash, this year at the Anaheim Convention Centre, California
Apparently, I’ve been going to SolidWorks World for the last 11 years. It said so on my badge. I’ve been there for the major announcements, the major shifts in technology, and I’ve seen the staff change and evolve over the years. But 2010 saw the most dramatic shift for the company in nearly a decade. This was the year that SolidWorks World was ‘Dassaultified’.
Solidorks World 2010, at the Anaheim Convention Centre, California
With 5,000+ attendees all dedicated to the SolidWorks cause and made up of users, resellers and partners, this is a huge event. As is tradition, things really kick into gear with the first day’s general session, starting off with SolidWorks’ CEO, Jeff Ray, who welcomed the crowd in his usual affable manner.
However, the theme for Ray’s keynote this year was slightly different as he took the attendees through a potted history of SolidWorks’ parent company, Dassault Systèmes - starting with its foundation by Marcel Dassault, and through the evolution of and eventual spin off from Dassault Aviation. While the audience was digesting this break from the norm, as Ray exited stage left I was more than a little surprised to see Bernard Charlès, CEO of Dassault Systèmes, enter stage right.
Charlès stepped the crowd through a Dassault Systèmes roadmap, which was a significantly edited down version of those shown at Dassault events. While this included SolidWorks, it mainly focussed on the core Dassault brands and technology sets of Enovia, Delmia, Simulia, and 3DVia - and was followed up by a quick demo of the 3DVia app for the iPhone.
Next, as Charlès was rejoined by Ray, it quickly became clear that this was going to be a defining moment in the relationship between SolidWorks and Dassault. We were about to see something that’s been speculated on and discussed in hushed tones since Dassault acquired SolidWorks in 1997. We were given a technology preview of a future generation of SolidWorks and while it was never officially stated it didn’t take a genius to work out that it was built on the V6 platform from Dassault, the same technology that underpins Catia, Enovia et al. The software being demoed was even labelled SolidWorks V6. For more on this turn to page 32.
Electric dreams
Following the technology preview demonstration, Ray brought out Jeremy Luchini, one of the ever-present SolidWorks team at the event along with Mike North from the Discovery Channel’s Prototype This, who also presented at SolidWorks World in 2009.
With previous events having seen the Orange County Choppers guys bring out a custom motorcycle, the bar had been raised pretty high, but the vehicle they rolled out was incredible. A ‘33 Ford Coupe hot rod, built and designed in conjunction with long term SolidWorks user Factory Five racing.
The special thing about this vehicle it that it’s all-electric. While this might sound like milk float, this thing screams with 300BHP in a 1,000kg car. It’s the first project in a new initiative to engage with SolidWorks users, with a series of community led projects in the style of a TV show (details can be found at letsgodesign.tv).
All about The Cameron
The following day’s general session brought the main event - one Mr James Cameron, director of the current CGI movie of the year, Avatar - fortuitous timing as just that morning, Avatar gained 9 Academy award nominations. Former CEO and founder Jon Hirschtick sat down with Cameron to discuss his work in both the movie industry and his exploration projects, from diving to rediscover both the Titanic and the Bismark, as well as future planned projects to take a manned submersible down to the bottom of the Mariana trench.
James Cameron, director of the current CGI movie of the year, Avatar
While Cameron is clearly spearheading these projects, his interest in engineering and design goes way beyond Hollywood clichés, and he discussed just how important simulation is when you’re building a sea vehicle to withstand the 110kPa found at 11 kilometres below sea level.
We were also treated to a look behind the scenes of Avatar and how the immersive environment was combined with live action and motion capture to deliver a film I’m told is breathtaking in its richness (I’ve very little interest in actually seeing it if I’m honest).
2011 Sneak Peak
The Wednesday session is the one that users get the most excited about, as it’s when the SolidWorks team presents a glimpse into what’s coming in the next major release. While there’s all manner of information out there in the blog community (I’d recommend Ricky Jordan’s write up at rickyjordan.com), here’s a snippet of what’s coming.
Revolve up to a surface is a new capability and one that many users have been requesting for some time. There’s also a raft of new assembly features coming including sweeps, fillets and chamfers and a new weld bead tool.
De-feature allows internal components to be removed and the assembly converted to a part file. In other systems this is often called shrink-wrap and assists predominately with removing detail for client/customer communications where you don’t want to give away your IP.
De-feature allows internal components to be removed to help product IP
With the original PhotoWorks being phased out in favour of the Luxology-driven PhotoView 360, 2011 should see more control and fine-tuning capabilities for PhotoView 360 and the ability to render motion studies.
One of the most interesting new features is the planar simplification tools for simulation. These allow a cross section of a model to be used as the basis for idealised FEA runs and if used wisely if the conditions are correct (it’s not just about geometric symmetry) could save a lot of time for simulation users.
Planar simplification tools allow a cross section of a model to be used as the basis for idealised FEA
The single feature that got the biggest cheer was the new feature lock tool, which allows users to lock a feature tree at a specific point and stop those above it from rebuilding. This can make editing of highly complex (read: large feature count) models rebuild more efficiently.
SolidWorks PLM
Another new service on show was SolidWorks PLM. This is essentially a subset of what Dassault is working on with Enovia V6 and provides a hosted service through which users can upload 3D models and seemingly conduct collaboration sessions. While details were thin on the ground, it looks to take advantage of Dassault’s 3D Live technology for data exploration, combined with all the community/threaded discussion tools that are collected under the banner “social media.” It’s due for launch later this year and should see the first of the new breed of tools and services come to market as a result of SolidWorks’ greater co-operation with Dassault.
SolidWorks PLM is a hosted collaboration service based on Enovia V6
Conclusion
While we’ve barely skimmed the surface of what goes on at SolidWorks World, not covering the huge range of learning and networking sessions that makes up the bulk of the conference, this is the key information for those with an interest in SolidWorks and its future. SolidWorks World is a wonderful event in the 3D design technology event season and one I always look forward to. If there’s a downside, it’s the fact that it’s a US-centric event, when there are a great deal of users outside that region that could benefit from attendance. We can but wish for a SolidWorks World Europe.
www.solidworks.com/swworld
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PTC Media and Analyst Event 2010
01 March 2010
Process types: Collaborate and Manage
From chilly Boston, Al Dean reports on the latest developments from industry giant PTC. From announcements of a healthy growth in PLM license revenue to exciting developments in technical publications, this year’s event had it all
PTC held its Annual Media and Analyst day in a rather chilly Boston last month. I’ve been hopping over the pond for this event for a couple of years now and there’s always some good industry nuggets to be found, as well as getting a sneak peek at what’s coming from PTC in the next twelve months. PLM has been a driving theme for many years, but this year the stakes were raised, evident from the event’s tagline of “Conquering PLM.” Apparently, this means “getting credit for being the clear leader” and PTC seemed to be rather annoyed that it’s not being given the credit as the leader of the industry. The way in which the executives seemed more than a little aggrieved was quite surprising.
PTC stated that PLM has ‘come of age’ with a greater number of companies looking to build their infrastructure for the future. This was backed up by news that the company had experienced a 137% license growth in PLM in Q1 2010, compared to last year, with a projected 30% growth over the full year. These may appear solid figures but it should be taken into account that the company’s 2009 PLM revenues were down by 25% on 2008.
PTC is in the late stages of development of a new technical illustration package which uses its ProductView and Isodraw technologies to compete with the likes of Dassault’s 3DVia Composer
The company’s license growth in PLM software does not appear to be directly from within its customer base, with reports of many companies adopting Windchill-based products that weren’t already Pro/Engineer customers. As Jim Heppelmann, chairman and chief operating officer, PTC explained, “These aren’t existing customers that we sold more stuff to,” quoting EADS, Nokia, GE, and IKEA. “People that started with somebody else’s product and switched to ours somewhere along the way.
“Every time we announce that a big customer switched, it makes it easier to convince the next big customer to switch.” Heppelmann referred to this as the domino effect and keeps this separate from sales into existing customers (citing the John Deere deal).
Following the stage presentations I got to sit down with Heppelmann and talk through some of the key topics and product directions discussed at the event.
The Cloud
One subject that had been on the tip of everyone’s tongue following SolidWorks’ user event the previous week, was ‘The Cloud’, an area that PTC has been ahead of the curve on for some time with it’s PLM OnDemand offering in conjunction with IBM. I asked Heppelmann what he thought about the recent announcements and tech demos.
“Clouds are made of vapour,” he said. “People have spinned it out of control. It’s just another way to deliver software. If it works, they’ll buy it. If it doesn’t work, they won’t buy it. That’s why most people aren’t buying it.”
When asked about the barriers to adoption, Heppelmann replied, “Part of it’s emotional, part of it’s technical, but people are saying ‘It would be great if I didn’t have to install any software or worry and I was instantly in production but if it means it takes an extra 30 minutes to download an assembly I want nothing to do with it. If it means there’s a chance my data might get compromised by my competitor, I want nothing to do with it.’ Those are real problems.
Jim Heppelmann, PTC’s Chairman and Chief Operating Officer
“If you’re in a big company and you have 50 applications in your data centre and you put one in the cloud - nothing changes. It’s not like suddenly your whole IT department is super-productive, because you’ve got the other 49 applications - can you put those on the cloud? No. Probably not. I just think this whole cloud thing has blown so out of control. It’s like SaaS, SOA - It’s all magic pixie dust to solve all of our problems when it’s really just… tools. Sometimes they work, sometimes they don’t.”
Technical Publications
From various noises coming out of the event, it was clear that PTC is working on something new for the technical publications space. The developments centre on taking PTC’s existing Arbotext and Isodraw products and linking them to a web-based delivery mechanism. This was referred to as Service Information Solutions (SIS). Alongside this, there appears to be a new product that combines the company’s expertise in technical illustration through Isodraw with its ProductView lightweight visualisation technology.
Heppelmann was very animated about PTC’s SIS development, “I think we have an opportunity to reinvent how after-market service is done and I’m very excited and personally drove this change to start thinking about more efficient ways to create manuals - and to start thinking about more efficient ways to do service processes. We realised that manuals aren’t efficient in the first place. If you develop something to make something more efficient that’s not efficient in the first place, what do you gain?”
ProductPoint
Last year’s event was all about the release of PTC’s ProductPoint. This was a system that took lessons learned with Windchill and combined it with SharePoint to create a data management and collaboration environment - or to use PTC’s words, Social Product Development.
I think (ProductPoint)becomes important as we get much bigger volumes and as we penetrate the SolidWorks and Inventor base with it.”
Jim Heppelmann, Chairman and Chief Operating Officer, PTC
So how was ProductPoint performing in the year since its launch? Heppelmann said that the original goal was to sell the system to 100 companies in the first 12 months and that target was exceeded by 40. This year’s goal is 300, but after just one quarter they’ve already hit 100, so are more than on target for 2010.
I asked Heppelmann about how important ProductPoint was to PTC, “From a revenue standpoint, it’s not yet that important because it tends to be small deals because that’s what we designed it for. So I think it becomes important as we get much bigger volumes and as we penetrate the SolidWorks and Inventor base with it.”
What about Pro/Engineer?
There was very little discussion of Pro/Engineer and with the software now on a 24-month release cycle and Wildfire 5.0 launched in Autumn 2009, this was to be expected. I did manage to catch up with Brian Shepherd who heads up the development effort and we quickly discussed the Wildfire 6.0 release. While there will be the usual enhancements, the key feature set that people are interested in comes from the merging of the CoCreate direct modelling technology within Pro/Engineer.
While Brian admitted that CoCreate users are a loyal bunch, the team is looking to combine the toolsets to offer them a compelling reason to make the leap. It was also interesting to hear his views on the benefits of using the Pro/Engineer geometry kernel as the basis for direct modelling.
Products like CoCreate operate within very specific topological limits (i.e. it doesn’t handle them too well). According to Shepherd Pro/Engineer’s geometry kernel handles topology changes in a much more robust manner. This sounds interesting and I’m sure we’ll learn more later this year.
Conclusion
PLM is a business concept that’s gaining traction. We know this from talking to our readers. Products are increasingly complex, processes are increasingly complex, and supply chains are increasingly complex - across all industry sectors. In the last few months PTC has announced some pretty major deals for Windchill that has seen its revenues swell in that sector - I seem to recall that last year’s poorer financial results were the result of delayed orders so by moving into this financial period has helped fuel that growth.
But alongside all of the posturing around PLM, for me, the most interesting news out of the event was the work the company is doing in the technical service information field. Most other vendors seem to ignore it or have point solutions (Dassault/SolidWorks has 3DVia Composer and Autodesk is previewing its technical publications technology) that focus on the illustration side of things. But the fact is that the illustration technology is a small component of a very complex process.
At the event, a gentleman from Komatsu, a mining and construction equipment manufacturer, went through the result of his company’s transition from a FrameMaker-based process to one based on Arbortext and Isodraw. Komatsu is expecting to save 50% in translation costs and this is huge considering that the addition of Spanish translations of their manuals cost in excess of $1 million. On top of this it will no longer outsource illustrations which cost over $120,000 per year and it will also benefit from a reduction in cycle time and repetition of work. That’s a pretty compelling pitch to anagement to invest in a technology that fits a need, reduces a serious financial outlay and adds value. For me, that’s where the action will be in the coming year. Let’s see what comes of it.
www.ptc.com
