Executive Summary
Computer-aided tribology (CAT) was analyzed in all of its complexities by TLT readers answering this month’s Sounding Board survey. Proponents cite CAT’s speed of calculations and ability to perform complex experiments without excessive costs. CAT helps verify that designs meet customer specifications, they say, and also prevents expensive testing of inferior prototypes. Less-enthusiastic readers noted computer modeling’s high costs and the difficulties in accurately replicating real-life conditions. “I could deduce from experience with a lot less work to get the same results,” said one reader. Moral: The prudent tribologist will recognize CAT as a valuable tool in the correct circumstance. “The combination of the empirical plus simulations is most powerful,” said one reader. “It is up to the tribologist to strike a good balance.”
Q.1. Please discuss the advantages of using computer modeling in your particular tribological application.
Nonsense in is nonsense out. It seems that we get enthusiastic about all kinds of gadgets, but we no longer understand the basics of tribology. Ask people only one question: What is the single most important property of a lubricant? You will be flabbergasted about the answer, and maybe 10% get it right.
Higher number of failure data in short time span. Complex design of experiments are achieved without excessive cost. Aids in product modification and trial testing at early stages to reduce losses.
None. Needs for root cause analysis usually involve finding out what has changed. Could be very useful to have a rule-based system, but they call that AI now.
We currently don’t use CFD or other software for simulation or analysis due to the high cost. For our routine hydraulic applications, we rely on spreadsheets to provide quick answers for viscosity selection. In the future, we would want to tie into our Solidworks CAD software with CFD to better predict deficiencies in our system designs for fluid selections, which is mainly in the mobile market where temperature fluctuations can be extreme, and also in specialized industrial systems. Knowing the exact pressure drops to be encountered can help minimize cooler requirements, thus reducing cost and package size. We also would benefit from software from a company like Matlab from Mathworks to simulate and predict system functionality at various temperatures and pressures.
Boundary lubrication is very complex and needs advancement. Potentially, computer modeling could create relatively simple design curves that are material and application specific. This would be very helpful! My application is a reciprocating shaft with a little rotation included and with a high moment on the shaft. The shaft is supported by two plain bearings. The moment and the shaft-bearing contact area is dependent on the displacement of the shaft. Plus the contact area increases as the bearing wears. This is a very simple application, but from an analytical standpoint it is complex.
While I currently do not use computer modeling, previous software I have tried required a lot of test data results. I could deduce from experience with a lot less work to get the same results.
I am retired, but we used computer modeling for bearing and rotor dynamics applications. In-rotor dynamics bearings were represented by spring and damping coefficients. A more accurate method is to compute the bearing characteristics at each time step. Advances in computer technology allows the more accurate method to be applied. I believe in computer modeling as an accurate time saver over testing, and I encourage continued development of computer programs in all phases of tribology.
Routine calculations of contact stress, lubricant film thickness and friction heating using various models are all time saving and helpful when conducting basic and applied research studies. Plotting and modeling contact fatigue life also is helpful.
Computer simulations can help engineers verify that designs (bearings, seals, lubricants, additives, lubrication systems) will meet customer requirements for efficiency, reliability and cost. Where applicable, simulations can reduce the testing, time and money required to qualify component designs and choose tribological technologies.
It may show some tendencies of similar failure modes of like machines in similar environments. Rotating equipment tends to exhibit unique profiles in service.
Leveraging computer modeling technologies to solve tribological application problems is a new concept in my country. Maybe some institutions are making efforts on the tools. Effective, visible, application or equipment specific? Quite promising technology in tribological research. Cross-disciplinary team needed for pushing technology into reality.
Very few advantages.
Speed of calculations.
Faster advance in estimating the impact of potential lubricant formulation changes on a tribological application. Early go/no-go decisions can be made on candidate formulations.
Solving coupled Reynolds, energy, continuity and deformation equations.
Most tribometers have to simulate a situation from practice. In order to have the correct settings, software helps a lot, e.g., a Hertzian contact stress, a sliding speed, the amount of spin.
The use of numerical tribological models gives us the opportunity to scan the complex parameter space of a tribological problem. Working on a predictive model forces us to deepen our understanding of our tribological application.
Prevents expensive prototyping and testing of inferior prototypes.
Precise and also quicker and wider calculations especially when the non-linear differential equations should be solved.
Do you think a multi-disciplinary team has higher possibility of success when using computer modeling for solving tribological problems?
Definitely
58%
Somewhat
34%
Not really
8%
Definitely not
0%
Based on responses sent to 15,000 TLT readers.
© Can Stock Photo / halfpoint
Q.2. Discuss any significant limitations you think computer-aided tribology (CAT) has for your specific tribological applications.
Common sense, knowledge and understanding must prevail.
Computing time increases as simulation becomes complex, leading to increases in cost and time. CAT needs inputs from physical characterization. CAT simulations are performed in controlled condition whereas practical application encounter multiple conditions, which are difficult to account in simulations.
Useful for trend plotting and data analysis and collection. Programs need significant verification regarding results and inputs. Garbage in, garbage out, as they say.
Some multi-component interactions are nearly impossible to simplify to a level required for informative output from a computational model.
High cost is paramount, both in initial purchase price and annual subscriptions.
I suspect computer modeling would be complex, expensive and, hence, time and resource consuming. I don’t utilize computer modeling and am not aware of any functional computer modeling for practical applications.
The software models I have seen require you to build a database that takes a lot of time and effort. I do not have the manpower or time to accomplish.
The only limitation is having personnel well-versed in computer programing.
I do not see the ability to accurately predict frictional behavior or wear rates of yet untried material combinations, especially when it comes to predicting sliding friction stability and the ability to predict key conditions for transitions such as scuffing and galling. The more complex the machinery, the less confident I am in the ability to precisely model them by computer to take into account the many variables that could impact behavior. Some systems and components lend themselves better to modeling than others, so the usefulness of models depends on the specifics of the application and the degree to which model validation can be accomplished. Modeling could have an impact on product development in some cases, especially, for example, in predicting component loads for competitive product designs.
Computer simulations still have limited practical application for certain systems. Prediction of surface damage in rolling element bearings and modeling systems that don’t operate in air atmospheres are examples.
Human knowledge and experience and expertise are very valuable and difficult to replace.
Maybe the database for specific equipment or application urgently need to be established. There probably is a long way between research and industrial applications.
CAT can only make recommendations based on information that has been. Computer-aided tribology is not real world; nothing will replace experience, logic and the ability to reason.
The model can only be as good as its database. Aging information or deviation from real life parameters might result in wrong assumptions/actions.
Understanding the operating details specific to mixed lubrication applications.
The result of computations is still not so advanced that one can do without tribometers. To be very sure you still have to do experiments.
The level of complexity because of the physics and chemistry involved limits the fidelity of the model. As a consequence, one must resort to empirical input for the hard-to-simulate elements or go through the multiscale cascade of density functional theory, molecular dynamics and continuum models. Both approaches are time consuming. Often, the time required is so prohibitive that a well-designed experiment yields much greater insight compared to a low-fidelity model. Still, the combination of both is most powerful. It is up to the tribologist to strike a good balance.
Availability of correct mathematical models.
Any limitations with CAT would be in the data input and subsequent review. If bad data is entered into the computations, and/or you’re unable to analyze what the data is telling you, then what good is it? I supposed it would be more of an experience/training limitation more than anything.
Sometimes it is difficult to obtain quick conversions of solutions.
Do you think predicting surface damages using computer modeling can have significant impact on product development?
Definitely
61%
Somewhat
36%
Not really
3%
Definitely not
0%
Based on responses sent to 15,000 TLT readers.