I'm about 280 pounds and shopping for a new mattressIf you have experience please let me know how thick your mattress or possibly the brandI'd rather not sink to the box spring but I'm not a fan of a firm mattressAny advice would be great, thanks!
My husband is a big boy and a memory foam mattress was/is heaven for both of us (me being all of 100 pounds) We used to go through a mattress every couple of years because no matter how many individually wrapped coils there are, the big person pulls the littler person, and the pressure is too muchThe foam mattress we have now is 16 years old, and started to show a little sag on his side, so we got a 2 memory foam topper to perk it up so we expect it will last another 15 years When we got our mattress, we had a 90-day return policy, no matter what, but memory foam is so comfortable, I doubt anyone returns themThe only issue I have is the sheets - standard nice thread count bottom sheets are not suitable for a memory foam as they don't have enough flex, so you do have to get either very cheap, crappy faux silk bottom sheets with flex (but those bunch) or specially-designed stretchy bottom sheetsOh, and NO mattress pad or you are again defeating the reason for having memory foam! I use a plush artificial fiber blanket as a mattress pad and that works very nicely.
If the choice is between these two, the chrom-moly will do betterAluminum is subject to work hardening or stress hardening.
Should local damage really your primary concern when it comes to selecting materials? Or should you be more concerned with weight, or the overall integrity of the structure as a whole? 4130 CrMo is certainly more ductile than 6061 aluminum6061 is a precipitation- hardening alloy, it's excellent strength (for aluminum) comes at the expense of lower ductility and malleabilityIn other words, it's more brittle How exactly are you doing your stiffness calculations? Using 6061 aluminum you should be able realize significant weight savings, provided you do your design work in a thorough and competent enough manner Designing the structure to be of equal weight in the aluminum may give you a significant safety factor in terms of strengthI say Maystiffness is not really a function of yield strength, it is mainly a function of length, outside radius, and the elastic modulus (which is somewhat lower in Al) In other words, to increase stiffness in the aluminum you may wish to increase the outside radius of the tubing Also in terms of denting it's fair to compare a tube to a flat plateYield strength and toughness considerations aside, it's much more difficult to dent a flat plate when it is 2.5 times thickerNote that safety factor is something that is designed into a structure, it has nothing to do with the intrinsic properties of the material itselfNote that 4130 is equally subject to work hardeningThis is true of almost any ductile material, for example steel, aluminum, copper, nylon, etc.
