Product Innovations offers 25+ years of engineering experience including product development, materials selection, process selection, optimization and control. Particular areas of expertise include materials selection for a range of challenging applications, failure analysis, joining including welding, brazing and adhesive bonding, and metals finishing. Oftentimes materials selection is a latent opportunity, not often recognized as a solution by designers.
At Product Innovations, we aim to provide the best engineering solutions based on the following evaluation criteria:
Understand root cause(s) of existing issues(s), and make sure the root cause is corrected, not just address symptoms.
Select solutions with minimum risk to overall project cost, schedule and technical factors.
Evaluate the potential for unintended consequences of the proposed solution and adjust or mitigate accordingly.
Validate proposed solutions physically since not all good ideas work as expected.
We're easy to work with. We offer solutions scaled to your technical challenge. You can avoid hiring, training, and managing specialized skills and just get the answers you need to keep your engineering team or operations on track. Our terms are flexible and customized to your needs.
Please contact us for help with your challenging applications.
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Materials & Process Selection
Materials selection offers another degree of freedom to engineering. Beyond the basic application of materials to the end use, materials selection is the basis for how a part will be made, how much it will cost, the availability in the desired form factor, the cost to assemble and robustness to supply issues.
Metals: cast, sheet metal formed, machined, forged, pressed and sintered.
Ceramics: Pressed, extruded, injection molded then fired.
Plastics: Injection molded, blow molded, thermoformed.
Within each family, specific materials have properties that are a better fit for specific manufacturing approaches. At the assembly level, materials selection has impacts on joining, corrosion, finishing and reliability.
Parts can be integrated via overmolding, bonding, welding, soldering and brazing, but these must be considered during materials selection phase.
Materials each have their strengths and limitations. Selecting a material should consider processing, availability, and assembly in addition to the end use.
Assembling parts must be robust and simple as possible to meet the end item requirements. Methods of attachment are listed below from (generally) simplest to most complex.
Sheet metal seam
Tolerances can stackup creating challenges in alignment and accumulate across multiple subassemblies. There may be opportunities to machine the assembly or integrate multiple parts into one.
Design reviews can help work through opportunities in the design early. The longer opportunities go unnoticed, the harder they will be to implement, if at all. Early recognition of opportunities can open up design freedom and cost savings.
As an engineering partner, we can review designs along the way and make suggestions. The time spent on a design review pays dividends to the overall project cost, schedule and technical performance. The final product may benefit from lower cost and/or higher reliability.
Despite the best design practices and reviews, there are sometimes unforeseen issues. When something goes wrong, it's also an opportunity to improve. The key is learning the right lesson through thorough investigation and understanding of the failure mode. Failure Analysis is how we advance the art of engineering.
Below is an image of a crack in the heat affected zone (HAZ) of a weld that eventually propagated to failure. The HAZ is right next to the weld, where the metal is heated nearly to the melting point, thus changing its microstructure causing it to lose strength. Thermal contraction and solidification shrinkage of the solidifying filler metal applies stress to the substrate being welded. The combined effect of loss of strength in the HAZ and stress can cause cracking of the HAZ. In this case, welding process parameters could be adjusted to resolve the cracking issue.
Adhesive Bonding Analysis Example
An example of the stress development in an adhesive bonded lap joint is shown in the figures below. (similar configuration to ASTM D1002 used to test adhesives, except the adherends were shortened to minimize excessive FEM mesh size.)
In the case that the stiffness of the adhesive is low compared to the adherend, the shear stress in the adhesive tends to be more uniform across the bonded joint (the adhesive just stretches a little). But when the adherend is made of thin, compliant material, the stress tends to concentrate at the edge of the bond. If the adhesive begins to fail due to the concentrated stress, the stress concentration glides across the bonded joint (unzips).
Picture a long, thin plastic sheet (like tape) glued to a tabletop with one end hanging free. If the free end is pulled, the thin plastic sheet will likely tear at the edge of the table. Due to the low stiffness of the thin plastic sheet, the stresses don't distribute evenly across the bonded area. Increasing the length of tape stuck to the tabletop will have minimal effect.
Getting optimum performance from a bond requires balancing the stiffness (moduli), thickness of adherends and adhesive, overlap and may include tapering the adherends to introduce stress gradually as shown in the figure bottom. A design study model can be performed to identify the key characteristics and optimize across multiple variables without the need to build and measure multiple custom prototypes.
Of course, the practical aspect of making consistent, reliable adhesive bonds comes down to excellent surface preparation, bond pressure and controlled curing conditions - we can help there too.
FEA Analysis of a simple lap-shear bond showing shear stress.
Grossly exaggerated yielding of the lap-shear bond above.
Various fundamental adhesive joint types designed to distribute stresses more evenly throughout the bonded area.
Heat Flow Analysis Example
In the image below, a heat flux was applied to the model from the adhesive bonding example. A resulting temperature gradient can be seen. Heat flows through the substrate, across the bonded interface and through the opposite substrate. This sets up the basic premise of heat sinking through a bonded joint. The same basic model could also be used for soldered or brazed lap joints.
For any given design, the optimal substrate thickness, material choices, bond thickness and overlap distance could be found without the need to make dozens of samples and carefully measure each.